JP6031990B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device used for fixing a toner image on a recording medium, and an image forming apparatus such as a copying machine, a printer, a facsimile, and a composite machine using the fixing device. In particular, a fixing member having an elastic layer is heated by a heating body to fix a toner image on a recording medium between the fixing member and a pressure member, and toner is separated by a separation claw disposed in a non-contact manner on the fixing member. In a fixing device in which a recording medium on which an image is fixed is separated from a fixing member, a change in state due to thermal expansion of the elastic layer is detected, and a pressure contact state between the fixing member and a pressure member is detected according to the detected state Alternatively, it is characterized in that the start of the fixing operation is controlled so that the fixing member and the separation claw do not come into contact with each other at an optimal interval.

  Conventionally, in an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile, and a composite machine thereof, generally, a recording medium onto which a toner image is transferred from a photoconductor is guided to a fixing device, and this fixing is performed. In the apparatus, the toner image is fixed on the recording medium.

  Here, as one of such fixing devices, the following is conventionally used. The fixing device rotates a fixing roller heated by a heating device and presses a pressure member such as a pressure roller against the fixing roller, and a toner image is transferred between the fixing roller and the pressure member. The recorded medium is heated and pressurized to fix the toner image on the recording medium. Then, the recording medium on which the toner image is fixed is separated from the fixing roller by a separation claw in contact with the outer peripheral surface of the fixing roller.

  In such a fixing device, when the separation claw is always brought into contact with the outer peripheral surface of the fixing roller, the outer peripheral surface of the fixing roller in contact with the separation claw is locally worn, resulting in an image on the recording medium after fixing. There have been problems such as streaks, a reduction in the life of the fixing roller, and the inability to perform stable separation.

  Conventionally, as disclosed in Japanese Patent Application Laid-Open No. H10-228707, there is one in which a separation claw is disposed in non-contact with a fixing roller. This Patent Document 1 discloses a fixing roller having at least one elastic layer in a radial direction, a plurality of separation claws for coming close to the fixing roller in a non-contact manner and peeling a recording material, and a nail support for supporting the separation claws A member, and adjusting means for adjusting a gap (gap) between the surface of the fixing roller and the claw.

  In this type of apparatus, the gap needs to be very small in order to properly separate the recording medium from the fixing roller. In particular, in order to separate a thin recording medium with a large amount of toner in a color image, the gap needs to be on the order of 1 mm or less. For this reason, in said patent document 1, the means to adjust a gap for every separation nail | claw is provided, and the gap is adjusted at the time of an assembly.

  However, as in Patent Document 1, even if the gap is adjusted by the adjusting means, the position of the surface of the fixing member changes due to the thermal expansion of the elastic layer of the fixing member, so that the gap between the separation member and the fixing member can be kept constant. First, the separation member comes into contact with the fixing member, the fixing member is damaged, streaks occur in the fixed image, and conversely, the separation member and the gap widen, and the recording medium cannot be separated from the fixing member. There is a problem that jam occurs.

  Regarding the above-described problem, a fixing member having a configuration in which a fixing belt and an inner roller having an elastic layer inside the fixing belt are disposed will be described. In this type of fixing device, the fixing belt has a heat generating layer, and the fixing belt is heated by, for example, induction heating. At room temperature, there is a gap between the inner roller and the fixing belt, and the fixing belt is bent. On the other hand, when the fixing belt is heated, an elastic layer such as silicon sponge of the inner roller is thermally expanded, so that the inner roller and the fixing belt are in close contact with each other and the fixing belt is in a tensioned state.

  Immediately after introducing the recording medium into the fixing nip from normal temperature and starting the fixing operation, there is a gap between the fixing belt and the inner roller, the fixing belt is in a loose state, and in order to perform the fixing operation, When the pressure member presses the fixing member with a predetermined pressure to form the fixing nip, the fixing belt is swollen in the vicinity of the fixing nip. Further, the separation claw is disposed in the vicinity of the downstream side of the fixing nip.

  When the position of the separation claw is adjusted so that the recording medium can be separated in the state where the fixing belt is swollen in this way, the fixing belt is stretched when the elastic layer of the inner roller is thermally expanded by heating the fixing belt. As the fixing belt moves to the inner roller side, the gap widens, and the recording medium cannot be separated from the fixing belt, causing jamming.

  On the contrary, when the position of the separation claw is adjusted so that the recording medium can be separated in a state where the elastic layer of the inner roller is thermally expanded and the fixing belt is stretched, the pressure member becomes the fixing member from room temperature. When the fixing nip is formed by pressure contact with a predetermined pressure, the fixing belt bulges outside and contacts the separation claw, scratches occur on the fixing belt, and streaks occur in the fixed image.

  Patent Document 2 describes that the deformation due to thermal expansion of the elastic layer of the fixing roller is detected by a fixing roller position variation detection sensor, and the nip width is adjusted by adjusting the position of the pressure roller. Yes. However, this Patent Document 2 does not describe any separation claw for separating the recording medium from the fixing roller, and the above problem between the thermal expansion of the elastic layer of the fixing roller and the gap between the separation claw. There is no description or suggestion about the point.

JP-A-8-87197 JP 2012-42756 A

  According to the present invention, a fixing member having an elastic layer is heated by a heating body, a toner image is fixed on a recording medium between the fixing member and a pressure member, and a separation claw disposed in a non-contact manner on the fixing member. Another object of the present invention is to solve the above-described various problems in a fixing device in which a recording medium on which a toner image is fixed is separated from a fixing member.

  That is, in the present invention, the pressing state of the fixing member and the pressing member or the start of the fixing operation is controlled according to the state of the elastic layer due to thermal expansion, and the fixing member and the separation claw are optimal without contact. It is an object of the present invention to prevent the wear of the outer peripheral surface of the fixing member and the surface of the separation claw as well as to ensure that the recording medium is properly separated from the fixing member.

In the fixing device according to the present invention, a fixing member having an elastic layer, a heating means for heating the fixing member, a pressure member that presses the fixing member to form a fixing nip, and a recording medium is used as the fixing member. In a fixing device having a separation claw for separating from
The separation claw is fixed near the downstream of the fixing nip and disposed in a non-contact manner with respect to the fixing member. The fixing member includes an inner layer having a fixing belt and an elastic layer disposed inside the fixing belt. The roller has a gap between the fixing belt and the inner roller at normal temperature. Detection means for detecting a change in state, and when the detection means detects that the fixing belt and the inner roller are in close contact with each other, the pressure member pressurizes the fixing member with a predetermined pressure, and the fixing nip To be formed.

  In the fixing device according to the present invention, the inner roller has an elastic layer on a metal core made of a metal roller, and the detection means detects the temperature of the end of the metal core of the inner roller, Detects state changes due to thermal expansion. In this way, the thermal expansion state of the elastic layer can be detected at the temperature of the core metal, and the fixing member and the separation claw are controlled by controlling the pressure contact state between the fixing member and the pressure member according to the detected state. The recording medium can be separated from the fixing member by the separation claw at an optimum interval without contacting with each other.

  In the fixing device according to the present invention, the pressure member includes a pressure roller, and the detection unit detects an inter-axis distance between the inner roller and the pressure roller, and the inter-axis distance is equal to or greater than a predetermined value. Then, the pressure roller presses the fixing member with a predetermined pressure. If it does in this way, the thermal expansion state of an elastic layer can be detected with the distance between the axes of an inner roller and a pressure roller, and the press-contact state of a fixing member and a pressure member is controlled according to the detection state Thus, the recording medium can be separated from the fixing member by the separation claw at an optimum interval without contact between the fixing member and the separation claw.

Further, in the fixing device according to the present invention, the detection means can be configured to detect a state change due to thermal expansion of an elastic layer of the fixing member.

In the fixing device according to the present invention, a fixing member having an elastic layer, a heating means for heating the fixing member, a pressure member that presses against the fixing member to form a fixing nip, and a recording medium are provided. A fixing device having a separation claw for separating from a fixing member;
The separation claw is fixed near the downstream of the fixing nip and disposed in a non-contact manner with respect to the fixing member, and has a detecting unit that detects a change in state due to thermal expansion of the elastic layer of the fixing member, When the detecting means detects that the change in the position of the fixing member is stable, the recording medium is introduced into the fixing nip and the fixing operation is started. In this way, the change in the position of the fixing member is stable, and the recording member is introduced after the optimal interval without contact between the fixing member and the separation claw, and the occurrence of jam is eliminated. The recording medium can be separated from the fixing member by the separation claw.

  In the fixing device according to the present invention, the fixing member includes a fixing belt and at least two rollers that stretch the fixing belt, and one of the rollers has an elastic layer that forms a fixing nip. It is an inner roller, and one of the rollers can be a tension roller that applies tension to the fixing belt.

  In the fixing device according to the present invention, the fixing member includes a fixing belt and an inner roller having an elastic layer disposed inside the fixing belt, and a gap is formed between the fixing belt and the inner roller at room temperature. As described above, the inner diameter of the fixing belt and the outer diameter of the inner roller can be set.

  In the fixing device of the present invention, a fixing roller having an elastic layer can be used as the fixing member.

  In the image forming apparatus of the present invention, the toner image is fixed on the recording medium using the fixing device.

  According to the present invention, even when the elastic layer of the fixing member is thermally expanded and the position of the surface of the fixing member is fluctuated, the recording medium is stably separated from the fixing member without causing the separation member to contact and damage the fixing member. can do.

1 is a schematic explanatory view showing an example of an image forming apparatus using a fixing device according to an embodiment of the present invention. FIG. 2 is a schematic explanatory view, partly in section, illustrating the fixing device according to the first embodiment of the present invention. FIG. 2 is a schematic explanatory view showing a fixing member and a heating roller of the fixing device according to the first embodiment of the present invention. 2A and 2B are schematic explanatory diagrams illustrating an inner roller of a fixing member of the fixing device according to the first exemplary embodiment of the present invention, in which FIG. FIG. 2 is a block diagram illustrating a control configuration of the image forming apparatus according to the first embodiment of the present invention. FIG. 6 shows a change in the state of the fixing device according to the first embodiment of the present invention, where (A) shows a state immediately after the heating of the fixing member is started, and (B) shows a state where the elastic member of the inner roller of the fixing member has undergone predetermined thermal expansion. (C) is a schematic explanatory view showing a state at the time of fixing with a pressure roller being brought into pressure contact therewith. FIG. 4 is a schematic explanatory diagram illustrating a state in which an elastic member of an inner roller of a fixing member is in pressure contact before being thermally expanded to a predetermined size. FIG. 4 is a diagram illustrating a relationship between displacement of the fixing belt and time in the fixing device according to the first embodiment of the present invention. In the fixing device according to the first embodiment of the present invention, it is a schematic explanatory diagram showing a state of measuring the distance between the inner roller and the pressure roller. FIG. 5 is a schematic explanatory view showing a fixing device according to a second embodiment of the present invention. FIG. 6 shows a change in the state of the fixing device according to the second embodiment of the present invention, where (A) shows a state immediately after the heating of the fixing member is started, (B) shows a state immediately after the pressure roller is pressed against the fixing member, C) is a schematic explanatory view showing a state at the time of fixing when the elastic member of the inner roller of the fixing member is thermally expanded to a predetermined size. FIG. 10 is a diagram illustrating a relationship between displacement of a fixing belt and time in a fixing device according to a second embodiment of the present invention. FIG. 6 is a schematic explanatory view showing a fixing device according to a third embodiment of the present invention. FIG. 10 is a schematic explanatory diagram illustrating a fixing operation of a fixing device according to a third embodiment of the present invention. FIG. 6 is a schematic explanatory view showing a fixing device according to a fourth embodiment of the present invention. FIG. 6 is a schematic front view illustrating a fixing device according to a fourth embodiment of the present invention. FIG. 6 shows a change in the state of a fixing device according to a fourth embodiment of the present invention, where (A) shows a state immediately after the heating of the fixing member is started, (B) shows a state immediately after the pressure roller is pressed against the fixing member, C) is a schematic cross-sectional explanatory view showing a state at the time of fixing when the elastic member of the inner roller of the fixing member is thermally expanded to a predetermined size. FIG. 10 is a diagram illustrating a relationship between a displacement of a fixing belt and time in a fixing device according to a fourth embodiment of the present invention.

  A fixing device according to an embodiment of the present invention and an image forming apparatus using the fixing device will be specifically described with reference to the drawings. The fixing device and the image forming apparatus according to the present invention are not limited to those shown in the following embodiments, and can be appropriately modified and implemented without departing from the scope of the invention.

  In the image forming apparatus 1 of this embodiment, as shown in FIG. 1, four imaging cartridges 10A to 10D are mounted therein.

  Here, in each of the imaging cartridges 10A to 10D, the photosensitive member 11, the charging device 12 for charging the surface of the photosensitive member 11, and the surface of the charged photosensitive member 11 are exposed according to image information. An exposure device 13 for forming an electrostatic latent image on the surface of the photoconductor 11, a developing device 14 for supplying toner to the electrostatic latent image formed on the surface of the photoconductor 11 to form a toner image, and a photoconductor And a cleaning device 15 for removing toner remaining on the surface of the photoconductor 11 after the toner image formed on the surface of the photoconductor 11 is transferred to the intermediate transfer belt 21.

  Further, in each developing device 14 in each of the imaging cartridges 10A to 10D, the color of the toner to be stored is different, and black, yellow, magenta, and cyan toners are stored.

  In this image forming apparatus 1, in each of the imaging cartridges 10A to 10D, the surface of the photoconductor 11 is charged by the charging device 12, and the surface of each photoconductor 11 thus charged is exposed to the exposure device. 13, exposure is performed according to image information, an electrostatic latent image corresponding to the image information is formed on the surface of each photoconductor 11, and the electrostatic latent image formed on the surface of each photoconductor 11 is applied to the electrostatic latent image described above. The respective color toners are supplied from the respective developing devices 14 to form toner images of the respective colors on the surface of the respective photoreceptors 11.

  Next, the toner images of each color formed on the surface of each photoconductor 11 in each of the imaging cartridges 10 </ b> A to 10 </ b> D are sequentially transferred to the intermediate transfer belt 21 and synthesized on the intermediate transfer belt 21. The formed toner image is formed, and the toner remaining on the surface of each photoconductor 11 after transfer is removed from the surface of each photoconductor 11 by the cleaning device 15.

  On the other hand, the recording medium S accommodated in the image forming apparatus 1 is fed by a paper feed roller 22 and guided to a timing roller 23, and the recording medium S is fed to the intermediate transfer belt at an appropriate timing by the timing roller 23. The toner image guided between the roller 21 and the transfer roller 24 and formed on the intermediate transfer belt 21 is transferred to the recording medium S. The toner remaining on the intermediate transfer belt 21 without being transferred to the recording medium S is removed from the intermediate transfer belt 21 by the second cleaning device 25.

  In addition, the recording medium S on which the toner image is transferred as described above is guided to the fixing device 30, and the fixing device 30 fixes the toner image on the recording medium S, and then the recording on which the toner image is fixed. The medium S is discharged by the discharge roller 27.

  Here, for example, the fixing device 30 includes a pressure roller (pressurization) so as to face and come into contact with the fixing member 31 including a fixing belt 310 and an inner roller 311 disposed inside the fixing belt 310. Member) 32, and the fixing belt 310 is driven to rotate by the rotation of the pressure roller 32. In addition, the rotating fixing belt 311 is heated by the induction heating type heating device 33, and the toner image is heated and fixed on the recording medium S between the fixing belt 311 and the pressure roller 32 thus heated. The recording medium S on which the toner image is fixed is separated from the fixing belt 311 by a separation claw 34 disposed in the vicinity of the fixing belt 311.

  Next, the fixing device 30 according to the first embodiment will be described. As shown in FIG. 2, the fixing device 30 according to the first embodiment includes a fixing member 31, a pressure roller (pressure member) 32 disposed so as to face and contact the fixing member 31, and fixing. The separation claw 34 is disposed in proximity to the member 31.

  2 and 3, the fixing member 31 includes a fixing belt 310 and an inner roller 310 having an elastic layer 311b disposed inside the fixing belt 310. The inner roller 310 and the pressure roller 32 are arranged in parallel, and both end sides are rotatably supported by bearing members (not shown), and the pressing roller 32 is rotated in the direction of the rotation axis of the inner roller 310 by a pressing mechanism using a spring or the like (not shown). The fixing nip N is formed by a predetermined pressure. As will be described later, the pressurizing mechanism unit 300 is controlled by the control device 100.

  The fixing belt 310 includes a magnetic material that receives a magnetic flux generated by the heating device 33 and induces an induced current, thereby generating heat. For example, the fixing belt 310 has an inner diameter of 40 mm and a thickness of 40 μm on a nickel (Ni) base layer, a 0.2 mm thick silicon rubber elastic layer, and a 50 μm thick PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer). ) Surface layer (not shown). In the inner roller 311, a silicon sponge elastic layer having a thickness of 8.5 mm is provided as an elastic layer 311 b on an aluminum core 311 a having a diameter of 23 mm. Further, as will be described later, a core metal temperature sensor 39 for detecting the temperature of the end of the core metal part of the inner roller 311 is provided.

  For example, the pressure roller 32 is provided with a silicon elastic layer 322 having a thickness of 4 mm and a PFA tube surface layer (not shown) having a thickness of 50 μm on an aluminum core 321 having a diameter of 40 mm.

  As shown in FIG. 4A, the fixing member 31 in the first embodiment has a gap between the fixing belt 310 and the inner roller 311 and is kept in a relaxed state at room temperature. When the fixing belt 310 is heated and the elastic layer 311b of the inner roller 311 is thermally expanded, as shown in FIG. 4B, the fixing belt 310 is in close contact and the fixing belt 310 is stretched. Each dimension such as the inner diameter of the fixing belt 310 and the outer diameter of the inner roller 311 is determined.

  In the state of FIG. 4B, when the fixing belt 310 is at a predetermined constant temperature and the elastic layer 311b is heated by heat from the fixing belt 310 after a predetermined time has passed, the elastic layer 311b is heated. Inflated and in close contact with the fixing belt 310. In the first embodiment, as a detecting means for detecting that the fixing member 31 is in the state shown in FIG. 4B, the temperature at the end of the core metal part of the inner roller 311 detected by the core metal temperature sensor 39 is used as a reference. Judge as. That is, the control device 100 described later receives the detected temperature detected from the core metal temperature sensor 39, and when the detected temperature reaches a predetermined temperature, the control device 100 is in close contact with the fixing belt 310 due to thermal expansion of the elastic layer 311b. It is determined that the state (B) has been reached. The core metal temperature sensor 39 may be a non-contact infrared sensor, for example. The relationship between the temperature detected by the core metal temperature sensor 39 and the thermal expansion state of the elastic layer 311b is determined based on the temperature of the core metal when the elastic layer 311b of a predetermined size is measured in advance. do it.

  The fixing member 31 is heated by the heating device 33 as the Ni layer of the fixing belt 310 generates heat. The heating device 33 is disposed opposite to the outer periphery of the fixing belt 310 and is disposed in parallel with the inner roller 311 along the longitudinal direction of the fixing belt 310. In the heating device 33, an exciting coil 331 and a magnetic core 332 are covered with a coil bobbin 334.

  The temperature of the fixing belt 310 is measured by the temperature sensor 37. As the temperature sensor 37, for example, a non-contact infrared sensor can be used. Based on the measured value of the surface temperature of the fixing belt 311 by the temperature sensor 37, the control device 100 described later applies an excitation coil 331 to the heating device 33. By increasing or decreasing the power supply to the fixing belt 310, the surface temperature of the fixing belt 310 is controlled to be a predetermined temperature.

  The pressure roller 32 is rotationally driven at a predetermined peripheral speed in a clockwise arrow direction in the figure by a heating roller driving unit 320 including a driving mechanism described later. The fixing member 31 is driven to rotate in the counterclockwise arrow direction in the figure by the rotation of the pressure roller 2 at the fixing nip N.

  In the fixing operation, the pressure roller 32 is pressed by a pressing force that can secure a fixing nip width sufficient for fixing. In this embodiment, this state is referred to as a pressure contact state. Except during the fixing operation, this state in which the fixing member 31 is pressed with a light pressure enough to follow and rotate is referred to as a light pressure contact state. Control of the pressure applied by the pressure roller 32 is performed by the control device 100 controlling the pressure mechanism unit 300.

  The fixing operation is controlled so that the pressure roller 32 is driven to rotate, the fixing member 31 is driven to rotate, and the fixing belt 310 is heated by the heating device 33 so that the surface temperature of the fixing belt 310 becomes a predetermined temperature. In this state, the pressure roller 32 is pressed against the fixing member 31 so that the fixing member 31 and the pressure roller 32 are in a pressure contact state. Then, the recording medium S on which the toner image is transferred is guided to the fixing device 30 and introduced into the fixing nip N. In the introduced recording medium S, the surface on which the toner image is transferred faces the fixing belt 310. The recording medium S introduced into the fixing nip N is conveyed while being sandwiched by the fixing nip N, heated by the fixing belt 310, and an unfixed toner image is melt-fixed on the recording medium S. The recording medium S is separated from the fixing belt 310 by the separation claw 34 and discharged. In this embodiment, the position of the separation claw 34 is adjusted so that the gap (g) between the separation claw 34 and the fixing belt 310 is 0.4 mm. After the fixing operation, the pressure contact state between the fixing member 31 and the pressure roller 32 is released, and the light pressure contact state is restored.

  Next, the control configuration of the image forming apparatus 1 according to the first embodiment of the present invention will be described with reference to FIG. As shown in FIG. 5, the control device 100 performs various controls of the image forming apparatus 1, and includes a CPU, a program storage unit in which various control programs are stored, a temperature sensor 37, and a core metal temperature sensor 39. And a data storage unit for temporarily storing the temperature detection data detected in step 1 and other measurement data.

  The control device 100 controls the image forming unit 110 including the imaging cartridges 10 </ b> A to 10 </ b> D, the intermediate transfer belt 21, and the transfer roller 24 so as to form a toner image on the intermediate transfer belt 21. Then, the toner image formed on the intermediate transfer belt 21 is transferred to the recording medium S.

  The control device 100 controls the recording medium driving unit 120 including the paper feed roller 22, the timing roller 23, and the paper discharge roller 27, feeds the recording medium S by the paper feed roller 22, and guides it to the timing roller 23. The recording medium S is guided by the timing roller 23 between the intermediate transfer belt 21 and the transfer roller 24 at an appropriate timing, and the toner image formed on the intermediate transfer belt 21 is transferred to the recording medium S. Then, the recording medium S to which the toner image is transferred is guided to the fixing device 30, and the toner image is fixed to the recording medium S in the fixing device 30, and the recording medium S on which the toner image is fixed is discharged by the paper discharge roller 27. The various rollers are controlled so that the paper is discharged.

  The temperature sensor 37 measures the temperature of the fixing belt 310 and gives the measurement result to the control device 100. The control device 100 controls the heating device 33 based on the measurement result from the temperature sensor 37 so that the surface temperature of the fixing belt 310 becomes a predetermined constant temperature.

  The temperature of the end portion of the core bar of the inner roller 311 detected by the core bar temperature sensor 39 is given to the control device 100. The control device 100 determines the thermal expansion state of the elastic layer 311b based on the received temperature detected by the core metal temperature sensor 39, and when the core metal temperature exceeds a predetermined value, the elastic layer 311b is in close contact with the fixing belt 310. It is determined that the state shown in FIG.

  The control device 100 controls the pressure roller driving unit 320 and controls the rotational driving of the pressure roller 32. And the control apparatus 100 controls the pressurization mechanism part 300 based on the detected temperature from the metal core temperature sensor 39, and controls the pressurizing force of the pressurization roller 32 to a light press-contact state or a press-contact state.

  Next, in this 1st Embodiment, the timing of the press-contact of the said pressure roller 32 is demonstrated based on FIGS. FIG. 7 shows a case where pressure is applied by the pressure roller 32 immediately after the start of heating from room temperature to bring it into a pressure contact state. FIG. 8 shows time and belt displacement.

  Here, immediately after heating from room temperature, when the pressure roller 32 is pressurized and brought into a pressure contact state, the fixing belt 310 is greatly displaced as shown by a one-dot chain line B in FIG. 8, and as shown in FIG. The separation claw 34 contacts the fixing belt 310. This is because the thermal expansion of the elastic layer 311b of the inner roller 5 is not yet sufficient immediately after heating is started from room temperature, and the fixing belt 310 is loose. In this state, when the pressure roller 32 is pressed against the inner roller 311 side with a predetermined pressure to form the fixing nip N, the fixing belt 310 is separated by the separation claw 34 along with the deformation of the elastic layer 311b of the fixing nip N. This is because it moves greatly to the side.

  In contrast, in the first embodiment, as shown in FIGS. 6 and 8, immediately after the heating is started from room temperature, as shown in FIG. 6A, the inner roller 311 and the fixing belt 310 There is a gap between them. When the inner roller 311 is heated by the heating device 33 via the fixing belt 310, the elastic layer 311b of the inner roller 311 is thermally expanded, and the fixing belt 310 reaches a predetermined constant temperature. When a predetermined time elapses, the elastic layer 311b is thermally expanded and comes into close contact with the fixing belt 310 as shown in FIG. In this embodiment, the core metal of the inner roller 311 detected by the core metal temperature sensor 39 that the elastic layer 311b of the inner roller 311 is in thermal contact with the fixing belt 310 as described above is detected. The control device 100 detects the temperature based on the temperature of the end portion. That is, based on the temperature detected by the core metal temperature sensor 39, the state of thermal expansion of the elastic layer 311b of the inner roller 311 is detected. When the temperature detected by the core metal temperature sensor 39 becomes equal to or higher than a predetermined temperature, the control device 100 causes the pressure roller 32 to press the inner roller 311 with a predetermined pressure, as shown in FIG. The pressure mechanism 300 is controlled to be in a pressure contact state.

  During the operation in the press contact state, as shown in FIGS. 6C and 8, the elastic layer 311b of the inner roller 311 is in close contact with the fixing belt 310 due to thermal expansion, so that the elastic layer 311b is deformed by the press contact. Even so, as shown in FIG. 8A, the fixing belt 311 is hardly deformed, the movement of the fixing belt 310 toward the separation claw 34 becomes small, and the separation claw 34 may come into contact with the fixing belt 310. Can be prevented. Here, the gap between the fixing belt 310 and the separation claw 34 is a predetermined gap as shown in FIG. In this embodiment, the gap is 0.4 mm.

  In this way, the temperature of the core metal 311a of the inner roller 311 is measured by the core metal temperature sensor 39, and the temperature becomes equal to or higher than a predetermined temperature, so that the gap between the fixing belt 310 and the separation claw 34 becomes a predetermined gap. In this state, the control device 100 drives the recording medium driving unit 120 to perform the fixing operation so that the recording medium S is introduced into the fixing nip N. In this way, the fixing operation can be performed without damaging the fixing belt 310. In cases other than starting from room temperature, the cored bar temperature of the inner roller 311 is high to some extent, so that the temperature reaches a predetermined temperature quickly, and the fixing operation is started quickly.

  In the first embodiment, the cored bar temperature sensor 39 is used as the detecting means for detecting the state change due to the thermal expansion of the elastic layer 311b of the inner roller 311. However, in addition to measuring the temperature of the end of the cored bar. As shown in FIG. 10, the distance sensor 40 may be used to detect the interaxial distance d between the inner roller 311 and the pressure roller 32 using the distance sensor 40 to detect the state of thermal expansion. It is. That is, when the elastic layer 311b of the inner roller 311 is thermally expanded, the pressure roller 32 is moved in the direction of separating. Therefore, the inter-axis distance d between the inner roller 311 and the pressure roller 32 is measured, and the inter-axis distance d between the inner roller 311 and the pressure roller 32 becomes a predetermined size due to the thermal expansion of the elastic layer 311b. What is necessary is just to comprise so that a press-contact operation may be started when the distance d between axes at the time of reaching is reached.

  Next, a second embodiment of the present invention will be described. In the second embodiment, as shown in FIG. 10, a portion corresponding to the fixing member 31 of the first embodiment is stretched between the heating roller 312, the inner roller 311, the heating roller 312, and the inner roller 311. And an endless fixing belt 310. Other configurations are the same as those in the first embodiment. In FIG. 1, the configuration is the same except that the configuration of the fixing device 30 is changed to the above configuration. The control configuration is the same as the configuration shown in FIG.

  A halogen heater 313 is provided inside the heating roller 312 as a heating device, and the fixing belt 310 is heated by the halogen heater 313. In order to adjust the temperature of the fixing belt 310 to an appropriate temperature, the temperature of the fixing belt 310 is measured by the temperature sensor 37, and based on the measured temperature, the control device 100 serves as a heating device built in the heating roller 312. The halogen heater 313 is turned on / off to control the fixing belt 310 to an appropriate temperature.

  A pressure roller 32 having an elastic layer 322 provided on the outer periphery of the cored bar 321 is provided at a position facing the inner roller 311 via the fixing belt 310, and the pressure roller 32 is rotated so that the fixing belt 310 described above is rotated. Is driven to rotate. The recording medium S on which the toner image is transferred is guided to the fixing nip N formed between the inner roller 311 and the pressure roller 32 via the fixing belt 310 heated by the heating roller 312, and the toner image Is fixed to the recording medium S by heating. The fixed recording medium S is separated from the fixing belt 310 by the separation claw 34 and discharged.

  The inner roller 311 in the second embodiment is formed by providing a silicon rubber elastic layer 311b having a thickness of 10 mm on a cored bar 311a made of stainless steel (SUS) having a diameter of 40 mm, for example. The heating roller 312 is made of an aluminum pipe having a diameter of 40 mm and a thickness of 2 mm. The fixing belt 310 is formed by providing a polyimide rubber base layer having a thickness of 70 μm, a silicon rubber elastic layer having a thickness of 0.2 mm, and a PFA tube surface layer having a thickness of 50 μm. A core metal temperature sensor 39 that detects the temperature of the end of the core metal 311a of the inner roller 311 is provided.

  Next, the timing for starting the fixing operation in the second embodiment will be described with reference to FIGS.

  In this second embodiment, as shown in FIGS. 11 and 12, immediately after heating is started from room temperature, fixing is performed as the pressure roller 32 rotates in a light pressure contact state as shown in FIG. 11A. The belt 310 is driven to rotate, and the fixing belt 310 is heated by the halogen heater 313. When the fixing belt 310 is heated, the elastic layer 311b of the inner roller 311 is thermally expanded, but the thermal expansion of the elastic layer 311b is slight immediately after the heating.

  When the fixing belt 310 is heated to some extent, the heating roller 32 is pressed against the controller 100 as shown in FIG. At this time, the thermal expansion of the elastic layer 311b is not sufficient, and the gap (g) between the separation claw 34 and the surface of the fixing belt 310 is large at the timing of sheet passing 1 shown in FIG. For this reason, when the sheet is passed at the timing indicated by (A) in FIG. 12, the recording medium S is not separated from the fixing belt 310 by the separation claw 34, and a jam occurs.

  Further, when the fixing belt 310 is heated and the fixing belt 310 reaches a predetermined temperature and a predetermined time elapses as shown in FIGS. 11C and 12, the elastic layer 311b further thermally expands, and the fixing belt. 310 approaches the separation claw 34 side, and the gap (g) between the separation claw 34 and the surface of the fixing belt 310 becomes equal to or smaller than the gap at which the recording medium S can be separated from the fixing belt 310. In this state, that is, at the timing of sheet passing 2 shown in FIG. 12B, the control device 100 drives the recording medium driving unit 120 to fix the recording medium S so that the recording medium S is introduced into the fixing nip N. Perform the action.

  Here, in the second embodiment, the control device 100 determines that the gap (g) between the separation claw 34 and the surface of the fixing belt 310 is in the state shown in FIG. It is detected that the temperature of the end part of the inner metal part of the inner roller 311 detected by the core metal temperature sensor 39 has reached a predetermined temperature, and the temperature of the end part of the core part detected by the core metal temperature sensor 39 in this way. After the temperature exceeds a predetermined temperature, the fixing operation is performed as described above.

  In this way, the recording medium S is appropriately separated from the fixing belt 310 by the separation claw 34, and fixing can be performed without causing jamming.

  Even in this case, the core metal temperature of the inner roller 311 is increased to some extent except when heating is started from room temperature. Therefore, the core metal temperature of the inner roller 311 quickly reaches a predetermined temperature and is quickly fixed. Operation starts.

  In the second embodiment, the cored bar temperature sensor 39 is used as the detecting means for detecting the state change due to the thermal expansion of the elastic layer 311b of the inner roller 311. However, in addition to measuring the temperature of the end of the cored bar. As in the case of the first embodiment, the inter-axis distance d between the inner roller 311 and the pressure roller 32 is detected, and the inter-axis distance d between the inner roller 311 and the pressure roller 32 is determined so that the elastic layer 311b is heated. The pressure contact operation may be started when the inter-axis distance d at the time of expansion to a predetermined size is reached.

  Further, as a detecting means for detecting a change in state due to thermal expansion of the elastic layer 311b of the inner roller 311, the surface of the inner roller 311 is measured by, for example, a laser displacement meter, the displacement is measured, and the thermal expansion is performed to a predetermined size. It may be controlled to start the pressing operation when it is detected.

  Further, the position of the fixing belt 30 in the vicinity of the separation claw 34 is measured by, for example, a laser displacement meter, and the swelling of the fixing belt 310 due to the thermal expansion of the elastic layer 311b of the inner roller 311 is detected. You may control to start a press-contact operation | movement at the time of detecting having displaced to the separation nail | claw 34 side.

  Next, a third embodiment of the present invention will be described. In the third embodiment, as shown in FIGS. 13 and 14, the fixing member 31 in the second embodiment is constituted by a single fixing roller 31a. The configuration other than the fixing member 31 is the same as that of the second embodiment. Similar to the second embodiment, the configuration of the fixing device 30 is the same as that of the second embodiment except that the configuration of the fixing device 30 is changed to the above configuration. The control configuration is the same as the configuration shown in FIG.

  Here, the fixing roller 31a has, for example, a core metal pipe 31c made of a carbon steel pipe for machine structure (STKM) having a diameter of 50 mm, a pipe diameter of 30 mm, and a thickness of 20 mm, and a silicon elastic layer 31d having a thickness of 10 mm. A PFA tube surface layer (not shown) having a thickness of 50 μm is provided, and the fixing roller 31a is heated by a halogen heater 31e serving as a heating device provided therein and an external heating roller 315 contacting the surface of the fixing roller 31a. . A core metal temperature sensor 39 that detects the temperature of the end of the core metal pipe 31c is provided.

  A pressure roller 32 provided with an elastic layer 321 is disposed so as to face the fixing roller 31a. In addition, a separation claw 34 that forms a predetermined gap with the surface of the fixing roller 31a when the elastic layer 31d of the fixing roller 31a is thermally expanded to a predetermined size is disposed in the vicinity of the fixing roller 31a. .

  Then, the pressure roller 32 is rotated, the fixing roller 31a is driven to rotate, and the toner is fed to the fixing nip N formed by the fixing roller 31a and the pressure roller 32 heated by the halogen heater 31e. The recording medium S to which the image is transferred is guided, and the toner image is heated and fixed on the recording medium S. The recording medium S on which the toner image is fixed is separated from the fixing roller 31a by the separation claw 34 and discharged.

  Also in the third embodiment, the temperature of the core metal 31c is detected by the core metal temperature sensor 39, and the temperature of the core metal 31c detected by the core metal temperature sensor 39 becomes equal to or higher than a predetermined temperature, as shown in FIG. In addition, in the state where the elastic layer 31d of the fixing roller 32a is thermally expanded and the gap between the surface of the fixing roller 31a and the separation claw 34 becomes a predetermined value, the recording medium S is transferred by the control device 100 as described above. The recording medium driving unit 120 is driven so as to be introduced into the fixing nip N, and a fixing operation is performed.

  In this way, the recording medium S is appropriately separated from the fixing belt 310 by the separation claw 34, and fixing can be performed without causing jamming.

  Next, 4th Embodiment of this invention is described based on FIGS. 15-18.

  In the fourth embodiment, as shown in FIGS. 15 and 16, even if the fixing belt 310 is heated and the elastic layer 311 b of the inner roller 311 is thermally expanded, the space between the inner roller 311 and the fixing belt 310 is not limited. Each dimension of the fixing belt 310 and the inner roller 311 is set so that there is a gap. Then, both ends of the fixing belt 310 are held by the cap flanges 315, and each cap flange 315 is held at three points by using the rollers 310b, and the fixing belt 310 is arranged. The above two points are different from the first embodiment, and other configurations are the same as those of the first embodiment. In FIG. 1, the configuration of the fixing device 30 is the same except that the configuration is changed to the above configuration. The control configuration is the same as the configuration shown in FIG.

  Here, for example, the inner roller 311 has an overall diameter of 38 mm, and a 9 mm thick silicon rubber elastic layer 331 b is provided on a SUS cored bar 311 a having a diameter of 20 mm.

  Next, the timing for starting the fixing operation in the fourth embodiment will be described with reference to FIGS.

  In this 4th Embodiment, as shown in FIG.17 and FIG.18, immediately after starting a heating from normal temperature state, as shown to FIG. The fixing belt 310 is driven to rotate, and the fixing belt 310 is heated by the heating device 33. When the fixing belt 310 is heated, the elastic layer 311b of the inner roller 311 is thermally expanded, but the thermal expansion of the elastic layer 311b is also slight immediately after heating.

  When the fixing belt 310 is heated to some extent, the heating roller 32 is pressed against the controller 100 as shown in FIG. At this time, the thermal expansion of the elastic layer 311b is not sufficient, and the gap (g) between the separation claw 34 and the surface of the fixing belt 310 is large at the timing of sheet passing 1 shown in FIG. For this reason, when the paper is passed at the timing shown in FIG. 18A, the recording medium S is not separated from the fixing belt 310 by the separation claw 34, and a jam occurs.

  Further, when the fixing belt 310 is heated and the fixing belt 310 reaches a predetermined temperature and a predetermined time elapses as shown in FIGS. 17C and 12, the elastic layer 311b further thermally expands and the fixing belt 310 is heated. 310 approaches the separation claw 34 side, and the gap (g) between the separation claw 34 and the surface of the fixing belt 310 becomes equal to or smaller than the gap at which the recording medium S can be separated from the fixing belt 310. In this state, that is, at timing (C) shown as paper passing 2 in FIG. 18, the control device 100 drives the recording medium driving unit 120 so that the recording medium S is introduced into the fixing nip N, and the fixing operation. I do.

  Here, also in the fourth embodiment, when the gap (g) between the separation claw 34 and the surface of the fixing belt 310 is in the state shown in FIG. It is detected that the temperature of the end part of the inner metal part of the inner roller 311 detected by the core metal temperature sensor 39 has reached a predetermined temperature, and the temperature of the end part of the core part detected by the core metal temperature sensor 39 in this way. After the temperature exceeds a predetermined temperature, the fixing operation is performed as described above.

  In this way, the recording medium S is appropriately separated from the fixing belt 310 by the separation claw 34, and fixing can be performed without causing jamming.

  Even in this case, the core metal temperature of the inner roller 311 is increased to some extent except when heating is started from room temperature. Therefore, the core metal temperature of the inner roller 311 quickly reaches a predetermined temperature and is quickly fixed. Operation starts.

  In the fourth embodiment, the cored bar temperature sensor 39 is used as the detecting means for detecting the state change due to the thermal expansion of the elastic layer 311b of the inner roller 311. However, in addition to measuring the temperature of the end of the cored bar. As in the second embodiment, the inter-axis distance d between the inner roller 311 and the pressure roller 32 is detected, and the inter-axis distance d between the inner roller 311 and the pressure roller 32 is determined so that the elastic layer 311b is heated. The pressure contact operation may be started when the inter-axis distance d at the time of expansion to a predetermined size is reached.

  Further, as a detecting means for detecting a change in state due to thermal expansion of the elastic layer 311b of the inner roller 311, the surface of the inner roller 311 is measured by, for example, a laser displacement meter, the displacement is measured, and the thermal expansion is performed to a predetermined size. It may be controlled to start the pressing operation when it is detected.

  Further, the position of the fixing belt 30 in the vicinity of the separation claw 34 is measured by, for example, a laser displacement meter, and the swelling of the fixing belt 310 due to the thermal expansion of the elastic layer 311b of the inner roller 311 is detected. You may control to start a press-contact operation | movement at the time of detecting having displaced to the separation nail | claw 34 side.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10A-10D Imaging cartridge 11 Photoconductor 12 Charging apparatus 13 Exposure apparatus 14 Development apparatus 15 Cleaning apparatus 21 Intermediate transfer belt 22 Paper feed roller 23 Timing roller 24 Transfer roller 25 2nd cleaning apparatus 27 Paper discharge roller 30 Fixing apparatus 31 Fixing member 310 Fixing belt 311 Inner roller 311a Core metal 311b Elastic layer 32 Pressure roller (Pressure member)
33 Heating device 34 Separation claw 37 Temperature sensor 39 Metal core temperature sensor 40 Distance sensor d Center distance S Recording medium

Claims (13)

A fixing member having an elastic layer; a heating unit that heats the fixing member; a pressure member that presses against the fixing member to form a fixing nip; and a separation claw that separates the recording medium from the fixing member. In the fixing device,
The separation claw is fixed near the downstream of the fixing nip and disposed in a non-contact manner with respect to the fixing member. The fixing member includes an inner layer having a fixing belt and an elastic layer disposed inside the fixing belt. It is composed of a roller and has a gap between the fixing belt and the inner roller at normal temperature. The inner diameter of the fixing belt and the outer diameter of the inner roller are set so that the two adhere to each other after heating, and due to the thermal expansion of the elastic layer Detection means for detecting a change in state, and when the detection means detects that the fixing belt and the inner roller are in close contact, the pressing member pressurizes the fixing member with a predetermined pressure, and the fixing nip A fixing device formed.   2. The fixing device according to claim 1, wherein the inner roller has an elastic layer on a metal core made of a metal roller, and the detection unit detects the temperature of the end of the metal core of the inner roller, and heats the elastic layer. A fixing device that detects a change in state due to expansion.   2. The fixing device according to claim 1, wherein the pressure member includes a pressure roller, and the detection unit detects an inter-axis distance between the inner roller and the pressure roller, and the inter-axis distance is equal to or greater than a predetermined value. In this case, the fixing device pressurizes the fixing member with a predetermined pressure. The fixing device according to claim 1, wherein the detection unit detects a state change due to thermal expansion of an elastic layer of the fixing member. A fixing member having an elastic layer; a heating unit that heats the fixing member; a pressure member that presses against the fixing member to form a fixing nip; and a separation claw that separates the recording medium from the fixing member. In the fixing device,
The separation claw is fixed near the downstream of the fixing nip and disposed in a non-contact manner with respect to the fixing member, and has a detecting unit that detects a change in state due to thermal expansion of the elastic layer of the fixing member, When the detection unit detects that the change in the position of the fixing member is stabilized, a fixing medium is started by introducing a recording medium into the fixing nip.   6. The fixing device according to claim 5, wherein the fixing member includes a fixing belt and at least two rollers that stretch the fixing belt, and one of the rollers has an elastic layer that forms a fixing nip. A fixing device, wherein the fixing device is an inner roller, and one of the rollers is a tension roller that applies tension to the fixing belt.   6. The fixing device according to claim 5, wherein the fixing member includes a fixing belt and an inner roller having an elastic layer disposed inside the fixing belt, and a gap is provided between the fixing belt and the inner roller at room temperature. The fixing device is characterized in that an inner diameter of the fixing belt and an outer diameter of the inner roller are set.   The fixing device according to claim 5, wherein the fixing member includes a fixing roller having an elastic layer.   8. The fixing device according to claim 5, wherein the elastic layer of the fixing member is formed on a metal core roller made of metal, and the detection unit is configured to detect the temperature of the end of the metal core roller. And a fixing device that starts a fixing operation by introducing a recording medium into the fixing nip when the detecting means detects a temperature equal to or higher than a predetermined temperature.   8. The fixing device according to claim 5, wherein the elastic layer of the fixing member is formed on a metal core roller made of metal, and the pressure member is made of a pressure roller. The detecting means detects an inter-axis distance between the inner roller and the pressure roller, and when the inter-axis distance exceeds a predetermined value, introduces a recording medium into the fixing nip and starts a fixing operation. Fixing device. 8. The fixing device according to claim 5, wherein the detection unit detects a state change caused by thermal expansion of an elastic layer of the fixing member. 9. 12. The fixing device according to claim 1, wherein the separation claw is disposed at a position where a gap between the separation claw and the fixing member when the fixing nip is formed becomes a predetermined value. A fixing device characterized. An image forming apparatus comprising a fixing device for fixing a toner image onto a recording medium, wherein the fixing device according to claim 1 is used.

Images