Image forming apparatus

Abstract

To improve operability when applying and releasing tension to a belt that conveys a sheet.SOLUTION: A drying belt unit that conveys a sheet on which an image has been formed in an image forming unit includes a flexible endless belt that conveys the sheet by rotation, a plurality of stretching rollers that stretch the belt, a tension roller 10 capable of applying tension to the belt, a heater that is provided in at least one of the stretching rollers and the tension roller 10 to perform heating, a first pressing section 31 that is switchable between a first state in which the tension roller 10 does not apply tension to the belt and a second state in which the tension roller 10 applies tension to the belt with a first biasing force, a second pressing section 32 that is switchable between the second state switched by the first pressing section 31 and a third state in which the tension roller 10 applies tension to the belt with a second biasing force greater than the first biasing force, and first and second levers 3316a and 3317a that can operate the first pressing section 31 and the second pressing section 32.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus that forms an image on a sheet. [Background technology]

[0002] In image forming apparatuses, a configuration in which a belt that conveys a sheet is heated is widely used as a configuration for drying a sheet, which is a recording medium. For example, an inkjet recording apparatus that forms an image on a sheet with ink includes a process of drying the sheet, and a drying device has been developed that conveys the sheet with a belt and heats the sheet with the belt to dry the sheet.

[0003] In an image forming apparatus that uses such a belt transport, it is desirable to be able to control the belt position in the axial direction of the roller that tensions the belt even when the belt expands due to heat generated when a sheet is heated. Therefore, for example, a configuration has been proposed in which a steering unit that applies a biasing force to a belt drive device that has multiple heating rollers and tensions the belt is made movable in the thickness direction of the belt, and the amount of displacement in the thickness direction is adjusted based on the results of belt position detection (see Patent Document 1). In this image forming apparatus, a heater is provided inside the roller that tensions the belt, and the heater heats the roller, thereby heating the belt and the sheet being transported. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-90344 Summary of the Invention [Problem to be solved by the invention]

[0005] In the image forming apparatus described in Patent Document 1, a heater provided in a roller heats the sheet via the belt, so the belt is required to have heat resistance. For this reason, a material with excellent heat resistance is used for the belt, such as a heat-resistant resin, which has a higher rigidity than a normal belt that does not have high heat resistance, and a large tension must be applied to the belt to keep it stretched without slack.

[0006] However, the image forming apparatus described in Patent Document 1 uses a heat-resistant, highly rigid belt for heating, which can lead to the following problem: The belt may need to be detached from the apparatus body for maintenance of the belt or peripheral devices, which can require the belt's biasing force to be released and then reapplied. In this case, if the belt is highly rigid, the operating force required to manually release and reapply the biasing force, such as by operating a lever, can be large, potentially reducing workability.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can improve operability when applying and releasing tension to a belt that conveys a sheet. [Means for solving the problem]

[0008] The image forming apparatus of the present invention comprises an image forming unit that forms an image on a sheet, and a sheet conveying unit that conveys the sheet on which the image has been formed in the image forming unit, and the sheet conveying unit comprises: a flexible endless belt that conveys the sheet by rotation; a plurality of tension rollers that tension the belt; a tension roller that can urge the belt; a heater that is provided on at least one of the tension rollers and the tension roller to heat the belt; a first pressure unit that can switch between a first state in which the tension roller does not urge the belt and a second state in which the tension roller urges the belt with a first urging force; a second pressure unit that can switch between the second state switched by the first pressure unit and a third state in which the tension roller urges the belt with a second urging force greater than the first urging force; and an operation unit that can operate the first pressure unit and the second pressure unit. [Effects of the Invention]

[0009] According to the present invention, it is possible to improve the operability when applying and releasing tension to a belt that conveys a sheet in an image forming apparatus. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an inkjet recording apparatus according to a first embodiment. [Figure 2] 1 is a schematic cross-sectional view showing the configuration of a drying module according to a first embodiment. [Figure 3] FIG. 2 is a perspective view showing a steering portion of the drying belt unit according to the first embodiment, as viewed from the front side. [Figure 4] FIG. 2 is a perspective view showing a steering portion of the drying belt unit according to the first embodiment, as viewed from the rear side. [Figure 5] FIG. 2 is a perspective view showing a tension unit of the drying belt unit according to the first embodiment in a first state. [Figure 6] FIG. 6 is a partially enlarged view of FIG. 5. [Figure 7]FIG. 4 is a perspective view showing a tension unit of the drying belt unit according to the first embodiment in a second state. [Figure 8] FIG. 8 is a partially enlarged view of FIG. [Figure 9] FIG. 4 is a perspective view showing a tension unit of the drying belt unit according to the first embodiment in a third state. [Figure 10] FIG. 10 is a partially enlarged view of FIG. [Figure 11] FIG. 3 is a perspective view seen from the front side showing a state in which a tension unit is attached to the drying belt unit according to the first embodiment. [Figure 12] FIG. 4 is a perspective view seen from the rear side showing a state in which a tension unit is attached to the drying belt unit according to the first embodiment. [Figure 13] FIG. 10 is a perspective view showing a tension unit of a drying belt unit according to a second embodiment in a first state. [Figure 14] FIG. 14 is a partially enlarged view of FIG. [Figure 15] FIG. 10 is a perspective view showing a tension unit of a drying belt unit according to a second embodiment in a second state. [Figure 16] FIG. 16 is a partially enlarged view of FIG. [Figure 17] FIG. 10 is a perspective view showing a tension unit of the drying belt unit according to the second embodiment in a third state. [Figure 18] FIG. 18 is a partially enlarged view of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] First Embodiment A first embodiment will be described with reference to Figs. 1 to 12. First, a schematic configuration of an inkjet recording apparatus 100 of this embodiment will be described with reference to Fig. 1. In this embodiment, the front side of the apparatus refers to the front side of the inkjet recording apparatus 100, where an operation unit and the like are arranged and where a user is positioned when using or operating the apparatus. In the drawings, the front side is referred to as the forward direction F, the rear side as the rearward direction B, the upper side as the upward direction U, the lower side as the downward direction D, the right side as viewed from the front as the rightward direction R, and the left side as the leftward direction L.

[0012] [Inkjet recording device] The inkjet recording apparatus 100 of this embodiment uses an inkjet recording method in which ink is ejected to form an image on a sheet, and is a so-called sheet-fed inkjet recording apparatus that forms an ink image on a sheet using two liquids: a reaction liquid and ink. An inkjet recording apparatus is an example of an image forming apparatus. The sheet may be any recording material that can accept ink, such as paper such as plain paper or cardboard, plastic film such as an overhead projector sheet, specially shaped sheets such as envelopes or index paper, or cloth.

[0013] 1, the inkjet recording apparatus 100 of this embodiment includes a feeding module 1000, a printing module 2000, and a drying module 3000. The inkjet recording apparatus 100 further includes a fixing module 4000, a cooling module 5000, an inverting module 6000, and a stacking module 7000. The sheet S supplied from the feeding module 1000 undergoes various processes as it is transported along the transport path within each module, and is finally discharged to the stacking module 7000.

[0014] The feeding module 1000 to the stacking module 7000 may each have a separate housing, and these housings may be connected to form the inkjet recording apparatus 100. Alternatively, the feeding module 1000, print module 2000, drying module 3000, fixing module 4000, cooling module 5000, reversing module 6000, and stacking module 7000 may be arranged in a single housing.

[0015] The feeding module 1000 has storage cabinets 1500a, 1500b, and 1500c for storing sheets S, and the storage cabinets 1500a to 1500c are provided so that they can be pulled out to the front side of the apparatus to store sheets S. The front side of the apparatus refers to the front side of the inkjet recording apparatus 100, where the operation unit and the like are located and where the user stands when using or operating the apparatus. The sheets S are fed one by one in each of the storage cabinets 1500a to 1500c by a separation belt and a conveyance roller, and are conveyed to the print module 2000. The number of storage cabinets 1500a to 1500c is not limited to three, and the number may be one, two, four, or more.

[0016] The print module 2000 is an example of an image forming unit and forms an ink image on a sheet. The print module 2000 includes a pre-imaging registration correction unit (not shown), a print belt unit 2010, and a recording unit 2020. The sheet S transported from the feeding module 1000 has its tilt and position corrected by the pre-imaging registration correction unit before being transported to the print belt unit 2010. The recording unit 2020 is positioned opposite the print belt unit 2010 with respect to the transport path. The recording unit 2020 is an inkjet recording unit that forms an image by ejecting ink onto the transported sheet S from above using a recording head. Multiple recording heads that eject ink are arranged along the transport direction. In this embodiment, the unit has a total of five line-type recording heads corresponding to the four colors of Y (yellow), M (magenta), C (cyan), and Bk (black), as well as reaction liquids. The sheet S is adsorbed and transported by the print belt unit 2010, ensuring clearance between the sheet S and the recording heads.

[0017] The number of ink colors and recording heads is not limited to the five mentioned above. The inkjet method can be a method using a heating element, a piezoelectric element, an electrostatic element, or a MEMS (Micro Electro Mechanical Systems) element. Each color of ink is supplied to the recording head from an ink tank (not shown) via an ink tube. The ink contains 0.1% to 20.0% by mass of a resin component, water, a water-soluble organic solvent, coloring material, wax, additives, etc., based on the total mass of the ink.

[0018] When the sheet S on which an image is formed by the recording unit 2020 is transported by the print belt unit 2010, it is detected by an inline scanner (not shown) arranged downstream of the recording unit 2020 in the transport direction of the sheet S. Here, the misalignment and color density of the image formed on the sheet S are detected, and based on this image misalignment and color density, the image to be formed on the sheet S, density, etc. are corrected.

[0019] The drying module 3000 dries the sheet S by blowing air onto the sheet S being transported to the drying belt unit 5. As shown in FIG. 2, the drying module 3000 includes a decoupling unit 40, a drying belt unit 5, and a hot air blowing unit 8. The drying module 3000 reduces the liquid content of the ink and reaction liquid applied to the sheet S to improve the fixation of the ink on the sheet S by the subsequent fixing module 4000. The sheet S with an image formed thereon is transported to the decoupling unit 40 located within the drying module 3000. In the decoupling unit 40, frictional force is generated between the sheet S and the belt by the wind pressure of air blown from above, causing the sheet S to be transported by the belt. In this way, the sheet S placed on the belt is transported by frictional force, preventing the sheet S from shifting as it is transported between the print belt unit 2010 and the decoupling unit 40. The sheet S transported from the decoupling section 40 is adsorbed and transported by the drying belt unit 5, and hot air is blown onto the sheet S from the hot air blowing unit 8 arranged above the belt, thereby drying the ink and reaction liquid applied to the sheet S.

[0020] 1, a fixing module 4000 as a fixing system has a fixing belt unit 4100 as a fixing device. The fixing belt unit 4100 fixes ink onto the sheet S by passing the sheet S conveyed from the drying module 3000 between a heated upper belt unit and a heated lower belt unit.

[0021] The cooling module 5000 has a plurality of cooling sections 5001, which cool the high-temperature sheet S transported from the fixing module 4000. The cooling sections 5001, for example, use a fan to draw outside air into a cooling box to increase the pressure inside the cooling box, and then cool the sheet S by blowing air out of the cooling box through a nozzle due to the pressure onto the sheet S. The cooling sections 5001 are arranged on both sides of the transport path of the sheet S, and cool both sides of the sheet S.

[0022] The cooling module 5000 is provided with a transport path switching unit 5002. The transport path switching unit 5002 switches the transport path of the sheet S depending on whether the sheet S is transported to the reversing module 6000 or to a double-sided transport path for double-sided printing, in which images are formed on both sides of the sheet S.

[0023] The reversing module 6000 has a reversing section 6400. The reversing section 6400 reverses the sheet S being conveyed, changing the orientation of the sheet S when it is discharged to the stacking module 7000. The stacking module 7000 has a top tray 7200 and a stacking section 7500, and stacks the sheet S conveyed from the reversing module 6000.

[0024] During double-sided printing, the sheet S is transported to a transport path below the cooling module 5000 by the transport path switching unit 5002. The sheet S then passes through a double-sided transport path including the fixing module 4000, drying module 3000, print module 2000, and feeding module 1000, and is returned to the print module 2000. The double-sided transport section of the fixing module 4000 is provided with an inverting unit 4200 that inverts the sheet S. An image is formed with ink on the other side of the sheet S that has been returned to the print module 2000, and the sheet S is then ejected from the drying module 3000 through the inverting module 6000 and onto the stacking module 7000.

[0025] [Drying module] Next, the drying module 3000 will be described in detail with reference to FIG. 2. The drying module 3000 has a decoupling unit 40, a drying belt unit 5, and a hot air blowing unit 8. These are collectively referred to as the drying function unit 300. The drying function unit 300 is disposed above the drying module 3000, and has a linear sheet transport path for receiving the sheet S discharged from the print module 2000, drying the sheet S, and then delivering the sheet S to the fixing module 4000. With respect to the sheet transport direction D1 of this sheet transport path, the upstream and downstream portions of the drying function unit 300 have different functions.

[0026] A decoupling section 40 is disposed upstream of the drying function section 300. The decoupling section 40 includes a decoupling belt unit 2 and a cold air blowing unit 3. The cold air blowing unit 3 is disposed vertically above the decoupling belt unit 2, which transports the sheet S in a substantially horizontal direction. The decoupling belt unit 2 includes a rotating endless belt 2a. The cold air blowing unit 3 blows cold air (air) from above the decoupling belt unit 2, thereby pressing the sheet S against the belt 2a and transporting the sheet S. The decoupling belt unit 2 has a plurality of holes for allowing the air blown from the cold air blowing unit 3 to escape from the blowing surface to the side opposite the belt. Note that, hereinafter, air that is not heated by a heater or the like is also referred to as "cold air."

[0027] In the decoupling belt unit 2, the belt 2a is tensioned by a drive roller 3231, a tension roller 3211, and tension rollers 3270a and 3270b. The drive roller 3231 and tension rollers 3270a and 3270b are rotatably supported by a frame. The tension roller 3211 is supported by a slide rail 3213, displaceable in a predetermined direction, and rotatably supported. The tension roller 3211 tensions the belt 2a by biasing it from the inside with the biasing force of a tension spring 3214. One end of the tension roller 3211 in the rotational axis direction is supported by a steering arm (not shown) that rotates around a rotating part. In this embodiment, the rotational axis direction of the tension roller 3211 is the front-to-rear direction of the inkjet recording apparatus 100. The steering arm is rotated by controlling the rotation amount of a steering motor having an eccentric steering cam based on the detection result of an edge sensor 3225 that detects the end position of the belt 2a. As a result, the position of the belt 2a in the direction of the rotation axis is adjusted, and meandering is regulated.

[0028] When the leading edge of the sheet S reaches the decoupling belt unit 2 of the drying module 3000, the trailing edge of the sheet S is still on the print belt unit 2010 of the print module 2000. The print belt unit 2010 has an endless print belt 4 that sucks and transports the sheet. An image is formed on the sheet S on the print belt 4, and the sheet S is sucked and transported on the print belt 4. To prevent disturbance to this image formation process, the force pressing the sheet S against the belt 2a is weaker than the suction force of the print belt 4, and the belt 2a is driven at a slightly faster speed than the print belt 4. In other words, while the trailing edge of the sheet S is on the print belt 4, the sheet S is always sliding against the belt 2a.

[0029] On the other hand, the moment the trailing edge of the sheet S leaves the area of ​​the print belt 4, the transport of the sheet S becomes dependent on the belt 2a. At this time, the air blowing force of the cool air blowing unit 3 must be controlled to prevent the sheet S from slipping due to transport resistance. Therefore, the speed of the air blown from the cool air blowing unit 3 onto the sheet S transported on the belt 2a is controlled to a predetermined pressure using a pressure sensor (not shown) installed inside the cool air blowing unit 3 and an intake fan (not shown) installed in the intake section. The cool air blowing unit 3 has a blowing surface with numerous blowing holes for passing air so that a uniform pressing force is applied to the sheet S. The belt 2a has numerous holes and is supported by a perforated metal 3202 located on the back side of the belt 2a on the sheet transport surface. The perforated metal 3202 has holes smaller than the holes in the belt 2a, allowing the air blown from the cool air blowing unit 3101, which blows air onto areas other than the sheet S, to escape. Furthermore, in order to prevent excessive binding force from being generated due to the belt 2a being charged by friction between the sheet S and the belt 2a, the static eliminator 3250 eliminates static electricity from the belt 2a using static eliminator needles 3251.

[0030] [Drying section] Next, the drying section 6 will be described with reference to FIG. 2. The drying section 6 is disposed downstream of the drying function section 300. The sheet S conveyed from the decoupling section 40 passes through an internal paper discharge guide 3240 and is sent to the drying section 6. The drying section 6 includes a drying belt unit 5 and a hot air blowing unit 8. The hot air blowing unit 8 is disposed vertically above the drying belt unit 5. The drying belt unit 5 is an example of a sheet conveying section and conveys the sheet S bearing an ink image in a substantially horizontal direction. In the drying section 6, the drying belt unit 5 sucks the sheet S to adhere it to the drying belt 7, while the hot air blowing unit 8 blows hot air from above in the vertical direction to dry the sheet S, thereby conveying the sheet S while suppressing waviness known as cockling. Note that, although the drying method employs hot air blowing and belt heating in this embodiment, the present invention is not limited thereto. For example, in addition to blowing hot air, a method of irradiating the surface of the sheet S with electromagnetic waves (ultraviolet rays, infrared rays, etc.) or a conductive heat transfer method by contact with a heat generating element may be combined.

[0031] [Drying belt unit] Next, the drying belt unit 5 will be described with reference to FIG. 2. The drying belt unit 5 has a drying belt 7, which is an example of a rotating, flexible, endless belt. The drying belt 7 is stretched over a rotatably fixed driving roller 3331, heating rollers 3351a and 3351b, a tension roller 10 that is displaceable in a predetermined direction and rotatably supported, and a steering roller 3321. The drying belt 7 is transported by the rotation of the driving roller 3331. A hot air blowing unit 8 disposed above the drying belt unit 5 blows hot air heated by a heater (not shown) toward the drying belt unit 5 onto the ink-coated sheet S. A suction unit 3360 is provided inside the drying belt 7. A suction duct 3362 and the drying belt 7 form a suction chamber 3361, and a fan 3366 below exhausts air to an exhaust duct 3367, generating negative pressure in the suction chamber 3361.

[0032] The drying belt 7 has countless small holes with a diameter of about 0.4 mm, which generates an adhesive force on the drying belt 7 above the suction unit 3360. This adhesive force and the air pressure from the warm air blowing unit 8 hold the sheet S on the drying belt 7 and transport it. In order to support the drying belt 7 in a predetermined position, the suction unit 3360 has countless rotatable rollers 3364 arranged therein, which support the drying belt 7 from the inside without interfering with the suction by the fan 3366.

[0033] During the conveyance of the sheet S, the ink is dried by the blowing of hot air from the hot air blowing unit 8 and the heating from the drying belt 7. The drying belt 7 is heated by a belt heating unit 3350 having a first heating roller 3351a and a second heating roller 3351b. The first heating roller 3351a and the second heating roller 3351b, which are examples of tension rollers, each have a heater 3353 supported therein. The first heating roller 3351a and the second heating roller 3351b are heated by the heater 3353, and the temperature rise is controlled to a set temperature based on the detection results of a roller temperature detection sensor 3356 that detects the temperature of each roller. Because heating by the heater 3353 consumes a lot of power, it is necessary to efficiently heat the drying belt 7 and the sheet S in order to reduce the power consumption of the product. In order to improve the temperature rise efficiency of the drying belt 7, it is effective to increase the contact area of ​​the drying belt 7 with the first heating roller 3351a and the second heating roller 3351b. In this embodiment, the first heating roller 3351a has a diameter of 110 mm, and the second heating roller 3351b has a diameter of 60 mm, which are large diameters, to ensure a large contact area.

[0034] The heat applied to the drying belt 7 is dissipated by contact with the atmosphere and the tensioning rollers as the drying belt 7 is conveyed. Therefore, in order to efficiently transfer heat from the drying belt 7 to the sheet S, it is effective to dispose the belt heating section 3350 upstream of the drying belt unit 5 in the sheet conveying direction D1.

[0035] In this embodiment, the second heating roller 3351b is disposed upstream of the drying belt unit 5 in the sheet conveying direction D1, and the first heating roller 3351a is provided further upstream. Furthermore, a tension roller 10 presses the drying belt 7 from the outside between the first heating roller 3351a and the second heating roller 3351b. The tension roller 10 is an example of a tension roller and is capable of pressing the drying belt 7. In this embodiment, in terms of temperature rise efficiency of the drying belt 7, pressing the tension roller 10 from the outside of the drying belt 7 increases the contact area between the first heating roller 3351a and the second heating roller 3351b and the drying belt 7. However, this is not limited to this, and pressing from the inside of the drying belt 7 is also possible.

[0036] The temperature rise of the drying belt 7 is detected by a non-contact belt surface temperature detection sensor 3343 such as an infrared sensor, and the difference from the set temperature is determined by the control unit and reflected in the temperature setting of the heater 3353. Note that the second heating roller 3351b is not limited to being a roller that stretches the portion of the drying belt 7 facing the sheet conveying path, but may be another roller. A heat-resistant resin belt is used as the drying belt 7. However, the present invention is not limited to this, and a metal belt that is highly durable and has a large heat capacity may also be used.

[0037] The sheet S is heated by the temperature rise via the drying belt 7 and the hot air from the hot air blowing unit 8, and after being transported to the internal paper discharge unit 3340, is discharged to the fixing module 4000 by the internal paper discharge roller 3345. The temperature of the drying belt unit 5 rises to about 80°C by the hot air blowing section 3401, the first heating roller 3351a, and the second heating roller 3351. In response to this, the decoupling section 40 blows non-heating air from the cool air blowing unit 3, and the air blowing unit 3102 provided above the connection with the drying belt unit 5 exhausts and sucks in non-heating air, circulating the air and blocking the hot air from the hot air blowing unit 8. Therefore, there is no significant temperature rise upstream of the drying belt unit 5 in the sheet transport direction D1, and the impact is limited.

[0038] [Steering unit] 3 and 4 show the configuration of the steering unit of the drying belt unit 5. When the drying belt 7 conveys the sheet S, belt position control is required to prevent significant deviation in the conveying position in the direction of the rotation axis before and after conveyance. In this embodiment, a steering roller 3221 is used as a tension roller between the drive roller 3331 and the first heating roller 3351a. One end of the steering roller 3321 is rotatably supported by each of the steering arms 3323a and 3323b, and the first steering arm 3323a is rotatable around the first rotation shaft 3326a. The steering motor 3324 supports an eccentric steering cam (not shown). A steering arm spring 3327 biases a portion of the first steering arm 3323a in a direction that brings it into contact with the steering cam 3322. This allows the first steering arm 3323a to rotate by the amount of eccentricity of the steering cam 3322 when rotated by the steering motor 3324.

[0039] The steering motor 3324 has a flag 3328 on the shaft opposite the steering cam, and the detected position is determined by detecting the position with a flag sensor 3329, thereby controlling the amount of rotation. The other end of the steering roller 3321 is rotatably supported by a second steering arm 3323b, and the second steering arm 3323b is rotatable around a second rotation shaft 3326b. The second steering arm 3323b rotates only enough to absorb the twist that occurs when the first steering arm 3323a rotates, and does not significantly change the position of the steering roller 3321.

[0040] With this configuration, the first steering arm 3323a in the forward direction F rotates in a predetermined direction, generating a thrust force in the direction of the rotation axis on the transported drying belt 7, thereby controlling the position of the drying belt 7. Note that a configuration may also be adopted in which the second steering arm 3323b is fixed without providing the second rotating shaft 3326b, and the play in the support portion of the steering roller 3321 absorbs the twist that occurs when the first steering arm 3323a rotates.

[0041] [Tension unit] Next, the configuration of the tension unit 30 that applies tension to the drying belt 7 in this embodiment will be described with reference to Figs. 5 to 10. Figs. 5, 7, and 9 are perspective views showing the internal structure of the tension unit 30. Figs. 6, 8, and 10 are detailed views explaining the pressure mechanism of the tension unit 30. Note that Figs. 6, 8, and 10 are views showing the pressure configuration on one side of the approximate center of the tension roller 10 in the axial direction, but the opposite side has the same configuration.

[0042] The tension unit 30 is a unit that is detachable from the drying belt unit 5. The tension unit 30 has a first pressure unit 31 that operates a first lever 3316a to bring the tension roller 10 into contact with and urge the drying belt 7, and a second pressure unit 32 that operates a second lever 3317a to apply additional urging force to the tension roller 10. In this embodiment, two first pressure units 31 are provided, and they are arranged at two different locations on the tension unit 30 in the direction of the rotation axis of the tension roller 10. Similarly, two second pressure units 32 are provided, and they are arranged at two different locations on the tension unit 30 in the direction of the rotation axis. In this embodiment, the first pressure units 31 are arranged at both ends of the tension unit 30 in the direction of the rotation axis, and the second pressure unit 32 is arranged in the center. Furthermore, the first lever 3316a and the second lever 3317a are arranged on one side of the tension unit 30 in the direction of the rotation axis, in this case, on the front side.

[0043] The first pressure applying unit 31 includes roller support plates 3312 and 3313, a first spring 3314a, a first cam 3316c, and a first lever shaft 3316b. The roller support plates 3312 and 3313 are an example of a support member, rotatably support the tension roller, and are movable in an orthogonal direction (here, the left-right direction) perpendicular to the rotation axis direction. The first spring 3314a is an example of a first biasing member, and biases the roller support plates 3312 and 3313 in a direction in which the first pressure applying unit 31 switches from a first state to a second state (described later), here, in the leftward direction L. The first cam 3316c positions the roller support plates 3312 and 3313 against the biasing force of the first spring 3314a. The first lever shaft 3316b is an example of a first shaft, and is fixed to the first cam 3316c and rotatably provided. The first lever 3316a is an example of a first operating member and operating part, and is fixed to the first lever shaft 3316b. By rotating the first lever shaft 3316b, the first pressure applying part 31 can be operated to switch between a first state and a second state.

[0044] The second pressure applying unit 32 includes a second spring 3314b, a second cam 3317c, and a second lever shaft 3317b. The second spring 3314b is an example of a second biasing member and biases the roller support plates 3312 and 3313 in a direction in which the second pressure applying unit 32 switches from the second state to the third state, in this case, in the left direction L. The second cam 3317c positions the roller support plates 3312 and 3313 against the biasing force of the second spring 3314b. The second lever shaft 3317b is an example of a second shaft and is fixed to the second cam 3317c and rotatably provided. The second lever 3317a is an example of a second operating member and operating unit and is fixed to the second lever shaft 3317b. By rotating the second lever shaft 3317b, the second pressure applying unit 32 can be operated to switch between the second state and the third state.

[0045] The second spring 3314b is disposed at a different position from the first spring 3314a in the direction of the rotation axis. In this embodiment, the first spring 3314a is disposed at both ends of the tension unit 30 in the direction of the rotation axis, and the second spring 3314b is disposed at the center. The second spring 3314b is connected to the roller support plates 3312 and 3313 by a link member 3319.

[0046] The tension roller 10 is rotatably supported by roller support plates 3312 and 3313, which are supported on a tension frame 3315 via slide rails (not shown) so as to be movable in a predetermined direction. A pressure plate 3318 is supported on the tension frame 3315 via slide rails (not shown) so as to be movable in a predetermined direction, and a link member 3319 is supported so as to be rotatable about a link shaft 3319c. The roller support plates 3312 and 3313 are biased by a first spring 3314a, pushing the tension roller 10 in a biasing direction T1, which is a direction in which the tension roller 10 protrudes from the main body. The pressure plate 3318 is also biased by a second spring 3314b, pressing the link member 3319, which in turn presses the roller support plates 3312 and 3313, thereby exerting a force that pushes the tension roller 10 in the biasing direction T1.

[0047] In this embodiment, the drying belt 7 is made of a highly heat-resistant resin material. A large force must be applied to the drying belt 7 in a tensioned state like a pulley to ensure it is tensioned without slack. For example, in this embodiment, when the tension unit 30 is incorporated into the drying belt unit 5 and biases the drying belt 7, a large tension of, for example, 370 N is applied to the drying belt 7. Applying and releasing the biasing force requires a large force from the operator. Therefore, in this embodiment, to reduce the burden on the operator, the first lever 3316a and the second lever 3317a switch between applying and releasing the biasing force in two stages. The first lever 3316a and the second lever 3317a are connected to the first lever shaft 3316b and the second lever shaft 3317b, respectively, and are rotatably supported by the tension frame 3315.

[0048] [Procedure for applying and canceling force] Next, a procedure for applying and releasing the urging force will be described. In this embodiment, the tension state of the drying belt 7 is switched among three states, a first state, a second state, and a third state. Each state will be described in detail below.

[0049] [First state] 5 and 6 show a first state in which the first lever 3316a and the second lever 3317a are in the pressure release position and no tension is applied to the drying belt 7. The roller support plates 3312 and 3313 are provided with contact portions 3312b and 3313b, respectively. An eccentric first cam 3316c connected to the first lever shaft 3316b contacts the contact portions 3312b and 3313b, and urges the roller support plates 3312 and 3313 in the direction opposite to the urging direction of the first spring 3314a.

[0050] As a result, the tension roller 10 is positioned away from the drying belt 7. At the same time, the eccentric second cam 3317c connected to the second lever shaft 3317b comes into contact with the contact portion 3318b provided on the pressure plate 3318, and urges the pressure plate 3318 in the direction opposite to the urging direction of the second spring 3314b. As a result, the pressure plate 3318 is in a position where the force pressing the roller support plates 3312 and 3313 via the link member 3319 is released.

[0051] [Second state] Next, when the first lever 3316a is rotated in the direction of arrow R1 in Fig. 7 from the first state shown in Fig. 5 and Fig. 6, the state changes to the second state shown in Fig. 7 and Fig. 8. At this time, the first cam 3316c moves away from the contact portions 3312b and 3313b of the roller support plates 3312 and 3313, respectively. The roller support plates 3312 and 3313 are then biased by the first spring 3314a, and the tension roller 10 comes into contact with the drying belt 7. The drying belt 7 is in a slack state in the first state where there is no load, and the position of the drying belt 7 is maintained by the biasing force of the first spring 3314a.

[0052] 7, the first cam 3316c again contacts the contact portions 3312b and 3313b, moving the roller support plates 3312 and 3313 in a direction away from the drying belt 7. This returns the tension roller 10 to the first state. In this embodiment, the force (first biasing force) with which the tension roller 10 presses the drying belt 7 in the second state is set to 80 N.

[0053] [Third state] Next, when the second lever 3317a is rotated in the direction of arrow R2 in FIG. 9 from the second state shown in FIGS. 7 and 8, the third state shown in FIGS. 9 and 10 is reached. At this time, the second cam 3317c moves away from the contact portion 3318b of the pressure plate 3318. The pressure plate 3318 is then biased by the second spring 3314b, and the pressure plate 3318 presses one end 3319a of the link member 3319. The link member 3319 rotates about the link shaft 3319c, and the other end 3319b abuts against and presses the abutment portions 3312c and 3313c of the roller support plates 3312 and 3313, respectively. As a result, the roller support plates 3312 and 3313 are subjected to the biasing force of the second spring 3314b via the link member 3319 in addition to the biasing force of the first spring 3314a. The drying belt 7 receives a desired biasing force from the tension roller 10 and enters the third state in which it is stretched, and is ready for use during image formation.

[0054] 9, the second cam 3317c again contacts the contact portion 3318b, moving the pressure plate 3318 to a position where the biasing force of the second spring 3314b is released. This releases the force transmitted to the roller support plates 3312 and 3313 via the link member 3319, returning the device to the second state. In this embodiment, the force (second biasing force) with which the tension roller 10 presses the drying belt 7 in the third state is set to 370 N. In other words, a biasing force of 80 N (approximately 22%) is applied in advance in the second state to the biasing force of 370 N that tensions the drying belt 7 until it reaches the usage state (third state).

[0055] In this way, the first pressure applying unit 31 is switchable between a first state in which the tension roller 10 does not apply pressure to the drying belt 7, and a second state in which the tension roller 10 applies a first pressure force (80N) to the drying belt 7. The second pressure applying unit 32 is switchable between the second state applied by the first pressure applying unit 31, and a third state in which the tension roller 10 applies a second pressure force (370N) to the drying belt 7 that is greater than the first pressure force (80N).

[0056] In this way, the biasing force is distributed in two stages by the first lever 3316a and the second lever 3317a, reducing the operating force required to apply and release the biasing force. Also, after applying a biasing force to maintain the tensioned position of the drying belt 7 in the first stage, a biasing force of 370 N is applied in the second stage. This reduces the impact load on the drying belt 7 and improves durability, compared to when a biasing force of 370 N is suddenly applied to the drying belt 7 from a slackened state in an unloaded state (first state), which places a large load on the drying belt 7.

[0057] In this embodiment, as shown in Fig. 9, when in the third state, the second lever 3317a is arranged to overlap the front side of the first lever 3316a. This causes an operator who attempts to switch from the third state to the first state to operate the second lever 3317a first, and guides the operator in the correct operating order.

[0058] [Attaching and detaching the tension unit] Next, the procedure for attaching and detaching the tension unit 30 will be described with reference to Figures 11 and 12. Figures 11 and 12 show the state in which the tension unit 30 is assembled to the drying belt unit 5. The tension unit 30 is in the first state in which the tension roller 10 is retracted by operating the first lever 3316a and the second lever 3317a, and is assembled from the right side of the drying belt unit 5.

[0059] The tension frame 3315 of the tension unit 30 is guided by guide portions 3303b and 3304b provided on the front side plate 3303 and the rear side plate 3304, respectively. This reduces the risk that the surface of the tension roller 10 comes into contact with the drying belt 7, and that other areas may inadvertently come into contact and damage the surface of the drying belt 7. The positioning portions 3303c and 3304c of the front side plate 3303 and the rear side plate 3304, respectively, and the positioning portions 3315b and 3315c of the tension frame 3315 are fitted into the positioning shafts, thereby positioning the tension unit 30 with respect to the drying belt unit 5.

[0060] As described above, the tension unit 30 of this embodiment has the first pressure unit 31 that can be switched between the first state and the second state, and the second pressure unit 32 that can be switched between the second state and the third state. Therefore, when switching the tension roller 10 from the first state to the third state, the operation can be performed in two stages, which reduces the operating force per operation compared to operating in one stage. This improves the operability when applying and releasing tension to the drying belt 7.

[0061] Furthermore, in addition to the above-described effects, the tension unit 30 of this embodiment can distribute the urging force so that a large urging force is not suddenly applied to the drying belt 7 from an unloaded state. This reduces the impact load on the drying belt 7 and improves durability, compared to when a large load is applied to the drying belt 7 by suddenly applying a urging force of 370 N from the slack state of the unloaded first state.

[0062] <Second embodiment> Next, a second embodiment of the present invention will be described in detail with reference to Figures 13 to 18. This embodiment differs from the first embodiment in that a first cam 3391c and a second cam 3391d are coaxial and operated by a single operating lever 3391a. However, other configurations are the same as those of the first embodiment, so the same reference numerals are used and detailed description will be omitted.

[0063] The configuration of the tension unit 30 of this embodiment will be described with reference to Figures 13 to 18. Figures 13, 15, and 17 are perspective views showing the internal structure of the tension unit 30. Figures 14, 16, and 18 are detailed views explaining the pressure mechanism of the tension unit 30. Note that Figures 14, 16, and 18 are views showing the pressure configuration on one side of the approximate center of the tension roller 10 in the axial direction, but the opposite side has a similar configuration.

[0064] As in the first embodiment, in the tension unit 30, roller support plates 3312 and 3313, which rotatably support the tension roller 10, are supported by a tension frame 3315 via slide rails (not shown). A pressure plate 3318 and a link member 3319 are also supported by the tension frame 3315. Furthermore, the roller support plates 3312 and 3313 are biased by a first spring 3314a, and the pressure plate 3318 is biased by a second spring 3314b.

[0065] The first pressure applying unit 31 has a first cam 3391c that positions the roller support plates 3312 and 3313 against the biasing force of the first spring 3314a, and a rotatable rotation shaft 3391b fixed to the first cam 3391c. The second pressure applying unit 32 has a second cam 3391d that positions the roller support plates 3312 and 3313 against the biasing force of the second spring 3314b, and is rotatably fixed to the rotation shaft 3391b.

[0066] The operating lever 3391a is connected to a rotating shaft 3391b and rotatably supported by the tension frame 3315. An eccentric first cam 3391c and a second cam 3391d are connected to the rotating shaft 3391b. As shown in FIGS. 13 and 14, the first cam 3391c abuts against the abutment portions 3312b and 3313b of the roller support plates 3312 and 3313, respectively, and biases the roller support plates 3312 and 3313 in the direction opposite to the biasing direction of the first spring 3314a. At the same time, the second cam 3391d abuts against the abutment portion 3318b of the pressure plate 3318, and biases the pressure plate 3318 in the direction opposite to the biasing direction of the second spring 3314b. This places the tension roller 10 in a first state in which it is separated from the drying belt 7.

[0067] Next, the operating lever 3391a is rotated 90 degrees in the direction of arrow R3 shown in Fig. 15. Then, as shown in Figs. 15 and 16, the first cam 3391c moves away from the contact portions 3312b and 3313b of the roller support plates 3312 and 3313, respectively, and the roller support plates 3312 and 3313 move in the biasing direction T1 due to the biasing force of the first spring 3314a. This causes the tension roller 10 to come into contact with the drying belt 7, and the position of the drying belt 7 is maintained, entering the second state.

[0068] Next, the operating lever 3391a is rotated another 90 degrees in the direction of arrow R3 shown in Fig. 17. Then, as shown in Figs. 17 and 18, the second cam 3391d moves away from the contact portion 3318b of the pressure plate 3318, and the pressure plate 3318 is biased by the second spring 3314b to press one end 3319a of the link member 3319. The link member 3319 rotates about the link shaft 3319c, and the other end 3319b abuts against and presses the abutment portions 3312c and 3313c of the roller support plates 3312 and 3313, respectively. As a result, the roller support plates 3312 and 3313 are applied with a biasing force from the second spring 3314b via the link member 3319 in addition to the biasing force from the first spring 3314a, and the drying belt 7 enters a third state in which it is tensioned and receives a desired biasing force from the tension roller 10. In this way, the biasing force applied by the tension roller 10 to the drying belt 7 varies depending on the phase in which the operating lever 3391a is operated, and the operating force can be reduced.

[0069] As described above, in this embodiment, the operating lever 3391a is fixed to the rotary shaft 3391b, and by rotating the rotary shaft 3391b, the operating lever 3391a can be switched between the first state and the second state, and between the second state and the third state. Therefore, the operation of applying and releasing the urging force can be performed in two stages by changing the phase of the single operating lever 3391a. This achieves the same effects as in the first embodiment, that is, it reduces the operating force required to apply and release the urging force to the drying belt 7, and it is possible to distribute the urging force so that a large urging force is not suddenly applied to the drying belt 7 from an unloaded state.

[0070] In the above-described embodiments, the belt heating unit 3350 has two rollers, the first heating roller 3351a and the second heating roller 3351b, but this is not limiting. For example, a heater may be provided inside the tension roller 10. That is, it is sufficient that a heater is provided in at least one of the first heating roller 3351a, the second heating roller 3351b, and the tension roller 10. Alternatively, a heater may be provided on the outer periphery of the roller to heat the roller.

[0071] In addition, in each of the above-described embodiments, the steering roller 3321 is displaced by the first steering arm 3323a that rotates about the rotation center to control the meandering of the belt, but the present invention is not limited to this. For example, the present invention can be applied to a configuration in which the position of the steering roller 3321 cannot follow changes in the circumferential length of the drying belt 7, or in which the meandering control characteristics deteriorate. For example, the present invention can be applied to an automatic centering mechanism that provides a regulating rib at the end of the drying belt 7 to regulate the amount of meandering of the drying belt 7, or a meandering control mechanism that generates a tension difference at the belt end.

[0072] Furthermore, in each of the above-described embodiments, the operating member used to apply and release tension is a lever, but this is not limited thereto, and tension may be applied by a wire or the like.

[0073] Furthermore, in each of the above-described embodiments, the present invention has been described as being applied to the inkjet recording apparatus 100 as an image forming apparatus, but is not limited to this. For example, the present invention can also be applied to an electrophotographic image forming apparatus that uses toner, and the same effects as those of the present embodiment can be obtained. [Explanation of symbols]

[0074] 5... drying belt unit (sheet conveying section), 7... drying belt (belt), 9... tension roller, 10... tension roller, 31... first pressure section, 32... second pressure section, 100... inkjet recording device, 2000... print module (image forming section), 2020... recording section (inkjet recording section), 3270a, 3270b... tension roller, 3312, 3313... roller support plate (support member), 3314a... first spring (first biasing member), 3314b... second spring (second biasing member), 33 16a...first lever (first operating member, operating unit), 3316b...first lever shaft (first shaft), 3316c...first cam, 3317a...second lever (second operating member, operating unit), 3317b...second lever shaft (second shaft), 3317c...second cam, 3319...link member, 3351a...first heating roller (tension roller), 3351b...second heating roller (tension roller), 3352...heater, 3391a...operating lever (operating member, operating unit), 3391b...rotating shaft, 3391c...first cam, 3391d...second cam

Claims

1. an image forming unit that forms an image on a sheet; a sheet conveying unit that conveys a sheet on which an image has been formed in the image forming unit, The sheet conveying unit a flexible endless belt that rotates to transport a sheet; a plurality of tension rollers for tensioning the belt; a tension roller capable of biasing the belt; a heater provided on at least one of the tension roller and the tension roller for heating; a first pressure unit that can be switched between a first state in which the tension roller does not urge the belt and a second state in which the tension roller urges the belt with a first urging force; a second pressure unit that can be switched between the second state switched by the first pressure unit and a third state in which the tension roller urges the belt with a second urging force greater than the first urging force; an operating unit capable of operating the first pressure unit and the second pressure unit, An image forming apparatus characterized by:

2. the first pressure unit is disposed at two different positions in the sheet conveying unit in the rotation axis direction of the tension roller, the second pressure units are disposed at two different positions in the sheet conveying unit in the rotation axis direction; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. the operation unit is disposed on one side of the sheet conveying unit in the direction of the rotation axis; 3. The image forming apparatus according to claim 2, wherein the image forming apparatus is a recording medium.

4. The operating unit includes a first operating member that can operate the first pressure unit and a second operating member that can operate the second pressure unit.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

5. The first pressure unit is a support member that rotatably supports the tension roller and is movable in a direction perpendicular to the rotation axis direction of the tension roller; a first biasing member that biases the support member in a direction in which the first pressure unit switches from the first state to the second state; a first cam that positions the support member against the biasing force of the first biasing member; a first shaft fixed to the first cam and rotatable thereon; the first operating member is fixed to the first shaft, and switches the first pressure unit between the first state and the second state by rotating the first shaft; 5. The image forming apparatus according to claim 4.

6. The second pressure unit is a second biasing member that biases the support member in a direction in which the second pressure unit switches from the second state to the third state; a second cam that positions the support member against the biasing force of the second biasing member; a second shaft fixed to the second cam and rotatable thereon; the second operating member is fixed to the second shaft, and switches the second pressure unit between the second state and the third state by rotating the second shaft; 6. The image forming apparatus according to claim 5,

7. the second biasing member is disposed at a position different from that of the first biasing member in the rotational axis direction, The second pressure applying portion has a link member that connects the second biasing member and the support member.

7. The image forming apparatus according to claim 6, wherein the image forming apparatus is a recording medium.

8. the operating unit has one operating member that can operate the first pressure unit and the second pressure unit, 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

9. The first pressure unit is a support member that rotatably supports the tension roller and is movable in a direction perpendicular to the rotation axis direction of the tension roller; a first biasing member that biases the support member in a direction in which the first pressure unit switches from the first state to the second state; a first cam that positions the support member against the biasing force of the first biasing member; a rotation shaft fixed to the first cam and rotatable thereon, The second pressure unit is a second biasing member that biases the support member in a direction in which the second pressure unit switches from the second state to the third state; a second cam that positions the support member against the biasing force of the second biasing member and is fixed to the rotation shaft so as to be rotatable, the operating member is fixed to the rotation shaft, and by rotating the rotation shaft, the first pressure applying unit is switched between the first state and the second state, and the second pressure applying unit is switched between the second state and the third state.

9. The image forming apparatus according to claim 8,

10. the second biasing member is disposed at a position different from that of the first biasing member in the rotational axis direction, The second pressure applying portion has a link member that connects the second biasing member and the support member.

10. The image forming apparatus according to claim 9,

11. the image forming unit is an inkjet recording unit that forms an image on a sheet using ink; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

Images