Patent Grant
11294311
The present invention relates to an image forming apparatus for forming an image of toner on a recording material. This image forming apparatus is used as a copying machine, a printer, a facsimile machine, and a multi-function machine having a plurality of functions of these.
The image forming apparatus of an electrophotographic type forms the image on the recording material by using the toner containing a parting agent (sometimes known as a “releasing agent” or “wax releasing agent”). Further, the image forming apparatus includes a fixing device for fixing the image on the recording material by heating and pressing the recording material carrying the toner image thereon.
In a fixing device described in Japanese Laid-Open Patent Application (JP-A) 2017-120284, a nip is formed between a fixing roller and a pressing roller, and the recording material is passed through this nip and thus the toner image is fixed on the recording material.
Further, the image forming apparatus described in JP-A 2017-120284 includes a constitution for collecting dust generated by heating of the toner containing the parting agent. Specifically, this image forming apparatus is provided with an opening of a duct at a position where the image forming apparatus opposes the fixing roller, and this opening extends along a longitudinal direction of the fixing roller. This duct is connected to an air discharging passage including a fan and guides the air in the neighborhood of a fixing belt to the air discharging passage. In the air discharging passage, a filter such as an electrostatic filter is provided, and removes the dust contained in the air.
In such an apparatus, it has been required that dust removing power is maintained over a long term.
The present invention aims at providing an image forming apparatus of which dust removing power is maintained over a long term.
According to an aspect of the present invention, there is provided an image forming apparatus comprising: an image forming portion for forming a toner image on a recording material at a first position by using toner containing a parting agent; a fixing portion for fixing an unfixed toner image, at a second position, formed on the recording material by the image forming portion; a heat discharging duct, including an inlet between the first position and the second position with respect to a recording material feeding direction, for discharging air heated by the fixing portion; a heat discharging fan for generating an air flow in the heat discharging duct; a collecting duct, including an inlet between the first position and the second position with respect to the recording material feeding direction, for collecting particles with a predetermined particle size resulting from the parting agent; a collecting fan for generating an air flow in the collecting duct; and a controller for controlling operations of the heat discharging fan and the collecting fan, wherein the controller actuates the collecting fan while stopping the operation of the heat discharging fan when a temperature in a neighborhood of the fixing portion is a first temperature, and actuates the heat discharging fan while stopping the operation of the collecting fan when the temperature in the neighborhood of the fixing portion is a second temperature higher than the first temperature.
According to another aspect of the present invention, there is provided an image forming apparatus comprising: an image forming portion for forming a toner image on a recording material at a first position by using toner containing a parting agent; a fixing portion including a rotatable heating member and a rotatable region member that fix the toner image, at a second position, fed from the first position by nipping and feeding the recording material through heat and pressure; a duct provided with an air suction port between the first position and the second position; a filter, provided on the duct, for collecting dust resulting from the parting agent; a fan for generating an air flow for sucking air into the duct; temperature detecting means for detecting a spatial temperature in a neighborhood of the rotatable heating member; and a controller for controlling an operation of the fan, wherein, when a surface temperature of the rotatable heating member is Tb (° C.), a dust generation temperature of the toner in Tws (° C.), and the spatial temperature detected by the temperature detecting means is Ta (° C.), the controller actuates the fan at a predetermined first efficiency when the following condition formulas (A) and (B) are satisfied, and causes the fan to be in a non-actuation state or actuates the fan at a predetermined second efficiency lower in efficiency than the first efficiency in a case that the following condition formulas are not satisfied:
Tb≥Tws−Z formula (A),
where Z is a peripheral adjusting temperature value (° C.), and
Tws−Ta>first temperature formula (B),
where the first temperature is a peripheral threshold temperature.
According to a further aspect of the present invention, there is provided an image forming apparatus comprising: an image forming portion for forming a toner image on a recording material at a first position by using toner containing a parting agent; a fixing portion including a rotatable heating member and a rotatable region member that fix the toner image, at a second position, fed from the first position by nipping and feeding the recording material through heat and pressure; a cooling duct provided with an air suction port between the first position and the second position; a cooling fan for generating an air flow for sucking air into the cooling duct; temperature detecting means for detecting a spatial temperature in a neighborhood of the rotatable heating member; and a controller for controlling an operation of the cooling fan, wherein, when a surface temperature of the rotatable heating member is Tb (° C.), a dust generation temperature of the toner is Tws (° C.), and the spatial temperature detected by the temperature detecting means is Ta (° C.), the controller causes the cooling fan to be in a non-actuation state or actuates the cooling fan at a predetermined second efficiency lower in efficiency than a first efficiency in a case that the following condition formulas are satisfied:
Tb≥Tws−Z formula (A),
where Z is a peripheral adjusting temperature value (° C.), and
Tws−Ta>first temperature formula (B),
where the first temperature is a peripheral threshold temperature.
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In the following, the present invention will be specifically described using embodiments. Incidentally, unless otherwise specified, within a concept of the present invention, various constitutions described in an embodiment may also be replaced with other known constitutions.
(1) General Structure of Image Forming Apparatus
Before a characteristic (feature) portion of this embodiment is described, a general structure of an example of an image forming apparatus 1 will be described.
The printer 1 forms an image (unfixed toner image) by an image forming portion 7 using an electrophotographic process and transfers this image onto a recording material P at a transfer portion 12a. The recording material P is a recording medium on which the image is to be formed at a surface thereof. As an example of the recording material P, it is possible to cite plain paper, thick paper, an OHP sheet, coated paper, label paper, or the like. In the following, the recording material is referred to as a sheet or is also referred to as a paper or form. The sheet P on which the image is transferred is heated at a fixing portion 103, so that the image is fixed on the sheet P.
The printer 1 used in description of this embodiment is a four-color-based full-color multi-function printer (color image forming apparatus) using the electrophotographic process. Incidentally, the printer 1 may also be a monochromatic multi-function printer or a single-function printer. In the following, the printer 1 will be specifically described using the drawings.
The printer 1 includes a control circuit portion (CNTRLR) A (
The control circuit portion A is electrically connected to various constituent elements including an input device B including external information terminal (not shown) such as a personal computer and an image reader 2, and an operating panel (not shown), and the like, and is capable of transferring signal information therebetween. The control circuit portion A carries out integrated control of the respective constituent elements in the apparatus on the basis of an image signal inputted from the input device B.
Further, the control circuit portion A includes a temperature detecting means (DETECTOR) 67 for detecting a temperature of the neighborhood of a fixing belt 105 (rotatable heating member) described later in
As shown in
The stations 5Y, 5M, 5C and 5K are constituted substantially similar to each other except that colors of toners used are different from each other. For that reason, in the case where detailed structures of the stations 5Y, 5M, 5C and 5K are described, a first station 5Y will be described as a representative example.
The first station 5Y includes a rotation drum-type electrophotographic photosensitive member (hereinafter referred to as a drum) 6 as an image bearing member on which the image is to be formed. Further, the first station 5Y includes, as process means actable on this drum 6, a cleaning member (not shown), a developing unit (unnumbered, to the left of drum 6 in the perspective of
The first station 5Y accommodates a developer (hereinafter referred to as toner) of the color of yellow (Y) in a toner accommodating chamber of the developing unit. The second station 5M accommodates toner of the color of magenta (M) in a toner accommodating chamber of the developing unit. The third station 5C accommodates toner of the color of cyan (C) in a toner accommodating chamber of the developing unit. The fourth station 5K accommodates toner of the color of black (K) in a toner accommodating chamber of the developing unit. 9aY, 9aM, 9aC and 9aK are toner supplying mechanisms to the developing units in the stations 5Y, 5M, 5C and 5K, respectively.
On a side below the image forming portion 7, a laser scanner unit 8 as an image information exposure means for the drums 6 in the respective stations 5Y, 5M, 5C and 5K is provided. On an upper side of the image forming portion 7, an intermediary transfer belt unit 10 (hereinafter referred to as a transfer unit) is provided.
The transfer unit 10 includes an intermediary transfer belt (hereinafter referred to as a transfer belt) 10c and a driving roller 10a for driving the transfer unit 10. Further, first to fourth primary transfer rollers 11 corresponding to the respective stations 5Y, 5M, 5C and 5K are provided in parallel to each other inside the belt 10c. The respective primary transfer rollers 11 are provided opposed to the drums 6 of the respective stations. Upper surface portions of the drums 6 of the image forming portion 7 contact a lower surface of the belt 10c in positions of the primary transfer rollers 11. This contact portion is called a primary transfer portion.
The driving roller 10a is a roller for rotationally driving the belt 10c, and a secondary transfer roller 12 is provided outside a portion of the belt 10c backed up by the driving roller 10a. The belt 10c contacts the secondary transfer roller 12 which is a transfer means, and this contact portion is called a secondary transfer portion 12a (transfer portion: first position). Outside a portion of the belt 10c backed up by a tension roller 10b, a transfer belt cleaning device 10d is provided. At a portion below the laser scanner value 8, a cassette 3 for accommodating the sheets P is provided.
As shown in
An image forming sequence will be described. In the case where the printer 1 performs an image forming operation, a control circuit portion (control portion, controller) A carries out the following control. The control circuit portion A causes the drums 6 of the first to fourth stations 5Y, 5M, 5C and 5K to be rotationally driven at a predetermined speed in the clockwise direction in the figure in synchronism with image formation timing. The control circuit portion A controls drive of the driving roller 10a so that the transfer belt 10c is rotated normally at a speed depending on a rotational speed of the drum 6 in the rotational direction of the drum 6. Further, the control circuit portion A causes the laser scanner unit 8 and charging rollers (not shown) to be actuated.
The above-described control is carried out, so that the printer 1 forms a full-color image in the following manner. First, the charging rollers (not shown) electrically charge the surfaces of the drums 6 uniformly to a predetermined polarity and a predetermined potential. Next, the laser scanner unit 8 subjects the surfaces of the drums 6 to scanning exposure with laser beams modulated depending on image information signals of the respective colors of Y, M, C and K. Thus, on the surfaces of the respective drums 6, electrostatic latent images depending on the corresponding colors are formed. The formed electrostatic latent images are developed as toner images by the developing units.
The toner images of the respective colors of Y, M, C and K formed as described above are synthesized by being successively primary-transferred superposedly onto the transfer belt 10c. Thus, a full-color unfixed toner image obtained by synthesizing the toner images of the four colors of Y+M+C+K is formed on the transfer belt 10c. Then, this unfixed toner image is fed to the secondary transfer portion 12a (transfer portion) by rotation of the transfer belt 10c. The surfaces of the drums 6 after the toner images are primary-transferred onto the transfer belt 10c are cleaned by cleaning members.
On the other hand, the sheets P in the cassette 3 are fed correspondingly to one sheet by the feeding roller 4a and the retard roller 4b and are conveyed to the registration roller pair 4c. The registration roller pair 4c conveys the sheet P toward the secondary transfer portion 12a in synchronism with the toner image on the transfer belt 10c. To the secondary transfer roller 12, a secondary transfer bias of an opposite polarity to a normal charge polarity of the toner is applied. For that reason, when the sheet P is nipped and fed (conveyed) to the secondary transfer portion 12a, the four color toner images on the transfer belt 10c are collectively secondary-transferred onto the sheet P.
When the sheet P fed from the secondary transfer portion 12a is separated from the transfer belt 10c and is fed to the fixing device 103, the toner images are heat-fixed on the sheet P. The sheet P fed from the fixing device 103 passes through a guiding member 15 and the discharging roller pair 14 and is discharged onto the discharge tray 16. Transfer residual toner remaining on the surface of the transfer belt 10c after the toner image is secondary-transferred onto the sheet P is removed from the belt surface by the transfer belt cleaning device 10d.
Incidentally, at a peripheral portion of the fixing device 103, a plurality of fans and ducts for generating air flow are provided. When the sheet P containing water content is heated by the fixing device 103, in addition to heat generated from the fixing device 103, water vapor generates from the sheet P. By this water vapor, a space C on a side downstream of the fixing device 103 with respect to the sheet feeding direction is in a state in which humidity is high. When the humidity is high, there is a possibility that a water droplet generates on the guiding member 15. When the water droplet on the guiding member 15 deposits on the fed sheet P, an occurrence of image defect is caused.
For that reason, the printer 1 sucks air (outside air) from an outside of the printer 1 into an inside thereof by a second fan 62 and blows the air against the guiding member 15, and lowers the humidity of the space C. The water vapor discharged from the space C by air blowing from the second fan 62 is not only discharged toward the discharge tray 16 along an air flow (current) Fc but also discharged to the outside of the printer 1 along air flows 63a by a third fan 63 (see
Here, in the following description, an upstream side and a downstream side are the upstream side and the downstream side with respect to a feeding direction X (see
Further, the printer 1 includes a cooling duct 42 and a fourth fan (transfer portion cooling fan) 64 being a cooling suction portion, which discharge heat in a space on the side upstream of the fixing device 103, i.e., a space between the secondary transfer portion 12a being the transfer portion and the fixing device 103. Further, the printer 1 includes a filter unit 50 for collecting and removing dust D (
The filter unit 50 includes a first fan (dust collecting fan) 61 which is a suction portion as shown in
(2) Fixing Device
Next, the fixing device 103 and the dust D generating in the neighborhood of the fixing device 103 will be described.
(2-1) Fixing Device 103
Part (a) of
The fixing device 103 includes the fixing belt unit 101 (hereinafter referred to as a fixing unit) including the belt 105 as a rotatable heating member, a pressing roller 102 as a rotatable supporting member (predetermined pressing member), a planar heater 101a as a heating portion, and a casing 100.
As shown in part (a) of
In this embodiment, the sheet inlet 400 is disposed below the sheet outlet 500 with respect to a direction of gravitation, and therefore, the sheet P is fed from below toward above with respect to the direction of gravitation. This constitution is referred to as a vertical path constitution. On a side downstream of the sheet outlet 500, the guiding member 15 for generating feeding of the sheet P passed through the nip 101b is provided.
(2-2) Constitution of Fixing Unit 101
The fixing unit 101 is a unit such that the fixing unit 101 contacts the pressing roller 102 described later and forms the nip 101b between the belt 105 and the pressing roller 102, and fixes the toner image on the sheet P in the nip 101b.
The fixing unit 101 is an assembly constituted by a plurality of members as shown in part (a) of
The heater 101a is a heating member for heating the belt 105 in contact with an inner surface of the belt 105. In this embodiment, as the heater 101a, a ceramic heater generating heat by energization is used. The ceramic heater includes an elongated thin ceramic substrate and a resistance layer provided on a surface of the substrate and is a low thermal capacity heater which quickly generates heat as a whole by energizing the resistance layer.
The heater holder 104 is a holding member for holding the heater 101a. The holder 104 in this embodiment has an arcuate shape in cross-section and regulates a shape of the belt 105 with respect to a circumferential direction. As a material of the holder 104, a heat-resistant resin (material) may desirably be used.
The pressing stay 104a is a member for pressing uniformly the heater 101a and the heater holder 104 against the belt 105 with respect to a longitudinal direction. The pressing stay 104a may desirably be a material which is not readily bent even when a high pressing force is applied thereto. In this embodiment, as the material of the pressing stay 104a, SUS304 which is stainless steel was used. On the pressing stay 104a, a thermistor TH is provided. The thermistor TH outputs, to the control circuit portion A, a signal depending on a temperature of the belt 105.
The belt 105 is a rotatable member for imparting heat to the sheet P in contact with the sheet P. The belt 105 is a cylindrical (endless) belt and has flexibility as a whole. The belt 105 is provided so as to cover the heater 101a, the heater holder 104 and the pressing stay 104a from an outside.
The flanges 106L and 106R are a pair of members for rotatably holding longitudinal end portions of the belt 105. Each of the flanges 106L and 106R includes, as shown in part (b) of
The flange portion 106a is a portion for restricting movement of the belt 105 in a thrust direction of the belt 105 by receiving an end surface of the belt 105 and has an outer configuration larger than a diameter of the belt 105. The back-up portion 106b is a portion for holding a cylindrical shape of the belt 105 by holding an end portion inner surface of the belt 105. The portion-to-be-pressed 106c is provided on an outer surface side of the flange portion 106a and receives a pressing force by pressing springs 108L and 108R (see
(2-3) Constitution of Fixing Belt
Part (a) of
The belt 105 in this embodiment is constituted by a plurality of layers. Specifically, the belt 105 sequentially includes, from an inside toward an outside, an endless (cylindrical) base layer 105a, a primer layer 105b, an elastic layer 105c, and a parting layer 105d.
The base layer 105a is a layer for ensuring strength of the belt 105. The base layer 105a is a base layer made of metal such as SUS (stainless) and has a thickness of about 30 μm so that the belt 105 can withstand thermal stress and mechanical stress.
The primer layer 105b is a layer for bonding the base layer 105a and the elastic layer 105c to each other. The primer layer is formed on the base layer 105a by applying a primer in a thickness of about 5 μm.
The elastic layer 105c performs a function such that the parting layer 105d is closely contacted to the toner image by being deformed when the toner image is press-contacted to the belt 105 in the nip 101b. As the elastic layer 105c, a heat-resistant rubber can be used.
The parting layer 105d is a layer having a function of preventing deposition of the toner and paper dust on the belt 105. As the parting layer 105d, it is possible to use a fluorine-containing resin (material) such as PFA resin excellent in parting property and heat-resistant property. A thickness of the parting layer 105d in this embodiment is 20 μm in consideration of a heat-conductive property.
(2-4) Constitution of Pressing Roller and Pressing Method
The pressing roller 102 is a nip forming member for forming the nip 101b between itself and the belt 105 in contact with an outer peripheral surface of the belt 105. The pressing roller 102 in this embodiment is a roller member constituted by a plurality of layers. Specifically, the pressing roller 102 includes a core metal 102a of metal (aluminum or iron), an elastic layer 102b formed of a silicone rubber or the like, and a parting layer 102c covering the elastic layer 102b. The parting layer 102c is a tube using a fluorine-containing resin (material) such as PFA as a material thereof and is bonded onto the elastic layer.
As shown in
The other end side of the core metal 102a is connected to a gear G, and when the gear G receives drive from a driving motor (not shown) controlled by the control circuit portion A, the pressing roller 102 is rotationally driven as a rotatable driving member in an arrow R102 direction at a predetermined peripheral speed.
The fixing unit 101 is supported by the side plate 107L and the side plate 107R so as to be slidable and movable in a direction toward and away from the pressing roller 102. Specifically, the flanges 106L and 106R are provided so as to engage with guiding grooves (not shown) of the side plate 107L and the side plate 107R. Then, by the pressing springs 108L and 108R supported by spring supporting portions 109L and 109R, the portions-to-be-pressed 106c of the flanges 106L and 106R are pressed in a direction toward the pressing roller 102 by a predetermined pressing force T.
By the pressing force T, entirety of the flanges 106L and 106R, the pressing stay 104a and the heater holder 104 is urged in the direction of the pressing roller 102. Here, the fixing unit 101 faces the pressing roller 102 on a side where the heater 101a is provided. For that reason, the heater 101a presses the belt 105 toward the pressing roller 102. By such a constitution, the belt 105 and the pressing roller 102 are deformed, so that the nip 101b (see part (b) of
Thus, when the pressing roller 102 rotates (R102) in a state in which the fixing unit 101 and the pressing roller 102 are in an intimate contact with each other, by a frictional force between the belt 105 and the pressing roller 102 in the nip 101b, a rotation torque acts on the belt 105. The belt 105 is rotated (R105) by the pressing roller 102. At this time, a rotational speed of the belt 105 substantially corresponds to a rotational speed of the pressing roller 102. That is, in this embodiment, the pressing roller 102 has a function as a driving roller for rotationally driving the belt 105.
Incidentally, at this time, an inner peripheral surface of the belt 105 and the heater 101a slide with each other, and therefore, it is desirable that grease is applied onto the inner surface of the belt 105 and a sliding resistance is decreased.
(2-5)
By using the above-described constitution, the fixing device 103 performs the fixing process during the image forming process. When the fixing process is performed, the control circuit portion A controls the driving motor (not shown), so that the pressing roller 102 is rotationally driven in the rotational direction R102 (
Further, the control circuit portion A starts energization to the heater 101a through a power source circuit (not shown). The heater 101a generating heat by this energization imparts heat to the belt 105 rotating while the inner surface thereof slides with the heater surface in intimate contact with the heater surface in the nip 101b. Thus, the belt 105 to which the heat is imparted gradually becomes a high temperature.
Here, the thermistor TH is provided on a top surface of the pressing stay 104a and elastically contacts the inner surface of the rotating belt 105. By this, the thermistor TH detects a temperature of the belt 105 and feeds back a detection temperature information thereof to the control circuit portion A. The control circuit portion A controls electric power supplied to the heater 101a on the basis of a signal outputted by the thermistor TH so that a surface temperature Tb of the belt 105 is a target temperature Tp (see part (a) of
When the belt 105 is heated to the target temperature Tp, the control circuit portion A controls the respective constituent elements, so that the sheet P carrying the toner image S (part (a) of
In a process in which the sheet P is nipped and fed, heat of the heater 101a is imparted to the sheet P through the belt 105. The unfixed toner image S is melted by the heat of the heater 101a, and is fixed on the sheet P by pressure exerted on the nip 101b. The sheet P passed through the nip 101b is guided to the discharging roller pair 14 by the guiding member 15, and is discharged on the discharge tray 16 through the discharging roller pair 14. In this embodiment, the above-described step is called the fixing process.
(3) Dust
Next, generation of ultrafine particles (hereinafter, referred to as dust) resulting from a parting agent (hereinafter, referred to as a wax) contained in the toner, and a property of the dust will be described.
(3-1) Relationship Between Wax Contained in Toner and Dust
As described above, the fixing device 103 fixes the toner image S on the sheet P by causing the high-temperature belt 105 to contact the sheet P. In the case where the fixing process is performed by using such a constitution, a part of the toner is transferred (deposited) on the belt 105 during the fixing process in some instances. This is called an offset phenomenon. The offset phenomenon causes an image defect, and therefore, it is desirable that this is solved.
Therefore, in this embodiment, a wax (parting agent) consisting of paraffin is incorporated in the toner used for formation of the toner image S. This toner is constituted such that the wax therein melted and bleeds out when the toner is heated. For that reason, when the image formed by this toner is subjected to the fixing process, the surface of the belt 105 is covered with the melted wax. On the belt 105 covered with the wax at the surface thereof, by parting action of the wax, the toner is not readily deposited.
In this embodiment, in addition to a pure wax, a compound containing a molecular structure of the wax is also called the wax. For example, a compound obtained by reaction of a resin molecule of the toner with a wax molecular structure of a hydrocarbon chain or the like is also referred to as the wax. Further, as the parting agent, in addition to the wax, a substance having parting action, such as silicone oil may also be used.
A part of the wax deposited on the belt 105 vaporizes when a surface temperature of the belt 105 is a certain temperature or more. Further, when a vaporized (gassified) wax is cooled in the air, particles with a predetermined particle size, specifically, dust (fine particles) of about several nm to about several hundred nm generates. Incidentally, most of the dust generated is predicted to have a particle size of several nm to several tens of nm.
This dust generation (formation) phenomenon is called nucleation and is caused by subjecting a vaporized wax component vaporized by heating to a lower temperature environment. This is referred to as overcooling. This phenomenon is the same as a phenomenon that when a temperature of water vapor is below a dew-point temperature, the water vapor becomes a small water droplet and generates fog. A degree of the overcooling can be represented by an overcooling degree ΔT which is a difference between a dust generation temperature Tws (see part (b) of
Overcooling degree ΔT=Tws−Ta formula (1)
As ΔT is larger, the vaporized wax component is quickly cooled, so that the nucleation is liable to occur. This means that the nucleation occurs at more places. That is, it means that as ΔT is larger, particles are capable of being formed in a larger amount. Further, as ΔT becomes small, the number of places where the nucleation occurs decreases. Further, at that time, gas agglomerates on the formed nuclei, and therefore, particles become large.
Large ΔT-->Small dust generates in a large amount.
Small ΔT-->Large dust generates in a small amount.
The dust comprises a wax component having adhesiveness, and therefore, is liable to deposit on each of places of inside constituent elements of the printer 1 (see part (b) of
However, the filter 51 deteriorated also by, in addition to suction of the dust D, suction of paper powder generating from paper and scattered toner resulting from the unfixed toner on the sheet P. For that reason, the first fan 61 for sucking the air into the filter 51 may desirably actuate only when the dust D generates. In this embodiment, generation of the dust D is predicted by the overcooling degree ΔT, and the first fan 61 is properly controlled.
(3-2) Generation of Dust with Fixing Process
(3-2-1) Property of Dust
In the following, a property of the dust will be specifically described using parts (a) to (c) of
As shown in part (a) of
Further, the volatile matter 21a which was not changed to the dust gathers and agglomerates at a peripheral portion of the minute dust 21b, and in addition, coalescence due to collision between particles of the minute dust 21b occurs, and therefore, the minute dust 21b grows to large dust 21c. At this time, agglomeration/dust formation of the gas in the air is hindered as shown in part (c) of
That is, the dust formation is hindered with a smaller overcooling degree ΔT. Lines L1 and L2 in part (c) of
That is, the dust generation is promoted as the overcooling degree ΔT is large, so that many particles of the dust are formed (generated). Further, when the overcooling degree ΔT becomes large and enters a region which is leftward above the line L2, the dust size becomes smaller and at the same time, the number of formation of the particles also becomes larger. This is because when the overcooling degree ΔT becomes large, the number of places where the nucleation occurs also increases.
Incidentally, although the line L2 is shown as a line defining a large particle size dust generation region and a small particle size dust generation region, there is no clear criterion for defining large particle size dust and small particle size dust in actuality. The dust particle size gradually changes by a change in overcooling degree ΔT.
Next, in part (b) of
Thus, the dust possesses two properties that coalescence is promoted under high temperature and is formed in particles with the large particle size and that the dust is liable to deposit on a peripheral object by the formation of the dust with the large particle size. Incidentally, ease of the coalescence of the dust depends on a component, a temperature and a density (concentration) of the dust. For example, a component liable to adhere becomes high temperature and soft, and when a collision probability between dust particles increases under a high density, the dust particles are liable to coalescence.
(3-2-2) Dust Generation Temperature Tws
By using a device shown in part (a) of
In the following, the control in which the first fan 61 is made non-actuation may also be control in which the efficiency of the first fan 61 is lowered (control in which the efficiency is switched from the first efficiency to the second efficiency). Control of the fourth fan 64 is also similar to the control of this first fan 61.
The dust generation temperature Tws is used for calculation of the overcooling degree ΔT, and is a physical value intrinsic to the toner, so that here details of a measuring method will be described.
The dust generation temperature Tws is measured using a chamber of an inside volume of 0.5 m3. The chamber is set at a temperature of 23±2° C., a humidity of 50±5% and a ventilation rate of 4 times/h. Further, a heater plate provided inside the chamber is increased in temperature from normal temperature at a temperature increasing rate of 3° C./min. On the heater plate, the toner containing the wax is provided. The dust generating from the wax contained in the toner is measured by FMPS Model 3091 (manufactured by TSI) which is a nanoparticle-particle size distribution measuring device connected to the 0.5 m3-chamber.
Next, an analyzing method of the dust generation temperature Tws will be described. From a result obtained as shown in part (b) of
In this experiment, 179° C. was the dust generation temperature Tws. Incidentally, the temperature at which the dust generates depends on the spatial temperature in the chamber as apparent from part (c) of
(3-2-3) Difference Between Generation Temperature of Dust in Printer and Tws
In the printer 1, the dust generates from the wax deposited on the belt 105. A surface temperature of the belt 105 when the dust starts to generate is the generation temperature of the dust in the printer 1. However, this temperature is about 20° C. lower than Tws obtained by the above-described dust generation temperature measuring method. This results from that a space where the dust generates in the printer 1, i.e., a temperature of the space in the neighborhood of the belt 105 is liable to become lower than a temperature of a dust generation space above the heater plate.
The space in the neighborhood of the heated belt 105 is liable to become low temperature because cold air is sucked from the outside air by the air flow generated with the rotation of the belt 105, and therefore, is liable to become the low temperature. On the other hand, in the device of part (a) of
When description is made using part (c) of
Generation temperature of dust in printer 1=dust generation temperature Tws−Z
When the above-described temperature lowering range is a preset adjusting temperature value Z (° C.), the dust generation temperature Tws in the printer 1 is represented by the following formula as a general formula.
Generation temperature of dust in printer 1=dust generation temperature Tws−Z
(3-2-4) Generation Place of Dust D
Next, a generation place of the dust D will be described on the basis of
When the present inventors conducted verification, it turned out that as regards the dust D generating from the fixing device 103, a generation amount is larger on an upstream side of the nip 101b than on a downstream side of the nip 101b. In the following, a mechanism thereof will be described.
Heat is taken by the sheet P on the surface (parting layer 105d) of the belt 105 immediately after the belt 105 passes through the nip 101b, and therefore, a temperature thereof lowers to about 100° C. On the other hand, the temperature of an inner surface/back surface (base layer 105a) of the belt 105 is kept at high temperature by contact with the heater 101a. For that reason, after the belt 105 passes through the nip 101b, the heat of the base layer 105a kept at the high temperature is conducted to the parting layer 105d through the primer layer 105b and the elastic layer 105c.
Therefore, the temperature of the surface (parting layer 105d) of the belt 105 increases after the belt 105 passes through the nip 101b in a process in which the belt 105 rotates in the arrow R105 direction (
On the other hand, the wax bleeding out of the toner on the sheet P exists at an interface between the belt 105 and the toner image S when the fixing process is performed. Thereafter, a part of the wax deposits on the belt 105. As shown in part (a) of
When the sheet P advances in the nip 101b, the wax is in a state in which the wax exists over a substantially full circumference (135b) of the belt 105. Of this, in a region 135c, the belt becomes high temperature, and therefore, the wax is liable to volatilize. Then, when the wax volatilized from the region 135c condenses, the dust D generates. For that reason, many particles of the dust D exist in the neighborhood of the region 135c, i.e., in the neighborhood of (on the side upstream) of the entrance of the nip 101b.
Further, the dust D in the neighborhood of the entrance of the nip 101b diffuses in an arrow W direction by air flows shown in
When the air flow F1 and the air flow F2 collide with each other in the neighborhood of the nip 101b, the air flow F2 generates along a direction (W direction) in which the air flow F3 moves away from the nip 101b. Although details will be described later, the filter 51 for removing the dust is disposed in the W direction which is a direction in which the dust D is carried by the air flow F3 (
(3-2-5) Measuring Point of Spatial Temperature Ta and Manner of Acquiring Ta
A position of a measuring point Tp of the spatial temperature Ta used for calculation of the overcooling degree ΔT (=Tws−Ta) will be described using
It is difficult to accurately measure a range of the space in which the nucleation occurs, but as a result that the present inventor measured a dust density of the peripheral portion of the belt 105, it was predicted that the nucleation occurred within a range of 20 mm or less from the belt 105 toward the direction of the transfer portion 12a.
Further, in the case where the position of the measuring point Tp is excessively close to the belt 105, the measuring point Tp is strongly influenced by the heat of the belt 105, so that there is a possibility that the spatial temperature Ta cannot properly measured. For that reason, it would be considered that there is a need to space the measuring point Tp from the belt 105 by at least 1 mm.
Therefore, the position of the measuring point Tp may pass through a cross-sectional plane center of the belt 105 and a central portion of the belt 105 with respect to a longitudinal direction of the belt 105, and may fall within a range of 1 mm or more and 20 mm or less from the surface of the belt 105 toward the transfer portion 12a. In this embodiment, a distance h from the belt 105 to the measuring point Tp is 6 mm.
Incidentally, as a manner (method) of acquiring the temperature of the measuring point Tp, i.e., the spatial temperature Ta, other than a method of measuring the spatial temperature Ta by a temperature detector, a method of predicting the spatial temperature Ta from temperature information of the printer and operation information of the fan would be considered. In this embodiment, a latter method is used, and a temperature detecting means 67 incorporated in the control circuit portion A shown in
When
an inside temperature of the image forming apparatus measured by the above-described inside temperature sensor 65 of the image forming apparatus is Tin,
an outside temperature measured by the outside temperature sensor 66 of the image forming apparatus is Tout,
a surface temperature of the belt 105 predicted from a temperature of the thermistor TH is Tb,
Duty of the first fan 61 during actuation is FAN 1_duty,
Duty of the second fan 62 during actuation is FAN 2_duty,
Duty of the third fan 63 during actuation is FAN 3_duty, and
Duty of the fourth fan 64 during actuation is FAN 4_duty,
the temperature detecting means 67 predicts Ta from the following formula.
Ta=Tin+A×Tb−B×Tout×FAN 1_duty−C×Tout×FAN 2_duty−D×Tout×FAN 3_duty−E×Tout×FAN 4_duty
Incidentally, Tb is a value obtained by subtracting 10° C. from a detection temperature of the thermistor TH. A constituent material of the belt 105 has a resistance of heat conduction, and therefore, the surface temperature of the belt 105 is about 10° C. lower than a back-surface temperature of the belt detected by the thermistor TH. Further, in the formula, A, B, C, D and E are constants.
A first term of a right(-hand) side in the above-described formula means that Ta is determined on the basis of the inside temperature Tin of the image forming apparatus. A second term means that Ta which is the spatial temperature of the measuring point Tp is increased by the heat of the surface temperature Tb of the belt 105. For that reason, a sign of the second term is plus.
A third term to sixth term mean that Ta is influenced by actuation of the fans having a function of sucking the outside air (temperature Tout) to the measuring point Tp. That is lower than Tin and Ta, and therefore, Ta shifts in a lowering direction by the actuation of the fans. For that reason, signs of the third, fourth, fifth and sixth terms are minus. The constants A, B, C, D and E are determined so that a temperature obtained by actually measuring the temperature at the measuring point Tp through an experiment and a predicted value Ta by the above-described formula coincide with each other.
Incidentally, as parameters used for predicting Ta, in addition to the above parameters, a size, a feeding speed and the number of fed sheets for the sheet P, and Duty of the fans during actuation, and further an operation frequency of each of the fans may also be included.
(3-3) Measurement of Dust Generation Amount
(3-3-1) Measuring Device of Dust Generation Amount
In part (a) of
(3-3-2) Analyzing Method of Dust Generation Amount
Also as regards an analyzing method, similarly, analyzation is performed in accordance with RAL-UZ 205. In part (b) of
Further, from a dust density Cp (t), a measuring time t, a time difference Δt between consecutive two data points, the particle disappearance coefficient β, and a chamber volume Vk, the following instantaneous emulation rate (hereinafter referred to as an instantaneous ER) PER(t) [1/s] is calculated.
The instantaneous ER PER (t) contains disappearance of particles in calculation thereof, and therefore, shows an amount of the dust emitted per unit time at the time t by the printer. When the above-described formula is subjected to time integration over a full printer time (range), a total amount of the dust emitted during the printing can be acquired.
(3-3-3) Relationship Between Instantaneous ER and Overcooling Degree ΔT
In part (a) of
Part (b) of
As shown in part (a) of
At time of 80%-emission of dust D:
elapsed time: 207 sec (147 sec after start of printing), overcooling degree ΔT: 120.9° C.,
At time of 90%-emission of dust D:
elapsed time: 256 sec (196 sec after start of printing), overcooling degree ΔT: 116.4° C., and
At time of 100%-emission of dust D:
elapsed time: 395 sec (335 sec after start of printing), overcooling degree ΔT: 109.6° C.
The above is the case where the surface temperature of the belt 105 is B, and also as regards the case of the temperature A, the elapsed time and the overcooling degree ΔT when the dust generation amount reaches 80%, 90% and 100% relative to the integrated amount of the entire dust generation amount by a similar method.
In part (b) of
First temperature ΔT_stop during 80%-emission of dust=120.9° C.
First temperature ΔT_stop during 90%-emission of dust=116.4° C.
First temperature ΔT_stop during 100%-emission of dust=109.6° C.
This value becomes substantially constant unless physical properties such as a boiling point of the wax of the toner and ease of agglomeration of a wax volatile matter are changed.
Further, in order to achieve the function of the printer, the physical properties of the wax have to fall within certain ranges. As a result, the above values are not largely changed even in the case where a constitution of the printer and the toner are changed. That is, when the overcooling degree ΔT is acquired in accordance with the measuring method and the measuring condition which are described above, it is possible to predict the time of the end of the dust emission on the basis of the value of the above-described ΔT_stop for a printer using toner different from the toner in this embodiment and for a printer with a different structure.
(4) Collecting Method of Dust D
Based on the property of the dust described above, a collecting method of the dust D (see
(4-1) Structure of Filter Unit
The filter unit 50 is positioned, as shown in
The filter unit 50 collects the dust D by sucking the air containing the dust D as shown in
The first fan 61 is an air sucking portion for sucking the air in the neighborhood of the sheet inlet 400 to the outside of the printer 1. The first fan 61 includes a fan air suction port 61a and an air discharge port 61b, and generates an air flow from the fan air suction port 61a toward the air discharge port 61b.
The fan air suction port 61a is an opening which is connected to an air discharge port 52e of the duct 52 and which is for sucking the air in the duct 52. The air discharge port 61b is an opening which is provided toward the outside of the printer 1 and which is for discharging the air, sucked through the fan air suction port 61a, toward the outside of the printer 1. The duct 52 is a guiding portion for guiding the air in the neighborhood of the sheet inlet 400 toward the outside of the printer 1. The duct 52 includes an air suction port 52a in the neighborhood of the sheet inlet 400 and the air discharge port 52e apart from the neighborhood of the sheet inlet 400.
The cooling duct 42 includes the fourth fan 64 (
The printer 1 of this embodiment uses a blower fan as the first fan 61 and uses an axial fan as the fourth fan 64. The blower fan is characterized by high static pressure and is capable of ensuring a certain volume of air (air suction amount) even when an air communication resistor such as the filter 51 exists. On the other hand, the cooling duct 42 is not provided with the air communication resistor such as the filter 51, and therefore, the axial fan characterized by a high air flow rate is suitable for the fourth fan 64.
The air suction port 52a is an operation positioned between the nip 101b and the transfer portion 12a and is provided toward the nip side. By such a constitution, the air suction port 52a is capable of receiving the dust D, as shown in
The air discharge port 52e is provided in a side surface, of a plurality of side surfaces of the duct 52, which is on an outside of the air suction port 52a with respect to a longitudinal direction thereof and which is a side opposite from the air suction port 52a. As described above, the air discharge port 52e is connected to the fan air suction port 61a.
Further, on the duct 52, the filter 51 is mountable so as to cover the air suction port 52a. Specifically, the duct 52 is provided with an edge portion 52c of the air suction port 52a and ribs 52b each including a curved portion 52d. When the filter 51 is fixed to the duct 52 so as to be supported by the edge portion 52c and the ribs 52b, the air suction port 52a is covered with the filter 51. The filter 51 in this embodiment is bonded to the edge portion 52c and the ribs 52b with no gap by a heat-resistant adhesive. For that reason, the air passing through the air suction port 52a always passes through the filter 51.
Further, the filter 51 in this embodiment is bonded along the curved portions of the edge portion 52c. In other words, the duct 52 holds the filter 51 in a curved state. At this time, the filter 51 curves in a direction in which a central portion with respect to a widthwise (short length) direction thereof is spaced apart from the nip 101b. In other words, the filter 51 projects toward an inside of the duct 52 at the widthwise central portion thereof
(4-1-1) Property of Filter
The filter 51 is a filtering member for filtering (collecting, removing) the dust D from the air passing through the air suction port 52a. In the case where the dust D resulting from the wax is collected, the filter 51 may desirably be an electrostatic nonwoven fabric filter. The electrostatic nonwoven fabric filter is prepared by forming fibers holding static electricity in a nonwoven fabric shape, and is capable of filtering the dust D at high efficiency.
The electrostatic nonwoven fabric filter is high in filtering performance as the fibers have high density. This relationship is ditto for the case where a thickness of the electrostatic nonwoven fabric is made thick. Further, when charging strength (strength of the static electricity) of the fibers is made high, the filtering performance can be improved while maintaining pressure loss at a constant level. The thickness and fiber density of the electrostatic nonwoven fabric and the charging strength of the fibers may desirably be appropriately set depending on the filtering performance required for the filter.
As regards the electrostatic nonwoven fabric used for the filter 51, the fiber density, the thickness and the charging strength are set so that when a passing air speed is 10 cm/s, an air communication resistance is about 40 Pa and a collecting percentage is about 95%. Incidentally, in the case where the toner in the discharged air is intended to be filtered, the electrostatic nonwoven fabric is used with the air communication resistance of 10 Pa or less at the passing air speed of 10 cm/s. Accordingly, it can be said that the filter 51 in this embodiment uses the electrostatic nonwoven fabric which is relatively large in air communication resistance.
As regards the air communication resistance of the electrostatic nonwoven fabric, 30 Pa or more and 150 Pa or less at a passing air speed at which use of the filter is assumed (5 cm/s or more and 70 cm/s or less in this embodiment) is desirable. When the air communication resistance of the electrostatic nonwoven fabric is larger than 150 Pa, it is difficult to obtain a necessary air speed in an air discharging fan mountable in the printer 1. When the air communication resistance of the electrostatic nonwoven fabric is less than 30 Pa, as regards the air speed of the air passing through the filter 51, non-uniformity is liable to occur with respect to the longitudinal direction.
An amount per unit time of the air passing through the filter 51 becomes larger as the air speed of the air passing through the filter 51 is higher (faster). However, the air speed of the air passing through the filter 51 is higher, the temperature of the air in the neighborhood of the sheet inlet 400 is liable to make lower. For that reason, in the case where collecting efficiency of the dust D is enhanced, the air speed of the air passing through the filter 51 may desirably be an appropriate speed.
Specifically, the air speed of the air when the air passes through the filter 51 may desirably be 5 cm/s or more and 70 cm/s or less. In the constitution of this embodiment, the collecting percentage of the dust D in the filter 51 is approximately 100% at the air speed of 5 cm/s and is about 70% at the air speed of 70 cm/s. For that reason, when the air speed falls within this range, the dust D can be collected at high efficiency. Incidentally, the first fan 61 is capable of adjusting the air speed of the air passing through the filter 51 in a range from 5 cm/s to 70 cm/s.
(4-2-1) Dimension of Filter
The filter 51 has an elongated shape, as shown in part (a) of
A region shown by a hatched line on the sheet P of part (b) of
Incidentally, the fixing device 103 in this embodiment feeds the sheet P on the basis of a center of the belt 105 with respect to the widthwise direction (center(-line) basis feeding). For that reason, in order to collect the dust D efficiently, it is desirable that the dust D is reliably collected at least in this region. Accordingly, a dimension Wf of the filter 51 may desirably be longer than the region Wp-max in the sheet P with a minimum width size. Or, the dimension Wf may desirably be longer than the sheet P with the minimum-sheet size.
Further, the dust D is capable of generating in the region Wp-max on the maximum-width-size sheet P capable of being introduced into the fixing device 103. For that reason, in order to reliably collect the dust D, it is desirable to collect the dust D in an entire region of this region. Accordingly, the dimension Wf of the filter 51 may desirably longer than the region Wp-max in the maximum-width-size sheet P. Or, the dimension Wf of the filter 51 may desirably be longer than the maximum-width-size sheet P.
In the case where the printer 1 is capable of utilizing sheet P with a plurality of width sizes and in the case where the sheet P with a width size highest in frequency of use is known, in the width Wp-max of the sheet P thereof, it is desirable to satisfy Wf>Wp-max.
Incidentally, in this embodiment, a maximum size of the usable sheet is an A3 size, and a minimum size of the usable sheet is a post card size. The width of the sheet P with respect to the feeding direction is 297 mm for the A3 size and is 100 mm for the postcard size. Wp-max described above is a region excluding a blank region (non-image region) of 3 mm at each of end portions from the entire region of the sheet P with respect to the widthwise direction. For that reason, the width Wp-max on the A3-size sheet P is 291 mm (=297−3−3), and the width Wp-max of the post card-size sheet p is 94 mm (=100−3−3).
(4-1-3) Arrangement of Filter
The filter 51 is disposed in the neighborhood of the belt 105 as shown in
Specifically, an interval (shortest distance) between the filter 51 and the belt 105 may desirably be 5 mm or more. On the other hand, in order to reliably collect the dust D, the filter 51 may desirably be disposed within 100 mm on the basis of the nip 101b.
As described above, when the filter 51 is mounted on the air suction port 52a of the duct 52, there is no need to employ a constitution of guiding the air toward the filter 51. For that reason, the filter unit 50 can be downsized.
Further, as described above, when the filter 51 extending in the longitudinal direction is disposed in the neighborhood of the belt 105, the passing air speed of the air in the air suction port 52a of the duct 52 becomes uniform with respect to the longitudinal direction. In other words, by disposing the filter 51 which is the air communication resistor on the air suction port 52a, an entire region of a rear surface region of the filter 51 can be maintained at a certain negative pressure. That is, the negative pressures at points 53a, 53b, 53c shown in part (b) of
This is because the air communication resistance of the filter 51 is considerably larger than the air communication resistance in the duct 52. When the negative pressures at the points 53a, 53b and 53c are at the same level, the air speed of air F4 sucked by the filter 51 is uniformized over the entire surface of the filter 51. As a result of uniformization of the air speed, the filter unit 50 is capable of collecting efficiently (at a minimum air flow rate) the dust D generating from the belt 105.
When the air suction amount by the filter unit 50 is small, an amount of the air flowing into the neighborhood of the belt 105 also becomes small. For that reason, a lowering in temperature in the neighborhood of the belt 105 can be made small. As a result, generation of the dust D can be suppressed, so that collection efficiency of the dust D is also improved. Further, the temperature lowering of the belt 105 is suppressed, and therefore it is also advantageous for energy saving.
(4-1-4) Shape of Filter
As described above, the central portion of the filter 51 with respect to the short length direction is curved in the direction in which the filter 51 is spaced away from the nip 101b (
(4-2) Air Flow Constitution
Next, an air flow in the printer 1 will be described. In the case where the dust D is efficiently collected, the air flow in the printer 1, particularly the air flow at a peripheral portion of the fixing device 103 may desirably be controlled appropriately. In the following, a constitution relating to the air flow at the peripheral portion of the fixing device 103 will be specifically described.
(4-2-1) First Fan
As described above, when the air flow rate of the first fan 61 which is the air sucking portion is large, the air can be sucked in a large amount, while the temperature of the air in the neighborhood of the sheet inlet 400 is liable to be lowered. The lowering in temperature of the air increases the overcooling degree ΔT and promotes the dust generation. For that reason, the air flow rate of the first fan 61 is needed to be appropriately set. The air flow rate from 20 L/min to 100 L/min is a proper range, and the printer 1 of this embodiment is set at 50 L/min (in air flow rate).
Incidentally, the filter 51 is deteriorated by sucking the dust D, paper powder generating from the sheet P and scattered toner scattering in a very small amount from the unfixed image on the sheet P during feeding. This is because deposition of the dust D, the paper powder and the scattered toner onto the filter 51 lowers the charging strength of the electrostatic nonwoven fabric which is the material of the filter 51. For that reason, the first fan 61 may desirably be at rest in the case where the dust D does not generate.
(4-2-2) Second Fan and Third Fan
When the sheet P containing water content is heated by the fixing device 103, water vapor generates from the sheet P. By this water vapor, a space C (
The second fan 62 is a fan for preventing the occurrence of the dew condensation on the guiding member 15. The second fan 62 sucks the air from the outside of the printer 1 and blows the air against the guiding member 15, and thus lowers the humidity of the space C.
Specifically, by the air blowing from the second fan 62, the water vapor in the neighborhood of the guiding member 15 diffuses to the peripheral portion of the space C, and therefore, local temperature rise in the neighborhood of the guiding member 15 is suppressed. Even in the case where only the second fan 62 is used, the dew condensation on the guiding member 15 can be suppressed to some extent.
However, designation of discharge of the water vapor is only a gap existing in the peripheral portion of the discharging roller pair 14, so that the humidity in the space C gradually increases. Therefore, in this embodiment, by the third fan 63, the humidity in the neighborhood of the guiding member 15 is discharged to the outside of the image forming apparatus.
(4-2-4) Fourth Fan
The fourth fan 64 which is the cooling air sucking portion has action of discharging hot air in a space between the fixing device 103 and the transfer portion 12a in order to prevent temperature rise in the neighborhood of the transfer portion 12a. When the temperatures of the transfer belt 10c and the secondary transfer roller 12 which constitute the transfer portion 12a excessively increase, the toner forming the unfixed image becomes soft and has the influence on the transfer process, and therefore, the fourth fan 64 discharges the hot air of the peripheral portion of these members. The air flow rate of the fourth fan 64 is set at about 500 L/min larger than 50 L/min of the first fan 61.
The suction port 42a of the cooling duct (heat discharging duct) 42 positions in the neighborhood of a longitudinal central portion of the belt 105 as shown in
Incidentally, when the overcooling degree ΔT is large, it is understood from the above-described formula (1) that the temperature of the peripheral portion of the belt 105 becomes low. For that reason, even if the fourth fan 64 is stopped when the overcooling degree ΔT is large, there is no problem.
(4-3) Control Flow
In this embodiment, by controlling the first fan 61 and the fourth fan 64 depending on the overcooling degree ΔT, while suppressing the generation of the dust D, the dust D is effectively removed by the filter 51, and deterioration of the filter 51 is prevented. Further, the temperature rise of the transfer portion 12a is also prevented.
In the following, operations of the first fan 61 and the fourth fan 64 will be described on the basis of
(Surface temperature Tb of belt 105)>Tws−20° C. formula (2)
(Dust generation temperature Tws of toner)−(spatial temperature Ta of measuring point Tp)>first temperature formula (3)
The formula (2) is a formula for discriminating whether or not the surface temperature at which the dust is capable of being generated. In part (a) of
The peripheral (ambient) temperature of the belt 105 lowers by sucking the peripheral air flow (air current) with rotation of the belt 105 as described above. The overcooling degree is increased by the temperature lowering, and therefore, the dust generates at a temperature 20° C. lower than the temperature in the device of part (a) of
The formula (3) is a formula for discriminating whether or not the overcooling degree ΔT (=Tws−Ta) defined by the formula (1) satisfies an emission end condition of the dust. When this formula is satisfied, discrimination that there is no emission of the dust is made. In part (b) of
In this embodiment, actuations of the first fan 61 and the fourth fan 64 are switched when the emission of the dust D is completed by 100%, and therefore, the first temperature of the formula (3) is 109° C. However, in many cases, when the dust D is discharged by 80% or more, dust contamination of a component part such as the guiding member 15 can be sufficiently alleviated in many instances. For that reason, a first temperature as a threshold temperature may only be required to be appropriately set in a range of 109° C. or more and 121° C. or less in the case where the measuring point Tp is in a position of 6 mm from the belt (rotatable heating member) 105 toward the direction of the transfer portion (first position) 12b.
In the case where the formula (2) and the formula (3) described above are satisfied, a generation condition of the dust D is satisfied, so that the step goes to S104 and the first fan 61 is actuated. By the actuation of the first fan 61, the dust D can be removed immediately after a start of the printing. Incidentally, at this time, the fourth fan 64 becomes non-actuation (non-operation). This is because discharge of the dust D by the actuation of the fourth fan 64 without through the filter 51 is prevented.
Parts (a), (b) and (d) of
Then, after the printing is started (S106), the control circuit portion A discriminates whether or not the following formula (4) is satisfied.
Ta≥second temperature formula (4)
The second temperature is set at 90° C. as shown in part (c) of
Although the first fan 61 is small in air flow rate compared with the fourth fan 64, the first fan 61 can suck the hot air in the entire longitudinal region of the belt 105, and therefore the cooling efficiency is high. By the actuation of the first fan 61, deterioration of the filter 51 advances, but in this embodiment, image quality maintenance is prioritized and the first fan 61 is actuated. In the case where the formula (4) is not satisfied in S107, the step goes to S109. Otherwise, the step goes to S108.
In S109, similar to S103, whether or not the formula (2) and the formula (3) are satisfied is discriminated. In the case of satisfaction, the case is regarded as that the dust D generates, and the first fan 61 is actuated. The fourth fan 64 is non-actuation (S110). In the case where the formula (2) and the formula (3) are not satisfied, the step goes to S111, and the first fan 61 is non-actuation and the fourth fan 64 is actuation, so that the hot air of the peripheral portion of the transfer portion 12a is discharged (S111).
During the printing, the formula (2) and the formula (3) are satisfied at the time when an elapsed time after the start of the printing reaches 207 sec in
After S110 and S111, whether or not a printing end condition is satisfied is discriminated (S112). In the case where the printing end condition is not satisfied, the step returns to S107, and discriminations of the formula (2), the formula (3) and the formula (4) are repeated. Otherwise, the printing is ended (S113).
The control of the above-described first fan 61 in this embodiment 1 is summarized as follows.
When
a surface temperature of the belt (rotatable heating member) 105 is Tb (° C.),
a dust generation temperature of the toner is Tws (° C.), and
a spatial temperature detected by the temperature detecting means 67 is Ta (° C.),
the control circuit portion A causes the first fan 61 to actuate at predetermined first efficiency in the case where the following condition formulas (1) and (2) are satisfied, and causes the first fan 61 to be non-actuation or to actuate at predetermined second efficiency lowered in efficiency than the predetermined first efficiency in the case where the condition formulas (1) and (2) are not satisfied.
Tb≥Tws−Z formula (A)
where Z is a preset adjusting temperature value (° C.), and
Tws−Ta>first temperature formula (B)
where the first temperature is a preset threshold temperature (° C.).
The printer 1 of this embodiment is capable of preventing the deterioration of the filter 51 by the above-described constitution and operation to suppress actuation of the first fan 61 while removing the dust D by the filter 51. That is, the dust generation is predicted, and by actuating the filter 51 only during the dust generation, lifetime elongation of the filter 51 can be realized. Further, the fourth fan 64 is actuated when the overcooling degree ΔT sufficiently becomes large and there is no dust generation, and therefore an effect of the filter 51 can be maximized.
(5) Other Matters
In the above, the present invention was described using the embodiment 1, but the present invention is not limited to the constitution described in embodiment 1. Numerical values such as the dimension exemplified in the embodiment are an example and may appropriately be set in a range in which the effect of the present invention is obtained. Further, within the range in which the effect of the present invention is obtained, a part of the constitution and control described in the embodiment may also be replaced with other constitutions and pieces of control which have similar functions.
For example, the temperature detecting means 67 may also be a temperature sensor provided at the measuring point Tp. The first temperature may also be deviated from the range from 109° C. to 121° C. In the case where the overcooling degree ΔT exceeds 121° C., dust emission is below 80%, but may only be required that the contamination of the guiding member 15 can be suppressed to a practically sufficient level. In the case where Ta and Tb do not satisfy the formula (2) and the formula (3), the first fan 61 may also be actuated at a low duty. In the case where Ta and Tb become satisfy the formula (2) and the formula (3), the duty of the fourth fan 64 is not increased stepwise, but may also be increased linearly.
As described in the embodiment 1, on the side upstream of the fixing device 103, the temperature increases when the printing progresses, so that the transfer portion 12a positioned on the side upstream of the fixing device 103 increases in temperature and the toner forming the unfixed image melts and has the influence on the transfer process. For that reason, the fourth fan (transfer portion cooling fan) 64 is provided and cools the side upstream of the fixing device 103. However, the side upstream of the fixing device 103 is cooled by the fourth fan 64, so that an environment in which the dust is liable to generate is formed.
Therefore, by controlling the operation of the fourth fan 64, the dust generation is suppressed, and further, an effect of the filter 51 for removing the dust can be increased.
That is, when
a surface temperature of the belt (rotatable heating member) 105 is Tb (° C.),
a dust generation temperature of the toner is Tws (° C.), and
a spatial temperature detected by the temperature detecting means 67 is Ta (° C.),
the control circuit portion A causes fourth fan (cooling fan) 64 to be non-actuation or to actuate at predetermined second efficiency lowered in efficiency from predetermined first efficiency in the case where the following condition formulas (A) and (B) are satisfied.
Tb≥Tws−Z formula (A)
where Z is a preset adjusting temperature value (° C.), and
Tws−Ta>first temperature formula (B)
where the first temperature is a preset threshold temperature (° C.).
The control circuit portion A causes the first fan (dust collecting fan) 61 to be non-actuation when Ta (° C.) and Tws (° C.) satisfy the following condition formulas (C) and (D). Or, the control circuit portion A causes the efficiency to actuate at predetermined second efficiency lowered in efficiency from predetermined first efficiency. At the same time, the control circuit portion A causes the fourth fan (cooling fan) 64 to actuate.
Tws−Ta≤first temperature formula (C), and
Ta≤second temperature formula (D),
where the second temperature is a preset threshold temperature lower than the first temperature.
When Ta (° C.) and Tws (° C.) satisfy, the following condition formulas (E) and (F), the control circuit portion A causes the first fan (dust collecting fan) 61 and the fourth fan (cooling fan) 64 to actuate.
Tws−Ta≤first temperature formula (E)
Ta>second temperature formula (F)
A feature of this embodiment 2 is in that the operation of the fourth fan 64 is controlled by predicting the generation of the dust. By this, suppression of the dust generation and an increase in effect of the filter for removing the dust are realized. A hardware constitution and a software constitution of the printer 1 are similar to those of the embodiment 1 (all figures), and therefore, will be omitted from repetition description. . . .
Also in the printer 1 of this embodiment 2, similarly as in the embodiment 1, may also be replaced with other constitutions having similar functions. For example, the temperature detecting means 67 may also be a temperature sensor provided at the measuring point Tp. The first temperature may also be deviated from the range from 109° C. to 121° C. In the case where the overcooling degree ΔT exceeds 121° C., dust emission is below 80%, but may only be required that the contamination of the guiding member 15 can be suppressed to a practically sufficient level.
1) In the above, the embodiments of the present invention was described, but the constitution according to the present invention are not limited to the embodiments. For example, the fixing device 103 may also be a heating roller type or may also be a type utilizing electromagnetic induction heating.
2) In the embodiments, the fixing device in which the unfixed toner image is heat-fixed on the sheet was described as an example, but the present invention is not limited to this, and in order to improve glossiness (gloss) of the image, a device in which a toner image once fixed or temporarily fixed on the sheet is heated again may also be used. This case is also called the fixing device.
3) In the embodiments, as the image forming apparatus 1, a multi-function printer provided with a plurality of drums 6 was described. However, the present invention is also applicable to an image forming apparatus mounted in a monochromatic multi-function printer and a single-function printer which include a single drum 6.
4) Sheet feeding is not limited to the center basis feeding. The sheet feeding may also be one-side basis feeding.
According to the present invention, there is provided the image forming apparatus of which dust removing power is maintained for a long term.
The present invention is not limited to the above-described embodiments, but can be variously changed and modified without departing from the spirit and the scope of the present invention. Accordingly, the following claims are attached for making the scope of the present invention public.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2018-084970 | Apr 2018 | JP | national |
This application is a continuation of International Patent Application No. PCT/JP2019/018651, filed Apr. 25, 2019, which claims the benefit of Japanese Patent Application No. 2018-084970, filed Apr. 26, 2018. The foregoing applications are incorporated herein by reference in their entireties.
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| Office Action dated Jan. 25, 2022 in counterpart Japanese Application No. 2018-084970, together with English translation thereof. |
| Number | Date | Country | |
|---|---|---|---|
| 20210055678 A1 | Feb 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2019/018651 | Apr 2019 | US |
| Child | 17077422 | US |
