JP2011013669A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can prevent troubles from occurring due to the abutment of a heat-receiving unit on a part to be cooled.SOLUTION: The image forming apparatus includes: an image carrier 2; a developing unit 4 having a developer carrier 40 for supplying a developer to the image carrier 2; a positioning means for positioning the developing unit 4 onto the image carrier 2; and a cooler having the heat-receiving unit 61 that is arranged to abut on the developing unit 4. The direction in which the heat-receiving unit 61 abuts on the developing unit 4 is substantially orthogonal to the direction in which the image carrier 2 faces the developer carrier 40.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine of these.

  It is generally known that in an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a complex machine of these, the temperature of the atmosphere in the apparatus is increased by radiant heat from an apparatus or a unit provided in the apparatus. For example, when a heat fixing type fixing device is used as a fixing device for fixing an image on recording paper, the air in the device is warmed by the heat of the fixing device. Further, the developing unit is provided with a developer stirring member that stirs the developer, a developer regulating member that regulates the layer thickness of the developer carried on the developer carrier, and the like. The air in the apparatus is also warmed by frictional heat due to sliding contact with the developer and frictional heat due to sliding contact between the developers.

  When the temperature of the atmosphere in the apparatus rises, the charge amount of the toner decreases, the toner adhesion amount increases, and a predetermined image density may not be obtained. Further, when the toner is melted due to the temperature rise in the atmosphere in the apparatus, the melted toner is fixed to the developer regulating member, the developer carrier or the image carrier, and streaky density unevenness may occur in the image. In recent years, in order to reduce energy consumption at the time of image fixing, a toner having a low melting temperature may be used. In particular, when such a toner having a low melting temperature is used, the toner easily melts. The density unevenness due to the fixing of the toner tends to occur.

  The image forming apparatus is generally provided with a cleaning unit for removing the toner remaining on the photosensitive member as the image carrier and the intermediate transfer belt. The cleaning unit has a cleaning blade that abuts on the surface of the image carrier, and the toner remaining on the surface is scraped off by the cleaning blade as the image carrier rotates. Thereafter, the scraped toner is conveyed to a collecting unit outside the unit by a conveying screw or the like provided in the cleaning unit.

  However, when the temperature in the cleaning unit rises due to heat generated by the waste toner conveyance operation, heat of the fixing device, or the like, the toner may be melted and fixed in the unit. When the toner is fixed and aggregated, there is a possibility that the toner transportability is lowered.

  In order to suppress the harmful effects caused by the temperature increase in the apparatus, it is necessary to suppress an excessive temperature increase in the developing unit and the cleaning unit. For this reason, conventionally, an image forming apparatus including a cooling device for cooling a developing unit or the like has been proposed (for example, see Patent Documents 1 and 2 below). The cooling device includes an air cooling type and a liquid cooling type.

  The air-cooled cooling device has, for example, an air-cooling fan, and the outside air taken in by the air-cooling fan is sent to a blower duct (air passage) formed around the developing unit so that the temperature of the developing unit does not increase excessively. (See Patent Document 1). However, due to the recent demand for downsizing of the apparatus, there is no room for arranging the air cooling fan and the air duct, and it is difficult to secure the installation space for them. In addition, when an airflow is generated around the air by air cooling, dust such as toner is generated, causing problems such as staining the inside and outside of the apparatus.

  On the other hand, the liquid cooling type cooling device includes, for example, a heat receiving portion that forms a cooling flow path that contacts the developing unit and passes the cooling liquid therein, a heat radiating portion that radiates heat of the cooling liquid, and a heat receiving portion. A circulation pipe (flow path) that circulates the cooling liquid between the heat radiating unit and a pump that sends out the cooling liquid (see Patent Document 2). The coolant is circulated by the pump, so that the heat of the developing unit is taken from the heat receiving portion to be cooled. Further, by providing a pressure lever or the like that presses the heat receiving portion against the developing unit, it is possible to increase the contact area (heat receiving area) between the heat receiving portion and the developing unit, thereby improving the cooling efficiency. Such a liquid cooling type cooling device can cool more efficiently than an air cooling type cooling device. In addition, since the liquid-cooled circulation pipe requires less installation space than the air-cooled air duct, the liquid-cooled circulation pipe can be arranged in an image forming apparatus that has less space around the developing unit due to downsizing.

  By the way, when a developing unit using a two-component developer including toner and carrier is used, as shown in FIG. 21, a photosensitive member 100 as an image carrier and a developer carrier included in the developing unit 200 are used. The developing rollers 210 are arranged at a constant interval, that is, with a developing gap G therebetween. Since this development gap G is extremely important in forming high image quality, much attention has been paid to the management of the development gap G. Accordingly, the positioning of the developing unit 200 (or developing roller 210) with respect to the photoreceptor 100 must be performed with high accuracy.

  However, as shown in FIG. 21, when the heat receiving unit 300 for cooling the developing unit 200 is brought into contact or pressure contact in the direction indicated by the arrow in the drawing, the developing unit 200 is brought into contact with the photoreceptor 100 by the contact force of the heat receiving unit 300. Receives force in the direction of approaching. As a result, the development gap G may change and the predetermined image quality may not be maintained.

  Further, when the heat receiving portion is brought into contact or pressure contact with the unit in order to cool the cleaning unit that cleans the image carrier, the contact pressure or contact angle of the cleaning blade with respect to the image carrier is caused by the contact or pressure contact. If it changes, there is a possibility that the cleaning property may be deteriorated or the cleaning function cannot be exhibited. For example, if the contact pressure of the cleaning blade decreases, the toner on the image carrier cannot be sufficiently scraped off, so that the formed image becomes dirty or the device stops due to clogging with dust when used repeatedly. There is a fear. On the other hand, when the contact pressure increases, the cleaning blade may bend, and the cleaning blade and the image carrier (intermediate transfer belt) may be damaged.

  Therefore, in view of such circumstances, an object of the present invention is to provide an image forming apparatus capable of preventing the adverse effects caused by bringing the heat receiving portion into contact with the cooled portion.

  The invention of claim 1 includes an image carrier, a development unit having a developer carrier for supplying a developer to the image carrier, positioning means for positioning the development unit with respect to the image carrier, An image forming apparatus including a cooling device having a heat receiving portion disposed so as to be able to contact the developing unit, wherein the contact direction between the heat receiving portion and the developing unit is determined according to the image carrier and the developer carrier. It is comprised so that it may cross substantially orthogonally to the opposing direction.

  In the present invention, the abutting direction of the heat receiving portion and the developing unit and the opposing direction of the image carrier and the developer carrying member are configured to be substantially orthogonal to each other, so that the developing unit is mainly brought into contact with the heat receiving portion. The direction of the force received can be made to act in a direction substantially orthogonal to the facing direction. As a result, even when the developing unit is displaced by contact with the heat receiving portion, the positional relationship between the image carrier and the developer carrier in the facing direction is not easily affected. Therefore, since the positional relationship between the image carrier and the developer carrier in the facing direction can be maintained with high accuracy, high-quality image formation is possible. Further, in the present invention, since the contact direction and the facing direction need only be substantially orthogonal, a complicated mechanism for maintaining the position of the developing unit with high accuracy is not necessary. For this reason, the structure can be simplified and the apparatus can be miniaturized.

  A second aspect of the present invention is the image forming apparatus according to the first aspect, further comprising a pressurizing unit that pressurizes the heat receiving portion against the developing unit.

  By pressurizing the heat receiving portion to the developing unit by the pressurizing means, a large contact area of the heat receiving portion with the developing unit can be ensured, and the cooling effect is improved. As described above, when the heat receiving portion is pressurized to the developing unit, the developing unit is easily displaced by the pressing force from the heat receiving portion, but as described above, the contact direction between the heat receiving portion and the developing unit, and the image By configuring the opposing direction of the carrier and the developer carrier to be substantially orthogonal to each other, the positional relationship in the opposing direction between the image carrier and the developer carrier can be maintained with high accuracy.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the developing unit includes a plurality of the developing units, and the cooling device has one heat receiving portion that can contact each developing unit.

  The configuration in which one heat receiving portion is brought into contact with each developing unit can simplify the structure and reduce the number of parts compared to the configuration in which one heat receiving portion is brought into contact with each developing unit one by one. Can be planned. In this case, since the rigidity of the entire apparatus, particularly the rigidity of the image forming portion is improved, the image forming ability can be stabilized and the reliability is improved.

  A fourth aspect of the present invention is the image forming apparatus according to any one of the first to third aspects, further comprising: a latent image forming unit that forms an electrostatic latent image on the image carrier; The heat receiving portion can be brought into contact with both of the developing units.

  By bringing the heat receiving portion into contact with the latent image forming unit in addition to the developing unit, the latent image forming unit can be cooled together with the developing unit. Thereby, image defects such as color misregistration can be more effectively suppressed, and high-quality image formation is possible.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, a plurality of the developing units are arranged in parallel in the vertical direction, and the cooling capacity of the cooling device for each developing unit is set to the upper side. The developing unit arranged in the above is configured to be higher.

  Air warmed in the image forming apparatus accumulates in the upper part of the apparatus. Accordingly, when a plurality of developing units are arranged in the vertical direction, the temperature of the developing units disposed on the upper side is more likely to rise. Therefore, the higher the developing unit disposed on the upper side, the higher the cooling effect of the heat receiving section, so that each developing unit can be cooled to a more uniform temperature regardless of the position of the developing unit, and high-quality image formation can be achieved. It becomes possible to carry out stably.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the developing unit includes a plurality of the developing units and a fixing device that fixes an image on a recording medium by heat. The cooling capacity of the developing device is configured such that the developing unit disposed closer to the fixing device has a higher cooling capacity.

  The developing unit closer to the fixing device tends to have a higher temperature. For this reason, the higher the cooling effect of the heat receiving portion, the more the development unit disposed closer to the fixing device, it is possible to cool each development unit to a more uniform temperature regardless of the placement position. It is possible to stably perform image formation.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, a plurality of the image carriers and the developing units are provided, and images transferred from the image carriers are recorded. An intermediate transfer rotator for transferring to a medium, a fixing device for fixing an image on the recording medium by heat, and a duplex printing transport device for transporting the fixed recording medium to the intermediate transfer rotator again for duplex printing. The cooling capacity of the cooling device for each developing unit is configured such that the developing unit disposed upstream in the rotation direction starts from the transfer position of the intermediate transfer rotator to the recording medium. is there.

  When performing duplex printing, the recording medium heated by the fixing device is conveyed again to the image transfer position of the intermediate transfer rotator, where it contacts the intermediate transfer rotator, so that the temperature of the intermediate transfer rotator rises. Then, the temperature increasing portion of the intermediate transfer rotator approaches the developing unit as the intermediate transfer rotator rotates, whereby the temperature of the developing unit increases. At this time, the temperature of the developing unit that is earlier in the order in which the temperature rising portion of the intermediate transfer member approaches is more likely to rise. In other words, the temperature rise becomes more remarkable as the developing unit is disposed upstream in the rotation direction starting from the transfer position of the intermediate transfer rotator to the recording medium. Therefore, as the developing unit disposed on the upstream side in the rotation direction, by increasing the cooling effect of the heat receiving portion, each developing unit can be cooled to a more uniform temperature regardless of the position of the developing unit. High-quality image formation can be stably performed.

  The invention of claim 8 is the image forming apparatus according to any one of claims 1 to 7, wherein the cooling device conveys the cooling liquid, the heat receiving part, a cooling part for cooling the cooling liquid, and the cooling liquid. And a coolant transporting means for transporting the coolant from the cooling unit to the heat receiving unit via the channel.

  The liquid cooling type cooling device as described above has an advantage that the installation space can be made smaller than that of the air cooling type cooling device. For this reason, a liquid cooling type cooling device is suitable for an image forming apparatus having a high density inside for downsizing. In general, the constant volume heat capacity of water is 3000 times or more that of air. For this reason, the liquid cooling type cooling device can transfer a large amount of heat at a small flow rate, and can be cooled more efficiently than the air cooling type cooling device.

  According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the developing unit and the cooling device are integrally detachable from the main body of the image forming apparatus.

  Since the developing unit and the cooling device can be integrally attached and detached, maintenance and the like of the developing unit and the cooling device are facilitated. Moreover, since it is not necessary to separate the components constituting the cooling device at the time of attachment and detachment, there is no risk of leakage of the coolant from the separation portion, and the reliability is improved.

  According to a tenth aspect of the present invention, in the image forming apparatus according to the eighth or ninth aspect, a plurality of the developing units are provided, and the cooling liquid is conveyed to the heat receiving portion in order from the developing units that are likely to increase in temperature. It is what.

  By transporting the cooling liquid to the heat receiving unit in order from the developing unit that tends to increase in temperature, the cooling effect of the heat receiving unit can be enhanced as the developing unit tends to increase in temperature. Thereby, each developing unit can be cooled to a more uniform temperature, and high-quality image formation can be performed stably.

  The invention according to claim 11 is the image forming apparatus according to any one of claims 8 to 10, wherein the developing unit includes a plurality of the developing units, and the temperature of the developing unit that is likely to increase in temperature has a contact area with the heat receiving portion. It is configured to be enlarged.

  By increasing the contact area with the heat receiving part, the cooling effect by the heat receiving part can be enhanced as the developing unit tends to rise in temperature. Thereby, each developing unit can be cooled to a more uniform temperature, and high-quality image formation can be performed stably.

  According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the eighth to eleventh aspects, the cooling liquid that is provided with a plurality of the developing units and that is more likely to increase in temperature is conveyed to the heat receiving portion. The flow rate per unit time is increased.

  By increasing the flow rate of the cooling liquid conveyed to the heat receiving unit per unit time, the cooling effect by the heat receiving unit can be enhanced as the developing unit tends to rise in temperature. Thereby, each developing unit can be cooled to a more uniform temperature, and high-quality image formation can be performed stably.

  According to a thirteenth aspect of the present invention, in the image forming apparatus according to any one of the eighth to twelfth aspects, a plurality of the developing units are provided, and the cooling units are arranged one by one so as to correspond to the developing units. The developing unit that is more likely to rise in temperature is configured to have a higher cooling effect of the corresponding cooling unit.

  By configuring the developing unit that tends to increase in temperature so that the cooling effect of the corresponding cooling unit is enhanced, each developing unit can be cooled to a more uniform temperature, and high-quality image formation is stably performed. be able to.

  According to a fourteenth aspect of the present invention, in the image forming apparatus according to the thirteenth aspect, the cooling unit includes a radiator that dissipates the cooling liquid, and the developing unit that easily rises in temperature increases the size of the corresponding radiator. It is a thing.

  By increasing the size of the corresponding radiator, the amount of heat radiation of the radiator can be increased as the developing unit is likely to rise in temperature. Thereby, each developing unit can be cooled to a more uniform temperature, and high-quality image formation can be performed stably.

  According to a fifteenth aspect of the present invention, in the image forming apparatus according to the thirteenth or fourteenth aspect, the cooling unit includes a radiator that dissipates the cooling liquid and a cooling fan that blows air to the radiator, and the temperature is likely to increase. The developing unit is configured to increase the air volume of the corresponding cooling fan.

  By increasing the air flow rate of the corresponding cooling fan, the heat radiation amount of the radiator can be increased for the developing unit whose temperature rises more easily. Thereby, each developing unit can be cooled to a more uniform temperature, and high-quality image formation can be performed stably.

  According to a sixteenth aspect of the present invention, there is provided an image carrier, a cleaning unit having a cleaning member that contacts and cleans the image carrier, positioning means for positioning the cleaning unit with respect to the image carrier, and the cleaning unit. And a cooling device having a heat receiving portion disposed so as to be able to come into contact with the image forming apparatus. The contact direction between the heat receiving portion and the cleaning unit is determined by the contact between the image carrier and the cleaning member. It is configured to be substantially orthogonal to the direction.

  In the present invention, the contact direction between the heat receiving portion and the cleaning unit is configured to be substantially orthogonal to the contact direction between the image carrier and the cleaning member, so that the cleaning unit is brought into contact with the heat receiving portion. The direction of the force mainly received can be made to act in a direction substantially orthogonal to the contact direction of the cleaning member. As a result, even if the cleaning unit is displaced due to contact with the heat receiving portion, the positional relationship in the contact direction between the image carrier and the cleaning member is not easily affected. Therefore, the positional relationship in the contact direction between the image carrier and the cleaning member can be maintained with high accuracy, and the cleaning performance can be maintained well. Further, in the present invention, since the contact direction of the heat receiving portion and the contact direction of the cleaning member need only be substantially orthogonal, a complicated mechanism or the like for maintaining the position of the cleaning unit with high accuracy is not necessary. . For this reason, the structure can be simplified and the apparatus can be miniaturized.

  According to the present invention, the positional relationship in the facing direction or the contact direction between the image carrier and the cooled portion (developing unit or cleaning unit) can be maintained with high accuracy with a simple configuration. It is possible to achieve high-quality image formation while achieving high speed.

1 is a schematic diagram illustrating an overall configuration of an intermediate transfer tandem type color image forming apparatus according to Embodiment 1 of the present invention. FIG. FIG. 3 is a front perspective view of the image forming unit. It is a back side perspective view of an image forming unit. It is a schematic block diagram which shows the structure which provided the metal roller in the both ends of the developing roller. It is a schematic plan view of a cooling device. It is the schematic of a heat receiving part. It is the schematic of the cooling device which concerns on Example 2 of this invention. It is the schematic of the cooling device which concerns on Example 3 of this invention. It is the schematic of the cooling device which concerns on Example 4 of this invention. FIG. 10 is a schematic diagram illustrating a part of an image forming apparatus according to Embodiment 5 of the present invention. FIG. 9 is a schematic diagram illustrating a part of an image forming apparatus according to Embodiment 6 of the present invention. It is the schematic which shows the modification of the said Example 6. FIG. FIG. 10 is a schematic diagram illustrating a part of an image forming apparatus according to Embodiment 7 of the present invention. It is the schematic which shows the modification of the said Example 7. FIG. It is the figure which conceptualized and showed the structure which concerns on Example 8 of this invention. It is the figure which showed one image forming unit among the several image forming units shown in FIG. It is a figure for demonstrating the contact direction of a heat receiving part and a developing unit, (a) shows an example of the contact state of a heat receiving part and a development unit, (b) is another example of the said contact state. Show. It is the figure which showed one image forming unit among the several image forming units shown in FIG. FIG. 10 is a schematic diagram illustrating a part of an image forming apparatus according to Embodiment 9 of the present invention. 1 is a diagram illustrating a direct transfer tandem color image forming apparatus. FIG. FIG. 10 is a diagram illustrating a contact state between a heat receiving unit and a developing unit in a conventional image forming apparatus.

FIG. 1 is a schematic diagram of an image forming apparatus according to Embodiment 1 of the present invention.
The image forming apparatus shown in FIG. 1 is a color image forming apparatus, and four image forming units 10Y, 10M, and 10C that form images of different colors of yellow, magenta, cyan, and black corresponding to color separation components of a color image. , 10K are provided in parallel. Each of the image forming units 10Y, 10M, 10C, and 10K includes drum-shaped photosensitive members 2Y, 2M, 2C, and 2K as image carriers, charging units 3Y, 3M, 3C, and 3K as charging means, and developing means. The two-component developing type developing units 4Y, 4M, 4C, and 4K and the drum cleaning units 5Y, 5M, 5C, and 5K as cleaning means are integrally accommodated in a frame (not shown). These image forming units 10Y, 10M, 10C, and 10K are configured to be detachable from the main body of the image forming apparatus so that consumable parts can be replaced at a time. A reading device 7 for reading a document is disposed on the upper part of the image forming apparatus.

  Above the image forming unit 1, an exposure unit 6 as a latent image forming unit is disposed. Laser light emitted from the exposure unit 6 is applied to each of the photoreceptors 2Y, 2M, 2C, and 2K. A transfer unit 8 is disposed below the image forming unit 1. The transfer unit 8 includes an intermediate transfer belt 9 as an intermediate transfer rotator, four primary transfer rollers 11Y, 11M, 11C, and 11K as primary transfer means. The intermediate transfer belt 9 is stretched around a plurality of rollers, and when one of these rollers is driven to rotate as a driving roller, the intermediate transfer belt 9 is configured to run around (rotate) in the direction of the arrow in the figure. ing. The four primary transfer rollers 11Y, 11M, 11C, and 11K are in contact with the inner peripheral surface of the intermediate transfer belt 9 at positions facing the photoconductors 2Y, 2M, 2C, and 2K. By contact of these primary transfer rollers 11Y, 11M, 11C, and 11K with the intermediate transfer belt 9, the intermediate transfer belt 9 comes into contact with each of the photoreceptors 2Y, 2M, 2C, and 2K, and forms a primary transfer nip at the contact portion. ing.

  Below the transfer unit 2, a secondary transfer device 14 as a secondary transfer unit is disposed. The secondary transfer device 14 includes a secondary transfer roller 12 to which a voltage is applied by a power source (not shown), and the secondary transfer roller 12 is a counter roller 13 that is one of the rollers that span the intermediate transfer belt 9. In contact with the outer peripheral surface of the intermediate transfer belt 9. A secondary transfer nip is formed at a contact portion where the secondary transfer roller 12 and the intermediate transfer belt 9 are in contact with each other.

  On the right side of the secondary transfer device 14, a paper feed unit 17 that feeds recording paper to the secondary transfer device 14 one by one from a paper feed cassette (not shown) containing recording paper is disposed. A fixing device 15 for fixing an image on a recording sheet as a recording medium is disposed on the left side of the secondary transfer device 14 in the drawing. A conveyance belt 16 for conveying the recording paper to the fixing device 15 is disposed between the fixing device 15 and the secondary transfer device 14. Further, on the left side of the drawing of the fixing device 15, a paper discharge unit 19 that conveys the recording paper that has passed through the fixing device 15 to the outside of the apparatus or the conveyance device 18 for duplex printing is disposed.

  The basic operation of the image forming apparatus will be described below with reference to FIG. In the following description, the subscripts Y, M, C, and K representing the identification of each color of yellow, magenta, cyan, and black are omitted for convenience.

  First, a document is set on a document table or contact glass (not shown), and image information of the document is read by the reading device 7. In parallel with the reading of the original, each photoconductor 2 is rotated counterclockwise in the figure by a driving device (not shown), and the surface of each photoconductor 2 is uniformly charged to a predetermined polarity by the charging unit 3. . The surface of each charged photoconductor 2 is irradiated with laser light from the exposure unit 6 to form an electrostatic latent image on the surface of each photoconductor 2. At this time, the image information to be exposed on each photoconductor 2 is monochromatic image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. In this way, the electrostatic latent image formed on the photosensitive member 2 is supplied with toner by each developing unit 4, whereby the electrostatic latent image is visualized as a toner image.

  When the drive roller that stretches the intermediate transfer belt 9 is driven to rotate, the intermediate transfer belt is driven to travel in the direction indicated by the arrow in the figure. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the toner charging polarity is applied to each primary transfer roller 11. As a result, a transfer electric field is formed at the primary transfer nip between each primary transfer roller 11 and each photoconductor 2. Then, the toner images of the respective colors formed on the respective photoreceptors 2 are sequentially superimposed and transferred onto the intermediate transfer belt 9 by the transfer electric field formed in the primary transfer nip. Thus, the intermediate transfer belt 9 carries a full-color toner image on its surface.

  The recording paper sent out by the paper supply unit 17 is timed by a pair of registration rollers 20 and sent to the secondary transfer nip between the secondary transfer roller 12 and the intermediate transfer belt 9. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 9 is applied to the secondary transfer roller 12, and a transfer electric field is formed in the secondary transfer nip. Then, the toner image on the intermediate transfer belt 9 is collectively transferred onto the recording paper by the transfer electric field formed in the secondary transfer nip. The recording paper on which the toner image has been transferred is conveyed to the fixing device 15, and when the recording paper passes through the fixing device 15, heat and pressure are applied to melt and fix the toner image. The recording paper on which the toner image is fixed is discharged out of the apparatus by the paper discharge unit 19.

  When performing duplex printing, the recording paper is transported from the paper discharge unit 19 to the duplex printing transport device 18 without discharging the recording paper to the outside of the apparatus. The recording sheet is turned upside down while passing through the duplex printing conveyance device 18 and guided again to the secondary transfer nip. In the same manner as described above, after the image is transferred and fixed on the back surface of the recording paper, the recording paper is discharged out of the apparatus.

  The residual toner adhering to the surface of each photoconductor 2 after the toner image is transferred is removed from the surface of the photoconductor 2 by each drum cleaning unit 5, and then the surface is removed by a static eliminator (not shown). Upon receiving the charge eliminating action, the surface potential is initialized to prepare for the next image formation.

  The above description is an image forming operation when a full-color image is formed on a recording sheet. A single-color image is formed using any one of the four image forming units 10, or two or three images are formed. It is also possible to form a two-color or three-color image using the forming unit 10.

  FIG. 2 is a front perspective view of one of the image forming units 10Y, 10M, 10C, and 10K, and FIG. 3 is a rear perspective view of the image forming unit. Since the image forming units 10Y, 10M, 10C, and 10K have the same configuration, the subscripts Y, M, C, and K representing the identification of each color are omitted for convenience in FIGS. ing.

  As shown in FIG. 2, the photoreceptor 2 includes a photosensitive tube 21 coated with a photosensitive layer, a front flange 22, and a back flange 23. The front side flange 22 and the back side flange 23 of the photosensitive member 2 are rotatably supported by the frame 30 of the image forming unit 10. Specifically, a drum shaft 24 that is a support shaft of the photosensitive member 2 is rotatably fitted to bearings provided on the front positioning plate 31 and the back positioning plate 32 as positioning means. Thereby, the photoreceptor 2 is positioned. A photosensitive member motor 25 that rotates the photosensitive member 2 is attached to one end of the drum shaft 24 of the photosensitive member 2.

  The development unit 4 is temporarily positioned on the frame 30 of the image forming unit 10 and then positioned by the front positioning plate 31 and the back positioning plate 32. The developing unit 4 has a developing roller 40 as a developer carrier, and a roller shaft (not shown) of the developing roller 40 is rotatably fitted to bearings provided on the positioning plates 31 and 32. The positioning plates 31 and 32 are each formed with a secondary reference hole made of a long hole, and a secondary reference pin 33 fixed to both ends of the developing unit 4 is fitted in the secondary reference hole. . Thus, the rotation of the developing roller 40 around the central axis of the developing unit 4 is restricted by fitting the slave reference pin 33 into the slave reference hole.

  In a state where the developing roller 40 and the photosensitive member 2 are supported by the positioning plates 31 and 32, a constant developing gap is maintained between the developing roller 40 and the photosensitive member 2. By maintaining this development gap at a predetermined interval, a high-quality toner image can be developed on the photoreceptor 2.

  As shown in FIG. 4, metal rollers 41 and 42 are provided at both ends of the developing roller 40, and the metal rollers 41 and 42 are brought into contact with the flanges 22 and 23 of the photosensitive member 2 so that the developing roller 40 and the photosensitive member are brought into contact with each other. 2 may be positioned through a predetermined development gap.

  The positioning plates 31 and 32 are preferably formed of resin from the viewpoint of cost reduction and weight reduction, but metal may be applied.

  By the way, in recent years, due to a demand for downsizing of an image forming apparatus, the inside of the apparatus is being increased in density. The image forming apparatus according to the present invention is also downsized, and the inside of the apparatus is densified. For this reason, as shown in FIG. 1, the fixing device 15 is disposed below the transfer unit 8, and the intermediate transfer belt 9 is close to the fixing device 15.

  As described above, when the intermediate transfer belt 9 is disposed close to the fixing device 15, the intermediate transfer belt 9 may be deformed by the heat of the fixing device 15 and image defects such as color misregistration may occur. is there. Further, such image defects tend to become prominent when the amount of heat generated in the apparatus increases as the speed of the image forming apparatus increases. When double-sided printing is performed, the recording paper heated by the fixing device 15 is conveyed again to the secondary transfer position of the intermediate transfer belt 9 and contacts the intermediate transfer belt 9 there. However, the temperature rises, and it becomes a more severe condition for good image formation. Further, since heat is transmitted to the photosensitive member 2 and the developing unit 4 via the intermediate transfer belt 9, the temperature of the photosensitive member 2 and the developing unit 4 is also increased. Due to these temperature rises, an image density abnormality due to a decrease in the charge amount of the toner, an image density unevenness due to the fused toner adhering to the photosensitive member, the developing roller, etc. are likely to occur.

  Therefore, as shown in FIG. 1, a heat insulating device 50 is disposed between the fixing device 15 and the intermediate transfer belt 9. The heat insulating device 50 is mainly composed of a heat receiving plate 51 as a heat receiving member, a heat pipe 52 as a heat transfer means (heat transport means), a heat radiating plate 53 as a heat radiating member, a duct 54 and an exhaust fan (not shown). ing. The heat receiving plate 51 is formed of a material that easily absorbs heat, and is disposed between the fixing device 15 that is a heat generation source and the transfer unit 8 that is a protection target portion that is to be protected from the influence of the heat. One end (lower end) of the heat pipe 52 is attached to the lower surface of the heat receiving plate 51, and the other end is attached to the heat radiating plate 53. The heat radiating plate 53 is made of a material that easily releases heat, and is disposed in the duct 54. In this embodiment, the duct 54 extends from the front surface to the back surface of the image forming apparatus. An air inlet is provided at the end of the duct 54 on the front side of the device, and an exhaust port is provided at the end of the back side of the device. An exhaust fan (not shown) is provided at the exhaust port.

  The heat insulating device 50 configured as described above receives heat from the fixing device 15 by the heat receiving plate 51, and the heat is transmitted to the heat radiating plate 53 by the heat pipe 52. Then, heat is released from the heat radiating plate 53, and the released heat is discharged outside the machine by an exhaust fan (not shown). Note that it is possible to perform natural cooling without providing an exhaust fan. In this way, the heat generated from the fixing device 15 is absorbed by the heat receiving plate 51 in front of the transfer unit 8, and the heat is discharged out of the apparatus, thereby increasing the temperature of the transfer unit 8 due to the heat of the fixing device 15. I try to suppress it. Further, by suppressing the temperature rise of the transfer unit 8, the temperature rise of the photoconductor 2 and the developing unit 4 is also suppressed. As a result, it is possible to prevent problems such as an image position shift due to deformation of the intermediate transfer belt 9, an image density abnormality due to a decrease in toner charge amount, and an image density unevenness due to toner fixation.

  Each developing unit 4 is carried on a developer agitating / conveying member that stirs and conveys the developer (toner) accommodated in the developing unit 4 or on a developing roller before the developer is conveyed to the developing region. It has a developer regulating member that regulates the layer thickness of the developer (not shown). Friction caused by sliding contact between the developer agitating / conveying member or the developer regulating member and the developer when the developer is agitated and conveyed by the developer agitating / conveying member or when the layer thickness of the developer is regulated by the developer regulating member The temperature in the developing unit 4 rises due to heat and frictional heat due to sliding contact between the developers. When the temperature in the developing unit 4 rises, there is a risk that image density abnormality due to a decrease in the toner charge amount, density unevenness due to toner sticking to the developing roller, the developer regulating member, or the like may occur. In particular, when a toner having a low melting temperature is used for the purpose of reducing energy consumption at the time of image fixing, the toner is easily melted, so that the toner is easily fixed. Further, when the printing speed is increased, the developing unit 4 is likely to be at a high temperature, so that the above-described image defect is likely to occur.

  Therefore, the image forming apparatus according to the present invention includes a cooling device that cools each developing unit 4.

FIG. 5 is a schematic plan view of the cooling device. Here, a liquid cooling type cooling device is used as the cooling device.
As shown in FIG. 5, the cooling device 60 includes four heat receiving portions 61Y, 61M, 61C, and 61K disposed under the image forming units 10Y, 10M, 10C, and 10K, and three cooling portions 62. A cooling pump 64, a reserve tank 65, and a circulation pipe 63 as a flow path connecting them are provided.

  The cooling unit 62 is a cooling unit that cools the coolant. Each cooling unit 62 includes a radiator 66 and a cooling fan 67 as heat dissipation means. The radiator 66 has a housing portion made of aluminum or the like having a high thermal conductivity. By accommodating the cooling liquid in the accommodating portion, the cooling liquid is radiated to cool. The cooling fan 67 is for improving the heat dissipation effect of the radiator 66 by sending air to the radiator 66. In this embodiment, three radiators 66, four heat receiving portions 61Y, 61M, 61C, 61K, a cooling pump 64, and a reserve tank 65 are connected in series by a circulation pipe 63.

  The cooling unit 62 may be one or two, or four or more. By providing a plurality of cooling units 62, a sufficient cooling effect can be exhibited even if the cooling effect of each cooling unit 62 is relatively low. In the case of cooling by a plurality of cooling units 62, compared with the case of cooling by one cooling unit 62, the heat radiation area per one can be reduced, and as a result, downsizing can be achieved. Further, in this embodiment, the cooling fan 67 is provided for each cooling unit 62, but it may be configured such that outside air is supplied to each radiator 66 by one cooling fan 67.

  The cooling pump 64 is a cooling liquid conveying means for circulating the cooling liquid between the heat receiving parts 61Y, 61M, 61C, 61K and the cooling parts 62 via the circulation pipe 63. In this case, the coolant is circulated by the cooling pump 64 in the direction of the arrow in the figure. The reserve tank 65 is a tank for storing excess coolant.

  The coolant as the heat transport medium is mainly composed of water. Here, propylene glycol or ethylene glycol for lowering the freezing temperature is added to the coolant, or a rust inhibitor (for example, phosphate-based material: potassium phosphate for preventing rust of metal parts). Salt, inorganic potassium salt, etc.) are used.

  FIG. 6 is a schematic view of the heat receiving portion 61. In addition, since each heat receiving part 61Y, 61M, 61C, 61K is comprised similarly, in FIG. 6, the subscript Y, M, C, K showing the identification of each color is abbreviate | omitted for convenience.

  As shown in FIG. 6, the heat receiving portion 61 has a pipe line 68 for passing the coolant and a case 69 in which the pipe line 68 is accommodated. The pipe 68 and the case 69 are formed of a member having high thermal conductivity. For example, copper having a thermal conductivity of about 400 [W / mK] or aluminum having a thermal conductivity of about 200 [W / mK] can be used as the material for the pipe 68 and the case 69. Further, a material such as silver or gold having higher thermal conductivity may be applied to the pipe line 68 and the case 69. The pipe 68 is bent in a U shape within the case 69, and both end portions 68 a and 68 b of the pipe 68 protrude from one end of the case 69. Circulating pipes 63 are connected to the projecting ends 68a and 68b, respectively.

  As shown in FIG. 1, each heat receiving portion 61Y, 61M, 61C, 61K is disposed in contact with the lower surface of each color developing unit 4Y, 4M, 4C, 4K. Further, the heat receiving portions 61Y, 61M, 61C, and 61K are pressurized to the developing units 4Y, 4M, 4C, and 4K of the respective colors by a pressing unit such as a spring (not shown). As a result, the heat receiving portions 61Y, 61M, 61C, 61K can be pressed against (adhered to) the developing units 4Y, 4M, 4C, 4K, and the contact area (heat receiving area) is increased to improve the cooling effect. I am letting.

  Further, when the heat receiving portions 61Y, 61M, 61C, and 61K are pressed against the developing units 4Y, 4M, 4C, and 4K, the circulation pipe 63 is configured with a flexible or flexible member such as a rubber tube or a resin tube. It is preferable to do. By configuring the circulation pipe 63 with a member having flexibility or flexibility, the circulation pipe 63 can be deformed following the displacement of the heat receiving portions 61Y, 61M, 61C, 61K during pressure contact. For this reason, it is possible to prevent problems such as the circulation pipe 63 coming off from the heat receiving portions 61Y, 61M, 61C, 61K. However, the entire circulation pipe 63 may not be configured with a rubber tube or the like. It is preferable that a part of the circulation pipe 63 is made of a metal pipe in that moisture permeability can be suppressed as much as possible.

Hereinafter, the operation of the cooling device 60 will be described.
The coolant cooled by the radiator 66 is sequentially sent to the heat receiving units 61Y, 61M, 61C, and 61K by the cooling pump 64. The cooling liquid absorbs heat from the developing units 4Y, 4M, 4C, and 4K while passing through the heat receiving portions 61Y, 61M, 61C, and 61K, and is returned to the radiator 66 again. Then, the radiator 66 cools the coolant by dissipating heat. By blowing air to the radiator 66 by the cooling fan 67, the heat dissipation effect of the radiator 66 can be enhanced. Further, the cooling fan 67 may be configured to be able to be switched between driving and stopping according to a desired heat radiation amount. Or you may comprise so that the rotational speed of the cooling fan 67 can be adjusted according to the heat radiation amount. By thus circulating the cooling liquid and cooling the developing units 4Y, 4M, 4C, and 4K, it is possible to suppress the occurrence of problems such as abnormal image density and uneven density.

  Further, the liquid cooling type cooling device has an advantage that the installation space can be reduced as compared with the air cooling type cooling device. For this reason, a liquid cooling type cooling device is suitable for the image forming apparatus having a high density inside as in the present embodiment. In general, the constant volume heat capacity of water is 3000 times or more that of air. For this reason, the liquid cooling type cooling device can transfer a large amount of heat at a small flow rate, and can be cooled more efficiently than the air cooling type cooling device.

  As described above, when double-sided printing is performed, the recording paper heated by the fixing device 15 warms the intermediate transfer belt 9 at the secondary transfer unit, so that the photoreceptor 2Y is rotated along with the subsequent rotation of the intermediate transfer belt 9. , 2M, 2C, 2K and development units 4Y, 4M, 4C, 4K also rise in temperature. At this time, the warmed portion of the intermediate transfer belt 9 is contacted in the order of the photosensitive member 2Y, the photosensitive member 2M, the photosensitive member 2C, and the photosensitive member 2K (in order from the left photosensitive member in FIG. 1). The faster the photosensitive member and the developing unit facing the photosensitive member, the higher the temperature rise. Therefore, it is desirable to increase the cooling effect by the heat receiving portions 61Y, 61M, 61C, and 61K as the developing unit tends to increase in temperature. In other words, the cooling capacity for each developing unit is configured so as to increase as the developing unit disposed upstream in the rotation direction starts from the transfer position (secondary transfer position) of the intermediate transfer belt 9 to the recording paper. It is desirable.

  Therefore, in this embodiment, the cooling liquid is sent in order from the heat receiving portion in contact with the developing unit whose temperature tends to increase (in the order of 61Y, 61M, 61C, 61K in FIG. 5). By sending the cooling liquid in this way, a developing unit whose temperature is likely to rise can be sent to the heat receiving unit in a state where the cooling liquid is cooled, and the cooling effect of the heat receiving unit can be enhanced. Accordingly, each developing unit can be cooled to a more uniform temperature regardless of the arrangement position, and high-quality image formation can be stably performed. In addition, the same effect as described above can be obtained by increasing the heat receiving area of the heat receiving section as the developing unit tends to have a high temperature.

  Further, the developing unit arranged near the fixing device 15 tends to have a higher temperature. Therefore, the developing unit closer to the fixing device 15 may have a higher cooling effect on the heat receiving unit.

FIG. 7 is a schematic view of a cooling device according to Embodiment 2 of the present invention.
In the first embodiment of the present invention, the heat receiving portions 61Y, 61M, 61C, and 61K are connected in series. However, as in the second embodiment shown in FIG. 7, the heat receiving portions 61Y, 61M, 61C, and 61K are connected. You may connect in parallel. In this case, similarly to the above, as the developing unit tends to have a high temperature, each developing unit can be cooled to a more uniform temperature regardless of the arrangement position by increasing the heat receiving area of the heat receiving unit. Is possible.

FIG. 8 is a schematic view of a cooling device according to Embodiment 3 of the present invention.
As shown in FIG. 8, in Example 3 of the present invention, a plurality of cooling units 62 and a plurality of heat receiving units 61Y, 61M, 61C, 61K are alternately connected in series. That is, the cooling liquid cooled by each cooling part 62 does not supply the cooling liquid to the other heat receiving parts 61 until the cooling liquid is supplied to the corresponding heat receiving parts 61Y, 61M, 61C, 61K. Yes. Moreover, you may arrange | position the several cooling part 62 corresponding to each heat receiving part 61Y, 61M, 61C, 61K connected in parallel shown in FIG. In these cases, by varying the size (heat radiation amount) of the radiator 66 for each cooling unit 62 or by varying the air volume of the cooling fan 67 that blows air to the radiator 66, the cooling effect on each developing unit is different. It can be given. Therefore, the cooling unit 62 arranged corresponding to the developing unit whose temperature tends to be high can enhance the cooling effect, thereby cooling each developing unit to a more uniform temperature regardless of the arrangement position. Is possible. Further, in this embodiment, as described above, the effect similar to the above can be obtained by increasing the heat receiving area of the heat receiving portion for the developing unit whose temperature tends to be high.

FIG. 9 is a schematic view of a cooling device according to Embodiment 4 of the present invention.
As shown in FIG. 9, in the fourth embodiment of the present invention, the first cooling device 60a for cooling the two developing units 4Y and 4M and the second cooling device for cooling the other two developing units 4C and 4K. 60b is provided. In this case, since the circulation pipes 63 of the two cooling devices 60a and 60b are independent, the flow rate (flow velocity) per unit time of the respective coolants can be made different. For example, when the two left development units 4Y and 4M in the figure are more likely to rise in temperature than the two right development units 4C and 4K in the figure, the flow rate or flow rate of the first cooling device 60a is set to the second cooling unit. Each developing unit can be cooled to a more uniform temperature by making it higher or faster than the flow rate or flow rate of the apparatus 60b. Further, if the flow rate or flow rate of the cooling liquid can be varied for each of the heat receiving units 61Y, 61M, 61C, and 61K, the flow rate is increased as the heat receiving unit disposed in the developing unit whose temperature tends to increase. Alternatively, each developing unit can be cooled to a more uniform temperature by increasing the flow rate. Further, in each of the cooling devices 60a and 60b, the cooling effect can be made different by changing the size (radiation amount) of the radiator 66 or changing the air volume of the cooling fan 67 that blows air to the radiator 66. Is possible. In addition, the heat receiving area of the heat receiving unit may be increased as the developing unit tends to have a high temperature.

  As mentioned above, although the cooling device which concerns on Examples 2-4 of this invention was demonstrated, since it is the structure similar to Example 1 except the structure demonstrated above, description is abbreviate | omitted. 7-9, the same code | symbol as FIG. 5 shows the same member or apparatus.

FIG. 10 is a schematic view showing a part of an image forming apparatus according to Embodiment 5 of the present invention.
In the embodiment shown in FIG. 1, the four image forming units 10Y, 10M, 10C, and 10K are arranged side by side in the horizontal direction (the left-right direction in the figure). In the fifth embodiment shown in FIG. Two image forming units 10Y, 10M, 10C and 10K are arranged side by side in the vertical direction (vertical direction in the figure). This image forming apparatus is also provided with heat receiving portions 61Y, 61M, 61C, 61K for cooling the developing units 4Y, 4M, 4C, 4K. In this case, each of the heat receiving portions 61Y, 61M, 61C, 61K is disposed in contact with the right end surface of the corresponding developing unit 4Y, 4M, 4C, 4K.

  10 is similar to the image forming apparatus shown in FIG. 1, the photosensitive members 2Y, 2M, 2C, 2K, the charging units 3Y, 3M, 3C, 3K, and the developing units 4Y, 4M, Image forming units 10Y, 10M, 10C, and 10K having 4C, 4K, and the like, an exposure unit 6, a transfer unit 8 having an intermediate transfer belt 9, a secondary transfer roller 12, and a fixing device 15 are provided. Other configurations and operations are the same as those in the embodiment described with reference to FIG.

  By the way, the air heated by the fixing device 15 and the like in the image forming apparatus is accumulated in the upper part of the apparatus. Therefore, as shown in FIG. 10, when a plurality of image forming units 10Y, 10M, 10C, and 10K are arranged in the vertical direction, the temperature of the developing unit disposed on the upper side is likely to increase. In addition, in this case, when double-sided printing is performed, the intermediate transfer belt 9 that has received heat from the recording sheet after fixing comes in contact with the upper photosensitive member in order, and therefore the temperature is more likely to rise in the upper developing unit. Therefore, in this embodiment, the cooling effect of the heat receiving portion is enhanced as the developing unit disposed on the upper side. As a result, each developing unit can be cooled to a more uniform temperature regardless of the arrangement position. In addition, what is necessary is just to select and use suitably the method quoted in each said Example as a method of making the cooling effect of a heat receiving part high.

FIG. 11 is a schematic view showing a part of an image forming apparatus according to Embodiment 6 of the present invention.
In the image forming apparatus shown in FIG. 11, four developing units 4Y, 4M, 4C, and 4K are arranged in the horizontal direction. In each of the above embodiments, one heat receiving portion is brought into contact with each of the four developing units. However, in Embodiment 6, one heat receiving portion 61 is provided for each of the developing units 4Y, 4M, 4C, and 4K. It is in contact. In other words, here, a heat receiving portion that abuts on the developing units 4Y, 4M, 4C, and 4K is integrally configured. In this case, the heat receiving portion 61 is disposed so as to contact the upper surface of each of the developing units 4Y, 4M, 4C, and 4K. A through hole 70 is formed through which laser light irradiated to 2Y, 2M, and 2C passes.

FIG. 12 is a schematic diagram showing a modification of the sixth embodiment.
In this case, the four developing units 4Y, 4M, 4C, and 4K are arranged side by side in the vertical direction. However, as in the embodiment shown in FIG. 11, each developing unit 4Y, 4M, 4C, and 4K One heat receiving portion 61 is brought into contact with the heat receiving portion 61. In addition, a through hole 70 is formed at a predetermined location of the heat receiving portion 61 for allowing the laser light irradiated from the exposure unit 6 to the photoreceptors 2Y, 2M, and 2C.

  As described above, when the heat receiving portions that are in contact with each developing unit are integrally configured, the structure can be simplified and the number of parts can be reduced compared to the case where a plurality of heat receiving portions are provided independently. Can be reduced. Further, the configuration of the flow path of the coolant can be simplified, and the coolant can be efficiently circulated with little pressure loss, so that the cooling capacity is improved. Further, by integrally configuring the heat receiving part, the rigidity of the entire apparatus, particularly the rigidity of the image forming part is improved, so that the image forming ability is stabilized and the reliability is improved.

FIG. 13 is a schematic view showing a part of an image forming apparatus according to Embodiment 7 of the present invention.
In the image forming apparatus shown in FIG. 13, the developing units 4Y, 4M, 4C, and 4K are arranged in the horizontal direction. In this case, the heat receiving portion 61 is in contact with the exposure unit 6 in addition to the developing units 4Y, 4M, 4C, and 4K. The rest of the configuration is basically the same as that of the embodiment shown in FIG.

FIG. 14 shows a modification of the seventh embodiment.
In the image forming apparatus shown in FIG. 14, the developing units 4Y, 4M, 4C, and 4K are arranged in the vertical direction. Also in this case, the heat receiving portion 61 is in contact with each of the developing units 4Y, 4M, 4C, 4K and the exposure unit 6. The rest of the configuration is basically the same as that of the embodiment shown in FIG.

  As described above, by bringing the heat receiving portion into contact with the exposure unit in addition to the development unit, the exposure unit can be cooled together with the development unit. Thereby, image defects such as color misregistration can be more effectively suppressed, and high-quality image formation is possible. Further, in the embodiment shown in FIGS. 13 and 14, one heat receiving portion is in contact with each developing unit and the exposure unit. However, a plurality of heat receiving portions are in contact with each developing unit one by one. It is also possible to adopt a configuration in which the heat receiving portion is also brought into contact with the exposure unit.

FIG. 15 shows an eighth embodiment of the present invention.
In the eighth embodiment of the present invention, the image forming units 10Y, 10M, 10C, and 10K and the cooling device 60 are configured to be detachable from the image forming apparatus main body. FIG. 15 shows how the image forming units 10Y, 10M, 10C, and 10K and the cooling device 60 are taken out in the direction of the arrows in the figure. In FIG. 15, reference numeral 6 denotes an exposure unit, and reference numeral 8 denotes a transfer unit. The cooling device 60 includes a heat receiving portion 61, a cooling pump 64, a reserve tank 65, a radiator 66, a circulation pipe 63 connecting them, and a cooling fan 67, as in the above embodiments. FIG. 15 conceptually shows the configuration according to the eighth embodiment of the present invention, and illustration and description of a specific attachment / detachment mechanism of the image forming unit and the cooling device are omitted.

  With such a configuration, maintenance of the image forming units 10Y, 10M, 10C, and 10K and the cooling device 60 is facilitated. Further, since the developing units 4Y, 4M, 4C, and 4K do not have to be separated from the heat receiving unit 61 at the time of attachment / detachment, a heat conductive sheet or the like is provided between the developing units 4Y, 4M, 4C, 4K and the heat receiving unit 61. When a heat conducting member such as heat conducting grease is interposed, consumption of these heat conducting members can be suppressed. For this reason, durability of the heat conductive effect by interposing a heat conductive member can be prolonged. Furthermore, since it is not necessary to separate the components constituting the cooling device 60 when attaching and detaching, there is no risk of leakage of the coolant from the separation location, and reliability is improved.

FIG. 16 is a diagram showing one image forming unit among the plurality of image forming units 10Y, 10M, 10C, and 10K shown in FIG. In FIG. 16, subscripts Y, M, C, and K representing the identification of each color are omitted for convenience.
As described above, the developing unit 4 is positioned with respect to the photosensitive member 2, and in this state, a developing gap G is maintained between the developing roller 40 of the developing unit 4 and the photosensitive member 2. The development gap G is more information is set at the distance of closest approach of a straight line X passing through the center O ₄₀ of the developing roller 40 and the center O ₂ of the photosensitive member 2.

  Further, a heat receiving portion 61 is disposed in contact with the lower end surface of the developing unit 4. That is, the heat receiving portion 61 and the developing unit 4 are in contact with each other in the vertical direction in the figure. On the other hand, the photosensitive member 2 and the developing roller 40 of the developing unit 4 face each other in the left-right direction in the drawing. Therefore, the contact direction of the heat receiving portion 61 and the developing unit 4 and the facing direction of the photoreceptor 2 and the developing roller 40 are configured to be substantially orthogonal to each other.

Here, the "opposite direction" of the photosensitive member 2 and the developing unit 4, specifically refers to the direction of a straight line X passing through the center O ₄₀ above the developing roller 40 and the center O ₂ of the photosensitive member 2. Moreover, the heat receiving part 6
1 and the “contact direction” of the developing unit 4 are defined as the same direction as the direction of the force that the developing unit 4 receives mainly by the contact with the heat receiving portion 61. For example, as shown in FIG. 17A, when the contact surface between the developing unit 4 and the heat receiving portion 61 is horizontal, the force f1 that the contact surface of the developing unit 4 receives from the heat receiving portion 61 is Since all of them act upward in the figure, the force F1 mainly received by the resultant force is also directed upward in the figure. Accordingly, in this case, the “contact direction” is the upward direction in the figure, which is mainly the same direction as the force F1 received. Further, as shown in FIG. 17B, when the contact surface between the developing unit 4 and the heat receiving portion 61 is curved, the force f2 received by the contact surface of the developing unit 4 from the heat receiving portion 61 is different. However, the force F2 mainly received by the resultant force is upward in the figure. Therefore, also in this case, the “contact direction” is an upward direction in the figure, which is mainly the same direction as the force F1 received. In addition, when the contact surface between the developing unit 4 and the heat receiving unit 61 is curved, a larger contact area (heat receiving area) can be secured than when the contact surface is a flat surface, and the cooling effect is improved. Can be improved.

  On the other hand, in the conventional example shown in FIG. 21, unlike the present invention, the contact direction of the heat receiving unit 300 and the developing unit 200 and the facing direction of the photoconductor 100 and the developing roller 210 are set to be substantially the same direction. In this case, since the direction of the force received by the developing unit 200 from the heat receiving unit 300 is substantially the same as the direction of the gap of the developing gap G, the developing gap G is likely to change. Therefore, in the conventional example, when the developing unit 200 and the heat receiving unit 300 are brought into contact with each other, there is a possibility that the developing gap G changes and the predetermined image quality cannot be maintained.

  On the other hand, in the present invention, the developing unit 4 is configured so that the contact direction of the heat receiving unit 61 and the developing unit 4 and the facing direction of the photoreceptor 2 and the developing roller 40 are substantially orthogonal to each other. The direction of the force mainly received by contact with 61 acts in a direction substantially orthogonal to the facing direction. As a result, even if the developing unit 4 is displaced due to contact with the heat receiving portion 61, the developing gap G is less susceptible to the influence. Therefore, according to the present invention, a change in the development gap G due to the contact between the development unit 4 and the heat receiving portion 61 can be suppressed, and the development gap G can be maintained with high accuracy. Image quality can be formed. In particular, as in the present embodiment, when the heat receiving portion 61 is in pressure contact with the developing unit 4 by the pressurizing unit, the force received by the developing unit 4 increases and the developing unit 4 is more easily displaced. By adopting the configuration as in the invention, it is important to suppress the fluctuation of the development gap G. Further, according to the present invention, it is only necessary to make the contact direction and the facing direction substantially perpendicular to each other, so that a complicated mechanism for maintaining the position of the developing unit 4 with high accuracy is not necessary. For this reason, the structure can be simplified and the apparatus can be miniaturized.

  In the embodiment shown in FIG. 16, the heat receiving portion 61 is in contact with the lower surface of the developing unit 4, but the heat receiving portion 61 is placed on the upper surface of the developing unit 4 as in the embodiments shown in FIGS. 11 and 13. The contact direction between the heat receiving portion 61 and the developing unit 4 and the facing direction between the photoconductor 2 and the developing roller 40 can also be made substantially orthogonal to each other by the contact. Further, in FIG. 16, the case of having a plurality of heat receiving portions has been described as an example, but the same operation and effect can be obtained when a plurality of heat receiving portions as shown in FIGS. 11 and 13 are integrally configured. .

FIG. 18 is a diagram showing one image forming unit among the plurality of image forming units 10Y, 10M, 10C, and 10K shown in FIG. In FIG. 18, subscripts Y, M, C, and K representing the identification of each color are omitted for convenience.
In this case, the heat receiving portion 61 is disposed in contact with the right end surface of the developing unit 4 in the drawing. That is, the heat receiving portion 61 and the developing unit 4 are in contact with each other in the left-right direction in the figure. On the other hand, the photoreceptor 2 and the developing unit 4 face each other in the vertical direction in the figure. Accordingly, also in this case, the contact direction of the heat receiving portion 61 and the developing unit 4 and the facing direction of the photosensitive member 2 and the developing roller 40 are configured to be substantially orthogonal to each other. Similarly to the above, the "opposite direction" of the photosensitive member 2 and the developing roller 40, refers to a direction of a straight line X passing through the center O ₄₀ of the developing roller 40 and the center O ₂ of the photosensitive member 2. Further, the “contact direction” between the heat receiving portion 61 and the developing unit 4 is defined as the same direction as the direction of the force that the developing unit 4 receives mainly by the contact with the heat receiving portion 61.

  As described above, the abutting direction of the heat receiving portion 61 and the developing unit 4 and the facing direction of the photosensitive member 2 and the developing roller 40 are configured to be substantially orthogonal to each other. Even if the developing gap G is displaced by contact with the portion 61, the development gap G can be made less susceptible to the influence. Thereby, the fluctuation | variation of the developing gap G can be suppressed and the holding | maintenance of the developing gap G with high precision is attained.

  Further, in FIG. 18, the case where a plurality of heat receiving portions are provided has been described as an example, but the same operation and effect can be achieved when a plurality of heat receiving portions as shown in FIG. 12 or 14 are integrally configured. .

FIG. 19 shows the configuration of the ninth embodiment of the present invention.
FIG. 19 is a schematic diagram of a cleaning unit 43 that cleans the surface of the intermediate transfer belt 9 disposed in the image forming apparatus. The cleaning unit 43 includes a cleaning blade 44 and a cleaning brush 45 as cleaning members, a flicker 46, a conveying screw 47, an application brush 48 and an application blade 49 as lubricant application means, and the like.

  The cleaning brush 45, the cleaning blade 44, the application brush 48, and the application blade 49 are in contact with the surface of the intermediate transfer belt 9 in order from the upstream side to the downstream side (from the lower side to the upper side in the drawing) of the intermediate transfer belt 9 in the traveling direction. ing. In addition, the cleaning unit 43 is positioned with respect to the intermediate transfer belt 9 by positioning means (not shown), and in particular, the cleaning blade 44 is in contact with the intermediate transfer belt 9 at a predetermined contact pressure and contact angle. Yes.

  When the intermediate transfer belt 9 is run, paper dust and the like attached to the surface is removed by the cleaning brush 45. Next, the residual toner on the intermediate transfer belt 9 is scraped off by the cleaning blade 44. Then, a lubricant is applied to the surface of the intermediate transfer belt 9 from which paper dust and toner have been removed by the application brush 48, and the applied lubricant is extended onto the intermediate transfer belt 9 by the application blade 49. Further, paper dust or the like adhering to the cleaning brush 45 is scraped out by a flicker 46 that contacts the cleaning brush 45. Then, the scraped paper dust and the toner removed by the cleaning blade 44 are transported by the transport screw 47 and merged with the waste toner in the image forming apparatus and accumulated.

  Further, in this embodiment, the temperature in the cleaning unit 43 rises due to heat generated by the transport operation of the waste toner by the transport screw 47 or the heat of the fixing device (not shown), and the toner melts and adheres in the unit. In order to prevent this, the heat receiving portion 61 of the cooling device is attached to the cleaning unit 43. Since this cooling device is applicable to the liquid-cooled configuration similar to each of the above embodiments, detailed description thereof is omitted.

  Here, the contact direction A of the heat receiving portion 61 with respect to the cleaning unit 43 is configured to be substantially orthogonal to the contact direction B of the cleaning blade 44 with respect to the intermediate transfer belt 9. For this reason, the direction of the force (in the direction of arrow A) that the cleaning unit 43 receives mainly by contact with the heat receiving portion 61 acts in a direction substantially orthogonal to the direction of contact of the cleaning blade 44 (in the direction of arrow B). Can be made.

  As a result, even if the cleaning unit 43 is displaced by contact with the heat receiving portion 61, the positional relationship in the contact direction (the direction of the arrow B) between the intermediate transfer belt 9 and the cleaning blade 44 is less affected. . Accordingly, the positional relationship in the contact direction between the intermediate transfer belt 9 and the cleaning blade 44 can be maintained with high accuracy, and the contact pressure and contact angle of the cleaning blade 44 with respect to the intermediate transfer belt 9 can be prevented from changing. Therefore, it is possible to maintain good cleaning properties. In addition, both the cleaning effect and the cooling of the unit can be realized only by making the contact direction of the heat receiving portion 61 and the contact direction of the cleaning blade 44 substantially orthogonal, so that the position of the cleaning unit 43 can be set with high accuracy. There is no need for complex mechanisms to maintain. For this reason, the structure can be simplified and the apparatus can be miniaturized.

  In the ninth embodiment, the case where the present invention is applied to the cleaning unit that cleans the intermediate transfer belt as the image carrier is described as an example, but the same applies to the cleaning unit that cleans the photosensitive member as the image carrier. The configuration of the present invention can be applied to.

  As mentioned above, although each Example of this invention was described, this invention is not limited to the above-mentioned Example, Of course, a various change can be added in the range which does not deviate from the summary of this invention. For example, in the above-described embodiment, one of the contact direction of the heat receiving unit 61 and the developing unit 4 and the facing direction of the photosensitive member 2 and the developing roller 40 is the vertical direction (vertical direction), and the other is the horizontal direction (horizontal direction). However, the direction is not particularly limited as long as the contact direction and the facing direction are substantially orthogonal to each other. For example, one of the contact direction and the facing direction may be the front-rear direction and the other may be the left-right direction.

  Further, in the above-described embodiments, the configuration in which the developing unit and the photoconductor are positioned by the positioning plate and the developing unit is integrated with the photoconductor as an image forming unit is described as being detachable from the image forming apparatus main body. However, the developing unit may be detachably attached to the image forming apparatus main body. In this case, when the developing unit is mounted on the image forming apparatus main body, the developing unit is positioned by positioning means provided on the image forming apparatus main body, and the developing gap between the photosensitive member and the developing roller is set at a predetermined interval. Retained. As described above, the contact direction between the heat receiving portion and the development unit and the facing direction between the photoconductor and the development roller are substantially orthogonal to each other even when the development unit is detachable as described above. With this configuration, it is possible to maintain a highly accurate development gap.

  The present invention has been described with respect to an image forming apparatus that employs a two-component development system in which a development gap is formed between a developing roller and a photosensitive member. However, development is performed by bringing the developing roller into contact with the photosensitive member. The present invention can also be applied to an image forming apparatus that employs a one-component developing method. Also in an image forming apparatus employing this one-component development method, the contact direction between the heat receiving portion and the development unit and the facing direction (contact direction) between the photosensitive member and the development roller are substantially the same as in the conventional example. When set, the heat receiving portion is brought into contact with or pressed against the developing unit, thereby causing a problem such as an increase in contact pressure between the developing roller and the photosensitive member. In contrast, as in the present invention, the contact direction of the heat receiving portion and the developing unit and the facing direction (contact direction) of the photosensitive member and the developing roller are configured to be substantially orthogonal to each other, so It is possible to suppress an increase in contact pressure between the developing roller and the photosensitive member due to contact.

  The present invention is not limited to an intermediate transfer tandem color image forming apparatus as shown in FIG. For example, as shown in FIG. 20, a direct transfer tandem type color image formation that directly transfers an image formed on each of the photoreceptors 2Y, 2M, 2C, and 2K onto a recording sheet conveyed by a conveyance belt 80 as a conveyance unit. It can also be applied to devices. Further, the present invention is not limited to a color image forming apparatus, but can be applied to a monochrome image forming apparatus having only one image forming unit (or a photoreceptor).

2 Photoconductor (image carrier)
4 Development unit 6 Exposure unit (latent image forming means)
9 Intermediate transfer belt (intermediate transfer rotating body)
15 Fixing device 18 Transport device for double-sided printing 31 Front positioning plate (positioning means)
32 Back positioning plate (positioning means)
40 Development roller (developer carrier)
43 Cleaning unit 44 Cleaning blade (cleaning member)
60 Cooling device 61 Heat receiving part 62 Cooling part 63 Circulation pipe (flow path)
64 Cooling pump (coolant transport means)
66 Radiator 67 Cooling fan

JP-A-10-133550 JP 2005-164927 A

Claims (16)

An image carrier, a developing unit having a developer carrier for supplying a developer to the image carrier, positioning means for positioning the developer unit with respect to the image carrier, and contact with the development unit In an image forming apparatus provided with a cooling device having a heat receiving portion disposed,
An image forming apparatus, wherein a contact direction between the heat receiving portion and the developing unit is configured to be substantially perpendicular to a facing direction between the image carrier and the developer carrier.   The image forming apparatus according to claim 1, further comprising a pressurizing unit that pressurizes the heat receiving unit against the developing unit.   The image forming apparatus according to claim 1, wherein the image forming apparatus includes a plurality of the developing units, and the cooling device includes one heat receiving portion that can contact each developing unit.   4. The apparatus according to claim 1, further comprising: a latent image forming unit configured to form an electrostatic latent image on the image carrier, wherein the heat receiving unit can be brought into contact with both the latent image forming unit and the developing unit. The image forming apparatus described in the item.   5. The apparatus according to claim 1, wherein a plurality of the developing units are arranged side by side in a vertical direction, and the cooling capacity of the cooling device with respect to each developing unit is configured to be higher as the developing unit disposed on the upper side. The image forming apparatus described.   A plurality of the developing units and a fixing device that fixes an image on a recording medium by heat are provided, and the cooling capacity of the cooling device with respect to each developing unit becomes higher as the developing unit is disposed closer to the fixing device. The image forming apparatus according to claim 1, configured as described above. A plurality of image carriers and a plurality of the developing units, an intermediate transfer rotator for transferring an image transferred from each image carrier to a recording medium, a fixing device for fixing the image on the recording medium by heat, and a post-fixing A double-sided printing transport device that transports the recording medium to the intermediate transfer rotator again for double-sided printing,
The cooling capacity of the cooling device with respect to each developing unit is configured to increase as the developing unit disposed upstream in the rotation direction starts from the transfer position of the intermediate transfer rotator to the recording medium. 7. The image forming apparatus according to any one of items 1 to 6.   The cooling device conveys the cooling liquid from the cooling section to the heat receiving section via the flow path, a cooling section that cools the cooling liquid, a flow path for conveying the cooling liquid, and the flow path. The image forming apparatus according to claim 1, further comprising a cooling liquid transport unit.   The image forming apparatus according to claim 8, wherein the developing unit and the cooling device are configured to be detachable with respect to the main body of the image forming apparatus.   The image forming apparatus according to claim 8 or 9, wherein a plurality of the developing units are provided, and the cooling liquid is conveyed to the heat receiving portion in order from the developing units that are likely to rise in temperature.   11. The image forming apparatus according to claim 8, wherein a plurality of the developing units are provided, and the developing unit that is likely to increase in temperature is configured to have a larger contact area with the heat receiving unit.   12. The structure according to claim 8, wherein a plurality of the development units are provided, and the flow rate per unit time of the cooling liquid transported to the heat receiving unit is increased as the development unit easily rises in temperature. Image forming apparatus.   A plurality of the developing units are provided, and the cooling units are arranged one by one so as to correspond to each developing unit, and the developing unit that easily rises in temperature is configured to increase the cooling effect of the corresponding cooling unit. The image forming apparatus according to claim 8.   The image forming apparatus according to claim 13, wherein the cooling unit includes a radiator that dissipates heat of the cooling liquid, and the size of the corresponding radiator is increased as the developing unit easily increases in temperature.   The cooling unit includes a radiator that radiates heat of the cooling liquid and a cooling fan that blows air to the radiator, and the developing unit that easily rises in temperature increases the air volume of the corresponding cooling fan. The image forming apparatus according to 13 or 14. An image carrier, a cleaning unit having a cleaning member that contacts and cleans the image carrier, a positioning unit that positions the cleaning unit with respect to the image carrier, and a contactable member disposed on the cleaning unit And an image forming apparatus including a cooling device having a heat receiving portion.
An image forming apparatus, wherein a contact direction between the heat receiving portion and the cleaning unit is substantially orthogonal to a contact direction between the image carrier and the cleaning member.

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