JP4357899B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus.

  2. Description of the Related Art Conventionally, in an image forming apparatus that forms an image by an electrophotographic method such as a copying machine, a laser printer, and a facsimile, the toner image is fixed on the recording medium by applying heat and pressure to the recording medium on which the toner image is transferred A fixing device is provided.

  As a basic configuration of such a fixing device, a configuration in which an outer peripheral surface of a pressure roller having a heat generating element inside and a fixing roller having a heat generating element are in contact with each other, or a heat generating element inside is provided. There is known a configuration in which a pressure roller having a heating roller having a heating element therein and a fixing belt stretched between the fixing roller are in contact with each other.

  Here, in order to prevent toner melted at a high temperature at the time of fixing from sticking to the fixing roller or the fixing belt, a fixing device that supplies release oil to the fixing roller or the fixing belt is provided. It is known (see, for example, Patent Document 1). Furthermore, in the invention of Patent Document 1, a fixing blade is provided for making the applied state of the supplied release oil uniform and scraping off excess oil. The fixing blade is located over the entire width of the recording medium conveyed in the fixing device.

  In the fixing device disclosed in Patent Document 1, since the release oil is scraped off by the fixing blade in the entire region in the width direction of the recording medium to be conveyed, the recording medium is released during the scraping. Therefore, it is necessary to always supply a large amount of release oil in order to supplement the scraped release oil. For this reason, an oil circulation mechanism that circulates and re-supplys the release oil scraped off by the fixing blade is provided.

JP 2001-125417 A

  Therefore, in the fixing device disclosed in Patent Document 1, it is necessary to provide an oil circulation mechanism. By providing such an oil circulation mechanism, the device becomes complicated and the cost increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that achieves downsizing with a simple structure of a mechanism relating to supply of release oil, and an image forming apparatus including such a fixing device.

According to a first aspect of the present invention, there is provided a fixing device having a nip portion with which an outer peripheral surface is in contact, a pair of rotating members that apply heat and pressure to a recording medium conveyed through the nip portion, and at least one of them. An oil supply device that supplies release oil to the surface of the rotating body, and an oil that is positioned outside a sheet passing range of a maximum-size recording medium conveyed through the nip portion and contacts the surface of the rotating body A recovery tank for storing the release oil recovered below the oil recovery member, and a guide portion for guiding the recording medium to the nip portion in a part of the recovery tank. but that has been formed.

  Accordingly, the release oil supplied to the outer peripheral surface of the rotating body is pressed and spreads at the nip portion of the pair of rotating bodies, and when the recording medium passes through the nip portion, it is attached to the recording medium little by little and carried. It is. When image formation is continuously performed on a small-sized recording medium and excessive release oil that does not adhere to the recording medium is generated, the excess release oil is applied to the oil recovery member in the rotating body. When it moves to the contact position, it is recovered by the oil recovery member. For this reason, the amount of release oil recovered by the oil recovery member is reduced, and it is not necessary to always supply a large amount of release oil to the rotating body as described in the conventional example. It is not necessary to provide a mechanism for circulating the release oil for reuse. As a result, the fixing device does not require a mechanism for circulating the release oil, and has a simplified and miniaturized and inexpensive structure.

In addition, when the oil recovery member comes into contact with the rotating body and collects excess release oil, a part of the releasing oil is generated at the contact portion with the oil recovery member on the surface of the rotating body. Since the portion with which the collecting member is in contact is outside the sheet passing range of the recording medium, the stripped release oil does not adversely affect the recording medium or image.
Further, the release oil recovered by the oil recovery member is stored in the recovery tank. Further, since the recording medium conveyed toward the nip portion is guided by the guide portion formed in the collection tank, it is not necessary to provide a dedicated guide portion, and the number of parts is reduced.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the length of one of the rotating bodies in the direction of the rotation center is longer than the length of the other rotating body in the direction of the rotation center, The oil recovery member is in contact with a portion of the body that is longer in the direction of the rotation center than the other rotating body.

  Therefore, surplus release oil collects on the outer peripheral surface side of the rotating body on the side where the oil recovery member is in contact, so that the oil recovery member can efficiently recover.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the pair of rotating bodies includes a pressure roller having a heat generating element therein and a fixing roller having a heat generating element therein.

  Therefore, in the fixing device in which the pressure roller and the fixing roller are brought into contact with each other to form the nip portion, the same operation as that of the first or second aspect of the invention is achieved.

  According to a fourth aspect of the present invention, in the fixing device according to the first or second aspect, the pair of rotating members includes a pressure roller having a heating element therein, a heating roller having a heating element therein, and a fixing roller. It is a fixing belt stretched between them.

  Therefore, in the fixing device in which the nip portion is formed by bringing the fixing belt and the pressure roller, which are stretched between the heating roller and the fixing roller, into contact with each other, the same effect as in the first or second aspect of the invention is exhibited. .

According to a fifth aspect of the present invention, there is provided the fixing device according to any one of the first to fourth aspects, wherein an oil path that guides the release oil overflowing from the recovery tank and a release part that is guided through the oil path. A fixing lower cover for storing oil is provided.

  Therefore, when the release oil stored in the recovery tank exceeds the capacity of the recovery tank, the release oil overflowing from the recovery tank is stored in the lower fixing cover through the oil path. Further, it is possible to provide a margin for the maintenance period of the recovery tank, and to prevent the surroundings from being contaminated by the release oil overflowing from the recovery tank.

According to a sixth aspect of the present invention, there is provided an image forming apparatus for forming a toner image by an electrophotographic method, transferring the formed toner image onto a recording medium, and fixing the toner image transferred onto the recording medium. And a fixing device according to any one of claims 1 to 5 .

Therefore, this image forming apparatus has the same operation as that of any one of the first to fifth aspects.

According to the fixing device of the first aspect of the invention, since the amount of release oil recovered by the oil recovery member is reduced, a mechanism for circulating the recovered excess release oil for reuse is provided. Therefore, the apparatus can be simplified and downsized.
Also, the release oil recovered by the oil recovery member can be stored in the recovery tank, and it is not necessary to provide a dedicated guide part for guiding the recording medium conveyed toward the nip part. The score can be reduced.

  According to the second aspect of the present invention, surplus release oil collects on the outer peripheral surface side of the rotating body on the side where the oil recovery member abuts, so that recovery by the oil recovery member can be performed efficiently. .

  According to the invention described in claim 3, in the fixing device in which the pressure roller and the fixing roller are brought into contact with each other to form the nip portion, the same effect as in the invention described in claim 1 or 2 is obtained.

  According to the fourth aspect of the present invention, in the fixing device in which the nip portion is formed by contacting the fixing belt and the pressure roller that are stretched between the heating roller and the fixing roller. The same effect as that of the present invention can be obtained.

According to the invention described in claim 5 , when the release oil stored in the recovery tank exceeds the capacity of the recovery tank, the release oil overflowing from the recovery tank passes through the oil path. Thus, it can be stored in the fixing lower cover, and the maintenance period of the recovery tank can be given, and the surrounding area can be prevented from being contaminated by the release oil overflowing from the recovery tank.

According to the image forming apparatus of the invention described in claim 6, the same effects as in the invention described in any one of claims 1 to 5 are obtained.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a longitudinal side view showing an internal structure of a laser printer as an image forming apparatus. In the apparatus main body 2 of the laser printer 1, an image forming unit 3, an optical writing device 4, a fixing device 5, a paper feed cassette 6, and the like are arranged.

  The image forming unit 3 includes a drum-shaped photoconductor 7 as an image carrier, a charger 8 arranged around the photoconductor 7 in the order of the image forming process, a developing device 9, a transfer device 10, a cleaning device 11, and the like. ing. In the image forming unit 3, the outer peripheral surface of the photosensitive member 7 is uniformly charged by the charger 8, and the photosensitive member 7 is scanned by scanning the outer peripheral surface of the charged photosensitive member 7 with a scanning line from the optical writing device 4. An electrostatic latent image is formed on the outer peripheral surface of the body 7, and this electrostatic latent image is developed with toner supplied from the developing device 9 to become a toner image. This toner image is transferred by the transfer device 10 onto the recording medium S fed and conveyed from the paper feed cassette 6.

  FIG. 2 is a vertical side view showing the fixing device 5. The fixing device 5 includes a pressure roller 12 that is a rotating body, a fixing roller 13 that is a rotating body, an oil supply device 14, and an oil recovery member 15 as main components.

  The pressure roller 12 and the fixing roller 13 are rotatably supported with a parallel axis, and an outer peripheral surface is brought into contact with each other to form a nip portion 16. The pressure roller 12 is provided with three rubber layers on a steel hollow core metal surface layer, an inner base layer is a conductive silicon rubber layer, and an intermediate layer is a fluororubber layer for preventing oil swelling. The surface layer is a high release silicone rubber layer. The fixing roller 13 also has the same three rubber layers. A heater 17 that is a heating element is provided in the pressure roller 12, and a heater 18 that is also a heating element is provided in the fixing roller 13.

  The pressure roller 12 and the fixing roller 13 have different lengths in the rotation center direction, the pressure roller 12 is formed longer than the fixing roller 13, and the pressure roller 12 has both ends in the rotation center direction outside the fixing roller 13. It is arranged so as to protrude in the direction. The length of the fixing roller 13 in the direction of the rotation center is set to be slightly larger than the sheet passing range of the maximum size recording medium S that can be used in the laser printer 1. Therefore, the portion of the pressure roller 12 that protrudes outward from the fixing roller 13 is located outside the sheet passing range of the maximum size recording medium S that can be used in the laser printer 1.

  The oil supply device 14 is a device for supplying release oil such as silicone oil to the fixing roller 13, and includes a supply tank 19, a coating felt 20, an oil supply roller 21 that can rotate around its axis, and a shaft center. It is constituted by an oil application roller 22 that can rotate around. Release oil is stored in the supply tank 19, and the lower end of the coating felt 20 is immersed in the release oil in the supply tank 19, and the upper end extends out of the supply tank 19. Part of the outer peripheral surface of the oil supply roller 21 is in contact with the upper end of the application felt 20 and the outer peripheral surface of the oil application roller 22, and part of the outer peripheral surface of the oil application roller 22 is in contact with the outer peripheral surface of the fixing roller 13. ing. As a result, the release oil in the supply tank 19 rises along the application felt 20, and the raised release oil passes through the oil supply roller 21 and the oil application roller 22 to the outer peripheral surface of the fixing roller 13. Applied.

  The oil recovery member 15 is a member that recovers excess release oil out of the release oil supplied from the oil supply device 14, and is formed of felt. The oil recovery member 15 is a portion that protrudes outward from the fixing roller 13 on the outer peripheral surface of the pressure roller 12, that is, outside the sheet passing width of the maximum size recording medium S that can be used in the laser printer 1. It is in contact with the part.

  A recovery tank 23 is provided below the oil recovery member 15, and release oil recovered by the oil recovery member 15 is stored in the recovery tank 23.

  A guide portion 24 that guides the recording medium S on which the toner image is transferred toward the nip portion 16 is formed in a part of the collection tank 23.

  In such a configuration, the image forming unit 3 forms a toner image and transfers the formed toner image to the recording medium S, and the recording medium S onto which the toner image has been transferred is subjected to a fixing process in the fixing device 5. The

  In the fixing process in the fixing device 5, the oil supply device 14 supplies the release oil to the outer peripheral surface of the fixing roller 13 in order to prevent the toner image from adhering to the fixing roller 13 and improve the releasability. Is called. The supplied release oil adheres to the recording medium S and is carried by a small amount when the recording medium S passes through the nip portion 16. For this reason, as the amount of the release oil to be supplied, it is sufficient to supply the minimum amount capable of maintaining the releasability.

  When image formation is performed on a large-sized recording medium S having a wide sheet passing width, almost all of the supplied release oil adheres to the recording medium S and is carried. Therefore, it is necessary to collect the release oil. Does not occur.

  On the other hand, when image formation is performed on a small-sized recording medium S, excess release oil that does not adhere to the recording medium S is generated. The excess release oil is recovered by the oil recovery member 15 and stored in the recovery tank 23 when it moves on the outer peripheral surface of the pressure roller 12 to a position where the oil recovery member 15 contacts. . However, since a small amount of release oil is originally supplied, the amount of recovered release oil is also small, and it is not necessary to circulate the recovered release oil for reuse, and a circulation mechanism is provided. It is not necessary. For this reason, the fixing device 5 does not require a mechanism for circulating the release oil, and has a simplified structure and an inexpensive structure.

  Further, when the oil recovery member 15 comes into contact with the pressure roller 12 and recovers excess release oil, the portion of the pressure roller 12 on the surface where the oil recovery member 15 is in contact with the oil recovery member 15 However, since the portion with which the oil recovery member 15 is in contact is outside the sheet passing range of the maximum size recording medium S used in the laser printer 1, the stripped release oil is recorded. There is no adverse effect on the medium S or image.

  A second embodiment of the present invention will be described with reference to FIGS. The same parts as those described in FIGS. 1 to 3 are denoted by the same reference numerals, and description thereof is also omitted (the same applies to the following embodiments).

  The fixing device 5a in the laser printer according to the present embodiment includes a pressure roller 12, which is a rotating body, a fixing roller 13a, a heating roller 25, and a rotating body that is stretched between the heating roller 25 and the fixing roller 13a. The fixing belt 26, the oil supply device 14, and the oil recovery member 15 are main constituent members. Inside the heating roller 25, a heater 27 as a heating element is provided.

  The pressure roller 12 and the fixing roller 13a are rotatably supported with parallel axes, and the outer peripheral surface of the fixing belt 26 and the outer peripheral surface of the pressure roller 12 that are stretched between the fixing roller 13a and the heating roller 25. Are in contact with each other to form a nip portion 16.

  The fixing roller 13a is made of silicon foam rubber. The heating roller 25 is made of aluminum and has a hollow shape, and a heater 27 that is a heating element is provided therein. The fixing belt 26 is formed by covering a surface layer of a heat-resistant resin substrate such as polyimide with high-release silicone rubber.

  The pressure roller 12 and the fixing belt 26 have different lengths in the rotation center direction, the pressure roller 12 is formed longer than the fixing belt 26, and both ends of the pressure roller 12 in the rotation center direction are outside the fixing belt 26. It is arranged so as to protrude in the direction. The length of the fixing belt 26 in the rotational center direction is set to be slightly larger than the sheet passing range of the maximum size recording medium S that can be used in the laser printer 1. Accordingly, the portion of the pressure roller 12 that protrudes outward from the fixing belt 26 is located outside the sheet passing range of the maximum size recording medium S that can be used in the laser printer 1.

  The oil supply device 14 is substantially the same as that of the first embodiment except that the oil application roller 22 is in contact with the outer peripheral surface of the fixing belt 26. As a result, the release oil in the supply tank 19 rises along the application felt 20, and the released release oil reaches the outer peripheral surface of the fixing belt 26 via the oil supply roller 21 and the oil application roller 22. Applied.

  In such a configuration, the image forming unit 3 forms a toner image and transfers the formed toner image to the recording medium S, and the recording medium S onto which the toner image has been transferred is subjected to a fixing process in the fixing device 5a. The

  In the fixing process in the fixing device 5a, the oil supply device 14 supplies the release oil to the outer peripheral surface of the fixing belt 26 in order to prevent the toner image from adhering to the fixing belt 26 and improve the releasability. Is called. The supplied release oil adheres to the recording medium S and is carried by a small amount when the recording medium S passes through the nip portion 16. For this reason, as the amount of the release oil to be supplied, it is sufficient to supply the minimum amount capable of maintaining the releasability.

  When image formation is performed on a large-sized recording medium S having a wide sheet passing width, almost all of the supplied release oil adheres to the recording medium S and is carried. Therefore, it is necessary to collect the release oil. Does not occur. On the other hand, when image formation is performed on a small-sized recording medium S, excessive release oil that does not adhere to the recording medium S is generated, and this excessive release oil is used as the outer peripheral surface of the pressure roller 12. When moving up to a position where the oil recovery member 15 is in contact with the oil, the oil recovery member 15 recovers it and stores it in the recovery tank 23.

  However, as in the case of the first embodiment, since a small amount of release oil is originally supplied, a small amount of release oil is recovered, and the recovered release oil is reused. Therefore, it is not necessary to circulate, and it is not necessary to provide a circulation mechanism. For this reason, the fixing device 5a does not require a mechanism for circulating the release oil, and has a simplified structure and an inexpensive structure.

  A third embodiment of the present invention will be described with reference to FIG. The fixing device 5b of the present embodiment has the same basic configuration as that of the fixing device 5a of the second embodiment. The oil path 28 guides the release oil overflowing from the recovery tank 23, and this oil. A difference is that a fixing lower cover 29 for storing the release oil guided through the path 28 is provided.

  In such a configuration, when the release oil recovered by the oil recovery member 15 and stored in the recovery tank 23 exceeds the capacity of the recovery tank 23, the release oil overflows from the recovery tank. The oil is stored in the fixing lower cover 29 through the oil path 28. As a result, it is possible to provide a margin in the maintenance period in which the release oil stored in the recovery tank 23 is disposed of, and the surroundings are contaminated by the release oil overflowing from the recovery tank 23. Is prevented.

1 is a longitudinal side view illustrating a schematic structure of a laser printer according to a first embodiment of the present invention. It is a front view which is a vertical side view which shows the fixing device of the laser printer. It is the front view. It is a vertical side view which shows the fixing device of the 2nd Embodiment of this invention. It is the front view. It is a vertical side view which shows the fixing device of the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Image forming part 5 Fixing apparatus 5a Fixing apparatus 5b Fixing apparatus 12 Pressure roller, rotary body 13 Fixing roller, rotary body 13a Fixing roller 14 Oil supply apparatus 15 Oil recovery member 16 Nip part 17 Heating element 18 Heating element 23 Recovery tank 24 Guide unit 25 Heating roller 26 Fixing belt, rotating body 27 Heating element 28 Oil path 29 Fixing lower cover S Recording medium

Claims (6)

A pair of rotators that have a nip portion that abuts the outer peripheral surface, applies heat and pressure to a recording medium that is conveyed through the nip portion, and release oil on at least one surface of the rotator And an oil recovery member positioned outside the sheet passing range of the maximum size recording medium conveyed through the nip portion and in contact with the surface of the rotating body ,
The oil recovery tank for storing the recovered release oil below the collecting member is arranged, the recovery guide for guiding portions that have been formed fixing device to the nip the recording medium in the part of the tank.   The length of one rotating body in the direction of the rotation center is formed longer than the length of the other rotating body in the direction of the rotation center, and the length of the one rotating body in the direction of the rotation center is longer than the length of the other rotating body. The fixing device according to claim 1, wherein the oil recovery member is in contact with the formed portion.   3. The fixing device according to claim 1, wherein the pair of rotating bodies includes a pressure roller having a heating element inside and a fixing roller having a heating element inside. 4. 3. The fixing device according to claim 1, wherein the pair of rotating bodies are a pressure roller having a heating element inside, and a fixing belt stretched between a heating roller having a heating element inside and the fixing roller. . An oil path for guiding the overflowed releasing oil from the previous SL recovery tank, any one of from the lower fixing cover for storing a releasing oil guided to the oil path claims 1 provided 4 The fixing device described. The toner image formed by the electrophotographic method, an image forming unit for transferring a formed toner image onto a recording medium, a fixing according to any one of claims 1 to 5 for fixing the toner image transferred onto the recording medium And an image forming apparatus.

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