JP5370666B2 - Fixing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image fixing unit which can efficiently cool a presser without degrading the image quality and shorten the waiting time when lowering a temperature of a fixing nip, and also to provide an image forming device incorporating this fixing unit. <P>SOLUTION: This image fixing unit has an image fixing belt 12 made free to turn, a heater 14h to directly or indirectly heat the image fixing belt 12, a pressure roller 13 disposed free to turn under the fixing belt 12 in contact with it to form the image fixing nip N, an oil applicator 22 having an oil tank 22a which holds oil O and disposed under the pressure roller 13 and partly dipping the pressure roller 13 in this oil tank 22a to apply the oil O, and an oil cooler 24 to cool the oil O in the oil tank 22a. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a fixing device and an image forming apparatus including the fixing device, and more specifically, a fixing device that heats and fixes toner on a transported recording medium and a toner image formed using an electrophotographic method on the recording medium. The present invention relates to an image forming apparatus provided with the fixing device such as a copying machine, a printer, a facsimile machine, or a complex machine for fixing an image after transfer.

  In a fixing device in an electrophotographic image forming apparatus such as a copying machine or a printer, fixing performance is maintained while oil is used for a fixing member or the like to improve releasability from toner. In particular, in a full-color electrophotographic apparatus, a lot of oil is used in the fixing device.

  In recent years, a technique using an endless fixing belt as a fixing member of a fixing device has been widely employed because of shortening of the warm-up time (see, for example, Patent Document 1). This fixing device is provided with an oil application device that applies oil to the fixing belt. When oil is applied to the fixing belt, the fixing belt is rotated to move to the fixing nip portion, and the toner image is transferred. This contributes to releasability from the recording medium (transfer paper). Next, in the fixing nip part, part of the oil of the fixing belt has moved to the pressure roller surface, and the release property of the pressure roller is also improved.

  However, in the conventional fixing device, the amount of oil adhering to the pressure member (pressure roller) side may be reduced, and the releasability of the fixed recording medium on the pressure member may deteriorate. . In order to solve the shortage of oil in the pressure member, a fixing device having an oil application device on the pressure member side has been proposed.

  By the way, the image forming apparatus is required to support various types of paper such as thick paper, thin paper, coated paper, and non-coated paper. In that case, in the fixing device in the electrophotographic system, depending on the thickness and type of the paper. It is necessary to adjust the amount of heat applied to the paper.

  At this time, the fixing set temperature of the fixing nip portion is changed. Generally, however, it takes more time to lower the fixing member temperature than to increase the fixing member temperature. When the temperature of the fixing member is raised, the temperature can be increased efficiently by operating the heating means. However, when the temperature of the fixing member is lowered, the heating means is turned off and the fixing member is idled. This is because it is common to dissipate heat in the air. In this case, when the temperature of the fixing member is lowered only by heat radiation in the air, it may take several times as long as the temperature of the fixing member to be raised depending on how the fixing member itself is warmed or the heat capacity. In particular, a pressure member such as a pressure roller often has a larger heat capacity than the fixing member, and when the temperature of the fixing nip portion is lowered, the temperature of the pressure member is often waited for.

  Therefore, in the prior art, there is known a method of forcibly cooling the pressure roller by directly applying air blown by a fan to the roller for air cooling or by bringing a cooling roller into contact therewith. However, the air-cooling method has an insufficient cooling effect, and the method in which the cooling roller is brought into contact with the pressure roller may damage the surface layer of the pressure roller and adversely affect the image quality.

  The present invention has been made in view of the above-described problems in the prior art. The waiting time in the case where the temperature of the fixing nip portion is lowered by efficiently cooling the pressure member without degrading the image quality is provided. It is an object to provide a shortenable fixing device and an image forming apparatus including the fixing device.

The present invention provided to solve the above problems is as follows.
[1] A fixing member that is rotatably provided, a heating unit that directly or indirectly heats the fixing member, and a fixing nip portion that is rotatably provided below the fixing member and abuts the fixing member. A pressure member to be formed; an oil tank that holds oil and is provided below the pressure member; and an oil application device that applies oil by immersing a part of the pressure member in the oil tank; An oil cooling device for cooling the oil in the oil tank,
When the temperature of the fixing nip portion is lowered, the oil cooling device cools the oil in the oil tank, and the pressure member partially immersed in the oil tank is rotated to rotate the pressure member. constant Chakusochi characterized in that cooled.
[2] A fixing member that is rotatably provided, a heating means that directly or indirectly heats the fixing member, and a fixing nip portion that is rotatably provided below the fixing member and contacts the fixing member. A pressure member to be formed; an oil tank that holds oil and is provided below the pressure member; and an oil application device that applies oil by immersing a part of the pressure member in the oil tank; An oil cooling device for cooling the oil in the oil tank,
A pressure depressurization unit that switches between a pressure state in which the pressure member is brought into contact with the fixing member and a pressure depressurization state in which the pressure member is separated; and when the temperature of the fixing nip portion is lowered, the oil cooling device The oil in the tank is cooled, and the pressure member rotating the pressure depressurizing means is separated from the fixing member and immersed deeply in the oil tank to cool the pressure member. It shall be the constant Chakusochi.
[3] The fixing device according to [1] or [2], wherein the oil cooling device has a fan mechanism for air-cooling a metal casing of the oil tank.
[4] The fixing device according to [1] or [2], wherein the oil cooling device includes a Peltier cooling mechanism that cools a metal casing of the oil tank.
[5] The oil cooling device includes a heat conduction member provided to extend from the inside of the oil tank to the outside of the tank, and a fan mechanism for air-cooling a portion of the heat conduction member that extends to the outside of the oil tank. The fixing device as described in [1] or [2] above.
[6] The oil cooling device includes: a heat conduction member that extends from the inside of the oil tank to the outside of the tank; and a Peltier cooling mechanism that cools a portion of the heat conduction member that extends outside the oil tank. The fixing device according to [1] or [2], which has the fixing device.
[7] An image forming apparatus comprising the fixing device according to any one of [1] to [6] .

  According to the present invention, when the temperature of the fixing nip portion is lowered, the pressure member immersed in the oil tank is brought into direct contact with the oil cooled by the oil cooling device, so that the cooling is accelerated. The waiting time until the part reaches the target temperature can be shortened.

FIG. 2 is a cross-sectional view illustrating a configuration of a fixing device according to the present invention. FIG. 3 is a schematic diagram illustrating a configuration of a pressure depressurizing unit in the fixing device according to the present invention. It is sectional drawing which shows the structure of the 1st oil application apparatus in the fixing device which concerns on this invention. It is a perspective view which shows the principal part structure of the 1st oil application apparatus used by this invention. It is sectional drawing which shows the structure of the 2nd oil application | coating apparatus in the fixing device which concerns on this invention. FIG. 3 is a cross-sectional view showing a main configuration (1) of the fixing device according to the present invention. FIG. 3 is a cross-sectional view showing a main configuration (2) of the fixing device according to the present invention. FIG. 3 is a schematic diagram illustrating a main configuration (3) of the fixing device according to the present invention. FIG. 6 is a schematic diagram illustrating a main configuration (4) of a fixing device according to the present invention. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to the present invention. It is the schematic which shows the structure of the oil circulation mechanism in the image forming apparatus of FIG. It is sectional drawing which shows another structural example (1) of the pressure member in the fixing device which concerns on this invention, and a fixing member. It is sectional drawing which shows another structural example (2) of the pressure member in the fixing device which concerns on this invention, and a fixing member. It is sectional drawing which shows another structural example (3) of the pressure member in the fixing device which concerns on this invention, and a fixing member.

The configurations of the fixing device and the image forming apparatus according to the present invention will be described below.
First, the basic configuration of the fixing device according to the present invention will be described.
As shown in FIG. 1, the fixing device 100 used in the present invention includes a fixing member (fixing member) that is a first nip forming member that is stretched around a fixing roller 11 and a heating roller 14 inside a fixing cover 100c. A pressure member (pressing member) that is a second nip forming member that forms a fixing nip portion (also simply referred to as a nip portion) N by being pressed against the fixing member (fixing belt 12) in a rotatable manner on the lower side. A pressure roller 13) and a recording medium discharge side of the fixing nip portion N, and a tip thereof is disposed in the vicinity of the fixing member (fixing belt 12) so that the recording medium P is wound around the fixing member (fixing belt 12). A separation claw 16a having a fluorine coating on the surface to be prevented, and a recording medium discharge side of the fixing nip portion N, the tip of which is disposed in contact with a pressure member (pressure roller 13). Addition Comprises a separation pawl 16b on the surface to prevent the winding of the recording medium P to the rollers 13) is a fluorine coating has been subjected, a cleaning mechanism 17 for cleaning the fixing belt 12 is pressed against the cleaning web, the.

  Here, the fixing belt 12 is an endless belt, and has a two-layer structure in which an elastic layer such as a silicone rubber layer is formed on a base material such as nickel, stainless steel, or polyimide. The fixing roller 11 has a metal core and silicone rubber. In order to shorten the warm-up time, foamed silicone rubber may be used so that the heat of the fixing belt 12 is not easily absorbed. The heating roller 14 is an aluminum or iron hollow roller and has heating means (heat source) including a heater 14h such as a halogen heater inside. The heat source may be an induction heating mechanism (IH). A plurality of hollow pipes are formed in the thick portion of the hollow roller of the heating roller 14 so that the longitudinal direction thereof is the width direction of the heating roller 14, and a heat pipe 14a embedded uniformly in the circumferential direction of the heating roller 14 is provided. Have. The heat pipe 14a improves the heat transfer from the heater 14h to the roller surface, and the fixing belt 12 is heated quickly and uniformly.

  When the fixing device 100 is driven, for example, the pressure roller 13 rotates in the direction in which the recording medium P is discharged (counterclockwise in FIG. 1), and the fixing belt 12 rotates. Alternatively, the fixing belt 12 is rotated in the clockwise direction in the drawing so that the fixing belt 12 ejects the recording medium P in a state where an appropriate tension is applied by the pressing of the tension roller 15 (clockwise direction in FIG. 1). You may make it rotate. Further, at the time of fixing, the fixing belt 12 is heated to a predetermined temperature (for example, a temperature suitable for toner fixing) detected by a thermistor (not shown) due to heat generated by a heater 14 h disposed inside the heating roller 14. Is done. In the present invention, the fixing belt 12 (endless belt) shown in FIG. 1 is shown as the fixing member. However, the fixing member is not limited to this and may be a hollow cylindrical roller (fixing roller).

  The pressure roller 13 is usually a cylindrical roller in which an elastic layer such as silicone rubber is provided on a core metal such as aluminum or iron. When necessary, such as during fixing, the pressure roller 13 is heated to a predetermined temperature by the heat generated by the heater 13h disposed therein.

  Further, the pressure roller 13 can be switched between a pressure state in contact with the fixing belt 12 and a pressure-release state after being separated by the pressure-decompression means 30.

FIG. 2 shows the configuration of the pressure depressurizing means of the pressure roller 13.
The pressurizing / depressurizing means 30 includes a pressurizing cam 31 that rotates by a driving force input from the outside, a first pressurizing arm 32, a second pressurizing arm 33 (shaded portion in the figure), a first pressurizing arm 32, and The elastic member 34 is fixed to each end of the second pressure arm 33, the first pressure arm 32 is fixed to the frame of the fixing device 100, and the support shaft 35 is common to the second pressure arm 33.

  Here, the pressurizing / depressurizing means 30 moves the pressure roller 13 toward the fixing belt 12 to apply pressure, and moves the pressure roller 13 in the direction away from the fixing belt 12 to depressurize as follows. Is called.

(Pressurizing operation)
First, when the pressure cam 31 is rotated by a constant rotation angle in the direction of the arrow in the figure by an external driving force, the pressure cam 31 pushes up the top portion of the first pressure arm 32 (( 1) Arrow direction of part).
When the top portion of the first pressure arm 32 is pressed, the first pressure arm 32 rotates around the support shaft 35 (counterclockwise direction in FIG. 2). Then, the elastic member 34 fixed to the end of the first pressure arm 32 opposite to the support shaft 35 also rotates, and the elastic member 34 is fixed to the end of the second pressure arm 33 with a constant pressure. Is pushed up (in the direction of the arrow in FIG. 2 (2)).
Next, when the end of the second pressure arm 33 on the elastic member 34 side is pushed up, the second pressure arm 33 rotates about the support shaft 35 (counterclockwise direction in FIG. 2).
Next, the pressure portion 33a located between the end of the second pressure arm on the elastic member 34 side and the support shaft 35 abuts against the shaft end portion 13j of the pressure roller 13 and acts toward the fixing roller 11. (The arrow direction in the (3) part of FIG. 2).
Finally, the pressure roller 13 comes into contact with the fixing roller 11 via the fixing belt 12 and is in a state of being pressed with a constant pressure based on the elastic force of the elastic member 34, thereby forming the fixing nip portion N (FIG. 2 ( 4) Arrow direction of part).
As described above, when the fixing device 100 is driven, the pressing / depressurizing unit 30 presses the pressing roller 13 against the fixing belt 12 with a constant pressure in the direction of the fixing belt 12.

(Decompression operation)
First, when the pressure cam 31 is further rotated by a fixed rotation angle from the angular position when the pressure is applied by an external driving force, the pressure cam 31 moves the top portion of the first pressure arm 32. Pushing up is released (in the direction opposite to the arrow in part (1) in FIG. 2).
When the push-up of the first pressure arm 32 is released, the first pressure arm 32 is applied with the support shaft 35 as the central axis with a repulsive force via the fixing nip portion N, the pressure portion 33a, and the elastic member 34. It rotates in the opposite direction to the pressure (clockwise direction in FIG. 2). Next, the end of the second pressure arm 33 together with the elastic member 34 fixed to the end of the first pressure arm 32 opposite to the support shaft 35 is pulled in the direction opposite to that in the case of pressurization ( (The direction opposite to the arrow in part (2) of FIG. 2).
Next, when the end of the second pressure arm 33 on the elastic member 34 side is pulled down, the second pressure arm 33 moves in the direction opposite to the direction of pressure with the support shaft 35 as the central axis. It rotates (clockwise direction in FIG. 2).
Next, the pressing portion 33a located between the end of the second pressing arm on the elastic member 34 side and the support shaft 35 rotates in the opposite direction to that in the case of pressing, so that the shaft end 13j of the pressing roller 13 It moves away (in the direction opposite to the arrow in (3) in FIG. 2).
As a result, the pressure roller 13 is released from being pressed, so that the pressure roller 13 moves away from the fixing roller 11, and the formation of the fixing nip portion N is eliminated and the pressure is released (see FIG. (The direction opposite to the arrow in the portion (4) in FIG. 2).
Thus, when the driving of the fixing device 100 stops, or when the pressure roller 13 is immersed and cooled in the oil tank 22a as will be described later, the pressure depressurizing means 30 applies the pressure to the fixing belt 12 of the pressure roller 13. Is released from the fixing belt 12 (depressurized state).

  The separation claw 16b comes into contact with the pressure roller 13 when the pressure roller 13 contacts the fixing belt 12 and enters the pressure state, and the pressure roller 13 moves away from the fixing belt 12 and is released from the pressure state. When it becomes, it is separated from the pressure roller 13.

  Further, in the present invention, the form of the pressure roller 13 (roller type) shown in FIG. 1 is shown as the pressure member. However, the present invention is not limited to this, and an endless belt shape spanned between two rollers is used. It is good also as a pressurizing member (belt type).

  In the fixing device 100, the surface of the fixing belt 12 is heated to a predetermined temperature while the fixing belt 12 and the pressure roller 13 are rotationally driven, and the recording in which the unfixed toner T is formed in the fixing nip portion N is performed. The medium P is passed (paper passing from the right side to the left side in the drawing), and fixing is performed by thermally fusing unfixed toner onto the recording medium P by pressurization and heating at the fixing nip N.

  Next, the toner-fixed recording medium P is discharged from the fixing nip portion N. At this time, the recording medium P may come out while being wound around the fixing belt 12 or the pressure roller 13. As countermeasures, the oil applying device 21 which is a first oil applying device (oil applying means) for applying oil to the fixing belt 12 to improve the releasability and the releasability by applying oil to the pressure roller 13. An oil application device 22 which is a second oil application device for improving the above is provided. The oil used here is preferably a heat-resistant and non-volatile oil, such as silicone oil. In addition, the recording medium P is separated from the fixing belt 12 or the pressure roller 13 by the tips of the separation claws 16 a and 16 b coming into contact with the leading end of the recording medium P. The recording medium P discharged from the fixing nip N passes through a predetermined discharge path and is sent out from the fixing device 100.

Here, a configuration example of the first oil application device used in the fixing device 100 will be described.
FIG. 3 is a schematic diagram of a main part related to the first oil application device in the fixing device according to the present invention. That is, the fixing device 100 of the present invention includes a fixing member (fixing belt 12) that is rotatably provided, and a pressure member (pressure roller) that contacts the fixing member and forms a fixing nip portion (fixing nip portion N). 13), an oil application part (application roller 23) for applying oil to a predetermined width of the fixing member or pressure member, and an oil supply part (oil input port 21a, oil reservoir part 21b) for supplying oil to the oil application part , A support plate 21c, a supply felt 21d, a supply roller 21e, and a metering blade 21f), a first oil application device (oil supply device 21), and the oil supply unit from an oil supply device (described later) A bowl-shaped recess for storing oil that is supplied and supplied from an oil inlet, and the longitudinal direction of the recess is parallel to the width direction of the oil application part. An oil reservoir (oil reservoir 21b) is provided above an adjacent oil supply member (supply felt 21d), and when oil is poured into the oil reservoir, the oil overflows from the upper portion of the oil reservoir. It is configured to be supplied to an adjacent oil supply member.

FIG. 4 is a perspective view showing the configuration of the oil reservoir 21b, the support plate 21c, and the supply felt 21d, which are the main parts of the oil supply unit.
The oil reservoir 21b is a bowl-shaped depression formed of a flange 21b2 having a V-shaped cross section and a side plate 21b3 provided in a manner to block the groove of the flange at both longitudinal ends of the flange 21b2. At this time, the support plate 21c is above the supply roller 21e and the longitudinal direction of the flange portion 21b2 is parallel to the width direction of the supply roller 21e (that is, the width direction of the application roller 23 and the width direction of the fixing belt 12). It is supported by. In FIG. 4, the oil reservoir portion 21b is formed with a flange portion 21b2 by a folded end portion of the support plate 21c and a band plate fixed to the folded portion, and side plates at both longitudinal ends of the flange portion 21b2. Although the configuration in which 21b3 is fixed is shown, the present invention is not limited to this, and the flange portion 21b2 may be formed by sheet metal and the side plate 21b3 is attached, or the flange portion 21b2 and the side plate 21b3 may be integrally formed. . The oil reservoir 21b may be made of a heat-resistant metal material or plastic that does not react with the oil used.

  In addition, the end facing the adjacent oil supply member (supply felt 21d) is the other end (the other end of the flange 21b2 and the end of the side plate 21b3) of the open end of the oil reservoir 21b. It becomes a mouth cut part (mouth cut part 21b1) whose height position is lower than that. When the fixing device 100 is driven, oil is introduced into the center of the oil reservoir 21b in the width direction until the oil overflows from the oil reservoir 21b (injected from the arrow position in the figure). Oil preferentially overflows from 21b1 and is supplied to the oil application part (application roller 23) via the adjacent oil supply member (supply felt 21d) and supply roller 21e. At this time, since oil overflows from the entire width of the mouth cut portion 21b1, oil is supplied to a predetermined width (for example, full width) of the supply roller 21e and the application roller 23 via the supply felt 21d, and then the predetermined width of the fixing belt 12 is reached. The oil is applied to (for example, full width).

  The support plate 21c has a U-shaped cross section and supports the oil reservoir 21b and the supply felt 21d. At this time, the supply felt 21d can be brought into contact with the supply roller 21e with a constant pressing force if an appropriate spring characteristic is given, such as a metal material processed by sheet metal.

  The supply felt 21d is disposed adjacent to the oil reservoir 21b, and supplies oil from the upper portion of the oil reservoir 21b to the oil application part (application roll 23) side. Specifically, the supply felt 21d is between the oil reservoir 21b and the supply roller 21e and protrudes at the same height as or above the end of the mouth cut portion 21b1 of the oil reservoir 21b. It arrange | positions in contact with the oil reservoir part 21b. Further, the supply felt 21d is a compressed sheet made of, for example, a fiber that does not react with heat-resistant oil (for example, a meta-aramid fiber), and allows the oil to pass between the fibers while holding the oil inside. Is. Therefore, the fiber basis weight (mesh) of the supply felt 21d may be coarser than that for the purpose of filtering impurities. Thereby, the supply felt 21d can receive the oil overflowing from the mouth cut portion 21b1, and can flow the oil along the supply felt 21d. Here, oil flows from the upper part of the oil reservoir 21b to the supply roller 21e by the action of gravity (free fall), and the supply felt 21d supplies oil to the supply roller 21e at the contact portion with the supply roller 21e.

  In addition, the oil supply unit includes a supply roller 21e that receives oil from the supply felt 21d, and a metering blade 21f that adjusts the oil adhesion amount (holding amount) of the supply roller 21e. Among these, the supply roller 21e is made of a material corresponding to the oil used on the surface, and is made of, for example, silicone rubber. The metering blade 21f is a blade made of a material that does not damage the surface of the supply roller 21e while restricting the amount of oil adhering to the supply roller 21e, and is preferably formed of, for example, fluororubber.

With the above configuration, oil is supplied from the oil supply unit to the oil application unit as follows.
(S11) First, when the driving of the fixing device 100 is started, the fixing belt 12 is rotated with the rotation of the pressure roller 13, and the rotational driving of the supply roller 21e is started to contact the fixing belt 12 and the supply roller 21e. The rotation of the application roller 23 is also started.
(S12) At the same time, oil starts to be supplied from the oil input port 21a to the oil reservoir 21b, and the oil is stored in the oil reservoir 21b.
(S13) The oil is continuously supplied, and the oil overflows from the oil reservoir 21b. At this time, the oil overflows from the full width of the mouth cut portion 21b1 and is supplied to the supply felt 21d (full width).
(S14) In the supply felt 21d, the oil passes through the inside from the upper side (upper side) of the oil reservoir 21b to the lower side, and the oil is supplied to a predetermined width of the supply roller 21e at the contact portion of the supply roller 21e.
(S15) The portion of the supply roller 21e to which the oil is supplied moves by the rotation of the supply roller 21e, and then the amount of oil adhering to the supply roller 21e is regulated by the contact of the metering blade 21f.
(S16) The oil of the supply roller 21e is supplied to a predetermined width of the application roller 23 at the contact portion with the application roller 23. Finally, the oil adhering to the application roller 23 is applied to a predetermined width of the fixing belt 12.

  As described above, in the oil application device 21, in the course of oil supply from the oil supply unit to the oil application unit, the oil flows from the upper side to the lower side using the action of gravity from the oil reservoir 21b to the supply roller 21e. Since it is configured to drop, a sufficient amount of oil can be stably supplied.

Next, a configuration example of the second oil application device used in the fixing device 100 will be described.
FIG. 5 shows a schematic diagram of a main part relating to the second oil application device in the fixing device 100 used in the present invention.
That is, the fixing device 100 according to the present invention includes a first nip forming member (fixing member (fixing belt 12)) that is rotatably provided and a second nip that is rotatably provided below the first nip forming member. A nip forming member (pressure member (pressure roller 13)) is in contact with the nip forming member (pressing roller 13) so as to form a fixing nip portion (fixing nip portion N), and holds the second oil (oil O) while holding the oil (oil O). An oil tank (oil tank 22a (sub oil pan 22a1)) provided below the nip forming member and in which a part of the second nip forming member is immersed, and the second nip forming member rotating downstream of the oil tank. And a second oil application device (oil application device 22) that is provided in front of the fixing nip portion and has an oil restriction member (blade 22b) that restricts the amount of oil adhering to the second nip forming member.

  Here, the oil tank 22a holds the oil O and a sub oil pan 22a1 that is an immersion tank in which a part of the pressure roller 13 is immersed, and a main oil pan that is an oil receiver in which the entire sub oil pan 22a1 is stored. 22 a 2, which has a two-tank structure and is fixedly arranged in the cover 100 c of the fixing device 100. At this time, the oil O applied to the pressure roller 13 is supplied to the sub oil pan 22a1 from the outside of the oil applying device 22 (oil receiver that collects excess oil of the oil applying device 21), and the oil O is supplied to the sub oil pan 22a1. It has a structure that can be stored in. The sub oil pan 22a1 is a rectangular oil pan, and its length in the longitudinal direction is at least equal to the width of the roller portion of the pressure roller 13.

  Further, the pressure roller 13 has the entire width of the roller, and a part of the roller radial direction is always immersed in the sub oil pan 22a1 without any trouble as a device. That is, the oil level of the sub oil pan 2a1 is sufficiently higher than the lower end of the pressure roller 13 in the pressurized state, and the lower end of the pressure roller 13 is in a state where the pressure roller 13 is released. The bottom surface of the sub oil pan 22a1 is not in contact.

  The main oil pan 22a2 is an oil receiver that receives the oil O overflowing from the sub oil pan 22a1. Further, an oil discharge port to an oil tank (described later) for collecting the oil O is provided at the lower part of the main oil pan 22a2.

  Note that it is preferable to use a metal material, plastic, or the like that does not react to the oil used and is heat resistant for both the sub oil pan 22a1 and the main oil pan 22a2.

  The blade 22b is a spatula-like elastic member having a width at least equal to or greater than the width of the pressure roller 13, and its longitudinal direction is always in contact with the surface of the pressure roller 13 in the width direction. The oil adhering amount at 13 is regulated to be a predetermined amount while being uniform in the width direction. The blade 22b is made of a material that does not damage the surface of the supply roller 21e, and is formed of, for example, fluororubber.

  Here, the pressure roller 13 is made of a material corresponding to the oil O used on the surface. For example, when the oil O is silicone oil, the pressure roller 13 is formed of silicone rubber. Therefore, when the pressure roller 13 is immersed in the oil O in the oil tank 22a, the silicone rubber swells and holds the oil O, but the blade 22b pressurizes the surface of the pressure roller 13 in this state. The abutment is made at the lower position of the roller 13 so that the oil O is scraped off from the pressure roller 13. Specifically, the blade 22b is disposed so that the angle θ formed between the tip of the blade 22b and the tangent line of the pressure roller 13 is an acute angle of less than 90 degrees, and the tip is opposed to the rotation direction of the pressure roller 13. It functions to scrape off excess oil O on the surface of the pressure roller 13 toward the oil tank 22a. As a result, the surface of the pressure roller 13 is in a state where a sufficient amount of oil is uniform in the width direction to ensure releasability. In addition, surplus oil in the pressure roller 13 is collected in the oil tank 22a, and a circulation system that is used for oil application to the pressure roller 13 again is configured.

  Further, the oil application device 22 preferably has a cleaning felt 22c, which is a cleaning member that contacts the pressure roller 13 and cleans the surface of the pressure roller 13 between the oil tank 22a and the blade 22b. The cleaning felt 22c is a compressed sheet made of, for example, a fiber that does not react with heat-resistant oil (for example, a meta-aramid fiber), and permeates the oil while capturing fine solid impurities inside. It is. Thereby, it is possible to remove fine solid impurities (for example, dust or calcium carbonate derived from the recording medium P) in the oil O while leaving the oil O on the surface of the pressure roller 13.

  The cleaning felt 22c is supported by an appropriate support member so as to come into contact with the pressure roller 13. However, the support member should be provided with appropriate spring characteristics, such as a metal material processed by sheet metal. For example, the cleaning felt 22c can be brought into contact with the pressure roller 13 with a constant pressing force to adjust the oil adhesion amount.

With the above configuration, oil application from the oil application unit 22 to the pressure roller 13 is performed as follows.
(S21) First, when the driving of the fixing device 100 is started, the rotation of the pressure roller 13 is started, and then the pressure roller 13 comes into contact with the fixing belt 12 with a constant pressure by the pressure depressurizing means. Part N is formed. At the same time, the fixing belt 12 starts to rotate as the pressure roller 13 rotates.
(S22) By the rotation of the pressure roller 13, the roller surface of the pressure roller 13 immersed in the oil tank 22a (sub oil pan 22a1) is pulled up in the direction of the fixing nip N with the oil O attached thereto.
(S23) Next, the oil O adhering to the surface of the pressure roller 13 passes through the cleaning felt 22c, and solid impurities are removed.
(S24) Next, the adhesion of the oil O on the surface of the pressure roller 13 is regulated by the blade 22b so as to be uniform in the width direction, and in this state, the oil moves to the fixing nip portion N.

  As described above, in the present invention, the oil application is performed by the dipping method using the space below the pressure roller 13 with respect to the pressure roller 13 below the fixing nip portion N. It is possible to supply a stable amount of oil. The oil tank 22a may include only the sub oil pan 22a1 that holds the oil O and is provided below the pressure roller 13 and in which a part of the pressure roller 13 is immersed.

  Incidentally, the fixing device 100 is configured to be compatible with various recording media P such as thick paper, thin paper, coated paper, and non-coated paper. However, the recording medium P to be passed is changed from thick paper to thin paper. In some cases, it is necessary to reduce the amount of heat applied to the recording medium P at the fixing nip N, that is, to lower the temperature of the fixing member (fixing belt 12).

  Specifically, at this time, the fixing set temperature of the fixing nip portion N is changed, and the corresponding heating control is performed. In the conventional fixing device, power supply to the heaters 13h and 14h is turned off to prevent heat generation, and the fixing belt 12 and the pressure roller 13 are idled to release heat in the air to lower the temperature. However, a waiting time several times longer than that when the temperature of the fixing belt 12 is increased may be required.

  The inventors have examined the details of this problem, and the pressure roller 13 that contacts the fixing belt 12 at the fixing nip portion N needs to be lowered in temperature. The pressure roller 13 has a larger heat capacity than the fixing belt 12. From this, it was understood that a longer waiting time was required until the temperature was lowered to the target temperature than that of the fixing belt 12 in the case of cooling only by turning off the heater. And based on this knowledge, earnest examination was carried out to attempt to solve this problem, and the present invention was achieved. Hereinafter, the configuration of the main part of the present invention will be described.

FIG. 6 is a cross-sectional view of the main configuration (1) of the fixing device according to the present invention.
The fixing device (fixing device 100) according to the present invention includes a fixing member (fixing belt 12) that is rotatably provided, a heating unit (heater 14h) that directly or indirectly heats the fixing member, and the fixing member. A pressure member (pressure roller 13) that is rotatably provided below and forms a fixing nip portion (fixing nip portion N) in contact with the fixing member, and holds oil under the pressure member. An oil tank (oil tank 22a) is provided, an oil application device (oil application device 22) for applying oil by immersing a part of the pressure member in the oil tank, and cooling the oil in the oil tank And an oil cooling device (oil cooling device 24).

  Here, the oil cooling device 24 has a mechanism for directly or indirectly cooling the oil tank 22a, and cools the oil O in the oil tank 22a by cooling the oil tank 22a at a predetermined timing. is there.

  FIG. 6 shows an oil cooling device 24 having a fan mechanism 24a that operates to blow air onto the metal casing of the oil tank 22a to cool the air. Specifically, for example, the casing of the oil tank 22a is formed of an aluminum plate or an iron plate having a thickness of 1.2 mm or less, the fan mechanism 24a is disposed under the oil tank 22a, and the fan mechanism 24a is used to cool the pressure roller 13. And air cooling is performed by blowing air to the bottom of the casing of the oil tank 22a. This configuration is suitable when the oil tank 22a is composed only of the sub oil pan 22a1.

FIG. 7 shows a cross-sectional view of the main configuration (2) of the fixing device according to the present invention.
Here, as the oil cooling device 24, instead of the fan mechanism 24a of FIG. 6, a Peltier cooling mechanism 24b is provided at the bottom of the metal casing of the oil tank 22a, and the other configuration is the same as FIG. Are given the same reference numerals.

  Here, the Peltier cooling mechanism 24b is a cooling device using a conventionally known Peltier element which is a semiconductor element utilizing the Peltier effect. Specifically, for example, the casing of the oil tank 22a is formed of an aluminum plate or an iron plate having a thickness of 1.2 mm or less, and a Peltier cooling mechanism 24b is disposed at the bottom of the oil tank 22a. The mechanism 24b is operated to cool the casing bottom side of the oil tank 22a.

  FIG. 8 shows a main configuration (3) of the fixing device according to the present invention. 8A is a view of the fixing device 100 as viewed from the recording medium discharge side, and FIG. 8B is a side view of the fixing device 100 as viewed from an arrow A in FIG. 8A.

  Here, as the oil cooling device 24, instead of the fan mechanism 24a of FIG. 6, a heat conduction pipe (also referred to as a heat pipe) 24c, which is a heat conduction member provided to extend from the inside of the oil tank 22a to the outside of the tank, And a fan mechanism 24a that air-cools a portion of the heat conduction pipe 24c that extends outside the oil tank 22a. Other configurations are the same as those in FIG. This configuration is effective when there is no space in the lower portion of the oil tank 22a and the arrangement as shown in FIG. 6 cannot be adopted. For example, it is effective when the oil tank 22a includes a sub oil pan 22a1 and a main oil pan 22a2 as shown in FIG. 5. In this case, a heat conduction pipe 24c is provided in the sub oil pan 22a1.

  Here, the heat conduction pipe 24c is integrally formed in the oil tank 22a. Specifically, for example, the two heat conduction pipes 24c are arranged at the bottom of the oil tank 22a so as to be in direct contact with the oil O in the tank (FIG. 8B). At this time, the heat conducting pipe 24c is arranged so that its longitudinal direction is parallel to the axial direction of the pressure roller 13 and in the vicinity of the portion where the pressure roller 13 is immersed.

  In this configuration, when the pressure roller 13 is desired to be cooled, the fan mechanism 24a is operated to cool the air by blowing air to a portion of the heat conduction pipe 24c extending outside the oil tank 22a. The oil O in the oil tank 22a is cooled via the 24c.

FIG. 9 shows a main configuration (4) of the fixing device according to the present invention.
Here, as the oil cooling device 24, instead of the fan mechanism 24a of FIG. 8, a Peltier cooling mechanism 24b is provided in a portion extending out of the oil tank 22a of the heat conduction pipe 24c. The configuration is the same as in FIG.

  In this configuration, when the pressure roller 13 is to be cooled, the Peltier cooling mechanism 24b is operated to cool the portion of the heat conduction pipe 24c that extends outside the oil tank 22a, and the oil is passed through the heat conduction pipe 24c. The oil O in the tank 22a is cooled.

  In the fixing device 100 having the above-described configuration, when the temperature of the fixing nip portion N is lowered, one of the oil cooling devices 24 described above is operated to cool the oil O in the oil tank 22a and the oil tank 22a. The pressure roller 13 that is partially immersed in is rotated, and the pressure roller 13 is cooled by removing the heat of the outer peripheral portion of the pressure roller 13 mainly with the cooled oil O. As a result, the pressure roller 13 is efficiently cooled, and the temperature of the fixing nip portion N can be lowered to a desired temperature in a short time.

  It should be noted that when the temperature of the fixing nip portion N is lowered, the pressure depressurizing means 30 described above may be used. That is, the oil cooling device 24 is operated to cool the oil O in the oil tank 22a, and the pressure roller 13 rotating the pressure depressurizing means 30 is operated so as to be separated from the fixing belt 12. The contact area of the pressure roller 13 with the oil O is increased by immersing the pressure roller 13 deeply in the oil tank 22a, and the heat of the pressure roller 13 mainly in the outer peripheral portion is taken away by the cooled oil O. As a result, the pressure roller 13 is further cooled. As a result, the pressure roller 13 is cooled more efficiently, and the temperature of the fixing nip portion N can be lowered to a desired temperature in a shorter time.

Next, the image forming apparatus according to the present invention will be described.
FIG. 10 shows a configuration of a tandem type color copying machine which is an image forming apparatus according to the present invention.
A color copying machine 200, which is an image forming apparatus of the present invention, includes an image forming unit 200A positioned at the center of the apparatus main body, a paper feeding unit 200B positioned below the image forming unit 200A, and an upper side of the image forming unit 200A. The image forming unit is a high-speed machine having an image reading unit (not shown), and the fixing device 100 of the present invention is incorporated in the image forming unit 200A.

  The image forming unit 200A is provided with a transfer belt 210 having a transfer surface extending in the horizontal direction, and a configuration for forming an image of a color complementary to the color separation color on the upper surface of the transfer belt 210. Is provided. That is, photoconductors 205Y, 205M, 205C, and 205K as image carriers that can carry images of toners of complementary colors (yellow, magenta, cyan, and black) are juxtaposed along the transfer surface of the transfer belt 210. ing.

  Each of the photoconductors 205Y, 205M, 205C, and 205K is configured by a drum that can rotate in the same direction (counterclockwise direction), and around the optical writing device 201 that performs image forming processing in the rotation process, Charging devices 202Y, 202M, 202C and 202K, developing devices 203Y, 203M, 203C and 203K, primary transfer devices 204Y, 204M, 204C and 204K and a cleaning device are arranged. Each developing device 203Y, 203M, 203C, 203K contains a respective color toner.

  The transfer belt 210 is configured to be able to move in the same direction at a position facing the photoconductors 205Y, 205M, 205C, and 205K by being wound around a driving roller and a driven roller. Further, a transfer roller 212 is provided at a position facing a roller 211 that is one of the driven rollers. Further, the conveyance path of the recording medium P from the transfer roller 212 to the fixing device 100 is a horizontal path, and a conveyance belt 213 as shown in FIGS. 6 to 9 is provided.

  The paper feed unit 200B separates the paper feed tray 220 on which the recording medium P as a recording medium is stacked and the recording medium P in the paper feed tray 220 from the top one by one in order from the transfer roller 212. It has a transport mechanism that transports it to a position.

  In image formation in the image forming apparatus 200 of the present invention, the surface of the photoreceptor 205Y is uniformly charged by the charging device 202Y, and an electrostatic latent image is formed on the photoreceptor 205Y based on image information from the image reading unit. Is done. The electrostatic latent image is visualized as a toner image by a developing device 203Y containing yellow toner, and the toner image is primarily transferred onto the transfer belt 210 by a primary transfer device 204Y to which a predetermined bias is applied. Is done. The other photoconductors 205M, 205C, and 205K also form similar images only with different toner colors, and the toner images of the respective colors are sequentially transferred onto the transfer belt 210 by the electrostatic force and superimposed.

Next, the toner image T primarily transferred from the photoconductors 205Y, 205M, 205C, and 205K onto the transfer belt 210 is transferred to the recording medium P conveyed by the roller 211 and the transfer roller 212. The recording medium P onto which the toner image T has been transferred is further conveyed to the fixing device 100 and is fixed at a fixing nip N between the fixing belt 12 and the pressure roller 13. Appropriate amounts of oil are applied to the fixing belt 12 and the pressure roller 13 by the oil applying devices 21 and 22, respectively, and if necessary, separation claws 16a and 16b arranged on the exit side of the fixing nip N Since it functions, the recording medium P is discharged to the exit side of the fixing nip N without being wound around the fixing belt 12 and the pressure roller 13.
Next, the recording medium P discharged from the fixing nip N is sent out to the stacker 215 along the discharge path.

  As described above, in the present invention, the image forming apparatus having the fixing device 100 can provide a more advanced fixing separation function, and can reduce various paper types (from thin paper to thick paper) and images (image leading margin). Possible).

  In the image forming apparatus 200, an oil tank 251 that collects oil for improving the releasability of the recording medium P used in the fixing apparatus 100 attached to the fixing apparatus 100, and the oil in the oil tank 251 is again used. An oil circulation mechanism such as an oil pump 252 that supplies the fixing device 100 is provided.

FIG. 11 shows a schematic configuration of an oil circulation mechanism provided in the image forming apparatus 200.
The oil circulation mechanism 250 includes an oil tank 251 that holds oil to be used, an oil pump 252 that uses a piezoelectric element, a conveyance path 253 that connects the oil pump 252 to the oil application device 21 of the fixing device 100, and an oil application device. 21, an oil receiver 254 that receives excess oil, a tube 255 that conveys the oil in the oil receiver 254 to the oil application device 22, and a conveyance path 256 that connects the oil application device 22 to the oil tank 251. The oil tank 251, the oil pump 252, the transport paths 253 and 256 are outside the fixing device 100, and the oil receiver 254 and the tube 255 are inside the fixing device 100. The oil tank 251 has an oil near-end sensor 251a that detects the remaining amount of oil inside. As a result, the first oil application device (oil application device 21) that applies oil O to the first nip forming member (fixing belt 12) and the second oil oil that is applied to the second nip formation member (pressure roller 13). 2 Assuming an oil application device (oil application device 22), an oil receiver (oil receiver 254) that collects excess oil O in the oil application device 21 and a supply path for supplying oil O from the oil receiver to the oil application device 22 ( Tube 255), an oil recovery unit (conveying path 256, oil tank 251) for recovering oil O from the oil application device 22, and an oil supply device for supplying the oil O recovered in the oil recovery unit to the oil application device 21 (An oil pump 252 and a conveyance path 253), and an oil circulation mechanism 250 is configured.

  In the image forming apparatus 200, the oil circulation mechanism 250 circulates and uses oil in the above-described path, and the oil application apparatuses 21 and 22 can continuously apply the oil to the fixing belt 12 and the pressure roller 13. .

  In such a configuration, the oil heated on the fixing belt 12 side in the oil application device 21 is sent to the oil application device 22, and the pressure roller 13 when the temperature of the fixing nip portion N is lowered. It becomes an impediment to cooling. The present invention is also effective in this case. As described above, the oil cooling device 24 is operated to cool the oil O sent from the oil application device 21 and accumulated in the oil tank 22a. The pressure roller 13 which is partially immersed is rotated, and the pressure roller 13 is cooled by removing the heat of the outer peripheral portion of the pressure roller 13 mainly by the cooled oil O. As a result, the pressure roller 13 is efficiently cooled, and the temperature of the fixing nip portion N can be lowered to a desired temperature in a short time.

  Although the present invention has been described with the embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and other embodiments, additions, modifications, deletions, etc. Can be changed within the range that can be conceived, and any embodiment is included in the scope of the present invention as long as the effects and advantages of the present invention are exhibited.

For example, instead of the fixing device 100 in FIG. 1, a fixing device in which the rollers contact each other to form the fixing nip portion N may be used.
FIG. 12 is a cross-sectional view showing another configuration example (1) of the pressure member and the fixing member in the fixing device of the present invention. In this fixing device 100, the fixing member is changed from the fixing belt type in the fixing device 100 of FIG. 1 to the fixing roller 12R, and the fixing roller 12R and the pressure roller 13 come into contact with each other to form the nip portion N. It has become. The fixing roller 12R is heated by a heater 12h.

Alternatively, instead of the fixing device 100 shown in FIG. 1, a fixing device using a pressure belt shown in FIGS. 13 and 14 may be used.
FIG. 13 is a cross-sectional view showing another configuration example (2) of the pressure member and the fixing member in the fixing device of the present invention. In the fixing device 100, a fixing roller 12R that is rotatably disposed on the upper side, a pressure belt 13a that is rotatably and rotatably supported by rollers 13R, 14R, and 15R below the fixing roller 12R. Are arranged so that the fixing nip portion N can be formed by a backup member 13b which is a pressure pad on the back surface of the pressure belt 13a. The fixing roller 12R is heated by the heater 12h, and the pressure belt 13a is heated by the heater 14h.
Further, at least the backup member 13b is provided with a pressure depressurization means for performing the same pressure control as described above.

FIG. 14 is a cross-sectional view showing another configuration example (3) of the pressure member and the fixing member in the fixing device of the present invention. In this fixing device 100, a fixing roller 12R that is rotatably disposed on the upper side, and a pressure belt 13a that is supported in a tension-free state by a support member 13e under the fixing roller 12R come into contact with each other to contact the pressure belt. A fixing nip portion N can be formed by a backup member 13d which is a pressure member on the back surface of 13a. The fixing roller 12R is heated by a heater 12h.
Further, at least the backup member 13d is provided with a pressure depressurizing means for performing the same pressure control as described above.

11, 12R Fixing roller 12 Fixing belt 12h, 13h, 14h Heater 13 Pressure roller 13a Pressure belt 13b, 13d Backup member 13e Support member 13j Pressure roller shaft end 13R, 14R, 15R Roller 14 Heating roller 14a Heat pipe 15 Tension rollers 16a, 16b Separation claw 17 Cleaning mechanism 21, 22 Oil application device 21a Oil inlet 21b Oil reservoir 21b1 Opening portion 21b2 Gutter 21b3 Side plate 21c Support plate 21d Supply felt 21e Supply roller 21f Metering blade 22a Oil tank 22a1 Sub oil pan (immersion tank)
22a2 Main oil pan (oil receiver)
22b Blade 22c Cleaning felt 23 Application roller 24 Oil cooling device 24a Fan mechanism 24b Peltier cooling mechanism 24c Heat conduction pipe 30 Pressure depressurizing means 31 Pressure cam 32 First pressure arm 33 Second pressure arm 33a Pressure unit 34 Elastic member 35 Support shaft 100 Fixing device 100c Fixing cover 200 Image forming apparatus (color copying machine)
200A Image forming unit 200B Paper feeding unit 201 Optical writing device 202Y, 202C, 202M, 202K Charging device 203Y, 203M, 203C, 203K Developing device 204Y, 204M, 204C, 204K Primary transfer device 205Y, 205C, 205M, 205K Photoconductor 210 transfer belt 211 driven roller 212 transfer roller 213 transport belt 215 stacker 220 paper feed tray 250 oil circulation mechanism 251 oil tank 251a oil near-end sensor 252 oil pump 253, 256 transport path 254 oil receiver 255 tube N fixing nip O oil P recording Medium T Toner

JP 2003-302857 A

Claims (7)

A fixing member provided rotatably;
Heating means for directly or indirectly heating the fixing member;
A pressure member which is rotatably provided under the fixing member and forms a fixing nip portion in contact with the fixing member;
An oil tank that holds oil and is provided below the pressure member, and applies oil by immersing a part of the pressure member in the oil tank;
An oil cooling device for cooling the oil in the oil tank, and a fixing device comprising:
When the temperature of the fixing nip portion is lowered, the oil cooling device cools the oil in the oil tank, and the pressure member partially immersed in the oil tank is rotated to rotate the pressure member. constant Chakusochi characterized in that cooled. A fixing member provided rotatably;
Heating means for directly or indirectly heating the fixing member;
A pressure member which is rotatably provided under the fixing member and forms a fixing nip portion in contact with the fixing member;
An oil tank that holds oil and is provided below the pressure member, and applies oil by immersing a part of the pressure member in the oil tank;
An oil cooling device for cooling the oil in the oil tank, and a fixing device comprising:
A pressure depressurization means for switching between a pressure state in which the pressure member is brought into contact with the fixing member and a pressure release state in which the pressure member is separated from the fixing member;
When the temperature of the fixing nip portion is lowered, the oil cooling device cools the oil in the oil tank, and the pressure member on which the pressure depressurizing means is rotating is separated from the fixing member, and by deeply immersed by the oil tank, characterized by cooling the pressure member constant Chakusochi. The oil cooling device, a fixing device according to claim 1 or 2 characterized by having a fan mechanism for cooling the metal casing of the oil tank. The oil cooling device, a fixing device according to claim 1 or 2, characterized in that it has a Peltier cooling mechanism for cooling the metal casing of the oil tank. The oil cooling device includes a heat conduction member provided to extend from the inside of the oil tank to the outside of the tank,
The fixing device according to claim 1 or 2, characterized in that it has a, a fan mechanism for cooling a portion extending into the oil tank outside of the heat conducting member. The oil cooling device includes a heat conduction member provided to extend from the inside of the oil tank to the outside of the tank,
The fixing device according to claim 1 or 2, characterized in that it has a, a Peltier cooling mechanism for cooling a portion extending into the oil tank outside of the heat conducting member. An image forming apparatus comprising: a fixing device according to any one of claims 1 to 6.