Image forming device

Abstract

To provide an image forming apparatus including a cooling device capable of driving a pair of belts for sandwiching, transporting and cooling a recording material, with one drive motor.SOLUTION: A roller drive unit 500 connected to a drive motor M is provided on one end side in a rotation axis direction of a first belt tension roller 501e in order to transmit a rotation of the drive motor M. The rotation of the drive motor M that drives a first belt 501 is transmitted from a first belt tension roller 501e to a second belt tension roller 502e via a drive gear portion 510, and a second belt 502 is rotated. A second unit 502U is provided with respect to a first unit 501U, so as to be movable to a contact position where the second belt 502 and the first belt 501 are in contact with each other, and a separated position where the second belt 502 and the first belt 501 are separated from each other. When the second unit 502U is moved from the separated position to the contact position, a first drive gear portion 510b swings to mesh gears, due to a contact between a second transmission gear 504a and a first transmission gear 504b.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a printer, a copier, a facsimile, or a multifunction machine. [Background technology]

[0002] Conventionally, an image forming apparatus that forms an image on a recording material includes a pair of rotating belts that contact each other and sandwich and transport the recording material (also called a sheet), and a cooling device that cools the recording material. The cooling device cools the belts to prevent the recording materials stacked on a discharge tray from adhering to each other, for example, and then sandwiches and transports the recording material after the toner image has been fixed by the fixing device between the cooled belts to lower the temperature of the recording material (Patent Document 1). In such a cooling device, when the pair of belts stop with the recording material sandwiched between them (so-called jam), one of the belts is movable between a contact position where it contacts the other belt and a separation position where it is separated so that a user can remove the recording material sandwiched between the belts. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-181055 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, when one belt is movable between a contact position and a separation position with respect to the other belt, a drive motor for driving one belt and a drive motor for driving the other belt are generally provided in separate belt units together with the respective belts. However, if a drive motor is provided in each of the belt units, this leads to an increase in costs. Therefore, a configuration in which one drive motor drives both belts is conceivable, but a configuration in which one drive motor drives both belt units has not yet been proposed in a cooling device in which one belt is movable (approaching and separating) relative to the other belt.

[0005] An object of the present invention is to provide an image forming apparatus including a cooling device capable of driving a pair of belts that nip, convey and cool a recording material with one driving motor. [Means for solving the problem]

[0006] An image forming apparatus according to an embodiment of the present invention includes a fixing device that heats a sheet on which a toner image has been formed to fix the toner image to the sheet, and a cooling device that is provided downstream of the fixing device in a sheet conveying direction and cools the sheet heated by the fixing device, the cooling device including a first unit having a first belt and a first roller that stretches and rotates the first belt, a second unit having a second belt that forms a nip portion that sandwiches and conveys a sheet together with the first belt, a heat sink that contacts an inner circumferential surface of the second belt, and a second roller that stretches and rotates the second belt. a second unit movable between a contact position where the first belt and the second belt contact each other to form the nip portion and a separation position where the first belt and the second belt separate from each other to open the nip portion; a drive motor for rotating the first roller and the second roller; a drive transmission section having at least four gears and transmitting a rotational drive force of the drive motor to the first roller and the second roller as the gears rotate, the drive transmission section comprising: a first drive gear section provided in the first unit and having a first gear to which the rotational drive force from the drive motor is transmitted and a first transmission gear to which the rotational drive force is transmitted from the first gear; a second drive gear section provided in the second unit and having a second transmission gear meshing with the first transmission gear to which the rotational drive force from the first transmission gear is transmitted and a second gear for transmitting the rotational drive force transmitted from the second transmission gear to the second roller; and a biasing means for biasing the first drive gear section so that the first transmission gear moves toward the second transmission gear, The second unit From the separated position of Contact position When the first drive gear portion moves to the first drive gear portion, the first drive gear portion moves against the biasing force of the biasing means by the first transmission gear being pressed against the second transmission gear. It is characterized in that it is movably provided. Effect of the Invention

[0007] According to the present invention, it is possible to provide an image forming apparatus equipped with a cooling device capable of driving a pair of belts that nip, convey and cool a recording material by a single drive motor. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. 4 is a perspective view showing the recording material cooling device when the belt is in the contact position. [Figure 4] FIG. 4 is a perspective view showing the recording material cooling device when the belt is in the separated position. [Diagram 5] FIG. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. 13 is a schematic diagram showing an example in which a recording material cooling device is provided outside an image forming apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <Image forming device> Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, the configuration of an image forming apparatus of this embodiment will be described with reference to FIG. 1. The image forming apparatus 100 shown in FIG. 1 is a tandem-type full-color printer of an electrophotographic system. The image forming apparatus 100 has image forming units Pa, Pb, Pc, and Pd that form images of yellow, magenta, cyan, and black, respectively. The image forming apparatus 100 forms a toner image on a recording material S in response to image information from a document reading device (not shown) connected to the apparatus main body 100A or an external device (not shown) such as a personal computer connected to the apparatus main body 100A so as to be able to communicate therewith. Examples of the recording material S include various types of sheet materials such as plain paper, thick paper, rough paper, textured paper, coated paper, and the like, plastic film, and cloth.

[0010] The recording material conveying process of the image forming apparatus 100 will be described. The recording material S is stored in a stacked form in a paper feed cassette 10, and is sent out from the paper feed cassette 10 by a paper feed roller 13 in accordance with the image formation timing. The recording material S sent out by the paper feed roller 13 is conveyed to a registration roller 12 arranged in the middle of a conveying path 114. Then, after the registration roller 12 performs skew correction and timing correction on the recording material S, the recording material S is sent to a secondary transfer section T2. ​​The secondary transfer section T2 is a transfer nip section formed by a secondary transfer inner roller 14 and a secondary transfer outer roller 11, and a toner image is transferred onto the recording material in response to the application of a secondary transfer voltage to the secondary transfer outer roller 11.

[0011] The process of forming an image sent to the secondary transfer portion T2 at the same timing as the process of conveying the recording material S to the secondary transfer portion T2 described above will be described. First, the image forming portions will be described. The image forming portions Pa, Pb, Pc, and Pd for each color are configured almost the same except that the toner colors used in the developing devices 1a, 1b, 1c, and 1d are different, that is, yellow, magenta, cyan, and black. Therefore, the following description will be given of the black image forming portion Pd as a representative, and the description of the other image forming portions Pa, Pb, and Pc will be omitted.

[0012] The image forming section Pd is mainly composed of a developing device 1d, a charging device 2d, a photosensitive drum 3d, a photosensitive drum cleaner 4d, and an exposure device 5d. The surface of the photosensitive drum 3d, which rotates in the direction of the arrow R1 in the figure, is uniformly charged in advance by the charging device 2d, and then an electrostatic latent image is formed by the exposure device 5d, which is driven based on a signal of image information. Next, the electrostatic latent image formed on the photosensitive drum 3d is developed into a toner image using a developer by the developing device 1d. Then, in response to the application of a primary transfer voltage to a primary transfer roller 6d arranged with the image forming section Pd and the intermediate transfer belt 20 sandwiched therebetween, the toner image formed on the photosensitive drum 3d is primarily transferred onto the intermediate transfer belt 20. A small amount of primary transfer residual toner remaining on the photosensitive drum 3d is collected by the photosensitive drum cleaner 4d and prepared for the next image forming process again.

[0013] The intermediate transfer belt 20 is tensioned by a secondary transfer inner roller 14, a tension roller 15, and a tension roller 16, and is driven in the direction of the arrow R2 in the figure. In this embodiment, the tension roller 16 also serves as a drive roller for driving the intermediate transfer belt 20. The image forming processes for each color, which are processed in parallel by the image forming units Pa to Pd, are performed at a timing when they are sequentially superimposed on the toner images of the upstream colors that have been primarily transferred onto the intermediate transfer belt 20. As a result, a full-color toner image is finally formed on the intermediate transfer belt 20, and is transported to the secondary transfer unit T2. The secondary transfer residual toner after passing through the secondary transfer unit T2 is collected by a transfer cleaner device 22.

[0014] Through the above-described conveying process and image forming process, the timing of the recording material S and the full-color toner image coincides at the secondary transfer portion T2, and the secondary transfer is performed. After that, the recording material S is conveyed to the fixing device 30, where a predetermined pressure and heat are applied to fix the toner image on the recording material. The fixing device 30 conveys the recording material S on which the toner image has been formed by sandwiching and conveying it, and heats and pressurizes the conveyed recording material S to fix the toner image on the recording material S. That is, the toner of the toner image formed on the recording material S is melted and mixed by the heating and pressurization, and is fixed on the recording material S as a full-color image. In this manner, a series of image forming processes is completed. In this embodiment, the recording material S on which the toner image has been fixed is conveyed from the fixing device 30 to the recording material cooling device 50 and cooled. For example, the temperature of the recording material S is about 90° C. immediately before the recording material cooling device 50, but is reduced to about 60° C. after passing through the recording material cooling device 50.

[0015] In the case of single-sided image formation, the recording material S cooled by the recording material cooling device 50 is sandwiched and conveyed between a pair of discharge rollers 105, and is directly discharged onto a paper discharge tray 120. On the other hand, in the case of double-sided image formation, a switching member 110 (also called a flapper, etc.) switches the conveying path from the path continuing to the paper discharge tray 120 to a double-sided conveying path 111, and the recording material S sandwiched and conveyed between the discharge rollers 105 is sent to the double-sided conveying path 111. Thereafter, the leading and trailing ends are switched by a reversing roller 112, and the recording material S is again sent to a conveying path 114 via a double-sided path 113. The subsequent conveying and the image forming process on the back side (second side) are the same as those described above, and therefore will not be described.

[0016] <Recording material cooling device> Next, the recording material cooling device of this embodiment will be described with reference to FIGS. 2 to 7. The recording material cooling device 50 described below is a belt-cooling type cooling device. As shown in FIG. 2, the recording material cooling device 50 has an endless second belt 502 and an endless first belt 501 that conveys the recording material S by pinching it between the second belt 502 and the recording material S. For example, the second belt 502 and the first belt 501 are made of high-strength polyimide, and are set to a thickness of 100 μm and a circumferential length of 942 mm. The recording material cooling device 50 also has a heat sink 503 as a cooling means for cooling the second belt 502. In this embodiment, the heat sink 503 is in contact with the second belt 502 that contacts the recording material S on the side on which the toner image is formed by the fixing device 30 (see FIG. 1). Note that the second belt 502 is not limited to being cooled by the heat sink 503. For example, the cooling means may be a belt fan capable of cooling the second belt 502 by blowing air to the second belt 502.

[0017] The first belt 501 is wound around a plurality of first belt tension rollers 501a to 501e, and one of the first belt tension rollers 501a to 501e is rotated via a roller drive unit 500 connected to a drive motor M. The roller drive unit 500 has, for example, a belt member and a gear unit that transmit the rotation of the drive motor M, and in this embodiment, is provided on one end side of the first belt tension roller 501e in the rotation axis direction. The roller drive unit 500 can rotate the first belt tension roller 501e counterclockwise in FIG. 2 in response to the rotation of the drive motor M. In this way, the first belt tension roller 501e functions as a drive roller that drives the first belt 501.

[0018] In this embodiment, a drive gear unit 510 is provided as a drive transmission unit on the other end side in the rotation axis direction of the second belt tension roller 502e (second roller) and the first belt tension roller 501e (first roller). The drive gear unit 510 is provided to rotate the second belt 502 by transmitting the rotational drive force of the first belt tension roller 501e, which rotates in accordance with the drive motor M, to the second belt tension roller 502e, which will be described later. The drive gear unit 510 will be described later.

[0019] On the other hand, the second belt 502 is wound around a plurality of second belt tension rollers 502a to 502e so as to be able to come into contact with the first belt 501. In this embodiment, the second belt tension roller 502e is rotated in accordance with the transmission of the rotational driving force by the drive gear unit 510, so that the second belt 502 is rotated in the direction of the arrow B. That is, the second belt 502 and the first belt 501 are rotated in the same direction in the cooling nip portion T4 in accordance with the rotation of the drive motor M, which is the same driving source. In this embodiment, the second belt tension roller 502e and the first belt tension roller 501e, which are connected to each other so as to be able to transmit the driving force by the drive gear unit 510, are not involved in the formation of the cooling nip portion T4. That is, the second belt tension roller 502e and the first belt tension roller 501e are disposed outside the range of the cooling nip portion T4 in the conveying direction of the recording material S, and do not form the cooling nip portion T4.

[0020] In this embodiment, the second belt tension roller 502b and the first belt tension roller 501b are steering rollers provided to control the deviation of the second belt 502 and the first belt 501, respectively. These steering rollers (502b, 501b) press the second belt 502 and the first belt 501 from the inner circumferential side toward the outer side so that the tension of the second belt 502 and the first belt 501 is, for example, about 39.2 N (about 4 kgf). To do so, the second belt tension roller 502b is biased by a spring 507a, and the first belt tension roller 501b is biased by a spring 508a. The steering rollers (502b, 501b) are separately steered by the steering mechanism 400 with the center of the rotation axis direction (width direction) as a pivot point, thereby controlling the meandering of the second belt 502 and the first belt 501.

[0021] Pressure rollers 509a and 509b are provided on the inner circumferential side of the first belt 501 to pressurize the first belt 501 toward the heat sink 503 of the second unit 502U. The pressure rollers 509a and 509b press the first belt 501 with a pressure of, for example, 9.8 N (1 kgf). This allows the second belt 502 to be brought into contact with the heat sink 503 (a heat receiving portion 503a, described in detail later) via the first belt 501, thereby reliably forming the cooling nip portion T4.

[0022] The recording material S on which the toner image has been fixed is sandwiched between the second belt 502 and the first belt 501, and is conveyed in the conveying direction (arrow D direction) by the rotation of these belts. At that time, the recording material S passes through a cooling nip portion T4 formed by the second belt 502 and the first belt 501. In the case of this embodiment, the second belt 502 is cooled by a heat sink 503. The heat sink 503 is arranged so as to abut against the inner circumferential surface of the second belt 502 at a location forming the cooling nip portion T4 in order to efficiently cool the recording material S. The recording material S is cooled through the second belt 502 when passing through the cooling nip portion T4. For example, if the temperature of the recording material S is about 90° C. before passing through the recording material cooling device 50, the recording material S is cooled so that the temperature becomes about 60° C. after passing through the recording material cooling device 50. As the recording material S is cooled, the toner on the recording material S is cooled and fixed.

[0023] The heat sink 503 is a heat dissipation plate made of a metal such as aluminum. The heat sink 503 has a heat receiving section 503a for contacting the second belt 502 to take heat from the second belt 502, a heat dissipation section 503b for dissipating heat, and a fin base 503c for conducting heat from the heat receiving section 503a to the heat dissipation section 503b. The heat dissipation section 503b is formed of a large number of heat dissipation fins to increase the contact area with the air and promote efficient heat dissipation. For example, the heat dissipation fins are set to a thickness of 1 mm, a height of 100 mm, and a pitch of 5 mm, and the fin base 503c is set to a thickness of 10 mm. In addition, a cooling fan 513 is provided to blow air toward the heat sink 503 (more specifically, the heat dissipation section 503b) in order to forcibly cool the heat sink 503 itself. The air volume of the cooling fan 513 is set to, for example, 2 m 3 / min. The cooling of the heat sink 503 is not limited to the cooling fan 513. Also, instead of the heat sink 503, the first belt 501 and the second belt 502 may be cooled using a belt cooling fan that blows air toward the belts, a water cooling unit in which a pipe through which cooled liquid is circulated is brought into contact with the belts, or the like.

[0024] In the recording material cooling device 50, since endless belts such as the second belt 502 and the first belt 501 are supported and rotated by a plurality of rollers, a meandering phenomenon in which the rotating endless belt moves in the width direction may occur. Therefore, one of the plurality of rollers stretching the second belt 502 and the first belt 501 is tilted as a steering roller to move the second belt 502 and the first belt 501 in the width direction, thereby suppressing the meandering phenomenon. To achieve this, a sensor unit 390 is provided at one point on the rotation path of the second belt 502 and the first belt 501 to detect the end positions of the second belt 502 and the first belt 501. Based on the detection signal of the sensor unit 390, the end positions of the rotating second belt 502 and the first belt 501 are detected. Then, the steering mechanism 400 described above is operated based on the detected end positions, and the steering angle of the steering rollers (502b, 501b) is adjusted.

[0025] <About belt connection and disconnection> 2 to 4, the recording material cooling device 50 is roughly divided into a first unit 501U and a second unit 502U. The first unit 501U includes a first belt 501, the above-mentioned driving motor M, first belt tension rollers (501a to 501e), a first driving gear portion 510b described later, pressure rollers 509a and 509b, a sensor portion 390, and the like. On the other hand, the second unit 502U includes a second belt 502, second belt tension rollers (502a to 502e), a second driving gear portion 510a described later, a heat sink 503, a sensor portion 390, and the like. In this embodiment, the second unit 502U is provided so as to be movable by a rotation mechanism 550 between a contact position where the second belt 502 and the first belt 501 are in contact with each other and a separation position where the second belt 502 and the first belt 501 are separated from each other with respect to the first unit 501U. At the contact position, a cooling nip portion T4 is formed, and at the separated position, the cooling nip portion T4 is opened.

[0026] As described above, the drive motor M is provided in the first unit 501U which is stationary relative to the movable second unit 502U. Here, the stationary first unit 501U refers to a configuration which does not move relative to the second unit 502U which rotates when removing the recording material S held in the cooling nip portion T4, and also includes a configuration which is movable with some rattling or during maintenance of the second unit 502U. In this way, when the drive motor M is provided in the stationary first unit 501U, it is possible to prevent a connection line (not shown) which connects the drive motor M to a control board (not shown) or the like from being pinched between the first unit 501U and the second unit 502U when the second unit 502U rotates.

[0027] The second unit 502U is provided so as to be rotatable with respect to the first unit 501U around a rotation axis (not shown) of the rotation mechanism 550 shown in FIG. 4 as a rotation center. The second unit 502U can move between a contact position where the second belt 502 and the first belt 501 contact each other to form the cooling nip portion T4, and a separation position where the second belt 502 and the first belt 501 are separated from each other so as not to form the cooling nip portion T4. FIG. 3 shows the case where the second unit 502U is in the contact position, and FIG. 4 shows the case where the second unit 502U is in the separation position. Note that here, a rotation center may be provided at one end side of the second unit 502U in the width direction, and the entire second unit 502U may be movable with respect to the first unit 501U using a slide mechanism or the like. In addition, although an example in which the second unit 502U is rotated upward in the direction of gravity with respect to the first unit 501U has been shown, the present invention is not limited thereto, and one end side of the width direction of the first unit 501U may be rotated downward in the direction of gravity with respect to the second unit 502U. In this case, the drive motor M may be provided in the second unit 502U that does not rotate.

[0028] <Drive gear section> In this embodiment, the rotation of the drive motor M that drives the first belt 501 is transmitted from the first belt tension roller 501e to the second belt tension roller 502e via the drive gear portion 510, thereby rotating the second belt 502. As shown in Figs. 3 and 4, the drive gear portion 510 can be roughly divided into a second drive gear portion 510a provided in the second unit 502U and a first drive gear portion 510b provided in the first unit 501U. The drive gear portion 510 is separated into the second drive gear portion 510a and the first drive gear portion 510b in response to the swinging of the second unit 502U, and is provided so as to be movable between a state in which a second transmission gear 504a and a first transmission gear 504b, which will be described later, are engaged with each other and a state in which they are not engaged with each other.

[0029] In this manner, the drive motor M is provided on one end side of the rotation shaft of the first belt tension roller 501e (the same side as the side where the turning mechanism 550 is provided), and the drive gear portion 510 is provided on the opposite side to the drive motor M. In this manner, when the second unit 502U turns around the turning mechanism 550, the second drive gear portion 510a and the first drive gear portion 510b can be easily engaged or disengaged. Note that, as long as the second drive gear portion 510a and the first drive gear portion 510b can be engaged or disengaged, the second drive gear portion 510a and the first drive gear portion 510b may be provided on the same end side as the drive motor M with respect to the first belt tension roller 501e, and the drive may be transmitted to the first unit 501U and the second unit 502U.

[0030] As described above, by adopting a configuration in which the entire second unit 502U can move upward relative to the first unit 501U using a slide mechanism or the like, the second drive gear portion 510a and the first drive gear portion 510b can be smoothly engaged or disengaged. In addition, the drive motor M may be provided on the other end side (opposite the side where the turning mechanism 550 is provided) of the rotation shaft of the first belt tension roller 501e, and the second drive gear portion 510a and the first drive gear portion 510b may be provided on one end side of the rotation shaft of the first belt tension roller 501e. The drive motor M, the second drive gear portion 510a, and the first drive gear portion 510b may all be provided on one end side of the rotation shaft of the first belt tension roller 501e to transmit drive to the first unit 501U and the second unit 502U.

[0031] The second drive gear portion 510a has a second gear 506a and a second transmission gear 504a. The second gear 506a is rotatably provided on the rotation shaft of the second belt tension roller 502e via a one-way clutch 505 described later. The second transmission gear 504a is rotatably provided on a second idler shaft 531 fixed to a side plate of the second unit 502U via a bearing (not shown). The second gear 506a and the second transmission gear 504a are always engaged with each other so as to transmit a driving force, regardless of the oscillation of the first drive gear portion 510b described later. The one-way clutch 505 will be described later.

[0032] The first drive gear portion 510b has a first gear 506b and a first transmission gear 504b. The rotating shaft of the first belt tension roller 501e has an end portion with a D-shaped cross section, and the first gear 506b has a shape that fits into this D-shape and is not rotatable with respect to the rotating shaft of the first belt tension roller 501e. In other words, the first gear 506b is configured to rotate integrally with the first belt tension roller 501e and its rotating shaft. The support member 522 is rotatably provided on the rotating shaft of the first belt tension roller 501e via a bearing (not shown). This allows the support member 522 to rotate with respect to the rotating shaft of the first belt tension roller 501e. The first transmission gear 504b is rotatably provided on a first idler shaft 532 fixed to the support member 522 via a bearing (not shown). The support member 522 is biased by a spring member 521, one end of which is fixed to a fixed member (not shown) provided on a side plate of the first unit 501U, so that the first transmission gear 504b moves toward the second transmission gear 504a (see FIG. 5). That is, the first drive gear portion 510b is provided so as to be able to swing about the rotation center of the first gear 506b (which is also the rotation center of the first belt tension roller 501e). The first gear 506b and the first transmission gear 504b are always engaged with each other so as to be able to transmit a driving force, regardless of the swing of the first drive gear portion 510b.

[0033] In this embodiment, the second gear 506a, the second transmission gear 504a, the first gear 506b, and the first transmission gear 504b are all formed to have the same module. However, the number of teeth of the second transmission gear 504a and the first transmission gear 504b is greater than the number of teeth of the second gear 506a and the first gear 506b. For example, the number of teeth of the second transmission gear 504a and the first transmission gear 504b is the same, 24 teeth, and the number of teeth of the second gear 506a and the first gear 506b is the same, 23 teeth. By making the number of teeth different as described above, the second gear 506a and the second transmission gear 504a, which always mesh to transmit the driving force, and the first gear 506b and the first transmission gear 504b do not mesh at the same position. In addition, in this embodiment, the second gear 506a, the second transmission gear 504a, the first gear 506b, and the first transmission gear 504b are all spur gears, making it easier for the gears to mesh with each other when the second unit 502U moves from a separated state to a contact state with respect to the first unit 501U.

[0034] As shown in Fig. 3, when the second belt 502 and the first belt 501 are in contact with each other to form the cooling nip portion T4, the second transmission gear 504a of the second driving gear portion 510a and the first transmission gear 504b of the first driving gear portion 510b mesh with each other to transmit the driving force. On the other hand, as shown in Fig. 4, when the second belt 502 and the first belt 501 are not in contact with each other to form the cooling nip portion T4, the second transmission gear 504a and the first transmission gear 504b do not mesh with each other to transmit the driving force.

[0035] As described above, in this embodiment, the first driving gear portion 510b is provided so as to be able to swing about the rotation center of the first gear 506b. When the second unit 502U is moved from the separated position (see FIG. 4) to the abutting position (see FIG. 3), the first driving gear portion 510b moves clockwise (in the direction of arrow Q) against the bias of the spring member 521, as shown in FIG. 5. This is because the second transmission gear 504a of the second driving gear portion 510a comes into contact with and presses the first transmission gear 504b of the first driving gear portion 510b in response to the movement of the second unit 502U.

[0036] Moreover, when the second unit 502U is moved from the contact position (see FIG. 3) to the separated position (see FIG. 4), the first driving gear portion 510b moves counterclockwise due to the bias of the spring member 521. Here, when the first driving gear portion 510b is moved counterclockwise, the rotation restriction portion 523 formed on the support member 522 interferes with the protrusion portion 524 (see FIG. 3 and FIG. 4) provided on the side plate of the first unit 501U, and the rotation of the first driving gear portion 510b is restricted. In this way, the first driving gear portion 510b and the second driving gear portion 510a are stopped at a predetermined angle. In the case of this embodiment, this predetermined angle is set so that the second transmission gear 504a and the first transmission gear 504b mesh with each other to transmit the driving force when the second unit 502U is moved from the separated position to the contact position. In addition, the gears of the second driving gear portion 510a and the first driving gear portion 510b are arranged so that when the first belt 501 is rotated by the driving motor M (see FIG. 2), the first transmission gear 504b rotates while always being biased against the second transmission gear 504a.

[0037] The arrangement of the second drive gear portion 510a and the first drive gear portion 510b will be specifically described. As shown in FIG. 5, a straight line connecting the rotation center O of the second transmission gear 504a and the rotation center L of the first transmission gear 504b is defined as a straight line OL. In addition, a tangent point where the pitch circle of the second transmission gear 504a and the pitch circle of the first transmission gear 504b are in contact with each other when the tips of the teeth of the second transmission gear 504a and the teeth of the first transmission gear 504b are in contact with each other (a state in which the drive can be transmitted) is defined as a point K. A straight line connecting this point K and the swing center J of the first drive gear portion 510b is defined as a straight line JK. In addition, a straight line perpendicular to the straight line LK passing through the rotation center L and the point K is defined as a line segment KN. The line segment KN is a tangent line of the second transmission gear 504a and the first transmission gear 504b. The second transmission gear 504a and the first transmission gear 504b are capable of transmitting driving force to each other, and the transmission of the driving force acts in the direction of a line segment obtained by adding a pressure angle to the line segment KN. In this embodiment, the pressure angle is set to 20°.

[0038] The direction in which the driving force is transmitted by the second transmission gear 504a and the first transmission gear 504b is a line segment PK inclined by the pressure angle with respect to the line segment KN. Compare the line segment PK with the straight line JK shown in FIG. 5. In the case of this embodiment, the line segment PK indicating the direction in which the driving force is transmitted by the second transmission gear 504a and the first transmission gear 504b is upstream of the straight line JK in the rotation direction (arrow G direction) of the first transmission gear 504b, and is located at a position that is more intrusive to the second transmission gear 504a side (second transmission gear side) than the straight line JK. In this way, when the first belt 501 is rotated by the drive motor M, the force generated by the second transmission gear 504a and the first transmission gear 504b causes the first transmission gear 504b to operate so as to be intrusive to the second transmission gear 504a.

[0039] Also, when the second unit 502U moves from the separated position to the contact position and the first transmission gear 504b and the second transmission gear 504a do not mesh with each other, the tips of the teeth of the gears come into contact with each other, so the straight line OL becomes longer than the straight line OL at the contact position. Then, when the second unit 502U moves from the separated position to the contact position, and the first transmission gear 504b is in contact with the second transmission gear 504a by the spring member 521 as the biasing means, the first transmission gear 504b is maintained in contact with the second transmission gear 504a by the spring member 521 as the biasing means. Then, when the first belt 501 is rotated by the drive motor M, the first drive gear portion 510b rotates clockwise, and the second transmission gear 504a and the first transmission gear 504b mesh with each other.

[0040] That is, when the tip of the tooth of the second transmission gear 504a hits the tip of the tooth of the first transmission gear 504b as the second unit 502U moves from the separated position to the abutting position, the first driving gear portion 510b moves against the biasing force of the spring member 521 while the tip is in contact. After the second unit 502U moves to the abutting position, when the first belt tension roller 501e is rotated by the driving motor M (in the direction of the arrow E) while the tip of the tooth is in contact, the first transmission gear 504b is transmitted with the driving force and rotates clockwise (in the direction of the arrow F). When the first transmission gear 504b rotates, a shift occurs in the contact position between the tooth of the first transmission gear 504b and the tooth of the second transmission gear 504a, which are abutting against each other. When a shift occurs in the contact position, the first driving gear portion 510b moves toward the second driving gear portion 510a due to the biasing force of the spring member 521. As a result, the first transmission gear 504b and the second transmission gear 504a mesh with each other. To achieve this, the second driving gear portion 510a and the first driving gear portion 510b are provided as described above.

[0041] In addition, when the first driving gear portion 510b is made swingable as in this embodiment, when the first transmission gear 504b and the second transmission gear 504a are in mesh with each other, the transmission of the driving force from the first transmission gear 504b to the second transmission gear 504a is easily hindered. This is because the first driving gear portion 510b is biased toward the second transmission gear 504a by the spring member 521, and the first transmission gear 504b and the second transmission gear 504a are strongly meshed with each other by the biasing force of the spring member 521. In view of this, in this embodiment, the axial distance between the second transmission gear 504a and the first driving gear portion 510b is secured, so that the first transmission gear 504b and the second transmission gear 504a are meshed with an appropriate force for driving transmission, regardless of the biasing force of the spring member 521. Specifically, as shown in FIG. 6, an inter-axis regulating member 580 is disposed to ensure the inter-axis distance between the second transmission gear 504a and the first driving gear portion 510b (not shown in FIGS. 2 to 6). The inter-axis regulating member 580 is provided on the rotating shaft of the second transmission gear 504a in the second unit 502U, and contacts the rotating shaft of the first transmission gear 504b when the second unit 502U is in the contact position. The inter-axis regulating member 580 has a portion that contacts the rotating shaft of the first transmission gear 504b formed in an arc shape. This ensures the inter-axis distance between the second transmission gear 504a and the first driving gear portion 510b even if the contact position is slightly shifted in the conveying direction of the recording material S (see the direction of the arrow D in FIG. 2) when the inter-axis regulating member 580 contacts the rotating shaft of the first transmission gear 504b.

[0042] As described above, in this embodiment, when the second unit 502U is moved from the separated position to the abutment position, the second transmission gear 504a of the second driving gear portion 510a contacts the first transmission gear 504b of the first driving gear portion 510b, and the first driving gear portion 510b swings. That is, even if the teeth of the second transmission gear 504a and the teeth of the first transmission gear 504b hit each other when the second unit 502U moves to the abutment position, the first driving gear portion 510b moves to escape, so that they are unlikely to be damaged. Also, even if the teeth of the second transmission gear 504a and the teeth of the first transmission gear 504b do not mesh with each other when the second unit 502U is moved to the abutment position, the teeth of the second transmission gear 504a and the teeth of the first transmission gear 504b mesh with each other according to the subsequent rotation of the first belt tension roller 501e. Even in this case, since excessive force can be prevented from being applied to the teeth of the first transmission gear 504b and the teeth of the second transmission gear 504a, they are less likely to be damaged.

[0043] <One-way clutch> In a configuration in which the recording material S is nipped and conveyed between the second belt 502 and the first belt 501 so as to cool the recording material S at the cooling nip portion T4, it is desirable to make the moving speed of the second belt 502 and the moving speed of the first belt 501 approximately equal to each other in order to stabilize the conveyance of the recording material S. In the case of this embodiment, the moving speed of the first belt 501 rotated by the first belt tension roller 501e directly driven by the drive motor M is used as a reference. Therefore, it is desirable to configure the moving speed of the second belt 502 rotated by the second belt tension roller 502e to which the drive of the drive motor M is indirectly transmitted via the drive gear portion 510 to be equal to the moving speed of the first belt 501.

[0044] However, in the past, the moving speed of the second belt 502 and the moving speed of the first belt 501 did not generally match. For example, when the diameter of the second belt tension roller 502e is smaller than that of the first belt tension roller 501e due to machining accuracy, the moving speed of the second belt 502 is likely to be faster than that of the first belt 501. In this way, when the moving speed of the second belt 502 is increased due to the variation in the diameter of the second belt tension roller 502e, the longer the rotation time of the second belt 502, the faster the moving speed of the second belt 502 becomes, and the difference with the moving speed of the first belt 501 may become large. In this case, the conveyance of the recording material S nipped and conveyed between the second belt 502 and the first belt 501 becomes unstable, which is undesirable.

[0045] In addition, in the configuration in which the first driving gear portion 510b is biased toward the second transmission gear 504a by the biasing force of the spring member 521 as described above, when the moving speed of the second belt 502 becomes faster than the moving speed of the first belt 501, the rotation speed of the second transmission gear 504a becomes faster than the rotation speed of the first transmission gear 504b. Then, the first transmission gear 504b, which rotates by the driving force of the driving motor M, is repelled by the second transmission gear 504a, and the meshing between the second transmission gear 504a and the first transmission gear 504b is released against the biasing force of the spring member 521. Although the second transmission gear 504a and the first transmission gear 504b that have been released from meshing can mesh again due to the biasing force of the spring member 521, as long as there is a rotational speed difference between the second transmission gear 504a and the first transmission gear 504b (the rotational speed difference between the second belt 502 and the first belt 501), the first transmission gear 504b is repelled, causing the gears to frequently release from meshing. In this case, the driving force of the drive motor M is no longer transmitted to the second belt 502, and the second belt 502 acts to stop relative to the first belt 501 to which the driving force of the drive motor M continues to be transmitted, which may cause poor conveyance of the recording material S.

[0046] In this embodiment, a one-way clutch is provided in the drive gear unit 510 to suppress the occurrence of a speed difference between the moving speed of the second belt 502 and the moving speed of the first belt 501. When a speed difference occurs between the second belt 502 and the first belt 501, the one-way clutch automatically switches between transmitting and cutting off the drive, thereby making it possible to reduce the speed difference between the second belt 502 and the first belt 501. Hereinafter, the drive gear unit 510 provided with the one-way clutch will be described using FIG. 7 with reference to FIGS. 2, 3, and 5.

[0047] As shown in FIG. 5, in this embodiment, the one-way clutch 505 as the drive switching unit is disposed inside the second gear 506a so that the center of rotation of the second gear 506a and the center of rotation of the one-way clutch 505 are the same. Specifically, as shown in FIG. 7, the one-way clutch 505 is attached to the rotation shaft 502ea of ​​the second belt tension roller 502e, which is the center of rotation of the second belt tension roller 502e, so as to be rotatable integrally with the second gear 506a in a state in which the one-way clutch 505 is pressed into the second gear 506a. That is, the second gear 506a is journaled on the rotation shaft 502ea via the one-way clutch 505. When the second gear 506a rotates clockwise (in the direction of the arrow H) in FIG. 5, the one-way clutch 505 rotates integrally with the rotation shaft 502ea, and allows the transmission of drive from the second gear 506a to the second belt tension roller 502e. If the second gear 506a rotates counterclockwise in FIG. 5 (the opposite direction of the arrow H), the one-way clutch 505 rotates idly relative to the rotating shaft 502ea, and the drive transmission from the second gear 506a to the second belt tension roller 502e is interrupted.

[0048] For example, when the driving motor M (see FIG. 2) starts to drive in order to rotate the first belt 501, the first gear 506b of the first driving gear unit 510b starts to rotate counterclockwise (in the direction of the arrow E), and the first transmission gear 504b rotates clockwise (in the direction of the arrow F). Then, the second transmission gear 504a of the second driving gear unit 510a to which the driving force is transmitted from the first gear 506b rotates counterclockwise (in the direction of the arrow G), and the second gear 506a rotates clockwise (in the direction of the arrow H).

[0049] When the second gear 506a rotates clockwise, the one-way clutch 505 puts the second gear 506a and the rotating shaft of the second belt tension roller 502e into a drive transmission state, causing the second belt tension roller 502e to rotate clockwise. In this way, the second belt tension roller 502e rotates clockwise, causing the second belt 502 to rotate clockwise (in the direction of arrow B in FIG. 2). At this time, the rotation speed of the second gear 506a and the rotation speed of the second belt tension roller 502e are the same. Then, as the rotation speed of the drive motor M is increased to a predetermined rotation speed, the movement speed of the second belt 502 and the movement speed of the first belt 501 also increase. Here, if the diameter of the second belt tension roller 502e and the diameter of the first belt tension roller 501e are the same, the movement speed of the second belt 502 and the first belt 501 are the same. However, as described above, if the diameter of the second belt tension roller 502e is larger than the diameter of the first belt tension roller 501e, for example, a speed difference may occur between the moving speed of the second belt 502 and the moving speed of the first belt 501.

[0050] As in this embodiment, by providing the one-way clutch 505 on the drive gear unit 510, the speed difference between the second belt 502 and the first belt 501 can be suppressed. Here, when the second belt tension roller 502e and the second gear 506a move in the opposite directions relative to each other, the one-way clutch 505 does not transmit the driving force of the second gear 506a to the rotating shaft 502ea of ​​the second belt tension roller 502e. That is, when the moving speed of the second belt 502 becomes faster than the moving speed of the first belt 501, the one-way clutch 505 causes the second gear 506a and the rotating shaft 502ea of ​​the second belt tension roller 502e to be in a drive interrupted state. In that case, the second belt tension roller 502e rotates freely (idle) with respect to the second gear 506a. That is, regardless of the drive transmission by the drive gear unit 510, the second belt tension roller 502e and the second belt 502 rotate.

[0051] In this way, by providing the one-way clutch 505, when the moving speed of the second belt 502 becomes faster than the moving speed of the first belt 501, the second gear 506a rotates by receiving the driving force of the driving motor M via the first driving gear portion 510b, but the second belt tension roller 502e rotates by receiving the rotation of the second belt 502. In this case, the second belt 502 simply rotates together with the first belt 501 that contacts it at the cooling nip portion T4, and no driving force is applied by the driving motor M. Therefore, the moving speed of the second belt 502 gradually decreases to be equal to the moving speed of the first belt 501, following the moving speed of the first belt 501.

[0052] As described above, the moving speed of the second belt 502 follows the moving speed of the first belt 501, and the peripheral speed of the second belt tension roller 502e drops to or below the peripheral speed of the second gear 506a driven by the drive motor M. Then, the one-way clutch 505 again puts the second gear 506a and the rotating shaft of the second belt tension roller 502e into a drive transmission state. When the one-way clutch 505 puts the second gear 506a and the rotating shaft of the second belt tension roller 502e into a drive transmission state, the drive gear unit 510 transmits a driving force to the second belt tension roller 502e, and the second belt tension roller 502e rotates according to the driving force. Then, when the moving speed of the second belt 502 becomes faster than the moving speed of the first belt 501 again, the one-way clutch 505 puts the second gear 506a and the rotating shaft of the second belt tension roller 502e into a drive interruption state as described above.

[0053] In this way, the one-way clutch 505 is provided so as to be able to change between transmission and interruption of the drive force between the second gear 506a and the rotating shaft of the second belt tension roller 502e. In this way, when a speed difference occurs between the moving speed of the second belt 502 and the moving speed of the first belt 501, the one-way clutch 505 repeatedly switches between transmission and interruption of the drive force between the second gear 506a and the rotating shaft of the second belt tension roller 502e. This makes it possible to suppress the occurrence of a speed difference between the second belt 502 and the first belt 501.

[0054] <Other embodiments> In the above-described embodiment, the recording material cooling device 50 is provided inside the apparatus main body 100A of the image forming apparatus 100 (see FIG. 1), but the present invention is not limited to this. For example, the recording material cooling device 50 may be provided outside the apparatus main body 100A. FIG. 8 shows an example in which the recording material cooling device 50 is provided outside the apparatus main body 100A.

[0055] As shown in Fig. 8, an external cooling device 101 is connected to the apparatus main body 100A. The external cooling device 101 is configured to be connectable to the image forming apparatus 100 as one of peripheral devices (called an optional unit, etc.) that can be added later to expand the functions of the image forming apparatus 100. The external cooling device 101 is disposed to cool the recording material S discharged from the discharge port and to lower the temperature of the recording material S, which is higher than that before fixing, to a predetermined temperature or lower. The external cooling device 101 has the above-mentioned recording material cooling device 50 to cool the recording material S.

[0056] In this embodiment, when an external cooling device 101 is connected to the image forming apparatus 100 as an external device as shown in Fig. 8, the image forming apparatus 100 and the external cooling device 101 are collectively referred to as the image forming apparatus. In other words, in this embodiment, the entire apparatus involved from when the recording material S on which an image is to be formed is fed to when it is discharged to the outside of the apparatus is referred to as the image forming apparatus. Also, when a sheet processing apparatus that performs binding processing, punching processing, etc. on the recording material S is connected downstream of the external cooling device 101, the configuration including the image forming apparatus 100, the external cooling device 101, and the sheet processing apparatus is referred to as the image forming apparatus that forms an image on the recording material S.

[0057] The recording material S cooled by the external cooling device 101 is discharged from the external cooling device 101 by discharge rollers 83 and loaded onto a paper discharge tray 120. The paper discharge tray 120 is provided so as to be freely attached to and detached from the external cooling device 101 and the image forming apparatus 100. That is, when the external cooling device 101 is not connected to the image forming apparatus 100, the paper discharge tray 120 is attached to the image forming apparatus 100 (see FIG. 1). Then, when the external cooling device 101 is connected to the image forming apparatus 100, the paper discharge tray 120 is removed from the image forming apparatus 100 and replaced with the external cooling device 101 by a user.

[0058] In addition, a plurality of external cooling devices 101 may be connected as peripheral devices. By increasing the number of external cooling devices 101 to be connected, an operator can easily improve the cooling capacity of the existing image forming apparatus 100 for the recording material S.

[0059] As in the above-described embodiment, the present invention is not limited to being applied to the recording material cooling device 50, but may also be applied to a belt-type sheet conveying device in which the recording material S is sandwiched and conveyed by a pair of belts. That is, in a configuration in which the recording material S is sandwiched and conveyed through a nip portion formed by a pair of abutting belts, this embodiment can be applied to prevent the moving speed of one of the belts from becoming faster than the circumferential speed of the drive gear. This prevents the toner on the sandwiched and conveyed recording material S from being rubbed or the recording material S from being wrinkled due to the speed difference between the belts.

[0060] In the above embodiment, the first belt tension roller 501e and the second belt tension roller 502e are shown to be capable of transmitting the drive force via the first transmission gear 504b and the second transmission gear 504a, but the present invention is not limited to this. For example, the first belt tension roller 501e and the second belt tension roller 502e may be directly meshed to transmit the drive force, or the drive force may be transmitted via more transmission gears. When the first belt tension roller 501e and the second belt tension roller 502e are directly meshed with each other, it is preferable to sharpen the teeth of the first gear 506b and the teeth of the second gear 506a that mesh with each other to make it easier for the gears to mesh with each other.

[0061] In the above embodiment, the one-way clutch 505 is provided as the drive switching unit, but the present invention is not limited to this, and the same effect can be obtained even if the drive switching unit is provided with, for example, a torque limiter or an electromagnetic clutch. In the above embodiment, the one-way clutch 505 is provided on the rotating shaft of the second belt tension roller 502e, but it may be provided on either the gear shaft of the second driving gear portion 510a or the first driving gear portion 510b, which are the drive transmission path. For example, the first idler shaft 532 of the first transmission gear 504b may be a shaft that can rotate with respect to the support member 522, and the one-way clutch 505 may be provided between this shaft and the first transmission gear 504b. In addition, a similar configuration may be provided on the second idler shaft 531 of the second transmission gear 504a. [Explanation of symbols]

[0062] 30...fixing device, 50...cooling device (recording material cooling device), 500...roller driving section, 501...first belt, 501e...first roller (first belt tension roller), 501U...first unit, 502...second belt, 502e...second roller (second belt tension roller), 502U...second unit, 503...cooling means (heat sink, heat sink), 504a...second transmission gear, 504b...first transmission gear, 505...drive switching section (one-way clutch), 506a...second gear, 506b...first gear, 510...drive transmission section (drive gear section), 510a...second drive gear section, 510b...first drive gear section, 521...urging means (spring member), 580...regulating member (axis-to-axis regulating member), S...recording material

Claims

1. a fixing device that heats the sheet on which the toner image is formed to fix the toner image to the sheet; a cooling device provided downstream of the fixing device in a sheet conveying direction and configured to cool the sheet heated by the fixing device; The cooling device includes: A first unit including a first belt and a first roller for tensioning and rotating the first belt; a second unit including a second belt that forms a nip portion for nipping and conveying a sheet together with the first belt, a heat sink that contacts an inner peripheral surface of the second belt, and a second roller that stretches and rotates the second belt, the second unit being movable between a contact position where the first belt and the second belt contact each other to form the nip portion and a separation position where the first belt and the second belt are separated from each other to open the nip portion; a drive motor that rotates the first roller and the second roller; a drive transmission unit having at least four gears, the drive transmission unit transmitting a rotational drive force of the drive motor to the first roller and the second roller by the rotation of the gears; The drive transmission unit includes: a first drive gear portion provided in the first unit, the first drive gear portion having a first gear to which a rotational drive force from the drive motor is transmitted and a first transmission gear to which a rotational drive force is transmitted from the first gear; a second drive gear portion provided in the second unit, the second drive gear portion including: a second transmission gear to which a rotational driving force from the first transmission gear is transmitted by meshing with the first transmission gear; and a second gear to transmit the rotational driving force transmitted from the second transmission gear to the second roller; a biasing means for biasing the first drive gear portion so that the first transmission gear moves toward the second transmission gear, When the second unit moves from the separated position to the contact position, the first driving gear portion is movable against the biasing force of the biasing means by the first transmission gear being pressed by the second transmission gear.

1. An image forming apparatus comprising:

2. the second unit is provided to be rotatable relative to the first unit about a rotation axis extending along a sheet transport direction in the cooling device; the drive motor is provided on the same side as a rotation center of the second unit in a rotation axis direction of the first roller, 2. The image forming apparatus according to claim 1,

3. the drive transmission unit is provided on an opposite side of the first belt from the drive motor in a rotational axis direction of the first roller, 2. The image forming apparatus according to claim 1,

4. when the first transmission gear and the second transmission gear are not engaged with each other in a state in which the second unit is moved to the abutting position, the first driving gear portion rotates in response to rotation of the first roller and moves so as to engage with the second transmission gear.

2. The image forming apparatus according to claim 1,

5. the second drive gear portion has a regulating member that ensures an axial distance between the first transmission gear and the second transmission gear when the second unit is moved to the abutting position.

5. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

6. The first gear and the second gear have the same number of teeth, The number of teeth of the first transmission gear and the second transmission gear is the same and is greater than the number of teeth of the first gear and the second gear.

6. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

7. the cooling device includes a drive switching unit that does not transmit the driving force of the second drive gear unit to the second roller when the peripheral speed of the second roller becomes faster than the peripheral speed of the second gear, and transmits the driving force of the first drive gear unit to the second drive gear unit to drive the second roller when the peripheral speed of the second roller becomes equal to or lower than the peripheral speed of the second gear.

7. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

8. the drive switching unit is a one-way clutch that cuts off the drive transmission from the second gear to the second roller when the second gear rotates in a direction opposite to that of the second roller.

8. The image forming apparatus according to claim 7,

Images