JP6088407B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus.

  For example, an image forming apparatus such as a laser printer or a multifunction peripheral has a fixing unit that fixes a toner image transferred to a sheet to the sheet, and a discharge tray that discharges the sheet on which the toner image is fixed by the fixing unit. ing. The discharge tray is usually formed on the top of a housing that houses a fixing unit and the like. Further, the casing is formed with a discharge port for discharging the sheet to the discharge tray. On the other hand, a toner container is often arranged below the paper discharge tray.

  Since the fixing unit fixes the toner image by heating and pressurizing the sheet, the sheet discharged to the discharge tray is in a high temperature state. When the number of sheets discharged to the discharge tray increases, the temperature of the toner container increases due to the heat of the sheets, and the toner stored in the toner container tends to aggregate.

  Therefore, as described in Patent Document 1, a cooling air flow path is formed below the sheet discharged to the discharge tray to cool the sheet, and is formed between the cooling air flow path and the toner container. It is known to provide a heat shielding air flow path through which air that has passed through the cooling air flow path flows. The heat shielding air flow path is formed below the entire discharge tray. And the heat | fever discharge | released from the sheet | seat of a discharge tray is shielded with the air which flows through the air flow path for thermal insulation.

  By the way, in general, the image forming apparatus is configured to be able to form an image on sheets of various sizes such as an A4 size and an A3 size, and is sized so that the discharge tray can receive the largest sheet. Yes. For example, it is preferable that the width of the discharge tray in the direction orthogonal to the sheet discharge direction is approximately the same as the width of the maximum sheet.

JP 2009-288742 A

  However, since the maximum number of sheets, such as A3 size, is usually formed with a relatively small number of sheets per unit time, the amount of heat per unit area released downward from a plurality of sheets stacked on the discharge tray. There are few. On the other hand, a relatively small standard A4 size sheet or the like has a large number of images formed per unit time. Therefore, per unit area discharged downward from a plurality of sheets stacked on the discharge tray. The amount of heat increases.

  Therefore, the heat released from the sheets of various sizes discharged to the discharge tray cannot be efficiently shielded simply by forming the heat shielding air flow path below the entire discharge tray.

  The present invention has been made in view of such a point, and an object of the present invention is to reduce the heat released from the sheet discharged to the discharge tray to the heat shielding air flow path formed below the discharge tray. It is to shield efficiently by air.

The image forming apparatus according to the present invention includes a fixing unit that fixes the toner image on the sheet by heating and pressurizing the sheet on which the toner image is formed, and the sheet on which the toner image is fixed by the fixing unit. A discharge section that discharges; a discharge tray on which the sheet discharged from the discharge section is placed; a toner container that is disposed below the discharge tray and stores toner; and the discharge tray and the toner container A heat-insulating air flow path through which air for shielding heat released from the sheet placed on the discharge tray toward the toner container flows, and orthogonal to the discharge direction of the sheet depending on the width of the sheet in a direction, and a switching mechanism for switching the width of the thermal barrier air flow path in a direction perpendicular to the discharge direction of the sheet, the switching mechanism, A detecting means for detecting the width of the sheet discharged to the discharge tray, a plurality of air inlets for introducing air into the heat shielding air flow path, and the detecting means detected the width of the sheet. And an opening / closing mechanism that opens and closes the air inlet according to the width of the sheet, and the detection means has a lever that protrudes from the discharge tray and that falls on contact with the sheet. The open / close mechanism includes an open / close valve that closes the air inlet when the lever protrudes from the discharge tray, and opens the air inlet when the lever falls down .

  According to the present invention, the heat released from the sheet discharged to the discharge tray can be efficiently shielded by the air in the heat shielding air passage formed below the discharge tray.

FIG. 1 is a sectional view showing a schematic structure of the image forming apparatus. FIG. 2 is a side sectional view showing the discharge tray and the heat shielding air flow path. FIG. 3 is a side cross-sectional view showing a discharge tray and a heat shielding air flow path in which A4 sheets are stacked. FIG. 4 is a plan view showing a discharge tray on which A4 sheets are stacked and a heat shielding air flow path. FIG. 5 is a side cross-sectional view showing a discharge tray and a heat shielding air flow path in which A3 sheets are stacked. FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. FIG. 7 is a plan view showing a discharge tray on which A3 sheets are stacked and a heat shielding air flow path.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiment.

  FIG. 1 is a cross-sectional view illustrating a schematic structure of the image forming apparatus 1. The image forming apparatus 1 is, for example, a tandem color printer. As shown in FIG. 1, the intermediate transfer belt 7, the primary transfer unit 8, the secondary transfer unit 9, and the fixing unit respectively housed in the housing 2. A unit 11, an optical scanning unit 15, and a plurality of image forming units 16 are provided.

  A paper feed cassette 3 is disposed below the inside of the housing 2 of the image forming apparatus 1. The paper feed cassette 3 accommodates paper (not shown) that is a sheet before printing. A first paper transport unit 21 is provided on the side of the paper feed cassette 3. The first paper transport unit 21 receives the paper fed from the paper feed cassette 3 and transports the paper to the upper secondary transfer unit 9.

  A manual paper feed unit 5 is provided on the right side of the paper feed cassette 3. A second paper transport unit 22 is provided on the left side of the manual paper feed unit 5. The second paper transport unit 22 receives the paper sent from the manual paper feed unit 5 and transports it to the first paper transport unit 21.

  The optical scanning unit 15 is disposed above the second paper transport unit 22 and irradiates the image forming unit 16 with laser light based on the image data received by the image forming apparatus 1. For example, four image forming units 16 are provided above the optical scanning unit 15. An endless intermediate transfer belt 7 is provided above each image forming unit 16. The intermediate transfer belt 7 is wound around a plurality of rollers and is rotationally driven by a driving device (not shown).

  As shown in FIG. 1, the four image forming units 16 are arranged in a line along the intermediate transfer belt 7, and respectively form yellow, magenta, cyan, or black toner images. That is, in each image forming unit 16, an electrostatic latent image of the original image is formed by the laser light irradiated by the optical scanning unit 15, and each color toner image is formed by developing the electrostatic latent image. .

  The primary transfer unit 8 is disposed above each image forming unit 16. The primary transfer unit 8 includes a transfer roller that primarily transfers the toner image formed by the image forming unit 16 to the surface of the intermediate transfer belt 7.

  Then, the intermediate transfer belt 7 is driven to rotate, and the toner image of each image forming unit 16 is transferred to the intermediate transfer belt 7 at a predetermined timing, so that the surface of the intermediate transfer belt 7 has yellow, magenta, A color toner image in which toner images of four colors of cyan and black are superimposed on each other is formed.

  As shown in FIG. 1, the secondary transfer unit 9 has a transfer roller 18 disposed on the left side of the intermediate transfer belt 7. The secondary transfer unit 9 applies a transfer bias voltage having a polarity opposite to that of the toner to the sheet sent from the first sheet transport unit 21 so as to transfer the toner image from the intermediate transfer belt 7 to the sheet. It has become.

  The fixing unit 11 is provided above the secondary transfer unit 9. Between the secondary transfer unit 9 and the fixing unit 11, a third paper transport unit 23 that transports the paper on which the toner image is secondarily transferred to the fixing unit 11 is formed.

  The fixing unit 11 includes a pressure roller 31 and a fixing roller 32. Each roller 31 and 32 is arrange | positioned so that an axial direction may become mutually parallel so that a nip part may be formed. The fixing unit 11 heats and presses the sheet conveyed from the third sheet conveying unit 23 by the pressure roller 31 and the fixing roller 32 to fix the toner image on the sheet.

  2 to 6 show the discharge tray 38 and the heat shielding air flow path 40. As shown in FIGS. 1 to 3, on the upper part of the housing 2, a discharge unit 37 that discharges the paper P on which the toner image is fixed by the fixing unit 11 and a paper P discharged from the discharge unit 37 are placed. A discharge tray 38 is provided. The discharge tray 38 is provided on the side of the discharge unit 37 and is formed by the upper surface of the housing 2.

  Thus, the paper P is discharged from the discharge portion 37 in the side paper discharge direction A and stacked on the discharge tray 38. The sheet P discharged to the discharge tray 38 is heated by the fixing unit 11 and is in a high temperature state.

  As shown in FIG. 2, a plurality of toner containers 30 as toner containers are arranged below the discharge tray 38. Further, the toner container 30 is disposed above the intermediate transfer belt 7. The toner containers 30 are arranged in a line along the discharge tray 38. The toner container 30 contains yellow, magenta, cyan, or black toner. The toner in the toner container 30 is supplied to the image forming unit 16.

  Between the discharge tray 38 and the toner container 30, a heat shielding air flow path 40 through which air for shielding heat released from the paper P placed on the discharge tray 38 toward the toner container 30 circulates. Is formed. A duct 41 for introducing air into the heat shielding air flow path 40 is connected to the side of the heat shielding air flow path 40. The duct 41 is provided with a fan 42 for sending air into the duct 41.

  Here, the width in the direction perpendicular to the paper discharge direction A (direction perpendicular to the paper surface in FIG. 2) is simply referred to as “width”. The duct 41 extends in the width direction of the discharge tray 38. A plurality of air introduction ports 43 through which air is introduced into the heat shielding air flow path 40 are provided at a connection portion between the duct 41 and the heat shielding air flow path 40. On the other hand, an exhaust port 44 through which air is discharged from the heat shielding air flow path 40 is provided at a position facing the air introduction port 43.

  The image forming apparatus 1 includes a switching mechanism 50 that switches the width of the heat shielding air flow path 40 in accordance with the width of the paper P. That is, as shown in FIGS. 4 and 7, the heat shielding air flow path 40 includes a first air flow path 40a formed at the center of the heat shielding air flow path 40 in the width direction, and a first air flow path 40a. And a second air flow path 40b provided on both sides in the width direction. The sum of the width of the first air flow path 40a and the width of the two second air flow paths 40b is the same as the entire width of the heat shielding air flow path 40.

  Here, the image forming apparatus 1 is configured to be able to form an image on at least a standardly used A4 size paper P and a larger A3 size paper P. The A4 sheet P and the A3 sheet P are discharged from the discharge unit 37 in the longitudinal direction of the sheet P, respectively.

  As shown in FIG. 7, the width of the discharge tray 38 and the width of the heat shielding air flow path 40 are substantially the same as the width of the A3 paper P (that is, the width of the short side of the paper P). Further, the length of the discharge tray 38 and the length of the heat shielding air flow path 40 (that is, the length in the discharge direction A of the paper P) are the length of the A3 paper P (that is, the length of the long side of the paper P). It is almost the same size. The width of the first air flow path 40a is substantially the same as the width of the A4 paper P as shown in FIG.

  When the switching mechanism 50 detects the width of the paper P discharged by the discharge tray 38, the detection means 51 for detecting the width of the paper P, the plurality of air introduction ports 43, and the detection means 51 detect the width of the paper P. An opening / closing mechanism 52 that opens and closes the air inlet 43 according to the width of the paper P is provided.

  The detection means 51 has a lever 55 that protrudes from the discharge tray 38 and falls down when the paper P comes into contact therewith. The lever 55 is provided above the air introduction port 43 of the second air flow path 40 b and can swing around a rotation axis extending in the width direction of the discharge tray 38.

  The opening / closing mechanism 52 closes the air inlet 43 of the second air passage 40b when the lever 55 protrudes from the discharge tray 38, while the air inlet of the second air passage 40b when the lever 55 falls down. On-off valve 56 for opening 43 is provided.

  The on-off valve 56 of the present embodiment is configured to swing integrally with the lever 55. That is, the on-off valve 56 closes the air introduction port 43 of the second air passage 40b when the lever 55 is in the projecting state, while introducing air into the second air passage 40b when the lever 55 is in the lying state. The mouth 43 is opened.

  Therefore, when the A4 paper P is discharged to the discharge tray 38, the A4 paper P is discharged above the first air flow path 40a in the discharge tray 38 as shown in FIGS. That is, since the A4 paper P is discharged between the two levers 55, it does not contact the lever 55. Therefore, since the lever 55 is maintained in the protruding state, the on-off valve 56 closes the air inlet 43 of the second air flow path 40b. As a result, the air in the duct 41 is not introduced into the second air flow path 40b but is introduced only into the first air flow path 40a. As a result, the heat released from the A4 paper P is shielded by the air flowing through the first air flow path 40a.

  On the other hand, when the A3 paper P is discharged to the discharge tray 38, the A3 paper P is discharged above the first and second air flow paths 40a and 40b in the discharge tray 38 as shown in FIGS. The That is, since the A3 paper P comes into contact with the two levers 55, the lever 55 swings and falls due to the weight of the A3 paper P. At this time, the on-off valve 56 swings integrally with the lever 55 to open the air inlet 43 of the second air flow path 40b. As a result, the air in the duct 41 is introduced not only into the second air flow path 40b but also into the first air flow path 40a. Accordingly, the heat released from the A3 paper P is shielded by the air flowing through the first and second air flow paths 40a and 40b.

  As described above, in the present embodiment, the width of the sheet P discharged to the discharge tray 38 in the image forming apparatus 1 in which the heat shielding air flow path 40 is formed between the discharge tray 38 and the toner container 30. Accordingly, a switching mechanism 50 for switching the width of the heat shielding air flow path 40 is provided. As a result, the heat released from the paper P discharged to the discharge tray 38 can be efficiently shielded by the air in the heat shielding air flow path 40.

  That is, for example, when the A3 paper P is discharged to the discharge tray 38, the lever 55 falls down by contacting the A3 paper P, and the air introduction port 43 of the second air flow path 40b is opened. As a result, the heat released from the A3 paper P to the lower side of the discharge tray 38 is preferably caused by the air flowing through the first and second air flow paths 40a and 40b (that is, the entire heat shielding air flow path 40). Can be shielded.

  On the other hand, when the A4 sheet P is discharged to the discharge tray 38, the lever 55 is brought into a protruding state without contacting the A4 sheet P, and the air introduction port 43 of the second air flow path 40b is closed. Accordingly, the heat released from the A4 paper P to the lower side of the discharge tray 38 can be efficiently shielded by the air flowing through the first air flow path 40a.

  That is, since A4 paper P used as a standard has a larger number of images formed per unit time than other paper P such as A3 paper P, it is discharged downward from the A4 paper P stacked on the discharge tray 38. The amount of heat per unit area is greater than that of the other paper P.

  On the other hand, in the present embodiment, when the narrow A4 paper P is discharged to the discharge tray 38, the air introduction port 43 of the second air flow path 40b is closed and the air is only supplied to the first air flow path 40a. Was introduced. As a result, the air flow rate in the first air flow path 40a is increased and the heat shielding capability per unit area of the paper P is increased, so that the heat released from the A4 paper P to the lower side of the discharge tray 38 is reduced to the first. It can be efficiently shielded by the air of the one air flow path 40a. Therefore, toner aggregation in the toner container 30 can be suppressed.

  On the other hand, when the wide A3 sheet P is discharged to the discharge tray 38, the air introduced into the entire first and second air flow paths 40a and 40b is discharged from the entire A3 sheet P to the lower side of the discharge tray 38. Heat can be shielded. At this time, the heat shielding capability per unit area of the paper P is reduced as compared with the case where air is introduced only into the first air flow path 40a, but the number of images that are normally formed on the A3 paper P per unit time. Is significantly less than the A4 paper P, the heat flowing from the A3 paper P can be sufficiently shielded by the air flowing through the first and second air flow paths 40a and 40b.

  Furthermore, since the detecting means for detecting the width of the paper P is configured by the lever 55 that falls down when the paper P contacts, the width of the paper P can be detected appropriately with a simple configuration.

  In the above-described embodiment, the color printer is described as an example of the image forming apparatus. However, the present invention is not limited to this. Also good.

  As described above, the present invention is useful for an electrophotographic image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Fixing part 30 Toner container 37 Ejection part 38 Ejection tray 40 Heat insulation air flow path 40b First air flow path 40a Second air flow path 43 Air introduction port 44 Exhaust port 50 Switching mechanism 51 Detection means 52 Opening and closing Mechanism 55 Lever 56 On-off valve

Claims (2)

A fixing unit for fixing the toner image on the sheet by heating and pressurizing the sheet on which the toner image is formed; and
A discharge unit for discharging the sheet on which the toner image is fixed by the fixing unit;
A discharge tray on which the sheet discharged from the discharge unit is placed;
A toner container disposed below the discharge tray and containing toner;
A heat shielding air passage formed between the discharge tray and the toner container and through which air flows to shield heat released from the sheet placed on the discharge tray toward the toner container. When,
A switching mechanism that switches the width of the heat shielding air flow path in the direction orthogonal to the sheet discharge direction according to the width of the sheet in the direction orthogonal to the sheet discharge direction ;
The switching mechanism includes detection means for detecting the width of the sheet discharged to the discharge tray, a plurality of air inlets for introducing air into the heat shielding air flow path, and the detection means includes the sheet An opening / closing mechanism that opens and closes the air inlet according to the width of the sheet when detecting the width of the sheet,
The detection means includes a lever that protrudes from the discharge tray and falls down when the sheet comes into contact with the detection tray.
The open / close mechanism has an open / close valve that closes the air inlet when the lever protrudes from the discharge tray, and opens the air inlet when the lever falls. apparatus. The image forming apparatus according to claim 1 .
An image forming apparatus, comprising: an exhaust port provided at a position facing the air introduction port, through which air is discharged from the heat shielding air flow path.

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