JP5058927B2 - Paper feeding device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a paper feeding device used in an image forming apparatus such as a printer, a copier, a facsimile machine, or a multi-function machine having these functions in combination, and an image forming apparatus having the same.

  Conventionally, in image forming apparatuses such as printers, copiers, and facsimiles, sheet-like recording media that can be continuously fed are usually limited to high-quality paper and cut sheets such as plain paper designated by the copier manufacturer. It was used. Such a cut sheet such as high-quality paper or plain paper has a relatively low surface smoothness and thus has a relatively low adhesion between sheets. Therefore, when feeding cut sheets one by one from a sheet stacking unit such as a paper feed tray, it is relatively easy to prevent multiple feeds in which a plurality of cut sheets are supplied in close contact. In addition, when these cut sheets are used, even if double feeding occurs, it is possible to send out the cut sheets one by one relatively well by providing a separation roller, a separation pad or a separation claw. It was.

  However, in recent years, sheet-shaped recording media have been diversified, and only sheets with low surface smoothness such as high-quality paper and plain paper are not used. In particular, with the development of colorization technology for image forming devices, coated paper with increased whiteness and glossiness (a coating color, a type of paint, is applied to both sides or one side of the sheet for the purpose of improving printability) Those having high surface smoothness such as a coated composite sheet) have been used. That is, in recent years, not only high-quality paper and plain paper, but also the above-mentioned coated paper, as well as film sheets, tracing paper, and the like, there is an increasing demand for conveyance by the same model. Here, coated paper, film sheets, tracing paper, etc. have strong adhesion between the sheets, so it is difficult to prevent double feeding of sheets, and special measures are required for paper feeding (sheet feeding). It becomes.

  In addition, the sheet bundle placed on the sheet stacking unit is likely to contain a lot of moisture because its upper surface and outer peripheral part are in contact with the outside air. That is, while the upper surface and side surface of the sheet bundle swell due to moisture absorption, the degree of swelling is lower because the inside of the sheet bundle has less moisture than the upper surface and side surface. As a result, the inner space (space between sheets) of the sheet bundle becomes negative pressure, and the sheets are in close contact with each other.

  Therefore, in a large-sized copying machine or the like, a mechanism that blows warm air on the side surface of the sheet bundle in order to release the adhesion between the sheets and spread the sheet bundle prior to feeding (hereinafter referred to as “lateral warm air assist”). A paper feeding device having the above is employed.

For example, Patent Document 1 discloses a technique for improving the drying efficiency of a sheet by appropriately adjusting the humidity of the lateral warm air blown to the side surface of the sheet bundle in the sheet rolling method using the lateral warm air assist.
JP 2001-48366 A Japanese Patent Laid-Open No. 2003-150024 JP 2006-264917 A JP 2007-62894 A Japanese Utility Model Publication No. 7-12359

  However, with the conventional sheet-rolling technology using the above-mentioned lateral hot air assist, it is difficult for hot air to reach the area away from the hot air outlet, so the hot air is blown around the outer periphery of the sheet with particularly strong adhesion. It is not easy. That is, in the case of using the conventional lateral hot air assist, a favorable wind effect cannot be obtained unless a large-sized one is used as the configuration of the hot air blowing means, heater means, drive source, and the like required for this. For this reason, the conventional sheet-rolling technique using the side warm air assist has been limited to application to a relatively large feeding deck having about 2000 to 4000 sheets.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sheet feeding device provided with a sheet blowing mechanism by hot air assist that can be installed even in a small space, and an image forming apparatus provided with the sheet feeding device.

  A sheet feeding device according to an aspect of the present invention includes a sheet storage unit that stores a sheet bundle composed of a plurality of sheet-like recording media, a sheet placement plate that is provided in the sheet storage unit and stacks the sheet bundle. A pickup roller that comes into contact with the upper surface of the sheet bundle and feeds the uppermost sheet-like recording medium of the sheet bundle; a sheet feeding position where the upper surface of the sheet bundle comes into contact with the pickup roller; and the upper surface of the sheet bundle An elevating mechanism that displaces the sheet placing plate between a pickup roller and a separation position separated by a certain distance, and a sheet feeding direction of a sheet bundle stored in the sheet storage unit at least during a sheet feeding preparation period A first hot air mechanism that blows hot air from a first hot air outlet on parallel side surfaces, a sheet specifying unit that specifies the type of sheet-like recording medium to be fed, and the first sheet-like recording During the warm air blowing operation by the first warm air mechanism during the sheet feeding preparation period before the body sheet feeding operation is started, the sheet placing plate is displaced between the sheet feeding position and the separation position. And a control means for controlling the raising / lowering drive of the raising / lowering mechanism, wherein the control unit changes the lowering amount of the sheet placing plate according to the type of the sheet-like recording medium specified by the sheet specifying unit. It is characterized by doing.

  Among the sheet bundles placed on the sheet placing plate, the upper surface and the outer peripheral portion of the sheet bundle are in contact with the outside air, so that they easily contain a lot of moisture and swell due to moisture absorption. On the other hand, the degree of swelling is relatively low because the inside of the sheet bundle has less moisture than the top and side surfaces. For this reason, the inner side of the sheet bundle (the space between the sheets) has a negative pressure, and in particular, the upper layer of the sheet bundle has high adhesion between the sheets and is difficult to roll.

  Thus, in the sheet bundle, the upper layer has higher adhesion between the sheets than the middle and lower layers. For this reason, even if hot air is blown from the first hot air mechanism to the side surface parallel to the sheet feeding direction, the hot air is only applied between the middle and lower layer sheets having relatively low adhesion between the sheets. Warm air may enter and the upper layer with high adhesion may be in close contact with the upper layer and may be lifted by the warm air. For this reason, it is particularly difficult to prevent double feeding of the upper layer of the sheet bundle immediately after the start of sheet feeding, and special measures are required.

  Therefore, according to the above configuration, the control unit performs the hot air blowing operation by the first hot air mechanism during the paper feeding preparation period before starting the paper feeding operation of the first sheet-like recording medium. The raising / lowering drive of the raising / lowering mechanism is controlled so that the sheet placing plate is displaced between the sheet feeding position and the separation position. As described above, if the sheet placing plate is separated during the warm air blowing operation by the first warm air mechanism during the sheet feeding preparation period, the sheet feeding speed (productivity) is decreased due to the separating operation. Will not invite you.

  Furthermore, by adopting a configuration in which the descending amount is changed in accordance with the type of the sheet-like recording medium specified as the sheet feeding target, for example, a sheet-like recording medium having a high basis weight (weight per unit area) and difficult to float. Can be lowered to an optimum separation position according to the type of the sheet-like recording medium to be fed, such as setting a lowering amount to be small. For this reason, hot air can be blown into the sheet bundle more efficiently than when the separation position is constant regardless of the type of sheet-like recording medium to be fed. The sheet-like recording medium of the uppermost layer of the bundle can be made sufficiently bright. As a result, the sheet can be fed from the first sheet-like recording medium to a predetermined conveyance path without a problem of double feeding without causing a decrease in the sheet feeding speed.

  As described above, the control unit changes the descending amount according to the type of the sheet-like recording medium specified as the sheet feeding target, and performs the separation operation between the sheet feeding position and the separation position during the sheet feeding preparation period. By performing control so as to be performed, it becomes easy to efficiently blow even a small amount of warm air up to a place away from the first warm air outlet. This makes it possible to realize a hot air assist mechanism that has higher sheet rolling efficiency than a conventional large-sized side warm air assist, and thus the entire sheet feeding device can be downsized.

  In the above-described configuration, a position detection unit that detects that the upper surface of the sheet bundle is at the sheet feeding position is provided, and the amount of lowering according to the type of each type of sheet-like recording medium specified by the sheet specifying unit A storage unit for storing each corresponding descent drive time; and a timer for measuring each descent drive time; and the control unit includes a descent drive time corresponding to the type of sheet specified by the sheet specifying unit. Is read from the storage unit, and after the descent drive of the elevating mechanism is started, the descent drive time is counted from when the position detection unit no longer detects that the upper surface of the sheet bundle is at the sheet feeding position. It is desirable to control the elevating mechanism so as to lower the sheet placing plate until it does so (Claim 2).

  In the above configuration, when the descending drive continues even after a predetermined time has elapsed after the start of the descending drive, the control unit controls the elevating mechanism so as to stop the descending drive. It is desirable (Claim 3).

  Usually, after starting the lowering drive of the elevating mechanism, the upper surface of the sheet bundle is separated from the pickup roller after a predetermined time, and the position detecting unit is in a non-detecting state. However, when the upper surface of the sheet bundle is not separated from the pickup roller due to the occurrence of a jam or the like, the position detection unit continues to detect that the upper surface of the sheet bundle is at the sheet feeding position. . In this case, the first timer for measuring the descent drive time does not operate, and the descent driving of the sheet placing plate by the elevating mechanism continues, and the sheet feeding device is damaged in this state. Therefore, according to the above configuration, when the descending drive is in a continuous state even after a predetermined time has elapsed after the start of the descending drive, the control unit controls the descending drive to stop. Yes. Accordingly, it is possible to prevent the sheet feeding device from being damaged due to the sheet placing plate continuing to descend even after a predetermined time has elapsed.

  The predetermined time may be set shorter than the time required from the start of the descending drive until the sheet placement plate reaches the lowest position (retracted position).

  In the above configuration, the elevating mechanism further includes a push-up member that pushes up the sheet placing plate, and the sheet placing plate is rotatably supported at the upstream end in the sheet feeding direction in the sheet storage unit, The push-up member may be configured such that one end of the push-up member is rotatably supported by a rotation shaft and the other end abuts on the bottom surface of the sheet placement plate to push up the sheet placement plate. Item 4).

  The above-described cantilever raising / lowering mechanism (mechanism for raising and lowering a sheet placing plate whose upstream end in the paper feeding direction is rotatably supported) is often used for a small paper feeding device. In such a small sheet feeding device, it is difficult to install a sheet rolling mechanism using a large hot air mechanism. Therefore, a hot air mechanism that has high sheet-rolling efficiency and can efficiently roll the sheet-like recording medium stored in the sheet storage portion prior to feeding even with a small amount of hot air is preferable. Therefore, the paper feeding device of the present invention includes the warm air mechanism and the cantilever lifting mechanism, and can be particularly suitably used as a small paper feeding device.

  In the above configuration, the elevating mechanism stores a stepping motor that rotates the drive shaft forward and backward, and the number of descending steps corresponding to the descending amount corresponding to the weight of each type of sheet specified by the sheet specifying unit. The controller reads out the number of descending steps corresponding to the type of sheet specified by the sheet identifying unit, and descends the sheet placement plate by the number of descending steps. It is good also as a structure which controls the said raising / lowering mechanism so that it may carry out (Claim 5).

  In the above configuration, the second temperature that can blow the warm air from the second warm air outlet provided above the upper surface of the sheet bundle in the state of being accommodated in the sheet accommodating portion toward the upper surface of the sheet bundle. It is desirable that the control unit includes a wind mechanism and controls the second hot air mechanism to blow warm air onto the upper surface of the sheet bundle at least during a paper feed preparation period.

  According to the above configuration, as the sheet blowing mechanism by blowing hot air, in addition to the first hot air mechanism, the second hot air outlet provided above the upper surface of the sheet bundle is directed toward the upper surface of the sheet bundle. The second warm air mechanism for blowing warm air is provided. Here, the hot air blown from the hot air outlet to the upper surface of the sheet bundle flows so as to cover the outer periphery of the sheet-like recording medium bundle. Among the sheet bundle, the upper surface and the side surface are swollen by moisture absorption, and have high adhesion and are difficult to spread. For this reason, the negative pressure inside the sheet bundle (the space between the sheet-like recording media) can be eliminated by quickly reducing the moisture absorption of the upper surface and the outer peripheral portion of the sheet bundle and eliminating the swelling state of the portion. Accordingly, it is possible to reduce the adhesion between the sheet-like recording media stored in the sheet storage unit, and to efficiently bundle the sheet-like recording medium bundle prior to paper feeding. In this way, by using the second warm air mechanism (upper warm air mechanism) having the above-described configuration together with the first warm air mechanism (lateral warm air mechanism), the sheet-shaped recording medium bundle can be efficiently used prior to paper feeding. Can be whispered.

  An image forming apparatus according to another aspect of the present invention includes the sheet feeding device having the above-described configuration and an image forming apparatus main body that forms an image on a sheet-like recording medium fed from the sheet feeding device. (Claim 7).

  According to the above configuration, since the sheet heating mechanism using warm air can realize a lateral warm air unit having higher sheet rolling efficiency than a conventional large-sized lateral warm air assist, the paper feeding device is small. Can be realized. As a result, it is possible to reduce the size of the entire image forming apparatus having a sheet feeding device having a sheet winding mechanism using warm air.

  According to the present invention, it is possible to provide a sheet feeding device equipped with a sheet blowing mechanism by hot air assist that can be installed even in a small space and an image forming apparatus provided with the sheet winding efficiency by improving the sheet blowing efficiency by warm air.

  Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings. In addition, in each drawing, the member etc. which attached | subjected the same code | symbol are the same structures, The duplication description about these shall be abbreviate | omitted suitably. Moreover, in each drawing, members and the like that are not necessary for the description are omitted as appropriate.

<First Embodiment>
With reference to FIG. 1 and FIG. 2, an image forming apparatus including a sheet feeding device according to an embodiment of the present invention will be described.

  FIG. 1 is a perspective view illustrating an appearance of an image forming apparatus including a sheet feeding device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the internal structure of the image forming apparatus.

  As shown in FIG. 1, a color printer 1 as an image forming apparatus according to an embodiment of the present invention includes a printer main body 200 connected directly to a personal computer (PC) (not shown) or the like via a LAN, A sheet supply unit 100 is provided below the printer main body 200 and configured to store sheets P of various sizes according to the sizes. The color printer 1 also includes other components provided in a general color printer, such as a control circuit that controls the operation of the color printer X.

  As shown in FIG. 2, the printer body 200 includes toner containers 900Y, 900M, 900C, and 900K, an intermediate transfer unit 92, an image forming unit 93, an exposure unit 94, a sheet supply unit 100, a fixing unit 97, a paper discharge unit 96, An apparatus main body casing 90, a top cover 911, and a front cover 912 are provided.

  The image forming unit 93 includes a yellow toner container 900Y, a magenta toner container 900M, a cyan toner container 900C, and a black toner container 900K. 10K.

  The image forming unit 93 is further provided with a photoreceptor drum 17 (a photoreceptor on which a latent image is formed by an electrophotographic method) that carries toner images of respective colors. As the photoreceptor drum 17, a photoreceptor drum using an amorphous silicon (a-Si) material can be used. Each photosensitive drum 17 is supplied with yellow, magenta, cyan, and black toner from the corresponding toner containers 900Y, 900M, 900C, and 900K.

  Note that the image forming unit 93 of the present embodiment is configured to form a full-color image as described above, but is not limited thereto, and is configured to form a monochrome image or a color image that is not full-color. It may be.

  Around the photosensitive drum 17, a charger 16, a developing device 10 (10Y, 10M, 10C, 10K), a transfer device (transfer roller) 19, a cleaning device 18 and the like are arranged. The charger 16 uniformly charges the surface of the photosensitive drum 17. The surface of the photosensitive drum 17 after charging is exposed by the exposure unit 94 to form an electrostatic latent image. The developing devices 10Y, 10M, 10C, and 10K develop the electrostatic latent images formed on the respective photosensitive drums 17 using the toners of the respective colors supplied from the toner containers 900Y, 900M, 900C, and 900K, respectively ( Visualization). The transfer roller 19 forms a nip portion with the photosensitive drum 17 across the intermediate transfer belt 921, and primarily transfers the toner image on the photosensitive drum 17 onto the intermediate transfer belt 921. The cleaning device 18 cleans the peripheral surface of the photosensitive drum 17 after the toner image is transferred.

  Each of the developing devices 10Y, 10M, 10C, and 10K includes a housing 20, in which a two-component developer having a magnetic carrier and toner is stored. In the housing 20, two agitation rollers 11 and 12 (developer agitation members) are rotatably arranged in parallel near the bottom of the housing with the longitudinal direction as an axial direction.

  A developer circulation path is set on the inner bottom surface of the housing 20, and the stirring rollers 11 and 12 are disposed in the circulation path. In the axial direction between the stirring rollers 11 and 12, a partition wall 201 erected from the bottom of the housing is provided. The partition wall 201 divides the circulation path, and the circulation path is formed so as to go around the partition wall 201. The two-component developer is charged while being stirred and conveyed by the stirring rollers 11 and 12 through this circulation path.

  The two-component developer circulates in the housing 20 while being stirred by the stirring rollers 11 and 12, the toner is charged, and the two-component developer on the stirring roller 11 is attracted to the magnetic roller 14 located on the upper side. Are transported. The sucked two-component developer forms a magnetic brush (not shown) on the magnetic roller 14, the layer thickness of which is regulated by the doctor blade 13, and the potential difference between the magnetic roller 14 and the developing roller 15 A toner layer is formed on the developing roller 15. Then, the electrostatic latent image on the photosensitive drum 17 is developed by the toner layer on the developing roller 15.

  The exposure unit 94 includes various optical system devices such as a light source, a polygon mirror, a reflection mirror, and a deflection mirror, and is based on image data on the peripheral surface of the photosensitive drum 17 provided in each of the image forming units 93. Irradiate light to form an electrostatic latent image.

  The intermediate transfer unit 92 includes an intermediate transfer belt 921, a driving roller 922, and a driven roller 923. The intermediate transfer belt 921 primarily transfers toner images from a plurality of photosensitive drums 17 in an overcoated state, and secondarily transfers the toner images to the sheet P supplied from the paper supply unit 130 at the secondary transfer unit 98. . The driving roller 922 and the driven roller 923 drive the intermediate transfer belt 921 to rotate. The driving roller 922 and the driven roller 923 are rotatably supported by a housing (not shown).

  The sheet feeding unit 130 stores a sheet bundle S composed of a plurality of sheets P on which images are formed, and is detachably attached to the housing 90.

  The fixing unit 97 performs a fixing process on the toner image on the sheet P that has been secondarily transferred from the intermediate transfer unit 92. It is discharged toward the discharge unit 96 formed in the above.

  The paper discharge unit 96 discharges the sheet P conveyed from the fixing unit 97 onto a top cover 911 serving as a paper discharge tray.

  The sheet supply unit 100 includes a plurality of stages (three stages in the present embodiment) of paper feed units (paper feeders) 130 that are detachably attached to the printer main body 200. Each stage of the sheet feeding unit 130 stores the sheet bundle S of each size, and the selected sheet feeding unit 130 is driven by a pickup roller 40 provided in the sheet feeding unit 130. The uppermost sheet P of the sheet bundle S is taken out one by one, fed out to the paper feed conveyance path 133, and introduced into the image forming unit 93.

  Each of the paper feed units 130 includes a transport mechanism that can be stacked and installed later on the lower part of the printer main body 200, so that a desired number of paper feed units 130 can be attached to the printer main body 200 at any time later. That is, by stacking a plurality of paper feed units 130 below the printer body 200, the transport mechanisms of the paper feed units 130 are coupled to each other to form a single paper feed transport path 133 extending to the printer body 200. Is done. As a result, a plurality of stacked sheet feeding units 130 can be attached later.

  In this embodiment, an example is given in which the sheet supply unit 100 is configured by a three-stage sheet feeding unit 130, but the present invention is not limited to this, and the sheet feeding unit 130 is one-stage or two-stage, or four The present invention can be similarly applied to an image forming apparatus such as a printer configured with a sheet feeding unit of more than one stage.

  Next, with reference to FIG. 1 and FIGS. 3 to 5, the configuration of each sheet feeding unit (sheet feeding device) 130 mounted on the sheet feeding unit 100 of the color printer 1 according to the present embodiment will be described in detail. To do.

  FIG. 3 is a cross-sectional view illustrating a configuration of the paper feeding device according to the present embodiment. FIG. 4 is a perspective view showing a state in which the paper feeding cassette in the paper feeding device shown in FIG. 3 is pulled out from the paper feeding device body. FIG. 5 is an explanatory diagram illustrating a position detection sensor mounted on the sheet feeding device illustrated in FIG. 3.

  As shown in FIGS. 3 and 4, the sheet feeding unit 130 has a lift plate (sheet stacking plate) for stacking a sheet bundle S composed of a plurality of sheets (sheet-like recording media) P on the inner bottom surface of the sheet storage unit 35. ) 31. The lift plate 31 is rotatably supported at its upstream end (left end portion in FIG. 3) in the sheet feeding direction by a support portion 38. That is, the lift plate 31 is rotatable in the vertical plane by the support portion 38 with the downstream end as a free end inside the sheet storage portion 35. The support portions 38 are provided on both side walls of the sheet storage portion 35 that are arranged to face each other in the width direction of the sheet P (a direction orthogonal to the sheet feeding direction).

  A sheet feeding cassette 130A of the sheet feeding unit 130 includes a width alignment cursor pair 34a and 34b for positioning the sheet P stored in the sheet storage unit 35 in the width direction, a rear end cursor 33 for aligning the rear end of the sheet P, It has. The width alignment cursor pairs 34a and 34b are provided so as to be able to reciprocate in the sheet width direction (arrow AA ′ direction in FIG. 4) along guide rails (not shown). Here, since the sheet P is sent out in the direction of arrow B, the rear end cursor 33 is provided so as to be capable of reciprocating along the guide rails 33a and 33b in parallel with the sheet conveying direction (in the direction of arrow BB 'in FIG. 4). The sheet bundle S is stored in a predetermined position in the sheet feeding unit 130 by moving the width alignment cursor pair 34a and 34b and the rear end cursor 33 in accordance with the size of the stacked sheets. The sheet feeding unit 130 includes a cassette cover 43, and the surface side (side seen from the direction of arrow C in FIG. 4) is exposed to the outside and constitutes a part of the exterior surface of the color printer 1.

  A drive shaft 36, a push-up member 32, and a drive connecting member (not shown) are provided as a lifting mechanism 30 (FIG. 13) that lifts and lowers the lift plate 31 below the downstream portion of the lift plate 31 in the sheet feeding direction. Further, a receiving member (not shown) corresponding to the drive connecting member and a forward / reversely movable lift motor M (FIG. 13) connected to the receiving member are provided on the sheet feeding unit main body 130B side. In a state where the paper feed cassette 130A is housed in the paper feed unit main body 130B, the drive connecting member of the sheet storage unit 35 on the paper feed cassette 130A side is engaged with and connected to the receiving member on the paper feed unit main body 130B side. Thereby, the power of the lift motor M can be transmitted to the drive shaft 36. The drive shaft 36, the push-up member 32, the drive connecting member, the receiving member, and the lift motor M constitute an elevating mechanism that displaces the lift plate 31 between the paper feed position and the retracted position. The sheet feeding position is a position where the lift plate 31 is lifted and the upper surface of the sheet bundle S placed on the lift plate 31 comes into contact with the pickup roller 40 and can feed paper. The retracted position is a position where the lift plate 31 is lowered to the lowest position.

  The type of sheet P to be fed can be selected by the sheet setting unit 39. The sheet setting unit 39 can be provided on an operation panel (not shown) of the paper feeding unit 130 or the printer main body 200.

  In addition, as the lift motor M which comprises the raising / lowering mechanism 30 which raises / lowers the lift board 31, a stepping motor, a DC motor, etc. can be used, for example.

  Further, as shown in FIG. 3, the paper feed unit 130 includes a paper feed roller 41 provided on the downstream side in the transport direction of the pickup roller 40, and a separating roller 42 provided below the paper feed roller 41. Yes. Further, a transport roller 37 is provided on the downstream side in the transport direction of the pickup roller 40 and the paper feed roller 41. The paper feed roller 41 is provided along with the pickup roller 40 on the paper feed unit main body 130B side, while the separating roller 42 and the transport roller 37 are provided on the paper feed cassette 130A side. In a state where the paper feed cassette 130A is mounted on the paper feed unit main body 130B, the paper feed roller 41 and the separating roller 42 come into contact with each other.

  The paper feed roller 41 feeds the sheet P taken out by the pickup roller 40 to the transport roller 37. The paper feed roller 41 rotates in a direction in which the sheet P can be conveyed downstream, whereas the separating roller 42 rotates in a direction in which the sheet P is sent back upstream. Even if the sheets P picked up by the conveyance pickup roller 40 are overlapped, the separation roller 42 can prevent the sheet P other than the uppermost sheet P from being fed in the direction of the conveyance roller 37. Only the sheet feed roller 41 is transported to the transport roller 37. The transport roller 37 transports the sheet P to the paper feed transport path 133 (see FIG. 2). A conveyance switch 49 that detects the leading edge of the sheet P is provided adjacent to the conveyance roller 37 on the downstream side in the sheet feeding direction of the conveyance roller 37.

  Further, as shown in FIGS. 5A and 5B, the sheet feeding unit 130 detects that the uppermost sheet P of the sheet bundle S placed on the lift plate 31 is at the sheet feeding position. A position detection sensor PS is provided. The position detection sensor PS includes a light shielding member PSA and an optical sensor PSB. The optical sensor PSB includes a light emitting element fixedly provided near the pickup roller 40 and a light receiving element that receives light emitted from the light emitting element. On the other hand, the light shielding member PSA is provided on the support member 50 of the pickup roller 40. Further, the support member 50 is provided so as to be rotatable about the rotation axis of the paper feed roller 41. As a result, when the upper surface of the sheet bundle S placed on the lift plate 31 moves to the sheet feeding position shown in FIG. 5B by the lift of the lift plate 31, the pickup roller 40 pushes up to the uppermost sheet P. Then, it rotates around the rotation axis of the paper feed roller 41 and is displaced slightly upward. At this time, the light shielding member PSA is lifted upward in conjunction with the pickup roller 40 to shield the optical path of the optical sensor PSB and to detect that the upper surface of the sheet bundle S is at the paper feeding position.

  In the sheet feeding unit 130 having the above-described configuration, the lift member 32 pushes up the downstream end side of the lift plate 31 while being engaged with the bottom surface of the lift plate 31 by the operation of the lift motor M. As a result, the upper surface of the sheet bundle S stacked on the lift plate 31 is displaced to the paper feed position where it abuts on the pickup roller 40 provided above the paper feed cassette 130A.

  At this time, as shown in FIG. 5B, when the position detection sensor PS detects the displacement of the pickup roller 40 to the paper feed position, the drive of the lift motor M is stopped. When the position detection sensor PS is not detected due to the decrease of the sheet P during sheet feeding, the lift motor M is operated to lift the sheet bundle S to the sheet feeding position.

  In this embodiment, the detected portion (light shielding member) PSA is provided on the support member 50 of the pickup roller 40, but the present invention is not limited to this. For example, the upper surface of the sheet bundle S near the pickup roller 40 may be directly detected, or a detection mechanism other than the optical sensor may be used.

  As shown in FIGS. 2, 3, and 6 to 9, the sheet feeding unit 130 according to the present embodiment includes a lateral warm air mechanism (first warm air mechanism) 150 as a sheet blowing mechanism by blowing warm air. Yes.

  FIG. 6 is an explanatory diagram illustrating the configuration of the sheet feeding device according to the present embodiment. FIG. 7 is a horizontal cross-sectional view showing a main part of the horizontal warm air mechanism mounted on the paper feeding device according to the present embodiment. FIG. 8 is an explanatory diagram showing the hot air blowing direction of the horizontal hot air mechanism according to the present embodiment. FIG. 9 is an explanatory diagram for explaining a hot air blowing state of the horizontal hot air mechanism according to the present embodiment.

  The horizontal warm air mechanism 150 is provided on the paper feed unit main body 130B side. As shown in FIG. 6, a top plate 56 is formed on the upper surface of the sheet feeding unit main body 130 </ b> B where the side warm air mechanism 150 and the later-described upper warm air mechanism (second warm air mechanism) 140 are not formed. The sheet storage space is closed with the top plate 56.

  As shown in FIG. 6, the horizontal hot air mechanism 150 is provided along one side surface of the paper feeding cassette 130 </ b> A in the paper feeding direction. Further, as shown in FIG. 7, the lateral warm air mechanism 150 includes a first fan (air blowing unit) 151 and a first heater (heating unit) 152 provided in the lateral warm air chamber 153.

  As shown in FIG. 7, the horizontal hot air mechanism 150 is configured to suck in air in the paper feed unit 130 from a first suction port (air blowing unit) 154 provided in the paper feed unit 130. When the air in the side warm air chamber (air blowing unit) 153 moves to the first heater 152 side by the rotation of the first fan 151, the air in the sheet feeding unit 130 enters the side warm air chamber 153 from the first suction port 154. Is captured. The air that has moved to the first heater 152 side is heated by the first heater 152, and is blown out from the first hot air outlet (air blowing unit) 155 toward the side surface of the sheet bundle S.

  Here, as shown in FIG. 5, the first hot air outlet 155 of the horizontal hot air mechanism 150 that blows the hot air to the side surface of the sheet bundle S at the sheet feeding position is connected to the pickup roller 40 in a vertical section in the sheet conveying direction. Oriented at a point N where the upper surface of the sheet bundle S abuts. As a result, the hot air can be concentrated on the side surface of the sheet bundle S that is exactly taken out by the pickup roller 40, and the hot air can be efficiently blown between the sheets of the portion. Therefore, even if the horizontal hot air mechanism 150 is not large, the sheet bundle S can be efficiently spread prior to paper feeding.

  Further, as shown in FIG. 8, the first hot air outlet 155 sends the warm air straight (in parallel) in the width direction of the sheet bundle S (the direction of arrow C in FIG. 8, which is a direction orthogonal to the sheet feeding direction). Instead of blowing out, as shown by an arrow B in FIG. 8, the hot air is blown out at an angle to the sheet center direction side with respect to the width direction of the sheet bundle S. The reason is as follows.

  When hot air is blown out in the direction of arrow C in FIG. 8, as shown in FIG. 9B, the hot air escapes from the side surface of the sheet bundle S to the downstream side in the sheet feeding direction. It is difficult to reach the back of S, and the efficiency of blowing by the side warm air is low. Therefore, the horizontal hot air mechanism 150 according to the present embodiment forms a first hot air outlet 155 that blows the hot air toward the center side of the sheet bundle S to be fed, as indicated by an arrow B in FIG. ing. As a result, the hot air blown from the first hot air outlet 155 can be confined between the sheets of the sheet bundle S as shown in FIG. That is, when the hot air is blown toward the center side of the sheet bundle S, the upstream and downstream sides in the sheet feeding direction hang down with the weight of the sheet P and the lid is closed, and the hot air escapes to the outside. A wide range of hot air can be blown into the back of the sheet without any problems. As a result, the sheet bundle S can be efficiently spread prior to feeding even with the same amount of hot air.

  As shown in FIGS. 2, 3, 6, and 10, the sheet feeding unit 130 according to the present embodiment includes an upper warm air mechanism 140 as a sheet blowing mechanism by blowing hot air in addition to the lateral warm air mechanism 150. I have.

  FIG. 10 is a vertical cross-sectional view illustrating a configuration of a main part of the upper warm air mechanism mounted on the paper feeding device according to the present embodiment.

  The upper warm air mechanism 140 is provided on the side of the paper feed unit main body 130 </ b> B, similarly to the above-described horizontal warm air mechanism 150. As shown in FIG. 10, the upper warm air mechanism 140 takes in air from the second suction port (air blowing unit) 144 and is provided above the upper surface of the sheet bundle S stored in the sheet storage unit 35. The hot air is blown out from the hot air outlet (air blowing unit) 145 toward the upper surface of the sheet bundle S.

  Further, the upper warm air mechanism 140 includes a second fan (air blowing unit) 141 and a second heater (heating unit) 142 in the upper warm air chamber (air blowing unit) 143. The second suction port 144 is provided above the second fan 141 on the upper surface of the upper warm air chamber 143. That is, the air in the upper warm air chamber 143 moves to the second heater 142 side by the rotation of the second fan 141, and outside air is taken into the upper warm air chamber 143 from the second suction port 144. The air that has moved to the second heater 142 side is heated by the second heater 142 and is blown out from the second hot air outlet 145 provided on the lower surface of the upper hot air chamber 143 toward the upper surface of the sheet bundle S. It has become. The second warm air outlet 145 is formed on the downstream side in the sheet feeding direction in the upper warm air mechanism 140 in a state where the upper warm air mechanism 140 is mounted on the sheet feeding unit 130.

  In the above configuration, when a predetermined paper feeding unit 130 is selected for image formation, the lift plate 31 is driven to rise, the sheet bundle S is raised toward the pickup roller 40, and the upper warm air mechanism 140 is driven. Then, warm air is blown toward the upper surface of the sheet bundle S from the second warm air outlet 145.

  Here, among the sheet bundle S, the upper surface and the outer peripheral portion of the sheet bundle S are in contact with the outside air, so that it is likely to contain a lot of moisture. That is, while the upper surface and side surface of the sheet bundle S swell due to moisture absorption, the degree of swelling is relatively low because the inside of the sheet bundle S has less moisture than the upper surface and side surface. As a result, the inside of the sheet bundle S (the space between the sheets) becomes a negative pressure, causing a phenomenon that the sheets are in close contact with each other.

  However, the sheet feeding unit 130 according to the present embodiment includes the upper warm air mechanism 140, so that the relative humidity of the sheet bundle S in the sheet feeding unit 130 (the upper surface and the outer peripheral portion of the sheet bundle S and the other portions). (Relative humidity) is instantaneously reduced.

  That is, the upper hot air mechanism 140 can concentrate the hot air from the upper surface of the sheet bundle S having particularly high adhesion to the outer periphery and feed the hot air uniformly. Accordingly, the relative humidity of the sheet bundle S (the upper surface and the outer peripheral portion of the sheet bundle S and other portions is reduced by quickly reducing the moisture absorption of the upper surface and the outer peripheral portion of the sheet bundle S and eliminating the swelling state of the portion. ) Can be reduced instantaneously, and the negative pressure inside the sheet bundle S (space between sheets) can be eliminated. As a result, the adhesion between the sheets can be reduced, and the sheet bundle S can be efficiently spread prior to feeding.

  Further, as shown in FIG. 3, the upper warm air mechanism 140 according to the present embodiment is provided upstream of the pickup roller 40 in the paper feeding direction and behind the paper feeding direction in the paper feeding unit 130. . Here, since the second warm air outlet 145 is provided on the downstream side in the sheet feeding direction in the upper warm air mechanism 140 as described above, it faces the upper surface of the sheet bundle S accommodated in the sheet accommodating portion 35. It can spray favorably from the 2nd warm air blower outlet 145. In this way, by installing the upper hot air mechanism 140 having high sheet-spreading efficiency by making effective use of the empty space in the paper feed unit 130, the sheet-rolling mechanism by hot air assist that can be applied to a small paper feeder. Can be realized.

  That is, the configuration in which the sheet bundle S placed on the lift plate 31 is raised and lowered by the cantilever raising / lowering mechanism as in the paper feeding unit (paper feeding device) 130 according to the present embodiment is used for a relatively small paper feeding device. However, when the cantilever raising / lowering mechanism is used, the sheet bundle S is lifted on the downstream side in the sheet feeding direction where the pickup roller 40 is provided, and sheet conveyance mechanisms such as the pickup roller 40 and the sheet feeding roller 41 are provided. However, since the sheet bundle S is not lifted on the upstream side in the sheet feeding direction, there is a relatively large space. If the upper warm air mechanism 140 is incorporated into the space with sufficient margin as in the present embodiment, it is not necessary to increase the outer shape of the paper feeding unit 130 in order to install the upper warm air mechanism 140. It is also suitable for a paper device.

  Next, with reference to FIG. 11 and FIG. 12, a sheet rolling effect in a configuration in which an upper warm air mechanism 140 is provided in addition to the lateral warm air mechanism 150 as a warming air assist sheet rolling mechanism will be described.

  FIG. 11 is a perspective view of the paper feed cassette for explaining the direction in which the lateral warm air and the upper warm air are blown in the paper feeder according to the present embodiment. FIG. 12 is an explanatory diagram showing the direction in which the lateral warm air and the upper warm air are blown in the paper feeder according to the present embodiment.

  As described above, the sheet feeding unit 130 according to the present embodiment blows warm air toward the upper surface of the sheet bundle S by the upper warm air mechanism 140 as shown in FIG. Therefore, warm air is blown toward the side surface of the sheet bundle S that is exactly taken out by the pickup roller 40. As a result, the sheet bundle S can be spread more efficiently prior to paper feeding than in a configuration including only the horizontal warm air mechanism 150.

  In the above configuration, when a predetermined paper feeding unit 130 is selected for image formation, the lift plate 31 is driven to rise, the sheet bundle S is raised toward the pickup roller 40, and the upper warm air mechanism 140 is driven. Then, warm air is blown toward the upper surface of the sheet bundle S from the second warm air outlet 145. Further, when the remaining sheet amount detection unit 211 detects that the upper surface of the sheet bundle S is in contact with the pickup roller 40 and the sheet bundle S has been raised to the sheet feeding position, the lateral warm air mechanism 150 is driven and the first warm air blowing is performed. Also from the outlet 155, warm air is blown toward the side surface of the sheet bundle S that is exactly located at the position taken out by the pickup roller 40.

  12 (a) to 12 (c) schematically show how the sheet bundle S can be efficiently spread by the upper warm air mechanism 140 and the lateral warm air mechanism 150. FIG.

  Initially, the upper surface and side surfaces of the sheet bundle S swell due to moisture absorption, and the inside of the sheet bundle S (the space between the sheets) becomes negative pressure, and the sheets are in close contact with each other, as shown in FIG. In addition, by the double warm air blowing by the upper warm air mechanism 140 and the lateral warm air mechanism 150, the state immediately shifts to the state shown in FIG.

  That is, the upper hot air mechanism 140 can concentrate the hot air from the upper surface of the sheet bundle S having particularly high adhesion to the outer periphery and feed the hot air uniformly. Thereby, the moisture absorption of the upper surface and outer peripheral part of the sheet bundle S is quickly reduced, and the swelling state of the part is eliminated. In particular, the upper surface of the sheet bundle S that receives the warm air directly from the upper warm air mechanism 140, and the side surface of the sheet bundle S that receives the warm air simultaneously from the upper warm air mechanism 140 and the lateral warm air mechanism 150 on the side of the lateral warm air mechanism 150. , The swelling state is eliminated first, and the state shown in FIG. 12B is obtained. Further, the state immediately shifts to the state shown in FIG. 12C (the state where the sheet bundle S is rolled).

  That is, by the warm air blowing of the upper warm air mechanism 140 and the lateral warm air mechanism 150, the swollen state of the side surface of the sheet bundle S on the opposite side to the lateral warm air mechanism 150 is instantly eliminated. The hot air passes between the sheets and goes out of the sheet bundle S, and the sheet bundle S is spread.

  In addition, in this embodiment, although the horizontal ventilation part and the heating part, and the upper ventilation part and the upper heating part were each demonstrated to the structure respectively provided in the side warm air mechanism 150 and the upper warm air mechanism 140, respectively. These members are not necessarily provided integrally. For example, one of the air blowing unit and the heating unit is provided on the paper feed cassette 130A side, and the other is provided on the paper feed unit main body 130B side. May be.

  Next, with reference to FIG. 13 to FIG. 17, control processing of the sheet rolling operation by hot air blowing according to the present embodiment will be described.

  FIG. 13 is a functional block diagram of a control unit that controls a warm air blowing operation with a separating operation according to an embodiment of the present invention. FIG. 14 is a flowchart showing a control process by the control unit shown in FIG. 15 to 17 are longitudinal sectional views of main parts of the sheet feeding unit according to the present embodiment. FIG. 15 illustrates a sheet bundle being rolled by blowing hot air at the sheet feeding position, and FIG. FIG. 17 shows a state in which several sheets of the upper layer having high adhesion between the sheets in the sheet bundle are lifted up while being in close contact with each other. FIG. 18 is a time chart for explaining the control process of the hot air blowing operation accompanied by the separation operation during the paper feed preparation period according to the embodiment of the present invention.

  In the present embodiment, as shown in FIGS. 15 to 18, after the hot air blowing control accompanied by the separation operation during the paper feeding preparation period is performed, the continuous paper feeding is performed.

  As shown in the functional block diagram of FIG. 13, the paper feed unit 130 according to this embodiment displaces the lift plate 31 between the paper feed position and the separation position during the hot air blowing operation during the paper feed preparation period. A control unit 300 is provided to perform control so that the separation operation is repeated.

  Here, the sheet feeding position is a position where the upper surface of the sheet bundle S placed on the lift plate 31 comes into contact with the pickup roller 40, and the separation position is the separation surface where the upper surface of the sheet bundle S is separated from the pickup roller 40. The upper layer sheet Q (FIG. 17) having high adhesion between the sheets in the sheet bundle is lowered so as to be positioned within the range of the first hot air outlet 155.

  In the present embodiment, the descending amount is changed according to the type of the sheet P selected as the sheet feeding target. Thereby, for example, when a sheet P of a type having a high basis weight (weight per unit area) that is difficult to float is selected, the amount of lowering is set to be small. Can be lowered to a proper separation position.

  For this reason, hot air can be blown into the sheet bundle S more efficiently than when the separation position is constant regardless of the type of sheet P to be fed. As shown in FIG. 15, the sheet P can be made sufficiently bright from the uppermost sheet P of the sheet bundle. As a result, the sheet can be fed from the first uppermost sheet P to the predetermined conveyance path without a problem of double feeding without causing a decrease in the sheet feeding speed.

  As described above, the type of the sheet P to be fed can be selected, for example, by the sheet setting unit 39 provided on the sheet feeding unit 130 or the operation panel (not shown) of the printer main body 200. The present embodiment is not limited to this, and may be configured to detect the type of sheet P to be fed directly using, for example, a reflective sensor (not shown).

  The types of sheets P to be fed can be classified based on the basis weight (weight per unit area) Dp of the sheet P as shown in the following table, for example.

  In the example shown in Table 1, the coated paper as the sheet P to be fed is classified into two in descending order of thickness from top to bottom depending on the thickness.

  The specification of the type of the sheet P to be fed in the present embodiment is not limited to the case of specifying the type of the sheet P such as plain paper, coated paper, film sheet, tracing paper, etc. Among the same type of sheets (for example, coated paper), the case where the type of the sheet P is specified based on the difference in thickness (basis weight) is also included.

  As described above, the descending amount is changed according to the type of the sheet P selected as the sheet feeding target, and the separation operation between the sheet feeding position and the separation position is performed as shown in FIGS. By performing it during the preparation period, even if the amount of warm air is small, it becomes easy to efficiently blow warm air between the sheets up to a position away from the first warm air outlet 155. As a result, it is possible to realize the lateral warm air mechanism 150 that has higher sheet rolling efficiency than the conventional large lateral warm air assist, and thus it is possible to reduce the size of the entire sheet feeding device.

  As shown in FIG. 13, the control unit 300 includes an information input / output unit 85, a hot air control unit 90, an elevating mechanism control unit 80, and a storage unit 84.

  The information input / output unit 85 includes a sheet type signal from the sheet setting unit 39, a position detection signal from the position detection sensor PS, a first time-up signal from the first timer 86, a second time-up signal from the second timer 87, and a printer body. A hot air request signal, a paper feed command signal, and the like are input from the CPU 210 on the 200 side.

  The warm air control unit 90 controls the driving of the lateral warm air mechanism 150 and the upper warm air mechanism 140 based on the paper feed command signal and the warm air request signal. That is, based on these input signals, the warm air control unit 90 sends control signals for driving the lateral warm air mechanism 150 and the upper warm air mechanism 140 via the information input / output unit 85. It outputs to 150 drive motors (not shown).

  The elevating mechanism control unit 80 includes a descending drive determining unit 82 and an ascending drive determining unit 83, and is based on the first time-up signal from the first timer 86 and the second time-up signal from the second timer 87. The lifting / lowering drive of 30 is controlled, and the lift plate 31 is controlled so as to repeat the separating operation that is displaced between the paper feeding position and the separating position.

  The descending drive determination unit 82 outputs a control signal for driving the descending member 32 to descend based on the sheet type signal and the first time-up signal to the lift motor M via the information input / output unit 85.

  Based on the paper feed command signal and the second time-up signal, the ascending drive determination unit 83 sends a control signal for raising the lift plate 31 via the push-up member 32 to the lift motor M via the information input / output unit 85. Output.

  In the storage unit 84, for example, the first type-up value of the first timer 86, the second time-up value of the second timer 87 corresponding to the type of sheet to be fed selected by the sheet setting unit 39, and each An operation program for the control unit and the like are stored. In addition, the storage unit 84 is provided with a storage area for temporarily storing determination results and other information.

  The control unit 300 can be configured by, for example, a CPU, a memory (such as a ROM and a RAM), an input interface, and an output interface.

  Next, based on the flowchart of FIG. 14, a control process during paper feed preparation by the control unit 300 according to the present embodiment will be described.

  First, when the paper feed cassette 130 is attached to the color printer 1 (S1), the ascending drive determination unit 83 of the elevating mechanism control unit 80 controls a control signal for driving the lift plate 31 up via the push-up member 32. The signal is output to the lift motor M via the signal output unit 85. Thereby, the lift drive of the lift plate 31 is started (S2). Then, the lift drive determination unit 83 of the lift mechanism control unit 80 outputs a control signal for driving the lift plate 31 to lift up via the push-up member 32 to the lift motor M via the control signal output unit 85.

  When it is determined that the lift plate 31 has been raised to the paper feed position based on the position detection signal from the position detection sensor PS (FIG. 5) (S3), the ascending drive determination unit 83 stops the operation of the lift motor M. As a result, the lift drive of the lift plate 31 is stopped (S4). At this paper feed position, a standby state is entered until a paper feed command is issued. When a paper feed command signal and a sheet type signal are input via the information input unit 85, a paper feed preparation period is started (S5). At the same time, the warm air control signal unit 90 is based on the paper feed command signal and the warm air request signal, and the warm air control unit 90 includes the first fan 151 and the first heater 152 of the lateral warm air mechanism 150, and the upper warm air. Control signals for driving these heaters and fans are output to the second fan 141 and the second heater 142 of the mechanism 140 via the information input / output unit 85 (S6).

  Next, the descending drive determination unit 82 starts the descending drive of the lift plate 31 and sets the descending drive time corresponding to the selected sheet type to the first based on the sheet type signal from the sheet setting unit 39. The first timer 86 is started by reading from the storage unit 84 as a predetermined time (S7). Then, the descent drive determination unit 82 continues the descent drive of the lift plate 31 during the first predetermined time.

  The counting of the descent driving time may start at the timing of the descent driving as in the above example, or the position detection sensor 39 is turned off as indicated by T3 in the time chart of FIG. May be started at a timing (a timing at which the upper surface of the sheet bundle S moves away from the pickup roller 40 after a predetermined time (T2 in FIG. 18) from the start of the descent driving).

  That is, the descent drive determination unit 82 determines whether or not a preset first predetermined time has elapsed based on the first time-up signal from the first timer 86 (S8). If it is determined that the first predetermined time has elapsed based on the first time-up signal (YES in S8), the descent drive determination unit 82 stops the operation of the lift motor M and stops the descent drive of the lift plate 31 ( S9).

  Here, after the start of the descent drive of the lift plate 31, if the descent drive continues even after the predetermined limit time has elapsed, the control unit 300 forcibly stops the descent drive of the lift plate 31. In addition, it is desirable that the lifting mechanism 30 be controlled.

  Usually, after starting the lowering drive of the lift plate 31 by the elevating mechanism 30, the upper surface of the sheet bundle S is separated from the pickup roller 40 after a predetermined time, and the position detection unit PS is in a non-detection state. However, due to the occurrence of a jam or the like, for example, a plurality of sheets P including the sheet P to be fed are sandwiched between the sheet feeding roller 41 and the separating roller 42 provided below the sheet feeding roller 41, and the sheet bundle S When the upper surface of the sheet bundle falls into a state where it does not move away from the pickup roller 40, the position detection unit PS continues to detect that the upper surface of the sheet bundle S is at the sheet feeding position. In this case, the first timer 86 that counts the descent drive time does not operate, and the descent driving of the lift plate 31 by the elevating mechanism 30 continues, and the sheet feeding unit 130 is damaged in this state.

  Therefore, after the start of the descent drive of the lift plate 31 by the elevating mechanism 30, if the descent drive is continued even after a predetermined limit time has elapsed, the descent drive of the lift plate 31 is forced by the control unit 300. If the control is performed so that the lift plate 31 is stopped, it is possible to prevent a problem of damage to the sheet feeding unit 130 due to the lift plate 31 continuing to descend even after a predetermined limit time has elapsed.

  The predetermined limit time may be set shorter than the time required from the start of the lowering drive until the lift plate 31 reaches the lowest position (retracted position).

  Next, the ascending drive determination unit 83 determines whether or not a preset second predetermined time (decrease holding time: T4 in FIG. 18) has elapsed based on the second time-up signal from the second timer 87. (S10). The second timer 87 keeps counting until the second predetermined time elapses, and the lift plate 31 is held at the separated position. On the other hand, when it is determined that the second predetermined time has elapsed based on the second time-up signal (YES in S10), the ascending drive determining unit 83 is a control signal for driving the lift plate 31 to rise through the push-up member 32. Is output to the lift motor M via the information input / output unit 85. As a result, the lift motor M is actuated, and the ascending drive of the push-up member 32 is started (S11).

  Next, when it is detected based on the position detection signal from the position detection sensor PS that the lift-up member 32 has lifted the lift plate 31 to the paper feed position, the lift drive determination unit 83 stops the lift motor M. (Sliding drive stop) (S12).

  If the predetermined number of separation operations have not been completed (NO in S13), the lift plate 31 is moved up and down between the paper feed position (FIG. 15) and the separation position (FIGS. 16 and 17). The operation (S7 to S12) is repeated. When the predetermined number of separation operations are completed (YES in S13), the paper feeding operation is started (S14).

  As described above, the sheet feeding unit 130 according to the present embodiment is provided in the sheet storage unit 35 that stores the sheet bundle S composed of a plurality of sheets P and the sheet storage unit 35 and stacks the sheet bundle S. A pickup plate 40 that contacts the lift plate 31 and the upper surface of the sheet bundle S and feeds the uppermost sheet P of the sheet bundle S, and a sheet feeding position and the sheet bundle S where the upper surface of the sheet bundle S contacts the pickup roller 40. The lift mechanism 30 that displaces the lift plate 31 between the upper surface of the pickup roller 40 and a separation position separated from the pickup roller 40 by a certain distance, and the sheet bundle S stored in the sheet storage unit 35 at least during the paper feed preparation period. The horizontal warm air mechanism 150 that blows warm air on the side parallel to the paper feeding direction, the sheet setting unit 39 that selects the type of the sheet P to be fed, and the feeding operation of the first sheet P are started. The raising / lowering drive of the elevating mechanism 30 is controlled so that the lift plate 31 is displaced between the paper feeding position and the separation position during the warm air blowing operation by the horizontal hot air mechanism 150 during the paper feeding preparation period before the paper feeding. And a controller 300, and the amount of lowering of the lift plate 31 is changed according to the type of the sheet P selected by the lift plate 31.

  Here, even among the sheet bundle S placed on the lift plate 31, the upper surface and the outer peripheral portion of the sheet bundle S are in contact with the outside air, so that they easily contain a lot of moisture and swell due to moisture absorption. On the other hand, since the inside of the sheet bundle S has less moisture than the top and side surfaces, the degree of swelling is relatively low. For this reason, the inner side of the sheet bundle S (the space between the sheets) has a negative pressure, and in particular, the upper layer Q (FIG. 17) of the sheet bundle S has high adhesion between the sheets and is difficult to roll.

  Thus, in the sheet bundle S, the upper layer Q has higher adhesion between the sheets than the middle and lower layers. For this reason, even if warm air is blown from the first warm air outlet 155 of the lateral warm air mechanism 150 to the side surface parallel to the sheet feeding direction of the sheet bundle S, the warm air has a relatively low adhesion between the sheets. The hot air may enter only between the sheets of the layers, and the upper layer Q having high adhesion may be lifted by the hot air while being in close contact. For this reason, it is particularly difficult to prevent double feeding of the upper layer Q of the sheet bundle S immediately after the start of sheet feeding, and special measures are required.

  Therefore, according to the above configuration, the lift plate 31 is moved to the sheet feeding position during the warm air blowing operation by the horizontal warm air mechanism 150 during the sheet feeding preparation period before the sheet feeding operation of the first sheet P is started. Ascending / descending drive of the elevating mechanism 30 is controlled so as to be displaced between the position and the separated position. Thus, if the separating operation of the lift plate 31 is performed during the warm air blowing operation by the lateral warm air mechanism 150 during the sheet feeding preparation period, the sheet feeding speed (productivity) associated with the separating operation is reduced. Absent.

  Furthermore, by adopting a configuration in which the descending amount is changed in accordance with the type of the sheet P selected as a sheet feeding target, for example, a sheet P of a type having a high basis weight (weight per unit area) and difficult to float is selected. If it has been done, it can be lowered to an optimum separation position according to the type of the sheet P to be fed, such as setting a lowering amount to be small. Therefore, hot air can be blown into the sheet bundle S more efficiently than when the separation position is constant regardless of the type of the sheet P to be fed. The sheet S can be made sufficiently bright from the uppermost sheet P of the bundle S. As a result, the sheet P can be fed from the first sheet P to a predetermined conveyance path without a problem of double feeding without causing a decrease in the sheet feeding speed.

  As described above, the lowering amount is changed according to the type of the sheet P selected as the sheet feeding target, and the separation operation between the sheet feeding position and the separation position is performed during the sheet feeding preparation period, thereby reducing the temperature. Even with the air volume, it becomes easy to efficiently blow up to a place away from the hot air outlet 155. This makes it possible to realize a hot air assist mechanism that has higher sheet rolling efficiency than a conventional large-sized side warm air assist, and thus the entire sheet feeding device can be downsized.

  In addition, the control part 300 which concerns on this embodiment is controlling the descending amount of the lift board 31 using the timer. However, the present invention is not limited to this, and a stepping motor (not shown) that rotates the drive shaft 36 in the forward and reverse directions may be employed, and the descending amount may be controlled by the number of drive steps.

  In this case, the number of driving steps of the stepping motor required for driving the lift plate 31 downward through the push-up member 32 and displacing the lift plate 31 from the paper feed position to the separation position is determined by the type of the sheet P to be fed. In addition, a plurality of values corresponding to the size, the printing speed, and the like are stored in the storage unit 84, and the descending drive determination unit 82 is appropriately read from the storage unit 84 according to the selected condition. Can do.

  Then, based on the detection result of the first position detection sensor PS1, the control unit 300 reads the number of descending drive steps of the stepping motor corresponding to the type of the sheet P from the storage unit 84, and the number of descending drive steps is What is necessary is just to set it as the structure which controls the downward drive of the lift board 31 so that a stepping motor may be rotated.

  The sheet feeding device of the present invention can be applied to all image forming apparatuses such as a printer, a copier, a facsimile, or a complex machine having these functions combined, and is particularly suitable for a small-sized image forming apparatus. It can be used suitably.

1 is a perspective view illustrating an appearance of a printer including a paper feeding device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating an internal configuration of the printer illustrated in FIG. 1. It is sectional drawing which shows the structure of the paper feeding apparatus which concerns on one Embodiment of this invention. FIG. 4 is a perspective view illustrating a state in which a sheet feeding cassette in the sheet feeding device illustrated in FIG. 3 is pulled out from a sheet feeding device body. It is explanatory drawing which shows the position detection sensor mounted in the paper feeder shown in FIG. It is explanatory drawing explaining the structure of the paper feeder which concerns on one Embodiment of this invention. It is sectional drawing of the horizontal direction which shows the principal part of the side warm air mechanism mounted in the paper feeder shown in FIG. It is explanatory drawing which shows the warm air blowing direction of the horizontal warm air mechanism in the paper feeder shown in FIG. It is explanatory drawing for demonstrating the warm air blowing state of the side warm air mechanism in the paper feeder shown in FIG. FIG. 4 is a vertical cross-sectional view illustrating a main part configuration of an upper warm air mechanism mounted on the sheet feeding device illustrated in FIG. 3. FIG. 7 is a perspective view of a paper feed cassette for explaining a direction in which the lateral warm air and the upper warm air are blown in the paper feeder shown in FIG. 6. It is explanatory drawing which shows the blowing direction of side warm air and top warm air in the paper feeder shown in FIG. It is a functional block diagram of the control part which controls the warm air blowing operation | movement accompanying the separation operation | movement which concerns on one Embodiment of this invention. It is a flowchart which shows the control processing of the warm air blowing operation | movement accompanied by the separation operation | movement which concerns on one Embodiment of this invention. It is a principal part longitudinal cross-sectional view of the paper feed unit concerning one Embodiment of this invention. It is a principal part longitudinal cross-sectional view of the paper feed unit which concerns on one Embodiment of this invention. It is a principal part longitudinal cross-sectional view of the paper feed unit which concerns on one Embodiment of this invention. It is a time chart explaining the control process of the warm air blowing operation | movement accompanying the separation operation | movement during the paper feed preparation period which concerns on one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Color printer (image forming apparatus), 30 ... Elevating mechanism, 31 ... Lift plate (sheet stacking plate), 32 ... Push-up member (elevating mechanism), 35 ... Sheet storage unit, 36 ... Drive shaft (Lifting mechanism), 37... Transport roller, 38... Support section, 39... Sheet selection section (sheet specifying section), 40... Pickup roller, 41. ... Elevating mechanism control unit, 82... Descending drive determining unit, 83... Ascending drive determining unit, 84... Storage unit, 85. 90... Hot air control unit, 100... Sheet supply unit, 130... Paper feeding unit (paper feeding device), 130 A. 140 …… Upper hot air mechanism (second hot air mechanism) 141 …… Second fan (blower), 142 …… Second heater (heater), 143 …… Upper hot air chamber (blower), 144 …… Second suction port (blower), 145 …… First 2 hot air outlet (blower), 150 .. side hot air mechanism (first hot air mechanism), 151... First fan (air blower), 152... First heater (heater), 153. Hot air chamber (air blowing unit), 154... First suction port (air blowing unit), 155... First hot air outlet (air blowing unit), 200... Printer body, 300... Control unit (control means), PS ... Position detection sensor (position detection unit), P ... Sheet, S ... Sheet bundle, M ... Lift motor (lifting mechanism)

Claims (7)

A sheet storage portion for storing a sheet bundle composed of a plurality of sheet-like recording media;
A sheet placing plate that is provided in the sheet storage unit and stacks the sheet bundle;
A pickup roller that contacts the upper surface of the sheet bundle and feeds the uppermost sheet-like recording medium of the sheet bundle;
An elevating mechanism for displacing the sheet placing plate between a paper feeding position where the upper surface of the sheet bundle contacts the pickup roller and a spaced position where the upper surface of the sheet bundle is separated from the pickup roller by a certain distance;
A first hot air mechanism that blows hot air from a first hot air outlet on a side surface parallel to the paper feeding direction of the sheet bundle stored in the sheet storage portion at least during a paper feed preparation period;
A sheet specifying unit for specifying the type of sheet-like recording medium to be fed;
During the hot air blowing operation by the first hot air mechanism during the paper feeding preparation period before starting the paper feeding operation of the first sheet-like recording medium, the sheet placing plate is moved between the paper feeding position and the separation position. Control means for controlling the lifting drive of the lifting mechanism so as to be displaced between,
The sheet feeding device according to claim 1, wherein the control unit changes a descending amount of the sheet placing plate in accordance with a type of the sheet-like recording medium specified by the sheet specifying unit. A position detection unit that detects that the upper surface of the sheet bundle is at the sheet feeding position;
A storage unit for storing each descent driving time corresponding to a descent amount according to the type of each type of sheet-shaped recording medium specified by the sheet specifying unit;
A timer for measuring each descent driving time, and
The controller is
Read the descent drive time corresponding to the type of sheet specified by the sheet specifying unit from the storage unit,
After starting the lowering drive of the lifting mechanism, the sheet placing plate from when the position detecting unit no longer detects that the upper surface of the sheet bundle is at the sheet feeding position until counting the lowering driving time. The sheet feeding device according to claim 1, wherein the elevating mechanism is controlled so as to lower the position.   When the descending drive is in a continuous state even after a predetermined time has elapsed after the start of the descending drive, the control unit controls the lifting mechanism so as to stop the descending drive. The sheet feeding device according to claim 1 or 2. The elevating mechanism further includes a push-up member that pushes up the sheet placing plate,
The sheet placement plate is rotatably supported at the upstream end in the sheet feeding direction in the sheet storage unit,
The push-up member is configured such that one end of the push-up member is rotatably supported by a drive shaft, and the other end contacts the bottom surface of the sheet placement plate to push up the sheet placement plate. The sheet feeding device according to any one of claims 1 to 3.   A stepping motor in which the elevating mechanism rotates the drive shaft forward and backward, and a storage unit that stores a descent step number corresponding to a descent amount according to the weight of each type of sheet specified by the sheet specifying unit; The control unit reads out the number of descending steps corresponding to the type of sheet specified by the sheet identifying unit from the storage unit, and lowers the sheet placing plate by the number of descending steps. The sheet feeding device according to claim 1, wherein the lifting mechanism is controlled. And a second hot air mechanism capable of blowing warm air from a second hot air outlet provided above the upper surface of the sheet bundle stored in the sheet storage portion toward the upper surface of the sheet bundle. Including
6. The control unit according to claim 1, wherein the control unit performs control so as to blow warm air from the second warm air mechanism onto an upper surface of the sheet bundle at least during the sheet feeding preparation period. The paper feeder described in 1. A paper feeding device according to any one of claims 1 to 6,
An image forming apparatus comprising: an image forming apparatus main body that forms an image on a sheet-like recording medium fed from the paper feeding apparatus.

Images