JP2011046459A - Paper feeder and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper feeding cassette capable of always making the uppermost part of sheets loaded on the paper feeding cassette in contact with a pick-up roller (sheet feeding means) at a defined pressure in a constitution using a simple lift motor and the like, and an image forming device having the same. <P>SOLUTION: After a preset stop stand-by time has elapsed from when an arrival of the uppermost part of the sheets of the paper feeding cassette to a defined position is detected, energization to a lift motor is stopped. A stop stand-by time is set according to a loading amount of the sheets of the paper feeding cassette. Concretely, in order to stop the uppermost part of the sheets of the paper feeding cassette always at the same position, the larger loading amount of the sheets of the paper feeding cassette, the longer a stop stand-by time is set, and the smaller loading amount of the sheets of the paper feeding cassette, the shorter a stop stand-by time is set. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a paper feeding device in which a paper feeding cassette on which paper is stacked is detachably provided and an image forming apparatus provided with the same, and more particularly to lift control of paper loaded in the paper feeding cassette. is there.

An image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine of these is provided with a paper feed cassette on which paper can be loaded. When the paper in the paper feed cassette runs out, the paper feed cassette is pulled out from the image forming apparatus by the user, and after the paper is replenished, it is mounted on the image forming apparatus again.
In addition, the image forming apparatus includes a lift mechanism that raises the paper toward the pickup roller so that the uppermost part of the paper loaded in the paper feed cassette comes into contact with the pickup roller (see, for example, Patent Document 1). This lift mechanism raises a lift plate on which a sheet is placed by a driving force of a lift motor.
Specifically, in the image forming apparatus, when the paper feed cassette is mounted on the image forming apparatus, the lift motor is driven to raise the lift plate, and the top of the paper in the paper feed cassette has reached the predetermined position. By being detected, the lift motor stops and the lift plate stops. As a result, the pickup roller and the uppermost portion of the paper loaded on the paper feed cassette come into contact with each other, and the pickup roller can supply the paper from the uppermost portion of the paper.

JP 2006-306582 A

By the way, in order to simplify and reduce the configuration of the sheet feeding device and the image forming apparatus, it is desirable to use a simple motor such as a small DC brush motor as a lift motor for operating the lift mechanism. It is also desirable that the motor drive circuit for controlling the lift motor is a simple one that does not have a brake function.
However, when such a simple lift motor and motor drive circuit are used, the lift motor does not stop immediately even if the energization of the lift motor is stopped, and it rotates with inertia (inertia) for a short time. The lift plate will rise. At this time, the lift width of the lift plate after the energization of the lift motor is stopped varies depending on the sheet loading amount (load) of the sheet feeding cassette.
Therefore, if the timing of stopping energization of the lift motor is always the same, the contact pressure between the top of the paper and the pickup roller varies depending on the amount of paper loaded in the paper cassette, and the paper feeding performance by the pickup roller is kept constant. The problem arises that it cannot be maintained.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to use a simple lift motor or the like in a configuration in which the uppermost portion of the paper stacked on the paper feed cassette and the pickup roller (paper supply) It is an object of the present invention to provide a sheet feeding cassette and an image forming apparatus including the same.

In order to achieve the above object, the present invention comprises a paper feed cassette on which paper is stacked, a paper supply means for contacting the top of the paper stacked on the paper feed cassette and supplying the paper from the top, A lift mechanism that lifts the paper loaded in the paper cassette toward the paper supply means, a lift motor that operates the lift mechanism, and that the top of the paper in the paper cassette has reached a predetermined position. A paper feeding device comprising: a paper position detecting means for detecting; and a lift raising control means for stopping energization of the lift motor after elapse of a preset stop waiting time after detection by the paper position detecting means. And a stop standby time setting means for setting the stop standby time in accordance with the sheet stacking amount of the paper feed cassette. Configured as. The present invention may be understood as an image forming apparatus including the paper feeding device.
According to the present invention, even when a simple DC brush motor or the like is used for the lift motor, the stop waiting time is set according to the sheet stacking amount of the sheet feeding cassette, so that the sheet feeding is performed. Regardless of the amount of paper in the cassette, the uppermost part of the paper is stopped at a predetermined position, and the uppermost part of the paper and the paper supply means are always brought into contact with each other at a predetermined pressure. It can be kept constant. Also, the motor drive circuit for controlling the lift motor does not require a brake function or a speed control function, so that the configuration can be simplified.

Specifically, the increase amount due to the inertia after the energization of the lift motor is stopped is smaller as the sheet loading amount of the sheet feeding cassette is larger, and is increased as the sheet loading amount is smaller. Therefore, the stop standby time setting means sets the stop standby time longer as the amount of sheets loaded in the paper cassette increases, and sets the stop standby time shorter as the amount of sheets stacked in the paper cassette decreases. It is thought that it is. Thereby, it is possible to stop the uppermost part of the sheet at a certain position.
For example, the stop standby time setting means may respond to a time required until detection by the paper position detection means after the paper feed cassette is mounted on the paper feed device and the lift motor is driven. It is conceivable that the stop waiting time is set. That is, the required time can be used as an index indicating the amount of sheets loaded in the sheet feeding cassette. According to such a configuration, it is possible to omit a sensor for detecting the amount of paper loaded in the paper feed cassette, so that a simpler and lower cost configuration can be realized.
Further, in this case, the stop standby time setting means sets the stop standby time gradually shorter as time elapses from the start of driving the lift motor until detection by the paper position detection means. It is possible that there is. In such a configuration, since the stop waiting time is updated as needed before the detection by the paper position detection means, for example, the amount of paper loaded in the paper cassette is small, and the detection by the paper position detection means is performed. This is suitable when the lift motor is stopped immediately after.
More specifically, the stop standby time setting means has stop standby time correspondence information storage means in which stop standby time correspondence information indicating the relationship between the sheet stacking amount of the paper feed cassette and the stop standby time is stored. Thus, it is conceivable that the stop standby time is set in accordance with the amount of sheets loaded in the paper feed cassette and the stop standby time correspondence information stored in the stop standby time correspondence information storage means. .

  According to the present invention, even when a simple DC brush motor or the like is used for the lift motor, the stop waiting time is set according to the sheet stacking amount of the sheet feeding cassette, so that the sheet feeding is performed. Regardless of the amount of paper in the cassette, the uppermost part of the paper is stopped at a predetermined position, and the uppermost part of the paper and the paper supply means are always brought into contact with each other at a predetermined pressure. It can be kept constant. Also, the motor drive circuit for controlling the lift motor does not require a brake function or a speed control function, so that the configuration can be simplified.

1 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic cross-sectional view illustrating a schematic configuration of a sheet feeding device according to an embodiment of the present invention. The schematic diagram for demonstrating the ventilation aspect in the paper feeder which concerns on embodiment of this invention. FIG. 4 is a schematic diagram for explaining an example of a sheet position detecting unit in the sheet feeding device according to the embodiment of the present invention. 6 is a flowchart for explaining an example of a procedure of lift control processing executed in the image forming apparatus according to the embodiment of the present invention. 5 is a flowchart for explaining an example of a procedure of air blowing control processing executed in the image forming apparatus according to the embodiment of the present invention. 9 is a flowchart for explaining another example of lift control processing executed in the image forming apparatus according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
In the present embodiment, as an example of a paper feeding device and an image forming apparatus according to the present invention, a paper feeding device 130 and a color printer X including the paper feeding device 130 will be described as an example. The present invention can be applied to various image forming apparatuses such as a printer, a copying machine, a facsimile machine, and a multifunction machine of these, and a paper feeding device used therefor.
First, a schematic configuration of the color printer X according to the embodiment of the present invention will be described with reference to FIGS. 1 to 4, and then lift control processing (see the flowchart of FIG. 5) executed by the color printer X. explain.

As shown in FIG. 1, the color printer X is roughly divided into a paper supply unit 100 that supplies paper used for image formation in the color printer X, and an image for the paper supplied from the paper supply unit 100. And a printer main body 200 that performs the formation. The color printer X is directly or indirectly connected to an information processing apparatus such as a personal computer (not shown) via a LAN or the like. The color printer X executes a printing process based on image data input from the information processing apparatus (not shown).
The color printer X includes a control unit (not shown) (hereinafter referred to as “control unit α”) that controls the color printer X in an integrated manner. The control unit α includes control devices such as a CPU, a RAM, and a ROM, and executes various processes including an image forming process (printing process) according to a predetermined control program. In particular, the control unit α executes a lift control process (see the flowchart of FIG. 5) described later.

The printer main body 200 includes a toner container 900 (900Y, 900M, 900C, 900K), an intermediate transfer unit 92, an image forming unit 93, an exposure unit 94, a fixing unit 97, a paper discharge unit 96, a casing 90, a top cover 911, and the like. A front cover 912 and the like are provided. Each of the toner containers 900 (900Y, 900M, 900C, 900K) contains toner corresponding to each color of yellow, magenta, cyan, and black.
The image forming unit 93 includes a photosensitive drum 17 that carries toner images corresponding to yellow, magenta, cyan, and black, a charger 16, a developing device 10 (10Y, 10M, 10C, and 10K), and a primary transfer roller 19. And a cleaning device 18 and the like.
The charger 16 uniformly charges the photosensitive drums 17, and electrostatic latent images are formed on the uniformly charged photosensitive drums 17 by exposure by the exposure unit 94. The
Each of the developing devices 10 contains a two-component developer having a magnetic carrier and toner inside the housing 20, and develops the electrostatic latent image formed on each of the photosensitive drums 17 with toner. Note that toner is supplied from each toner container 900 to the housing 20 of each developing device 10. The casing 20 is provided with stirring rollers 11 and 12 for stirring the developer via a partition wall 201, and the magnetic roller 14 and the developing roller 15 are stirred while the toner is stirred by the rotation of the stirring rollers 11 and 12. To be transported. The developing roller 15 develops the electrostatic latent image formed on the photosensitive drum 17 as a toner image. The casing 20 is also provided with a regulating blade 13 that regulates the layer thickness of the toner on the magnetic roller 14.

Thereafter, the toner image formed on each of the photosensitive drums 17 is transferred onto the intermediate transfer belt 921 by the primary transfer roller 19 in an overlapping manner. As a result, a color image is formed on the intermediate transfer belt 921. The intermediate transfer belt 921 is provided in the intermediate transfer unit 92 and is stretched by a driving roller 922 and a driven roller 923.
The color image formed on the intermediate transfer belt 921 is transferred to the paper supplied from the paper supply unit 100 in the secondary transfer unit 98 disposed opposite to the driving roller 922. Thereafter, the sheet on which the toner image is transferred by the secondary transfer unit 98 is fused and fixed by the fixing unit 97, and is discharged onto the top cover 911 by the paper discharge unit 96.

Next, the paper supply unit 100 will be described.
As shown in FIG. 1, the paper supply unit 100 includes a plurality of paper supply devices 130. As shown in FIGS. 1 and 2, each of the paper feeding devices 130 includes a paper feeding cassette 130A, a cassette mounting portion 130B, an upper blower fan 140, a side blower fan 150, and the like.
The paper feed cassette 130A is for loading various sizes of paper and is detachably provided in the cassette mounting portion 130B. The sheets loaded on the sheet feeding cassette 130A are conveyed to the secondary transfer unit 98 by various conveying rollers provided on the sheet feeding conveying path 133.
The upper blower fan 140 and the side blower fan 150 are used when sheets having high adhesion between sheets are stacked on the paper feed cassette 130A, and it is easy to blow hot air on the sheets. It is. A configuration having only one of the upper blower fan 140 and the side blower fan 150 is also conceivable as another embodiment.

Here, FIG. 3 is a schematic diagram of a main part for explaining an example of a mode of air blowing by the upper air fan 140 and the side air fan 150, and (a) is the upper air fan 140 and the side portion. FIG. 5B is a schematic diagram of the blower fan 150, and FIG. 7B is a view for explaining a blow mode by the upper blower fan 140 and the side blower fan 150.
The upper blower fan 140 and the side blower fan 150 have a heater (not shown) inside, and blow warm air heated by the heater. In addition, the structure which does not have the said heater (not shown) is also considered.
Specifically, as shown in FIG. 3A, the upper blower fan 140 passes from the blower opening 145 located above the paper feed cassette 130A to the top of the paper stacked on the paper feed cassette 130A. The hot air heated with the said heater is blown toward. In addition, the side blower fan 150 is a heater that moves from a blower port 155 located on the side of the leading end in the paper feeding direction of the paper loaded on the paper feed cassette 130A toward the side of the paper bundle. The heated warm air is blown.
In this way, in the paper feeding device 130, as shown in FIG. 3B, the upper temperature from the upper blower fan 140 is applied to the paper P stacked in the paper feeding cassette 130A as necessary. The wind and the side warm air from the side blower fan 150 are blown. The driving of the upper blower fan 140 and the side blower fan 150 is controlled by the control unit α.

On the other hand, as shown in FIG. 2, the paper feed cassette 130 </ b> A includes a paper storage unit 35 that stores the paper P, a cursor 33 that defines a rear end position of the paper P in the paper supply direction in the paper storage unit 35, A cursor 34a that determines a paper position in a direction orthogonal to the paper feeding direction of the paper storage unit 35, a lift mechanism 30 that lifts and lowers the paper P loaded in the paper feeding cassette 130A with respect to a pickup roller 40 described later, A conveyance roller 37 and the like are provided.
The cassette mounting portion 130B is provided with a pickup roller 40 and conveying rollers 41 and 49. The pickup roller 40 abuts on the uppermost part of the paper P of the paper feed cassette 130A and feeds the paper in order from the uppermost part, and is an example of a paper supply unit.
Then, the paper P discharged by the pickup roller 40 is conveyed to the conveyance rollers 37 and 49 one by one by the conveyance roller 41 and the separation roller 42, and the secondary transfer roller 922 through the paper supply conveyance path 133. To be transported. Each component of the paper feed cassette 130A and the cassette mounting portion 130B described here may be provided in either the paper feed cassette 130A or the cassette mounting portion 130B.

As shown in FIG. 2, the lift mechanism 30 is capable of rotating the lift plate 31 provided at the bottom surface of the paper container 35 and the rear end of the lift plate 31 in the paper feeding direction. A support portion 38 that supports the shaft, a push-up member 32 that lifts and lowers the tip of the lift plate 31 relative to the pickup roller 40, and a drive shaft 36 that pivotally supports the push-up member 32 so as to be rotatable. .
In the present embodiment, the lift mechanism 30 raises and lowers the tip of the lift plate 31 in the paper feeding direction of the paper P with respect to the pickup roller 40, so that the uppermost portion of the paper P in the paper feeding direction. The case where only the leading end is moved up and down with respect to the pickup roller 40 will be described as an example. Of course, a configuration in which the entire sheet P is translated up and down (up and down) may be used.

The cassette mounting portion 130B of the paper feeding device 130 includes a lift motor (not shown) (hereinafter referred to as “lift motor M”) and a worm gear that actuate the lift mechanism 30 by driving the drive shaft 36 forward and backward. Is provided.
The lift motor M is a DC brush motor that can be rotated forward and backward in accordance with the direction of energization, and the lift motor M is driven by the control unit α, which will be described later (see the flowchart in FIG. 5). Is controlled. The lift motor M is not limited to a DC brush motor, and other simple motors can be used.
The lift motor M is connected to the drive shaft 36 via the worm gear when the paper feed cassette 130A is mounted on the cassette mounting portion 130B.
Here, the worm gear is a mechanism in which a screw gear (worm) and a helical gear (worm wheel) matching the worm gear are combined, and transmits the rotational force of the lift motor M to the drive shaft 36. When the motor M is not rotating, the rotation of the drive shaft 36 is limited.

For example, the control unit α energizes the lift motor M in the forward direction to cause the lift motor M to rotate forward, and the drive shaft 36 to rotate forward to rotate the push-up member 32 in the direction of the arrow R1. Move. As a result, the lift plate 31 rotates in the direction of the arrow R <b> 2, and the leading edge of the paper P on the lift plate 31 rises toward the pickup roller 40.
Further, the controller α reversely rotates the lift motor M by energizing the lift motor M in the reverse direction, reverses the drive shaft 36, and rotates the push-up member 32 in the direction of arrow R3. As a result, the lift plate 31 rotates in the direction of the arrow R4, and the leading end of the paper P on the lift plate 31 descends from the pickup roller 40.
When the lift motor M is stopped, the lift plate 31 is held at the position after being lifted or lowered by the worm gear. Note that the mechanism for holding the lift plate 31 at the position after being raised or lowered is not limited to the worm gear, but may be any mechanism that can exhibit the same function.

  The cassette mounting portion 130B includes a position detection sensor 39 (an example of a paper position detection unit) that detects that the uppermost portion of the paper P of the paper feed cassette 130A has reached a predetermined position, and the paper feed cassette 130A. A mounting detection sensor (not shown) including a limit switch and an optical switch for detecting the presence or absence of mounting is provided. The detection result by the position detection sensor 39 and the detection result by the mounting detection sensor (not shown) are input to the control unit α.

FIG. 4 is a schematic diagram for explaining a specific example of the position detection sensor 39, where (a) shows an undetected state and (b) shows a detected state.
As shown in FIG. 4, the position detection sensor 39 includes a light shielding member 39A and an optical sensor 39B. The optical sensor 39B has a light emitting part and a light receiving part. The position detection sensor 39 determines whether the uppermost part of the paper P of the paper feed cassette 130A is a predetermined position depending on whether the light path between the light emitting part and the light receiving part of the optical sensor 39B is shielded by the light shielding member 39A. Detect whether or not.
Specifically, the light shielding member 39A is provided on a support member 50 that supports the pickup roller 40, and the support member 50 is provided so as to be rotatable about the rotation axis of the transport roller 41. Yes.

As shown in FIG. 4A, the light shielding member 39A does not block the optical path of the optical sensor 39B when the uppermost portion of the paper P of the paper feed cassette 130A is not in contact with the pickup roller 40. . Accordingly, the position detection sensor 39 detects that the uppermost part of the paper in the paper feed cassette 130A has not reached the predetermined position.
On the other hand, as shown in FIG. 4B, the uppermost portion of the paper P of the paper feed cassette 130A comes into contact with the pickup roller 40, and the pickup roller 40 and the support member 50 rotate the rotation shaft of the transport roller 41. When slightly rotated to the center, the light shielding member 39A that rises together with the support member 50 shields the optical path of the optical sensor 39B. Accordingly, the position detection sensor 39 detects that the uppermost part of the paper in the paper feed cassette 130A has reached the predetermined position. That is, the predetermined position is determined by the positional relationship between the optical sensor 39B and the light shielding member 39A. Of course, the position detection sensor 39 is not limited to this, as long as it can detect that the uppermost portion of the sheet of the sheet feeding cassette 130A has reached the predetermined position.

Hereinafter, an example of the procedure of the lift control process executed by the control unit α in the color printer X will be described with reference to the flowchart of FIG. In the figure, S1, S2,... Represent processing procedure (step) numbers.
In the present embodiment, the case where the lift control process is executed by the control unit α will be described as an example. However, the sheet feeding device 130 is provided with a control unit (control circuit) separate from the control unit α. In another embodiment, the lift control process is executed by the control unit.

(Step S1)
First, in step S1, the control unit α determines whether or not an operation of attaching / detaching one of the plurality of paper feed cassettes 130A to / from the cassette mounting unit 130B has been performed. Specifically, the control unit α determines the presence / absence of the detachment work depending on whether the detection state by the attachment detection sensor (not shown) has changed from non-attachment to attachment (No in S1).
If it is determined that the paper feed cassette 130A has been removed (Yes side of S1), the process proceeds to step S2, and if the paper feed cassette 130A has not been removed (No side of S1). , The process proceeds to step S11 described later.

(Steps S2 to S3)
In step S2, the control unit α starts energizing the lift motor M in the direction in which the lift motor M rotates forward. As a result, the lift motor M rotates in the forward direction, the lift mechanism 31 raises the lift plate 31, and the paper on the lift plate 31 rises toward the pickup roller 40.
In step S3, which is executed substantially simultaneously with step S2, the control unit α determines that the position after the paper feed cassette 130A is mounted on the paper feed device 130 and the drive of the lift motor M is started. The measurement of the required time t1 until the detection by the detection sensor 39 is started.

(Steps S4 to S5)
Thereafter, in step S4, the control unit α waits for the uppermost part of the paper in the paper feed cassette 130A to reach a predetermined position by the position detection sensor 39 (No side of S4).
Here, if it is determined that the detection by the position detection sensor 39 has been made (Yes side of S4), the control unit α shifts the process to step S5, and at the required time t1 started in step S3. End timing.

(Step S6)
In the following step S6, the control unit α sets a stop waiting time T1 until the drive of the lift motor M is stopped according to the sheet stacking amount of the sheet feeding cassette 130A, and is detected by the position detection sensor 39. Start timing later. Here, the control unit α when executing the setting process corresponds to stop standby time setting means.
Specifically, the required time t1 from when the paper feeding cassette 130A is mounted on the paper feeding device 130 and the drive of the lift motor M is started until the detection by the position detection sensor 39 is performed is as follows. It fluctuates depending on the amount of sheets loaded in the sheet cassette 130A. That is, the required time t1 between the steps S3 to S5 serves as an index of the amount of paper loaded in the paper feed cassette 130A.
Therefore, the control unit α detects the sheet stacking amount of the paper feed cassette 130A according to the required time t1 between the steps S3 to S5, and sets the stop waiting time T1 according to the stacking amount. It is possible. It should be noted that the correspondence between the required time t1 and the paper stacking amount of the paper feed cassette 130A may be set in advance according to the results of experiments and simulations. According to such a configuration, it is possible to simplify by omitting a sensor for detecting the amount of paper loaded in the paper feed cassette 130A.
At this time, the control unit α determines whether or not the sheet loading amount of the sheet feeding cassette 130A exceeds an upper limit loading amount set in advance as a loading amount corresponding to the overloading. When the upper limit stacking capacity is exceeded, it may be possible to display a warning on the display unit (not shown) that the sheets in the paper feed cassette 130A are overloaded.
The required time t1 is an index indicating the paper stacking amount of the paper feed cassette 130A. Therefore, the stop waiting time T1 is set according to the required time t1 without detecting the paper stacking amount. May be. Of course, in a configuration having a sensor or the like for detecting the amount of paper loaded in the paper feed cassette 130A, the stop standby time T1 may be set according to the detection result by the sensor.

At this time, the control unit α loads the sheets in the sheet feeding cassette 130A so that the uppermost portion of the sheets in the sheet feeding cassette 130A always stops at the same position and always contacts the pickup roller 40 with a predetermined pressure. The stop waiting time T1 is set longer as the amount increases, and the stop waiting time T1 is set shorter as the amount of sheets loaded in the paper feed cassette 130A decreases. Specifically, the control unit α always has the same sum of the uppermost amount of increase of the sheet after the energization of the lift motor M is stopped and the uppermost amount of increase of the sheet during the stop waiting time T1. Thus, the stop waiting time T1 is set. It should be noted that the correspondence between the sheet stacking amount of the sheet feeding cassette 130A and the uppermost amount of the sheet after the energization of the lift motor M is stopped may be measured in advance through experiments or simulations.
More specifically, the control unit α stores an internal memory (stop standby time correspondence information storage) for storing stop standby time correspondence information indicating the relationship between the sheet stacking amount of the paper feed cassette 130A and the stop standby time T1. It is conceivable that the stop standby time T1 is set according to the sheet stacking amount of the paper feed cassette 130A and the stop standby time correspondence information stored in the internal memory. .
Here, it is conceivable that the stop standby time correspondence information is an arithmetic expression indicating the relationship between the sheet stacking amount of the paper feed cassette 130A and the stop standby time T1. In addition, the stop standby time correspondence information may be classified into a plurality of stages of paper stacking amounts of the paper feed cassette 130A, and a stop standby time T1 corresponding to each of the classifications may be determined.

(Steps S7 to S8)
Thereafter, the control unit α waits until the stop standby time T1 set in step S6 elapses after detection by the position detection sensor 39 (No side of S7).
When it is determined that the stop standby time T1 has elapsed (Yes in S7), the control unit α shifts the process to step S8 and stops energization of the lift motor M. Here, the control unit α for stopping the energization of the lift motor M after elapse of the preset stop waiting time T1 after the detection by the position detection sensor 39 corresponds to the lift raising control means. To do.
At this time, even after the energization of the lift motor M is stopped, the lift motor M rotates by inertia and the lift plate 31 slightly rises, and the amount of the rise is equal to the amount of sheets loaded in the paper feed cassette 130A. In this embodiment, the difference in the amount of increase is absorbed by the adjustment of the stop standby time T1, so that the top of the paper in the paper feed cassette 130A is always at the same position. Will stop.

Thus, in the color printer X, the lift motor M is executed so that the uppermost part of the paper in the paper feed cassette 130A always stops at the same position by the lift control processing being executed by the control unit α. The timing of stopping energization of the paper is changed in accordance with the paper stacking amount of the paper feed cassette 130A.
Therefore, even when a simple DC brush motor or the like is used for the lift motor M, the top of the paper in the paper feed cassette 130A and the pickup roller are used regardless of the paper stacking amount in the paper feed cassette 130A. The contact pressure with 40 can always be a predetermined pressure, and the paper supply performance by the pickup roller 40 can be kept constant. Also, the motor drive circuit that controls the lift motor M does not require a brake function or a speed control function, so that the configuration can be simplified.

When the uppermost portion of the sheet in the sheet feeding cassette 130A comes into contact with the pickup roller 40 in steps S1 to S8, the process proceeds to step S11.
Further, the processing after step S11 is executed before the start of air blowing by the upper blower fan 140 or the side fan 150 or during the air blow. Note that the air blowing operation by the upper air fan 140 and the side air fan 150 will be described in the first embodiment.

(Step S11)
In step S <b> 11, the control unit α determines the necessity of blowing air to the paper in the paper feed cassette 130 </ b> A by the upper blower fan 140 and the side blower fan 150.
Specifically, when special paper such as coated paper is loaded on any of the plurality of paper feed cassettes 130A and the special paper is used for printing processing, It is determined that it is necessary to blow air on the paper in the stacked paper cassette 130A (Yes in S11). In this case, the control unit α shifts the process to step S12. Note that the control unit α determines that the paper loaded on the paper feed cassette 130A is a special paper according to the detection result by a sensor (not shown) for detecting the paper type of the paper feed cassette 130A or the initial setting by the user. Determine whether or not.
Hereinafter, the paper feed cassette 130A on which the special paper is stacked among the plurality of paper feed cassettes 130A is referred to as a special paper feed cassette 130AS.
On the other hand, when no special paper is stacked on any of the plurality of paper feed cassettes 130A, or when printing processing is performed using a paper feed cassette 130A different from the special paper feed cassette 130AS, It is determined that there is no need to blow by the upper blower fan 140 and the side blower fan 150 (No side of S11). In this case, the process returns to step S1, and the determination process in step S1 and step S11 is repeated as appropriate.

(Step S12)
In step S12, the control unit α acquires the current special paper stacking amount of the special paper feed cassette 130AS used in the printing process.
Specifically, the control unit α calculates an initial stack amount of special paper in the special paper feed cassette 130AS according to the required time t1 measured in steps S3 to S5. The control unit α stores and stores the amount of special paper used in the special paper feed cassette 130AS after the special paper feed cassette 130AS is mounted. Get the current special paper load by reducing the amount.
Of course, a sheet remaining amount detecting means such as an optical sensor for detecting the remaining amount of special sheets in the special sheet feeding cassette 130AS is provided, and the current amount of special sheets loaded is acquired from the remaining sheet amount detecting means. It may be. For example, it is conceivable to detect the current loading amount of special paper by detecting the rotational position of a predetermined gear of the lift mechanism 30 that is rotationally driven by the lift motor M.

(Step S13)
In step S13, the control unit α sets the separation movement time T2 in accordance with the current special paper stacking amount. The separation movement time T2 is used to separate the uppermost sheet of the special sheet feeding cassette 130AS from the pickup roller 40 when blowing by the upper blowing fan 140 and the side blowing fan 150. This is the time during which the lift plate 31 is lowered by the mechanism 30.
Specifically, the control unit α shortens the separation movement time T2 as the amount of sheets loaded in the special sheet feeding cassette 130AS increases within a range where the lowered position by the lift mechanism 30 does not exceed a predetermined lower limit position. The smaller the paper stacking amount of the special paper feed cassette 130AS is, the longer the separation movement time T2 is set. The predetermined lower limit position is an overload on the lift mechanism 30 and the lift motor M, for example, a lower limit position in a range where the lift plate 31 of the lift mechanism 30 does not contact the frame of the cassette mounting portion 130B. This is the lower limit position of the range where does not work.
Here, the control unit α includes a storage memory (not shown) in which information on correspondence between separated movement times indicating the relationship between the sheet stacking amount of the special sheet feeding cassette 130AS and the separated movement time T2 is stored. It is conceivable to set the separation movement time T2 in accordance with the amount of sheets loaded in the special sheet feeding cassette 130AS and the separation movement time correspondence information stored in the storage memory. Of course, the method is not limited to this, and for example, the control unit α may calculate the separation movement time T2 from the sheet stacking amount of the special sheet feeding cassette 130AS according to a preset relational expression.

(Steps S14 to S15)
Next, the control unit α starts the lowering operation of the lift plate 31 by the lift mechanism 30 by driving the lift motor M in reverse (S14). At this time, the control unit α starts measuring time from the start of driving the lift motor M.
In step S15, the control unit α waits for the elapse of the separation movement time T2 set in step S13 (No side in S15). If it is determined that the separation movement time T2 has elapsed (Yes in S15), the process proceeds to step S16.

(Step S16)
In step S <b> 16, the control unit α ends the lowering operation of the lift plate 31 by the lift mechanism 30 by stopping the drive of the lift motor M. The lift plate 31 is moved by the lift mechanism 30 when the lift motor M is driven by the control unit α after the air blow by the upper fan 140 or the side fan 150 is finished or during the air blow. The position is raised to a position where the roller 40 comes into contact.
Thus, the separation movement time T2, which is the lowering time of the lift plate 31, exceeds the predetermined lower limit position of the lowering position by the lift mechanism 30 according to the amount of special paper loaded in the special paper feed cassette 130AS. In this range, the lift plate 31 or the like is set so as not to contact the frame or the like of the cassette mounting portion 130B.
Accordingly, in the paper feeding device 130, for example, when the special paper stacking amount of the special paper feeding cassette 130AS is maximum (or overloaded), the lowering time of the lift plate 31 can be shortened. The overloading of the lift mechanism 30 and the lift motor M can be prevented, and the breakage and failure thereof can be prevented.

In the first embodiment, in the color printer X, an example of the air blowing control process executed by the control unit α to control the driving of the upper air blowing fan 140 and the side air blowing fan 150 will be described. 6A and 6B are flowcharts for explaining an example of the procedure of the air blowing control process, and S21, S22,... Represent process procedure numbers.
6A shows a case where the upper blower fan 140 and the side blower fan 150 are driven in parallel with the lowering operation of the lift plate 31, and FIG. The example of a process in the case of driving the said upper ventilation fan 140 and the said side ventilation fan 150 after completion | finish of operation | movement is shown. Hereinafter, the example of the ventilation control process shown in FIG. 6A will be described first, and then the example of the ventilation control process shown in FIG. 6B will be described.

(Step S21)
In the air blowing control process shown in FIG. 6A, the control unit α, as in step S11 (see FIG. 5), uses the upper air blowing fan 140 and the side air blowing fan 150 to feed the paper in the paper feed cassette 130A. The necessity of blowing air is determined (S21).
If it is determined that the special paper cassette 130AS needs to be blown to the paper (Yes in S21), the process proceeds to step S22. On the other hand, if it is determined that blowing of the special sheet feeding cassette 130AS is not necessary (No in S21), the upper blowing fan 140 and the side blowing fan 150 are not driven, and the process is performed in step S21. I will wait.

(Steps S22 to S24)
Next, in step S22, the control unit α starts driving the upper blower fan 140 and the side blower fan 150 and starts measuring the drive time thereof.
In step S23, it is determined whether or not a preset blowing time T3 has elapsed. If it is determined that the blowing time T3 has elapsed (Yes in S23), the process proceeds to step S24. In step S24, the control unit α stops driving the upper blower fan 140 and the side blower fan 150.
That is, the control unit α relates to the lowering amount (separation movement time T2) of the lift plate 31 determined in accordance with the amount of special paper loaded in the special paper feed cassette 130AS in the lift control process (see FIG. 5). However, the upper blower fan 140 and the side blower fan 150 are always driven during the constant blowing time T3. In this way, even when the separation movement time T2 is short, the blowing time T3 is not shortened, so that the special paper is rolled by the pickup roller 40 regardless of the special paper stacking amount of the special paper feed cassette 130AS. Performance can be increased.

Next, the ventilation control process of FIG.6 (b) is demonstrated. In addition, the same code | symbol is attached | subjected to the process sequence similar to the ventilation control process shown to Fig.6 (a), and the description is abbreviate | omitted.
In the air blowing control process shown in FIG. 6B, if it is determined in step S21 that air blowing to the paper of the special paper feed cassette 130AS is necessary (Yes side of S21), the process proceeds to step S211. .

(Step S211)
In step S211, the control unit α sets a blowing time T3 for driving the upper blower fan 140 and the side blower fan 150 according to the amount of special paper loaded in the special paper feed cassette 130AS.
Specifically, the controller α decreases the blowing time T3 as the separating movement time T2 is long so that the total time of the separating movement time T2 and the blowing time T3 is constant. The air blowing time T3 is set longer as T2 is shorter. Of course, it is considered as another embodiment that the total time of the separation movement time T2 and the blowing time T3 is not constant.

(Step S212)
Then, the control unit α determines whether or not the lowering operation of the lift plate 31 by the lift control process is completed (S212). Here, if it is determined that the lowering operation of the lift plate 31 is completed (Yes in S212), the process proceeds to Step S22. On the other hand, if it is determined that the lowering operation of the lift plate 31 has not been completed (No in S212), the process waits in step S212.
Thereafter, after the lift plate 31 is blown by the upper blower fan 140 and the side blower fan 150 for the preset blow time T3, the lift motor M is driven by the control unit α. As a result, the lift mechanism 30 moves up to a position where it comes into contact with the pickup roller 40.
As described above, in the air flow control process shown in FIG. 6B, the control unit α is determined according to the amount of special paper loaded in the special paper feed cassette 130AS in the lift control process (see FIG. 5). The blowing time T3 is changed according to the descending amount of the lift plate 31 (separation movement time T2). Therefore, when the distance between the uppermost portion of the special paper and the pickup roller 40 is small and the blowing efficiency to the entire uppermost portion of the special paper is low, the blowing time T3 can be lengthened, and the pickup roller 40 Can improve the performance of special paper. Further, if the blowing time T3 is set so that the total time of the separation time T2 and the time required for returning the lift plate 31 and the blowing time T3 is constant, the printing process for each special sheet is performed. In the range where the interval is not widened, that is, in the range in which the delay of the printing process can be prevented, the special paper sheeting performance by the pickup roller 40 can be enhanced.

By the way, when a simple lift motor M and a motor drive circuit are used, not only when the lift plate 31 is raised, but also when the lift plate 31 is lowered, inertia (inertia) after the lift motor M stops energization. And the lift plate 31 is slightly lowered. The descending width of the lift plate 31 after the energization of the lift motor M is stopped also varies depending on the sheet stacking amount (load) of the special sheet feeding cassette 130AS.
For this reason, if the energization stop timing of the lift motor M when the lift plate 31 is lowered is always the same timing, the stop position of the lift plate 31 varies depending on the sheet loading amount of the special paper feed cassette 130AS. In some cases, the lowering position of the lift mechanism 30 exceeds a predetermined lower limit position, and the lift mechanism 30 or the lift motor M may be damaged or broken.
Therefore, when using a simple lift motor M and a motor drive circuit, the separation movement time T2 is set in consideration of the descending amount due to the inertia of the lift plate 31 after the energization of the lift motor M is stopped. Is desirable.

FIG. 7 is a flowchart for explaining another example of the lift control process. In the figure, S1, S2,... Represent process procedure (step) numbers, and the same process steps as those described with reference to FIG.
As shown in FIG. 7, in the lift control process according to the third embodiment, the control unit α sets the stop waiting time T1 between the step S3 and the step S4 instead of the process of the step S6. A setting process is executed (S31).
In step S31, the control unit α sets the stop waiting time T1 to be gradually shortened as time elapses after the drive of the lift motor M is started until detection by the position detection sensor 39 is performed. Note that the initial value of the stop waiting time T1 may be set to the longest time corresponding to the case where the paper stacking amount of the paper feed cassette 130A is the maximum amount.
Specifically, the control unit α gradually shortens the stop standby time T1 in accordance with an increase in the required time t1 at which time measurement is started in step S3. As a result, the longer the required time t1, that is, the smaller the amount of paper loaded in the paper feed cassette 130A, the shorter the stop waiting time T1 is set.
According to such a configuration, when the position detection sensor 39 detects in step S4, the stop waiting time T1 is already set. Therefore, it is possible to prevent a time lag after detection by the position detection sensor 39, for example, when the sheet loading amount of the paper feed cassette 130A is small and the lift motor M is stopped immediately after detection by the position detection sensor 39. It is suitable for.

X ... Color printer (an example of an image forming apparatus)
DESCRIPTION OF SYMBOLS 30 ... Lift mechanism 31 ... Lift plate 32 ... Push-up member 33, 34a ... Cursor 35 ... Paper storage part 36 ... Drive shaft 37, 41, 49 ... Conveyance roller 38 ... Support part 39 ... Position detection sensor (an example of paper position detection means) )
39A ... Light-shielding member 39B ... Optical sensor 40 ... Pickup roller (an example of paper supply means)
42 ... roller 50 ... support member 98 ... secondary transfer unit 100 ... paper supply unit 130 ... paper feed device 130A ... paper feed cassette 130B ... cassette mounting unit 140 ... upper fan 145 ... air outlet 150 ... side air fan 155 ... Blower port 200 ... Printer body S1, S2 ..., processing procedure (step) numbers S11, S12 ..., processing procedure (step) numbers S21, S22 ..., processing procedure (step) numbers

Claims (6)

A paper feed cassette on which paper is stacked, a paper supply means that abuts on the top of the paper stacked on the paper feed cassette and supplies the paper from the top, and a paper loaded on the paper feed cassette A lift mechanism that lifts the paper toward the paper supply means; a lift motor that operates the lift mechanism; a paper position detection means that detects that the top of the paper in the paper feed cassette has reached a predetermined position; and the paper position A lift raising control means for stopping energization of the lift motor after elapse of a preset stop waiting time after detection by the detection means,
A paper feed device comprising stop standby time setting means for setting the stop standby time in accordance with a paper stacking amount of the paper feed cassette.   The stop standby time setting means sets the stop standby time longer as the amount of sheets loaded in the paper cassette increases, and sets the stop standby time shorter as the amount of sheets stacked in the paper cassette decreases. The paper feeding device according to claim 1.   The stop standby time setting means is configured to determine the time required for the detection by the paper position detection means after the paper feed cassette is mounted on the paper feed device and the drive of the lift motor is started. The sheet feeding device according to claim 1, wherein a stop waiting time is set.   4. The stop standby time setting unit is configured to set the stop standby time to be gradually shorter as time elapses after the lift motor starts to be driven until detection by the paper position detection unit. Paper feeder.   The stop standby time setting means includes stop standby time correspondence information storage means in which stop standby time correspondence information indicating the relationship between the sheet loading amount of the paper feed cassette and the stop standby time is stored. 5. The stop standby time is set according to the amount of sheets loaded in a paper cassette and the stop standby time correspondence information stored in the stop standby time correspondence information storage means. The paper feeder described.   An image forming apparatus comprising the paper feeding device according to claim 1.

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