JP2005067853A - Paper feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper feeder capable of forcibly stopping a transfer paper placing plate promptly, and reducing loads on a driving motor raising the transfer paper placing plate or various parts. <P>SOLUTION: This paper feeder comprises a transfer paper placing plate driving means for raising the transfer paper placing plate and a transfer paper sheet on a transfer paper feeding part; the transfer paper placing plate, an upper limit detecting means for detecting the upper end position of the transfer paper placing plate or the transfer paper placed on the transfer paper placing plate in association with the raising operation of the transfer paper placing plate, a transfer paper detecting means for detecting the presence or absence of the transfer paper placed on the transfer paper placing plate in association with the raising operation of the transfer paper placing plate, a rotational angular velocity detecting means for detecting a change in the rotational angular velocity of the driving means, and a stop control means for controlling timing in stopping the operation of the driving means based on each detection signal from the upper limit detecting means, the transfer paper detecting means and the rotational angular velocity detecting means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a paper feeding device used in an image forming apparatus such as a copying machine, a printer, and a facsimile machine. More specifically, the present invention relates to an overrun (excessive overload) of a transfer paper mounting plate that supports a transfer paper. The present invention relates to a sheet feeding device provided with a control mechanism for effectively preventing (raising).

  In the image forming apparatus as described above, the toner image formed on the surface of the photosensitive drum is transferred onto the transfer paper, and the transferred toner image is fixed on the surface of the transfer paper with heat or pressure, thereby forming an image. Is called. In such an image forming apparatus, a transfer sheet on which an image is to be formed is normally loaded in a paper feed cassette and conveyed to a predetermined image forming area from a paper feed cassette mounted on the image forming apparatus. .

  As such a sheet feeding cassette, there is known a structure having a transfer sheet placing plate that is lifted by driving rotation of a lift plate that is rotationally driven by a motor. In such a paper feed cassette, a stack of transfer paper is placed on the transfer paper placement plate, and when the paper feed cassette is mounted on the image forming apparatus in this state, the motor is driven to rotate the lift plate. Then, the transfer paper placing plate rises, and the transfer paper on the transfer paper placing plate comes into contact with a pickup roller provided in the image forming apparatus. In this state, the transfer paper is conveyed to a predetermined image forming area by rotating the pickup roller during image formation.

By the way, since the transfer paper placing plate as described above is excessively raised (overrun), the apparatus is damaged. Therefore, a control method of the transfer paper placing plate to prevent overrun has been proposed. . In other words, the motor is driven by the signal transmitted when the paper feed cassette is mounted, and the lift plate is raised. Stop driving. Also, if the upper limit switch did not operate due to a failure or the like, the motor was stopped after a certain period of time after the paper detection switch was turned on, and the paper feed cassette was loaded without setting the transfer paper In this case, since the paper detection switch is not turned on, the motor is stopped after a certain time has elapsed since the paper feed cassette was mounted (see Patent Document 1).
JP 2002-255396 A.

  By the way, in the control method as described above, since the rotation stop position of the lift plate (forced stop position of the transfer paper placement plate) is defined by the timer, for example, the coupling between the shaft of the motor and the shaft of the lift plate It is defined by a time setting that has a margin including the meshing time (play driving time) and variations in the number of rotations of the motor, etc., and the accuracy is low. There still remains a problem that the motor and various components are subjected to a great load and are liable to cause damage to the apparatus.

  Accordingly, an object of the present invention is to provide a paper feeding device in which the transfer paper placing plate is forcibly stopped quickly, and the load applied to the drive motor and various components for raising the transfer paper placing plate is reduced. is there.

According to the present invention,
Transfer paper placing plate for placing the transfer paper;
Paper feeding unit for supplying transfer paper to the image forming unit;
A transfer paper placement plate driving means for lifting the transfer paper placed on the transfer paper placement plate to the paper feed unit;
An upper limit detection means for detecting the transfer paper placement plate or the upper end position of the transfer paper placed on the transfer paper placement plate in accordance with the lifting operation of the transfer paper placement plate;
A transfer paper detection means for detecting the presence or absence of the transfer paper placed on the transfer paper placement board in accordance with the lifting operation of the transfer paper placement board;
Rotational angular velocity detection means for detecting a change in rotational angular velocity of the drive means;
Stop control means for controlling the timing of stopping the operation of the drive means based on the respective detection signals from the upper limit detection means, the transfer paper detection means and the rotational angular velocity detection means;
A sheet feeding device is provided.

In the present invention, the stop control means operates in any of the following (a) to (c) after the transfer paper placing plate lifting operation is started, and stops the operation of the drive means. Is preferred.
(A) When the upper limit detecting means detects the upper end position of the transfer paper placing plate or the transfer paper placed on the transfer paper placing plate and issues a detection signal;
(B) The transfer paper detecting means detects the presence of the transfer paper placed on the transfer paper placing plate and generates a detection signal, and the detection signal from the upper limit detection means is not issued. When a predetermined time has elapsed since the detection signal was transmitted from the transfer paper detection means;
(C) None of the transfer paper detection means and the upper limit detection means generates a detection signal, and the rotation angular speed detection means detects that the rotation angular speed of the transfer paper placing plate driving means has become substantially zero. When a detection signal is issued;

  In the present invention, the rotational angular velocity detection means is provided as a safety device, reads the rotational angular velocity of the shaft of the motor that is the transfer paper placement plate driving means, and outputs a detection signal when the rotational angular velocity becomes substantially zero. The motor can be forcibly stopped by driving the motor (the transfer paper placing plate is lifted). That is, when the transfer paper on the transfer paper placement plate or the transfer paper placement plate is lifted in a state where the transfer paper placement plate is in contact with the pickup roller disposed in the paper feeding unit, naturally, A load is applied to the driving means (motor) for lifting the transfer paper placing plate, and when the pickup roller reaches the upper limit position, the rotational angular velocity of the rotation shaft of the driving means becomes zero (although the motor operates, the transfer paper) The mounting plate does not rise). If this state continues, a great load is applied to the motor, and a large load is also applied to the pickup roller and the member supporting it, which easily causes damage to the apparatus. In the present invention, such a change in the rotational angular velocity is read by the rotational angular velocity detection means, and controlled so that the driving of the motor can be stopped according to the detection signal, so that both the upper limit detection switch and the transfer paper detection switch Even if a malfunction occurs due to a failure, etc., the motor can be stopped quickly without taking into account the drive play time and motor rotation variations, reducing the load on the motor, etc. Can be prevented.

The present invention will be described below based on specific examples shown in the accompanying drawings.
FIG. 1 is a diagram showing a schematic structure of a paper feeding device according to the present invention, FIG. 2 is a schematic perspective view of a paper feeding cassette used in the paper feeding device, and FIG. FIG. 4 is a schematic perspective view showing a state in which the transfer paper placement plate is removed, and FIG. 4 is a perspective view showing the transfer paper placement plate incorporated in the paper feed cassette of FIG. FIG. 5 is a diagram showing a transfer paper detection switch (transfer paper detection means) provided in the paper feeding device of FIG.

  In FIG. 1, the paper feeding device includes a transfer paper storage portion A provided in an image forming apparatus such as a copying machine and a paper feed portion B disposed on the transfer paper storage portion A.

  The transfer paper container A is loaded with a paper feed cassette 1 as a whole, and this paper feed cassette 1 has a box shape as a whole as shown in FIGS. A pair of side wall frames 2, 2 extending in the mounting direction of the image forming apparatus (indicated by an arrow X in FIGS. 2 and 3), and a pair of side wall frames 3, 3 extending in a direction perpendicular to the mounting direction X; The bottom wall frame 4 is integrally joined to the frames 2 and 3.

  The bottom wall frame 4 is formed with a large number of recesses or notches for attaching various parts. For example, a pair of side fences 5 and 5 and a rear end that can slide according to the size of the transfer paper A fence 6 is provided. A rotating shaft 8 extending along the mounting direction X is incorporated in the bottom wall frame 4, and a lift plate 9 that rotates integrally with the rotating shaft 8 is attached to the rotating shaft 8. That is, when the paper feed cassette 1 is mounted on the image forming apparatus, the rotation of the motor (not shown) as a driving means is transmitted to the rotary shaft 8 by gears or the like.

  A transfer paper placing plate 10 having the shape shown in FIG. 4 is attached on the bottom wall frame 4. The transfer paper placing plate 10 is held by the side wall frames 3 and 3 so as to rotate with the rear end side as a fulcrum (in FIG. 4, a portion indicated by 10a is a bearing portion). The side fence 5 and the rear end fence 6 are allowed to slide. Further, the transfer paper placing plate 10 is provided with a long hole 12 for a transfer paper detection switch, which will be described later, at its tip portion.

  Returning to FIG. 1 again, a bundle of transfer papers 15 is placed on the transfer paper placing plate 10 of the paper feed cassette 1, and in this state, the paper feed cassette 1 is placed in the transfer paper accommodating portion A of the image forming apparatus. Mounting.

  The paper feeding section B disposed on the transfer paper storage section A is an area for supplying the transfer paper 15 to an image forming section (for example, an area in which the photosensitive drum is disposed) of the image forming apparatus. 1, the pickup roller 20 for feeding the transfer paper 15, the paper feed roller 22 positioned on the downstream side in the transfer conveyance direction with respect to the pickup roller 20, and the paper feed roller 20 are arranged to face each other. The separation roller 23 is provided, and a conveyance guide 25 is arranged from the pickup roller 20 toward the nip portion between the paper feed roller 22 and the separation roller 23.

  The pick-up roller 20 and the paper feed roller 22 have their rotation shafts engaged with the gear 26, and rotate in synchronization with each other in the same direction (clockwise in FIG. 1). Further, the separation roller 23 is provided to rotate in the reverse direction (counterclockwise in FIG. 1). That is, the transfer paper 15 on the transfer paper placing plate 10 is conveyed toward the paper feed roller 22 by the pickup roller 20 and further fed to a predetermined image forming unit by the paper feed roller 22. In this case, the shaft 23a of the separation roller 23 is provided with a torque limiter so that it does not rotate until a certain torque is applied. Accordingly, when a plurality of transfer sheets 15 are fed in a double manner, the lower transfer sheet 15 is blocked by the separation roller 23 whose rotation is stopped, and only the uppermost transfer sheet 15 is transferred. Paper is fed by the paper feed roller 22.

  In the paper feeding section B, the rotation shaft 22a of the paper feed roller 22 is supported by the upper housing 27, and the rotation shaft 23a of the separation roller 23 is supported by the lower housing 28. The upper housing 27 and the lower housing 28 is fixed to the image forming apparatus. On the other hand, the rotation shaft 20 a of the pickup roller 20 and the rotation shaft 26 a of the gear 26 are supported by a swing arm 30 provided in the upper housing 27 so as to be rotatable with respect to the rotation shaft 22 a of the paper feed roller 22. These are provided so as to be able to turn around the rotating shaft 22a as a fulcrum while maintaining the engagement relationship with the rotating shaft 22a as the swinging arm 30 turns.

  That is, when the transfer paper 15 on the transfer paper placing plate 10 that is lifted by the rotation of the lift plate 9 comes into contact with the pickup roller 20 held at a predetermined position (initial position), the pickup roller 20 is moved to the transfer paper 15 (transferring). When there is no paper 15, it is lifted by the transfer paper placing plate 10) and pivots upward around the rotation shaft 22 a of the paper feed roller 22 together with the swing arm 30. On the other hand, as the transfer paper 15 on the transfer paper placing plate 10 is consumed, the pickup roller 20 descends by its own weight (that is, pivots downward integrally with the swing arm 30), and all the transfer is performed. When the paper 15 is consumed, the pickup roller 20 comes into direct contact with the transfer paper placement plate 10. Note that there is a limit to the swing of the swing arm 30, and the upward swing is restricted by contact with the upper housing 27, for example, and at this time, the pickup roller 20 is positioned at the top.

  In the present invention, as shown in FIGS. 1 and 5, a transfer paper detection switch 40 (see FIG. 5) and an upper limit detection switch 42 (see FIG. 1) are arranged in parallel in the upper housing 27.

  The transfer paper detection switch 40 includes a paper detection arm 40a that is swingably held in the upper housing 27, a shielding plate 40b that rotates as the arm 40a rotates, and an optical sensor unit 40c (light emitting element and light receiving element). (See FIG. 5). In other words, the paper detection arm 40a is positioned on the long hole 12 of the transfer paper placing plate 10 described above, and when the transfer paper placing plate 10 is lifted with the transfer paper 15 loaded, the paper detection arm 40a is moved. The screen is lifted by the transfer paper 15 and turned, and the shielding plate 40b is rotated. The light blocking by the optical sensor unit 40c is released, the switch is turned on, and a paper detection signal is generated. When the transfer paper 15 does not exist, the paper detection arm 40a enters the slot 12 as it is, so it does not rotate and remains switched off, and no paper detection signal is issued.

  On the other hand, the upper limit detection switch 42 includes a shielding plate 42a that is held by the swing arm 30 that holds the pickup roller 20, and an optical sensor unit 42b that is held by the upper housing 27 (from the light emitting element and the light receiving element). (See FIG. 1). That is, when the transfer paper placing plate 10 is raised, the pickup roller 20 is lifted by the transfer paper 15 or the transfer paper placing plate 10 itself (when there is no transfer paper 15), the swing arm 30 is raised, and the shielding plate 42a. Also rises. When the shielding plate 42a is raised to a predetermined position (that is, when the pickup roller 20 is raised to a predetermined position), the light at the optical sensor unit 42b is blocked (switched on), and an upper limit detection signal is generated.

  In the present invention, a rotational angular velocity detection switch for detecting the rotational angular velocity of the motor drive shaft for rotationally driving the lift plate 9 is provided. In FIG. 6 showing the structure of this switch, the rotational angular velocity detection switch denoted as 50 as a whole is composed of an encoder 50a attached to the drive shaft 52 of the motor, and an optical sensor unit 50b arranged so as to sandwich the encoder 50a. (See FIG. 6A). In the encoder 50a, slits 50c are formed at a constant pitch, and the rotational angular velocity of the drive shaft 52 is detected by counting the rotational drive pulses by the slit 50c by the rotation of the drive shaft 52 of the motor. When the number of counts per unit time drops below a certain value, a detection signal indicating that the rotational angular velocity has become substantially zero is issued. The rotation angular velocity detection switch 50 may be attached to the drive rotation shaft 8 of the lift plate 9 instead of being attached to the drive shaft 52 of the motor. The rotation angular velocity detection switch 50 operates as a safety device. When neither the transfer sheet detection switch 40 nor the upper limit detection switch 42 described above operates, the rotation angular velocity detection switch 50 indicates that the rotation angular velocity is substantially zero. A signal is issued, which stops the motor drive.

  The sheet feeding device of the present invention described above operates as follows.

  First, when the paper feed cassette 1 is mounted on the image forming apparatus, the switch of the drive motor is designed to be automatically turned on. The rotation shaft 8 is rotated by the operation of the drive motor, and the lift plate 9 is rotated. Rotates.

  When the lift plate 9 rotates, the transfer paper placement plate 10 on which the transfer paper 15 is placed rotates with the rear end side as a fulcrum, and the front end side rises. As a result, the bundle of transfer papers 15 placed on the transfer paper placing plate 10 comes into contact with the pickup roller 20, and when the pickup roller 20 is lifted to some extent, the driving of the motor is stopped and waits in this state. To do. That is, when the start button of the image forming apparatus is turned ON, as described above, the pickup roller 20 rotates, the transfer paper 15 starts to be fed, and the transfer paper 15 at the upper end position passes through the paper feed roller 22. Then, the sheet is conveyed into a predetermined image forming area to form an image, and the feeding of two sheets is suppressed by the separation roller 23.

  In the present invention, the rising timing of the transfer paper placing plate 10 is performed by stopping the drive motor based on the various detection signals from the switches 40, 42 and 50 described above. This control pattern is shown in FIGS. In FIG. 7, when there is a sheet ((a), (b), (c)), the time until the motor stops is compared on the assumption that the same number of transfer sheets 15 are placed.

  First, when each switch operates normally (normal state), when the paper feed cassette is mounted with the transfer paper 15 placed on the transfer paper placing plate 10, as shown in FIG. Thus, at the same time when the paper feed cassette 1 is mounted, the motor is driven (motor ON), and the transfer paper placing plate 10 is raised by the rotation of the lift plate 9.

  As the transfer paper stacking plate 10 is raised, the transfer paper detection switch 40 detects the presence of the transfer paper 15 (switch ON). Further, when the transfer paper placing plate 10 is raised, the placed transfer paper 15 comes into contact with the pickup roller 20 and the pickup roller 20 is lifted. When the pickup roller 20 is lifted up to a predetermined position, as described above, the upper limit detection switch 42 is turned on, the drive of the motor is stopped based on the detection signal (motor OFF), and the transfer paper placing plate 10 is raised. Stops. The time from the start of driving of the motor to the stop at this time is Ta. The time from when the transfer paper detection switch 40 is turned on until the motor is stopped is T1.

  In the above case, when the transfer paper 15 is consumed by image formation, the pickup roller 20 is lowered by its own weight, the upper limit detection switch 42 is turned off again, the motor is driven again, and the upper limit detection switch 42 is turned on. The transfer paper placing plate 10 is raised until it becomes. When the transfer paper 15 runs out, the transfer paper detection switch 40 is turned off, and a message to that effect is displayed on the operation panel of the image forming apparatus, and replenishment of the transfer paper 15 is requested.

  In addition, when each switch operates normally (normal state), when the paper feed cassette is mounted without placing the transfer paper 15 on the transfer paper placing plate 10, as shown in FIG. In addition, the upper limit detection switch 42 detects the upper limit position of the pickup roller 20 while the transfer sheet detection switch 40 remains OFF (switch ON), and the driving of the motor is stopped based on the detection signal (motor OFF). In this case, since the transfer paper detection switch 42 remains OFF, after the predetermined time has elapsed, a display indicating no paper is displayed on the operation panel. At this time, the time from the start to stop of the motor is Tb, and since there is no transfer paper 15, Ta <Tb.

  On the other hand, when the upper limit detection switch 42 does not operate due to a failure or the like, when the paper feed cassette is mounted with the transfer paper 15 placed on the lift plate 10, as shown in FIG. The detection switch 42 remains OFF, and after a predetermined time has elapsed since the transfer paper detection switch 40 was turned ON, the driving of the motor is stopped and the transfer paper placing plate 10 is prevented from rising. At this time, the time from the start to stop of the motor is Tc, and usually Ta <Tc. At this time, the time from when the transfer paper detection switch 40 is turned on until the motor is stopped is T2, and T1 <T2.

  Furthermore, when the upper limit detection switch 42 does not operate due to a failure or the like, when the paper feed cassette is mounted without the transfer paper 15 being placed on the transfer paper placement plate 10, as shown in FIG. Both the transfer paper detection switch 40 and the upper limit detection switch 42 remain OFF. Accordingly, in this case, the rotational angular velocity detection switch 50 described above detects that the rotational angular velocity of the motor shaft has become substantially zero, stops the driving of the motor by the detection signal, and the transfer paper placing plate Stop climbing 10

  That is, when the transfer paper placing plate 10 is raised by driving the motor, the pickup roller 20 is lifted to a position where it cannot be raised. Therefore, in this state, a load is applied to the motor shaft or the pickup roller 20. In the present invention, such a state is immediately detected and the driving of the motor is stopped.

  For example, when the driving of the motor is stopped in this way, it is the time Td from the start of the driving of the motor to the stop, and Tb <Td. On the other hand, in such a case, according to a conventionally known technique, the driving of the motor is stopped when a predetermined time Te is exceeded from the start of the driving of the motor. Therefore, it is considerably long, and Td <Te as shown in FIG. That is, in the present invention, it is possible to stop the driving of the motor more quickly than in the prior art, and to reduce the load applied to the motor shaft and the pickup roller 20.

  Further, when both the upper limit detection switch 42 and the transfer paper detection switch 40 break down and the paper feed cassette is loaded with the transfer paper 15 placed thereon, as shown in FIG. Both the detection switch 40 and the upper limit detection switch 42 remain OFF, and the rotational angular velocity detection switch 50 confirms that the rotational angular velocity of the motor shaft has become substantially zero as in the case of FIG. Detection is performed, the drive of the motor is stopped by the detection signal, and the rising of the transfer paper placing plate 10 is stopped. The time Tf from the start to the stop of the motor at this time is faster than that in the case of FIG. 7D by the amount of the transfer paper 15, and Tf <Td. It is much shorter than the time Te in the known technique (Tf <Td <Te).

  As described above, according to the present invention, even when neither the transfer sheet detection switch 40 nor the upper limit detection switch 42 operates due to a failure or the like, the drive of the motor is quickly stopped, and the load applied to the drive motor or the pickup roller 20 Can be reduced, and damage to the apparatus can be effectively avoided.

  In the description of FIG. 7 described above, when the transfer sheet 15 exists, the upper limit detection switch 42 is activated after the transfer sheet detection switch 40 detects the transfer sheet. For example, it is possible to set the timing at which the transfer sheet detection switch 40 operates (switch ON) at the same time or after the detection by the upper limit detection switch 42.

FIG. 3 is a diagram illustrating a schematic structure of a sheet feeding device according to the present invention. FIG. 3 is a schematic perspective view of a paper feed cassette used in the present invention. FIG. 3 is a perspective view showing a state where a transfer paper placement plate is removed from the paper feed cassette of FIG. 2. FIG. 3 is a perspective view showing a transfer paper placement plate incorporated in the paper feed cassette of FIG. 2. FIG. 2 is a diagram illustrating an arrangement of transfer sheet detection switches provided in the sheet feeding device of FIG. 1. The figure which shows an example of the structure of the rotation angular velocity detection means used for this invention. The figure which shows the control pattern of the transfer paper mounting board in this invention.

Explanation of symbols

1: Feed cassette 8: Rotating shaft 9: Drive rotating piece 10: Lift plate 12: Long hole 20: Pickup roller 40: Transfer paper detection switch 32: Upper limit detection switch

Claims (2)

Transfer paper placing plate for placing the transfer paper;
Paper feeding unit for supplying transfer paper to the image forming unit;
A transfer paper placement plate driving means for lifting the transfer paper placed on the transfer paper placement plate to the paper feed unit;
An upper limit detection means for detecting the transfer paper placement plate or the upper end position of the transfer paper placed on the transfer paper placement plate in accordance with the lifting operation of the transfer paper placement plate;
A transfer paper detection means for detecting the presence or absence of the transfer paper placed on the transfer paper placement board in accordance with the lifting operation of the transfer paper placement board;
Rotational angular velocity detection means for detecting a change in rotational angular velocity of the drive means;
Stop control means for controlling the timing of stopping the operation of the drive means based on the respective detection signals from the upper limit detection means, the transfer paper detection means and the rotational angular velocity detection means;
A paper feeding device comprising: 2. The stop control unit operates in any of the following (a) to (c) after the transfer paper placing plate lifting operation is started, and stops the operation of the drive unit. Paper feeder:
(A) When the upper limit detecting means detects the upper end position of the transfer paper placing plate or the transfer paper placed on the transfer paper placing plate and generates a detection signal;
(B) The transfer paper detecting means detects the presence of the transfer paper placed on the transfer paper placing plate and issues a detection signal, and the detection signal from the upper limit detection means is not issued. When a predetermined time has elapsed since the detection signal was transmitted from the transfer paper detection means;
(C) None of the transfer paper detection means and the upper limit detection means generates a detection signal, and the rotation angular speed detection means detects that the rotation angular speed of the transfer paper placing plate driving means has become substantially zero. When a detection signal is issued.

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