JP2001039553A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly feed recording paper loaded on a cassette by detecting size of the recording paper in a recording paper loading means, and controlling rotation of a paper feeding roller to be increased when a signal indicating that a predetermined size of recording paper is loaded is received. SOLUTION: When a copy start button is pushed, a paper existing sensor 10 confirms existence of recording paper in a cassette. When the recording paper exists, a cassette size detecting sensor 11 determines whether the recording paper of a predetermined size such as B5 size is set. When the determination is YES, a stepping motor 21 is rotated at a relatively high speed. After the motor rotation becomes stable, a paper feeding solenoid 24 is excited, and rotation of a paper feeding roller starts a pick up operation. When a size other than B5 is detected, the stepping motor 21 is rotated at a relatively low speed, and after a predetermined period the paper feeding solenoid 24 is operated to start the pick up operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly to a recording apparatus which separates recording paper one by one and feeds the recording paper to an image forming section along a curved conveyance guide. The present invention relates to motor control of a paper separating and feeding device.

[0002]

2. Description of the Related Art A conventional image forming apparatus such as a copying machine or a printer includes a cassette having a middle plate on which recording paper is loaded and a spring for urging the middle plate in a direction of constantly pushing up the recording paper. At the time of feeding, it has a half-moon-shaped feed roller which is separated from the uppermost recording sheet pushed up by the middle plate and comes into contact with the recording sheet when feeding the recording sheet. In such a conventional image forming apparatus, the pick-up operation, the paper feed / separation operation, and the transport operation of the recording paper are performed at a constant speed for all recording paper sizes. Also, in the image forming apparatus, if the pressure of the spring for urging the middle plate is too strong, when the recording paper is pulled out from the cassette, the removal of the claw from the separation claw becomes worse, and the paper feeding performance is reduced and the skew is increased. Occurs. For this reason, the cassette of the conventional image forming apparatus is configured so that the spring pressure can be switched in two stages, that is, large-size recording paper (A4, A4, B4, B5) and small-size recording paper (A4R, B5R). ), The pressure of the spring can be switched.

[0003]

However, the conventional method of switching the spring pressure in two stages cannot deal with recording papers of all sizes in detail.
When a medium-sized recording sheet classified as a large-sized recording sheet, for example, a B5 recording sheet is fed, the spring pressure becomes too high, the sheet feeding performance is reduced, and skew, leading edge breakage, and heavy weight occur. Sending and jams occurred. Further, when the amount of paper loaded on the cassette (the number of papers loaded) is large, there is a problem that the spring pressure becomes too high, and the paper feeding performance is reduced.

[0004] The present invention has been made based on the above circumstances, and has as its object to provide an image forming apparatus capable of reliably feeding recording paper loaded on a cassette.

[0005]

In order to achieve the above object, an image forming apparatus according to the present invention comprises a recording sheet loading means having a push-up mechanism for constantly pushing up an intermediate plate on which a plurality of recording sheets are loaded. An image forming apparatus comprising: a paper feed unit having a paper feed roller for sequentially feeding the recording paper stacked on the recording paper stacking unit; and a rotary drive unit for driving the paper feed unit. Size detecting means for detecting the size of the recording paper, and control for speeding up the rotation of the paper feed roller when receiving a signal indicating that recording paper of a predetermined size is loaded from the size detecting means. And control means for performing the control.

Further, the image forming apparatus according to the present invention has a recording paper loading means having a push-up mechanism for constantly pushing up an intermediate plate on which a plurality of recording papers are loaded, and a recording paper loaded on the recording paper loading means. In an image forming apparatus including a paper feeding unit having a paper feeding roller for sequentially feeding paper, and a rotation driving unit for driving the paper feeding unit, a stacking unit that detects a stacking amount of recording paper stacked on the recording paper stacking unit. An amount detection unit, and a control unit that controls the rotation of the paper feed roller to be faster when a signal indicating that a predetermined amount of recording paper is stacked is received from the stack amount detection unit. It is characterized by the following.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Configuration of First Embodiment]
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a paper feeding device in a copying machine according to a first embodiment of the present invention, FIG. 2 is a schematic perspective view showing a cassette of the paper feeding device, and FIG. FIG. 4 is a diagram for explaining the operation of the sheet feeding roller, and FIG. 4A is a diagram showing a state before the sheet feeding operation by the sheet feeding roller is started, and FIG. FIG. 4 is a diagram showing a state at the moment when the paper feed roller contacts the recording paper, and FIG. 4C is a diagram showing a state where the paper feed roller feeds the recording paper. As shown in FIG. 1, the sheet feeding device according to the first embodiment includes an outer box 100, a sheet feeding roller 1 formed in a substantially half-moon shape, and a pair of rollers 2 and 3.
And a separation / conveyance unit 4 for feeding only one sheet of recording paper fed by the paper feed roller 1 to a conveyance unit (not shown) of the copying machine body, and a cassette 5 for stacking and holding a plurality of recording sheets.
And a paper feed sensor 15 that detects a recording paper fed from the separation / conveyance unit 4 by the paper feed roller 1 and generates a signal. The other parts such as the image forming unit are well-known technologies, and therefore, detailed description thereof will be omitted to simplify the description.

As shown in FIG. 2, the cassette 5 has an intermediate plate 501 on which recording paper is placed, separation claws 503 and 503 for separating recording paper being conveyed from other recording paper, and a conveying direction of the recording paper. And a side regulating plate 504 for regulating the conveyance of the recording paper in a direction orthogonal to the feeding direction. One end of the middle plate 501 in the longitudinal direction is rotatably supported, and the other end is pushed up by a spring 502 to push up the stacked recording papers toward the half-moon-shaped paper feed roller 1. The separation claw 503 is configured to regulate the stacking height of the recording paper and to allow the recording paper to pass above the separation claw when the recording paper is sent out to the separation conveyance unit by the paper feed roller.

As shown in FIGS. 3 and 4, the paper feed roller 1 is arranged so as to face upward so that the arc portion 1b does not come into contact with the recording paper during standby. Also,
The arc portion 1b of the paper feed roller has an arc length such that the recording paper can be sent to the separation / conveyance portion 4 in one rotation (or n rotations). In the following embodiment, it is assumed that the arc length is formed so that the recording paper is fed to the separation / conveyance unit every time the paper feed roller makes one rotation. As shown in FIG. 3, the shaft 1a of the feed roller 1 has a toothless portion 23a.
A toothless gear 23 having a toothed portion 23b is attached.

FIG. 5 is a block diagram of a control unit according to this embodiment. As shown in FIG. 5, the control unit according to the present embodiment controls the entire copier by reading and executing a control program from the ROM 14 in which a control program or the like defining a paper feeding procedure described later is stored. And a RAM 13 in which various data are stored. Also, C
The PU 7 has a motor driver 8 for driving a stepping motor 21 for conveying the recording paper via an I / O (not shown), an operation unit 9 for performing various settings, and a recording paper in a mounted cassette. A paper presence sensor 10 for detecting whether or not the paper is loaded, a cassette size detection sensor 11 for detecting the paper size of the loaded cassette, a paper feed sensor 15 for detecting whether or not paper feeding is normally performed; And a paper feed solenoid 24 for controlling start and end of the paper operation.
Note that, in FIG. 5, only a portion related to the present embodiment is displayed, and other image forming units and the like are omitted.

When the motor driver 8 drives the stepping motor 21 in response to an instruction from the CPU 7, as shown in FIG.
The driving force is transmitted to the motor. The rotary cam 2 with which the lever 24a of the paper feeding solenoid 24 is engaged and disengaged coaxially with the toothless gear 23.
9 are attached. The rotary cam 29 is pulled by a spring 25 in the direction of the arrow L25 shown. That is, when the paper feed roller 1 is in a standby state in which the arc portion 1b is facing upward, it is receiving a force in the rotation direction for feeding paper by the spring 25, but the lever portion 24a of the paper feed solenoid 24 is rotated by the rotary cam. It is engaged with the engaging portion 29a of 29 to prevent its rotation. In this state, the toothless gear 23
The toothless portion 23a has a positional relationship normally facing the gear 22 on the drive source side, and the driving force is not transmitted.

The paper feed operation is started by the CPU 7 operating (turning on / off) the paper feed solenoid 24. When the paper feeding solenoid 24 operates, the lever portion 24a
Is disengaged from the engaging portion 29a of the rotating cam 29, and the gear 2
The toothless gear 23 is rotated by the spring 25 to the point where the gear 2 and the toothed portion 23b mesh with each other. Then, the missing gear 23
Is driven to rotate by a gear 22, whereby the paper feed roller 1 rotates, and a paper feed operation is performed. When the sheet feeding roller makes one rotation, the lever 24a and the engaging portion 29a are engaged again, thereby preventing the rotation of the toothless gear 23 and stopping the sheet feeding operation.

Next, the middle plate spring pressure for urging the middle plate of the cassette in the pushing direction will be described. A spring 502 for urging the middle plate in a direction to push the middle plate upward, a spring 50
An auxiliary spring (not shown) is provided to urge the middle plate upward in the same manner as in the second embodiment. Middle plate spring pressure is spring 5
02 and the spring 50
2 and a second spring pressure urged by the auxiliary spring. In the present embodiment, when a large-sized recording paper (A3, B4, A4, B5) is set in the cassette, the middle plate is urged by the spring 502 and the auxiliary spring to increase the middle plate spring pressure. Second
And a small-size recording paper (A4R, B
When 5R) is set, in order to reduce the middle plate spring pressure, the middle plate spring pressure is automatically switched so as to be the first spring pressure f1 for urging the middle plate with only the spring 502. Since this switching mechanism is a known technique,
Detailed description is omitted.

FIG. 6 is a diagram for explaining the paper feed pressure applied to the paper feed roller. The middle plate spring pressure f is applied to the middle plate by the spring.
The middle plate spring pressure f acts to rotate the middle plate counterclockwise, and the weight (loading amount) of the recording paper.
Acts to rotate the middle plate clockwise. Therefore, the paper feed pressure P, which is the force for pushing up the paper feed roller,
Is a value corresponding to the middle plate spring pressure f and the amount of recording paper loaded Mg. In FIG. 1, the force with which the paper feed roller 1 pulls out the recording paper from the separation claw is referred to as a paper feed conveyance force F.

FIG. 7 is a diagram showing the relationship between the loading amount (loading number) for each size of recording paper and the middle plate spring pressure in a copying machine having the above-mentioned switching mechanism. As is clear from FIG. 7, especially in the case of B5 size recording paper, if the number of stacked sheets is large, the switching mechanism alone cannot sufficiently reduce the middle plate spring pressure. The pressure increases, the paper feeding performance decreases, and skewing, double feeding, and the like occur.
In the configuration of the present embodiment, the middle plate spring pressure is 3
It is desirable to be within the range of 00 to 600 gf.

In the present embodiment, when a recording sheet of B5 size is fed, as described below, the sheet feeding force F when the sheet feeding roller picks up the recording sheet is reduced so that the middle plate can be fed. Control for lowering the spring pressure (that is, the paper feed pressure) is performed. As a result, it is possible to improve the paper feeding performance when feeding B5 size recording paper, and to prevent skew or double feeding.

Next, the operation when the paper feed roller 1 rotates to pick up a B5 size recording sheet will be described. FIG. 4A shows a state in which the paper feed roller is not in contact with the recording paper. The position of the upper end surface of the recording paper at this time is set as a reference position. Further, a position lower by h than this reference position is a target position in a sheet feeding state by the sheet feeding roller. When the paper feeding solenoid 24 is operated and the paper feeding operation is started, the paper feeding roller 1 vigorously comes into contact with the upper end surface of the recording paper in the cassette. The sinking amount from the position is H
Becomes At this time, as shown in FIG. 4B and FIG. 6, the stacked recording papers fall downward together with the middle plate 501 and the separation claw 503, and the middle plate spring pressure f is applied to the middle plate, so that the sheet feeding pressure P Is obtained. Instantaneous sinking amount H generated at this time
Is a value corresponding to the rotation speed of the paper feed roller 1 and the pushing force of the spring 502 pushing up the middle plate 501 in the cassette 5. FIG. 8 is a diagram showing the characteristics of the amount of sinking of the middle plate in the present embodiment. As shown in FIG. 8, the sinking amount once overshoots to H, and thereafter,
As shown in (c), the target paper feed pressure converges to the sinking amount h that can be obtained. Further, assuming that the spring pressure is constant, the sinking amount H increases as the rotation speed of the feed roller 1 increases, and the sinking amount H decreases as the rotation speed decreases. Then, as the sinking amount becomes larger, the paper feeding pressure becomes smaller and the paper feeding force by the paper feeding roller becomes smaller. vice versa,
The smaller the sinking amount is, the larger the paper feeding pressure is, and the larger the paper feeding force by the paper feeding roller is. In the present embodiment, the size of the recording paper set in the cassette is detected, and when the size of the recording paper is B5, in order to reduce the excessively high paper pressure to the paper feeding roller 1, the driving time of the paper feeding roller is reduced. By increasing the rotation speed compared to the rotation speed when driving other recording paper sizes and using the above phenomenon,
Optimum paper feed pressure is obtained.

FIG. 9 is a diagram showing a time chart of the rotation speed of the motor in the sheet feeding operation of the present embodiment.
In the conventional method, when the cassette size detection sensor 11 issues a signal indicating that the B5 size recording paper is set in the cassette, the CPU 7 generates a drive pulse at the time of driving the motor similarly to the other size recording paper. At 350 PPS, the paper feed roller is driven to rotate. Therefore, as described above, the conventional method has a problem that the paper feeding pressure is too high and the paper feeding performance is reduced. On the other hand, in the present embodiment, when the cassette size detection sensor 11 issues a signal indicating that B5 size recording paper is set in the cassette, the CPU 7
Increases the driving pulse at the time of driving the motor to about 700 PPS, and drives the paper feed roller to rotate. As a result, the sinking amount H when the paper feed roller comes into contact with the recording paper becomes larger than in the conventional method, and the paper feed pressure becomes smaller. As a result, it is possible to improve the paper feeding performance when picking up the B5 size recording paper, and it is possible to suppress the occurrence of skewing, breakage of the leading edge, double feeding, jam, and the like. The value of the drive pulse is not limited to 700 PPS, but can be set to an optimum value according to the manufacturer and model of the copying machine.

[Operation of the First Embodiment] FIG. 10 is a flowchart of the present embodiment. When the copy start button is pressed, this flow is executed. In step S111, it is checked whether or not there is recording paper in the cassette. If there is a recording sheet in the cassette, the process proceeds to step S112, and the cassette size detection sensor determines whether B5 size recording sheet is set in the cassette. Step S112
When it is determined that the recording paper set in the cassette is B5 size, the process proceeds to step S113.
The stepping motor 21 is driven by a drive pulse of about 700 PPS. In step S114, a no-load operation of the stepping motor is performed. In order to wait for the rotation of the motor to stabilize, set a timer (not shown) for a predetermined time (about 0.5 seconds).
To check that the time has gone up. If it is confirmed in step S114 that the timer has expired, the flow shifts to step S115 to operate the sheet feeding solenoid. As a result, the paper feed roller rotates to start the pickup operation. In step S116, it is checked whether the paper feed sensor 15 has been turned on. If the recording paper is normally fed to the separation / conveyance unit, the paper feed sensor 15 is turned on. If the paper feed sensor 15 is on, the process proceeds to step S117 to check whether the paper feed sensor 15 has been turned off. If the recording paper normally passes through the separation conveyance section, the paper feed sensor is turned off. Step S
If the paper feed sensor is turned off in the determination of step 117, the drive of the stepping motor is stopped (step S11).
8), this process ends.

On the other hand, if it is determined in step S112 that the cassette size detection sensor detects a size other than B5, the process proceeds to step S119, and the stepping motor 21 is driven by a drive pulse of about 350 PPS.
In step S120, a no-load operation of the stepping motor is performed. In order to wait for the rotation of the motor to stabilize, the timer is set to a predetermined time (about 0.5 seconds), and it is confirmed that the time has elapsed. When it is confirmed in step S120 that the timer has expired, the flow proceeds to step S121 to operate the sheet feeding solenoid. As a result, the paper feed roller rotates to start the pickup operation. In step S122, it is checked whether the paper feed sensor 15 has been turned on. When the paper feed sensor is turned on, the process proceeds to step S123, and the drive pulse is slowed up to about 700 PPS. This is because the paper feed speed on the main body side is about 700 PPS, which is adjusted to this.
After that, the processing shifts to step S117 to perform the above-described processing. Although not shown, Step S116, Step S116
If the paper feed sensor is not turned on or off within a predetermined period of time in the processing of step 117 and step S122, it means that an abnormality has occurred in the paper feed, so that processing such as issuing an alarm (not shown) )I do.

[Second Embodiment] Next, a second embodiment of the present invention will be described. FIG. 11 is a block diagram of a control unit according to the second embodiment, and FIG. 12 is a diagram for describing a load amount detection sensor according to the present embodiment. The second embodiment is different from the first embodiment in that a load detection sensor 18 is provided. Other configurations are the same as those of the first embodiment.
Components having the same functions as those in the first embodiment are given the same reference numerals or corresponding reference numerals, and detailed descriptions thereof will be omitted.

The middle plate 5010 of the cassette of this embodiment is
It has a lever portion 5010a formed in a substantially flag shape. An opening 5011 is formed in the cassette case so that the tip of the lever portion 5010a can protrude outside the case and move up and down. Other configurations of the cassette are the same as those of the first embodiment. Further, the load detection sensor 18 of the present embodiment is a transmission type photo interrupter that detects an object passing between the light emitting element and the light receiving element, and when the lever 5010a of the middle plate is in the load detection sensor, When this is detected, a signal is issued to the CPU 7. In the present embodiment, when less than about half of the recording paper is loaded in a cassette capable of loading 500 sheets when fully loaded, the loading amount detection sensor is turned off, and
When about 250 or more and 500 sheets of recording paper are loaded on the cassette, the loading amount detection sensor is set to be turned on. As can be seen from FIG. 7, for paper sizes other than the paper size (A3, A4R) set as a reference, the middle plate spring pressure tends to increase when the stacking amount becomes 250 sheets or more. Therefore, when the stacking amount is set to about 250 sheets or more, the rotation speed at the time of driving the paper feed roller is increased in order to reduce the paper feed pressure that is too high for the paper feed roller. As a result, the sinking amount H when the paper feed roller comes into contact with the recording paper increases, and therefore the paper feed pressure decreases. As a result, even when the stacking amount is large, it is possible to improve the paper feeding performance when picking up the recording paper. As in the first embodiment, it is possible to improve the skew, the broken edge, the double feed, the jam, etc. Occurrence can be suppressed.

FIG. 13 is a flowchart of the second embodiment. When the copy start button is pressed, this flow is executed. In step S211, it is checked whether there is a recording sheet in the cassette. If there is a recording sheet in the cassette, the flow shifts to step S212 to determine whether or not the loading amount detection sensor has been turned on. If 250 or more sheets of recording paper are set in the cassette, the loading amount detection sensor is turned on, and the process proceeds to step S213 to drive the stepping motor 21 with a drive pulse of about 700 PPS. In step S214, the no-load operation of the stepping motor is performed. In order to wait for the rotation of the motor to stabilize, a timer (not shown) is set to a predetermined time (about 0.5 seconds), and it is confirmed that the time has elapsed. Step S21
After confirming that the timer has timed out in step 4, the process proceeds to step S215 to operate the sheet feeding solenoid.
As a result, the paper feed roller rotates to start the pickup operation. In step S216, it is checked whether the paper feed sensor 15 has been turned on. If the recording paper is normally fed to the separation / conveyance unit, the paper feed sensor 15 is turned on. If the paper feed sensor 15 is on, the process proceeds to step S217 to check whether the paper feed sensor 15 has been turned off. If the recording paper normally passes through the separation conveyance section, the paper feed sensor is turned off. If it is determined in step S217 that the sheet feeding sensor is in the OFF state, the driving of the stepping motor is stopped (step S218), and the process ends.

On the other hand, if it is determined in step S212 that the number of recording sheets set in the cassette is less than 250, the process proceeds to step S219, and the stepping motor 21 is driven by a drive pulse of about 350 PPS. In step S220, a no-load operation of the stepping motor is performed. In order to wait for the rotation of the motor to stabilize, the timer is set to a predetermined time (about 0.5 seconds), and it is confirmed that the time has elapsed. When it is confirmed in step S220 that the timer has expired, the flow proceeds to step S221 to operate the sheet feeding solenoid. As a result, the paper feed roller rotates to start the pickup operation. Step S
At 222, it is determined whether or not the paper feed sensor 15 has been turned on. If the paper feed sensor is turned on, the process proceeds to step S223, where the drive pulse is slowed up to about 700 PPS. This means that the paper feed speed on the main unit side is about 7
Because it is 00 PPS, it is in order to match this. After that, the process shifts to step S217 to perform the above-described processing. Although not shown, step S216, step S216
If the paper feed sensor is not turned on or off within a predetermined time in the processing of step 217 and step S222, it means that an abnormality has occurred in the paper feed, and a processing such as issuing an alarm (not shown) )I do.

[Third Embodiment] Next, a third embodiment of the present invention will be described. The third embodiment is different from the above embodiments in that the present embodiment controls the feeding of the recording paper based on signals from both the cassette size detection sensor 11 and the load amount detection sensor 18. is there. Other configurations are the same as those of the first embodiment and the second embodiment. Therefore, detailed descriptions of the schematic diagram of the cassette and the block diagram of the control unit are omitted.

FIG. 14 is a flowchart of this embodiment. When the copy start button is pressed, this flow is executed. In step S311, it is checked whether there is any recording paper in the cassette. If there is recording paper in the cassette, the process proceeds to step S312, where the cassette size detection sensor detects that B5 recording paper has been set in the cassette, and
Alternatively, it is determined whether or not the load detection sensor is turned on.
If 250 or more recording sheets of B5 have been set in the cassette, the process proceeds to step S313, and the stepping motor 21 is driven by a driving pulse of about 700 PPS. In step S314, a no-load operation of the stepping motor is performed. In order to wait for the rotation of the motor to stabilize, a timer (not shown) is set to a predetermined time (about 0.5 seconds), and it is confirmed that the time has elapsed. If it is confirmed in step S314 that the timer has expired, the flow shifts to step S315 to operate the sheet feeding solenoid. As a result, the paper feed roller rotates to start the pickup operation. In step S316, the sheet feed sensor 1
It is checked whether or not 5 is turned on. If the recording paper is normally fed to the separation / conveyance unit, the paper feed sensor 15 is turned on. If the paper feed sensor 15 is on, the process proceeds to step S317 to check whether the paper feed sensor 15 has been turned off. If the recording paper normally passes through the separation conveyance section, the paper feed sensor is turned off. Step S3
If the paper feed sensor is turned off in the determination of 17, the driving of the stepping motor is stopped (step S318).
This processing ends.

On the other hand, if it is determined in step S312 that recording paper other than B5 is set in the cassette, or if the number of recording papers set in the cassette is less than 250, the process proceeds to step S319, and the stepping motor is started. 21 is driven by a drive pulse of about 350 PPS.
In step S320, a no-load operation of the stepping motor is performed. In order to wait for the rotation of the motor to stabilize, the timer is set to a predetermined time (about 0.5 seconds), and it is confirmed that the time has elapsed. When it is confirmed in step S320 that the timer has expired, the flow shifts to step S321 to operate the sheet feeding solenoid. As a result, the paper feed roller rotates to start the pickup operation. In step S322, it is checked whether the paper feed sensor 15 has been turned on. If the paper feed sensor is turned on, the process proceeds to step S323, and the drive pulse is slowed up to about 700 PPS. This is because the paper feed speed on the main body side is about 700 PPS, which is adjusted to this.
After that, the processing shifts to step S317 to perform the above-described processing. Although not shown, step S316 and step S316
If the paper feed sensor is not turned on or off within a predetermined time in the processing of step 317 and step S322, it means that an abnormality has occurred in the paper feed, and a processing such as issuing an alarm (not shown) )I do.

[Effects of the Embodiment] According to the first embodiment, when a B5-size recording sheet is set in the cassette, this is detected, and the drive pulse of the motor is increased to increase the power supply. Increase the rotation speed of the paper roller,
By reducing the sheet feeding pressure P, the sheet feeding performance can be improved, and occurrence of skewing, breakage of the leading edge, double feeding, jam, and the like can be suppressed.

According to the second embodiment, when about 250 or more sheets of recording paper set in the cassette are set, this is detected, and the drive pulse of the motor is increased to thereby increase the rotation of the sheet feeding roller. By increasing the speed and decreasing the sheet pressure P, the sheet feeding performance can be improved.
It is possible to suppress breakage of the tip edge, double feed, jam and the like.

According to the third embodiment, when B5 size recording paper is set in the cassette, or when about 250 or more recording papers are set in the cassette, this is detected and the motor drive pulse is detected. , The paper feed roller can be driven at a higher rotational speed, the paper feed pressure P can be reduced, and the paper feed performance can be improved. Can be suppressed.

[Other Embodiments] The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the invention. For example, in the first and third embodiments described above, a case has been described in which the rotation of the motor is controlled by detecting that a B5-size recording sheet has been set in the cassette. The present invention is not limited to this, and as is apparent from FIG. 7, it is also possible to detect the B4 or B5R recording paper and control the motor rotation speed. In this case, the driving pulse at the time of driving may be changed for each size. As a result, fine control of the paper feed roller is performed,
Paper feeding performance can be more reliably improved. Also,
In the second and third embodiments, the load capacity is about 250
Although the case where it is detected that the number is more than has been described,
The stacking amount may be detected in three or more stages, and the rotation of the feed roller during driving may be controlled according to the detected stacking amount. Thereby, the paper feeding performance can be further improved. Therefore, according to the present invention, by controlling the rotation speed at the time of driving the paper feed roller for each size and according to the stacking amount, the feeding can be more reliably performed according to the size and the stacking amount of the recording paper. Paper performance can be improved. Furthermore, in each of the embodiments described above, the case where the rotation drive unit is a stepping motor has been described. However, the present invention is not limited to this.
A motor such as a C brushless motor may be used.

[0032]

As described above, according to the present invention, it is possible to reduce the excessively high paper feed pressure by controlling the rotation speed of the paper feed roller at the time of driving, thereby improving the paper feed performance. Thus, it is possible to provide an image forming apparatus capable of suppressing the occurrence of skewing, breakage of the leading edge, double feed, jam, and the like.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a sheet feeding device according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view illustrating a cassette of the sheet feeding device according to the embodiment.

FIG. 3 is a schematic perspective view illustrating a configuration of a driving unit of the sheet feeding device according to the exemplary embodiment.

FIGS. 4A and 4B are diagrams illustrating a sheet feeding operation according to the present exemplary embodiment. FIG. 4A is a diagram illustrating a state before a sheet feeding operation is started by a sheet feeding roller, and FIG. FIG. 4C is a diagram illustrating a state at the moment of contact, and FIG. 4C is a diagram illustrating a state in which a paper feed roller feeds a recording paper.

FIG. 5 is a block diagram of a control unit according to the first embodiment.

FIG. 6 is a diagram for explaining a sheet feeding pressure applied to a sheet feeding roller.

FIG. 7 is a diagram illustrating a relationship between a stacking amount (stacking number) for each size of recording paper and a middle plate spring pressure in a copying machine having a switching mechanism.

FIG. 8 is a diagram showing the characteristics of the amount of sinking of the middle plate in the present embodiment.

FIG. 9 is a diagram illustrating the timing of a sheet feeding operation according to the present embodiment.

FIG. 10 is a flowchart of the first embodiment.

FIG. 11 is a block diagram of a control unit according to the second embodiment.

FIG. 12 is a diagram for explaining a load amount detection sensor according to a second embodiment.

FIG. 13 is a flowchart of the second embodiment.

FIG. 14 is a flowchart of the third embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 paper feed roller 1 a shaft 1 b arc section 4 separation / transport section 5 cassette 7 CPU 8 motor driver 9 operation section 10 paper presence sensor 11 cassette size detection sensor 13 RAM 14 ROM 15 paper feed sensor 18 loading amount detection sensor 21 stepping motor 24 feed Paper solenoid 501 Middle plate 503 Separating claw 502 Spring

Claims (3)

[Claims] 1. A recording paper stacking means having a push-up mechanism for constantly pushing up an intermediate plate on which a plurality of recording papers are stacked, and a paper feed roller for sequentially feeding the recording papers stacked on the recording paper stacking means. In an image forming apparatus including a paper supply unit and a rotation driving unit that drives the paper supply unit, a size detection unit that detects a size of the recording paper loaded on the recording paper loading unit, An image forming apparatus, comprising: a control unit for performing control to increase the rotation of the paper feed roller when receiving a signal indicating that recording paper of a predetermined size is stacked. 2. A recording paper stacking means having a push-up mechanism for constantly pushing up an intermediate plate on which a plurality of recording papers are stacked, and a paper feed roller for sequentially feeding the recording papers stacked on the recording paper stacking means. In an image forming apparatus including a paper feeding unit and a rotation driving unit that drives the paper feeding unit, a loading amount detection unit that detects a loading amount of recording paper loaded on the recording paper loading unit, and the loading amount detection An image forming apparatus provided with control means for performing control to increase the rotation of the paper feed roller when receiving a signal indicating that a predetermined amount of recording paper has been stacked from the means. 3. A loading amount detecting means for detecting a loading amount of the recording paper loaded on the recording paper loading means, wherein the control means receives a predetermined amount of recording paper from the loading amount detecting means. Receiving a signal indicating that the recording paper has been loaded, or receiving a signal indicating that recording paper of a predetermined size has been stacked from the size detection means, performing control to increase the rotation of the paper feed roller. The image forming apparatus according to claim 1, wherein: