JP2002274664A - Paper feeder and image forming apparatus having it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper feeder capable of reducing the maximum load of a driving source and an image forming apparatus having it. SOLUTION: In feeding a sheet, a sheet mounting block 3 is turned upward by an energizing means 4 to press sheets stacked on the sheet mounting block 3 to a sheet feeding means 2, so that the sheet is fed out by the sheet feeding means 2. After the sheet is fed, the sheet mounting block 3 is turned downward against the energizing force of the energizing means 4 by a moving means 5 fitted to a driving shaft 10 rotated by the driving source 1 to separate the sheet from the sheet feeding means 2. The load of the driving source 1 for driving the sheet feeding means 2 is reduced by an assisting means adapted to accumulate elastic energy when the sheet mounting block 3 is turned upward by the energizing means 4 and release the elastic energy when the sheet mounting block 3 is lowered by the moving means 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeder and an image forming apparatus provided with the same, and more particularly to a configuration for reducing a load on a driving source for driving the paper feeder.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus such as a copying machine, a laser printer, a facsimile or the like usually has a paper feeding device for feeding a sheet to an image forming section. FIG.
FIG. 2 is a diagram showing a configuration of an image forming apparatus using such a sheet feeding device and using a conventional electrophotographic process.

In FIG. 1, reference numeral 100 denotes an image forming apparatus;
Reference numeral 00A denotes an image forming apparatus main body (hereinafter, referred to as an apparatus main body).
And a sheet feeding device 100C for feeding the sheet P to the image forming unit 100B.

The image forming unit 100B includes a photosensitive drum 201 and a charging roller 20 for charging the surface of the photosensitive drum.
2. Transfer the electrostatic latent image formed on the photosensitive drum to the toner container 2
07, a developing sleeve 205 for forming a toner image on the photosensitive drum by developing with the toner 206 and transferring the toner image to the sheet P, the toner remaining on the photosensitive drum is removed, and the waste toner container 210 is removed. A process cartridge 200 having a cleaning blade 209 to be housed therein, and a transfer roller 208 which presses against the photosensitive drum 201 and forms a transfer portion for transferring a toner image onto the sheet P
And a laser exposure device 203 for forming an electrostatic latent image on the photosensitive drum.

[0005] Further, a sheet feeding device 100C includes a sheet feeding tray 103A for storing sheets P, and a sheet feeding tray 103A.
Roller 102 for feeding out the sheet P stored in the
And the sheet P sent out by the feed roller 102
And a separation pad 115 for separating the sheets one by one.

The image forming apparatus 1 having such a configuration
In 00, when an image is formed on the sheet P, the photosensitive drum 201 is first rotated in the direction of the arrow, and a charging voltage is supplied from the high voltage power supply 216 to the charging roller 202 to uniformly charge the surface of the photosensitive drum. Next, the laser beam L emitted from the laser exposure device 203 is reflected by the reflection mirror 2.
The light is reflected on the photosensitive drum 201 and irradiated on the photosensitive drum 201 to form an electrostatic latent image on the photosensitive drum.

Next, the developing sleeve 205 is rotated, and with the rotation of the developing sleeve 205, the toner 206 filled in the toner container 207 is charged and supplied onto the photosensitive drum. Thereby, the toner 20 on the developing sleeve is
6 adheres to the electrostatic latent image on the photosensitive drum 201, and as a result,
The latent image is developed and visualized as a toner image.

Further, in parallel with such a toner image forming operation, the paper feed roller 102 is rotated to rotate the paper feed tray 103A.
The sheet P stored in the image forming unit 100 </ b> B is sent out by the separation pad 115 pressed by the paper feed roller 102, and then separated by the transport roller 113 and the registration roller pair 120. Feed to The friction coefficient of the surface of the separation pad 115, the contact angle with the paper feed roller 102, and the shape of the separation pad 115 are adjusted so that only the uppermost sheet P1 is fed each time the sheet P is fed.

Then, after the sheet P is fed to the transfer section, a voltage having a polarity opposite to that of the toner image is applied to the transfer roller 208, so that the toner image is applied to the sheet P fed to the transfer section. Transcribe

Next, the sheet P on which the toner image has been transferred as described above is conveyed to a fixing device 211 having a pressure roller 211a and a heating roller 211b. The image is permanently fixed on the sheet. After the toner image is fixed in this way, the sheet P is reversed through the rear of the fixing unit, and is discharged to the upper portion of the apparatus main body by the discharge roller 212.

After the transfer of the toner image, the toner remaining on the photosensitive drum 201 is removed by the cleaning blade 20.
9 and is stored in the waste toner container 210. Then, the photosensitive drum 201 whose surface has been cleaned as described above repeatedly enters the next image forming process.

The rollers such as the photosensitive drum 201, the feed roller 102, the transport roller 113, the pressure roller 211a, and the discharge roller 212 are driven by a motor (not shown). , And is driven by being branched and transmitted. Note that when the sheet feeding device 102 and the image forming apparatus 100 are separate bodies,
If the apparatus is large even if it is integrated, a motor that is a drive source may be provided on each of the paper feeding apparatus side and the image forming apparatus side in some cases.

FIG. 14 shows a conventional paper feeder 100C.
It is a perspective view which shows a structure of. In the figure, reference numeral 101 denotes a motor serving as a rotation drive source, and 103 denotes a sheet cassette 103A.
And a rotatable sheet stacking table 104 for stacking sheets, and a sheet stacking table 103 for pressing the sheets stacked on the sheet stacking table 103 against the sheet feeding roller 102.
Is a sheet stacking table spring for rotating the spring upward.

Reference numeral 105 denotes a sheet-loading table elevating cam capable of pushing down the sheet-loading table 103 against the spring force of the sheet-loading table spring 104, and 109 denotes a toothless portion 109a.
And a paper feed shaft 110 having a locking piece 109b provided on the side surface. Reference numeral 110 denotes a paper feed shaft on which the paper feed roller 102, the sheet loading / lowering cam 105, and the paper feed gear 109 are coaxially fixed. .

Reference numeral 111 denotes a drive gear to which rotational drive is transmitted from the motor 101 via a gear train (not shown);
Is a solenoid having an operating rod 112a, and 116 is a separation pad spring that pushes up a holder 115A holding the separation pad 115 at the upper end to press the separation pad 115 against the paper feed roller 102.

FIGS. 15 and 16 are a sectional view and a side view for explaining the operation of the conventional sheet feeding apparatus 100C. In the figure, the operations of the sheet feeding roller 102, the sheet stacking table 103, the sheet stacking table elevating cam 105, and the conveying roller 113 are illustrated in a left sectional view to facilitate understanding of the operation. The operations of the gear 109 and the solenoid 112 are shown in the right side view,
2, the fact that the sheet stacking table elevating cam 105 and the sheet feeding gear 109 are coaxially fixed to the sheet feeding shaft 110 is represented by a chain line.

FIG. 15A shows a state in which a sheet feeding operation is started. In this state, when a start signal is input to the sheet feeding device, the motor 101 rotates to rotate the conveying roller 113 and the driving gear 111. At this time, the sheet feeding gear 109 is operated by the operating rod of the solenoid 112. 112a
Is locked to the locking piece 109b, and the toothless portion 109a
Is at a position facing the drive gear 111 and is stopped. Therefore, the paper feed shaft 110 does not rotate. At this time, the sheet loading table lifting cam 105 has the sheet loading table 1
03 is pressed against the sheet stacking table spring 104 in the direction B in the figure.

Next, when a paper feed signal is input to the paper feeder, the solenoid 112 is energized and the operating rod 112a is sucked in the direction A in the drawing, whereby the locking of the locking piece 109b is released. Here, when the locking of the locking pieces 109b is released in this way, the sheet feeding table 109 pressed against the sheet loading table lifting cam 105 causes the sheet feeding gear 109 to move through the sheet loading table lifting cam 105. It rotates in the direction C shown in the drawing by receiving an initial rotational force, and comes into mesh with the drive gear 111.

Thus, continuous rotation drive transmission to the paper feed gear 109 is started. The sheet feeding gear 109, the sheet stacking table elevating cam 105, and the sheet feeding roller 102 rotate at the same speed because they are coaxially fixed on the sheet feeding shaft.

FIG. 2B is a diagram showing a state immediately after the sheet feeding shaft 110 starts rotating. The rotation of the sheet feeding gear 109 causes the sheet loading table lifting cam 105 to move away from the phase in which the sheet loading table 103 is pushed down. This shows a state that has transitioned to the phase.

Here, when the sheet loading platform lifting / lowering cam 105 transitions from the phase of pushing down the sheet loading platform 103 to the phase of separating the same, the sheet P loaded on the sheet loading platform 103 by the action of the sheet loading platform spring 104. Is pressed against the sheet feeding roller 102 in the direction D in the figure. In addition,
At this time, since the sheet stacking table spring 104 is only released from the compressed state, the motor 101 does not receive a large load.

FIG. 3C is a view showing a state in which the rotation of the paper feed shaft 110 progresses and the paper feed roller 102 feeds the sheet P. At this time, the uppermost sheet P1 is separated by only one sheet and sent to the conveying roller 113 by the action of the frictional conveying force of the sheet feeding roller 102 and the frictional force of the separation pad 115. At this time, the motor 101 A load corresponding to the conveying force by the load 102 is received.

In FIG. 16D, the rotation of the paper feed shaft 110 is further advanced, and the top sheet P1 is
It is a figure showing the state where it reached No. 3. At this time, the sheet stacking table elevating cam 105 is in a state of transition from the phase separated from the sheet stacking table 103 to the phase of pushing down the sheet stacking table 103.
2, the conveyance force by the paper feed roller 102 does not work. In this case, the motor 101 does not receive the load corresponding to the conveying force of the sheet feeding roller 102, but the motor 101 is opposed to the sheet loading table spring 104.
3 will be loaded.

FIG. 3E is a view showing a state in which the sheet stacking table 103 has been pressed down and the sheet feeding shaft 110 has made substantially one revolution. At this time, the missing tooth portion 109a of the paper feed gear 109 reaches the meshing portion with the drive gear 111, and is locked by the operating rod 112a of the solenoid 112 in a state where the rotation drive transmission is stopped. As a result, the paper feed gear 109 stops, and the paper feed roller 102 stops. Note that, even in this case, the rotation of the transport roller 113 is continued, and the sheet P1 is transported to the image forming apparatus (image forming unit).

By the way, as described above, the feeding gear 10
9 missing tooth portion 109a and operating rod 112 of solenoid 112
The feed shaft 110 rotates intermittently due to the action of a, but the load applied to the motor 101 from the start to the end of the rotation varies over time. In contrast, the transport roller 1
Since the rollers 13 and the rollers provided on the side of the image forming apparatus are continuously rotating, the motor 101 constantly receives a substantially constant load over time, although there is a slight increase or decrease depending on the presence or absence of a sheet.

Until now, after the lock by the operating rod 112a is released, the initial rotational force until the engagement starts is transferred from the sheet loading table 103 to the sheet feeding roller 103 via the sheet loading table lifting cam 105. 102 has been described, for example, Japanese Patent Application Laid-Open No. 08-19383.
An example in which a spring force is externally applied to a sheet feeding gear as in No. 0, and an example in which a sheet feeding gear is divided into two and a spring is provided therein as in JP-A-10-153247 have been put to practical use. .

By the way, in an image forming apparatus having such a sheet feeding device, particularly in a popular image forming device, the sheet feeding device and the image forming device share one drive source, and the drive of the shared drive source is performed. Is generally transmitted to a roller that conveys a sheet, such as the above-described sheet feeding roller, conveying roller, photosensitive drum, fixing roller, and sheet discharging roller via a gear train, and is rotated.

Therefore, in general, the load of the motor which is the driving source in the sheet feeding device and the image forming apparatus is generated only at the time of (A) the sheet feeding operation, and the temporary load disappears at the end of the sheet feeding operation. (B) Although there is a slight increase or decrease depending on the presence / absence of the sheet, it can be classified into two types: a steady load generated due to the constant rotation of the roller.

FIG. 17 schematically shows a temporal change of a load of a motor provided in such a conventional sheet feeding apparatus. The horizontal axis represents time, and the vertical axis represents load torque of the motor.

Then, (a) added on the horizontal axis,
(B), (c), (d), and (e) show (a),
(B), (c) and (d) and (e) of FIG. 16, and (A) added to the vertical axis is the above (A),
That is, (B) corresponds to the above-mentioned (B), that is, a stationary load.

Here, if the sheet feeding device and the image forming apparatus share a motor, the ratio of (B) increases, and if the sheet feeding device is provided with a dedicated motor, the ratio of (B) increases. Becomes smaller. The magnitude of the load P1 in the range (c) depends on the frictional conveyance force of the paper feed roller 102, and the magnitude of the load P2 in the range (d) is the load when the sheet loading table lifting cam 105 pushes down the sheet loading table 103. As described above.

[0032]

In such a conventional paper feeder and an image forming apparatus provided with the same, when the total load of the motor is as shown in FIG. 17, it is adjusted to the maximum load Pmax. Motor must be selected.

Here, when a stepping motor is used as the motor, since this stepping motor is driven by open-loop control, it is necessary to always output and drive a torque corresponding to the maximum load Pmax. When the motor is driven in this manner, surplus energy is generated as shown by a hatched portion Q in FIG.
Noise and vibration that are harmful to the paper feeder often occur.

Therefore, in the conventional sheet feeding device, the maximum load Pm
When ax is large, (1) a low output motor cannot be selected, and (2) when an attempt is made to output a high output with the same motor, it is necessary to drive with a high voltage and a large current. (3) When a motor driven by open loop control such as a stepping motor is used, noise or vibration due to excess torque is likely to occur.
This is a major technical problem in designing the drive system of the sheet feeding device and the image forming apparatus.

On the other hand, in recent years, with the spread of printers and facsimile machines, there is a strong demand in the market to increase the number of stacked paper feeders, and it is necessary to stack more sheets on the sheet stacking table 103 in order to respond to this. Here, in order to allow more sheets to be stacked on the sheet stacking table 103, the lifting width of the sheet stacking table 103 must be increased, and accordingly, the spring force of the sheet stacking table spring 104 is also increased. There is a need. In addition, there is a strong demand in the market to increase the printing speed. In order to respond to the demand, if the conveying speed is increased to maintain the same sheet feeding performance, it is necessary to increase the spring force of the sheet loading table spring 104 as well. .

In other words, it is necessary to increase the spring force of the sheet stacking base spring 104 whether the number of stacked sheets is to be increased or the speed of printing is to be increased. Here, as described above, the maximum load Pmax of the sheet feeding device is set against the sheet loading table 1 against the spring force of the sheet loading table spring 104.
Since the spring force is increased in this manner, the maximum load is further increased since the spring force is increased, and as a result, the problems (1) to (3) described above are further reduced. It will make it more serious. This means
This is a major problem that is an obstacle to improving the performance of the sheet feeding device and the image forming apparatus.

In the conventional example described above, an example is shown in which the separation pad 115 is constantly pressed against the paper feed roller 102. However, the separation pad 115 is always pressed against the paper feed roller 10.
2, the friction is always generated on the back surface of the sheet, so that the conveying force increases and the separation of paper dust adversely affects durability, reliability, and paper feeding accuracy and image quality. There were problems such as adverse effects.

Therefore, as a configuration for avoiding these problems, there has been proposed a sheet feeding device in which the separation pad is separated from the sheet feeding roller after the separation operation of the separation pad is completed.

FIG. 18 is a diagram showing another configuration of such a conventional sheet feeding device. In the drawing, reference numeral 303 denotes a sheet stacking table; 303a, an abutting portion provided on the lower surface of the sheet stacking table 303; 315, a separation pad; 315A, a holder holding the separation pad 315 at the upper end; This is the abutted part. For comparison, the position of the separation pad (holder) of the conventional example is indicated by a dotted line.

Here, in the sheet feeding device having such a configuration, after the separation operation of the separation pad 315 is completed, the separation pad 315 is separated from the sheet feeding roller 102 as shown in FIG. At the lowest point where the lifting / lowering cam 105 pushes down the sheet stacking table 303, the separation pad 315 is pushed down via the sheet stacking table 303 against the separation pad spring.

However, in such a configuration, the load for pushing down the sheet loading table 303 is the sum of the load of the sheet loading table spring and the load of the separation pad spring, which results in further increasing the maximum load. (1)-(3)
This will make the problem even more serious. This is a serious problem that becomes an obstacle in improving reliability and image quality by providing the sheet feeding device with a function of separating the separation pad from the sheet feeding roller.

Accordingly, the present invention has been made to solve such a conventional problem, and provides a paper feeder capable of reducing the maximum load of a driving source and an image forming apparatus having the same. It is intended to do so.

[0043]

SUMMARY OF THE INVENTION The present invention comprises a rotatable sheet loading table and sheet feeding means for feeding out a sheet, and when the sheet is fed, the sheet loading table is moved by an urging means. In the sheet feeding device configured to press the sheets stacked on the sheet stacking table against the sheet feeding unit, the sheet feeding unit is attached to a driving source that drives the sheet feeding unit and a driving shaft that is rotated by the driving source. Moving the sheet stacking table against the urging force of the urging means after feeding the sheet, and moving the sheet stacking table away from the sheet feeding means; and Storing elastic energy when moving by force means,
An assisting unit that releases the elastic energy to reduce the load on the driving source when the sheet stacking table is separated from the sheet feeding unit by the moving unit.

Further, according to the present invention, the assisting means includes a cam mounted on the drive shaft, an arm swingably supported by the apparatus body, and swinging with the rotation of the cam, and one end of the arm. An arm spring supported by the cam, when the sheet stacking table rotates upward, the cam swings the arm against the arm spring by the cam to store elastic energy in the arm spring, The cam is urged in a direction to reduce the load on the driving source via the arm by elastic energy released when the sheet stacking table rotates downward. is there.

Further, in the present invention, the driving source is a stepping motor.

Further, the present invention is characterized in that the direction in which the arm swings so as to store elastic energy in the arm spring is the same as the rotation direction of the cam.

The present invention is characterized in that the arm and the cam do not come into contact with each other when the drive shaft is not rotating.

Further, the present invention provides a separating member for contacting a sheet fed by the sheet feeding means and separating and feeding the sheets one by one, and a separating spring for pressing the separating member against the sheet feeding means. Wherein the sheet stacking table separates the separating member from the sheet feeding means against the separation spring when the sheet stacking table rotates downward. .

Further, the present invention is characterized in that the cam is integrally provided with a paper feed gear fixed to the drive shaft and transmitting the drive of the drive source to the drive shaft.

The present invention also supports a paper feed gear fixed to the drive shaft and transmitting the drive of the drive source to the drive shaft, a solenoid for intermittently rotating the paper feed gear, and the solenoid. A supporting member, and the arm is swingably supported by the supporting member and the apparatus main body,
Further, the arm and the solenoid are arranged so that a part thereof overlaps in a direction orthogonal to a sheet feeding direction.

According to the present invention, there is provided an image forming apparatus including an image forming unit and a sheet feeding device for feeding a sheet to the image forming unit, wherein the sheet feeding device is as described above. It is characterized by the following.

[0052]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view showing the configuration of a sheet feeding device according to the first embodiment of the present invention. This paper feeder is provided in, for example, the image forming apparatus as shown in FIG. 13 described above.

In FIG. 1, reference numeral 1 denotes a motor as a rotary drive source, 2 denotes a paper feed roller as sheet feeding means for feeding a sheet, and 3 denotes a rotation (movement) for stacking recording paper as a sheet.
A sheet stacking table spring 4 is a biasing means for urging the sheet stacking table 3 to rotate upward and pressing the recording paper stacked on the sheet stacking table 3 against the paper feed roller 2. Reference numeral denotes a sheet-loading table elevating cam, which is a moving unit that pushes down the sheet-loading table 3 against the sheet-loading table spring 4 and separates the recording sheet from the sheet feeding roller 2. In the present embodiment, a stepping motor is used as the motor 1.

Reference numeral 11 denotes a drive gear to which rotational drive is transmitted from the motor 1 via a gear train (not shown), 12 denotes a solenoid having an operating rod 12a, and 13 denotes a rotatable member inside the sheet feeder or the image forming apparatus. A transport roller for transporting recording paper next to the paper feed roller 2, a frame 14 provided in the paper feeder main body, and a recording roller 15 acting on the back surface of the recording paper and loaded on the sheet loading table 3. A separation pad 16 is a separation member that separates and feeds the paper one by one. A separation pad spring 16 is a separation spring that pushes up a holder 15A holding the separation pad 15 at an upper end to press the separation pad 15 against the paper feed roller 2. It is.

Reference numeral 6 denotes an assisting arm which is supported by the frame 14 so as to be swingable. Reference numeral 7 denotes one end of which is supported by the frame 14.
An assisting arm spring 8 whose other end is supported by the assisting arm 6, for example, an arm spring constituted by a tension spring;
Is an assisting cam which is a cam. Reference numeral 9 denotes a sheet feeding gear having a toothless portion 9a and a locking pawl 9b formed thereon, and 10 denotes a sheet feeding roller 2, a sheet loading table elevating cam 5, an assisting cam 8, and a sheet feeding gear 9.
Is a paper feed shaft which is a drive shaft fixed coaxially.

Here, when the assisting cam 8 is rotated by the rotation of the paper feed shaft 10, the assisting arm 6 is rotated. That is, when the assisting cam 8 rotates, the assisting arm 6 first moves to the assisting cam 8.
To rotate against the assisting arm spring 7. At this time, elastic energy is accumulated in the assisting arm spring 7.

When the paper feed shaft 10 is further rotated thereafter, the pressing of the assisting cam 8 is released due to the shape of the assisting cam 8, but this time, the assisting arm 6 is released by the elastic energy accumulated in the assisting arm spring 7. Presses against the assisting cam 8, whereby the assisting arm 6 rotates with the rotation of the assisting cam 8.

Next, the operation of the paper feeder having such a configuration will be described with reference to FIGS. In FIG. 1, the operations of the sheet feeding roller 2, the sheet stacking table 3, the sheet stacking table elevating cam 5, and the transport roller 13 inside the sheet feeding device frame are shown in a left sectional view 1 in order to facilitate the operation. The operation of the assisting cam 8 and the assisting arm 7 is shown in the central sectional view 2, and the operation of the driving gear 11, the sheet feeding gear 9, and the operation of the solenoid 12 for intermittently rotating the sheet feeding gear 9 outside the sheet feeding device frame. The right side view shows that the sheet feeding roller 2, the sheet stacking table elevating cam 5, the assisting cam 8, and the sheet feeding gear 9 are coaxially fixed to the sheet feeding shaft 10 by an alternate long and short dash line.

FIG. 2A shows a state in which the sheet feeding operation is started. In this state, when a start signal is input to the sheet feeding device, the motor 1 rotates to rotate the conveying roller 13 and the driving gear 11. At this time, the sheet feeding gear 9 operates by the operation of the solenoid 12. The rod 12a is locked by the locking piece 9b, and is stopped because the toothless portion 9a is at a position facing the drive gear 11. For this reason, the feed shaft 10
Does not rotate. At this time, the sheet loading table elevating cam 5
The sheet stacking table 3 is pressed against the sheet stacking table spring 4 in the direction B in the drawing.

Next, when a paper feed signal is input to the paper feeder, the solenoid 12 is energized and the operating rod 12a is
In this direction, whereby the locking of the locking piece 9b is released. Here, when the locking of the locking pieces 9b is released in this way, the sheet feeding gear 9 is shown via the sheet loading table lifting cam 5 by the sheet loading table 3 pressed against the sheet loading table lifting cam 5. Upon receiving the initial rotational force in the direction C, the rotor rotates and meshes with the drive gear 11.

Thus, the continuous rotation drive transmission to the paper feed gear 9 is started. Note that the sheet feeding gear 9, the assisting cam 8, the sheet stacking table elevating cam 5, and the sheet feeding roller 2
It rotates at the same speed because it is coaxially fixed on zero.

FIG. 7B is a view showing a state immediately after the sheet feeding shaft 10 starts rotating. The sheet loading table elevating cam 5 is separated from the phase in which the sheet loading table 3 is pushed down by the rotation of the sheet feeding gear 9. The state which changes to a phase is shown.

Here, when the sheet loading table lifting / lowering cam 5 shifts from the phase of pushing down the sheet loading table 3 to the phase of separating, the sheet loading table spring 4 rotates by the action of the sheet loading table spring 4, Thus, the stacked recording papers P are pressed against the paper feed roller 2 in the direction D in the drawing. At this time, since the sheet loading table spring 4 is only released from the compressed state, the motor does not receive a large load.

However, at this time, since the assisting cam 8 shifts to the phase as shown in the figure, the assisting arm 6 rotates in the direction E in the drawing against the assisting arm spring 7. Accordingly, the assisting arm spring 7 is pulled in the direction F in the drawing, and as a result, elastic energy is accumulated in the assisting arm spring 7. The rotation load of the assisting arm 6 is controlled by the feeding gear 9.
, The motor 1 receives a load corresponding thereto.

FIG. 9C is a view showing a state in which the rotation of the paper feed shaft 10 advances and the paper feed roller 2 feeds the recording paper P.
At this time, the uppermost recording sheet P1 is separated by one sheet by the action of the frictional conveying force of the paper feed roller 2 and the frictional force of the separation pad 15, and is sent to the conveying roller 13.
The motor 1 receives a load corresponding to the conveying force of the paper feed roller 2.

FIG. 3D is a view showing a state in which the rotation of the paper feed shaft 10 has further progressed and the uppermost recording paper P 1 has reached the transport roller 13. At this time, the sheet loading platform lifting cam 5 is in a state of transition from a phase separated from the sheet loading platform 3 to a phase of pushing down the sheet loading platform 3,
As a result, the sheet stacking table 3 rotates downward, and the recording paper is separated from the paper feed roller 2, so that the conveyance force by the paper feed roller 2 does not work. In this case, the motor 1 does not receive the load corresponding to the conveying force of the sheet feed roller 2, but receives the load for pushing down the sheet stacking table 3 against the sheet stacking table spring 4.

At the same time, when the assisting cam 8 shifts to the phase as shown in the figure, the assisting arm 6 is pulled by the elastic energy accumulated in the assisting arm spring 7 as shown by G in FIG. And presses against the assisting cam 8. Here, this pressing force acts in the same direction as the rotation direction of the motor 1, so that the rotation force of the motor 1 is assisted,
Therefore, the load seen from the motor 1 decreases. That is, if the load received from the sheet stacking table 3 is a positive load, the assisting force of the assisting arm 6 acts on the motor 1 as a negative load.

FIG. 9E is a view showing a state in which the press-down operation of the sheet stacking table 3 is completed and the sheet feeding shaft 10 has made substantially one revolution. At this time, the toothless portion 9a of the paper feed gear 9 is
And is stopped by the operating rod 12a of the solenoid 12 in a state where the rotation drive transmission is stopped.
As a result, the paper feed gear 9 stops, and the paper feed roller 2 stops. Note that, even in this case, the rotation of the transport roller 13 is continued, and the recording paper P1 is transported to the image forming apparatus (image forming unit).

FIG. 4 schematically shows a change over time of the load of the motor in the sheet feeding device of the present embodiment. The horizontal axis represents time, and the vertical axis represents load torque of the motor.

Then, (a) added on the horizontal axis,
(B), (c), (d), and (e) correspond to (a),
These correspond to the states (b) and (c) and the states (d) and (e) in FIG. (A) added to the vertical axis is the sum of the stationary load received from the transport roller 13 and each of the continuously rotating rollers and the temporary load received from the sheet feeding roller 2 and the sheet loading table lifting cam 5. This is the conventional example shown in FIG.
Equal to 7.

On the other hand, (B) shows the load received from the supporting arm 6 via the supporting cam 8, and (C) shows the load of the total sum which is the sum of (A) and (B). is there.

Here, the load in (a) and (b) of (B) is a positive load (shown + shaded portion indicated) for rotating the assisting arm 6 against the assisting arm spring 7. The load in (d) is reduced by the load seen from the motor because the motor 1 receives an assisting force via the assisting arm 6 and the assisting cam 8 by the elastic energy of the assisting arm spring 7, and the negative load ( (Illustrated-indicated hatched portion).

As described above, in the present embodiment, the assisting means constituted by the assisting arm 6, the assisting arm spring 7, and the assisting cam 8 constitutes the assisting cam 8 in (a) and (b).
By accumulating elastic energy in the supporting arm spring 7,
In (d), the assisting arm 6 regenerates (discharges) the elastic energy accumulated by assisting the assisting cam 8.

In other words, in the present embodiment, as shown in FIG. 4C, the assisting means is in the state where the total load is the smallest while the sheet feeding gear 9 is rotating (a)-(b).
Accumulates elastic energy in the sheet loading table 3
When the total sum of the loads when pushing down is the largest (d)
The regeneration of the elastic energy stored in is performed.

As a general theory, the elastic energy of a spring is potential energy, and theoretically the stored energy and the regenerated energy are equal irrespective of the path and time of the storage and regeneration. Although there is actually a loss due to friction or the like, it can be said that the stored energy (illustrated + indicated hatched portion) and the regenerated energy (illustrated-indicated hatched portion) are substantially equal.

With this configuration, the maximum load of the apparatus can be reduced while maintaining the work load of the entire apparatus corresponding to the shaded area indicated by P in FIGS. Can be reduced to Pmax shown in FIG.

Further, as described above, the elastic energy of the spring is substantially equal to the energy stored (illustrated + indicated hatched portion) and the regenerated energy (illustrated-indicated hatched portion) irrespective of the path and time of accumulation and regeneration. Since they are equal, regeneration is performed so that a large load (illustrated p1) can be applied in a short time (illustrated t1) according to the peak of the maximum load of the device, and a long time (illustrated t2) can be applied with a small load (illustrated p2). If the shapes of the assisting arm 6 and the assisting cam 8 and the load of the assisting arm spring 7 are set so as to perform accumulation, the effect of the present invention can be further enhanced.

FIGS. 5 and 6 are views showing the positional relationship between the assisting cam 8 and the assisting arm 6. FIG. It should be noted that FIG.
FIGS. 6A and 6B are diagrams showing a state of an elastic energy accumulating operation of the assisting cam 8 and the assisting arm 6 of the present embodiment, and FIGS. 6B and 7B show states of an assisting operation by the elastic energy. FIGS.
FIG. 6 is a diagram illustrating a state of an accumulation operation and an assisting operation when an assisting arm 6 is arranged on a side opposite to FIG. 5 as a comparative example of the present embodiment.

Here, as shown in FIG. 5A, in the present embodiment, the direction of rotation of the assisting cam 8 and the direction in which the assisting arm 6 swings during the energy storage operation are the same in CCW. In the case of the comparative example, the swing direction of the assisting arm 6 is CW as shown in FIG.

When comparing FIGS. 5A and 5B with FIGS. 6A and 6B, in the accumulation operation, in the case of the configuration of the present embodiment, the center of the assist arm 6 is determined. The arm length A from the center to the application point is long, and the arm length B from the center of the support arm 6 to the application point in the assisting operation is short.

As a result, assuming that the rotational torque of the assisting arm 6 is constant, in the arrangement of the present embodiment, the energy storing operation is performed with a small load because the arm is longer during the energy storing operation. Since the arm at is short, it is possible to assist with a large load. By arranging the assisting cam 8 and the assisting arm 6 in such a manner that the rotation direction of the assisting cam 8 and the direction in which the assisting arm 6 swings during the accumulation operation, the mechanical efficiency is increased. And the effect of the present invention can be further enhanced.

After the paper feed shaft 10 is stopped, the assisting arm 6 is held at a position not in contact with the assisting cam 8 by a stopper (not shown). Excessive load can be prevented from being applied to the assisting cam 6 except for the regenerating operation.

As described above, the assisting means constituted by the assisting arm 6, the assisting arm spring 7, and the assisting cam 8 allows
When the sheet loading table 3 rises, it stores elastic energy,
The work load for the motor 1 of the entire apparatus is the same, but the maximum load on the motor 1 is reduced by arranging the sheet loading table 3 to release elastic energy when the sheet loading table 3 is lowered by the sheet loading table lifting cam 5. can do.

In other words, even if the overall work load remains the same, elastic load accumulated under a small load is regenerated under a large load, thereby dispersing the load and thereby maximizing the load. Can be reduced. This makes it possible to use a low-power and inexpensive motor, and accordingly, it is possible to drive the motor 1 with a low voltage and a small current. As a result, low power consumption and low heat generation of the sheet feeding device are realized, and noise and vibration can be minimized.

Further, when the number of sheets to be stacked is increased and the printing speed is increased, the spring force of the sheet stacking table spring 4 is increased, and the performance and quality are improved by adding a mechanism for releasing the separation pad 15. It is also possible to carry out these operations while maintaining the maximum output of the motor 1. The effects of low power consumption, low heat generation, low noise, low vibration, and the like are remarkable particularly when the motor 1 is a stepping motor that performs open loop control instead of feedback control.

In the present embodiment, an example has been described in which the urging force required to start the rotation of the sheet feeding gear 9 is received from the sheet stacking table 3.
A similar effect can be obtained even in a configuration in which a spring means is separately provided as shown in Japanese Patent No. 830 or a configuration in which a toothless gear divided into two stages is provided as shown in Japanese Patent Application Laid-Open No. 10-153247. Can be.

In the present embodiment, the assisting arm spring 7
Described an example of a tension spring, but the same effect can be obtained with any of a compression spring, a torsion coil spring, and a leaf spring as long as elastic energy can be accumulated and regenerated.

Next, a second embodiment of the present invention will be described.

FIG. 7 is a perspective view showing the configuration of the sheet feeding device according to the present embodiment. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts.

In the figure, reference numeral 39 denotes a paper feed gear, and the paper feed gear 39 is integrally provided with an assisting cam 39c. Then, as described above, the assisting cam 3 is
By integrally providing 9c, an effect similar to that of the above-described first embodiment can be obtained with a simpler configuration.

Next, a third embodiment of the present invention will be described.

FIGS. 8 and 9 are diagrams for explaining the operation of the sheet feeding device according to the present embodiment. Note that, in the figure, the same reference numerals as those in FIGS. 2 and 3 indicate the same or corresponding parts.

In the figure, reference numeral 43 denotes a sheet stacking table on which the recording paper P is stacked, 43a denotes an abutting portion provided on the sheet stacking table 43, 45 denotes a separation pad, and 45A denotes a holder for holding the separation pad 45 at the upper end. And 45a are contact portions provided on the holder.

Here, in the sheet feeding device of the present embodiment, at the lowest point where the sheet loading table lifting cam 5 pushes down the sheet loading table 43, the separation pad 1 is moved through the sheet loading table 43.
5 (holder 45A) is pressed down against the separation pad spring 16.

After the separation operation of the separation pad 45 is completed, the separation pad 45 is separated from the paper feed roller 2 to increase the conveying force and to separate the paper dust, thereby adversely affecting the durability reliability. It tries to prevent negative effects on paper feed accuracy and image quality.

On the other hand, FIG. 10 schematically shows a temporal change of the load of the motor in the sheet feeding device of the present embodiment. The horizontal axis represents time, and the vertical axis represents load torque of the motor.

Then, (a) added on the horizontal axis,
(B), (c), (d), and (e) show (a),
This corresponds to the states of (b) and (c) and (d) and (e) of FIG. (A) added to the vertical axis is the sum of the stationary load received from the transport roller 13 and each of the continuously rotating rollers and the temporary load received from the sheet feeding roller 2 and the sheet loading / lowering cam 5. .

(B) is a view from the supporting arm 6 to the supporting cam 8.
(C) shows the load of the total sum which is the sum of (A) and (B).
Also, the solid line in (A) shows the load of the present embodiment, and the dotted line P1 shows the load of the first embodiment.

Here, as shown in the figure, P2, which is the maximum load received from the sheet loading table elevating cam 5 in the present embodiment, is larger than the maximum load P1 in the first embodiment. This is because the separation pad 45 is pressed down against the separation pad spring in a state where the sheet stacking table 43 is pressed down to the lowest point.

However, even in the case of the structure in which the separation pad 45 is pushed down through the sheet stacking table 43, the elastic energy accumulated under a small load is regenerated under a large load, thereby dispersing the load. That is, the maximum load can be reduced to Pmax shown in (C) by the elastic energy accumulating action and the regenerating action of the assisting means constituted by the assisting cam 8 and the like shown in FIG. The same effect as in the embodiment can be obtained. In the case of a sheet feeding apparatus having a mechanism for separating the separation pad 45 via the sheet stacking table 3 as in the present embodiment, the effect is further increased because the maximum load is further increased.

Next, a fourth embodiment of the present invention will be described.

FIG. 11 is a perspective view of a sheet feeding device according to the present embodiment, and FIG. 12 is a side view of a main part thereof. 11 and 12, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts.

In FIGS. 11 and 12, reference numeral 56 denotes an assisting arm which is swingably supported by the frame 14 of the sheet feeding device.
Is a supporting arm spring acting on the supporting arm 56, 59 is a sheet feeding gear, 62 is a solenoid for locking the sheet feeding gear 59, 6
Reference numeral 7 denotes a support member for fixing the solenoid 62.

In this embodiment, the support member 67 has a hole 6 for pivotally supporting the center of rotation of the assisting arm 56.
7b is provided so that the assisting arm 56 is supported by both the support member 67 and the frame 14 of the sheet feeding device. As a result, it is possible to ensure the support accuracy and rigidity of the assisting arm 56.

In the present embodiment, the solenoid 62 is provided on the front surface 67 a of the support member 67, and the assisting arm 56 is arranged on the back side of the support member 67. Then, as described above, the surface 67a of the support member 67 is
Is provided with a solenoid 62 and the supporting arm 56 is
By arranging the assist arm 56 and the solenoid 62 on the back side of the sheet 7, it is possible to partially arrange the assisting arm 56 and the solenoid 62 so that they are partially overlapped when viewed from a side surface direction that is a direction orthogonal to the sheet feeding direction. Thus, the degree of freedom in disposing the assisting arm 56 and the like near the paper feed shaft 100 can be increased.

In the above description, the sheet feeder provided with the rotatable sheet loading table 3 has been described. However, the present invention is not limited to this, and the sheet loading table 3 having the vertically movable sheet loading table 3 is provided. Needless to say, the present invention can be applied to a paper feeding device.

[0108]

As described above, according to the present invention, there is provided an assisting means configured to store elastic energy when the sheet stacking table rises and to release elastic energy when lowering the sheet stacking table. With this configuration, the maximum load on the driving source that drives the sheet feeding unit can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a sheet feeding device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the paper feeding device.

FIG. 3 is another diagram illustrating the operation of the paper feeding device.

FIG. 4 is a diagram schematically showing a temporal change of a load of a motor in the sheet feeding device.

FIG. 5A shows an operation of accumulating elastic energy of an assisting cam and an assisting arm constituting assisting means provided in the sheet feeding device of the present embodiment, and FIG. 5B shows a state of an assisting operation by elastic energy. FIG.

FIG. 6A is a diagram illustrating a state of an elastic energy storing operation of an assisting cam and an assisting arm according to a comparative example of the present embodiment, and FIG.

FIG. 7 is a perspective view illustrating a configuration of a sheet feeding device according to a second embodiment of the present invention.

FIG. 8 is a diagram illustrating an operation of a sheet feeding device according to a third embodiment of the present invention.

FIG. 9 is another diagram illustrating the operation of the paper feeding device.

FIG. 10 is a diagram schematically illustrating a temporal change in a load of a motor in the sheet feeding device.

FIG. 11 is a perspective view of a sheet feeding device according to a fourth embodiment of the present invention.

FIG. 12 is a side view of a main part of the paper feeding device.

FIG. 13 is a diagram illustrating a configuration of a conventional image forming apparatus.

FIG. 14 is a perspective view showing a configuration of a conventional sheet feeding device.

FIG. 15 is a diagram illustrating the operation of a conventional sheet feeding device.

FIG. 16 is another diagram illustrating the operation of the paper feeding device.

FIG. 17 is a diagram schematically showing a temporal change of a load of a motor in the sheet feeding device.

FIG. 18 is a diagram showing another configuration of a conventional sheet feeding device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 motor 2 paper feed roller 3 sheet loading table 4 sheet loading table spring 5 sheet loading table elevating cam 6 assisting arm 7 assisting arm spring 8 assisting cam 9 sheet feed gear 10 sheet feed shaft 11 drive gear 12 solenoid 14 frame 15 separation pad Reference Signs List 16 separation pad spring 39 paper feed gear 39c assisting cam 43 sheet loading table 45 separation pad 56 assisting arm 57 assisting arm spring 62 solenoid 67 support member 100 image forming apparatus 100B image forming unit

Continued on the front page F term (reference) 3F343 FA02 FB02 FB03 GA02 GB01 GC01 GD01 HD09 HD10 HD18 JA18 KB03 LA04 LA15 LC11 LC20 LD25 LD26 LD29 LD30 MB12 MC05 MC12

Claims (9)

[Claims] 1. A sheet feeding device, comprising: a rotatable sheet stacking table; and sheet feeding means for feeding a sheet.
In a sheet feeding device configured to move the sheet stacking table by an urging unit to press sheets stacked on the sheet stacking table against the sheet feeding unit, a driving source that drives the sheet feeding unit; Attached to a drive shaft rotated by a drive source, after feeding the sheet, moving the sheet stacking table against the urging force of the urging means, and moving the sheet away from the sheet feeding means. Means for storing elastic energy when the sheet loading table is moved by the urging means, and discharging the elastic energy when the sheet loading table is separated from the sheet feeding means by the moving means, and Means for reducing the load on the source. 2. The assisting means includes a cam attached to the drive shaft, an arm swingably supported by an apparatus main body, an arm swinging with rotation of the cam, and one end supported by the arm. An arm spring that swings the arm against the arm spring by the cam when the sheet stacking table rotates upward, stores elastic energy in the arm spring, and stores the sheet stacking table. 2. The device according to claim 1, wherein the cam is biased in a direction to reduce a load on the drive source via the arm by elastic energy released when the device rotates downward. 3. Paper feeder. 3. The sheet feeding device according to claim 1, wherein the driving source is a stepping motor. 4. The sheet feeding device according to claim 2, wherein a direction in which the arm swings so as to store elastic energy in the arm spring is the same as a rotation direction of the cam. 5. The paper feeder according to claim 2, wherein the arm and the cam do not contact each other when the drive shaft is not rotating. 6. A separating member that abuts on a sheet fed by the sheet feeding means and separates and feeds the sheets one by one, and a separation spring that presses the separating member against the sheet feeding means. 6. The sheet loading table according to claim 1, wherein when the sheet loading table rotates downward, the separation member is separated from the sheet feeding means by the sheet loading table against the separation spring. A sheet feeding device according to any one of the preceding claims. 7. The cam according to claim 2, wherein the cam is provided integrally with a paper feed gear fixed to the drive shaft and transmitting the drive of the drive source to the drive shaft. A paper feeder according to claim 1. 8. A paper feed gear fixed to the drive shaft and transmitting the drive of the drive source to the drive shaft, a solenoid for intermittently rotating the paper feed gear, and a support member for supporting the solenoid. Wherein the arm is swingably supported by the support member and the apparatus main body, and the arm and the solenoid are arranged so as to partially overlap in a direction orthogonal to a sheet feeding direction. The sheet feeding device according to any one of claims 2 to 7, wherein: 9. An image forming apparatus comprising: an image forming unit; and a sheet feeding device for feeding a sheet to the image forming unit, wherein the sheet feeding device is any one of claims 1 to 8. An image forming apparatus characterized in that: