JPH03279126A - Sheet supply device - Google Patents

Abstract

PURPOSE:To obtain a stable sheet supply function by driving a means for pushing up an intermediate plate through the intermediary of a resilient member in accordance with a signal indicating a detection of the upper surface of a sheet in a cassette so as to hold the upper surface of the sheet at a level higher than a sheet feed position by a predetermined value. CONSTITUTION:A control section 60 receives a signal from a sensor 65 for detecting the upper surface of a sheet 17 in such a condition that a semiconductor sheet feed roller 19 rests, and controls the drive of a motor. Then, a pressing arm 62 is rotated by way of gears 72, 71, 70, a tension spring 69 and a pressing lever 68 so as to gradually push up an intermediate plate. The sensor 65 detects an arrival of the upper surface of the sheet up to a predetermined height so as to stop the motor, and accordingly, the upper surface of the sheet 17 is held at an equilibrium point P. The supply of the sheet is made by rotating the sheet feed roller 19 so as to lower the upper surface of the sheet 17 by a predetermined value (h), and accordingly, the sheet supply pressure is set to be constant by the tension of the tension spring 69 corresponding to the value (h).

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a sheet feeding device made of transfer material in an image forming apparatus such as a copying machine. The present invention relates to a sheet feeding device whose paper feeding action is not affected by the size of density.

(B) Prior Art Conventionally, in a sheet feeding device made of transfer material for an image forming apparatus such as a copying machine, as shown in FIG. 5 and FIG. Supported middle plate C
A sheet P is stacked thereon, and the middle plate C is pushed up by a compression spring d to press the sheet P against a paper feed roller e attached to the main body of the copying machine.

Thus, the sheet P is fed, that is, the half-moon-shaped feed roller e
Assuming that the pressing force Fl (see Fig. 5) by which the cylindrical part presses the middle plate C on which no sheets P are stacked is Fg (see Fig. 6), and the force Fg exerted by the stacked sheets P on the compression spring d (see Fig. 6), Fig. 6 The pushing force F3 of the compression spring d shown in is F3=F'l+Ft.

(c) Problems to be Solved by the Invention However, in the conventional sheet feeding device described above, the pressing force F that presses the intermediate plate C on which no sheets P are stacked;
When the sheets P are loaded on the middle plate C, the force applied to the compression spring d is F2, and the reaction force of the compression spring d at that time is F2.
Since the relationship between Must.

That is, Fs - Ft is constant. This only occurs when the push-up force F3 of the compression spring d increases almost in proportion to the thickness of the sheets P loaded on the intermediate plate C, and for this purpose, the weight related to the thickness of the bundle of sheets P must be increased. In other words, when the size of the sheet P changes, when a sheet P of the same size has absorbed moisture, or when a sheet P with a large specific gravity is loaded, the size and spring constant of the compression spring d should be changed. Not only is it complicated to have to replace the sheet P, but as the loading capacity of the sheet P increases, if the spring constant of the compression spring d is not adjusted appropriately, the paper feed pressure may be insufficient by 50% or more, resulting in misfeeds. Otherwise, the paper feeding pressure may become excessive by 50% or more, causing problems such as double feeding.

Therefore, the present invention aims at achieving stable sheet feeding performance by pushing up the middle plate through an elastic member and controlling the top surface of the bundle of sheets to be positioned a predetermined amount higher than the sheet feeding position. The purpose is to provide a feeding device.

(d) Means for solving the problem The present invention has been made in view of the above-mentioned circumstances, and includes:
For example, referring to FIGS. 1 and 3, a sheet (1
7), a sheet feeding means (19) for feeding the sheets (17) on the sheet stacking member (63), and pushing up the sheet stacking member (63). A sheet feeding device (
6O), the sheet feeding means (19) has a first state in which the sheet (17) is fed by contacting the upper surface of the sheet (17), and a second state in which the sheet feeding means (19) is separated from the sheet. and driving means (73) for driving the push-up means (62).
), the push-up means (62) and the drive means (73).
An elastic member (69) is interposed between the sheet (17
) is provided, and in response to a signal from the detection means (65), the drive means (73) drives the push-up means (62), and the sheet (17)
A control means (76) is provided for supporting the upper surface at a predetermined height when the sheet feeding means (19) is in the second state.

(f) Function Based on the above configuration, sheets (17) are stacked on the sheet stacking member (63) of the sheet feeding device (60), and the sheet stacking member (63) is pushed up by the pushing up means (62). Then, the uppermost sheet (17) is fed by the sheet feeding means (19).

At this time, the upper surface of the sheet (17) is detected by the detection means (65), and a signal is sent to the detection means (65) or the control means (76). ) to drive the push-up means (62) through the drive means (73
) to feed the upper surface of the sheet (17).
9) Support at a predetermined height in the second state.

Note that the reference numerals in parentheses are for illustrative purposes only, and do not limit equivalent configurations.

(f) Example The present invention will be described in detail below with reference to the drawings.

FIG. 4 shows a copying machine with multiple developing devices that implements the present invention.

Note that this copying machine is configured to enable double-sided image formation and multiple image formation in different colors.

The original 2 placed on the original placing glass 1 is irradiated by the lamp 3, and the light beams are reflected by the reflecting mirrors 4° 5.6, 7, 8.
．． 9 and a zoom lens 1o, the light is guided onto the photosensitive drum 11.

Lamp 3, mirror 4 and mirrors 5 and 6 are respectively indicated by arrow A
The document 2 is scanned by moving in the direction at a predetermined speed. on the other hand,
Since the photosensitive drum 11 is also rotated in the direction of arrow B after its outer surface is uniformly charged by the primary charger 12,
Electrostatic latent images corresponding to the original image are sequentially formed on the outer surface of the photosensitive drum 11 . A color developer (green developer 13C) containing color toner (for example, green) and a black developer 14 containing black toner are arranged around the photosensitive drum 11. These developing units 13C and 14 are movable in the directions of arrows c and c', respectively, and are brought close to the photosensitive drum 11 to develop the electrostatic latent image on the photosensitive drum 11 according to a desired color image. become

In the case of this figure, since the color developer (green developer 13C) is far away and the black developer 14 is close, a black image is formed on the photosensitive drum 11. This image is transferred onto a transfer material 17 by a transfer charger 15. Thereafter, the photosensitive drum 11 reaches a cleaner 16, where residual toner on the outer surface of the drum is removed, and the process proceeds to the next image forming step in the same manner.

The transfer material 17 is supplied as follows, and an original image is formed. The following methods are available for supplying the transfer material 17 to the image forming means mainly composed of the photosensitive drum 11. In the first method, the transfer material 17 loaded in the cassette 18 or the paper feed roller 1
9 and sent to a pair of rollers 20. Said roller pair 20
The transfer material 17 after passing through the guide plate 2], 22, 28,
It reaches the registration roller 23 via the feeding roller pair 50 and the guide plates 51, 52, and 53. In the second method, cassette 2
The transfer material 17 loaded on the roller 4 is fed to a pair of rollers 26 by a paper feed roller 25. Transfer material 17 is roller pair 2
6, guide plates 27, 28, 21, feeding roller pair 5
0. The registration roller 23 reaches the registration roller 23 via the guide plates 51, 52, 53. The registration roller 23 starts rotating at a timing such that the visible image on the photosensitive drum 11 and the transfer material 17 match, and the upper transfer guide 31, sending the transfer material 17 to the outer surface of the photosensitive drum 11 via the lower transfer guide 32;
As mentioned above, the image on the outer surface of the photosensitive drum 11 is transferred to the transfer material 17 by the transfer charger 15, and the image is transferred to the transfer material 17 by the separation charger 3.
3 and is separated from the outer surface of the drum 11 and sent via a conveying section 34 to a fixing device 35 having a heating roller, a pressure roller, and the like. The image on the transfer material 17 heated and pressurized by the fixing device 35 is fixed as a permanent image. Next, the transfer material 17 is sent to the first ejection roller 36, and then reaches the second ejection roller 39 via flappers 37, 38, and is ejected out of the machine. In this figure, the flapper 38 is blocking the transfer material path, but this flapper 38 is made of a light material and is rotatable in the direction of the arrow. Since it is pushed up by the leading edge of the transfer material 17 and retracted from the transfer material 17, there is no problem in passing the transfer material 17.

Next, the flow of the transfer material 17 in the double-sided image forming mode and the multiple image forming mode will be described.

When the image forming device is instructed to select double-sided image forming mode,
The original image is transferred and fixed on one side (first side) of the transfer material 17 in the same way as in the single-sided image forming mode described above.
As the transfer material 17 is sent to the second ejection roller 39 and ejected onto a tray outside the machine (not shown), the rear end of the transfer material 17 is detected by a transfer material detection mechanism consisting of a detection lever 40 and an optical sensor 41, and then for a certain period of time. (That is, the time required for the rear end of the transfer material 17 to pass through the flapper 38), the second discharge roller 39 starts rotating in reverse and feeds the transfer material 17 into the machine again. Then, the transfer material 17 is transferred to the flapper 38, the left slope of the flapper 37, and the guide plate 4 with the rear end first.
2, further guided by guide plates 43 and 44, and sent to a pair of rollers 45. After that, the transfer material 17 is transferred to the roller pair 4.
6 and reaches the horizontal registration roller 47. At this point, the lateral registration rollers 47 have stopped, and after the transfer material 17 has completely abutted against this pair of rollers 47, the pair of rollers 45.4
6 also stops. The transfer material 17 then waits for the image forming operation on the second surface. Then, when the front and back sides are reversed and an image forming signal for the second side is issued, the horizontal registration roller pair 4
7 starts rotating and is guided by guide plates 49 and 51 to feed the transfer material 17 to the registration rollers 23. Registration roller 2
3, the side edge of the transfer material 17 is detected by an optical sensor (not shown), and the horizontal registration roller pair 47 transfers the image so that the side edge is at the same position as when forming the image on the first surface. The lateral position of the transfer material 17 is corrected by moving in a direction perpendicular to the traveling direction of the transfer material 17, that is, in a direction perpendicular to the drawing. The operation after the transfer material 17 reaches the registration roller 23 is the same as in the case of single-sided image formation, and the transfer material 17 with the image formed on the second side is finally transferred to the second discharge roller 39.
is discharged onto a tray outside the machine.

Further, when the image forming apparatus is instructed to perform the multiple image forming mode, the operation during the first image forming is performed in the same manner as in the case of single-sided image forming. After the first image formation, the flapper 37 is located in the state shown by the broken line, and therefore, the transfer material 17 is sent out by the first discharge roller 36 with the front end first and follows the right slope of the flapper 37. It is then sent to guides 42 and 43, and further sent to roller 45 via guides 43 and 44. Thereafter, the transfer material 17 passes through the roller 46 and reaches a pair of lateral registration rollers 47. Transfer material 1
7 is detected by the detection lever 40 and the optical sensor 41, and after a predetermined period of time, the flapper 37 returns to the position indicated by the solid line. Then, when the second image forming signal is issued, the horizontal registration roller pair 47 starts rotating, but the movement of the transfer material 17 at this time is the same as in the case of image formation on the second side of double-sided image formation. be. The transfer material 17 on which the second image has been formed in this way is finally transferred to the second discharge roller 3.
9, it is discharged onto a tray outside the machine. Note that although the explanation has been given regarding multiple image formation twice, the movement of the transfer material 17 is basically the same even when multiple image formation is performed more frequently.

However, in such a case, the return of the flapper 37 from the broken line value device to the solid line position is performed before the final image formation.

Next, the transfer material feeding device 60 will be explained with reference to FIGS. 1 to 3, focusing on the cassette 18.degree. 24 installed in the copying machine. Incidentally, since cassettes 18 and 24 are the same, the cassette 18 is targeted.

Reference numeral 18 denotes a paper feed cassette, and the half-moon-shaped paper feed roller 19 is located at the upper right side of the cassette 18 when the cassette 18 is installed in the copying machine.

As shown in FIGS. 1 and 2, the side plate 1 of the cassette 18
A pressure shaft 61 is pivotally supported at the middle lower part of 8a, and this pressure shaft 6
A pressure arm 62 is attached to 1, and this pressure arm 62
An intermediate plate 63 placed on the tip of the side plate 18a is pivotally supported by the side plate 18a by a shaft 63a. The transfer material 17 is loaded on this intermediate plate 63.

Further, the tip of the sensor lever 64, which is supported on the copying machine body by a shaft 64a, comes into contact with the upper surface of the transfer material 17, and the sensor lever 64 is lifted by the transfer material 17 to the position indicated by the broken line. A sensor 65 is provided in the main body of the copying machine, which turns off when the copying machine is turned off.

Then, when the paper feed roller 19 is at rest (the missing circular portion 1
9b is facing downward), when the sensor 65 is turned on, the control section 76 drives the motor 73, and when the sensor 65 is turned off, the motor 73 is stopped.

Further, as shown in FIGS. 2 and 3, a drive shaft 67 is pivotally supported on a side plate 66 of the cassette mounting portion of the main body of the copying machine, and a pressure lever 68 is attached to this shaft 67.
One end of a tension spring 69 is attached to the tip of the spring 8, and the other end of this spring 69 is attached to a sector-shaped gear 7o.
It is attached to a shaft 70a that is pivotally supported by the side plate 66. Further, a gear 71 that is pivotally supported by a side plate 66 is meshed with the gear 70, and a gear 72 that is attached to the shaft of a motor 73 that is attached to the main body of the copying machine is also meshed with this gear 71.

A coupling 74 is provided at the end of the drive shaft 67 on the cassette 18 side, and a coupling 75 connected to this coupling 74 is attached to the pressurizing shaft 61.

Next, the operation of the transfer material supply device 60 will be explained.

When the cassette 18 loaded with the recording material 17 is installed in the main body of the apparatus, the coupling 75 is connected to the coupling 74. Then, a signal is sent to a control section 76 (not shown).

When the cutout 19b of the paper feed roller 19 is at rest with the cutout facing downward, when the sensor 65 is turned on (the top surface of the recording material 17 is lower than a predetermined height), the control section 76 receives the signal and starts the motor 73. Drive, gears 72, 71, 70, spring 6
9. Rotate the pressure arm 62 clockwise in FIG. 3 via the pressure lever 68, couplings 74, 75, and pressure shaft 61 to gradually push up the middle plate 63. .

Then, the transfer material 17 on the intermediate plate 63 rotates the sensor lever 64 in the clockwise direction in FIG. 1, and this lever 64 turns off the sensor 65.

Then, the motor 73 stops, and the upper surface of the recording material 17 is held at the balance point P. That is, the tension of the tension spring 69 and the middle plate 63
is in equilibrium with the force that supports it. Note that when the paper feed roller 19 is feeding paper (when the cylindrical portion 19a is pushing down the recording material 17), the control unit 76 does not drive the motor 73 even if the sensor 65 is turned on.

Next, when the operator instructs the start of the paper feeding operation, the paper feeding roller 19 is started by turning on a clutch (not shown).

Here, there is a predetermined difference between the contact point (paper feeding point) Q of the cylindrical portion 19a of the roller 19 with the recording material 17 (see FIG. 1) and the detection position (balance point P) of the sensor 65. Therefore, the paper feed roller 19 feeds the paper while pushing down the transfer material 17 by a predetermined amount. and,
The tension generated by the extension amount ΔL (see FIG. 3) corresponding to a predetermined amount of the tension spring 69 is set as the paper feeding pressure (approximately 350 g in the embodiment). When the sheet feeding is finished, the sheet feeding roller 19 stops with the notch 19b facing downward, and the upper surface of the recording material 17 returns to the balance point P.

Also, the paper feeding pressure is determined by a tension spring 69 for a predetermined depressing amount.
Since the tension is due to the elongation amount ΔL, it does not vary depending on the number of recording materials 17 loaded in the cassette 18 or the density of the recording materials 17.

In addition, since the decrease in the above-mentioned predetermined pressing amount is suppressed to 10% or less between when the recording material 17 is fully loaded and when it is consumed,
The reduction in paper feeding pressure is within 10%, which is sufficiently smaller than in the conventional example, and does not pose any problem to the paper feeding operation.

Note that the drive section of the transfer material supply device 60 of this embodiment may be provided on the device main body side or may be provided within the paper feed cassette 18.

(G) As described in detail, according to the present invention, the upper surface of the sheet is detected by the detection means, a signal is sent to the control means, and the control means that receives the signal pushes up the sheet through the elastic member. The means is driven by the driving means, and the upper surface of the sheet is supported at a predetermined height when the paper feeding means is in the second state, so that the elastic member generates a predetermined amount of paper feeding pressure when the paper feeding means is in the first state. Therefore, paper feeding conditions can always be stabilized regardless of sheet type, size, etc.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional side view of a sheet feeding device according to an embodiment of the present invention, FIG. 2 is a plan view thereof, FIG. 3 is a side view from the other side, and FIG. FIG. 5 is a cross-sectional side view of a conventional sheet feeding device, and FIG. 6 is a cross-sectional side view showing the state when sheets are loaded. 19...Sheet feed 62...Pushing up means 63...Sheet loading member 65...Detection means (sensor) (tension spring) (motor) 76...Control unit 17...Sheet (transfer material ) Feeding means (paper feed roller) (pressure arm) (middle plate) 69...Elastic member 73...Drive means stage (control section)

Claims (1)

[Scope of Claims] 1. A sheet feeder comprising: a sheet stacking member for stacking sheets; a sheet feeding means for feeding the sheets on the sheet stacking member; and a push-up means for pushing up the sheet stacking member. In the feeding device, the sheet feeding means has a first state in which the sheet is brought into contact with an upper surface of the sheet to feed the sheet, and a second state in which the sheet is separated from the sheet, and drives the pushing up means. an elastic member is interposed between the push-up means and the drive means, a detection means for detecting the upper surface of the sheet is provided, and upon receiving a signal from the detection means, the drive means A sheet feeding apparatus, comprising: a control means for driving a pushing up means to support the upper surface of the sheet at a predetermined height in a second state of the sheet feeding means.