JPH0442278Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a paper conveying device used in copying machines, liquid crystal printers, laser beam printers, etc. that apply electrophotographic technology.

[Prior art and its problems]

Generally, in an image forming apparatus that applies electrophotographic technology, a paper transport device is used that feeds the paper in synchronization with the leading edge of the image in order to transfer a toner image formed on the surface of a photoreceptor onto paper. FIG. 4 is a configuration diagram showing an example of an image forming apparatus equipped with a conventional paper conveyance device.

In the figure, the image forming apparatus includes a photosensitive drum 1
a charger 2 that uniformly charges the surface of the photoreceptor drum 1 disposed around the photoreceptor; an exposure section 3 that exposes recorded information onto the uniformly charged photoreceptor; A developing device 4 that develops the electrostatic latent image formed on the surface of the photoreceptor with toner, a paper feeding device 5 that transports paper sheets one by one in synchronization with the toner image formed on the surface of the photoconductor, and a toner image on the surface of the transported paper 6. It is comprised of a transfer device 7 for transferring, a cleaner 8 for cleaning untransferred toner that has not been transferred onto the paper 6, and the like. The paper feeding device 5 includes a paper feeding roller 12 that conveys the topmost sheet of paper 6 stacked in a cassette 9 and pressed from below via a bottom plate 11 by a spring 10, and the paper feeding roller 12. A guide plate 13 for reversing the paper 6 separated and conveyed by a separating claw 9a provided at the front end of the cassette 9, a slip roll 14, a resist plate 15 provided so as to be able to enter and retreat into the paper conveyance path, and a paper sheet. It is composed of a guide plate 16 etc. that guides the image to the transfer section. Here, the resist plate 15 swings in response to a timing signal from a control device (not shown) and enters the paper conveyance path to abut and stop the leading edge of the paper. During this time, the slip roll 14 is slipping and the paper is waiting.

In the image forming apparatus having such a configuration, the slip roll 14 of the paper feeding device 5 is in a slip state with the paper 6 when the leading edge of the paper 6 is in contact with the registration plate 15 and is in a standby state. Sometimes contradictory conditions must be met, such as the need to reliably grip the paper without slipping. Therefore, if the paper does not slip when it should, or if the paper slips when it should be conveyed by nipping, the leading edge of the image may not match, or malfunctions such as misprinting, jamming, or paper folding due to uneven paper feeding speed may occur. It was the cause.
Furthermore, the conveyance force of the slip roll depends on the type of paper,
It is easily affected by environmental conditions such as temperature and humidity, and it has been difficult to obtain stable slip and conveying force with conventional paper conveying devices.

[Purpose of invention]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the conventional paper, it is an object of the present invention to provide a paper transport device that can reliably carry out paper transport and standby operations.

[Key points of the idea]

In order to achieve the above object, the present invention includes at least a feeding roller that temporarily stops in the middle of a rotational movement of approximately one rotation, separates one sheet from stacked sheets of paper by the rotational movement, and feeds it to a conveyance path. a pair of transport rolls, one of which is rotationally driven to sandwich the fed paper and further transport it to the downstream transport path by a transport force based on the nipping force, and the roll can freely enter and retreat into the downstream transport path; a swingable blocking member that comes into contact with the leading edge of the conveyed paper to block its forward movement when it enters, and enables the paper to be conveyed again when it is evacuated;
Rotates in synchronization with the rotation of the paper feed roller, and
a cam that engages with the blocking member and swings the blocking member into the downstream conveyance path when the paper feed roller is once stopped, and the conveyance roll is at least fed into the downstream conveyance path; In a paper conveyance device configured to continue rotating from the time the paper is nipped until the paper is conveyed again, the paper conveyance device engages with the conveyance roll and the blocking member and swings in conjunction with the swinging operation of the blocking member. , a lever member is provided for changing the clamping force of the conveyance roll at the time of the approach so as to be smaller than the clamping force at the time of the retreat; It is characterized in that the conveying force is decreased to align the sheets while sliding with the sheets, and when the conveying force is increased, the conveying force is increased to convey the sheets.

[Example of idea]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of essential parts of an embodiment of the paper conveyance device of the present invention, and FIGS. 2a, b, and c are configuration diagrams showing the operating state. Here, the same parts as in the conventional example will be described with the same numbers assigned. The paper transport device includes a paper feed roller 12 that transports the topmost paper 6, which is stacked in a cassette 9 and pressed from below via a bottom plate 11 by a spring 10, in approximately one rotation; A cam 17 fixed on the same axis,
A guide plate 13 for reversing the paper 6 separated and conveyed by the paper feed roller 12 and the separation claw 9a provided at the front end of the cassette 9, and a slip roll 14 that is constantly rotating while the main motor of the apparatus is rotating. ,
A bearing 18 provided at the shaft end of the slip roll 14, a conveyance roll 19 that conveys the paper in pressure contact with the slip roll 14, and a conveyor roll 19 that can enter and retreat into the paper conveyance path by rotation of the cam 17. A resist plate 20 provided, a pressure lever 22 semi-rotatable about a shaft 21, a pressure spring 23 that biases the pressure lever 22, and a guide plate 16 that guides the paper 6 to the transfer section. It is composed of etc.

The resist plate 20 is semi-rotatably supported by a shaft 24 and comes into contact with the cam surface of the cam 17 at a downwardly protruding contact portion 20a, and as the cam 17 rotates, the resist plate 20 rotates on the side opposite to the contact portion 20a. The registration section 20b installed upright can enter and retreat into the paper conveyance path. Further, the crimping lever 22 is semi-rotatably supported by the shaft 21, and is provided so as to be able to press the bearing 18 provided at the end of the slip roll 14 with a pressing portion 22a extending downward. Further, an engaging portion 2 extending downward at the tip of the crimp lever 22 is provided.
2b is pressed and biased by a compression spring 23 so as to be in constant contact with the upper surface of the resist plate 20. Therefore, the contact portion 20a of the resist plate 20 is connected to the cam 17.
When in contact with the low cam surface, the pressing portion 22a of the crimping lever 22 presses the bearing 18 of the slip roll 14 downward. In addition, the contact portion 20
When a is in contact with the high cam surface of cam 17,
The engaging portion 22b of the crimp lever 22 that is in contact with the upper surface of the resist plate 20 moves upward against the biasing force of the crimp spring 23, and the pressing portion 22a prevents the bearing 18 of the slip roll 14 from pressing. unlock.

The paper feeding operation of the paper conveyance device of the present invention constructed as above will be explained with reference to FIGS. 2 and 3. Incidentally, FIG. 3 is a timing chart of the paper conveyance device of the present invention. Before the sheet feeding operation, as shown in FIG. 2a, the sheet feeding roller 12 is stopped with the cutout surface 12a facing down (in the direction of the sheet 6), and the registration portion 20b of the registration plate 20 is aligned with the sheet conveyance path. are evacuating from. In addition, the resist plate 20
Since the contact portion 20 a is in contact with the low cam surface of the cam 17 , the pressure lever 22 in contact with the upper surface of the resist plate 20 is pushed down by the biasing force of the pressure spring 23 and the slip roll 14 is pushed down. Press the bearing 18. Therefore, the slip roll 14
and the transport roll 19 are in contact with each other with a strong clamping force. Next, a main motor (not shown) starts rotating in response to a recording start signal _t1 from an operation unit (not shown).
At the same time, the drive from the main motor is transmitted to the paper feed roller 12 via a spring clutch (not shown) or the like.
Then, as shown in FIG. 2b, the paper feed roller 12
It rotates in the direction of arrow A, and the uppermost sheet 6 stored in the cassette 9 is separated one by one by the separating claw 9a and conveyed toward the guide plate 13. Paper feed roller 12
When the cam 17 is rotated by a predetermined angle, the cam 17 fixed coaxially with the cam 17 also rotates, and the peak of the cam surface abuts against the abutting portion 20a of the resist plate 20. Then, the resist plate 20 rotates upward, and the resist portion 20b
protrudes into the paper transport path. Figure 2c shows this state, and Figure 3 shows its timing t ₂
shows. Here, when the resist plate 20 is rotated upward by the cam 17, the engaging portion 22b of the crimp lever 22, which was in contact with the upper surface of the cam 17, rotates upward against the biasing force of the crimp spring 23. . As the crimp lever 22 rotates upward, the pressing portion 22a
is separated from the bearing 18 of the slip roll 14, and the slip roll 14 contacts the conveying roll 19 only by its own weight. Therefore, the clamping force between both rolls becomes weaker, and the tip ends of the resist portion 20b of the resist plate 20.
The paper 6 stopped at is maintained in a standby state while being constantly applied with a weak conveying force. The paper feed roller 12 is
It then rotates slightly and stops at t ₃ .
Next, the paper feed roller 12 rotates by a predetermined angle until t ₆ and then stops in response to a timing signal t ₄ from an operation unit (not shown). Along with this, the abutment part 20a of the resist plate 20, which had been riding on the peak of the cam 17, comes off the peak and rotates downward, so the resist part 20b retreats from the conveyance path (Fig. 3 _{, t5} ). ). Further, as the resist plate 20 rotates downward, the crimp lever 22, which has been biased by the crimp spring 23, also pivots downward, and the pressing portion 22a presses the bearing 18 of the slip roll 14. Therefore, the slip roll 14 and the transport roll 19, which constitute the standby roll, are strongly pressed against each other and transport the paper 6 with a strong clamping force. The slip roll 14 and the transport roll 19 continue to rotate and transport the paper 6 in the state shown in FIG. 2a. This state is also a state of waiting for the next paper 6 to be conveyed by the paper feed rollers 12.

In this way, the paper conveying device of the present invention is capable of handling the paper 6
Since the gripping force of the slip rolls changes between standby and conveyance, reliable conveyance and standby operations can be realized.

In the above embodiment, the resist plate 20 is moved by the movement of the cam 17 coaxially fixed to the paper feed roller 12.
Although an example in which the resist plate 20 is oscillated has been described, the resist plate 20 is not limited to this, and the resist plate 20 may be moved by an electric signal using a solenoid or the like. Furthermore, the same effect can be obtained by controlling only the crimp lever 22 with a solenoid or the like and changing the clamping force of the slip roll 14 without interlocking the operation of the resist plate 20 and the crimp lever 22.

[Effects of the invention] As explained above in detail, according to the paper conveyance device of the present invention, the clamping pressure of the slip rolls can be selectively changed during paper conveyance and during standby, so that In addition to reliably conveying the paper, the conveying force is weakened during standby so that the leading edge of the paper does not bend or wrinkle.

Furthermore, since the paper is transported with a strong clamping force, malfunctions such as paper jams and paper folds caused by poor paper feeding can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the main parts of the paper conveying device of the present invention, FIGS. 2 a, b, and c are explanatory diagrams showing the operating state of the paper conveying device of the present invention, and FIG. The timing chart of the paper conveyance device, Figure 4, is as follows:
1 is a configuration diagram of an image forming apparatus including a conventional paper conveying device. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Charger, 3... Exposure section, 4... Developing device, 5... Paper feeding device, 6... Paper, 7... Transfer device, 8... Cleaner, 9... ...Cassette, 9a...Separation claw, 10...Spring, 11...
Bottom plate, 12... Paper feed roller, 12a... Notch surface, 13... Guide plate, 14... Slip roll, 15, 20... Resist plate, 16... Guide plate, 17... Cam, 18... Bearing, 19...Transport roll, 20a...Contact portion, 20b...Resist portion, 21, 24...Shaft, 22...Crimp lever, 2
2a...pressing part, 22b...engaging part, 23...pressing spring.

Claims (1)

[Scope of utility model registration request] A feeding roller that stops once in the middle of a rotational movement of approximately one rotation, separates one sheet from the stacked sheets by rotational movement, and feeds it to a conveyance path, and at least one of which is rotationally driven to collect the fed paper. A pair of conveyor rolls that clamp and further convey the paper to the downstream conveyance path by a conveyance force based on the clamping force, and a pair of conveyor rolls that can freely enter and retreat into the downstream conveyance path, and that come into contact with the leading edge of the conveyed paper when entering. a swingable blocking member that prevents the forward movement of the sheet and enables re-conveying of the paper when retracting; a cam that swings the blocking member to enter the downstream conveyance path when the roller is once stopped, and the conveyance roll at least clamps the fed paper until it is conveyed again. In the paper conveyance device configured to continue rotating for a period of time, the conveyance roll engages with the blocking member, swings in conjunction with the swinging movement of the blocking member, and reduces the pinching force of the conveyance roll at the time of entry. A lever member is provided for changing the clamping force to be smaller than the clamping force at the time of retraction, and based on the change in the clamping force, the transport roll is reduced in the transporting force against the paper at the time of the approach, and slides with the paper. A paper conveyance device, characterized in that the paper is aligned and the conveyance force is increased during the retraction to convey the paper.