JP2000095394A - Register, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate any image blur by eliminating a shock in starting pairs of register rollers caused by the braking force applied thereto. SOLUTION: Drive is inputted in a register lower roller 2 through a register clutch 11. The drive of the register lower roller 2 is transmitted to a register upper roller 1 through gears 17, 18. A brake clutch (an electromagnetic clutch) 23 is connected to the register lower roller 2 through gears 22, 23a. The brake clutch 23 is clutched off when the register roller pairs 1, 2 are changed from a stopped condition to a rotating condition to release the braking force. The brake clutch 23 is clutched on when the register roller pairs 1, 2 are changed from a rotating condition to a stopped condition to apply the braking force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a registration device provided in an image forming apparatus such as a printer, a copying machine, a facsimile, and the like.

[0002]

2. Description of the Related Art FIG. 7 shows a configuration around an image forming section of a conventional electrophotographic image forming apparatus (laser beam printer).

Reference numeral 42 denotes a photosensitive drum, and an electrostatic latent image formed on the surface by a laser scanning system (not shown) is developed as a toner image by a developing device (not shown). A transfer separation charger 44 transfers the toner image on the photosensitive drum 42 to a recording sheet and separates the transferred recording sheet from the photosensitive drum 42.

A recording sheet transport system for transporting a recording sheet to the photosensitive drum 42 includes the following members. From the upstream side, a pair of pre-registration conveying rollers 6 for conveying the recording sheets S separated and fed one by one from a sheet feeding device (not shown), and guide plates 5 (5a, 5) for guiding the recording sheets S
b), a pre-registration guide 3 (3a, 3b) which receives the recording sheet S from the guide plate 5 and guides the recording sheet S, and a registration upper roller 1 and a registration lower roller for sending the recording sheet S to the image forming section at a predetermined timing. The roller 2 (registration roller pair) is a pre-transfer guide 4 (4a, 4b) for guiding the recording sheet S to the photosensitive drum 42.

FIG. 8 shows a detailed configuration of the registration roller pairs 1 and 2.

Registration upper roller 1 and registration lower roller 2
Are rotatably supported by the front plate 8 and the rear plate 9 of the registration unit via bearings (ball bearings) 32, respectively. A registration input gear 30 driven by a drive mechanism (not shown) meshes with a gear 31 a of an electromagnetic clutch 31 provided on the shaft of the registration lower roller 2.
The electromagnetic clutch 31 transmits the drive of the registration input gear 30 to the registration lower roller 2 at a predetermined timing. On the other hand, an elastic resin-made friction brake 7 is disposed so as to sandwich the shaft of the registration lower roller 2 on the side of the rear plate 9 (see FIG. 7).
The resist lower roller 2 receives a constant braking force during rotation. The setting of the braking force of the friction brake 7 is such that the strongest of the recording sheets S to be handled is abutted against the registration roller pairs 1 and 2, and the recording sheet S is abutted for the longest possible time. Even if it continues, the force is set to be sufficiently strong so that the registration rollers 1 and 2 are not rotated by the force.

In the above configuration, the recording sheets S separated and fed one by one from a sheet feeding device (not shown) are conveyed along a guide plate 5 by a pair of pre-registration rollers 6 and further guided to a pre-registration guide 3. As a result, the leading end of the sheet abuts on the nip formed by the registration rollers 1 and 2 that have stopped rotating.

The pre-registration roller pair 6 is controlled based on the position information of the recording sheet S detected by the recording sheet front end detecting means (not shown), and is provided after the front end of the sheet strikes the nip of the pair of registration rollers 1 and 2. The recording sheet S is conveyed by a predetermined amount and is temporarily stopped. At this time, a loop is formed in the recording sheet S in the space formed by the pre-registration guides 3 (3a, 3b) (the state shown in FIG. If the recording sheet S is sent skewed, the skew is absorbed by the formed loop,
The sheet leading end position is set at a fixed position.

When the recording sheet S hits the nip between the pair of registration rollers 1 and 2, a force for rotating the pair of registration rollers 1 and 2 that has stopped rotating due to the stiffness of the recording sheet S acts. Since the rotation is controlled by the action of the friction brake 7, the leading end of the recording sheet S can be positioned at a fixed position without penetrating the nip.

Since the position of the leading end of the sheet is set at a fixed position without skew by the above operation, the position of the leading end of the sheet, the position of writing the latent image on the photosensitive drum 42, and the process speed are calculated to form the photosensitive drum 42. The registration roller pairs 1 and 2 and the pre-registration roller pair 6 are restarted in synchronization with the toner image and the recording sheet S is sent to the transfer section (between the photosensitive drum 42 and the transfer separation charger 44). The toner image can be transferred from a desired position. Thereafter, the toner image is fixed on the recording sheet S by a fixing device (not shown) and then discharged, and the printing operation ends.

[0011]

However, the above-mentioned prior art has the following problems.

First, since a friction force is constantly applied to the registration rollers 1 and 2 by the friction brake 7, a large shock is generated when the registration rollers 1 and 2 are restarted. Or the photosensitive drum was shaking. Registration roller pair 1,
At the restart timing of 2, the image writing to the photosensitive drum 42 is performed by the laser scanning system, so that the image blur due to the above-mentioned shock is likely to occur and the image quality is degraded.

In particular, recently, it is necessary to handle various recording sheets, and a stiff recording sheet such as a thick paper sheet is often used. In order to prevent the tip from piercing through the nips 1 and 2, it was necessary to set a strong braking force, and the shock tended to increase. Further, in recent years, a method in which a resist unit is drawn out and jammed in an easy-to-see state without reaching into the apparatus main body when a sheet jam occurs has become widespread. When the registration unit is to be pulled out, it is a general practice to retract the registration unit once by rotating the photosensitive drum 42 which is easily damaged, and then pull out the registration unit. When it is made rotatable, fixing to the apparatus main body is likely to be unstable, and it is easy to receive a shock due to a change in driving force.

As a further problem, the friction brake 7 lacks the stability of the braking force, and the initial setting itself varies, and the braking force also changes due to durability, resulting in a variation in the position of the front end of the seat. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to reliably prevent the rotation of the recording sheet when the rotation of the registration roller stops, and to reduce the shock at the start of rotation of the registration roller. It is intended to provide a device.

[0016]

SUMMARY OF THE INVENTION The present invention for achieving the above object relates to a registration apparatus provided with a registration roller pair for carrying a sheet while appropriately stopping rotation and rotating.

In order to achieve the above object, the present invention is characterized in that it has a brake means capable of selecting application and release of a braking force to the pair of registration rollers.

As the brake means, for example, an electromagnetic clutch is used.

[0019]

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

FIG. 1 shows the overall configuration of an electrophotographic image forming apparatus (laser beam printer) to which the present invention is applied, and FIGS. 2 to 5 show the configuration of a resist apparatus of the present invention.

First, the overall configuration of the image forming apparatus will be briefly described.

Around the photosensitive drum 42, a primary charging device 41 for uniformly charging the drum surface, a laser scanning system 40 for writing an electrostatic latent image on the drum surface, and a developing device 43 for developing the latent image are arranged in this order. Have been. Further, a transfer separation charger 44 for separating the recording sheet S from the photosensitive drum 42 after transferring the toner image to the conveyed recording sheet S,
Cleaning device 4 for collecting residual toner on drum surface
7 are provided.

On the upstream side of the photosensitive drum 42, a pre-registration conveying roller pair 6, which conveys the recording sheet S sent from a sheet feeding device (not shown) toward the registration roller pairs 1 and 2,
A guide plate 5 (5a, 5b) for guiding the recording sheet S,
The registration sheet guide 3 (3a, 3b), which receives the recording sheet S from the guide plate 5 and guides the recording sheet S, a registration sensor 12 for detecting the leading end position of the recording sheet S immediately before the pair of registration rollers 1, 2, and the recording sheet S The upper roller 1 and the lower resist roller 2 for sending the recording sheet S to the image forming section at a predetermined timing, and the pre-transfer guides 4 (4a, 4b) for guiding the recording sheet S to the photosensitive drum 42 are provided.

The pre-registration guide 3, the registration sensor 12, the registration roller pairs 1 and 2, and the pre-transfer guide 4
The transfer separation charger 44 is configured as a unit as the resist device 13. The resist device 13 can be rotated about the rotation fulcrum 53 by the resist pressing device 14 in a direction substantially approaching and separating from the photosensitive drum 42.
When the registration device 13 rotates in the direction approaching the photosensitive drum 42, the abutment portion 51 formed integrally with the front and rear side plates (not shown) and the registration positioning roller 52 abut against the registration device 13, Positioned.

Downstream of the transfer / separation charger 44, there is placed a transport section 45 composed of a driving roller, a driven roller, and a belt. Further downstream, the toner image is fixed on the recording sheet S by heat and pressure. A fixing device 46 is provided.

The resist device 13 and the resist pressurizing device 1
4. The transport unit 45 and the fixing unit 46 are mounted on a unit bottom plate 48 to form an integrated unit. A slide rail (left) 49 and a slide rail (right) 50 are provided on both sides of the unit bottom plate 48, and the entire unit can be pulled out from the image forming apparatus main body together with the unit bottom plate 48 to the front side.

Next, the resist device 13 of the present invention will be described in detail. FIG. 3 is a view of the registration device 13 as viewed from the front side, and FIG. 4 is a view of the registration device 13 as viewed from the rear side.

In FIG. 2 and FIG. 3, a pre-registration gear 22 which rotates integrally with the roller shaft is connected to the front end of the registration lower roller 2 by a parallel pin.
On the other hand, the brake shaft 24 caulked to the resist front side plate 9
, A gear 23a of the brake clutch 23 is engaged with the pre-registration gear 22.

In FIGS. 2 and 4, a registration clutch (electromagnetic clutch) 11 is attached to an end of the registration lower roller 2 on the rear surface side.
The first gear 11a rotates integrally with the registration lower roller 2 when the clutch is turned on. on the other hand,
An input gear (idler gear) 26 attached to an input shaft 25 caulked to the registration rear side plate 8 is engaged with the gear 11 a of the registration clutch 11.

In FIG. 2, the resist upper roller 1 is attached to the resist front side plate 9 and the resist rear side plate 8 via a bearing holder 16 in which a ball bearing is wrapped with a resin holder. The bearing holder 16
A vertically long hole (not shown) provided in both side plates 8 and 9 slides up and down. The resist lower roller 2 is directly supported by ball bearings 15 attached to both side plates 8 and 9. The ball bearing 15 is provided on both side plates 8,
9 is positioned by a fitting hole provided in the hole 9. Brake bearings 20 made of resin having a predetermined coefficient of friction are further attached before and after the resist lower roller 2 (at positions corresponding to the respective bearing holders 16). A pressure spring 19 whose both ends are hooked on hook portions provided on the bearing holder 16 is attached so as to wind around the outer periphery of the brake bearing 20 by half a turn. The roller pressure is obtained. FIG. 5 is a perspective view showing the periphery of the brake bearing 20 for easy understanding of the pressure spring 19.

The rotation of the registration lower roller 2 is controlled by a pair of gears 1.
The light is transmitted to the upper registration roller 1 via 7 and 18. In this case, even if the resist upper roller 1 is drawn toward the resist lower roller 2 by the pressure spring 19, the gears 17
8 has a constant backlash.

A drive coupling 27 from the main body side is coaxial with an input gear 26 which rotates around an input shaft 25 which does not rotate and which is caulked by the resist rear side plate 8.
Are combined. As described above, the registration device 13
Can be pulled out to the front side together with the unit bottom plate 48, but the coupling mechanism ensures the drive transmission with the main body even after the resist device is drawn out.

Next, the operation of the image forming apparatus will be described with reference to FIG.

The recording sheets S separated and fed one by one from a sheet feeding device (not shown) are conveyed by a pair of pre-registration conveying rollers 6 along a guide plate 5 and further guided to a pre-registration guide 3 to be described later. The leading edge of the sheet is abutted against the nip formed by the registration roller pairs 1 and 2 that have stopped rotating based on the sequence performed.

The pre-registration conveying roller pair 6 is controlled based on the position information of the leading end of the recording sheet S detected by the registration sensor 12, and is set in advance after the recording sheet S abuts the nip of the pair of registration rollers 1 and 2. The recording sheet S is transported by the predetermined amount and temporarily stopped. At this time, a loop is formed in the recording sheet S in the space formed by the pre-registration guides 3 (3a, 3b) (the state shown in the drawing), and the leading end of the sheet is pressed against the nip by the waist of the recording sheet S. Even if the recording sheet S is sent skewed, the skew is absorbed by the formed loop, and the leading end position of the sheet is set at a fixed position.

Since the position of the leading end of the sheet is set at a fixed position without skew by the above operation, the position of the leading end of the sheet, the position of writing the latent image on the photosensitive drum 42, and the process speed are calculated. The registration roller pairs 1 and 2 and the pre-registration conveyance roller pair 6 are restarted in synchronization with the transferred toner image, and the recording sheet S is sent to the transfer section (between the photosensitive drum 42 and the transfer separation charger 44). , The toner image can be transferred from a desired position. Thereafter, the transferred recording sheet S is sent to the fixing device 46 by the transport unit 45, and is discharged after the toner image is fixed on the recording sheet S, and the printing operation is completed.

Here, the control sequence of the registration clutch 11 and the brake clutch 23 will be described with reference to FIG. FIG. 6A shows control voltage signals of the registration clutch 11 and the brake clutch 23 when two sheets are printed, and transmission torque generated by the clutches 11 and 23 corresponding thereto. FIG. 6B shows the leading end position of the recording sheet S.

First, in a state where the brake clutch 23 has been turned ON in advance, the leading end of the sheet reaches the nip of the pair of registration rollers 1 and 2 at point a. In the present embodiment, whereas the conventional example brakes the registration roller pairs 1 and 2 by relying solely on the friction brake 7, the brake is applied to the registration roller pairs 1 and 2 by the electromagnetic clutch. In this state, even if the thick paper enters at high speed, the registration rollers 1 and 2 do not turn and the registration does not go out of order.

Next, the brake clutch 23 is turned off immediately before the timing b of the registration clutch 11 being turned on. In general, an electromagnetic clutch has an OF delay due to a response delay due to an inductance of an internal coil and a suction time of a suction surface.
The actual transmission torque decreases with a delay with respect to the F signal. In this embodiment, the brake electromagnetic clutch used is about 3
Since there was a response delay of 0 msec, a control sequence for turning off the brake clutch 11 50 msec before the registration clutch 11 was turned on was adopted in consideration of variations.

Thus, the registration clutch 11 is turned on.
If the control for turning off the brake clutch 23 is performed prior to this, the braking force remains even if the drive starts to be transmitted to the registration roller pairs 1 and 2, and rather a large shock is generated to disturb the image, and the drive system components may be disturbed. Damage can be prevented from occurring.

When the brake clutch 23 is turned off before the registration clutch 11 is turned on, a loop is formed in a short time between the time when the braking force is lost and the time when the registration rollers 1 and 2 should start to rotate. The registration roller pair 1, 1
There is a concern that 2 will rotate. However, it is most likely that the leading end of the recording sheet S rotates the registration roller pairs 1 and 2 because the registration roller pairs 1 and 1 that have stopped rotating.
The moment the leading edge of the sheet collides with the nip portion of No. 2 (FIG. 6B)
Point a), at which time the brake clutch 23 is turned on.
Therefore, the rotation of the registration rollers 1 and 2 is effectively prevented. Subsequent recording sheet S
Is relatively small, the time during which the transmission torque of the brake clutch 23 is lost (20 msec in the case of the present embodiment) may be short, and there is no registration shift that is almost problematic. .

In the present embodiment, in order to further minimize the displacement of the registration, the registration roller pairs 1 and 2 are used.
A brake that always works with a weak force has been added. That is, the brake bearing 20 is provided before and after the resist lower roller 2. The brake bearing 20 receives a force of a pressure spring 19 that applies a holding force to the pair of registration rollers 1 and 2, and provides a sliding resistance in a direction that hinders rotation of the registration lower roller 2. In the present embodiment, a pressure spring 19 that generates a force of 1 kgf on one side, which is a pressing force necessary for the registration roller pairs 1 and 2 to stably convey a sheet, is used, and the pressure spring 19 is calculated from the spring force. By selecting a bearing material (20) having an appropriate friction coefficient, the brake bearing 20 was set so as to always generate a load torque of 100 g · cm on both sides. This load is always applied to the pair of registration rollers 1 and 2, but since the value is small, if the load torque is as large as this, the shock of the registration clutch 11 ON does not adversely affect the image. Also, since the braking force is small, there is no problem in durability of the brake bearing 20. By the function of the brake bearing 20, while the transmission torque of the brake clutch 23 is reduced to zero, the leading end of the recording sheet generated by the loop overcomes the force of trying to rotate the pair of registration rollers 1 and 2, and the registration force is reduced. Since the leading end position of the sheet is kept at a predetermined position until the clutch 11 is turned on, the registration accuracy is improved.

The description returns to the control sequence. After the registration clutch 11 is turned on, the trailing edge of the sheet passes through the pair of registration rollers 1 and 2, and the registration clutch 1
1 becomes OFF (point c). Here, taking into account the response delay when the registration clutch 11 is turned off, the brake clutch 23 is delayed by 50 msec from the point c for the same reason as described above.
N was set. In the present embodiment, the brake clutch 23 is turned on with a margin by setting the delay time of the brake clutch 23 ON to 50 msec. However, the timing of the brake clutch 23 ON after the registration clutch 11 is turned off is such that the leading end of the next recording sheet S is the registration roller pair , 2 before the point d, which is the point where the nip is reached.
There is no problem if is turned on.

Hereinafter, similarly, the second recording sheet S
The brake clutch 23 is turned on to prevent the recording sheet S from jumping out before the leading end of the pair reaches the nip of the pair of registration rollers 1 and 2, and the brake clutch 23 is turned off immediately before the registration clutch 11 is turned on to record without shock. The sequence for accurately registering and sending out the sheet S is continued.

As described above, in the present embodiment, the brake clutch 23 is provided to effectively apply a braking force to the registration rollers 1 and 2 against the force of the recording rollers entering the nip of the registration rollers 1 and 2. The drive shock was prevented by turning off the brake clutch 23 earlier than turning on the resist clutch 11 in accordance with the characteristics of the electromagnetic brake in accordance with the characteristics of the electromagnetic brake.

As in the present embodiment, the entire resist device 13 can be pulled out toward the apparatus main body, and
The mechanism by which the registration device 13 is rotatable and the registration device 13 is positioned with respect to the side plate of the photosensitive drum unit is as follows.
The jammed recording sheet can be processed not in the interior of the apparatus, but in the front, and the registration device 13 can be accurately positioned with respect to the photosensitive drum 42, which is an important component. Apparatus 1
3 was susceptible to a drive shock, and the shock was likely to be transmitted to the photosensitive drum 42 in some cases. But,
When the drive shock is reduced as in the present embodiment, the disadvantage is almost eliminated, and the advantage of the configuration in which the registration device 13 is rotated and positioned in a pull-out manner can be utilized. In addition, since the pull-out type resist device 13 is excellent in the maintenance property from the beginning, in the present embodiment, since the brake clutch 23 is arranged on the front side of the resist device 13, the clutch can be replaced or the clutch can be removed. There is also an effect that maintenance work such as replacement of the pair of registration rollers 1 and 2 can be easily performed.

In the present embodiment, as a means for constantly applying a braking force, a spring (a pressure spring 19) for generating a clamping force between the registration roller pairs 1 and 2 is used.
And a bearing as a brake member (brake bearing 20)
However, the purpose of the present invention is not impaired by other means. For example, a brake pad system that sandwiches the shaft of the registration lower roller 2 as in the conventional example may be used, or a constant torque load may be applied using a torque limiter.

Further, in this embodiment, the leading end of the recording sheet S is brought into the nip of the pair of registration rollers 1 and 2 by the loop of the recording sheet S formed between the pair of pre-registration conveyance rollers 6 and the pair of registration rollers 1 and 2. Although an example of generating the abutting force has been described, the method is not limited to this method.For example, a slip roller pair having a small conveying force relative to the registration roller pairs 1 and 2 is used as a pre-registration conveyance roller pair. A method in which the slip force of the slip roller pair is used as the abutting force may be used.

Further, the registration apparatus of the present invention can be widely applied not only to the laser beam printer described in the embodiment but also to an image forming apparatus for forming an image on a sheet fed one by one.

[0050]

As described above, according to the present invention,
It has a brake means for selecting and applying a braking force to the registration roller pair, and when the registration roller pair changes from the rotation stop state to the rotation state, the brake means is in a braking force release state, and the registration roller pair is changed from the rotation state. When changing to the rotation stop state, the brake means is set to the braking force application posture.

Therefore, the shock at the start of rotation of the registration roller due to the application of the braking force is eliminated, and the driving torque at the time of rotation of the registration roller can be reduced.

Further, according to the present invention, since the electromagnetic clutch is used as the braking means, it is possible to easily control the braking force applying state and the braking force releasing state.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional side view showing the overall configuration of an electrophotographic image forming apparatus (laser beam printer) to which the present invention is applied.

FIG. 2 is a vertical sectional front view showing the configuration of the resist device of the present invention.

FIG. 3 is a side view showing the configuration of the resist apparatus of the present invention as viewed from the front side.

FIG. 4 is a side view showing the configuration of the resist apparatus of the present invention as viewed from the rear side.

FIG. 5 is a perspective view showing a configuration around a brake bearing.

FIG. 6 is a diagram illustrating a control sequence of a registration clutch and a brake clutch.

FIG. 7 is a schematic vertical sectional side view showing a configuration around an image forming unit of a conventional electrophotographic image forming apparatus (laser beam printer).

FIG. 8 is a front view showing a configuration of a registration device provided in the image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Upper roller of registration (registration roller pair) 2 Lower roller of registration (registration roller pair) 13 Registration device 20 Brake bearing (auxiliary brake means, brake member) 23 Brake clutch (brake means)

Claims (14)

[Claims] 1. A registration device comprising a pair of registration rollers that conveys a sheet while appropriately setting a rotation stop state and a rotation state, wherein a brake means capable of selecting application or release of a braking force to the pair of registration rollers. A resist device comprising: 2. The method according to claim 1, wherein the skew state of the sheet is corrected by stopping the rotation of the registration roller pair, and the sheet after the skew state correction is conveyed by rotating the registration roller pair at a predetermined timing. The resist device according to claim 1, wherein 3. The registration apparatus according to claim 1, wherein an electromagnetic clutch is used as said brake means. 4. The registration apparatus according to claim 1, wherein said brake means is in a state of applying a braking force when said pair of registration rollers is in a rotation stopped state. 5. The registration apparatus according to claim 1, wherein the brake unit is in a braking force release state when the registration roller pair is in a rotating state. 6. The system according to claim 4, wherein when the pair of registration rollers changes from the rotation stop state to the rotation state, the brake means is in a state of releasing the braking force a predetermined time earlier than the registration roller pair. 3. The resist device according to 1. 7. The braking device according to claim 4, wherein when the pair of registration rollers changes from a rotating state to a rotation stop state, the brake means is in a state of applying a braking force a predetermined time later than the pair of registration rollers. 6. The resist device according to 5. 8. The registration device according to claim 1, further comprising an auxiliary brake unit that constantly applies a predetermined braking force to the registration roller pair. 9. The registration device according to claim 8, wherein a brake member that slides on the shaft of one of the registration rollers is used as the auxiliary brake unit. 10. The registration apparatus according to claim 9, wherein said brake member is brought into a rubbing state by a force for pressing said pair of registration rollers. 11. An image forming apparatus for forming an image on recording sheets fed one by one, as means for conveying the fed recording sheets to the image forming unit at a predetermined timing. An image forming apparatus, comprising: the resist device according to any one of the first to tenth aspects. 12. The image forming apparatus according to claim 11, wherein the registration device is detachably attached to an image forming apparatus main body. 13. The image forming apparatus according to claim 11, wherein the registration device is rotatably attached to the image forming apparatus main body so as to be able to contact and separate from the image forming section. Image forming apparatus. 14. An image forming apparatus according to claim 12, wherein said brake means provided in said registration device is arranged on a drawer side of said registration device.