JPH0526938U - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce noise during standby in high-speed paper feeding in an image forming apparatus including a paper feeding unit that feeds paper at high speed. [Construction] A leading edge detection sensor 31 for detecting arrival of the leading edge of a sheet is provided in a sheet path before the standby roll 10. The clutches A and B are turned on to start the high speed conveyance of the paper by the paper feed roll 7 and the conveyance roll 9, and when the front end detection sensor 31 detects the front end of the paper, the clutch B is turned off to temporarily stop the conveyance ( t ₂ ) and then the clutch C is turned on to switch the transport speed of the transport roll 9 from the high speed to the low speed (or to switch from the high speed to the low speed without stopping the transport) and the sheet is rushed into the standby roll 10. Let After that, when a predetermined amount of deflection is generated on the sheet (t ₄ ), the clutch D is turned on to rotate the standby roll 10 at a low speed, and the sheet is re-conveyed in time with the image on the photosensitive drum 13.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as various printers, copiers, and facsimiles, and more particularly to an image forming apparatus including a paper feeding unit that feeds paper at high speed.

[0002]

[Prior Art]

 Generally, in the image forming apparatus as described above, a paper feeding unit for feeding a sheet cut into a predetermined size to the image forming unit via the standby unit is constituted by a plurality of stages, so that a paper feeding cassette can be replaced. Conventionally known is a device configured to be efficient and to form an image on a plurality of types of paper. As an example thereof, FIG. 5 shows the overall configuration of a page printer device having a two-stage paper feed unit.

As shown in FIG. 1, in this printer apparatus, a first paper feed section F ₁ is built in the apparatus main body M, and an optional second paper feed section F ₂ is arranged below the apparatus main body M. As a result, the two paper feed units F ₁ and F ₂ are arranged in two upper and lower stages.

The first paper feed unit F ₁ is detachable from the main body M of the apparatus and is a paper feed cassette 1 as a paper loading unit for loading and storing paper P, and a bottom plate 1 a of the paper feed cassette 1. Bottom plate push-up plate 2, a paper feed roll 3 for feeding the paper P in the paper feed cassette 1, and when the paper is fed by the paper feed roll 3, the paper P is separated from the top paper one by one. It is composed of a separating member 4 and the like which are sequentially sent out.

The second sheet feeding portion F ₂ is configured such that the entire _second sheet feeding portion F ₂ can be attached to and detached from the bottom portion of the apparatus main body M, and has a configuration similar to that of the _first sheet feeding portion F _1. In addition to the cassette 5, the bottom plate push-up plate 6, the paper feed roll 7 and the separating member 8, a transport roll 9 provided upstream of the paper feed roll 7 along the paper feed direction is provided to assist the paper feed. The paper feed roll 7 and the transport roll 9 form a transport unit.

In addition to the first paper feed section F ₁ , the apparatus main body M temporarily waits for the paper sheets conveyed from the paper feed sections F ₁ and F ₂ , and then the image on the photosensitive drum 13 to be described later. A standby roll 10 as a standby part for re-transporting at a timing, a transport guide plate 11 forming a paper path for guiding the sheets fed from the respective sheet feeding parts F ₁ and F ₂ to the standby roll 10, and a manual feed And a manual feed guide portion 12 for feeding the paper. Further, the apparatus main body M includes a photosensitive drum 13 as an image carrier, a charger 14 and a print head 15, which are sequentially arranged in the vicinity of the peripheral surface of the apparatus, as in a normal printer apparatus adopting an electrophotographic system. An image forming unit including a developing device 16, a transfer device 17, and a cleaner 18 is provided, a fixing roll 19, a transporting roll 20, a paper discharging roll 21, a paper discharging tray 22, and the like are further provided, and each paper feeding unit F ₁ , It is provided with a printed circuit board 23 which constitutes a control circuit for controlling the drive of F ₂ , the standby roll 10 and the image forming section.

In the printer device having the above-described configuration, since the lengths of the paper passages from the paper feed units F ₁ and F ₂ to the standby roll 10 are different from each other, if the paper is conveyed at the same speed, The feeding time differs depending on the sheet feeding units F ₁ and F ₂ , and it is difficult to set the continuous printing speed common to the sheet feeding units F ₁ and F ₂ . Therefore, as a countermeasure against this, the conveyance speed of the paper is increased on the side of the second paper feed unit F _{2 having} a long paper path, and the speed is controlled so as to match the conveyance time on the side of the first paper feed unit F _{1 having} a short paper path. Mono is proposed.

[0008]

[Problems of conventional technology]

Generally, in an apparatus in which a standby unit such as the standby roll 10 is arranged between the image forming unit and the paper feeding unit, the leading edge of the sheet conveyed from the paper feeding roll of the paper feeding unit enters the standby unit. Then, stop the paper feed roll with a few mm of bending on the paper, and then release the paper standby by the standby unit at the timing of the image on the photoconductor drum and transfer the paper to the image forming unit. Controlled to re-transport. The same control as this has been performed in an apparatus including the two-stage sheet feeding units F ₁ and F ₂ as shown in FIG. 5, and such an apparatus has the following problems. Was there.

A) As described above, on the side of the second paper feed unit F ₂ where the paper path is long, after the paper feed by the paper feed roll 7 and the transport roll 9 is started, the leading edge of the paper is moved to the standby roll 10. Since the sheet is conveyed at high speed without changing the conveying speed until the sheet bends and a predetermined deflection is generated on the sheet, a large impact sound is generated when the leading edge of the sheet enters the standby roll 10.

B) After the leading edge of the sheet of paper has rushed into the standby roll 10, when the sheet feeding roll 7 and the transport roll 9 that rotate at high speed on the second sheet feeding section F ₂ side are suddenly stopped, the leading edge of the sheet of paper rolls to the standby roll 10. Since the inertial force of the paper feed roll 7 and the transport roll 9 acts on the paper in a state of being bitten by the paper, this inertial force acts on the standby roll 10 through the paper, and there is no place for the force to escape. Vibrates or is irregularly curved, and this collides with peripheral members such as the transport guide plate 11 and produces a significantly louder noise than at low speeds.

Here, if only the impact sound described in A above is not so noticeable for those around the apparatus, the noise described in B above is generated almost at the same time as this impact sound. These sounds overlap each other and become a very offensive noise.

It is to be noted that such a problem is caused by an apparatus having one or more sheet feeding sections for high-speed conveyance, in addition to the apparatus having a plurality of sheet feeding sections having different sheet passages as described above. If so, it was occurring similarly.

[0013]

[The purpose of the device]

 The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide an image forming apparatus capable of reducing noise during standby due to high-speed paper feeding.

[0014]

[Key points of the device]

 In order to achieve the above-mentioned object, the present invention has a conveying unit that is provided between a sheet stacking unit and a standby unit and that conveys a sheet toward the standby unit. In the image forming apparatus configured to re-convey the image on the image carrier at a timing after it is made to stand by at the section, the leading edge of the sheet is arranged in the sheet path between the standby section and the conveying unit. A leading edge detection sensor for detecting the leading edge of the sheet; and a control section for switching the transporting speed of the transporting means from a high speed to a low speed based on the detection of the leading edge of the sheet by the leading edge detecting sensor so as to thrust the sheet into the standby section at the low speed Is characterized by.

[0015]

【Example】

 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a configuration diagram of the main parts of the paper feed unit and the standby unit in one embodiment of the present invention. A page printer device is shown here as an example, the overall configuration is the same as that shown in FIG. 5, and the overall appearance is as shown in FIG.

In FIG. 2, the difference from the configuration of FIG. 5 in terms of mechanism is that the first and second sheet feeding units F are₁, F ₂ It is shown in the figure that a leading edge detection sensor 31 for detecting arrival of the leading edge of the sheet is provided at a position that is a distance L from the standby roll 10 in the paper path from the standby roll 10 to the standby roll 10 as a standby unit. Not the second paper feed section F₂The drive roll 9a of the transport roll 9 (drive roll 9a and driven roll 9b) in FIG. 2 is connected to separate drive shafts for high speed and low speed via two separate clutches (clutch B and C). The point is that the configuration is possible. Here, the high speed means the second paper feed unit F.₂The paper transport speed according to the above, and the low speed is the paper transport speed in the image forming unit. The paper feed roll 7 can be connected to a high speed drive shaft by a clutch A (not shown), and the standby roll 10 can be connected to a low speed drive shaft by a clutch D (not shown).

Further, in the present embodiment, the control circuit as the control means included in the printed circuit board 23 (FIG. 5) performs the same control as the conventional _{one with} respect to the first paper feed section F _{1 having} a short paper path. However, the control unique to the present embodiment is performed for the second paper feed unit F _{2 having} a long paper path. Hereinafter, a specific example of the sheet feeding operation in the _second sheet feeding unit F ₂ will be described using the time chart of FIG.

As shown in FIG. 1, when a paper feed start signal is first output, the clutches A and B are turned on at the falling edge thereof, whereby the paper feed roll 7 and the transport roll 9 start rotating at high speed. , Paper is fed at high speed. After the transportation of the paper by the transportation roll 9 is started, the clutch A is turned off and the driving of the paper feeding roll 7 is stopped, and the paper is transported only by the driving of the transportation roll 9 (at this time, the paper feeding roll 7 is It rotates following the transfer of paper). The sheet is conveyed along the conveyance guide plate 11 at high speed, and when the leading edge of the sheet reaches the leading edge detection sensor 31, the leading edge detection sensor 31 is turned on, and at this time, the clutch B is turned off and the driving force to the transport roll 9 is increased. Is cut off. After that, the carrier roll 9 takes a short time t due to the inertial force.₁After it continues to rotate, it stops completely, and at this point, the high-speed conveyance of paper also stops. Here, the distance L between the standby roll 10 and the leading edge detection sensor 31 shown in FIG. ₁ It is set in advance within a range in which the leading edge of the paper does not rush into the standby roll 10 by rotating only.

As described above, the clutch C is turned on after a predetermined time t ₂ (> t ₁ ) has passed since the leading edge detection sensor 31 was turned on, whereby the transport roll 9 starts to rotate at a low speed and the paper It is conveyed to the standby roll 10 at a low speed. Here, the time t ₂ is longer than the time t ₁ , is set within a range in which the transport roll 9 is completely stopped (that is, the transport of the paper is completely stopped), and the rotation of the standby roll 10 described later is performed. It is set to a time t ₄ + t ₃ minutes earlier than the start of (starting rotation in synchronism with the image on the image carrier of the image forming unit). When time t ₃ elapses after the transport roll 9 starts rotating at a low speed and the leading edge of the sheet plunges into the standby roll 10, the leading edge of the sheet stops while the transport roll 9 continues to rotate, so that the sheet begins to bend. .. Then, when a predetermined amount of flexure occurs on the paper after a lapse of time t ₄ , the clutch D is turned on, whereby the standby roll 10 starts rotating at low speed and the paper is sent to the image forming unit. .. After that, after the trailing edge of the paper leaves the transport roll 9, the clutch C is turned off to stop the rotation of the transport roll 9, and subsequently, after the trailing edge of the paper leaves the standby roll 10, the clutch D is turned off and waits. The rotation of the roll 10 is stopped. After that, the same operation is repeated each time the paper feed start signal is output.

As described above, in this embodiment, the sheet conveyed at a high speed from the second sheet feeder F _{2 is} completely stopped before the standby roll 10 and then at a low speed until the standby roll 10. Since the sheet is re-conveyed, the sheet plunges into the standby roll 10 at a low speed, and the impact noise at the plunge can be suppressed to a very low level. Moreover, even if the transport roll 9 is stopped during the stand-by after the plunge, the transport roll 9 is stopped from the low-speed rotation, so that a large inertial force is not generated in the transport roll 9, so that the paper roll like the conventional high-speed rotation is stopped. There is almost no vibration or irregular curvature, and when the paper is stopped by the standby roll 10 when it is temporarily stopped after high-speed conveyance, the paper feed roll 7 and the conveyance roll 9 have inertial force through the paper. It does not act on the standby roll 10 and therefore produces almost no noise. In this way, noise during standby due to high-speed paper feeding can be significantly reduced.

Next, another specific example of the sheet feeding operation in the _second sheet feeding section F ₂ will be described with reference to the time chart of FIG. First, when the paper feed start signal is output, as in the case of FIG. 1, the clutches A and B are turned on, the paper feed roll 7 and the transport roll 9 start rotating at high speed, and the paper is transported by the guide plate 11. It is conveyed at high speed along. When the leading edge of the sheet reaches the leading edge detection sensor 31 and the leading edge detection sensor 31 is turned on, the clutch B is turned off and the clutch C is turned on at the same time, whereby the feeding speed of the sheet by the feeding roll 9 is increased. Instantly switch from high speed to low speed. At this time, the conveyance speed of the paper does not change gradually from high speed to low speed, but is switched discontinuously and immediately.

In this way, after the time t ₁₁ has passed since the conveyance speed was switched to the low speed, the leading edge of the sheet plunges into the standby roll 10, and the time t ₁₂ (= t _{4) while the} conveyance roll 9 rotates at a low speed. ) Has passed and a predetermined amount of deflection has occurred on the sheet, the clutch C is turned off, whereby the low-speed conveyance of the sheet by the conveyance roll 9 is stopped. After that, the clutch D is turned on when a predetermined time t ₁₃ elapses while maintaining the above-described predetermined amount of deflection, whereby the standby roll 10 starts low-speed rotation and the sheet is sent to the image forming unit. At this time, the conveying roll 9 slips or is driven to rotate as the sheet is conveyed by the standby roll 10. After that, after the trailing edge of the sheet leaves the standby roll 10, the clutch D is turned off and the rotation of the standby roll 10 is stopped. Thereafter, the same operation is repeated each time the paper feed start signal is output.

As described above, it is possible to cause the paper to plunge into the standby roll 10 at a low speed by simply switching the paper conveyance speed from high speed to low speed without temporarily stopping the paper before the standby roll 10. Therefore, as in the case of FIG. 1, high-speed sheet feeding can be realized with low noise.

In the above embodiment, the leading edge detection sensor 31 is provided near the standby roll 10 as shown in FIG. 2 and the conveyance roll 9 is controlled immediately after the leading edge of the sheet is detected. May be provided in the vicinity of the sheet feeding section. In that case, after the leading edge of the sheet is detected, a timer or the like is activated so that the high speed conveyance of the conveyance roll 9 is temporarily stopped after a predetermined time. The modified form of the control may be performed, or the form of the modification of the second embodiment may be performed by switching the transport roll 9 from the high speed to the low speed after the predetermined time.

Further, in the above-described embodiment, the second sheet feeding section for options in the image forming apparatus having a plurality of sheet feeding sections is described, but the first sheet feeding section also performs high-speed sheet feeding. Even in such a case or in the case of a high-speed machine having a single paper feed unit, by applying the present invention, it is possible to realize low noise during high-speed paper feed.

Further, the present invention can be applied not only to the printer device as shown in the above embodiment, but also to various image forming apparatuses such as a copying machine and a facsimile device.

[0027]

EFFECTS OF THE INVENTION According to the present invention, the paper conveyance speed is controlled so that the paper conveyed at a high speed is switched to a low speed before the standby section (or is stopped and then switched to a low speed). Can be rushed into the standby part at low speed. Therefore, the impact noise at the time of the rush can be suppressed to a very low level, and even if the conveyance means (paper feed roll or conveyance roll) is stopped during the subsequent standby, a large inertial force is not generated because it is stopped at a low speed. Since there is almost no vibration or curving of the paper compared to when stopped from high speed, the noise during standby due to high speed paper feeding can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a time chart showing the main operation of one embodiment of the present invention.

FIG. 2 is a main part configuration diagram of a sheet feeding unit and a standby unit in the embodiment.

FIG. 3 is an external perspective view of the same embodiment.

FIG. 4 is a time chart showing the main operation of another embodiment of the present invention.

FIG. 5 is an overall configuration diagram of a conventional image forming apparatus.

[Explanation of symbols]

7 Paper Feed Roll 9 Transport Roll 10 Standby Roll 11 Transport Guide Plate 13 Photosensitive Drum 23 Printed Circuit Board 31 Leading Edge Detection Sensor F ₁ First Paper Feeding Section F ₂ Second Paper Feeding Section

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location G03G 15/00 110 7369-2H H04N 1/00 108 M 4226-5C

Claims (1)

[Scope of utility model registration request] 1. A transfer unit is provided between a sheet stacking unit and a standby unit for transporting a sheet toward the standby unit, and after the sheet transported from the sheet stacking unit is temporarily held in the standby unit. An image forming apparatus configured to be re-conveyed in synchronism with an image on the image carrier, a front end detection sensor disposed in a paper passage between the standby unit and the conveying unit to detect arrival of a front end of a sheet. An image forming apparatus comprising: a control unit configured to switch the conveyance speed of the conveyance unit from a high speed to a low speed to cause the paper to enter the standby unit at the low speed based on the detection of the paper front end by the front end detection sensor. apparatus.