JP2003182880A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase printing speed without increasing a paper sheet carrying rate at an image forming position when forming an image on a plurality of paper sheets 3 continuously. <P>SOLUTION: In feeding paper sheets 3 one by one in spaced relation from a paper sheet feeding section through a paper sheet feeding roller 12, the paper sheet carrying speed, which is controlled by the third paper sheet carrying means 11 arranged in properly spaced relation in a paper sheet carrying passage, a second paper sheet carrying passage 10 and a resist roller 9, is set so as to become slower as the paper sheet advances downstream in order, and they are provided with clutch means 70, 80, 81 and 82, respectively. Paper sheet sensors 54, 55 and 56 are arranged between the carrying means adjacent to each other upstream and the carrying means adjacent to each other downstream to detect the tip sections of paper sheets in the carrying direction. Based on the detection signals from these sensors, the clutch means 70, 80, 81 and 82 are controlled so that the carrying means upstream of the carrying direction of the adjacent paper sheet is made to be a non-transferring state. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser printer,
The present invention relates to an electrophotographic image forming apparatus used in a copying machine, a facsimile machine, or the like, and more specifically, by devising a form of conveying a recording medium such as a sheet from a paper feeding unit to an image forming unit, The present invention relates to a configuration for increasing the number of images formed per unit time.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus such as a laser printer uses a toner image formed on a photoconductor as a transfer roller as disclosed in Japanese Patent Laid-Open No. 10-35941. After being transferred to a recording medium such as a sheet of paper which is passed between the photoconductor and the recording medium, the recording medium is passed between one heating roller and one pressure roller to heat and melt the toner, The toner image is fixed on the recording medium. In that case, the recording mediums are conveyed from a paper feeding position for feeding the recording mediums stacked in a paper feeding unit (paper feeding tray) one by one to an image forming position which is a contact portion between the photoconductor and the transfer roller. A paper feed roller, a plurality of intermediate transport rollers, and a registration roller are provided in the transport path to be operated, and the registration rollers are intermittently driven while the plurality of intermediate transport rollers are driven. At that time, the leading end of the recording medium is temporarily abutted against the stopped registration roller so that the recording medium has a slack (deflection) in the middle thereof, thereby aligning the leading ends of the recording medium and the image formation. The timing of feeding paper to a set is adjusted.

By the way, when images are continuously formed on a plurality of recording media, the feeding start timing for the second and subsequent sheets is set as follows. When the recording mediums are separated and fed one by one by the paper feeding unit, if the trailing edge of the preceding recording medium and the leading edge of the following recording medium are fed too close to each other, Due to the variation in the leading end position of the recording medium in the paper feeding unit, the paper sensor in the transport path from the paper feeding unit to the paper discharging unit detects the succeeding paper before the completion of passage of the preceding paper (recording medium) ( The leading end of the recording medium) may be conveyed to the paper sensor position. In this case, it is determined that the preceding recording medium is not conveyed and remains, and error processing is performed when a paper jam occurs.

Further, if the succeeding recording medium is sent out before the trailing end of the preceding recording medium is separated from the paper feed roller, an unnecessary force acts on the preceding recording medium and a stable conveying operation is performed. May interfere with So usually,
In consideration of the development time of image data and the like, when separating the sheets one by one at the paper feeding position, a predetermined amount of space is provided between the trailing edge of the preceding recording medium and the leading edge of the succeeding recording medium. The paper feed start timing for the second and subsequent sheets has been set so that the paper intervals, for example, about 60 mm, are available.

[0005]

However, in recent years, there is a strong demand for speeding up of the image forming apparatus, that is, an increase in the number of finished images (sheets / minute) per unit time. In particular, as the peripheral speed (process speed) of the photoconductor is increased, the influence of the time loss for securing the predetermined amount of paper interval, for example, 60 mm becomes large.

Therefore, it is an object of the present invention to provide an image forming apparatus capable of increasing the number of finished images (sheets / minute) per unit time by reducing the time loss due to the sheet interval. Is.

[0007]

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention has a paper feed path through which a recording medium is fed from a paper feed section and a paper feed path. In an image forming apparatus including an image forming unit that forms an image on a recording medium that is conveyed along the recording medium, the image forming apparatus is arranged at at least two positions in the sheet conveying path at appropriate intervals.
A plurality of conveying means in which the conveying speed is set so that the one on the downstream side in the conveying direction gradually decreases from the one on the upstream side in the conveying direction, and the conveying drive force from the drive source is transmitted or not transmitted to the conveying means. The clutch means is placed in order to bring the adjacent conveying means on the upstream side in the conveying direction into the non-transmission state when the conveying leading end portion of the recording medium is sandwiched between the clutch means to be in the state and the conveying means on the downstream side in the conveying direction. And control means for controlling.

The invention described in claim 2 is the same as claim 1.
In the image forming apparatus described in (1), the front end of the recording medium is brought into contact with at least one of the conveying means stopped to adjust the distance from the rear end of the preceding recording medium. Is.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, between the adjacent conveying means on the upstream side in the conveying direction and the conveying means on the downstream side in the conveying direction. Sheet detecting means for detecting the recording medium is provided, and the control means makes the adjacent conveying means upstream in the conveying direction non-transmitting state based on the detection result by the sheet detecting means. It is characterized by controlling.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the control means detects the trailing edge of the preceding recording medium by the sheet detecting means and the succeeding recording medium. Based on the detection of the leading end of the recording medium, the stop period of the following recording medium by the conveying means on the downstream side in the conveying direction is controlled.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the conveying means is composed of a driving roller and a driven roller that rotates together with the driving roller. The drive roller is provided with clutch means.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the clutch means is a friction clutch such as an electromagnetic clutch. is there.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the conveying unit separates the recording medium stacked in the sheet feeding unit to separate the recording medium.
It is arranged between a sheet feeding position for feeding the sheets one by one and an image forming position for forming an image on a recording medium, and the conveying speed from the sheet feeding position to the image forming position is gradually reduced on the downstream side in the conveying direction. It is configured as follows.

According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the trailing edge of the preceding recording medium does not overlap the trailing edge of the following recording medium at the image forming position. In addition, the transport speed of each transport means is set.

Further, in the image forming apparatus according to the present invention, a paper feed roller for separating the recording mediums stacked in the paper feed unit one by one, and the paper feed roller are used for the separation. A paper conveyance path along which the recording medium is conveyed, and an image forming unit that forms an image by transferring the developer image on the photoconductor onto the recording medium conveyed along the paper conveyance path by a transfer roller. In an image forming apparatus provided with the recording medium, the recording medium is arranged between the paper feed roller and the transfer roller in a conveyance direction, and has a peripheral speed lower than that of the paper feed roller and higher than that of the transfer roller. A first conveying roller; a clutch means provided on the paper feeding roller and the first conveying roller for making a conveying driving force from a driving source into a transmission state and a non-transmission state; and a recording medium preceding the first conveying roller. The trailing edge of the medium passes Then, the leading end of the succeeding recording medium is brought into contact with the first conveying roller stopped, and the distance between the trailing end of the preceding recording medium and the leading end of the succeeding recording medium is adjusted. (1) Control means for controlling to drive the conveying roller.

According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the peripheral speed is arranged between the paper feed roller and the first transport roller in the transport direction of the recording medium. Is provided with a second transport roller that is slower than the peripheral velocity of the paper feed roller and faster than the peripheral velocity of the first transport roller, and the transport drive force from the drive source is transmitted or not transmitted to the second transport roller. And a control means for bringing the paper feed roller into a non-transmission state when the transporting front end portion of the recording medium is nipped by the second transport roller and the first transport roller. When the transporting front end of the recording medium is sandwiched, the second transport roller is brought into a non-transmitting state, and when the transporting front end of the recording medium is sandwiched between the transfer roller and the photoconductor, the first transport roller is held. To make the non-transmission state And controls the serial clutch means.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described. FIG. 1 is a schematic side sectional view showing an embodiment of a laser printer as an image forming apparatus of the present invention,
2 is a side view showing a conveyance path from the sheet feeding position to the image forming position, FIG. 3 is a diagram showing a drive system, and FIG. 4 is a control function block diagram.

In FIG. 1, a laser printer 1 has a main body case 2 in which a plurality of stages of feeders 4 for feeding a recording medium 3 are formed, and a predetermined image is formed on the fed sheet 3. A process unit 18 for forming an image and a fixing device 19 as fixing means are provided.

Each of the feeders 4 has a paper feed tray 6 that is detachably mounted on the bottom of the main body case 2, a paper pressing plate 8 provided in the paper feed tray 6, and one end of the paper feed tray 6. A paper feed roller 12 and a separating pad means 13 provided above the side end portion are provided. Then, the paper feed roller 12
From the image forming position (photoreceptor drum 23 and transfer roller 25
A conveyance path 7 for the sheet 3 up to a contact portion thereof, that is, a transfer position where the toner image on the photosensitive drum 23 is transferred to the sheet 3.
1 is formed in a curved shape as shown in FIGS. 1 and 2, and in the transport path 7, a paper feed roller 12 as a fourth transport means, a third transport means 11 and The second conveying means 10 and the registration roller 9 as the first conveying means arranged immediately before the image forming position are arranged at appropriate intervals.

The sheet pressing plate 8 is capable of stacking sheets 3 in a stacked form and is swingably supported at the end portion far from the paper feed roller 12, so that the near end portion is vertically moved. It is movable in the direction, and is urged upward from the back side by a spring 8a. The paper feed roller 12 and the separation pad means 13 are arranged to face each other, and the separation pad 13a made of a member having a large friction coefficient is separated by the spring 13b arranged on the back side of the pad support 13c of the separation pad means 13. It is pressed toward the paper feed roller 12. Paper feed roller 12 and separation pad 1
The contact position with 3a corresponds to the paper feeding position in the claims.

The separating pad 13a and the paper feed roller 1
The width dimension of the sheet 2 in the direction orthogonal to the conveying direction of the sheet 3 is formed to be shorter than the width dimension of the sheet 3, and the sheet 2 is arranged so as to contact only the substantially central portion of the sheet 3 in the width direction during sheet feeding. There is.

The uppermost sheet 3 among the sheets 3 stacked on the sheet pressing plate 8 is pressed toward the sheet feeding roller 12 as the fourth conveying means, and is fed by the rotation of the sheet feeding roller 12. After being sandwiched between the roller 12 and the separating pad means 13, the sheets are fed one by one. The fed paper 3 is transported by the third transport means 11, and then sequentially sent to the second transport means 10 and the registration roller 9 as the first transport means, and after the paper 3 is subjected to predetermined registration, image formation is performed. I am trying to send it to the position.

A multi-purpose tray 14 for manually feeding the paper 3 and a paper 3 stacked on the multi-purpose tray 14 are provided on one side of the main body case 2 above the uppermost feeder section 4. Is provided with a multi-purpose side sheet feeding roller 15a and a multi-purpose side sheet feeding pad 15b, and a multi-purpose side sheet feeding roller is provided by a spring 15c provided on the back side of the multi-purpose side sheet feeding pad 15b. The pad 15b is pressed toward the multi-purpose side sheet feeding roller 15a. The sheets 3 stacked on the multi-purpose tray 14 are sandwiched between the rotating multi-purpose side sheet feeding roller 15a and the multi-purpose side sheet feeding pad 15b, and then fed one by one to the conveying roller pair 16. It is sent to the registration roller 9 through the above.

The scanner unit 17 is arranged on the lower surface side of the paper discharge tray 36 in the upper portion of the main body case 2, and has a laser emitting portion (not shown), a polygon mirror 20 which is driven to rotate, lenses 21a and 21b, The process unit 18 is provided with a reflecting mirror 22 and the like, and passes or reflects a laser beam based on predetermined image data emitted from the laser emitting section through the polygon mirror 20, the lens 21a, the reflecting mirror 22, and the lens 21b in this order. The surface of the photoconductor drum 23, which is an example of the photoconductor (image carrier) in FIG.

The process unit 18 is composed of a drum cartridge having a photoconductor drum 23 as a photoconductor, a scorotron charger 37, a transfer roller 25 as a transfer means, and a developing cartridge 24 detachably attached to the drum cartridge. Has been done. Developer cartridge 2
4 includes a toner storage portion 26, a developing roller 27 as a developing means, a layer thickness regulating blade 28, a toner supply roller 29, and the like.

The toner accommodating portion 26 is filled with a positive charging non-magnetic one-component polymerized toner as a developer.
The toner is supplied to the developing roller 27 by the toner supply roller 29, and at this time, the toner supplied to the developing roller 27 is positively frictionally charged between the toner supply roller 29 and the developing roller 27. As the roller 27 rotates, it is carried on the developing roller 27 as a thin layer having a constant thickness by the rubbing of the layer thickness regulating blade 28. on the other hand,
The rotating photosensitive drum 23 is arranged to face the developing roller 27, the drum body is grounded, and the surface thereof is formed of a positively chargeable photosensitive layer made of an organic photosensitive material such as polycarbonate. Has been done.

In this laser printer 1, the transfer roller 2
The residual toner remaining on the surface of the photoconductor drum 23 after the toner image is transferred to the sheet 3 by means of 5 is collected by the developing roller 27, that is, the so-called cleanerless system is used to collect the residual toner. If the residual toner on the surface of the photoconductor drum 23 is collected by such a cleanerless system, it is not necessary to provide a cleaner device such as a blade or a waste toner storage means, so that the device configuration is simplified, downsized, and the cost is reduced. Can be reduced.

Scorotron type charger 3 as charging means
7 are provided above the photoconductor drum 23 with a predetermined interval so as not to contact the photoconductor drum 23. The scorotron-type charger 37 is a scorotron-type charger for positive charging that generates corona discharge from a charging wire such as tungsten, and is configured to uniformly charge the surface of the photoconductor drum 23 to the positive polarity. ing.

The surface of the photoconductor drum 23 is first uniformly positively charged by the scorotron charger 37 as the photoconductor drum 23 rotates, and then the laser beam from the scanner unit 16 is emitted. It is exposed by high-speed scanning to form an electrostatic latent image based on predetermined image data.

Then, when the developing roller 27 rotates, the toner carried on the developing roller 27 and positively charged is formed on the surface of the photosensitive drum 23 when the toner contacts the photosensitive drum 23 in an opposed manner. Electrostatic latent image, that is,
Of the surface of the photosensitive drum 23 which is uniformly positively charged, it is supplied to an exposed portion where the potential is lowered by being exposed by a laser beam, and it is selectively carried to form a visible image. The statue is achieved.

The transfer roller 25 is arranged below the photosensitive drum 23 so as to face the photosensitive drum 23, and is supported by the drum cartridge so as to be rotatable clockwise in FIG. This transfer roller 25
The metal roller shaft is covered with a roller made of an ion conductive rubber material, and a transfer bias (transfer forward bias) is applied from a transfer bias applying power source during transfer. Therefore, the toner image carried on the surface of the photoconductor drum 23 is transferred onto the paper 3 while the paper 3 passes between the photoconductor drum 23 and the transfer roller 25.

Next, the structure of the fixing device 19 as fixing means will be described. As shown in FIG. 1, the fixing device 19 is disposed downstream of the process unit 18 in the conveying direction, and includes one heating roller 31 and the heating roller 3.
A pressure roller 32 arranged to press 1 and a pair of conveying rollers 33 provided on the downstream side of the pressure roller 32 are provided. The heating roller 31 is made of metal such as aluminum and is provided with a heater such as a halogen lamp for heating, and the toner transferred onto the sheet 3 in the process unit 18 is
The sheet 3 is heat-fixed while passing between the heating roller 31 and the pressure roller 32. After that, the paper 3 is transferred to the transport roller 3
3, the sheet is conveyed by the conveying roller 34 and the sheet discharging roller 35 in the sheet discharging path on one side in the main body case 2, and then discharged onto the sheet discharging tray 36.

Further, in this embodiment, a re-conveying unit 41 for forming images on both front and back surfaces of the paper 3 is provided. The re-conveying unit 41 includes a reversing mechanism section 42 and a re-conveying tray 43 that are integrally formed, and the reversing mechanism section 42 is externally attached to the rear side of the main body case 2.
3 is detachably mounted in a state in which it is inserted above the uppermost feeder unit 4.

The reversing mechanism portion 42 has a casing 44 having a substantially rectangular cross section attached to the rear wall of the main body case 2, a flapper 45, a reversing roller 46 and a re-conveying roller 4 inside the casing 44.
It consists of 7 mag. A reversing guide plate 48 projects upward from the upper end of the casing 44.

The flapper 45 is rotatably arranged in the rear portion of the main body case 2 near the downstream side of the transport roller 33.
By switching the excitation and non-excitation of an electromagnetic solenoid (not shown), the sheet 3 image-formed on one surface and conveyed by the conveyance roller 33 is directed toward the conveyance roller 34,
It can be selectively switched to the direction toward the reversing roller 46. When ejecting the single-side printed sheet 3 to the sheet ejection tray 36, the flapper 45 is rotated upward. When performing double-sided printing, the flapper 45 is switched to the direction toward the reversing roller 46. Then, the sheet 3 nipped by the reversing roller 46 capable of switching the forward / reverse rotation is first transferred to the reversing roller 4
The sheet 3 is conveyed toward the reversing guide plate 48 by the forward rotation of 6 and then the sheet 3 is fed back to the re-conveying roller 47 by the reverse rotation of the reversing roller 46. The skew roller 51 conveys the sheet 3 while the side edge of the sheet 3 is in contact with a reference plate (not shown), and returns the sheet 3 to the second conveying unit 10 via the re-conveying guide plate 53. This allows the second
Conveying means 10, registration roller 9 as first conveying means
At the position of, the non-printing surface of the paper 3 is inverted so that it faces the upper surface, and when the image forming position is passed in that state,
An image can be formed on the back surface of the sheet 3.

Next, referring to FIG. 2, the sheet 3 from the sheet feeding roller 12 as the fourth conveying means to the image forming position.
More specifically, the configuration of the conveyance path 7 will be described. A pair of guide plates 7a that guide the wide surface of the sheet 3 to form the curved conveyance path 7 from the sheet feeding position to the image forming position in the uppermost feeder 4. , 7b are arranged. The third conveying means 11 on the side closer to the paper feeding roller 12 is composed of a pair of a driving roller 11a and a driven roller 11b, and similarly,
The second conveying means 10 also includes the driving roller 10a and the driven roller 10
The registration roller 9 as a first conveying means is also composed of a pair of a driving roller 9a and a driven roller 9b. A third sheet sensor 54 is arranged immediately upstream of the third conveying unit 11 in the conveying direction, and a second sheet sensor 55 is arranged immediately before upstream of the second conveying unit 10 in the conveying direction.
A registration roller 56 as a first sheet sensor is arranged immediately upstream of the registration roller 9 as a first conveyance unit in the conveyance direction. Immediately after the registration roller 9 on the downstream side in the conveying direction, the image timing sensor 5
7 are arranged.

Each of the sensors 54 to 57 is pressed by the front end of the sheet 3 being conveyed and can be rotated by a sensor lever 58.
a, 58b, 58c, 58d and the positions of the rotating sensor levers 58a to 58d on the other end side to detect that the leading edge of the sheet 3 has reached a predetermined position, such as a photo interrupter. It consists of containers 59a, 59b, 59c and 59d.

The transport roller pair 16 is also composed of a drive roller and a driven roller, and a fourth paper sensor (not shown) is arranged immediately upstream of the transport roller pair 16 in the transport direction. The fourth sheet sensor is the sensors 54 to 57.
It has the same configuration as.

FIG. 3 shows the drive rollers 9a, 10a, 1
1a, the feed roller 12 and the gear train of the drive system for driving the photosensitive drum 23 are shown. First, the first transmission gear group 62 for rotationally driving the feed roller 12 as the fourth conveying means of the feeder unit 4 is shown. Represents the driving force of the first drive motor 63 from the pinion gear 63a via the common transmission gears 62a, 62b to the gears 62c, 62d, 62e, 62f, 62g, 6
It is configured to be transmitted to the gear 62i attached to the drive shaft of the paper feed roller 12 via 2h.

Further, for the third conveying means 11 and the second conveying means 10, the gears 64a, 64b, 64 as the second transmission gear group 64 from the common transmission gears 62a, 62b.
The drive shaft of the drive roller 11a of the third conveying means 11 is rotated clockwise in FIG. 3 via c. Further, from the gear 64c to the gear 65 as the third transmission gear group 65.
Second transfer means 10 via a, 65b, 65c, 65d
The drive shaft of the drive roller 10a is rotated clockwise in FIG.

On the other hand, the driving force of the second drive motor 66 is transmitted from the pinion gear 66a through the gears 67a, 67b and 67c as the fourth transmission gear group 67 to the photosensitive drum 23.
Transmitted to the drive shaft of. Also, from the gear 67a to the fifth
The drive roller 9 of the registration roller 9 as the first conveying means via the gears 68a, 68b, 68c of the transmission gear group 68.
The rotational force is transmitted to a. First to first transport means 9
The clutch means 82, the second clutch means 81 for the second conveying means 10, and the third clutch means 80 for the third conveying means 11 are electromagnetic clutches (not shown) inserted on the corresponding drive roller side. Therefore, when each electromagnetic clutch is turned on, the corresponding clutch means is brought into the driving force transmission state (joint state). When the respective electromagnetic clutches are turned off, the corresponding clutch means are set in a non-transmitted state (non-joint state) of the driving force, and the drive rollers and the driven rollers at the locations corresponding to the clutch means are configured to be idle. ing.

In this embodiment, the photosensitive drum 23
When the peripheral speed (sheet conveying speed) of the photosensitive drum 23 at the contact portion (transfer portion) between the transfer roller 25 and the transfer roller 25 is Vo,
Paper transport speed V at the registration roller 9 as the transport means
1 is a speed that is 15% higher than the paper transport speed Vo (V1 =
1.15Vo), similarly, the sheet transport speed V2 in the second transport means 10 is set to 15% higher than the sheet transport speed V1 (V2 = 1.15V1), and the third transport means 1
The sheet conveyance speed V3 at 1 is 15 times the sheet conveyance speed V2.
%, And the sheet conveying speed Vs by the sheet feeding roller 12 as the fourth conveying unit is 15% higher than the sheet conveying speed V3 (Vs = 1.15V).
3), the rotational speeds of the first drive motor 63 and the second drive motor 66, the reduction ratios of the transmission gear groups 62 to 68, the diameters of the rollers, and the like are set.

In other words, the plurality of conveying means 9, 1
The conveyance speeds of 0, 11, and 12 are set so that the one on the downstream side in the conveyance direction sequentially decreases from the one on the upstream side in the conveyance (Vo <V1 <V2 <V3 <Vs), and at the image forming position. The sheet transport speed Vo is set to the required speed.

As shown in FIGS. 4 and 5, the embodiment of the clutch means 70 for switching between the transmission state and the non-transmission state of the driving force in the sheet feeding roller 12 is, as shown in FIGS. 4 and 5, the toothless gear in the first transmission gear group 62. 62g and 62h and a cam disk 71 with a locking step portion 71a integrally formed between them are fixed to a shaft 72. One tooth missing gear 62
g is opposed to the drive-side intermediate gear 62f, and the other toothless gear 62h is arranged to face the driven-side gear 62i provided coaxially with the sheet feeding roller 12. The cam board 72
One end of the locking lever 73 that rotates so as to be able to move toward and away from the peripheral surface of the locking lever 73 is connected to the rod 74a of the electromagnetic solenoid 74 as an actuator, and the locking lever 73 is biased by the biasing spring 75. The engaging claw 73a at the end is urged in a direction to engage with the locking step 71a. Then, the other end of the rotation urging spring 77 whose one end is rotatably connected to the eccentric shaft 76 on the side surface of the tooth-chipped gear 62g (or 62h) is mounted on a frame (not shown), and the tooth-chipped gear 62g, 62
The h and the cam plate 71 are integrally biased so as to rotate counterclockwise in FIG.

The engaging claw 73a of the locking lever 73
When the gear is locked to the locking step portion 71a of the cam disk 71 and the rotation thereof is stopped, the gear 62f faces the toothless portion of the one toothless gear 62g so that the tooth portions are meshed with each other. The other toothless gear 62h
The phase is set so that the gear 62i faces the tooth-missing portion in the position where the tooth portions are out of mesh with each other. In this state, the first drive motor 63 (see FIG. 3)
Is not transmitted to the driven gear 62i,
The gear 62i can freely rotate, and therefore the paper feed roller 12 can also freely rotate (idle).

Normally, when the electromagnetic solenoid 74 is temporarily (intermittently) excited by receiving a predetermined signal at the start of the paper feeding operation, the rod 74a resists the urging force of the urging spring 75.
Is pulled in, and the engaging claw 73a of the locking lever 73 is disengaged from the locking step 71a of the cam board 71. Then,
By the urging force of the rotation urging spring 77, the toothless gear 62g (62h) is rotated counterclockwise in FIGS. 4 and 5 together with the cam disk 71, and the tooth portion of the toothless gear 62g is rotated by the gear 62f.
While the rotational driving force is transmitted by meshing with the gear, the other toothless gear 62h meshes with the driven gear 62i, and the rotational force is transmitted to the sheet feeding roller 12. The electromagnetic solenoid 7
Since the excitation of No. 4 is temporary, when the electromagnetic solenoid 74 returns to the non-excitation state, the engagement lever 73 is brought into sliding contact with the peripheral surface of the cam disk 71 by the urging force of the urging spring 75. In this state, after one rotation of the cam board 71, the engagement claw 73a is again engaged with the engagement stepped portion 71a to interrupt the power transmission.

In this non-transmitted state, the paper feed roller 12 can idle, and the leading end side of the paper 3 is the downstream side of the conveying means 1.
When the sheet 3 is nipped and conveyed by 1 or the like, even if the rear portion of the sheet 3 is sandwiched between the sheet feeding roller 12 and the separation pad means 13, the sheet 3 is idly rotated by the sheet feeding roller 12 only and the sheet 3 is conveyed downstream. Be transported smoothly.

Next, the operation control of the plurality of conveying means for improving the image finishing speed on the paper will be described. FIG. 6 is a functional block diagram of the control means 84,
The control means 84 is an electronically controlled controller such as a microcomputer, and includes a registration roller 9, a second transport means 10, and a third transport means 1 as the plurality of transport means.
1. CPU (Central Processing Unit) 85 that executes various calculations for controlling the transport operation of the paper feed roller 12, and ROM (Read Only Memory) 8 that stores control programs and the like
6, a RAM (memory readable / writable at any time) 87 for temporarily storing various data, an input / output interface (not shown), and the like. The image data, the image forming (printing) command, and the like are transmitted from the host controller 89 such as a computer.

The third paper sensor 54, the second paper sensor 55, the first paper sensor (registration sensor) 56 and the image timing sensor 57 are connected to the CPU 85 via an input interface, and the detection signals from the respective sensors are sent. It is input to the CPU 85. On the other hand, a first drive motor 63, a second drive motor 66, a fourth clutch means 70 for the paper feed roller 12, a third clutch means 80 for the third transport means 11, and a second drive motor 63 which are output system external devices. Transporting means 10
The second clutch means 81 for and the first clutch means 82 for the first conveying means (registration roller) 9 are connected to the CPU 85 via the output interface.

Next, a mode of controlling the conveyance operation of the sheet 3 will be described. First, a case where the feeder unit 4 has one stage will be described with reference to the flowchart of FIG. 7 and the time chart of FIG.

First, when the power is turned on, the second drive motor 66 and the like are activated, the photosensitive drum 23, the transfer roller 25, and the developing roller 27 in the process unit 18 are rotated, and the heating roller 31 of the fixing device 19 is rotated. Then, the initial operation such as turning on the heater of the heating roller 31 is executed (S1). Next, the CPU 85 determines whether or not a print command is received from the host controller 89 (S2), and when it is received (S2: yes), the size data of the paper 3 to be printed subsequently, for example, A4. The data to the effect and the image data are sent, and the image data is sequentially developed and stored in the RAM 87 in the print format (S3).

Next, when the development of the predetermined amount of image data is completed and a paper feed signal is input to the CPU 85 (S4: yes
), The CPU 85 energizes (ON) the electromagnetic solenoid 74 of the clutch means 70 for a short time in order to transmit the driving force to the paper feeding roller 12, and then de-energizes (OFF) to drive the paper feeding roller 12 (S5). As a result, as described above, only the uppermost sheet 3 of the plurality of sheets 3 stacked on the sheet pressing plate 8 of the feeder unit 4 is drawn between the sheet feeding roller 12 and the separation pad 13a. Then, the sheet 3 is separated from the lower layer sheet 3, and the sheet 3 is conveyed at the sheet conveying speed Vs by the sheet feeding roller 12 so that the leading end of the sheet 3 approaches the third sheet sensor 54 in the conveying path.

First predetermined time ΔT from the time when the paper feed signal is output
After the lapse of 1 time (see FIG. 8), the leading edge of the sheet 3 rotates the third sheet sensor 54, and the third sheet sensor 54 becomes OF.
The CPU 85 determines whether or not it is turned on from F (S
6). Estimating the elapse of this first predetermined time ΔT1 is
In particular, assuming that a predetermined sheet interval exists between the succeeding sheets 3, the third sheet sensor 54 detects the preceding sheet 3 at the time when the second and subsequent sheet feeding signals are output. Therefore, it is longer than the time required for the preceding paper 3 to complete passing through the third paper sensor 54 from the time the paper feed signal is output, and the paper may not pass through the distance corresponding to the paper interval. A preset time within the required time is defined as a first predetermined time ΔT1 (see FIG. 8). This first predetermined time Δ
When the third paper sensor 54 is ON at the time when T1 has elapsed, the CPU 85 considers the occurrence of a paper jam and interrupts the paper conveyance.

When the third paper sensor 54 is turned on (S6:
yes), the CPU 85 immediately turns on the third clutch means 80.
By setting to N, the driving of the third conveying means 11 is started (S7). Then, when the leading end of the sheet 3 is conveyed between the driving roller 11a and the driven roller 11b in the third conveying unit 11 by the sheet feeding roller 12, the sheet 3 is moved to the third sheet.
The sheet is conveyed by the conveying unit 11 in the direction of the second conveying unit 10 at a sheet conveying speed V3 (<Vs). In the state in which the sheet is conveyed by the third conveying means 11, the sheet feeding roller 12 is in the idling state as described above, and therefore the second half of the sheet 3 is not constrained by the sheet feeding roller 12 and one sheet is fed. The whole 3 is conveyed to the downstream side by the driving force of the third conveying means 10.

Then, after the elapse of the second predetermined time ΔT2,
The leading edge of the sheet 3 rotates the second sheet sensor 55 to determine whether the second sheet sensor 55 is turned from OFF to ON.
U85 determines (S8). Note that this second predetermined time Δ
T2 (see FIG. 8) is also preset for the same reason as the first predetermined time ΔT1.

That is, at the time when the third sheet sensor 54 detects the succeeding sheet 3 and the third conveying means 11 starts driving, the second sheet sensor 55 detects the preceding sheet 3, so that 3 The time required to complete the passage of the sheet 3 through the second sheet sensor 55 from the time when the sheet conveying unit 11 starts driving is equal to or more than the time corresponding to the sheet interval.
The time set in advance within the time required to complete the passage is defined as the second predetermined time ΔT2. This second predetermined time Δ
When the second paper sensor 55 is ON at the time when T2 has elapsed, the paper jam is determined by the CPU 85 and the paper conveyance is interrupted.

Similarly to the above, when the second paper sensor 55 is turned on (S8: yes), the CPU 85 immediately turns on the second clutch means 81 to start driving the second conveying means 10 ( S9). 2nd at the tip of paper 3
The time required from when the paper sensor 55 is turned on until the leading edge of the paper 3 is nipped between the driving roller 10a and the driven roller 10b in the second conveying means 10, that is, the third predetermined time ΔT3. Later (see FIG. 8), C
The PU 85 turns off the third clutch means 80 in order to idle the third conveying means 11 on the upstream side of the conveying (S1).
0).

As a result, the entire one sheet 3 is transported to the downstream side (register roller 9 side) at the sheet transport speed V2 (<V3) by the second transport means 10.

Then, after the lapse of the fourth predetermined time ΔT4 (see FIG. 8).
3), the first sheet sensor (registration sensor) 56 located upstream of the registration roller 9 in the conveying direction,
The CPU 85 determines whether or not the leading edge of the sheet is hit and the first sheet sensor 56 is turned on (S11). This 4th
The predetermined time ΔT4 is also set for the same reason as the setting of the second predetermined time ΔT2.

Some time (fifth predetermined time ΔT) has passed since the first paper sensor (registration sensor) 56 was turned on.
After the lapse of 5), the CPU 85 turns on the first clutch means 82 to drive the rotation of the registration roller 9,
At the same time, the second clutch means 81 is turned off to put the second carrying means 10 in the idling state (S12). Therefore, for the entire sheet 3, the sheet conveying speed V1 (<V
In 2), it is conveyed in the direction of the image forming position.

It should be noted that the drive roller 9a and the driven roller 9b of the registration roller 9 are arranged so that the axes thereof are orthogonal to the conveying path, and the paper is compared with the stopped drive roller 9a and the driven roller 9b. The leading edge of the sheet 3 abuts, and the leading edge of the sheet 3 is slightly loosened so that the leading edge of the sheet 3 is orthogonal to the transport path, and then the CPU 85 rotationally drives the drive roller 9a. The resist action of eliminating the variation in the orientation of the sheet can be performed by nipping and conveying by the driving roller 9a and the driven roller 9b.

Next, when the leading edge of the sheet 3 comes into contact with the image timing sensor 57 located immediately downstream of the registration roller 9 in the conveying direction and the image timing sensor 57 is turned on (S13: yes), the CPU 85 causes the scanner unit 85 to operate. 17 is operated to start the irradiation of the rotating photosensitive drum 23 with the laser beam (S14). As a result, a latent image of image data can be formed, and the subsequent developing roller 27
Visible image (toner image) manifested by the toner supplied above
Reaches the image forming position.

After the lapse of the sixth predetermined time ΔT6, which is the time from when the image timing sensor 57 is turned on to when the paper 3 is nipped by the photosensitive drum 23 and the transfer roller 25 (see FIG. 8), the CPU 85 Turns off the first clutch means 82 and idles the drive roller 9a of the registration roller 9 (S15). This allows the paper 3
The leading edge of the sheet 3 is nipped by the photosensitive drum 23 and the transfer roller 25, and the entire sheet 3 is conveyed at the sheet conveying speed Vo (<V1). The visible image (toner image) reaching the contact point (image forming position) is transferred onto the sheet 3.

Then, at the location of the first paper sensor (registration sensor) 56, the completion of passage of the trailing edge of the paper 3 is judged by the CPU.
When 85 detects (S16: yes), after the lapse of the seventh predetermined time ΔT7, which is the time from the time of the detection to the completion of the trailing edge of the sheet 3 passing the registration roller 9, the trailing edge of the sheet 3 is changed. Since it has completed passing through the registration roller 9, the driving roller 9a and the driven roller 9b of the registration roller 9 pressed by a predetermined pressure stop.

Then, based on another control program, C
When the PU 85 determines whether or not the printing is completed based on the size of the image data, and when images are continuously formed on the plurality of sheets 3, the process returns to the step before step S4 and repeats the processing.

The timing for outputting the second and subsequent sheet feeding signals is when the trailing edge of the preceding sheet 3 is conveyed by a predetermined amount L from the sheet feeding position to the downstream side in the conveying direction.

When a continuous image is formed on a plurality of sheets 3,
At the position of the paper feed roller 12, the paper feed start timing is executed at a distance of a predetermined L (for example, 60 mm) between the trailing edge of the preceding paper 3 and the leading edge of the following paper 3, and The sheet 3 is conveyed at the conveying speed Vs,
As described above, the third transport means 11 on the transport downstream side of the third transport means 11
When the leading edge of the paper 3 reaches the sheet, the paper transport speed V3 (<Vs)
When the sheet is nipped and conveyed by, the paper feed roller 12 on the upstream side in the conveyance idles, so that the entire one sheet 3 is conveyed at the sheet conveyance speed V3 without slack. Third transport means 11
And the second transporting means 10, between the second transporting means 10 and the first transporting means (registration roller) 9, and between the first transporting means 9 and the image forming position, the above-mentioned reduction in speed, By executing the operation of idling of the conveying means on the upstream side (however, at the place where one sheet 3 is passing),
In the sheet conveying path from the sheet feeding roller 12 to the image forming position, the sheet interval between the trailing edge of the preceding sheet 3 and the leading edge of the succeeding sheet 3 is shortened.

In the first embodiment, the paper feed roller 1
The paper distance between the two places is 60 mm, and the paper distance Lo between the trailing edge of the preceding paper 3 and the leading edge of the following paper 3 at the image forming position is set to be about 10 mm. In this embodiment, if the conventional image finishing speed is 38 sheets / minute, the sheet interval is 60 m.
By shortening the length from m to 10 mm, it is possible to shorten the time corresponding to the paper interval of 50 mm. Therefore, it is shortened by 38 sheets × 50 mm = 1900 mm per minute, and if the vertical dimension of A4 size paper 3 is 297 mm, it is 1900 m.
m ÷ 297 mm ≒ 6.3 sheets / minute only for the photosensitive drum 2
Even if the peripheral speed of No. 3 is not changed, the image finishing speed is increased.

At the time when the fifth predetermined time ΔT5 has passed from the time when the first paper sensor (registration sensor) 56 detected the leading edge of the paper 3, the second conveying means 10 was made to idle and the registration roller 9 was driven. In the case of printing a plurality of sheets continuously, a timer is provided for measuring the time from the time when the trailing edge of the preceding sheet 3 is detected by the first sheet sensor 56 to the time when the leading edge of the succeeding sheet 3 is detected. If the timing to start driving the registration rollers 9 is adjusted based on the time counted by the timer, the variation in the leading end position of the sheet 3 in the sheet feeding unit is adjusted to set the sheet interval to a desired value. be able to. The adjustment of the sheet interval can be realized by adjusting the drive start timing of the third conveying means 11 or the second conveying means 10 without using the registration roller 9.

A second embodiment of the conveyance operation control of the paper 3 shown in the flowchart of FIG. 9 and the time chart of FIG. 10 will be described. In this embodiment, the paper feed roller 1
The electromagnetic clutch (not shown) is the same as the third clutch means 80, the second clutch means 81, and the first clutch means 82 for the first conveying means (registration roller) 9 shown in the first embodiment as the clutch means for 2. And Therefore,
When each electromagnetic clutch is turned on, the corresponding clutch means is in a driving force transmission state (joint state). OF of each electromagnetic clutch
At F, each corresponding clutch means is in a non-transmitted state (non-joint state) of the driving force, and each drive roller and driven roller at a location corresponding to each clutch means is configured to be idle.

First, when the power is turned on, the second drive motor 66 and the like are operated, the photosensitive drum 23, the transfer roller 25, and the developing roller 27 in the process unit 18 are rotated, and the heating roller 31 of the fixing device 19 is also rotated. Then, an initial operation such as turning on the heater of the heating roller 31 is executed (S21). Next, the CPU 85 determines whether or not a print command is received from the host controller 89 (S22),
When received (S22: yes), subsequently, the data of the size of the paper 3 to be printed, for example, the data indicating that it is A4 and the image data are sent, and the image data is sequentially expanded in the printing format and stored in the RAM 87 (S23). .

Next, when the development of a predetermined amount of image data is completed and a paper feed signal is input to the CPU 85 (S24: ye
s) First, the CPU 85 turns on the clutch means, the third clutch means 80, and the second clutch means 81 of the paper feed roller 12.
Then, the sheet feeding roller 12, the third conveying unit 11 and the second conveying unit 10 are driven to rotate (S25). This allows
As described above, the uppermost sheet 3 of the plurality of sheets 3 stacked on the sheet pressing plate 8 of the feeder unit 4
Only the paper is separated from the paper feed roller 12 and the separation pad 13a, and the paper 3 is conveyed by the paper feed roller 12 at the paper conveyance speed Vs such that the leading edge of the paper 3 approaches the third paper sensor 54 in the conveyance path. .

Next, the leading edge of the sheet 3 is the third sheet sensor 54.
The third paper sensor 54 is turned on by rotating the
The CPU 85 determines whether or not (S26). When the third paper sensor 54 is turned on (S26: yes), the CPU 85 immediately supplies the feed after the lapse of the tenth predetermined time ΔT10 (see FIG. 10) from the time when the third paper sensor 54 is turned on (S26: yes). The clutch means of the paper roller 12 is turned off to allow the paper feed roller 12 to idle (S2).
7). The tenth predetermined time ΔT10 is a required transport time from when the third sheet sensor 54 is turned on at the leading edge of the sheet 3 until the leading edge reaches the holding position of the third transporting unit 11. As a result, the leading edge side of the sheet 3 is located at the third conveying means 1.
While the sheet 3 is nipped and conveyed by the sheet feeding roller 1, the second half of the sheet 3 is not constrained by the idling of the sheet feeding roller 12, and the entire sheet 3 moves toward the second conveying unit 10 at the sheet conveying speed V3.
It is transported at (<Vs).

Next, at the position of the second paper sensor 55, the paper 3
The CPU 85 determines whether the leading edge of the sheet is detected, that is, whether the second sheet sensor 55 is turned on (S28). When the second paper sensor 55 is turned on (S28: yes), C
The PU 85 turns off the third clutch means 80 after the lapse of the eleventh predetermined time ΔT11 from the time when the second paper sensor 55 is turned on (see FIG. 10) to allow the third transport means 11 to idle (S29). The eleventh predetermined time ΔT11 is a required transport time from the time when the second sheet sensor 55 is turned on at the leading edge of the sheet 3 until the leading edge reaches the holding position of the second transporting unit 10. As a result, the leading end side of the sheet 3 is nipped and conveyed by the second conveying means 10, while the third side is conveyed.
The second half of the sheet 3 is not constrained by the idling of the conveying unit 11, and the entire sheet 3 is conveyed as the first conveying unit toward the registration roller 9 at the sheet conveying speed V2 (<V3). It will be.

Similarly, next, it is determined whether or not the leading edge of the sheet 3 is detected at the position of the first sheet sensor (registration sensor) 56, that is, whether or not the registration sensor 56 is turned on.
U85 determines (S30). The registration sensor 56 is O
12th predetermined time ΔT1 from the time point N (S30: yes)
After the lapse of 2 (see FIG. 10), the CPU 85 turns off the second clutch means 81 to allow the second transport means 10 to idle (S31). The twelfth predetermined time ΔT12 is the required conveyance from the time when the registration sensor 56 is turned on at the leading edge of the sheet 3 to the position where the leading edge of the sheet 3 is clamped by the registration roller 9 and the leading edge of the sheet 3 is aligned. It's time. As a result, the sheet 3 can receive the resisting action that the leading ends of the sheet 3 are aligned in the same manner as described above.

When the twelfth predetermined time ΔT12 has elapsed (see FIG. 10), the CPU 85 drives the registration roller 9 (S32). As a result, the leading end side of the sheet 3 is nipped by the registration rollers 9 and conveyed, while the second conveying unit 10 idles and the second half of the sheet 3 is not constrained and the entire sheet 3 is image-formed. The sheet is conveyed at the sheet conveying speed V1 (<V2) in the direction of the position.

Next, when the leading edge of the sheet 3 comes into contact with the image timing sensor 57 located immediately downstream of the registration roller 9 in the conveying direction and the image timing sensor 57 is turned on (S33: yes), the CPU 85 causes the scanner unit 85 to operate. 17 is operated, and the irradiation of the laser beam to the rotating photosensitive drum 23 is started (S34). This allows
A latent image of the image data can be formed, and the visible image (toner image) that is visible by the toner supplied on the developing roller 27 reaches the image forming position.

After the lapse of the 14th predetermined time ΔT14 from the time when the image timing sensor 57 is turned on (when the leading edge of the sheet 3 reaches the contact point (image forming position) between the photosensitive drum 23 and the transfer roller 25 and is pinched). After the required time has passed, the first clutch means 82 is turned off and the drive roller 9a of the registration roller 9 is idled (S35). As a result, the leading edge of the sheet 3 is nipped by the photosensitive drum 23 and the transfer roller 25, and the entire sheet 3 is conveyed at the sheet conveying speed Vo (<V1). Visible image (toner image) reaching the contact point (image forming position) with the transfer roller 25
Are transferred onto the sheet 3.

Then, at the location of the first paper sensor (registration sensor) 56, the completion of passing the trailing edge of the paper 3 is detected by the CPU.
When it is detected by 85 (S36: yes), an appropriate time (fifteenth predetermined time ΔT15, which is the time from the time of the detection to the completion of the trailing edge of the paper 3 passing through the registration roller 9).
10), the trailing edge of the sheet 3 has completed passing through the registration roller 9, so that the driving roller 9a and the driven roller 9b of the registration roller 9 pressed by a predetermined pressure stop.

Then, based on another control program, C
When the PU 85 determines whether or not the printing is completed based on the size of the image data, and when images are continuously formed on the plurality of sheets 3, the process returns to the step before step S4 and repeats the processing.

When printing the second and subsequent sheets, the third conveying means 11 operates from the time when the third sheet sensor 54 is turned off until the trailing edge of the sheet 3 passes through the third conveying means 11. The driving is restarted after the lapse of the 16th predetermined time ΔT16. Further, in the second conveying means 10, the trailing edge of the sheet 3 is the second sheet from the time when the second sheet sensor 55 is turned off.
The driving is restarted after the lapse of the seventeenth predetermined time ΔT17, which is the time until the passage of the conveying means 10 is completed.

It should be noted that, in response to the input of the sheet feed signal for the first sheet, the third transport means 11 and the second transport means 10 as well as the sheet feed roller 12 may be controlled to start driving at the same time. good. Further, in each of the above embodiments, ΔT1 to ΔT
The time count of 17 was set in the paper feed section without depending on the detection signal of the leading end of the conveyed paper 3 or the detection signal of the rear end of the paper 3 by the paper sensors 54 to 56 and the image timing sensor 57. Based on the information on the size of the paper and the data on the length of each transport path from the paper feed roller 12 which is the fourth transport means to the third transport means 11, the second transport means 10, and the first transport means 9, each transport means It may be configured to control the ON / OFF operation of each of the clutch means 70 to 82 by calculating the drive timing and the slip timing such as idling.

Further, in the case where the feeder section 4 is installed in two stages and paper is fed from the lower feeder section 4 ', as shown in FIG. 1, it is conveyed downstream from the lower sheet feed roller 12'. Since the sheet 3 is conveyed from the fifth conveying means 11 'on the side to the third conveying means 11 on the upper stage, the fifth clutch means 83 for the fifth conveying means 11' as shown in the functional block of FIG. Is provided so that the sheet conveying speed by the fifth conveying means 11 ′ is set to be driven so as to be higher than the sheet conveying speed by the third conveying means 11, while the fifth clutch means 83 is also the same as in each of the above embodiments. The operation is controlled.

In each of the above-described embodiments, the transport speeds of a plurality of transport means (the number of which is not limited) in the transport path are set so that the transport speed on the downstream side in the transport direction gradually decreases from that on the upstream side in the transport direction. , When the transporting end of the recording medium is sandwiched by the transporting device on the downstream side in the transporting direction, the clutching device is controlled to bring the adjacent transporting device on the upstream side in the transporting direction into the non-transmitting state. In order to continuously form images on the sheets of paper (recording medium),
Even if the sheet is fed at the sheet feeding timing such that the interval (sheet interval) between the trailing edge of the preceding sheet 3 and the leading edge of the succeeding sheet 3 becomes wide, the sheet interval is shortened immediately before the image forming position. Therefore, it is possible to reduce the time loss due to the paper interval and to increase the number of finished images per unit time (sheet /
Minutes) can be increased.

Further, the friction coefficient differs depending on the type of the sheet 3, and slippage occurs between the rollers in each conveying means, so that the peripheral speed of each conveying means and the conveying speed of the sheet 3 do not match. Generally, the transport speed of the sheet 3 is slower. Therefore, based on the designed peripheral speed of each transport means,
If the timing for turning ON / OFF each clutch means or the idling start of the conveying means is set, there is a problem that the deviation occurs. Therefore, as in the present invention, the sheet detecting means is provided immediately before the conveying upstream side of each conveying means. By arranging the clutch means and controlling the clutch means so that the adjacent conveying means on the upstream side in the conveying direction are brought into the non-transmitting state based on the detection result, it is possible to accurately execute the timing for controlling each conveying means. .

Since the plurality of conveying means are composed of the driving roller and the driven roller which rotates together with the driving roller, and the clutch means is provided for the driving roller, the idling action of the driving roller is executed. This has the effect that the configuration for the above can be made extremely simple.

Since the clutch means is characterized by being a friction clutch such as an electromagnetic clutch, it is possible to quickly switch the connection and disconnection of the power, and it is possible to more easily increase the printing speed. Play.

The plurality of conveying means are provided between a sheet feeding position for separating the recording mediums stacked in the sheet feeding section and feeding them one by one, and an image forming position for forming an image on the sheet 3. It is arranged so that the conveying speed from the sheet feeding position to the image forming position is sequentially decreased on the downstream side in the conveying direction, and it is simple to add clutch means to the conveying means conventionally arranged on the conveying path. There is an effect that it becomes a simple structure.

Further, at the image forming position, the conveying speed of each conveying means is set so that the trailing edge of the preceding sheet 3 does not overlap the leading edge of the succeeding sheet 3. In this case, there is an effect that paper jam such as overlapping of adjacent papers does not occur.

In the above-described embodiment, the paper feed roller 12 may have a paper-conveying surface and a non-conveying surface, such as a D-shaped side view. Further, although the separation sheet is a friction separation type in which a separation pad made of a material having a large coefficient of friction is arranged on the peripheral surface of the sheet supply roller 12 so as to face each other, the sheet at the uppermost position of the stacked sheets is not separated by the sheet supply roller. While the peripheral surfaces are brought into contact with each other, the leading edges of the stacked sheets are arranged so as to be substantially orthogonal to the sheet conveying path and blocked by the bank member, and the uppermost position to be conveyed when the sheet feeding roller is driven to rotate. The present invention is also applicable to a so-called bank-separated paper feeding unit in which paper can be fed over the bank due to the stiffness of the paper.

In the above-described embodiment, the present invention is applied to the laser printer 1. However, even when it is used in a color laser printer, an ink jet printer, a thermal printer, a dot impact printer, etc., the time loss due to the paper interval is reduced, The number of finished images per unit time can be increased without adversely affecting image formation.
In the above-described embodiment, the photoconductor drum 2 is used as the photoconductor.
However, it may be a photoconductor belt. Further, although the transfer roller is used as the transfer means, a corona discharge type may be used. Further, the multi-purpose side paper feed roller 15
The conveyance speed may be sequentially reduced from the a, the conveyance roller pair 16, and the registration roller 9 from the downstream side in the conveyance direction.

[0092]

As described above, according to the first aspect of the invention, the image forming apparatus according to the first aspect of the invention has a sheet conveying path through which a recording medium is conveyed from a sheet feeding section, In an image forming apparatus including an image forming unit that forms an image on a recording medium conveyed along a sheet conveying path, the image forming apparatus is arranged at at least two positions in the sheet conveying path, and the conveying speed is A plurality of conveying means set so that the one on the downstream side in the conveying direction is sequentially lowered from the one on the upstream side in the conveying direction, and the clutch means for making the conveying driving force from the drive source in the transmitting state and the non-transmitting state to the conveying means. And a control means for controlling the clutch means so as to bring the adjacent conveying means on the upstream side in the conveying direction into a non-transmission state when the conveying tip on the recording medium is sandwiched by the conveying means on the downstream side in the conveying direction. Is equipped with

Therefore, in order to continuously form an image on a plurality of sheets of paper (recording medium), the gap between the trailing edge of the preceding recording medium and the leading edge of the succeeding recording medium (paper Even if the paper is fed at the paper feed timing at which the (interval) becomes a predetermined paper interval, the paper interval can be shortened immediately before the image forming position. Number of finished images per sheet (sheets /
That is, it is possible to increase (minute) (printing speed).

The invention described in claim 2 is the same as claim 1
In the image forming apparatus described in (1), the front end of the recording medium is brought into contact with at least one of the conveying means stopped to adjust the distance from the rear end of the preceding recording medium. Therefore, even if there is a variation in the leading end position of the recording medium in the paper feeding section, there is an effect that the interval of the recording medium can be set to a desired value.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, between the adjacent conveying means on the upstream side in the conveying direction and the conveying means on the downstream side in the conveying direction. Sheet detecting means for detecting the recording medium is provided, and the control means makes the adjacent conveying means upstream in the conveying direction non-transmitting state based on the detection result by the sheet detecting means. It is characterized by controlling.

Therefore, the coefficient of friction varies depending on the type of recording medium (paper), and slippage occurs between the rollers of each conveying means, and the peripheral speed of each conveying means and the conveying speed of the recording medium. Does not match, and generally the recording medium is conveyed at a slower speed. Therefore, based on the designed peripheral speed of each conveying means, ON / OFF of each clutch means
If you set the timing to start idling of the transportation means and
Since there is a problem that the deviation occurs, as in the present invention, the sheet detecting means is arranged immediately before the conveying upstream side of each conveying means, and the adjacent conveying direction upstream side conveying means is determined based on the detection result. If the clutch means is controlled so as to be in the non-transmission state, there is an effect that the timing for controlling each conveying means can be accurately executed.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the control means detects the trailing edge of the preceding recording medium by the sheet detecting means and the succeeding recording medium. It is characterized in that the stop period of the succeeding recording medium by the conveying means on the downstream side in the conveying direction is controlled based on the detection of the leading end of the recording medium. Even if there is, there is an effect that the interval of the recording medium can be set to a desired value.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the conveying means is composed of a driving roller and a driven roller that rotates together with the driving roller. Since the drive roller is provided with the clutch means, the structure for executing the idling action of the drive roller can be extremely simplified.

According to a sixth aspect of the invention, in the image forming apparatus according to any of the first to fifth aspects, the clutch means is a friction clutch such as an electromagnetic clutch. Therefore, there is an effect that it is possible to quickly switch the connection and disconnection of power, and to increase the printing speed more easily.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the conveying unit separates the recording medium stacked in the sheet feeding unit to separate the recording medium.
It is arranged between a sheet feeding position for feeding the sheets one by one and an image forming position for forming an image on a recording medium, and the conveying speed from the sheet feeding position to the image forming position is gradually reduced on the downstream side in the conveying direction. With such a configuration, there is an effect that it becomes a simple configuration in which the clutch means is simply added to the transport means conventionally arranged on the transport path.

According to an eighth aspect of the invention, in the image forming apparatus according to the seventh aspect, at the image forming position, the trailing edge of the preceding recording medium does not overlap the leading edge of the following recording medium. In addition, since the speed of each transport means is set, in addition to the effect of the invention according to any one of claims 1 to 5, adjacent recording media overlap each other in the transport path. This has the effect of not causing paper jams.

Further, in the image forming apparatus of the present invention, the paper feed roller for separating the recording media stacked in the paper feed unit one by one, and the paper feed roller A paper conveyance path along which the recording medium is conveyed, and an image forming unit that forms an image by transferring the developer image on the photoconductor onto the recording medium conveyed along the paper conveyance path by a transfer roller. In an image forming apparatus provided with the recording medium, the recording medium is arranged between the paper feed roller and the transfer roller in a conveyance direction, and has a peripheral speed lower than that of the paper feed roller and higher than that of the transfer roller. A first conveying roller; a clutch means provided on the paper feeding roller and the first conveying roller for making a conveying driving force from a driving source into a transmission state and a non-transmission state; and a recording medium preceding the first conveying roller. The trailing edge of the medium passes Then, the leading end of the succeeding recording medium is brought into contact with the first conveying roller stopped, and the distance between the trailing end of the preceding recording medium and the leading end of the succeeding recording medium is adjusted. (1) Control means for controlling to drive the conveying roller. Therefore, even if the leading end position of the recording medium in the paper feeding unit varies,
The effect is that the distance between the recording media can be set to a desired value.

According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the peripheral speed is arranged between the paper feed roller and the first transport roller in the transport direction of the recording medium. Is provided with a second transport roller that is slower than the peripheral velocity of the paper feed roller and faster than the peripheral velocity of the first transport roller, and the transport drive force from the drive source is transmitted or not transmitted to the second transport roller. And a control means for bringing the paper feed roller into a non-transmission state when the transporting front end portion of the recording medium is nipped by the second transport roller and the first transport roller. When the transporting front end of the recording medium is sandwiched, the second transport roller is brought into a non-transmitting state, and when the transporting front end of the recording medium is sandwiched between the transfer roller and the photoconductor, the first transport roller is held. To make the non-transmission state And controls the serial clutch means.

Therefore, in order to continuously form images on a plurality of sheets of paper (recording medium), the gap between the trailing end of the preceding recording medium and the leading end of the succeeding recording medium (paper Even if the paper is fed at the paper feed timing at which the (interval) becomes a predetermined paper interval, the paper interval can be shortened immediately before the image forming position. Number of finished images per sheet (sheets /
That is, it is possible to increase (minute) (printing speed).

[Brief description of drawings]

FIG. 1 is a schematic side sectional view showing an embodiment of a laser printer as an image forming apparatus of the present invention.

FIG. 2 is a side view showing a sheet transport path and a transport unit.

FIG. 3 is a diagram showing a power transmission mechanism for a conveying unit and the like.

FIG. 4 is a side view of a clutch unit for intermittently driving a sheet feeding roller.

FIG. 5 is a perspective view of a main part of a clutch unit of a sheet feeding roller.

FIG. 6 is a functional block diagram of control means.

FIG. 7 is a flow chart for a first embodiment of motion control.

FIG. 8 is a time chart showing the timing of each sensor of the first embodiment and the operation of the conveyance means.

FIG. 9 is a flowchart for a second embodiment of motion control.

FIG. 10 is a time chart showing the timing of each sensor of the second embodiment and the operation of the conveyance means.

[Explanation of symbols]

1 laser printer 3 Paper as recording medium 7 Transport route 9 Registration roller as first conveying means 10 Second Transport Means 11 Third Conveying Means 12 paper feed rollers 13 Separation pad means 54 Third Paper Sensor 55 Second paper sensor 56 Registration sensor as first paper sensor 57 Image timing sensor 63 First drive motor 66 Second drive motor 70 Fourth Clutch Means 80 Third Clutch Means 81 Second Clutch Means 82 First Clutch Means

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H072 AA09 AA16 AA24 AA32 AB07                       BA03 BA12 CA01 CA02 CA05                       CB09 FA01 JA02                 3F049 AA10 DA11 DA12 EA14 EA28                       EA29 LA03 LA05 LA07 LB03                 3F343 FA02 FB02 FB03 GA03 GB01                       GC01 GD02 HB01 HB03 HC04                       HC05 HD17 JA01 JD08 KB04                       KB06 KB20 LD10 LD24 LD30                       MA13 MA15 MA33 MB03 MB13                       MB15 MC04 MC10

Claims (10)

[Claims] 1. An image forming apparatus, comprising: a paper transport path through which a recording medium is transported from a paper feeding section; and an image forming unit that forms an image on the recording medium transported along the paper transport path. A plurality of transporting units arranged at appropriate intervals in at least two positions in the sheet transporting path, the transporting speed being set so that the transporting speed downstream side sequentially decreases from the transporting direction upstream side. The transfer driving force from the drive source is transmitted to the transfer means,
When the front end of the recording medium is sandwiched between the clutch means that is in the non-transmitting state and the conveying means that is on the downstream side in the conveying direction, the adjacent conveying means that is on the upstream side in the conveying direction is in the non-transmitting state. An image forming apparatus comprising: a control unit that controls the unit. 2. The distance between the leading end of the recording medium and the leading end of the recording medium is adjusted by bringing the leading end of the recording medium into contact with at least one of the conveying means stopped. The image forming apparatus according to item 1. 3. A paper detecting means for detecting the recording medium is provided between the adjacent conveying means on the upstream side in the conveying direction and the conveying means on the downstream side in the conveying direction, and the control means comprises the paper detecting means. 3. The image forming apparatus according to claim 1, wherein the clutch means is controlled based on the detection result of the means so as to bring the adjacent conveying means on the upstream side in the conveying direction into the non-transmitting state. 4. The control means detects the trailing edge of the preceding recording medium by the paper detecting means and the leading edge of the succeeding recording medium based on the detection of the trailing edge of the succeeding recording medium. The image forming apparatus according to claim 3, wherein a stop period of the recording medium is controlled. 5. The transporting means comprises a driving roller and a driven roller that rotates together with the driving roller, and clutch means is provided for the driving roller. The image forming apparatus according to item 1. 6. The image forming apparatus according to claim 1, wherein the clutch unit is a friction clutch such as an electromagnetic clutch. 7. The sheet feeding position for separating the recording mediums stacked in a sheet feeding section and feeding them one by one,
It is arranged between an image forming position for forming an image on a recording medium and is configured so as to sequentially decrease the conveying speed from the paper feeding position to the image forming position on the downstream side in the conveying direction. The image forming apparatus according to any one of claims 1 to 6. 8. The carrying speed of each carrying means is set so that the trailing end of the preceding recording medium does not overlap the leading end of the following recording medium at the image forming position. The image forming apparatus according to claim 7. 9. A paper feed roller for separating the recording media stacked in the paper feed unit one by one, and a paper conveyance path for conveying the recording media separated by the paper feed roller,
An image forming apparatus, comprising: an image forming unit that transfers a developer image on a photoconductor by a transfer roller to form an image on a recording medium that has been conveyed along the sheet conveying path. A first transport roller that is disposed between the paper feed roller and the transfer roller in a direction and has a peripheral speed lower than the peripheral speed of the paper feed roller and higher than the peripheral speed of the transfer roller; A first conveying roller after a trailing edge of a recording medium preceding the first conveying roller passes through a clutch means which is provided on the first conveying roller and which makes a conveying driving force from a driving source transmitted or not transmitted; The first transport roller is driven after the leading end of the succeeding recording medium is brought into contact with the roller stopped and the distance between the trailing end of the preceding recording medium and the leading end of the succeeding recording medium is adjusted. Control to An image forming apparatus characterized by comprising a stage. 10. The recording medium is disposed between the paper feed roller and the first transport roller in the transport direction of the recording medium,
A second conveying roller having a peripheral speed lower than that of the sheet feeding roller and higher than that of the first conveying roller, wherein a conveying driving force from a driving source is transmitted to the second conveying roller;
A clutch means is provided to bring the recording medium into a non-transmission state, and the control means brings the paper feed roller into a non-transmission state when the conveyance leading end portion of the recording medium is nipped by the second conveyance roller, and the first conveyance roller. When the transporting front end of the recording medium is clamped by the second transport roller, the second transport roller is brought into a non-transmitting state, and when the transporting front end of the recording medium is clamped by the transfer roller and the photoconductor, 10. The image forming apparatus according to claim 9, wherein the clutch means is controlled so that the first conveying roller is in a non-transmitting state.