JPH0561295A - Driving mechanism used for electrophotographic device - Google Patents

Abstract

PURPOSE:To provide a driving mechanism used for an electrophotographic device capable of faithfully reproducing an original image by preventing the extension and contraction of an image. CONSTITUTION:In a step ST1, a CPU counts time (x) from timing that one photodetector obtains an on-state to timing that the other photodetector obtains the on-state, based on the signals of two photodetectors. Then, in a step ST2, the carrying speed FSPD (=L/x) of a form by a resist roller is calculated, based on a prescribed distance L between two photodetectors and the time (x). Then, in a step ST3, the peripheral speed DSPD of a photosensitive drum is calculated based on the rotational speed detecting signal of the photosensitive drum from a rotary encoder. Then, in a step ST4, the carrying speed (L/x) of the form by the resist roller and the peripheral speed DSPD of the photosensitive drum, are compared, and the duty width of a speed control signal is calculated so as to obtain L/X=DSPD. At last, in a step ST5, the speed control signal is fed back to a motor control circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive mechanism used in an electrophotographic apparatus.

[0002]

2. Description of the Related Art In an electrophotographic apparatus such as a copying machine or a laser printer, a driving mechanism including various rollers such as a feeding roller, a conveying roller, a fixing roller and a discharging roller, and a motor for driving a photosensitive drum. Is provided.

FIG. 7 is a sectional view showing the structure of a conventional copying machine.

As shown in FIG. 1, a conventional copying machine, which is an example of an electrophotographic apparatus, has a paper feed roller pair 10 and a conveyance roller pair 1.
1, a pair of registration rollers 12, a magnet roller 13, a photosensitive drum 14, a conveyor belt 15, a fixing roller 16, a pressure roller 17
And a movable part including the paper discharge roller pair 18, and a drive mechanism including a main motor 19.

The aforesaid movable part in the conventional copying machine is moved by a transmission mechanism composed of gears, pulleys, belts, etc.
It is configured to be driven by two main motors 19.

[0006]

Generally, in such a conventional copying machine, the above-mentioned movable parts, in particular, the photosensitive drum 14, the registration roller pair 12, the conveying roller pair 11 and the fixing roller 16 have processing dimensions. Due to variations in tolerance, the peripheral speed (rotational speed) of the photosensitive drum 14 and the moving speed of the paper on which the copy image is to be formed may not precisely match.

As a result, when the toner image formed on the photoconductor drum 14 is transferred from the photoconductor drum 14 to the paper at the image transfer position or when the toner image transferred to the paper is fixed, the photoconductor drum is fixed. There is a problem that the original image cannot be faithfully copied because the image expands and contracts along the moving direction of the paper with respect to the drum 14. Therefore, the conventional copying machine has a limit in performance when aiming at high resolution and high quality copying image quality.

The present invention provides a driving mechanism used in an electrophotographic apparatus capable of preventing expansion and contraction of an image and faithfully reproducing an original image.

[0009]

A conveying means for conveying a sheet to an image transfer position of a photoconductor, a driving means for driving the conveying means, and a first detecting means for detecting a moving speed of the photoconductor,
Second detecting means for detecting the conveying speed of the sheet conveyed by the conveying means, and the conveying speed of the sheet detected by the second detecting means are synchronized with the movement speed of the photoconductor detected by the first detecting means. And a control means for controlling the drive means.

[0010]

The movement speed of the photosensitive member is detected by the first detecting means, and the conveying speed of the sheet conveyed by the conveying means for conveying the sheet to the image transfer position of the photosensitive member is detected by the second detecting means. The control means controls the driving means for driving the conveying means so that the detected conveying speed of the paper sheet is synchronized with the moving speed of the photoconductor. Therefore, since the movement speed of the photoconductor and the conveyance speed of the paper can be always matched, the expansion and contraction of the image can be prevented, and the original image can be faithfully reproduced.

[0011]

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

FIG. 2 is an enlarged view of a main portion of a copying machine equipped with an embodiment of a driving mechanism for an electrophotographic apparatus according to the present invention.

As shown in the figure, the copying machine 20 of this embodiment
Is provided with a photoconductor drum 21, a registration roller 25, a sheet conveyance path 26 and a conveyance belt 27, and a charging device 22, a developing device 23 and a transfer device 24 are arranged in a known manner along the periphery of the photoconductor drum 21. Has been done.

A sheet on which a copy image is to be formed is supplied to a registration roller 25 by a sheet feeding roller described later, and is sent from the registration roller 25 to an image transfer position T through a sheet conveyance path 26 shown by a broken line in FIG. After the toner image formed on the photoconductor drum 21 is transferred, the toner image is transferred onto the conveyor belt 27.

FIG. 3 is a side view showing the construction of a copying machine provided with an embodiment of the drive mechanism of the electrophotographic apparatus according to the present invention, and mainly illustrates the transmission mechanism. FIG. 3 shows a view from the opposite side to FIG.

As shown in FIGS. 3 and 2, the copying machine 20 of this embodiment further includes a drive motor 28 for exclusively driving the photosensitive drum 21, an output gear 29, a gear 30, and a registration roller.
Drive motor 31 for driving 25, output gear 32, gear 3
3, transmission belt 34, pulley 35, drive motor 36, transmission belt 37, waste toner roller 38, pulley 39, fixing heat roller 40, transmission belt 41, paper discharge roller 42, belt 43, pulley
44 and 45, a developing magnet roller 46, a toner supply / conveyance roller group 47, and paper feed rollers 48, 49 and 50.

The photosensitive drum 21 is configured to be driven by a drive motor 28 which exclusively drives the photosensitive drum 21. An output gear 29 provided on the output shaft of the drive motor 28 directly meshes with a gear 30 provided on the side of the photosensitive drum 21.

Therefore, the drive system of the photosensitive drum 21, that is, the drive motor 28 is separated from the drive system of the other movable parts of the copying machine 20, and the drive motor 28 is affected by the fluctuation of the load of the other movable parts. Since it is not received, a stable rotation speed of the photosensitive drum 21 is secured.

The registration roller 25 and the conveyor belt 27 are configured to be driven by a drive motor 31 different from the drive motor 28.

Generally, the rotation speed of the registration roller 25 is
Since it is directly related to the conveyance speed of the paper, it has an important influence on the copy image quality. Therefore, in this embodiment, as shown in FIG. 3, the output gear 32 provided on the output shaft of the drive motor 31 meshes with the gear 33 of the registration roller 25, and the registration roller 25 is directly driven by the drive motor 31. It is configured to be driven.

Therefore, the registration roller 25 is also not affected by load fluctuations and vibrations of other movable parts, and a stable rotation speed is secured.

The rotation of the registration roller 25 is transmitted to the conveyor belt 27 via the transmission belt 34 and the pulley 35.

In this embodiment, the copying machine 20 has a drive motor.
36 is provided, and the drive motor 36 is configured to drive the remaining movable part of the copying machine 20. That is, the rotation of the drive motor 36 is first transmitted to the waste toner roller 38 and the pulley 39 by the transmission belt 37. The rotation of the pulley 39 is transmitted to the fixing heat roller 40 by the gear train, and further transmitted from the fixing heat roller 40 to the paper discharge roller 42 via the gear train and the transmission belt 41.

The rotation of the drive motor 36, on the other hand, is transmitted by the belt 43 to the pulleys 44 and 45. The rotation of the pulley 44 is transmitted to the developing magnet roller 46 by the gear train, and the rotation of the developing magnet roller 46 is further transmitted to the toner supply / conveyance roller group 47 by the belt transmission mechanism. or,
The rotation of the pulley 45 is sequentially transmitted to the paper feed rollers 48, 49 and 50 by the gear train.

As shown in FIG. 2, a speed detection device 51 for detecting the speed at which the paper sent from the registration roller 25 is conveyed is provided in the paper conveyance path 26 from the registration roller 25 to the image transfer position T. ing.

In this embodiment, the speed detecting device 51 traverses the sheet conveying path 26, and the light emitting element 52 and the light receiving element 53 provided on the registration roller 25 side and the light emitting element arranged on the image transfer position T side. The element 54 and the light receiving element 55 are included.

The signals from the light receiving elements 53 and 55 are sent to a central control unit (CPU) described later. Photoconductor drum 21
Is detected by a rotary encoder (not shown) attached to the photoconductor drum 21 or the drive motor 28, and the detected signal is also sent to the CPU.

Next, a drive motor for driving the registration rollers
The speed control of 31 will be described.

FIG. 4 shows a drive motor for driving the registration rollers.
FIG. 31 is a block configuration diagram showing a configuration example of a speed control circuit of 31.

As shown in FIG. 3, the speed control circuit 56 has a configuration shown in FIG.
It is included in the copying machine 20 shown in FIG. 1 and has a CPU 57 and a motor control circuit 58.

The CPU 57 is attached to the photoconductor drum 21 or a drive motor 28 for exclusively driving the photoconductor drum 21, and a rotary encoder 59 for detecting the rotation speed of the photoconductor drum 21 and light receiving elements 53 and 55. The rotation speed detection signal RE of the photoconductor drum 21 from the rotary encoder 59 and the paper conveyance speed detection signal from the light receiving elements 53 and 55 are connected to the CPU 57.

The CPU 57 is turned on according to the procedure described later.
FMON signal 60, which is an (ON) / OFF (OFF) signal,
FMCO, a speed control signal consisting of a pulse width signal
The N signal 61 and the motor control circuit 58 are sent to the motor control circuit 58. The motor control circuit 58 controls the drive motor 31 for driving the registration rollers based on these signals, so that the rotation speed of the drive motor 31 (that is, paper conveyance). Speed).

The photoconductor drum 21 is an example of the photoconductor of the present invention. The registration roller 25 is an embodiment of the conveying means of the present invention. The drive motor 31 is an embodiment of the drive means of the present invention. The speed detecting device 51 is an embodiment of the second detecting means of the present invention. The speed control circuit 56 is an embodiment of the control means of the present invention. The rotary encoder 59 is an embodiment of the first detecting means of the present invention.

FIG. 1 shows a drive motor for driving the registration rollers.
13 is a flowchart of a program executed by a CPU 57 to control the rotation speed of 31. FIG. 5 shows light receiving elements 53 and 55.
7 is a time chart showing a time interval in which is turned on. FIG. 6 is a graph showing an example of the relationship between the FMCON signal 61, which is a speed control signal, and the sheet conveyance speed FSPD.

The speed detecting circuit 56 included in the copying machine 20 is provided with a ROM (read only memory) not shown in the figure, and the drive motor 31 for driving the registration rollers shown in FIG. CPU57 to control the rotation speed
The program executed by is stored in this ROM. The program stored in the ROM can be read and executed by the CPU 57.

As shown in FIG. 1, in step ST1, CP
U57 turns on the light receiving element 55 from the timing when the light receiving element 53 is turned on based on the signals from the light receiving elements 53 and 55.
Time to reach the state x (seconds) (see Fig. 5)
To measure.

Next, at step ST2, the CPU 57 determines the sheet conveying speed FSPD by the registration rollers 25 based on the predetermined distance L between the light receiving element 53 and the light receiving element 55 and the time x.
(= L / x) is calculated.

Next, at step ST3, the rotational speed detection signal RE of the photosensitive drum 21 from the rotary encoder 59 is received.
The peripheral speed DSPD of the photosensitive drum 21 is calculated based on

Next, at step ST4, the conveyance speed (L / x) of the paper by the registration roller 25 is compared with the peripheral speed DSPD of the photosensitive drum 21 so that L / x = DSPD.
Calculate the duty width of FMCON signal 61.

For example, if the duty of the FMCON signal 61 before speed control is T%, the required duty width is T × (DSPD
/ FSPD) × k. Here, k is a proportional constant with respect to the carrier speed FSPD of the FMCON signal 61, as shown in FIG.

Finally, in step ST5, the FMCON signal composed of the pulse width signal having the above-mentioned required duty width.
61 is fed back to the motor control circuit 58.

Therefore, the drive motor 31 for driving the registration rollers is controlled so that the rotation speed thereof, that is, the paper conveyance speed FSPD coincides with the peripheral speed DSPD of the photosensitive drum 21.

Incidentally, for example, the paper conveying speed FSPD is 260 mm.
Per second, the peripheral speed DSPD of the photosensitive drum 21 is 260 mm / second, which is equal to the paper transport speed FSPD. Further, assuming that the distance L between the light receiving element 53 and the light receiving element 55 is 16.6 mm, the time x from the timing when the light receiving element 53 is turned on to the timing when the light receiving element 55 is turned on is about 0.
It is 06 seconds, and control can be performed based on these data.

According to the above-described embodiment, when the toner image formed on the photoconductor drum 21 at the image transfer position T of the copying machine 20 is transferred to the paper, the peripheral speed of the photoconductor drum 21 and the registration roller 25 are set. Since it always matches the sheet conveyance speed due to, the expansion and contraction of the image due to the disagreement of the speeds of both can be prevented, and the original image can be faithfully reproduced.

Further, the drive motor 28 for driving the photosensitive drum and the drive motor 31 for driving the registration roller are separately provided and separated from the drive motors for driving the other movable parts. Since the drum 21 and the registration roller 25 are not affected by load fluctuations and vibrations of other movable parts, a stable rotation speed is secured.

[0046]

As described above, according to the present invention, the transport means for transporting the sheet to the image transfer position of the photoconductor, the drive means for driving the transport means, and the first speed detecting the moving speed of the photoconductor. A detection unit; a second detection unit that detects the conveyance speed of the sheet conveyed by the conveyance unit; and a photosensitive member whose conveyance speed of the sheet detected by the second detection unit is detected by the first detection unit. Since the control means for controlling the drive means is provided so as to be synchronized with the movement speed, the expansion and contraction of the image can be prevented, and the original image can be faithfully reproduced.

[Brief description of drawings]

FIG. 1 is a flowchart of a program executed by a CPU to control the rotation speed of a drive motor for driving registration rollers.

FIG. 2 is an enlarged view of a main part of a copying machine including an embodiment of a driving mechanism of an electrophotographic apparatus according to the present invention.

FIG. 3 is a side view showing the configuration of a copying machine provided with an embodiment of a driving mechanism for an electrophotographic apparatus according to the present invention, as seen from the side opposite to that in FIG.

FIG. 4 is a block configuration diagram showing a configuration example of a speed control circuit of a drive motor for driving the registration rollers.

FIG. 5 is a time chart showing a time interval in which two light receiving elements are in an ON state.

FIG. 6 is a graph showing an example of a relationship between a speed control signal and a sheet conveyance speed.

FIG. 7 is a cross-sectional view showing the configuration of a conventional copying machine.

[Explanation of symbols]

 20 Copier 21 Photoconductor drum 25 Registration rollers 28, 31 Drive motor 51 Speed detection device 56 Speed control circuit 57 CPU 58 Motor control circuit 59 Rotary encoder

Claims (1)

[Claims] 1. A transporting means for transporting a sheet to an image transfer position of a photoconductor, a driving means for driving the transporting means, a first detecting means for detecting a moving speed of the photoconductor, and a transporting means by the transporting means. Second detecting means for detecting the conveying speed of the sheet to be conveyed, and the conveying speed of the sheet to be detected by the second detecting means is synchronized with the movement speed of the photoconductor detected by the first detecting means. A drive mechanism used in an electrophotographic apparatus, further comprising: a control unit that controls the drive unit.