JP5109630B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for preventing image quality deterioration due to an emergency stop.

  In the intermediate transfer type image forming apparatus, the temperature of the photosensitive drum and the intermediate transfer body is increased during image formation due to heat generated by the fixing device. Thereafter, when the standby state is entered, the temperature of the photosensitive drum and the intermediate transfer member is decreased. At this time, the temperature of the photosensitive drum is lowered faster than that of the intermediate transfer member, but since these are in contact with each other even during standby, a difference occurs in the temperature of the photosensitive drum between the nip portion and other portions. Since the photosensitivity characteristics of the photosensitive drum change depending on the temperature, when an image is formed in a state where there is a temperature difference, a belt-like image defect occurs.

In order to solve such a problem, a technique has been developed in which the photosensitive drum and the intermediate transfer member are rotated little by little during standby. In this way, since the nip position moves little by little on the photosensitive drum, the temperature difference on the surface of the photosensitive drum can be reduced and image defects can be eliminated (see Patent Document 1).
The charging device for charging the surface of the photosensitive drum generates nitrogen oxide (NOx) or ozone by corona discharge. If a specific portion of the photosensitive drum is exposed to the photosensitive drum for a long time, the photosensitive drum The state of the surface changes, and an image defect such as a fogged image or a decrease in density occurs. Such a problem can be solved by continuing to rotate the photosensitive drum little by little.
JP 2000-75683 A

  Now, because the image forming apparatus has to transport the recording sheet when forming an image, a paper jam sometimes occurs. When a paper jam is detected, the operator is notified of the paper jam position and the drive system power supply is shut off. As a result, it is possible to prevent the operator from receiving an electric shock when the recording sheet is removed or the circuit from being destroyed due to a short circuit.

However, when the drive system power supply is cut off, the photosensitive drum cannot continue to rotate, so that a specific part of the photosensitive drum remains directly under the charging device for a long time, and image defects are unavoidable. .
In addition, it is conceivable to use a backup power supply to rotate the photosensitive drum when the drive system power supply is cut off. However, providing such a backup power supply increases the cost of the image forming apparatus and reduces the size of the image forming apparatus. In the first place, it is not suitable for the purpose of preventing electric shock and circuit destruction.

  The present invention has been made in view of the above-described problems, and is capable of preventing image quality deterioration caused by an emergency stop while suppressing an increase in cost and size of the image forming apparatus. The purpose is to provide.

  In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus that forms an image while rotating a photosensitive drum by an electric motor, and generates a rotational driving force by an elastic restoring force of an elastic body. An auxiliary drive unit that transmits and blocks the rotational driving force generated by the auxiliary drive unit to the photosensitive drum, and an auxiliary drive unit coupler that drives the photosensitive drum when the electric motor rotates. Control means for connecting the auxiliary drive unit coupler when power supply to the electric motor is cut off.

In this way, by adopting an auxiliary drive unit that rotationally drives the photosensitive drum by elastic restoring force, a photoconductor such as nitrogen oxide at the time of emergency stop while suppressing an increase in cost and size of the image forming apparatus. It is possible to prevent deterioration in image quality due to uneven adhesion to the drum.
In this case, if a speed governor that adjusts the rotational driving force generated by the auxiliary driving unit to a rotational driving force lower than that of the electric motor is provided, the auxiliary driving unit can be photosensitive for a longer period of time. The body drum can be driven to rotate.

Further, the speed governor includes a ratchet mechanism, and if it outputs a driving force that rotates intermittently, a ratchet mechanism that operates using a solenoid or the like that operates at a low voltage can be employed.
In the image forming apparatus according to the present invention, the rotational driving force generated by the electric motor is transmitted to and cut off from the photosensitive drum, and the photosensitive drum is driven to rotate while the electric motor coupler is cut off. And a second control means for generating a rotational driving force in the opposite direction to the electric motor and accumulating elastic energy in the elastic body. In this way, since the elastic energy is accumulated in the auxiliary drive unit using the electric motor, the auxiliary drive unit can be used repeatedly.

  An image forming apparatus according to the present invention includes an electric motor coupler that transmits and blocks a rotational driving force generated by an electric motor to a photosensitive drum, and an intermittent rotation that restricts the rotational driving force generated by an auxiliary drive unit. The elastic body generates a rotational driving force in the reverse direction to the case where the photosensitive drum is rotationally driven with the ratchet mechanism that does not restrict the rotation in the reverse direction and the electric motor coupler being cut off. A second control means for storing elastic energy in the motor, the electric motor transmits a rotational driving force to the auxiliary drive unit via the ratchet mechanism, and the auxiliary drive unit rotationally drives the photosensitive drum via the ratchet mechanism. It is characterized by doing. In this way, it is possible to prevent image quality deterioration due to uneven deposition of nitrogen oxides or the like by rotating the photosensitive drum even during an emergency stop.

  Further, it is preferable that the elastic body is a mainspring.

Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings, taking a tandem color image forming apparatus as an example.
[1] Configuration of Image Forming Apparatus First, the configuration of the image forming apparatus according to the present embodiment will be described.
FIG. 1 is a diagram illustrating a main configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 includes image forming units 100 </ b> Y to 100 </ b> K, a control unit 101, and an intermediate transfer belt 102.

The control unit 101 controls the image forming units 100Y to 100K according to image data generated by reading a document or image data received from an external personal computer or the like.
The image forming units 100 </ b> Y to 100 </ b> K form toner images of yellow (Y), cyan (C), magenta (M), and black (K), respectively, under the control of the control unit 101, and are formed on the intermediate transfer belt 102. Transcript. The toner image on the intermediate transfer belt 102 is transferred to recording paper, thermally fixed, and then discharged.

[2] Configuration of Image Creating Units 100Y to 100K Next, the configuration of the image creating unit will be described. The image forming units 100Y to 100K all have the same configuration with respect to the present invention, and therefore will be collectively described as the image forming unit 100.
FIG. 2 is a diagram illustrating a main configuration of the image forming unit 100. As shown in FIG. 2, the image forming unit 100 includes a photosensitive drum 201, a charging charger 202, an exposure unit 203, a developing unit 204, a transfer charger 205, and a toner collecting unit 206.

At the time of image formation, the photosensitive drum 201 rotates in the direction of arrow A in the figure.
Further, members other than the photosensitive drum 201 are arranged in the order of the charging charger 202, the exposure unit 203, the developing unit 204, the transfer charger 205, and the toner collecting unit 206 from the upstream in the arrow A direction.
The charging charger 202 charges the outer peripheral surface of the photosensitive drum 201 to a predetermined potential by corona discharge. The exposure unit 203 irradiates the outer peripheral surface of the photosensitive drum 201 with laser light in accordance with the image signal to form an electrostatic latent image. The developing unit 204 supplies toner of each color to the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 201 to form a toner image.

The transfer charger 205 is disposed opposite to the photosensitive drum 201 with the intermediate transfer belt 102 interposed therebetween, and transfers the toner image formed on the outer peripheral surface of the photosensitive drum 201 onto the intermediate transfer belt 102 by electrostatic attraction. . The toner collecting unit 206 collects toner remaining on the outer peripheral surface of the photosensitive drum 201 after the transfer.
[3] Driving Mechanism of Photosensitive Drum 201 Next, the driving mechanism of the photosensitive drum 201 will be described.

FIG. 3 is a diagram showing a main drive mechanism of the photosensitive drum 201. As shown in FIG. 3, the image forming unit 100 includes a transmission shaft 301, clutch mechanisms 302 and 304, a drive motor 303, a ratchet gearing 305, a mainspring 306, and a case 307.
Under the control of the control unit 101, the clutch mechanism 302 transmits or blocks the rotational driving force generated by the drive motor 303 and the mainspring 306 to the photosensitive drum 201. Similarly, the clutch mechanism 304 transmits or blocks the rotational driving force generated by the mainspring 306 to the photosensitive drum 201, and transmits or blocks the rotational driving force generated by the drive motor 303 to the mainspring 306. Or

The drive motor 303 rotationally drives the transmission shaft 301 via gears 303a and 303b under the control of the control unit 101. With the clutch mechanism 302 connected and the clutch mechanism 304 disconnected, the drive motor 303 rotationally drives the photosensitive drum 201 in the direction of arrow A.
Further, the drive motor 303 rotates the transmission shaft 301 in the direction of arrow B via the ratchet mechanism 305 in a state where the clutch mechanism 302 is disconnected and the clutch mechanism 304 is connected. As a result, the mainspring 306 is rewound.

The ratchet mechanism 305 regulates the rotation of the transmission shaft 301 in the arrow A direction under the control of the control unit 101. Note that rotation in the direction of arrow B is not restricted.
FIG. 4 is a diagram illustrating a main configuration of the ratchet mechanism 305. As shown in FIG. 4, the ratchet mechanism 305 includes a pawl wheel 401, a pawl 402, a housing 403, a tension spring 404, a yoke 405, and a solenoid 406.

The ratchet wheel 401 is formed with six ratchet teeth 401a and one central hole 401b, and the transmission shaft 301 is fitted in the central hole 401b. The ratchet teeth 401a engage with the tip of the pawl 402 to restrict the rotation of the pawl wheel 401 in the arrow A direction. Note that the rotation of the ratchet wheel 401 in the arrow B direction is not restricted.
The pawl 402 and the housing 403 are each formed with a notch, and the pawl 402 is swingably attached to the housing 403 by loosely fitting these notches.

A tension spring 404 is locked to one end of the pawl 402, and the other end of the tension spring 404 is locked to the housing 403. The tension spring 404 biases the other end of the pawl 402 with the ratchet teeth 401a with the notch as a fulcrum.
The yoke 405 and the solenoid 406 are stored inside the housing 403. The solenoid 406 is energized under the control of the control unit 101 to generate magnetism in the yoke 405 and attract the pawl 402. As a result, the meshing between the end of the pawl 402 and the ratchet teeth 401a is released.

  One end of the mainspring 306 is locked to the protrusion 301 a of the transmission shaft, and the other end is locked to the inside of the case 307. As described above, the mainspring 306 is wound by the drive motor 303. In addition, in a state where the clutch mechanisms 302 and 304 are connected, the control unit 101 intermittently releases the engagement between the ratchet teeth 401a and the pawl 402, so that the photosensitive drum 201 is rotationally driven intermittently.

Case 307 stores mainspring 306. The case 307 is fixed to a support member (not shown) with a screw 307a. Further, the pivot shaft 307c pivotally supports the transmission shaft 301 with the washer 307b interposed therebetween.
[4] Configuration of Control Unit 101 Next, the configuration of the control unit 101 will be described.

FIG. 5 is a block diagram illustrating a main configuration of the control unit 101. As shown in FIG. 5, the control unit 101 includes a CPU (Central Processing Unit) 501, a RAM (Random Access Memory) 502, a ROM (Read On Memory) 503, a control IO (Input / Output) 504, and a timer IC 505 as internal buses. At 506, they are connected to each other.
The CPU 501 reads a control program from the ROM 503 onto the RAM 502 and executes it when the image forming apparatus 1 is powered on. The CPU 501 controls the operation of the drive motor 303 and the solenoid 406 via the control IO 504 according to the control program.

Further, when the CPU 501 sets a timer value in the timer IC 505, the CPU 501 receives a timer interrupt from the timer IC 505 after a time corresponding to the timer value has elapsed. The CPU 501 controls the current that flows through the solenoid 406 in response to the timer interruption.
The control unit 101 and the solenoid 406 are driven by a 5V DC power supply, while the drive motor 303 is driven by a 24V DC power supply. Motors other than the drive motor 303 and the fixing device also receive power from the 24 system power supply.

[5] Operation of Image Forming Apparatus 1 Next, the operation of the image forming apparatus 1 will be described, particularly focusing on the rotation control of the photosensitive drum 201.
FIG. 6 is a timing chart showing the operation of the image forming apparatus 1. As shown in FIG. 6, when forming an image, the image forming apparatus 1 rotates the photosensitive drum 201 by connecting the clutch mechanism 302 and rotating the drive motor 303 in a normal state with the clutch mechanism 304 disconnected. .

When the 24V power supply is turned off due to a paper jam or the like that occurs during image formation, the image forming apparatus 1 connects the clutch mechanism 304 and intermittently energizes the solenoid 406 in the control unit 101.
When the solenoid 406 is intermittently energized, the meshing between the ratchet teeth 401a and the pawl 402 is intermittently released as described above, so that the photosensitive drum 201 is driven to rotate intermittently by the mainspring 306.

As a result, the specific portion of the photosensitive drum 201 stays directly under the charging device for a long time, and image defects caused by exposure to nitrogen oxides or ozone generated by corona discharge can be eliminated.
Thereafter, when the paper jam or the like is resolved and the 24V system power supply is turned on, the image forming apparatus 1 disconnects the clutch mechanism 302 and reversely rotates the drive motor 303 so that the mainspring 306 is rewound. When the mainspring 306 has been rewound, the interrupted image formation is resumed.

[6] Processing of Control Unit 101 In order to cause the image forming apparatus 1 to perform the operation as described above, the control unit 101 executes the following processing.
FIG. 7 is a flowchart showing the processing of the control unit 101. As shown in FIG. 7, when the 24V system power supply is turned off (S701: Yes), the control unit 101 connects the clutch mechanism 302 (S702). As a result, the rotational force of the mainspring 306 is transmitted to the photosensitive drum 201.

Next, the control unit 101 sets a predetermined timer value (30 seconds) in the timer IC 505 (S703), and when a timeout is detected by an interrupt from the timer IC 505 (S704: Yes), the solenoid 406 is turned on and off (S705). .
That is, the control unit 101 energizes the solenoid 406 to release the engagement between the ratchet teeth 401 a and the pawl 402, and then immediately stops energization of the solenoid 406, so that the next ratchet engages the 401 a and the pawl 402.

Since the ratchet wheel 401 has six ratchet teeth 401 a, the photosensitive drum 201 rotates by 60 degrees when the solenoid 406 is turned on and off once. Accordingly, it is possible to prevent image quality deterioration due to uneven distribution of nitrogen oxides or the like on the surface of the photosensitive drum 201.
Thereafter, when the 24 system power supply is not turned on (S706: No), the timer is set again (S703). If the 24 system power supply is turned on (S706: Yes), the process returns to step S701.

[7] Modifications Although the present invention has been described based on the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .
(1) Although not particularly mentioned in the above embodiment, as the mainspring 306, for example, the following may be used. That is, if a contact-type spiral spring made of SUS (Stainless Used Steel) 31 with a plate width of 8 mm and a total number of turns of 22 is used, the case 307 has an inner diameter of 50 mm and the transmission shaft 301 has a shaft diameter of 10 mm, the photosensitive member is exposed to a torque of 100 Nmm. The body drum 201 can be rotated 10 times.

Further, the mainspring 306 may be made of carbon tool steel or the like in addition to the stainless steel strip.
(2) Although the case where the number of ratchet teeth 401a of the ratchet wheel 401 is six has been described in the above embodiment, it goes without saying that the present invention is not limited thereto. You may do it.
For example, when the diameter of the photosensitive drum 201 is 60 mm and the width of the charging charger 202 is 27 mm, the ratchet teeth 401a are used to move the peripheral surface of the photosensitive drum 201 by 54 mm (= 27 mm × 2) in the circumferential direction. It is sufficient to provide four. Moreover, what is necessary is just to provide six ratchet teeth 401a to move 30 mm.

  In view of the purpose of shortening the time during which a specific part of the photosensitive drum 201 is exposed to nitrogen oxides or the like, it is desirable that the central angle of the part of the photosensitive drum 201 covered with the charging charger 202 is larger. Further, in order to lengthen the time for which the photosensitive drum 201 is rotationally driven by the mainspring 306, it is desirable to reduce the rotational angle to be driven at a time within a range not smaller than the central angle.

(3) In the above-described embodiment, the case where the photosensitive drum 201 is rotationally driven exclusively using the mainspring 306 has been described. However, it is needless to say that the present invention is not limited to this, and a device other than the mainspring is used. The body drum may be driven.
That is, the mainspring 306 is rewound by the drive motor 303 to store elastic energy, and when the 24V system power supply is turned off, the photosensitive drum 201 is rotationally driven using the elastic energy. Therefore, even if the driving source is other than the mainspring, the effect of the present invention can be obtained by using a driving source that stores elastic energy by the driving motor 303 and rotates the photosensitive drum 201 using the elastic energy. .

In this case, considering the demand for downsizing of the image forming apparatus, it is desirable that the drive source for storing and using elastic energy is as small as the mainspring.
(4) In the above embodiment, the case where the mainspring 306 is individually arranged in the image forming units 100Y to 100K and the photosensitive drum 201 is rotationally driven has been described. However, the present invention is not limited to this. Needless to say, the following may be used instead.

That is, since the 24V system power supply is turned off in common for the image forming units 100Y to 100K, the photosensitive drums of the image forming units 100Y to 100K may be driven to rotate by a common mainspring. (5) Although not particularly mentioned in the form, it is more preferable to arrange a torque limiter on a path for transmitting the rotational force of the drive motor 303 to the mainspring 306. By doing so, it is possible to prevent the mainspring 306 from being damaged by the drive motor 303 winding the mainspring 306 too much.

  (6) In the above embodiment, the case where the meshing of the ratchet teeth 401a and the pawl 402 is released every 30 seconds has been described. Needless to say, the present invention is not limited to this, and a period other than 30 seconds. Thus, the meshing between the ratchet teeth 401a and the pawl 402 may be released. For example, when it is estimated that the time when the 24V system power supply is turned off is at most one hour, the cycle may be determined in consideration of the maximum number of rotations of the mainspring 306 and the number of ratchet teeth 401a.

  (7) Although not specifically mentioned in the above embodiment, the 24 system power source is a high voltage system power source that supplies power to the drive motor 303, the fixing device, and the like, while the 5V system power source is the control unit 101, the operation panel, and the like. It is a low-voltage power supply that supplies power to In carrying out the present invention, the image forming apparatus may use a high-voltage power supply other than 24V or a low-voltage power supply other than 5V, and the effects of the present invention can be obtained regardless of the power supply voltage value. it can.

The clutch mechanisms 302 and 304 are also driven by a low voltage system power supply.
(8) In the above-described embodiment, the case where the drive source is switched exclusively using the clutch mechanism has been described. However, it goes without saying that the present invention is not limited to this, and instead of the clutch mechanism or with the clutch mechanism, A power switching mechanism may be used. For example, the power may be switched by meshing and separating the gears.

(9) In the above embodiment, the case where the mainspring is rewound when the 24V system power supply is restored has been described. However, it goes without saying that the present invention is not limited to this, and in addition, the following may be performed. .
That is, it is not uncommon for all power supplies to be shut off while the 24V power supply is turned off when a malfunction or the like occurs. In such a case, if the mainspring is returned to the normal operation without being rewound, the photosensitive drum cannot be sufficiently driven to rotate when the 24V system power supply is turned off next time.

On the other hand, if the mainspring is rewound when the power is turned on in addition to when the 24V system power supply is restored, the above-described problem can be solved.
FIG. 8 is a flowchart showing the rewinding process according to this modification. As shown in FIG. 8, as the rewinding process, the control unit 101 first disconnects the clutch mechanism 302 (S801), connects the clutch mechanism 304 (S802), and then reversely rotates the drive motor 303 (S803). ).

  The control unit 101 continues to reversely rotate the drive motor 303 until the mainspring 306 has been wound, and when the mainspring 306 has been wound (S804: Yes), the drive motor 303 is stopped (S805). Then, the clutch mechanism 304 is disconnected (S806), and the clutch mechanism 302 is connected (S807).

  The image forming apparatus according to the present invention is useful as a technique for preventing image quality deterioration due to nitrogen oxides or the like generated during an emergency stop or the like adhering to a photoreceptor.

1 is a diagram illustrating a main configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the main structures of the image creation part 100 which concerns on embodiment of this invention. FIG. 2 is a diagram illustrating a main drive mechanism of a photosensitive drum 201 according to an embodiment of the present invention. It is a figure which shows the main structures of the ratchet mechanism 305 which concerns on embodiment of this invention. It is a block diagram which shows the main structures of the control part 101 which concerns on embodiment of this invention. 3 is a timing chart illustrating the operation of the image forming apparatus 1 according to the embodiment of the present invention. It is a flowchart which shows the process of the control part 101 which concerns on embodiment of this invention. It is a flowchart which shows the rewinding process of the control part 101 which concerns on the modification (9) of this invention.

Explanation of symbols

1 …………………… Image forming apparatus 100 ……………… Image forming unit 101 ……………… Control unit 102 …………………… Intermediate transfer belt 201 ………… ……… Photoconductor drum 202 ………………… Charging charger 203 ………………… Exposure unit 204 ………………… Development unit 205 ………………… Transfer charger 206 ……… ............ Toner recovery part 301 .................. Transmission shaft 301 a ............ Protrusions 302, 304 ............ Clutch mechanism 303 ……………… Drive motors 303 a, 303 b ...... Gear 305 ... ……………… Ratchet mechanism 306 ………………… Mainspring 307 ………………… Case 307a ……………… Screw 307b ……………… Washer 307c ……………… Pivot shaft 401 …………………… Paper wheel 401a ……………… Ratchet Teeth 401b ……………… Center hole 402 …………………… Patent 403 ………………… Housing 404 ………………… Tension spring 405 ………………… Yoke 406 …… …………… Solenoid 501 …………………… CPU (Central Processing Unit)
502 ………………… RAM (Random Access Memory)
503 ………………… ROM (Read Ony Memory)
504 ... Control IO (Input / Output)
505 …………… Timer IC
506 …………………… Internal bus

Claims (2)

An image forming apparatus that forms an image while rotating a photosensitive drum with an electric motor,
An auxiliary drive unit that generates a rotational drive force by the elastic restoring force of the elastic body;
An auxiliary drive unit coupler that transmits and blocks the rotational driving force generated by the auxiliary drive unit to the photosensitive drum; and
A control means for disconnecting the auxiliary drive unit coupler when the electric motor is rotating the photosensitive drum, and for connecting the auxiliary drive unit coupler when power supply to the electric motor is interrupted ;
An electric motor coupler that transmits and interrupts the rotational driving force generated by the electric motor to the photosensitive drum;
A ratchet mechanism that regulates the rotational driving force generated by the auxiliary drive unit to intermittent rotation, but does not regulate the reverse rotation;
Second control means for causing the electric motor to generate a rotational driving force in a direction opposite to that when the photosensitive drum is rotationally driven in a state where the electric motor coupler is cut off, and to store elastic energy in the elastic body. And comprising
The electric motor transmits a rotational driving force to the auxiliary driving unit via the ratchet mechanism,
The image forming apparatus, wherein the auxiliary drive unit rotationally drives the photosensitive drum via the ratchet mechanism . The image forming apparatus according to claim 1, wherein the elastic body is a mainspring.

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