JP2007164106A - Attaching/detaching controller, image forming apparatus equipped with the same, and attaching/detaching control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately perform an attaching/detaching operation of two members attachably/detachably facing each other so as to form an image even by using an inexpensive driving source such as a DC brushless motor, and to accurately control the attaching/detaching position at any time, irrespective of the individual difference and secular change of members constituting the attaching/detaching mechanism. <P>SOLUTION: The attaching/detaching controller comprises an attaching/detaching means 1, an attaching/detaching drive means 2, an attaching/detaching state detecting means 3 and a control means 4. When the control means 4 starts to control the attaching/detaching drive means 2 to drive the attaching/detaching means 1, the first member for image formation is attached/detached to/from the second member arranged in a position facing the first member, then, the attaching/detaching state is detected by the attaching/detaching state detecting means 3. The control means 4 measures a time until the attaching/detaching state changes to the prescribed one by a timer 8, and a drive time until the attaching/detaching drive means 2 is stopped is set and stored by the control means 4 based on the measurement result. Thereafter, the drive of the attaching/detaching drive means 2 is stopped based on the set drive time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is provided in an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multi-function machine thereof, and is a contact / separation control device for controlling the contact / separation operation of two members that are detachably opposed to each other for image formation And an image forming apparatus including the contact / separation control device, and a contact / separation control method thereof.

The image forming apparatus as described above is provided with various members that face each other so as to come into contact with and separate from each other. For example, a tandem color image forming apparatus includes a plurality of transfer rollers for sequentially transferring the toner images of the respective colors formed on the surface of the photosensitive drum in the image forming units for the respective colors onto the transfer belt. Each of the transfer rollers is a member that can contact and separate from the photosensitive drum of each image forming unit via a transfer belt.
The transfer belt is pressed against the photosensitive drum by the transfer roller when the predetermined image transfer area moves to a position corresponding to the photosensitive drum of the image forming unit of each color of cyan, magenta, and yellow. The toner images of the respective colors are sequentially superimposed and transferred to the image transfer area. When this transfer operation is completed for each photosensitive drum corresponding to three colors, a full-color toner image is formed in a predetermined image forming area of the transfer belt. The toner image is transferred onto a transfer sheet by secondary transfer.

  In such an image forming apparatus, a contact / separation device for bringing a transfer roller into contact with and separating from each photosensitive drum is formed by a mechanical mechanism, and the toner image on the photosensitive drum is transferred onto the transfer belt without excess or shortage by the mechanism. In order to achieve this, it is necessary to perform accurate contact / separation control so that the transfer belt is pressed against the photosensitive drum for a predetermined time by the transfer roller and then separated.

  The mechanical mechanism of such a contact / separation device is, for example, a lever for moving one member that can be contacted / separated, a contact / separation cam, a motor for rotating the contact / separation cam, and a contact / separation state The sensor etc. are comprised. In the conventional contact / separation control device, in general, when the transfer belt is pressed against or separated from the photosensitive drum by the transfer roller, the sensor is pressed or separated after the motor is started to drive the contact / separation cam. Is detected, the movement of the transfer roller is controlled by stopping the motor at that time or after a predetermined time has elapsed.

Further, as can be seen from Patent Document 1, there is also an image forming apparatus in which a toner image formed on the surface of a photosensitive drum (image carrier) is directly transferred onto a transfer sheet pressed by a transfer roller. In this example, as a contact / separation mechanism between the transfer roller and the photosensitive drum, which are two members facing each other for image formation, the transfer roller is attached to the tip of the swing lever, and the lever is rocked by a solenoid and a spring. There is provided a mechanism for moving the transfer roller against the photosensitive drum by moving it.
A sensor for detecting the intrusion and passage of the leading edge of the transfer paper is disposed at a position slightly upstream of the position where the photosensitive drum and the transfer roller abut on the transfer paper transport path, and based on the detection signal of the sensor. The energization to the solenoid is controlled at timing to control contact / separation between the transfer roller and the photosensitive drum.

  Alternatively, Patent Document 2 discloses an apparatus for controlling contact / separation of a platen and a thermal head, which are two members that are detachably opposed to each other in image formation, in a thermal printer. In this example, at least two sensors are provided so as to sandwich a connecting member that contacts and separates the thermal head from the platen and a sensor plate provided in a peripheral portion of a circular cam that is rotated by a motor that drives the thermal head. The contact / separation state of the thermal head to the platen is controlled in accordance with a signal detected by the sensor.

Further, in Patent Document 3, in an image forming apparatus provided with a cleaning device having a rotating brush that comes in contact with and separates from the surface of a photosensitive drum (image carrier), two oppositely facing parts that are related to image formation can be contacted. There is disclosed a technique in which a rotating brush is brought into and out of contact with a photosensitive drum as a member by using an eccentric cam and a stepping motor.
JP-A-8-314927 JP-A-3-227253 JP 2000-98839 A

However, in the conventional two-member contacting / separating device for image formation in the conventional image forming apparatus, the contacting cam / lever and the motor for rotating the cam / lever or the solenoid / spring are used. Due to differences in torque due to individual differences such as the above, variations in shape, changes over time, etc., the contact / separation position has become inaccurate.
In particular, when an inexpensive DC brushless motor is used as the drive source of the contact / separation mechanism, the rotational speed per unit time has a rotation unevenness of about ± 25%, so accurate contact / separation position control is possible. Was difficult.

  This problem can be improved if the contact / separation mechanism is driven by a stepping motor, and the moving distance of the contact / separation cam or the like is managed by the number of pulses supplied to the stepping motor. Is more expensive than a DC brushless motor, which increases the cost of the entire device. In addition, it is impossible to solve problems caused by individual differences of members constituting the contact / separation mechanism and problems due to secular change.

  The present invention has been made to solve such a problem, and a contact / separation operation of two members that are detachably opposed to each other for image formation in an image forming apparatus as described above is performed like a DC brushless motor. Even with the use of an inexpensive drive source, it is possible to accurately control the contact / separation position at all times, even if there are individual differences or aging of the members that make up the contact / separation mechanism. An object of the present invention is to always maintain a good quality of an image to be formed.

  In order to achieve the above object, the contact / separation control device according to the present invention is configured so that the first member for image formation provided in the image forming apparatus is disposed at a position facing the first member. Contact / separation means for contacting / separating the member, contact / separation drive means for driving the contact / separation means, and the first member and the second when the contact / separation drive means drives the contact / separation means A contact / separation state detection means for detecting a contact / separation state with the member; and a contact / separation state detected by the contact / separation state detection means after the contact / separation drive means starts driving the contact / separation means. And control means for measuring and setting the drive time until the contact / separation drive means is stopped based on the measurement result.

After the control means sets the drive time, the control for starting the contact / separation drive means and then stopping the drive can be performed based on the set drive time.
One or both of the first member and the second member are often rotating members.
The control means makes an error if a change in the contact / separation state detected by the contact / separation state detection means does not occur within a predetermined time after the contact / separation drive means starts driving the contact / separation means. Can do.

  The first member may be a first rotating member for transferring the toner image to the transfer member, and the second member may be a second rotating member for conveying the toner image to the transfer member. . In that case, the first rotating member is often a transfer roller, and the second member is often a photosensitive drum or an intermediate transfer belt.

An image forming apparatus according to the present invention includes a contact / separation control device that controls contact / separation of two members facing each other so as to be able to contact / separate.
The control means of the contact / separation control device may perform control for setting the drive time during an initialization process for preparing for image formation.

  In the contact / separation control method according to the present invention, the first member relating to image formation provided in the image forming apparatus is contacted / separated by the contact / separation unit with respect to the second member disposed at a position facing the first member. A contact / separation control method for contact / separation, wherein the contact / separation state between the first member and the second member is detected when the contact / separation means is driven, Measure the time from the start of driving of the contact / separation means until the detection result of the contact / separation state changes to a predetermined value, and set the time until the contact / separation drive means is stopped based on the measurement result. It is characterized by storing.

After the drive time is set, control can be performed based on the set drive time after the contact / separation drive means starts driving and then stops the drive.
In addition, an error can be caused if the contact / separation state does not change within a predetermined time after the driving of the contact / separation means is started.
About the said 1st member and a 2nd member, the thing similar to the case of the said contact / separation control apparatus can be made into object.

According to the present invention, when the contact / separation means between the first member for image formation and the second member disposed at a position opposite thereto is driven, the contact / separation state between the first member and the member Measures the time from the start of driving of the contact / separation means until the detection result of the contact / separation state changes to a predetermined value, and driving until the contact / separation drive means is stopped based on the measurement result Since the time is set and stored, the drive of the contact / separation drive means can be stopped based on the set drive time thereafter, so an inexpensive drive source such as a DC brushless motor is used as the contact / separation drive means. However, the contact / separation position between the first member and the second member can always be accurately controlled, even if there are individual differences or secular changes in the members constituting the contact / separation means. It is hardly affected.
Therefore, the image formed by the image forming apparatus according to the present invention can always maintain good quality.

The best mode for carrying out the present invention will be specifically described below with reference to the drawings.
First, a basic embodiment of a contact / separation control device according to the present invention will be described with reference to a functional block diagram shown in FIG.
This contact / separation control device includes contact / separation means 1, contact / separation drive means 2, contact / separation state detection means 3, and control means 4.

The contact / separation means 1 brings a first member for image formation provided in the image forming apparatus into contact with and separates from a second member disposed at a position facing the first member.
The contact / separation drive means 2 drives the contact / separation means 1, and the contact / separation state detection means 3 detects the contact between the first member and the second member when the contact / separation drive means 2 drives the contact / separation means 1. Detects contact / separation status.
The control means 4 measures the time until the contact / separation state detected by the contact / separation state detection means 3 changes to a predetermined value after the contact / separation drive means 2 starts driving the contact / separation means 1. Based on the result, the drive time until the contact / separation drive means 2 is stopped is set and stored. Thereafter, when contact / separation control is performed, after the drive of the contact / separation drive means 2 is started, it is possible to perform control to stop the drive based on the set drive time.

  This control means 4 is a microcomputer comprising a CPU 5 as a central processing unit, a ROM 6 as a memory storing its operation program, a RAM 7 as a memory for temporarily storing data, a timer 8 as a time measuring means, and the like. In addition, the contact / separation control according to the present invention described above is performed, and when this contact / separation control device is provided in the image forming apparatus, various controls relating to the image formation can also be executed. The CPU 5 performs these processes by executing programs stored in the ROM 6. The timer 8 may be a soft timer based on time measurement processing by the CPU 5.

  When the CPU 5 starts the contact / separation control according to the present invention, the CPU 5 outputs a rotation instruction (motor on) signal to the contact / separation driving means 2 and then monitors the contact / separation state detection status from the contact / separation state detection means 3. The time until the contact / separation state changes is measured by the timer 8 which is a time measuring means, and the time until the contact / separation driving means 2 is stopped is set based on the measured time, and information on the set time is obtained. Write in RAM7. When the elapsed time after the rotation instruction (which continues to be measured by the timer 8) reaches the set time, a stop instruction (motor off) signal is output to the contact / separation driving means 2.

  The contact / separation drive means 2 is a drive source such as a DC brushless motor, and starts to rotate in response to a rotation instruction signal output from the control means 45, and the drive force is applied to the contact / separation cam of the contact / separation means 1 by a connecting gear train or the like. And the contact / separation mechanism is started. Thereby, the contact / separation state of the first member and the second member facing each other is changed, and the contact / separation state detection means 3 detects the state. The contact / separation state detected by the contact / separation state detection means 3 is input to the control means 4, and the time until the contact / separation state changes as described above is measured.

  According to this contact / separation control device, the rotation unevenness of the drive source such as the DC brushless motor in the contact / separation drive means 2, the individual difference or secular change of each component constituting the drive force transmission mechanism and the contact / separation means 1, etc. Even when the contact / separation state between the first member and the second member is actually detected, the time until the contact / separation driving means 2 is stopped according to the time until the contact / separation state changes is determined. Since it sets, the contact / separation state of a 1st member and a 2nd member can always be controlled correctly.

Further, the control means 4 starts the contact / separation drive means 2 to start driving the contact / separation means 1 and then the contact / separation state detected by the contact / separation state detection means 3 does not occur within a predetermined time. Can be determined as an error, the driving of the contact / separation driving means 2 is stopped, an error display can be made on the operation panel of the image forming apparatus, or a warning sound can be generated.
The contact / separation control operation described above by the control means 4 of the contact / separation control apparatus may be executed during initialization processing for preparing for image formation in the image forming apparatus.

Next, an electrophotographic tandem color printer which is an embodiment of an image forming apparatus provided with a contact / separation control device according to the present invention will be described. FIG. 2 is a diagram showing a schematic configuration thereof, but the illustration of the contact / separation control device is omitted, which is shown in FIGS. 3 and 4.
In the color printer 10 shown in FIG. 2, a paper feed tray 13 is detachably attached to the lower part of the housing 12, and the transfer paper P stored therein is fed by a paper feed roller 14. . A waste toner box 15 is detachably mounted on the front side of the upper portion, and a waste toner full detection sensor 17 is provided on the waste toner box 15.
The contact / separation control device according to the present invention shown in FIGS. 3 and 4 is provided on the back side of the waste toner box 15, but is not shown in FIG. 2.

An intermediate transfer belt 16, which is an endless belt wound around a tension roller 18 and a driving roller 19, is stretched substantially horizontally in the left-right direction in FIG. 2 at the center in the depth direction of the color printer 10. The drive roller 19 is driven by a drive motor (not shown) and rotates counterclockwise to rotate in the direction indicated by the arrow.
A function having a function of creating toner images of black, magenta, cyan, and yellow colors by an electrophotographic process at an interval from the upstream side to the downstream side in the rotation direction along the upper side of the intermediate transfer belt 16. Image cartridges (referred to as “OAI cartridges”) 20B, 20M, 20C, and 20Y are sequentially arranged.

  Each of the image forming cartridges 20B, 20M, 20C, and 20Y has the same structure except that the color of the toner to be used is different. Therefore, the configuration of the image forming cartridge 20B for black will be described in detail, and the other image forming cartridges will be described. Although the description of 20M, 20C, and 20Y is omitted, the components of the image forming cartridges 20M, 20C, and 20Y are replaced with B attached to the respective components of the image forming cartridge 20B, and M, C, and Y The reference numerals distinguished by are attached. Note that the reference numerals of the details of the image forming cartridges other than the image forming cartridge 20B are partially omitted for the sake of space.

  The black image forming cartridge 20B includes a photosensitive drum 21B that rotates in the direction of the arrow and a cleaning unit 24B that includes a charging roller 22B, a developing unit 23B, a cleaner blade 241B, and a waste toner collecting roller 242B. Provided. The developing unit 23B includes a toner tank 231B having a toner agitation paddle 235B, a developing roller 232B, a supply roller 233B, a developing blade 234B, and the like provided in the vicinity of the lower end thereof, and the black in the toner tank 231B. The toner is supplied to the developing roller 232B by the supply roller 233B, and the amount sent to the photosensitive drum 21B by the developing blade 234B is regulated to be constant.

  An exposure device 30 is provided above the image forming cartridges 20B, 20M, 20C, and 20Y, and laser light 31B that is exposure light corresponding to the image color formed by each of the image forming cartridges 20B, 20M, 20C, and 20Y. , 31M, 31C, and 31Y are irradiated onto the portions of the photosensitive drums 21B, 21M, 21C, and 21Y that are uniformly charged by the charging rollers 22B, 22M, 22C, and 22Y, and electrostatic latent It is configured to form an image.

  Primary transfer rollers 25B, 25M, 25C, and 25Y are rotatably and contactable so as to face each other below the photosensitive drums 21B, 21M, 21C, and 21Y with the intermediate transfer belt 16 interposed therebetween. In this embodiment, the primary transfer rollers 25B, 25M, 25C, and 25Y are first members related to image formation, and the photosensitive drums 21B, 21M, 21C, and 21Y are located at positions that face the first members. It is the 2nd member arranged. The contact / separation mechanism and the contact / separation control device will be described later.

Further, a secondary transfer roller 32 is provided so as to face the drive roller 19 with the intermediate transfer belt 16 and the transfer paper conveyance path 41 interposed therebetween and to rotate in contact with the intermediate transfer belt 16, and drive the intermediate transfer belt 16. A transfer belt cleaner 40 is provided above the end portion on the roller 19 side.
In the transfer paper conveyance path 41, a registration roller 33 and a registration sensor are disposed upstream of the secondary transfer roller 32, and a fixing device 35, a paper discharge sensor 36, and a paper discharge roller 37 are disposed on the downstream side. Reference numeral 42 denotes a double-sided conveyance path branched from the transfer paper conveyance path 41, which is provided with a double-sided conveyance roller 38 and a double-sided sensor 39, and is used when images are formed on both sides of the transfer paper.

At the time of image formation, first, the outer peripheral surface of the photosensitive drum 219B in the black image forming cartridge 20B is uniformly charged by the charging roller 22B in the dark, and then the laser beam 31B corresponding to the black image from the exposure device 30. To form an electrostatic latent image. The electrostatic latent image is visualized by the developing device 23B with black toner, and a black toner image is formed on the outer peripheral surface of the photosensitive drum 219B.

  This toner image is transferred onto the intermediate transfer belt 16 by the action of the primary transfer roller 25B at a position where the photosensitive drum 21B and the intermediate transfer belt 16 are in contact (primary transfer position). By this transfer, an image of black toner is formed on the transfer belt 5. After the transfer of the toner image, the photosensitive drum 21B waits for the next image formation after the unnecessary toner remaining on the outer peripheral surface is wiped off by the cleaner blade 241B of the cleaning unit 24B. The toner wiped off by the cleaner blade 241B is collected by the waste toner collecting roller 242B and sent to the waste toner box 15 through a duct (not shown).

  In this way, the intermediate transfer belt 16 onto which the black toner image is transferred by the image forming cartridge 20B is then conveyed to the position of the magenta image forming cartridge 20M. In the image forming cartridge 20M, a magenta toner image is formed on the outer peripheral surface of the photosensitive drum 21M by a process similar to the image forming process by the image forming cartridge 20B described above, and the toner image is formed by the action of the primary transfer roller 25M. The black image formed on the intermediate transfer belt 16 is transferred onto the black image.

The intermediate transfer belt 16 is further sequentially conveyed to the positions of the cyan and yellow image forming cartridges 20C and 20Y, and is formed on the photoreceptor 21Y and the cyan toner image formed on the photoreceptor 21C by the same operation. The yellow toner images thus formed are sequentially transferred onto the intermediate transfer belt 16 in a superimposed manner. Thus, a full-color image is formed on the intermediate transfer belt 5. The region of the intermediate transfer belt 5 on which the full-color superimposed image is formed passes through the tension roller 18 and moves downward in the direction indicated by the arrow (the leftward direction in FIG. 2) to be transferred to the secondary transfer roller 32. It is transported to the contact position.
When printing only black at the time of image formation, the primary transfer rollers 25M, 25C, and 25Y are retracted to positions separated from the photosensitive drums 21M, 21C, and 21Y, respectively, and the above-described image forming process is performed in black. The image forming cartridge 20B is used only to create a black and white toner image and transfer it onto the intermediate transfer belt 16.

  On the other hand, the transfer paper P stored in the paper feed tray 13 is sequentially fed out from the uppermost transfer paper by rotating the paper feed roller 2 counterclockwise, and after the leading edge is detected by the registration sensor 34, It waits at a position that reaches the registration roller 3. The driving of the registration roller 3 starts when the transfer sheet P is nipped between the intermediate transfer belt 16 and the secondary transfer roller 32 immediately before the toner image transferred onto the intermediate transfer belt 16 is brought into contact with the secondary transfer roller 32. The toner image on the intermediate transfer belt 16 is transferred onto the transfer sheet.

The transfer paper onto which the toner image on the intermediate transfer belt 16 has been transferred is conveyed to the fixing device 35 and the transferred toner image is fixed by heat and pressure, and the housing 12 is rotated by a paper discharge roller 37 that rotates in the direction of the arrow. The paper is discharged onto a paper discharge portion 12a formed on the upper surface of the paper.
After the secondary transfer of the toner image has been completed, the intermediate transfer belt 16 is rotated toward the image forming cartridge 20B in order to transfer a new toner image again after the toner remaining on the surface is removed by the transfer belt cleaner 40. Moved.

  When performing duplex printing, before the transfer paper P passes through the paper discharge roller 37 and the passage of the rear end thereof is detected by the paper discharge sensor 36, the rotation of the paper discharge roller 34 is reversed, and the transfer paper P It feeds into the duplex conveying path 42. The transfer sheet fed into the duplex conveyance path 42 is conveyed by the duplex conveyance roller 38, detected by the duplex sensor 39, and conveyed until the leading edge reaches the registration roller 33 again. Thereafter, the registration roller 33 is started at a predetermined timing, the transfer paper is re-supplied to the secondary transfer position by the secondary transfer roller 32, and the toner image is transferred to the opposite surface of the transfer paper from the previous time. The toner image is fixed on the transfer paper by heat and pressure in the fixing device 33, and the transfer paper is discharged onto the paper discharge unit 12 a by the paper discharge roller 37.

Here, the primary transfer rollers 25B, 25M, 25C, and 251Y that are the first members are sandwiched between the photosensitive drums 21B, 21M, 21C, and 21Y that are the opposing second members with the intermediate transfer belt 16 interposed therebetween. A contact / separation mechanism and a contact / separation control device for making contact / separation will be described with reference to FIGS.
FIG. 3 shows a state in which each primary transfer roller for color transfer is separated from the photosensitive drum, and FIG. 4 shows a state in which each primary transfer roller for color transfer is pressed against the photosensitive drum via a transfer belt. ing.

In these drawings, only the mechanical mechanisms constituting the contact / separation control device and the photosensitive drums 21B, 21M, 21C, 21Y and the upper portion of the intermediate transfer belt 16 in the image forming cartridge for each color are shown.
This contact / separation control device shows a specific configuration example of a portion corresponding to the contact / separation means 1, the contact / separation drive means 2, and the contact / separation state detection means 3 described with reference to FIG.

  The contact / separation means 1 constitutes a contact / separation mechanism for the primary transfer rollers 25M, 25C, 25Y for transferring the color toner image, and the primary transfer rollers 25M, 25C, 25Y are pivotally supported at the leading ends so as to be driven to rotate. The three contact / separation levers 58M, 58C, and 58Y can be rotated in a plane parallel to the paper surface of the drawing by the support shafts 61M, 61C, and 61Y provided on a fixing member (not shown) at a substantially central portion thereof. It is pivotally supported. Each of the contact / separation levers 58M, 58C, 58Y is rotated in the counterclockwise direction (the primary transfer rollers 25M, 25C, 25Y are the photosensitive drums 21M, 21) by coil springs 62M, 62C, 62Y engaged with the fixing members. 21C and 21Y).

  Further, the contact / separation lever moving unit 60 is supported by a support member (not shown) so as to be able to reciprocate in the left-right direction in FIGS. 3 and 4, and the support shafts 61M, 61C, 61Y are supported by the contact / separation lever moving unit 60. The three contact / separation lever abutting members 59M, 59C, 59Y are fixedly spaced at the same interval, and abut the lower end portions of the respective contact / separation levers 58M, 58C, 58Y to regulate their rotational positions. ing.

On the outside of the left end portion of the contact / separation lever moving unit 60 in the drawing, a contact / separation cam 57 is rotatably provided in a plane parallel to the paper surface of the drawing by a shaft 55 supported by the fixed portion. Reference numeral 57 denotes a deformed egg-shaped eccentric cam having a flat tip, the left end surface of the contact / separation lever moving unit 60 abuts on the outer peripheral surface thereof, and is always pressed by the urging force of the coil springs 62M, 62C, 62Y. ing.
Therefore, when the contact / separation cam 57 rotates, the contact / separation lever moving unit 24 moves in the horizontal direction in the drawing, and the contact / separation lever contact members 59M, 59C, 59Y move the contact / separation levers 58M, 58C, 58Y accordingly. As a result, the primary transfer rollers 25M, 25C, and 25Y are displaced to the separated positions shown in FIG. 3 and the press contact positions shown in FIG.

  That is, when the contact / separation cam 57 rotates in the direction of arrow A from the press contact position shown in FIG. 4, the contact / separation lever moving unit 24 moves in the direction of arrow A shown in FIG. , 25Y move in the direction indicated by arrow C (the direction away from the photosensitive drums 21B, 21M, 21C, 21Y). When the contact / separation cam 57 rotates in the direction of arrow A from the separation position shown in FIG. 3, the contact / separation lever moving unit 24 moves in the direction of arrow D shown in FIG. , 25Y move in the direction indicated by arrow E (the direction in which the photosensitive drums 21B, 21M, 21C, and 21Y are in pressure contact with each other).

  The contact / separation cam 57 for reciprocating the contact / separation lever moving unit 60 is driven by the contact / separation drive means 2. In this embodiment, a DC brushless motor 52 is used as a drive source and the rotational driving force is connected. The gear train 56 is transmitted to the contact / separation cam 57 to rotate it. The first gear on the motor side in the connecting gear train 56 is a worm gear fixed to the rotating shaft of the DC brushless motor 52, and the rotation is transmitted to the spur gear, and then the contact / separation cam 57 is connected via a large and small number of gears. Is transmitted to the terminal spur gear to which is fixed. The connecting gear train 56 may be included in the contact / separation means 1 or in the contact / separation drive means 2, but in this example, it extends over both.

  The primary transfer roller 25B facing the black photosensitive drum 21B is not contacted and separated, and the primary transfer roller 30B is always in pressure contact with the photosensitive drum 21B via the intermediate transfer belt 16.

  A filler 63 is fixed in the vicinity of the right end portion of the contact / separation lever moving unit 60, and a transmission type photosensor (hereinafter simply referred to as a photosensor) is located at a fixed position where the filler 63 enters and exits by the movement of the contact / separation lever moving unit 60. 53 is provided. The filler 63 and the photosensor 53 constitute the contact / separation state detection means 3, and when the filler 63 enters a position where the optical path of the photosensor 53 is blocked as shown in FIG. If the filler 63 comes out of a position where it does not block the optical path of the photosensor 53 as shown in FIG. 4, the detection signal of the photosensor 53 becomes high level to detect the pressure contact state. To do.

  Next, this contact / separation control device is different in torque due to uneven rotation of the DC brushless motor 52 and individual differences, variations in the mechanical mechanism of the contact / separation means 1 including the connecting gear train 56 and the contact / separation cam 57, and their aging. Even when the contact / separation conditions of the primary transfer rollers 25M, 25C, and 25Y with respect to the photosensitive drums 21B, 21M, 21C, and 21Y vary due to deterioration and the like, the driving time for always controlling the contact / separation state is constant. Explain how to set

FIG. 5 is a timing chart when setting the drive time of the DC brushless motor 52 that is the contact / separation drive means 2 in the contact / separation control device of the embodiment described above. The relationship between the separation state by the photosensor 53 (contact / separation state detection means 3) and the detection signal of a press-contact state is shown.
The control for setting the drive time shown in this timing chart is performed when the contact / separation state is unknown, such as when the color printer 10 is turned on or when the cover is opened / closed. For example, during the print preparation operation (initialization process) such as when the fixing device 35 shown in FIG. 2 is warmed up, it is executed according to the instruction of the control means 4 shown in FIG. This operation will be described with reference to FIG.

  First, the control unit 4 issues a rotation (ON) instruction to the DC brushless motor 52 that is the contact / separation drive unit 2, and drives the contact / separation cam 57 of the contact / separation unit 1 via the connecting gear train 56. The control means 4 does not use it for judgment even if the photo sensor 53 of the contact / separation state detection means 3 detects the change of the contact / separation state for t1 sec after the start of driving. This is because the rotation of the DC brushless motor 52 is slowing up and the speed is unstable, and if time is measured during this time, the time required for the state change detected by the photosensor 53 cannot be measured accurately. In this embodiment, t1 is set to 0.5 sec.

  When t1 sec elapses after the driving of the DC brushless motor 52 is started, the control unit 4 waits for the detection signal from the photosensor 53 to shift from the pressure contact separation state to the separation state (high to low). When the pressure contact / separation state shifts to the separation state (from high to low), time measurement by the timer 8 is started. This time measurement is performed until the detection signal from the photosensor 53 again shifts from the pressure contact / separation state to the separation state (high to low). The time t2 measured in this way corresponds to a period in which the contact / separation cam 57 rotates once, and is the time required for the contact / separation lever moving unit 60 to make one reciprocation.

When this time measurement is completed, the control means 4 refers to a table showing the relationship between the measurement time t2 stored in the ROM 6 and the set time T set as the drive time, and the set time corresponding to the previous measurement time t2. The value of T is set as the driving time and stored in the RAM 7.
The DC brushless motor 52 is instructed to stop rotation (off) when the set time T has elapsed from when the detection signal from the photosensor 53 last changed from the pressure contact / separation state to the separation state (from high to low). To stop driving.
Therefore, the primary transfer rollers 30M, 30C, and 30Y can be stopped in a state of being separated from the photosensitive drums 21B, 21M, 21C, and 21Y by an optimum distance.

Here, with reference to FIG. 6 and Table 1, a method for determining the drive time timer T for stopping the contact / separation cam 57 at a desired position will be described in detail.
FIG. 6 is a diagram in which the relationship between the rotation speed (rpm) of the contact / separation cam 57 and the amount of deviation (mm) from the ideal stop position of the contact / separation cam 57 is obtained by experiments. This figure shows that the position at which the contact / separation cam 57 stops when the DC brushless motor 52 rotates at an ideal rotation speed of 34.64 rpm is the ideal position, that is, the position where the deviation amount is 0 mm, and the rotation speed of the DC brushless motor 52 is This shows the amount of deviation when there is a rotation unevenness (± 8.49 rpm) of about ± 25% at maximum with respect to the ideal rotation speed.

  On the other hand, the “t2 count result” in Table 1 is a count value obtained when the timer counts the rotation cycle of the contact / separation cam 57 described above every 2 milliseconds. That is, the value obtained by multiplying the value of the t2 count result by 2 milliseconds and the reciprocal thereof by 60 seconds indicates the actual rotational speed (rpm) of the contact / separation cam 57. Using FIG. 6, the amount of deviation of the contact / separation cam 57 with respect to the actual rotational speed can be found. This amount of deviation can be corrected by continuing to drive the DC brushless motor 52 until the contact / separation cam 57 reaches the ideal stop position. In Table 1, the time for which this drive is continued is defined as “time until drive stop”.

  For example, if the DC brushless motor 52 rotates at an ideal rotation speed of 34.64 rpm, the “t2 count result” is 866, and the “time to stop driving” is 86 milliseconds. If the driving of the DC brushless motor 52 is continued for this time, the contact / separation cam 57 can be stopped at an ideal position. Further, the “time until drive stop” is set in the drive time timer T managed by the control means 4, but in this example, since the control means 4 performs the management every 2 milliseconds, Set the value obtained by dividing "Time" by 2 milliseconds. This value is the “count value set for timer T” in Table 1.

A control method of the contact / separation operation by the contact / separation control apparatus of this embodiment will be described with reference to the flowcharts of FIGS.
FIG. 7 is a flowchart showing a print preparation operation (initialization process) by the color printer 10 which is an image forming apparatus provided with the contact / separation control apparatus according to the present invention described with reference to FIGS. This process is started when the color printer 10 is turned on or when the cover of the housing 12 is opened or closed.

  First, in step S1, the heater of the fixing device 35 is energized to perform warm-up processing. In step S2, an image forming process adjustment process is performed. In step S3, a contact / separation operation process for setting the drive time of the contact / separation control apparatus according to the present invention is performed. When these processes are completed, the print preparation operation ends.

Next, details of the contact / separation operation process for setting the drive time of the contact / separation control device will be described with reference to FIGS. FIG. 8 and FIG. 9 are a series of flowcharts showing the flow of the contact / separation operation process, which are divided into two diagrams for convenience of illustration.
A program for performing this contact / separation operation processing is stored in the ROM 6 of the control means 4 of the contact / separation control device shown in FIG. 1, read out to the RAM 7 and executed by the CPU 5.
Since this contact / separation operation process is executed by the CPU 5 at a cycle of 2 ms, each addition process of the undetected section timer t1, the time measurement timer t2, the error detection timer terr, and the timer T in FIGS. 8 and 9 is performed every 2 ms. To be executed.

  This contact / separation operation process is started when the process adjustment process is completed in the above-described print preparation operation. First, in step S11 of FIG. 8, a rotation instruction is issued to the DC brushless motor 52 which is a contact / separation driving means. Next, in step S12, the undetected section timer t1 for measuring the undetected section is reset, and in step S13, the error detection timer terr for measuring the time of the contacting / separating error is reset in order to determine the contact / separation error. To “0”.

Next, in step S14, it is determined whether or not the value of the undetected section timer t1 has become 250. As described in the timing chart of FIG. 5, the undetected section timer t1 is a timer that measures time for preventing time measurement while the rotation of the DC brushless motor 52 is unstable. Yes, in this embodiment, this time is set to 0.5 sec. Therefore, when converted into a count value every 2 ms, “250” is obtained.
If the value of the undetected section timer t1 is less than 250, it is not completed. Therefore, the timer is counted up in step S15, the error detection timer terr is also counted up in step S16, and steps S14 to S16 are again performed 2 ms later. Repeat the process. When t1 = 250 in step S14, the process proceeds to step S17.

  In step S17, in order to measure a time corresponding to one cycle of the contact / separation cam 57, the time measurement timer t2 is initialized. Next, in step S18, it is determined whether or not the state detected by the photosensor 53, which is the contact / separation state detection means 3, has changed from press contact to separation. If it is determined that the pressure has shifted to the separation, the process proceeds to step S22 in FIG. 9, and it is determined whether or not the detected state detected again has changed from the pressure contact to the separation.

If it is determined in step S18 that the pressure contact or separation state remains unchanged and there is no change, or if the separation state shifts to the pressure contact state, the process proceeds to step S19 to increment the error detection timer terr, and step S20 Then, it is determined whether or not the value of the error detection timer has reached “1250”.
In this embodiment, since the error detection time is set to 2.5 seconds, it becomes “1250” when converted into a count value. If not, the process returns to step S18 to determine whether the state detected again has shifted from press contact to separation. If the value of the error detection timer terr is “1250” in step S20, it is determined that the proper transition of the contact / separation state has not been detected, and the contact / separation error flag is set in step S21. Proceed to step S31.

  This contact / separation error is a predetermined time after the drive of the contact / separation drive unit 2 is started due to a malfunction of the contact / separation drive unit 2, the contact / separation unit 1, the contact / separation state detection unit 3, or a combination thereof. If there is no change in the detection state by the contact / separation state detection means 3, it is determined that there is a failure.

  Here, the value of the error detection timer terr is a value when the speed fluctuates by 25% at the maximum with respect to the ideal rotation speed 34.64 [rpm] of the contact / separation cam 57, that is, the rotation speed is 25.98 [ rpm] is 2.5 seconds with a margin added to the time required for one rotation of about 2.31 seconds. In this embodiment, when the width of variation in the rotational speed of the contact / separation cam 57 is ± 25% or more, the correction is fixed. In addition, since an abnormality in which the rotational speed is greatly shifted to the high speed side is unlikely to occur, error processing may be performed only when the maximum variation on the low speed side is exceeded.

  The error processing by the contact / separation error flag is not shown in this flowchart, but the contact / separation error flag is monitored by another processing routine, and when it is confirmed that it is set, the operation of the color printer 10 is stopped. The occurrence of an error can be displayed on the operation panel or a warning sound can be generated for the user.

  On the other hand, if the process proceeds to step S22 in FIG. 9, the process proceeds to step S26 to count up the time measurement timer t2 until the detection state shifts from the pressure contact to the separation, and the value of the time measurement timer t2 is counted in step S27. Is determined to be “1250”. In this embodiment, since the maximum period of the contact / separation cam 57 is set to 2.5 seconds, it is determined whether or not t2 = 1250 is satisfied in step S27. If not, the process returns to step S22, and the processes of steps S26 and S27 are repeated until the detection state shifts from pressure contact to separation.

In the meantime, if the value of the time measurement timer t2 becomes “1250” in step S27, it is determined that the proper transition of the contact / separation state has not been detected, the time measurement is aborted, and the contact / separation error flag is set in step S28. Proceed to step S31.
The error processing in that case can be the same as the processing in the case where an error is detected by the error detection timer ter described above.

  If it is determined in step S22 that the detection state has shifted from pressure contact to separation, in step S23, the range of “t2 count result” is determined from the count value of the time measurement timer t2 with reference to the table of Table 1. The “count value to be set in the timer T” corresponding to the range is obtained as the set value of the drive time timer T, and the set value of the drive time timer T is stored in the RAM in step S24.

Next, in step S25, the value of the timer T is reset to “0”, and in step S29, it is determined whether or not the value of the timer T has reached the set value of the drive time timer T. If not, the timer T is counted up in step S30 and the process returns to step 29. The timer T counts up in step S30 every 2 ms until the value of the timer T reaches the set value of the driving time timer T. repeat.
When the value of the timer T becomes the set value of the driving time timer T, it is determined that the contact / separation cam 57 has reached a predetermined stop position, and a rotation stop instruction is issued to the DC coreless motor 52 which is the contact / separation drive means in step S31. To finish the process.

The rotation stop instruction in step S31 is also issued when the contact / separation error flag is set in step S21 or step S28, and the process is similarly terminated.
When the contact / separation operation process is completed, the print preparation is completed, and the color printer 10 can enter the printing operation. The set value stored in the RAM 7 is stored until the next print preparation operation (initialization process) is performed. When the contact / separation operation of the primary transfer rollers 30M, 30C, and 30Y is performed during the printing operation, the set value is stored. The DC coreless motor 52 is controlled for rotation stop timing using the set value stored in the RAM 7.
Therefore, the driving time of the DC coreless motor 52 can always be properly controlled regardless of the rotation unevenness, the variation of each part, or the secular change, and the accurate contact / separation position can be controlled.

The change in the contact / separation state detected is determined at the time of transition from pressure contact to separation, but may be determined at the time of transition from separation to pressure contact. In addition, the measurement of the drive time of the contact / separation drive means 2 is a period of one rotation of the contact / separation cam 57, but may be a period of 1/2 rotation or two or more rotations. Increasing the measurement time increases accuracy but increases processing time.
Further, the method of obtaining the set value of the drive time timer T from the measured value of the drive time is not limited to the method of looking up the storage table prepared in advance and stored in the ROM, and is obtained by calculating with a calculation formula. Also good.

The drive source of the contact / separation drive means 2 is described by way of example in the case of the DC coreless motor 52, but is not limited thereto.
In the above-described embodiments, the primary transfer roller for transferring the color toner image to the intermediate transfer belt in the tandem type color printer is brought into contact with and separated from the opposing photosensitive drum with the intermediate transfer belt interposed therebetween. Although this invention was applied to the secondary transfer roller 3

In various types of image forming apparatuses including color printers other than tandem printers, monochrome printers, copying machines, facsimile machines, etc., contact and separation with respect to photosensitive drums and photosensitive belts such as transfer rollers, charging rollers, developing units, cleaning brushes, etc. Control of contact and separation between the first member for image formation and the second member disposed opposite thereto, such as contact and separation of the feed roller with respect to the transfer paper, or contact and separation of the thermal head with the platen of the thermal printer All are applicable.
The first member is a rotating member such as a transfer roller for transferring the toner image to a transfer member (transfer paper or transfer belt), and the second member is a photosensitive drum for conveying the toner image to the transfer member. In the case of a rotating member such as a photosensitive belt or an intermediate transfer belt, it is particularly effective.

  By performing the contact / separation operation process according to the present invention described above with the contact / separation control device, the difference in torque due to individual differences such as the brushless motor used in the contact / separation drive means 52, the connecting gear train 56 including the contact / separation cam 57, Even when there is variation in the mechanical mechanism of the contact / separation device 51 and uneven rotation of the contact / separation cam 57 due to deterioration over time, the drive stop time of the contact / separation cam 57 for correcting this is set appropriately. Therefore, the primary transfer roller 30 that presses the transfer belt 16 used in the color printer 10 or the like against the photosensitive drum 21 can be retracted to the optimum separation position.

  As described above, the contact / separation control device and the contact / separation control method according to the present invention can be used for various image forming apparatuses such as a printer, a copier, a facsimile machine, or a multifunction machine thereof. As a result, the contact / separation state of the two members facing each other that can be contacted / separated for image formation can always be accurately controlled, so that a highly uniform image without variation can be formed. In addition, since an inexpensive motor or the like can be used as a drive source, the cost of the image forming apparatus can be reduced.

It is a functional block diagram which shows basic embodiment of the contact-separation control apparatus by this invention. 1 is a schematic configuration diagram of an electrophotographic tandem color printer which is an embodiment of an image forming apparatus according to the present invention. FIG. FIG. 3 is a diagram illustrating a configuration of a contact / separation control device provided in the color printer illustrated in FIG. 2 in a state where each primary transfer roller for color transfer is separated from a photosensitive drum. FIG. 3 is a diagram showing the configuration of the contact / separation control device in a state in which each primary transfer roller for color transfer is in pressure contact with a photosensitive drum via a transfer belt. It is a timing chart in the case of setting the drive time of the DC brushless motor which is a contact / separation drive means in the contact / separation control apparatus of embodiment of this invention.

FIG. 5 is a diagram showing a result of an experiment to obtain a relationship between a rotation speed (rpm) of the contact / separation cam in FIGS. 3 and 4 and a deviation amount (mm) from the ideal stop position. FIG. 5 is a flowchart showing processing of print preparation operation (initialization processing) by the color printer shown in FIGS. 2 to 4. FIG. It is a flowchart which shows the detail of the contact / separation operation | movement process for setting the drive time of the contact / separation control apparatus similarly. FIG. 9 is a flowchart continued from FIG. 8. FIG.

Explanation of symbols

1: contact / separation means 2: contact / separation drive means 3: contact / separation state detection means 4: control means 5: CPU 6: ROM 7: RAM 8: timer (time measurement means)
10: Color printer 12: Housing 13: Paper feed tray
14: Feed roller 15: Waste toner box 16: Intermediate transfer belt 17: Waste toner full detection sensor 18: Tension roller
19: Drive roller 20B, 20M, 20C, 20Y: Each image forming cartridge

21B, 21M, 21C, 21Y: photosensitive drum
22B, 22M, 22C, 22Y: charging rollers 23B, 23M, 23C, 23Y: developing units 24B, 24M, 24C, 24Y: cleaning units 25B, 25M, 25C, 25Y: primary transfer rollers

30: Exposure unit 31B, 31M, 31C, 31Y: Laser beam 32: Secondary transfer roller 33: Registration roller 34: Registration sensor 35: Fixing unit 36: Paper discharge sensor 37: Paper discharge roller
38: Double-sided conveyance roller 39: Double-sided sensor 40: Transfer belt cleaner 41: Transfer paper conveyance path 42: Double-sided conveyance path

52: DC brushless motor 53: Transmission type photo sensor 55: Shaft 56: Connection gear train 57: Contact / separation cam 58M, 58C, 58Y: Contact / separation lever 59M, 59C, 59Y: Contact / separation lever contact member 60: Contact / separation lever Moving unit 61M, 61C, 61Y: Support shaft 62M, 62C, 62Y: Coil spring 63: Filler P: Transfer paper

Claims (14)

Contact / separation means for contacting / separating a first member relating to image formation provided in the image forming apparatus with respect to a second member disposed at a position facing the first member;
Contact / separation drive means for driving the contact / separation means;
Contact / separation state detection means for detecting a contact / separation state between the first member and the second member when the contact / separation driving means is driven by the contact / separation drive means;
After the contact / separation drive means starts driving the contact / separation means, the time until the contact / separation state detected by the contact / separation state detection means changes to a predetermined value is measured, and based on the measurement result Control means for setting and storing a driving time until the contact / separation driving means is stopped.   After the control means has set the drive time, the control is performed based on the set drive time after the contact / separation drive means starts driving and then stops the drive. Contact / separation control device.   The contact / separation control device according to claim 1, wherein one or both of the first member and the second member are rotating members.   The control means determines that an error occurs if the contact / separation state change detected by the contact / separation state detection means does not occur within a predetermined time after the contact / separation drive means starts driving the contact / separation means. The contact / separation control device according to any one of claims 1 to 3, wherein   2. The first member is a first rotating member for transferring a toner image to a transfer member, and the second member is a second rotating member for conveying a toner image to a transfer member. The contact / separation control device according to any one of claims 1 to 4.   6. The contact / separation control device according to claim 5, wherein the first rotating member is a transfer roller, and the second member is a photosensitive drum or an intermediate transfer belt.   An image forming apparatus comprising the contact / separation control device according to claim 1.   8. The image forming apparatus according to claim 7, wherein the control means of the contact / separation control apparatus performs control for setting the driving time during initialization processing for preparing for image formation. . Contact / separation control method for contacting / separating a first member for image formation provided in an image forming apparatus with a contact / separation unit with respect to a second member disposed at a position facing the first member Because
Detecting the contact / separation state between the first member and the second member when the contact / separation means is driven,
Measure the time from the start of driving of the contact / separation means until the detection result of the contact / separation state changes to a predetermined value,
A contact / separation control method comprising: setting and storing a time until the contact / separation driving means is stopped based on the measurement result.   After the drive time is set, the contact / separation control method is characterized in that after the drive is started by the contact / separation drive means, control for stopping the drive is performed based on the set drive time.   The contact / separation control method according to claim 9 or 10, wherein one or both of the first member and the second member is a rotating member.   The contact / separation control according to any one of claims 9 to 11, wherein an error occurs if the change in the contact / separation state does not occur within a predetermined time after the driving of the contact / separation means is started. Method.   The first member is a first rotating member for transferring a toner image to a transfer member, and the second member is a second rotating member for transporting the toner image to the transfer member. The contact / separation control method according to claim 1. The contact / separation control method according to claim 13, wherein the first rotating member is a transfer roller, and the second member is a photosensitive drum or an intermediate transfer belt.

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