JP3501588B2 - Image recording device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides an unfixed image corresponding to desired image information on a recording paper (recording medium) by an appropriate image forming process mechanism such as an electrophotographic system, an electrostatic recording system and a magnetic recording system. An image recording device such as a laser printer or a copier that forms and carries the recording paper and introduces the recording paper into a fixing device (image heating and fixing device) to thermally fix an unfixed image on the recording paper to output an image recorded product. Forming device).

[0002]

2. Description of the Related Art For convenience, a laser printer using a transfer type electrophotographic process will be described as an example. The printer is
An electrophotographic photosensitive member (image bearing member, hereinafter referred to as a photosensitive drum), which is generally a rotating drum type, is rotationally driven at a predetermined peripheral speed (process speed), and the surface of the rotating photosensitive drum is charged with a predetermined polarity by a charging unit.・ The surface of the photosensitive drum is scanned and exposed by being charged to a potential, and the charged surface is scanned and exposed by the laser light output from the laser scanner section and modulated according to the time-series electric digital pixel signals of the target image information. An electrostatic latent image corresponding to target image information is formed. The electrostatic latent image is developed as a toner image by the developing means, and the toner image is transferred by the transfer means from the paper feeding portion to the transfer portion of the rotary photosensitive drum onto the recording paper fed at a predetermined timing. . Then, the recording paper on which the toner image (unfixed image) has been transferred is introduced into the fixing means, and the toner image is fixed on the recording paper as a permanently fixed image and output as an image formed product (print, copy). .

.. A heat roller type fixing device is generally used as a fixing means for fixing an unfixed image formed and carried on a recording sheet. The heat roller type fixing device incorporates a halogen heater as a heat source, and has a heat resistance such as a fixing roller (heat roller) which is heated and regulated to a predetermined temperature by the heat generated by the halogen heater and silicon rubber. In addition, a fixing roller formed of a material having a predetermined elasticity is brought into pressure contact with each other to form a fixing nip portion, the pair of rollers is rotated, and an unfixed toner image is formed and carried by the image forming portion in the fixing nip portion. The recording paper is introduced and nipped and conveyed, thereby applying heat and pressure from the fixing roller to fuse and fix the toner image on the recording paper.

However, in the heat roller type fixing device, the heat capacity of the fixing roller is large, and a halogen heater as a heat source is energized to raise the fixing roller from a normal temperature state to a predetermined fixing temperature to bring it into a temperature control state. It takes a considerable amount of warming time and lacks quick startability. In addition, the halogen heater is energized to keep the fixing roller in a preheated state even when the printer is not in use so that the image forming operation can be executed immediately after the fixing roller is once raised from the room temperature state to the predetermined fixing temperature. However, the halogen heater as a heat source has a problem in that it consumes a large amount of electric power because it has a low energy efficiency because it once converts electric energy into light. Further, maintaining the fixing roller in a preheated state by energizing the halogen heater even when the printer is not used also causes an unnecessary heating of the inside of the machine due to heat radiation from the fixing roller.

.. Therefore, in recent years, a quick start
From the viewpoint of power saving, the on-demand type fixing device is becoming the mainstream instead of the heat roller type fixing device.

As an on-demand type fixing device, for example, a film heating type device is known. In this apparatus, a heating member having a low heat capacity such as a ceramic heater and a thin heat transfer film material such as polyimide are used as a heating member to reduce the heat capacity of the heating member.

More specifically, Japanese Patent Laid-Open No. 63-313182
As disclosed in Japanese Patent Laid-Open Publication No. 2003-242242, a heat resistant film is sandwiched between a ceramic heater as a heating body (heat source) and a pressure roller as a pressure member to form a fixing nip portion, and the fixing nip portion is formed. Introduce recording paper on which an unfixed toner image is formed and supported between the heat-resistant film in the nip part and the pressure roller, and nip the fixing nip part together with the heat-resistant film to convey heat from the ceramic heater. The toner image is applied to the recording paper through the flexible film and heated to thermally fix the toner image on the recording paper.

Such a film heating type fixing device is
Since a ceramic heater as a heating element or a film with a low heat capacity is used and the temperature response is good, it is possible to quickly raise the fixing nip portion to the required fixing temperature by energizing the heater to bring it into a temperature control state. It has a quick start property, and it is possible to turn off the power supply to the heater except when the paper is being passed, and there is power saving. The temperature rise inside the machine can also be suppressed.

The heating element is made an electromagnetic induction heat-generating member, or the film is made an electromagnetic induction heat-generating member and they are fixed by electromagnetic induction heat generation (heat generation due to eddy current loss) by the action of the alternating magnetic field generated by the alternating magnetic field generating means. An electromagnetic induction heating type fixing device that heats a recording paper at the nip portion to heat-fix a toner image on the recording paper is also known, and these are also on-demand type and have a quick start property and a power saving property.

In the on-demand type fixing device as in the above example, a heat source is usually provided on the pressure roller side and the pressure roller is driven to rotate, whereby a heat-resistant film or electromagnetic induction as a moving member on the heating member side is provided. The heat-generating film is driven to move, and the recording paper introduced into the fixing nip portion is conveyed by the rotational driving force of the pressure roller, and is nipped and conveyed together with the film (pressure roller driving method, JP-A-4-44075 to 44083, 204980
No. 204984 publication).

[0011]

The on-demand type fixing device is effective because it has the quick start property and the power saving property as described above, but the following problems occur in the case of the pressure roller driving system. There is.

That is, in the case of a pressure roller drive type fixing device, the recording paper conveyance speed in the fixing nip portion is governed by the diameter of the pressure roller, so that when the pressure roller is cold at the beginning of recording. Compared to the recording paper conveyance speed in the fixing nip area due to the pressure roller diameter (initial diameter), the pressure roller is gradually heated by the heat of the heating member side during the continuous recording and thermally expands to a diameter larger than the initial diameter. When the pressure becomes large, a fluctuation phenomenon occurs in which the recording paper conveyance speed in the fixing nip portion increases due to the pressure roller diameter.

Therefore, when the recording operation is continued,
The recording paper conveyance speed in the fixing nip portion of the fixing device becomes faster than the recording paper conveyance speed (predetermined process speed) in the transfer portion (image forming portion), and a difference occurs between the two, and the recording paper is set to a predetermined portion in the transfer portion. When the recording paper is conveyed at the process speed and receives the toner image transfer, passes through the transfer section, and the leading edge of the recording paper reaches the fixing nip section of the fixing device and is nipped in the fixing nip section, the recording sheet is transferred at the predetermined process speed in the transfer section. The recording paper is conveyed at the recording paper conveyance speed in the fixing nip portion of the fixing device which is higher than the recording paper conveyance speed.

Therefore, when the leading edge of the recording paper reaches the fixing nip portion of the fixing device, the toner image transferred to the recording paper area portion between the pressure roller of the fixing device and the transfer portion is formed on the recording paper. The (recorded image) is stretched in the recording paper conveyance direction because the recording paper is pulled and conveyed at the recording paper conveyance speed in the fixing device fixing nip portion, which is higher than the recording paper conveyance speed that is the predetermined process speed in the transfer section. The image is stretched and the image is stretched. In some cases, the image extension causes the trailing edge of the image to deviate from the trailing edge of the recording sheet, resulting in loss.

FIG. 13 is a graph showing an example of the relationship between the number of recorded sheets and the recording image extension rate. In this image recording device,
At the time of 30 sheets of continuous recording, the recorded image is extended by about 1% compared to the initial stage, and thereafter, even if continuous recording is continued, the diameter increase gradient due to the thermal expansion of the pressure roller becomes almost 0, and the image extension rate is Saturate. Therefore, the 30th recorded image extends about 3 mm with respect to the 1st recorded image in the case of A4 size.

The left half of FIG. 14 shows the first output recording sheet. In this case, since the pressure roller of the fixing device is cold and in the initial diameter state at the beginning of recording, the fixing device is in the initial diameter state. The recording paper conveyance speed in the fixing nip part is almost the same as the recording paper conveyance speed in the transfer part, and even after the leading edge of the recording paper reaches the fixing nip part of the fixing device from the transfer part, the recording paper conveyance speed in the transfer part is The recording paper is conveyed at almost the same speed as the speed in the fixing nip portion, and there is no pulling conveyance of the recording paper at the transfer portion. Therefore, the recorded image formed on the recording paper does not substantially extend in the entire area from the leading edge to the trailing edge. .

The right half of FIG. 14 shows the 30th output recording sheet. In this case, as described above, the pressure roller is gradually heated by the heat of the heating member during the continuous recording until then. Since the diameter of the recording paper becomes larger than the initial diameter due to thermal expansion, the recording paper conveyance speed in the fixing nip part of the fixing device becomes faster than the recording paper conveyance speed in the transfer part. When the leading edge reaches the fixing nip portion of the fixing device, the recording image portion of the recording paper corresponding to the area between the pressure roller of the fixing device and the transfer portion does not extend, but the recording paper after that does not extend. The recording image portion corresponding to the area portion is an image extended in the recording paper conveyance direction for pulling and conveying. Therefore, if an image of 2 mm is continuously recorded on the A4 size recording paper up to the rear end, an image of about 3 mm extends and an image loss of 1 mm occurs on the 30th sheet.

Therefore, the present invention solves the above problems in an image recording apparatus equipped with a pressure roller drive system / on-demand type fixing device as an image fixing means, that is, in recording images during continuous recording. The purpose is to prevent stretching and reduce changes in image magnification within one page of recording paper.

[0019]

The present invention is an image recording apparatus characterized by the following configurations.

(1) Recording that has a photoconductor, an exposure unit that exposes the photoconductor according to image information, and a pressure roller that conveys a recording sheet, and carries an unfixed image transferred from the photoconductor A fixing unit that nip-conveys the paper to heat and fix the unfixed image on the recording sheet, a first drive motor that drives the photoconductor and the pressure roller, and a second drive unit that drives the exposure unit.
In the image recording apparatus having the drive motor of No. 1 and a control unit for controlling the first and second drive motors, the control unit is configured to perform the above-mentioned operation until the number of continuous image recordings or the continuous image recording time reaches a predetermined value. a first drive motor is driven at a first speed, said second drive motor and equal to or greater than a predetermined value
The image recording apparatus , wherein the first drive motor is driven at a second speed slower than the first speed without changing the drive speed of . (2) A recording medium having a photoconductor, an exposure unit that exposes the photoconductor according to image information, and a pressure roller that conveys the recording paper, and holds the unfixed image transferred from the photoconductor. A fixing unit that conveys and fixes the unfixed image on the recording paper by heating, a first drive motor that drives the photoconductor and the pressure roller, and a second drive motor that drives the exposure unit.
And a control means for controlling the first and second drive motors, the control means comprising:
The first drive motor is driven at a first speed until the number of continuous image recordings or the continuous image recording time reaches a predetermined value,
When the recording paper reaches the above-mentioned fixing means when the value exceeds a predetermined value
The first drive motor is driven at the first speed, and the drive speed of the second drive motor is changed after the recording paper reaches the fixing unit.
First, the first drive motor is set to the second speed slower than the first speed.
An image recording device characterized by being driven at a speed of.

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

That is, according to the present invention, means for varying the recording paper conveyance speed is provided, and the recording paper conveyance speed is changed on the basis of the number of continuous image recordings or the continuous image recording time, thereby rotating the fixing device. The change in the recording paper conveyance speed caused by the thermal expansion of the pressure member is canceled to prevent the extension of the recorded image.

The recording paper conveyance speed is changed at the time of non-image recording so as to minimize the number of changes in the image magnification within one page of the recording paper.

The recording paper conveyance speed after the leading edge of the recording paper from the image forming section reaches the nip formed by the heating member and the pressure member of the fixing device is based on the number of continuous image recordings or the continuous image recording time. By changing the values, the area in which the image magnification shifts within one page of the recording paper is minimized.

A stepping motor is used to drive the recording paper conveying means, and the recording paper conveying speed is changed by changing the drive pulse frequency of the stepping motor, so that the speed of the recording paper can be easily changed at low cost. It is a thing.

[0031]

DETAILED DESCRIPTION OF THE INVENTION

<Embodiment 1> (FIGS. 1 to 9) (1) Example of image recording apparatus FIG. 1 is a schematic configuration diagram of an example of an image recording apparatus. The image recording apparatus 1 of this example is a laser printer using a transfer type electrophotographic process.

Reference numeral 18 denotes a rotary drum type electrophotographic photosensitive member (photosensitive drum) as an image bearing member, which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed).

The photosensitive drum 18 is uniformly charged to a predetermined polarity and potential by the primary charging roller 19 during its rotation. Modulation control (ON / ON) corresponding to the time-series electric digital pixel signal of the target image information output from the laser scanner unit 8 to the uniformly charged surface of the rotating photosensitive drum 18 is performed.
The scanning exposure L is performed by the (OFF-controlled) laser light, and the electrostatic latent image of the target image information is formed on the surface of the rotary photosensitive drum 18.

The formed latent image is developed with toner in the developing device 20 and visualized. As a developing method, a jumping developing method, a two-component developing method, an FEED developing method, or the like is used, and it is often used in combination with image exposure and reversal developing.

On the other hand, the recording paper (transfer material) S as a recording medium accommodated in the paper feed cassette 2 is driven by the drive of the paper feed roller 5.
Is fed to a transfer nip portion T, which is a pressure contact portion between the photosensitive drum 18 and the transfer charging roller 21, by a pair of paper feeding / conveying rollers (registration roller) 6 at a predetermined control timing. Reference numeral 7 denotes a paper feed sensor provided downstream of the paper feed / conveyance roller pair 6 in the recording paper conveyance direction, and detects the conveyance state of the fed recording paper.

By feeding the recording paper S to the transfer nip portion T, the toner images on the surface of the photosensitive drum 18 are sequentially transferred onto the surface of the fed recording paper S. The recording paper S that has exited the transfer nip portion T is sequentially separated from the surface of the rotary photosensitive drum 18 and is introduced into a fixing device 10 as a heating device for thermally fixing the toner image to perform the heat fixing process of the toner image. receive. The fixing device 10 of this example will be described in detail in the following item (2).

The recording paper coming out of the fixing device 10 is ejected by a paper ejection roller 12.
Is printed out on the stacking tray 13.

The rotary photosensitive drum 18 after the recording paper is separated
The surface is cleaned by a cleaner 22 to remove adhered contaminants such as untransferred toner, and is repeatedly used for image formation.

In the printer 1 of this embodiment, four process devices including a photosensitive drum 18, a primary charging roller 19, a developing device 20, and a cleaner 22 are collectively configured as a process cartridge (image forming section) 9 which is detachably mountable to the printer body. .

In the laser scanner section 8, 14 is a laser unit, which emits a laser beam modulated based on an image signal (image signal VDO) sent from an external device 30 such as a personal computer. Reference numeral 15 is a polygon mirror for scanning the photosensitive drum 18 with laser light from the laser unit 14, 15a is a rotation motor (polygon motor) for the mirror, 16 is an imaging lens group, and 17 is a folding mirror.

3 is a cassette paper presence sensor for detecting the presence or absence of the recording paper S in the cassette 2, and 4 is the recording paper S in the cassette 2.
A cassette size sensor (composed of a plurality of micro switches) for detecting the size of the paper, and a paper ejection sensor 11 for detecting the recording paper conveyance state of the paper ejection unit.

Reference numeral 23 denotes a main motor, which feeds the roller 5
A driving force is applied to the sheet feeding roller clutch 24 via the sheet feeding roller clutch 24, each unit in the image forming unit 9 including the sheet feeding and conveying roller pair 6, the photosensitive drum 18, the fixing device 10, and the sheet discharging roller 1.
The driving force is also applied to the second class.

Reference numeral 26 is a printer control device (engine controller) for controlling the printer main body 1, which includes a timer and R
It is composed of an MPU (microcomputer) equipped with OM, RAM and the like, various input / output control circuits and the like.

The printer control device 26 is connected to a video control device (video controller) 28 via a video interface 27 which is an internal communication means, and the video control device 28 is further provided with a general-purpose interface 29 such as a Centronics interface. It is connected to an external device 30 such as a personal computer.

The video control device 28 converts the image information transmitted from the external device 30 to the printer body 1 via the general-purpose interface 29 into a video signal, and transmits it to the printer control device 26 via the video interface 27.

(2) Fixing Device 10 FIG. 2 is an enlarged cross-sectional model view of the main part of the fixing device 10. The fixing device 10 of this example is a so-called on-demand type / tensionless type disclosed in JP-A-4-44075 to 44083 and JP-A-4-204980 to 204984.
It is a pressure roller drive type film heating type device.

That is, a cylindrical (endless) heat-resistant film (fixing film) 10c is used as a moving body for heating, and at least a part of the perimeter of the film is tension-free (state in which no tension is applied), Pressure roller 1 using 10c as a pressure member (pressure rotating member)
It is designed to be rotationally driven by a rotational driving force of 0e.

Reference numeral 10d designates a film inner surface guide stay (stay) having a substantially semi-circular cross-section gutter type having rigidity and heat insulation, and a ceramic heater 10a as a heating body having a low heat capacity along the length on the outer lower surface of this stay. Is fixedly supported. The cylindrical film 10c is loosely fitted on the stay 10d including the heater 10a.

The pressure roller 10e comprises a core metal 10f and a heat-resistant elastic layer 10g such as a silicone rubber layer which is concentrically formed integrally with the outer periphery of the core metal and has excellent releasability. The bearing means is not shown. The film 10c is sandwiched by a biasing means with a predetermined pressing force, and the film 10c is arranged in pressure contact with the heater 10a. N is the pressure contact nip portion (heating nip portion / fixing nip portion). The pressure roller 10e is rotationally driven at a predetermined peripheral speed in the counterclockwise direction indicated by an arrow by transmitting a rotational driving force from a drive motor 23 via a power transmission system (not shown).

The film 10 is driven by the frictional force between the roller 10e and the outer surface of the film due to the rotational driving of the pressure roller 10e.
The rotational force acts directly on c (when the recording sheet S is introduced into the nip portion N, the rotational force indirectly acts on the film 10c via the recording sheet S), and the film 10c is moved to the ceramic heater 10a. While sliding in pressure contact with the lower surface of, it rotates following the clockwise direction indicated by the arrow.

The film inner surface guide stay 10d facilitates rotation of the film 10c. In order to reduce the sliding resistance between the inner surface of the film 10c and the surface of the ceramic heater 10a, a small amount of lubricant such as heat resistant grease may be interposed therebetween.

The ceramic heater 10a is heated by power supply to the energization heating element b of the ceramic heater 10a, and the heat generation heats the rotating film 10c in the nip portion N. Then, the film 10c at the nip portion N
The recording paper S is introduced between the pressure roller 10e and the pressure roller 10e with the unfixed toner image bearing surface facing the film 10c.
The recording paper S is in close contact with the film 10c and overlaps with the film to sandwich and pass through the nip portion N at a speed corresponding to the rotational peripheral speed of the pressure roller 10e.

Heat energy is applied to the recording paper S from the film 10c heated by the ceramic heater 10a while the recording paper S passes through the nip portion, and the unfixed toner image t on the recording paper S is heated and melted and fixed. . After passing through the nip portion N, the recording paper S is separated from the surface of the film 10c and discharged.

The film 10c has a total thickness of 100 μm or less, preferably 20 μm or more and 40 μm or less in order to reduce the heat capacity and improve the quick start property. As a material, a single layer of PTFE, PFA, FEP, or polyimide, polyamide imide, PEEK, PES, P having heat resistance, releasability, strength, durability, etc.
On the surface of films such as FA and FEP, PTFE, PFA,
It is a composite layer film coated with FEP or the like as a release layer.

Ceramic heater 10a as a heating element
Is a heater such as an elongated heat-resistant / insulating / heat-conductive alumina heater having a length perpendicular to the transport direction of the film 10c or the recording paper S in the heating nip portion N and having a width of 10 mm and a thickness of 1 mm. Substrate a, along the longitudinal direction of the substrate at the center in the lateral direction on the surface side of the substrate, for example, Ag /
Thickness of electrical resistance material such as Pd (silver palladium) is about 10μ
m, a width of 1 to 3 mm, which is formed by coating by screen printing or the like, an energization heating element b, power supply electrodes at both longitudinal ends of the energization heating element, and glass coated on the surface of the heater on which the energization heating element b is formed. A linear heating element having a low heat capacity as a whole, including a protective layer c made of fluororesin or the like, a thermistor d as a temperature detecting means of the heater, which is provided on the back surface side of the heater substrate.

The ceramic heater 10a is fixedly supported on the outer lower surface of the film inner surface guide stay 10d by exposing the surface side on which the electric heating element b is formed and provided downward.

The ceramic heater 10a includes an electric heating element b.
By supplying power to the power supply electrodes at both ends of the energizing heating element b
Generates heat over the entire length, and the temperature rises. The heater temperature is detected by a thermistor d which is a temperature detecting means,
The output of the thermistor d is A / D converted and taken into the printer control unit 26, and based on the information, the AC voltage applied to the energization heating element b of the ceramic heater 10a by the triac (not shown) is changed in phase and wave number. By controlling the temperature to a desired value by control or the like, the temperature of the ceramic heater 10a, that is, the temperature of the fixing device is controlled to be maintained at a predetermined temperature. That is, the energization to the energization heating element b is controlled so that the ceramic heater 10a is heated when the heater detection temperature of the thermistor d is lower than a predetermined set temperature, and when it is high, the ceramic heater 10a is cooled. The temperature of the ceramic heater 10a is adjusted so as to maintain a predetermined constant value during fixing.

The fixing device 10 as a film heating type heating device as in this example can use a ceramic heater 10a as a heat source and a fixing film 10c having a low heat capacity, so that the temperature can be raised quickly and the quick start property can be improved. It is a power-saving on-demand device that does not require preheating and energization.

Further, in the tensionless type film heating type fixing device 10 as in this embodiment, the nip portion N and the film inner surface guide stay outer surface portion on the upstream side of the nip portion N in the film rotation direction when the film is rotationally driven. The tension acts only on the film portion in the contact area with the film, and the tension does not act on most of the remaining film portion. Therefore, the shift force of the film 10c along the length of the stay in the film rotational driving state is small, and the film shift control means or the film shift control means can be simplified. For example, the film shift control means can be a simple member such as a flange member that receives the film end portion, and the film shift control means can be omitted to reduce the cost and size of the apparatus.

(3) Video Interface 27 FIG. 3 is a schematic diagram for explaining the structure of the video interface 27.

CPRDY: a signal indicating that the external device 30 can communicate, and is sent from the video control device 28 to the printer control device 26.

PPRDY: a signal indicating that the printer controller 26 can communicate, and is sent from the printer controller 26 to the video controller 28.

SBSY: Status valid signal, which is sent from the printer controller 26 to the video controller 28.

CBSY: Command valid signal, which is sent from the video controller 28 to the printer controller 26.

SC: Status / command signal,
When the status valid signal SBSY is TRUE, it is sent from the printer controller 26 to the video controller 28 as status data indicating the internal state of the printer. When the command valid signal CBSY is TRUE, the video controller 28 issues an instruction to the printer. The command data is sent from the video control device 28 to the printer control device 26.

CLK: Synchronous clock of the status / command signal SC, which is sent from the video controller 28 to the printer controller 26. For each command from the external device 30, the printer control device 26 returns one status corresponding to the command.

That is, the above SBSY, CBSY, SC, C
Handshake type serial communication is performed with each signal of LK.

RDY: Ready signal, which is set to TRUE when the printer controller 26 is in a printable state, and is sent from the printer controller 26 to the video controller 28.

PRINT: A print signal that is TRUE when the external device 30 gives an instruction to start printing, and is sent from the video control device 28 to the printer control device 26.

TOP: A vertical synchronizing signal for synchronizing the image output sent from the printer controller 26 to the video controller 28 in the vertical direction (sub-scanning direction / paper conveying direction).

HSYNC: A horizontal synchronizing signal for synchronizing the image output sent from the printer controller 26 to the video controller 28 in the horizontal direction (main scanning direction / laser scanning direction).

VDO: An image signal for the video controller 28 to serially send out a dot image to the printer controller 26 in synchronization with the vertical synchronizing signal TOP and the horizontal synchronizing signal HSYNC.

(4) Operation of Serial Communication FIG. 4 is a timing chart showing the operation of the serial communication.

When the printer main body 1 is powered on, initialization of the printer control device 26 is completed, and serial communication becomes possible, the printer control device 26 is set to PP.
Let RDY be TRUE.

On the other hand, when the video controller 28 is also turned on, initialization and the like are completed, and serial communication is possible, the video controller 28 sets CPRDY to TR.
UE. Further, the video control device 28 is PPRDY.
, It is determined that serial communication is possible after confirming that is TRUE for a predetermined time, and if necessary, CBSY is set to T
Set to RUE and transmit an 8-bit command from the SC line in synchronization with CLK. Then CBSY to FALS
The status is returned to E, and the printer controller 26 waits for the status to be returned.

When the printer control device 26 receives the command, the printer control device 26 sends back a status corresponding to the contents of the command to the SB.
Let SY be TRUE. Video controller 28 is SBSY
When TRUE is detected, the printer controller 26 starts transmitting CLK, returns the status from the SC line in synchronization with CLK, and sets SBSY to FALSE.

The printer control unit 26 uses the CPRDY
If it is checked for TRUE for a predetermined time, it is determined that serial communication is possible, and the command is determined to be valid.

(5) Normal Print Operation of Printer 1 FIGS. 5A and 5B are timing charts showing the normal print operation of the printer 1.

In FIG. 5A, when the printer control unit 26 becomes ready to accept a print, it sends RDY to TRU.
The result is E, and the video control device 28 is notified that the print can be accepted.

In response to this, when a print request is issued from the external device 30, the video control device 28 sets PRINT to TRUE and instructs the print start.

When the printer control device 26 detects TRUE of PRINT, the main motor 23 (first drive)
(Motor) and the polygon motor 15a (second drive motor) of the laser scanner unit 8 which is the exposure means are started.

When the main motor 23 is driven, the drive is transmitted to the paper feeding / conveying roller 6, the photosensitive drum 18, the fixing device 10, the primary charging roller 19, the developing device 20, the transfer roller 21, and the paper discharging roller 12. At this time, a predetermined high voltage application drive is also performed on the primary charging roller 19, the developing device 20, the transfer charging roller 21, and the like.

Further, the ceramic heater 1 in the fixing device 10
The heating of 0a is started, and the energization duty to the energization heating element b of the ceramic heater 10a is controlled so that the heater temperature detected by the thermistor d becomes 170 ° C., and the temperature of the heater (fixing device) is adjusted.

The printer controller 26 is the polygon motor 1
When the rotation of 5a reaches a steady state for t1 seconds, the paper feed clutch 24 is turned on for t2 seconds to drive the paper feed roller 5, and the recording paper S is fed toward the paper feed conveyance roller 6.

When the printer control device 26 detects that the leading edge of the recording paper S has passed the paper feed / conveyance roller 6 and reached the paper feed sensor 7, the vertical synchronization signal TOP is video-controlled after a predetermined time t3 seconds. To the device 28.

The video control device 28 synchronizes with TOP and t
After v seconds, the output of the image signal VDO for one page is started.

During this time, the printer controller 26 sends the horizontal synchronizing signal HSYNC to the video controller 28 at a predetermined timing synchronized with the laser scanning, and modulates the laser light emitted from the laser unit 14 based on the image signal VDO. To do.

As shown in FIG. 5B, the video control device 28 outputs the image signal VDO for one scan after th seconds in synchronization with the rising of the horizontal synchronizing signal HSYNC.

By the above operation, the recording paper S is sequentially conveyed to the paper feed roller 5, the paper feed / conveyance roller 6, the transfer nip portion T of the image forming section 9, the fixing device 10 and the paper discharge roller 12, and the image is formed. Records are made.

Then, the trailing edge of the recording paper S is fed to the paper discharge sensor 11
When detected by, the ceramic heater 10a of the fixing device 10
The temperature control is stopped, and the high voltage application drive to the primary charging roller 19, the developing device 20, the transfer charging roller 21 and the like is stopped.
After t4 seconds, the main motor 23 and the polygon motor 15a are stopped, and the normal printing operation is completed.

In the continuous print mode, the required number of continuous prints can be performed by repeating the cycle in which the next print operation is executed after a predetermined paper interval (interval, non-image recording period) after one print operation. When the discharge sensor 11 detects the trailing edge of the final recording sheet S, the temperature control of the ceramic heater 10a of the fixing device 10 is stopped, and the primary charging roller 19, the developing device 20, and the transfer charging roller 21 are stopped. The high-voltage application drive for etc. is stopped. Then t4
After a second, the main motor 23 and the polygon motor 15a are stopped, and the continuous printing operation is completed.

(6) Drive Control of Main Motor 23 FIG. 6 is a circuit diagram of a portion related to drive control of the main motor 23 of the printer controller 26.

Reference numeral 26a is a one-chip microcomputer, which comprises a ROM 26b, a RAM 26c and a timer 26d.

The main motor 23 is a four-phase stepping motor, and the windings of A phase, / A phase, B phase, and / B phase are
One of them is the NPN transistor 31, 32, 3 respectively.
It is connected to the collectors of 3, 34 and the other is +2
It is connected to a 4V power supply. NPN transistor 31,
The emitters of 32, 33, and 34 are connected to GND, and their bases are MPU output ports P0, P1, and
It is connected to P2 and P3. A surge absorbing diode for protecting each NPN transistor is omitted from the figure.

FIG. 7 is a timing chart showing an excitation pulse for driving the main motor 23. When rotating the main motor 23, the MPU 26a uses the built-in timer 26d to calculate the frequency of the excitation pulse, and outputs the A phase from the output ports P0, P1, P2, P3 at the predetermined frequency,
Excitation pulses of A phase, B phase, and / B phase are output. Therefore,
The rotation speed of the main motor 23 can be changed by changing the frequency of the excitation pulse.

That is, if the frequency of the excitation pulse is increased by the printer control device 26, the rotation of the main motor 23 becomes faster and the conveyance speed of the recording paper S becomes faster. On the contrary, if the frequency is lowered, the rotation of the main motor 23 becomes slower, and the conveying speed of the recording paper S becomes slower.

(7) Image Spread Correction Control As described above, the pressure roller 10e of the fixing device 10 is heated by the ceramic heater 10a during continuous printing operation.
Heated by the heat from the printer, the temperature rises and thermal expansion occurs, causing the outer diameter to increase from the initial diameter. As a result, as the number of continuous prints (the number of continuous image recordings) increases, the recording paper is pulled and conveyed in the transfer section. The image extends.

Therefore, in this example, in order to correct the extension of this image, the printer controller 26 counts the number of continuous prints and controls the rotation speed of the main motor 23 to gradually change the recording paper conveyance speed (every 10 sheets). ), The thermal expansion of the pressure roller 10e is saturated, and the image extension is saturated.

FIG. 8 is a flowchart of the above control.

That is, it is judged whether or not it is the tenth continuous print (step S1), and if it is the tenth print, the recording paper transport speed is reduced by 0.33% from the initial value (step S1).
2).

Next, it is judged whether or not it is the 20th continuous print (step S3), and if it is the 20th print, the recording paper transport speed is reduced by 0.66% from the initial value (step S3).
4).

Next, it is judged whether or not it is the 30th continuous print (step S5), and if it is the 30th print, the recording paper conveyance speed is reduced by 1.00% from the initial value (step S5).
6).

1) That is, when the main motor 23 is drive-controlled to reduce the rotation speed thereof, a recording paper conveyance path from the paper feed roller 5 to the paper discharge roller 12 is formed.
Recording is performed with the rotational peripheral speeds of the paper feed roller 5, the paper feed roller pair 6, the photosensitive drum 19, the transfer charging roller 21, the pressure roller 10e of the fixing device 10, and the paper discharge roller 12 being lower than the normal rotational peripheral speed. The paper transport speed will be lower than the normal transport speed.

2) Since the rotational peripheral speed of the photosensitive drum 18 is lower than the normal rotational peripheral speed with respect to the latent image forming speed by the exposure unit (laser scanner section) 8, the latent image formed on the photosensitive drum 18 is reduced. The toner image is formed by being contracted in the photosensitive drum rotation direction by a ratio corresponding to the amount of reduction in the rotational peripheral speed of the photosensitive drum 18. You
That is, this is the port of the laser scanner section 8 which is the exposure means.
Main motor without changing the drive speed of the Rigong motor 15a
By reducing the drive speed of 23.

3) Even if the main paper motor 23 is driven and controlled to reduce the recording paper conveyance speed, the recording paper conveyance speed in the fixing nip portion of the fixing device during continuous printing is increased due to the thermal expansion of the diameter of the pressure roller 10e. Therefore, it is in a state of being faster than the recording sheet conveyance speed in the transfer section, and the recording sheet is pulled and conveyed in the transfer section.

4) Therefore, as described in 2) above, the toner image formed on the surface of the photosensitive drum 18 by being contracted in the photosensitive drum rotation direction is extended in the recording paper conveyance direction with respect to the recording paper surface pulled and conveyed in the transfer portion. It is transferred and transcribed.

That is, at the time of continuous printing, as shown in the control flow chart above, the main motor 23 responds to the increase in the recording paper conveyance speed in the fixing nip portion due to the increase in the outer diameter due to the thermal expansion of the pressure roller of the fixing device. By controlling the driving of the recording paper to reduce the recording paper conveyance speed at an appropriate rate, the contraction amount of the toner image contracted and formed on the surface of the photosensitive drum 18 and the image extension amount at the time of transfer are offset,
A toner image whose extension has been corrected is transferred and formed on the recording paper surface.

In this example, the number of prints is counted up when the PRINT signal is received, and the recording paper conveyance speed is switched between the reception of the PRINT signal and the output of the TOP signal. That is, the timing at which the recording paper conveyance speed is changed is during non-image formation (non-exposure).

As a result, the expansion rate of the image on one page changes only once when the leading edge of the recording paper reaches the pressure roller.

FIG. 9 is a graph showing the rate of extension of the recorded image and the rate of decrease of the recording paper conveyance speed in the process of progressing the continuous print number. As can be seen from this graph, in this example, the extension of the image is suppressed within 0.33%.

In this example, the recording paper conveyance speed is changed according to the number of continuous prints, but the recording paper conveyance speed may be changed according to the continuous print time corresponding to the number of continuous prints.

<Embodiment 2> (FIGS. 10 and 11) The printer of this embodiment is different from the printer of Embodiment 1 described above in the timing of switching the recording paper conveyance speed. The other printer configurations are the same.

FIG. 10 shows a conventional example (=
(Right half of FIG. 14), the first embodiment, the second embodiment
FIG. 6 is a diagram showing a state in which the recorded image in FIG.

In the conventional example, when the pressure roller 10e expands as the continuous printing progresses, the recording paper S is pulled by the pressure roller 10e, so that the leading edge of the paper is transferred after reaching the nip portion N of the fixing device 10. The image stretches.

In the first embodiment described above, in order to correct this extension, the drive speed of the main motor 23 is slowed down and the recording paper transport speed is slowed down so that the conventional image extension portion becomes normal. However, in this case, when the leading edge of the recording paper reaches the nip portion N, the area where the image has already been transferred (pressure roller 10e
The area of the transfer roller 21) becomes a contracted image by directly transferring the toner image formed by being contracted on the surface of the photosensitive drum 18.

In an image forming apparatus in which the distance between the transfer roller 21 and the pressure roller 10e of the fixing device 10 is long, this image shrinkage area becomes large, which may cause a problem.

In this example, such a problem is reduced.

That is, FIG. 11 shows a control timing chart of this embodiment, and the control of the main motor 23 is different from that of FIG. 5 of the above-mentioned embodiment 1.

In this example, the leading edge of the recording paper is the pressure roller 10e.
The recording paper is always conveyed at the same speed (initial value) regardless of the number of continuous prints until the timing tk from the paper feed sensor 7 is reached, and after the leading edge of the recording paper reaches the pressure roller 10e. The recording paper conveyance speed is gradually reduced in the same manner as in the first embodiment to perform image extension correction.

As a result, from the leading edge of the recording paper to the pressure roller 1
The image in the recording paper area corresponding to the area between 0e and the transfer roller 21 can be an image without extension and contraction.

However, as shown in FIG. 10, the transfer roller 1
The small recording paper area corresponding to the laser exposure position from 0e is an image extension area. The tip of the recording paper is the pressure roller 10
This is because it has already been exposed when it reaches e.

<Embodiment 3> (FIG. 12) FIGS. 12A and 12B are schematic structural views of another example of the on-demand type fixing device 10. Both are electromagnetic induction heating type fixing devices.

In FIG. 2 (a), the horizontally long electromagnetic induction heating plate 10h (metal plate) is used in place of the ceramic heater 10a as the heating body in the tensionless type pressure roller drive type film heating system shown in FIG. , Conductors, resistors, magnetic bodies) are provided in the film inner surface guide stay 10d, and an alternating magnetic field is applied to the electromagnetic induction heating plate 10h inside the guide stay 10d.
It is provided with an alternating magnetic field generating means 10k composed of i and an exciting core 10j.

The electromagnetic induction heating plate 10h functions as a heating body by electromagnetic induction heat generation (heat generation due to eddy current loss) by the action of the alternating magnetic field generated by the alternating magnetic field generation means 10k, and the heat generation drives the rotation of the pressure roller 10e. Film 10 that rotates with
c is heated in the nip portion N. Then, the recording paper S is introduced between the film 10c and the pressure roller 10e in the nip portion N with the unfixed toner image bearing surface on the film 10c side, so that the recording paper S comes into close contact with the film 10c. Pressure roller 10e in an overlapping state with the film
The nip portion N is nipped and conveyed at a speed corresponding to the rotation peripheral speed of. Heat energy is applied to the recording paper S from the film 10c heated by the electromagnetic induction heating plate 10h while the recording paper S passes through the nip portion, and the unfixed toner image t on the recording paper S is heated and fused and fixed. After passing through the nip portion N, the recording paper S is separated from the surface of the film 10c and discharged.

In FIG. 2B, in the film heating system of the tensionless type and pressure roller drive type shown in FIG. 2, the ceramic heater 10a as a heating body is not used, and the film 10c is replaced by an electromagnetic induction heating film. To Further, inside the film guide 10d, an alternating magnetic field generating means 10k including an exciting coil 10i and an exciting core 10j for mainly applying an alternating magnetic field to the electromagnetic induction heating film portion of the nip portion N is provided.

The alternating magnetic field generated by the alternating magnetic field generating means 10k causes the electromagnetic induction heating film 10m to generate electromagnetic induction heat mainly in the region of the nip portion N. Then, the recording paper S is introduced between the film 10m and the pressure roller 10e of the nip portion N with the unfixed toner image bearing surface being on the film 10m side, so that the recording paper S is brought into close contact with the film 10m. Pressure roller 10 in an overlapping state with the film
The nip portion N is nipped and conveyed at a speed corresponding to the rotation peripheral speed of e. Heat energy is applied to the recording sheet S from the film 10m that generates heat by electromagnetic induction in the course of the recording sheet S passing through the nip portion, and the unfixed toner image t on the recording sheet S is heated and fused and fixed. After passing through the nip portion N, the recording paper S is separated from the surface of the film 10m and discharged.

<Others> 1) The pressure roller 10e of the fixing device 10 can be a driven rotating member of another form such as a rotating belt member.

2) The transfer means 21 of the image forming section may be other means such as a transfer corona charger.

3) The image forming section is not limited to the electrophotographic process of the embodiment, but an unfixed image corresponding to desired image information is formed on a recording sheet by a transfer method or a direct method such as an electrostatic recording process or a magnetic recording process. It can be of any suitable imaging process means that can be carried.

4) When the next print operation is to be performed without waiting too long after the end of the print operation, the fixing device 10
Since the pressure roller 10e may be warmed to some extent, the elapsed time from the end of the previous operation at the start of printing is referred to.
It is also possible to determine that e is warm, and conversely, if the elapsed time is long, it is determined that the pressure roller 10e is cold and control the recording material conveying speed during the next printing operation.

[0131]

As described above, according to the present invention, a photoconductor, an exposure means for exposing the photoconductor according to image information, and a pressure roller for conveying recording paper are provided. Fixing means for sandwiching and transporting the recording paper carrying the transferred unfixed image to heat and fix the unfixed image on the recording paper, a first drive motor for driving the photoconductor and the pressure roller, and the exposure. A second drive motor for driving the means;
In an image recording apparatus having a control unit for controlling the first and second drive motors, it is possible to cancel the change in the recording sheet conveyance speed caused by the thermal expansion of the pressure roller of the fixing unit and prevent the extension of the recorded image. It is possible to minimize the number of times the image magnification changes within one page of the recording paper, minimize the area where the image magnification shifts within one page of the recording paper, and reduce the cost of changing the speed of the recording paper. It is easy to do, and the intended purpose is often achieved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image recording apparatus (laser printer) according to a first embodiment.

FIG. 2 is a schematic configuration diagram of a fixing device (film heating method).

FIG. 3 is a schematic diagram of a video interface.

FIG. 4 is an operation timing chart of serial communication.

FIG. 5 is a timing chart of a normal print operation.

FIG. 6 is a circuit diagram of a motor control part.

FIG. 7 is a diagram showing a stepping motor excitation pattern.

FIG. 8 is a flowchart showing recording paper conveyance speed control.

FIG. 9 is a graph showing the relationship between the number of continuous prints, the image extension rate, and the recording paper conveyance speed decrease rate.

FIG. 10 is a diagram showing the expansion and contraction of recorded images in the conventional example, the first embodiment, and the second embodiment.

FIG. 11 is a timing chart showing a printing operation of the image recording apparatus according to the second embodiment.

FIGS. 12A and 12B are schematic configuration diagrams of another example of a pressure roller drive system / an on-demand type fixing device.

FIG. 13 is a graph showing the number of continuous prints and the image extension ratio in the conventional image recording apparatus.

FIG. 14 is an explanatory diagram of a recorded image state of the first output sheet and each recording sheet of the continuous recording thirty sheets.

[Explanation of symbols]

1 Laser printer (image recording device) 8 Laser scanner section 9 Image forming department T transfer part 10 Fixing device 10a Ceramic heater (heating body) 10c heat resistant film 10d Film inner surface guide stay 10e Pressure roller (rotating body for pressure transfer) 23 Main motor 26 Printer control device

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 21/14 G03G 21/00 370-540 G03G 15/20-15/20 302 G03G 15/00 510-534

Claims (2)

(57) [Claims] 1. A recording paper carrying a photoconductor, an exposing means for exposing the photoconductor according to image information, and a pressure roller for conveying the recording paper, and carrying an unfixed image transferred from the photoconductor. A fixing unit that nip-conveys and heats and fixes an unfixed image on a recording sheet; and a first unit that drives the photoconductor and the pressure roller .
No. 1 drive motor and a second drive for driving the exposure means
In an image recording apparatus having a motor and a control unit for controlling the first and second drive motors, the control unit may control the first image recording device until the number of continuous image recordings or the continuous image recording time reaches a predetermined value . the drive motor first
Drive at the speed of, and when the value exceeds a predetermined value, the second drive mode
The first drive motor without changing the drive speed of the motor .
An image recording apparatus characterized in that it is driven at a second speed lower than the above speed. 2. A recording paper carrying a photoconductor, an exposing means for exposing the photoconductor according to image information, and a pressure roller for conveying the recording paper, and carrying an unfixed image transferred from the photoconductor. A fixing unit that nip-conveys and heats and fixes an unfixed image on a recording sheet; and a first unit that drives the photoconductor and the pressure roller .
No. 1 drive motor and a second drive for driving the exposure means
In an image recording apparatus having a motor and a control unit for controlling the first and second drive motors, the control unit may control the first image recording device until the number of continuous image recordings or the continuous image recording time reaches a predetermined value . the drive motor first
The driven at speed, said first drive motor to the recording paper becomes a predetermined value or more reaches the fixing means at a first speed, after said recording sheet reaches the fixing unit second drive motor
The first drive motor without changing the drive speed of the motor .
An image recording apparatus characterized in that it is driven at a second speed lower than the above speed.