JPH1020734A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly set an image area by controlling the timing for forming a latent image onto a photoreceptor by an image forming means, on the basis of the outputs of a position detecting means and a speed detecting means. SOLUTION: A timer (mask timer) for deciding an image write inhibition timing, is started, when the detection of a rear end of a recording sheet, is ascertained by a paper supply sensor 3a. Then the setting for inhibitting the image write, is performed when the value of the mask timer becomes mx(sec). On this occasion, the value mx of the mask timer is setted to m0 or m1 (m1>m0). And an image area can be property set by delaying the timing of the printing inhibition area of a rear end of an image, when the number of printed sheets becomes more than an arbitrary number as the result of the counting of the number of sheets of recording mediums which are continuously printed and conveyed, by a counter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for conveying a recording medium to form an image.

[0002]

2. Description of the Related Art Heretofore, formation of a latent image on a photosensitive member has been prohibited after a certain period of time from the timing at which the recording medium detecting means on the conveyance path detects the rear end of the recording medium. FIG.
A conventional operation of setting a prohibited area at the rear end of an image will be described with reference to FIG. Conventionally, formation of a latent image of an image has been prohibited for a predetermined time m0 (sec) after the trailing edge of the paper is detected by the paper feed sensor 3a. That is, the paper trailing edge A shown in FIG.
The image printing was prohibited at the position.

[0003]

However, a fixing pressure roller 6c that performs fixing by applying temperature and pressure.
In an image forming apparatus such as a laser beam printer equipped with a fixing device, the fixing pressure roller 6c expands and increases in diameter as the temperature increases, and the speed of paper conveyance is increased by the paper conveying force of the fixing pressure roller 6c. . In the case where the paper conveyance speed is increased as described above, in a conventional apparatus in which the trailing edge of the recording paper is detected and the latent image formation of the trailing edge of the image is inhibited at a fixed timing, the original setting may be made depending on the speed. In some cases, the image printing process is prohibited at a timing earlier than the image prohibition region, and the image may be lost.

The operation of setting a prohibited area at the rear end of an image when the speed of paper conveyance is increased by the paper conveyance force of the fixing pressure roller will be described with reference to FIG. A predetermined time m0 (sec) after the trailing edge of the paper is detected by the paper feed sensor
c) When the latent image formation of the image is prohibited later, the time from the start of the latent image formation to the detection of the trailing edge of the paper becomes short because the paper conveyance speed is high, but the latent image formation on the photosensitive drum 5a is performed. Since the time and the rotation speed of the photosensitive drum 5a are constant,
The formation of an image is prohibited at a time corresponding to a position A ′ farther from the trailing edge of the paper than in the normal case. Accordingly, as shown in FIG. 11B, the image printing prohibited area is enlarged. That is, when the transport speed increases, it is necessary to prohibit image formation at a timing corresponding to the position A ″ away from the rear end of the paper.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. When it is detected that the transport speed of a recording sheet has increased, the present invention is not limited to detecting the trailing edge of the recording sheet and inhibiting image formation. It is an object of the present invention to provide an image forming apparatus capable of appropriately setting an image area by delaying the time of the normal operation from the normal time.

[0006]

In order to achieve the above object, a first means of the present invention comprises a conveying means for conveying a recording medium and a light scanning means for scanning light on a photosensitive member based on input image data. An image forming means for forming a latent image by causing the latent image on the photoreceptor formed by the image forming means to be transferred onto the recording medium using toner; and A heat fixing unit that conveys the recording medium in cooperation with the conveying unit while thermally fixing the toner image transferred onto the recording medium at a high temperature and a high pressure, and a position of a rear end of the recording medium being conveyed. Position detecting means for detecting, speed detecting means for detecting a physical quantity related to the speed of the recording medium being conveyed, and the photoconductor by the image forming means based on outputs from the position detecting means and the speed detecting means To the top Characterized by comprising an image forming control means for controlling the timing of formation of the image.

[0007] The second means of the present invention is the first means described above.
In the means, the speed detecting means is a time measuring means for measuring a continuous printing time when performing a continuous printing operation, and the image forming control means is a predetermined time for the continuous printing time measured by the time measuring means. In this case, the timing for inhibiting the formation of the latent image is delayed.

[0008] The third means of the present invention is the above-mentioned first means.
In the means, the speed detecting means determines the number of horizontal synchronizing signals of the image forming means in a period from when a vertical synchronizing signal used in the image forming means is output to when a rear end of the recording medium is detected by the position detecting means. Counting means for counting, and when the number of horizontal synchronization signals detected by the counting means is less than the number of horizontal synchronization signals corresponding to a prescribed paper size, the image forming control means inhibits latent image formation. It is characterized in that the timing is delayed.

Further, a fourth means of the present invention is the above-mentioned first means.
In the means, the speed detecting means is a temperature change detecting means for detecting a temperature change amount when the driving of the heat fixing means is stopped for a predetermined time, and when the detected temperature change amount is smaller than the predetermined amount, Is characterized in that the image forming control means delays the timing of inhibiting the latent image formation.

[0010] The fifth means of the present invention is the above-mentioned first means.
In the means, the speed detecting means is a number measuring means for counting the number of the recording medium continuously printed and conveyed, and when the measured number exceeds a predetermined number, the image forming means The control means delays the timing of inhibiting the formation of the latent image.

According to the first aspect of the present invention, the position detecting means detects that the rear end of the recording medium has passed a predetermined position, and the speed detecting means detects a physical quantity related to the conveying speed of the recording medium. I do. The image forming control unit prohibits the image forming unit from forming a latent image after a predetermined time corresponding to the output of the speed detecting unit has elapsed from the time when the rear end of the recording medium has passed the predetermined position. I do.

According to the second aspect of the present invention, the magnitude of the speed of the recording medium is determined by the continuous printing tube measured by the timer, and when the continuous printing time is equal to or longer than a predetermined time, the image forming control means is controlled. Delays the timing of inhibiting the formation of a latent image.

According to the third aspect of the present invention, the magnitude of the speed of the recording medium is determined during the period from when the vertical synchronizing signal used in the image forming means is output to when the rear end of the recording medium is detected by the position detecting means. Is determined by the counting result of the counting means for counting the number of horizontal synchronizing signals. If the counting result is less than a predetermined number, the image forming control means delays the timing of inhibiting the latent image formation.

According to the fourth aspect of the present invention, the magnitude of the speed of the recording medium is determined based on the detection result of the temperature change detecting means for detecting the amount of temperature change when the driving of the heat fixing means is stopped for a predetermined time. When the amount of temperature change at this time is smaller than the predetermined amount, the image forming control means delays the timing of prohibiting the latent image formation.

According to the fifth aspect of the present invention, the magnitude of the speed of the recording medium is determined by the number of continuous prints counted by the number of prints measuring means. The control means delays the timing of inhibiting the formation of the latent image.

[0016]

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

(Embodiment 1) FIG. 1 shows Embodiment 1 of the present invention.
1 is a cross-sectional view illustrating a configuration of a laser beam printer according to the first embodiment.

In FIG. 1, 1 is a laser beam printer main body, and 2 is a cassette paper feed port. The recording medium is fed and transported by the driving of the paper feed roller 3 and the transport roller 3b. The paper feed sensor 3a detects when the leading edge and the trailing edge of the recording medium have passed, which is the basis of the timing for starting image writing and image trailing edge masking. Reference numeral 4 denotes an optical unit which modulates video data of an image sent via a video interface, emits a laser beam from a laser emitting unit 4a based on the modulated video data, and reflects the laser beam by a polygon motor 4b to perform horizontal synchronization. Photoconductor 5 using signal
a is scanned to form a latent image. 5 is an image transfer unit,
An image is transferred onto a recording sheet serving as a recording medium to be conveyed using toner. Note that the image transfer unit 5 includes a photosensitive drum 5a.
And the transfer roller 5b and other components.
The image forming process in the image transfer unit 5 is not directly related to the present invention, and the description thereof is omitted.

Reference numeral 6 denotes a fixing unit, 6a denotes a ceramic heater as a heating element, 6b denotes a film, and 6c denotes a pressure roller. Here, heat and pressure are applied to the recording medium on which the transfer process has been completed to fix the toner forming the image.
A paper discharge roller 7 discharges the recording medium that has passed through the fixing unit 6 to a paper discharge tray 8. The DC controller (engine sequence controller) 9 includes a CPU, ROM, RA
Control means including an M, a counter, a timer, and the like controls each device as a whole based on a control procedure stored in a ROM in advance.

FIG. 2 is a block diagram showing the configuration of the control system of the present embodiment.

In FIG. 2, the video controller 12
Receives coded image information (code data) from the host computer 10 or the like via the external video interface 11 and converts the code data into dot image video data.
The video data is sequentially transmitted to the DC controller 9 via the video interface 13 in synchronization with the sub-scanning synchronization signal.
To send to. The DC controller 9 forms an image on a recording paper based on video data using the paper feed roller 3, the paper feed sensor 3a, the optical unit 4, the image transfer unit 5, the fixing unit 6, and the like.

FIG. 3 is a flowchart showing a control procedure according to this embodiment. As described above, in the fixing unit 6 of the laser beam printer including the fixing pressure roller that performs fixing by applying temperature and pressure, a desired temperature is obtained by controlling the ceramic heater 6a. When the temperature rises, the fixing pressure roller 6c expands and its diameter increases, and the paper conveyance speed at the fixing pressure roller 6c increases the paper conveyance speed. In this embodiment, as means for detecting the expansion of the diameter of the fixing pressure roller 6c, means for counting the number of continuously printed sheets is D.
It is provided in the C controller 9.

FIG. 3 is a flowchart showing a procedure to be performed by the DC controller 9 in this embodiment. Hereinafter, the operation of the present embodiment will be described with reference to FIG.

First, in step S101, a continuous printing operation sheet number counter CM (hereinafter, referred to as a counter CM) is set to 0, and a timer (hereinafter, referred to as an intermittent timer) measuring a time from the end of the printing operation of the previous page is set to t1 (sec). ), The mask timer is initialized to m0 (sec).

Step S102 is a standby state, and waits for reception of a print signal.

In step S103, the value of the intermittent timer for starting the measurement in step S110 described later is t1 (se
c) Determine whether or not: If t1 (sec) or less, the process proceeds to step S104, and the intermittent timer is stopped at the state of the time data.

In step S105, the reception of the print signal is monitored. If the print signal has not been received, the process returns to the standby state, and the processing from step S102 to step S104 is continued.

If a print signal has been received in step S105, the intermittent timer is stopped in step S106, and it is determined in step S107 whether the value of the intermittent timer is less than t1. Here, if it is equal to or more than t1, the counter CM is cleared in step S108, and if less than t1, the process jumps to step S109 without clearing the counter CM.

In step S109, temperature control of the fixing device is performed. Then, the intermittent timer is started by 0 at a predetermined timing during which the fixing control and other controls are performed (step S110).

In step S111, 1 is added to the value of the counter CM, and a temperature control target temperature corresponding to this value is set.

In step S112, it is determined whether or not the value of the counter CM has reached a predetermined set number c1 at which the fixing pressure roller warms and the diameter expands to affect the conveying speed. Is c1, the image write max timing data is switched from m0 (sec) to m1 (sec) (m1> m0) (step S1).
113), and jump to step S105. If the value of the counter CM is not c1 in step S112, the process jumps to step S105.

Next, the image writing operation of this embodiment using the image writing mask timing data will be described with reference to the flowchart of FIG. 4 and the explanatory diagram of FIG.

FIG. 4 is a flowchart of the print image paper trailing edge prohibition (mask) control. First, when the detection of the trailing edge of the recording paper is determined by the paper feed sensor 3a shown in FIG. 5A (step S201), a timer (hereinafter, referred to as a mask timer) for determining an image writing prohibition timing is started. (Step S202). Next, the value of the mask timer is m
When x (sec) is reached, image write prohibition setting is performed (step S203). Here, the value mx of the mask timer
Is m0 or m1 (m1) set in the process shown in FIG.
> M0).

As described above, according to the present embodiment,
When the number of printed sheets becomes equal to or more than an arbitrary number by using a measuring means for counting the number of recording media continuously printed and conveyed, the image area is shifted by delaying the timing of the print prohibition area at the rear end of the image as shown in FIG. It can be set appropriately as shown in FIG.

Further, in the present embodiment, the image writing mask timing data m is changed due to a difference in the degree of expansion of the fixing roller and a change in the accuracy of setting the rear end image mask area.
A plurality of values of 1 or the set number c1 may be set.

Next, (Embodiment 2) to (Embodiment 4) will be described. The difference between (Embodiment 2) to (Embodiment 4) and (Embodiment 1) is that the conveyance of the recording medium is performed. These are a speed detecting means for detecting a physical quantity related to the speed, and a program executed by the DC controller 9, and other configurations are the same as those of the first embodiment.
In the following description, only this different point will be described, and other description will be omitted.

(Embodiment 2) In Embodiment 2 of the present invention, the magnitude of the speed of the recording medium is determined using a thermistor for detecting the temperature of the fixing unit 6. The operation of the present embodiment will be described below with reference to FIGS.

FIG. 6 is a flowchart showing the control contents of this embodiment, and FIG. 7 is an explanatory diagram showing the control mode of the fixing section 6, the thermistor voltage, and the state of the fixing heater drive signal. As shown in FIG. 7, the control mode of the fixing unit 6 includes a normal printing temperature control mode, an inter-paper low temperature control mode, and an initial state of the inter-paper low temperature control mode during the continuous printing fixing control. The mode is divided into a mode in which a fixing heater driving driver signal is turned off in a stage and a temperature change amount is measured.

In FIG. 6, first, in step S300,
The mask timing data is set to m0.

Next, in step S301, the control waits for the low temperature control timing.

When the low-temperature temperature control timing comes, the flow advances to step S302 to turn off the drive signal for driving the fixing heater. In step S303, the thermistor voltage data 1 at that time is taken and stored.

In step S304, a timer (hereinafter, referred to as a system measurement timer) for measuring the temperature of the system including the fixing pressure roller is started. A time tz (sec) preset in the system measurement timer is monitored (step S
305), thermistor voltage data 2 is fetched at the timing of tz (step S306).

In step S307, the deviation between the thermistor voltage data 1 and 2 is calculated. Next, in step S308, it is determined whether or not the calculation result is smaller than tmp0 preset as a value at which the temperature of the system including the fixing pressure roller is high. If the calculation result is smaller than tmp0, it is determined that the paper conveyance speed by the fixing pressure roller is high, and step S309 is performed.
To set m1 as the image write mask timing data. The image writing control using the image writing mask timing data m1 is as described in the first embodiment.

As described above, according to the present embodiment,
By detecting the amount of temperature change when the heat fixing drive is turned off for a certain period of time in the heat fixing unit and performing control to delay the timing of prohibiting the latent image formation by the image forming control unit when the change amount is small, The region can be set appropriately.

(Embodiment 3) In Embodiment 3 of the present invention,
A timer (hereinafter, referred to as a continuous print timer) for measuring the time during which the continuous print operation is performed is provided in the C controller 9, and the continuous print timer is used to determine the magnitude of the transport speed of the recording medium. is there. Hereinafter, FIG.
The operation of the present embodiment will be described with reference to FIG.

FIG. 8 is a flowchart showing the control contents of this embodiment. First, in step S401, m0 is initially set in the mask timer as image writing masking data.

Next, in step S402, the continuous print timer is cleared.

In step S403, input of a print signal is waited in a standby state.

If a print signal has not been received in step S404, the process jumps to step S402. If a print signal has been received in step S404, the flow advances to step S405 to determine whether the continuous print timer is operating. Here, if it is not operating, the process proceeds to step S406 to start the continuous print timer, and if it is already operating, the timer jumps to step S407 without starting the timer.

In step S407, it is determined whether or not the value of the continuous print timer has become equal to or greater than a preset determination value tm1. If the time has passed, it is determined that the fixing pressure roller has sufficiently warmed and expanded and the conveyance speed of the paper conveyance by the pressure roller has increased, and the flow advances to step S408 to change the image writing mask timing data. Set to m1. Thereafter, step S404 is performed again.
To determine whether to accept the print signal.

The image writing control using the image writing mask timing data m1 is as described in the first embodiment.

As described above, according to the present embodiment,
When the continuous printing time measured by the timer for measuring the printing time when the printing operation is continuously performed is longer than a predetermined time, the timing of prohibiting the latent image formation by the image forming controller is delayed. By performing the control, the image area can be appropriately set.

(Embodiment 4) In Embodiment 4 of the present invention,
A counter for measuring the number of main scanning synchronization signals (horizontal synchronization signals) used in the optical unit 4 for forming an image in the C controller 9 is provided in the DC controller 9, and the rear end of the recording medium is detected using this counter. The detection of the number of horizontal synchronization signals at the time of detection signal output from the sensor that performs the determination of the transport speed of the recording medium is performed.

FIG. 9 is a block diagram showing a configuration of a counter for measuring the number of horizontal synchronizing signals (hereinafter, referred to as BD signals). In FIG. 9, the CPU 20 includes a paper feed sensor 3a.
Outputs a vertical synchronizing signal TOP at a predetermined timing when detecting the leading edge of the conveyed paper. When the vertical synchronization signal TOP is output from the CPU 20, the counter 21 starts counting the number of BD signals output from the optical unit 4 using the vertical synchronization signal TOP as a load signal. Then, the count value C1 of the measurement result is read into the CPU 20 at the timing when the paper feed sensor 3a detects the rear end of the conveyed paper.

FIG. 10 is a flowchart showing the control contents of this embodiment. Hereinafter, the operation of this embodiment will be described with reference to FIG.

In FIG. 10, first, in step S501, m0 is initially set as image writing mask timing data, and C0 is initially set as a numerical value of a BD signal corresponding to a prescribed paper size. When the vertical synchronization signal TOP is output from the CPU 20 in such a state, the counter 21 at that point
Start counting the number of D signals.

In step S502, the process waits for the trailing edge detection of the conveyed paper by the paper feed sensor.

When the detection of the trailing end is determined, step S503 is performed.
To read the count value C1 from the counter 21.

Next, the flow advances to step S504 to compare the read count value C1 with the initially set count value C0. If the measured count value C1 is smaller, it is determined that the paper conveyance speed is high, and the process advances to step S505 to set m1 as image writing mask timing data. Image write mask timing data m
1 is the same as that described in the first embodiment.

As described above, according to the present embodiment,
The number of horizontal synchronizing signals detected by the counting means for counting the number of horizontal synchronizing signals during the period from the output of the vertical synchronizing signal by the image processing means to the detection of the trailing edge of the recording medium by the conveyance detecting means is reduced to a specified paper size. If the number of corresponding horizontal synchronization signals is less than the number, the image area can be appropriately set by performing control to delay the timing of prohibiting latent image formation by the image formation control means.

[0061]

As described above, according to the present invention, in a laser beam printer provided with a fixing pressure roller for performing fixing by applying temperature and pressure, a system including the fixing pressure roller is warmed and a fixing heater is provided. When the temperature increases, the fixing pressure roller expands and the diameter increases, and when the speed of paper conveyance by the paper conveyance force at the fixing pressure roller increases, it is detected that the conveyance speed has increased. Since the mask timing of the image can be delayed, the following effects can be obtained.

(1) It is possible to obtain an image forming apparatus capable of properly setting an image area without causing image loss even when the system of the fixing pressure roller is warmed and the conveyance speed is changed.

(2) By determining the transport speed based on the physical quantity related to the temperature state of the system of the fixing pressure roller, the transport speed of the fixing pressure roller can be changed regardless of the type (length or thickness) of the paper. Accordingly, an image forming apparatus capable of appropriately setting an image area can be obtained.

(3) It is not necessary to set the image area larger than necessary in advance, so that it is possible to prevent the inside of the apparatus from being stained without the occurrence of the state without the rear end mask.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a laser beam printer according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a control system of the image forming apparatus according to the embodiment of the present invention.

FIG. 3 is a flowchart illustrating control contents according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating an image writing permission control procedure according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram for explaining the operation of the first embodiment of the present invention.

FIG. 6 is a flowchart showing control contents according to the second embodiment of the present invention.

FIG. 7 is an explanatory diagram for explaining the operation of the second embodiment.

FIG. 8 is a flowchart illustrating control contents according to a third embodiment of the present invention.

FIG. 9 is a block diagram illustrating a configuration of a counter according to a fourth embodiment of the present invention.

FIG. 10 is a flowchart illustrating control contents according to a fourth embodiment.

FIG. 11 is an explanatory diagram for describing an image prohibited area setting operation of the laser beam printer according to the embodiment of the present invention.

FIG. 12 is an explanatory diagram for explaining an image prohibited area setting operation of a conventional laser beam printer.

[Explanation of symbols]

 3a Feed Sensor 3b Conveyance Roller 5a Photosensitive Drum 6a Fixing Heater 6c Pressure Roller 9 DC Controller 20 CPU 21 Counter

Claims (10)

[Claims] A transport unit configured to transport a recording medium; an image forming unit configured to scan a light on a photosensitive member based on input image data to form a latent image; and the photosensitive unit formed by the image forming unit. Developing transfer means for transferring a latent image on the body onto the recording medium using toner; heat-fixing the toner image transferred onto the recording medium by the developing transfer means at high temperature and high pressure; Heat fixing means for transporting the recording medium in cooperation with the apparatus, position detecting means for detecting the position of the rear end of the recording medium being transported, and detecting a physical quantity related to the speed of the recording medium being transported. A speed detecting unit; and an image forming control unit configured to control timing of forming a latent image on the photoconductor by the image forming unit based on outputs of the position detecting unit and the speed detecting unit. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the physical quantity related to the speed of the recording medium is a continuous printing time. 3. The image forming apparatus according to claim 2, wherein the speed detecting means is a time measuring means for measuring a continuous printing time when performing a continuous printing operation, and the image forming control means is configured to execute the image forming control means. An image forming apparatus characterized in that, when the continuous printing time measured by the timing means exceeds a predetermined time, the timing of prohibiting the formation of a latent image is delayed. 4. The image forming apparatus according to claim 1, wherein the physical quantity related to the speed of the recording medium is set after the output of the vertical synchronizing signal used in the image forming unit from the recording medium by the position detecting unit. An image forming apparatus, wherein the number of horizontal synchronizing signals of the image forming means in a period until end detection is performed. 5. An image forming apparatus according to claim 4, wherein said speed detecting means is configured to output a vertical synchronization signal used by said image forming means and to detect a rear end of said recording medium by said position detecting means. Counting means for counting the number of horizontal synchronizing signals of the image forming means in a period.If the number of horizontal synchronizing signals detected by the counting means is less than the number of horizontal synchronizing signals corresponding to a specified paper size, An image forming apparatus, wherein the image forming control means delays a timing at which latent image formation is prohibited. 6. The image forming apparatus according to claim 1, wherein the physical quantity related to the speed of the recording medium is a temperature change when the heat fixing unit stops for a predetermined time. apparatus. 7. An image forming apparatus according to claim 6, wherein said speed detecting means is a temperature change detecting means for detecting a temperature change amount when driving of said heat fixing means is stopped for a predetermined time. The image forming apparatus according to claim 1, wherein when the detected temperature change amount is smaller than a predetermined amount, the image forming control unit delays the timing of prohibiting the latent image formation. 8. The image forming apparatus according to claim 1, wherein the physical quantity related to the speed of the recording medium is the number of the recording medium continuously printed and conveyed. 9. The image forming apparatus according to claim 8, wherein said speed detecting means is a number measuring means for counting the number of recording media continuously printed and conveyed, and said measured number is a predetermined number. The image forming control means delays the timing of prohibiting the formation of the latent image when the number of images exceeds the number of images. 10. The image forming apparatus according to claim 1, wherein said image forming apparatus is a laser beam printer.