JP2017102292A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an increase in first print output time when preparation of a laser scanner for image formation is not completed during printing on a recording material including a margin part at its leading end.SOLUTION: An image forming apparatus comprises: a top sensor 108; an image forming part 120 that transfers, to a sheet S, an image formed on a photoconductor drum 109 exposed by a laser scanner 113 according to image data from a video controller 202 that outputs image data, and performs image formation; and an engine control part 201 that controls conveyance of the sheet S. When preparation of the image forming part 120 excluding the laser scanner 113 for image formation is completed and preparation of the laser scanner 113 for image formation is not completed, the engine control part 201 starts conveyance of the sheet S if the sheet S includes a margin part at its leading end (S604), and determines timing to output a vertical synchronous signal according to the state of the laser scanner 113 when the top sensor 108 detects the leading end of the sheet S to be conveyed (S605, S606).SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus for forming an image on a recording medium, and more particularly to shortening of a first print output time.

  Conventionally, in an image forming apparatus, when a printing operation is performed, conveyance of a sheet on which printing is performed is started when an actuator or an image forming unit completes preparation for printing. Therefore, the conveyance of the sheet cannot be started until the printing preparation is completed, and the time from the start of the printing operation to the end of the printing operation on the first sheet (first print output time, hereinafter also referred to as FPOT). Difficult to shorten. In particular, the motor that drives the laser scanner that forms an electrostatic latent image on the photosensitive drum has a stable rotational speed after the start of driving, compared to other motors that are required for image formation, such as a motor that drives the photosensitive drum. It takes a long time to complete (reach steady rotation). For this reason, among image forming apparatuses, there is an image forming apparatus that starts conveyance of a sheet after a predetermined time has elapsed until the motor that drives the laser scanner reaches steady rotation even under the worst conditions (low temperature, deterioration, etc.). . For example, Patent Document 1 includes a detection unit that detects that a motor that drives a laser scanner has reached a steady rotation. When the detection unit detects a steady rotation of the motor, the conveyance of the paper is started to shorten the FPOT. An image forming apparatus for achieving the above has been introduced.

JP-A-5-2298

  However, in the conventional image forming apparatus, even when there is no area to be printed at the leading edge of the paper, that is, when there is a blank portion in the leading edge area of the paper, preparation for printing is performed in accordance with the timing when the leading edge of the paper reaches the image forming unit. Is going. For this reason, even when there is no image to be printed at the leading edge of the sheet, the image forming apparatus has started to convey the sheet at a uniform timing, and thus FPOT cannot be shortened.

  The present invention has been made under such circumstances, and suppresses an increase in the first print output time when the image forming preparation of the laser scanner is not completed when printing a recording material having a blank portion at the leading end. For the purpose.

  In order to solve the above-described problems, the present invention has the following configuration.

  (1) Detection means for detecting a recording material, output means for outputting image data based on a vertical synchronization signal and a horizontal synchronization signal, and exposing an image carrier in accordance with the image data output from the output means An image forming means for forming an image on a recording material by transferring an image formed on the image carrier to a recording material, and outputting the vertical synchronizing signal and the horizontal synchronizing signal. And a control means for controlling the conveyance of the recording material, wherein the control means is activated when the image forming means is activated and image forming means other than the exposure part are ready for image formation, and the image of the exposure part When the formation preparation is not completed, if the leading edge of the recording material has a blank portion, the conveyance of the recording material is started, and the exposure unit when the detecting means detects the leading edge of the recording material to be conveyed Depending on the state, the vertical sync signal Image forming apparatus and determines the timing for outputting the.

  According to the present invention, it is possible to suppress an increase in the first print output time when the image forming preparation of the laser scanner is not completed at the time of printing a recording material having a blank portion at the front end.

Configuration Schematic of Image Forming Apparatus of Embodiments 1 and 2 Communication interface diagram of engine controller and video controller of image forming apparatus of first and second embodiments, and control block diagram of engine controller FIG. 6 is a diagram for explaining the relationship between the / TOP signal, the / BD signal, the paper margin, and the image writing position in the first and second embodiments. 6 is a flowchart illustrating a control sequence of image forming operation according to the first exemplary embodiment. 7 is a flowchart illustrating a control sequence of an image forming operation according to the second exemplary embodiment.

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

[Configuration of Image Forming Apparatus]
FIG. 1 is a schematic cross-sectional view illustrating an overall configuration of a laser beam printer 101 that is an image forming apparatus according to a first embodiment. The laser beam printer 101 includes an image forming unit 120, a fixing device 114 as a fixing unit, a laser scanner 113 as an exposure unit, a paper cassette 102, and the like. The image forming unit 120 includes a photosensitive drum 109 serving as an image carrier, a transfer roller 110, a charging roller 111, and a developing device 112 serving as a developing unit.

  The laser beam printer 101 includes a video controller 202 (see FIG. 2A) for generating a video signal and a print instruction, and an engine control unit 201 (see FIG. 2) for controlling an image forming operation based on the instruction from the video controller 202. 2 (a)). Upon receiving a print instruction from the video controller 202, the engine control unit 201 starts preparation for printing (printing operation). Here, “preparation for printing” refers to activation of each actuator, laser scanner 113, image forming unit 120, and fixing device 114. When the pre-print preparation (image formation preparation) is completed, the engine control unit 201 drives the paper feed roller 103 to feed the paper S, which is a recording material, from the paper cassette 102, which is the recording material holding unit. S is sent out to the conveyance path. The fed paper S is transported to the top sensor 108 by the transport rollers 105, 106, and 107. When the top sensor 108 detects the leading edge of the conveyed paper S, it notifies the engine control unit 201 of the detection result, and the paper S is further conveyed to the image forming unit 120.

  The laser scanner 113 includes a laser light source 113a that emits laser light L, a rotary polygon mirror 113b that is a rotating unit that deflects the laser light L emitted from the laser light source 113a, and a scanner motor 113c that controls the rotation of the rotary polygon mirror 113b. doing. Further, the laser scanner 113 includes a mirror 113 d that reflects the laser light L deflected by the rotary polygon mirror 113 b to the photosensitive drum 109. The laser light source 113a emits laser light L in accordance with a video signal 205 (see FIG. 2A) described later. Further, the laser scanner 113 has a BD (Beam Detector) unit that outputs a / BD signal that is a horizontal synchronization signal when detecting the laser light L deflected by the rotary polygon mirror 113b.

  In the image forming unit 120, the photosensitive drum 109 is uniformly charged by the charging roller 111, and then a laser beam L corresponding to the video signal 205 is irradiated from the laser scanner 113, thereby forming an electrostatic latent image on the surface of the photosensitive drum 109. Is done. The electrostatic latent image formed on the surface of the photosensitive drum 109 is visualized as a toner image by being attached with toner by the developing device 112. Then, the photosensitive drum 109 rotates in the arrow direction (clockwise direction) in the drawing to convey the toner image to the transfer roller 110, and the sheet S is also conveyed to the transfer roller 110 in synchronization with the rotation of the photosensitive drum 109. In the transfer portion where the photosensitive drum 109 and the transfer roller 110 abut, a voltage having a polarity opposite to that of the toner image is applied to the transfer roller 110, so that the toner image on the photosensitive drum 109 (on the image carrier) is applied to the paper S. Transcribed.

  The sheet S on which the toner image is transferred is conveyed to the fixing device 114 and heated and pressurized by the fixing device 114, and the toner image is fixed on the sheet S. The sheet S on which the toner image is fixed is conveyed by the triple roller 116, the intermediate discharge roller 117, and the discharge roller 118, and is discharged to the discharge tray 121, and the printing operation is finished. The laser beam printer 101 includes a manual paper feeding unit 119 that can manually feed the paper S in addition to the paper cassette 102 as a paper S feeding unit. Similarly to the paper feeding operation from the paper cassette 102, the engine control unit 201 drives the paper feeding roller 124 to convey the paper S placed on the manual paper feeding unit 119 to the image forming unit 120.

[Signal interface between engine control unit and video controller]
FIG. 2A is a diagram illustrating a signal interface between the engine control unit 201 and the video controller 202 of the laser beam printer 101 according to this embodiment. The laser beam printer 101 generates a video signal of an image to be printed and gives a print instruction to the engine control unit 201. The engine control unit 201 controls an image forming operation based on an instruction from the video controller 202. have. The video controller 202 and the engine control unit 201 transmit and receive control data such as a command related to a print job via a communication signal 206. During printing, the engine control unit 201 transmits a / TOP signal 203 to the video controller 202 to notify the leading edge position of the paper S, and transmits a / BD signal 204 to transmit the horizontal edge position of the paper S. To be notified. The / TOP signal 203 is a vertical synchronization notification signal to the video controller 202 and is a signal for notifying the timing when the leading edge in the transport direction of the paper S reaches the transfer position where the photosensitive drum 109 and the transfer roller 110 abut. The / BD signal 204 is a horizontal synchronization notification signal to the video controller 202 and is a signal for notifying the image formation timing at the end in the direction orthogonal to the transport direction of the paper S.

  The video controller 202 transmits a video signal 205 as image data to the engine control unit 201 in synchronization with the / TOP signal 203 and the / BD signal 204. Based on the / BD signal 204, the engine control unit 201 irradiates the photosensitive drum 109 with the laser light L in accordance with the video signal 205 received from the video controller 202, and electrostatically charges the photosensitive drum 109. A latent image is formed. The formed electrostatic latent image is attached with toner by the developing device 112 to form a toner image, and the toner image is transferred to the paper S conveyed at the transfer position.

[Paper transport control of engine control unit]
Next, FIG. 2B is a control block diagram in which functions related to the conveyance control of the paper S in the engine control unit 201 of the image forming apparatus of the present embodiment are blocked. The paper transport control of the engine control unit 201 includes a paper feed timing adjustment unit 302, a paper feed transport control unit 303, a BD cycle detection unit 304, a / TOP signal output adjustment unit 305, a BD counting unit 306, and a / BD signal output control unit. 307. The information about the unprinted blank area at the leading edge of the paper S on which image formation is performed, that is, the distance information from the leading edge of the paper S to the area where printing starts is acquired from the video controller 202. 301.

  The engine control unit 201 includes a CPU (not shown) that controls image formation of the image forming apparatus, a ROM (not shown) in which a control program is written, and a RAM (not shown) that stores data used for control and image data. doing. Further, the CPU has a timer for measuring time, and performs setting and acquisition of timer values (reading of timer values). The above-described paper feed timing adjustment unit 302, paper feed / conveyance control unit 303, BD cycle detection unit 304, / TOP signal output adjustment unit 305, BD counting unit 306, and / BD signal output control unit 307 are included in the engine control unit 201. The function executed by is shown. Below, the control content of the engine control part 201 is demonstrated using the name of these execution functions. The leading edge margin storage unit 301 is provided in a RAM which is a storage unit.

  The laser scanner 113 outputs a / BD signal to the engine control unit 201 according to the rotation state of the rotary polygon mirror 113b driven by the scanner motor 113c. The top sensor 108 outputs a detection signal to the engine control unit 201 when detecting the leading end of the sheet S conveyed in the conveyance path in the conveyance direction. The transport unit 308 is a transport mechanism that transports the paper S from the paper cassette 102 to the paper discharge tray 121 via the image forming unit 120 and the fixing device 114. The transport unit 308 includes a transport motor (not shown), a paper feed roller 103 driven by the transport motor, transport rollers 105, 106, 107, and the like.

  Next, the function of each control block of the engine control unit 201 illustrated in FIG. 2B will be described. The paper feed timing adjustment unit 302 determines whether the paper from the paper cassette 102 is in accordance with the completion status of the pre-printing preparation and the presence / absence of a blank portion that is stored in the front margin storage unit 301 and is not printed at the front end of the paper S to be printed. The sheet feeding timing of S is adjusted. Note that the video controller 202 transmits to the engine control unit 201 a print instruction attached with leading margin information including information about the presence / absence of a margin portion that is not printed at the leading end of the paper S and the length of the margin portion. The engine control unit 201 stores the received leading edge margin information in the leading edge margin storage unit 301.

  As described above, the preparation for printing includes activation of each actuator, the laser scanner 113, and the image forming unit 120, and starting up the fixing device 114 to a predetermined temperature. In general, the scanner motor 113c of the laser scanner 113 is required from the start of rotation to a steady state stabilized at a predetermined rotational speed, compared to a motor that drives the image forming unit such as the photosensitive drum 109. Long time. For this reason, even if preparations for other devices are completed, the rotational speed of the scanner motor 113c may not be stable, and the preparations for the laser scanner 113 may not be completed. In such a case, if the printing operation is started after the preparation of the scanner motor 113c is completed, the FPOT becomes large (long). For this reason, in this embodiment, the paper feed timing adjustment unit 302 has a blank portion that is not printed at the leading edge of the paper S when the preparation of the other apparatus is completed even when the preparation of the laser scanner 113 is not completed. In this case, it instructs the paper feed conveyance control unit 303 to start conveyance of the paper S. Then, the preparation of the laser scanner 113 is completed before the image formation on the image area following the blank portion of the paper S is started, thereby suppressing the FPOT from becoming long. In response to a paper feed instruction from the paper feed timing adjustment unit 302, the paper feed conveyance control unit 303 controls the conveyance unit 308 to start conveyance of the paper S placed on the paper cassette 102. In addition, the paper feed conveyance control unit 303 can adjust a conveyance speed of the paper S (switching of the conveyance speed) by controlling a conveyance motor (not shown) (see Example 2).

  The BD cycle detection unit 304 detects the / BD signal output from the laser scanner 113, calculates the time interval (cycle) between the currently detected / BD signal and the previously detected / BD signal, and calculates the calculated BD cycle. save. The calculated BD cycle is a time required for each mirror surface of the rotary polygon mirror 113b driven by the scanner motor 113c to rotate, and the BD cycle changes according to the rotation speed of the scanner motor 113c. When the / TOP signal output adjustment unit 305 detects a detection signal for detecting the leading edge of the paper S from the top sensor 108, the TOP cycle output unit 305 reads the latest BD cycle. Then, the / TOP signal output adjustment unit 305 determines whether or not the rotation cycle of the rotary polygon mirror 113b of the laser scanner 113 is a predetermined cycle based on the read latest BD cycle. The / TOP signal output adjustment unit 305 outputs the / TOP signal 203 to the video controller 202 at a predetermined timing when determining that the rotation period of the rotary polygon mirror 113b is a steady period. On the other hand, when the / TOP signal output adjusting unit 305 determines that the rotation period of the rotary polygon mirror 113b has not reached the steady period, a predetermined timing in the steady period is determined according to the latest / BD period. The / TOP signal 203 is output at an earlier timing. When the / TOP signal 203 is output, the / BD signal 204 is also output at the same time.

  The BD counter 306 counts and stores the number of / BD signals output from the laser scanner 113 after the / TOP signal 203 is output by the / TOP signal output adjusting unit 305. When the / BD signal output control unit 307 detects the / BD signal from the laser scanner 113, the / BD signal output control unit 307 reads the output number of the / BD signal from the BD counting unit 306, and outputs the / BD signal 204 having the output number corresponding to the blank portion of the paper S. Is output to the video controller 202. The / BD signal output control unit 307 outputs the / BD signal from the laser scanner 113 to the video controller 202 when determining that the number of output / BD signals 204 corresponding to the blank portion has not been output. On the other hand, the / BD signal output control unit 307 outputs the / BD signal from the laser scanner 113 to the video controller 202 when it is determined that the number of / BD signals 204 corresponding to the margin is output. Control not to.

[/ TOP signal, / BD signal output timing]
Next, the timing at which the engine control unit 201 outputs the / TOP signal 203 as a vertical synchronization signal and the / BD signal 204 as a horizontal synchronization signal to the video controller 202 during printing will be described with reference to FIG. FIGS. 3A and 3B show the / TOP signal when the paper S is transported when preparations for other devices excluding the laser scanner 113 are completed and there is a margin at the leading edge of the paper S. FIG. 6 is a schematic diagram for explaining the timing at which the output adjustment unit 305 outputs a / TOP signal 203. 3C and 3D are diagrams showing the relationship between the position corresponding to the / TOP signal 203 on the paper S and the image writing position when there is a margin at the leading edge of the paper S. FIG.

(When the rotation period of the laser scanner is a steady period)
FIG. 3A is a schematic diagram illustrating a conveyance path between the top sensor 108 and a position where the photosensitive drum 109 and the transfer roller 110 abut (hereinafter referred to as a transfer position). “Scanner rotation period” in the figure indicates the state of the rotation period of the rotary polygon mirror 113b of the laser scanner 113, and “steady period” is a steady period in which the rotation period of the rotary polygon mirror 113b is a predetermined rotation period. It shows that there is. On the other hand, the “fluctuation period” is a period in which the rotation period of the rotary polygon mirror 113b is longer than the predetermined rotation period, and the rotary polygon mirror 113b is driven at a speed slower than the predetermined rotation speed and reaches the predetermined rotation period. It shows that it is not in the state. In FIG. 3A, the scanner rotation period that was the “variation period” at the start of conveyance of the sheet S transitions from the “variation period” to the “steady period” before the sheet S reaches the top sensor 108. . As a result, when the top sensor 108 detects the leading edge of the paper S and outputs a detection signal to the engine control unit 201, the most recent BD cycle stored in the BD cycle detection unit 304 is the rotation of the rotating polygon mirror 113b. The cycle is in a state indicating a steady cycle.

  In FIG. 3A, when the top sensor 108 detects the leading edge of the sheet S being conveyed and outputs a detection signal to the engine control unit 201, the / TOP signal output adjustment unit 305 has a BD nearest to the BD period detection unit 304. Read the period. The / TOP signal output adjustment unit 305 determines that the rotation period of the laser scanner 113 is a steady period from the most recent BD period, and at the timing when the leading edge of the paper S passes the position P1 in the drawing, the / TOP signal 203 Is output to the video controller 202. The position P1 is a position before the distance L1 from the transfer position where the photosensitive drum 109 and the transfer roller 110 abut. The distance L1 is the distance from the position where the laser beam L from the laser scanner 113 is applied to the photosensitive drum 109 until the photosensitive drum 109 rotates in the arrow direction (clockwise direction) in FIG. It is also a distance. Note that the distance from the position where the top sensor 108 is disposed to the position P1 where the / TOP signal 203 is output is known in advance, and the speed at which the paper S is conveyed is also constant. Therefore, the / TOP signal output adjusting unit 305 calculates the timing (time) at which the leading edge of the paper S passes the position P1 in the drawing by dividing the distance that the paper S is transported by the transport speed of the paper S. be able to. When the / TOP signal output adjustment unit 305 receives the detection signal from the top sensor 108, the timer is reset and started, and when the calculated time has elapsed, the / TOP signal 203 is output to the video controller 202, and the leading edge of the paper Notify the image writing position.

  FIG. 3C is a schematic diagram showing the relationship between the position P1 which is the notification position of the vertical synchronization signal and the image writing position when there is a blank which is not printed on the paper S up to a position which is a distance L3 away from the leading edge of the paper. is there. The position P1 described in FIG. 3A corresponds to the leading edge of the paper S in the transport direction. Further, the / BD signal 204 is output from the engine control unit 201 to the video controller 202 X times while a blank portion having a distance L3 from the leading edge of the paper S passes the transfer position. When the (X + 1) th / BD signal 204 is output, a video signal 205 is output from the video controller 202 to the engine control unit 201 in synchronization with the / BD signal 204 at this time, and an image on the sheet S is output. Formation takes place. That is, the video controller 202 receives the / TOP signal 203, detects the X number of / BD signals 204, which is the number of outputs of the / BD signal 204 corresponding to the margin distance L3, and (X + 1) th / BD signal After receiving 204, the video information 205 is used to output image information. In this way, the video controller 202 aligns the position of the image area to be printed with respect to the paper S. For example, consider the number of outputs of the / BD signal 204 when the image resolution is 600 dpi and the number of laser light sources 113a of the laser scanner 113 is two (two laser light sources). In this case, the output number of the / BD signal 204 per inch output from the engine control unit 201 to the video controller 202 is 300 times (= 600 dpi / 2).

(When the rotation period of the laser scanner is a fluctuation period)
Next, the control when the scanner rotation period when the leading edge of the conveyed paper S is detected by the top sensor 108 is a fluctuation period will be described. FIG. 3B is a schematic diagram of the transport path between the top sensor 108 and the transfer position where the photosensitive drum 109 and the transfer roller 110 abut. The way of viewing the drawing is the same as in FIG. Omitted. In FIG. 3B, unlike in FIG. 3A, the scanner rotation cycle that was the “variation cycle” at the start of conveyance of the paper S is in the “variation cycle” state even when the paper S reaches the top sensor 108. It is. Then, the scanner rotation cycle transitions to the “steady cycle” after the sheet S passes through the position P1 (FIG. 3A) where the / TOP signal 203 is output when the scanner rotation cycle is the steady cycle. In FIG. 3B, the rotation period of the laser scanner 113 does not reach the steady period at the time when the / TOP signal 203 is output to the video controller 202 at the timing when the leading edge of the paper S reaches the position P1. Thereafter, the rotation cycle of the laser scanner 113 transitions to a steady cycle until the leading edge of the conveyed paper S reaches the transfer position. In the meantime, since the rotation period of the rotary polygon mirror 113b varies toward the steady period, the size of the electrostatic latent image formed on the photosensitive drum 109 by the laser light L also varies, leading to a reduction in image quality.

  Therefore, in this embodiment, the / TOP signal output adjustment unit 305 notifies the vertical synchronization timing based on the BD cycle detected by the BD cycle detection unit 304 when the paper S reaches the top sensor 108 / The notification position of the TOP signal 203 is adjusted. That is, the / TOP signal output adjustment unit 305 stores the latest BD cycle information detected by the BD cycle detection unit 304 and the leading edge margin storage unit 301 at the timing when the top sensor 108 detects the leading edge of the paper S. The presence / absence information on the leading edge of the paper S is read. The / TOP signal output adjustment unit 305 outputs the / TOP signal 203 to the video controller 202 when it is determined that the BD cycle does not reach the steady cycle and there is a blank portion at the leading edge of the paper S. Adjust the timing to do as follows. That is, the / TOP signal output adjustment unit 305 adjusts the timing so that the / TOP signal 203 is output when the paper S passes the position P2 upstream of the position P1 in the transport direction of the paper S.

As shown in FIG. 3B, the adjusted position P2 that is the output position of the / TOP signal 203 is a distance L2 from the position P1 that is the output position of the / TOP signal 203 when the BD period is a steady period. The upstream side of the sheet S in the transport direction. Here, the distance L2 can be calculated by the following formula (1). In Equation (1), T1 is the rotation cycle (ie, BD cycle) of the rotary polygon mirror 113b in the steady cycle state of the laser scanner 113, and T2 is the rotation when the leading edge of the paper S reaches the top sensor 108. The rotation period of the polygon mirror 113b is shown.
L2 = L3 × (T2 / T1-1) = L3 × ((T2-T1) / T1) (1)
The distance L2 is the distance L3 of the margin portion of the sheet S, and the rotation period T2 of the rotating polygon mirror 113b at the timing when the leading edge of the sheet S reaches the top sensor 108 with respect to the rotation period T1 of the rotating polygon mirror 113b in the steady period state. The distance multiplied by the ratio of the increase (T2-T1).

  If the engine control unit 201 outputs the / TOP signal 203 at a position upstream of the conveyance path from the position P1 when there is no margin at the leading edge of the sheet S, the video controller 202 displays a video signal corresponding to the image data. 205 is transmitted to the engine control unit 201. The engine control unit 201 forms an electrostatic latent image on the photosensitive drum 109 by the laser scanner 113 in accordance with the received video signal 205. On the other hand, the paper S is transported at a predetermined transport speed regardless of the rotation period of the laser scanner 113. Therefore, when the toner image formed on the photosensitive drum 109 reaches the transfer position, the leading edge of the paper S does not reach the transfer position, and no image is formed on the paper S. Therefore, in this embodiment, even if preparations for other apparatuses except for the laser scanner 113 are completed, if there is no margin at the leading edge of the paper S, the paper S is not transported and the laser scanner 113 is turned on. When the pre-preparation of all the apparatuses including it is completed, the conveyance of the paper S is started.

  FIG. 3D shows a notification position of the / TOP signal 203 corresponding to FIG. 3B described above in the case where there is a margin in the paper S that is not printed up to a position that is a distance L3 away from the leading edge of the paper. It is a schematic diagram which shows the relationship between the position P2 and an image writing position. The position P2 described with reference to FIG. 3B corresponds to a position before the distance L2 from the position P1 corresponding to the leading end of the sheet S in the transport direction. FIG. 3C is a schematic diagram showing the relationship between the position P1, which is the notification position of the / TOP signal 203, and the image writing position when the scanner period is a steady period. On the other hand, FIG. 3D is a schematic diagram showing the relationship between the position P2 which is the notification position of the / TOP signal 203 and the image writing position when the scanner period is the fluctuation period.

  Also, in FIG. 3D, the / BD signal 204 is X times and the engine control section while the margin part that is a distance L3 away from the leading edge of the sheet S passes the transfer position from the timing when the / TOP signal 203 is output. 201 to the video controller 202. In FIG. 3C, the / BD signal 204 is output X times while the sheet S is conveyed by the distance L3. In FIG. 3D, while the sheet S is conveyed by the distance (L2 + L3). The difference is that the / BD signal 204 is output X times. When the (X + 1) th / BD signal 204 is output, a video signal 205 is output from the video controller 202 to the engine control unit 201 in synchronization with the / BD signal 204 at this time, and an image on the sheet S is output. Formation takes place. That is, the video controller 202 receives the / TOP signal 203, detects the X number of / BD signals 204, which is the number of outputs of the / BD signal 204 corresponding to the margin distance L3, and (X + 1) th / BD signal After receiving 204, the video information 205 is used to output image information.

  When detecting the / BD signal output from the laser scanner 113, the BD counting unit 306 described above outputs to the video controller 202 and counts the number of output / BD signals output after the / TOP signal 203 is output. Since the rotation cycle of the rotary polygon mirror 113b of the laser scanner 113 fluctuates toward a steady rotation (steady cycle), the BD cycle is earlier than when the top sensor 108 detects the leading edge of the paper S ( Shorter). For this reason, the BD counting unit 306 outputs / BD from the laser scanner 113 until the printing start position (hereinafter also referred to as an image writing position) that is a distance L3 away from the leading edge of the paper S reaches the transfer position. The signal is detected X times or more. The BD counting unit 306 counts the number of outputs of the / BD signal 204 from the position P2 at the timing when the / TOP signal 203 is output, and exceeds the number of X times until the paper S reaches the image writing position. The number of outputs of the / BD signal 204 is adjusted so that is not output. Therefore, the BD counting unit 306 adjusts the output of the / BD signal 204 by the following method. That is, when the number of outputs of the / BD signal 204 reaches X times, the BD counting unit 306 determines that the (X + 1) th / BD signal 204 is a position where the image writing position on the paper S is a predetermined position on the conveyance path. Adjustment is performed so that the output is performed at the timing of reaching P1. Further, the BD counting unit 306 thins out the / BD signal output from the laser scanner 113 once every N times so as not to output to the video controller 202 according to the BD cycle detected by the BD cycle detecting unit 304. To adjust the number of / BD signal outputs.

[Control sequence of image forming operation]
FIG. 4 is a flowchart showing a control sequence of the image forming operation of this embodiment. The processing in FIG. 4 is executed by the engine control unit 201 when the video controller 202 that has received a print request from the user transmits a print instruction and the engine control unit 201 receives the print instruction from the video controller 202.

  In step (hereinafter referred to as “S”) 601, the engine control unit 201 reads out the leading margin information set in the print instruction from the video controller 202 and stores it in the leading margin storage unit 301. The leading edge margin information is information indicating the length of the margin area from the leading edge of the paper in the paper S, and is indicated by, for example, the number of / BD signals or the distance from the leading edge of the paper to the area where the image is formed. In step S602, the engine control unit 201 starts preparation before printing. Here, the pre-print preparation refers to activation of each actuator, the laser scanner 113, and the image forming unit 120, startup of the fixing device 114 to a predetermined temperature, and the like. In step S603, the engine control unit 201 determines whether the pre-print preparation is completed. If it is determined that the preparation is not completed, the process returns to step S603. Is advanced to S604. In the present embodiment, the engine control unit 201 determines whether the pre-print preparation has been completed as follows. That is, when the engine control unit 201 determines that the preparation of all the devices such as activation of each actuator, the laser scanner 113, and the image forming unit 120 and the start-up of the fixing device 114 to a predetermined temperature are completed. In step S604, the process proceeds to step S604.

  On the other hand, when there is a device that has not been prepared in advance, the engine control unit 201 determines whether or not the preparation of each device other than the laser scanner 113 has been completed, and determines that the device has not been completed. In step S603, the process returns to step S603. When the engine control unit 201 determines that the preparations of the respective devices except for the laser scanner 113 have been completed, the engine control unit 201 reads the leading edge margin information from the leading edge margin storage unit 301 and determines whether there is a margin at the leading edge of the paper S. To do. If the engine control unit 201 determines that there is a margin at the leading edge of the sheet S, the process proceeds to step S604. If the engine control unit 201 determines that there is no margin, the process returns to step S603. As a result, the engine control unit 201 determines that if there is a margin at the leading edge of the sheet S, the preparations of the other devices are completed even if the preparations of the laser scanner 113 are not completed. The process proceeds to S604, and the conveyance of the paper is started.

  In step S <b> 604, the engine control unit 201 controls the transport unit 308 to start a paper feeding operation for transporting the paper S from the paper cassette 102 at a predetermined transport speed. In step S <b> 605, the engine control unit 201 determines whether the fed sheet S has been conveyed and the top sensor 108 has detected the leading edge of the sheet S. If the detection signal is received from the top sensor 108, the engine control unit 201 determines that the sheet S has arrived and proceeds to S606. If the detection signal is not received, the engine control unit 201 proceeds to the top sensor 108. It is determined that it has not been reached, and the process returns to S605.

  In S606, the engine control unit 201 reads the latest BD cycle stored in the BD cycle detection unit 304, and outputs the / TOP signal 203 to the video controller 202 depending on whether the read BD cycle is a steady cycle. (Output position) is determined. When the engine control unit 201 determines that the read BD cycle is a steady cycle, the timing (output position) for outputting the / TOP signal 203 to the video controller 202 is determined as the position P1 in FIG. To do. On the other hand, when the engine control unit 201 determines that the read BD cycle is not a steady cycle but a fluctuation cycle, the timing (output position) for outputting the / TOP signal 203 to the video controller 202 is as shown in FIG. The position P2 of b) is determined. When the engine control unit 201 determines the timing (output position) for outputting the / TOP signal 203 to the video controller 202, the engine control unit 201 resets and starts the timer, and advances the process to S607.

  In step S <b> 607, the engine control unit 201 refers to the timer to determine whether the leading edge of the sheet S has reached a position where the / TOP signal is output. The distance from the top sensor 108 to the position P1 or P2 can be calculated by subtracting the distance L1 (known) or the distance (L1 + L2) from the distance (known) between the top sensor 108 and the transfer position. Then, by dividing the calculated distance from the top sensor 108 to the position P1 or P2 by the transport speed of the paper S, the time required for the paper S to reach the position P1 or P2 after being detected by the top sensor 108 Can be calculated. Therefore, whether or not the leading edge of the paper S has reached the position P1 or P2 where the / TOP signal 203 is output is determined by the time required for the paper S to reach the position P1 or P2 after being detected by the top sensor 108. It can be detected by referring to the timer. In S607, when the engine control unit 201 determines that the leading edge of the sheet S has reached the position where the / TOP signal 203 is output, the process proceeds to S608, where the engine control unit 201 has reached the position where the / TOP signal 203 is output. If it is determined that there is not, the process returns to S607.

  In step S <b> 608, the engine control unit 201 outputs the / TOP signal 203 and the / BD signal 204 to the video controller 202. In step S <b> 609, the engine control unit 201 confirms the number of / BD signals output from the laser scanner 113 after the / TOP signal 203 is output from the BD counting unit 306 in order to confirm the number of outputs of the / BD signal 204. read out. In S610, the engine control unit 201 reads out the leading edge margin information from the leading edge margin storage unit 301, calculates the number of / BD signals 204 to be output corresponding to the margin part, and reads out from the laser scanner 113 read out in S609. Compare with the number of output / BD signals. When the number of / BD signals 204 to be output is the same as the number of / BD signals output from the laser scanner 113, the engine control unit 201 determines that the number of outputs of the / BD signal 204 is OK. Then, the process proceeds to S612. For example, if there is no margin at the leading edge of the paper S, the number of / BD signals 204 to be output is one, and since the / BD signal 204 has already been output in S608, the engine control unit 201 Advances the process to S612. On the other hand, when the number of / BD signals 204 to be output is not the same as the number of / BD signals output from the laser scanner 113, the engine control unit 201 determines that the number of output / BD signals 204 is OK. It is determined that there is no (less), and the process proceeds to S611.

  In step S611, the engine control unit 201 determines whether the image writing position on the paper S has reached the position P1. If the engine control unit 201 determines that the image writing position has not reached the position P1, the process returns to step S609. If the engine control unit 201 determines that the image writing position has not reached the position P1, the activation of the laser scanner 113 is not in time, and is normal. If it is determined that a correct image cannot be formed, the process advances to step S615. Here, for example, in the case of FIG. 3C, the image writing position is an image writing position that is a position on the paper S that is a distance L3 that is a margin part from the leading edge of the paper S. ) Indicates a position (timing) that passes the position P1. The timing at this time can be calculated as follows. That is, the distance from the top sensor 108 to the image writing position in the case described above can be calculated by subtracting the distance (L1-L3) from the distance (known) between the top sensor 108 and the transfer position. Then, by dividing the calculated distance from the top sensor 108 to the image writing position by the transport speed of the paper S, the time required for the paper S to be detected by the top sensor 108 and reaching the image writing position is calculated. can do. Therefore, the engine control unit 201 can determine whether or not the image writing position of the paper S has been conveyed to the position P1 by referring to the timer started in S606. In step S615, the engine control unit 201 cannot perform normal image formation. Therefore, the engine control unit 201 performs an error process for displaying a message such as a print failure on a display unit (not illustrated), and ends the process.

  In S612, the engine control unit 201 has already finished outputting the / BD signal 204 up to the image writing position on the paper S, so the / BD signal 204 output from the laser scanner 113 is output to the video controller 202. Stop. In step S613, the engine control unit 201 determines whether or not the image writing position on the paper S has reached the position P1. If the engine control unit 201 determines that the position has not reached, the process returns to step S613 to determine that the position has been reached. If so, the process advances to S614. Note that the method for determining whether or not the image writing position on the paper S has reached the position P1 is the same as that in S611, and the description thereof will be omitted. In step S614, the engine control unit 201 performs the / BD signal normal output by outputting the / BD signal 204 output from the laser scanner 113 to the video controller 202 as it is, and ends the processing.

  In FIG. 4, the method of outputting the required number of / BD signals 204 after outputting the / TOP signal 203 and / BD signal 204 in S608 has been described. It is not limited to. For example, based on the current rotation period of the rotary polygon mirror 113b of the laser scanner 113, the distance to the image writing position, and the number of outputs of the / BD signal 204 up to now, the number of outputs of the / BD signal 204 that will be required in the future Confirm. When it is determined that more / BD signals 204 than the / BD signals 204 that need to be output in the future are output by the time the image writing position of the paper S reaches the position P1, the / BD signal 204 Process to thin out the output. As a result, the number of outputs of the / BD signal 204 can be adjusted.

As described above, in this embodiment, in preparation for printing, when preparations for apparatuses other than the laser scanner 113 are completed and there is a blank portion at the leading edge of the paper S to be printed, the preparation for the laser scanner 113 is not waited for completion. Then, the feeding of the paper S is started. Then, the timing for outputting the / TOP signal 203 is adjusted according to the state of the rotation period of the laser scanner 113, and the number of outputs of the / BD signal 204 corresponding to the blank portion is adjusted to match the image writing position following the blank portion. Therefore, it is possible to form an image without shifting the position. As a result, an increase in FPOT can be suppressed as compared to the case where the sheet conveyance is started after the preparation of the laser scanner 113 is completed.
As described above, according to this embodiment, it is possible to suppress an increase in the first print output time when the image forming preparation of the laser scanner is not completed at the time of printing a recording material having a blank portion at the front end. .

  In the first embodiment, when there is a margin at the leading edge of the paper to be printed, if the pre-preparation of the apparatus other than the laser scanner 113 is completed in the pre-printing preparation, the paper feeding start is advanced so that the FPOT is started. A method for suppressing the increase in the above has been described. However, if the start of feeding is made earlier, if the timing at which the rotation period of the laser scanner 113 reaches the steady period is delayed, an image is formed on the sheet with the rotation speed of the laser scanner 113 being insufficient, and image quality may be deteriorated. is there. Therefore, in this embodiment, when the activation of the laser scanner 113 is slow, a process for extending the timing until the rotation period of the laser scanner 113 reaches a steady rotation is performed by delaying the conveyance of the sheet. This makes it possible to form an image without causing an image shift when forming an image on a sheet. The configurations of the image forming apparatus, the engine control unit, and the video controller in the present embodiment are the same as those in the first embodiment, and the same reference numerals are used for the same configurations, and description thereof is omitted.

[Control sequence of image forming operation]
FIG. 5 is a flowchart showing a control sequence of the image forming operation of this embodiment. 5, as in FIG. 4 of the first embodiment, the video controller 202 that has received a print request from the user transmits a print instruction, and the engine control unit 201 receives a print instruction from the video controller 202. It is executed by the engine control unit 201.

  In FIG. 5, the processing of S801 to S812 is the same as the processing of S601 to S612 of FIG. In S813, the engine control unit 201 determines whether or not the rotation speed of the laser scanner 113 is steady. If it is determined that the rotation speed is steady, the process proceeds to S818. The process proceeds to S814. Note that the engine control unit 201 reads the latest BD cycle stored in the BD cycle detection unit 304, and determines that the rotation speed of the laser scanner 113 is steady if the read BD cycle is a steady cycle. On the other hand, the engine control unit 201 determines that the rotation speed of the laser scanner 113 is not steady unless the read BD cycle is a steady cycle.

  In step S <b> 814, the engine control unit 201 controls a conveyance motor (not illustrated) by the paper feed conveyance control unit 303, switches the conveyance speed, and reduces the conveyance speed of the paper S to a predetermined speed. In S815, the engine control unit 201 determines whether or not the rotation speed of the laser scanner 113 is steady by the same process as in S813. If the rotation speed is determined to be steady, the process proceeds to S817 and is not steady. If it is determined, the process proceeds to S816. In step S816, the engine control unit 201 determines whether the image writing position on the paper S has reached the conveyance speed return position. If the engine control unit 201 determines that the image writing position on the paper S has not reached the conveyance speed return position, the process returns to S815. On the other hand, when the engine control unit 201 determines that the image writing position on the paper S has reached the transport speed return position, the engine control unit 201 determines that the paper transport speed cannot be switched in time and normal image formation cannot be performed. The process proceeds to S820. In S820, as in S615 of FIG. 4 of the first embodiment, the engine control unit 201 cannot perform normal image formation, and thus performs an error notification process for displaying a message such as a print failure on a display unit (not shown). End the process. Here, the conveyance speed return position is a distance necessary for accelerating (returning) the conveyance speed of the paper S from a predetermined decelerated speed to a steady speed from the position P1 which is the image writing position on the paper S. , The upstream position in the transport direction of the paper S. When the image writing position on the paper S passes the conveyance speed return position, image formation is not appropriately performed at the image writing position on the paper S.

  In S817, the engine control unit 201 controls a transport motor (not shown) by the paper feed transport control unit 303, switches the transport speed, and returns the transport speed of the paper S from a predetermined reduced speed to a steady speed. The process proceeds to S818. In this embodiment, the engine control unit 201 sets the transport speed when the sheet S is decelerated to a predetermined decelerated speed, but is not limited to this speed. For example, the conveyance speed at the time of deceleration is a speed at which the conveyance speed of the decelerated paper S can be returned to the steady speed within a predetermined time after detecting that the rotation speed of the laser scanner 113 has become steady. Good. Note that the processing of S818 to S820 is the same as the processing of S613 to S615 of FIG. 4 of the first embodiment, and a description thereof is omitted here.

As described above, according to the present embodiment, as in the first embodiment, an increase in FPOT can be suppressed as compared with the case where the sheet conveyance is started after the preparation of the laser scanner 113 is completed. Further, even when the rotation period of the laser scanner 113 does not reach the steady period, by slowing the conveyance speed of the sheet S, the image writing timing of the sheet is matched with the timing when the rotation period of the laser scanner 113 reaches the steady period. Can be adjusted. As a result, it is possible to prevent image formation that causes a reduction in image quality from being performed compared to the case where the conveyance speed of the paper S is not switched.
As described above, according to this embodiment, it is possible to suppress an increase in the first print output time when the image forming preparation of the laser scanner is not completed at the time of printing a recording material having a blank portion at the front end. .

108 Top sensor 113 Laser scanner 120 Image forming unit 201 Engine control unit 202 Video controller

Claims (16)

Detection means for detecting the recording material;
Output means for outputting image data based on the vertical synchronization signal and the horizontal synchronization signal;
An exposure unit that exposes the image carrier in accordance with the image data output from the output unit, and forms an image on the recording material by transferring the image formed on the image carrier to the recording material Image forming means for
Control means for outputting the vertical synchronization signal and the horizontal synchronization signal to control conveyance of the recording material;
With
When the image forming unit is activated and the image forming unit except for the exposure unit is ready for image formation and the exposure unit is not ready for image formation, the control unit is arranged at the leading edge of the recording material. When there is a blank portion, the conveyance of the recording material is started, and the timing for outputting the vertical synchronization signal is determined according to the state of the exposure unit when the detection unit detects the leading edge of the conveyed recording material. An image forming apparatus.   When the image forming unit is activated and the image forming unit except for the exposure unit is ready for image formation and the exposure unit is not ready for image formation, the control unit is arranged at the leading edge of the recording material. The image forming apparatus according to claim 1, wherein the conveyance of the recording material is not started when there is no blank portion.   The image forming means includes the image carrier, the exposure unit that forms a latent image on the image carrier, a developing unit that develops the latent image to form a toner image, and the toner image as a recording material. The image forming apparatus according to claim 1, further comprising: a transfer unit that transfers the image and a fixing unit that heats and fixes the toner image to the recording material.   The image forming apparatus according to claim 3, wherein the detection unit is disposed upstream of the transfer unit in a conveyance direction of the recording material on a conveyance path in which the recording material is conveyed.   The image forming apparatus according to claim 4, wherein the output unit notifies the control unit of the length of the margin in the recording material conveyance direction before the image forming unit is activated. The exposure unit has a rotating unit for exposing the image carrier,
The image forming apparatus according to claim 5, wherein the control unit determines a state of the exposure unit based on a rotation period of the rotation unit and determines a timing for outputting the vertical synchronization signal.   In the case where the rotation period is a first rotation period when the exposure unit is in a steady state in which image formation preparation has been completed, the control means sends the vertical synchronizing signal to the leading edge of the recording material on the conveyance path. The image forming apparatus according to claim 6, wherein the image forming apparatus outputs when a predetermined position is passed.   The image forming apparatus according to claim 7, wherein the control unit outputs the horizontal synchronization signal in accordance with the rotation period.   When the rotation period is a second rotation period that is longer than the first rotation period, the control means is configured such that the leading edge of the recording material has the length of the margin, the first rotation period, and the first rotation period. The image forming apparatus according to claim 7, wherein the vertical synchronization signal is output when a position on the conveyance path corresponding to a second rotation cycle is passed.   The position on the transport path is the predetermined length by a length obtained by multiplying the length of the margin by the ratio of the difference between the second rotation period and the first rotation period with respect to the first rotation period. The image forming apparatus according to claim 9, wherein the image forming apparatus is determined at a position upstream of the position of the conveyance path.   The control means outputs the horizontal synchronization signal according to the rotation period, and stops outputting the horizontal synchronization signal after outputting the horizontal synchronization signal according to the length of the margin. The image forming apparatus according to claim 9 or 10.   The image forming apparatus according to claim 11, wherein the control unit outputs the horizontal synchronization signal when an image writing position following the margin portion of the recording material reaches the predetermined position.   13. The image forming apparatus according to claim 12, wherein the control unit performs error notification when the image writing position reaches the predetermined position before stopping the output of the horizontal synchronization signal. apparatus.   When the rotation period when the output of the horizontal synchronization signal is stopped is the second rotation period, the control unit changes the conveyance speed of the recording material from the first conveyance speed to the first conveyance speed. The image forming apparatus according to claim 11, wherein the image forming apparatus switches to a second conveyance speed that is slower than the second conveyance speed.   15. The control unit according to claim 14, wherein when the rotation period reaches the first rotation period, the control unit switches the recording material conveyance speed from the second conveyance speed to the first conveyance speed. Image forming apparatus.   The control means determines that the image writing position following the margin of the recording material changes the recording material conveyance speed from the second conveyance speed to the first before the rotation period reaches the first rotation period. The image forming apparatus according to claim 14, wherein an error notification is performed when a position on the conveyance path where the conveyance speed is switched is reached.

Images