JP3657512B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus using a drive motor that requires a rise time until stable rotation as a drive unit of an optical scanning system.
[0002]
[Prior art]
In general, an image forming apparatus scans a photosensitive member with a light beam such as a laser beam modulated by an electric signal, thereby forming a desired electrostatic image on the photosensitive member and statically using a developer such as toner. It is known that an electric image is developed and a print image can be formed by transferring it to a final transfer medium.
[0003]
In the optical scanning system of this image forming apparatus, a method is generally used in which a rotary polygon mirror (polygon mirror) or the like is rotated by a drive motor to deflect a laser beam irradiated to the rotary polygon mirror.
[0004]
Further, when image formation is performed while avoiding the position of a joint where normal image formation is impossible on the image carrier, a startup operation is performed to stably rotate the drive motor of the rotary polygon mirror after the print start instruction, and The latent image must be started after the position detecting means detects the position of the joint of the image carrier. Therefore, in such an image forming apparatus, it is necessary to shorten the time (first print time) required from the start of printing until the first image is obtained.
[0005]
Therefore, as an image forming apparatus, for example, as disclosed in JP-A-1-267668, an endlessly movable image carrier is used, and the rotation speed when the optical scanning system is started up is detected by an encoder or the like. Some of them are detected by means and controlled to start the peripheral movement of the image carrier as soon as a predetermined speed is reached. Further, the rotation of the image carrier is started when a predetermined time elapses after the start-up operation of the drive motor of the optical scanning system is disclosed.
[0006]
In other image forming apparatuses, as disclosed in, for example, Japanese Patent Application Laid-Open No. 8-65466, based on a scanning start time of a reading unit that reads a document and a predetermined time required for a drive motor of an optical scanning system to rise. Thus, the driving start timing of the optical scanning system is determined and the driving motor of the optical scanning system is rotated, and control is performed so as to start image formation at the same time as the start-up of the driving motor is completed. Further, the image forming is started by controlling the drive motor to start up at or before the time when the reading data processing becomes possible after the scanning of the reading means starts.
[0007]
[Problems to be solved by the invention]
By the way, it is easy to use an image carrier having a seam from the viewpoint of cost. In this case, in order to perform image formation while avoiding a seam position where normal image formation is impossible, the position of the seam is directly set. Alternatively, it is necessary to provide a means for detecting indirectly. Even in the case where there is no seam, in an image forming apparatus that obtains a color image by a plurality of times of superposition transfer, it is necessary to provide a detection unit that detects a predetermined position of the image carrier to perform color superposition with high accuracy.
[0008]
In such an image forming apparatus, after completion of the start-up of the drive motor of the optical scanning system, image formation must be started after detecting a predetermined position of the image carrier at least once, and the rise time of the drive motor The first print time was influenced by.
[0009]
For example, when the process speed is 85 mm / sec (surface speed of the image carrier) and the dot density is 600 DPI, the rotational speed of the 6-sided rotary polygon mirror is about 20079 rpm. At this time, the rise time of the drive motor of the rotary polygon mirror (the time required for stable rotation) was 3.5 to 4 seconds. However, the rise time of the drive motor varies greatly depending on the environmental temperature, and the rise time increases if the environmental temperature is low. (6-8 seconds at 10 ° C. or lower). Furthermore, if the process speed is increased, the required number of rotations of the drive motor is increased, so that the rise time is increased. In this respect, the drive motor has been devised to shorten the rise time, but it consumes a large amount of current during start-up, resulting in an increase in the amount of heat generated, and noise and vibration of the drive motor during start-up. The new problem of becoming will also arise.
[0010]
In the above-mentioned publication for such a problem, the rotational speed of the drive motor at the time of start-up is measured, the time that the drive motor will rise is predicted, and the peripheral movement of the image carrier is started. In order to reduce wasted time on the sequence. Alternatively, a control sequence is constructed in advance with the rising time of the drive motor of the optical scanning system as a fixed value.
[0011]
However, in order to measure the speed of the drive motor, an apparatus such as an encoder is required, and the rise time of the drive motor increases in a low temperature environment. Therefore, a control sequence must be constructed in consideration of these factors.
[0012]
The present invention has been made in view of such points, and the object of the present invention is to maximize the time (first print time) from the image formation command to the end of image formation with a simpler mechanism and easy control. An object of the present invention is to provide an image forming apparatus that can be shortened to the limit.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has an optical scanning system for deflecting a light beam emitted from a light source by irradiating a rotary polygon mirror, and the light beam deflected by the optical scanning system is used on the image carrier. Assuming an image forming apparatus in which an image image is latently formed and forming an image on a final recording medium, the optical scanning system includes a drive motor for rotating a rotary polygon mirror, and a stop state of the drive motor. A control system is provided for measuring the rise time until a stable rotation state is reached. The control system controls the stop position of the image carrier according to the measured rise time of the drive motor.
[0014]
Due to this specific matter, when there is an image forming apparatus that requires superimposing transfer, or when there is a seam on the image carrier that makes normal image formation impossible, the drive motor of the optical scanning system at the next image formation The start-up operation completion timing and the image formation start timing at a desired predetermined position of the image carrier are adjusted so as to avoid a place (seam) where image formation is impossible. Therefore, by controlling the stop position of the image carrier based on the rise time of the drive motor of the optical scanning system and adjusting the start-up operation completion timing of the drive motor and the image formation start timing of the image carrier, a desired first Print time can be obtained.
[0015]
Furthermore, the individual variations in the rise time of the drive motor of the optical scanning system are absorbed by the control system, and it becomes possible to realize the first print with the shortest time in each image forming apparatus.
[0016]
In particular, the following configuration is listed as one that can safely shorten the first print time.
[0017]
In other words, storage means for storing the drive motor rise time measured until the previous time is provided, and the drive system rise time is measured by the control system, and the measurement time and the previous drive stored in the storage means are measured. When the rise time of the motor is different, it is determined whether or not the stored contents are updated, and the stop position of the image carrier is controlled according to the rise time of the drive motor up to the previous time.
[0018]
Even if the time required to start up the drive motor increases due to the deterioration of the drive motor over time or the wear of the bearings that support the rotary polygon mirror, etc. due to this specific matter, the rise time of the drive motor by the storage means By updating the stored contents in a timely manner, it is possible to always obtain the shortest first print time at that point in time.
[0019]
In addition, it is possible to provide a margin for the stored time value by determining whether or not to change the storage contents of the storage means in consideration of variations due to the measurement accuracy of the rise time of the drive motor. For this reason, even if the startup time varies every time, the image carrier can be stopped at a predetermined position on the image carrier where image formation can be performed after completion of the startup, and the first print time can be safely reduced. Can be realized.
[0020]
In particular, the following configuration is listed as a method for predicting the rise time of the drive motor.
[0021]
In other words, an in-apparatus temperature detecting means for detecting the temperature in the image forming apparatus is provided, and an image corresponding to the rise time of the drive motor of the optical scanning system based on the temperature detected by the in-apparatus temperature detecting means by the control system. The control of the stop position of the carrier is corrected.
[0022]
Due to this specific matter, the temperature in the image forming apparatus is detected, so that the rise time of the drive motor can be predicted.
[0023]
In addition, the stop position of the image carrier can be changed with respect to the rise time of the optical scanning system drive motor that varies depending on the ambient temperature. For example, even in a low temperature environment where the rise time is long, it is the highest in that environment. It becomes possible to realize the first print of the speed.
[0024]
In addition, the storage capacity can be increased by giving a margin to the value stored in the storage means (rising time of the drive motor) by giving the temperature region a width, for example, changing the storage location in increments of 3 ° C. The desired first printing time can be realized while reducing the size.
[0025]
In particular, the following configuration is listed as a means for predicting the rise time of the drive motor with higher accuracy.
[0026]
That is, an optical scanning system temperature detecting means for directly or indirectly detecting the temperature of the optical scanning system is provided, and the stop position of the image carrier is determined by the control system based on the temperature detected by the optical scanning system temperature detecting means. I try to control it.
[0027]
Due to this particular matter, the temperature of the direct optical scanning system is measured, so that it is possible to predict the rise time of the drive motor with higher accuracy.
[0028]
In particular, the following configuration is listed as a means for minimizing the next first print time.
[0029]
In other words, temperature detection means for detecting the temperature inside the apparatus main body or the temperature of the optical scanning system during standby of the apparatus main body is provided, and the drive system of the image carrier is rotated by the control system based on the temperature detected by the temperature detection means. By moving, the stop position of the image carrier is moved.
[0030]
Due to this specific matter, when it is calculated that the drive motor start-up time required for the next image formation at the time of stoppage changes compared to the drive motor start-up time that was used when the device was stopped after the end of the previous image formation. The next first print time can be minimized by changing the stop position of the image carrier.
[0031]
In particular, the following configuration is listed as a means for efficiently obtaining the first print time.
[0032]
In other words, a position detection unit that detects a predetermined position on the image carrier is provided, and the detection time required to detect the predetermined position on the image carrier by the position detection unit after the start of image formation from the image formation stop state It is set to be shorter than the rise time of the drive motor of the optical scanning system from the start of formation.
[0033]
This specific matter makes it possible to know the desired image forming position of the image carrier during the drive motor startup process, and prepares to output image data to the optical scanning system by the time when the drive motor startup is completed. In addition, the image forming process can be performed immediately after the start-up of the drive motor, and the first print time can be efficiently obtained.
[0034]
In particular, in the case where a plurality of optical scanning systems are provided, the following configuration is listed as a means that the next first print time can always be the fastest.
[0035]
In other words, two or more optical scanning systems in which an image is formed by toners of a plurality of colors and a control system that individually measures the rising times of the drive motors of these optical scanning systems are provided. The stop position of the image carrier is controlled based on the slow rise time of the drive motor.
[0036]
By this particular matter, even when there are a plurality of optical scanning systems, pay attention to the driving motor of the optical scanning system with the slowest rise time, and perform a simple calculation to determine the position to stop the image carrier The first print time at the next image formation can always be the fastest. For example, in a color printer, since the frequency of use of black increases, the rise time of the drive motor of the optical scanning system that latently images a black image becomes slower than the drive motors of other optical scanning systems due to the use over time. Therefore, even in such a case, the apparatus can be operated with the fastest first print time that can be realized at that time.
[0037]
In particular, in the case where a plurality of optical scanning system drive motors are sequentially started up, the following configuration is listed as one that can always achieve the fastest first print time.
[0038]
In other words, the control system measures the time until all the drive motors start up when sequentially starting the drive motors of the plurality of optical scanning systems, and controls the stop position of the image carrier based on the measurement time. ing.
[0039]
Due to this specific matter, even when multiple optical scanning systems are started up with a time difference, the time required to start up all the optical scanning system drive motors is measured and stored, so that it is always the fastest. It is possible to realize the first print time.
[0040]
In addition, the measurement is started at the start of start-up of the optical scanning system drive motor that starts driving first, and the measurement is completed when the start-up of the optical scanning system drive motor that starts driving last is completed. It is possible to measure the time until all the drive motors of the optical scanning system start up by a single control system.
[0041]
In particular, in the case where a plurality of optical scanning systems are sequentially started up, the following configuration is listed as one that can control the stop position of the image carrier.
[0042]
That is, the control system measures the rising time of the driving motor of the optical scanning system that is activated last when the optical scanning systems are sequentially activated, and controls the stop position of the image carrier based on the measurement time. I am doing so.
[0043]
Due to this specific matter, even if there are variations in the startup times of the plurality of optical scanning systems, in the case of sequential startup, the startup is completed in the order of startup, and thus the variation can be ignored. Therefore, it is possible to measure only the rising time of the optical scanning system that is last raised, and to control the stop position of the image carrier based on the measurement time.
[0044]
In particular, in the case where a plurality of optical scanning systems are sequentially started up, the following configurations are listed as those capable of always realizing a desired first print.
[0045]
In other words, the control system starts up the drive motor of the optical scanning system that requires the most rise time, measures the rise time of the drive motor, and controls the stop position of the image carrier based on the measurement time. ing.
[0046]
By this specific matter, the optical scanning system that requires the most rising time is started up last time, and the desired first print is always realized by changing the stop position of the image carrier only by measuring the rising time. It becomes possible. For example, in a color image forming apparatus, since only black is used frequently, the drive system of the optical scanning system is different from that of other colors in order to increase the durability. The first print can be easily shortened by paying attention only to the black optical scanning system, even if it becomes larger than that of the optical scanning system of the above color.
[0047]
On the other hand, the drive system of the optical scanning system that is used most frequently is finally started up by the control system, the rise time of the drive motor is measured, and the stop position of the image carrier is controlled based on the measurement time. In this case, the optical scanning system that is frequently used and expected to increase in rising time over time is started last, and the stop position of the image carrier is changed only by measuring this rising time. It is possible to always achieve a desired first print. For example, in a color image forming apparatus, since the frequency of use of black increases, it becomes possible to start up the optical scanning system for forming a black image last and perform the above control.
[0048]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0049]
<First Embodiment>
FIG. 1 is a schematic configuration diagram of an image forming apparatus X according to the first embodiment of the present invention.
[0050]
In FIG. 1, in the image forming apparatus X, there is provided a photosensitive belt 2 as an image carrier that is stretched between a pair of upper and lower conveying rollers 2a, 2a. It is made to go around.
[0051]
The photosensitive belt 2 includes a charging member 5 for uniformly charging the photosensitive layer, an LSU 1 as an optical scanning system which is a laser writing unit for forming an electrostatic latent image on the charged photosensitive belt 2, and First to fourth image forming stations S1 to S4 for converting the latent electrostatic image into a visible image, and developing devices 4a to 4 for storing toners (black, cyan, magenta, yellow) having different colors for each station. 4d, the cleaning device 6 for collecting the residual toner after the first transfer, the joint 3 of the photosensitive belt 2 on which the normal image cannot be obtained on the photosensitive belt 2, and the detection of the joint 3 And a seam detector 12 as means. In this case, even if the seam detector 12 directly detects the seam 3, or although not shown, a detection mark provided at a position on the photosensitive belt 2 that is a predetermined distance away from the seam 3. Or a hole may be detected to indirectly detect the position of the seam from the image forming area. In addition, when it is necessary to form an image at a predetermined position on the photosensitive belt 2 for other reasons, a means that can determine the predetermined position may be used.
[0052]
Below the photosensitive belt 2, there is provided an intermediate transfer belt 7 as an image carrier that is stretched between a pair of left and right conveying rollers 7a, 7a. The intermediate transfer belt 7 moves in the direction of arrow P. It is made to do.
[0053]
The intermediate transfer belt 7 is in contact with the photosensitive belt 2 at the transfer position. The toner image formed on the photoconductor belt is sequentially superimposed and transferred onto the intermediate transfer belt 7 by the voltage applied to the first transfer roller 8 disposed in the vicinity of the transfer position, and finally conveyed on the paper path 11. The transfer medium is collectively transferred by a voltage applied to the second transfer roller 10. The intermediate transfer belt 7 is provided with a cleaning device 9 for cleaning and collecting residual toner after the second transfer. After batch transfer, the toner is melted and fixed on the final transfer medium by a fixing device (not shown), and a printed image can be obtained.
[0054]
In the LSU 1, a Bolgon mirror 21 that is a rotary polygon mirror and a drive motor 22 that rotationally drives the Bolgon mirror 21 are provided. The drive motor 22 and the polygon mirror 21 are connected by a rotating shaft 23, and a fluid bearing is adopted as a bearing for the rotating shaft 23. Reference numeral 24 denotes a semiconductor laser as a light source, and reference numerals 25 and 26 denote an imaging lens group for condensing the laser beam generated from the semiconductor laser 24 and forming an image on the photosensitive belt 2.
[0055]
As shown in FIG. 2, a PLL (phase control) IC 27 is used as a motor driver for driving the drive motor 22. The general function of the IC 27 will be described. When a pulse corresponding to the final speed of the predetermined drive motor 22 is input to the IC 27 and a drive command signal is given, the rotational speed of the drive motor 22 is controlled to a predetermined speed. Start up operation. When the predetermined speed is reached, that is, when the given pulse and the drive pulse of the drive motor 22 coincide with each other, the drive motor synchronization signal is actively output. Therefore, the start-up time of the drive motor 22 is measured by setting the time at the start-up of the drive motor 22 to 0 and measuring the time until the synchronization signal of the drive motor 22 becomes active.
[0056]
The measurement of the start-up time of the drive motor 22 is performed by timer interrupt processing of the CPU 28 as a control system. Further, the CPU 28 simultaneously performs other processing, for example, control of the main motor drive system of the image forming apparatus X, control of the paper transport system, and control of the development high-pressure system. FIG. 2 shows the configuration concept, and FIG. 3 shows a timing chart of the processing.
[0057]
The flowchart in FIG. 3A shows the flow of control in the main processing section of the CPU 28. In step ST1 of this flowchart, the drive motor drive signal is activated in the main process routine and at the same time the drive motor 22 is activated. The variable time T for measuring the rise time is cleared, and the flag A for permitting the operation of the interrupt routine is cleared. On the other hand, the flowchart of FIG. 3B shows an interrupt processing routine in the timer processing unit of the CPU 28. In step ST2 of this flowchart, it is determined whether or not the flag A is cleared. If the flag A is cleared, it is checked in step ST3 whether or not the drive motor 22 has reached the specified rotation. In step ST4, a time T until the drive motor 22 starts up is measured. Next, in step ST5, when the drive motor 22 starts up, the flag A is set to stop the operation of the interrupt routine, and the measurement of the time T is ended. At this time, the measured time T can be stored in a non-volatile storage RAM 29 as a storage means, and the stored contents can be recalled in a timely manner.
[0058]
By using the timer function of the CPU 28 as in this configuration, the startup time of the drive motor 22 can be easily measured. Note that the timer interrupt speed of the CPU 28 does not need to be so fast, and may be determined by the required accuracy of the stop positions of the photosensitive belt 2 and the intermediate transfer belt 7 which are the final purposes. In the present embodiment, the start-up time of the drive motor 22 is about 3.6 to 3.8 seconds in a normal temperature environment, the minimum interrupt rate of the timer of the CPU 28 is 10 msec, and the photosensitive belt 2 and the intermediate transfer belt 7 are The minimum control value of the stop position was performed at 10 msec intervals. Although the control of other drive systems and the like was performed with an accuracy of 1 msec, the weight of the interrupt process was set to about one-tenth of the other control, so that the CPU 28 is not loaded and other processes are normally performed. I was able to.
[0059]
4 and 5 are a control flowchart and a timing chart for explaining the embodiment of the present invention in more detail. Here, it is assumed that the startup time T of the drive motor 22 is a certain constant value. Actually, the time T is determined by a control method described later.
[0060]
First, a control example of the image forming apparatus X of the present invention will be described based on the flowchart of FIG.
[0061]
The flowchart of FIG. 4A shows the flow of control in the drive processing unit of the image forming apparatus X of the CPU 28. In step ST6 of this flowchart, a print instruction is issued from the standby state of the image forming apparatus X without a print instruction. In step ST7, the drive of the drive motor 22 of the LSU 1 is started and the circumferential movement of the photosensitive belt 2 and the intermediate transfer belt 7 is started. In step ST8, the start-up of the drive motor 22 is completed. When the detection of the joint 3 (position detection mark) of the photosensitive belt 2 is completed in step ST9, the printable state is entered. In the flowchart of FIG. 4A, step ST8 and step ST9 are processed in a permutation, but the order may be reversed or a parallel condition may be used. In addition, the joint 3 and the joint detector 12 are arranged so that the detection timing of the joint 3 is exactly the start timing (first line) of image formation. By changing the position of the joint 3 or the arrangement position of the joint detector 12 so that the detection timing of the joint 3 comes earlier than this timing, it is necessary to detect the joint 3 of the photosensitive belt 2 in step ST9 described above. The time T0 is smaller than the time T until the start-up of the drive motor 22 in step ST8 is completed, and the detection of the joint 3 of the photosensitive belt 2 can be determined before the start-up of the drive motor 22 is completed. It becomes. In other words, it is possible to shift to the image forming process without unnecessary idling of the photosensitive belt 2.
[0062]
Thereafter, after a desired number of printing processes are performed in step ST10, if there is no next printing instruction in step ST11, the image forming apparatus X is stopped. Then, after performing the cleaning process of the photosensitive belt 2 and the intermediate transfer belt 7, in step ST12, the elapsed time t from the time of detection of the joint 3 is the circumferential length and the circumferential speed (process speed) of the photosensitive belt 2. ) For the position detection cycle T0 of the photosensitive belt 2 and the start-up time T of the drive motor 22 of the LSU 1
t = T0-T
In step ST13, the circumferential movement of the photosensitive belt 2 is stopped and the image forming apparatus X is set in a standby state.
[0063]
Further, the flowchart of FIG. 4B shows a control flow in the position detection processing unit of the CPU 28. In this case, since the elapsed time t from the time point of detection of the joint 3 in step ST12 is a variable that is incremented at regular intervals by the timer process of the CPU 28, in step ST14 of the flowchart of FIG. When position 3 is detected, the elapsed time t from joint detection is cleared to 0 in step ST15.
[0064]
In this way, by controlling the stop position of the photosensitive belt 2 based on the rise time T of the drive motor 22 of the LSU1, at the time of the next print instruction, the print starts immediately (latently when the start of the drive motor 22 of the LSU1 is completed. The first print time can be minimized.
[0065]
Here, the flowcharts of FIGS. 4A and 4B will be described by rewriting the timing chart shown in FIG.
[0066]
As described above, when the elapsed time t from the detection time point of the joint 3 of the photosensitive belt 2 is T0-T, the image forming apparatus X is set in a standby state, so that it is necessary to start printing at the next printing start-up. It is a feature of the present invention that time is minimized.
[0067]
Therefore, in the present embodiment, a case will be described in which the circumferential lengths of the photosensitive belt 2 and the intermediate transfer belt 7 are set to 140π mm and the process speed is set to 85 mm / sec. Thereby, the sensing interval T0 (position detection cycle) of the joint 3 of the photosensitive belt 2 is as follows.
T0 = 140π / 85 = 5174 msec
It becomes. The time T required to start up the drive motor 22 of the LSU 1 varies depending on the drive motor one by one or depending on the environment, but it is guaranteed that the start-up operation is always completed in 3800 msec in all these states. Therefore, T = 3800 msec, and the image forming apparatus can be put into a standby state (stopped) at the timing t = T0-T.
[0068]
As described above, in the image forming apparatus X, the start-up time of the drive motor 22 of the LSU 1 is measured and the measured value is associated with the CPU 28, whereby image formation is started from the time when the image forming apparatus X is started for printing. It is possible to control the start-up process of the drive motor 22 of the LSU 1 that requires the most start-up process time by the start and to minimize the time from the start of printing to the start of image formation. Furthermore, useless circumferential movement of the photoreceptor belt 2 and the like can be suppressed.
[0069]
In the present embodiment, the seam 3 and the seam detector 12 are provided on the photosensitive belt 2, but the seam of the intermediate transfer belt 7 may be detected by the seam detector.
[0070]
<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIG.
[0071]
In the present embodiment, the rise time T of the drive motor 22 of the LSU 1 is fixed by measuring the rise time of the drive motor 22 of the LSU 1 and storing the time in a storage means (non-volatile memory or the like) in a timely manner. The start-up time T of the drive motor 22 is controlled according to the stored content value stored in the storage means without being handled as a value.
[0072]
Specifically, the rise time T of the drive motor 22 of the LSU 1 has individual variation. That is, there is a difference in the first print time that can be achieved for each image forming apparatus X. Further, the rise time T of the drive motor 22 tends to gradually increase due to deterioration over time such as the bearing of the rotating shaft 23. In order to absorb these and always realize the fastest first print time at that time, the startup time T of the drive motor 22 is controlled in accordance with the stored content value stored in the storage means. In this case, the start-up time T of the drive motor 22 of the LSU 1 is measured at the time of each print start based on the above-described timing chart of the timer interrupt process of the CPU 28 in FIG. The CPU 28 is configured to store the time T in a non-volatile storage means (storage RAM 29) and to control the stop position of the photosensitive belt 2 after the printing is finished according to the stored contents.
[0073]
That is, after there is no print instruction in step ST11 of the flowchart shown in FIG. 4 and the image forming apparatus X is stopped, the current drive motor 22 measured at the start of printing in step ST16 of the flowchart of FIG. Is compared with the previous rise time T of the drive motor 22 stored in the storage RAM 29. If the current rise time T ′ of the drive motor 22 is longer, the content of the storage RAM 29 is replaced with the current rise time T ′ of the drive motor 22 in step ST17, and in step ST18. After determining the stop position of the photosensitive belt 2 with this value, the process proceeds to step ST12 in FIG.
[0074]
By controlling in this way, even if the current rise time T of the drive motor 22 is gradually increased due to changes over time, the stop position of the photosensitive belt 2 during printing standby is gradually changed accordingly. Thus, the fastest first print time at that time can always be realized.
[0075]
<Third Embodiment>
Next, a third embodiment of the present invention will be described.
[0076]
In this embodiment, the CPU 28 is configured by lowering the priority of the interrupt priority of the timer of the CPU 28 used for the rise time T of the drive motor 22 so as not to affect other processes. In this case, the actual accuracy of the measured value was about 20 to 30 msec. In consideration of these points, in this embodiment, the process of step ST16 in FIG. 6 is improved as follows.
[0077]
That is, the content of the storage RAM 29 is updated only when the current rise time T of the drive motor 22 is 30 msec longer than the time in the storage RAM 29, and the update content is updated to the rise time T of the drive motor 22. A value obtained by adding 30 msec.
[0078]
As a result, a margin can always be given to the stop position, and variations in measurement values of the start-up time measurement can be absorbed.
[0079]
<Fourth embodiment>
Next, a fourth embodiment of the present invention will be described with reference to FIG.
[0080]
The present embodiment focuses on the rise time of the drive motor 22 of the LSU 1 depending on the environmental temperature.
[0081]
That is, in the present embodiment, if the environmental temperature is low, the rise time of the drive motor 22 becomes long, so that the apparatus stop position needs to be closer than usual. Furthermore, it has been found that it strongly depends on the temperature of the bearing of the rotary shaft 23 of the drive motor 22.
[0082]
FIG. 7 shows measured values of the rise time T of the drive motor 22 with respect to the environmental temperature. As shown in FIG. 1, a thermistor 41 (temperature detection means) having a negative characteristic is used for environmental temperature measurement, and the thermistor 41 is installed inside the unit of the LSU 1. Furthermore, a non-contact type thermopile (not shown) is used for measuring the temperature of the bearing of the rotating shaft 23 as an optical scanning system temperature detecting means for detecting the temperature without contact with infrared rays. In any of the detection methods, the temperature is divided into areas of 5 ° C., and the rising time T of the drive motor 22 corresponding to each temperature area is stored in the storage RAM 29 as necessary, and based on the value of the time T. The stop position of the photosensitive belt 2 is controlled.
[0083]
More specifically, the temperature area is set in increments of 5 ° C to 10 ° C, 11 ° C to 15 ° C, and the following 5 ° C. In addition, the correction value is added to the value written to the storage RAM 29 so that the object of the present invention is guaranteed in each area. As a result, it is possible to cope with an increase in the startup time T of the drive motor 22 due to a change over time, due to a change in environmental temperature.
[0084]
Here, the control sequence of this embodiment is demonstrated based on the flowchart of FIG.
[0085]
In step ST11 of the flowchart shown in FIG. 4 described above, after there is no print instruction and the stop process of the image forming apparatus X is performed, the thermistor 41 is stopped until the image forming apparatus X is stopped in step ST19 of the flowchart of FIG. The average value of the start-up time T of the drive motor 22 corresponding to the environmental temperature measured in step 1 is read from the storage RAM 29 and compared with the start-up time T of the drive motor 22 measured at the start of printing in step ST20. Then, the comparison is made taking into account the variation of the measured value and the correction value α in the temperature area. After that, if it is necessary to rewrite the storage RAM 29 as a result of the comparison in step ST20, the location corresponding to the temperature area of the storage RAM 29 is rewritten in step ST21. Then, in step ST22, the current rise time T of the drive motor 22 is replaced, and the process proceeds to step ST12 of FIG. 4 described above to control the stop position of the photosensitive belt 2 with the current rise time T of the drive motor 22. To do.
[0086]
Although the thermistor is provided in the LSU 1 in this embodiment, it may be provided in the image forming apparatus X to detect the temperature in the apparatus and indirectly measure the temperature of the LSU 1.
[0087]
<Fifth embodiment>
Next, a fifth embodiment of the present invention will be described.
[0088]
In the present embodiment, control for changing the stop position by rotating the photosensitive belt 2 during standby for printing is performed.
[0089]
That is, in the present embodiment, the environmental temperature is measured even during printing standby, and when the current stop position cannot form an image immediately after startup, that is, when the drive motor 22 rises during the previous printing. When it can be determined that the time is longer than that, and when it can be determined that the time is shorter due to the reverse, control is performed to change the stop position by rotating the photosensitive belt 2 during standby for printing.
[0090]
Thereby, for example, the problem of an increase in the initial rise time of the drive motor 22 due to a temperature drop of the drive motor 22 of the LSU 1 when left for a long time can be overcome.
[0091]
The determination and the change of the stop position of the photosensitive belt 2 do not need to be performed sequentially, and may be performed every arbitrary period. For example, in this embodiment, since the low power mode is entered after 30 minutes have elapsed since the stop, the determination is made every 10 minutes. Since the warm-up operation for preparing for printing of the image forming apparatus X is performed after the low power return, the stop position of the photosensitive belt 2 may be controlled again at the end of the warm-up operation.
[0092]
<Sixth Embodiment>
Next, a sixth embodiment of the present invention will be described with reference to FIG.
[0093]
In this embodiment, as shown in FIG. 9, a tandem intermediate transfer type image forming apparatus X ′ using four color toners of black (BK), cyan (C), magenta (M), and yellow (Y) is configured. Yes. The image forming apparatus X ′ includes first to fourth image forming stations S5 to S8 that make a latent electrostatic image visible, and toners (black, cyan, magenta, yellow) having different colors for each station. ), Photosensitive drums 51,... As image carriers for the respective colors provided for the stations S5 to S8, and a pair of left and right so as to be in sliding contact with the photosensitive drums 51. An intermediate transfer belt 52 as an image carrier that is stretched between the conveying rollers 52a and 52a, a seam 53 on the belt that is provided on the intermediate transfer belt 52 and should avoid image formation, and the seam. And a seam detector 54 as means for detecting 53. The LSU 55 of each of the stations S5 to S8 is provided with a rotary polygon mirror drive motor that requires time until stable rotation, although not shown. Although the LSUs 55 of the stations S5 to S8 have the same specifications, there is a difference in the rise time of the drive motor of each LSU 55. Inside each LSU 55, there are provided temperature detectors 56,... As optical scanning system temperature detecting means for directly and directly detecting the temperature in the LSU 55, respectively. Note that a temperature detector may be installed in the image forming apparatus X ′, and the approximate temperature of each LSU may be indirectly measured by detecting the temperature in the image forming apparatus X ′.
[0094]
When the printing start is received during the printing standby state of the image forming apparatus X ′, the driving of the four LSUs 55,... Is started simultaneously, and after the driving motors of the LSUs 55 of the stations S 5 to S 8 are started, Since an image must be formed while avoiding the joint 53, a CPU (not shown) as a control system for measuring the rise time of the drive motor of each LSU 55, specifically, four CPU timers are used. , The time from the start of simultaneously driving the LSUs 55 of the stations S5 to S8 to the end of the start-up of the drive motor of the LSU 55 that has the latest rise time is measured, and based on the measurement time, the intermediate transfer belt is measured. By controlling the stop position of 52, when the next print instruction is given, the rise time is the slowest. In start-up completion of the drive motor 55, for immediately it is possible to print start (latent image starts), it is possible to minimize the first print time.
[0095]
<Seventh embodiment>
Next, a seventh embodiment of the present invention will be described.
[0096]
In the present embodiment, in the sixth embodiment, four CPU timers are required for time measurement, and when the four LSUs 55 are simultaneously started to drive, an instantaneous power supply voltage drop occurs, affecting the others. Therefore, the control method has been improved as follows.
[0097]
That is, the four LSUs 55 are not started at the same time but are started up sequentially with a little time shift. The CPU for time measurement has only one timer, the clearing timing of the timer is the LSU 55 that starts up first, and the timing of the end of measurement is the rising time of the fourth LSU 55. Although the rise times of the four LSUs 55 vary, the start-up process is guaranteed to end in the order of start-up by sequentially starting up with a time difference greater than the variation, so that the CPU can be configured with one measurement timer. . Then, by controlling the stop position of the intermediate transfer belt 52 based on the measured value, even when the four LSU 55 moving motors are started up with a time difference, all the drive motors are started up. By measuring and storing the time required for
The first print time can also be shortened for the image forming apparatus X ′ having four LSUs 55.
[0098]
Furthermore, since it is guaranteed that the start-up process is completed in the order of start-up, when four LSUs 55,... Are started at regular intervals, it is sufficient to measure the rise time of the LSU that is finally started up. Become.
[0099]
Therefore, among the four LSUs 55,..., The color image forming apparatus having the LSU 55 that is the most frequently used and the change in rise time with time is remarkably slowed. The stop position of the intermediate transfer belt 52 can be controlled according to the rise time.
[0100]
Also, when only one LSU 55 has an initial rise time longer than that of the other LSU 55, for example, to prevent an increase in the rise time due to changes over time with respect to the black LSU 55 described above, or to extend the lifetime. In addition, when taking structural measures, the drive motor of the LSU 55 is finally started up, and the stop position of the intermediate transfer belt 52 is controlled according to the rise time of the drive motor, so that the desired first print is always performed. Can be realized.
[0101]
As described above, in the image forming apparatus X ′, the rise time of the drive motor of the LSU 55 is measured and the measured value is associated with the CPU, so that the image is started from the driving start time of the image forming apparatus X ′ for starting printing. It is possible to control the start-up process of the drive motor of the LSU 55 that requires the start-up processing time most before the start of formation, and to minimize the time from the start of printing to the start of image formation. . Furthermore, useless circumferential movement of the intermediate transfer belt 52 and the like can be suppressed.
[0102]
【The invention's effect】
As described above, the stop position of the image carrier is controlled by the control system in accordance with the rise time of the drive motor of the optical scanning system, so that the seam is formed on the image forming apparatus or the image carrier that requires overlay transfer. In some cases, a desired position can be obtained by controlling the stop position of the image carrier based on the rise time of the drive motor of the optical scanning system, and adjusting the start-up operation completion timing of the drive motor and the image formation start timing of the image carrier. You can get first print time. In addition, individual variations in the rise time of the drive motor of the optical scanning system can be absorbed by the control system, and the first print with the shortest time can be realized in each image forming apparatus.
[0103]
In particular, when the measurement time of the drive motor rise is different from the previous drive motor rise time stored in the storage means, the stop position of the image carrier is determined according to the drive motor rise time up to the previous time. By controlling, the content of the rise time of the drive motor by the storage means is updated in a timely manner as the drive motor deteriorates over time or due to wear over time such as the bearing that supports the rotating polygon mirror. The shortest first print time can be obtained. In addition, by determining whether or not to change the storage contents of the storage means in consideration of variations due to measurement accuracy of the rise time of the drive motor, a margin for the stored time value is given, and after the start-up is completed The image carrier can be stopped at a predetermined position of the image carrier, and the first print time can be shortened safely.
[0104]
In particular, the rise time of the drive motor is corrected by correcting the control of the stop position of the image carrier in accordance with the rise time of the drive motor of the optical scanning system based on the temperature in the image forming apparatus detected by the temperature detection means in the apparatus. Can be predicted. Moreover, the stop position of the image carrier can be changed with respect to the rise time of the drive motor of the optical scanning system that fluctuates depending on the environmental temperature, and the fastest first print can be realized even in a low temperature environment. it can. Further, by providing a width in the temperature region and a margin in the value stored in the storage means, it is possible to realize a desired first printing time while reducing the storage capacity.
[0105]
In particular, by controlling the stop position of the image carrier based on the detected temperature of the optical scanning system detected directly or indirectly by the optical scanning system temperature detecting means, the temperature of the optical scanning system is measured, and the driving is performed with higher accuracy. The rise time of the motor can be predicted.
[0106]
In particular, by moving the drive system of the image carrier based on the temperature inside the device main body during standby or the temperature of the optical scanning system detected by the temperature detection means, the stop position of the image carrier is moved, so that the previous time If it is calculated that the drive motor start-up time required for the next image formation has changed after the end of the image formation, the next first print time can be minimized by changing the stop position of the image carrier.
[0107]
In particular, the detection time required from the start of image formation to the detection of a predetermined position on the image carrier by the position detector after the start of image formation is set to be smaller than the rise time of the optical scanning system drive motor from the start of image formation. As a result, the image data can be processed before the drive motor startup is completed, and the image formation process can be performed immediately after the drive motor startup is completed, so that the first print time can be efficiently obtained.
[0108]
In particular, the rise times of two or more optical scanning system drive motors are individually measured, and the stop position of the image carrier is controlled based on the rise time of the slowest rise of the black or other optical scanning system drive motor. Thus, a simple calculation is performed to determine the position where the image carrier is stopped, and the first print time at the next image formation can always be the fastest.
[0109]
In particular, when the drive motors of a plurality of optical scanning systems are started up sequentially, the stop positions of the image carrier are controlled based on the startup times of all the drive motors, so that a plurality of optical scanning systems are started up with a time difference. The fastest first print time can always be realized even in the case of the finishing process. In addition, the measurement is started at the start of start-up of the optical scanning system drive motor that starts driving first, and the measurement is completed when the start-up of the optical scanning system drive motor that starts driving last is completed. Measurement of the start-up time of all the drive motors in the optical scanning system can be measured by a single control system.
[0110]
In particular, when a plurality of optical scanning systems are sequentially started up, the stop position of the image carrier is controlled based on the rising time of the driving motor of the optical scanning system that is started up last, so that even if the driving motors are started up sequentially, Since the start-up is completed in the ascending order, the variation can be ignored, and the stop position of the image carrier can be controlled based on the last rise time of the optical scanning system.
[0111]
In particular, the drive motor of the optical scanning system that requires the most rise time is started last, and the stop position of the image carrier is controlled based on the rise time of the drive motor, so that the drive motor that requires the most rise time is started. Only by measuring the raising time, the desired first print can always be realized by changing the stop position of the image carrier.
[0112]
On the other hand, the drive motor of the optical scanning system such as black that is most frequently used is started up lastly, and the stop position of the image carrier is controlled based on the rise time of the drive motor, so the use frequency is high. In addition, the optical scanning system capable of predicting an increase in the rise time with time can be started last, and the stop position of the image carrier can be changed to always realize a desired first print.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a block configuration diagram showing each component of the image forming apparatus.
FIG. 3A is a flowchart showing a control flow in the main processing unit of the CPU. (B) is a flowchart figure which similarly shows the flow of control in the timer process part of CPU.
FIG. 4A is a flowchart showing the flow of control in the drive processing unit of the image forming apparatus of the CPU. (B) is a flowchart figure which similarly shows the flow of control in the position detection process part of CPU.
FIG. 5 is a timing chart showing a flow of control in the drive processing unit and control in the position detection processing unit of the image forming apparatus of the CPU.
FIG. 6 is a flowchart for explaining a CPU control sequence according to the second embodiment of the present invention by inserting it between step ST11 and step ST12 of FIG. 4B.
FIG. 7 is a characteristic diagram illustrating a characteristic of a measured value of a rise time T of a drive motor 22 with respect to an environmental temperature in a CPU control sequence according to a fourth embodiment of the present invention.
FIG. 8 is a flowchart for explaining a CPU control sequence similarly inserted between step ST11 and step ST12 in FIG. 4B.
FIG. 9 is a schematic configuration diagram of an image forming apparatus according to a sixth embodiment of the present invention.
[Explanation of symbols]
1,55 LSU (optical scanning system)
2 Photosensitive belt (image carrier)
7,52 Intermediate transfer belt (image carrier)
21 Polygon mirror (rotating polygon mirror)
22 Drive motor
24 Semiconductor laser (light source)
28 CPU (control system)
29 RAM (storage means)
41 Thermistor (temperature detection means)
56 Temperature detector (optical scanning system temperature detection means)
X, X 'image forming apparatus

Claims (11)

An optical scanning system that deflects the light beam emitted from the light source by irradiating the rotary polygon mirror, and a latent image is formed on the image carrier by the light beam deflected by the optical scanning system, and the final recording medium In an image forming apparatus configured to perform image formation on
The optical scanning system is
A drive motor for rotating the rotary polygon mirror;
With a control system that measures the rise time from the stop state of this drive motor to the stable rotation state,
The image forming apparatus, wherein the control system controls a stop position of the image carrier in accordance with the measured rise time of the drive motor. In the image forming apparatus according to claim 1,
Comprising storage means for storing the rise time of the drive motor measured up to the previous time,
The control system measures the rise time of the drive motor. 2. The image forming apparatus according to claim 1, wherein the stop position of the image carrier is controlled in accordance with the determination and the rise time of the drive motor up to the previous time. In the image forming apparatus according to claim 1 or 2,
In-device temperature detection means for detecting the temperature in the image forming apparatus,
The control system is configured to correct the control of the stop position of the image carrier according to the rise time of the drive motor of the optical scanning system based on the temperature detected by the temperature detecting means in the apparatus. An image forming apparatus. In the image forming apparatus according to any one of claims 1 to 3,
Optical scanning system temperature detection means for directly or indirectly detecting the temperature of the optical scanning system,
An image forming apparatus, wherein the control system controls a stop position of the image carrier based on the temperature detected by the optical scanning system temperature detecting means. The image forming apparatus according to claim 1, wherein:
Provided with temperature detecting means for detecting the temperature inside the apparatus main body or the temperature of the optical scanning system during standby of the apparatus main body,
The control system is configured to move the stop position of the image carrier by rotating the drive system of the image carrier based on the temperature detected by the temperature detecting means. apparatus. In the image forming apparatus according to any one of claims 1 to 5,
A position detecting means for detecting a predetermined position on the image carrier,
The detection time required until the position detection unit detects a predetermined position on the image carrier after the start of image formation from the image formation stop state is made shorter than the rise time of the optical scanning system drive motor from the start of image formation. An image forming apparatus that is set. The image forming apparatus according to any one of claims 1 to 6,
Two or more optical scanning systems on which an image is formed by a plurality of color toners;
A control system that individually measures the rise time of the drive motor of these optical scanning systems,
This control system controls the stop position of the image carrier on the basis of the rise time of the drive motor having the slowest rise. The image forming apparatus according to claim 7, wherein
The control system measures the time until all the drive motors start up when the drive motors of the plurality of optical scanning systems are started up sequentially, and controls the stop position of the image carrier based on the measurement time. An image forming apparatus. The image forming apparatus according to any one of claims 1 to 6,
The control system measures the rise time of the drive motor of the optical scanning system that is activated last when the plurality of optical scanning systems are sequentially activated, and controls the stop position of the image carrier based on the measurement time. An image forming apparatus characterized by being made. The image forming apparatus according to claim 9, wherein
The control system is configured to start up the drive motor of the optical scanning system that requires the most rise time, measure the rise time of the drive motor, and control the stop position of the image carrier based on the measurement time. An image forming apparatus. The image forming apparatus according to claim 9, wherein
The control system starts up the drive motor of the optical scanning system that is used most frequently, measures the rise time of the drive motor, and controls the stop position of the image carrier based on the measurement time. An image forming apparatus.

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