JP2011218669A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that an electrophotographic image forming apparatus using a light emitting element array head has a problem that an electrostatic latent image formed on a photoreceptor drum shifts in a sub scanning direction between respective blocks and printing quality is degraded, and even when a high-performance light emitting element is adopted to solve the problem, a significant specification change of a printer as a whole is required to improve the printing quality.SOLUTION: The image forming apparatus includes: a main control part 111 which determines a drive cycle for controlling on/off of the LED element of an LED array 40 by a nonvolatile memory 41 for recording performance information of the LED array 40 and an LED drive time table 200 for storing the drive cycle corresponding to the performance information; and an LED array control part 102 for controlling on/off by sequentially switching on/off of the LED element of the LED array 40 based on the drive cycle.

Description

  The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus using a light emitting element array head.

  Conventionally, in this type of image forming apparatus, a large number of LED elements are arranged in a straight line to form an LED array, and these elements are divided into a plurality of blocks. Image formation was performed by suppressing the current required for light emission of the LED element by the method of causing the LED element to emit light at different times. However, in this method, a relative movement occurs between the LED array head and the photosensitive member in the process of sequentially emitting the LED elements in units of blocks in one main scanning line, so that an electrostatic latent image formed on the photosensitive member. However, there is a problem that the printing quality is deteriorated between the blocks in the sub-scanning direction. As one solution to this problem, a method has been proposed in which the total light emission time of the LED elements per main scanning line is set to ½ or less of the period of the main scanning line synchronization signal (for example, see Patent Document 1). ).

Japanese Patent Laid-Open No. 11-58814 (second page, FIG. 6)

  The time difference for light emission of a plurality of divided element blocks is often determined based on the ability of lower-performing LED elements in circulation at that time. Even in the case of adopting an LED having excellent performance, it was necessary to change the specifications of the entire printer in order to improve the printing quality.

  An object of the present invention is to provide an image forming apparatus capable of improving the print quality according to the LED performance to be employed without significantly changing the specifications of the entire printer.

An image forming apparatus according to the present invention includes a light emitting element array composed of a plurality of light emitting elements arranged on a line, and the plurality of light emitting elements are divided into a plurality of predetermined groups, and the predetermined number of each group is determined. The light emitting elements are sequentially turned on / off at different times, and an electrostatic latent image is formed on the electrostatic latent image carrier that is driven to rotate in the sub-scanning direction with respect to the light emitting element array by light emission of the light emitting elements. An image forming apparatus that
A determining unit that determines a driving cycle when the on / off control of the light emitting elements is performed based on performance information of the light emitting element array, and the predetermined of each group based on the driving cycle determined by the determining unit And a light emitting element array control means for sequentially switching on / off a plurality of light emitting elements and controlling on / off of the plurality of light emitting elements of the light emitting element array.

  According to the present invention, the driving cycle for driving the light emitting element array is determined according to the performance of the light emitting element constituting the light emitting element array to be used. It becomes easy to suppress dot deviation in the sub-scanning direction of the electrostatic latent image formed on the body.

1 is a schematic configuration diagram for explaining a main configuration of a printer according to a first embodiment based on an image forming apparatus of the present invention. It is a schematic diagram for demonstrating the structure of a LED head. In Embodiment 1, it is a block diagram which shows the principal part structure of the part regarding control of the LED array which concerns on this invention among the control systems of a printer. It is the figure which showed typically the relationship between the drive of an LED array, and an electrostatic latent image. (A) is a drive waveform diagram showing an on / off drive example when an LED element with poor performance is used, and (b) is superior to the LED used in the on / off drive example of (a). FIG. 7 is a drive waveform diagram showing a normal on / off drive example as a comparative example when using an LED element with a different performance, and (c) is the same as the LED element used in the on / off drive example of (b). It is a drive waveform diagram which shows the on / off drive example performed based on this invention using the LED element of performance. In Embodiment 1, it is the figure which showed typically the relationship between the drive of an LED array, and an electrostatic latent image. In Embodiment 1, it is a figure which shows the example of data stored in the LED drive time table. 4 is a flowchart illustrating processing contents executed by a main control unit at the time of initial setting of a printer in the first embodiment. In Embodiment 2, it is a block diagram which shows the principal part structure of the part regarding control of the LED array which concerns on this invention among the control systems of a printer. In Embodiment 2, it is a figure explaining the case where remainder time Tx is made into minimum value Tx 'in the example of FIG.5 (c) demonstrated in Embodiment 1. FIG. In Embodiment 2, it is a figure which shows the example of data stored in the LED drive time table. 9 is a flowchart illustrating processing contents executed by a main control unit at the time of initial setting of a printer in the second embodiment. FIG. 10 is a diagram illustrating a display example of a printer speed selection screen displayed on a PC screen in the second embodiment.

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram for explaining a main configuration of a printer 500 according to the first embodiment based on the image forming apparatus of the present invention.

  As shown in the figure, the printer 500 is provided with a medium feeding unit 3, a toner transfer unit 5, and a heat fixing unit 6 along a medium conveyance path 2 that conveys the print medium 1 in the direction of arrow A, which is the conveyance direction. It is. A cassette 7 containing the printing medium 1 is detachably provided at one end of the medium conveyance path 2, and a discharge tray 8 for discharging the printed printing medium 1 is provided at the other end.

  The medium feeding unit 3 includes a paper feed roller 9 that rotates in the direction of the arrow and feeds the printing medium 1 from the force set 7 one by one. The print medium 1 inserted into the transport path 2 by the pickup of the paper feed roller 9 is transported to the toner transfer unit 5 by registration rollers 12 and 13 that rotate in the directions of the arrows shown in the drawing. At this time, the writing sensor 35 on the conveyance path 2 detects that the leading edge of the printing medium 1 has passed, and thereby controls the writing timing to the printing medium 1. The toner transfer portion 5 corresponds to a contact portion between the photosensitive drum 21 and the transfer roller 22 that rotate in the arrow direction.

  The charging roller 23 rotates in contact with the photosensitive drum 21 and applies a negative charge to the entire surface of the photosensitive drum 21 to negatively charge it. The LED head 24 emits light corresponding to the print pattern and exposes it to the negatively charged surface of the photosensitive drum 21. In the photosensitive drum 21, the state of charge on the exposed surface portion changes and the potential becomes close to zero, and this portion becomes an electrostatic latent image.

  The toner filled in the toner cartridge 29 is supplied to the developing roller 25 through the supply roller 27. The toner supplied to the developing roller 25 is negatively charged when it is thinned on the surface of the developing roller 25 by a developing blade (not shown). In the contact portion 26 between the photosensitive drum 21 and the developing roller 25, the negatively charged toner is present at a portion where the photosensitive drum 21 is not exposed, that is, where a negative charge imparted by the charging roller 23 remains. The toner is adhered to the electrostatic latent image portion where the electric potential becomes zero by exposure, but it becomes visible as a developed image.

  The photosensitive drum 21 to which the developing toner is attached reaches the transfer unit 5 by rotation, and transfers the developing toner to the transported printing medium 1. At this time, the transfer roller 22 applies a positive high potential from the back side of the print medium 1, so that the negatively charged development toner on the photosensitive drum 21 is separated and placed on the recording medium 1. The recording medium 1 to which the developing toner has been transferred is conveyed to the heat fixing unit 6 on the conveyance path 2.

The thermal fixing unit 6 includes a fixing roller 10 and a pressure roller 11 that rotate in the directions of the arrows. The fixing roller 10 includes a heat source such as a halogen lamp, and the developing toner adhering to the printing medium 1 is heat-fixed at a pressure contact portion with the pressure roller 11. The print medium 1 on which the thermal fixing of the image has been completed is transported in the transport path 2 in the direction of arrow A by transport rollers 31 and 32 that rotate in the direction of the arrow, and is further fed onto the discharge tray 8 by the discharge rollers 33 and 34. .
Each roller other than the medium feeding roller 9 is driven by a transmission mechanism (not shown).

  FIG. 2 is a schematic diagram for explaining the structure of the LED head 24.

  The LED head 24 is provided in close proximity to the photosensitive drum 21. The photosensitive drum 21 is rotatably held by a support mechanism (not shown) and is driven to rotate using a motor (not shown) as a drive source. Further, a moving means for relatively moving the photosensitive drum 21 and the LED head 24 in the sub-scanning direction is configured by these support mechanisms and motors. An arrow C in FIG. 2 indicates the moving direction of the peripheral surface of the photosensitive drum 21 that moves relative to the fixed LED head 24 in the sub-scanning direction.

  The LED head 24 includes an LED array 40 in which a large number of LED elements (not shown) are arranged on a straight line in the main scanning direction, and a rod lens array 52 interposed between the LED array 40 and the photosensitive drum 21. And have. Each LED element in the LED array 40 is controlled to be lit by a later-described LED array control unit 102 (FIG. 3) to which image data is transferred to emit light. The arrow drawn with a dotted line in the figure schematically shows how the LED element emits light. The LED array control unit 102 determines the timing of lighting control according to the performance of the LED element, as will be described later.

  FIG. 3 is a block diagram showing a main configuration of a part related to control of the LED array 40 according to the present invention in the control system of the printer 500.

  The printer 500 includes a control unit 100 and an LED driving time table 200. The control unit 100 includes a main control unit 101 that controls the operation of the entire printer 500 and an LED array control unit 102 that controls driving of the LED array 40. As will be described later, the LED drive time table 200 corresponds to the performance level of the LED array 40 constituted by a plurality of LED elements and the drive cycle information when driving the LED array 40 of each performance level. Stored.

  When the printer 500 starts the initialization process, the main control unit 101 is provided integrally with the LED array 40 and has three performances of “excellent”, “good”, and “possible” according to the performance of the corresponding LED array. The performance information of the LED array 40 is acquired from the nonvolatile memory 41 in which the evaluation result evaluated at the level is written in advance. Hereinafter, the LED array 40 and the nonvolatile memory 41 provided in a pair with the LED array 40 are referred to as an LED unit 51.

  Next, the main control unit 101 acquires drive cycle information corresponding to the performance level of the LED array 40 by referring to the LED drive time table 200 based on the acquired performance information, and notifies the LED array control unit 102 of the drive cycle information. To do. FIG. 7 is a diagram illustrating an example of data stored in the LED driving time table 200. As shown in the figure, the table includes on / off drive control of the LED elements of each LED array 40 for each of the three levels of “excellent”, “good”, and “possible” performance levels. The on / off time information of the driving cycle for the purpose is stored correspondingly. The LED array control unit 102 controls on / off of the LED array 40 at a received drive cycle corresponding to the performance of the LED array 40.

  Therefore, in order to obtain an evaluation of “excellent” for the LED array 40 to be used, all the LED elements constituting the LED array 40 are turned on / off in a driving cycle consisting of an on time 30 (μS) and an off time 20 (μS). Must be possible LED elements. In addition, in order to obtain an evaluation of “good” for the LED array 40 to be used, all the LED elements constituting the LED array 40 can be turned on / off in a driving cycle consisting of an on time 35 (μS) and an off time 30 (μS). It must be a possible LED element. Further, in order to obtain a “good” evaluation for the LED array 40 to be used, all the LED elements constituting the LED array 40 can be turned on / off in a driving cycle consisting of an on time 40 (μS) and an off time 35 (μS). It must be a possible LED element. As described above, a predetermined correspondence is established in advance between the driving cycle information recorded in the LED driving time table 210 and the LED elements constituting the LED array of each performance level.

  Next, the control contents in which the LED array control unit 102 controls driving of the LED array 40 based on the acquired driving time information of the LED array 40 will be further described.

  First, the relationship between the driving time of the LED array 40 and the electrostatic latent image formed on the photosensitive drum 21 will be described. FIG. 4 is a diagram schematically showing the relationship between the light emission of the LED array 40 and the electrostatic latent image.

  The plurality of LED elements arranged in the LED array 40 are generally divided into four groups as shown in FIG. 4, and the LED elements arranged at the corresponding positions of each group emit light simultaneously, and The LED array control unit 102 controls the light emission timing so that light is emitted at four different timings in order in each group, and the emitted light passes through the rod lens array 52 and is electrostatically charged for one line on the photosensitive drum 21. A latent image is formed. In FIG. 4, for convenience, the LED elements of each group are sequentially numbered 1 to 4, and the LED elements arranged at corresponding positions in each group are numbered the same.

  Therefore, in FIG. 4, when creating a straight image extending in the left and right directions parallel to the rotation axis of the photosensitive drum 21, the LED elements of each group arranged in the LED array 40 are 1 to 4 described in FIG. 4. Lights sequentially. In addition, the LED element numbered 1 in each group is referred to as a 1-block LED element, the LED element numbered 2 is referred to as a 2-block LED element, and the LED numbered 3 The element is referred to as a 3-block LED element, and the LED element numbered 4 is referred to as a 4-block LED element.

  While each LED element of the LED array 40 sequentially emits light from 1 to 4, the photosensitive drum 21 is shown in a substantially circular shape on the left with the rotation axis extending in the left and right directions parallel to the paper surface in FIG. As indicated by the arrow, the peripheral surface portion facing the front side of the paper rotates so as to move downward from the upper side of the paper. Therefore, an image that should originally be a straight line is (1) to (4) in FIG. ). That is, if the surface of the photosensitive drum 21 is rotated and moved by L1 shown in the figure between the time when one block of LED elements in each group emits light and the time when four blocks of LED elements emit light, the number ( Since the center of the dot of 1) and the dot of number (4) are shifted by L1, the printed straight line is blurred in a fine step shape when viewed closely.

  Here, for the sake of simplicity, description will be made assuming that the light emitting element emits light unconditionally at the light emission timing, but actually light emission at each light emission timing is determined according to print data.

  FIG. 5 is a diagram for explaining the ON / OFF time of the driving cycle, which varies depending on the difference in the performance of the LED array 40.

5A, 5 </ b> B, and 5 </ b> C, the unit time Tr is the time required for the electrostatic image forming surface to move by one line due to the rotation of the photosensitive drum 21. It is determined by the rated number of prints per minute. That is, suppose that the number of prints output by the printer 500 per minute is n (sheets), the print resolution is md (dpi), and the length of the print medium 1 in the sub-scanning direction is Lm (inch). Sec) Tr = 60 × 10 ⁶ / (n · md · Lm) (1)
It becomes. For a printer that prints 30 sheets of A4 vertical paper at a printing resolution of 600 dpi per minute, the unit time Tr is about 300 μsec.

  FIG. 5A shows an example of on / off driving when an LED array with a low performance level is used. The LED element is energized only during energization (on) time Td1 and emits light, and is shut off (off) time. During ΔT1, the energization is interrupted to cool the LED element. That is, in the LED array 40 used here, it is assumed that all of the LED elements constituting the LED array 40 are configured with LED elements that can be turned on / off in a driving cycle consisting of an on time Td1 and an off time ΔT1. .

During the unit time Tr, the LED elements of 1 to 4 blocks of each group of the LED array are sequentially turned on / off in a controlled manner to emit light by repeating this on / off drive 4 times for one line. An electrostatic image is formed. The numbers (1) to (4) shown in FIG. 5 indicate the block numbers of the LED elements of each group that emit light when turned on. Therefore, if the driving cycle of the total of the on / off times of the LED elements is T1, T1 = Td1 + ΔT1 = Tr / 4
It is.

  Therefore, the dots formed by the LED elements of 1 block to 4 blocks of each group that are evenly turned on / off during the unit time Tr are the same for the photosensitive drum 21 during the unit time Tr as shown in FIG. , When it is rotated and moved by L1, the dots are gathered as shown in (1) to (4) as shown in FIG.

  Here, a normal on / off drive example when the LED array 40 having a performance superior to that of the LED array 40 used in the on / off drive example of FIG. ). Here, as described above, one driving cycle of the LED determined by the number of printed sheets n (sheets) output per minute of the printer 500, the printing resolution md (dpi), and the length Lm (inch) of the medium in the sub-scanning direction. Let Tr be the same value as in FIG.

  In the case of this comparative example, even when the LED array 40 with good performance that only requires Td2 shorter than Td1 in FIG. The drive cycle T1 (= Tr / 4) is kept longer. Accordingly, in this case as well, the LED elements of 1 to 4 blocks in each group are equally turned on / off during the unit time Tr, and the dots formed by this drive are shown in FIG. As shown in the figure, if it is rotationally moved by L1 during the unit time Tr, it is formed as a collection of dots shown in (1) to (4) in a staggered state as shown in FIG.

  Next, the present invention uses an LED element having the same performance as the LED element used in the on / off driving example of FIG. 5 (b), which is superior to the LED used in the on / off driving example of FIG. 5 (a). An example of on / off driving performed based on the above will be described with reference to FIG.

  Here, the energization time of the LED element is set as Td2, the cutoff time ΔT2, and the cutoff time ΔT2 is set shorter than the above-described cutoff time ΔT ′ and longer than the minimum period necessary for cooling the LED element. is doing. That is, in the LED array 40 used here, it is assumed that all the LED elements constituting the LED array 40 are configured by LED elements that can be controlled on / off in a driving cycle composed of an on time Td2 and an off time ΔT2. .

Then, irrespective of the unit time Tr required for the photosensitive drum 21 to rotate by one line, a driving cycle T2 calculated by the following equation:
T2 = Td2 + ΔT2 (<T1 = Tr / 4)
Thus, the on / off drive is repeated four times to form an electrostatic image for one line so that the LED elements of blocks 1 to 4 in each group of the LED array are sequentially turned on / off to emit light. And the remaining remainder time Tx calculated by the following equation,
Tx = Tr-4 (Td2 + ΔT2) (2)
Shall do nothing.

  In this case, as compared with the control in the comparative example described in the on / off drive example in FIG. 5B, the electrostatic charge for one line on the photosensitive drum 21 is shorter than the unit time Tr by the extra time Tx. A latent image is formed. Accordingly, assuming that the photosensitive drum 21 rotates at the same speed as in the case of FIGS. 5A and 5B described above, the photosensitive drum 21 does not emit light until the fourth element emits light after the first element emits light. The amount of movement of the surface of the body drum 21 is shorter than L1 shown in FIG. 4. If this is L2, the distribution of dots for one line is illustrated in FIG. The center misalignment between the dot of number (1) and the dot of number (4) is L2, and the step-like blur is smaller than the comparative example shown in FIG. 4, and a more beautiful output is obtained.

  In the present embodiment, the performance of these LED arrays and the on / off time information of the driving cycle for controlling the on / off driving of each LED array are the LED driving time table shown in FIG. 200 corresponding to 200.

  FIG. 8 is a flowchart showing the processing contents executed by the main control unit 101 at the time of initial setting of the printer 500 so as to perform the control shown in FIG.

  As shown in the flowchart, when the initial setting of the printer 500 is started, the main control unit 101 accesses the LED unit 51 and writes in the nonvolatile memory 41 in advance, and the performance of the paired LED array 40. Evaluation information (any of “excellent”, “good”, and “possible”) is acquired (step S1), and the driving period corresponding to the performance evaluation information is turned on / off with reference to the LED driving time table 200. Time information is acquired (step S2) and notified to the LED array controller 102 (step S3). Thereafter, the LED array control unit 102 performs on / off control of the LED array 40 at a driving cycle based on the received on / off time information.

  As described above, according to the image forming apparatus of the present embodiment described above, it is possible to drive the LED element group on / off substantially in accordance with the performance of the LED array without changing the specifications of the entire printer. By controlling the period, it is possible to reduce the dot deviation of printing and improve the printing quality.

Embodiment 2. FIG.
FIG. 9 is a block diagram showing a main configuration of a part related to the control of the LED array 40 according to the present invention in the control system of the printer 600 according to the second embodiment based on the image forming apparatus of the present invention.

  The main difference between the control system of the printer 600 and the control system of the printer 500 according to the first embodiment shown in FIG. 3 is the contents of processing executed by the main control unit 111. Accordingly, in the printer 600 having this control system, parts common to those of the printer 500 (FIG. 1) of the first embodiment are denoted by the same reference numerals, or the description is omitted by omitting the drawings. Explain mainly. The main configuration of the printer 600 according to the present embodiment is the same as the main configuration of the printer 500 according to the first embodiment shown in FIG. 1 except for the processing executed by the main control unit 111. 1 is referred to.

  As shown in FIG. 9, the printer 600 includes a communication unit 150, a control unit 110, a photosensitive drum driver 103, and an LED driving time table 210. The control unit 110 includes a main control unit 111 that controls the overall operation of the printer 600 and an LED array control unit 102 that controls driving of the LED array 40. The communication unit 150 communicates with the PC 300 that is a host device, transmits necessary information to the user via the PC 300, and acquires information necessary for initial setting of the printer 600 from the user. In the LED drive time table 210, as described above, the performance level of the LED array 40 composed of a plurality of LED elements, the drive cycle information when driving the LED array 40 of each performance level, and the performance level When printing processing is performed by the printer 600 using the LED array 40, the maximum value and the minimum value of the printing speed (ppm) are stored in correspondence with each other.

  When the printer 600 starts the initialization process, the main control unit 111 is provided integrally with the LED array 40 and has three performances of “excellent”, “good”, and “possible” according to the performance of the corresponding LED array. The performance information of the LED array 40 is acquired from the nonvolatile memory 41 in which the evaluation result evaluated at the level is written in advance. Here, the LED array 40 and the nonvolatile memory 41 provided in a pair with the LED array 40 are referred to as an LED unit 51.

  Next, the main control unit 111 acquires drive cycle information corresponding to the performance level of the LED array 40 with reference to the LED drive time table 210 based on the acquired performance information, and notifies the LED array control unit 102 of the drive cycle information. . FIG. 11 is a diagram illustrating an example of data stored in the LED driving time table 210. As shown in the figure, the table is used for on / off drive control of each LED array with respect to each LED array 40 having three levels of “excellent”, “good”, and “possible” performance levels. The on / off time information of the driving cycle and the maximum value and the minimum value of the printing speed of the printer 600 are stored corresponding to each other.

  The LED array control unit 102 controls on / off of the LED array 40 at a received drive cycle corresponding to the performance of the LED array 40. Therefore, for example, in order to obtain an evaluation of “excellent” for the LED array 40 to be used, all of the LED elements constituting the LED array 40 are turned on / off in a drive cycle consisting of an on time 30 (μS) and an off time 20 (μS). The LED element must be capable of being turned off. In this way, a predetermined correspondence is established in advance between the driving cycle information recorded in the LED driving time table 210 and the LED elements constituting the LED array of each performance level.

  Further, the main control unit 111 acquires the maximum value and the minimum value of the printing speed of the printer 600 corresponding to the performance of the LED array 40 from the LED driving time table 210, and the user is notified to the user via the communication unit l50 and the PC 300. The requested printing speed is inquired, and the printing speed value requested by the user is acquired. FIG. 13 shows a display example of the speed selection screen of the printer 600 displayed on the screen of the PC 300 when the performance level of the LED array 40 is “excellent”. Here, the user confirms the displayed screen, considers the printing speed and quality, and uses the utility program of the displayed printer 600, clicks the [▲] button or the [▼] button, and ranges from 29 to 32 ppm. The printing speed is designated by clicking the [OK] button and the set speed is transmitted to the printer 600.

  The designated printing speed is transmitted to the main control unit 111 via the communication unit 150. The main control unit 111 transfers the received printing speed to the photosensitive drum driver 103, and the photosensitive drum driver 103 drives the photosensitive drum 21 at the received speed.

  Next, the drive control content of the LED array 40 by the LED array control unit 102 and the rotational speed control of the photosensitive drum 21 by the photosensitive drum driver 103 will be described.

  In the present embodiment, the driving cycle of the on / off control of the LED array 40 according to the performance of “excellent”, “good”, and “possible” of the LED array 40 is the same as the method described in the first embodiment. And the printing speed of the printer 600 is made variable by changing the rotation speed of the photosensitive drum 21 in accordance with the set driving cycle.

As derived from the previous formula (2) described in the first embodiment, the unit time Tr required for the photosensitive drum 21 to rotate by one line and the driving of the on / off control of the LED element once are driven. The relationship between the cycle T (Td (energization time) + ΔT (cutoff time)) and the remainder time Tx is expressed by the following equation: Tr = 4 (Td + ΔT) + Tx (3)
It can be expressed as

On the other hand, assuming that the number of prints output by the printer 600 per minute is n (sheets), the print resolution is md (dpi), and the length of the print medium 1 in the sub-scanning direction is Lm (inch), the unit time Tr (μ Second) as shown in the previous equation (1),
Tr = 60 × 10 ⁶ / (n · md · Lm)
Therefore, n expressed as a printing speed (ppm) is n = 60 × 10 ⁶ / (Tr · md · Lm)
If md and Lm are fixed values, the printing speed n increases as the unit time Tr decreases.

This will be further described with reference to FIG. FIG. 10 is a diagram illustrating a case where the remainder time Tx is set to the minimum value Tx ′ in the example of FIG. 5C described in the first embodiment. In this case, the unit time Tr ′ required for the photosensitive drum 21 to rotate by one line.
Tr ′ = 4 (Td2 + ΔT2) + Tx ′ (4)
And can be shortened by (Tx−Tx ′) with respect to the unit time Tr obtained from the previous equation (2) described in the example of FIG. 5C described in the first embodiment. . That is, it is possible to increase the printing speed of the printer 600 by accelerating the rotation of the photosensitive drum 21 correspondingly.

Here, it is necessary to consider the following points when setting the printing speed.
1) Assume that the printer 600 sets a reference printing speed at which printing is possible, assuming that the LED array 40 whose performance evaluation is “permitted” is used.
2) If the rotation of the photosensitive drum 21 is made faster, the amount of movement of the drum surface during the operation of the LED elements that are driven in four blocks of each block increases, so that the deviation of dots increases.

  Therefore, in the printer 600, as shown in FIG. 11, in the LED driving time table 210, the maximum value and the minimum value of the printing speed (ppm) possible for each performance level of the LED array are stored in advance. In the example of FIG. 11, when the LED array 40 whose performance evaluation is “possible” is used, the printing speed of the printer 600 is 29 ppm of the reference speed at the maximum, but the LED array 40 whose performance is “good” and “excellent” is used. When it is adopted, the maximum values are set to 30 ppm and 32 ppm, respectively, and the speed selection screen shown in FIG. 13 of the screen of the PC 300 is displayed as described above, and the user sets the print speed while taking the print quality into consideration. I can do it.

  Note that the maximum value of the printing speed in “good” and “excellent” varies depending on the setting value of the remainder time Tx ′, and by decreasing this, each maximum value can be set larger, but here, as described above The maximum values are 30 ppm and 32 ppm, respectively.

  FIG. 12 is a flowchart showing the processing contents executed by the main control unit 111 at the time of initial setting of the printer 600 in order to perform the speed setting described above.

  As shown in the flowchart, when the initial setting of the printer 600 is started, the main control unit 111 accesses the LED unit 51 and writes the performance of the paired LED array 40 that has been written in the nonvolatile memory 41 in advance. Evaluation information (any one of “excellent”, “good”, and “possible”) is acquired (step S101), and the LED driving time table 210 is referenced to turn on / off the driving cycle corresponding to the performance evaluation information. The maximum value and the minimum value of the off time information and the printing speed are acquired (step S102). Next, based on the acquired printing speed, the main control unit 111 displays the speed selection screen shown in FIG. 13 on the PC 300 that is the host device via the communication unit 150 (step S103). FIG. 13 shows the case where the performance evaluation information of the LED array 40 is “excellent” (printing speed is 29 to 32 ppm) as described above.

  Here, the user checks the displayed screen, considers the printing speed and quality, clicks the [▲] or [▼] button to specify the printing speed, and clicks the [OK] button to set it. The speed is transmitted to the printer 600. Although an example in which a speed selection screen is displayed on the screen of the PC 300 is shown here, in addition to this, an I / O module such as a touch panel is provided in the printer 600 so that the user can directly input through this. May be.

  When receiving the printing speed designated by the user (step S104), the main control unit 111 notifies the LED array control unit 102 of the driving cycle on / off time information read from the LED driving time table 210 in step S102 (step S102). In step S105, the photosensitive drum driver 103 is notified of the driving speed of the photosensitive drum 21 corresponding to the printing speed acquired in step S104 (step S106). Thereafter, the LED array control unit 102 performs on / off control of the LED array 40 at a driving cycle based on the received on / off time information, and the photosensitive drum driver 103 performs the photosensitive drum 21 at the speed instructed in step S106. Control the rotation of

  As described above, according to the image forming apparatus of the present embodiment described above, the same effects as those of the image forming apparatus of the first embodiment can be obtained, and in addition, the photosensitive drum can be matched to the performance of the LED unit. By making the rotation speed variable, the user can determine the required specifications by taking into account the relative effects of beautiful printing with less dot shift and faster output printing, providing a more convenient printer it can.

  In the above-described embodiment, an example in which the present invention is adopted in an electrophotographic printer has been described. However, the present invention is not limited to this. In addition, an LED head such as an MFP (Multi Function Printer), a facsimile, a copying machine, or the like is used. It can also be used for all image forming apparatuses that employ the photosensitive method used.

  DESCRIPTION OF SYMBOLS 1 Print medium, 2 Medium conveyance path, 3 Medium delivery part, 5 Toner transfer part, 6 Thermal fixing part, 7 Cassette, 8 Discharge tray, 9 Paper feed roller, 10 Fixing roller, 11 Pressure roller, 12 Registration roller, 13 Registration Roller, 21 photosensitive drum, 22 transfer roller, 23 charging roller, 24 LED head, 25 developing roller, 26 contact portion, 27 supply roller, 29 toner cartridge, 31 transport roller, 32 transport roller, 33 discharge roller, 34 discharge roller Paper roller, 35 writing sensor, 40 LED array, 41 non-volatile memory, 51 LED unit, 52 rod lens array, 100 control unit, 101 main control unit, 102 LED array control unit, 103 photosensitive drum driver, 110 control , 111 main control unit, 150 communication unit, 200 LED driving time table, 210 LED driving time table, 300 PC, 500 printer, 600 printer.

Claims (10)

A light-emitting element array comprising a plurality of light-emitting elements arranged on a line, the plurality of light-emitting elements being divided into a plurality of groups each having a predetermined number, and the predetermined number of light-emitting elements in each group being shifted in time; An image forming apparatus that sequentially controls on / off, and forms an electrostatic latent image on an electrostatic latent image carrier that is driven to rotate in the sub-scanning direction with respect to the light emitting element array by light emission of the light emitting element,
Determining means for determining a driving cycle when performing on / off control of the light emitting element based on performance information of the light emitting element array;
A light emitting element array that sequentially switches on / off the predetermined number of light emitting elements of each group based on the driving cycle determined by the determining means, and controls on / off of the plurality of light emitting elements of the light emitting element array. An image forming apparatus comprising: a control unit.   A non-volatile memory that accompanies the light-emitting element array and stores performance information of a plurality of light-emitting elements of the light-emitting element array is provided, and the determining unit obtains the performance information of the light-emitting element array from the non-volatile memory. The image forming apparatus according to claim 1. First storage means for storing drive periods set corresponding to different performance levels of the performance information;
The determination unit acquires a driving cycle corresponding to the performance level of the acquired performance information from the first storage unit, and sets the acquired driving cycle as a driving cycle when the light emitting element is turned on / off. The image forming apparatus according to claim 2.   The said performance information is the information set based on the energization time required in order to drive the said light emitting element array on / off normally, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. Image forming apparatus.   A plurality of light emitting elements of the light emitting element array are divided into the predetermined number of blocks for each light emitting element in a corresponding position of each of the plurality of groups, and the on / off control is sequentially performed by shifting the time for each block. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein the light emitting element is an LED element. Drive control means for driving and controlling the electrostatic latent image carrier at a drive speed determined by the determination means;
The image forming apparatus according to claim 1, wherein the determining unit determines the driving speed based on performance information of the light emitting element array. Second storage means for storing a drive speed range set corresponding to different performance levels of the performance information;
The determination means acquires drive speed range information corresponding to the performance level of the acquired performance information from the second storage means, and drives the electrostatic latent image carrier based on the acquired drive speed range information. A screen to the effect that the speed is designated by the user is displayed on the display unit, and the driving speed designated by the user is set as the driving speed when the drive control means drives and controls the electrostatic latent image carrier. 8. The image forming apparatus according to claim 7, wherein:   4. The image forming apparatus according to claim 3, wherein the performance information is set to a plurality of performance levels based on a driving cycle necessary for normally turning on / off the light emitting element array.   The said 1st memory | storage means memorize | stores the drive period required in order for the said light emitting element array of each performance level to carry out a normal on / off drive corresponding to these performance levels. The image forming apparatus according to 9.

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