JPH08118754A - Image forming apparatus - Google Patents

Abstract

PURPOSE: To accurately feed a recording medium while always obtaining a high-grade recording image by performing control so that the relative displacement to the recording medium of a drive roller shaft before the first feed of the recording medium becomes same and inputting the pulse number stored in a memory means to a pulse motor to intermittently feed the recording medium. CONSTITUTION: Before the formation of an image is started, feed rollers 1, 3 are preliminarily rotated counterclockwise until the flags 9a, 9b provided on the pulleys 5a, 5b fitted to the end parts of the feed rollers 1, 3 shield photointerruptors 10a, 10b. The moment the photointerruptors 10a, 10b are shielded by the flags 9a, 9b the pulse motors 6a, 6b driving the feed rollers 1, 3 are stopped by the control of a CPU. The CPU drives the pulse motor 6a on the basis of the data of the number of drive pulses of the first line preliminarily stored in a memory device. The feed roller 1 feeds a recording medium by the quantity equal to the recording width of one line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus which intermittently conveys a recording medium and forms an image line by line according to an image signal or the like.

[0002]

2. Description of the Related Art Conventionally, image forming apparatuses equipped with various recording systems have been put into practical use. Among them, inkjet systems, thermal transfer systems, etc. are relatively inexpensive and can be downsized and quiet, so that they can be used for personal use. It is used in a wide range from to office use. In an image forming apparatus equipped with these recording methods, it is common to move a recording medium relative to a recording unit in the apparatus to form an image. In a serial scan type printer using an inkjet method or the like, a recording medium is intermittently stepwise fed by a predetermined width, and an image is formed by the predetermined width.
In order to convey the recording medium, it is general to use a conveying system including a conveying roller, a pulse motor that drives the roller, a pulley that transmits the drive to the roller, a gear, a belt, and the like.

[0003]

However, in the case of using the recording method in which the recording medium is intermittently moved relative to the recording unit in the apparatus to form an image, the recording medium is accurately conveyed by a predetermined width. Since this is necessary, if this is not achieved and the transport amount is insufficient, image overlap (black stripes) occurs, and if the transport amount is large, image discontinuity (white stripes) occurs. was there. Further, in the case of an image of a plurality of colors, it may cause color misregistration, which significantly deteriorates the image quality.

The main causes of difficulty in carrying the desired recording medium are eccentricity of the carrying roller, pulley and gear,
Motor speed unevenness, stop position accuracy, belt and pulley gear cutting accuracy, etc. can be mentioned, but the greatest influence is the eccentricity of the transport roller and pulley. In order to solve this problem, conventionally, when each element having an eccentricity makes one rotation or an integer rotation, the device is set so as to have a desired carry amount, and variation from the desired carry amount due to eccentricity is suppressed. A method can be considered.

However, in the case of the conveying roller as an example, when conveying a predetermined amount in one rotation, the conveying amount will deviate from the predetermined amount unless the diameter is accurately processed. Further, in the case of a general device, the predetermined recording width of the recording head is about several mm to several tens of mm, but in this case, the diameter of the conveying roller becomes several mm, and its longitudinal direction (perpendicular to the conveying direction). It is very thin compared to the length (direction) and causes other problems such as warping and bending.

Therefore, under the present circumstances, it is unavoidable that the device is set so that the feed amount becomes an integral multiple of the predetermined feed amount when the feed roller makes one rotation, and the feed amount due to the eccentricity of the roller is fed several times by the predetermined feed amount. There are many ways to offset the variations. However, this method cannot be said to be a very effective method because the carry amount for each line has a certain degree of variation.

Even in the entire conveying system, it is difficult to completely cancel the variation in the predetermined conveying amount due to the influence of each element, such as the relative phase of the belt or pulley and the conveying roller is different for each recording medium. . Further, it takes time and cost to process the conveying roller, the pulley and the like with high precision, and the cost increase is inevitable.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and the object thereof is to inexpensively convey a recording medium accurately without using a complicated mechanism and always To obtain high-quality recorded images.

[0009]

A typical constitution of the present invention for achieving the above object is to provide an image forming apparatus which intermittently conveys a recording medium and forms an image line by line.
At least one roller pair including a driving roller and a driven roller; and a pulse motor for driving the driving roller,
Conveying means for transmitting driving force from the pulse motor to the driving roller, and conveying means for conveying the recording medium in the image forming section, and an image according to the length of the recording medium or the length of the image to be recorded. Control means for controlling the rotational displacement of the drive roller before the start of formation, and storage means for storing the number of pulses input to the pulse motor in correspondence with the number of lines for conveying the recording medium when the drive roller makes one rotation. And controlling so that the relative displacement of the drive roller shaft with respect to the recording medium before the first conveyance of the recording medium becomes the same,
The number of pulses stored in the storage means is input to the pulse motor to intermittently convey the recording medium.

[0010]

In the above structure, the relative displacement of the drive roller shaft before the first conveyance of the recording medium with respect to the recording medium is controlled to be the same, and the pulse number stored in the storage means is supplied to the pulse motor. Since the recording medium is input and conveyed intermittently, it is possible to always match the conveyance amount of the recording medium for each line when forming an image with the recording width of the recording head with high accuracy. It is possible to form a high-quality image in which black stripes, white stripes, and the like do not occur.

[0011]

【Example】

[First Embodiment] An embodiment of the image forming apparatus according to the present invention will be specifically described below with reference to the drawings. In this embodiment, an ink jet recording apparatus is exemplified as the image forming apparatus. FIG. 1 is a perspective view of a recording unit of an inkjet recording apparatus to which the present invention is applied, and FIG. 2 is a main sectional view of the apparatus.

In FIG. 1, 1 is a conveying roller arranged in the upstream direction of the recording portion, and 2 is a driven roller for urging the recording medium to the roller 1. Similarly, a discharge roller 3 is provided downstream of the recording unit, and a driven roller 4 for urging the recording medium toward the roller 3.
Is arranged.

Pulleys 5a and 5b are press-fitted at one ends of the transport roller 1 and the discharge roller 3, respectively, and are driven by pulse motors 6a and 6b via motor pulleys 7a and 7b and transmission belts 8a and 8b.

The pulse motors 6a and 6 used in this embodiment
b is a high-resolution 5-phase stepping motor with a basic step angle of 0.36 °, and a motor driver (not shown)
Driven by half step (0.18 ° rotation per pulse). In FIG. 1, the pulleys 5a and 5b and the motor pulleys 7a and 7b, which are press-fitted to the ends of the drive rollers, respectively.
The ratio of the number of teeth is set to 3: 1.

Further, the pulleys 5a and 5b press-fitted to the ends of the respective drive rollers have flags 9a and 9b, and the photo interrupters 10a and 10b provided on the main body side are shielded from light so that they are in a predetermined rotational displacement. , It is possible to detect this.

Reference numeral 11 denotes a platen for supporting the recording medium in the recording section, which has a large number of small holes on the recording medium passage surface and is connected to the suction blower 12 in order to prevent the recording medium from floating during recording. . Reference numeral 13 denotes an ink jet type recording head. In the case of this embodiment, cyan (C), magenta (M), yellow (Y),
Black (B) four-color recording heads 13C, 13M, 13Y,
13B are arranged side by side in the scanning direction (arrow direction in the figure).
16.2 by ejecting ink from 256 nozzles in a row
Record a width of 56 mm. In the case of this apparatus, the recording width of one line is set to 1/3 of the length of the conveying roller 1 and the discharging roller 3, which corresponds to one rotation of the motor pulleys 7a and 7b. The processing accuracy of 7a and 7b does not affect the recording accuracy.

The recording head 13 is removably mounted on a carriage 14 and scans on two guide rails 15a and 15b in a direction perpendicular to the conveying direction of the recording medium (the arrow direction in the figure). The carriage 14 is driven via a pulse motor (not shown) and a drive belt 16.

In FIG. 2, 17 is a CPU (central processing unit) for controlling the drive of the motor, and 18 is a memory device for storing the number of drive pulses input to the motor at the time of image formation for each line.

In this embodiment, the ratio of the urging pressure of the driven roller 2 urging the conveying roller 1 to the urging pressure of the driven roller 4 urging the discharging roller 3 is about 4: 1. Therefore, as shown in FIG. 3, after the leading edge of the recording medium is sandwiched by the pair of conveying rollers 1 and 2, the trailing edge of the recording medium is fed one time before (1 to Up to the ninth time, the conveyance amount of the recording medium is governed by the conveyance roller pair 1 and 2. Further, the trailing edge of the recording medium is the pair of transport rollers 1 and 2.
At the number of feeding times (10th time) for exiting the recording medium, the conveyance amount of the recording medium is affected by both the conveyance roller pairs 1 and 2 and the discharge roller pairs 3 and 4. When the recording medium is held only by the discharge roller pairs 3 and 4 (11th to 12th feeding), the amount of conveyance of the recording medium is controlled by the discharge roller pairs 3 and 4.
The number of times of conveyance in FIG. 3 is the case where the recording medium of A4 size is laterally fed (the same applies hereinafter).

FIG. 4 is a main cross-sectional view of the image forming portion of this apparatus, showing the dimensional relationship between each roller which is the transport system and the recording position. As shown in FIG. 4, the axial distance between the transport roller 1 and the discharge roller 3 is set to a length of 4X with respect to the recording width X (16.256 mm). Further, the center of the transport roller 1 and the discharge roller 3 and the center of the recording head 13 (recording position)
The distances they make are both 2X long. Therefore, in this apparatus, when the recording medium is conveyed after the image formation of the second line is completed, the front end of the recording medium protrudes into the nip portion of the discharge rollers 3 and 4, and the rear end of the recording medium is conveyed. After passing through the nip portion of the roller pair 1 and 2, the image is formed on the final line when the sheet is further conveyed once.

Next, the operation of forming an image on a recording medium with this apparatus will be described. Before the start of image formation, the transport roller 1 and the discharge roller 3 are counterclockwise until the flags 9a, 9b provided on the pulleys 5a, 5b press-fitted at the ends thereof shield the photo interrupters 10a, 10b. Rotate. At the moment when the photo interrupters 10a, 10b are shielded by the flags 9a, 9b, the pulse motors 6a, 6b for driving the conveying roller 1 and the discharging roller 3 are CP
It is stopped by the control of U17, excited, and held at its stop position. The same operation is performed when the photo interrupters 10a and 10b are already shielded by the flags 9a and 9b at the start of the above operation.

Here, the control when the A4 size recording medium is laterally fed will be described. A4 length in the feed direction is 21
The recording length is 205 mm because the margins are set to 2.5 mm for each of the front and rear edges. Therefore, the record is 1
Approximately 195.1m for each line width of 16.256mm for 12 lines from line 2 to line 13 for 9.9mm half length
Record in m. The pulse motors 6a and 6b for driving the carry roller 1 and the discharge roller 3 have the number of pulses (1218 pulses) corresponding to the recording amount of the first line, that is, the feeding amount of the first line.
However, it is reversely rotated (reverse to the transport direction), stopped, excited, and held at the stop position.

Incidentally, when the A4 size recording medium is fed longitudinally, the length of the A4R in the feeding direction is 297 mm, and the margins are set to 2.5 mm for each of the leading and trailing edges, so the recording length is It is 292 mm. Therefore, the recording is performed by recording about 15.6 mm for the half end on the 1st line and 17 lines from the 2nd to 18th lines with a total of about 276.4 mm for each head width of 16.256 mm. The pulse motors 6a and 6b for driving the motor are reversely rotated (reverse direction to the conveying direction) by the number of pulses (1919 pulses) corresponding to the recording amount of the first line, that is, the feeding amount of the first line, and are stopped, and are excited. It is held at its stop position.

By the above operation, the relative displacement of the conveyance roller shaft before the first conveyance of the recording medium with respect to the recording medium is controlled to be the same.

In FIG. 2, the leading end of the recording medium fed from the cassette 19 by the feeding device 20 shields the timing sensor 33 from light. Conveyor roller 1 at that time
Starts rotating, holds the recording medium, and conveys it to the image forming start position of the first line.

By performing the above-described operation at the start of image formation for each recording medium, the relationship between the image forming position on the recording medium and the rotational displacement of the transport roller 1 is always constant.

Now, the leading end of the recording medium is the pair of conveying rollers 1,
When it is sandwiched by two and reaches the image forming start position of the first line, the carriage 14 carrying the recording heads 13C, 13M, 13Y, 13B scans on the guide rails 15a, 15b, and the image of the first line is formed on the recording medium. Form.

Next, the CPU 17 sends a control signal to a motor driver (not shown) based on the information on the number of drive pulses of the first line stored in the memory device 18 in advance to drive the pulse motor 6a. The transport roller 1 is the conductive belt 8
The recording medium is conveyed by an amount equal to the recording width of one line by rotating about 1/3 through a or the like.

The above-described operation is repeated, and the recording medium on which the recording of the second line has been completed is conveyed by the conveying roller 1. After this time, the discharging roller 3 is also driven when the recording medium is conveyed. Then, the leading end of the recording medium reaches the ejection roller 3 and is nipped by the ejection roller pair 3 and 4. That is, also in the discharge roller 3, the relationship between the position where the image is formed on the recording medium and the rotational displacement thereof is constant for each recording medium.

After that, the above operation is repeated to form an image for each line. However, in order to prevent the recording medium from floating on the platen 11 and wrinkles, the number of driving pulses of the discharge roller 3 is increased. Is set to be slightly larger than the number of drive pulses of the conveyance roller 1 (in this embodiment, the conveyance amount is increased by about 2%).

The rotation amounts of the carrying roller 1 and the discharging roller 3 for each line are sent by the CPU 17 to a motor driver (not shown) based on the driving pulse information stored in the memory device 18 in advance, and the respective rollers 1 , 3 are controlled by pulse motors 6a and 6b.

The above operation is repeated, and after the time when the trailing edge of the recording medium is conveyed out of the conveying roller 1, the discharge roller 3 is set to have a slightly larger conveying amount. Approximately 1/3 until the image formation on the rear edge of the
The recording medium is conveyed by rotating each rotation. The recording medium for which image formation has been completed is discharged onto a discharge tray outside the apparatus by the pair of exit rollers 21 in FIG.

The above is the operation when an image is actually formed by this apparatus, and the procedure for determining the number of drive pulses of the pulse motor for each line will be described below.

When the assembly of the apparatus is completed, for example, in the final step of the manufacturing process, the apparatus actually outputs an image in the above procedure. The image pattern to be output is preferably a grid-like continuous pattern, for example, in order to measure the carry amount of the recording medium with a monochromatic image. The data of this recording pattern is stored in the device as a ROM in advance.

The drive pulses input to the drive motors (pulse motors 6a and 6b) for driving the transport roller 1 and the discharge roller 3 for each line are initially stored in the number of pulses (2000 pulses) corresponding to one rotation of the motor. Has been done. As described above, in this apparatus, when each motor drive shaft makes one rotation, the transport roller 1 and the discharge roller 3 each rotate 1/3, and the transport amount of the recording medium at that time is calculated, It becomes equal to the recording width.

Regarding the discharge roller 3, when the trailing edge of the recording medium is sandwiched between the pair of transport rollers 1 and 2, in the initial state, the transport amount of the discharge roller 3 is increased by about 2% of that of the transport roller 1. From the time of feeding when the trailing edge of the recording medium passes through the pair of conveying rollers 1 and 2, it is calculated and driven by a conveying amount equal to the width of the recording head (see FIG. 5).

In this state, a grid pattern is recorded on the entire area of the recording medium, and the amount of conveyance of the recording medium for each line is measured from the pitch of the lattice pattern using a reading device or the like. The measured feed amount for each line is affected by the runout of the transport roller 1, the discharge roller 3, or the pulleys 5a and 5b pressed into the roller ends, or the leading end of the recording medium enters the nip portion of the discharge roller pair 3 and 4. Due to the influence of the movement of the recording medium and the trailing edge of the recording medium coming out of the nip portion of the pair of conveying rollers 1 and 2, it is not actually constant.

However, when the image formation is performed by the above procedure, the relative rotational displacements of the transport roller 1 and the discharge roller 3 with respect to the apparatus at the start of image formation for each recording medium are always the same. Therefore, the influence of the runout of the transport roller 1 and the discharge roller 3 and the influence of the recording medium when the recording medium plunges into and out of the nip portion of the roller pair appear similarly for each recording medium, and as described above, the pulse motors 6a and 6b. The runout of the motor pulleys 7a and 7b attached to the recording medium does not affect the conveyance amount of the recording medium because the circumferential length is equal to the recording width.

The dotted and broken lines shown in FIG. 5C represent the upper and lower limit data of the feed amount of the recording medium of each line when the measurement is performed on the samples of 10 recording mediums in the above state. For the above-mentioned reason, the carry amount of the recording medium for each line is very small. Therefore, it is possible to measure the conveyance amount of the recording medium for each line with high accuracy by measuring only one recording sample.

As described above, in this apparatus, the pulse motors 6a and 6b have a basic step angle of about 0.18 °, and the conveying roller 1 and the discharging roller 3 have a circumferential length of 3 as the recording width.
It is equal to double and is driven from the motor at a reduction ratio of 1/3.
Therefore, one pulse input to the pulse motors 6a and 6b corresponds to 8.128 μm in terms of the carry amount of the recording medium.

Based on the carry amount of the recording medium for each line measured according to the above procedure, in order to obtain the desired carry amount of the recording medium, the number of driving pulses for each line in the initial state is increased or decreased, The number of drive pulses for each line is stored in the memory device 18.

According to the present embodiment, the conveyance amount of the recording medium is controlled by the conveyance roller 1 until the trailing edge of the recording medium passes through the conveyance roller pair 1 and 2, and the rear end of the recording medium is conveyed by the conveyance roller pair 1. , 2, the conveyance amount of the recording medium is controlled by both the conveyance roller 1 and the discharge roller 3, and the conveyance amount of the recording medium is controlled only by the discharge roller 3 in the subsequent feeding times.

Therefore, in order to increase or decrease the carry amount of the recording medium on the 1st to 9th lines, the driving pulse number input to the pulse motor 6a for driving the carry roller 1 is set to the carry amount of the recording medium on the 10th line. Pulse motor 6 to increase / decrease
With respect to the number of drive pulses input to both a and 6b, the number of drive pulses input to the pulse motor 6b for driving the discharge roller 3 is increased or decreased after the 11th to 12th lines.

FIG. 6 shows the number of drive pulses of the carry roller 1 and the discharge roller 3 for realizing a constant carry amount, and the carry amount of the recording medium at that time. The dotted and broken lines in FIG. 6 indicate the upper and lower limits of the carry amount for each line of the recording medium when 10 sheets of the recording medium are carried in the above state. As shown in FIG. 6, the transport amount of the recording medium for each line remains within ± 10 μm or less from the target value over the entire area of the recording medium. That is,
This device, which stores the number of drive pulses of each motor 6a, 6b for each line in the memory device 18 according to the above-described procedure, can always realize a desired transport amount of the recording medium when the consumer uses it in the market. It is possible.

As described above, in this embodiment, it is possible to intermittently and highly accurately convey the recording medium from the front end to the rear end with a width equal to the recording width. Therefore, it is possible to output a high-quality image over the entire area of the recording medium while minimizing the margins at the leading and trailing edges of the image.

FIG. 10 shows the carry amount of the recording medium for each line when the recording medium is carried by the apparatus having the configuration shown in FIG. 4 without applying the present invention. Despite the use of parts processed with extremely high precision (the eccentricity of the transport roller and the discharge roller is about 10 μm and the eccentricity of each pulley press-fitted to the end of the roller is about 10 μm), Since the influence of the eccentricity of the parts appears different each time, the variation of the recording medium on the same line reaches ± 20 μm as shown in FIG. Further, in the vicinity of 10 lines shown in FIG. 10, the conveyance amount of the recording medium is affected by the fact that the pair of rollers for conveying the recording medium is only the discharge roller pair and the influence of the conveyance resistance change due to the suction at the platen portion. The average value is significantly reduced, and the value reaches about 50 μm at worst.

[Second Embodiment] In the first embodiment, the rotational displacements of the conveying roller and the pulse motor output shaft at the start of image formation are made the same for each recording medium, but this embodiment will be described below. In the example, not only the conveying roller and the pulse motor output shaft at the start of image formation but also their relative displacements including the transmission means are made the same for each recording medium.

FIG. 7 is a schematic diagram showing the second embodiment of the present invention. The parts having the same functions as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Further, the apparatus configuration and the operation at the time of image formation are substantially the same as those in the above-described first embodiment, but in this embodiment, the conveyance roller 1, the discharge roller 3 and the pulse motors 6a and 6b are set for each recording medium before the start of recording. In order to return not only the initial state of the belts 8a and 8b, but also the transmission belts 8a and 8b, which are the drive transmission means, to the initial state, detection means for detecting the positions of the belts 8a and 8b are provided. In the following, since the drive unit of the transport roller and the drive unit of the discharge roller are exactly the same, only the drive unit of the transport roller will be described.

The device is set so that the number of teeth of the motor pulley 7a and the roller pulley 5a is an integer ratio, and the number of teeth of the roller pulley 5a and the transmission belt 8a is an integer ratio. The transmission belt 8a is provided with slit-shaped notches outside the range of meshing with the pulleys 5a and 7a. After the image formation is completed and the recording medium is discharged to the outside of the apparatus, the pulse motor 6a continues to rotate, and when the cutout portion of the transmission belt 8a reaches the position of the photointerrupter 10c provided on the main body side, the photointerrupter 10c The shading is released, CPU
A drive pulse stop signal is sent from 17 (see FIG. 2) to a motor driver (not shown) to stop the drive. As a result, the drive unit of the transport roller 1 returns to the initial state before image formation.

Here, the control when the A4 size recording medium is laterally fed will be described. A4 length in the feed direction is 21
The recording length is 205 mm because the margins are set to 2.5 mm for each of the front and rear edges. Therefore, the record is 1
Approximately 195.1m for each line width of 16.256mm for 12 lines from line 2 to line 13 for 9.9mm half length
Record in m. The pulse motors 6a and 6b for driving the carry roller 1 and the discharge roller 3 have the number of pulses (1218 pulses) corresponding to the recording amount of the first line, that is, the feeding amount of the first line.
However, it is reversely rotated (reverse to the transport direction), stopped, excited, and held at the stop position.

Incidentally, when the A4 size recording medium is vertically fed, the length of the A4R in the feeding direction is 297 mm, and the margins are set to 2.5 mm at each of the front and rear ends, so the recording length is It is 292 mm. Therefore, the recording is performed by recording about 15.6 mm for the half end on the 1st line and 17 lines from the 2nd to 18th lines with a total of about 276.4 mm for each head width of 16.256 mm. The pulse motors 6a and 6b for driving the motor are reversely rotated (reverse direction to the conveying direction) by the number of pulses (1919 pulses) corresponding to the recording amount of the first line, that is, the feeding amount of the first line, and are stopped, and are excited. It is held at its stop position.

By the above operation, the relative displacement of the transport roller shaft before the first transport of the recording medium with respect to the recording medium is controlled to be the same.

As described above, only by providing the detection means (photointerrupter 10c) for detecting the position of the transmission belt 8a (and the transmission belt 8b), which is the drive transmission means, the drive unit of the conveyance system for conveying the recording medium. Since it is possible to return the whole to the initial state before recording, the reproducibility of the carry amount for each recording is further improved, and by using it together with the correction of the motor drive pulse number shown in the first embodiment described above. The transport accuracy of the recording medium is further improved.

Further, when the number of teeth of the belt and the pulley cannot be set to an integer ratio due to the problem of the device configuration, etc., the above-mentioned first
The flag 9 and the photo interrupter 10 shown in the embodiment,
By using the belt position detecting means in combination, the same effect as described above can be obtained.

[Third Embodiment] Next, a third embodiment of the present invention for achieving the same object as the above embodiment will be described. As shown in FIG. 8, the structure of the apparatus and the process steps of image formation are substantially the same as those described in the above embodiment.

A method for keeping the relative displacements of the conveying roller, the transmission belt, and the pulse motor output shaft constant in preparation for the next image formation on the recording medium after the image formation is described below.

In this apparatus, a counter (not shown) for counting the drive pulses input to the pulse motor 6a
Is provided. This counter increments when a drive pulse in the direction in which the pulse motor 6a rotates during image formation is input, and subtracts when a drive pulse in the direction opposite to the rotation direction is input. Then, the state before image formation is set to 0, and the number of pulses is accumulated by the counter according to the number of drive pulses input during image formation, and the value is stored in the memory at the same time.

After the image formation is completed, the pulse motor 6a is driven in the opposite direction to that when the recording medium is conveyed until the total number of drive pulses stored in the memory (not shown) becomes zero.

In this example, the number of drive pulses measured by the counter is always stored in the memory, and the contents of the memory are retained even when the power is cut off. Further, when the power is cut off, the supply voltage of the solenoid 22a is cut off at the same time, and the leaf spring 23a operates to restrain the rotational displacement of the pulse motor 6a. Further, when the paper jam is cleared, the transport roller 1
By releasing the driven roller 2 for urging, it is possible to deal with it without displacing the conveying roller 1, the transmission belt 8a, the pulse motor 6a, and the like.

When the power is turned on again, the final number of drive pulses stored in the memory is referred to until the state where the total number of drive pulses becomes 0 (the origin of the pulse motor),
The pulse motor 6a is driven.

A similar method is applied to the discharge roller side (solenoid 22
b, the leaf spring 23b), the roller pulley 5a press-fitted at the end of the conveying roller, the roller pulley 5b press-fitted at the end of the discharge roller, and the transmission belt 8 for driving each.
a, 8b, and the motor pulleys 7a, 7b attached to the pulse motors 6a, 6b, even if the number of teeth of each of the motor pulleys 7a, 7b does not maintain an integer multiple relationship, when performing the image formation of the next recording medium, the previous image formation is performed. It is possible to maintain the same relative displacements of the output shafts of the transport roller 1, the discharge roller 3, the transmission belts 8a and 8b, and the pulse motors 6a and 6b at the start.

[Fourth Embodiment] Next, a fourth embodiment of the present invention will be described. In the first embodiment, the operation for actually forming an image and the fact that it is necessary to determine the number of drive pulses of the pulse motor for each line have been described, but in the present embodiment, the number of drive pulses is determined. An example of the procedure at that time is shown. The image forming operation is the same as in the first embodiment.

The present embodiment is applied to an image forming apparatus such as a copying machine or a facsimile equipped with a reading device for reading image information, or an image forming device to which the above reading device is connected via a personal computer or the like.

First, the copy recording operation of the copying machine using the ink jet system according to this embodiment will be described. FIG.
FIG. 6 is a schematic diagram showing a fourth embodiment of the present invention. First, the reading device will be described.

In FIG. 9, reference numeral 24 is a reader carriage on which a CCD sensor 25, an optical system (not shown), an illumination system (not shown), a printed circuit board (not shown), etc. are mounted. The drive of the motor 27, which is a drive source, is transmitted to the reader carriage 24 by the drive belt 26 and scans the two rails 28a and 28b to read an image having the same or slightly larger number of pixels than the recording head 13. Next, the rail base 29 is driven by the motor 31 via the drive transmission wire 30, and the rail 32a,
The image is read on the next line by moving along the line 32b in the direction perpendicular to the scanning direction of the reader carriage 24 by the recording width. Based on the read information, the image forming section records on the recording medium line by line. By repeating this operation, copy recording of the document is performed. The details of the image forming method in the image forming unit are the same as those in the first embodiment described above, and therefore the description thereof is omitted.

A procedure for determining the number of drive pulses of the pulse motor for each line will be described. Similar to the first embodiment,
In order to measure the carry amount of the recording medium, a continuous pattern, for example, a grid pattern of a monochromatic image, which is stored in a ROM in the apparatus and is stored in advance, is recorded. The recording medium on which this pattern is recorded is set on the mounting table (not shown) of the reading device so that the recording direction on the recording medium and the reading direction of the image by the reading device are orthogonal to each other. Then, the reader carriage 24 is scanned once at the central portion of the recording medium in accordance with the transport amount measurement sequence stored in ROM in advance and the grid pattern is read. At this time, it is desirable that the scanning speed be slower than that at the time of normal reading, and that the reading be performed as accurately as possible.

The read information is analyzed in the image processing section to determine the carry amount of each line. Further, the difference between the measured carry amount and the desired carry amount is converted into the number of drive pulses of the pulse motor, the drive pulse correction value for each line is determined, and stored in a nonvolatile memory as a table. Keep it. After that, when printing is performed, the CPU sends a control signal to the motor driver based on the information in this table to control the drive pulse of the pulse motor that drives each roller.

The above operation is performed, for example, at the time of shipment from the factory.
Alternatively, the operation is performed once when the apparatus is installed, and thereafter, when it becomes necessary to replace a component of the transport system such as the transport roller, the above operation is performed again after the replacement. As a result, the table on the memory storing the number of drive pulses is rewritten, and the recording medium can be conveyed again by a desired amount. Further, it is possible to cope with a change with time such as wear of the roller.

[0069]

As described above, the relative displacement of the conveyance roller shaft before the first conveyance of the recording medium is controlled to be the same, and the number of pulses stored in the memory device as the storage means is controlled. By inputting (corresponding to the number of lines for conveying the recording medium when the conveying roller makes one rotation) to the pulse motor to convey the recording medium intermittently It is possible to always match the conveyance amount of the recording medium for each line with a predetermined recording width of the recording head with high accuracy, and at a low cost and without using a complicated mechanism, it is possible to obtain high-quality images without black stripes, white stripes, or the like. A recorded image can be obtained.

Further, in the present invention, since the relative displacement of the conveyance roller shaft before the first conveyance of the recording medium with respect to the recording medium is controlled to be the same, regardless of the size of the recording medium or the size of the image, The above effect can be obtained.

Further, if the present invention is applied, the conveyance precision of the recording medium does not depend on the machining precision of the motor, the pulley attached to the roller end, the conveyance roller, etc., so that the manufacturing cost of those parts is greatly reduced. can do.

Further, by providing an image reading device to read an output image of a specific pattern, recognize the optimum number of conveyance pulses, and store them, it is possible to prevent the conveyance accuracy from deteriorating due to a change with time of the rollers and the like.

[Brief description of drawings]

FIG. 1 is a perspective view of an image forming unit of an image forming apparatus to which the present invention is applied.

FIG. 2 is a main sectional view of an image forming apparatus to which the present invention is applied.

FIG. 3 is a diagram showing rollers that control a conveyance amount of a recording medium for each line of an image forming apparatus to which the present invention is applied.

FIG. 4 is a diagram showing a dimensional relationship of an image forming unit of an image forming apparatus to which the present invention is applied.

FIG. 5 is a diagram showing the number of drive pulses of the motor for each line and the carry amount of the recording medium at that time in the initial state of the image forming apparatus to which the present invention is applied.

FIG. 6 is a diagram showing the number of drive pulses of the motor for each line and the carry amount of the recording medium at that time when the image forming apparatus to which the present invention is applied is actually used.

FIG. 7 is a perspective view of an image forming unit of an image forming apparatus according to a second embodiment of the present invention.

FIG. 8 is a perspective view of an image forming unit of an image forming apparatus according to a third exemplary embodiment of the present invention.

FIG. 9 is a schematic diagram of an image reading apparatus of an image forming apparatus according to a fourth exemplary embodiment of the present invention.

FIG. 10 is a diagram showing an example of the conveyance amount of the recording medium for each line when the present invention is not applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Conveyor roller 2, 4 ... Followed roller 3 ... Ejection roller 5a, 5b ... Roller pulley 6a, 6b ... Pulse motor 7a, 7b ... Motor pulley 8a, 8b ... Transmission belt 9a, 9b ... Flag 10a, 10b, 10c ... Photointerrupter 11 ... Platen 12 ... Suction blower 13 ... Recording head 14 ... Carriage 15a, 15b ... Guide rail 16 ... Carriage drive belt 17 ... CPU 18 ... Memory device 19 ... Cassette 20 ... Feeding device 21 ... Exit roller pair 22a, 22b ... Solenoid 23a , 23b ... Leaf spring 24 ... Reader carriage 25 ... CCD sensor 26 ... Drive belt 27 ... Motor 28a, 28b ... Rail 29 ... Rail base 30 ... Drive transmission wire 31 ... Motor 32a, 32b ... Rail 33 ... Timing sensor

Claims (6)

[Claims] 1. An image forming apparatus for intermittently conveying a recording medium to form an image on a line-by-line basis, wherein at least one roller pair including a driving roller and a driven roller, and a pulse motor for driving the driving roller. ,
A transporting unit that transports the drive from the pulse motor to the drive roller and transports the recording medium in the image forming unit; and an image depending on the length of the recording medium or the length of the image to be recorded. Control means for controlling the rotational displacement of the drive roller before the start of formation, and storage means for storing the number of pulses input to the pulse motor in correspondence with the number of lines that convey the recording medium when the drive roller makes one rotation, The recording medium is controlled so that the relative displacement of the drive roller shaft before the first conveyance of the recording medium with respect to the recording medium is the same, and the number of pulses stored in the storage means is input to the pulse motor. An image forming apparatus, wherein the image forming apparatus is configured to be intermittently conveyed. 2. The image forming apparatus according to claim 1, wherein the driving of the driving roller is controlled so that half-finished image recording is performed on the first line. 3. The image forming apparatus according to claim 1, wherein the speed reduction ratio or the speed increase ratio between the pulse motor and the driving roller when transporting the recording medium is an integer. 4. The detection means for detecting when at least one of the drive roller, the transmission means, and the output shaft of the pulse motor is in a specific rotational displacement, the detection means is provided. Image forming device. 5. The pulse motor for driving the driving roller, wherein the conveying unit has at least one pair of rollers, which are a driving roller and a driven roller, on an upstream side and a downstream side of a recording position in the image forming unit. The image forming apparatus according to claim 1, further comprising: a transmission unit that transmits a drive from the pulse motor to the drive roller. 6. The image forming apparatus includes an image reading device, which reads an output image of a specific pattern and measures a carry amount of a recording medium for each line at the time of image formation, and obtains a difference between the carry amount and a print width. The image forming apparatus according to claim 1, wherein the number of pulses input to the pulse motor is increased / decreased in accordance therewith, and the value is stored.