JPH09216749A - Sheet carrying device and recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the accuracy of a sheet feeding amount without raising the machining accuracy (outer diameter error, off-centered amount) of a carrying roller and a pulley for transmitting the drive to the carrying roller especially. SOLUTION: A carrying roller 1 feeds a record sheet S by every prescribed amount intermittently step by step onto a platen 11. A joint is generated on a record image when the sheet feeding amount of the roller 1 is not matched with the record width of a recording head by the outer diameter error of the roller 1 and the eccentricity of the roller 1 and pulley 5a. Here, the sheet feeding amount of the roller 1 is corrected as follows based on the data of the error and eccentricity. A correction roller 20 which can change a position for strengthening the tension of a belt 8a to a position for weakening is provided on the tension side of the belt 8a for transmitting the drive of a stepping motor 6a to the pulley 5a on the shaft of the roller 1 When the data concept shows a plus correction (a few feeding amount), the tension of the belt 8a is strengthened by the correction roller 20 and when the data concept shows a minus correction (a lot of feeding amount), the tension of the belt 8a is weakened by the correction roller 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus provided in a recording apparatus or the like for recording an image on a recording sheet which is intermittently stepwise conveyed by a predetermined amount.

[0002]

2. Description of the Related Art Various recording systems such as an ink jet system and a thermal transfer system are adopted in a recording apparatus for recording by recording means on recording sheets fed one by one.

FIG. 17 shows the construction of a recording section of a conventional recording apparatus (printer) for recording an image on a recording sheet by serially scanning an inkjet recording head.

Reference numeral 1 is a conveying roller arranged upstream of the recording section, and 3 is a driven roller for urging the recording sheet S toward the conveying roller 1. Reference numeral 2 is a paper discharge roller arranged on the downstream side of the recording portion, and 4 is a driven roller for urging the recording sheet S toward the paper discharge roller 2.

A recording sheet S moving on the platen 11.
Are intermittently stepped by a predetermined width by the transport roller 1. Then, when the recording sheet S is stopped, the recording head 13 mounted on the carriage 14 and serially scanned performs recording with a predetermined width (X).

In the case of this ink jet system, the recording sheet S expands when ink is contained in the recording portion. Therefore, when the recording sheet S is conveyed in the recording unit, it is necessary to consider the elongation due to the ink.

Therefore, the following measures are taken here. That is, (1) By setting the ratio (P1: P2) of the urging pressure (P1) of the driven roller 3 on the transport side and the urging pressure (P2) of the driven roller 4 on the paper discharge side to about 4: 1. ,
Even when the recording sheet S is held between the rollers 1 and 2, the amount of conveyance of the recording sheet S depends on the side of the conveying roller 1. (2) The carry amount of the discharge roller 2 is set to be larger than the carry amount of the carry roller 1.

Since this is done, the paper discharge roller 2 will carry the recording sheet S while slipping,
A recording sheet S containing ink between both rollers 1 and 2.
There will be no floating or slack.

When the recording sheet S is held only by one roller, the amount of conveyance of the recording sheet S depends only on that roller.

The carriage 14 reciprocates once, and the recording head 1
3 records an image with a width of X, the conveying roller 1 conveys the recording sheet S by a distance equal to the recording width (X),
Prepare for the next record. By repeating this operation, images are sequentially recorded on the recording sheet S.

In order to print a seamless image on the recording sheet S, the carry amount of the recording sheet S must be equal to the recording width (X) of the recording head 13. Here, the outer circumference of the transport roller 1 is 3X (3
Double) and rotate the roller 1 by 120 degrees,
A method of feeding the recording sheet S by the same distance X as the recording width is adopted.

From the experience, the next inconspicuous recording sheet S
The accuracy of the feed amount is 1 of the inkjet nozzle pitch.
/ 2 or less. Therefore, for example, when the nozzle pitch is 63.5 μm (400 DPI), ± 31.
Accuracy of 7 μm or less is required.

[0013]

However, even if the conveyance amount of the recording sheet S is made equal to the recording width (X) of the recording head 13 by the above-described method, the accuracy of the feeding amount of the recording sheet S is improved. There are various factors that reduce the image quality, and the reality is that the image has a stitch. The main factors that affect the accuracy of the feed amount of the recording sheet S are listed below. (1) Since the outer diameter accuracy of the transport roller 1 varies by about ± 10 μm, the outer diameter of the transport roller 1 is ± 31.4 μm.
Changes, and as a result, the feeding amount of the recording sheet S is ± 1.
An error of 0.5 μm occurs. (2) An eccentricity of about 15 μm occurs in the pulley that drives the conveying roller 1. The diameter ratio of the pulley and the roller has less effect on the feed amount, but if the phase where the effect of eccentricity is the largest is used, the error of the feed amount becomes ± 8.7 μm. (3) The transport roller 1 is eccentric about 7.5 μm, and the error of the feed amount is ± 13 μm at maximum. (4) The feed amount varies by about ± 10 μm depending on the width, thickness and material of the recording sheet S being conveyed.

Even if only the above factors (1) to (4) are summed up, the error of the feed amount becomes ± 42.2 μm, and the target is exceeded by simply rotating the conveying roller 1 by 120 degrees accurately. Will end up.

The above-mentioned problem can be solved by increasing the processing accuracy of the conveying roller 1 or the like, but since the numerical values of the errors of the above (1) to (4) are close to the limit of the processing accuracy, a higher accuracy is required. However, it causes a significant cost increase and is not a realistic countermeasure.

Therefore, conventionally, the following method has been adopted as a measure for increasing the accuracy of the feed amount. That is, a test print is performed at the time of completion of the recording device in the factory, the feed correction amount obtained by analyzing the data is stored in the device, and the feed amount is increased by increasing or decreasing the number of steps of the stepping motor that drives the conveyance roller 1. Correcting.

According to this method, the accuracy of the feed amount can be improved without extremely improving the processing accuracy of the conveying roller 1 and the like. However, for example, if it is attempted to correct a recording width of 32.512 mm of a 512 nozzle head with a pitch of 63.5 μm in 20 μm steps, the pulse of the stepping motor is 1626.
It takes a pulse, and if it is attempted to finish the conveyance of the recording sheet S in about 0.2 seconds in order to increase the speed, one rotation is 1000
It is necessary to drive the pulse stepping motor at 8 KHz. Therefore, it is necessary to use a 5-phase stepping motor, and it is inevitable that the recording apparatus becomes large. Also,
The motor and motor driver are also expensive.

Therefore, the present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a sheet conveying apparatus capable of improving the accuracy of the sheet feeding amount without particularly improving the processing accuracy of the conveying roller and the like. To aim.

[0019]

The present invention relates to a sheet conveying apparatus for intermittently stepwise feeding a sheet by a predetermined amount by a pair of conveying rollers.

In order to achieve the above object, the present invention corrects the sheet conveying amount of the pair of conveying rollers one by one, and a control for controlling the correcting means based on the correction data. And means.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 shows the overall configuration of an inkjet recording apparatus including a sheet conveying apparatus to which the present invention is applied. Further, FIG. 2 shows a detailed configuration of a recording unit of the recording apparatus. The sheet conveying device of the present invention is used for this recording unit.

In FIG. 2, reference numeral 1 is a conveying roller arranged on the upstream side of the recording section, and 3 is a conveying roller 1 on which a recording sheet S is attached.
It is a driven roller for urging. Reference numeral 2 is a paper discharge roller arranged on the downstream side of the recording portion, and 4 is a driven roller for urging the recording sheet S toward the paper discharge roller 2.

Here, the ratio (P1: P2) of the urging pressure (P1) of the driven roller 3 on the conveying side and the urging pressure (P2) of the driven roller 4 on the paper discharging side is set to about 4: 1. There is. By doing so, the carry amount of the recording sheet S depends on the carry roller 1 side. Further, the carry amount of the discharge roller 2 is equal to that of the carry roller 1.
It is set to be larger than the carry amount of. As a result, the paper discharge roller 2 conveys the recording sheet S while slipping, so that the recording sheet S is interposed between the rollers 1 and 2.
There is no floating or sagging.

Pulleys 5a and 5b are press-fitted at one ends of the transport roller 1 and the paper discharge roller 2, respectively.
Is driven by a pulse motor 6a via a motor pulley 7a and a transmission belt (timing belt) 8a. The pulley 5b is driven by a pulse motor 6b via a motor pulley 7b and a transmission belt (timing belt) 8b.

Pulse motors 6a, 6 used here
Since b is driving the PM type stepping motor having a basic step angle of 7.5 ° by half step driving, the pulleys 5a and 5b rotate once by 96 pulse step driving.

The ratio of the number of teeth of the motor pulleys 7a and 7b (same number of teeth) to the number of teeth of the pulleys 5a and 5b (same number of teeth) is 1: 3.
Since the outer circumference of the transport roller 1 is three times the recording width (X), the recording sheet S is fed by the recording width (X) when the motor 6a makes one rotation, and 96 × 3.
The driving of 1 pulse of 288 pulses causes the transport roller 1 to rotate once.

Further, the outer peripheral length of the discharge roller 2 is set to be 2% longer than the outer peripheral length of the conveying roller 1, and this difference is the slip amount.

Reference numeral 11 is a platen for supporting the recording sheet S in the printing section, and 13 is an ink jet recording head. Since this recording head 13 performs full-color printing,
Recording heads 13C, 13M, 13Y, and 13Bk of four colors of cyan, magenta, yellow, and black are arranged in parallel in the scanning direction of the recording heads, and 512 nozzles are arranged in one row for each color at a pitch of 400 DPI (63.5 μm). Ink is ejected from.

The recording head 13 is mounted on the carriage 14, and scans the guide rails 15a and 15b in the directions of arrows B1 and B2, and the recording sheet S has a maximum length in the conveying direction (maximum recording width). 0.0635 × 512 = 32.51
Record 2 mm. Each time recording on one line is completed, the recording sheet S is conveyed in the direction of arrow A by a distance equal to the recording width, and this operation is repeated to record an image on the recording sheet S.
Since the motor 6a sends the maximum recording width in 96 pulses, the carry amount for one pulse is 0.339 mm.

The carriage 14 is driven via a pulse motor and a drive belt (not shown).

In FIG. 1, reference numeral 17 is a CPU (central processing unit) as a control means for controlling the drive of the pulse motors, the drive head 13, the conveyance amount correction mechanism, and the like, and 38
Is a memory means for storing data relating to the carry amount correction. The memory means 38 is a non-volatile element.

The recording sheets S are separated one by one from one of the cassettes 18 by the pickup roller 19, are conveyed by the roller pairs 32 and 12, and are conveyed by a predetermined amount after the leading edge of the sensor 10 is detected, and the rotation is stopped. Abutting on the nip portion 34 of the transport roller 1 and the driven roller 3,
After that, the roller pairs 32 and 12 are also stopped to prepare for image recording. When the recording operation starts, the transport roller 1 rotates, and the recording sheet S is sent to the recording position.
Since the clamping force is smaller than that of the transport roller 1, it does not affect the transport amount. Incidentally, the recording sheet S for which recording has been completed is discharged onto the tray 33.

Since the transport roller 1 and the pulley 5a have processing errors as described above, the following configuration is used to correct them.

As shown in FIG. 3, the tension roller 23 is urged by the coil spring 25 via the tension arm 24 on the loose side of the belt 8a for driving the conveying roller 1. On the other hand, on the tight side, the stepping motor 2
When the cam follower 22 follows the cam 26 rotated by 7, the pushing amount of the correction roller 20 to the belt 8a via the arm 21 is changed.

When the correction roller 20 is displaced in the direction away from the belt 8a (direction of arrow C), the tension of the belt 8a is weakened. At this time, when the motor pulley 7a is rotated in the carrying direction, the pulley 5a is delayed in rotation due to the looseness of the belt 8a, and the carrying amount of the carrying roller 1 is reduced.

When the correction roller 20 is displaced in the direction in which the belt 8a is pushed in (the direction of arrow D), the tension of the belt 8a is strengthened, so that both the pulley 5a and the motor pulley 7a receive a rotational force. At this time, the pulley 5a having a larger radius has a larger rotational moment (three times in this case), and the motor pulley 7a receives resistance due to the detent torque or the exciting torque of the motor 6a.
a does not rotate, only the pulley 5a rotates slightly in the carrying direction, and as a result, the carrying amount of the carrying roller 1 increases.

From the above description, it is apparent that the displacement of the correction roller 20 can correct the transport amount of the transport roller 1.

Although the motor pulley 7a is rotated after the displacement of the correction roller 20 to correct the conveyance amount of the recording sheet S here, the correction roller 20 is rotated during the rotation of the motor pulley 7a.
May be displaced. In addition, the discrepancy in the rotation amounts of the motor pulley 7a and the pulley 5a is caused by the tension roller 2 on the loosening side.
Absorbed by a displacement of 3.

In this configuration, there is such a dimensional relationship that the carry amount can be adjusted by about 0.4 mm by the displacement of the correction roller 20 by 6 mm. Also,
The profile of the cam 26 is formed so that the rotation amount of the cam 26 and the correction amount of the carry amount have a linear relationship.
To describe the profile of the cam 26 in FIG. 3, the profile is a curve starting at a point 90 ° clockwise from the end of the tab 30 and continuing to increase the radius R up to 180 ° counterclockwise.

The stepping motor 27 is a PM type motor of 48 pulses per rotation, and the amount of correction of the carry amount is 2 pulses per pulse.
Since the setting is 0 μm, the cam 26 has half a revolution of 24 pulses,
Correction up to a cumulative 0.48 mm is possible. This is because the roller 1 sent by a low-precision motor having a feed amount of 0.339 mm per pulse is corrected by a correction means using a low-precision motor in units of 20 μm.
This means obtaining a feed accuracy of ± 10 μm.

As described in the conventional example, the main factors that cause the feed amount error are as follows. (1) Outer Diameter Accuracy of Conveyor Roller 1 (2) Eccentricity of Pulley 5a (3) Eccentricity of Conveyor Roller 1 (4) Properties, Size, and Thickness of Recording Sheet S Here, among these, (1), The factors (2) and (3) are collectively corrected, and a specific correction method will be described below. <Error measuring operation> First, the pulley 5a is pressed into the transport roller 1 and rotated in an assembly state, and the diameter and eccentricity of the roller 1 and the eccentricity of the pulley 5a are measured. From this data, the diameter error of the roller 1 and the amount and phase of the combined eccentricity of the pulley 5a and the roller 1 when the pulley 5a was rotated by the belt 8a were calculated, and as shown in FIG. 6 °
With respect to the pulley 5a having holes 36 formed therein, holes 3 having a specific angle from the position serving as a reference for the phase of the eccentricity of the roller 1 are formed.
The tab 28 shown in FIG.

The feed amount due to the rotation of the roller 1 due to the combined eccentricity can be approximated with a simple sine curve with no problem.

As shown in FIG. 6, an annular shallow groove 35 is formed on the side surface of the pulley 5a, and a hole 3 is formed in the groove 35.
Sixty six are opened at a pitch of 6 °. The tab 28 has a pin 37, and when the pin 37 is fitted into the hole 36, the main body of the tab 28 is also housed in the groove 35. Since the diameter of the pin 37 is slightly larger than the diameter of the hole 36, the inserted tab 28 cannot be removed.

Here, the line Y connecting the virtual center of the roller 1 and the center of rotation passes through the roller phase detection sensor 29 (FIG. 3) on the side where the radius of rotation increases due to the combined eccentricity. Sometimes the tab 28 is inserted at a position where a signal is generated.

Since the position where this signal is generated represents the point where the positive feed error becomes maximum, the reference of the phase is 0 °.
Although the positional accuracy of the tab 28 is ± 3 °, this is an amount that can be ignored for correcting the influence of eccentricity.

With this work, the diameter error d1 of the roller 1
Tab 2 that represents the combined eccentricity amount d2 and the 0 ° phase of the combined eccentricity
8 is obtained. Here, d1 = 0.015, d2 =
It is 0.02. <Data Input> Before shipment of the recording apparatus, the correction data d1, d are stored in the memory means 38 in the recording apparatus main body.
Remember 2. The CPU 17 of the recording apparatus performs the subsequent calculation and the correction operation of the feed amount. <Correction of Feeding Amount during Recording> (1) Every time the recording sheet S is changed, the cam 26 is initialized before recording is started.

When the diameter error d1 is positive, the diameter of the carrying roller 1 is larger than the planned value, so that the carrying amount is reduced (-correction), and when it is negative, the diameter is smaller than the planned value, and therefore the carrying amount is increased (-correction). It is necessary to add correction to (+ correction). This recording apparatus can use recording sheets S of A3 size at the maximum, and 13 partial recordings are required to record the entire A3 size.

Therefore, in the A3 size, if eccentricity correction is also added, the cam 26 may be rotated in one direction to make a correction of about 15 pulses.
In No. 6, it is not possible to continuously correct a plurality of recording sheets S. Therefore, it is necessary to initialize the cam 26 at the start of recording.

As shown in FIG. 3, the tab 26 is provided on the cam 26.
The correction cam phase detection sensor 31 is arranged at the same height as the rotation center of the cam 26 in the recording apparatus main body. In order to initialize the cam 26, first the cam 26
Rotate counterclockwise, and set the sensor 3 at the position shown in the figure.
Rotate until 1 detects tab 30.

When the diameter error data is positive, the cam 26 is rotated counterclockwise by 28 pulses with respect to the detected position, and the correction roller 20 is deeply cut into the belt 8a as shown in FIG. As the home position,
After that, the correction is mainly performed while rotating in the counterclockwise direction (-correction direction). If the diameter error data is negative,
As shown in FIG. 5, the home position is defined as a position where the correction roller 20 which has rotated the cam 26 from the detection position by rotating for 4 pulses in the clockwise direction is shallowly biting into the belt 8a, and thereafter mainly in the clockwise direction (+ correction direction). ) Rotate to add correction. Here, since d1 is positive, the home position shown in FIG. 5 is obtained. (2) To correct the eccentricity, the phase relationship between the recording sheet S and the transport roller 1 is detected.

As shown in FIG. 8, the recording apparatus is provided with a roller phase detection sensor 29 which is displaced from the nip portion 34 by 90 ° (72 pulses) in the conveying direction (counterclockwise direction) by the rotation of the pulley 5a. The tab 28 blocks the optical path of the sensor 29 and generates a signal each time the transport roller 1 makes one rotation.
Therefore, if the current pulse number is known from the signal, the phase of the roller 1 can be determined.

Here, after the recording apparatus main body is powered on and before the recording operation is started, the conveying roller 1 is rotated in the counterclockwise direction, and after the sensor 29 detects the tab 31, the conveying roller 1 is always turned on. It has been stopped. The drive pulse of the conveyance roller 1 is monitored by the CPU 17, and the roller 1 is driven after the recording sheet S is brought into contact with the nip portion 34. Therefore, the phase relationship between the leading end of the recording sheet S and the roller 1 is always grasped. ing.

Since the rotation of the roller 1 is constantly monitored by the CPU 17, it is not necessary to detect a signal in the pre-rotation for the second and subsequent recording sheets S. (3) Calculation of correction amount The recording sheet S sent from the cassette 18 is the cassette 1
Since the size is detected by a detection device (not shown) in 8, the length in the carrying direction is already known.

FIG. 9 shows a dimensional relationship when full recording is performed on an A3 size sheet S.

A3 size sheet S has a total length of 420 mm,
The front 4 mm and the rear 13 mm are margins. The margin at the tip is to prevent ink from being applied to the platen 11. The trailing edge margin is such that the recording sheet S is conveyed by the conveyance roller 1 even during the final recording.
This is because it is bitten by the nip portion 34 of the driven roller 3, and the dimension is a distance 10 mm from the nip portion 34 and the end of the recording portion of the head 13 plus a margin 3 mm.

The allocation of the recording width is calculated by the CPU 17 and the first
The number of nozzles near the total recording length divided by the maximum recording width of the head 13 is 12.856 mm, that is, the number of nozzles is 12.827 mm, and the second and subsequent recordings are 32.512 mm each. Record 12 times.

On the basis of the above results, the first transport carries out the feed of 4 + 13 + 10 = 27 mm and 80 pulses from the nip 34, but the feed amount is not corrected at this time because it is not necessary to connect the images. From the second time onward, 96 pulses are conveyed, and correction is required here.

Now, as shown in FIG. 8, the phase of the roller 1 when the recording sheet S is in contact with the nip portion 34 of the conveying roller 1 is 16 pulses (20 ° of 20 °) in the counterclockwise direction, as shown in FIG. It was equivalent to rotation).

The phase of the roller 1 may be forcibly adjusted each time the recording sheet S changes, and the phase of the roller 1 when the recording sheet S is in contact with the nip portion 34 may be set as a constant. Since the management is not performed, this phase changes every time the recording sheet S changes.

Using the position of 16 pulses as a reference (0 °), the nip portion 34 when the roller 1 rotates by p pulses
The error e of the feeding amount in Eq. (3) is approximately obtained by the following equation (1) in which the error due to the diameter of the roller 1 and the error due to the eccentricity are added.

[0061]

## EQU00001 ## e (p) = d1.times..pi..times.p / 288 + d2.times.sin (p + 288-72-16 / 288.times.360) (1) The number of feed pulses from the reference when the n-th time is carried is p
(N), the feed error E (n) at the nth time is
It is calculated by the following equation (2).

[0062]

## EQU00002 ## E (n) = e (p (n))-e (p (n-1)) (2) The correction pulse number is obtained by rounding E (n) /0.02.

In this case, this calculation is carried out each time the paper is conveyed.

The correction pulse calculated for the entire surface of the A3 size sheet is shown in the following Table 1 associated with FIG.

[0065]

[Table 1] From Table 1, it can be understood that the feed error was within ± 10 μm except the influence of the recording sheet S by repeating the correction of +1 pulse, −1 pulse, and −2 pulse. Since the error of the feed amount due to the recording sheet S is about ± 10 μm,
Even if these are combined, the error of the feed amount is about ± 20 μm, and it is possible to clear the target ± 31.7 μm or less with a margin.

Further, since the phase relationship between the transport roller 1 and the recording sheet S is not limited, it is not necessary to initialize the transport roller 1, and the time is shortened accordingly.

If the feed amount is corrected by the rotation of the transport roller 1, the rotation of the roller 1 by 120 ° is broken.
Even with the maximum total number of correction pulses of 15 possible for A3 size, the deviation is 0.3 mm and the rotation angle is only 1.1 °, and there is no problem in correcting the influence of eccentricity.

The size of the recording sheet S may be designated by an operator's input. <Second Embodiment> FIGS. 10 and 11 show another configuration example of the correction mechanism.

The structure and operation of the recording unit are the same as those of the first embodiment except for the correction mechanism.

Here, the carry amount is corrected by the following configuration.

The conveying roller 1 has the same bearings 40a, 40
supported by b. Both bearings 40a and 40b are slidable in the sheet conveying direction.

The cams 45a and 45b having the same profile, which are connected by the shaft 47, are connected to each other by the stepping motor 48.
When rotated by, the cam followers 44a and 44b follow. This movement is transmitted to the correction rollers 42a and 42b via the arms 43a and 43b, and the correction rollers 42a and 42b are
Bearings 42a, 42b that are in contact with the right side (upstream side)
Moves in the sheet conveying direction.

On the left side (downstream side) of the bearings 40a, 40b, the spring members 41a, 41b urge the bearings 40a, 40b to the right, so that the bearings 44a, 44b are accurately moved to the correction rollers 42a, 42b. Following, and as a result, the transport roller 1 moves in parallel corresponding to the cams 45a and 45b.
When the transport roller 1 moves to the downstream side, the transport amount of the roller 1 increases, and when it moves to the upstream side, the transport amount of the roller 1 decreases, so that the transport amount can be corrected.

As shown in FIG. 14, the profiles of the cams 45a and 45b are formed in such a shape that the rotation amount and the correction amount of the carry amount of the carry roller 1 have a linear relationship. This profile is a curve that begins at a point 90 ° clockwise from the end of the tab 49 and continues to increase in radius R up to 180 ° counterclockwise. However, the actual radius R
The maximum difference is 1 mm, so the shape is almost a circle.

The stepping motor 48 is a PM type motor having 48 pulses per rotation, and the amount of correction of the carry amount is 20 μm per pulse.
Therefore, it is possible to correct 24 pulses by a half rotation of the cams 45a and 45b, and a cumulative correction of 0.48 mm.

Here, since the recording sheet S sags when the carry amount in the increasing direction is corrected after the carrying operation is completed, the carrying is carried after the displacement of the correction rollers 42a and 42b.
The correction rollers 42a and 42b may be displaced during conveyance.
Alternatively, the paper discharge roller 2 may be slightly rotated after the correction.

A specific correction method will be described below. <Measurement work of error> The conveyance roller assembly is the above first
Since it is the same as the case of the above embodiment, the diameter error d1, the amount of combined eccentricity d2, and the setting position of the tab 28 are also the same. <Data Input> This is also the same as in the case of the first embodiment. The CPU 17 of the recording apparatus performs the subsequent calculation and the correction operation of the feed amount. <Feed Correction During Recording> (1) Every time the recording sheet S changes, the cams 45a and 45b are initialized before recording is started.

When the diameter error d1 is positive, the diameter of the carrying roller 1 is larger than the planned value, so that the carrying amount is decreased (-correction). When the diameter error d1 is negative, the diameter is smaller than the planned value. It is necessary to add correction to (+ correction). This recording apparatus can use recording sheets S of A3 size at the maximum, and 13 partial recordings are required to record the entire A3 size.

Therefore, in the A3 size, if the eccentricity correction is also added, the cams 45a and 45b may be rotated in one direction to make a correction of about 15 pulses. With the cams 45a and 45b having a maximum correction of 24 pulses, It is not possible to continuously correct a plurality of recording sheets S. Therefore, it is necessary to initialize the cams 45a and 45b at the start of recording.

As shown in FIG. 11, the main body of the recording apparatus is
The correction cam phase detection sensor 50 is arranged at the same height as the rotation center of the cam 45a. In order to initialize the cams 45a and 45b, first, the cams 45a and 45b are rotated counterclockwise until the sensor 50 detects the tab 49 at the position shown in the figure.

When the diameter error data is positive, the cams 45a and 45b are rotated counterclockwise by 28 pulses with respect to the detected position, and the correction rollers 42a and 42b are moved to the conveying roller 1 as shown in FIG. The position moved to the upstream side is set as the home position, and thereafter, the correction is added mainly while rotating in the counterclockwise direction (-correction direction). Also,
When the diameter error data is negative, as shown in FIG. 13, the correction rollers 42a and 42b rotated by 4 pulses in the clockwise direction by reversing the cams 45a and 45b from the detection position moved the conveying roller 1 to the downstream side. The position is set to the home position, and thereafter, the correction is mainly performed while rotating in the clockwise direction (+ correction direction). Here, since d1 is positive,
Becomes the home position of. (2) To correct the eccentricity, the phase relationship between the recording sheet S and the transport roller 1 is detected.

The contents are the same as in the case of the first embodiment. (3) Calculation of Correction Amount The phase of the roller 1 when the recording sheet S is in contact with the nip portion 34 of the transport roller 1 is the same as in the case of the first embodiment, and as shown in FIG. Further, there are 16 pulses in the counterclockwise direction (corresponding to rotation of 20 °).

Since the contents of the correction are the same as in the case of the first embodiment, the result is the same as in FIG. 9 and Table 1.

Here, the drive of the conveying roller 1 is driven by the belt 8
However, since the correction of the feed amount is different from the rotation of the roller 1, the conveyance roller 1 may be driven by a driving method other than the belt 8a.

Although the cams 26, 45a and 45b are used in a half rotation also in the above-mentioned first and second embodiments, the cams may be symmetrical and both surfaces may be used. You may use a profile that uses less than half rotation or more than half rotation for correction. For example, if one cam rotation is used for correction, the feed amount can be corrected in 10 μm steps with the same configuration.

In the first and second embodiments, the correction amount is calculated each time the paper is conveyed, but the correction amount may be calculated first for all times and then the correction may be performed.

In the first and second embodiments, the conveyance amount of the recording sheet S is corrected for the maximum recording width of the recording head 13. However, the accumulated feeding error is an arbitrary feeding amount. Since the amount can also be calculated, it is naturally possible to add a correction to an unspecified feed amount.

In this case, even if the size of the recording sheet S is unknown, the nip portion 3 is detected from the timing of the detection signal of the trailing edge passage of the recording sheet S detected by the sensor 10 shown in FIG.
The remaining amount of the recording sheet S from 4 is calculated, and based on the remaining amount, the feeding and correction of the maximum recording width or less are performed at the time of the next and subsequent feeding, so that the trailing end portion of the recording sheet S is printed at the time of the final printing. Can be left in the nip portion 34 of the transport roller 1.

Furthermore, in the first and second embodiments described above, the diameter error of the conveying roller assembly and the combined eccentricity amount are used as the data input to the memory means 38, but the means for obtaining the correction amount is not limited. Since there is no such data, for example, data such as the feed amount data for one round of the transport roller may be used. After completion as a recording device, a test pattern is actually recorded on the recording sheet S and the recorded pattern is analyzed. Error data may be obtained by <Third Embodiment> Next, with reference to FIG. 16, a correction method different from the above first and second embodiments will be described. The configuration of the correction mechanism is the same as that in the case of the first embodiment (FIG. 2).

In the first and second embodiments, the correction amount is calculated by the CPU 17 in the recording apparatus, but here, the correction amount is calculated by the CPU 17 outside the CPU 17.
Input the correction amount data to. For this reason, when carrying out the correction, the carrying roller 1 needs to carry the paper at the portion of the phase corresponding to the correction amount data.

The correction method will be described below. <Correction amount setting work outside the recording device> (1) Measure error data.

Here, the diameter error of the transport roller assembly and the combined eccentricity amount are measured. Since the transport roller assembly is the same as that of the first embodiment, the diameter error d
1 = 0.015 mm, combined eccentricity d2 = 0.02 mm, and the setting position of the tab 28 is the phase reference (0 °) position. (2) A feed amount correction amount is calculated based on the measured error data.

3 from a position apart from the reference of the phase of the synthetic eccentricity amount d2 of the conveying roller 1 by a prescribed angle (0 ° in this case).
The correction amount is calculated under the condition that the conveyance of the correction target (A3 size sheet) by 2.512 mm is started.

The error e of the feed amount at the nip portion 34 when the roller 1 is rotated by p pulses from the reference (0 °) is approximated by the following equation (3) in which the error due to the diameter and the error due to the eccentricity are added. Required to.

[0095]

## EQU00003 ## e (p) = d1.times..pi..times.p / 288 + d2.times.sin (p / 288.times.360) (3) The number of feed pulses from the reference when the n-th time is carried is p
Assuming that (n), the feed error E (n) at the nth time is obtained by the following equation (4).

[0096]

## EQU00004 ## E (n) = e (p (n))-e (p (n-1)) (4) The correction pulse number is obtained by rounding E (n) /0.02.

Here, p is constant and 96 pulses, and if 3 times are calculated, the subsequent steps may be repeated.

The calculation results are the first time = −2 pulses, the second time = + 1 pulses, and the third time = −2 pulses. <Input of Correction Data> Before shipping the recording apparatus, the correction pulse data is stored in the memory means 38 in the recording apparatus main body. Subsequent calculations, correction operations, etc. are performed by C
PU17 does. <Correction of Feeding Amount during Recording> (1) Every time the recording sheet S is changed, the cam 26 is initialized before recording is started.

The correction amounts stored in the memory means 38 are added, and if the value is positive, the correction is +, and if the value is negative, the correction is −.
Therefore, as described above, (-2) + (+ 1) + (-2)
When = -3, it is -correction.

The initialization method and its result are the same as those in the first method.
This is the same as the embodiment. (2) Every time the recording sheet S is changed, the conveyance roller 1 is initialized before recording is started.

Since the recording method here is the same as that in the case of the first embodiment, no correction is made at the first feeding of the half-edge amount, and the feeding amount is set for the constant feeding of 32.512 mm after the second feeding. Although the correction will be performed, the phase of the roller 1 at the time of correction is defined, and therefore the phase relationship between the recording sheet S and the transport roller 1 needs to be aligned.

Since the length of the recording sheet S sent from the cassette 18 is already known, first, the first carry amount without correction is calculated. Since the A3 size recording sheet is conveyed here, the conveyance amount for the first time is 27 mm (80 pulses) as in the case of the first embodiment.

Next, according to this result, after the first conveyance, the conveyance roller 1 is initialized so that the nip portion 34 of the conveyance roller 1 comes to the reference position of the phase for correction (here, 0 °).

Since the roller phase detection sensor 29 of the recording apparatus is displaced from the nip portion 34 by 90 ° (corresponding to 72 pulses) in the conveying direction of the pulley 5a, the conveying roller 1 is moved counterclockwise as shown in FIG. From the position where the tab 28 intercepts the sensor 29 and generates a signal by rotating, 288-72-80 =
The roller 1 is stopped by sending 136 pulses. This completes the initialization. (3) Correction of feed amount After waiting for the recording sheet S to be conveyed at the initializing position, the recording sheet S abuts the nip portion 34, and then the conveyance roller 1 is rotated in the 80-pulse feeding direction for the first time. Record position. At this time, in the nip portion 34, the phase of the roller 1 is at the reference (0 °) position.

From the second conveyance, according to the correction pulse data in the memory means 38, −2 pulse, +1 pulse, −
By repeating the correction by the rotation of the cam 26 of 2 pulses, the conveyance with an error of ± 10 μm is achieved except for the influence of the recording sheet.

Here, since the trigonometric function is not calculated in the recording device, the load on the CPU 17 is reduced. Also,
The correction means + or-information, and the initialization position of the conveyance roller 1 with respect to a standard recording sheet is previously stored in the memory means 3.
If it is stored in 8, the calculation related to the correction becomes unnecessary.

The correction method shown here can also be applied to the correction mechanism of the second embodiment.

Although the diameter error of the transport roller assembly and the combined eccentricity amount are input to the memory means 38 as the correction data here, for example, after the completion of the recording apparatus, the test pattern is actually printed on the recording sheet. It is also possible to record and input the recorded pattern as correction data.

In the above first to third embodiments,
Since the roller 1 returns to its original phase after being conveyed three times, the first three
If the correction amount for each time is known, the correction can be performed by repeating the fixed amount feeding, but for example, in the recording device of the feed amount that the feed pulse does not return to the original phase such as 121 pulses, the correction amount is calculated for each feed. To do so.

Further, in the above-mentioned first to third embodiments,
Although the motors of the transport roller 1 and the discharge roller 2 are separate, the drive of the motor pulley 7a of the transport roller 1 may be transmitted to the pulley 5b of the discharge roller 2.

Further, in the above-mentioned first to third embodiments,
Although only the feed amount for the transport roller 1 is corrected,
If the feed amount of the discharge roller 2 in addition to the feed roller 1 is corrected, the feed amount is guaranteed even after the recording sheet S is removed from the feed roller 1. Therefore, the recording sheet S is fed by the feed roller during the final recording. 2 need not remain in the nip 34,
It enables recording with little trailing margins.

Further, although the correction mechanism of the first to third embodiments uses a dedicated motor (stepping motor), the drive of another drive system may be used via a clutch or the like. Absent.

Further, in the above-mentioned first to third embodiments,
Although the cam is used as the correction mechanism, a means other than the cam such as a linear motion motor may be used.

In the first to third embodiments described above, the error of the feed amount due to the difference in the size of the recording sheet is not corrected, but the conveyance error due to the difference in the size of the recording sheet is also corrected, so that the memory means is used. It is also possible to store the error amount or the correction amount for each size of the recording sheet in 38 and call it as needed to add it to the error amount or the correction amount for the transport roller 1 to set the correction pulse amount. According to this correction method, although the capacity of the memory means 38 is increased, it is possible to correct the feed amount with higher accuracy including an error due to the recording sheet.

[0115]

As described above, in the sheet conveying apparatus of the present invention, the sheet conveying amount of the conveying roller pair for intermittently stepping the sheet by a predetermined amount is corrected, so that the conveying roller pair is driven. A small stepping motor can be used as a source.

Further, if the correcting means performs the correction based on the error data, the accuracy of the sheet feeding amount can be improved without specially improving the processing accuracy of the conveying roller or the like.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view showing an overall configuration of an inkjet recording apparatus including a sheet conveying apparatus to which the present invention is applied.

FIG. 2 is a perspective view showing a detailed configuration of a recording unit of the recording apparatus.

FIG. 3 is a side view showing a configuration of a drive transmission mechanism that transmits driving of a stepping motor to a conveyance roller that conveys a recording sheet and a correction mechanism that corrects a sheet conveyance amount of the conveyance roller in the recording unit.

FIG. 4 is a side view illustrating an operation during plus correction.

FIG. 5 is a side view for explaining an operation at the time of minus correction.

FIG. 6 is a side view showing a configuration of a pulley that transmits driving of a stepping motor to a conveyance roller.

FIG. 7 is a perspective view showing a configuration of a tab attached to the pulley.

FIG. 8 is a side view showing a configuration for detecting a phase of a transport roller.

FIG. 9 is a plan view showing a recording width allocation configuration when full recording is performed on an A3 size sheet.

FIG. 10 is a perspective view showing another configuration example of the correction mechanism.

FIG. 11 is a side view showing another configuration example of the correction mechanism.

FIG. 12 is a side view showing the operation at the time of minus correction.

FIG. 13 is a side view showing an operation during plus correction.

FIG. 14 is a side view showing the shape of a cam of the correction mechanism.

FIG. 15 is a side view showing a configuration for detecting the phase of a transport roller.

FIG. 16 is a side view illustrating an operation when performing correction using correction amount data.

FIG. 17 is a vertical cross-sectional side view showing a configuration of a recording unit of a recording apparatus (inkjet printer) of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 conveyance roller (roller on the side where drive is transmitted) 2 driven roller 13 recording head (recording means) 17 CPU (control means) 20, 42a, 42b correction roller (correction means) 29 roller phase detection sensor (signal output means) 31 , 50 Correction cam phase detection sensor (signal output means) 38 Memory means S Recording sheet

Claims (11)

[Claims] 1. A sheet conveying device for intermittently stepping a sheet by a predetermined amount by a pair of conveying rollers, and a correction unit for correcting the sheet conveying amount of each of the pair of conveying rollers, and data for the correction. And a control unit that controls the correction unit based on the sheet conveyance device. 2. The correction unit corrects the sheet conveyance amount of the conveyance roller pair by increasing / decreasing the rotation amount of the drive-transmitted roller of the conveyance roller pair. The sheet conveying apparatus according to item 1. 3. The correction means corrects the sheet conveyance amount of the conveyance roller pair by moving the drive-side roller of the conveyance roller pair in the sheet conveyance direction. The sheet conveying device according to claim 1. 4. The sheet conveying apparatus according to claim 1, wherein the control unit calculates a correction amount based on error data stored in the storage unit and controls the correction unit. 5. The sheet conveying apparatus according to claim 1, wherein the control unit controls the correction unit based on the correction amount data stored in the storage unit. 6. A signal output means for issuing a signal at least once at a predetermined position while the roller on the drive transmission side of the pair of conveying rollers makes one rotation, and the control means has the signal output means. 5. The sheet conveying apparatus according to claim 4, wherein the rotation phase of the roller at the time of feeding the sheet is determined based on the signal issued by, and the correction amount is calculated based on the determined rotation phase. 7. A signal output means for outputting a signal at least once at a predetermined position while the roller on the drive transmission side of the pair of conveying rollers makes one rotation, and the control means has the signal output means. The sheet conveying apparatus according to claim 5, wherein the phase of the roller is set to a predetermined phase with respect to the leading edge of the sheet entering the nip of the pair of conveying rollers based on the signal issued by the roller. 8. The control unit is configured such that the pair of conveying rollers is one.
6. The sheet conveying apparatus according to claim 4, wherein the correction unit is returned to the initial position before the conveyance of the next sheet is started and the conveyance of the next sheet is started. 9. The control means has a signal output means for issuing a signal when the correction means is at a specific position, and the control means determines the position of the correction means based on the signal issued by the signal output means. The sheet conveying apparatus according to claim 8, wherein the sheet conveying apparatus is a sheet conveying apparatus. 10. The sheet conveying apparatus according to claim 9, wherein the control unit sets the initial position of the correction unit based on error data or correction amount data stored in the storage unit. . 11. A sheet conveying device according to claim 1, and an image of a predetermined width is recorded on a recording sheet which is intermittently stepwise fed by a predetermined amount by the sheet conveying device. A recording device comprising: