JPH0664258A - Recording device - Google Patents

Abstract

PURPOSE:To prevent the dispersion of the quantity of a recording medium carried, which is generated resulting from the eccentricity, etc., of a driving roller. CONSTITUTION:The perimeter of an upstream-side driving roller 31 is equal to the whole length in the row direction of the recording element 11 of a recording head 1, and the perimeter of a downstream-side driving roller 41 is made slightly larger than the whole length. Both driving rollers can move a recording medium 8 at every fine size. A paper-end sensor 7 is arranged on the upstream side farther than a distance corresponding to the overall length of the recording head 1 from the upstream-side driving roller 41. The pushing force of an upstream-side follower roller 32 is varied by the signal of the paper-end sensor 7. According to the constitution, periodic deviation by the eccentricity, etc., of both driving rollers is offset in the quantity of the recording medium 8 carried, absolute deviation due to the dispersion, etc., of the outside diameters of both driving rollers can be corrected discretely, and no deviation is generated even at the time of delivery between both driving rollers, and deviation is kept constant at all times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus for recording a character or an image by a recording head having a plurality of recording elements arranged side by side.
In particular, the present invention relates to a recording apparatus that conveys a recording medium linearly on the front surface of a recording head and records characters or images.

[0002]

2. Description of the Related Art FIG. 6 is a diagram for explaining a method of transporting a recording medium in a conventional recording apparatus. A driving roller 38 is arranged in front of a recording head 1 and a recording medium 8 is sandwiched between the driving rollers 38. Driven rollers 39, 49 pressed by 38
Thus, the recording medium 8 is wound around the drive roller 38, and the recording medium 8 is conveyed by the rotation of the drive roller 38.

However, according to this method, the recording medium 8 is driven by the drive roller 38 in the recorded portion facing the recording head 1.
Since the curved surface runs along the
The distance between the central portion and the end portion of the recording medium 8 is not uniform, high recording accuracy is difficult to obtain, and it is difficult to cope with recording medium such as thick paper or envelope that is not easily bent. It was

As a method of conveying a recording medium for solving these problems, Japanese Patent Laid-Open No. 1-258974 shown in FIG. 7 has been proposed. In FIG. 7A, reference numeral 31 denotes an upstream drive roller provided on the upstream side of the recording head 1, and the upstream driven roller 32 is pressed. Reference numeral 41 denotes a downstream drive roller provided on the downstream side of the recording head 1, and the downstream driven roller 42 is pressed. The recording medium 8 is sandwiched between the upstream drive roller 31 and the upstream driven roller 32, and also sandwiched between the downstream drive roller 41 and the downstream driven roller 42. Are kept straight so that the gap is uniform. Downstream drive roller 4
The peripheral speed of 1 is set to be higher than the peripheral speed of the upstream drive roller 31, and the pressing force of the upstream driven roller 32 is larger than the pressing force of the downstream driven roller 42.

The recording medium conveying operation of the recording apparatus having such a configuration is as follows.

The recording medium 8 is conveyed in the column direction of the recording heads 1 by the rotation of the upstream drive roller 31 and the downstream drive roller 41. At this time, since the pressing force of the upstream driven roller 32 is set to be larger than the pressing force of the downstream driven roller 42, the downstream drive roller 41 whose peripheral speed is set faster than that of the upstream drive roller 31 is recorded. Slip occurs with the medium 8. Therefore, the conveyance amount of the recording medium 8 is determined by the rotation amount of the upstream drive roller 31. Also,
A tension is applied to the recording medium 8 by the conveying force of the downstream drive roller 41, so that the recording medium 8 is kept flat on the front surface of the recording head 1 and a stable conveying operation is obtained.

The operation of the printing apparatus for printing a continuous pattern such as an image will be described in more detail below.

By moving the recording head 1 in which n recording elements 11 are arranged in the column direction in the row direction and during this movement, the recording elements 11 are selectively driven according to print data,
A first recording area (hereinafter referred to as a band) is formed on the recording medium 8.

The upstream drive roller 31 and the downstream drive roller 41 are rotationally driven to move the recording medium 8 in the column direction of the recording head 1 by the total length of the print head 1 in the column direction (the number of recording elements is n, recording in the column direction). P × when the element pitch is p
Carry only n). In this carrying operation, the rotation amount of the upstream drive roller 31 that determines the carry amount is set to the upstream drive roller 3
It is obtained by setting a constant angle θ such that the arc length on the outer circumference of 1 is equal to the total length of the recording head 1 in the column direction.

The recording head 1 is again moved in the row direction and the recording element 11 is selectively driven to form a second band adjacent to the first band on the recording medium 8. Hereinafter, rotation of the first drive roller 31 by a constant angle θ,
Recording for one band is repeated up to near the end of the recording medium 8.

In the vicinity of the trailing end of the recording medium 8, 1 to 8 after the trailing end of the recording medium 8 is disengaged from the upstream drive roller 31.
Regarding the printing of several bands, the conveyance of the recording medium 8 is performed only by rotating the downstream drive roller 41 at a constant angle.

Then, the recording for one page was completed.

[0013]

However, in this case, the upstream drive roller 31 or the downstream drive roller 4 is used.
Due to the inevitable manufacturing error, the arc length (circumferential length) on the outer circumference of the drive roller corresponding to the rotation at a constant angle is not constant. As shown in FIGS. 7 (b) and 7 (c), this is due to a periodic deviation due to eccentricity between the drive center of the upstream drive roller 31 and the outer diameter center (peripheral length a and circumference in FIG. 7 (b)). This is because there is a deviation (difference between the peripheral length c and the peripheral length d in FIG. 7C) due to the variation in the outer diameter of each upstream drive roller 31. Therefore, the conveyance amount of the recording medium 8 conveyed by the rotation of the upstream drive roller 31 (or the rotation of the downstream drive roller 41 near the trailing end) is also not constant. As a result, the pitch between the above-mentioned bands is too narrow or too wide than the specified amount depending on the position within one page of the recording medium 8 or for each recording device, and the band is spread over the bands. It can be identified as a striped pattern of recording (hereinafter referred to as banding) in characters and images, which is a major factor that deteriorates the recording quality. Further, this error occurs more frequently during the transfer from the rotation by the rotation of the upstream drive roller 31 to the transfer by only the downstream drive roller 41.

The present invention has been made in order to solve such a problem. Even if a drive roller having an error such as eccentricity or variation in outer diameter dimension is used, the pitch between the bands is made constant. An object of the present invention is to obtain a recording apparatus in which a recording stripe pattern (banding) due to the conveyance of the recording medium is less likely to occur from the front end to the rear end of the recording medium.

[0015]

A recording apparatus of the present invention is provided with a recording head in which a plurality of recording elements are arranged in a column direction, and is provided on the upstream side of a recording medium path with respect to the recording head, and has a perimeter of the recording medium. An upstream drive roller that is equal to or a whole fraction of the total length of the recording head in the column direction (p × n when the number of recording elements is n and the pitch between recording elements in the column direction is p) and the upstream drive An upstream side recording medium conveying means for conveying the recording medium in the column direction of the recording head, and an upstream side driven roller having an arbitrary peripheral length pressed by the roller; and a downstream side of the recording medium path with respect to the recording head. A downstream drive roller having a peripheral length slightly larger than that of the upstream drive roller and a downstream driven roller having an arbitrary peripheral length pressed by the downstream drive roller. Downstream transport in the row direction And recording medium conveying means, characterized by comprising a. Further, the recording head and the recording medium can be relatively moved by a minute amount smaller than a pitch p between recording elements of the recording head. Further, an end face detecting means of the recording medium is provided on the upstream side of the recording medium path, and a pressing force of the driven roller is made variable by a signal of the end face detecting means. In addition, the end face detecting means is provided on the upstream side of the upstream side recording medium conveying means, which is farther than the distance corresponding to the entire length of the recording head in the column direction.

[0016]

According to the above-mentioned structure of the present invention, since the peripheral lengths of the two drive rollers are substantially equal to the total length p × n of the recording head in the column direction, or are substantially an integer, When the print head is conveyed by the total length p × n (that is, when moving from one band to the next band), the drive roller makes one rotation or an integer rotation. The periodic deviation of the transport amount of the recording medium due to the eccentricity is offset, and the transport amount is always constant. Further, since the recording head and the recording medium can be moved by a small amount relative to each other, it is possible to individually correct the difference in the conveyance amount of the recording medium due to the variation in the outer diameter of the driving roller (due to individual difference). Therefore, by sufficiently increasing the resolution of the minute amount movement, the conveyance amount of the recording medium by the driving roller can be made as close as possible to the total length p × n of the recording head. Further, the position of the end face detection means is arranged on the upstream side of the upstream drive roller farther than the upstream recording medium transport means by a distance corresponding to the entire length of the recording head. After the transport operation is completed, the detection signal is used to shift to the transport operation in the downstream recording medium transport means, so that the transport of the print medium between the two drive rollers is performed in an almost integral rotation. Therefore, the carry amount does not change. As a result, it is possible to realize a recording device in which banding is less likely to occur from the leading edge to the trailing edge of the recording medium.

[0017]

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

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a perspective view thereof.

In these figures, 1 is a recording head, and a plurality of recording elements 11 from # 1 to #n in the column direction A.
Are arranged at a constant inter-element pitch p. Hereinafter, for the purpose of description using specific numerical values, for example, it is assumed that recording elements having the number of elements n = 192 are arranged at an element pitch p = 1/360 inches in the column direction.

Reference numeral 2 denotes a carriage which carries the recording head 1 and is driven by a carriage motor 21 via a timing belt 24 to move in the row direction (arrow B) along the guide shafts 22 and 23.

An upstream drive roller 31 is arranged upstream of the recording head 1 in the path of the recording medium 8.
The upstream drive roller 31 has a value such that the outermost circumference thereof is equal to the total length in the column direction of the recording head 1 (p × n when the number of recording elements is n and the pitch between recording elements in the column direction is p). It is manufactured with the aim of measuring. Specifically, the perimeter L = p × n = 1/360 × 192 = 192/360 inches, that is, the diameter d is converted into the diameter d = L / π = 19.
2 / (360π) inches = 4.31 millimeters. The upstream drive roller 31 is supported by a plurality of upstream bearings 33 provided on the support plate 91, and the upstream bearing 33 is supported.
From the opposite side to the upstream driven roller 32 that presses the upstream driving roller 31 by a spring (not shown) and has an arbitrary peripheral length. By rotating with a sandwich,
The recording medium 8 is conveyed in the column direction A. Upstream driven roller 3
The pressing force of the second drive roller 31 on the upstream drive roller 31 is variable. That is, it is possible to switch between the normal state and the state where the pressing force is weak by releasing the pressing force by changing the stroke of the spring by the power of a solenoid (not shown) or the like.

An upstream drive gear 311 is directly connected to the upstream drive roller 31.

Reference numeral 41 denotes a downstream drive roller, which is arranged downstream of the recording head 1 in the path of the recording medium 8.
The downstream side drive roller 41 has at least the upstream side drive roller 31 with the outermost circumferential length taking into account manufacturing errors.
In order not to overlap with, the target size is manufactured with a value slightly larger than the circumferential length of the upstream drive roller 31.

In the above-mentioned specific example, for example, the manufacturing error of the diameter is set to ± 0.03 mm, and the diameter of the downstream drive roller 41 is set to d ′ = 4.37 mm. The circumference of the drive roller 41 does not fall below the circumference of the upstream drive roller 31.
Similarly to the upstream drive roller 31, the downstream drive roller 41 is supported by a plurality of downstream bearings 43 provided on the support plate 91, and the downstream drive roller 41 is supported by a spring (not shown) from the opposite side of the downstream bearing 43. The recording medium 8 is arranged in the column direction by engaging with one or a plurality of downstream driven rollers 42 having an arbitrary circumference to form a downstream recording medium conveying means and rotating the recording medium 8 with the recording medium 8 interposed therebetween. It is conveyed to (arrow A). In the normal state, the pressing force of the downstream driven roller 42 against the downstream driving roller 41 is set to be weaker than the pressing force of the upstream driven roller 32 against the upstream driving roller 31. Therefore, the recording by the downstream recording medium conveying means is performed. The carrying force of the medium 8 is set to be weaker than the carrying force of the recording medium 8 by the upstream recording medium carrying means. On the contrary, when the pressing force of the upstream driven roller 32 is switched to weak, the conveying force of the recording medium 8 by the downstream recording medium conveying means is stronger than the conveying force by the upstream recording medium conveying means. It is set.

A downstream drive gear 411 is directly connected to the downstream drive roller 41.

The upstream drive roller 31 and the downstream drive roller 41 are required to have high bending strength, a low friction coefficient with respect to the bearings 33 and 43, and a high friction coefficient with respect to the recording medium 8. It is desirable to partially coat the shaft with a thin coating of ceramic or rubber.

Reference numeral 7 is an end face detecting means of the recording medium 8,
It is a paper edge sensor. The paper edge sensor 7 is arranged on the upstream side of a distance corresponding to the entire length (p × n) of the recording head 1 in the column direction from the upstream recording medium conveying means.

Reference numeral 51 denotes a paper feed roller, which has a built-in one-way clutch (not shown), and is rotationally driven only in one direction by a paper feed roller shaft 52 so that the recording medium 8 stored in the paper feed tray 53 is used as a recording device. Send in. A paper feed gear 511 is directly connected to the paper feed roller shaft 52.

Reference numeral 65 is a paper feeding motor, which is a paper feeding gear 511.
The paper feed motor pinion 66 that engages with is fixed, and drives the paper feed roller 51.

Reference numeral 6 denotes a conveying motor, which is an upstream drive gear 3
11 and the transport motor pinion 61 engaging with the downstream drive gear 411 are fixed and drive the upstream drive roller 31 and the downstream drive roller 41. The gear ratio (reduction ratio) of the upstream drive gear 311, the downstream drive gear 411, and the carry motor pinion 61 is an integer. Therefore, the upstream drive gear 311 and the upstream drive gear 411 make one rotation by the integral rotation of the carry motor pinion 61, that is, the carry motor 6
The upstream drive roller 31 and the downstream drive roller 41 make one rotation by the integral rotation of Also, deceleration is
In the illustrated example, the single-stage deceleration is used, but it is also possible to perform the multi-stage deceleration by setting the reduction ratio between the respective stages to an integer. Further, a power switching mechanism is provided to engage the transport motor pinion 61 depending on the rotation direction of the transport motor 6.
It is also possible to eliminate the paper feed motor 65 by switching between 1 and the upstream drive gear 311 and the downstream drive gear 411.

As the carry motor 6, a general step motor can be applied. Below, a case in which a reduction ratio of 5 is used with a 96-pole step motor and the above-described specific example is combined is illustrated. Transport motor 6 which is a 4-phase 96-pole step motor
Can be driven with a resolution of 192 steps per revolution by 1-2 phase excitation drive in which 1-phase excitation and 2-phase excitation are alternately repeated. In this case, the unit movement amount of the upstream drive roller 31 driven through the engagement of the transport motor pinion 61 and the downstream drive gear 411 at the reduction ratio = 5 (the upstream drive roller per step of the transport motor 6) The rotation amount of 31, that is, the conveyance amount of the recording medium 8 per step of the conveyance motor 6) is the upstream drive roller 31.
1 / (192 × 5) of the perimeter L of Similarly, the unit movement amount of the downstream drive roller 41 is slightly larger than the unit movement amount of the upstream drive roller 31. In the specific example, the unit movement amount of the upstream drive roller 31 is 192 /
360 inches × 1/960 = 1/1800 inches≈14
The distance becomes micron, and the unit movement amount of the downstream drive roller 41 becomes a value slightly larger than this. That is, in each case, the recording medium 8 is recorded in minute amounts smaller than the element pitch p = 1/360 inch≈71 microns in the column direction of the recording head 1.
It is configured to be able to move.

As is clear from the above description, in the specific example, the number of drive steps of the carry motor 6 corresponding to one rotation of the upstream drive roller 31 and the downstream drive roller 41 is 192 × 5 = 960 steps. It is configured to be.

Next, the operation of the recording apparatus having the above structure will be described.

When the print data is received from the host computer or the like, the paper feed motor 65 starts rotating for paper feed.
The rotation of the sheet feeding motor 65 drives the sheet feeding roller 51, and one recording medium 8 stored in the sheet feeding tray 53 is selected and sent to the upstream side recording medium conveying means. For the selected recording medium 8, when the leading edge of the recording medium 8 is detected by the paper edge sensor 7 located between the paper feed roller 65 and the upstream recording medium conveying means, the leading edge of the recording medium 8 moves upstream from that position. It is fed by a predetermined amount that sufficiently reaches the side recording medium conveying means. The leading end of the recording medium 8 is an upstream drive roller 31 and an upstream driven roller 32 of the upstream recording medium conveying means.
The sheet feeding motor 65 is pressed against the tangent to the sheet and the rotation of the sheet feeding motor 65 is stopped in a state where the skew is corrected and the sheet feeding operation ends.

Next, the conveyance motor 6 starts to rotate so as to locate the recording medium 8. The upstream drive roller 31 and the downstream drive roller 41 are driven by the rotation of the carry motor 6. The recording medium 8 is sent while being sandwiched between the upstream drive roller 31 and the upstream driven roller 32, faces the recording head 1, and the cueing operation is completed. The paper feed roller 51
Is idled in the pull-out direction of the recording medium 8 by a built-in one-way clutch, and the recording medium 8 is pulled out from the paper feed tray 53 with a small load. The driving amount at the time of cueing is set to the amount of feeding the recording medium 8 by the same amount as the total length (p × n) of the recording head 1 in the column direction. That is, the upstream drive roller 31 whose intended circumference is equal to the total length of the recording head 1 is driven by one rotation. At this time, the interlocking downstream drive roller 41 is also driven for one rotation.

After the feeding and the cueing operation of the recording medium 8 are completed as described above, the carriage motor 2 is driven. After the carriage 2 moves in the row direction and the recording element 11 of the recording head 1 mounted on the carriage 2 reaches the recording area in the row direction, the recording element 11 is selectively energized according to the recording data, and the recording medium An arbitrary character or image for one band is recorded in the row direction recording area of 8.

After the recording of the first band is completed, the driving of the carriage motor 2 is stopped, the conveyance motor 6 is driven, and the recording medium 8 is rotated by one rotation of the upstream drive roller 31 in the same manner as described above. The entire length of the recording head 1 is conveyed. After that, the carriage motor 2 is reversely driven to move the recording head 1 in the opposite direction, and the second band adjacent to the first band is recorded. Hereinafter, the movement operation and the transportation operation of the carriage 2 are repeated. Due to the positional relationship between the upstream side recording medium conveying means and the downstream side recording medium conveying means, the leading end of the recording medium 8 reaches the downstream side recording medium conveying means at an arbitrary time point, and the recording medium 8 becomes the downstream side drive roller 41. And the downstream driven roller 42.

The peripheral length of the aim is slightly larger than the peripheral length of the upstream drive roller 31. The transport amount of the recording medium 8 by the downstream drive roller 41 is larger than the transport amount by the upstream drive roller 31, but in the normal state, The pressing force of the downstream driven roller 42 against the downstream driving roller 41 is set to be weaker than the pressing force of the upstream driven roller 32 against the upstream driving roller 31, and therefore, the conveying force of the recording medium 8 by the downstream recording medium conveying means. Is set to be weaker than the conveying force of the recording medium 8 by the upstream recording medium conveying means, the conveying amount of the recording medium 8 is determined by the conveying amount of the upstream drive roller 31. That is, the recording medium 8 is
While being slightly slipped in the downstream side recording medium conveying means, it is pulled by the downstream side recording medium conveying means,
The upstream drive roller 31 and the downstream drive roller 41 are stably conveyed by the upstream drive roller 31 without slack.

When the recording approaches the end of the recording medium 8, the end of the recording medium 8 passes the paper edge sensor 7 at an arbitrary point in the course of the conveying operation, and the paper edge sensor 7 detects the end of the recording medium 8. . At this time, the transport operation of the recording medium 8 which is currently operating is continued as it is, and the transport of the entire length (p × n) of the recording head 1 in the column direction is completed by one rotation of the upstream drive roller 31. Since the position of the paper edge sensor 7 is on the upstream side of the upstream drive roller 31 and beyond the distance corresponding to the entire length of the recording head 1, the trailing edge of the recording medium 8 will not fall off the upstream drive roller 31 by this operation.

After the end of one conveyance operation after the detection of the end, the pressing force of the upstream driven roller 32 is switched by the detection signal of the end of the recording medium 8 to make it weaker than the pressing force of the downstream driven roller 42. As a result, the subsequent transport operation is
The conveyance amount of the recording medium 8 is determined by the rotation amount of the downstream drive roller 41. The conveyance amount of the recording medium 8 by the downstream drive roller 41 is also determined by the recording medium 8
Is set so as to convey the same as the total length (p × n) in the column direction. That is, the downstream drive roller 41 whose circumference is slightly larger than the upstream drive roller 31 is driven by an amount slightly smaller than one rotation.

As described above, the transition from the transport operation in which the upstream drive roller 31 is dominant to the transport operation in which the downstream drive roller 41 is dominant is one rotation of the upstream drive roller 31 and the downstream drive roller 41. There is no switching in the middle of. That is, the trailing edge of the recording medium 8 passes past the position of the upstream drive roller 31 during the conveyance operation in which the upstream drive roller 31 is dominant, so that the downstream drive roller 41
Does not switch to the dominant transport operation.

(Hereinafter, the recording medium 8 in which the conveyance by the upstream drive roller 31 is predominant is conveyed upstream and the conveyance by the downstream drive roller 41 is predominant.
The transport state of is referred to as downstream transport. If the paper edge sensor 7 is arranged on the upstream side beyond a distance corresponding to twice the total length of the recording head 1, it is possible to add another upstream conveyance operation.

After that, the moving operation of the carriage 2 and the lower conveying operation for one to several times are repeated until the final band allocated by the end of the recording medium 8 is recorded, and the recording for one page is completed.

Here, the conveying operation of the recording medium 8 by the rotation of the upstream drive roller 31 or the downstream drive roller 41 will be described in more detail.

The conveyance amount of the recording medium 8 conveyed by the rotation of the upstream side drive roller 31 or the downstream side drive roller 41 has an error due to the variation of the parts precision which cannot be avoided in manufacturing.

The errors are roughly classified into the upstream drive roller 31.
(Downstream drive roller 41), upstream drive gear 311 (downstream drive gear 411), conveyance motor pinion 61, and other rotational system components due to deviation (eccentricity) between the drive center and the outer diameter center, and cyclic conveyance amount error And the individual outer diameter dimensions of the upstream drive roller 31 (downstream drive roller 41)
It can be divided into an absolute transport amount error due to variations.

The first error of the periodic carry amount due to eccentricity is
This is caused when the outer peripheral lengths corresponding to the respective angles θ differ when they are rotated by an arbitrary constant angle θ about a certain point deviated from the center of the outer diameter.

An outline will be given with reference to FIG. In FIG. 3, the drive center is P, the outer diameter center is O, and the eccentricity amount is OP = e, and the outer diameter is a perfect circle. The difference between the circumferential length AB when rotated about the drive center P by an arbitrary angle θ and the circumferential length CD corresponding to the angle θ (centering around the outer diameter center O) of the perfect circle is the circumferential length due to eccentricity. There will be an error. Maximum circumference error is an arbitrary angle θ
Occurs in a positional relationship in which OP is divided into two parts (a position shown in the figure or a position shifted in phase by π by the radian method). Here, if the true circle radius is r, an arbitrary angle is θ, and the true circle center angle ∠AOB corresponding to the arc AB is α, the maximum circumference error ε is ε = arc AB−arc CD = rα−rθ .

From the positional relationship shown in FIG. 3, a relationship of e.sin (.theta. / 2) = r.sin ((. Alpha .-. Theta.) / 2) is obtained, and e is small, and sin ( In the range where (α−θ) / 2) ≈ (α−θ) / 2 holds, ε = r (α−θ) = 2e · sin (θ / 2) is obtained as an approximate solution.

That is, the outer peripheral length error ε due to the eccentricity can be expressed in the form of ε = 2e · sin (θ / 2) ... (1).

According to the configuration of this embodiment, during upstream conveyance, the peripheral length of the upstream drive roller 31 that determines the conveyance amount of the recording medium 8 is the total length (p × x) of the recording heads 1 in the column direction.
Since the target size is set to a value equal to n), the target conveying operation of the recording medium 8 for arranging the recording bands and the recording bands at an equal pitch is completed by one rotation of the upstream drive roller 31. To do. Therefore, the circumference error due to eccentricity is ε = 2e · sin (2π / 2) =
It becomes 0, and the periodic carry amount error due to the eccentricity of the upstream drive roller 31 does not occur. Similarly, the upstream drive roller 31
The upstream drive gear 311 that is directly connected to the above ends the operation in one rotation, and a cyclic conveyance amount error due to the eccentricity of the upstream drive gear 311 does not occur. Further, the carry motor pinion 61 engaged with the upstream drive gear 311 at an integer reduction ratio ends its operation at an integer rotation, and the circumferential length error due to the eccentricity of the carry motor pinion 61 is ε = 2e · from the equation (1). sin (2mπ / 2)
= 0 (m is an integer), and no periodic error occurs. Therefore, the intended carrying operation of the recording medium 8 for arranging the recording bands at equal pitches can be realized by suppressing the periodic carry amount error due to the eccentricity of the rotary system to zero.

The periodic carry amount error during the downstream carry will be described later.

Next, the second, mainly upstream drive roller 31
An absolute conveyance amount error due to variation in outer diameter dimension of the (downstream drive roller 41) will be described.

The outer diameter of the upstream drive roller 31 (downstream drive roller 41) has an unavoidable error in terms of manufacturing. As a specific example, assuming that the upstream drive roller 31 has a reasonable manufacturing error of about ± 30 μm with respect to the above-mentioned diameter d = 4.31 mm, the circumference of the upstream drive roller 31 is The length will have an error of ± 30 microns × π≈ ± 94 microns with respect to the desired dimension. That is, the recording medium 8 having a target value, which is equal to the total length (p × n) of the recording head 1 in the column direction,
When the upstream drive roller 31 is rotated once in order to obtain the conveyance amount, the maximum feed amount of about 94 μm or the feed amount may be insufficient.

According to the configuration of this embodiment, this error can be corrected by adjusting the number of driving steps of the carry motor 6. That is, with respect to the number of drive steps of the transport motor 6 corresponding to one rotation of the upstream drive roller 31 (one transport operation of the recording medium 8), the upstream drive roller that is insufficiently fed by one rotation is insufficient. The number of drive steps corresponding to the amount can be added, and the upstream drive roller that causes excessive feeding in one rotation can be corrected by reducing the number of drive steps corresponding to the excessive amount. The correction is performed for each recording device, and the unit movement amount of the upstream drive roller 31 (the conveyance amount of the recording medium 8 per one step of the conveyance motor 6) is small, and the recording medium 8 can be moved by a minute amount. Accurate correction is possible from a possible configuration.

A more detailed description will be given based on the above-mentioned specific example. For example, the outer diameter of the upstream drive roller 31 used is
It is assumed that it is manufactured to be 30 microns smaller than the target size, and the transport amount of the recording medium 8 by one rotation of the upstream drive roller 31 is about 94 microns shorter than the target. Since the unit movement amount of the upstream drive roller 31 per one step of the carry motor 6 is about 14 microns as described above, in this case, the correction amount is 94 microns / 14 (microns / step) ≈6.7 steps. , Takes a close integer, and becomes 7 steps. That is, the number of driving steps of the carry motor 6 corresponding to one carrying operation of the print medium 8 in this printing apparatus corresponds to one rotation of the upstream drive roller 31.
By setting a value of 967 steps, which is obtained by adding 7 steps to 0 steps, the absolute carry amount error can be reduced to, for example, 14 (microns / step) × 7 steps−94 microns = 4 microns. . The above-described correction can be performed with an accuracy of ½ of the unit movement amount of the upstream drive roller 31 by selecting either of the integer step numbers sandwiching the correction amount. If is 14 microns, an accuracy in the range of ± 7 microns can be obtained. In the actual recording apparatus, the total length (p × n) of the recording head 1 in the column direction has a slight error, and other drive systems also have an error. By carrying out the process in the final step, the total absolute carry amount error including these errors can be reduced to, for example, ± 7 microns or less. According to the experiments by the inventors, 36 per inch
In a printing device with a density of about 0 dots, it has been found that the banding of printing is not noticeable if the bands are arranged with an accuracy of about ± 15 microns or less, and the above values are sufficiently high. It can be called precision. Further, by making the unit movement amount of the upstream drive roller 31 per step of the carry motor 6 smaller, it is possible to further improve the correction accuracy.

Although the above-mentioned correction induces a slight eccentricity error, the amount thereof is sufficiently small and does not spoil the purpose. For example, in the case of setting 967 steps obtained by adding 7 steps as a correction amount to 960 steps corresponding to one rotation of the upstream drive roller 31 in the specific example described above, as the number of transport drive steps of the upstream drive roller 41 in the recording apparatus. The rotation angle of the upstream drive roller 31 for one transport operation of the recording medium 8 is θ = 2π ×
(967/960). The amount of eccentricity of the upstream drive roller 31 is, for example, about e = 30 microns, which is a reasonable manufacturing error. Even in this case, the peripheral length error of the upstream drive roller 31 due to the eccentricity is ε =
2e · sin (θ / 2) ≈1.4 microns, which is sufficiently small. Next, a transport amount error during downstream transport will be described. At the time of downstream transport, the transport amount of the recording medium 8 is determined by the downstream drive roller 41. As described above, the peripheral length of the downstream drive roller 41 is slightly larger than the peripheral length of the upstream drive roller 31 so as not to overlap at least the upstream drive roller 31 in consideration of manufacturing error. Manufactured as dimensions. Therefore,
The aiming conveyance operation of the recording medium 8 for arranging the recording bands and the recording bands at an equal pitch is performed by the downstream drive roller 41.
It finishes in slightly less than one revolution. Although this motion slightly induces an eccentricity error, its amount is sufficiently small that it does not hurt the purpose. In the above-mentioned specific example, for example, the target diameter d = 4.31 mm of the upstream drive roller 31 and the target diameter d ′ = 4.37 mm of the downstream drive roller 41 are manufactured. And In this case, the downstream drive roller 41
The rotation angle for one downstream transport operation of the recording medium 8 is θ = 2π × (4.31 / 4.37). If the eccentricity of the downstream drive roller 41 is about e = 30 μm, the transport amount error due to the eccentricity of the downstream drive roller 41 at the time of downstream transport is ε = 2e · sin (θ /
2) ≈ 2.6 microns, which is sufficiently small. Further, the correction of the absolute carry amount error due to the variation in the outer diameter dimension of the downstream drive roller 41 can be performed in the same manner as in the case of the upstream drive roller 31 described above.

Here, as described above, the upstream drive roller 3
It is important that the shift from the transport operation in which 1 is dominant to the transport operation in which the downstream drive roller 41 is dominant does not switch in the middle of one rotation of the upstream drive roller 31 and the downstream drive roller 41. Is. If switching is performed during one rotation, the upstream drive roller 31 or the downstream drive roller 4
A transport mode with an arbitrary rotation angle of 1 can occur. That is, ε = 2e · si in the upstream drive roller 31.
There is a possibility that a conveyance amount error due to eccentricity of the maximum value of n (θ / 2) of 60 μm may occur, and a conveyance amount error of 60 μm at the maximum may occur in the downstream drive roller 41 after switching. Depending on the phase relationship of the drive rollers, a total carry amount error of 120 microns may occur.

As described above in detail, according to the configuration of this embodiment, the recording medium 8 is conveyed by one rotation of the upstream drive roller 31 during the upstream conveyance and the downstream drive roller 31 during the downstream conveyance. Since the rotation is performed by substantially one rotation of 41, the periodic deviation of the carry amount of the recording medium 8 due to the eccentricity of the both drive rollers is offset, and the carry amount is always constant.

Further, since the recording medium 8 can be moved by a minute amount smaller than the pitch p between the recording elements of the recording head 1, the outer diameter of the upstream drive roller 31 or the downstream drive roller 41 varies (due to individual differences). It becomes possible to correct the difference in the amount of conveyance of the recording medium 8, and by making the unit movement amount sufficiently small, the upstream drive roller 31
Also, the transport amount of the recording medium 8 by the downstream drive roller 41 can be made as close as possible to the total length (p × n) of the recording head 1 in the column direction.

Further, the position of the paper edge sensor 7 is arranged on the upstream side beyond the distance corresponding to the entire length of the recording head 1 from the upstream drive roller 31, and after one conveyance operation after the end of the recording medium 8 is detected, Since it is decided to shift to the downstream transport operation by this detection signal, the shift from the upstream transport operation to the downstream transport operation does not switch during the rotation of the upstream drive roller 31 and the downstream drive roller 41, and the recording medium There is no periodic deviation of the carry amount due to the eccentricity of the upstream drive roller 31 or the downstream drive roller 41 when the paper 8 is delivered.

From the above, it is possible to convey the recording medium 8 from the front end to the rear end with high precision, to record from the front end to the rear end of the recording medium 8 and to prevent banding. It can be realized without raising.

Since the drive roller has a small diameter,
The effect that the recording device can be made small and lightweight can be obtained.

FIG. 4 is a sectional view showing a second embodiment of the present invention.

The recording head 1 is fixed to the slider 255. The slider 255 is supported by a bearing 257 that engages with a slide shaft 256 fixed to the carriage 2, and a drive plate 258 that engages with a screw rod 254, and is held by the spring 259 in a state without rattling with respect to the carriage 2. ing. Screw rod 25
Reference numeral 4 denotes a drive plate 2 which is rotatably supported by the carriage 2 and has a male screw or the like on its outer periphery, which engages by rotating.
58, the drive plate 258, a pair of sliders 255, and the recording head 1 fixed to the sliders 255 can be moved in the column direction. Screw rod 2
54 is directly connected to the rod gear 253, and is driven by the fine movement motor 251 through the engagement of the rod gear 253 and the fine movement motor pinion 252. A step motor or the like can be applied to the fine movement motor 251, and the recording head 1 can be moved by a minute amount of about 5 microns per driving step by selecting the reduction ratio and the screw of the screw rod 254.

With this configuration, in the present embodiment, correction of an absolute carry amount error due to individual variations in outer diameter dimension of the upstream drive roller 31 or the downstream drive roller 41 shown in the first embodiment is performed. This is performed by fine movement of the recording head 1 in the column direction.

The conveying operation of the recording medium 8 is as follows.

At the time of upstream conveyance, the number of drive steps of the conveyance motor 6 is set on the assumption that the upstream drive roller 31 has an intended outer diameter. Therefore, the recording medium 8 is transported by the entire length (p × n) of the recording head 1 in the column direction if the upstream drive roller 31 is formed with the intended outer diameter. However, at this time, there is a possibility that the transport amount of the recording medium 8 may be over-sent or insufficient due to individual variations in the outer diameter of the upstream drive roller 31. This correction is performed by finely moving the recording head 1 by driving the fine movement motor 251. The fine movement motor 251 is driven by a preset number of drive steps corresponding to the individual overfeed amount or underfeed amount of the recording apparatus, and the recording head 1 is moved in a direction to correct the overfeed amount or underfeed amount. Move slightly.

Similarly, during downstream conveyance, the number of driving steps of the conveyance motor 6 is set assuming that the downstream drive roller 41 has an intended outer diameter dimension, and the outer diameter dimension of the downstream drive roller 41 varies. The deviation of the conveyance amount of the recording medium 8 due to is caused by driving the fine movement motor 251.

The drive of the transport motor 6 and the drive of the fine movement motor 251 can be performed simultaneously, and the transport time of the recording medium 8 is not impaired. By repeating the carrying operation and the printing operation and resetting the fine movement motor 251 when the printing of one page is completed, the printing head 1 returns to the initial position.

According to the present embodiment, since it is possible to correct the absolute carry amount error independently of the carrying operation of the recording medium 8, no eccentricity error occurs due to the correction. Further, since the unit movement amount of the recording medium 8 by the upstream drive roller 31 or the downstream drive roller 41 can be freely set, the characteristics of the carry motor 6 can be maximized and the carry speed can be further increased. . Further, the unit movement amount of the recording head 1 for correction can be reduced, and more accurate correction can be performed.

As the third embodiment, in the first and second embodiments, the upstream drive gear 311 and the downstream drive gear 4 are provided.
11 shows an example in which the reduction ratio between 11 and the conveyance motor pinion 61 is not an integer.

The outer diameter of the upstream drive roller 31 or the downstream drive roller 41, which is the final stage of the recording medium conveyance system, is such that the circumference is matched with the total length (p × n) of the recording head 1 in the column direction. For example, in the above-mentioned specific example, the diameter is very small, about 4.3 mm. The periodic error of the amount of rotation due to the eccentricity of the rotating system is half rotation or integer rotation +
Since it can take the maximum value in half a rotation, as a specific example,
The reduction ratio of the upstream drive gear 311 and the downstream drive gear 411 to the transport motor pinion 61 is 4.5, the transport motor pinion 61 has a pitch circle diameter of 12 mm, and the upstream drive gear 311 and the downstream drive gear 411 have a pitch. The operation will be described by taking as an example the case where the diameter of the circle is 54 mm and the upstream drive roller 31 and the downstream drive roller 41 have an outer diameter of about 4.3 mm.

In this case, the recording medium 8 is conveyed once,
That is, the upstream drive gear 311 and the downstream drive gear 41
1 (upstream drive roller 31 and downstream drive roller 41)
The conveyance motor pinion 61 rotates 4.5 times for each rotation. Assuming that the eccentricity of the carry motor pinion 61 is, for example, a reasonable manufacturing error of about e = 30 μm, the maximum error of the outer circumference of the carry motor pinion 61 due to eccentricity is ε = 2e · sin (θ / 2) from the equation (1). ) = 2
It can be × 30 × sin ((4.5 × 2π) / 2) = 60 microns. That is, the conveyance motor pinion 61 has a possibility of causing over-feeding or under-feeding of up to 60 microns on the pitch circumference with respect to the target rotation amount, and the upstream drive gear 311 and the downstream drive gear that engage with this may occur. The gear 411 also causes overfeed or underfeed of up to 60 microns on the pitch circumference. However, in this embodiment, the outer diameters of the upstream drive roller 31 and the downstream drive roller 41 are sufficiently (one digit or more) smaller than the outer diameters (pitch circle diameters) of the upstream drive gear 311 and the downstream drive gear 411. Therefore, as shown in FIG. 5, the excessive feed amount or the insufficient feed amount 82 on the outer circumference of the upstream drive roller 31 and the downstream drive roller 41, which are directly connected to the upstream drive gear 311, and the downstream drive gear 411, is It can be sufficiently (one digit or more) smaller than the excessive feed or the insufficient feed amount 81 on the pitch circumference of the side drive gear 311 and the downstream drive gear 411. In the above-mentioned specific example, the outer diameters of the upstream drive roller 31 and the downstream drive roller 41 are about 4.3 mm, and the outer diameters (pitch circle diameters) of the upstream drive gear 311 and the downstream drive gear 411 are Since the distance is 54 mm, the upstream drive gear 311 and the downstream drive gear 411, which can generate a maximum of about 60 μm, are fed too much or insufficiently 81 on the pitch circumference. On the outer circumference of the upstream drive roller 31 and the downstream drive roller 41 due to the eccentricity of the transport motor pinion 61, the overfeed or underfeed amount 82 on the outer circumference of the upstream drive roller 31 and the downstream drive roller 41 is at most 60 microns × 4. 3/54 ≒
The size of the recording medium 8 is about 5 microns, and the recording medium 8 can be conveyed with sufficiently high accuracy.

Although each of the above-described embodiments has been described by way of specific examples for the purpose of explanation, the dimensions and numerical values are not limited to these in applying the present invention.

In each embodiment, the pressing force of the upstream driven roller 32 is variable, but the downstream driven roller 42 is
The pressing force may be variable between a normal state and a state stronger than the pressing force of the upstream driven roller 32.

[0077]

As is apparent from the above description, according to the present invention, the peripheral length of the driving roller is approximately equal to the total length p × n of the recording head in the column direction or is a fraction of an integer. When the medium is conveyed by the total length p × n of the recording head (that is, when moving from one band to the next band), the drive roller makes one rotation or an integer rotation, and the drive roller drive center and the outside The periodic deviation of the transport amount of the recording medium due to the eccentricity from the radial center is canceled out, and the transport amount is always constant.

Further, since the recording head and the recording medium can be moved relative to each other by a small amount, it is possible to individually correct the difference in the conveying amount of the recording medium due to the variation of the outer diameter of the driving roller (due to individual difference). By sufficiently increasing the resolution of the minute amount movement, it is possible to make the amount of conveyance of the recording medium by the driving roller as close as possible to the total length p × n of the recording head.

Further, the position of the paper edge sensor is arranged on the upstream side beyond the distance corresponding to the entire length of the recording head from the upstream side driving roller, and after one conveyance operation after the end of the recording medium is detected, this detection signal is used. Since the operation is shifted to the downstream conveyance operation, even when the recording medium is delivered between the two drive rollers, the recording medium is delivered in an integral number of revolutions, so that the delivery amount does not vary.

As a result, it is possible to realize a recording apparatus in which banding due to the conveyance of the recording medium does not easily occur from the front end to the rear end of the recording medium without increasing the precision of parts.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of an embodiment of a recording apparatus of the present invention.

FIG. 2 is a perspective view of the recording apparatus shown in FIG.

FIG. 3 is a principle explanatory diagram of an embodiment of a recording apparatus of the present invention.

FIG. 4 is a cross-sectional view showing the configuration of another embodiment of the recording apparatus of the present invention.

FIG. 5 is an explanatory diagram of a third embodiment of the present invention.

FIG. 6 is a diagram showing a conventional example.

FIG. 7 is a diagram showing a conventional example.

[Explanation of symbols]

 1: Recording head 11: Recording element 2: Carriage 31: Upstream drive roller 311: Upstream drive gear 32: Upstream driven roller 41: Downstream drive roller 411: Downstream drive gear 42: Downstream driven roller 6: Conveyance Motor 61: Transport motor pinion 7: Paper edge sensor 8: Recording medium

Claims (4)

[Claims] 1. A recording head in which a plurality of recording elements are arranged in a column direction, and a perimeter is provided on an upstream side of a recording medium path with respect to the recording head and has a perimeter of the entire length in the column direction (the number of recording elements). Is n and p is the pitch between the recording elements in the column direction, p ×
n), which comprises an upstream drive roller which is equal to or a fraction of an integer, and an upstream driven roller which has an arbitrary circumference and is pressed by the upstream drive roller, and conveys the recording medium in the column direction of the recording head. Upstream recording medium conveying means, which is provided on the downstream side of the recording medium path with respect to the recording head, and is pressed by the downstream driving roller and the downstream driving roller having a circumferential length slightly larger than that of the upstream driving roller. And a downstream driven roller having an arbitrary circumferential length, the downstream recording medium transporting unit transporting the recording medium in the column direction of the recording head. 2. The recording apparatus according to claim 1, wherein the recording head and the recording medium can be moved relative to each other by a minute amount smaller than a pitch p between recording elements of the recording head. 3. An end face detecting means of the recording medium is provided on the upstream side of the recording medium path, and a pressing force of the driven roller is made variable by a signal of the end face detecting means. The recording apparatus according to 1. 4. The recording apparatus according to claim 1, wherein the end face detecting means is provided on the upstream side of the upstream side recording medium conveying means, which is further than a distance corresponding to the entire length of the recording head in the column direction.