JP2003098680A - Image recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image recording device for optimumly forming an image by correcting a change in image forming magnification caused by an expansion/contraction difference between mechanical parts, etc., for moving a printing plate, a rotary supporting body and a recording head. SOLUTION: A temperature α near a rotating drum 16 outputted from a temperature sensor 40 and a temperature β near a shaft 48 outputted from a temperature sensor 42 are obtained at a step S10, a size variation Δα corresponding to the temperature αis obtained from a size variation table 66 and a pitch variation Δβ corresponding to the temperature β is obtained from a pitch variation table 67 at a step S12, and a difference ΔL between the size variation Δα and the pitch variation Δβ is calculated at a step S14. The corrected rotating speed ω of a motor is obtained at a step S16 based on the calculated difference ΔL, and the obtained corrected rotating speed ω of the motor is outputted to a driving motor 58 at a step S18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording for scanning and recording an image by moving a recording head in an axial direction of a rotary support while rotating a printing plate wound around a peripheral surface of the rotary support. It relates to the device.

[0002]

2. Description of the Related Art In recent years,
A technique has been developed in which a sheet-shaped recording material, in particular, a printing plate having a photosensitive layer provided on a support is used and an image is directly recorded on the photosensitive layer (emulsion surface) of the printing plate by a laser beam or the like ( Printing plate exposure device). With such a technique, it is possible to quickly record an image on a printing plate.

In a printing plate automatic exposure apparatus which uses the technique of recording an image on a printing plate, the printing head is wound around the peripheral surface of a rotating drum while the rotating drum is rotated at high speed (main scanning), and the recording head is rotated. An image is recorded on the printing plate by moving the (exposure head) along the axial direction of the rotary drum (sub scanning).

Generally, the movement of the recording head is
Although a ball screw mechanism is used, the ball screw mechanism is composed of a shaft having a male screw formed on the outer periphery and a moving block screwed to the shaft and prevented from rotating axially. The recording head moves by being attached to a stage fixed to this moving block.

By the way, the shaft of the ball screw mechanism, the rotary drum, and the printing plate expand and contract due to temperature changes in the apparatus. Therefore, the thermal expansion of the shaft changes the feed speed of the recording head during driving, and the size of the printing plate also changes due to the thermal expansion. If the material forming the shaft and the material forming the support of the rotary drum or printing plate are different, they have different coefficients of thermal expansion, so the magnification during image recording changes Image formation cannot be performed.

Particularly in the case of color image recording on a printing plate, C (cyan), M (magenta), Y (yellow),
Record four color images of K (black) on different printing plates,
Although it is required that the image recording position does not shift, the deterioration of the register accuracy appears as a major cause of image shift.

Further, the temperature difference of each part tends to become particularly large when the apparatus is started up at a low temperature, the difference in magnification change between the ball screw and the printing plate becomes large, and the registration accuracy deteriorates.

The present invention has been made in order to solve the above-mentioned problems, and provides an image forming magnification which is caused by a difference in expansion and contraction amounts of a printing plate, a rotary support, a mechanism portion for moving a recording head, and the like. An object of the present invention is to provide an image recording device capable of correcting changes and performing appropriate image formation.

[0009]

In order to solve the above-mentioned problems, the present invention arranges a recording head in an axial direction of a rotary support while rotating a printing plate wound around a peripheral surface of the rotary support. An image recording device for scanning and recording an image by moving the shaft along a shaft, which is arranged in the vicinity of a first temperature sensor arranged in the vicinity of a printing plate and a driving means including the shaft. A second temperature sensor, a change amount table that stores in advance the change amount of the printing plate and the change amount of the shaft corresponding to the temperature change, and the change amount of the printing plate corresponding to the output of the first temperature sensor and A change amount of the shaft corresponding to the output of the second temperature sensor is acquired from the change amount table, and a deviation of the recording magnification due to a change in the size of the printing plate and the shaft length is changed based on the acquired change amount. And adjusting means for adjusting the moving speed of the recording head as Tadashisa, it is configured to include a.

When the image recording apparatus is driven, the temperature inside the apparatus rises, and the temperature rise causes thermal expansion of the printing plate, the rotary support, and the shaft. Due to this thermal expansion, the size of the printing plate expands and the shaft also extends, but since the printing plate and the shaft are generally made of different materials, the coefficient of thermal expansion is different, and the recording head is moved at the speed before thermal expansion to produce an image. If it is formed, an appropriate image corresponding to the enlargement of the printing plate cannot be formed. Further, especially when the apparatus is started up at a low temperature, the temperature difference between the respective parts in the apparatus is large, so that the temperature difference also occurs between the printing plate and the shaft. Therefore, in the present invention, the temperature near the printing plate is measured by the first temperature sensor arranged near the printing plate, and the temperature near the driving unit is measured by the second temperature sensor arranged near the driving unit. In the change amount table, the change amount of the printing plate and the change amount of the shaft corresponding to the temperature change are stored in advance, and the change amount of the printing plate and the second change amount corresponding to the output of the first temperature sensor are adjusted by the adjusting means. The amount of change of the shaft corresponding to the output of the temperature sensor is acquired from the change amount table, and the deviation of the recording magnification due to the change of the size of the printing plate and the shaft length is corrected based on the acquired amount of change. Thus, the moving speed of the recording head is adjusted.

According to the present invention, the temperature is detected at two places near the printing plate and near the driving means, and the change amount of the printing plate corresponding to the detected temperature near the printing plate and the detected temperature near the shaft are dealt with. Since the moving speed of the recording head is adjusted based on the amount of change in the shaft to be used, appropriate image formation can be performed and image recording can be performed in response to changes in image magnification due to differences in the coefficient of thermal expansion between the printing plate and shaft. Even if there is a difference in the temperature of each part of the device, it is possible to perform appropriate adjustment corresponding to each temperature.

According to a second aspect of the present invention, the adjusting means obtains the rate of change of each of the printing plate and the shaft from the amount of change in the dimension of the printing plate and the amount of change in the shaft length, and prints. By adjusting the moving speed of the recording head by multiplying the moving speed by the difference between the plate changing rate and the shaft changing rate, the adjustment corresponding to the change of the image magnification due to the thermal expansion of the printing plate and the shaft can be performed. it can.

Further, according to the present invention, as described in claim 3,
A male screw is formed on the peripheral surface of the shaft, and the driving means includes a moving block screwed to the male screw and prevented from rotating around an axis, and a support body connected to the moving block and supporting the recording head. Can be further included.

Further, according to the present invention, as described in claim 4,
By disposing the second temperature sensor on the moving block, the temperature affecting the shaft can be measured.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an image recording apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an exposure section 10 of the printing plate automatic exposure apparatus of the present embodiment, and FIG. 2 shows a ball screw mechanism section 14 incorporated in the exposure section 10.

The exposure section 10 is mainly composed of a rotary drum 16 for winding and holding the printing plate 12 on its peripheral surface, a recording head 18, and a ball screw mechanism section 14.

As shown in FIG. 1, in the exposure unit 10, a base 20 is installed as a support for supporting the whole, and a pair of side plates 26, 28 parallel to the base 20 are attached to the rotary drum. 16 rotary shafts are pivotally supported. A pulley 32 is attached to a rotary shaft 30 protruding from one side plate 26, and a belt 34 is wound around the outer circumference of the pulley 32. A drive motor 27 is attached to the side plate 26 side of the base 20, and the belt 34 is also wound around a pulley 36 attached to the rotation shaft of the drive motor 27. As a result, the rotary drum 16 is rotated by the driving force of the drive motor 27.

The base 20 has a pair of rails 22, 2 parallel to each other from one side plate 26 to the other side plate 28.
4 is laid horizontally. A sub-scanning stage 38 is mounted on the rails 22 and 24, and the recording head 18 is arranged and supported on the sub-scanning stage 38. The sub-scanning stage 38 is movable in the axial direction of the rotary drum 16 along the rails 22 and 24, and moves in this direction to perform sub-scanning to form an image.

A temperature sensor 40 is attached to the side plate 26 near the rotary drum 16, and the temperature at this position is output from the temperature sensor 40 to a correction unit (not shown).

A slit hole penetrating the front and back surfaces of the base 20 is provided between the rails 22 and 24 of the base 20, and the support base 38 is attached to the back surface side of the base 20 via a head connecting member 44. Ball screw mechanism 14
Is connected with. A through hole 46 is formed in the head connecting member 44.
Is provided, and the shaft 48 constituting the ball screw mechanism portion 14 penetrates in the axial direction of the rotary drum 16. A male screw 50 is formed on the outer periphery of the shaft 48, and both ends of the male screw 50 are pivotally supported at positions equivalent to those of the side plates 26 and 28.

A moving block 52 is screwed onto the male screw 50 of the shaft 48, and the moving block 52 is attached to the head connecting member 44 via a tubular member 54. As a result, the moving block 52 is prevented from rotating, and the movement of the moving block 52 itself can be transmitted to the recording head 18 via the head connecting member 44. The moving block 52 has a temperature sensor 4
2 is attached, and the temperature at this position is output to a correction unit (not shown).

One end of the shaft 48 has a motor connecting portion 5
The shaft 48 is connected to the rotary shaft 60 of the drive motor 58 via 6, and the shaft 48 can be rotated by the drive force of the drive motor 58. By the rotation of the shaft 48, the moving block 52 moves in the axial direction of the shaft 48, and accordingly, the recording head 18 can be moved in the axial direction of the rotary drum 16.

In the present embodiment, steel (iron) can be used as the material of the shaft 48, and aluminum can be used as the material of the printing plate 12. The thermal expansion coefficient α1 of steel is 1.0 × 10
^-5 , and the thermal expansion coefficient α2 of aluminum is 2.3 ×
It is 10 ^-5 .

Next, the configuration of the control system of this embodiment will be described.

As shown in the block diagram of FIG. 3, the control system of the present embodiment comprises a correction section 62, a memory 64, a drive motor 58, a temperature sensor 40, and a temperature sensor 42. The correction unit 62 is composed of a microcomputer including a CPU, a ROM, and a RAM, and is connected to the memory 64, the drive motor 58, the temperature sensor 40, and the temperature sensor 42, respectively.

In the memory 64, the size change amount due to the temperature change of the printing plate 12 (hereinafter simply referred to as "size change amount").
Size change amount table 66 storing the
Pitch change amount table 6 storing the pitch distance change amount due to temperature change (hereinafter, simply referred to as “pitch change amount”) 8.
7 is stored.

The size change table 66 is shown in FIG.
, The size change amounts Δα1, Δα2, ..., Δαn corresponding to the temperatures α1, α2, ..., αn are stored. Further, as shown in FIG. 4B, the correction table 67 stores pitch change amounts Δβ1, Δβ2, ..., Δβn corresponding to temperatures β1, β2, ..., βn.

The size change amount stored in the pitch change amount table 66 and the pitch change amount stored in the pitch change amount table 67 are the change amount of the printing plate 12 and the change of the shaft 48 due to the temperature change for each device. The amount is detected and stored in advance.

Further, in the memory 64, as shown in FIG. 5, the difference ΔL = Δ between the size change amount Δα and the pitch change amount.
A corrected rotation speed graph showing the relationship between α-Δβ and the corrected rotation speed ω is stored. The corrected rotation speed ω indicates the motor rotation speed when the drive motor is adjusted so that an image with a magnification corresponding to the difference ΔL between the size change amount Δα and the pitch change amount is recorded.

Next, the operation of this embodiment will be described.

When the size of the printing plate is input from the input unit (not shown) and the exposure process of the printing plate exposure apparatus is started, the correction unit 62 starts the correction process according to the flowchart shown in FIG.

In step S10, the temperature α near the rotary drum 16 output from the temperature sensor 40 and the temperature β near the shaft 48 output from the temperature sensor 42 are acquired. A great difference occurs in the temperature of each part in the automatic printing plate exposure apparatus, especially when the apparatus is started up at a low temperature. Therefore, the temperature that affects the printing plate 12 is set as the temperature α and the temperature sensor 4
The temperature that affects the shaft 48 is measured by the temperature β
As a result, the temperature sensor 42 measures.

In step S12, the size change amount Δα corresponding to the temperature α is acquired from the size change amount table 66, and the pitch change amount Δβ corresponding to the temperature β is acquired from the pitch change amount table 67. In step S14, the difference ΔL between the size change amount Δα and the pitch change amount Δβ is calculated. In step S16, the motor correction rotation speed ω is obtained based on the calculated ΔL. The motor correction rotation speed ω is shown in FIG.
It is obtained by referring to the graph shown in FIG. 9 which shows the relationship between ΔL and ω. In step S18, the obtained motor correction rotational speed ω is output to the drive motor 58, and this processing ends.

The drive motor 58 is driven by adjusting the number of drive pulses so that the rotation of the drive motor becomes the motor corrected rotation speed ω output from the correction section 62.

On the other hand, the printing plate 12 is guided by a conveyance guide unit (not shown) and fed in from the tangential direction of the rotary drum 16. At a predetermined timing, the rotary drum 16
Is rotated in the mounting exposure direction of the printing plate 12 (direction of arrow A in FIG. 1) by the drive motor 27. The sent printing plate 12 is tightly wound around the peripheral surface of the rotary drum 16 by a front end chuck and a rear end chuck (not shown), and positioning for exposure is completed. When the mounting of the printing plate 12 on the rotary drum 16 is completed, the image data is read,
The exposure process is started by the light beam from the recording head unit 18. The feed speed of the recording head 18 in the sub-scanning direction at this time is corrected by the above-described correction processing, and proper image formation is performed according to the thermal expansion of the printing plate and the shaft.

The exposure process is performed by so-called scanning exposure in which the recording head unit 18 is moved in the axial direction of the rotary drum 16 while rotating the rotary drum 16 at high speed (main scanning).

According to this embodiment, the pitch change amount of the shaft corresponding to the temperature change near the shaft and the size change amount of the printing plate corresponding to the temperature change near the printing plate are stored in advance in the correction table. The temperature sensor measures the temperature near the printing plate and the temperature near the shaft, and the pitch change amount and the size change amount corresponding to the measured temperature are obtained from the change amount table, and the pitch change amount and the size change are obtained. Calculate the difference from the quantity. Then, the correction rotation speed corresponding to the calculated difference is obtained from the correction rotation speed graph, and the rotation speed of the drive motor is corrected, so that it is appropriate to cope with the change in the image magnification due to the difference in the thermal expansion coefficient between the printing plate and the shaft. Images can be formed, and magnification accuracy and registration accuracy can be improved.

In particular, since the temperature inside the apparatus is not stable when the apparatus is started up at a low temperature, there is a tendency that a temperature difference occurs between the temperature of the shaft and the temperature of the printing plate, and the relative displacement of the image writing position becomes large. However, since the temperature near the shaft and the temperature near the printing plate are measured and the correction is made according to the measured temperature, it is possible to make an appropriate correction corresponding to the thermal expansion at low temperature startup. It is possible to improve magnification accuracy and register accuracy.

In the present embodiment, the corrected rotation speed graph showing the relationship between the difference between the pitch change amount and the size change amount and the corrected rotation speed is stored in advance, and the corrected rotation speed is obtained by referring to the graph. As shown in FIG. 7, each change rate is obtained from the pitch change amount and the size change amount, and the difference between the obtained change rates is multiplied by the rotation speed when there is no adjustment amount to form an image of appropriate magnification. It is also possible to calculate the corrected rotational speed and drive the drive motor based on the calculated corrected rotational speed to make adjustment.

Further, although the outer drum type rotary drum 16 is applied as the rotary support in the present embodiment, the same effect can be obtained by applying the inner drum type rotary support.

[0042]

As described above, according to the present invention, the first temperature sensor arranged near the printing plate measures the temperature near the printing plate, and the second temperature sensor arranged near the driving means. Measures the temperature near the drive means. In the change amount table, the change amount of the printing plate and the change amount of the shaft corresponding to the temperature change are stored in advance, and the change amount of the printing plate and the second change amount corresponding to the output of the first temperature sensor are adjusted by the adjusting means. The amount of change of the shaft corresponding to the output of the temperature sensor is acquired from the change amount table, and the moving speed of the recording head is adjusted based on the amount of change. Therefore, it is possible to form an appropriate image corresponding to the change in the image magnification due to the difference in the thermal expansion coefficient between the printing plate and the shaft, and even if there is a difference in the temperature of each part of the image recording device, It has an excellent effect that appropriate adjustment can be performed.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an exposure unit of a printing plate automatic exposure apparatus.

FIG. 2 is a side view of a ball screw mechanism portion.

FIG. 3 is a block diagram of a control system.

FIG. 4A is an example of a correction table for a size change amount, and FIG. 4B is an example of a correction table for a pitch change amount.

FIG. 5 is a graph showing the relationship between the difference between the size change amount and the pitch change amount and the motor corrected rotation speed.

FIG. 6 is a flowchart of correction processing.

FIG. 7 is another flowchart of correction processing.

[Explanation of symbols]

10 Exposure part 12 printing plates 14 Ball screw mechanism 16 rotating drum (rotating support) 18 recording head 40 Temperature sensor (first temperature sensor) 42 Temperature sensor (first temperature sensor) 48 shaft 50 male screw 52 Moving block 58 drive motor 62 Corrector 64 memory 66, 67 Change table

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C362 AA46 AA47 BA27 BA29 BA31                       BB28 BB40                 2C480 CA11 CA45 CB02 DA29 EA01                       EC17                 2H084 AA30 AE05 AE06 AE07 AE08                       CC05                 2H097 AA03 AA16 AB08 BA10 LA01

Claims (4)

[Claims] 1. An image recording apparatus for scanning and recording an image by rotating a printing plate while being wound around a peripheral surface of a rotary support, and moving a recording head along a shaft arranged in the axial direction of the rotary support. A first temperature sensor arranged near the printing plate, a second temperature sensor arranged near the driving means including the shaft, and a second temperature sensor corresponding to the temperature change. A change amount table that stores in advance the change amount of the dimension and the change amount of the shaft length, and the change amount table that corresponds to the output of the first temperature sensor and the change amount of the second temperature sensor that corresponds to the output of the first temperature sensor. A change amount of the shaft length is acquired from the change amount table, and based on the acquired change amount, a deviation of the recording magnification due to the change of the dimension of the printing plate and the shaft length is corrected. Image recording apparatus having an adjustment means for adjusting the moving speed, the. 2. The adjusting means obtains the rate of change of each of the printing plate and the shaft from the amount of change in the dimension of the printing plate and the amount of change in the shaft length, and changes the dimension of the printing plate and the change in shaft length. The image recording apparatus according to claim 1, wherein the moving speed of the recording head is adjusted by multiplying the moving speed by a difference from the ratio. 3. A male screw is formed on a peripheral surface of the shaft, and the driving unit includes a moving block screwed to the male screw and prevented from rotating around an axis, and the recording head connected to the moving block. The image recording apparatus according to claim 1 or 2, further comprising: a support that supports the image recording medium. 4. The image recording apparatus according to claim 1, wherein the second temperature sensor is arranged on the moving block.