JPH04310064A - Scanning carrier device - Google Patents

Abstract

PURPOSE:To realize the carrying with high accuracy by providing a dynamic damper acting in the travelling direction in the inside of a carrying track of the scanning carrier device and making a weight of the dynamic damper not in contact with a bottom face of the carrier device to absorb minute unevenness of carrying. CONSTITUTION:A carrier track 12 carried by a screw shaft driven by a drive motor is provided with a dynamic damper 50 comprising a weight 58, dampers 60, 62 and springs 64,66. Moreover, two magnets 70 fixed to the weight 58 and two magnets 72 fixed to a bottom 68 of a case 52 make the weight 58 not in contact with the bottom 68 of the carrying track 12. Since the moment of inertia of the damper 50 due to the fluctuation in the carrying speed is always larger than the friction force by forming the dynamic damper to be a system without friction, the damper 50 is operated in an excellent way thereby absorbing the resonance due to the coincidence between the resonance frequency of the carrier system including the carrying track 12 and the frequency of external vibration such as rotating frequency of the motor and absorbing unevenness of random travelling speed.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a scanning conveyance device applied to image recording devices, image reading devices, etc., which uses a screw transmission device and achieves high-precision scanning conveyance with extremely little conveyance unevenness. Regarding equipment.

0002

2. Description of the Related Art Optical scanning such as raster scanning and slit scanning is applied to various image recording devices, image reading devices, and the like.

In such image recording devices and image reading devices, for example, in devices that apply raster scanning, a light beam for recording or reading is deflected one-dimensionally in the main scanning direction, recording material in orthogonal directions,
By conveying an object to be scanned such as a document in a sub-scanning direction, the entire surface of the object to be scanned is two-dimensionally scanned by the light beam, thereby recording an image on a recording material or reading an image of the document.

On the other hand, in a device that applies slit scanning,
Reading is performed by scanning a slit-shaped reading or recording light source in a direction substantially perpendicular to the longitudinal direction of the slit, or by scanning and transporting a recording material, document, or other object to be scanned against the slit-shaped light source. Alternatively, the object to be scanned is entirely scanned with recording light to record or read an image.

[0005] Scanning and conveying devices for objects to be scanned in devices that apply such raster scanning and devices that apply slit scanning include scanning and conveying devices that use nip rollers arranged at positions sandwiching scanning lines, and belt conveyors. An example is a scanning conveyance device to which this is applied.

[0006] Furthermore, as a means for conveying large originals or recording materials, a scanning conveyance device is well known in which a conveyance table that fixes an object to be scanned such as a document is moved by a screw transmission device. 61-184367 discloses an image recording apparatus that performs sub-scanning conveyance using a conveyance device with a screw transmission device, and for the purpose of performing accurate sub-scanning conveyance without unevenness, a rotary drive source of a screw shaft is disclosed. An image recording apparatus using a servo motor has been proposed.

[0007]

[Problems to be Solved by the Invention] Generally, a scanning conveyance device that moves a conveyance table using a screw transmission device fixes a nut such as a ball screw nut to the conveyance table that fixes a sheet-like object to be scanned by suction or the like. A screw shaft screwed into this nut is rotated by a motor, and by moving the nut, the conveyor table is moved.

Therefore, in a scanning conveyance device that uses a screw transmission to move a conveyance table, it is necessary to prevent vibrations of the conveyance table in order to perform good image recording and accurate image reading. When performing image recording or image reading, if the conveyance platform that holds the conveyed object vibrates, especially in the conveyance direction, the formed image will be distorted in the image recording device, and the reproduced image will be distorted in the image reading device. There is uneven color in the sub-scanning direction,
This results in an image with uneven density.

A major cause of such vibrations in the conveyor table is that the vibration frequency of the drive system, such as the rotational frequency of the motor serving as the conveyance drive source, and the resonant frequency of the conveyor system match. vibration in the conveying direction of the conveyor table due to uneven conveyance speed of the conveyor table.

[0010] A scanning conveyance device that uses a screw transmission to move a conveyance table generally has a nut fixed to the conveyance table, and a screw shaft screwed into the nut is rotated by a motor.
The conveyor table is moved by moving the nut. However, in this device, the weight of the transport platform is relatively heavy, and the resonant frequency of the transport system is relatively low. , or its harmonic frequency, match the frequency of the vibration of an external vibration system in a relatively low frequency range, and the conveyance table resonates, which tends to cause unevenness in the conveyance speed of the object to be scanned.

[0011] In addition, unevenness in the conveyance speed of the conveyor table, including those caused by the rotation accuracy of the screw transmission device and the motor that is the drive source, as well as the resonance of the conveyor table mentioned above, occurs in the direction of movement of the conveyor table (
vibration in the scanning direction).

[0012] When there is such vibration in the traveling direction of the conveyance table, the image formed by the image recording device or the image reproduced by the image reading device may have stripes in a direction (sub-scanning direction) substantially perpendicular to the traveling direction. This results in unevenness. In particular, in the image recording apparatus that applies the aforementioned raster scanning, if there is any unevenness in the conveyance speed (sub-scanning speed) of the object to be scanned, the pitch of the main scanning lines will be uneven.
This results in an image with noticeable striped unevenness in the sub-scanning direction.
This has become a problem.

In order to solve these problems, the inventors of the present invention have made extensive studies and installed a dynamic damper inside the conveyor table to absorb the vibrations of the conveyor table and to reduce the pitch unevenness of the main scanning line. Invented a scanning conveyance device that reduced
This was proposed earlier (Japanese Patent Application No. 2-281078).

As is well known, a dynamic damper is a sub-vibration system attached to the main vibration system (transfer platform), which absorbs the vibrations of the main vibration system as sub-vibration system vibrations and suppresses the vibrations of the main vibration system. Specifically, it is composed of a weight disposed inside the conveyor table, a damper, a spring, etc. that engages with the weight, and the vibration of the conveyor table is absorbed by the vibration of the weight. absorb vibrations. In the above-mentioned scanning conveyance device, by providing a dynamic damper inside the conveyance table that acts in the moving direction (scanning direction) of the conveyance table, the resonant frequency of the conveyance system and the rotational frequency of the drive source overlap. This suppresses vibrations of the conveyor table caused by resonance and uneven conveyance speed of the conveyor table, making it possible to move the conveyor table with higher precision.

[0015] According to this scanning conveyance device, vibrations of the conveyance table are well absorbed by the action of the dynamic damper, and highly accurate image recording and image reading can be performed without uneven scanning and conveyance. However, in devices that basically have high transportation precision, such as scanning conveyance devices applied to printing plate-making equipment, the fluctuations in the moving speed of the conveyor table are small, so friction between the bottom of the conveyor table and the weight of the dynamic damper increases. may interfere with the vibration of the weight, and the dynamic damper may not operate smoothly. Therefore, further improvements are required to realize a sub-scanning conveyance device with higher precision.

An object of the present invention is to solve the problems of the prior art as described above, by fixing an object to be scanned, such as a document or recording material, or an object to be transported, such as a light source, to a transport table. This is a scanning conveyance device that scans and conveys the object to be scanned or conveyed by moving it with a screw transmission device, and eliminates vibrations caused by resonance of the conveyance table and uneven conveyance (scanning) speed, etc. An object of the present invention is to provide a scanning conveyance device capable of conveying a table with extremely high precision.

[0017]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a scanning conveyance device that moves a conveyance table in a scanning direction by applying a screw transmission device, wherein a weight is installed inside the conveyance table. and at least one of a damper and a spring that engages with the weight, and has a dynamic damper that acts at least in the scanning direction, and the weight of the dynamic damper and the bottom surface of the conveyance table are substantially non-contact. A scanning conveyance device is provided.

[0018] Furthermore, it is preferable that the weight of the dynamic damper is suspended by magnetic force so that the bottom surface of the conveyance table and the weight are not in contact with each other.

[0019]

The scanning conveyance device of the present invention having the above-mentioned predetermined configuration is a scanning conveyance device that moves a conveyance table by a screw transmission device, and has a dynamic damper inside the conveyance table. The constituting weight and the bottom surface of the interior of the conveyor platform where the dynamic damper is installed are substantially non-contacting.

In an image recording device, an image reading device, etc. that uses a scanning conveyance device that places an object to be scanned on a conveyance table and performs scanning conveyance, the conveyance of the conveyance table is a cause of deterioration of the accuracy of image recording/reading. Examples include vibrations of the conveyor table caused by speed unevenness, resonance of the conveyor table, and the like. Such vibrations of the transport table cause striped unevenness in the formed image in the image recording device and in the reproduced image in the image reading device in a direction substantially perpendicular to the transport direction (sub-scanning direction). turn into.

In contrast, in the scanning conveyance device of the present invention, a dynamic damper that acts in the traveling direction (scanning direction) is provided inside the conveyance table, and this dynamic damper prevents resonance of the conveyance table, uneven conveyance speed, etc. This absorbs the vibration caused by the transport table in the direction of movement, making it possible to perform highly accurate scanning transport.

Moreover, since the weight of the dynamic damper and the bottom surface inside the conveyance platform are substantially non-contact, the frictional force between the bottom surface of the conveyance platform and the weight of the dynamic damper does not adversely affect the operation of the dynamic damper. Even when using a basically high-precision scanning conveyance device such as a printing plate-making machine, the dynamic damper absorbs the vibrations of the conveyance table extremely well, making it possible to achieve an extremely high-precision sub-base with no conveyance unevenness. Scanning conveyance can be realized.

Therefore, by applying the scanning conveyance device of the present invention to an image recording device or an image reading device, the image recording device can output an image, and the image reading device can reproduce a reproduced image without density unevenness, color unevenness, etc. In particular, even when raster scanning is performed and the image is applied to a high-quality image recording device such as a printing plate-making device, the image is free from striped unevenness. You can get the image.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The scanning and conveying apparatus according to the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

FIG. 1 shows a schematic diagram of an example of a scanning conveyance device according to the present invention. The scanning conveyance device shown in Figure 1 (
10 (hereinafter referred to as a conveyance device) is a screw transmission device that fixes a scanned object A such as a recording material or a document on a conveyance table 12, and is composed of a screw shaft 14 and a nut 16 screwed onto the screw shaft 14. By moving the conveyance table 12 in the direction of arrow a or the opposite direction using the device, the scanned object A fixed on the conveyance table 12 is scanned and conveyed. It has a driving source 18, a speed reducer 20, and the like. Further, a dynamic damper 50 is provided inside the conveyance table 12.

When such a conveying device 10 is applied to an image recording (reading) device using raster scanning, various optical systems main scan the light beam in the direction perpendicular to the paper surface of FIG. By moving the conveyance table 12 in the opposite direction), the object A to be scanned is conveyed in the sub-scanning direction, and the entire surface of the object A to be scanned is two-dimensionally scanned by the light beam. In addition, the conveying device 10 is used for image recording (
When applied to a reading) device, an optical system having a slit light source whose longitudinal direction is perpendicular to the plane of the paper in FIG. Recording (reading) from the optical system by
The object A to be scanned is entirely scanned with light.

In the conveying device 10 , the rotational driving force from the drive source 18 is transmitted to the reducer 20 via the coupling 22 and reduced to a predetermined rotational speed, and further transmitted to the screw shaft 14 via the coupling 24 . The screw shaft 14 rotates at a predetermined speed.

Drive source 18 applied to the conveyance device of the present invention
There are no particular limitations on servo motors, step motors,
Various known drive sources such as brush motors and brushless motors can be used, and various servo motors are particularly suitable. Further, there is no limitation to the speed reducer 20, and any of various known speed reducers can be applied.

A screw shaft 14 connected to such a drive system
is rotatably supported at both ends by supports 26 and 28, and is rotated at a predetermined speed. The screw shaft 14 applied to the conveying device 10 of the present invention is not particularly limited, and all screw shafts applied to known screw transmission devices, such as ball screws and sliding screws, are applicable.

A nut 16 is screwed onto the screw shaft 14. In the illustrated transport device 10, a housing 30 is fixed to the lower surface of the transport table 12, and in a preferred embodiment, a spring 32 (biasing member) is used to push the nut 16 into the housing 30.
By crimping the housing 30 and the nut 16, the nut 16 and the conveyor table 12 are integrally connected.

As mentioned above, in a conveyance device using a screw transmission device, the resonant frequency of the conveyance system tends to overlap with the vibration frequency of an external vibration source such as the rotational frequency of the drive source, and the conveyance system tends to resonate. Unevenness occurs in the conveyance of the conveyor table.

On the other hand, in the illustrated conveying device 10, a biasing member such as a spring 32 is used to push the nut 16.
By integrally coupling the conveyance table 12 with the conveyance table 12, the resonant frequency of the conveyance system can be changed by changing or adjusting characteristics such as the spring constant of the spring 32. Therefore, by selecting the characteristics of the biasing member and setting the resonant frequency of the conveyance system so as to keep it away from the frequency of the external vibration source, it is possible to minimize conveyance unevenness due to resonance of the conveyance system (transfer platform). This allows for more accurate movement of the conveyance table 12 and provides favorable results.

[0033] Such a configuration is described in detail in Japanese Patent Laid-Open No. 2-226102 by the present applicant.

As the nut 16 applied to the present invention, any nut that is applied to a normal screw transmission device, such as a ball screw nut or a sliding screw nut, can be applied depending on the above-mentioned screw shaft 14, and there are no particular limitations. There isn't.

[0035] In the conveying device 10 of the present invention,
The method of coupling the nut 16 and the conveyance table 12 is not limited to using a biasing member as shown in the illustrated example, and the nut 16 may be fixed to the conveyance table 12 or the housing 30.

The conveyor table 12 is used to fix the object A to be scanned, such as various recording materials or original documents, in a predetermined position using a fixing member such as a magnet, suction, or the like. The illustrated transport device 10 moves the transport table 12 in the direction of arrow a and in the opposite direction by moving the nut 16, and scans and transports the object A to be scanned.

In the conveying device 10 of the present invention, a dynamic damper 50 that acts at least in the scanning direction is provided inside the conveying table 12, and a weight 58, which is a component of the dynamic damper 50, is provided inside the conveying table 12. stand 12
is configured so as to be substantially non-contact with the bottom surface of.

As is well known, a dynamic damper is a sub-vibration system attached to the main vibration system (transfer table 12), which absorbs the vibrations of the main vibration system as sub-vibration system vibrations and absorbs the vibrations of the main vibration system. It is something to suppress.

In the conveyance device 10 of the present invention, a dynamic damper 50 that acts in the moving direction (scanning direction) of the conveyance table 12 is provided inside the conveyance table 12, and the resonance frequency of the conveyance system, the rotational frequency of the drive source, etc. This suppresses vibrations of the conveyor table 12 caused by resonance of the conveyor table 12 due to overlapping of the conveyor table 12 and uneven conveyance speed of the conveyor table 12, etc., thereby making it possible to move the conveyor table 12 with higher precision. Further, by making the weight 58 and the conveyance platform 12 substantially non-contact, the conveyance device 1
0 is basically highly accurate and allows the dynamic damper 50 to operate well even when the fluctuation in conveyance speed is small. FIG. 2 shows a schematic cross-sectional view of the transport platform 12. As shown in FIG.

In the illustrated example, the conveyance table 12 is fixed via a housing 52 whose top is open and a packing 54.
It is composed of a casing 52 and a lid 56. The dynamic damper 50 disposed inside is composed of a weight 58, dampers 60, 62, and springs 64, 66, which sandwich and support the weight 58 from both sides in the scanning direction (movement direction).

In other words, in the conveyance device 10 of the present invention, the weight 58 of the dynamic damper 50 disposed inside the conveyance table 12 is adjusted depending on the weight and resonance frequency of the conveyance table 12, the rotational frequency and rotational unevenness of the motor 18, etc. By selecting the weight and the characteristics of the dampers 60, 62 and springs 64, 66, it is possible to extremely reduce vibrations of the conveying table 12 caused by resonance of the conveying table 12, uneven conveying speed, etc.
Highly accurate scanning and conveyance of the scanned object A can be realized.

Regarding a scanning conveyance device to which such a dynamic damper is applied, the present applicant's patent application No. 2-2
It is detailed in the specification of No. 81078.

Here, in the present invention, the weight 58 and the conveyor table 12
The structure is such that the bottom surface 68 of the casing 52 and the bottom surface 68 of the casing 52 are substantially non-contact. By floating the weight 58 with two magnets 72 disposed on the bottom surface 68 of the carrier 52, the weight 58 and the transport platform 1
The bottom surface 68 of No. 2 is not in contact with the bottom surface 68 of No. 2.

In the illustrated transport device 10, the vibration of the transport table 12 is absorbed by the vibration of the weight 58 of the dynamic damper 50, and accurate movement of the transport table 12 (
Accurate sub-scanning conveyance) is realized.

In this system, if the fluctuation of the conveyance speed (vibration of the conveyor table = uneven conveyance speed) is Δv; its period is f; then the inertial force F acting on the weight 58 of weight m is approximately expressed by the following formula: Given. F=m・Δv・f

Therefore, in order for the weight 58 to properly vibrate and absorb the uneven conveyance speed of the conveyor table 12, this inertial force F is necessary.
must be larger than the frictional force between the weight 58 and the bottom surface 68. However, when the conveyance accuracy of the conveyance device 10 is basically high, such as a sub-scanning conveyance device applied to a printing plate-making device, the inertia force F applied to the weight 58 is extremely small because Δv is small, and the weight 58 The frictional force between the bottom surface 68 and the bottom surface 68 may exceed the inertial force F, and the dynamic damper 50 may not operate properly.

On the other hand, in the conveyance device 10 of the present invention, the weight 58 and the bottom surface 68 are made substantially non-contact, thereby making the frictional force smaller than the inertia force F and reducing the small conveyance speed unevenness (Δv ), the weight 58 can vibrate well, and even in a high-precision transport device applied to a printing plate-making device, etc., the dynamic damper 50 can operate well, allowing more accurate scanning transport. In the illustrated example, this is achieved by floating the weight 58 using magnets 70 and 72.

The magnets 70 and 72 for floating the weight 58 of the dynamic damper 50 are not particularly limited, and may be any type of electromagnet, permanent magnet, etc. as long as they can generate a magnetic force that can float the weight 58 from the bottom surface. Any known magnetic force generating means can be applied. In addition, weight 58
When floating the weight 58 from the bottom surface 68, the method is not limited to the method using magnetic force as shown in the illustrated example, and various known methods such as a method of floating the weight 58 using air can be applied.

In addition, in the present invention, the weight 58 and the bottom surface 68
Methods for making the weight 58 substantially non-contact are not limited to floating the weight 58 as shown in the example, but include coating the contact surface between the weight 58 and the bottom surface 68 with a lubricant such as Teflon, The frictional force between the weight 58 and the bottom surface 68 is reduced by installing the weight 58 on the bottom surface, using a bearing, etc., and making this frictional force smaller than the inertial force. In other words, the bottom surface 68 is substantially A method for smoothing the surface is also exemplified. In other words, in the present invention, the weight 5
Making the weight 58 and the bottom surface 68 substantially non-contact is not limited to making the weight 58 and the bottom surface 68 completely non-contact as shown in the illustrated example, but can be made by various methods to make the weight 58 and the bottom surface 68 substantially non-contact. weight 5
8 and the bottom surface 68 are also included.

Dynamic damper 5 applied to the present invention
0 is not limited to the illustrated example, and may include a damper,
Instead of two springs, one spring may be provided, or three or more springs may be provided. Note that the numbers do not need to be the same. Further, the weight 58 may be supported only by the dampers 60 and 62 or only by the springs 64 and 66.

Furthermore, the weight 58 may not be supported from both sides in the scanning direction, but may be supported only from one side, and the weight 58 may be sandwiched between different devices such as a damper at the front in the scanning direction and a spring at the rear. Good too.

The weight 58 is not particularly limited, and may be made of metal, various resins, etc., depending on the weight, shape, etc.

[0053] There is no particular limitation on the damper to be applied, and any known damper such as an air damper or a hydraulic damper can be applied. Furthermore, various known springs such as coil springs and plate springs can be used. Further, instead of the spring, another biasing member such as an air spring or rubber may be used.

In the present invention, it is of course possible to prevent the vibration of the conveyor table by adjusting not only the characteristics of the spring and the damper but also the weight of the weight.

In addition to the members shown in the figure, the conveying device 10 of the present invention shown in FIG.
It may have various members as necessary.

By combining various optical systems, the conveying device of the present invention having the above configuration can be used in image recording devices that apply raster scanning as described above, image reading devices that apply raster scanning, and slit scanning devices. The present invention can be suitably applied as a conveying device for a scanned object in various devices such as an image recording device and a reading device.

Although the scanning conveyance device of the present invention has been described in detail above, the present invention is not limited to the above embodiments, and various changes and improvements can be made without departing from the gist of the present invention. Of course it's good too.

[0058]

As described above in detail, according to the scanning conveyance device of the present invention, a dynamic damper that acts in the advancing direction (scanning direction) is provided inside the conveyance table, and the weight of the dynamic damper and the conveyance table are By making the bottom surface virtually non-contact, the dynamic damper can operate well, even in high-precision transport devices such as the sub-scanning transport device of printing and plate-making equipment, and the transport system including the transport platform The resonance frequency of the conveyor table matches the frequency of external vibrations such as the rotational frequency of the motor, and vibrations in the direction of movement of the conveyor table caused by uneven conveyance speeds are absorbed, allowing for highly accurate scanning conveyance. This makes it possible to do the following. Therefore, by applying the scanning conveyance device of the present invention to an image recording device or an image reading device, the image recording device can output an image, and the image reading device can reproduce a reproduced image without uneven density or color. In particular, even when applied to an image recording device that performs raster scanning,
A good image without striped unevenness can be obtained. Furthermore, even when applied to a sub-scanning conveyance device that is basically highly accurate, such as printing plate making, it can satisfactorily absorb minute conveyance unevenness, and can perform sub-scanning conveyance with even higher precision.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a scanning conveyance device according to the present invention.

FIG. 2 is a schematic cross-sectional view of a conveyance table of the scanning conveyance device shown in FIG. 1;

[Explanation of symbols]

10 Scanning conveyance device 12 Transport platform 14 Screw shaft 16 Nut 18 Drive source 20　Reducer 22, 24 Coupling 26, 28 Pillar 30 Housing 32, 64, 66 spring 50 Dynamic damper 52 Housing 54 Packing 56 Lid body 58 Weight 60, 62 Damper 68 Bottom 70,72 Magnet

Claims (2)

[Claims] 1. A scanning conveyance device that uses a screw transmission to move a conveyance table in a scanning direction, wherein the conveyance table includes a weight and at least one of a damper and a spring that engage with the weight. 1. A scanning conveyance device comprising: a dynamic damper that acts at least in the scanning direction; and a weight of the dynamic damper and a bottom surface of the conveyance platform are substantially non-contact. 2. The scanning conveyance device according to claim 1, wherein the weight of the dynamic damper is suspended by magnetic force so that the bottom surface of the conveyance table and the weight are brought out of contact.