JP2733350B2 - Sheet transport mechanism and image scanning apparatus using the transport mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a sheet transport used for transporting a sheet such as a photosensitive film with extremely high precision in, for example, a medical image recording apparatus or an image reading apparatus. The present invention relates to a mechanism and an image scanning device using the transport mechanism.

[Prior Art] FIG. 5 shows an example of a sub-scanning transport mechanism of an apparatus for reading a stimulable phosphor sheet on which a radiation image has been recorded as described in JP-A-63-212645.

In FIG. 5, reference numeral 101 denotes a stimulable phosphor sheet which performs sub-scanning by being conveyed rightward in the figure, and at the same time performs main scanning by scanning the light beam 113 perpendicularly to the plane of the drawing. An image is read. The sheet 101 is sandwiched between two pairs of sub-scanning rollers 102, 103, 104, and 105. Reference numeral 108 denotes a motor, which transmits power to the sub-scanning roller 102 by a belt 110 hung between a pulley 109 connected to the output shaft and a pulley (not shown) attached to the shaft of the sub-scanning roller 102. Pulleys 106 and 107 are also connected to the shafts of the sub-scan rollers 102 and 104, and both of them are
It is tied at 4. The sheet between the two pairs of sub-scanning rollers is supported by guide plates 111 and 112. With the configuration described above, the clockwise rotation of the motor causes the clockwise rotation force to be transmitted to the sub-scanning rollers 102 and 104, so that the sheet 101 can be conveyed rightward on the paper.

FIG. 6 shows a sub-scanning transport mechanism similar to the conventional example described in JP-A-63-258339. FIG. 6 corresponds to a view of the conventional example shown in FIG. 5 as viewed from above, and the same reference numerals as in FIG. 5 indicate the same or equivalent members.

The difference between the example in FIG. 6 and the example in FIG. 5 is that the driving force of the motor 108 is transmitted using the connecting member 120 without using the belt 110. In the drawing, reference numeral 121 denotes a bearing, and 122 and 123 denote frames.

[Problem to be Solved by the Invention] However, in the above conventional example, there is a problem that the constant speed of the rotation speed of the sub-scanning roller is deteriorated compared to the constant speed of the rotation speed of the drive source.

Optical reading device of high-precision image like the conventional example,
In the printing apparatus, constant transport speed of the sheet in the sub-scanning direction is extremely important. In particular, in a medical recording apparatus, pitch line unevenness of a scanning line due to a disturbance in the transport speed causes image density unevenness, and in the worst case, a misdiagnosis may occur. Therefore, the wah-rhutter of the sheet conveyance speed is 0.2
% Must be reduced to about% or less.

By the way, assuming that the sheet conveying speed is 40 to 50 mm / sec, the diameter of the sub-scanning roller 102 is 20 to 40 mm, and the reduction ratio between the sub-scanning roller and the motor 108 is 1: 1, the rotation speed of the motor is 20 to 50.
rpm. It is extremely difficult to reduce the wow flatter to 0.2% or less in such a low rotation range, and requires extremely high precision motor control technology.

Also, for example, in the case of medical use, a sheet to be conveyed is often large, such as a B4 size or a half-cut size (43 cm × 35 cm), which is also a disadvantageous factor in securing constant conveyance speed. .

When power is transmitted using a belt as shown in FIG. 5, it is reported in Japanese Patent Application Laid-Open No. 63-212645 that the power spectrum of the drive shaft and the driven shaft is as shown in FIG. That is, even in the best case, the constant speed of the driven shaft is lower than that of the drive shaft.

Also, as shown in FIG. 6, when a connecting member is used,
The constant speed of the roller may be lower than that of the motor. For example, when a general metallic flexible coupling is used as the connecting member, the resonance frequency of the sub-scanning roller is determined by the inertial mass of the sub-scanning roller and the torsion spring constant of the flexible coupling. The wow flutter of the roller near this resonance frequency is significantly deteriorated. In addition, it has been confirmed by experiments by the inventor that if the large inertial mass of a flywheel or the like is not added to the sub-scanning roller, the resonance frequency may be in a region where harmful scanning line pitch unevenness occurs.

As described above, in the above-described conventional example, there is a fear that the constant speed of the sheet conveying speed is deteriorated.

In addition, the constant speed can be measured only after the device is assembled, so that quality control is difficult. Further, replacement of rollers and motors is not easy, and it is hard to say that constant speed is reproduced after replacement.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet conveying mechanism capable of obtaining extremely high conveying accuracy, and an image scanning apparatus that uses the conveying mechanism and is highly accurate and easy to maintain.

Means for Solving the Problems According to the present invention, which has been made to solve the above-mentioned problems, there is provided a roller for conveying a contacting sheet, a support portion rotatably supporting both sides of the roller, and driving the roller. A drive motor, and detection means for detecting a rotation speed of the drive motor,
A frame portion that holds the support portion, the drive motor, and the detection unit, wherein a rotation shaft of the roller and a rotation shaft of the drive motor are a common shaft, and a rotor of the drive motor is attached to the common shaft. A sheet conveying mechanism wherein a stator of the drive motor is attached to the frame portion; and an image scanning apparatus having a configuration in which a light source and a scanning optical system are added to the sheet conveying mechanism.

Embodiment An embodiment of the present invention will be described below in detail with reference to FIGS.

FIG. 1 is a perspective view of an embodiment of a sheet conveying mechanism according to the present invention, and FIG. 2 is a sectional view thereof. FIG. 3 shows a configuration diagram of a medical image recording apparatus in which the sheet transport mechanism shown in FIG. 1 is incorporated as a sub-scanning transport mechanism.

This type of image recording apparatus records an image by performing main scanning with a laser beam on a recording sheet conveyed in a sub-scanning direction, and uses a recording sheet S that is, for example, a photosensitive film to be used. The size of the half cut (about 35 × 43
cm), large angle (about 35 × 35 cm), large four (about 28 × 35 cm) and the like. In FIG. 3, reference numeral 21 denotes an apparatus main body of the image recording apparatus, in which a plurality of unused recording sheets S of the same size are stacked and stored in a supply magazine 22 which is mounted substantially horizontally. Have been. As we all know,
When the supply magazine 22 is loaded into the apparatus main body 1, the supply magazine 22 is loaded with the lid closed, and when light shielding inside the apparatus main body 1 is secured after loading, the lid is opened by a lid opening / closing mechanism (not shown). Then, the uppermost one of the internal sheets S can be taken out by the suction cup 23. The leading end of the sheet S sucked by the suction cup 23 is inserted between the belt 25 wrapped around the three rollers 24 and the transport roller 26,
Thereafter, the suction force of the suction cup 23 is released, and the sheet S is conveyed downward by the driving force of the conveyance roller 26.
A one-way clutch is provided between the transport roller 26 and its driving source, so that even if the driving source is stopped, the sheet S
Can be easily inserted between the transport roller 26 and the belt 25 in the left direction of the drawing.

The sheet S, which is sandwiched between the conveyance roller 26 and the belt 25 and has changed its direction in the vertical scanning direction, is a first conveyance roller pair 27 and a second conveyance roller pair 1
a, 16 and sequentially conveyed, after which it is stored in the receiving magazine 29 by free fall, but immediately before the sub-scanning roller pair 1a, 16 on the way, by the laser beam B from the optical unit 30. Main scanning is performed. A guide plate 31 for regulating the position of the sheet S is provided between the transport roller 26 and the transport roller pair 27, and a similar guide plate is provided between the transport roller pair 27 and the sub-scanning roller pair 1a, 16. The laser beam B is irradiated from a slight gap between the lower end of the guide plate 32 and the sub-scanning roller pair 1a, 16. Note that the inner surfaces of the guide plates 31 and 32 are smoothly finished to minimize friction with the sheet S. The first conveying roller pair 27 is supported by a reciprocating mechanism (not shown) so as to be able to advance and retreat in the sheet conveying path. FIG. 3 shows a state where the first conveying roller pair 27 has entered the sheet conveying path. At the retracted position, there is no contact with the sheet S.

As shown in FIG. 3, in the state where the pair of conveying rollers 27 has entered the sheet conveying path, the distance L1 of the conveying path between the pair of conveying rollers 27 and the pair of sub-scanning rollers 1a and 16 is different depending on the size of the sheet to be used. The length of the sheet S in the transport direction is smaller than the length of the shortest sheet S. Therefore, even when the sheet S having the shortest length in the transport direction is used, the leading end of the sheet S is pinched by the sub-scanning roller pair 28 before the trailing edge of the sheet S separates from the transport roller pair 27. Then, immediately after the leading edge of the sheet S is sandwiched between the sub-scanning roller pairs 1a and 16, the first transport roller pair 27 is retracted from the sheet transport path by the advance / retreat mechanism, and recording starts after the retraction.

The recording optical unit 30 has a built-in polygon mirror for scanning the laser beam B from the laser light source, and the emitted laser beam B is reflected by the mirror 33 and travels on the sheet S being conveyed in the sub-scanning direction. An image is recorded by main scanning. After leaving the sub-scanning roller pair 1a, 16, the sheet S on which the recording has been completed falls by its own weight and falls into the receiving magazine 29.
Is stored inside. Receive Magazine 29 is about more than a vertical line
The lid 29a, which is installed at a tilt of 20 degrees and opened and closed with its lower end closed, is opened in a substantially vertical state. When the receiving magazine 29 is also mounted in the apparatus main body 1, the cover 29a is set in a state where the cover 29a is opened by a cover opening / closing mechanism (not shown). Is closed to prevent exposure to light and then pulled out. In FIG. 1, 34
Denotes a controller unit including a control circuit for controlling the entire apparatus, a power supply, and the like.

Next, the sub-scanning transport mechanism will be described in more detail with reference to FIGS.

In the figure, reference numeral 1 denotes a sub-scanning roller, which includes a roller portion 1a and shaft portions 1b, 1c,
Has 1d. The roller portion 1a contacts the sheet, and the shaft portion 1b
Are supported by bearings 13a. The shaft portion 1c is supported by a bearing 13b, and the rotor 6 of the motor is mounted. Further, a rotor 7 of an optical encoder is generally coupled to the shaft portion 1d. The shaft portions 1b and 1c have grooves for locking the E-shaped retaining rings 12a and 12b, and a preload spring 10 and a washer 11 are pressed between the bearing 13a and the retaining ring 12a, and the sub-scanning is performed. An appropriate preload is applied in the axial direction of the roller 1. Reference numeral 2 denotes a frame. The frame 2 includes a connecting portion 2a for holding bearings 13a and 13b, portions 2b and 2c fitted to fitting portions of the frames 14 and 15 of the recording apparatus main body, and a frame 2 for fixing to the frame 14. Flange portion 2d, housing portion for holding motor stator 5
2e and an opening 2f provided in the connecting portion 2a. Reference numeral 3 denotes a pedestal coupled to the housing portion 2e for fixing the detecting portion 9 and the cover 4 of the encoder.

FIG. 1 also shows a driven roller 16 attached to the recording apparatus main body via a shaft 19 and a lever 17. A tension spring 18 is provided between the lever 17 and the shaft 20 attached to the main body.
, And the driven roller 16 is pressed against the sub-scanning roller 1a with an appropriate pressing force.

After the sheet S conveyed from above in FIG. 1 is sandwiched by the pair of sub-scanning rollers 1a and 16 and then sub-scanned downward, the main scanning by the laser beam B is performed.
Is recorded as a latent image.

As described above, unitizing the sub-scanning transport mechanism including the roller, the motor, and the encoder unit has the following effects.

(1) Since there is no element such as a belt or a flexible coupling that degrades the speed stability between the sub-scanning roller 1a that conveys the sheet and the driving source, the characteristics of the driving source are directly transmitted to the roller. Extremely stable sheet conveyance becomes possible, and a high-quality image can be obtained.

(2) Since the conditions when using the motor unit alone and the motor unit are almost the same, it is easy to optimally design the control characteristics of the motor, and to reduce the wobbling in a specific frequency band according to the visual characteristics. It is also possible to improve the image quality.

(3) By evaluating the performance of the motor unit alone, it is possible to estimate the performance in a state in which the motor unit is incorporated, and therefore, quality control in manufacturing is facilitated.

(4) When removing the motor unit from the apparatus main body, the entire unit can be pulled out in the direction C in FIG. 2 simply by removing a bolt (not shown) on the flange portion 2d, and the motor unit can be easily attached to and detached from the apparatus main body. Therefore, the serviceability at the time of assembly or after installation is improved. In addition, since the performance can be compensated for by the motor unit alone, the performance at the time of shipment can be reproduced simply by replacing the motor unit at the installation location even in the event of a failure.

(5) The drive system does not have a member such as a belt that changes over time, and the initial performance can be maintained for a long period of time.

Second Embodiment Next, FIG. 4 shows a second embodiment of the present invention. The same reference numerals as those in FIG. 2 denote the same or similar members. The difference from FIG. 2 is that an ultrasonic motor is used as a driving source and a laser rotary encoder is incorporated in an encoder.

In FIG. 4, reference numeral 51 denotes a stator made of an elastic material such as stainless steel, which is fixed to the frame 2. 51
An electrostrictive element 52 is attached to one side of the. Therefore, a traveling wave that progresses with time is generated in a portion of the stator 51 that contacts the rotor 53. The rotor 53 is fixed to the sub scanning roller 1. The left end is a laser rotary encoder, which includes a disc-shaped diffraction grating 54, an optical system 55 including a semiconductor laser, a photodiode, a prism, and the like, a reflection optical system 56, a cover 57, a pedestal 58, and the like.

When an ultrasonic motor is used as the driving source, almost the same effects as those of the previous embodiment are recognized, and there are some advantages.
Ultrasonic motors are small and lightweight, have extremely high speed stability even at low speed rotation, and generate high torque. Therefore, the stability of the conveyance speed of the sheet is improved, and the fluctuation of the conveyance resistance is enhanced, so that good recording and reading can be performed. Further, the rotary encoder is small and lightweight, has a small inertia in the rotating part, and can generate high-resolution pulses of 80,000 pulses or more per rotation. Therefore, higher-precision control becomes possible, which is suitable for an ultrasonic motor having good control response.

The embodiments of the apparatus according to the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications are possible.

For example, the encoder section does not necessarily need to use the same axis as the roller section and the motor section. It may be connected to a motor unit or a roller unit by a general flexible coupling or the like. This is because the encoder has a smaller inertial mass than the motor or the roller, and the torsional force applied to the coupling means between the encoder and the motor or the roller is smaller than the torsional force generated between the motor and the roller. Because it is extremely small.

Further, the position of the encoder does not necessarily have to be at the end of the motor unit, and the motor unit and the encoder unit may be separately disposed at both ends of the roller unit as long as the torsion of the shaft can be tolerated.

Although FIG. 1 shows an example in which the driven roller 16 is fixed to the main body, a configuration in which the driven roller 16 is fixed to the frame 2 on the motor unit side is also possible. By doing so, the difference between the performance characteristics of the motor unit alone and the performance characteristics when the motor unit is mounted on the device is further reduced. Therefore, quality control is further improved.

In the apparatus having the configuration shown in FIG. 3, a torque in the acceleration direction is applied to the sub-scanning roller during sheet conveyance by the weight of the sheet. Therefore, simply controlling the motor so as to accelerate only when the speed of the rotating portion is reduced may cause the roller to rotate at a speed higher than the set speed due to the weight of the sheet. Therefore, it is necessary to perform control also in the deceleration direction or to provide a built-in brake for canceling the torque due to the weight of the seat. The brake may be configured to include the motor unit.

In FIG. 1, for convenience, the roller 1 and the frame 2 are each composed of one member. However, if there is no problem in strength, the roller 1 and the frame 2 may be divided into several parts and assembled.

2 and 4, the bearing is disposed inside the roller, and the motor and the encoder are disposed outside the roller. However, one or both of the motor and the encoder unit are provided inside the bearing. Is also good.

Although FIG. 3 shows an example of an image recording apparatus, the present invention can be applied to an image scanning apparatus in general, and it goes without saying that the present invention can be similarly applied to an image reading apparatus as shown in the conventional example. No.

[Effects of the Invention] The present invention has the following effects.

(1) There is no factor that degrades the speed stability in a portion that transmits the driving force of the motor to the roller, and the accuracy of the sheet conveying speed is extremely improved.

(2) Optimal design of motor control characteristics is facilitated.

(3) Quality control becomes easy.

(4) It is easy to attach / detach from / to the apparatus main body, and maintenance is improved.

(5) There is almost no deterioration over time.

[Brief description of the drawings]

 FIG. 1 is a perspective view of a first embodiment of the present invention, FIG. 2 is a cross-sectional view thereof, FIG. 3 is a configuration diagram of a recording apparatus having a mechanism of the present invention, and FIG. FIG. 5 and FIG. 6 are configuration diagrams of a conventional example, and FIG. 7 is a power spectrum of a drive shaft and a driven shaft of the conventional example. Sub-scanning roller, 2 ... frame, 6 ... rotor of motor section, 5 ... stator of motor section, 7 ... rotor of encoder,

Claims (6)

(57) [Claims] A roller that conveys a contacting sheet; a support that rotatably supports both sides of the roller; a drive motor that drives the roller; and a detecting unit that detects a rotational speed of the drive motor; A frame that holds the support unit, the drive motor, and the detection unit, wherein a rotation axis of the roller and a rotation axis of the drive motor are a common axis, and a rotor of the drive motor is mounted on the common axis. Mounting,
A sheet conveying mechanism, wherein a stator of the drive motor is mounted on the frame. 2. The sheet conveying mechanism according to claim 1, wherein a rotor of said detecting means is attached to said common shaft. 3. The sheet conveying mechanism according to claim 1, wherein a driven roller urged to abut on said roller is attached to said frame portion. 4. The sheet conveying mechanism according to claim 1, wherein said drive motor is an ultrasonic motor. 5. The sheet conveying mechanism according to claim 3, wherein said detecting means is a laser rotary encoder. 6. A roller that conveys a contacting sheet, a support portion that rotatably supports both sides of the roller, a drive motor that drives the roller, and a detecting unit that detects a rotation speed of the drive motor. A frame that holds the support unit, the drive motor, and the detection unit, wherein a rotation axis of the roller and a rotation axis of the drive motor are a common axis, and a rotor of the drive motor is mounted on the common axis. Mounting,
A sheet transport mechanism in which a stator of the drive motor is attached to the frame portion; a light source; and an optical system that optically scans light from the light source onto a sheet transported by the rollers. Image scanning device.