JPS63224966A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce an impact by a thermal head upon a platen when the pressure contact of the thermal head is initiated and permit the pressure contact force to be easily controlled by providing a normal rotating and reversing motor which changes the tension of a spring energizing a supporting member in a direction where the platen and printing head are caused to contact with each other under pressure, through a moving member. CONSTITUTION:A kick roller is permitted to rotate by driving of a motor for a recording medium to feed a recording medium in a cassette and thereby, the recording medium is supplied into between a platen 52 and a thermal head 47. Next, a cam gear 75 is allowed to rotate clockwise by a predetermined value by driving of a pulse motor 71 to move a gear pin 89 from (A) point to (B) point. Following this movement, a cam pin 88 is absorbed by tension of a sprint 90, turning a head cam 78 to clockwise with a shaft 81 as a pivot. In this way, the thermal head 47 is permitted to contact the platen 52 without any resultant impact force. In addition, the pulse motor 71 is caused to rotate to change the tension of the spring 90, setting the pressure contact force of the thermal head 47 upon the platen 52 to a predetermined range for printing density variations.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an image forming apparatus such as a printer or a digital plate making machine (a plate making machine that perforates heat-sensitive stencil paper (master) using a thermal head) in which a platen and a head come into contact with each other. 2. Description of the Related Art Image forming apparatuses, such as thermal printers, supply paper between a platen and a print head (hereinafter referred to as the head) that are separated from each other, press the head against the platen, perform printing, and then print is completed. Then, the pressure welding is released. The solenoid is ON and OFF to move the head toward and away from the platen.
This is done by FF.

[Problems to be solved by the invention]

However, since the platen and the head are brought into contact with each other by turning on and off a solenoid, the following problems arise. (1) The contact noise between the head and the platen is loud at the start of pressure welding. (2) The impact at the start of pressure welding is large and the head is easily damaged. In other words, the life of the head is shortened. (3) Since only a constant pressure force can be obtained, it is difficult to adjust print density or handle multiple types of paper with different thicknesses.

[Object of the Invention] The present invention can prevent damage to the head by reducing the balance at the start of pressure contact between the platen and the head, and can easily change the pressure contact force, thereby facilitating image formation control and conveyance control. The purpose is to obtain equipment. [Solution 1] In other words, the present invention provides an image forming apparatus in which a recording medium is interposed between a platen and a head, and the head forms an image on the recording medium, in which the platen and the head are supported so as to be able to move toward and away from each other. a spring that has one end attached to the support member and biases the support member in a direction to press the platen and the head; and another end of the spring that is attached to change the tension of the spring. This image forming apparatus is characterized by comprising a moving member that is movable in a direction in which the moving member is moved, and a forward/reverse motor that moves the moving member. [Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. Configuration> First, the configuration will be explained. As shown in FIG. 1, an image forming apparatus such as a digital plate making machine [a plate making machine that perforates heat-sensitive stencil paper (hereinafter referred to as master) using a thermal head] (2) is a main body 2 having an operation section 8; 2, and a paper feed tray 20 on which a document to be fed is set. A removable paper feed cassette 3 is attached to the main body 2 that accommodates the master.
It reads the image of the original set on the paper feed tray 20 and forms the image on the recording medium (master, HP paper, thermal paper, plain paper, etc.) stored in the paper feed cassette 3. ing. In the above, the master refers to a heat-sensitive stencil paper made by laminating a thermoplastic synthetic resin film and a porous support. Examples of the thermoplastic synthetic resin film include films of polyester, polypropylene, vinylidene chloride-vinyl chloride copolymer, and the like. Porous supports include, for example, natural fibers such as Manila hemp, kozo, and mitsumata; synthetic wA fibers such as polyester, polyvinyl alcohol, and polyacrylonitrile; and porous wIm! fibers whose main raw materials are semi-synthetic fibers such as rayon. Paper, nylon, Tetoron, silk gauze, etc. are used. The paper feed tray 20 is provided with paper feed guides 21 and 22 that are movable in the width direction for regulating the side edges of the set document as shown in FIGS. 1 and 2. The path for feeding the original set on the paper feed tray 20 and reading the image includes an empty sensor 65, a kick roller 23 for sending out the original, and a paper feeder for transporting the original sent out by the kick roller 23. A roller 24 is provided. A document that follows the document conveyed by the paper feed roller 24 is removed by a separation roller 25. Paper feed tray 20
The leading edge of the original set is regulated by the original stopper 26, and its passage is confirmed by the leading edge detection sensor 27 (for example, a lever set sensor) and the trailing edge detection sensor 28 (for example, a lever set sensor). It is fed by a feeding roller 29 and a driven roller 30. There are reference reflectors (white reference) 32 on the upper and lower sides of the conveyance path.
A document glass 33 housed in a glass presser plate 35 is provided, and the document is ejected by a paper ejection roller 31 pressed against the glass presser plate 35 with an appropriate pressure. Place the original on original glass 3.
While being conveyed over the document glass 3.3, it is illuminated by a light source, for example, a fluorescent lamp 34, provided at the bottom of the document glass 3.3.
The reflected light from the original illuminated by mirror 4 is reflected by mirror 4 and its direction is changed. The light supplied through this mirror 4 is sent to an image sensor, such as a CCD (Charge C
The image reading unit 5 includes an image processing unit 10 having an AID converter, etc., and an image processing unit 10 having an AID converter etc.
(Central processing unit)] 1. The paper feed roller 24 and kick roller 23 are belt driven and have a speed ratio of 1:. Further, the separation roller 25 is pressed against the paper feed roller 24 with an appropriate pressure, and rotates in the opposite direction at a speed ratio of about 70% of the paper feed roller 24. However, by means of a spring clutch (not shown), when the load exceeds a certain level, the document rotates in the forward direction, and when the load falls below a certain level, it rotates in the reverse direction, and the second and subsequent documents are not fed (reverse separation). It has become. Note that the paper feed roller 24 includes a one-way clutch, so that the document is forcibly conveyed even if the separation roller 25 is in pressure contact with the paper feed roller 24. In addition, the drive system from the output shaft of the document motor (pulse motor) that drives these is divided into two systems (using two one-way clutches), and the forward rotation feeds and separates the paper, and the reverse rotation performs reading.・Perform discharge. The feeding roller 29 and the paper ejecting roller 31 are belt driven and have a speed ratio of 1:1. The driven roller 30 is pressed against the feeding roller 29 with appropriate pressure, and provides paper feeding force. As the image sensor described above, MOS (Metal
Oxide SeIwiconductor) type image sensor and CI D (Charge Injector) type image sensor.
tion Device) or CP D (Ch
Other image sensors such as Pri+++ing Device) may also be used. On the other hand, in the path for feeding the recording medium and forming an image, there is formed an installation port 6 which serves as an inlet for the recording medium and into which the paper feed cassette 3 is installed. The paper feed cassette 3 is set. The paper feed cassette 3 is equipped with a means for detecting the type of paper feed cassette 3 set in the mounting slot 6 as shown in FIGS. 6 and 7, such as a magnetic sensor 6.
2,63. Further, the paper feed cassette 3 is provided with a push-up roller 64 and an empty sensor 46, such as a set of levers, for detecting whether or not there is a recording medium in the paper feed cassette 3. The recording medium set in the paper feed cassette 3 is sent out by a kick roller 42, separated and fed toward the recording medium conveyance path by a paper feed roller 43 and a separation roller 44. This conveyance path includes a rear end detection sensor 45, a platen 52, a thermal head 47 that moves toward and away from the platen 52, a head holder 51 that supports this thermal head 47, and a front end detection sensor 55 (for example, a transmission type sensor) and is provided alongside this sensor 55,
It includes a front/back detection sensor 56 for detecting the front/back sides of the master, a registration lever 57, and paper ejection rollers 58, 59. A one-way clutch is interposed in the kick roller 42. In addition, a paper feed roller 43 and a kick roller 42
is belt driven and the speed ratio is 1=1. Separation roller 44
The reverse speed ratio with respect to the paper feed roller 43 is 0.7:L. Further, the separation roller 44 is reversely separated by a spring clutch, similar to the document conveyance system. The thermal head 47 is supported by the head holder 51 via a head bracket 82 and a head holding plate 85, as shown in FIGS. 3 and 4. The head holder 51 is attached to a rotation shaft 81. A head cam 78 is attached to this rotation shaft 81, and the rotation of this head cam 78 causes the head 47 and the platen 52 to come into contact with each other and separate from each other. A drive mechanism for the head cam 78 and the head holder 51 is attached to a bracket 76. That is, a pulse motor 7 as a drive source, a gear 83 attached to the rotating shaft of this pulse motor 71, a gear 72 meshing with this gear 83, a gear 84 provided coaxially with this gear 72, and this A gear 73 meshing with the gear 84, and a gear 87 provided coaxially with the gear 73. The cam gear 75 that meshes with this gear 87 and the head cam 7
A head presser spring 90 is stretched between a cam bin 88 provided on the cam gear 8 and a gear bin 89 provided on the cam gear 75.
and a lever set sensor 91 (home position sensor) that detects the rotational state of the cam gear 75. The cam gear 75 includes an arcuate gear portion 75A and an arcuate recess 75F3. The paper feed cassette 3 includes a push-up plate 41 that presses the recording medium accommodated in a kick roller 42 by the urging force of a push-up roller 64 as shown in FIG. 2, and magnetic sensors 62 and 63 as shown in FIGS. 6 and 7. magnet accommodating parts 60.61 are provided at positions corresponding to the magnet accommodating parts 60.61
As shown in FIG. 8, the types of paper feed cassettes 3 can be distinguished depending on whether or not a magnet is housed in the paper feed cassette 3 (see the following table). Table x 1... Paper cassette containing master 3 x 2... Paper cassette containing thermal paper 3 x 3... Paper cassette containing OHP paper 3 x 4... Paper cassette 3 containing plain paper
Note that each paper feed cassette 3 is provided with a partition plate whose attachment position can be changed so as to correspond to the paper size. The design also takes into account the friction coefficients of the recording medium. Furthermore, when the plain paper feed cassette 3 is installed in the loading slot 6, the thermal transfer ribbon 7 is attached to the head 47 and the platen 5.
It is used by interposing it between 2 and 2. In this case, a ribbon feeding mechanism is required. Furthermore, depending on the type of recording medium, the printing processing conditions may be varied as follows, for example. (1) Setting the printing start position (heading) On the master, which will be the original printing plate, the reinforcing ears attached to the printing machine are fed blankly, and on thermal paper, etc., printing is started leaving a small margin. (2) The master for front and back detection has holes for front and back detection, and detects the front and back sides. Thermal paper or the like should have this front/back detection function disabled. (3) Determination of printing conditions ■ Control of printing pressure...Strong for master, weak for thermal paper. This is because it takes a lot of energy to print (41!i version). ■Control of printing pulse width and number of pulses...Thermal head energization time and how to apply energization pulses. That is, control is performed depending on whether printing is performed with one pulse (11th edition) or with multiple pulses. ■Switching between normal image and reverse image... determines the type of the paper feed cassette 3 set in the mounting slot 6, and switches whether to print with the normal image (plate making) or with the reverse image (plate making) . In other words, the master of the original printing plate is a reverse image (original image when printed),
Thermal paper prints on a normal image. ■ Appropriate γ for each paper for external data (read data)
Apply correction. (4) Setting the print end position and ejecting The end of the paper is detected, the end position of printing (11th edition) is set, and the paper is ejected as appropriate. Operation> In such a configuration, this device operates as follows. First, a document is placed face down on the paper feed table 20, the paper feed guides 21 and 22 are aligned with the width of the document, and the edge of the document is aligned with the document stopper 26, and the document is set. At this time, the empty sensor 65 detects ONL, and it is detected that the document is set on the paper feed table 20. On the other hand, when the paper feed cassette 3 is attached to the attachment port 6 in step S1 as shown in FIG. 9, the magnetic sensors 62 and 63 are turned on depending on whether or not a magnet is installed in the magnet storage portion 60, 61. 0FFL, the type of recording medium is determined. Then, in step S2, flags (starting positions of processing procedures) are set for each recording medium. Furthermore, the empty sensor 46 detects the presence or absence of a recording medium. When the paper feed cassette 3 is attached, the push-up roller 64 pushes up the push-up plate 41, and the recording medium is pressed against the kick roller 42. Furthermore, except in the printing state, the sensor 9] is O as shown in Fig. 3.
Operation ends with N. Sensor 91 becomes O due to external force.
When it is turned off, it returns to this state when the power is turned on. When the sensor 91 is in the state shown in FIG.
is pushed up, and the platen 52 and thermal head 47
It is separated from. In this state, when the start switch of the operation unit 8 is pressed, the solenoid (not shown) turns ON.Almost at the same time as the kick roller 23 goes down (due to its own weight), the document stopper 26 also goes down, and the document motor (not shown) goes down. (pulse motor) starts rotating. When the leading edge of the original turns on the original leading edge check sensor 27, the original is fed by a certain amount. At this time, the leading edge of the document hits the rolling contact portion between the feeding roller 29 and the driven rotor 30, creating a registration loop and correcting the skew. Thereafter, the document motor rotates in reverse, and the feed roller 29 and discharge roller 31 begin to feed the document. When the document is conveyed a certain amount so that it is engaged with the paper feed roller 29 and the driven roller 30, the solenoid is set to 0FFL, the kick roller 23 is raised, and the document stopper 26 is also raised. The document motor reverses, and the document trailing edge detection sensor 28 turns on.
L, then send a certain amount (from the FM paper sales tip to a certain position
...After approx. 5 mm), start reading. A fluorescent lamp 34 is used as a light source, and illumination reading is performed through the document glass 33. Note that during reading, the reference reflector 32 is read and shading correction is applied. Namely. The variation in the length direction of the light from the fluorescent lamp 34 is electrically corrected by reading the base color of the reference reflector 32 when the start switch is turned on. However, when making corrections to distinguish between the background and the image,
Approximately 60 m from the center of the document at the leading edge (approximately 3 mm) of the document
m data (background color of the original) is read and the slice level is changed. M8 rear edge detection sensor 28 is OFF (no original left)
After that, a certain amount is read, and then it is accelerated and conveyed for a certain period of time to be discharged. On the other hand, when the printing process is started in step S3, the kick roller is rotated by the drive of the recording medium motor, and the recording medium in the cassette 3 is sent out. Then, the paper is separated into one sheet by the paper feed roller 43 and the separation roller 44, and is supplied between the platen 52 and the thermal head 47. Thereafter, when the tip detection sensor 55 detects the tip, it stops after being fed a predetermined amount. Therefore, the leading edge of the recording medium comes out to the registration lever 57 and skew removal is performed. When the recording medium motor stops, the pulse motor 71 rotates and the registration lever 57 is retracted. The rotation of the pulse motor 71 causes the gears 83, 72, 84, 73,
The cam gear 75 rotates clockwise by a predetermined amount via the cam gear 87 . Accordingly, the gear pin 89 moves from point A to point B as shown in FIG. Therefore, the cam pin 88 is attracted by the tension of the spring 90, the head cam 78 rotates clockwise about the shaft 81, and the thermal head 47 comes into contact with the platen 52. When the pulse motor 71 rotates further, the pressure contact force of the thermal head 47 increases. Thereafter, if the recording medium is the master after approximately 15 mm of movement (step S4), front and back detection is performed in step S5, and if it is determined that the front and back are reversed in step S6, an error occurs in step S7. In step S8, the mode is switched to the discharge mode and the paper is discharged without making a master. In addition, in step S9, control of the print plate making start position is performed to find the beginning according to the type of recording medium. Then, in step S10, a printing and plate-making method suitable for the recording medium is selected, and in step S11, printing and plate-making operations are started. At this time, it is asked in step SL2 whether or not the image is a master, and if it is a master, the image is sent out as a reverse image in step 813, and if it is other than the master, the image is sent out as a normal image in step S14. Then, in step S15, the thermal head 47 is energized,
It is printed and made into plates. When the rear end of the recording medium is detected by the sensor 45, after a certain amount of printing and plate making, the recording medium motor is accelerated and the pulse motor 71 is reversed to weaken the tension of the spring 90 (the head 47 and platen 52 (weaken the pressing force) while draining. In step 816, it is determined whether all printing and plate making have been completed, and if not, the process returns to step S12.
Once completed, the process stops at step 817.

[Effects of Example 1 (1) Since a motor was used instead of a solenoid to connect and separate the thermal head 47 and the platen 52, the thermal head 47 could be connected to the platen 52 at low speed by adjusting the rotation speed of the motor. Can be pressure-welded. Therefore, the contact noise at the start of pressure welding can be significantly reduced, and the impact on the head 47 is reduced. Damage to the head 47 at the start of pressure welding can be prevented. (2) Since the head presser spring 90 is interposed between the cam pin 88 of the head cam 78 and the gear pin 89 of the cam gear 75 to press the head 47 against the platen 52,
As shown in FIG. 5, after the gear pin 89 moves from point A (the head 47 and platen 52 are separated) to point B and the head 47 contacts the platen 52, the amount of rotation of the motor 71 Since the tension of the spring 90 changes depending on where the zero point is, the platen 52 of the head 47
The pressing force can be set (variable) within a predetermined range. Therefore, the printing density can be changed by the pressure contact force of the head 47, and during master plate making, the degree of adhesion between the master and the thermal head (to improve thermal conductivity) required for perforation can be easily adjusted. Obtainable. In addition, it can easily handle multiple types of paper with different thicknesses and paper qualities. Furthermore, when making a master and discharging it, it is easy to change the pressure contact force during transport, such as increasing the pressure force during plate making and weakening the pressure force when discharging the rear end of the master. That is, a high pressure contact force is required for master plate making, but if the pressure contact force is also large when discharging the rear end, the load becomes too high and transportation becomes impossible. [Modifications] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and for example, the following modifications are possible. (1) In the above embodiment, the head was pressed against the platen, but
The platen may be pressed against the head, or the head and platen may be pressed against each other. (2) In the above embodiment, the head holder 51 is centered around the shaft 81.
, rotate the head cam 78 to move the head 47 to the platen 5.
2, the head 47 may be moved in parallel. (3) In the embodiment described above, one end of the spring 90 is supported by the gear pin 89 and the head cam 78 is pushed up when the pressure contact is released, but separate members may be used for each function. (4) In the above embodiment, a pulse motor was used as the motor, but a DC motor may also be used. In this case, for example, it is necessary to provide a sensor at the home position, a sensor at the low pressure position, and a sensor at the high pressure position.

【Effect of the invention】

As described above, in this invention, since the head is moved toward and away from the platen by forward and reverse rotation of the motor, it is possible to reduce the impact when the head starts pressing against the platen, and the image forming apparatus is capable of adjusting the pressing force. can be provided.

[Brief explanation of drawings]

Fig. 1 is a side view showing the external appearance of the digital plate making machine, Fig. 2 is a sectional view showing the outline of its internal structure, Figs. Fig. 6 is a schematic side view showing the part where the paper feed cassette is attached, Fig. 7 is a schematic sectional view showing the attached state, and Fig. 8 shows multiple paper feed cassettes. The perspective view and FIG. 9 are flowcharts showing the operation of the digital plate making machine. l...Digital plate making machine 3...Paper feed cassette 47
...Head 51...Head holder 52.
...Platen 71...Pulse motor 75...
・Cam gear 78...Head cam 90...Head presser spring patent Applicant: Riso Kagaku Kogyo Co., Ltd. Patent
Applicant: Japan Seimitsu Kogyo Co., Ltd. Figure 6 Figure 7 62.63 Figure 8

Claims (1)

[Claims] 1. In an image forming apparatus in which a recording medium is interposed between a platen and a head, and an image is formed on the recording medium by the head, a support member that supports the platen and the head so as to be movable toward and away from the head; One end is attached to the member;
a spring that biases the support member in a direction that presses the platen and the head; a moving member to which the other end of the spring is attached and that is movable in a direction to change the tension of the spring; An image forming apparatus characterized by comprising a forward/reverse movement motor.