JPH05330162A - Serial impact printer - Google Patents

Abstract

(57) [Abstract] [Purpose] Not only does it produce clear print quality over the entire printing paper of a multi-leaf sheet set, but it also produces less noise during printing, and by using a vibrating small platen. To reduce the energy required to vibrate the platen. This allows
The purpose of the present invention is to achieve a reduction in printing energy cost, and further to avoid an increase in size of the apparatus. A piezoelectric element 20 is connected to a platen 6 facing the print head 2 with the print paper P sandwiched therebetween, and the platen 6 is synchronized with the print head 2 to print the print paper P.
The rear surface of the platen is arranged so that it can run in the same direction, and the vibration of the platen 6 is synchronized with the printing operation of the print head 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial impact printer in which a print head runs along a surface of a print medium, and more particularly, to an improvement of a platen which is arranged to face the print head with the print medium sandwiched therebetween.

[0002]

2. Description of the Related Art Conventionally, in an impact printer, it is difficult to obtain clear printing over all the leaves, for example, when printing the print-receiving papers of a multi-leaf set in which the next and subsequent leaves are carbon paper. .. For example, if the dot impact force of the print head is increased, the topmost leaf paper surface will be punctured by dot wires. Conversely, if the impact force is weakened, the impact force will not be transmitted to the bottommost leaf paper, There is a problem that the print becomes unclear and difficult to see. Further, increasing the dot impact force causes a problem that the impact sound at the time of printing becomes loud and causes noise pollution, and further, the apparatus needs to be equipped with a platen capable of withstanding the impact force, which leads to a large scale of the device. there were.

Therefore, as a countermeasure against these problems, for example, as shown in Japanese Patent Publication No. 56-41429, an ultrasonic vibration oscillator is connected to a platen which is arranged so as to face the print head with a print sheet interposed therebetween. A printer is known that prints while vibrating the platen in whole or in part with high frequency. In this printer, when printing is performed by the print head, the impact force of the print head is applied to the print surface of the print paper and the vibration force of the platen is also applied from the back surface of the print paper. Even in such a case, clear printing quality can be obtained over the entire leaves of the printing paper.

[0004]

In the above configuration,
Since the platen is vibrated at a high frequency, there is a problem that a large amplitude cannot be obtained when the frequency becomes high. Therefore, the vibration frequency is set so that the print wire inevitably vibrates about 3 to 5 times while being pressed against the print medium. However, in the above-mentioned configuration, the time during which the print wire is brought into pressure contact varies, although it is minute, due to factors such as the variation in the number of leaves in the multi-leaf set and the distance between the head and platen. However, since the frequency is constant, the number of times the platen vibrates while the print wire is in pressure contact with the print medium varies depending on the conditions. Therefore, for example, a large difference in print quality occurs between the one that vibrates three times and the one that vibrates four times while the printing wire is pressed.

The present invention solves the above-described problems, and provides a serial impact printer which can obtain a clear print quality over all the leaves of the printing paper of a multi-sheet set and can maintain a stable print quality. The purpose is to do.

[0006]

In order to achieve the above object, the present invention is directed to a print head which runs along the surface of a print medium and a platen which is arranged to face the print head with the print medium interposed therebetween. In the serial impact printer having the above-mentioned, the platen is equipped with vibration applying means for applying vibration, and the vibration applying means is driven in synchronization with the printing operation by the print head.

[0007]

According to the above construction, vibration is applied to the platen by the vibration applying means controlled so as to be driven in synchronization with the printing operation by the print head. As a result, when printing is performed by the print head, the impact force of the print head is applied to the print surface of the print medium and the vibration force of the platen is also applied from the back surface of the print medium. Even in such a case, clear printing quality can be obtained over the entire leaves of the printing paper.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the vicinity of a print head and a platen of a printer according to this embodiment, and FIG. 2 is a sectional view of the same portion. The print head 2 is attached to the printer 1.
By being mounted on the carriage 5 supported by the main guide shaft 3 and the sub guide shaft 4, the carriage 5 is reciprocally movable in the axial direction at a position facing the print surface of the print medium P at a predetermined print position. There is. On the other hand, the platen 6 has a leaf spring 7
By being mounted on a carriage 11 supported by a main guide shaft 9 and a sub guide shaft 10 together with a frame 8 supported by a frame 8 at a position facing the print head 2 with the print medium P interposed therebetween. , Is reciprocally movable in the axial direction. The shafts 3, 4, 9 and 10 are arranged in parallel.

The carriage 5 on which the print head 2 is mounted and the carriage 11 on which the platen 6 is mounted are moored to the timing belts 12 and 13 at positions corresponding to each other. The timing belts 12 and 13 are stretched between drive rollers 15 and 16 of the same diameter fixed to a drive shaft 14 extending in a direction orthogonal to the main guide shafts 3 and 9, and rollers (not shown) corresponding to these. Has been done. Thus, the print head 2 and the platen 6 can move in the same direction in the state where they are constantly opposed to each other. The drive shaft 14 is connected to a drive mechanism from a motor (not shown). In addition, the print medium P
A pair of paper feed rollers 17a, 17b and 18a, 18b are provided on the upstream side and the downstream side in the conveyance direction of the.

The print head 2 includes a flexible substrate 19
Is connected, and print information from a control device (not shown) is sent to the print head 2 via the flexible substrate 19. A plurality of printing units are radially arranged in the print head 2, and a printing wire for printing the printing medium P, a piezoelectric element for each printing wire, and a piezoelectric element for each printing wire are provided in the printing unit 2. And a motion transmission mechanism that expands the expansion and contraction displacement and transmits it to the print wire.

FIG. 3 is a detailed view of the vicinity of the platen 6. A laminated piezoelectric element 20 is disposed on the surface of the leaf spring 7 opposite to the platen 6. The piezoelectric element 20 is configured to expand and contract in the direction of the platen 6 in response to an applied AC voltage in the ultrasonic range from several kHz.

The printing operation of the printer 1 thus constructed will be described. The print medium P is a pair of paper feed rollers 17 located upstream (lower side in the figure) in the paper transport direction.
It is sent to a predetermined printing position by a and 17b. Then, the plurality of print wires of the print head 2 print by hitting the print medium P sent to the predetermined print position via the ink ribbon IR. When the uppermost leaf of the print medium P is plain paper and the following leaf and below is carbon paper, the uppermost leaf is printed by the ink ribbon IR, but the following leaf and below can be copied by carbon due to the impact force of the print head 2. It is designed to be used.

When a plurality of print wires of the print head 2 print on the print medium P, an AC voltage is applied to the piezoelectric element 20, whereby the piezoelectric element 20 expands and contracts in the direction of the platen 6 to move the plate. Vibration is applied to the platen 6 via the spring 7.

The drive shaft 14 is rotated by a motor (not shown) in synchronization with the transmission of print information from a host computer (not shown), and the drive rollers 15 and 16 are rotated in accordance with the rotation. As a result, the carriage 5 having the print head 2 runs on the surface of the print medium P via the timing belt 12, and following this movement, the carriage 11 having the platen 6 carries the print medium P via the timing belt 13. On the back side of. The moving speeds are exactly the same because the drive rollers 15 and 16 have the same diameter. Therefore, the print head 2 runs along the surface of the print medium P while the platen 6 is vibrated by the piezoelectric element 20. In synchronism with the above, the print medium P is sandwiched and the rear surface of the print medium P is run. Then, when the printing of one line is completed, the print medium P is conveyed by a predetermined length by the pair of paper feed rollers 18a and 18b located at the downstream side (the upper side in the figure) of the sheet in the conveying direction.

Next, the control circuit of the device for driving the printing wire having the printing pin at the tip and the device for vibrating the platen 6 will be described with reference to FIG. This control circuit has a plurality of input terminals 21 corresponding to the number of print pins and a plurality of print pin driving switching elements 22 so that each print pin is driven by a signal input to the input terminals 21. .. Further, in order to vibrate the platen 6 in synchronism with the drive of the print pin, a waveform shaping circuit 23 that shapes the waveform of the signal input to the input terminal 21 and a multi-input that takes the logical sum of the outputs of the waveform shaping circuit 23 OR circuit 24,
Variable delay circuit 2 for delaying output of multi-input OR circuit 24
5 and a platen driving switching element 26 driven by the output of the variable delay circuit 25.

The waveform shaping circuit 23 is a circuit for shortening the input drive pulse width. The reason why this circuit is necessary is that a plurality of pulses for continuously driving the print pins are input to the input terminal 21. This is to prevent the output of the multi-input OR circuit 24 from erroneously operating continuously with the signal input for one signal. Particularly, when the arrangement of the printing wires is a diamond type or the like, since the time interval between one printing operation using the printing wires and the next printing operation is short, the platen 6 is set to 1 for each printing operation. It is necessary to shorten the drive pulse width in order to vibrate reliably. Further, the variable delay circuit 25 is necessary because the spring mechanism is interposed in the drive mechanism of the print pin, so that the operation of the print pin with respect to the input signal is delayed as compared with the vibration operation of the platen. is there.

Next, the operation of the control circuit 21 will be described with reference to the time chart of FIG. When a signal (drive pulse) relating to print information from a host computer or the like (not shown) is input to the input terminal 21, the drive pin causes the corresponding print pin drive switching element 22 to conduct, whereby the print pin is opened. Driven. Since a spring system is interposed in the drive mechanism of the print pin, the displacement of the print wire is delayed with respect to the rising of the drive pulse (L → H) as shown by the broken line, as shown in FIG. 6A.

On the other hand, the platen driving switching element 2
Since the drive pulse is given to the drive circuit 6 via the variable delay circuit 25, the drive pulse is delayed from the drive pulse of the print pin by the delay time T as shown in FIG. 6B. As a result, the platen 6 is displaced as shown by the broken line. The delay time T
Is the time required for the displacement of the print wire and the displacement peak of the platen 6 to coincide, and is fixed after the initial adjustment.

As described above, during printing, the impact force of the print head 2 is applied to the print surface of the print medium P and the vibration force of the platen 6 is applied from the back surface of the print medium P, so that the print sheets of the multi-sheet set are printed at the same time. Even in such a case, clear printing quality can be obtained over the entire leaves of the printing paper. Further, since the platen 6 is arranged so as to run in the same direction as the print head 2 in synchronization with the print head 2, the platen 6 can be downsized and the energy required for the vibration of the platen 6 can be suppressed. Further, since the platen 6 is vibrated in synchronization with the printing operation by the print head 2, the printing energy cost can be reduced.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, as shown in FIG. 4 showing the configuration near the platen, a leaf spring 27 is provided on the front surface of the frame 28, and both ends of the leaf spring 27 are bent to form the frame 2
The screws 29 may be fixed to both ends of the plate 8, and the piezoelectric element 30 may be arranged on the surface of the leaf spring 27 opposite to the surface facing the print head 2. In this case, the platen is not used, and the portion of the leaf spring 27 located on the front surface of the frame 28 is directly substituted by the platen. As a result, the vibration of the piezoelectric element 30 is directly transmitted to the back surface of the print medium P via the leaf spring 27, the sensitivity of the piezoelectric element 30 to the vibration is improved, and the printing quality is further improved. Further, in the above-described embodiment, the vibration is configured to vibrate only once during the printing operation in synchronization with the printing operation, but the vibration may be vibrated a fixed number of times subsequent to this vibration.

[0021]

As described above, according to the present invention, vibration is applied in synchronization with the printing operation by the print head. As a result, when printing is performed by the print head, the impact force of the print head is applied to the print surface of the print medium and the vibration force of the platen is also applied from the back surface of the print medium. Even in such a case, clear printing quality can be obtained over the entire leaves of the printing paper. Furthermore, since the number of vibrations of the platen is regulated while the print wire is pressed against the print medium, the print quality is kept substantially constant.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a serial impact printer according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of the serial impact printer according to the present embodiment.

FIG. 3 is a front view of the platen of this embodiment.

FIG. 4 is a front view of a platen according to another embodiment.

FIG. 5 is a control circuit diagram according to the present embodiment.

FIG. 6 is a diagram showing displacement of a print wire and a platen due to a pulse signal.

[Explanation of symbols]

 2 print head 6 platen 7 leaf spring 20 piezoelectric element 22 printing pin driving switching element 23 waveform shaping circuit 25 variable delay circuit 26 platen driving switching element P printing medium

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Ninomiya 15-1 Naeshiro-cho, Mizuho-ku, Nagoya City Brother Industries, Ltd.

Claims (1)

[Claims] 1. A serial impact printer having a print head which runs along a surface of a print medium and a platen which is arranged so as to face the print head with the print medium interposed therebetween, wherein vibration is applied to the platen. A serial impact printer, characterized in that it is equipped with a vibration applying means for driving the vibration applying means in synchronization with the printing operation by the print head.