CN1353045A - Printing equipment - Google Patents

Abstract

This invention relates to a printer, comprising: a tractor for feeding printing paper along a predetermined route, a roller coming into contact with the printing paper to revolve by the angle corresponding to the moving distance of the printing paper, a rotary code wheel revolved by the same angle as the roller and having a large number of parts to be detected formed thereto on the concentric circle centering around the center of revolution at a predetermined pitch, and a photoelectric sensor for detecting the parts to be detected to output a detection signal at each time when the printing paper moves by a predetermined distance.

Description

printing device

The present invention relates to a printing device having a function of detecting the state of conveyance of printing paper.

As a printing device capable of high-speed printing, there is, for example, a dot printer mainly used for business use. In such a conventional dot printer, there is a roller that abuts on the printing paper and rotates only by an angle corresponding to the moving distance of the printing paper, and a tachometer that rotates with the roller. By monitoring the voltage output from the tachometer, Jamming of printing paper can be detected.

However, in the above-mentioned conventional dot printers, there is a problem that it is not possible to judge the printing paper conveyance state with high accuracy.

That is, with the development of printing technology in recent years, it is required to increase the printing speed of the printing apparatus and to improve the printing quality. For example, it is required to eliminate printing misalignment during double printing; for this purpose, the moving distance of printing paper must be precisely grasped, and alignment must be carried out. In addition, with regard to printing paper jams, it is no longer enough to detect that the printing paper has completely stopped during conveyance. It is required to detect jams immediately when the conveying speed exceeds the allowable error and slows down, so as to minimize the printing paper and printing time. unnecessary consumption.

However, like the above-mentioned existing dot printers, in such a structure that judges the conveyance of printing paper based on the output voltage of the tachometer, although it is possible to detect a jam when the printing paper in conveyance stops completely, it cannot be high. Accurately detect the conveying speed and conveying distance of printing paper. As a result, the conveying device cannot be controlled according to the actual conveying condition of the printing paper, and the printing quality cannot be improved from the point of view of the conveying accuracy of the printing paper.

The present invention was conceived in consideration of the above circumstances, and an object of the present invention is to provide a printing apparatus capable of accurately determining the state of conveyance of printing paper.

Another object of the present invention is to provide a printing apparatus capable of controlling the stop position of printing paper with high precision.

In order to solve the above-mentioned problems, the present invention adopts the following technical means.

According to the first technical solution of the present invention, the printing device provided is characterized in that it has: a paper conveying unit that conveys the printing paper along a prescribed path, abuts against the printing paper, and only turns over the corresponding printing paper. The roller at the angle of the moving distance only rotates at the same angle as the roller, and forms a rotating body with a plurality of detected parts at a predetermined pitch on a concentric circle centered on the rotation center. By detecting the detected parts, the printing paper A detection unit that emits a detection signal every time a predetermined distance is moved.

According to the preferred embodiment, there should be a moving speed judging unit for judging whether the moving speed of the printing paper is appropriate based on the detection signal from the detecting unit.

Preferably, the printing unit further includes a cover that abuts against the inner side where the roller abuts the printing unit.

Preferably, the paper conveying unit includes a plurality of protrusions capable of engaging the printing paper, and a conveying belt supporting them.

Preferably, the paper transport unit is driven by a stepping motor, and the detection unit sends out a detection signal every time the printing paper moves a distance equivalent to one step of the stepping motor.

Preferably, the detecting unit is a photoelectric sensor including a light projecting unit and a light receiving unit.

Preferably, the rotating body includes a central portion provided corresponding to the center of rotation, and a plurality of protruding portions respectively formed in a radial direction from the central portion as a plurality of detected portions; the light projecting portion and the light receiving portion of the photoelectric sensor sandwich the protruding portion Relative position is formed.

According to another preferred embodiment, on the rotating body, as a plurality of detected parts, a plurality of slits extending along the radial direction centered on the rotation center and capable of transmitting light are formed; the light projecting part and the light receiving part of the photoelectric sensor are sandwiched The gaps are formed relative to each other.

According to yet another preferred embodiment, on the rotating body, as a plurality of detected parts are provided with a plurality of reflectors centered on the rotation center, extending along the radial direction and capable of reflecting light, and the light projecting part of the photoelectric sensor is arranged on the A position where light can be projected onto the reflector is formed, and the light receiving unit is arranged at a position that receives light reflected from the reflector.

According to the second technical solution of the present invention, the printing device provided is characterized in that it has: a paper transport unit for transporting printing paper along a predetermined path, a detection unit for detecting the actual moving distance of the printing paper, and The detection result controls the paper conveying section to control the control section for controlling the stop position of the printing paper.

According to a preferred embodiment, when the actual moving distance detected by the detecting unit is less than the moving distance to be transported by the paper transporting unit by a predetermined distance or more than a predetermined ratio, the control unit sends a message to the paper transporting unit that the printing should be transported at a low speed. The distance of the paper equivalent to the difference, after the paper conveying part conveys the printing paper according to its instruction, the actual moving distance detected by the detecting part is less than the moving distance to be conveyed by the paper conveying part by a predetermined distance or more than a predetermined ratio , it is judged that an abnormality has occurred in paper conveyance.

According to the third technical solution of the present invention, the printing device provided is characterized in that it has: a conveying belt having a portion that can contact the printing paper, and a paper for conveying the printing paper along a prescribed path by driving the conveying belt. Conveying section; a roller that touches the printing paper and rotates only at an angle proportional to the moving distance of the printing paper; rotates at the same angle as the roller and is formed at a predetermined pitch on a concentric circle centered on the center of rotation The rotating body of a plurality of detected parts; the detection part that sends out the detection signal every time the printing paper moves a predetermined distance by detecting the detected part; the actual moving distance of the printing paper is measured by calculating the detection signal sent from the detection part, based on this The control unit that controls the drive of the conveyor belt is measured.

Preferably, the control unit reduces the driving speed of the conveying belt when the actual moving distance of the printing paper is less than a predetermined moving distance to be conveyed by the conveying belt.

Preferably, after reducing the driving speed of the conveying belt, the actual moving distance of the printing paper is measured, and when the actual moving distance is less than the moving distance to be conveyed by the conveying belt by a predetermined amount, the driving of the conveying belt is stopped.

According to the present invention, since the printing machine has: a paper conveying part that conveys the printing paper along a prescribed path; The rotating body that forms many detected parts at a predetermined pitch on a concentric circle centered on the rotation center at the same angle as the passed angle; by detecting the detection part that sends a detection signal every time the printing paper moves a predetermined distance, Based on the detection signal from the detection unit, the printing paper conveyance status can be judged with high precision.

In addition, as according to the present invention, since the printing machine has: a paper conveying unit for conveying printing paper along a predetermined path, a detecting unit for detecting the actual moving distance for printing, and controlling the paper conveying unit for printing based on the detection result of the detecting unit. The control unit of the paper stop position can control the stop position of the printing paper with high precision by feeding back the actual moving distance of the printing paper to the paper conveying unit.

Other features and advantages of the present invention can be further understood from the following descriptions of the embodiments of the invention.

Fig. 1 is the concept explanatory diagram illustrating the overall structure of the printing device of the present invention; Fig. 2 is a front view of the dragging roller shown in Fig. 1; Fig. 3 is a plane view of the dragging roller shown in Fig. 1; Figure 1 is a conceptual explanatory diagram of the printing part; Figure 6 is a front view of the main part of the linear motor shown in Figure 5; Figure 7 is a top view of the main part of the linear motor shown in Figure 5; Figure 8 is set on the printing head shown in Figure 5 Figure 9 is a block diagram of the control circuit of the printing device shown in Figure 1; Figure 10 is a diagram illustrating the sequence of paper feeding processing implemented by the MPU shown in Figure 9; Figure 11 is another implementation Example of the front view of the linear scale; Figure 12 is another embodiment of the front view of the linear scale.

The preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a conceptual explanatory diagram illustrating the overall configuration of a printing apparatus of the present invention. This printing device has a paper bucket 1 , pressing paper rollers 2 a , 2 b , a platen roller 3 , a printing unit 4 , a tractor 5 , a guide roller 6 and a stacker 7 .

Printing paper 8 made of continuous paper is transported from the paper bucket 1 to the stacker 7 by the tractor 5 along a predetermined path. The drag roller 5 is driven by a stepping motor 11 through a belt 12 . Printing is performed on the printing paper 8 by the printing section.

FIG. 2 is a front view of the drag roller 5 . FIG. 3 is a top view of the drag roller 5 . Fig. 4 is a cross-sectional view along line A-A of Fig. 3 . 2 to 4 mainly show the detection mechanism for detecting the conveyance distance of the printing paper 8, and the other parts are schematically shown. A plurality of protrusions 16 protrude from the conveying belt 15 of the drag roller 5, and are inserted into holes formed at ends of the printing paper 8 in the width direction to convey the printing paper 8 in the direction of the arrow in FIG. 2 .

The disk-shaped roller 17 made of an elastic material such as natural rubber or synthetic rubber contacts the printing paper 8 and rotates only by an angle proportional to the moving distance of the printing paper 8 . At this time, since the cover 18 freely openable and closable installed on the pull roller 5 is in the closed state, the cover 18 can well suppress the printing paper 8 from floating up, ensuring the contact state between the printing paper 8 and the roller 17. The cover 18 is omitted in FIG. 3 .

On the rotating shaft 19 of the supporting roller 17, a rotating code wheel 20 is fixedly fixed, and the rotating code wheel 20 and the roller 17 rotate integrally. The rotary code wheel 20 has a plurality of protruding portions 20a protruding radially from the center, and the transmissive photoelectric sensors 21 are disposed on both sides of the rotary code wheel 20 in the axial direction. The photoelectric sensor 21 has a light projecting part 21a and a light receiving part 21b. If nothing exists between the light projecting part 21a and the light receiving part 21b, the light emitted from the light projecting part 21a is received by the light receiving part 21b. Therefore, as the moving roller 17 of the printing paper 8 rotates, if the rotary code wheel 20 and the roller 17 rotate integrally, that is, the state where the protruding portion 20a of the rotary code wheel 20 blocks the light emitted from the light projecting portion 21a and In the non-blocking state, a detection signal with a period inversely proportional to the moving speed of the printing paper 8 is output from the light receiving unit 21b.

FIG. 5 is a conceptual explanatory diagram of the printing unit 4 . This printing unit 4 has a printing head 31, a linear motor 32, a linear encoder 33, a moving body 34, a belt 35, pulleys 36a, 36b, a guide rod 37, and coil springs 38a, 38b.

At the front end of the moving body 34 are provided stoppers 39 a and 39 b that can slide freely on the guide rod 37 , and the printing head 31 and the moving body 34 can move along the guide rod 37 . The coil springs 38a, 38b are slidably sleeved on the guide rod 37 . The linear motor 32 makes the moving body 34 perform linear reciprocating motion in the direction of the arrow in FIG. 5 . As the moving body 34 moves, the belt 35 connected to the moving body 34 moves, and as the belt 35 moves, the printing head 31 connected to the belt 35 moves in a direction opposite to the moving body 34 . Therefore, when the moving body 34 moves rightward in FIG. 5 , the printing head 31 moves leftward, and the coil spring 38 b is sandwiched between the printing head 31 and the stopper 39 b of the moving body 34 and compressed. Conversely, when the moving body moves to the left in FIG. 5 , the printing head 31 moves to the right, and the coil spring 38 a is sandwiched between the printing head 31 and the stopper 39 a of the moving body 34 to be compressed.

FIG. 6 is a front view of an essential part of the linear motor 32 . Fig. 7 is a plan view of an essential part of the linear motor. The linear motor 32 has a plurality of pairs (six pairs in this embodiment) of pairs of permanent magnets 41a, 41b facing each other at predetermined intervals, and a coil support portion 42 of the moving body 34 is provided between the pairs of permanent magnets 41a, 41b. A plurality of (six in this embodiment) coils 43 are arranged on the coil support portion 42, and each coil 43 is located in a gap between each pair of permanent magnets 41a and permanent magnets 41b. Two coils 43 at both ends of these coils 43 function as constant speed coils; the remaining four coils 43 function as reverse coils. The reverse coil is mainly used to propel or brake the printing head 31 when it moves in the opposite direction to accelerate and decelerate the printing head 31; the constant speed coil is mainly used to propel the printing head 31 when the printing head 31 is moving at a constant speed. force. When the moving direction of the printing head 31 is reversed, the coil spring 38a or the coil spring 38b is compressed and deformed by the propulsive force applied by the linear motor 32 . As a result, the elastic restoring force of the coil spring 38a or the coil spring 38b acts on the printing head 31, and the moving direction of the printing head 31 is instantly reversed.

FIG. 8 is an explanatory diagram of a pin module provided on the printing head 31 . On the pin module 51, there is a predetermined interval between the inclined direction of the printing head 31 moving direction and the direction perpendicular to it shown by the arrow B in FIG. A plurality of (twelve in this embodiment) printing pins 52 are provided at predetermined intervals (pitches). On the printing head 31 , many pin modules 51 are arranged along the moving direction of the printing head 31 . The printing paper 8 is transported in the direction of arrow C in FIG. 8 . Driven by the printing pin 51, the printing paper 8 is pushed onto the platen roller 3 by the printing pin 52 through a paper belt (not shown in the figure) to print.

Fig. 9 is a circuit block diagram of the control section of the printing device of the present invention. This control unit has an MPU (microprocessing unit) 55 , a ROM (read only memory) 56 , a RAM (random access memory) 57 , and an interface circuit 58 . These MPU 55, ROM 56, RAM 57, and interface loop 58 are interconnected by bus. The coil 43 of the linear motor 32 , the photoelectric switch (not shown in the figure) of the linear encoder 33 , the light receiving part 21 b of the photoelectric sensor 21 , and the stepping motor 11 are connected to the interface circuit 58 .

The MPU 55 controls the entire printing unit.

The ROM 56 stores data such as control programs and setting values to be implemented by the MPU.

The RAM 57 memorizes various data used as the work area of the MPU 55 and the like.

The interface circuit 58 controls the transmission and reception of signals between the MPU 55 and the linear motor 32 , the linear encoder 33 , the photoelectric sensor 21 , and the stepping motor 11 .

The operation will be described below. FIG. 10 is a flowchart illustrating the sequence of paper feeding processing performed by the MPU 55. Such a program is executed by the MPU 55 every predetermined time. First, the MPU 55 judges whether it is necessary to feed paper (S1). That is, since the conveyance of the printing paper 8 and the printing of the printing head 31 are carried out alternately during printing, it is first necessary to know whether it is the required conveyance timing of the printing paper 8 .

If paper feeding is required (S1: Yes), the MPU 55 drives the stepping motor 11 at a prescribed normal speed (S2). Specifically, the MPU 55 supplies drive pulses to the stepping motor 11, and drives the stepping motor 11 by a predetermined number of steps. In this embodiment, when printing normal characters, the stepping motor 11 is driven in 24 steps for printing, and then the printing is driven in 36 steps, so that the 24-step driving and the 36-step driving are repeated and alternated. In addition, when image data is printed, the printing operation of driving the stepping motor 11 is repeated in 24 steps.

Next, the MPU 55 judges whether or not the printing paper 8 is conveyed at a predetermined distance (S3). Specifically, the MPU 55 counts the number of pulses of the detection signal from the photoelectric sensor 21, and based on the count, calculates the actual moving distance of the printing paper 8 to know whether it corresponds to, for example, about 24 steps of the stepping motor 11. At this time, since the pulse cannot be detected due to the conversion of the detection signal when the counting starts and the counting ends, the allowable range of error should be set in advance. That is, it is considered that the printing paper 8 is conveyed at a predetermined distance.

If the printing paper 8 is not conveyed at a predetermined distance (S3: NO), the MPU 55 drives the stepping motor 11 at a lower speed than normal (S4). Specifically, the MPU 55 calculates the distance not conveyed, and drives the stepping motor 11 only for the number of steps corresponding to the distance. At this time, since the stepping motor 11 is driven at a low speed, the step-out of the stepping motor 11 can be eliminated, and the probability that the printing paper 8 can be conveyed normally increases.

Then, the MPU 55 judges whether or not the printing paper 8 is conveyed by a predetermined distance (S5). The specific actions at this time are the same as step S3.

If the printing paper is conveyed for a predetermined distance (S5: Yes), the MPU 55 drives the printing unit 4 to print (S6), and the procedure ends.

In step S5, if the printing paper 8 has not been transported for a predetermined distance (S5: NO), the MPU 55 reports that a jam occurs (S7), and the routine ends. Such a notification can be displayed, for example, on a display screen (not shown) of a display device included in the printing device in characters or symbols indicating that a jam has occurred. Of course, it is also possible to indicate and display guidance release etc. on the basis of the notification. In addition, it is also possible to replace the display of such a display device or to add alarm sounds such as a violin sound or a buzzer sound on the display.

In step S3, if the printing paper 8 is conveyed by a predetermined distance (S3: Yes), it progresses to step S6.

In step S1, if feeding is not necessary (S1: NO), the routine is terminated.

In this way, since the printing machine has a drag roller 5, a roller 17, a rotating code wheel 20, and a photoelectric sensor 21, wherein the drag roller 6 is used to convey the printing paper 8 along a prescribed path, the roller 17 abuts against the printing paper 8 and only Rotate the angle corresponding to the moving distance of the printing paper 8, the rotary code wheel 20 only rotates the same angle as the roller 17 and forms a plurality of detected parts at a specified pitch on the concentric circle centered on the rotation center, and the photoelectric sensor 21, by detecting the detected portion of the rotating code wheel 20, a detection signal is sent out for every predetermined distance that the printing paper 8 moves. Therefore, based on the detection signal sent from the photoelectric sensor, the conveyance status of the printing paper 8 can be judged with high precision. .

In addition, since the printing machine has a dragging roller 5 that conveys the printing paper 8 along a predetermined path, a photoelectric sensor 21 that detects the actual moving distance of the printing paper 8, and controls the printing paper 8 by controlling the dragging roller 5 based on the detection result of the photoelectric sensor 21. The MPU 55 at the stop position can control the stop position of the printing paper 8 with high precision by feeding back the actual moving distance of the printing paper 8 to the drag roller 5.

In addition, when the actual moving distance detected by the photoelectric sensor 21 is less than the moving distance to be conveyed by the pulling roller 5 by a predetermined distance or more, an instruction that the printing paper 8 should be conveyed at a low speed by a distance equivalent to the difference is transmitted to the pulling roller. Roller 5, after dragging the roller 5 to transport the printing paper 8 according to this command, when the actual moving distance detected by the photoelectric sensor 21 is less than the predetermined ratio or more than the moving distance that should be transported by the pulling roller 5, it is judged as the transporting paper If an abnormality occurs, the stop position of the printing paper 8 can be controlled with high precision. At the same time, the synchronous motor 11 can be driven at a low speed to eliminate the imbalance of the synchronous motor 11, and the possibility of normal conveyance of the printing paper 8 can be improved.

In the above-described embodiment, the conveying state of the printing paper 8 is detected by the combination of the rotary code wheel 20 and the photoelectric sensor 21, but as shown in FIG. The conveyance state of the printing paper 8 is detected. In the linear scale 61 , many linear slits 63 are radially formed on the thin circular plate 62 . The slits 63 are processed, for example, by etching or the like, and are formed at a very fine pitch of, for example, about 80 μm on a circumference centered on the center of the circular plate 62 .

Or as shown in Figure 12, also can detect the conveyance state of printing paper 8 by the combination of line dial 71 and reflective photoelectric sensor, line dial 71 is to radially form many line reflectors 73 on the circular plate 72 and become. The reflector 73 can be provided, for example, by printing or the like, and is formed at a very fine pitch of, for example, about 80 μm on a circumference centered on the center of the circular plate 72 . The circular plate 72 absorbs light from the photosensor. Of course, the reflector 73 may not be used, but an absorber is provided to absorb the light from the photoelectric sensor. In this case, as the circular plate 72, a mechanism for reflecting light from the photoelectric sensor may be used.

If such a wire scale 61 or a wire scale 71 is used, higher-precision detection can be performed than in the case of using the rotary code wheel 20 . For example, when one step of the stepping motor 11 is equivalent to a printing density of 180dpi (bytes), every time the printing paper 8 moves 0.141mm, a detection pulse of one cycle is sent from the photoelectric sensor, such as setting the gap 63 or reflection The pitch of the body 73, that is, one cycle detection pulse can be obtained for every one step of driving the stepping motor, which is very easy to control while performing extremely high-precision detection. That is, by comparing the driving pulse of the stepping motor 11 with the pulse detected by the photoelectric sensor, the conveying condition of the printing paper 8 can be judged in units of one step of the stepping motor 11. The detection pulse from the photoelectric sensor controls the stepping motor 11, and the conveying speed and conveying distance of the printing paper 8 can be controlled with high precision and easily by the MPU 55 . Accordingly, a jam can be quickly detected before the printing paper 8 comes to a complete stop due to a reduction in the conveying speed of the printing paper 8 .

In addition, in the above-mentioned embodiment, one MPU 55 is configured to control the entire printing apparatus, but a plurality of MPUs may be provided, and in this case, functions are arbitrarily shared among the MPUs.

In the above-mentioned embodiment, continuous paper was used as the printing paper 8, but the present invention can be effectively used even if the printing paper is an intermittent paper.

Of course, the specific configuration of the printing device in the above-mentioned embodiment is just an example, and the present invention is not limited to such a specific configuration.

According to the present invention as described above, since the printing machine has: a paper conveying part that conveys printing paper along a predetermined path, a roller that abuts against the printing paper and only rotates an angle equivalent to the moving distance of the printing paper, and only rotates with the roller A rotating body that forms many detected parts at the same angle and at a predetermined pitch on a concentric circle centered on the rotation center, and a detection part that sends out a detection signal every time the printing paper moves a predetermined distance by detecting the detected parts, based on the The detection signal sent by the detection unit can judge the conveying condition of printing paper with high precision.

In addition, according to the present invention, since the printing machine has: a paper conveying unit for conveying the printing paper along a predetermined path, a detecting unit for detecting the actual moving distance of the printing paper, and controlling the printing by controlling the paper conveying unit based on the detection result of the detecting unit. The control unit of the paper stop position can control the stop position of the printing paper with high precision by feeding back the actual moving distance of the printing paper to the paper conveying unit.

Claims (14)

1. A printing device, characterized in that it has A paper conveying section that conveys printing paper along a prescribed path, The roller that comes into contact with the printing paper and rotates only by an angle corresponding to the moving distance of the printing paper, Only by rotating the same angle as the above-mentioned roller, a rotating body that forms a plurality of detected parts at a predetermined pitch on a concentric circle centered on the rotation center, A detecting unit that emits a detection signal every time the printing paper moves a predetermined distance by detecting the detected unit. 2. The printing apparatus according to claim 1, further comprising a moving speed judging unit for judging whether or not the moving speed of the printing paper is appropriate based on a detection signal from the detecting unit. 3. The printing device according to claim 1, characterized in that it includes a cover that abuts against the inner side of the contact between the roller and the printing paper. 4. The printing apparatus according to claim 1, wherein said paper conveying unit includes a plurality of protrusions capable of being joined to said printing paper and a conveying belt supporting them. 5. The printing device according to any one of claims 1 to 4, wherein the paper conveying unit uses a stepping motor as a driving source; A detection signal is issued when the distance is 1 step. 6. The printing apparatus according to any one of claims 1 to 4, wherein the detecting unit is a photoelectric sensor including a light projecting unit and a light receiving unit. 7. The printing device according to claim 6, wherein the rotating body has a center portion provided corresponding to the center of rotation, and a plurality of detected portions respectively formed radially from the center portion as the plurality of detected portions. As for the protruding part, the light projecting part and the light receiving part of the photoelectric sensor are opposed to each other with the position where the protruding part is formed. 8. The printing device according to claim 6, wherein a plurality of slits extending radially around the rotation center and capable of transmitting light are formed on the rotating body as the plurality of detected parts, The light projecting part and the light receiving part of the photoelectric sensor are opposed to each other with the slit formed therebetween. 9. The printing device according to claim 6, wherein on the rotating body, as the plurality of detected parts, a plurality of reflectors extending in the radial direction around the center of rotation and capable of reflecting light are provided. The light emitting unit of the photoelectric sensor is disposed at a position capable of projecting light to the position where the reflector is formed, and the light receiving unit is disposed at a position receiving light reflected from the reflector. 10. A printing device, characterized in that it has: A paper conveying section that conveys printing paper along a prescribed path, a detection unit that detects the actual moving distance of the printing paper, A control unit that controls the printing paper stop position by controlling the paper conveyance unit based on the detection result of the detection unit. 11. The printing apparatus according to claim 10 , wherein the control unit, when the actual movement distance detected by the detection unit is less than the movement distance to be transported by the paper transport unit by a predetermined distance or more than a predetermined ratio, will An instruction to convey the printing paper at a low speed by a distance corresponding to the difference is sent to the paper conveying section, and after the printing paper is conveyed by the paper conveying section according to the instruction, the ratio of the actual moving distance detected by the detecting section is given by When the moving distance to be conveyed by the paper conveyance unit is less than a predetermined distance or more than a predetermined percentage, it is determined that the paper conveyance is abnormal. 12. A printing device, characterized in that it has: Contains a conveying belt with a portion that can contact the printing paper, and a paper conveying part that can convey the printing paper along a predetermined path by driving the conveying belt, The roller that abuts against the aforementioned printing paper rotates only at an angle proportional to the moving distance of the printing paper, A rotating body that forms a plurality of detected parts at a predetermined pitch on a concentric circle centered on the rotation center by only rotating the same angle as the above-mentioned roller, By detecting the detection unit that sends out a detection signal every time the printing paper moves a predetermined distance, The control unit that controls the driving of the conveying belt based on the measurement of the actual moving distance of the printing paper by calculating the detection signal from the detection unit. 13. The printing apparatus according to claim 12, wherein the control unit reduces the driving speed of the conveying belt when the actual moving distance is shorter than the moving distance to be conveyed by the conveying belt by a predetermined value or more. 14. The printing device according to claim 13, characterized in that, after reducing the driving speed of the aforementioned conveying belt, the actual moving distance of the aforementioned printing paper is measured again, and when the actual moving distance is higher than what should be conveyed by the aforementioned conveying belt When the moving distance is shorter than a predetermined value, the driving of the conveyor belt is stopped.

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