JP3263531B2 - Paper transport device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an sheet conveying apparatus, and particularly relates to improvements in sheet conveying apparatus may be used preferably in the Thermal Help printer.

[0002]

2. Description of the Related Art In a thermal color printer, a thermal head having a plurality of arranged heating elements is disposed on an opposite side of an ink surface of an ink sheet on which inks of a plurality of colors are sequentially and repeatedly applied in a longitudinal direction. ing. And
A platen roller is disposed on the ink application surface side to face the thermal head, and the thermal sheet and the platen roller sandwich the ink sheet and the paper and press them with an appropriate pressure. Printing data is given to the thermal head, and electric energy is given to the heating element selected by the data. The heating element, which is a resistor, generates heat due to electric / heat energy change, and the ink on the ink sheet melts or sublimes. Since the ink sheet is in contact with the paper by the pressure of the thermal head, the melted or sublimated ink adheres to the paper. Since the ink sheet and the sheet are conveyed relatively to the thermal head, the attached ink solidifies as the temperature decreases, and an ink image is reproduced on the sheet.

[0003] The paper between the platen roller and the thermal head is transported by paper transport means. The sheet conveying means conveys the sheet by transmitting the rotation of the motor through a transmission system such as a transmission shaft or a reduction gear, thereby rotating a grid roller which is actually pressed against the sheet. If the paper is conveyed to a predetermined position where printing starts before printing of each color (referred to as a printing start position), the thermal head is pressed against the ink sheet and paper from the opposite side of the ink application surface, and then printing is performed. In the printing direction. When printing of the single color component is completed, release the thermal head from the paper,
The paper is transported to the print start position or print standby position.

As a method of transporting and printing a paper in a thermal color printer, a swing is employed in which after the printing of a single color component is completed, the thermal head is separated from the paper and the paper is transported in a direction opposite to the printing direction to a printing start position or a printing standby position. Platen winding, which feeds paper and winds it around the platen roller, rotates the platen roller in the same direction as the paper feed direction after the printing of the single color component, and conveys it to the print start position or print standby position There are methods.

In a conventional thermal color printer, a method of discriminating the paper size and controlling the printing start position on the paper uses a paper in which a part of the back surface of the paper is marked in advance in accordance with the paper size. The paper size is determined based on a change in signal level obtained by reading the marking by an optical sensor such as a reflection type photo interrupter disposed in the area, and the print start timing is dependent on the determined paper size. The print start position is controlled.

Referring to FIG. 26, a description will be given of a swing-back type sheet conveying device in a conventional thermal color printer. In this paper transport device, the grid roller 5 feeds paper between the thermal head 2 and the platen roller 4 disposed opposite to the thermal head 2 (the direction from the optical sensor 7 for determining the paper size to the platen roller 4).
The paper 3 is transported (this is called a paper feeding operation). At this time, the paper size is determined based on the above-described marking, and the printing start position is controlled based on the determined paper size.

When a sheet detection sensor (for example, a transmission type photo interrupter) 6 which functions as a sheet detecting means detects the rear end b of the sheet 3, the grid roller 5 stops conveying the sheet 3. Thereafter, the thermal head 2 presses the ink sheet 1 and the paper 3 against the platen roller 4 and
Transports the paper 3 in a printing direction opposite to the paper feeding direction (this is called a printing operation).

Since a color print image is obtained by superimposing multiple colors, the above-described printing operation is repeatedly performed for each color.

The above-described paper feeding operation and printing operation are similar in the platen winding method, but the operation of winding paper around the platen roller during paper feeding is included, and the paper is transported during printing. Is carried out by rotation of a platen roller around which is wound.

In connection with the paper size determination operation and the control of the printing start position, as shown in FIG. 27, the paper size is previously determined on the back surface opposite to the printing surface of the paper 3. Marking 3a is provided. When the paper 3 is fed, the size of the paper is determined by detecting a marking 3a corresponding to the paper size by an optical sensor 7 such as a reflective photo interrupter disposed in the paper transport area. Then, the printing start position is controlled depending on the timing at which the marking 3a is read.

[0011]

Here, the paper transport device in the conventional thermal color printer has the following problems.

(1) In order to determine the size of a sheet, it is necessary to apply a marking corresponding to the sheet size on the back side of the sheet in advance.

(2) Since an optical sensor for reading a marking corresponding to the paper size is required, the number of components of the paper transport device increases, and the miniaturization of the device is restricted.

(3) In a reflection type photointerrupter generally used as an optical sensor, various characteristics relating to individual differences and temperature of the photointerrupter itself, distance to the reflection surface, reflectance of the reflection surface, disturbance light and marking The resulting signal level greatly fluctuates due to the error of the above, so that the degree of freedom of mechanical and electrical design is restricted.

(4) Since the size of the paper on which no marking is made cannot be determined, it is not possible to print on paper of an arbitrary size.

SUMMARY OF THE INVENTION An object of the present invention is to provide a paper transport apparatus capable of printing on any paper without being limited to paper on which a specific marking has been made, and capable of printing on paper of different sizes. It is to provide. It is another object of the present invention to provide a paper transport device capable of achieving a high paper transport speed without deteriorating print quality. Still another object of the present invention is miniaturization,
An object of the present invention is to provide a sheet transport device suitable for simplification and cost reduction.

[0017]

In order to achieve the above object, in a thermal printer according to the present invention, a thermal head in which a plurality of heating elements are arranged is arranged.
Paper is pressed against the platen roller by the thermal head.
Printing is performed. Especially for thermal color printers
In this case, a thermal head having a plurality of heating elements arranged on a side opposite to the ink surface of the ink sheet is arranged using an ink sheet to which a plurality of colors of ink are sequentially and repeatedly applied in the longitudinal direction. . Then, a platen roller is arranged on the ink application side opposite to the thermal head so as to sandwich the ink sheet and the paper together with the thermal head, and the thermal head presses the ink sheet and the paper against the platen roller by the thermal head during printing. Printing is performed by causing the ink to adhere to the paper by the heat energy generated by the heating element.

[0018]

[0019]

[0020]

In such a thermal printer,
In the paper transport device according to the first aspect of the present invention, which can be used properly, the paper transport means for actually transporting the paper,
A paper detecting means for detecting an edge of the paper in the paper transport area is provided, and a pulse generating means for engaging with the operation of the paper transport means during paper transport and generating a pulse corresponding to the transport amount of the paper, Counting means for counting, first memory means for storing the count value of the counting means, and the paper size is determined based on the memory value of the paper size converted to the count value stored in the first memory means. A second memory for preliminarily storing optimum control values such as a print start timing and an ink sheet take-up amount corresponding to the paper size; and a paper size determined by the determination means. Is read from the second memory means to control the paper transport control so as to control the print start position in accordance with the paper size. It is characterized in that it comprises cormorants control means.

In a second aspect related to the first aspect of the present invention, the control means determines the paper size by the determination means at the time of feeding the paper, and detects the edge of the paper at the time of subsequent conveyance in the printing direction. The memory value of the count value representing the print start timing is read from the second memory means starting from the signal change from the paper detection means, and is actually counted to the read memory value of the count value representing the print start timing. The printing is started when the counted values match.

The third aspect which is further related to the first aspect of the present invention.
In the aspect, the second memory means may use a value obtained by converting a print timing corresponding to a paper size of a known size such as a postcard or a special paper previously selected as a standard paper size into a count value as a look-up table. When the paper size determined by the determination means is a standard size, the control means stores a memory value of a count value representing a print start timing corresponding to the standard size in the second memory means. Output from
When the paper size determined by the determination means is other than the standard size, the closest standard size is selected, and the memory value of the count value representing the print start timing corresponding to the selected standard size is output from the second memory means. It is characterized in that sheet conveyance control is performed by giving an instruction.

The fourth aspect related to the first aspect of the present invention
The counting means is characterized in that the counting means accumulates in the counting means by adding or subtracting a pulse from the pulse generating means for generating a pulse in accordance with the paper transport amount, and The pulse generating means for generating a pulse corresponding to
[Dpi] and the paper transport amount per pulse is X
When [mm / pulse], a pulse that satisfies X ≦ 6.35 / Y is generated.

In the paper transport apparatus according to the fifth aspect of the present invention, the paper transport means for actually transporting the paper and the paper detecting means for detecting the edge of the paper in the paper transport area are arranged. Pulse generating means for generating a clock pulse regardless of the above, counting means for counting the pulse, memory means for storing the count value of the counting means, and paper size converted to the count value stored in the memory means And a control unit for controlling the sheet conveyance so as to control the print start position in accordance with the sheet size based on the memory value of the sheet.

In the paper transport apparatus according to the sixth aspect of the present invention, a paper transport means for actually transporting the paper and a paper detection means for detecting the edge of the paper in the paper transport area are arranged. Pulse generating means for generating a clock pulse regardless of the above, counting means for counting the pulse, memory means for storing the count value of the counting means, and paper size converted to the count value stored in the memory means Determination means for determining the paper size according to the memory value of the printer, and further prepared in advance using optimum control values such as a print start timing and an ink sheet winding amount corresponding to each of a plurality of different paper sizes. Select the control program corresponding to the determined paper size from the control programs It is characterized in that it includes a control unit for performing sheet conveyance control.

In the paper transport apparatus according to the seventh aspect of the present invention, the paper transport means for actually transporting the paper and the paper detecting means for detecting the edge of the paper in the paper transport area are arranged. A pulse generating means for generating a clock pulse, a counting means for counting the pulse, and a first means for storing a count value of the counting means.
Memory means, determination means for determining the paper size based on the memory value of the paper size converted to the count value stored in the first memory means, printing start timing and ink sheet winding corresponding to the paper size. A second memory unit which stores in advance an optimum control value such as a take-up amount, and further reads a control value corresponding to the sheet size determined by the determination unit from the second memory unit. And a control means for controlling sheet conveyance so as to control the print start position in accordance with the sheet size.

In an eighth aspect related to the seventh aspect of the present invention, when the sheet is conveyed to a predetermined position in a direction opposite to the printing direction at a speed higher than at the time of printing, the control means includes:
When the paper is transported to a predetermined position such as a paper feeding end position or a printing start position, the paper size is determined by the determination unit,
Starting from a signal change from a sheet detecting means for detecting the edge of the sheet when the sheet is conveyed in a relatively low-speed printing direction, the second
The memory value of the count value representing the print start timing is read out from the memory means, and the printing is started when the count value actually counted matches the read count value memory value representing the print start timing. Paper transport control.

A ninth aspect further related to the seventh aspect of the present invention.
In the aspect of the invention, the second memory means uses a value obtained by converting a print start timing corresponding to a paper size of a known size such as a postcard or a special paper previously selected as a standard size into a count value as a look-up table. And the control means, as one of its roles,
If the paper size determined by the determination means is a standard size, an instruction is issued to output from the second memory means a memory value of a count value representing a print start timing corresponding to the standard size, and the paper size determined by the determination means If is not the standard size, select the closest standard size,
The paper transport control is performed by giving an instruction to output from the second memory means a memory value of a count value representing a print start timing corresponding thereto.

The first aspect which is further related to the seventh aspect of the present invention.
In the aspect of 0 , the memory means keeps holding the count value of the counting means as a memory value until the printing operation of one sheet is completed and while printing the same size paper continuously. It is characterized by.

The fifth aspect of the present invention, in the first one aspect associated with the sixth and seventh aspect, in the period of the pulse by the pulse generating means generates the T [s], sheet conveying speed at the time of printing Vp [m / s], the stability of Vp is Kp,
When the resolution of the printer is Y [dpi] and the displacement amount due to the variation of the paper transport speed Vp is X [mm], the condition is satisfied such that X = (1 + Kp) · Vp · T ≦ 6.35 / Y. It is characterized in that a suitable pulse is generated by the pulse generating means.

The first aspect of the present invention, in the fifth, sixth and seventh first and second aspects related to the aspect, the sheet detecting means for detecting the edge of the paper to be conveyed to the printing direction and the opposite direction It is arranged at a position where the end of the sheet can be detected in at least one of the sheet feeding directions, and the sheet conveyance control is performed by controlling the printing start position corresponding to the sheet size.

[0033]

[0034] In the first third aspect of the further related to the first and second aspects of the present invention, the sheet detection means for detecting the end and the presence or absence of paper sheets actually fed than the paper conveying means for conveying the sheet It is characterized by being arranged on the paper side.

[0035]

In the present invention, the paper transport means for actually transporting the paper includes a motor for generating a rotational driving force for transporting the paper, a transmission shaft for transmitting the rotational driving force of the motor, and a deceleration for reducing the transmission speed. It includes a transmission system including a gear, and a grid roller that actually presses and contacts the sheet and conveys the sheet by the frictional force of the contact surface. As the motor, for example, a DC motor can be used, which is rotated / stopped in response to a transport / stop control signal from the control means.
The rotation of the motor can also be used to rotate a pulse generating means connected to a rotation axis of the motor or an appropriate axis of a transmission system that rotates in conjunction therewith.

The paper detecting means disposed in the paper transport area is, for example, a transmission type photo interrupter, and outputs signals of different levels when the paper is not passing and when it is passing. When the leading edge of the paper conveyed by the paper conveying means passes through the paper detecting means, the signal level output from the paper detecting means changes from low level to high level (or from high level to low level), and When the sheet edge passes through the sheet detection means, the setting is made to change from high level to low level (or from low level to high level). At this time, the pulse of the pulse generating means for detecting a change in the signal level of the sheet detecting means and generating either a pulse corresponding to the sheet conveying amount or a clock pulse not directly related to the sheet conveying amount. By counting the number, the paper size is determined.

As the pulse generating means, either a means for generating a pulse corresponding to the amount of paper transport or a means for generating a constant clock pulse irrespective of the amount of paper transport may be used. Can be. The former is used by being connected to a sheet conveying means, and may be, for example, a rotary encoder connected to a shaft of a motor via a joint or built in the motor. In this encoder, the number of pulses generated per one rotation of the axis of the encoder is constant, and the number of pulses generated per unit time increases / decreases in accordance with a change in the number of rotations per unit time of the motor. For example, when the number of rotations of the motor is high, the number of generated pulses is large (the pulse period is short). Conversely, when the number of rotations of the motor is low, the number of generated pulses is small (the pulse period is long). Of course, if the number of rotations of the motor is constant, the number of generated pulses is also constant. That is, since the number of pulses generated by the encoder is proportional to the number of rotations of the motor, the correlation between the number of generated pulses and the paper conveyance amount is determined in advance, and the number of pulses from the start to the end of paper passage is determined. By counting, the paper transport amount corresponding to the size of the paper can be obtained. In addition, the printing start position corresponding to the paper size is stored in the memory in advance as the pulse count value, and the printing operation is performed based on the count value, whereby appropriate printing on paper of different sizes can be performed.

The latter type of pulse generating means operates independently without being connected to the sheet conveying means, and generates a clock pulse having a constant cycle regardless of the sheet conveyance / stop. This pulse generating means can be considered to be similar to a system clock which is the operation reference of the microcomputer. Even in the case of using the latter type of pulse generating means, the operation for obtaining the sheet conveyance amount and the sheet size is basically the same as that of the former type of pulse generating means.

At the next stage of the pulse generating means, there is provided a counting means for counting pulses. Normally, the operation of the counting means is controlled by the control means, that is, the operations of counting start, counting stop, and reset are controlled. In addition, in the counting means having the function of adding and subtracting pulses, in addition to starting, stopping, and resetting the counting, the addition and subtraction operations are controlled by the control means. Since the counting means counts the number of input pulses, if the pulse input is stopped and the count operation is completed, the count value is held at the time when the count is stopped or until the next pulse is input or reset. You.

The count value counted by the counting means is stored in the memory means when the control means issues a storage operation instruction to the memory means during the paper feeding operation, and the stored count value determines the paper size. Used to The stored count value is also used by the control means to specify a print start position and determine a timing for outputting a print start signal during a printing operation.

The memory means mainly stores the count value of the number of pulses corresponding to the sheet size counted by the counting means based on an instruction from the control means. When there are a plurality of memory means such as the first memory means and the second memory means, the first memory means stores the count value based on the instruction of the control means. The second memory means stores at least the paper size or the paper size converted into the count value and the print start timing information (the pulse generation means corresponding to the transport amount from one end of the paper to the print start position) corresponding to the paper size. Pulse count value) is stored as a storage item. These storage items are usually stored in the second memory means before the printing operation.

A RAM (read / write memory) is mainly used as the memory means or the first memory means.
As the second memory means, a ROM (read only memory) is mainly used. These memory means generally have a plurality of storage cells and can store values such as a plurality of count values. Therefore, the above-mentioned memory means, the first memory means, and the second memory means can be provided individually, but it is also possible to provide these memory means collectively.
It is also possible to provide these memory means together with other memory means.

Since the second memory means needs to store storage items such as print start timing information corresponding to the paper size before the printing operation, a ROM in which those storage items are stored in advance is used. It is generally used. However, the second memory means may be constituted by a RAM, and the storage items may be transferred from the data area of the control program to the RAM at the time of initialization such as when the power is turned on to prepare for the printing operation. However, when the RAM is used, if it does not have a function of always holding the memory value, the stored memory value is erased by turning off the power.

The discriminating means stores the memory value of the sheet size in terms of the count value of the pulse number corresponding to the sheet size counted by the counting means when the control means does not have the discriminating function. The paper size is determined by reading the memory value from (or the first memory means). The determination is performed by comparing a count value-converted sheet size corresponding to a plurality of sheet sizes held in the control unit or the judgment unit in advance with a memory value read from the memory unit. That is, of the count value converted paper sizes held by the control means and the determination means, the one closest to the memory value read from the memory means by the determination means is determined as the paper size.

The control unit recognizes the paper size based on the memory value from the memory unit or the output of the determination unit.
The control means also controls the printing start position based on the count value of the counting means after the detection of the sheet edge. The control means instructs the thermal head to start printing after specifying the printing start position, and sends print data stored in a video memory or the like to reproduce an image. The control means further uses a control program or a value stored in the second memory means to drive / operate the motor of the paper transport means in response to a paper end detection signal of the paper detection means or a print start timing.
Control the stop, start the count value of the counting means,
The operations of stop, reset, and addition / subtraction may be controlled, and storage and reset of the memory unit (including the first memory unit) may be controlled.

The thermal head starts printing in response to a print start signal from the control means. The print data given to the thermal head is image information stored in a video memory or the like provided separately from the paper transport device. Based on such print data, by selectively heating the heating elements arranged on the thermal head, the ink on the ink sheet is melted or sublimated, and the ink is deposited on the paper to form an image. It is formed.

By the above-described technical means of the present invention effectively functioning, the paper transporting apparatus can operate stably and accurately. The outline of the operation of the paper transport apparatus according to the present invention is as follows.

When a sheet for recording image information is inserted,
The paper is conveyed in the paper feeding direction for printing the first color.
For example, the paper is rotated /
The sheet is conveyed by a sheet conveying means including a motor for stopping, a transmission system for transmitting the rotation of the motor, and a grid roller for pressing the sheet to actually convey the sheet.
After one end of the paper is detected by the paper detection means placed in the paper transport area, the paper is transported until the other paper edge is detected. The paper transport amount during this time is, for example, a pulse from the pulse generating means for generating a pulse corresponding to the rotation of the shaft of the motor of the paper transporting means or a pulse generating means for generating a clock pulse irrespective of the transport of the paper. It can be obtained by counting the number. That is, the number of pulses output from the pulse generating means is counted by the counting means based on a change in the sheet edge detection signal from the sheet detecting means, and this count value is stored in the memory means. The sheet size (the length L in the main scanning direction) can be obtained by multiplying the memory value of the sheet size in terms of the count value stored in the memory unit by the sheet conveyance amount per pulse of the pulse generation unit. And the paper size can be determined. In this way, the sheet size is determined, and the sheet is conveyed to the sheet feeding end position, thereby completing the sheet feeding operation for printing the first color.

Next, the printing operation is started. At this time, the ink sheet is wound up to the printing start position so that printing of the first color can be performed.

When the ink sheet and the paper are ready to start printing, the thermal head presses the ink sheet and the paper against the platen roller based on the separation mechanism, and the paper transporting unit starts operating again to transport the paper. Convey in the printing direction,
Form the top margin of the paper to be printed due to the detection of the paper edge.

The control means detects the formation of the upper margin and, at the same time, takes out the image information stored in the video memory or the like, sends it to the thermal head as print data, and performs the printing operation of the first color sequentially. When the printing operation of the first color is completed, the thermal head is detached by the detachment mechanism.
The sheet is transported again in the sheet feeding direction, and the sheet feeding operation and the printing operation of the second color are performed in the same manner as in the case of the printing operation of the first color. Since the printing operation of multi-color superposition is performed,
Until the printing operation corresponding to the required number of colors is completed,
The paper feeding operation and the printing operation are repeatedly performed. Then, when the printing operation of the final color is completed, the paper is conveyed as it is in the printing direction and discharged by the paper discharging operation without performing the paper feeding operation again.

[0052]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a paper transport device of a thermal color printer will be described below.

(Embodiment 1) FIG. 1 schematically shows a main part of a swing-back type thermal color printer to which the present invention is applied. FIG. 2 is a block diagram showing a control system in the thermal color printer of FIG.

When the printing of the single-color component is completed, the thermal head of the swing-back type, which separates the thermal head from the paper and conveys the paper to a predetermined position in a direction opposite to the printing direction, performs one-color superposition for multi-color superposition. Each time the color printing operation is completed, the paper is reciprocated. The transport direction of the paper when printing is actually performed is called a print direction, and the reverse transport direction is called a paper feed direction.

In FIGS. 1 and 2, if the paper 3 on which an image is to be stored is inserted into the grid roller 5, the first
The paper 3 is conveyed in the paper feeding direction for printing the color. The paper 3 includes, for example, a motor 11 that rotates / stops in response to a transport / stop control signal, a transmission system that transmits the rotation of the motor 11, and a grid roller 5 that presses and contacts the paper to actually transport the paper. Transported by means. After the leading edge a of the sheet is detected by the sheet detecting sensor 6 of, for example, a transmission type photo interrupter as a sheet detecting means placed in the sheet conveying area, the sheet is conveyed until the trailing end b of the sheet is similarly detected. . The paper transport amount during this time can be obtained, for example, based on the number of pulses from the encoder 8 serving as pulse generating means attached to the shaft of the motor 11. That is, the paper detection sensor 6
The number of pulses pp output from the encoder 8 during the period from the rising edge to the falling edge of the sheet edge detection signal from the counter 9 is counted by a counter 9 as counting means,
This count value is stored in, for example, a RAM as a memory means.
(Read / Write memory). The paper size (length L in the main scanning direction) can be determined by multiplying the memory value of the paper size converted into the count value stored in the memory 10 by the paper transport amount per pulse of the encoder 8.

When the sheet size is determined and the sheet 3 is conveyed to the sheet feeding end position, the sheet feeding operation for printing the first color is completed.

Next, the printing operation is started. At this time, the ink sheet 1 needs to be wound up to the printing start position so that the printing of the first color can be performed. Here, the length of the ink sheet in the main scanning direction (the length in the winding direction) is longer than the sum of the expected length of the actual print area and the length of the margin of the paper, and the width in the print width direction is An ink sheet wider than a print width that can be expected is used.

When the ink sheet 1 and the paper 3 are ready to start printing, the thermal head 2 presses the ink sheet 1 and the paper 3 against the platen roller 4 by the thermal head separating / separating mechanism (not shown). Then, the sheet conveying means starts operating again to convey the sheet 3 in the printing direction, and forms an upper margin based on the detection of the trailing edge b of the sheet.

At this time, the control means 20 detects the formation of the upper margin, and at the same time, retrieves the image information stored in the video memory (not shown) and sends it to the thermal head 2 as print data. The operation is performed sequentially. When the printing of the first color is completed, the thermal head is detached by the separating mechanism, the paper 3 is transported again in the paper feeding direction, and the printing for the second color is performed in the same manner as the printing of the first color. A paper feeding operation and a printing operation are performed. In order to perform multi-color superposition, the above-described sheet feeding operation and printing operation are repeatedly performed until printing of a required number of colors is completed. When the printing of the final color is completed, the sheet 3 is discharged by a sheet discharging operation in which the sheet 3 is conveyed in the printing direction without entering the sheet feeding operation again. It is needless to say that the change of the sheet edge detection signal may not be from the above-mentioned rising edge to the falling edge but may be from the falling edge to the rising edge of the opposite logic.

Referring to FIG. 3, the paper feeding operation will be described in more detail. FIG. 3A shows a transport signal of the paper 3, which is, for example, a control signal given to a motor 11 for driving the grid roller 5.
The encoder 8 generates a pulse p shown in FIG. At this time, the motor 11 is controlled at a constant speed, and the paper 3 is conveyed at a constant speed. FIG. 3C shows a signal change of the sheet detection sensor 6. The sheet end detection signal changes from a low level to a high level by detecting the leading edge a of the sheet, and changes to a high level by detecting the trailing edge b of the sheet thereafter. The case where the level changes from the low level to the low level is shown.

As shown in FIG. 3D, the counter 9 counts the pulses pp generated by the encoder 8 only while the sheet detection signal in FIG. 3C is at the high level. The count value Np of the counter 9 is stored in the memory 10, and the transport amount from the leading edge a to the trailing edge b of the sheet, that is, the sheet size L can be obtained by multiplying the memory value by the sheet transport amount X per pulse. it can. This is because if there is no error in the transport amount due to slippage during paper transport, the number of pulses and the paper transport amount are proportional, and the slope of the proportional straight line is the paper transport amount X per one pulse of the encoder 8. .

The graph of FIG. 4 shows a straight line representing the proportional relationship between the number of pulses and the amount of paper transported, with the horizontal axis representing the number of pulses and the vertical axis representing the paper transport amount. Then, the slope of the proportional line corresponds to X.

The control means 20 reads the count value-converted memory value stored in the memory 10 and determines the paper size, thereby determining the paper transport amount, the pressing / separating of the thermal head 2, the timing of starting printing, and the like. Can be performed based on the count value of the pulse generated by the encoder 8.

After the memory 10 stores the count value Np, the count value of the counter 9 is reset to zero. This is because the counter 9 is also used to obtain a print start signal at the beginning of the printing operation.

Even if the paper size is determined, the paper 3 continues to be transported in the paper feeding direction, and the trailing end b of the paper is
Is stopped after being transported by a few pulses even after passing through. This is because if the trailing edge b of the paper is detected by the paper detection sensor 6 and the transport of the paper 3 is stopped at the same time, the transport of the paper 3 in the printing direction opposite to the paper feeding direction is detected. This is to prevent the trailing edge b of the sheet from being detected if the signal change of the sensor 6 is not correctly detected. Thus, the sheet feeding operation, which is a preparation for the printing operation of the first color, is completed. The transport amount for several pulses after the trailing edge b of the paper has passed through the paper detection sensor 6 (hereinafter referred to as an adjusted transport amount) is arbitrary, but from the viewpoint of shortening the time required for overall printing, the adjustment is performed. It is desirable that the transport amount be as small as possible. For example, if a paper transport amount of two pulses is given after the trailing edge b of the paper has passed the sensor 6 in the paper feeding direction, the trailing edge b of the paper can be correctly detected when the paper 3 is transported in the printing direction. It is sufficient to transport the paper 3 in the paper feed direction by an extra two pulses as the adjusted transport amount.

Next, the printing operation for the first color is started. Simultaneously with the completion of the above-described sheet feeding operation, the thermal head 2 starts moving toward the platen roller 4 by the separation / contact mechanism and presses the ink sheet 2 and the sheet 3 against the platen roller. The grid roller 5 conveys the paper 3 in the printing direction according to the rotation. When the paper 3 is conveyed in the printing direction, the trailing edge b of the paper is detected by the paper detection sensor 6, and the counter 9 is triggered by a signal level change from a low level to a high level of the paper edge detection signal of the paper detection sensor 6 as a trigger. , 0 starts counting. During this time, no print data is sent to the thermal head 2, and the paper 3 is not printed and the same paper transport speed Vp as at the time of printing.
Conveyed by. In this way, an upper margin is formed on the sheet.

FIG. 5 shows the relationship between the length of each portion of the sheet in the main scanning direction and the count value. The upper margin corresponds to the length Ls from the rear end b of the sheet.

When the formation of the upper margin is completed, the control means 20 determines whether the count value N input from the counter 9 is the calculated value Ns of the upper margin according to the sheet size or the control means 2.
A print start signal is generated at the time when the count value matches the count value converted memory value Ns corresponding to the size of the upper margin stored in the memory means included in advance in 0 or the individual memory means. An upper margin is formed by the paper transport amount Ls corresponding to the time from the start of counting by the counter 9 to the generation of the print start signal.

The thermal head 2 starts printing in response to a print start signal from the control means 20. The print data given to the thermal head 2 is image information stored in, for example, a video memory (not shown). Based on the print data, the heating elements arranged on the thermal head 2 are selected to generate heat, and the generated heat causes the ink on the ink sheet to melt or sublimate, thereby forming an image by adhering the ink onto paper. Is done.

When the paper size changes, the control means 20
Paper transport control so as to specify the print start position using the value Ns stored in advance in the memory means or another memory means according to the paper size or the calculated value Ns of the upper margin according to the paper size. Perform Here, as can be seen from FIG. 1, there is a certain distance between the paper detection sensor 6 and the thermal head 2. That is, even if printing is started at the same time that the paper detection sensor 6 detects the trailing edge b of the paper, a margin corresponding to this distance is formed.
Therefore, in order to obtain a desired upper margin, it is necessary to set the value of Ns in consideration of this distance.

The thermal head 2 receives image information stored in a video memory or the like as print data based on a print start signal, and starts printing corresponding to the print data. Normally, printing is continued until the printing of one screen of the first color is completed, during which time the paper transport means is driven at a constant speed according to the paper transport speed during printing. In the printing of one screen of the first color, the count value N of the counter 9 is (Nv + N
The process ends when s) is reached (see FIG. 5). After the printing of the first color is completed, the conveyance of the paper 3 is stopped, the thermal head 2 is separated from the ink sheet 1 and the paper 3 by the separating mechanism, and the printing operation of the first color is completed.

Next, the sheet feeding operation for the second color is started. At this time, the count value of the counting means 9 is reset. In this embodiment, the reset of the count value is performed from the generation of the printing start signal of the first color to the start of the printing operation of the second color. Normally, the count value is reset when the printing operation of the first color is completed or when the feeding operation of the second color is completed.

The feeding operation of the second color is started in the same manner as in the case of the first color, and the sheet 3 is stopped at a position where a rearward end b has passed the sheet detecting sensor 6 and after a fixed adjustment conveyance amount, and
Thus, the feeding operation of the second color is completed. In the case of the second-color paper feeding operation, since the paper size has already been determined, it is not necessary to count the pulses of the encoder 8 and determine the paper size as in the case of the first-color paper feeding operation. .

After the second color paper feeding operation is completed, the thermal head 2 applies the ink sheet 1 and the paper 3 again to the platen roller 4.
And the printing operation of the second color is started. The grid roller 5 conveys the paper 3 in the printing direction, and when the paper detection sensor 6 detects the trailing end b of the paper, the counting means 9
Starts counting again with the signal level change of the sheet detection sensor 6 as a trigger, and an upper margin is formed. When the count value Ns corresponding to the upper margin is obtained, a print start signal is output from the control means 20, and printing of the second color is started. Subsequent operations are the same as those of the first color, and a description thereof will be omitted. However, since the printing of all colors has been completed after the printing operation of the final color is completed, the paper 3 is discharged by the paper discharging operation of transporting the paper 3 in the printing direction without performing the paper feeding operation. You.

As described above, if the sheet size is determined by calculating the count value converted sheet size during the first sheet feeding operation, it is not necessary to determine the sheet size during the subsequent sheet feeding operation or printing operation. Absent. Also, in the case of continuously printing sheets of the same size, it is sufficient to determine the sheet size at the time of the first sheet feeding operation of the first sheet of paper, so that it is stored in the memory 10 unless the sheet size changes. It is not necessary to change the count value conversion paper size memory value.

Incidentally, a pulse motor may be used as the motor 11. In that case, the pulse motor may be driven to rotate using the excitation signal to the pulse motor, and the excitation signal may be counted by the counter 9 as a pulse signal.

Further, when determining the paper size,
Changes in the rising edge and falling edge of the sheet edge detection signal output by the sheet detection sensor 6, that is, a change from a low level to a high level by detecting the leading edge a of the sheet, and a high level to a low level by detecting the trailing edge b of the sheet. It is needless to say that not only the change in the logic level but also the level change when the logic level is inverted by devising the circuit configuration of the signal path may be used. For example, by inserting an inverter for inverting the logic level into the output of the encoder 8 or the input of the counter 9, the logic level of the signal for judging the sheet size is inverted, and from the falling edge to the rising edge of the sheet edge detection signal. That is, the number of pulses of the encoder 8 corresponding to the paper size is counted from the time when a change from the high level to the low level is detected by detecting the leading edge a of the paper to the time when it is changed from the low level to the high level when the trailing edge b is detected. To determine the paper size.

(Embodiment 2) Embodiment 2 will be described with reference to FIG. This embodiment is different from the first embodiment in that the counter 9 has an addition and subtraction function, and is otherwise the same as the first embodiment.

In this case, a counting error of about one pulse of the pulse output from the encoder 8 as the pulse generating means occurs. However, in order to determine the paper size, the error is an amount that can be ignored. . However, the number of pulses is added / subtracted by the counter 9 while accumulating the accumulated count value Ni of the pulses between the time of conveyance in the paper feeding direction and the time of conveyance in the printing direction. Has a direct effect on counting the print start timing. That is, if the printing start timing is shifted, the transport amount caused by the shift becomes the printing shift amount. Such a printing shift causes deterioration of image quality such as color shift in multi-color superposition such as thermal color printing. Cause. Therefore, it is necessary to set the resolution of the encoder 8, the paper transport amount per pulse of the motor 11, and the like so that the paper transport amount X [mm / pulse] per pulse is sufficiently smaller than the multi-color overlay accuracy. There is.

Therefore, in this embodiment, the motor 11
Is set so that the amount of paper transported per pulse due to the rotation of is sufficiently smaller than the multicolor superposition accuracy. The setting of the sheet transport amount will be described later in detail. Next, the printing operation of this embodiment will be described.

When the paper 3 is inserted into the grid roller 5, the paper 3 is transported in the paper feeding direction by the paper transport means for printing the first color. Then, the paper edge is detected by the paper detection sensor 6 placed in the paper transport area,
The pulse of the encoder 8 is counted up by the counter 9. This count value is the paper transport amount, that is, the size of the paper converted into the count value. The count value converted paper size is stored in the memory 10 as the memory value Np. The memory value of the sheet size in terms of the count value stored in the memory 10 is read out, and the control unit 20 determines the sheet size. In the first embodiment described above, the count value of the counter 9 for determining the paper size is reset when the memory value Np of the paper size in terms of the count value is stored in the memory 10, but in the second embodiment, , The counter 9 has an addition / subtraction function, and adds / subtracts the pulse generated by the encoder 8 to accumulate the count value as the paper position information.
The counter 9 is not reset. Further, the memory value of the count-size converted paper size stored in the memory 10 is stored until printing of all colors on one sheet is completed or while printing is continuously performed on the same size paper. Is done. That is, when the paper is fed, the paper size is determined, the count value-converted paper size is stored in the memory 10, and the counter 9 detects the leading edge a of the paper and stores
The count value of the pulse of the encoder 8 until the detection of is detected without being reset.

The sheet 3 has a sheet trailing end b whose sheet detection sensor 6
Is stopped after being transported for several pulses after passing through. The reason why the paper 3 is conveyed by several pulses after passing the paper detection sensor 6 is that, as described in the first embodiment, the level change of the paper end detection signal of the paper detection sensor 6 is not correctly detected, and the paper This is to prevent that the end b cannot be detected. In this way, the paper feed operation, which is a preparation for printing the first color, is completed.

The number of pulses during conveyance for several pulses (hereinafter referred to as adjustment pulses) after the trailing edge b of the sheet has passed the sensor 6 may or may not be counted. When the adjustment pulse is counted, the adjustment pulse may be considered when forming the upper margin during the conveyance in the printing direction. Specifically, the count value Ns of the pulse generated by the encoder 8 according to the size of the upper margin (the encoder 8 corresponding to the paper transport amount from the rear end b of the paper to the print start position)
By adding an adjustment pulse to the count value of the pulse generated by the encoder 8 or by including the adjustment pulse in the count value Ns of the pulse generated by the encoder 8 according to the size of the upper margin. The extra minute may be transported. When the adjustment pulse is not counted, the counter 9 is kept until the paper detection sensor 6 detects the rear end b of the paper again even in the conveyance in the printing direction.
If the counting is stopped and the counting is not performed, the count value does not change, so that no problem occurs. The number of adjustment pulses is arbitrary, but is preferably as small as possible in order to shorten the overall printing time.

Next, the printing operation of the first color is performed.
At the same time when the feeding operation of the first color is completed, the thermal head 2
Presses the ink sheet 1 and the paper 3 against the platen roller 4 by the separating mechanism, and then the motor 11 rotates, and the grid roller 5 conveys the paper 3 in the printing direction according to the rotation. When the paper 3 is conveyed in the printing direction, the trailing edge b of the paper is detected by the paper detection sensor 6, and the counter 9 counts by using a change in the paper end detection signal of the paper detection sensor 6 from a low level to a high level as a trigger. Start.
At this time, since the transport direction of the paper 3 is reversed in the paper feeding direction and the printing direction, the counter 9 counts down in this embodiment. During this time, print data is not sent to the thermal head, and the paper 3 is conveyed at a constant speed without printing. Thus, an upper margin is formed.

As shown in FIG. 7, the upper margin corresponds to the length Ls from the trailing edge b of the sheet, as represented by the relationship between the length of each portion of the sheet in the main scanning direction and the cumulative count value of the pulse.

At the time of forming the upper margin Ls, the control means 20 controls the accumulated count value Ni input from the counter 9.
Is calculated from the memory value of the count value Np corresponding to the paper size L stored in the memory 10, the calculated value Ns of the upper margin Ls corresponding to the paper size, or the memory means previously included in the control means 20 or another memory means (Np-Ns) obtained by subtracting the count value Ns of the pulses generated by the encoder 8 corresponding to the size of the upper margin Ls stored in
A print start signal is generated at the point in time when.

When the paper size changes, the control means 20
Using a value Ns stored in advance in a memory means or another memory means or a calculated value Ns of an upper margin corresponding to the paper size, and converting the value into an upper margin converted into a count value corresponding to the size of the upper margin Ls. The sheet conveyance control is performed so as to specify the print start position as the memory value Ns of the sheet. Here, as in the case of the first embodiment, since a certain distance exists between the paper detection sensor 6 and the thermal head 2, printing is started at the same time as the paper detection sensor 6 detects the rear end b of the paper. However, this fixed distance becomes an extra margin, and a desired upper margin cannot be obtained. Therefore, it is necessary to set the value of Ns in consideration of the fixed distance.
The paper transport amount from when the counter 9 starts counting down to when the print start signal is generated corresponds to the upper margin.

The thermal head 2 receives image information stored in a video memory or the like as print data based on a print start signal, and starts printing in accordance with the print data.
The counter 9 counts down during printing.
The control means 20 is a printer-specific print area (length Lv)
When the count value corresponding to N is Nv, the counter 9
Is controlled so that the printing is completed and the conveyance of the paper 3 is stopped when the count value of (Np−Ns−Nv) is reached (FIG. 7).
reference). After the printing of the first color is completed, the conveyance of the paper 3 is stopped, the thermal head 2 is separated from the ink sheet 1 and the paper 3 by the separation / contact mechanism, and the printing operation of the first color is completed.

Next, the sheet feeding operation for the second color is performed.
The sheet 3 is transported in the sheet feeding direction until the accumulated count value Ni is counted up to (Np-Nss). Nss
Is a value that can be arbitrarily determined within a range satisfying Ns> Nss ≧ 1. However, from the viewpoint of shortening the entire printing time, it is desirable that Nss is as large as possible. The count is incremented until the cumulative count value Ni becomes (Np-Nss), and the conveyance of the sheet 3 is stopped. Then, the thermal head 2 presses the paper sheet 3 against the ink sheet position in the direction of the platen roller 4. Next, when the grid roller 5 conveys the paper 3 in the printing direction and the counter 9 starts counting down, and the accumulated count value Ni becomes (Np-Ns), printing of the second color is started. (See FIG. 7). Also in the case of printing the second color, similarly to the case of printing the first color, the counter 9 counts down during printing, and when the accumulated count value Ni becomes (Np−Ns−Nv), the printing of the second color is performed. Ends. In the printing of the second and subsequent colors, the sheet feeding operation and the printing operation are performed as in the case of the second color. However, after the printing of the final color is completed, the paper feeding operation is not performed, and the paper discharging operation for transporting the paper 3 in the printing direction without any change is performed.
The paper 3 is discharged.

As described above, in the present embodiment, the counting means 9 is provided with a function of accumulating the number of pulses by addition / subtraction, so that the paper transport corresponding to the upper margin in the printing operation for the second and subsequent colors is performed. Can be saved, and as a result, the printing time as a whole can be shortened.

(Embodiment 3) Embodiment 3 is intended to convey paper at a higher speed than in Embodiment 2. The precautions in the second embodiment are summarized as follows. (1) Positional displacement of a degree equivalent to one pulse basically occurs. (2) The paper transport amount per pulse is appropriately set so that this positional shift does not affect the print quality. (3) Such accuracy is not required for determining the paper size.

Among these precautions, the precaution (2) from the restriction on the overlay accuracy in printing will be described more specifically. The overlay accuracy depends on the amount of positional deviation unique to the printer in the overlay and the fidelity of the count value of the pulse generated by the encoder 8 as the pulse generating means. Here, the paper transport amount per pulse is X [mm /
pulse] and the resolution of the printer is Y [dot / inch (dpi)], the amount of misalignment during multi-color superposition, ie, the amount of paper transported per pulse when there is a misalignment of one pulse Is less than or equal to 1/4 of the dot diameter of the print due to the resolution of the printer, the image quality degradation such as color misregistration is within an allowable range. In this case, the sheet transport amount X per pulse is represented by the following equation (1).

X ≦ 25.4 [mm / inch] / (Y × 4) = 6.35 / Y (1) Here, for example, when the resolution Y is 300 [dpi],
The right side of Expression (1) is calculated as in the following Expression (1a).

25.4 [mm / inch] / (300
[Dpi] × 4) = 0.02 [mm] (1a) Therefore, the paper transport amount X per pulse should be set so as to satisfy the following expression (2).

X ≦ 0.02 [mm / pulse] (2) By the way, regarding the pulse period T and the paper transport speed V,
The following equation (3) holds.

X = V · T (3) On the other hand, since the pulse from the pulse generating means 8 is an output from, for example, the encoder 8 attached to the shaft of the motor 11, the number of pulses per one rotation of the motor 11 To P [p
ulse / rev], the reduction ratio of a transmission system such as a reduction gear from the rotation of the motor 11 to the rotation of the grid roller 5 is Gr, and the effective radius of the grid roller 5 is R [mm]. Paper transport amount per pulse X
Is rewritten as the following equation (4).

X = 2π · R · Gr / P (4) Therefore, from equations (1) and (4), the following equation (5) is obtained.
Is obtained.

2π · R · Gr / P ≦ 6.35 / Y [mm] (5) From equation (4), the overlay accuracy is determined by the parameters R and G
Since r and P are determined at the time of designing the device, X = co
nst. Becomes Then, from equation (3), VT = con
st. Therefore, even if the paper transport speed V is changed, the overlay accuracy is not affected. That is, only the fidelity of the pulse count value with respect to the paper transport amount at the time of paper supply and at the time of printing determines the overlay accuracy. If there is no mistake in reading the pulse of the counter 9 serving as the counting means, the positional deviation at the start of printing will be independent of the paper transport speed Vp at the time of printing and the paper transport speed Vr at the time of paper feeding. Within the accuracy guaranteed by (2). Therefore, the paper transport speed Vr at the time of paper feeding can be made faster than the paper transport speed Vp at the time of printing without affecting the overlay accuracy. Here, it is assumed that there is no displacement between the grid roller 5 and the sheet 3 due to slippage.

From the above, the effective radius R of the grid roller 5, the reduction ratio Gr of the transmission system such as the reduction gear from the rotation of the motor 11 to the rotation of the grid roller 5, and the motor If the number of pulses P per rotation 11 is designed, it is possible to make the paper transport speed Vr at the time of paper feeding faster than the paper transport speed Vp at the time of printing regardless of the overlay accuracy, and as a whole Paper transport speed can be increased. As a result, the speeding up of the printer can be achieved, and the printing time as a whole can be shortened.

(Embodiment 4-1) With reference to FIG. 8, a description will be given of a determination method of a paper determination unit and a control method of a control unit in still another embodiment of the present invention.

When the sheet 3 is inserted and the leading edge a of the sheet is detected by the sheet detecting sensor 6, the counter 9 starts counting pulses generated by the encoder 8 in accordance with the sheet transport amount. It continues counting until it is detected by the paper detection sensor 6. The control means 20 instructs to temporarily store the count value converted paper size Np (see FIG. 5 or FIG. 7) as a memory value in the first memory 101 which is the first memory means. Then, the determination means 21 reads the memory value of the count value converted paper size stored in the first memory 101 and determines the paper size. For example, when the memory value of the count value converted paper size when the paper size (length L in the main scanning direction) is 140 mm is Np = 20,000, the memory value of the count value converted paper size corresponding to other paper sizes N
p is obtained from the following equation (6).

L = 140 × (Np / 20000) [mm] (6) The determination means 21 calculates the expression (6) based on the count value converted paper size memory value Np read from the first memory 101. It is possible to determine the paper size L.

Based on the value of the paper size L determined by the determination means 21, the control means 20 controls the paper transport amount, which is a control amount necessary for the subsequent paper feeding operation and printing operation,
The second memory 1 is used for calculating an ink sheet winding amount, a print start timing, or the like, or a second memory unit.
02, the control amounts are read out, and sheet transport control corresponding to the sheet size is performed.

The paper size per count corresponds to the paper transport amount per pulse generated by the encoder 8. This also corresponds to a paper size discrimination error when the counter 9 miscounts a pulse generated by the encoder 8, and the paper size detection error related to the count mistake is given by L / Np = 0.007 mm from equation (6).
The effect of image quality deterioration such as color misregistration is within the allowable range and causes no problem.

(Embodiment 4-2) With reference to FIG. 8, a description will be given of a method of determining a sheet determining unit and a method of controlling a control unit according to an embodiment 4-2.

When the sheet 3 is fed and the leading edge a of the sheet is detected by the sheet detecting sensor 6, the counter 9 starts counting pulses generated by the encoder 8 in accordance with the sheet transport amount. Counting is continued until is detected by the sheet detection sensor 6. The control means 20 instructs the first memory 101 to temporarily store the count value converted paper size Np (see FIG. 5 or 7) as a memory value. Then, the determination means 21 reads the memory value of the count value converted paper size stored in the first memory 101 and determines the paper size. For example,
When the paper size (length L in the main scanning direction) is 140 mm, the memory value of the paper size in terms of the count value is Np = 200.
In the case of 00, the memory value Np of the sheet size converted into the count value corresponding to the other sheet sizes is also equal to that of the embodiment 4-1.
Is obtained from the equation (6) shown in FIG.

This equation (6) has sufficient accuracy for determining the paper size. However, it takes time to calculate the control amounts such as the winding amount of the ink sheet and the printing timing in accordance with the paper size.
This is not preferable for increasing the speed and reducing the size of the device. If some paper sizes are limited as standard sizes, and a series of paper transport controls corresponding to the respective standard sizes are routinely performed in advance, it is not necessary to perform an operation related to the control amount. More specifically, for example, count values Np ₁ , for some standard paper sizes L ₁ , L ₂ , L ₃ ,.
Np ₂ , Np ₃ ,... Are obtained in advance. By comparing these count values with the count-value-converted paper size memory value Np actually obtained from the counter 9,
First, it is determined whether the size of the sheet 3 is a standard size or a non-standard size.

When the discrimination result is a standard paper size, a control amount such as a print start timing and an ink sheet winding amount corresponding to each standard size is optimized in advance and is included in a control program. Do what you want. If it is determined to be a non-standard size,
If the actually obtained count value converted memory value Np is not among the prepared count values, the paper size is determined by assuming that it is equal to the closest count value among the prepared count values.

For example, as shown in FIG. 9, when a count value Np is given in advance every time the paper size changes by 5 mm, if Np = 20,000, it is determined that the paper size is 140 mm. Also, Np = 21
142 (corresponding to 148 mm), Np ≒ 2142
8, it is determined that the paper size is 150 mm (A6 size is equivalent to 148 mm). When the paper size is determined in this way, the control means 20 calls a control program prepared corresponding to the determined paper size, and thereafter performs a paper transport control corresponding to the paper size according to the control program. Do.

FIG. 9 shows the count value N prepared in advance.
This is merely an example of the relationship between p and the paper size L, and it is not always necessary to calculate the count value every time the paper size changes by 5 mm, and the count value conversion paper size corresponding to 148 mm as the A6 size. May be registered. Further, the paper sizes to be registered are not limited to the five types shown in FIG. 9, and it goes without saying that more types of paper sizes may be registered.

(Embodiment 4-3) An embodiment 4-3 will be described with reference to FIG. This embodiment corresponds to the equation (5) of the third embodiment.
Is the same up to the point where is used, so a method of establishing the subsequent print start timing will be described. Second
The second memory 102, which is a memory means of, for example, RO
M, the print start timing information corresponding to the paper size (the memory value of the upper margin in terms of the count value of the pulse generated by the encoder 8 corresponding to the paper transport amount from the rear end b of the paper to the print start position) Ns). That is, the memory value Ns corresponds to the paper transport amount for forming the upper margin from the detection of the trailing edge b of the paper again during the printing operation to the formation of the upper margin and the start of printing when the print start signal is sent. This is a memory value converted into a count value of a pulse generated by the encoder 8.

Referring to the example of the paper size shown in FIG. 9, for the paper size L given every 5 mm, the memory value Ns of the upper margin converted into the count value representing the printing start timing is shown in FIG. It is provided as a look-up table (LUT) as shown in FIG.

The paper size information stored in the first memory 101 (from the leading edge a to the trailing edge b,
The paper size is determined by the determination means 21 based on the memory value Np of the paper size in terms of the count value of the pulse generated by the controller, and the control means 20 outputs print start timing information corresponding to the determined paper size. . For example,
Memory value Np = 2000 of count value conversion paper size
When 0 is obtained, the determination unit 21 determines that the paper size is 140 mm. Then, as the memory value of the upper margin converted into the count value corresponding to the determined paper size, Ns = 2000 (upper margin length Ls = 1)
(Equivalent to 4 mm) is output. When the memory value of the sheet size in terms of the count value is Np = 21142, the sheet size is A6 size (148 mm).
Since the paper size is determined based on the memory value of the paper size converted to the nearest count value, the paper size is 150 m.
m is approximated and determined. Ns = 2857 (Ls) is used as the memory value Ns of the upper margin in count value conversion, which is the print start timing information corresponding to the paper size.
= 20 mm) is output.

When the counter 9 adds / subtracts pulses from the encoder 8 and accumulates them as shown in FIG.
Similarly to the operation of the counter 9 described in the second embodiment, the count value of the counter 9 is not reset until the printing of one sheet is completed, and the count value is accumulated by performing addition / subtraction depending on the sheet conveyance direction. . The control means 20 determines that the current position of the thermal head on the paper 3, that is, the transport amount from the trailing end b of the count value converted by the counter 9 is Ni.
= Np-Ns, a print start signal is generated (see FIG. 7).

In the case where the counter 9 does not have the function of adding / subtracting the pulse from the encoder 8 like the counter shown in the first embodiment (see FIG. 2), after the paper size is determined and the next color is detected. Before the start of the printing operation (usually immediately after the determination of the paper size), the counter 9 is reset.
At the same time when the sheet detection sensor 6 detects the trailing edge b of the sheet, the pulse from the encoder 8 starts to be counted. Control means 2
A value of 0 performs sheet conveyance control so that a print start signal is generated when the sheet conveyance amount from the sheet rear end b counted by the counter 9 from the sheet rear end b becomes N = Ns.

In the above, the case where the control amount is the print start timing has been described in the present embodiment. However, for other control amounts such as the paper transport amount and the winding amount of the ink sheet, the control values are also used. The storage in the second memory 102 is the same as in the case of the print start timing. Even when these control amounts are used, control can be performed by calling a desired control amount from the second memory 102 as needed.

Further, the function of the discriminating means 21 shown in this embodiment can be included as a part of the function of the control means 20 as shown in the first embodiment.

(Embodiment 5) Referring to FIG.
Will be described. When the paper 3 is inserted into the grid roller 5, the paper is conveyed in the paper feeding direction for printing of the first color, and after the paper front end a is detected by the paper detection sensor 6 placed in the paper conveyance area, the paper rear end The sheet is conveyed until b is also detected. The operation up to this point is the same as in the previous embodiments. FIG. 12 is similar to FIG.
It represents a signal related to paper transport. FIG.
FIG. 1A shows a transport signal applied to the motor 11, and FIG.
2 (B) represents a pulse signal output from the pulse generator 12. Note that the period of the pulse in FIG. 12B is generally different from the period of the pulse in FIG. FIG. 12C shows a change in the output signal of the paper detection sensor 6. As shown in FIG. 12D, the counter 9 operates only when the paper detection signal in FIG. The pulses output from the pulse generator 12 are counted.

That is, among the pulses p from the pulse generating means 12 such as a crystal oscillator which generate a clock pulse regardless of the rotation of the motor 11 and the conveyance of the paper, the paper detection sensor 6 detects the leading edge of the paper. a pulse generated between the detection of a and the detection of the trailing edge b of the sheet
By counting p, the paper size is obtained as a converted value of the pulse count value. In this case as well, an error in determining the paper size corresponding to one pulse of the pulse generated by the crystal oscillator 12 occurs. However, unlike the above-described embodiment, since the pulse period is not directly related to the sheet conveyance, the pulse period T of the crystal oscillator 12 can be set sufficiently smaller than the pulse period generated by the encoder 8 described above. As to the determination of the paper size, it is not necessary to be as precise as in the case of preventing the shift of the printing start timing between the colors to be described later, so that an error of one pulse does not matter at all. In addition, when the encoder 8 is used, the count error increases when the paper transport speed is set to a low speed. However, in the present embodiment, the count error can be reduced even when the paper transport is performed at a low speed.

In this way, the count value converted paper size Np corresponding to the paper size is written as a memory value in the first memory 101, and the counter 9 is reset. This is because the counter 9 is also used to obtain a print start signal at the beginning of the printing operation. The first memory 101 keeps storing the memory value until printing of all colors on one sheet is completed or while printing is continuously performed on sheets of the same size.

The paper 3 has a paper trailing end b whose paper detection sensor 6
Stop after being further transported by a few adjustment pulses after passing through. Thus, the sheet feeding operation which is a preparation for printing the first color is completed. Next, the printing operation of the first color is started. The following printing operation of each color is the same as that of the above-described embodiment except that the counted pulse is not directly related to the conveyance of the sheet.

That is, simultaneously with the end of the paper feeding operation, the thermal head 2 applies the ink sheet 1 and the paper 3 to the platen roller 4.
To press. Next, the motor 11 rotates, and the grid roller 5 conveys the paper 3 in the printing direction according to the rotation. When the paper 3 is conveyed in the printing direction, the trailing edge b of the paper is detected by the paper detection sensor 6, and the counter 9 triggers the change of the paper edge detection signal from the paper detection sensor 6 from a low level to a high level as a trigger. It starts counting from 0 again. During this time, no print data is sent to the thermal head 2,
The paper 3 is conveyed without being printed at the same paper conveyance speed Vp as during printing. Thus, an upper margin (length from the rear end b of the sheet) Ls is formed.

The control means 20 determines that the count value N input from the counter 9 is a memory value Ns (second memory 102) of the upper margin converted into a count value corresponding to the length Ls of the upper margin.
Is stored, the print start signal is generated. The memory value Ns of the upper margin converted into the count value for generating the print start signal is stored in the second memory 102 in advance according to the paper size. As an example, a case where the paper size is 140 mm will be described. The memory value of the count value converted paper size input from the counter 9 and stored in the first memory 101 is Np = 200.
When the value is 00, Ns = 2000 is output as the memory value of the upper margin in count value conversion.
The thermal head 2 receives image information stored in a video memory or the like as print data based on a print start signal,
Printing according to the print data is started. When the print data is sequentially printed on the paper 3, the pulse is generated from the crystal oscillator 12 irrespective of the paper transport, but the paper transport means transports the paper 3 at a constant transport speed during printing. .

The print data for one screen or more is prepared in advance for the number of colors to be printed. When the control means 20 recognizes the print for one screen, the printing of the single color component is completed. In recognizing the printing of one screen, for example, even after counting the printing start timing, the counter 9 continuously counts the pulses generated from the crystal oscillator 12 regardless of the paper conveyance. The count value N of the counter 9 is the position where the printing of the first color is completed, that is, the upper margin N of the count value conversion.
Printing of the first color is performed until the sum of s (length Ls) and the print area Nv (length Lv) unique to the printer in terms of count value is obtained (see FIG. 5). In other words, the control means 20
When the count value N input from the counter 9 is (Ns + N
Until v), printing of the first color is performed by controlling the thermal head 2.

After the printing of the first color is completed, the thermal head 2
Is not sent, and the paper 3 is transported until the leading edge a of the paper 3 is detected by the paper detection sensor 6. At this time, it is not necessary to count pulses at the time of the next sheet feeding, and therefore, as in the above-described embodiment, at the same time as the end of printing or before the leading edge a of the sheet is detected by the sheet detecting sensor 6, for example, after the end of printing, The transport may be stopped after transporting several pulses generated by the oscillator 12. The paper transport amount after the end of printing is arbitrary,
In order to shorten the overall printing time, it is desirable to minimize the printing time.

The conveyance for the printing of the first color is stopped, and at the same time, the thermal head 2 separates from the ink sheet 1 and the paper 3 and the printing operation of the first color is completed.

During the period from when the first color printing start signal is generated to when the second color printing operation is started, the count value N of the counter 9 is reset again as in the case of the first color. . Then, the sheet feeding operation for the second color is performed. The paper 3 is conveyed in the paper feeding direction, and stops after advancing by a certain fixed conveyance amount as in the case of the first color after the rear end b of the paper is detected by the paper detection sensor 6,
Thus, the feeding operation of the second color is completed. Subsequent operations are the same as those in the above-described embodiment. The paper feeding operation and the printing operation are repeated for each color, and after the printing of the final color is completed, the paper feeding operation is not performed and the paper 3 is conveyed in the printing direction as it is. The paper 3 is discharged by the paper operation.

On the other hand, an error in counting the print start timing affects the quality of printing, so that it is necessary to consider the overlay accuracy in the same manner as in the above-described embodiment.

(Embodiment 6) Embodiment 6 enables higher-speed printing than Embodiment 5. In this case, the overlay accuracy is defined by the constant speed of the paper transport amount during printing and the pulse period T, so that a positional shift of about one pulse does not affect print quality such as color shift. , The pulse period T, the paper transport speed Vp during printing, and the stability of the paper transport speed Vp.

That is, when the pulse period T and the printing paper transport speed Vp are independent parameters, a linear relationship occurs between the change in the paper transport speed and the overlay accuracy. Therefore, the pulse period from the pulse generation means 12 that generates a pulse directly without transporting the paper is T [s], the paper transport speed during printing is Vp [mm / s], and the paper transport speed during printing is If the stability of Vp is KpＫδVp / Vp (where δVp is a peak-to-peak value of the variation with respect to the target value Vp), the displacement X [mm ] Is expressed as in the following equation (7).

X = (Vp + δVp) · T = (1 + Kp) · Vp · T (7) Assuming that the resolution of the printer is Y [dpi], at the time of multi-color superposition, there is a speed variation with respect to the paper transport speed Vp during printing. The displacement amount, that is, the variation amount of the paper transport amount due to the variation of the paper transport speed Vp in printing,
When the printing dot diameter is equal to or less than ４ of the printing dot diameter due to the resolution of the printer, image quality deterioration such as color misregistration is within an allowable range. The overlay accuracy at that time is expressed by the following equation (8).

25.4 [mm / inch] /4Y=6.35/Y (8) The displacement X due to the speed variation with respect to Vp is set to be smaller than the superposition accuracy of Expression (8), that is, The parameters are designed so that equation (9) is satisfied.

(1 + Kp) · Vp · T ≦ 6.35 / Y (9) For example, when the resolution Y is 300 [dpi], if Y = 300 is substituted into the equation (9), the following equation (10) is obtained. can get.

(1 + Kp) · Vp · T ≦ 0.02 [mm] (10) In order to satisfy the expression (10), Kp, Vp and T
Is set. Here, Kp or δVp is a constant determined by the characteristics of the motor control system, and Vp cannot be reduced to shorten the printing time, whereas T is generated independently of the paper conveyance. Since the period of the pulse to be obtained is an independent parameter, generally T
Will be adjusted. For example, pulse generating means 1
When 2 is composed of a crystal oscillator, its oscillation frequency is appropriately selected. Further, as compared with the third embodiment, even if the overlay accuracy changes, the reduction ratio Gr of the transmission system such as the reduction gear between the rotation of the motor 11 and the rotation of the grid roller 5 and the radius R of the grid roller 5 can be improved. There is also an advantage that adjustment can be performed only by changing T without changing the design value of the mechanical system. Here, it is assumed that there is no displacement between the grid roller 5 and the sheet 3 due to slip.

As is clear from the above, the paper transport speed Vr and the stability Kr during paper feeding are included in the equation.
Since ≡δVr / Vr is not included, it is possible to make the paper transport speed Vr at the time of paper feed faster than the paper transport speed Vp at the time of printing, thereby increasing the overall paper transport speed. it can. as a result,
Higher speed of the printer can be achieved, and overall printing time can be reduced.

In the above embodiment, two sets of grid rollers 5 are required, and the stability of the paper transport speed affects the image quality. Of the paper transport speed caused by the presence of the paper transport state by both sets of grid rollers when the transport of paper is switched from one set of grid rollers to the other set of grid rollers. It is necessary to suppress fluctuation.

Accordingly, an embodiment related to a printer including only one set of grid rollers as shown in FIG. 13 will be described below. In FIG. 13, parts corresponding to those in FIG. 1 are given the same reference numerals. 13 is characterized in that the paper detection sensor 6 is disposed on the paper feed side with respect to only one grid roller 5. In the printer shown in FIG.

(Embodiment 7) Operations from paper feeding to paper discharging in Embodiment 7 will be described in detail with reference to FIG. 14 to FIG. As shown in FIG. 16A, when the paper 3 for storing image information is set at the paper feed preparation position, the paper 3 is conveyed by the paper conveyance means for printing the first color. You. The paper transport means includes a motor 11 that rotates / stops according to a transport / stop control signal;
It includes a transmission system for transmitting the rotation and a grid roller 5 for pressing and conveying the sheet (see FIG. 14). FIG.
Reference numeral 5 (A) denotes a sheet transport signal, which is a control signal applied to, for example, a driver (not shown) for driving the motor 11. The motor stops at a low level of the control signal and rotates at a high level. Is shown. As shown in FIG. 15B, the encoder 8 generates a pulse p with the rotation of the motor 11 in response to the sheet transport signal (see FIG. 14). At this time, the motor 11 is controlled at a constant speed, and the paper 3 is conveyed at a low speed. FIG. 15C shows a signal change of the paper detection sensor 6, which is at a high level when the paper is set at the paper feed preparation position, and changes from a high level to a low level by detecting the paper edge b. Is represented. FIG. 16B shows the sheet detection sensor 6.
Indicates a state immediately after detecting the sheet edge b. In addition,
If the paper is not at the paper feed preparation position, it is processed as a paper error.

As shown in FIG. 15D, the counter 9 detects the pulse pp generated by the encoder 8 only while the detection signal of the paper detection sensor 6 is at a high level and the paper is in the transport state. Count. On the circuit, a pulse pp is obtained by the logical product (AND) of the detection signal of the paper detection sensor 6 (FIG. 15C) and the pulse p generated by the encoder 8 (FIG. 15B). This count value Np by the counter 9 is stored in the memory 10,
By multiplying the stored count value Np by the paper transport amount X per pulse, the length (L-Z) from the paper detection sensor 6 to the paper edge b expressed by the following equation (11) is obtained.
g) can be determined.

L-Zg = Np.X (11) Here, Zg is the distance between the grid roller 5 and the paper detection sensor 6, and it is assumed that there is no error in the transport amount due to slippage.

FIG. 19 is a graph showing a proportional straight line represented by the equation (11). In this graph, the horizontal axis represents the pulse number [pulse], and the vertical axis represents the paper size detection amount [mm]. The slope of the proportional line corresponds to X [mm / pulse].

The sheet size converted into the pulse count value thus obtained is stored in the memory 10 and
In the case of 0, the memory value is read and the paper size is determined, so that the control of the transport amount, the pressing / removing of the thermal head, and the timing of the start of printing can be performed based on the pulse count value generated by the encoder 8. Will be possible.

After the memory 10 stores the count value Np, the count value of the counter 9 is reset to zero. This is because the counter 9 is also used to obtain a print start signal at the beginning of the printing operation.

As shown in FIG. 17A, even if the paper size is determined, the paper 3 continues to be conveyed in the paper feeding direction, and after the paper edge b has passed the paper detection sensor 6, a few pulses remain. After being conveyed by the adjustment pulse, it is stopped. This is because if the conveyance of the paper 3 is stopped at the same time that the paper end b is detected by the paper detection sensor 6, the paper detection sensor is used to convey the paper 3 in the printing direction opposite to the paper feeding direction. This is to prevent the paper edge b from being detected if the signal change of No. 6 is not correctly detected. Thus, the sheet feeding operation, which is a preparation for printing the first color, is completed. Paper edge b is paper sensor 6
The adjustment conveyance amount for several pulses after passing through is arbitrary, but is preferably as small as possible in order to shorten the entire printing time. For example, if an adjusted conveyance amount for two pulses is given after the paper edge b has passed the sensor 6 in the paper feeding direction, if the paper edge b can be correctly detected when the paper 3 is conveyed in the printing direction, the paper It is sufficient to convey an extra sheet of paper in the paper feeding direction by two pulses after the end b has passed the sensor 6 in the paper feeding direction.

Next, the printing operation is started. At this time, the ink sheet 1 needs to be wound up to the printing start position so that printing of the first color can be performed. Here, the length of the ink sheet in the main scanning direction, that is, the length in the winding direction, is longer than the sum of the expected length of the actual printing area and the length of the margin (upper margin), and the length in the printing width direction. An ink sheet having a width larger than a print width that can be expected is prepared. At the same time when the above-described paper feed operation for printing the first color is completed, the thermal head 2 starts to move toward the platen roller 4 by the separation / contact mechanism to press the ink sheet 1 and the paper 3 against the platen roller 4, When the motor 11 rotates,
The grid roller 5 conveys the paper 3 in the printing direction according to the rotation.

The conveyance of the paper in the printing direction is performed, for example, as shown in FIG.
Is controlled according to the timing chart shown in FIG. FIG. 20A shows a sheet transport signal.
(B) represents a pulse p of the encoder 8 generated in response to the conveyance of the sheet. Note that, in general, the paper conveyance speed is different between paper feeding and printing, and the rotation speed of the motor 11 is different. Therefore, the cycle of the pulse output from the encoder 8 is different between paper feeding and printing. That is, the period of the pulse in FIG. 20B is generally different from the period of the pulse in FIG. FIG. 17 (B)
When the paper 3 is conveyed in the printing direction as shown in FIG. 2, the paper end b is detected by the paper detection sensor 6, and the counter 9 detects the paper end b in the paper detection sensor 6 shown in FIG.
The counting is started from 0, triggered by the signal level change from the low level to the high level in the sheet edge detection signal of FIG. At this time, the print data is not sent to the thermal head 2, and the paper 3 is conveyed without being printed at the same constant speed Vp as during printing. Thus, an upper margin is formed on the paper to be printed.

FIG. 21 shows the relationship between the length of each portion of the paper in the main scanning direction and the count value. The upper margin of the paper to be printed corresponds to the length Ls from the paper edge b.

When the upper margin is formed, the control means 20
The count value N input from the counter 9 is a calculated value of the upper margin corresponding to the paper size or the upper part of the count value conversion corresponding to the size of the upper margin previously stored in the control means or stored in another memory means. A print start signal is generated at the time when it matches the margin memory value Ns. This print start signal is shown in FIG. The upper margin Ls is a value obtained by adding the distance Zs between the thermal head 2 and the paper detection sensor 6 to the paper conveyance amount Lc corresponding to the time from the start of counting by the counter 9 to the generation of the print start signal (FIG. 18A).
), And is represented by the following equation (12).

Ls = Zs + Lc = Zs + Ns · X (12) Here, as can be seen from FIG. 17B, at the same time when the paper detection sensor 6 detects the paper end b (when Ns = 0 in FIG. 21). Even if printing is started, the portion corresponding to Zs becomes a blank, so that the distance Zs between the thermal head 2 and the paper detection sensor 6 is preferably as small as possible.

The thermal head 2 starts printing in response to a print start signal from the control means 20. The print data given to the thermal head 2 is, for example, image information stored in a video memory or the like. Based on the print data, the heating elements arranged on the thermal head 2 are selected to generate heat, and the heat causes the ink on the ink sheet to melt or sublimate, causing the ink to adhere to the paper, thereby forming an image. It is formed.

When the paper size changes, the control means 20
Using the value stored in advance in the memory means or another memory means according to the paper size or the calculated value of the upper margin according to the paper size, this is used as the count value corresponding to the size of the upper margin. As shown in FIG. 18 (A) and FIG. 21, the print start position is specified as the converted memory value Ns, and the paper transport control is performed. The thermal head 2 receives image information stored in a video memory or the like as print data in response to a print start signal, and starts printing in accordance with the print data. Normally, printing is continued until printing of one screen of the first color is completed, during which time the paper transport means is driven at a constant paper transport speed during printing. The printing of one screen of the first color ends when the count value N of the counter 9 reaches (Nv + Ns) (see FIGS. 20B and 20D). Here, as shown in FIG. 21, Nv is a count value corresponding to the print area length Lv, and has a relationship of Lv = Nv · X. After the printing of the first color is completed, the conveyance of the paper is stopped, the thermal head 2 is separated from the ink sheet 1 and the paper 3, and the printing operation of the first color is completed. In addition, as shown in FIG. 18B, the lower margin Le is not printed.

Next, the sheet feeding operation for the second color is started. At this time, the count value of the counting means 9 is reset again. In this embodiment, the reset of the count value is performed from the generation of the printing start signal of the first color to the start of the printing operation of the second color. Normally, the count value is reset when the printing operation of the first color is completed or when the feeding operation of the second color is completed.

The feeding operation of the second color is started in the same manner as in the case of the first color, and the paper 3 is stopped when the paper end b has passed a predetermined length after passing the paper detection sensor 6, whereby the second paper is stopped. The color feeding operation ends. At the time of the second color sheet feeding operation, since the sheet size has already been determined, it is not necessary to count the pulses of the encoder 8 and determine the sheet size as in the first color sheet feeding operation.

After the second color paper feeding operation is completed, the thermal head 2 applies the ink sheet 1 and the paper 3 again to the platen roller 4.
To start the printing operation for the second color. The grid roller 5 conveys the paper 3 in the printing direction. When the paper detection sensor 6 detects the paper end b, the counting means 9
Starts counting again with the signal level change of the sheet detection sensor 6 as a trigger, and an upper margin is formed. When the count value Ns corresponding to the upper margin is obtained, the control means 2
A print start signal is output from 0, and printing of the second color is started. Subsequent operations are the same as in the case of printing the first color, and a description thereof will be omitted. However, after the end of the printing operation of the final color, since all printing has been completed, the paper 3 is discharged by the paper discharging operation of transporting the paper 3 in the printing direction without performing the paper feeding operation.

As described above, if the sheet size is determined by calculating the count value-converted sheet size during the first sheet feeding operation, it is not necessary to determine the sheet size during the subsequent sheet feeding operation or printing operation. . Also, when printing sheets of the same size continuously, it is sufficient to determine the sheet size at the time of the first sheet feeding operation of the first sheet, so that the sheet size is stored in the memory 10 unless the sheet size changes. It is not necessary to change the memory value of the paper size converted into the count value.

In this embodiment, a pulse motor may be used as the motor 11. In that case, the pulse motor may be driven to rotate using the excitation signal to the pulse motor, and the excitation signal may be counted by the counter 9 as a pulse signal.

Further, when determining the paper size,
Not only in the case where the signal level of the sheet detection sensor due to the detection of the sheet is high and the signal change due to the detection of the sheet edge b changes from the high level to the low level, but also when the logical level is inverted due to a change in the circuit configuration. It goes without saying that it can be applied.

(Embodiment 8-1) Referring to FIG. 22, a description will be given of a determination method of a paper determination unit and a control method of a control unit of an embodiment 8-1. As shown in FIG. 16A, in a state where the paper 3 is set at the paper feed preparation position and is detected by the paper detection sensor 6, the control unit 2
“0” instructs the sheet conveying means to convey the sheet 3.
At the same time as the conveyance of the sheet 3 is started, the counter 9 starts counting pulses from the encoder 8 that generates a pulse corresponding to the sheet conveyance amount, and as shown in FIG. The counting is continued until b is detected by the paper detection sensor 6. The control unit 20 instructs the first memory 101 to temporarily store the count value converted paper size Np as a memory value. Then, the determination unit 21 reads the memory value of the count value converted paper size stored in the first memory 101 and determines the paper size. For example, when the memory value of the count value converted paper size when the paper size is L = 140 mm and Zg = 10 mm is Np = 20,000, the count value converted memory value Np corresponding to other paper sizes is expressed by the formula ( 11) is obtained from the following equation (13).

Np = (L−Zg) / X = (L−10) /0.0065 (13) FIG. 23 shows an example of the count value Np corresponding to the paper size L. The determination means 21 includes a first memory 101
Value-converted paper size memory value N read from
The paper size L can be determined based on p.

Based on the value of the paper size L determined by the determination means 21, the control means 20 controls the paper transport amount, which is the control amount necessary for the subsequent paper feeding operation and printing operation,
Calculation of the ink sheet take-up amount, print start timing, and the like, or reading of the control amounts from the second memory 102 are performed, and sheet conveyance control corresponding to the sheet size is performed.

By the way, when the counter 9 counts the pulses generated by the encoder 8, the discrimination error of the paper size becomes X = 0.0065 mm from the equation (13).
The effect on image quality deterioration such as color misregistration is sufficiently within an allowable range, and does not cause any problem.

(Embodiment 8-2) Referring to FIG. 22, a method of determining a sheet determining means and a method of controlling a control means in Example 8-2 will be described. As shown in FIG. 16A, in a state where the paper 3 is set at the paper feed preparation position and the paper is detected by the paper detection sensor 6, the control unit 20 transports the paper 3 so as to transport the paper 3. Instruct the means. At the same time as the conveyance of the paper 3 is started, the counter 9 starts counting pulses output from the encoder 8 that generates pulses corresponding to the paper conveyance amount, and as shown in FIG. The counting is continued until the sheet edge b is detected by the sheet detection sensor 6. The control unit 20 instructs the first memory 101 to temporarily store the count value converted paper size Np as a memory value. Then, the determination means 21
Then, the memory value of the count value converted paper size stored in the memory 101 is read to determine the paper size. For example, when the paper size (length L in the main scanning direction) is 140 mm, the memory value of the paper size in terms of the count value is Np = 2.
In the case of 0000, the memory value Np of the sheet size in terms of the count value corresponding to the other sheet sizes is also calculated by the equation (13).
Can be obtained from

Although the paper size can be determined with sufficient accuracy by the equation (13), the calculation for the control amounts such as the winding amount of the ink sheet and the printing timing is performed one by one according to the paper size. However, it takes a long time, which is not preferable because the speed and size of the apparatus are reduced. At this time, if some paper sizes are limited as standard sizes and a series of paper conveyance controls corresponding to the respective paper sizes are made into a routine in advance, there is no need to perform calculations. More specifically, for example, some standard paper sizes L ₁ , L
Count values Np ₁ , Np ₂ , Np for ₂ , L ₃ ,.
Find ₃ , ... in advance. First, it is determined whether the size of the sheet 3 is the standard size or the non-standard size by comparing these count values with the count value-converted sheet size memory value Np actually obtained from the counting means 9. It is.

When the result of the determination is a standard paper size, a control value such as a print start timing and an ink sheet winding amount corresponding to each standard size is optimized in advance and a corresponding control program is prepared. Do what you want. If it is determined to be a non-standard size,
If the actually obtained count value converted memory value Np is not among the prepared count values, the paper size is determined by assuming that it is equal to the closest count value among the prepared count values.

For example, as shown in FIG. 23, when a count value is given in advance every time the paper size changes by 5 mm, if Np = 20,000, it is determined that the paper size is 140 mm. Np = 2123
1 (equivalent to A6 size 148mm) NpＮ2
Since it is 1538, it is determined that the paper size is 150 mm. When the sheet size is determined in this way, the control means 20 calls a control program prepared corresponding to the determined sheet size, and thereafter performs sheet transport control corresponding to the sheet size.

FIG. 23 shows only an example of the relationship between the count value Np and the paper size L prepared in advance, and it is not always necessary to calculate the paper size count value at intervals of 5 mm. A count value converted paper size corresponding to 148 mm as the size may be registered. Further, the paper size to be registered is not limited to five.

(Embodiment 8-3) Similarly, referring to FIG.
A method for establishing the print start timing in the embodiment 8-3 will be described. For example, the second ROM
The memory 102 stores print start timing information (upper margin memory value Ns in terms of count value of pulses generated by the encoder 8 from the paper end b to the print start position) corresponding to the paper size. That is, the memory value Ns is a count value of the pulse generated by the encoder 8 corresponding to the paper transport amount in the upper margin from when the paper end b is detected again at the start of printing until the printing start signal is sent and printing starts. This is the converted memory value.

In the case of the same paper size as that of the embodiment 8-2, for the paper size L given every 5 mm, the memory value Ns of the upper margin converted into the count value representing the print start timing is shown in FIG. In a look-up table (LUT) as shown in FIG.

Here, how to find Ns will be described.
In FIG. 21, the following equation (14) holds between the upper margin Ls, the print area length Lv, and the lower margin Le.

L = Ls + Lv + Le (14) By substituting the equation (12) into the equation (14), the following equation (15) is obtained.

L = Ns.X + Zs + Lv + Le (15) Therefore, Ns is represented by the following equation (16).

Ns = (L−Zs−Lv−Le) / X (16) The value of Ns can be calculated by using the following equation (16): Zs = 20, Lv = 10
It is obtained by substituting 0, Le = 15, and X = 0.0065.

Based on the paper size information Np stored in the first memory 101, the determination unit 21 determines the paper size, and the control unit 20 outputs print start timing information corresponding to the determined paper size. . For example,
Np = 2 as the memory value of the paper size in count value conversion
When 0000 is obtained, the determination unit determines that the paper size is 140 mm. Then, Ns = 769 (the upper margin length Lc = 5) is used as the memory value of the upper margin converted into the count value corresponding to the determined paper size.
mm). Also, when the memory value of the count value converted paper size is Np = 21231,
Although it actually corresponds to the A6 size (148 mm), the sheet size is determined by considering the memory value of the nearest count value converted sheet size as in the sheet size determination operation described in the embodiment 8-2. . Therefore, this paper size is determined as being approximated to 150 mm, and Ns = 2308 as the memory value of the upper margin in count value conversion, which is the print start timing information corresponding to this paper size.
(Corresponding to Lc = 15 mm) is output.

The counter 9 is reset after the paper size is determined and before the printing operation of the next color is started (usually immediately after the determination of the paper size). The control means 20 starts counting the pulses from the encoder 8, and determines the count value N which is actually obtained, that is, the time when the sheet transport amount N from the sheet end b counted by the counter 9 becomes equal to Ns. To control the paper transport so as to generate a print start signal.

In the present embodiment, the print start timing is described as the control amount. However, other control amounts, such as the sheet conveyance amount and the ink sheet take-up amount, are also considered.
The control values can be stored in the second memory 102 as in the case of the print start timing. Even when these control amounts are used, the second memory 1
02, a desired control amount can be called at any time to perform control. Further, the function of the paper discriminating means shown in the present embodiment may be configured as a single discriminating means, but may be included in a part of the function of the control means 20 as shown in the seventh embodiment. Good.

(Embodiment 9) FIG. 25 is a schematic side view showing the case where the present invention is applied to a paper transport device of a platen winding type thermal color printer. In the platen winding method, the sheet 3 is fed as in the case described in the first embodiment, and the sheet size L is detected during the sheet conveyance. The leading end a of the fed sheet 3 is fixed by the clamper 22 of the platen roller 4. The paper 3 is wound around the outer peripheral surface of the platen roller 4 by the rotation of the platen roller 4, and the rear end b of the paper is also fixed to the platen roller 4, and the paper feeding operation is completed.

After the paper feeding operation is completed, the platen roller 4 is rotated, and the origin pulse of the encoder corresponding to the position of the clamper 22 or the pulse count value of the encoder 8 when the clamper comes to the position of the thermal head 2, or the thermal head The platen roller 4 is rotated until the paper end a comes to the position of the thermal head 2 based on a detection signal of a paper end detection means (not shown) composed of a reflection type photo interrupter or the like arranged on the same axis as the paper 2. (This is called a sheet leading edge alignment operation). After the leading edge a of the paper is aligned with the thermal head 2, multicolor superposition printing is performed in the same manner as described in the first embodiment. Prior to printing of each color, the leading edge of the paper is adjusted to perform monochrome printing. However, after the printing of the final color is completed, the paper 3 after printing is conveyed and the paper discharging operation is performed without performing the paper leading edge alignment operation.

The high-speed conveyance, the method of discriminating the paper discrimination means, the control method of the control means, and the like can be the same as those of the above-described embodiment of the swingback type thermal color printer. It can be understood that the present invention can be easily applied to a thermal color printer of a printing system.
However, in the platen winding method, the maximum printable paper size is naturally limited. That is, since the paper 3 is wound around the platen roller 4 and transported for printing, paper longer than the circumference of the platen roller 4 is printed.
Can not be wound around. Therefore, there is a restriction that the printable paper size is within the circumferential length of the platen roller 4.

[0179]

As described above, according to the present invention, a change in the output signal of the sheet detecting means for detecting the end of the sheet or the sheet is generated irrespective of the sheet conveyance amount or irrespective of the sheet conveyance. The number of pulses is counted by the counting means, and by using the memory value of the sheet size in terms of the count value stored in the memory means for storing the count value, the paper size is discriminated, thereby determining the paper size other than the marked paper. Printing can also be performed using paper. In the conventional paper transport apparatus, only a specific paper size can be used at all times. However, according to the present invention, even if paper of any different size is used, a series of printing operations is hindered. It is possible to print without any problem. In addition, it is not necessary to separately provide a means such as an optical sensor for reading the marking on the sheet in order to generate a timing signal for starting printing. Further, since a means for generating a timing signal for starting printing, such as an optical sensor for reading a marking, is not required, it is possible to reduce the size, simplification, and cost of the paper transport mechanism. Furthermore, by making the paper transport speed at the time of paper feeding faster than the paper transport speed at the time of printing, the overall paper transport speed can be increased and the overall printing time can be shortened.

More specifically, the paper detecting means for detecting the edge of the paper or the presence of the paper is provided at a position where the edge of the paper can be detected in at least one of the printing direction and the conveying direction in the opposite direction. , And the paper size can be determined by detecting the edge of the paper when the paper is conveyed during printing or paper feeding, so that the printer can perform printing without using the marked paper. Then, even if paper of any different size is used, printing can be performed without hindering a series of printing operations.

The memory value of the count value of the counting means stored in the memory means is read out, and the paper size is determined based on the memory value, and is prepared in advance using the optimum control value corresponding to each paper size. By using a control means for selecting an appropriate one of the control programs and controlling the sheet conveyance, an optimum sheet conveyance for each sheet size can be performed.

The memory means holds the first sheet size converted by the counting means as a memory value until printing of one sheet is completed or printing of the same size sheet continuously. Therefore, if the paper size is determined at the time of feeding the first color, it is not necessary to determine the paper size when printing the second color or printing on the same size paper, which hinders a series of printing operations. And the printing time as a whole can be shortened.

The count value of the counting means is stored as a memory value in the first memory means, and the memory value is read out, the paper size is determined by the determination means, and the memory value stored in the second memory means is read. , The paper transport control suitable for the determined paper size is performed, so that even if the paper size is different, only a single control program can be used, and the optimal paper transport for each paper size is performed. obtain.

The second memory means previously stores optimum control values such as print start timings corresponding to some selected paper sizes as a paper size as a look-up table. When the standard size is selected, the corresponding control value is output.When the standard size is not the standard size, the nearest standard size is selected and the corresponding control value is output. Optimal paper transport can be performed.

The controller counts the pulse count starting from a signal change from the sheet detector for detecting the edge of the sheet during the conveyance in the printing direction, and determines the value of the count value for the print start timing read from the second memory. By performing sheet conveyance control so that printing is started at the time when the memory value matches the memory value, it is possible to perform control so that printing is performed at an optimum position even with different sheet sizes.

The pulse period can be shortened by using a pulse generating means for generating a pulse irrespective of the transport of the paper, thereby reducing the error in paper discrimination and reducing the printing time of each color. Of the print start timing can be reduced. In addition, since pulses can be counted stably even at the time of low-speed paper conveyance, counting errors can be reduced and print quality is not impaired.

By providing the counting means with a function of adding / subtracting a pulse from the pulse generation means for generating a pulse in accordance with the paper conveyance amount, the paper conveyance corresponding to the upper margin at the time of paper feeding or printing is provided. Can be omitted, and the printing time as a whole can be shortened.

In connection with the pulse generating means for generating a pulse corresponding to the amount of paper transported, the print quality is set by setting the amount of misregistration for multi-color superposition to be 1/4 or less of the dot diameter. Speed can be achieved without impairing the printing speed, and the overall printing time can be shortened.

In connection with the generating means for generating a pulse irrespective of the transport of the paper, by setting the amount of misregistration of the multi-color superposition due to the speed fluctuation to be 1/4 or less of the dot diameter. In addition, the speed of the paper conveying device can be increased without deteriorating the printing quality, and the overall printing time can be shortened.

Further, only one set of grid rollers for directly pressing and contacting the sheet and conveying the sheet is provided, and sheet detecting means for detecting the end of the sheet and the presence of the sheet are provided on the sheet feeding side of the grid roller. Further downsizing, simplification, and cost reduction of the device can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a main part of a thermal color printer in which a paper transport device according to the present invention is used.

FIG. 2 is a block diagram illustrating flows of main signals and data in the first embodiment.

FIG. 3 is a timing chart for explaining a method of determining a paper size.

FIG. 4 is a graph showing a relationship between the number of pulses generated by a pulse generation unit and a sheet conveyance amount.

FIG. 5 is a diagram illustrating a relationship between a length of each portion of a sheet in a main scanning direction and a pulse count value.

FIG. 6 is a block diagram showing a flow of main signals and data in Embodiments 2 and 3.

FIG. 7 is a diagram showing the relationship between the length of each portion of the paper in the main scanning direction and the pulse count value when an accumulation counter is used.

FIG. 8 is a block diagram showing main signal and data flows in Embodiments 4-1 to 4-3.

FIG. 9 is a diagram illustrating an example of a look-up table of registered paper sizes L and corresponding pulse count values Np.

FIG. 10 is a diagram illustrating an example of a look-up table of registered paper sizes L and count values Ns of pulses representing print start timings.

FIG. 11 is a block diagram showing a flow of main signals and data in a fifth embodiment.

FIG. 12 is a timing chart illustrating a method of determining a paper size according to a fifth embodiment.

FIG. 13 is a schematic side view showing another thermal color printer to which the sheet transport device according to the present invention is applied.

FIG. 14 is a block diagram showing main signal and data flows in a seventh embodiment.

FIG. 15 is a timing chart for explaining a method of determining a paper size.

FIG. 16 is a diagram illustrating a sheet conveyance state in a positional relationship with each mechanism unit.

FIG. 17 is a diagram illustrating a sheet conveyance state in a positional relationship with each mechanism unit.

FIG. 18 is a diagram illustrating a sheet conveyance state in a positional relationship with each mechanism unit.

FIG. 19 is a graph showing the relationship between the number of pulses generated by the pulse generation means and the sheet conveyance amount.

FIG. 20 is a timing chart for explaining a method for obtaining a print start signal.

FIG. 21 is a diagram showing the relationship between the length of each portion of the paper in the main scanning direction and the pulse count value.

FIG. 22 is a block diagram showing a flow of main signals and data in Examples 8-1 to 8-3.

FIG. 23 is a diagram showing an example of a look-up table of registered paper sizes L and corresponding pulse count values Np.

FIG. 24 is a diagram illustrating an example of a look-up table of registered paper sizes L and count values Ns of pulses representing print start timings.

FIG. 25 is a schematic side view showing a platen wrapping type thermal color printer to which the paper transport device according to the present invention is applied.

FIG. 26 is a schematic side view showing a thermal color printer including a conventional paper transport device.

FIG. 27 is a diagram illustrating an example of a sheet used in a conventional sheet conveying apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink sheet 2 Thermal head 3 Paper 4 Platen roller 5 Grid roller 6 Paper detection sensor 7 Optical sensor 8 Encoder 9 Counter 10 Memory 101 First memory 102 Second memory 11 Motor 12 Crystal oscillator 20 Control means 21 Judgment means 22 Clamper a Leading edge of paper b Trailing edge of paper

Continued on the front page (72) Inventor Hiroyuki Hanato 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Masayoshi Keizawa 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (56) References JP-A-4-158068 (JP, A) JP-A-5-24318 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 13/00

Claims (15)

(57) [Claims] 1. A thermal printer in which a thermal head in which a plurality of heating elements are arranged is arranged, and the thermal head presses a paper against a platen roller to perform printing. Sheet detecting means for detecting the end of the sheet and the presence or absence of a sheet, pulse generating means for generating a pulse corresponding to the transport amount of the sheet, counting means for counting the pulses generated by the pulse generating means, and First memory means for storing a count value; determining means for determining a paper size based on the memory value stored in the first memory means; and an optimal control value of at least a print start timing corresponding to the paper size is determined in advance. A second memory means for storing the sheet, and a sheet conveying control for controlling a printing start position corresponding to the sheet size. And a control means. 2. The control means according to claim 1, wherein said control means determines a paper size by said determination means at the time of feeding the paper, and detects a change in a signal from said paper detection means which detects an edge of the paper at the time of conveyance in a printing direction. 2. The paper transport control according to claim 1 , wherein the paper transport control is performed so that printing is started when the count value actually counted matches the memory value of the count value representing the print start timing read from the means. Transport device. 3. A look-up table which converts print start timings of standard sizes corresponding to several known paper sizes selected in advance as standard paper sizes into count values. When the paper size determined by the determination means is a standard size as one of the roles, the control means stores a memory value of a count value representing a print start timing corresponding to the standard size in the second form. If the paper size determined by the determining means is other than the standard size, the standard size closest to the size is selected and the memory value of the count value indicating the print start timing is set to the memory value. claim and performing sheet conveyance control by instructing to output from the second memory means 1 or Sheet conveying device according to 2. Wherein said counting means, pulses addition and by the sheet conveying apparatus according to any one of claims 3 to claims 1, characterized in that accumulated by subtracting from said pulse generating means. 5. When the resolution of the printer is Y (dbi), the paper transport amount X (mm / pulse) per pulse generated by the pulse generating means is X ≦ 6.35 /
Claims 1, characterized in that it is set so as to satisfy the Y is the sheet conveying apparatus according to any one of the paragraphs 4. 6. A thermal printer in which a thermal head in which a plurality of heating elements are arranged is arranged, and the thermal head presses a sheet against a platen roller to perform printing.
Sheet conveying means for actually conveying the sheet, sheet detecting means for detecting the end of the sheet and the presence or absence of the sheet, pulse generating means for generating a clock pulse, counting means for counting the pulses, and counting by the counting means Memory means for storing a value, and control means for controlling sheet conveyance so as to determine a sheet size based on the memory value stored in the memory means and to control a print start position corresponding to the sheet size. Characteristic paper transport device. 7. A thermal printer in which a thermal head in which a plurality of heating elements are arranged is arranged, and the thermal head presses a paper against a platen roller to perform printing. Paper detecting means for detecting the end of the paper and the presence or absence of paper, pulse generating means for generating a clock pulse, counting means for counting the pulses, memory means for storing a count value of the counting means, and A discriminating unit for discriminating the paper size based on the stored memory value, and selecting one of a plurality of control programs prepared using at least an optimal control value of a print start timing corresponding to each different paper size The paper transport control to control the print start position according to the paper size. And a control unit. 8. A thermal printer in which a thermal head in which a plurality of heating elements are arranged is arranged, and the thermal head presses a paper against a platen roller to perform printing. Sheet detecting means for detecting the end of the sheet and the presence or absence of a sheet; pulse generating means for generating a clock pulse; counting means for counting the pulses; first memory means for storing a count value of the counting means; Determining means for determining the paper size based on the memory value stored in the first memory means; second memory means for storing at least an optimum control value of a print start timing corresponding to the paper size in advance; Control means for controlling sheet conveyance so as to control the printing start position in accordance with the image forming apparatus. Place. 9. The printing apparatus according to claim 1, wherein the paper transporting device has a function of transporting the paper to a predetermined position in a direction opposite to a printing direction at a speed higher than that at the time of printing. The paper size is discriminated by the discriminating means when the paper is conveyed, and read from the second memory means starting from a signal change from the paper detecting means for detecting the edge of the paper when the paper is conveyed in a relatively low speed printing direction. 9. The paper transport apparatus according to claim 8, wherein the paper transport control is performed such that printing is started at a point where the count value actually counted matches the memory value of the count value representing the print start timing. 10. The second memory means looks up a value obtained by converting a print start timing of a standard size corresponding to several known paper sizes previously selected as a standard paper size into a count value. When the sheet size determined by the determination unit is a standard size, the control unit stores a memory value of a count value indicating a print start timing corresponding to the standard size as one of the roles. If the paper size determined by the determination means is other than the standard size, the nearest standard size is selected and the memory value of the count value indicating the print start timing is set to the output value. claim and performing sheet conveyance control by instructing to output from the second memory means 8 Other sheet conveying device according to 9. 11. The first memory means stores the count value of the counting means during a period until a printing operation of one sheet is completed and an operation of continuously printing sheets of the same size. sheet conveying device according to any one of claims of from 5 and claims 7 to claims 1, characterized in that keeps holding the value 1 0. 12. The pulse period T [s] is such that the paper transport speed during printing is Vp [m / s], the stability of Vp is Kp, and the resolution of the printer is Y [dpi]. In some cases, the amount of color misregistration X [m
m] is set so as to satisfy X = (1 + Kp) · Vp · T ≦ 6.35 / Y.
6 to be the paper conveying apparatus according to any one of the paragraphs 1 1. 13. The sheet detecting means is arranged at a position where an end of a sheet can be detected in at least one of a printing direction and a sheet feeding direction opposite to the printing direction, and sets a printing start position according to a sheet size. paper transporting device according to any one of the paragraphs to sheet conveyance control by controlling the claims 1, characterized in that is carried out 12. 14. The paper detecting means, the sheet conveying device according to any one of claims 1 or 3, characterized in that it is arranged on the paper feeding side of the sheet conveying means. 15. A method according to claim 1, wherein the sheet size is determined at the time of sheet feeding, and the sheet conveyance control is performed so as to control a printing start position based on a signal change from a sheet detecting means for detecting an end of the sheet during conveyance in the printing direction. sheet conveying apparatus according to claim 1 4, characterized.