JPH05147291A - Printer - Google Patents

Abstract

PURPOSE:To provide a printer constituted so that the pressure contact force of a roller to a platen is made changeable at the times of printing and non- printing not only to prevent the cutting inferiority of printing paper at the time of printing but also to allow only rotation obstructing force to act on the platen in a degree possible to neglect at the time of non-printing. CONSTITUTION:In a printer wherein a printing head 12 is provided so as to be displaceable between a pressure contact position and a standby position with respect to a platen 8 and a roller 73 is brought into contact with the platen 8, the pressure contact force of the roller 73 to the platen 8 is made changeable so that it becomes strong at the standby position of the printing head 12 and weak at the pressure contact position thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer using long print paper such as roll-shaped print paper.

[0002]

2. Description of the Related Art A schematic side view of a conventional printer is shown in FIGS. 18 and 19,
The chassis 7 is composed of a main chassis 7a and a sub chassis 7b. A synchronous shaft 20 is rotatably supported by the main chassis 7a, and the synchronous shaft 20 is rotated by the rotational force of a paper storage unit drive mechanism (not shown). A pair of arm members 21 are provided at both ends of the synchronizing shaft 20, and the sub-chassis 7b is pivotally supported on the tip ends of the pair of arm members 21. A pair of slide members 23 are horizontally slidable on both sides of the main chassis 7a.
The sub-chassis 7b is pivotally supported at the tip of the.

The platen 8 is rotatably supported on the upper portion of the sub chassis 7b, and the platen 8 is rotated by the rotating force of a platen rotating mechanism (not shown). The print head 12 is fixed to a head supporting member 40, and the head supporting member 40 is axially supported by the main chassis 7a. A pair of left and right compression springs 42 is provided on the upper surface of the print head 12.
Acts to bias the print head 12 toward the platen 8 side. Further, the print head 12 is configured so that a pressing force of a head lifting mechanism (not shown) acts on the print head 12, and the print head 12 presses against the platen 8 by the spring force of the compression spring 42 (a solid line position in FIG. 18). .) And a standby position (an imaginary line position in FIG. 18) away from the platen 8 against the spring force.

The roller 72 is supported by the print head 12,
It is arranged at a position where the platen 8 is pressed. The paper storage unit 10 is provided inside the sub chassis 7b, and the roll-shaped print paper 11 is stored in the paper storage unit 10. The print paper 11 passes through the roller 73 and the platen 8 and between the print head 12 and the platen 8 and is arranged in a paper path system that reaches the paper discharge port 4. The paper discharge port 4 is formed on the front panel 1c, and a cutter 13 is provided inside the paper discharge port 4.

In the above structure, when the printing mode is selected with the paper storage unit 10 in the closed position and the printing head 12 in the standby position, the pressing force of the head elevating mechanism is released and the printing head 12 moves to the position shown in FIG. It is located at the pressure contact position indicated by the solid line at 18. Next, the platen 8 is rotated by the rotational force of the platen rotating mechanism and the printing head 12 is driven to start printing. When printing is completed, the print head 12 is returned to the standby position shown by the phantom line in FIG. 18 by the pressing force of the head lifting mechanism. Then, the operator cuts the print paper 11 output from the paper discharge port 4 by using the cutter 13.

When the paper storage unit open mode is selected,
The pair of arm members 21 are rotated by the rotational force of the paper storage unit drive mechanism, the sub-chassis 7b is rotated and ejected forward, and the paper storage unit 10 is in the open position as shown in FIG.
When the print paper 11 is replaced with a new one and the paper storage unit closing mode is selected, the pair of arm members 21 are rotated in the opposite direction by the rotational force of the paper storage unit drive mechanism, and the sub chassis 7b is rotated.
Is stored while rotating, and the paper storage unit 10 is at the closed position as shown in FIG. 18 (see Japanese Patent Laid-Open No. 3-130181).

[0007]

In the above conventional structure, the roller 73 increases the wrapping angle of the print paper 11 around the platen 8 at the time of printing to prevent the print paper 11 from slipping, and cuts at the time of non-printing. When printing on paper 11
The print paper 11 is prevented from being pulled out against the pulling force that acts on the sheet, and the cutter 13 makes it possible to perform a clean cut.

Here, if the pressure contact force of the roller 73 against the platen 8 is set to be weak, the pulling force at the time of cutting the print paper 11 cannot be resisted, and there is a possibility that cutting failure may occur, and the roller 73 may be damaged. If the pressure contact force to the platen 8 is set to be strong, there is a disadvantage that the rotation blocking force of the platen 8 at the time of printing becomes a nonnegligible magnitude.

Therefore, it is an object of the present invention to provide a printer which eliminates the above-mentioned drawbacks by varying the pressure contact force of the roller to the platen during printing and non-printing.

[0010]

To achieve the above object, a printer according to the present invention rotatably supports a platen with respect to a chassis and also supports a print head on the chassis, and the print head is provided with the print head. Is provided so as to be displaceable between a press contact position in which the platen is pressed against and a standby position separated from the platen, and the print paper is arranged in a paper path system that passes between the platen and the print head and reaches a paper discharge port. In a printer in which a roller is provided that is in pressure contact with a platen, and the position of the print head is changed to a pressure contact position during printing, and the print head is moved to a standby position during non-printing, the pressure contact force of the roller against the platen is changed by the print head. The strength is variable at the standby position and weak at the press contact position of the print head.

[0011]

[Operation] Since the roller has a weak pressure contact with the platen during printing, it exerts only a negligible rotation blocking force on the platen, and the non-printing force exerts a strong pressure against the platen when cutting the print paper. Can sufficiently counter the pulling force of.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 17 show an embodiment of the present invention. 2 is a perspective view of the printer when the paper storage portion is located at the closed position, FIG. 3 is a perspective view of the printer when the paper storage portion is located at the closed position, and FIG. 4 is an exploded perspective view of the printer.
FIG. 5 shows a partially cutaway front view of the printer.

2 to 5, the printer case 1 is made of a synthetic resin material, and includes a bottom cover 1a for closing the lower surface, a top cover 1b for closing the upper surface and both side surfaces, and a front panel 1c and a door panel 1d for closing the front surface. The rear panel 1e closes the rear surface. The operation switch 2 and the like are arranged on the upper part of the front panel 1c, and the large opening 3 is provided below the operation switch 2 and the like.

As shown in FIG. 2, the door panel 1d is arranged in the large opening portion 3 when the paper storage portion 10 is in the closed position, and the upper part of the large opening portion 3 which is not closed by the door panel 1d forms the paper discharge port 4. Constitute. Further, as shown in FIG. 3, when the paper storage unit 10 is in the open position, the sub-chassis 7 from the large opening 3 will be described below.
b is pulled out.

A mechanical block body 5 and the like fixed to a chassis 7 are housed on the front side of the case 1, and a substrate block body 6 is housed on the rear side.

6 and 7 are left and right side views of the mechanical block body 5 and the like when the paper storage portion 10 is located at the closed position, and FIG.
The right side views of the mechanical block body 5 and the like when the paper storage unit 10 is located at the open position are shown in FIG.

6 to 8, the chassis 7 is composed of a main chassis 7a and a sub-chassis 7b, both of which are made of metal members, and the main chassis 7a is attached to the bottom cover 1a. The front panel 1c is attached to the front side of the main chassis 7a,
Further, the door panel 1 is provided on the front side of the sub chassis 7b.
d is attached.

A platen 8 is rotatably supported on the upper end of the sub chassis 7b, and the platen 8 is made of a rubber material. Then, the platen 8 is rotated by a platen rotating mechanism C described below. Also, the sub chassis 7
A tray 9 having an arcuate lower surface is provided on the inner side of b, and a space above the tray 9 constitutes a paper storage unit 10. A thermosensitive print paper 11 wound in a roll is stored in the paper storage unit 10, and the paper storage unit 10 for replacing the print paper 11 is automatically opened / closed by a paper storage unit opening / closing mechanism A described below. The front end side of the print paper 11 passes between the platen 8 and the roller 73 and between the platen 8 and the print head 12, and is arranged in a paper path system that reaches the paper discharge port 4.

A print head 12 is supported on the upper end of the main chassis 7a, and the print head 12 is displaced by a head lifting mechanism B.

The cutter 13 is formed of a metal member and comprises a blade portion 13a and a blade mounting portion 13b which supports the blade portion 13a. The blade mounting portion 13b is swingably supported by the hooking portion 14 of the front panel 1c, and the cutter 13 is shown in FIG.
It is provided so as to be freely displaceable between the protruding position shown in FIG. 8 and the retracted position shown in FIG. Cutter 13 is torsion spring 15
The spring force (shown in FIG. 7) urges it toward the exit position. A cutter pressing portion 16 is provided on the sub chassis 7b, and a torsion spring 17 is provided on the main chassis 7a.
Is supported at one end side thereof. When the cutter pressing portion 16 presses one end of the pressed portion 18 of the cutter 13 at the closed position of the paper storage portion 10 and the other end of the pressed portion 18 is received by the torsion spring 17, the cutter 13 is a spring of the torsion spring 15. It is located in the protruding position against the force. Since the cutter 13 is grounded to the main chassis 7a via the torsion spring 17, electrostatic noise can be prevented. When the paper storage portion 10 is displaced from the closed position to the open position, the cutter pressing portion 16 of the sub chassis 7b is separated from the pressed portion 18 and the cutter 13 is displaced to the retracted position by the spring force of the torsion spring 15.

9 to 11 are right side views mainly showing the paper storage unit opening / closing mechanism A, respectively. 9 to 11, the paper storage unit opening / closing mechanism A automatically opens and closes the paper storage unit 10 as described above, and is configured as follows. That is, the synchronous shaft 20 is rotatably supported by both side plates 19 of the main chassis 7a, and a pair of arm members 21 are fixed at both ends of the synchronous shaft 20 and inside the both side plates 19. This pair of arm members 21
The front ends of the sub chassis 7b via the support pins 22.
It is pivotally supported at the rear end.

The pair of slide members 23 are arranged outside the side plates 19 of the main chassis 7a, and the guide pins 24 projecting from the side plates 19 are inserted into the elongated holes 23a of the slide members 23, respectively. Guide rollers 25 supported by both side plates 19 are in contact with the upper and lower surfaces of the pair of slide members 23, respectively, and the pair of slide members 23 are slidable in the front-rear direction by the guide pins 24 and the guide rollers 25. Has been. The front ends of the pair of slide members 23 slidably provided in this manner are pivotally supported by the front ends of the sub-chassis 7b via the support pins 26.

On the other hand, a fan gear 27 is fixed to the right end of the synchronous shaft 20, and the motor 2 is attached to the fan gear 27.
The rotating force of 8 is the gear 29 fixed to the rotating shaft of the motor 28.
Are transmitted via the two reduction gears 30 and 31.

The paper storage unit locking means 32 has a lock lever 33 swingably supported by the right side plate 19 of the main chassis 7a. The locking portion 33a of the lock lever 33 is between the locked position and the unlocked position. It is configured to be displaceable by. A spring 34 that urges the lock lever 33 toward the lock position acts, and the locking portion 33a is locked to the locked portion 23b of the right slide member 23 at the lock position.
Further, one end of a release lever 36 abuts against the pressed portion 33b of the lock lever 33, and a substantially central portion of the release lever 36 is pivotally supported by the main chassis 7a. Release lever 36
A cam pin 37 is provided at the other end of the
Is in contact with the second cam surface 46b of the control gear 46 described below. Then, the release lever 36 rotates according to the rotation of the control gear 46, and the lock lever 33 is displaced to the lock release position.

As shown in FIG. 10, when the paper storage unit 10 is in the closed position and the motor 28 is rotated in the unlocked state, this rotational force is transmitted to the synchronous shaft 20 so that the pair of arm members 21 are clocked. Rotate in the direction. Then, the sub-chassis 7b is guided by the pair of slide members 23 and is pulled out forward, and is rotated counterclockwise about the support pin 26 as a fulcrum to position the paper storage portion 10 at the open position as shown in FIG. .. In addition, by the reverse operation, the paper storage unit 1
0 is returned from the open position to the closed position.

12 to 14 are right side views mainly showing the head lifting mechanism B, respectively. 12 to 14, the head lifting mechanism B automatically displaces the print head 12 between the pressure contact position and the separation position, and is configured as follows. That is, the rear end of the head support member 40 is rotatably supported by the support shaft 41 on the upper end of the main chassis 7a, and the print head 12 is fixed to the lower surface on the front end side of the head support member 40. Printing head 12
The head supporting member 40 is configured to be displaceable between a pressure contact position where the head support member 40 is pressed against the platen 8 and an upper separation position which is sufficiently separated from the platen 8.
The print head 12 is, for example, a heat-sensitive type and is driven by a drive circuit (not shown).

A pair of left and right compression springs 42a, 42 are provided between the upper surface of the head support member 40 and the main chassis 7a.
b (shown in FIG. 5) is interposed, and the print head 12 is biased toward the pressure contact position side by this spring force. The printing head 12 is pressed against the platen 8 by this spring force at the pressing position.

On the other hand, one side of the substantially triangular operating plate 43 is rotatably supported by the right side plate 19 via a support pin 44. The pressing portion 4 is provided at the other corner of the operating plate 43.
3a is provided, and the pressing portion 43a is provided so that the lower surface of the head supporting member 40 can be pressed by the rotation of the operating plate 43. A cam pin 45 is provided on the other corner side of the operating plate 43, and the cam pin 45 is a control gear 46.
Is in contact with the first cam surface 46a.

The control gear 46 is supported by the right side plate 19, and a first cam surface 46a and a second cam surface 46b are provided on the inner surface side thereof. The first cam surface 46a is configured so that the distance from the center gradually changes as the rotation angle changes, and the rotation position of the operating plate 43 changes as the control gear 46 rotates. The second cam surface 46b is configured so that the distance from the center becomes short only in part, and the release lever 36 presses the lock lever 33 at this short position. The control gear 46 is configured such that the rotational force of the motor 47 is achieved by the gear 48 fixed to the rotation shaft of the motor 47, the timing belt 49, and the three reduction gears 50, 51, 52.

As shown in FIG. 12, when the print head 12 is in the pressure contact position and the motor 47 rotates, this rotational force is transmitted and the control gear 46 rotates. Then, the cam pin 45 of the operating plate 43 slides on the first cam surface 46a, and the operating plate 43
Rotates clockwise, and the pressing portion 43a of the operating plate 43 contacts the lower surface of the head supporting member 40. Further, the operating plate 43
When the head rotates, the head support member 40 moves the compression spring 42a,
The print head 12 is displaced upward against the spring force of 42b.
Is located at the standby position shown in FIG. When the operating plate 43 further rotates from this state, the head supporting member 40 is displaced upward and the printing head 12 is positioned at the separated position shown in FIG. 14 in the same manner as described above. Further, by the operation reverse to the above, the print head 12 is displaced from the separated position to the press contact position through the standby position.

15 and 16, the platen rotating mechanism C is shown.
The cross-sectional views mainly showing are respectively shown. 15 and 16, the platen rotation mechanism C includes a first support plate 55 fixed to the inside of the left arm member 21 and a second support plate 56 fixed to the inside of the left side of the sub chassis 7b.
Have and. A motor 57, a first reduction gear 59 that meshes with a gear 58 fixed to the rotation shaft of the motor 57, and a gear 60 that meshes with the first reduction gear 59 are supported by the first support plate 55. There is. Second
A second reduction gear 61 meshing with the gear 60, a gear 62 meshing with the second reduction gear 61, and a gear 63 further meshing with the second reduction gear 61 are supported by the support plate 56. The second reduction gear 61 is supported around a support pin 22 that pivotally supports the arm member 21 and the sub-chassis 7b, and the second reduction gear 61 and the gear 60 are irrespective of the relative rotational positions of the arm member 21 and the sub-chassis 7b. It is configured so that the distance between the rotation centers does not change. Therefore, even if the second reduction gear 61 and the gear 60 are displaced between the closed position of the paper storage unit 10 shown in FIG. 15 and the open position of the paper storage unit 10 shown in FIG.

A small-diameter gear 64 is integrally provided on the gear 63, and a timing belt 66 is hung between the gear 64 and a gear 65 fixed to the shaft 8a of the platen 8. The second support plate 56 is rotatably supported by the sub chassis 7b via the support pins 22. A tension spring 67 is applied between the second support plate 56 and the sub chassis 7b, and a constant tension is applied to the timing belt 66 by this spring force. Further, the second support plate 56 is provided with a temporary spring locking portion 56a. At the time of assembling the second reduction gear 61 and the like, one end of the tension spring 67 is hooked on the temporary spring locking portion 56a so that the second reduction gear 61 and the timing belt 66 are provided.
After completion of the assembly, if one end of the tension spring 67 is hooked on the spring locking portion 68 of the sub chassis 7b, the tension spring 67 can be assembled without receiving the spring force of the tension spring 67.

The platen rotating mechanism C configured as described above
When the motor 57 rotates, this rotational force is transmitted in order of the first reduction gear 59, the gear 60, the second reduction gear 61, the gear 62 and the gear 63. Then, the rotation of the gear 63 is transmitted via the timing belt 66 to rotate the platen 8.

The print head 12 is shown in FIGS.
Enlarged side views of each area are shown. Figure 1 (a)
In (b) and (b), a roller support member 70 is pivotally supported on the head support member 40 via a support pin 71. A shaft 72 is fixed to the lower end of the roller support member 70, and a plurality of rollers 73 are rotatably supported on the shaft 72. The shaft 72 of the roller 73 is arranged parallel to the shaft 8a of the platen 8. Further, a tension spring 74 is applied between the upper end of the roller support member 70 and the head support member 40, and the spring force biases the roller 73 toward the platen 8. When the paper storage unit 10 is not located at the closed position, the stopper end surface 70a is brought into contact with the head support member 40 to regulate the position. When the paper storage unit 10 is in the closed position, the roller 73 presses against the platen 8 via the print paper 11, but when the printing head 12 is in the press position, the stroke S of the tension spring 73 is short and the press contact force is small. When the print head 12 is weak, the stroke S of the tension spring 73 is long and the pressure contact force is strong when the print head 12 is in the standby position.

A paper pressing plate 75 is fixed to the front surface of the head supporting member 40, and the lower end of the paper pressing plate 75 is located below the printing head 12 by d.

As shown in detail in FIG. 17, the roller 7
3 is made of a synthetic resin material and comprises a cylindrical portion 73a and four shaft support portions 73b extending toward the center at 90 degree intervals from the inner peripheral surface of the cylindrical portion 73a. The shafts 72 are configured to be supported by the tip surfaces of the four shaft support portions 73b. Therefore, the roller 73 having the long dimension L can be formed by extrusion molding because the roller 73 has a structure in which the shaft insertion space and the space between the adjacent shaft support portions 73b communicate with each other to have one large hole 73c.

Returning to FIG. 4 and FIG. 5 again, the plate substrate 7
7 is supported on the right side plate 19 of the main chassis 7a with a constant space, and supports the tip ends of the shafts of the gears and the like supported by the main chassis 7a. In addition, the contact 78 provided on the control gear 46 or the sector gear 27 is brought into contact with the print pattern of the printed board 77 to control the control gear 46 or the sector gear 2.
7 rotational position detecting means is configured.

The operation of the above configuration will be described below.
First, the printing operation will be described. When the paper storage unit 10 is in the closed position and the print head 12 is in the standby position as shown in FIG. 13, when the print mode is selected, the head lifting mechanism B is driven and the print head 12 is moved. Figure 1
It is displaced to the press contact position shown in 2. When the print head 12 is displaced to the press contact position, the platen rotation mechanism C drives, the platen 8 rotates, and the drive circuit of the print head 12 drives. The printing paper 11 is fed at a constant speed in accordance with the rotation of the platen 8, and the printing head 12 appropriately heats the printing paper 11 for printing.

When printing is completed, the platen rotation mechanism C stops driving and the head elevating mechanism B drives to displace the printing head 12 from the pressure contact position shown in FIG. 13 to the standby position shown in FIG. The operator obtains a print image by cutting the print paper 11 output from the paper discharge port 4 with the cutter 13.

In the above operation process, FIG.
As shown in (b), the roller 73 is pressed against the platen 8 with a weak pressing force, so that only a negligible rotation blocking force acts on the platen 8. In addition, when not printing,
Since the roller 73 presses against the platen 8 with a strong press contact force as shown in FIG. 5, the tensile force at the time of cutting the print paper 11 can be sufficiently counteracted, so that the print paper 11 is cut well and does not cause defective cutting.

Next, the operation of replacing the print paper 11 will be described. When the paper storage unit open mode is selected at the standby position shown in FIG. 9, the head lifting mechanism B is driven to displace the printing head 12 to the separated position shown in FIGS. The lock of the lock means 32 is released. Next, the paper storage drive mechanism A is driven to displace the paper storage unit 10 to the open position shown in FIG. Due to the displacement of the paper storage unit 10, the cutter 13 is displaced to the retracted position.

The operator operates the print paper 11 in the paper storage unit 10.
The core is taken out, and a new print paper 11 is set with its tip side pulled out. Then, when the paper storage unit close mode is selected, the paper storage unit drive mechanism A drives to displace the paper storage unit 10 to the closed position shown in FIG. Next, the head elevating mechanism B is driven to move the printing head 12 to the position shown in FIGS.
It is returned to the standby position shown in 3 and completed.

[0043]

As described above, according to the present invention, the pressure contact force of the roller that is in pressure contact with the platen is strong when the print head is located at the standby position, and weak when the print head is located at the press position. Since it is variable so that when the print paper is cut, the pulling force that acts on the print paper is strong, which prevents the cut failure of the print paper.In addition, when printing, only a weak rotation blocking force acts on the printer, so the rollers rotate. The platen drive system can be designed by ignoring the blocking force.

[Brief description of drawings]

FIG. 1A is an enlarged side view of the vicinity of the printing head when the printing head is located at a standby position, and FIG. 1B is an enlarged side view of the vicinity of the printing head when the printing head is located at a pressure contact position (Example). ).

FIG. 2 is a perspective view (embodiment) of the printer when the paper storage unit is located at the closed position.

FIG. 3 is a perspective view (embodiment) of the printer when the paper storage unit is located at the open position.

FIG. 4 is an exploded perspective view of the printer (example).

FIG. 5 is a partially cutaway front view of the printer (example).

FIG. 6 is a right side view (embodiment) of the chassis block body and the like when the paper storage portion is located at the closed position.

FIG. 7 is a left side view (embodiment) of the chassis block body and the like when the paper storage portion is located at the closed position.

FIG. 8 is a right side view (embodiment) of the chassis block body and the like when the paper storage portion is located at the open position.

FIG. 9 is a right side view (embodiment) mainly showing the paper storage unit opening / closing mechanism in which the paper storage unit is in the closed position and in a locked state.

FIG. 10 is a right side view (embodiment) mainly showing the paper storage unit opening / closing mechanism in which the paper storage unit is in the closed position and in the unlocked state.

FIG. 11 is a right side view (embodiment) mainly showing the paper storage unit opening / closing mechanism when the paper storage unit is located at the open position.

FIG. 12 is a right side view (embodiment) mainly showing the head lifting mechanism when the printing head is located at the press contact position.

FIG. 13 is a right side view (embodiment) mainly showing the head lifting mechanism when the printing head is located at the standby position.

FIG. 14 is a right side view (embodiment) mainly showing the head lifting mechanism when the printing head is located at the separated position.

FIG. 15 is a cross-sectional view (embodiment) mainly showing the platen rotation mechanism when the paper storage portion is located at the closed position.

FIG. 16 is a cross-sectional view (embodiment) mainly showing the platen rotation mechanism when the paper storage portion is located at the open position.

FIG. 17 is a perspective view of a roller (example).

FIG. 18 is a schematic side view (conventional example) of the printer when the paper storage unit is located at the closed position.

FIG. 19 is a schematic side view (conventional example) of the printer when the paper storage unit is located at the open position.

[Explanation of symbols]

4 ... Paper discharge port, 7 ... Chassis, 8 ... Platen, 11 ... Print paper, 12 ... Printing head, 73 ... Roller.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B41J 25/312 25/316 25/304

Claims (1)

[Claims] 1. A platen is rotatably supported on a chassis and a print head is supported on the chassis, and the print head is displaceable between a press contact position where the print head is pressed against the platen and a standby position where the print head is separated from the platen. Installed in
A print paper is arranged in a paper path system that passes between the platen and the print head and reaches the paper discharge port, and a roller that presses the print paper against the platen is provided, and the print head is placed in a press contact position during printing, and when not printing. In a printer in which the position of the print head is changed to a standby position, the pressure contact force of the roller to the platen is changed so that it is strong at the standby position of the print head and weak at the press position of the print head. Characteristic printer.