JP2611229B2 - Thermal transfer printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer printer, and more particularly to a ribbon traveling mechanism and a head pressing / releasing mechanism.

[Prior Art] Conventionally, as shown in Japanese Utility Model Application Laid-Open No. 60-184660, a thermal transfer printer is driven by switching the rotation direction using a single motor for pressing / releasing a head and running an ink ribbon. Had been proposed. In such a motor, a spring clutch acts on a motor shaft to extract a normal rotation direction and a reverse rotation direction.

[Problems to be Solved by the Invention] In such a conventional example, at least one of the head pressing / releasing mechanism and the ribbon traveling mechanism is always connected to the motor shaft and acts as a load. Had.

In other words, due to the nature of the ink ribbon, it is easy for slack to occur.Therefore, there is a limit in the rotation direction even if the bobbin supporting the ink ribbon is rotated in order to remove the slack, and the ribbon rotates only in the direction in which the ribbon is originally wound. This has made it difficult to handle the ink ribbon, and has led to the occurrence of wrinkles and the like on the ribbon. In particular, this is not the case with wide-width ink ribbons.Moreover, when replacing the ink ribbon, pulling the ink ribbon in the reverse direction rotates the motor shaft, causing the platen position to change, and with a large force. There is a danger of accidents such as pulling of the gears of the drive system by pulling.

In a serial type thermal transfer printer, an ink ribbon is generally wound around a bobbin and stored in a cassette, and the bobbin is generally inserted into a core of a ribbon traveling mechanism while being adjusted. In such a configuration, since the core is connected to the motor shaft by a spring clutch, it can be rotated only in one direction, so that the ribbon is forcibly pulled when the convex portion of the core and the concave portion of the bobbin are aligned, or conversely. There were times when it was said that it would interfere with subsequent running of the ribbon due to force in the slack direction.

Further, after setting the ink ribbon, the core is often turned with a finger when removing the slack, and even in such a case, if the core is turned in the opposite direction to the running of the ribbon, the direction of rotation of the motor is turned. In some cases, the release / release mechanism was actuated, causing trouble.

An object of the present invention is to eliminate these disadvantages and to provide a mechanism in which the ribbon traveling mechanism and the head pressing / releasing mechanism can be separated from the motor shaft except during operation.

[Means for Solving the Problems] The present invention solves the above-described problems, and includes a motor,
A planetary gear mechanism having a sun gear with a planetary gear coupled to a motor; a motion direction converting mechanism having a rotating member for converting a circular motion of the rotating member into reciprocating motion; and a position detecting means for detecting a reference position of the rotating member And an elastic member that engages with the movement direction conversion mechanism and urges the thermal head to press against the platen, and selects between a position where the thermal head is pressed against the platen and a release position with the movement direction conversion mechanism and the elastic member as components. A head pressure contact / release function, a ribbon traveling mechanism for traveling the ink ribbon, and a planetary gear mechanism, which are provided so as to be installed in each of the head pressure contact / release mechanism and the ribbon traveling mechanism, are arranged at predetermined intervals. A driving force transmitting mechanism for selectively transmitting a driving force by arranging a planetary gear between the two gears and switching the rotation direction of the motor; The rotation member is rotatable only in one direction, and the head pressing / releasing mechanism and the ribbon traveling mechanism are simultaneously detachable from the motor. Even if an external force is applied to the side, this force is not transmitted to the motor and the head pressure contact / release mechanism.

The thermal transfer printer is a serial type thermal transfer printer that moves a carriage supporting the thermal head along the platen, and includes at least the motor, a head pressure contact / release mechanism, the ribbon traveling mechanism, and a driving force transmission mechanism. Is mounted on the carriage.

[Embodiment] FIGS. 1 (a), 1 (b), 2 and 3 are schematic views showing an embodiment of a thermal transfer printer according to the present invention. FIG. (A) and (b) are plan views, FIG. 2 is a perspective view, and FIG. 3 is a partially enlarged view. An embodiment will be described below in detail with reference to FIGS. 1 (a) and (b), FIGS. 2 and 3.

1 is a thermal head, 19 is a heat radiating plate which supports the thermal head rotatably around a shaft 21, and the shaft 21 is fixed to the carriage frame 20. Carriage frame 20
Are supported by a guide shaft 16 and are installed so as to be able to reciprocate in the directions of arrows E1 and E2. Reference numeral 4 denotes a step motor, which is a type of a motor provided at the lower portion of the carriage frame, and has a motor gear 8 fixed to a motor shaft 4a penetrating the carriage frame 20. The sun gear 9 meshes with this motor gear. The sun gear 9 has a planetary gear 11, and FIG. 3 shows an enlarged sectional view of this portion. Reference numeral 31 in FIG. 3 denotes a pin fixed to the carriage frame 20, and a support arm 10 that supports the sun gear 9 and the planetary gear is rotatably mounted on the pin 31 as an axis. The planetary gear 11 is rotatable about a shaft 32 erected on the support arm. Reference numeral 33 denotes a disc spring for transmitting the rotational movement of the gear 9 to the support arm, and presses the planetary gear 11 against the support arm.

Gears 12 and 13 transmit the rotation of the planetary gear 11 to the gear 14 engaged with the ink ribbon winding core 24.

FIG. 1A shows a state in which an ink ribbon take-up mechanism, which is a kind of ribbon traveling mechanism, is operating.

When the motor 4 rotates in the direction of the arrow A1, the sun gear 9 turns to the arrow
It rotates in the direction of B1, which is transmitted to the support arm 10, and the planetary gear 11 meshes with the gear 12. When the gear 13 rotates in the direction of arrow C1, the gear 14 rotates in the direction of arrow D1 and the core 24 rotates.
Is rotated so that an ink ribbon 25 of a ribbon cassette or the like (not shown) passes through the thermal head 1 and is wound around a spool in the ribbon cassette. Gears 12-14
The core 24 forms a ribbon winding mechanism.

Reference numeral 3 denotes a cam, which is a kind of a rotating member.
Can rotate more than 0 degree. This cam 3 has at least three cam positions with different radii to the outer circumference, the position of r1 having the smallest radius is the cam position 3a, the position of the maximum radius r3 is the cam position 3c, and the position of the companion radius r2 is This is the cam position 3b. A reflection section 6 is provided on the upper surface of the cam, and the reference position of the rotation position of the cam can be detected by the reflection type photo sensor 5. With this reflection part 6,
A position detecting means is constituted by the photo sensor 5 so that the cam positions 3a, 3b, 3c corresponding to the cam diameters r1, r2, r3 are accurately and quickly selected. By detecting the position of the rotating member and making it correspond to the rotation angle of the motor, the position of the thermal head can be substantially detected.

A spring supporting member, which is a kind of an engaging member, is provided on an outer periphery of the cam 3.
18 are in contact. The spring support member 18 has a receiving portion 18a integrally formed and is installed so as to be rotatable around the guide shaft 16. Supported by a spring support member 18, a compression coil spring 2, a kind of elastic member, indirectly engages with the cam 3 and selects the position of the cam 3 to move the thermal head 1 from behind to the platen 17 in the direction of arrow F <b> 1. It can be urged to receive the pressure contact force.

When the cam 3 is in contact with the spring support member 18 at the cam position 3a, the distance between the cam 3 and the thermal head 1 is widened, and the pressing force by the compression coil spring 2 is released. Then, the thermal head 1 is moved to the arrow F2 direction by the force of the tension coil spring 15, and is set at the release position where the thermal head 1 is separated from the platen 17, and the ink ribbon 25 and the printing paper (not shown) are inserted between the platen 17 and the ink ribbon 25. It becomes possible. Also, when printing, the cam position 3c
Is selected, the pressure contact force of the thermal head 1 becomes maximum,
At the cam position 3b, the pressure contact force is small.

FIG. 1B is a view showing a state in which the head pressure contact / release mechanism is driven by the step motor 4.

When the step motor 4 rotates in the direction of arrow A2, the sun gear 9 rotates in the direction of arrow B2, the planetary gear 11 engages with the gear 7 integrally formed with the cam 3, and the cam 3 rotates in the direction of arrow G. Since the outer peripheral portion of the rotating motion of the cam 3 has at least two radii having different radii, the member abutting on the outer peripheral portion can reciprocate, and the cam 3 and the spring supporting member 18 move in the moving direction. It constitutes a conversion mechanism. The spring support member 18 is installed so that the coil spring 2 maintains its position. The coil spring 2 engages with the movement direction changing mechanism to obtain a pressing force for pressing the thermal head 1 against the platen 17. It is possible to obtain two or more types of press contact force by selecting the position. In a thermal transfer printer, it is generally known that the printing density and printing quality are affected by the pressing force of a thermal head. For bond paper and plain paper having a low surface smoothness, the print quality is better when the head pressure is large, and when the transfer pressure is low, the print quality is good when the pressure is small. When the pressing force is further large, the energy for moving the carriage on which the thermal head is mounted becomes large. For this reason, it is very convenient to change the pressing force according to the printing mode, and in this embodiment,
The head pressure contact / release mechanism is a pressure contact force switching mechanism as it is.

When the photo sensor 5 detects the reflection part 6, the number of steps of the step motor 4 is controlled using the reflection part 6 as a reference position.
It is possible to determine the rotation angle of the cam 3 and select a predetermined cam position. The cam 3, which is a rotating member, moves in the direction of arrow G
It can rotate 360 degrees or more, and has a structure in which all cam positions can be selected by one-way rotation of the motor. This makes it possible to share the drive source of the head pressure contact / release mechanism with another drive source.

The planetary gear mechanism having the sun gear and the planetary gears described above constitutes a driving force transmission mechanism that selectively transmits the driving force of the motor according to its rotation direction.

The feature of this transmission mechanism is that only the driving force from the motor is transmitted, and is a feature that cannot be seen with a conventional spring clutch or the like. That is, when the motor is not rotating, they are completely independent of each other, and even if an external force is applied to one of the head pressing / releasing mechanism and the ribbon traveling mechanism, the force is not transmitted to the other. This is because the planetary gear is located between the gears engaged with the head press / release mechanism and the two gears installed in the ribbon traveling mechanism and arranged at a predetermined interval, and only the rotation of the motor is forcibly applied. In contrast to transmission to each mechanism, even if one mechanism is rotated by external force, the planetary gears escape and this rotation force is not transmitted to the motor or the other mechanism. It is.

Thus, even if the ink ribbon is pulled after the ink ribbon is attached, the ink ribbon is not transmitted to the motor shaft, and is not transmitted to the head pressure contact / release mechanism.

Therefore, even when the ink ribbon is mounted, the core does not receive a load from the motor shaft, so that the core can be easily fitted to the bobbin to be mounted and can be smoothly mounted.

FIG. 4 is a schematic diagram showing the configuration of the thermal transfer printer according to the present invention, and the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals and description thereof is omitted.

Reference numeral 1a denotes a heating resistor which is a kind of a heating element arranged on the surface of the thermal head 1, 1b denotes a flexible cable serving as an electrode of the thermal head 1, 31 denotes a head driving circuit, and 32 denotes light emission and reception for driving the reflection type photo sensor 5. Circuit, a first motor drive circuit 33 for driving the step motor 4; 37, a carriage motor for moving the carriage frame 20 in the column direction; 38, a second motor drive circuit as its drive circuit;
Is a CPU that controls the entire thermal transfer printer, and 34 is a RO that stores the number of rotation steps from the reference position of the cam 3 to each cam position in addition to the control program of the CPU 30.
M and 35 are RAMs having a counter 36 for counting the number of steps of the step motor 4 and the like. Reference numeral 39 denotes an interface for inputting print data.

When print data is input to the CPU 30 from the interface 39, the print mode is determined. First, the first motor drive circuit is operated and the step motor 4 is rotated in the print A2 direction to select the head pressure contact / release mechanism. Then, the thermal head 1 is pressed against the platen with a predetermined pressing force. At this time, CP
U30 is determined by the first motor drive circuit so that the step number of the step motor stored in the ROM 34 and the value of the counter 36 that counts the number of drive steps from the reference position obtained by the light emitting and receiving circuit 32 become the same. The cam 3 is rotated by the rotation angle of. Thereafter, the cam 3 is maintained at the selected position by reversing the step motor 4 in the direction of the arrow A1. Next, by further reversing the stepping motor 4, this drive source engages with the ribbon winding mechanism and starts the ribbon winding operation. At the same time as the second
The motor 37 is driven by the motor drive circuit described above, and the printing operation is performed while the carriage frame is being moved in the beam direction.
When the printing operation is completed, the step motor 4 is again moved to the arrow A1.
The thermal head 1 is separated from the platen by selecting the cam position 3a having the smallest radius of rotation. Thereafter, the carriage motor 37 is driven to return the carriage to the print start position.

There is a slip mechanism inside the core 24 and the ink ribbon
The step motor 4 is rotated at a high speed so that the ink ribbon 25 can be wound faster than the speed at which the ink ribbon 25 is ejected from the thermal head 1 in the direction of arrow H. In the present embodiment, a stepping motor is used as a driving source motor for the head pressing / releasing mechanism and the ink ribbon winding mechanism. For this reason, by rotating the motor by the number of steps stored in the storage means in advance with reference to the output of the detector indicating the reference position of the rotating member, the pressure contact / release of the head or the setting of the pressure force of the head can be extremely accurately determined. Becomes possible. Thus, the release position of the thermal head can be accurately set, a sufficient interval between the thermal head and the platen can be ensured, and high-speed running of the ink ribbon can be guaranteed. The above-mentioned detector may be a mechanical switch in addition to the photo detector shown in the embodiment.

Further, not only the cam used in the present embodiment but also a link mechanism can be used as the movement direction converting mechanism for changing the rotational movement into the reciprocating movement.

[Effects of the Invention] As described in detail above, according to the present invention, since the planetary gear mechanism is used for the driving force transmission mechanism that switches and transmits the driving force to the ribbon traveling mechanism and the head pressing / releasing mechanism, the motor rotates. Other than when the ribbon running mechanism and head pressure contact /
Both release mechanisms are separated from the motor shaft, and even if one of the mechanisms is actuated by an external force, this is not transmitted to the other mechanism, thereby increasing the reliability of the entire mechanism.

Also, even if the core to be set is rotated when the ink ribbon is mounted, no motor load is received,
Easy installation, resulting in low risk of damaging the ink ribbon.

Further, since almost all parts of the planetary gear mechanism are only rotational loads, there is a secondary effect that durability is improved as compared with a spring clutch having a constant sliding load. .

 As described above, the present invention has many excellent effects.

[Brief description of the drawings]

FIGS. 1 (a), (b), 2 and 3 are schematic views showing an embodiment of a thermal transfer printer according to the present invention, and FIGS. 1 (a) and (b) are plan views of the inside of a carriage unit. FIG. 2 is a perspective view, and FIG. 3 is a partially enlarged sectional view. FIG. 4 is a diagram showing the configuration of the thermal transfer printer according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Thermal head 2 ... Elastic member (coil spring) 3 ... Rotating member (cam) 4 ... Motor (step motor) 15 ... Release means (coil spring) 24 ... Ribbon winding core

Claims (2)

(57) [Claims] 1. A thermal transfer printer for transferring ink on an ink ribbon disposed between a thermal head and a platen to a recording paper while pressing a thermal head having a heating element disposed thereon against a platen opposed to the thermal head. A planetary gear mechanism having a motor, a sun gear connected to the motor and having a planetary gear, a rotation direction conversion mechanism having a rotating member and converting a circular motion of the rotating member into a reciprocating motion, Position detecting means for detecting a reference position of the member, an elastic member which engages with the movement direction converting mechanism and urges the thermal head to press against the platen, and comprises the movement direction conversion mechanism and the elastic member. A head pressing / releasing mechanism configured to be able to select a pressing position of the thermal head to the platen or a releasing position, and running the ink ribbon. The planetary gear is disposed between two gears including a ribbon traveling mechanism, the planetary gear mechanism, and each of the head pressing / releasing mechanism and the ribbon traveling mechanism being disposed at a predetermined interval. A driving force transmission mechanism for selectively transmitting a driving force by switching a rotation direction of a motor, wherein the rotating member is rotatable only in one direction by the planetary gear mechanism, and a head pressing / releasing mechanism. And a ribbon traveling mechanism that can be simultaneously separated from the motor. 2. A serial type thermal transfer printer in which the thermal transfer printer moves a carriage supporting the thermal head along the platen, wherein at least the motor, a head pressing / releasing mechanism, the ribbon traveling mechanism, and a driving force transmission. 2. A thermal transfer printer according to claim 1, wherein a mechanism is mounted on said carriage.