JP2672424B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a serial type thermal printer used as a printout device of a word processor or a personal computer.

[0002]

2. Description of the Related Art As an example of a serial type thermal printer, a thermal printing mode in which printing is performed by pressing a recording head opposed to a platen against a platen with a sheet interposed therebetween, and a ribbon (ink ribbon) drawn out from a sheet and a ribbon cassette ) Can be selected from a thermal transfer printing mode in which printing is performed by pressing the recording head against a platen with the print head interposed therebetween.

In this type of serial type thermal printer, a head-up / down mechanism for causing a recording head to perform a head-up / down operation is provided. here,
Head-up refers to an operation of switching the recording head to a standby position separated from the platen during non-printing, and head-down refers to an operation of switching the recording head from the standby position to a position where the platen is pressed during printing.

A head-up / down motor is used as a drive source for the head-up / down mechanism, and the motor is drive-controlled by a controller. This control device is also equipped with a recording head, and also controls a motor that drives a carriage unit that is moved in a direction perpendicular to the sheet feeding direction during printing.

By the way, in the printer in which the thermal printing mode and the thermal transfer printing mode can be selected as described above, the head pressure point is set according to each mode. That is, two types of head pressure points are set, and the print head is moved down from the standby position to these head pressure points during printing in each mode.

[0006]

By the way, a head up / down mechanism of this type is a cam constituted by a cam groove formed in a cam gear rotated by a motor and a cam follower pin engaging with the cam groove. A head down position in which a recording head is brought into contact with the platen by rotating a cam follower having the cam follower pin and a head pressing member connected to the cam follower around a fulcrum by the cam mechanism. And a head-up position separated from the platen.

FIG. 11 shows a cam diagram of a conventional cam mechanism. As is clear from the figure, in this cam mechanism, the standby position in the thermal printing mode and the thermal transfer printing mode is the common initial point a, the head pressure point in the thermal transfer printing mode is c, and the head pressure point in the thermal printing mode is d. There is. Here, the initial point a is set at one end of the cam groove where the cam radius, that is, the distance from the cam follower pin to the center of rotation of the cam gear is maximized, and the head pressure point d is set at the other end of the cam groove. A head pressure point c is set at an intermediate portion between the two. The cam radius at the head pressure point c is larger than the cam radius at the head pressure point d.

However, in this cam mechanism, in order to rotate the cam gear and switch the cam follower pin and the recording head to the position of the initial point d, it is necessary to pass through the initial point c on the way. At this initial point c, because of the mechanism, the relative movement of the cam follower pin and the cam groove is significantly decelerated, so that a sudden load change occurs on the output shaft of the motor when passing through the initial point c. Therefore, the initial point d
If the switching operation to (1) is performed at a high speed, there is a drawback that a large noise is generated. Further, since a driving torque is required only for a large load variation, the motor becomes large in size, leading to cost reduction.

A cam mechanism as shown in FIG. 12 is conceivable as a solution to the drawbacks of the cam mechanism. In this cam mechanism, the initial point a is set in the middle of the cam groove, and the initial point c is set at one end of the cam groove.
And the initial point d is set at the other end. According to this cam mechanism, when the cam gear is rotated from the initial point a in the CW direction (hereinafter, the clockwise rotation is referred to as the CW direction and the counterclockwise rotation is referred to as the CCW direction), the switching to the initial point c is performed. Done,
When rotating in the CCW direction, switching to the initial point d is performed, so the above-mentioned drawbacks can be eliminated.

However, this cam mechanism has the following new drawbacks. That is, according to the cam mechanism of FIG. 11, the total rotation angle of the cam gear is β ₂ , whereas the cam mechanism of FIG. 12 requires β ₁ + β ₂ . Where β ₁ is the rotation angle of the cam gear required to switch from the initial point a to the initial point c, β ₂
Is a rotation angle required to switch from the initial point a to the initial point d.

In order to form a cam, the total rotation angle β ₁
+ Β ₂ needs to be β ₁ + β ₂ <360 °. Therefore, the cam inclination angles α ₁ and α ₂ shown in FIGS.
In order to satisfy the condition that β ₁ + β ₂ <360 °, the cam radius must be increased to some extent or more. Therefore, there is a limit in downsizing the cam gear 130 and downsizing the head up / down mechanism, and eventually the device configuration.

Under the present circumstances, it has not been possible to realize a preferable cam mechanism for the above reasons.

13 and 14 show a specific example of the head up / down mechanism as described above. Motor 14
The cam gear 1 is attached to the pinion 141 connected to the 0 output shaft.
30 is meshed with each other, and a spiral cam groove 131 is formed on the upper surface of the cam gear 130. Cam groove 131
The cam follower pin 123 of the cam follower 120 is engaged with the cam follower pin 123 so as to be rotatable around the vertical pin 111.
A cam mechanism is constituted by both.

The vertical pin 111 is a cam follower 12
It serves as a fulcrum of rotation of the head pressing member 110 that is linked to 0. In addition, a connecting pin 112 is provided upright on the head pressing member 110. The connecting pin 112 is inserted into a long hole-like connecting hole 121 formed in the cam follower 120, and one end of a spring 122 formed of a coil spring is inserted. To the connecting pin 112, and the spring 122
The other end of the cam follower 120 is locked and connected to one end,
Both are linked so that they can be linked.

With such a configuration, when the cam gear 130 is rotated, the cam follower 120 and the head pressing member 110 are rotated around the vertical pin 111 in the CW direction or the CCW direction, whereby the recording head 30 is pressed against the platen 40. The head pressure point and the initial point which is separated from the platen 40 can be switched.

In addition, a spring 114 for constantly urging the head pressing member 110 toward the platen 40 is arranged in the rotation region of the head pressing member 110.

The action of the spring force by the two springs 122 and 114 will be briefly described below. In the head-down state where the printing shown in FIG. 14 is executed, the spring forces F ₁ and F ₂ generated by the springs 114 and 122, respectively. The resultant force as a head pressing force presses the recording head 30 against the platen 40 via the head pressing member 110.

On the other hand, in the standby state shown in FIG. 13, since the head pressing force by the spring 122 is not generated, only the spring force F ₁ ′ of the spring 114 is applied to the head pressing member 1.
10 and is in a state where the load is received by the cam mechanism via the cam follower 120. Here, since the spring lengths are different between the spring forces F ₁ and F ₁ ′, the relationship of F ₁ <F ₁ ′ is clearly established.

By the way, when the recording head 30 is switched from the state shown in FIG. 13 to the state shown in FIG. 14 by such a head up / down mechanism, the cam gear 13
It is necessary to rotate 0 against the large spring force F ₁ ′ of the spring 114. For that purpose, a force sufficient to overcome the spring force F ₁ ′ is required as the rotational torque of the cam gear 130. In order to obtain a large rotation torque, the gear ratio between the pinion 141 and the cam gear 130 should be increased, or a large, high rotation torque motor should be used.
Need to rotate.

However, in order to increase the gear ratio, the cam gear 130 having a large diameter is required. Therefore, in any of the above methods, there is a drawback that the device structure becomes large and the cost increases.

Further, in the standby state shown in FIG.
Even if the cam gear 130 is rotated by a slight amount due to external vibration or impact, the equilibrium state may be broken, and the spring force F ₁ ′ of the spring 114 may rotate the cam gear 130 in the CW direction to cancel the standby state. For this reason, it is necessary to take some measures, and there is a drawback that the device configuration becomes complicated and the size becomes larger.

The present invention solves the above-mentioned drawbacks of the prior art, and the head can be moved up and down with a small motor without generating a large amount of noise, thereby reducing the size of the apparatus and greatly reducing the cost. It is an object of the present invention to provide an image forming apparatus that enables the above.

Another object of the present invention is to provide an image forming apparatus capable of high speed printing.

Another object of the present invention is to provide an image forming apparatus that is resistant to external vibration and shock and can improve the reliability of the head up / down mechanism.

[0025]

In the image forming apparatus of the present invention, the recording head is headed down from the first standby position to the first contact position where the recording sheet is sandwiched and brought into contact with the platen. A print mode and a second mode in which the recording head is brought into contact with the platen with the sheet sandwiched from the second standby position.
The second print mode in which the head is moved down to the contact position for printing and the printing is possible , and from the first standby position
The tilt amount of the recording head to the first contact position is calculated by
Tilting the recording head from the standby position to the second contact position
An image forming apparatus having a motion amount larger than a moving amount , a determining unit for determining which of the first print mode and the second print mode is selected, and the first standby mode .
Between the position and the second standby position, and the first contact position and
Each operation position is set with the second contact position interposed therebetween,
The above-mentioned object is achieved by having a cam for switching the recording head to each position, and a switching mechanism for switching the recording head to any position by the cam according to the judgment result of the judging means.

Further, the image forming apparatus of the present invention is provided with a head-up / down mechanism for switching between a head-down position where the recording head is in contact with the platen with the paper sandwiched therebetween and a head-up position where the recording head is separated from the platen. In the head up / down mechanism,
A screw for pressing the recording head pressing member rotatable around the first fulcrum toward the platen around the second fulcrum.
A first spring, which is a coil spring, and a rotating member that is connected to a transmission system that uses a motor as a drive source and shares the first fulcrum so as to interlock with the recording head pressing member. Two springs, the second fulcrum and the first fulcrum
The first spring is used to determine the positional relationship with the point.
A spring force in the direction of the first fulcrum is generated during the pushing operation,
No spring force is generated in the direction of the first fulcrum during drawdown
And the first spring is connected to the recording head.
Rotation that reduces the drive load of the motor during the drop-down operation
A moment is generated , which achieves the above objective.

[0027]

A switching mechanism having a cam for switching the recording head to the four positions as described above is provided with a cam groove, and the cam groove has first and second initials corresponding to the first and second standby positions. Have points, first initial point and second
The first head pressure point corresponding to the first contact position on the first initial point side and the second head position corresponding to the second contact position on the second initial point side. And a cam follower that has a cam follower pin that engages with the cam groove of the cam and that moves the recording head to and from the platen by the rotation of the cam.

According to this structure, when the cam is rotated in the CW direction and the CCW direction across the first initial point and the first head pressure point, the recording head moves to the first standby position and the first contact position. Can be switched over. Similarly, by rotating the cam over the second initial point and the second head pressure point, the recording head can be switched between the second standby position and the second contact position. here
The recording head from the first standby position to the first contact position
The tilting amount of is recorded from the second standby position to the second contact position.
It is larger than the tilting amount of the recording head.

According to such a switching mechanism, it is not necessary to pass through another head pressure point in the middle of the switching operation, so that a rapid load change due to the rotation of the cam does not occur and the recording head can be smoothly moved. You can switch.

The first and first initial points are
Since the cam groove can be formed in a spiral shape around the rotation center and the cam radius can be made different by this, it is not necessary to increase the cam radius to the left.

Further, in the head up / down mechanism provided with the two springs as described above, the second support is provided.
The arrangement relationship between the point and the first fulcrum is described in the first splice.
During the head-up operation, it moves toward the first fulcrum
When set to so that rise to the spring force, amount that the spring force acts, when switching the recording head from the head-up state in the head-down state, can reduce the driving load of the motor serving as a conducting system and a drive source.

[0032]

Embodiments of the present invention will be described below.

FIG. 1 shows the system configuration of a serial type thermal printer. A carriage unit 3, which is reciprocally movable in a printing direction indicated by an arrow B and a return direction opposite to the printing direction indicated by an arrow B, is arranged opposite to a sheet feed roller 2 which conveys the sheet 1 upward by rotation in the direction of the arrow A. The carriage unit 3 is equipped with a recording head 30 that prints print data on the paper 1, and moves the carriage unit 3 in the direction of arrow B so that one line of print data is printed on the paper 1. Has become. When printing of one line of data is completed, the carriage unit 3 is returned to the original position. Subsequently, when the paper feed roller 2 feeds the paper 1 by a predetermined amount, the carriage unit 3 moves again in the direction of arrow B, and The printing of the line is performed.

Explaining a little now, this serial type thermal printer can select a thermal printing mode in which the recording head 30 is directly pressed against the paper 1 for printing and a thermal transfer printing mode in which printing is performed via a ribbon. When the thermal transfer printing mode is selected, the recording head 30 moves from the ribbon cassette (not shown) to the ribbon 5 as shown in the example.
The ribbon 5 is pulled out of the platen 40 and the recording head 3.
The printing in the thermal transfer printing mode is performed by bringing the sheet into contact with the sheet 1 passing between the printing papers 0 and 0. At this time,
The portions of the ribbon 5 located on both sides in the horizontal direction of the recording head 30 are guide plates 3 erected from the carriage unit 3.
6, 36. The platen 40 is long in the moving direction of the carriage unit 3 and is held by the platen holder 4.

Switching between the thermal printing mode and the thermal transfer printing mode is controlled by the CPU 6. That is, when it is confirmed from the detection signal from the ribbon detection switch 62 that the ribbon cassette is set in the printer main body, the operation mode is switched to the thermal transfer printing mode, and if it is determined that the ribbon cassette is not set, the thermal printing mode is executed. It has become.

The CPU 6 also controls the movement of the carriage unit 3, the head up / down control of the recording head 30, the heating control of the recording head 30, and the paper feed roller 2.
Is performed. The drive control of the carriage unit 3 is performed by controlling the drive of the motor 32 via the carriage motor driver 63. To explain a bit now,
A pinion 33 that meshes with a pulley gear 34 is connected to an output shaft of the motor 32. When the motor 32 is driven in the normal or reverse direction, the pinion 33 is wound around the shaft of the pulley gear 34 and is connected to the carriage unit 3. The timing belt 35 of FIG. 3 moves around, whereby the carriage unit 3 reciprocates. The reciprocating movement of the carriage unit 3 is guided by a guide bar 37.

Head up / down control of the recording head 30 is performed by driving and controlling a motor 140 described later via an up / down motor driver 64. Here, head-up of the recording head 30 refers to a state in which the recording head 30 is separated from the surface of the platen 40 by a predetermined angle, and is selected during non-printing. On the other hand, head down refers to a state in which the recording head 30 is pressed against the surface of the platen 40 with a predetermined pressure across the sheet 1 (or the sheet 1 and the ribbon 5).
Selected when printing.

The heating control of the recording head 30 is performed by the head driver 65, and the drive control of the paper feed roller 2 is performed by the paper feed driver 66.

When the thermal print mode or the thermal transfer print mode is selected, the CPU 6 executes these print modes in accordance with the control program stored in the ROM 60, and at that time, stores the obtained control data in the RAM 61. The above-mentioned control is performed according to the data stored in the RAM 61.

Next, details of the carriage unit 3 will be described with reference to FIGS. As shown in FIG.
The recording head 30 is supported by a head holder 102 which is rotatably supported by a horizontal support pin 101. The head up position shown in FIG. 3 and the head down position shown in FIG. (Rotation) is possible.

In the switching operation of the recording head 30, that is, the head up / down operation, a head pressing member 110 having a fan shape in plan view, a cam follower 120 having a parallelogram shape in plan view, and a cam groove 131 are formed on the upper surface side. Cam gear 130, and a motor 1 for rotationally driving the cam gear 130
Head up / down mechanism 100 composed of 40 and the like
Done by Hereinafter, the configuration of each unit will be specifically described.

The head pressing member 110 and the cam follower 12
0 is linked so as to be interlockable. That is, the portion of the head holding member 110 corresponding to the main part of the fan and the cam follower 1
20 are connected to each other at a corresponding position by a vertical pin 111, and at one end of an arc-shaped outer edge of the head pressing member 110, a connecting pin 112 formed to protrude upward is connected to a connecting hole of the cam follower 120. 121, and one end of a spring 122 composed of a coil spring is locked and connected to the connection pin 112, and the other end is locked to one end surface of a cam follower 120 located on the other end side of the outer edge of the head holding member 110. We are connecting the two.
The connection hole 121 is a long hole as can be seen from FIG.

In addition, a twisting coil spring is provided in the rotation region of the head pressing member 110 which is rotatable around the vertical pin 111, and the head pressing member 110 is attached to the platen 4.
A spring 113 that is constantly biased toward the zero side is provided. Specifically, the spring 114 is attached to the vertical support pin 115 by fitting the coil portion to the vertical support pin 115.

A cam follower pin 123 is formed by caulking at a portion of the cam follower 120 opposite to the spring locking position. The cam follower pin 123 is engaged with a cam groove 131 formed in the cam gear 130. The cam groove 131 is formed in a spiral shape around the rotation center O of the cam gear 130, as shown in FIGS. The cam radius r of the cam groove 131 changes as shown in FIG.
The head up / down operation of the recording head 30 is performed by the change of the engagement position with the head, and the details thereof will be described later.

The cam gear 130 meshes with a pinion 141 connected to the output shaft of the motor 140. Therefore, when the motor 140 rotates in the CW direction and the CCW direction, the cam gear 130 rotates in the CCW direction and the CW direction.

In addition to the above construction, the serial type thermal printer has a switching mechanism 1 for selectively rotating or not rotating the ribbon take-up reel 159 of the ribbon cassette.
60 will be equipped. The rotation of the ribbon take-up reel 159 is performed to take up the used ribbon 5 in the thermal transfer printing mode. Hereinafter, the switching mechanism 160 will be described in detail.

As shown in FIG. 2, on the lower surface of the cam gear 130, there is formed a cam groove 132 with which the engaging projection 151 formed at one end of the clutch lever 150 engages. As shown in FIGS. 3 to 6, the clutch lever 150 has a shape in which radial projections are formed in three directions from a central portion, and is rotatable around a rotation center axis 154 at the central portion. The cam groove 132 is provided for performing a switching operation of the clutch lever 150.

That is, as shown in FIG. 2, the ribbon take-up gear 152 is connected on the rotation center shaft 154 of the clutch lever 150, and the ribbon take-up gear 152 is connected to the other convex portion of the clutch lever 150. Switching gear 1
53 always meshes. Therefore, the cam gear 1 is formed by the cam mechanism constituted by the cam groove 132 and the engaging projection 151.
The clutch lever 150 is rotated through the rotation center shaft 154
When the switch gear 153 is rotated in the CW direction or the CCW direction, the position where the switching gear 153 meshes with the belt pulley gear 155 for winding the ribbon (see FIG. 4) and the position of the belt pulley gear 1
55 (see FIG. 3).

Belt pulley gear 15 for winding the ribbon
Reference numeral 5 is mounted on the carriage unit 3, connects the belt pulley gear 155 and the toothed pulley 156, and is supported by a connecting shaft 157 rotatably supported by the carriage unit 3. The toothed pulley portion 156 has the both ends fixed to the left and right sides of the chassis of the printer body, that is, the timing belt 1 for winding the ribbon in a fixed state.
58. Accordingly, when the carriage unit 3 moves in the direction of arrow B for printing, the belt pulley gear 155 moves integrally with the belt pulley gear 155 in the direction of arrow B and rotates in the CCW direction as shown in FIG.

The switching gear 153 is the belt pulley gear 155.
When the toothed pulley portion 156 rotates in the CCW direction while meshing with the belt pulley gear 155, the belt pulley gear 155 also rotates in the CCW direction. Rotate in the direction. A ribbon take-up reel 159 of a ribbon cassette is coaxially supported by the ribbon take-up gear 152. Accordingly, the ribbon take-up reel 159 rotates integrally with the ribbon take-up gear 152, whereby the portion of the ribbon 5 that has been subjected to printing in the thermal transfer printing mode is taken up by the ribbon take-up reel 159 having a predetermined length.

Next, details of the head up / down operation of the recording head 30 will be described. As shown in FIG. 2, in the present invention, the recording head 30 has a head-up angle θ
₁ and θ ₂ . Here, θ ₁ indicates the head-up angle of the recording head 30 in the thermal transfer printing mode, and θ ₂ indicates the head-up angle of the recording head 30 in the thermal printing mode. The recording head 30
If There was a head-up only head-up angle θ _1,
A ground plate (not shown) contacts the back surface of the recording head 30 to remove static electricity generated in the thermal transfer printing mode.

The setting of the head-up angles θ ₁ and θ ₂ and the head-down operation are set by the positional relationship between the cam follower pin 123 of the cam follower 120 and the cam groove 131 of the cam gear 130 described above. That is, when a ribbon detection signal is input to the CPU 6 from the ribbon detection switch 62, the CPU 6 determines that the ribbon cassette is set in the printer and the thermal transfer printing mode is selected, and performs initial processing of the printer. When the initial process is performed and the cam gear 130 is rotated by a predetermined angle, the cam follower 120 is moved to the position shown in FIG.

FIG. 7A shows a cam diagram of this cam mechanism, and the initial point a is a diagram in which the recording head 30 is set in a head-up state (head-up angle = θ ₁ ) in the thermal transfer printing mode. This corresponds to the state shown in FIG. Specifically, it corresponds to one end of the cam groove 131.

As is clear from FIG. 7A and FIG.
At this initial point a, the cam follower pin 12
3 and the distance r ₁ between the rotation center O is the largest.

As shown in FIG. 7B, when the cam follower pin 123 is located at the initial point a, the switching gear 153 and the belt pulley gear 155 are in the disengaged state.

When the motor 140 is driven from the state shown in FIG. 3 to rotate the cam gear 130 in the CW direction by a predetermined angle,
Guided by the cam groove 131, the cam follower pin 123
Moves to the position shown in FIG. In the cam diagram shown in FIG. 7A, the head moves to the head pressure point c. At the head pressure point c, printing in the thermal transfer printing mode is performed.

In the position shown in FIG. 4, the cam follower pin 1
23 is close to the rotation center O, the cam follower 1
Numeral 20 rotates about the vertical pin 111 as a fulcrum in the CW direction as a whole. With this rotation operation, the head holding member 11
Spring 122 for interlocking cam follower 120 with 0
Is pulled, and the spring 122 causes the connecting pin 112, that is, the head pressing member 110
Is pulled toward the platen 40 with the vertical pin 111 as a fulcrum. As a result, the head pressing member 110 presses the recording head 30, and the recording head 30 is
Is pivoted toward the platen 40 with. As a result, the recording head 30 comes into contact with the platen 40. That is, the head down operation of the recording head 30 is performed.
At this time, the recording head 30 is pressed against the platen 40 with a predetermined pressing force by the urging force of the spring 113 pressing the head pressing member 110. Thus, printing in the thermal transfer printing mode is performed. When the operation opposite to the above is performed from the state shown in FIG. 4, the head-up operation of the recording head 30 is performed.

As shown in FIG. 7B, when the cam follower pin 123 is located at the head pressure point c, the switching gear 153 and the belt pulley gear 155 are switched to the meshed state.

On the other hand, when the ribbon cassette detection signal is not input from the ribbon detection switch 62, the CPU 6 determines that it is in the thermal printing mode and causes the printer to perform the initial processing in the thermal transfer printing mode. When this initial processing is performed, the motor 140
0 to the position shown in FIG.
Are located at the other end of the cam groove 131 shown in FIG. This position corresponds to the initial point b in the cam diagram shown in FIG. 7A, and the recording head 30 is in the head-up state.

As is apparent from FIG. 7A, at the initial point b, the cam follower pin 123 and the center of rotation O.
Is r ₂ , and between r ₂ and r ₁ , r ₂ <r ₁
Is established. Therefore, the tilting amount of the CW direction of the cam follower 120 in the initial point b is not smaller than the tilt amount in the initial point a. Therefore, the head-up angle θ ₂ of the recording head 30 in the thermal print mode is smaller than the head-up angle θ ₁ in the thermal transfer print mode. That is, the relationship of θ ₁ > θ ₂ is established.

When the motor 140 is driven from the state shown in FIG. 5 to rotate the cam gear 130 in the CCW direction by a predetermined angle, the cam follower pin 123 is guided by the cam groove 131.
Moves to the state shown in FIG. 6, that is, the head pressure point d in the cam diagram shown in FIG. 7A. At this time, the cam follower 120 tilts by a predetermined amount in the CW direction about the vertical pin 111 as a fulcrum in the same manner as described above, and accordingly, the head down operation of the recording head 30 is performed, and the thermal printing is performed at this head pressure point d. Printing in the mode is performed. As shown in FIG. 7B, at the head pressure point d
Engagement projection 151 of cam groove 132 and clutch lever 150
The switching mechanism 153 and the belt pulley gear 155 are in the disengaged state (see FIG. 3) by the cam mechanism constituted by .

As described above, the cam mechanism for causing the recording head 30 to perform the head-up / down operation is provided with two initial points, and two head-up angles θ ₁ and θ are different in the thermal printing mode and the thermal transfer printing mode.
_{When 2} (θ ₁ > θ ₂ ) is set, the time required for the head-up operation and head-down operation of the recording head 30 in the thermal print mode can be shorter than that in the thermal transfer print mode, so that the print time in the thermal print mode is reduced. This is convenient for achieving high-speed printing of the printer.

Further, as shown in FIG. 7A, when a cam mechanism having two initial points and two head pressure points is used as described above, one initial point a (or The recording head 30 is moved from b) to one head pressure point c (or d).
It is not necessary to pass through another head pressure point d (or c) during the switching operation unlike the conventional example shown in FIG. Therefore, a large load fluctuation does not occur on the output shaft of the motor 140 during the switching operation, and it is not necessary to use a large-sized motor 140 having a driving torque capable of coping with the load fluctuation. Further, even if the switching operation is performed at a high speed, no loud noise is generated.

For this reason, according to the present invention,
Since the switching operation of the recording head 30 can be performed at a high speed by the small motor 140, it is possible to realize a serial thermal printer capable of high-speed printing at a low price.

When the cam groove 131 is formed in a spiral shape as described above and one end of the cam groove 131 is set at the initial point a and the other end is set at the initial point b, the cam radius Since two different initial points can be secured, the total rotation angle β ₃ (see FIG. 7) is 360
Even if it is equal to or more than 0 °, a small cam gear 130 can be realized as shown in FIGS. Therefore, since it is not necessary to use the large cam gear 130 as in the conventional example of FIG. 12, the device configuration can be downsized also in this respect.

Further, when the head up / down mechanism 100 having the two springs 113 and 122 as described above is used, it is convenient for downsizing of the apparatus structure and cost reduction. . Figure 8 below
The reason will be described with reference to FIG.

Since the spring 113 is composed of the torsion coil spring as described above, it produces a rotational moment about the vertical support pin 115 in the mounted state.
Then, the recording head 30 is pressed through the head pressing member 110 by using the spring force F ₁ ′ due to this rotation moment as the head pressing pressure. The head pressing member 110 is configured to rotate about the vertical pin 111 as a fulcrum as described above.

Here, the positions of the vertical pins 111 and the vertical support pins 115 are set in such a positional relationship that the component of the spring force of the spring 113 in the vertical pin direction becomes 0 when the head is down as shown in FIG. Has been done. Therefore, in the head-down state, only the component F ₁ orthogonal to the vertical pin 111 is generated.

When the cam gear 130 rotates from this state and the head pressing member 110 rotates to the standby state (head-up state) shown in FIG. 8, the spring 113 has the component F ₁ ′ x in the vertical pin direction and the component F ₁ ′ x. A resultant force F ₁ ′ with the component F ₁ ′ y in the direction orthogonal to is generated. Clearly, F ₁ ′> F ₁ ′ is present between the resultant force F ₁ ′ and the component F ₁ ′ y that rotates the head pressing member 110 to the platen 40 side.
The relationship of y is established.

Therefore, according to the present invention, the recording head 30
13 and FIG. 14 in which the maximum load with respect to the rotation of the cam gear 130 becomes F ₁ ′ y and the maximum load becomes F ₁ ′ when rotating from the standby state shown in FIG. 8 to the head-down state shown in FIG. The load can be remarkably reduced as compared with the conventional example shown in FIG.

In other words, in the present invention, the positional relationship between the vertical pin 111 and the vertical support pin 115 is such that the spring 113 fitted to the vertical support pin in the standby state.
Is set such that there is a vertical pin direction component of the spring force, and thereby the load generated due to the rotation of the cam gear 130 when the recording head 30 is switched from the standby state to the head-down state is reduced. Take composition.

Therefore, according to the present invention, the cam gear 130
It is possible to switch the recording head 30 from the standby state to the head-down state without increasing the gear ratio of the pinion 141 and with the small motor 140. Therefore, the device configuration can be downsized and the cost can be reduced.

Further, since the load on the rotation of the cam gear 130 can be reduced, in the standby state, there is no possibility that the cam gear 130 unexpectedly rotates due to external vibration or impact and the standby state is eliminated. Therefore, since there is no need to dispose a member for that purpose, there is an advantage in this respect as well, which can greatly contribute to downsizing and simplification of the device configuration.

Next, the control procedure of the CPU 6 for printing with the serial thermal printer of the present invention will be described with reference to the flowchart shown in FIG. When the control program for printing stored in the ROM 60 starts, the CP
U6 first sets the recording head 30 to the standby state in step S1. Here, the standby state in step S1 means that the rotational position of the cam gear 130 is the initial point a.
Set to. This process is performed by driving and controlling the motor 140 via the up / down motor driver 64.

Next, in step S2, the printing operation is started in response to the print command, and then in step S3, the presence or absence of the ribbon cassette is determined by the detection signal from the ribbon detection switch 62. When it is confirmed in step S3 that the ribbon cassette is set, it is determined that the thermal transfer printing mode is set, and in step S4, an initial operation for setting the rotational position of the cam gear 130 to the initial point a is performed. As a result, the recording head 30 is set to the standby position in the thermal transfer printing mode.

Then, in step S4, a head down command signal is issued to the up / down motor driver 64, and the motor 140 is driven and controlled via the head driver 65. As a result, the cam gear 130 rotates from the initial point a to the head pressure point c, and the cam follower 1
The recording head 30 is pressed against the platen 40 by sandwiching the paper 1 and the ribbon 5 via the head pressing member 110.

Next, in step S6, a print execution command signal is issued to the carriage motor driver 63, and the carriage motor 32 is sent via the carriage motor driver 63.
Is controlled to move the carriage unit 3 in the direction of arrow B. As a result, printing for one line is performed. At this time, at the same time, the recording head 3
0 heating control is performed.

Next, in step S7, a head- up command signal is issued to the up / down motor driver 64, the motor 140 is driven and controlled, the cam gear 130 is rotated to the initial point a, and the recording head 30 is set to the standby position in the thermal transfer printing mode. Head up. Then, step S
In 8 it is judged whether all the printing is completed, and if it is confirmed that the printing is not completed, in order to print the next line,
The carriage unit 3 is drive-controlled via the carriage motor driver 63 so as to position the recording head 30 at the head position for printing the next line (S9).

When the process of step S9 is completed, the process returns to step S5, and then the processes of steps S5 to S7 are performed again to print the next line. Then, the determination process of step S8 is performed again, and when it is confirmed that all printing is completed, the process returns to the standby state of step S1.

On the other hand, if it is determined in step S3 that the print mode is the thermal print mode, the process proceeds to step S10, in which an initial process for rotating the cam gear 130 to the initial point b is performed. As a result, the recording head 30 is set to the standby position in the thermal printing mode. Then, in step S11, the cam gear 130 is rotated to the head pressure point d in the same manner as described above, whereby the recording head 3 is rotated.
0 is headed down, and printing is executed in step S12. Next, in step S13, the recording head 30 is moved up, and in step S14, it is determined whether or not all printing is completed.

When it is confirmed that all the printing has not been completed, in order to print the next line (S15), the process returns to step S11 in the same manner as described above, the processes of steps S11 to S13 are repeated, and the process is completed. When it is confirmed (S14), the process returns to the standby state of step S1.

In the above embodiment, the case where the present invention is applied to the embodiment in which the head pressure points in both the print modes are different in the serial type thermal printer in which the thermal transfer print mode and the thermal print mode can be selected has been described. , In the thermal transfer printing mode,
The same can be applied to other embodiments in which printing is performed with different head pressure points for plain paper and recommended paper.

[0083]

According to the image forming apparatus of the first aspect,
Since it is possible to smoothly switch the recording head to a desired position without causing a sudden load change due to the rotation of the cam, it is not necessary to use a large motor having a large driving torque as a driving source of the cam. Further, no noise is generated even if the switching operation is performed at high speed. Further, since it can be realized without increasing the cam radius of the cam, the device configuration does not increase in size. For the above reasons, an image forming apparatus capable of high-speed printing can be realized with a small-sized and inexpensive apparatus configuration.

Further, according to the image forming apparatus of the second aspect, when the recording head is switched from the head-up state to the head-down state, the drive load of the conduction system and the motor serving as the drive source can be reduced. -There is an advantage that the down mechanism can be realized with a small and inexpensive device configuration.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a system configuration of a serial type thermal printer of the present invention.

FIG. 2 is a side view illustrating a configuration of a carriage unit.

FIG. 3 is a plan view of a carriage unit showing a head-up state of a recording head in a thermal transfer printing mode via a ribbon.

FIG. 4 is a plan view of the carriage unit showing a head down state of the recording head in a thermal transfer printing mode via a ribbon.

FIG. 5 is a plan view of the carriage unit showing a head-up state of the recording head in a thermal print mode.

FIG. 6 is a plan view of the carriage unit showing a head down state of the recording head in a thermal print mode.

FIG. 7 is a drawing comparing a cam diagram of a cam mechanism for head up / down and a cam diagram of a cam mechanism for switching a clutch lever.

FIG. 8 is a plan view of the carriage unit showing a spring force generated in a spring that constantly presses the recording head in a head-up state.

FIG. 9 is a plan view of the carriage unit showing a spring force generated in a spring that constantly presses the recording head in a head-down state.

FIG. 10 is a flowchart showing a control procedure of the CPU.

FIG. 11 is a cam diagram showing a conventional example of a cam mechanism.

FIG. 12 is a cam diagram showing another conventional example of the cam mechanism.

FIG. 13 is a plan view showing a conventional head-up / down mechanism in a head-up state.

FIG. 14 is a plan view showing a conventional head-up / down mechanism in a head-down state.

[Explanation of symbols]

 Reference Signs List 1 paper 2 paper feed roller 3 carriage unit 5 ribbon 6 CPU 30 recording head 32 motor 35 timing belt 40 platen 62 ribbon detection switch 100 head up / down mechanism 110 head pressing member 111 vertical pin 113 spring 115 vertical support pin 120 cam follower 122 spring 123 Cam follower pin 130 Cam gear 131 Cam groove 132 Cam groove 140 Motor 150 Clutch lever 151 Engagement projection 152 Ribbon winding gear 153 Switching gear 155 Belt pulley gear 156 Toothed pulley 158 Timing belt 160 Switching mechanism

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-62-95253 (JP, A) JP-A-64-20161 (JP, A) JP-A-62-74667 (JP, A)

Claims (2)

(57) [Claims] 1. A first printing mode in which the recording head is moved down from a first standby position to a first contact position where a recording medium is brought into contact with a platen and printing is performed, and the recording head is placed in a second standby position. A second contact position where the sheet is sandwiched and the platen is brought into contact with the platen;
Print mode can be selected , and the first standby
Amount of tilt of the recording head from the position to the first contact position
The recording from the second standby position to the second contact position.
An image forming apparatus larger than the tilting amount of the head, and determining means for determining one printing mode of the print mode and the print mode of the second first is selected, waiting for the first The first position between the position and the second standby position.
Each operating position is sandwiched between the contact position and the second contact position.
An image forming apparatus having a cam that is set and switches the recording head to each position, and a switching mechanism that switches the recording head to any position by the cam according to the determination result of the determination means. 2. A head-up position for switching a recording head between a head-down position where the recording head is in contact with a platen with a sheet sandwiched between the recording head and a head-up position where the recording head is separated from the platen.
In an image forming apparatus having a down mechanism, the head up / down mechanism includes a recording head pressing member that is rotatable about a first fulcrum and is moved to a second side of the platen side .
A first spring composed of a torsion coil spring that presses around a fulcrum of the motor and a first fulcrum connected to a conduction system having a motor as a drive source .
And a second spring that connects a rotating member that shares the same with the recording head pressing member so as to be interlocked with each other, and the positional relationship between the second fulcrum and the first fulcrum is the first
The spring is the first fulcrum when the head is moving up.
A spring force in the direction is generated, and at the time of head down, the first fulcrum
Direction is set so as not to generate a spring force, and the first spring causes a head-down operation of the recording head.
Occasionally generates a rotational moment that reduces the drive load of the motor.
An image forming apparatus that is adapted to be twisted .