JP2844009B2 - Automatic printer head gap adjustment device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic head gap adjusting device for automatically adjusting a gap between a print head and a recording paper surface in an impact type printer.

[Conventional technology]

In various printers, it is necessary to adjust a gap between a print head and a recording sheet (hereinafter, referred to as a head gap) in order to keep a print density in a predetermined state. In particular, a wire-dot type impact print head is required. The adjustment of the head gap is important for a printer using the printer. In other words, if the head gap is too large, the printing pressure will be weak and the printing will be thin, and if it is too small the printing pressure will be strong and the recording paper will be soiled by the ink ribbon or the ink ribbon will be pulled by the print wire. This is because not only does a trouble such as a jamming of a jammed paper occur, but also the wire itself is significantly worn and lacks durability.

In recent years, various mechanisms and devices for automatically adjusting the head gap have been developed.
An automatic head clearance adjusting device for a printer according to Japanese Patent No. 62-187063 has been disclosed. This automatic head gap adjusting device utilizes an eccentric shaft, and rotates the eccentric shaft by driving a step motor, thereby lowering the print head, pressing the print head against recording paper, detecting a zero position, and then detecting the zero position. By rotating the stepping motor in the opposite direction by a specified number of steps, the printing head is retracted from the zero position by a predetermined amount.

[Problems to be solved by the invention]

In such a conventional head gap automatic adjusting device, the number of steps of the step motor and the eccentric angle of the eccentric shaft (or the rotation angle of the guide shaft attached to the eccentric shaft) for vertically moving the print head are mechanically determined. Although there is a proportional relationship, since the eccentric angle and the head gap are substantially sine curves, the head gap corresponding to the thickness of the recording paper cannot be obtained only by controlling the specified number of steps when the print head is raised. That is,
As shown in FIG. 7 (a), when the eccentric curve I is a substantially sine curve that is upward from 45 ° (direct proportion), by driving the stepping motor with the specified number of motor steps P in the linear region, a predetermined value is obtained. Can be set, but in the non-linear region, the head gap g ₁ (G <g ₁ ) is too large even when driven at the same prescribed motor step number P. Also, as shown in FIG. 7 (b),
In the case where the eccentric curve II is a substantially sine curve whose angle is lower than 45 °, a predetermined head gap G can be set by driving the step motor with the specified motor step number P in the linear region. In this case, even if the motor is driven with the same specified number of motor steps P, the head gap g ₂ (G>
g ₂ ) is too small. Therefore, the head gap cannot be set to an appropriate value in accordance with the thickness of the recording paper.
In particular, in the case of thick copy paper, the eccentric angle becomes large, so that there is a problem that it is remarkable.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to make sure that the head gap is adjusted to an appropriate value when adjusting the head gap using an eccentric shaft. It is an object of the present invention to provide an automatic head clearance adjusting device for a printer, which can be set to the following.

[Means for solving the problem]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a printer head automatic adjustment that automatically adjusts the gap between the print head and the paper surface by an eccentric shaft while holding the print head so as to be able to advance and retreat relative to the paper surface. In the apparatus, a motor for moving the print head forward and backward, a rotation transmission mechanism for transmitting a rotational force of the motor to the eccentric shaft, and a rotation transmission mechanism provided in the rotation transmission mechanism until the print head comes into contact with a sheet surface from a set position thereof. Detector means for optically detecting the position of
A control unit for storing the number of steps corresponding to the detection signal of the detection means in advance, and driving the motor with the number of steps to retreat the print head.

[Action]

According to the present invention, when adjusting the head gap between the print head and the sheet surface, the head gap can be reliably set to an appropriate value regardless of the sheet thickness of the sheet.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a block diagram of a circuit configuration of a head gap automatic adjusting device of a printer according to the present invention, FIG. 2 is a perspective view of a printing head portion of a horizontal impact type printer, and FIG. 3 is an eccentric shaft type automatic head gap adjusting. FIGS. 4 (a) and 4 (b) are a sectional view and a partial plan view of the adjustment mechanism.

In FIG. 2, reference numeral 1 denotes a printing mechanism, which is a carriage 4 slidably held by a pair of guide shafts 2, 3 arranged vertically in parallel and a motor (not shown). The carriage 4 is driven by the guide shaft 2,
3, a timing belt 5 reciprocating along the carriage 3, a conventionally known wired print head 6 and a card holder 7 mounted on the carriage 4, an ink ribbon 8 and a platen 9 sent in the moving direction of the carriage 4. ing.

The print head 6 is supported so as to be able to advance and retreat in the vertical direction with respect to the recording paper 10 together with the carriage 4, and the gap with the paper surface, that is, the head gap (G) is independent of the paper thickness by a head gap automatic adjustment mechanism described later. It is automatically set to a constant value, and prints while moving in the left and right directions together with the carriage 4 along with the movement of the timing belt 5 at the start of printing, and the motor rotates in response to the end of printing for one line. Then, the printing operation is repeated while the print head 6 moves in the opposite direction, and the above operation is repeated. As the printing progresses, the recording paper 10 is gradually transferred in the direction of arrow a in FIG. It has become so.

FIGS. 3 and 4 show an automatic head gap adjusting mechanism 20 of the print head 6, and an eccentric shaft rotatably disposed on one side plate (left side frame) 21a and having one end of the guide shaft 2 connected thereto. 22, a stepping motor 24 disposed on a side plate 23 different from the above, a rotation transmitting mechanism 25 for transmitting the rotation of the stepping motor 24 to the eccentric shaft 22, and a print head 6
Is generally constituted by a spring 26 or the like that applies a rotational force in a direction in which the eccentric shaft descends to the eccentric shaft 22. The fitting hole of the eccentric shaft 22 into which the shaft end of the guide shaft 2 is fitted is eccentric with respect to the center of the outer shape of the eccentric shaft 22, and this outer shape is rotatable by a bearing hole provided in the side plate 21a. It is pivoted on. Therefore,
When the eccentric shaft 22 rotates, the guide shaft 2 moves up and down according to the amount of eccentricity of the fitting hole, whereby the head gap changes.

The rotation transmission mechanism 25 is connected to the output shaft 30 of the step motor 24.
And a first intermediate gear 32 meshed with the drive gear 31. The first intermediate gear 32 is
A sleeve 34 is integrally provided, is rotatably disposed on a shaft 33 protruding from the side plate 23, and has a slip gear on the sleeve 34.
A one-way clutch 36 integrally having 35 is provided. The slip gear 35 meshes with a second intermediate gear 38 rotatably disposed on a support shaft 37 projecting from the side plate 23. A third intermediate gear 39, which is also rotatable, is provided at the tip of the support shaft 37, and the third intermediate gear 39 is meshed with a driven gear 40 provided integrally with the eccentric shaft 22. A stop pin 41 is attached to the driven gear 40, and when the print head 6 is raised to the maximum height position, that is, the head lifting position, the retract micro switch 42 is urged by the pin 41. To stop the operation.

The one-way clutch 36 is free with respect to the first intermediate gear 32 during the operation of detecting the zero position of the print head 6 (the operation of pressing the lower surface of the head against recording paper), and keeps the print head 6 constant after the zero position is detected. At the time of the head gap setting operation (return operation) in which the first intermediate gear 32 is retracted upward by an amount, the rotation of the first intermediate gear 32 is rotated by the slip gear 35.
It is configured to transmit to.

The spring 26 is formed of a torsion coil spring fitted on the outer periphery of the other end of the guide shaft 2, one end is fixedly screwed to the other side plate (right side frame) 21 b, and the other end is screwed to the guide shaft 2. Stopped and fixed.

In this case, the spring 26 is attached to the guide shaft 2 in a twisted state, so that the spring 26 normally applies a rotational force to the eccentric shaft 22 in a direction in which the print head 6 descends. When the shaft 22 is rotated, it is released and the spring force is weakened.

The stepping motor 24 normally locks the rotation transmitting mechanism 25 by supplying a holding current sufficient to generate a driving force balanced with the spring force of the spring 26. This is to prevent the spring 26 from rotating the eccentric shaft 22 when the step motor 24 is stopped and the output shaft 30 is kept free. However, the holding current is not supplied to the step motor 24, and the claw operated by the solenoid or the like is driven by the driven gear.
The eccentric shaft 22 can also be locked by engaging the eccentric shaft 22. The stepping motor 24 is driven during the head gap setting operation and when the print head 6 is pushed up to the highest position.

The operation of the automatic head gap adjusting mechanism 20 will be described. First, the step motor 24 is driven by a signal from the control unit to raise the print head 6 to the maximum height position. At this time, the rotation of the stepping motor 24 is controlled by the driven gear 31, the first intermediate gear 32, the one-way clutch 36, the slip gear 35, the second intermediate gear 38, and the third intermediate gear 39.
The eccentric shaft 22 is rotated in the direction in which the print head 6 is retracted from the recording paper 10. Therefore, the spring 26 is squeezed to accumulate the spring force. When the print head 6 retreats to a predetermined height, the pin 41 provided on the driven gear 40 comes into contact with the retraction microswitch 42 and stops by urging it. When a predetermined time has elapsed after the print head 6 reaches the highest position, a holding current is supplied to the step heater 24 to lock the rotation transmitting mechanism 25.

Next, the recording paper 10 is fed to the lower part of the print head 6, and the zero position of the print head 6 is detected. At this time, the supply of the holding current is stopped, and the step motor 24 is stopped. Then
Since the rotation transmitting mechanism 25 is free with respect to the step motor 24, the eccentric shaft 22 is rotated by the spring force of the spring 26. As a result, since the guide shaft 2 rotates integrally with the eccentric shaft 22 and gradually descends, the print head 6 is pressed against the recording paper 10 via the card holder 7 and the ink ribbon 8.

Next, when the pressing operation is completed, a pulse of the number of steps corresponding to a predetermined head gap (G) is applied to the step motor 24 to drive the motor 24. Then, since the rotation of the output shaft 30 is transmitted to the driven gear 40 by the rotation transmission mechanism 25, the eccentric shaft 22 rotates together with the driven gear 40 to tighten the spring 26 and at the same time the guide shaft 2 is rotated by the rotation angle. , And a predetermined head clearance (G) is set. Then, after the step motor 24 is held in the driving state by the holding current and the rotation transmitting mechanism 25 is locked, the above-described printing operation by the printing head 6 is performed.

FIG. 1 is a block diagram of a circuit configuration for controlling a head gap according to the present embodiment. The main control unit 51 includes a microprocessor (hereinafter, CPU), a memory, and the like. A sub-control unit 52 and a head gap setting device 53 using a dip switch or the like are provided, and the main control unit 51 is provided with an output of the setting device 53 and has a higher rank than a computer or the like omitted from the drawing. Equipment (hereafter,
UCE).

The sub-control unit 52 is supplied with a command from the main control unit 51 and a detection signal from a rotation detection unit 55, which will be described later. , Motor) 24. The main control unit 51 and the sub-control unit 52 execute predetermined instructions while each CPU executes an instruction in the memory and accesses necessary data to the memory. The control operation is performed.

Here, the rotation detecting unit 55 is the same as that shown in FIGS.
A slit plate 56 mounted on the outer periphery of a one-way clutch 36 constituting the rotation transmission mechanism 25 shown in the figure, and a slit plate 56 disposed near the slit plate 56 and formed on the peripheral surface thereof at equal intervals (12 °). A plurality of (in this example, 36) photointerrupters 58 for generating pulses corresponding to the slits 57 are provided. When adjusting the head gap, the print head (PHD) 6 is moved to a predetermined position (headlet position). ) Is detected as a pulse number, and the distance 1 from the position where the sheet descends from the position and presses against the surface of the sheet 10, that is, the zero position, is detected as the number of pulses. And this sub-controller 52
Is to count the number of detection pulses input from the rotation detection unit 55, and to drive the motor 24 by the number of steps corresponding to the counted number at the time of detecting the zero position, thereby retreating the print head 6 by a certain distance d. Thus, a predetermined gap G is set between the paper surface 10 and the leading end 6a of the print head 6.

At this time, after detecting the zero position, the number n of steps for driving the motor 24 to retract the print head 6 is, for example, as shown in Table 1, the number of steps corresponding to the pulse count C before the zero position is detected in advance. A (integer) as data
It is stored in the CPU and controlled based on the count number. However, in Table 1, the pulse count C is an integer of 0 to 36, and C ≦ 12 or C
≦ 36, A = 200.

FIG. 5 shows an automatic head clearance adjustment (AG
This is for describing the operation of A), and is mainly performed by the sub-control unit 5.
2 is a flowchart of a main part of a control situation by the CPU.

In FIG. 5, first, "pulse period 200pps set"
The frequency division ratio of the frequency divider which divides the clock pulse and sends it to the drive circuit 54 is determined by 101, and the motor 24 is set to the normal rotation state with respect to the drive circuit 54 by the "motor rotation direction / forward setting" 102. A command is given, and the number of forward steps is set to "n = 360" 103 in a motor driving counter configured in the CPU. At the same time, the pulse counting counter in the CPU is reset by a "pulse count reset" 121, and then a drive pulse is sent from the drive circuit 54 by a "motor 1 step drive" 104, and "n = n-1" 10
The counter is decremented by 5 to check "n = 0?" 106. While this is N (NO), steps 104 and thereafter are repeated. At this time, the pulse counting counter performs an operation of sequentially counting pulses from the rotation detecting section 55 in accordance with the lowering of the print head 6 accompanying the step driving of the motor 24 (step 122).

When the step 106 becomes Y (YES), it is the end of the advance of the print head 6 (detection of the zero position), the "pulse cycle 230 pps set" 107 is performed similarly to the step 101, and the "motor rotation direction / reverse set" 108 is executed. This time, a command for the reverse rotation state is sent to the drive circuit 54, and according to the number of steps of the motor 24 corresponding to the pulse count C until the detection of the zero position, for example, "n = 36 + A" 109, the motor drive of the step 103 is performed. After setting the counter for the motor, the "motor 1 step drive" 110 and "n = n-1" 1 as in steps 104-106.
11. Execute "n = 0?" 112 and repeat step 110 and subsequent steps while step 112 is N. When step 112 becomes Y, retreat of print head 6 is completed, and a series of automatic head gap adjustments is performed. Complete (AGA).

As described above, according to the present embodiment, when adjusting the head gap, a pulse corresponding to the advance distance l from when the print head 6 is pressed to the surface of the sheet 10 from its reference position is counted.
Print head 6 with the number of steps corresponding to the count number C
The head gap can be set to an appropriate value for any paper thickness by driving the head. For example, the sixth
When one sheet of paper 10 is used as shown in FIG.
Assuming that the pulse count number C of the forward distance 1 is 31 ≦ C ≦ 35, the distance d is driven by 48 steps using pulses of a period of 230 pps during retreat (see Table 1). When the number of sheets 10 is eight as shown in FIG. 6B, if the count number C at the time of forward movement is set to C = 17, the distance d is driven by 40 steps at the time of backward movement.
An optimum head gap G corresponding to the paper thickness can be obtained.

Therefore, in the conventional apparatus, when the number of steps of the motor and the head gap are in a relatively proportional relationship, that is, only when the paper thickness is small, only the thin paper is effective. Although it is necessary, the head gap automatic adjusting device of the present invention has an advantage that it can cope with any paper thickness.

〔The invention's effect〕

As described above, the present invention relates to an automatic head gap adjusting device for a printer which holds a print head so as to be able to advance and retreat with respect to a sheet surface, and automatically adjusts a gap between the print head and the sheet surface by an eccentric shaft. A motor for moving the print head forward and backward, a rotation transmitting mechanism for transmitting the rotational force of the motor to the eccentric shaft, and a position provided in the rotation transmitting mechanism until the print head comes into contact with the paper surface from its set position. A detection unit for optically detecting the number of steps corresponding to the detection signal of the detection unit, and a control unit that drives the motor with the number of steps and retracts the print head. An appropriate head gap can be automatically set. Therefore, it is possible to perform good printing, prevent printing fading, dirt on the recording paper due to the ink ribbon, paper jam, etc., and enable the use of various papers with different paper thicknesses, and the durability of the print wire. And a great effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a circuit configuration of a head gap automatic adjusting device of a printer according to the present invention, FIG. 2 is a perspective view of a print head portion of a horizontal impact type printer, and FIG. 4 (a) and 4 (b) are a sectional view and a partial plan view of the eccentric shaft type head gap automatic adjusting mechanism in the example, and FIG. 5 is a head in the embodiment of FIG. Flow chart of gap adjustment control status,
FIGS. 6 (a) and 6 (b) are side views showing the state of adjustment of the head gap of the embodiment, and FIGS. 7 (a) and 7 (b) are eccentric angles of eccentric shafts for explaining the disadvantages of the conventional example. FIG. 4 is a diagram showing a relationship between the number of motor steps and a head gap. 2, 3 ... Guide shaft, 4 ... Carriage, 6 ... Print head, 8 ... Ink ribbon, 10 ... Recording paper, 20 ...
... Head gap automatic adjustment mechanism, 22 ... Eccentric shaft, 24 ... Step motor, 51 ... Control unit, 52 ... Sub-control unit, 53 ... Setting unit, 54 ... Drive circuit, 55 ... Rotation detection unit .

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-143884 (JP, A) JP-A-3-161381 (JP, A) JP-A-64-87379 (JP, A) JP-A-63-1987 114682 (JP, A) JP-A-63-233871 (JP, A) JP-A-2-39976 (JP, A) JP-A-1-195083 (JP, A) Japanese Utility Model Laid-Open No. 60-141255 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B41J 25/308 B41J 7/92

Claims (1)

(57) [Claims] 1. An automatic head gap adjusting device for a printer which holds a print head so as to advance and retreat with respect to a sheet surface and automatically adjusts a gap between the print head and the sheet surface by an eccentric shaft. A rotation transmitting mechanism that transmits the rotational force of the motor to the eccentric shaft; and a position provided in the rotation transmitting mechanism until the print head comes into contact with the sheet surface from the set position. A detection unit for detecting, and a control unit for storing the number of steps corresponding to the detection signal of the detection unit in advance and driving the motor with the number of steps to retract the print head. Head gap automatic adjustment device.