JPH0577514A - Setting device for home position of printer - Google Patents

Abstract

PURPOSE:To accurately and inexpensively detect the carriage home position of a serial printer. CONSTITUTION:A carriage 6 loaded with a recording head 10 traverses recording medium 9 to reciprocally move. The scale plate 7 constituting a linear encoder is provided along the moving direction of the carriage 6 and a position detection signal is outputted when the encoder module 4 provided to the carriage 6 passes through the non-detection part of the scale plate 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a home position setting device for a printer, and more particularly to a home position setting device for a serial printer having a carriage that reciprocates facing a recording medium.

[0002]

2. Description of the Related Art Generally, a serial printer reciprocates a carriage having a recording head in the platen axis direction by a carriage driving motor through a timing belt or the like for recording. Here, the carriage manages the distance from the reference position (so-called home position) set during the initialization operation of the printer by position detecting means such as an encoder and the number of driving steps (in the case of a stepping motor), and moves to a predetermined position for printing. I do.

In a conventional printer, home position setting is generally performed by providing a home position sensor such as a photo sensor or a micro switch and detecting that the carriage has moved to the home position. FIG. 8 shows a block diagram of a conventional example. Further, FIG. 9 shows a structural diagram of a conventional example. Here, 12 is a home position sensor, and 13 is a shielding plate provided on the carriage. The home position sensor is composed of a photo interrupter as shown in FIG. 6, for example. Reference numeral 3 is a DC motor for driving the carriage, and 11 is a rotary encoder directly connected to the rotary shaft of the carriage motor. The output pulse of the rotary encoder 11 is connected to the position counter 5, and addition and subtraction of the position counter 5 are performed according to the forward rotation and the reverse rotation of the DC motor, and the position management of the carriage 6 is performed. CPU1 during printer initialization
Drives the carriage motor 3 to move the carriage 6 toward the home position. At the same time, monitoring of the output of the home position sensor 12 is started. When the shield plate 13 on the carriage moves to a position where it blocks the home position sensor 12, the output of the home position 12 is changed by the CPU.
1, the carriage motor 3 is stopped and the position counter 5 is initialized. The home position has been set as described above, and the position management of the carriage for this transition is performed by the position counter 5.
When a stepping motor is used as a carriage driving motor, a position counter and a rotary encoder are generally unnecessary, and the excitation phase at the time of detecting a change in the output of the home position 12 is used as a reference position for position management by the number of phase switching times (steps). Is done.

As another method, there is a method of setting the position by colliding the carriage with a frame, a stopper or the like as disclosed in Japanese Patent Laid-Open No. 64-4377 and Japanese Patent Publication No. 26594/1990. The former functions as a home position sensor by colliding the carriage and establishing electrical connection between the carriage and the frame, thereby eliminating the sensor. In the latter case, a stepping motor is used as a carriage driving motor, and the home position is set by driving the motor for a specific time to collide with the frame and then exciting the motor in a specific phase.

[0005]

However, in the case of setting using various sensors, there is a drawback that the structure becomes complicated and the cost becomes high, and an error occurs in the detection position due to the structure and mounting accuracy of the printer. In other words, when the output edge of the home position sensor and the edge phase of the output pulse of the rotary encoder (or the timing of phase switching of the stepping motor) are very close to each other as shown in FIG. Due to the mechanical backlash, the home position is displaced each time the carriage is initialized.

In the apparatus for setting the position by colliding the carriage, when a stepping motor is used,
Since the post-phase holding is performed after colliding with the frame or the like and causing the step out, an error is likely to occur in the detection position. When a DC motor is used, the impact of collision causes vibration of the motor shaft, irregular output of encoder pulses, and malfunction of the position counter. In addition, there are drawbacks such as sound generation at the time of collision, deterioration of durability and reliability.

An object of the present invention is to provide a home position setting device which solves the above-mentioned conventional drawbacks, does not require a home position sensor, and is inexpensive and has improved detection position accuracy.

[0008]

SUMMARY OF THE INVENTION A home position setting device for a printer according to the present invention includes a carriage that mounts a recording head facing a recording medium and reciprocates, a DC motor that drives the carriage, and a carriage position. In a printer provided with position detecting means for detecting and a position counter for storing a position by an output pulse of the position detecting means, the position detecting means includes an encoder module mounted on a carriage and a home position side extending in a moving direction of the carriage. The predetermined distance at one end is composed of a scale plate that does not have a position detection part.When the printer is initialized, the DC motor for driving the carriage is driven to move the carriage to the home position side, and the output pulse of the encoder module exceeds the predetermined time. When it stops changing, drive the DC motor. It is stopped, and the position counter and wherein the initializing.

[0009]

When the carriage is moved toward the home position while observing the output pulse of the encoder module during the initialization operation of the printer, the carriage has a predetermined distance at one end of the scale plate where the position detection portion does not exist. When it reaches, the output pulse of the encoder module is interrupted. Therefore, the home position can be set by stopping the carriage driving motor and initializing the position counter at the time when this is detected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments shown in the drawings will be described below.

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an embodiment of the present invention.
In FIG. 1, 1 is a CPU, 2 is a carriage motor drive circuit, and 3 is a carriage motor. Reference numeral 4 is an encoder module, and 5 is a position counter. In FIG. 2, 6 is a carriage, and 3 is a carriage motor. Reference numeral 7 is a scale plate forming a linear encoder, and 4 is an encoder module. Reference numeral 8 is a platen, and 9 is a recording medium. Reference numeral 10 is a recording head, and a drive signal for the recording head 10 is an FPC (not shown).
Given through. The output pulse of the encoder module 4 is also transmitted to the control circuit and the CPU via the FPC. Here, the carriage motor 3 is a DC motor, and the encoder module 4 is a photo interrupter that electrically outputs A phase and B phase having a 90 ° phase difference.
Encoder module 4 controls the speed of the carriage motor
This is performed by the carriage motor drive circuit by the linear encoder configured by the scale plate 7. FIG. 3 shows a structural diagram of the scale plate. The scale plate 7 is processed so that the light transmitting portions and the light shielding portions serving as position detection portions appear alternately, and can be obtained by etching a metal plate, printing a plastic film, or the like. The resolution of the position detected portion is appropriately determined by the printing density of the printer and the control characteristics of the carriage motor. The portion A is a portion not provided with the position detected portion (either all transmitting portions or all shielding portions), and the output pulse of the encoder module does not change in this portion.

The operation of one embodiment of the present invention will be described with reference to FIGS. During the initialization operation of the printer (when the printer is powered on and when a reset signal is given), the carriage motor 3 is driven first, and the carriage 6 starts moving toward the home position.
The encoder module 4 detects the transmission part and the shield part of the position detection part of the scale plate and outputs a pulse. The CPU 1 starts monitoring this output pulse. When the carriage 6 continues to move and reaches the portion (portion in FIG. 3A) of the scale plate 7 where the position detection portion is not provided, the output pulse does not change. When the CPU 1 detects that the output pulse of the encoder module does not change even after the elapse of the predetermined time T1, the CPU 1 stops driving the carriage motor 3 and initializes the position counter 5. (That is, this position is the home position.) This is shown in FIG. Here, it goes without saying that the predetermined time T1 must be longer than the cycle of the output pulse of the encoder module according to the set moving speed of the carriage, but it is not erroneously detected when the carriage rises or when the speed changes during constant speed running. The time is set to such a time, and in the portion of FIG. 3A, the time can be detected and stopped as soon as possible. Further, in this embodiment, the position counter 5 is a 4-bit with a reset function.
It consists of UP / DOWN counter. Figure 5 shows the circuit diagram
Shown in. After stopping at the home position, the position counter is initialized by giving a signal to the reset terminal.

The home position setting of the printer is completed by the above operation, and thereafter, the position management is performed by the position counter. If the length of the part of the scale plate where the position detection part is not provided is longer than the distance required to stop the carriage motor after the stop command, the home position can be set without colliding the carriage with the frame or stopper. Become. If the distance cannot be structurally large, the frame and the stopper will collide with each other after the stop command is issued, but since the drive of the carriage motor is cut off and the collision is caused only by the inertial force, the impact force can be made extremely small. Further, since the encoder pulse does not change in the portion of the scale plate where the position detected portion is not provided, the position counter does not malfunction due to the vibration of the carriage during deceleration, stop, or collision. Further, since the reference position is uniquely determined by the setting of the position detected portion of the scale plate, there is no deterioration in the position accuracy due to the phase relationship as in the home position setting device using the rotary encoder and the home position sensor, and the printer with extremely high position accuracy is provided. Can be realized.

When the carriage is in a portion where the position detection portion is not provided (that is, in the home position) at the time of the initialization operation, the output pulse of the encoder module cannot change, so the carriage is pushed against the frame or the stopper. The carriage motor is stopped after a lapse of a predetermined time in the applied state, and the position counter is initialized. Therefore, the home position can be set by the same control as when the carriage is out of the home position. However, if it is necessary to prevent collision or pushing of the carriage, first move the carriage in the direction opposite to the home position during the initialization operation, confirm the change in the output pulse of the encoder module, and then move in the home position direction. For example, the home position setting operation can always be performed under the same conditions, and collision or pressing of the carriage against the frame or stopper can be avoided.

In this embodiment, the optical position detecting means including the photo interrupter and the scale plate provided with the light transmitting portion and the light shielding portion is used. However, the magnetoresistive element and the magnetic body are magnetized in multiple poles. A similar device can be configured by a magnetic type position detecting means including the scale plate provided. At this time, the portion where the position detection portion is not provided may be non-magnetized, or may be magnetized with only one of the N pole and the S pole.

[0016]

As described above, according to the present invention, it is possible to set the home position of the carriage with high position detection accuracy by simple control without providing a special sensor or the like, which is inexpensive and highly reliable. It is possible to provide a sex printer.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a structural diagram of a printer showing an embodiment of the present invention.

FIG. 3 is a structural diagram of a scale plate according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating the timing of output pulses of an encoder module according to an embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration example of a position counter according to an embodiment of the present invention.

FIG. 6 is a circuit diagram showing a configuration example of a conventional home position sensor.

FIG. 7 is a diagram illustrating output pulses of an encoder and a home position sensor of a conventional example.

FIG. 8 is a block diagram showing a conventional example.

FIG. 9 is a structural diagram of a printer showing a conventional example.

[Explanation of symbols]

 1 CPU 2 Carriage Motor Drive Circuit 3 Carriage Motor 4 Encoder Module 5 Position Counter 6 Carriage 7 Scale Plate 8 Platen 9 Recording Medium 10 Recording Head 11 Rotary Encoder 12 Home Position 13 Shielding Plate 14 Frame

Claims (2)

[Claims] 1. A carriage, which carries a reciprocating motion by mounting a recording head facing a recording medium, a DC motor for driving the position of the carriage, a position detecting means for detecting the position of the carriage, and a position detecting means of the position detecting means. In a home position setting device of a printer including a position counter that stores a position by an output pulse, the position detection unit includes an encoder module mounted on the carriage and a position detection target unit that causes the encoder module to generate an output pulse. And a scale plate provided for driving the DC motor during the initialization operation of the printer to move the carriage to the home position side, and when the output pulse of the encoder module does not change for a predetermined time or longer, the DC motor While stopping the drive of A home position setting device for a printer, wherein the position counter is initialized. 2. The home position setting device for a printer according to claim 1, wherein the position detected portion is not provided at a predetermined distance at one end of the scale plate on the home position side.