JPS6034886A - Printer - Google Patents

Abstract

PURPOSE:To reduce an overshoot of a carriage, by a construction wherein a carriage is stopped by an AND signal of a sensor signal and an indexing signal in a decelerated condition at a home position. CONSTITUTION:Output signals A-C from a rotary encoder 5 and an output signal D from the sensor 8 are inputted into a signal-converting circuit 10. Of outputs from the circuit 10, those obtained by inverting the signals C, D are inputted into an AND gate 11. When the carriage 2 is moved at the first velocity (high velocity) toward the left end (home position) and an interrupting plate 9 of the carriage 2 is detected by the sensor 8, the signal D is generated, which is converted into a signal i1 through the circuit 10, and the signal i1 is inputted into a CPU12. The CPU12 controls an electric current in accordance with the signal i1, and generates a command for rotating a motor at a velocity lower than the first velocity. Accordingly, the carriage can be stopped in the condition of little overshoot.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a printing device, and more particularly to a printing device having a carriage that carries a printing means and moves back and forth along a platen.

In serial printers such as prior art typewriters, the position of the carriage is different at the end of the previous printing. Therefore, when the power is turned on and printing is started again, the printer must accurately return the printer to its standby position (home position).

For this reason, a sensor is often used to detect when the carriage approaches the home position and stop the carriage at a predetermined position.

Normally, this sensor is called a left limiter because its home position is on the left side of the printer.

Microswitches and the like are used as sensors for this purpose, but when a microswitch is used, the signal timing of the microswitch, which is a mechanical switch, changes depending on the carriage return speed when the power is turned on, that is, during initialization. Therefore, it is difficult to always stop the carriage at an accurate home position. Additionally, a non-contact type photocoupler is sometimes used as a sensor, but in this case, thermal expansion occurs on the device side due to the heat generation state of the printer, and the mounting position of the photocoupler changes, so the position where the carriage is detected cannot be adjusted. Errors occur and it is difficult to stop at an accurate position.

Therefore, in order to eliminate the above-mentioned drawbacks, generally an encoder is provided in the DC motor for driving the carriage in addition to the sensor, and one or more pulse signals are generated every time the motor rotates, thereby reducing the disturbance. On the other hand, an index signal with less interference is created, the signal from the sensor and the index signal are ANDed, and this is often used as a stop signal for the carriage during initialization.

With this configuration, the carriage can always be stopped at a fixed position even if the sensor signal changes slightly, and the control circuit can be controlled by inputting the position signal generated from the motor encoder to the control circuit and counting this signal. can accurately determine the position of the carriage.

By the way, in a printing device equipped with such a mechanism, the speed at which the carriage is moved to the left end at the time of initialization is determined in advance, but normally the speed between the home position of the carriage and the position where the carriage contacts the stopper on the main body of the printing device is determined in advance. Since the distance between the two carriages is short, in order to minimize overshoot and stop the carriage by using the AND signal between the sensor and the index signal, it is necessary to take into account changes in the load when moving the carriage and to slow down the carriage sufficiently.

However, when the speed is reduced, for example, the carriage is located at the farthest right end from the home position, giving the driver a feeling of discomfort.

On the other hand, if the carriage speed is increased, the overshoot of the carriage increases, and if the size of the printing device is designed to be as small as possible, the carriage may sometimes collide with the left end during initialization.

Therefore, it was necessary to design the device taking into account the amount of overshoot.

SUMMARY OF THE INVENTION The present invention has been made in order to eliminate the drawbacks of the conventional art as described above, and provides a printing device configured to increase the normal carriage return speed as much as possible and significantly reduce carriage overshoot. is intended to provide.

EXAMPLES Hereinafter, the present invention will be explained in detail based on examples shown in the drawings.

Figure 1 and the following diagrams explain one embodiment of the present invention.
The figure shows the main parts of a serial printer to which the present invention is applied.

In FIG. 1, the reference numeral 1 indicates a platen, to which recording paper P is attached and guided.

A carriage equipped with a recording head 2a is arranged opposite to the platen 1. Carriage 2 is platen 1
The guide shaft 3 is slidably fitted to the guide shaft 3 arranged parallel to the guide shaft 3 .

On the other hand, the reference numeral 4 is a DC motor, and a rotary encoder 5 is connected to the opposite end of its output shaft.

The rotary encoder 5 basically includes a rotating disk having a large number of slits, and a light emitting element 5b and a light receiving element 5c sandwiched between the rotating disk and the rotary disk rotates as the DC motor 4 rotates. Detects the changing slit and detects the print position and stop position.

A pulley 6 is fixed to the other end of the output shaft of the DC motor 4, and an endless belt 7 is connected between the pulley 6 and a driven pulley 6a provided at a predetermined distance apart from the pulley 6.
is being strung up. The carriage 2 is placed in the middle of the belt 7.
are connected.

On the other hand, a sensor 8 is located near the home position of the printing device.
is provided. This sensor 8 is configured as a photocoupler, and when the optical path is interrupted by an interrupter plate 9 provided on the side of the carriage 2, this photocoupler detects the presence of the carriage 2 and generates a carriage detection signal.

The output signals A to C are input to the control circuit shown in FIG.

Next, details of the carriage drive control circuit shown in FIG. 2 will be explained.

In FIG. 2, the same or corresponding parts as in FIG. 1 are designated by the same reference numerals, and their explanation will be omitted.

In FIG. 2, the reference numeral 10 indicates a signal conversion circuit consisting of a group of inverters, and these signal conversion circuits 10 receive output signals A to C from the rotary encoder 5,
The output signal from is input.

Among the outputs of the signal conversion circuit 10, the output obtained by inverting the signals C and D is input to the AND gate 11.

Let the inverted output of the signal C be 11, the inverted output of the signal C be 12, and the output of the AND gate 11 be i3.

These signals 11+ and 13 are input to a CPU (central processing unit) 12. The signal i3 transmits a carriage stop signal and the position, rotation direction, and rotation speed of the carriage.

Incidentally, the CPU 12 writes the value of the drive current at the time of initializing the motor into the latch circuit 13 using a predetermined method. The output of the latch circuit 13 is D
- It is converted into an analog value by the operational amplifier 15 via the A converter 14, and the current value is instructed to the motor drive circuit 16.

Motor drive circuit 16 selectively operates transistors 17, 18 to rotate motor 4.

On the other hand, reference numeral 19 is a motor current detector which feeds back the motor current to the motor drive circuit 16 via an operational amplifier 20, and compares a preset current value with the actually flowing motor current.

Next, the operation of the control circuit configured as above will be explained. Now 1. When the carriage 2 moves at a first speed (high speed) toward the left end of the device, which is the home position, and the interrupter plate 9 of the carriage is detected by the sensor 8, a signal is generated and is transmitted through the signal conversion circuit 10. The signal becomes a signal 11 and is input to the CPU 12.

The CPU 12 controls the stain flow value using this signal i1 and instructs the motor to rotate at a further deceleration than the first speed.

As a result, the carriage 2 moves further toward the left end at the second speed, which is slower than the normal return speed.

Therefore, the carriage is stopped in a decelerated state, and can be stopped with almost no overshoot.

By the way, FIG. 3 explains the timing of the signals 11 to i3, and the position indicated by the symbol indicates the home position.

Note that in the range where the inversion signal i+ from the sensor 8 is "1" when the carriage moves toward the home position, the signal 12, which is an index signal accompanying the rotation of the motor, is 1.
It is set so that only 1 piece is output.

Therefore, only one output i3 of the AND gate 11 is output until the carriage reaches the home position.

When the signal i becomes [J, the carriage is decelerated, so when the stop signal i3 is output, the carriage can be stopped quickly with a slight overshoot.

Since this embodiment is configured as described above, the carriage can be stopped while the moving speed of the carriage is decelerated in the vicinity of the home position.
The carriage can be stopped quickly with almost no overshoot.

Therefore, no matter where the carriage is located, the carriage return speed can be relatively high until it reaches the home position, without causing any discomfort to the operator.

Further, since the control circuit has an extremely simple structure, it can be manufactured at an extremely low cost, and a small, regular-price printing device can be obtained.

As is clear from the explanation below, according to the present invention, no matter where the carriage is, the carriage return can be made fast to the vicinity of the home position, and the carriage can be returned with almost no overshoot. can be stopped.

[Brief explanation of drawings]

The drawings are for explaining one embodiment of the present invention; FIG. 1 is a perspective view, FIG. 2 is a block diagram of a control circuit, and FIG. 3 is a timing chart of control signals. DESCRIPTION OF SYMBOLS 1...Platen, 2...Carriage, 4...DC motor, 5...Rotary encoder, 8...Sensor, 9...Interrupter board, 10...Signal conversion circuit, 11... AND gate, 12... signal processing device, 13... latch circuit, 16... motor drive circuit. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] A carriage that reciprocates along a platen, a sensor that detects when the carriage is near a home position, a motor that drives the carriage, means for generating an index signal indicating the home position of the carriage, and a drive for the motor. In a printing device equipped with a control means, when the carriage returns, the carriage is moved at high speed until it reaches the vicinity of the home position, is decelerated at the home position, and in this decelerated state, the carriage is stopped by an AND signal between the sensor and the index signal. A printing device characterized by being configured as follows≦