JPH0345713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a serial printer that has a daisy-wheel type typeface and uses a stepping motor to select the typeface, and in particular sets the driving table of the stepping motor in accordance with the moment of inertia of the typeface. The present invention relates to a typeface control device for a printer.

Conventionally, in printers with dage-wheel type typefaces, stepping motors are used to drive the typefaces in order to accurately determine the rotation angle of the typefaces. There is a closed loop control method that immediately corrects the step-out by applying feedback when it occurs, and an open-loop control method that does not perform such control, but the former has a complicated drive circuit and is expensive, so Open loop control schemes are usually employed.

Now, in order to suppress damping of rotor vibration in a stepping motor, it is necessary to supply the stepping motor with drive pulses with a pulse interval that matches the moment of inertia of the load.
Therefore, in a printer that drives a stepping motor using an open-loop control method, when the type body is replaced with one having a different moment of inertia, the interval between drive pulses must be adapted to the moment of inertia of the type body.

However, conventionally, printers have not been equipped with a means to measure the moment of inertia of the typeface, and as a result, operators have to use typefaces with a moment of inertia that does not match the pulse width of the drive pulse. The disadvantage is that the vibration of the rotor increases, causing step-out and erroneous printing.

The present invention has been made in view of this drawback, and provides a means for detecting the moment of inertia of a type body using a simple configuration in a printer that drives a stepping motor using an open-loop control method. The purpose is to eliminate defects.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, 1 is a platen, and 2 is a carriage parallel to the platen 1 and movably supported on the machine frame in conjunction with a drive source (not shown). It is. M
is a stepping motor, and the drive shaft 3 is placed on the carriage 2 so as to face the platen 1.
At the tip is a daisy wheel type typeface 4.
is removable. 5 is a U-shaped frame body in which a light emitter L and a photoreceptor P are arranged facing each other vertically and placed on the carriage 2; The frame body 6 is configured to block the light emitting body L and the light receiving body P by a solid line in FIG. 3).

Next, the control circuit of this embodiment will be explained.
In Figure 4, the CPU is a central processing unit with arithmetic and input/output functions, the RAM is a dynamic storage circuit with multiple memories that can be arbitrarily addressed, and the ROM is a control program and a stepping motor M, which will be described later.
This is a static memory circuit that stores a table of drive pulses. DR is a drive circuit for controlling the stepping motor M based on instructions from the CPU, and SW
The start switch A of this control circuit, which can be manually operated, is an amplifier for amplifying the detection signal of the photoreceptor P, and I/0 is the switch between the CPU, the drive circuit DR, the start switch SW, and the amplifier A. It is an interface.

Next, the drive table for the stepping motor M provided in the ROM will be explained.

Now, Figures 5, 6, and 7 respectively show the starting, constant speed, and stopping modes of the stepping motor. X represents the time chart of each excitation phase that represents the appropriate drive pulse interval transition for driving the typeface with a small moment of inertia, and Y represents the time chart of the drive pulse for the typeface that has a large moment of inertia. This is a time chart of the excitation phase.

That is, in both X and Y, the startup mode (Figure 5) accelerates the stepping motor by gradually narrowing the interval between drive pulses, and the constant speed mode (Figure 6) keeps the interval between drive pulses constant. , in the stop mode (Figure 7), the stepping motor is decelerated by gradually increasing the interval between drive pulses, thus slowing down the stepping motor without giving the stepping motor a sudden speed change, and thus slowing down the stepping motor. Stepping motor step-out is prevented by not applying sudden speed changes to the stepping motor, but as shown in the figure, when the moment of inertia of the type is small, the appropriate drive pulse width is The moment of inertia of is narrower than that of larger one. In other words, there is a unique optimal drive pulse width corresponding to the moment of inertia.
Figure 8 is a time chart showing the damping of the vibration of each type body when type bodies with different moments of inertia are driven or stopped by a stepping motor under predetermined start, constant speed, and stop modes. , () is when a type body with a moment of inertia larger than the moment of inertia compatible with the drive pulse is attached, and () is when a type body with a moment of inertia smaller than the moment of inertia compatible with the drive pulse is attached. , () indicate the case where a typeface with a moment of inertia that matches the drive pulse is mounted. In other words, as shown in the figure, when the moment of inertia of the type body matches the drive pulse, the damping of the vibration of the type body is extremely fast; Even if it is small, the damping of vibrations in the typeface will be slow.

Therefore, considering the minimum moment of inertia _I0 and the maximum moment of inertia I of the plural type bodies used in this printer, various drive pulses with different pulse intervals are set, and the stepping motor M After stopping, the amplitude of the printed letters after a certain reference time T ₀ seconds was measured for a plurality of printed letters having different moments of inertia. Then _, as shown by the curves α and _β in FIG. By selectively setting one of the two, the amplitude of the typefaces can be suppressed to below the permissible amplitude Am that will not cause step-out of the stepping motor or misalignment of the printing position for all typefaces in the range of _I0 to _I1 . I realized that something was going to happen.

Based on this, the information on the drive pulse width optimized for the moment of inertia _I2 and the moment of inertia _I3 is sequentially stored in the ROM as tables X and Y in the starting mode, constant speed mode, and stop mode.
each stored in a separate address.

Next, the CPU control program for setting one of the ROM tables X and Y will be explained. In FIG. 10, when the power is turned on using the switch SW, the ROM table X is set. Next, based on the data of this table 6) is supplied, and the stepping motor M enters constant speed driving.

Next, it is determined whether the photoreceptor P is off, that is, whether the detector 6 is interposed between the light emitter L and the photoreceptor P. Note that the range in which the photoreceptor P is turned off is set to be equal to the amplitude Am shown in FIG. If the photoreceptor P is on, the stepping motor M continues to be driven at a constant speed, and if the photoreceptor P is off, a drive pulse in the stop mode (see Figure 7) is supplied to the stepping motor to start the step. When the ping motor M stops, the CPU timer is reset. In this way, the timer counts, and when the counted value exceeds a predetermined value T ₀ (FIG. 11), it is determined whether the photoreceptor P is on or not. If the photoreceptor P is turned on even once, the ROM
The table settings for can be switched from X to Y, but
After the predetermined time T ₁ (>T ₀ ) has elapsed, the program ends regardless of whether the photoreceptor P is detected to be on.

In the above configuration, the table setting operation of the ROM will be explained.

First, the typeface 4 is mounted on the drive shaft 3. At this time, the moment of inertia of the typeface 4 is as shown in FIG.
Assume that it is between I ₀ and I ₁ . When the switch SW is operated, table X in the ROM is set by the CPU. Subsequently, drive pulses for the start mode (FIG. 5) are created based on the pulse interval based on this table Starts to do so. Next, drive pulses in a constant speed mode (FIG. 6) are created according to pulse intervals based on table X and supplied to the stepping motor M, and the stepping motor M enters constant speed driving.
In this way, the drive shaft 3 of the stepping motor M rotates in the direction of arrow R (FIG. 3), and when the drive shaft 3 reaches a rotation angle at which the sensing body 6 blocks the light emitting body P, the stepping motor A drive pulse for stop mode (FIG. 7) is supplied to M, and the CPU timer is reset. In the stop mode, the stepping motor M stops driving, but due to the moment of inertia of the type 4 and the stepping motor M, the sensing body 6 turns off the photoreceptor P in the type 4 as shown in FIG. Damped oscillation is performed centering on the area H. Accompanied by the damped vibration, the detector 6 crosses between the photoreceptor P and the light emitter L, and the photoreceptor P turns on and off each time.

Now, if the magnitude of the moment of inertia of the typeface 4 currently installed is I ₄ (Figure 9), then the reference time
The amplitude of the typeface 4 after T ₀ is Am ₁ (Fig. 9),
Since this is larger than Am, there is a moment after T ₀ when the detector 6 moves from between the photoreceptor P and the light emitter L and the photoreceptor P turns on. Then, the ROM table is switched from X to Y based on the CPU's judgment. When the printing operation starts after the table is switched to Y, as shown in _FIG . Positional deviation does not increase.

In addition, as the type 4, the moment of inertia I ₅ (Fig. 9) is used as the drive shaft 3 of the stepping motor M.
When you install the and operate the switch SW, it will turn on again.
The table X of the ROM is set and the above-mentioned operation is repeated, but in this case, as shown in _{FIG .} Since the amplitude is small, the time chart of the amplitude becomes as shown in FIG. 11, and the table X in the ROM cannot be switched. That is, when the printing operation starts after this, since Am ₃ <Am,
Again, the step-out of the stepping motor M and the deviation of the printing position do not increase.

As described above, according to the present invention, in a printer in which a type body is driven by an open-loop controlled stepping motor, two types of driving pulses of a stepping motor are provided to correspond to type bodies having different moments of inertia. Separate ROM tables storing interval information are prepared in advance, the stepping motor rotates the typeface, stops at a predetermined rotation angle, detects the attenuation of the vibration of the typeface, and calculates its amplitude. When the value after a certain time is greater than a certain value
Since the table in the ROM is switched from one side to the other, the stepping motor drive pulse interval can be automatically set to match the moment of inertia of the type, and thus the stepping motor can be easily removed. Since the tonality can be suppressed, the printing position can be maintained properly.

Furthermore, since the stepping motor can be controlled in an open loop, its drive circuit can be simplified and costs can be reduced.

In the above embodiment, the rotation angle of the drive shaft 3 is detected by the U-shaped frame 5 and the detection body 6, but for example, a circular plate may be fixed to the drive shaft 3 and a plurality of circular plates or The rotation angle may be detected by a rotary encoder provided with a single slit.

Further, in the above embodiment, only one sensing body is provided, but in order to improve the detection accuracy of the sensing body, multiple sensing bodies are fixed to the drive shaft of the stepping motor at different phase angles, and these multiple sensing bodies are fixed to the drive shaft of the stepping motor at different phase angles. A plurality of frames 5 corresponding to the respective detection bodies may be arranged on the machine frame, and the rotation angle of the drive shaft may be detected when all the light receiving bodies L of each frame 5 are off.

[Brief explanation of drawings]

Fig. 1 is a perspective view of the main parts of the stepping motor with type attached, Figs. 2 and 3 are illustrations of the detection state of the rotation angle detection means of the drive shaft, and Fig. 4 is the control circuit. The block diagram and FIGS. 5 to 7 are time charts representing the drive pulses in start, constant speed, and stop modes and the step drive of the stepping motor based on the drive pulses in the start, constant speed, and stop modes, and FIGS. 8 () to (). is for a given drive pulse,
Figure 9 is a time chart showing the attenuation of vibration of type bodies with different moments of inertia. Figure 9 is a diagram showing the correspondence between the moment of inertia of the type body and its amplitude for a given drive pulse. Figure 10 is
CPU program flowchart, 11th,
12 is a diagram illustrating a detection state of the detection means with respect to the vibration of the typeface. 1...Platen, 2...Carriage, M...Stepping motor, 3...Stepping motor drive shaft, 4...Print, 5, 6, L, P...Detection means, DR...Driving means , ROM... storage means,
CPU: address means, control means.

Claims (1)

[Scope of Claims] 1. A stepping motor whose drive shaft is arranged to face the platen, and a plurality of protrusions extending radially from the central portion with letters formed at the ends thereof, and the central portion driven by the stepping motor. It has multiple type bodies that can be attached to and removed from the shaft, and the multiple type bodies are divided into groups with two types of moments of inertia, and one type body is selectively attached to the drive shaft of the stepping motor. In a printer configured to perform continuous printing, the information on the driving pulse train of the stepping motor is stored separately in two separate stores to store information on the driving pulse train with two types of pulse intervals that match the above-mentioned group of moments of inertia of the typeface. A storage means that stores data in a memory table, an address means that can be set to alternately select one side of the memory table and read out the stored information, and a signal generated by operation to act on the address means to read one of the memory tables. an operating means for selecting and setting; a driving means that acts in conjunction with the signal from the above operation and supplies a predetermined number of drive pulses to the stepping motor based on stored information read out by the addressing means; and an actuator mounted on the drive shaft. a detection means arranged in relation to the typeface, detecting the rotational position of the typeface due to the predetermined number of drive pulses, and generating an in-range signal when the rotational position is within a predetermined rotational direction range, and generating an out-of-range signal when the rotational position exceeds the range; , acting after a preset time, controlling the addressing means to stop the stepping motor in connection with the occurrence of the in-range signal and to switch the setting of the memory table to the other in connection with the occurrence of the out-of-range signal; A typeface control device for a printer, comprising: control means;