JPH0327028B2 - - 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 starting switch A of this control circuit, which can be manually operated, is an amplifier for amplifying the detection signal of the photoreceptor P, and the I/O is the connection between the CPU, the drive circuit DR, the starting 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 type body with a small moment of inertia, and Y represents the time chart of the drive pulse for the type body with a large moment of inertia. This is a time chart of each 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 (Fig. 7), the stepping motor is decelerated by gradually increasing the interval between the drive pulses, thereby decelerating the stepping motor without causing sudden speed changes to the stepping motor; Stepping motor stepout 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 Narrower than those with a large moment of inertia. 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. , if a type body with a moment of inertia larger than the moment of inertia compatible with the drive pulse is installed, and if a type body with a moment of inertia smaller than the moment of inertia compatible with the drive pulse is installed, then, This figure shows 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 Io and the maximum moment of inertia I of the plurality of type bodies used in this printer, various drive pulses with different pulse intervals are set to control the stepping motor M. After stopping, the amplitude of the printed letters after a certain reference time To 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 typeface can be kept below the permissible amplitude Am that will not cause stepping motor step-out or misalignment of the printing position for all typefaces in the range of I ₀ to _{I 1} . I found out that I can suppress it.

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 A driving pulse (see FIG. 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. If the photoreceptor P is on, constant speed driving of the stepping motor M is continued, and if the photoreceptor P is off, "0" is stored in a predetermined register of the CPU. Subsequently, constant speed driving of the stepping motor M is continued, and "1" is added to a predetermined register of the CPU. And the added value N is
When the number of drive pulses N 0 required to rotate the drive shaft 3 of the stepping motor M through 360° is equal to N ₀ , it is determined whether the photoreceptor P is on or not. Photoreceptor P
If the photoreceptor P is off, the process immediately sets the ROM table to Y if the photoreceptor P is on, and the process ends. In this program, we first store "0" in the register and then add "1" to it, but first we store "N ₀ " in the register and then gradually subtract this value. You can do it like this.

Now, in accordance with the above program, the rotation angle range in which the detection body 6 turns off the photoreceptor P is set in advance as follows.

That is, when a type body with a moment of inertia I ₀ and a type body with a moment of inertia I ₂ (Fig. 9) are driven on table X by the above N ₀ pulses,
_{I 0} and _{I 2} are moment of inertia values that are somewhat incompatible with table When the moment of inertia of the type is driven by the above-mentioned N ₀ pulses in the range of I ₀ to I ₂ in FIG. The width of the sensing body 6 in the rotational direction is set.

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

First, the type body 4 is mounted on the drive shaft 3.

At this time, it is assumed that the value of the moment of inertia of the typeface 4 is _I3 . When the switch SW is operated, the ROM
Table X is set. Next, the startup mode (fifth
The drive pulse shown in the figure) is generated and supplied to the stepping motor M, and thereby the stepping motor M starts driving. In both cases, "0" is stored in a predetermined register of the CPU. Next, drive pulses are created with pulse intervals based on table X,
The stepping motor M is supplied, and the stepping motor M enters constant speed driving. Moreover, "1" is added to the register of the CPU every time the stepping motor M is driven one step.

Now, the moment of inertia I ₃ of the typeface 4 does not conform to the table X, and the amplitude Am ₁ with respect to the reference time T ₀ is greater than Am. For this reason, typeface 4
The amplitude of the type 4 attenuates slowly (Fig. 8), and the next drive step is started before the amplitude has sufficiently attenuated. As shown in Fig. 12, the vibrations of the type body 4 are amplified each time the drive step advances, and the step Ping motor M
Since step-out frequently occurs, the rotation angle of the type body deviates from that in the case of driving an active body with a proper moment of inertia as shown in FIG. When the rotation of the stepping motor M progresses and the added value N in the register of the CPU reaches _N0 , the CPU determines whether the photoreceptor P is on or off. However, due to the accumulation of deviations in the rotational angles described above, at the time N=N ₀ , the sensing body 6 is moved forward or backward in the direction of arrow R from the position indicated by the chain line in FIG. Therefore, the CPU detects that the photoreceptor P is turned on, and as a result, the CPU switches the ROM table from X to Y. When the printing operation starts after the table is switched to Y, the amplitude of the type 4 becomes _Am2 , which is smaller than the allowable amplitude Am, so that step-out of the stepping motor M and deviation of the printing position do not increase.

In addition, as the type 4, the moment of inertia I ₄ (Fig. 9) is used as the drive shaft 3 of the stepping motor M.
If you attach it to the camera and operate the switch SW, it will turn on again.
_{ROM table _ _} The rotation angle of the motor M is the same as that of the photoreceptor P.
Therefore, table X in the ROM cannot be switched. That is, when the printing operation starts thereafter, since Am ₃ <Am, 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 drive pulse intervals of the stepping motor are provided, which correspond to type bodies having different moments of inertia. Separate ROM tables storing information are prepared in advance, and when the typeface is attached to the stepping motor, the ROM
set the table on one side, supply a predetermined number of drive pulses to the stepping motor, and detect the rotation angle of the stepping motor due to the drive pulses.
When the rotation angle is outside the predetermined range, it is assumed that the stepping motor is out of synch, and the moment of inertia of the type is determined to be unsuitable for that table, and the table is switched from one side to the other. Therefore, the driving pulse interval of the stepping motor can be automatically set to match the moment of inertia of the typeface, and step-out of the stepping motor can be suppressed, so the printing position can be set appropriately. can be kept.

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 rotor encoder provided with a single slit.

In addition, 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 are arranged on the machine frame, and the rotation angle of the drive shaft is detected in relation to the fact that all the light receptors L of each frame 5 are off. Good too.

[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 showing the drive pulses for start, constant speed, and stop modes and the step drive of the stepping motor based on the drive pulses based on ROM tables X and Y. FIGS. Figure 9 is a time chart showing the attenuation of vibrations of type bodies with different moments of inertia in response to drive pulses. Figure 10 is a flowchart of the CPU program, and Figure 11 is a time chart of the rotation angle of the type when driving a type with a moment of inertia that matches the table.
FIG. 2 is a time chart of the rotation angle of a type when driving a type whose moment of inertia is incompatible with the table. 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 font, detecting the rotational position of the font due to the predetermined number of driving pulses and generating an out-of-range signal when the rotational position exceeds a predetermined rotational direction range; Control means for acting on the means to switch the settings of the memory table to the other.