JPH03159766A - Pulse motor controller - Google Patents

Abstract

PURPOSE:To obtain a printer which is good in energy efficiency in feeding, capable of feeding paper stably by a method wherein a variation value is obtained by comparing a mean value of values detected with a sensor arranged to a medium feed mechanism with an initial value, and an over drive signal is obtained from the variation value to determine an exciting current of a motor from the over drive signal. CONSTITUTION:A load on a motor 19 is detected with a piezoelectric element 2, and is inputted to a CPU 15. In order to remove cyclic pressure noise, values of 10 pulses are averaged. The smoothed value is taken as a load detection signal, is compared with an initial value of the piezoelectric element 2, and pressure variation value is stored in a memory of the CPU 15. The load is detected on and after T9. When a motor exciting current is to be varied, the pressure variation value stored in the memory is converted to an over drive signal OVD1. The converted over drive signal OVD1 is outputted, and a motor exciting circuit value is determined.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pulse motor control device for feeding a print medium of a printer.

(Prior Art) Conventionally, DC motors, pulse motors, and the like have been used to feed print media in printers.

FIG. 11 is a diagram showing the media feeding mechanism of a conventional printer. In the figure, a DC motor or pulse motor motor 101 for media to be traversed drives a gear 102 and rotates a platen 106 . A printing medium 107 , for example, subrocket paper, is transported by a bin tractor 104 and wound around the surface of a platen 106 , whereupon printing is performed by an impact head 103 .

In a normal printer, the bin tractor 10
4 to feed the printing medium 107, and one to feed cut paper cut into standard sizes directly by winding it around the platen.
This is done using 05.

? The load applied to the motor 101 when feeding the print medium 107 is the force of rotating the platen 106 and the motor 10.
This is the force for rotating the gear 102 etc. that transmits the driving force of 1 to the platen 106, and the force for feeding the print medium 107. Among these, the force for feeding the print medium 107 depends on the thickness, type (distinction between subrocket paper and cut paper), shape (presence or absence of perforations shown in Fig. 12 in the case of subrocket paper), and paper feeding path of the print medium 107. It is affected by the friction load caused by etc. Further, when a PM type pulse motor is used as the motor 101, motor drive methods include a uni-bolar drive method, a bi-bolar drive method, and the like. Figure 13 is a drive circuit diagram of a univollar motor, which is configured with a constant voltage drive circuit. In the figure, Q. is a motor driver, Tr. and Tr■
is an overdrive transistor, Dl to D4 are diodes, Ds is a tsuenna diode, and M is a motor. Overdrive signal (OVD) that determines the start of motor excitation
I signal) via transistors Tr1 and Try? When voltage is sent to the motor driver Q, phase excitation signals PH+, P
Output signal ○I~0■ in synchronization with Hi, PIIs+PH4
occurs, and motor M rotates.

FIG. L4 is a signal waveform diagram when driving a conventional unipolar motor.

Each signal PH, and O. ．． PH2 and Oz. PH3 and ○z, P
H4 and 04 are synchronized and have the same phase. Moreover, the output signal O l-O s is an overdrive signal OVD
．． controlled by the overdrive signal OVD. When it turns off, it turns off as shown at time T2. In addition, since it is constant voltage control, the excitation Mi flowing to the motor M
ii Current is constant voltage ■. , motor winding constant resistance R, inductance L1 current Ik cos due to back electromotive force of the rotor
(ωt+θ). However, 1k is the current constant. FIG. 15 is a current waveform diagram when driving a conventional uniborular motor.

Output IS number 0. ,0. When , a current 1+ - 1 ( 1 - e - 111/L ) R ■, - ] y ( 1 e -1 & /L ) R flows through the coil of motor M as shown by the broken line. However, the current 1k cos (ωt+φ) flowing due to the back electromotive force of the motor M overlaps, and eventually the motor M
The exciting current is represented by the current shown by the solid line, and the waveform of the exciting current changes depending on the phase difference φ between the electrical angle and the mechanical angle. In addition, Fig. 16 is a drive circuit diagram of a bibolar type motor, and in the figure, Q
z is a motor variver, Trs is an overdrive transistor, R1 is a current value control resistor, and M is a motor. The overdrive signal OVIll. determines the motor magnetism.
The signal is sent to the motor driver Q. via the transistor Trs.
is input to the overdrive signal OVD, and the phase excitation signal PR. Or, when both pIIg are turned on, output signal 01 or 02 is turned on. The timing of each signal is
Regarding the uni-bolar type motor and rotation shown in Figure 3, in the case of the uni-bolar type motor, the output signal OI~04 is O~+■
. In contrast, in the case of a bibolar type morke, the output 0 + , O t is ±vD.
and is output in both positive and negative directions to drive.

The resistor R1 determines the current value in constant current drive, and is an internal resistor RI (not shown) of the motor driver Q2.
The it'a value is determined by the voltage ratio obtained by resistance division with M. Also, the chopping frequency during constant current control is Rx. C+, Cz. C*, R4 filter and motor M
The coil resistance R, which is the winding constant, and the inductance L{i
determined by

When starting rotation of either the uni-bolar or bi-bolar drive motor M described above, a phase excitation signal pulse train is applied in which a phase excitation signal lower than the self-starting frequency of the motor M is added and the phase excitation signal frequency gradually increases. used (hereinafter referred to as “
"acceleration table signal sequence". ). Figure 17 is a diagram showing the relationship between the acceleration table signal train and motor excitation current of a bipolar motor. As shown in the figure, acceleration table signal sequence T. ,T,,T 2 ,T a ,
The frequencies of T s and T h gradually increase, and T becomes a low-speed term region to excite the motor M at a constant frequency. The excitation t current is synchronized with the phase excitation signal train, and VD -F-(L-e-"") + Ik cos
After increasing by ((1) t+φ), it is sliced by the value of INAX and chopping is performed by the frequency by Rz and Cs. FIG. 18 is a diagram showing frequency/torque characteristics when the motor is driven using the drive circuit shown in FIG. 16.

The horizontal axis is the frequency, and the unit is the number of pulses per second, which corresponds to "rt-1" in Fig. 17.The vertical axis is the torque on the motor shaft. It can be seen that the constant current control current value is set to 500 mA.In this way, the pulse motor is driven more stably in the low frequency range, making it possible to drive the motor with high torque. Figure 19 is a diagram showing the current/torque characteristics when the constant current control T4 current value is changed. The horizontal axis represents "current value x number of windings", and the vertical axis represents output torque. Increasing the motor excitation current increases the output torque, but also increases heat generation. (Problem to be Solved by the Invention) However, in the above-mentioned pulse motor control device, when the pulse motor is used as the media feeding motor of the printer, it is impossible to detect the load applied to the pulse motor. This is possible, and even if the load increases and the device loses synchronization, it cannot be detected.

In addition, the current flowing through the pulse motor is always constant, and a maximum of 1t2ffi continues to flow assuming the maximum load, resulting in poor power supply efficiency and increased heat generation in the motor and circuit. Furthermore, if the current flowing through the motor is large and the amount of heat generated is large, the generation of heat must be prevented mechanically or by a control method.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional pulse motor control device described above, and to provide an excellent printer that can stably feed paper and has good energy efficiency during feeding. (Means for Solving the Problems) For this purpose, in the pulse motor control device of the present invention, a piezoelectric element is disposed in the medium feeding mechanism, and the average value of the values of 10 pulses detected by the piezoelectric element is calculated. Means for removing calculation noise and means for comparing the average value with an initial value to determine a change value are provided. A table of the above-mentioned change values and excitation current setting values is prepared in the cpυ memory, and means for obtaining an overdrive signal from the table is provided. The apparatus also includes means for determining the excitation current of the motor from the overdrive signal.

(Function) According to the present invention, as described above, a piezoelectric element is provided in the medium feeding mechanism, and a pressure signal is detected by the piezoelectric element. The detected pressure signal is averaged over 10 pulses to remove noise. The value from which noise has been removed becomes a load detection signal, which is compared with the initial value of the piezoelectric element to determine the pressure change value. The above pressure change value and jiJJMIT are stored in the CPU memory.
1? *A table of setting values is prepared, an overdrive signal is determined from the table, and the motor excitation current is determined from the overdrive signal.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram of a medium feeding mechanism of a printer employing the pulse motor control device of the present invention, and FIG. 2 is an enlarged view of the main parts of FIG.

In this embodiment, a piezoelectric element 2 is disposed in the medium feeding mechanism of a printer that uses a pulse motor 1 as a medium feeding motor to measure the load. That is, the drive output of the pulse motor 1 is transmitted to the idle gear 3 via the motor gear 8, and further transmitted to the platen 5 via the platen gear 4. Then, the force applied to the motor shaft 11 at that time is detected by the piezoelectric element 2. The piezoelectric element 2 is a piezoelectric element holder 2a made of plastic mold that protrudes from the printer housing.
is pressed against the motor shaft l1 and fixed. The piezoelectric element 2 used is a multilayer bimorph type piezoelectric element formed by laminating thick films, and has the characteristics shown in FIG. 3. Figure 4 shows the mounting position of the piezoelectric element. When transmitting the drive output from the motor gear 8 to the platen gear 5 through the idle gear 4, piezoelectric elements 2 can also be attached at positions a, b, and c in the figure. If the piezoelectric element 2 is attached to the motor shaft 1l, the force applied to the motor can be directly detected, and if the piezoelectric element 2 is attached to the platen shaft 9, the force applied to the platen by the medium can be directly detected. Furthermore, the piezoelectric element 2 is structurally easiest to attach to the idle gear shaft 10. Furthermore, although the mounting directions of the piezoelectric elements 2 are different in the mounting positions a, b, and C, they are mounted in the direction in which the load is applied during medium feeding. Next, a case in which the piezoelectric element 2 is attached to the motor shaft opening 1 will be described in detail.

When feedback control is performed by detecting the load applied to the motor as pressure by the piezoelectric element 2, noise-like pressure is applied to the piezoelectric element 2 due to vibrations generated during printing.

In that case, the output of the piezoelectric element 2 is the sum of the original load applied to the motor and the noise pressure. The source of noise pressure is the resonance frequency 3T of the printer body.
HZ vibration, platen 5 natural frequency 1.8K+12 vibration, impact head printing frequency approximately 2Kll
There is a vibration with a frequency of about 1.4κHZ due to the Z vibration and the rotation of the pulse motor 1 itself. In order to remove them and detect the original load, an RC filter can be inserted into the output of the piezoelectric element 2, but in this embodiment, CP[I
Filtering is performed by the calculation. FIG. 5 is a block diagram showing a first embodiment of the present invention. In the figure, 2 is a piezoelectric element, 14 is an A/D converter,
15 is a CPU, S16 is a D/A converter, l8 is a motor driver, and 19 is a motor. The pressure signal detected by the piezoelectric element 2 is transmitted to the transistor Tr.
s, and sent to A/D converter l4, where it is converted into a digital signal. The output of the A/D converter l4 is subjected to arithmetic processing within the CPU 15, and is converted into phase excitation signals Pll, . P
Hff and motor excitation current setting signal, that is, overdrive signal OVD. Output. Phase excitation signal PHr,P
Ht is input to the motor driver 18 and becomes a phase excitation signal for the motor 19. In addition, overdrive signal OVD. is converted into an analog signal via the D/A converter 16, and input to the motor driver l8 through the transistor Tra, thereby setting the motor excitation current. The sampling r@ period of the A/0 converter 14 is set to 20 KHz because the frequency response of the piezoelectric element 2 is about iooz. Next, the operation of the pulse motor control device of the present invention will be explained with reference to FIGS. 6 to 8.

FIG. 6 shows the overdrive signal OVD. 7th flowchart of arithmetic processing performed within CPU to determine
The figure is a timing waveform diagram of a phase signal, an overdrive signal, a motor excitation current, and a filtered piezoelectric element.

Store the initial pressure value of the step in memory.

Step ■ The recording medium is sucked in, CP[I15 turns on the overdrive signal Of/D, and the phase excitation signal Pl is turned on.
1. ,PH! Output. Then, the phase excitation signal PH1
．． Make PHz output the acceleration table.

T and T8 in FIG. 7 indicate an acceleration table signal train, and in the acceleration table signal train, the overdrive signal OVO is kept constant, so that the motor excitation current value is not changed and is kept at a constant value.

Stenbu■ Outputs phase excitation signal at constant speed.

Step (2) The load applied to the motor 19 is detected by the piezoelectric element 2 and inputted to the CPU 15.

Step (2) As described above, the output of the piezoelectric element 2 contains noise at various frequencies, and filtering is performed within the CPU 15 in order to remove these noises and obtain a stable load detection output. That is, an average of 10 pulses is taken to remove frequency pressure noise.

Step ■ The smoothed value is used as a load detection signal, is compared with the initial value of piezoelectric element 2, and the pressure change value is used as a load detection signal.
Store it in the memory of 5. Step ■T From now on, load detection is performed, and when changing the motor excitation current, the pressure change value stored in the memory is converted into an overdrive signal OVD+.

FIG. 8 is a diagram showing an output table of pressure change values and overdrive signals provided in advance in the CPU, and a relationship between overdrive signals and motor excitation current.

Step (2) Output the converted overdrive signal OVO, and determine the motor excitation current value.

In this embodiment, the table is divided into six stages, but by changing the memory data in the CPU 15, it can be divided into any stage from two stages. Also, when transferring the output of the piezoelectric element 2 to the CPU 15, and from the CPU 15, an overdrive signal OVO. , when inputting to the motor dryer 18, the A/D converter l4 and D
/A converter 16 is used, but within the CPLILS, the converter 14. 16 can be omitted. In this way, by attaching the piezoelectric element 2 to the motor shaft 1l and performing feedback control on the detected pressure value, real-time control becomes possible, and stable and efficient medium feeding can be performed.

The method of performing arithmetic processing by the CPU 15 and performing feedback control based on the result has been described above. Next, a method of performing feedback control using the output of the piezoelectric element 2 directly will be described.

FIG. 9 is a circuit diagram showing a second embodiment of the present invention. In the figure, the piezoelectric element 33 is connected to a resistor R. Rz and capacitor CI, C! The pressure value is transmitted to the power transistor Tr. Enter.

Resistance R,,R. A voltage obtained by the voltage division ratio is applied to the motor driver 27 via the Zener diode 29. Since the pressure value detected by the piezoelectric element 33 is detected with noise added to it, after smoothing it through the filter circuit described above, the pressure value is detected by the resistor R3. R. ．． The voltage is amplified to +vll' by the amplifier configured by R and the transistor Try, and becomes the drive voltage of the motor driver 27. In this way, the voltage applied to the motor 32 is determined by the output of the piezoelectric element 33.

FIG. 10 is a timing waveform diagram of the second embodiment of the present invention. The applied voltage +vI1' of the motor driver 27 is applied to the piezoelectric element 3
T l + T z, T 1
Even in the region of the acceleration table of Ta, the magnitude of the motor excitation iai flow fluctuates in the constant speed region from TS. Therefore, the motor output changes depending on the output of the piezoelectric element 2. Also,
By performing the above-mentioned control in printers such as electrophotographic printers and thermal transfer printers using LEfl lasers, it is possible to prevent jamming and heat generation of the motor due to rotational unevenness and motor step-out. Power consumption can also be reduced. Furthermore, the same effect can be obtained by using a pressure-sensitive sensor such as a strain gauge, load cell type sensor, Idl strain type force sensor, vibration type force sensor, or force balance sensor instead of the piezoelectric element 2.33 to detect the load. It will be done. In addition to pressure, similar effects can be obtained by detecting displacement and acceleration of the motor shaft and platen. Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention. For example, similar methods can be applied to paper feeders other than printers (automatic ticket issuing machines, cash dispensers, etc.). effect can be obtained.

(Effects of the Invention) As described above in detail, according to the present invention, it is possible to detect the load applied to the pulse motor when feeding print media of a printer, and the load applied to the pulse motor for feeding the media can be detected. This eliminates the need for current to flow.

Therefore, the amount of heat generated by the pulse motor and the motor drive circuit can be reduced, and power consumption can also be reduced. It also makes it possible to feed printing media stably against load fluctuations.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the media feeding mechanism of a printer that employs the pulse motor control device of the present invention, and FIG. 2 is an enlarged view of the main parts of FIG. 1.
Figure 3 is a characteristic diagram of a multilayer laminated bimorph type piezoelectric element, Figure 4
The figure shows the mounting position of the piezoelectric element, and FIG. 6 is a flowchart of the arithmetic processing performed in the CPU to determine the signal OVD+, and FIG. 7 is a block diagram of the pulse motor control device showing an embodiment of the present invention. Figure 8 is a timing waveform diagram of the filtered piezoelectric element; Figure 8 is an output table of pressure change values and overdrive signals provided in advance in the CPU; Figure 9 is a diagram showing the relationship between overdrive signals and motor excitation current; FIG. 10 is a tamming waveform diagram of the second embodiment of the present invention, and FIG. 1l is a media feeding mechanism section of a conventional printer. FIG. 12 is a perspective view of sprocket paper, FIG. 13 is a diagram showing the drive circuit of a uni-bolar motor, FIG. 14 is a signal waveform diagram when driving a conventional uni-bolar motor, and FIG. 15 is a diagram of a conventional uni-bolar motor. Figure 16 is a drive circuit diagram of a bipolar motor, Figure 17 is a diagram of the relationship between the acceleration table signal train and motor excitation current of a bipolar motor, and Figure 18 is a diagram of the current waveform when driving a uni-bolar motor.
The figure shows the frequency/torque characteristics when the motor is driven using the drive circuit shown in Fig. 16, and Fig. 19 shows the current/torque characteristics when the constant current control current value is changed. .

Claims (1)

[Scope of Claims] A pulse motor control device for a medium feeding mechanism that connects a pulse motor and a platen through a gear train and feeds a print medium while rotating the platen, comprising: (b) means for determining the average value of the values detected by the sensor; (c) means for comparing the average value with an initial value to determine a change value; and (d) the change value. A pulse motor control device comprising: means for determining an overdrive signal stored in a table from the table; and (e) means for determining a motor excitation current from the overdrive signal.