JP3018358B2 - Serial printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a serial printer with improved carriage running performance.

(Prior art) In a serial printer, a print head is mounted on a carriage, and a carriage drive mechanism for moving the print head left and right is provided.
This is a configuration driven by a DC motor. When a print command is given to a printer in which the carriage is stopped, the carriage needs to rise up with a shortest approach distance as soon as possible so that printing by the print head can be started immediately and enter a constant speed traveling state. . Therefore, this type of motor performs the following automatic control using, for example, PWM control.

That is, a rotary encoder is connected to the motor shaft, and a pulse is output at each predetermined rotation angle.
The period between the pulses (corresponding to the rotation speed of the motor) is obtained based on the encoder pulse train, and this is input to the microcomputer, and the control corresponding to the speed is executed. For example, as shown in FIG. 3, the motor is continuously energized (duty ratio 1) until the actual rotation speed ω _(t) reaches the speed ω ₂ from the state where the motor is stopped, and the speed ω
From ₂ to reach the speed omega ₁ motor is energized at a duty ratio of x _2, the motor is energized from the speed omega ₁ to reach the target velocity omega ₀ at a duty ratio of _{x 1 (x 1 <x 2} ) . Then, after the motor speed ω _(t) reaches the target speed ω ₀ , the motor is energized at the duty ratio x _0h when the speed exceeds the speed ω ₀ and x when the motor speed ω _(t) is lower than the target speed ω _0. field-back control for energizing at a duty ratio of _0l (x _0l> x _0h) is executed. The reason for gradually decreasing the duty ratio with ₁ → x 1 → x ₂ in the energizing pattern to reach the target velocity omega ₀ as described above, to reach the rotation speed of the motor as soon as possible to the target speed omega ₀ In order to suppress overshoot as much as possible.

In the conventional configuration, various control parameters (that is, the speeds ω ₂ , ω ₁ and the duty ratios x ₁ , x ₂ , x _0l , x _0h ) for performing such automatic control are _stored in memory as one value in advance. The microcomputer reads and refers to this as necessary, but these control parameters are fixed and cannot be changed in the middle.

(Problems to be Solved by the Invention) However, in a motor for driving a mechanism unit such as a carriage driving mechanism of a printer, the load of the motor is aging.
It cannot be avoided that it changes over time. The cause is
Changes in various external conditions, such as a change in the winding resistance of the ribbon due to a decrease in the amount of ink contained in the ink ribbon and an increase in friction of the bearing portion due to lack of oil, etc., can be cited. For this reason, fixed control parameters make it impossible to follow a change in load.For example, the carriage does not enter a constant speed traveling state until a position at which printing by the print head is actually started, which causes a disturbance in the printing position. This causes problems such as a decrease in print quality. In addition, even if a new printer has just been manufactured, even if a new printer has just been manufactured, there is a variation in control in each printer due to a variation in accuracy of each component constituting the mechanical unit. There is also a problem that variations between products occur, such as a different printing position depending on the product.

The present invention has been made in view of the above circumstances. Accordingly, an object of the present invention is to provide a serial printer capable of maintaining optimal automatic control, that is, optimal traveling control of a carriage and ensuring printing reliability even when a motor load changes with time or the like.

[Structure of the Invention] (Means for Solving the Problems) A serial printer according to the present invention includes a carriage having a print head, a motor for running the carriage, and a PWM signal generating circuit.
A driving unit for driving the motor at a duty ratio by a signal generation circuit, and at least one intermediate speed smaller than a target speed is set in advance, and when the carriage is accelerated from the start of travel toward the print start point, The motor is started at the start duty ratio from the start until the intermediate speed is reached, and after reaching the intermediate speed, the motor acceleration control is performed at an acceleration duty ratio smaller than the start duty ratio. Motor drive control means for driving the motor at a deceleration duty ratio when the rotation speed exceeds the target speed, and driving the motor at a speed increase duty ratio when the rotation speed is lower than the target speed;
Until the motor reaches the target speed, the rotation speed of the motor is measured at least once at a predetermined time corresponding to the intermediate speed, and the measured rotation speed at the predetermined time does not reach the intermediate speed. Sometimes, the intermediate speed is changed to a larger value, and when the measured rotation speed is higher than the intermediate speed, the setting of the acceleration duty ratio is changed, and after the rotation speed of the motor reaches the target speed, the rotation speed of the motor is changed. When the speed exceeds the target speed by a predetermined value, the setting is changed so as to decrease the duty ratio for deceleration, and when the rotation speed of the motor falls below the target value by a predetermined value, the duty ratio for speed increase is increased. It is characterized by a configuration provided with a changing means for changing the setting.

(Operation) Regarding the traveling control of the carriage, the acceleration control when accelerating from the start of traveling toward the printing start point and the low-speed control when printing after acceleration is affected on the printing reliability. Is what you do. In the above configuration, when the carriage is accelerated from the start of its travel toward the printing start point, the motor is started at the start duty ratio until the set intermediate speed is reached from the start of the motor. After reaching the intermediate speed, the motor is controlled at an acceleration duty ratio smaller than the start-up duty ratio, and when the motor rotation speed exceeds the target speed, the motor is driven at the deceleration duty ratio. When the speed falls below the target speed, the motor is driven at the speed increasing duty ratio.

Until the motor reaches the target speed, at a predetermined time corresponding to the intermediate speed, measure the rotation speed of the motor at least once, and when the measured rotation speed at the predetermined time has not reached the intermediate speed, The intermediate speed is changed to a larger value, and control is performed so as to increase the time during which the motor is driven at a large duty ratio to enhance the acceleration.
On the other hand, when the measured rotational speed is higher than the intermediate speed, the acceleration duty ratio is set and changed, and the acceleration is suppressed so as to prevent the overshoot from the target speed from becoming excessive. Therefore, when a change occurs in the load of the motor and the rising rotation speed of the motor deviates from the appropriate range, the rising rotation speed of the motor is changed by adjusting the duty ratio for driving the motor as described above. As a result, the start-up operation of the motor is optimized, and the running reliability of the carriage during acceleration is ensured.

After the rotation speed of the motor reaches the target speed, when the rotation speed of the motor exceeds the target speed by a predetermined value, the setting is changed so that the deceleration duty ratio is reduced, and the rotation speed of the motor is adjusted to the target speed. Since the speed is controlled so as to change the setting so as to increase the duty ratio for speed increase when the speed falls below a predetermined value, even if the motor load changes, the constant speed rotation speed is optimized. Thus, the running reliability of the carriage is ensured. In general, traveling reliability is ensured during acceleration and constant speed.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS.

The mechanical configuration is as schematically shown in FIG. 4. The carriage 11 to which the print head 10 is attached is capable of reciprocating left and right along the guide bar 12, and is mounted on the carriage 11 with the movement. This is a well-known configuration in which an ink ribbon (both not shown) of an ink ribbon cassette is gradually wound. The carriage 11 is driven by the motor 1 via a belt 13. The rotary encoder 2 is attached to the drive shaft 1a, and a pulse is output from the rotary encoder 2 every time the drive shaft 1a rotates by a minute predetermined angle. Therefore, when the rotation of the motor 1 is at a low speed, the pulse period is long, and when the rotation is high, the pulse period is short. As shown in FIG. 2, the rotary encoder 2
Is supplied to the period measuring circuit 3, where the speed ω _(t) of the motor 1 corresponding to the pulse period is calculated,
A speed signal corresponding to the speed ω _(t) is input to the CPU 4. As will be described in detail later, the CPU 4 performs PWM control of the motor 1 in accordance with the speed signal.
A signal generation circuit 5 and a motor drive circuit 6 are provided. The PWM signal generating circuit 5 receives the torque command τ ^* from the CPU 4 and generates a PWM signal having a pulse width corresponding to the torque command τ ^* ,
Based on this, the motor drive circuit 6 energizes the motor 1.
Further, a self-tuning mode setting switch 7 is connected to the CPU 4, and when the self-tuning mode is set based on the operation of this switch, the CPU 4 may rewrite control parameters for automatic control as described later. become able to.

The control parameters for automatic control of the motor 1 include the intermediate speeds ω ₂ , ω ₁ and the duty ratios x ₁ , x
₂ , x _0l , x _0h, etc., and these specific numerical values are stored in the control parameter storage means 8 in advance. And
The CPU 4 reads out these control parameters stored in the control parameter storage means 8 and performs the following control with reference to these as appropriate. The control parameter storage means 8 is composed of a writable and erasable ROM (EPPROM),
It is possible to rewrite the stored control parameters, and the information newly stored by the rewriting is not lost even if the power of the printer is cut off, and continues to be stored.

First, when a start signal of the motor 1 is given, the CPU 1 sends the actual speed ω of the motor 1 given from the cycle measuring circuit 3.
_{(t), the} control parameter memory means by comparing the initial value of the intermediate velocity omega ₂ and read from 8, between the actual speed omega _(t) is lower than the intermediate speed omega ₂ in the motor 1 at a duty ratio of 1
Is turned on. As a result, the speed ω _(t) rises rapidly. After the rotation speed ω _(t) reaches the intermediate speed ω ₂ , the actual speed ω _(t) is compared with the initial value of the intermediate speed ω ₁ read from the control parameter storage means 8. Speed ω
_(t) is lower speed range than the middle speed _{ω 1 (ω 2 ≦ ω (} t) <
ω ₁ ), the motor 1 is energized with the initial value of the duty ratio x ₂ read from the control parameter storage means 8 (x ₂
<1). As a result, the motor 1 is further accelerated, the rotational speed omega _(t) is to reach the intermediate speed omega _1. Then the CPU
4 shifts to a state where the speed ω _(t) is compared with the target speed ω ₀ . Speed range where the speed ω _(t) is lower than the target speed ω ₀ (ω ₁ ≦ ω _(t)
<Ω ₀ ), the motor 1 is energized with the initial value of the duty ratio x ₁ read from the control parameter storage means 8 (x ₁ <x ₂ ). Thus, the motor 1 is further accelerated, the rotational speed of finally becomes greater than the target speed omega _0. Then, the CPU 4 reads the initial value of the value x _0h set as the duty ratio when the target speed exceeds the target speed ω ₀ from the control parameter storage means 8 (x _0h <x ₁ ), and based on this, the motor 1 Is turned on. As a result, when the rotation speed ω _(t) of the motor 1 decreases and falls below the target speed ω ₀ , the initial value of the duty ratio x _{0l in} this case is read from the control parameter storage means 8 (x _0l > x _0h ). The motor 1 is energized based on this. Hereinafter, when the motor speed exceeds the target speed ω ₀ , the motor 1 is energized at the duty ratio x _0h , and when the motor speed is lower than the target speed ω ₀ , feedback control is performed to energize the motor 1 at the duty ratio x _0l. printing is started at the time t _p became is maintained substantially at the target velocity omega _0.

By the way, in this type of printer, when printing is repeated, the load of the motor 1 changes with the passage of time due to a change in the winding resistance of the ribbon due to a decrease in the amount of ink contained in the ink ribbon, an increase in friction of the bearing portion due to lack of oil, and the like. Inevitably change over time and over time. In addition, even in a printer immediately after manufacturing, the load of the motor 1 may greatly differ from product to product due to variations in components and the like. Therefore, in the present embodiment, the CPU 4 not only automatically controls the motor 1 as described above, but also measures the control result by the automatic control, and determines that the control result measured by the measuring means is within a predetermined range. Determining means for determining whether or not the control parameter is within the predetermined range; and when the determining means determines that the control result deviates from a predetermined range, the control parameter storing means 8
Is configured to function as control parameter changing means for rewriting each control parameter stored in the.
Since these functions are provided by the software of the CPU 4, they will be specifically described with reference to the flowchart of FIG.

First, during the normal printing operation, the CPU 4 reads the actual speed ω _(t) of the motor 1 as a control result by the automatic control (step S1). Next, it is determined whether or not the self-tuning mode is set, that is, whether or not the self-tuning mode setting switch 7 has been pressed (step S2). Here, if the self-tuning mode is set, the rewriting frequency counter X is initialized to “0” (step S3), and then the actual speed ω of the motor 1 is increased.
_It is determined whether or not _(t) is within a predetermined speed range (step S4). This is because it is determined whether or not the actual speed ω _(t) is equal to or lower than the upper limit speed ω _{m in} the area before the start of printing, and the actual speed ω _(t) is changed by a predetermined fluctuation range ± in the area after the start of printing.
This means that it is determined whether or not it is within Δω. If the speed ω _(t) of the motor 1 is not within the predetermined speed range (“NO” in step S4), the control parameters stored in the control parameter storage unit 8 are rewritten as follows.

First, when a predetermined time has elapsed since the start time t ₀
The speed and acceleration at t ₂ and t ₁ are measured in advance. If these results do not reach the predetermined value, it means that the rise is slow. Therefore, among the five control parameters stored in the control parameter storage means 8, the intermediate speed ω ₂ ,
A predetermined calculation based on the measurement result is performed so that ω ₁ is set to a larger value. If the intermediate speeds ω ₂ and ω ₁ are set to larger values, the motor 1 is energized with a large duty ratio at the time of start-up, so that the acceleration performance is improved. Conversely, when the speed and the acceleration measured at the time points t ₂ and t ₁ exceed the predetermined values, it means that the rise is too early, so that the overshoot becomes excessive and the speed stabilizes. It will take time. Therefore, a predetermined calculation based on the measurement result is performed to reduce the duty ratios x ₁ and x ₂ among the five control parameters stored in the control parameter storage unit 8. This is because if the duty ratios x ₁ and x ₂ at the time of rising are set to smaller values, acceleration is suppressed and overshoot is reduced. Further, when the actual speed region after the print start t _p omega _{of (t)} is out of the predetermined variation width ± [Delta] [omega, when for example the speed omega _(t) exceeds {ω _{0 +} Δω} are five control parameters Duty ratio
A predetermined calculation is performed to reduce _x0h and suppress the motor current. Conversely, when the speed ω _(t) falls below {ω ₀ −Δω}, a predetermined calculation is performed to increase the duty ratio x _0l and increase the motor current.

Thereafter, it is determined whether or not the calculation results are within a normal range (step S6). If the calculation results are outside the range, an error is displayed on a display device (not shown). Then, the rewriting of the control parameters is terminated by storing the information (step S7).

Next, by incrementing the number of times of rewriting counter X (step S8), (step S9) on condition that less than the maximum number of times of rewriting X _m, to perform a test run reached the step S10. In this test run, the motor 1 is controlled based on the newly rewritten control parameters, and the actual speed ω _(t) of the motor 1 as a result of the control is read. Then, returning to step S again, it is determined whether or not the speed ω _(t) is within a predetermined speed range. When the speed ω _(t) falls within the predetermined speed range as a result of the control parameter rewriting, the process returns to the normal automatic control, and the monitoring of the actual speed ω _(t) is continued. If the speed ω _(t) does not fall within the predetermined speed range even though the control parameters have been rewritten, steps S5, S6, and S7 are repeatedly executed again to rewrite the control parameters. Despite the re-writing, the speed ω in step S4
_{when (t)} is determined not to fall within the predetermined speed range, an error display is performed at reaching the maximum number of times of rewriting X _m (step S15).

When the control parameters are forcibly rewritten by an external device such as a host computer, the self-tuning mode setting switch 7 is operated to release the self-tuning mode. Therefore, after rewriting the counter X of the number of rewrites to "0" (step S11), it is determined whether or not there is an external designation of a control parameter from an external device such as a host computer (step S12). The data is written in the parameter storage means 8 (step S13), and a test run is executed based on the control parameters (step S1).
0). Results of the execution of this test run, if the speed omega _(t) is fit there within a predetermined speed range, return to the normal automatic control is continued monitoring of the actual speed omega (t), velocity omega _(t) is given If the speed does not fall within the speed range, steps S5, S6,
The control parameters are calculated and rewritten by repeatedly executing S7.

As described above, according to the present embodiment, when the friction of the bearing portion increases due to, for example, running out of oil, and the load on the motor 1 increases, the actual speed ω of the motor 1 during the printing operation is increased.
_{When (t)} falls below {ω ₀ −Δω}, “NO” is given in step S4. For this reason, in steps S5 to _S7 , rewriting of the control parameters for increasing the duty ratios x _0l , x _0h is executed, whereby the motor 1 is driven with a larger current, and the actual speed ω _(t) Is the target speed ω ₀
Will be maintained. Also, when there is a decrease in the torque of the motor 1 or a change in the ribbon winding resistance due to the deterioration of the motor brush, the actual speed ω _(t) of the motor 1 does not fall within a predetermined speed range. When this happens, the control parameters are also rewritten to correct the speed ω _(t) so as to fall within the predetermined speed range, and then automatic control is performed using appropriate control parameters. In addition, if the self-tuning is performed immediately after assembling the product, the variation in the product can be easily eliminated irrespective of the variation in component accuracy or the variation in assembly.

[Effects of the Invention] As described above, according to the present invention, even if a change occurs in the load on the motor, the motor is driven at a predetermined speed in the acceleration control from the stop state to the print start point. As described above, the motor can be started up quickly, and the constant speed control of the motor where the carriage performs the constant speed printing operation thereafter can be appropriately maintained, so that there is an excellent effect that the printing reliability can be secured well. .

[Brief description of the drawings]

1 to 4 are diagrams for explaining an embodiment of the present invention. FIG. 1 is a flowchart, FIG. 2 is a block diagram, and FIG. 3 is a graph showing a speed change of an automatically controlled motor. FIG. 4 is a perspective view showing a mechanical structure of a main part. In the drawings, 1 is a motor, 4 is a CPU (motor drive control means,
Change means) and 8 are control parameter storage means.

Claims (1)

(57) [Claims] 1. A carriage on which a print head is mounted, a motor for driving the carriage, a driving means having a PWM signal generating circuit for driving the motor at a duty ratio by the PWM signal generating circuit, At least one small intermediate speed is set, and when the carriage is accelerated from the start of traveling toward the printing start point, the motor is started at a start duty ratio from the start of the motor until the intermediate speed is reached. After reaching the intermediate speed, the motor acceleration control is performed at an acceleration duty ratio smaller than the start-up duty ratio, and when the motor rotation speed exceeds the target speed, the motor is driven at the deceleration duty ratio, Motor drive control means for driving the motor at a speed increasing duty ratio when the speed falls below; Until the target speed is reached, at a predetermined time corresponding to the intermediate speed, measure the rotation speed of the motor at least once, and when the measured rotation speed at this predetermined time has not reached the intermediate speed, The intermediate speed is changed to a larger value, and when the measurement circuit speed is higher than the intermediate speed, the setting of the duty ratio for acceleration is changed, and after the rotation speed of the motor reaches the target speed, the rotation speed of the motor is changed. When the motor speed exceeds the target speed by a predetermined value, the setting is changed so as to decrease the duty ratio for deceleration, and when the rotational speed of the motor becomes lower than the target value by a predetermined value, the duty ratio for increasing the speed is set to increase. A serial printer, comprising: changing means for changing.