JP2004167787A - Recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that accuracy of carriage is not enhanced when a carrying means is controlled by using a low resolution encoder. <P>SOLUTION: Speed information obtained from an encoder is compared with a target speed profile and if it is different from the target speed profile, speed is predicted based on the speed information obtained from the encoder and a carrying means is controlled based on the predicted information. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a recording device.
[0002]
[Prior art]
The basic configuration of a recording device (for example, a serial type printer) is that a print head is mounted on a carriage and is scanned left and right to record one band (for example, 128 nozzle width) on printing paper (recording medium). I do. This carriage driving mechanism is driven by a DC motor. In a normal printer, a line feed (transport) drive mechanism for transporting one band of printing paper after the carriage driving is completed is also driven by a DC motor similarly to the carriage.
[0003]
As the actual drive, when the print operation by the carriage drive is completed, the line feed drive immediately conveys the paper, and the line feed operation is performed in a short time and as high as possible so that the carriage can smoothly perform the next print. It is desired to end with accuracy. Therefore, this type of DC motor performs the following automatic control using, for example, PWM control.
[0004]
That is, a rotary encoder is connected to the DC 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 signal, and this is input to the microcomputer and the control corresponding to the speed is executed.
[0005]
Actually, the motor is driven so that the rotational speed of the motor follows a speed target curve called a target speed profile created in advance before the line feed driving. Here, the change of the driving state using the target speed profile will be described with reference to FIG.
[0006]
In this graph, the horizontal axis represents time [t] and the vertical axis represents speed [V], and shows the rotation state of the motor shaft driven by the motor. At first, the acceleration control is continued so as to reach the first target speed [V1] in [t1] seconds after the state in which the motor is stopped [V0], and after reaching the first target speed, [t2] at a constant speed. The constant speed control is performed until the second. After elapse of [t2] seconds, deceleration control is continued until after [t3] seconds, and low speed control is performed at the second target speed [V2] until after [t4] seconds.
[0007]
[Problems to be solved by the invention]
In this case, what is important in the line feed driving is to reduce the driving time and to reduce the speed [V2]. In other words, in order to stop with high accuracy, the speed [V2] is lowered as much as possible to stop in a short time. However, in the case of driving by a DC motor, the time interval of the pulse information from the rotary encoder in the low-speed driving region. And the accuracy of the speed information is reduced. As described above, when the accuracy of the speed information from the encoder is low, appropriate PWM control cannot be performed, the second target speed after [t3] is not stabilized, and the time variation until stopping is not achieved. Is generated, and the stoppage of the conveyed sheet is shifted.
[0008]
In addition, for a motor that drives a mechanism such as a line feed drive mechanism of a printer, the drive load changes over time and over time. Causes of this include changes in encoder and motor accuracy due to ink adhering from the recording head, changes in the state of the printer, such as an increase in friction of the bearing portion due to lack of oil, and the like.
[0009]
Further, in the case of a serial printer having a small body size, a rotary encoder capable of obtaining high accuracy cannot be incorporated in the device, and a rotary encoder having a low resolution may be unavoidably used. As a result, printing (recording) quality is degraded due to reduced transport accuracy, such as variations in the stop position of the transported paper, because control is performed with information that is less accurate than the information precision obtained with a high-resolution rotary encoder. There was a problem of doing.
[0010]
Further, in addition to the above-mentioned temporal change factors, even immediately after manufacturing, variations in the characteristics of the respective printers occur due to variations in the accuracy of the components constituting the mechanical unit. As a result, there is also a problem that variations between products occur, such as different printing positions for individual printers.
[0011]
The present invention has been made in view of the above circumstances. Therefore, the purpose is to maintain the second target speed by performing the optimum automatic speed control even when a low-resolution encoder is used in the line feed section of the serial printer or when there is a change with time, and the optimum paper feed is performed. An object of the present invention is to provide a recording apparatus capable of realizing high image quality and high reliability by performing control.
[0012]
[Means for Solving the Problems]
The recording apparatus according to the present invention includes: a motor that conveys a recording medium; an encoder that outputs a signal as speed information of the motor; and a setting unit that sets the motor to a first target speed and a second target speed. A speed prediction unit that calculates a speed prediction value based on the speed information so as to maintain the target speed, and a motor that controls driving of the motor based on a speed prediction value signal calculated by the speed prediction unit. The control means is provided.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 3 is a perspective view of the ink jet recording apparatus (printer). A recording head 105 is mounted on a carriage 104 and is capable of reciprocating in a longitudinal direction along a shaft 103. The ink discharged from the recording head reaches the recording material (recording medium) 102 whose recording surface is regulated by the platen 101 at a minute interval from the recording head, and forms an image thereon.
[0014]
An ejection signal is supplied to the print head via the flexible cable 119 in accordance with image data. Reference numeral 114 denotes a carriage motor for scanning the carriage 104 along the shaft 103. Reference numeral 113 denotes a wire that transmits the driving force of the motor 114 to the carriage 104. Reference numeral 118 denotes a transport motor that is coupled to the platen roller 101 to transport the recording material 102.
[0015]
The transport motor is a DC motor, and feedback control is performed by pulse information (PWM signal) from a rotary encoder directly or indirectly attached to the motor.
[0016]
The resolution of the recording head is 600 DPI. This recording head has an ink jet system in which 320 recording elements for black and 128 recording elements for color are arranged. The recording element includes a driving unit and a nozzle, and the driving unit can apply heat to the ink by a heater. The ink causes the film to boil due to the heat, and the pressure change caused by the growth or shrinkage of the bubble due to the film boiling causes the ink to be ejected from the nozzle.
[0017]
<Example 1>
When the rotation speed of the DC motor is low, the pulse period becomes long, and accurate speed information cannot be obtained. Therefore, by performing a speed prediction process, accurate DC motor control is performed.
[0018]
Hereinafter, description will be made with reference to the flowchart of FIG. As preparation before driving, a minimum acquisition speed (Vlimit), a target stop position, and a target speed profile that do not require speed prediction from the resolution of the currently used encoder are calculated (1-1). Using the periodic timer in the printer, the subsequent processing is repeated until the target position calculated in (1-1) is reached.
[0019]
When an interruption of the period timer occurs, speed information and position information are obtained from the rotary encoder (1-2). Next, it is determined whether the recorded speed information value is lower than the minimum acquisition speed (V limit) calculated in (1-1) (1-3).
[0020]
If the obtained speed information is lower than the minimum acquisition speed (V limit), the drive position is determined from the position information acquired in (1-2), and the acceleration drive regions (t0 to t1), FIG. It is checked which one of the constant speed drive area (t1 to t2), the deceleration drive area (t2 to t3) and the low speed drive area (t3 to t4) belongs (1-4). Note that t0 is the origin of time t.
[0021]
Therefore, if the drive area at the time of information acquisition is the acceleration drive area or the constant-speed drive area, the speed information acquired by the previous cycle timer is used for the current cycle timer even if the speed is lower than the minimum acquisition speed. (1-5).
[0022]
If the drive attribute at the time of information acquisition is the deceleration drive area or the low-speed drive area, the previously acquired speed information is compared with the target speed profile (1-6).
[0023]
If the previously obtained speed information is lower than the speed information calculated from the target speed profile, the predicted speed information is calculated based on the speed prediction method for underspeed, and is set as the speed information obtained during the current cycle timer ( 1-72). The calculation method includes a method using a moving average for speed prediction, a speed hold process, and the like. In the present embodiment, for example, a speed hold method is used. Note that the speed prediction method is not limited to this method, and another method may be used.
[0024]
On the other hand, when the previously recorded speed information is higher than the speed information calculated from the target speed profile, the predicted speed is calculated based on the speed prediction method for overspeed, and is set as the speed information acquired during the current cycle timer. (1-71).
[0025]
Then, the speed information derived in (1-5), (1-71), and (1-72) is stored for use in prediction calculation of the speed information in the next periodic timer (1-8).
[0026]
Next, PID control is performed using the speed information stored in (1-8) to actually drive the DC motor (1-9). Next, it is determined whether the target position has been reached (1-10). If it has not reached, the process returns to (1-2) and the repetitive processing is executed. This operation is repeated until the target position set in (1-1) is reached.
[0027]
As described above, according to the present embodiment, the low-speed region in which the speed information cannot be obtained from the rotary encoder is predicted from the current position information and the previously calculated speed information, and the speed is controlled to perform the low-resolution encoder. In this case, stable low-speed driving is possible. Stop position accuracy is improved.
[0028]
<Example 2>
In the first embodiment, the speed prediction method in the deceleration region and the low speed region has been described. However, another speed prediction method will be described. As described in the first embodiment, there is a minimum acquisition speed (V limit) at which an accurate speed cannot be obtained in a low-resolution rotary encoder.
[0029]
The deceleration control area is the stage before shifting to the low-speed control area, and is the section that has the highest effect on low-speed control. Therefore, stabilizing the deceleration control area leads to stable driving in the low-speed control area.
[0030]
In general, the time required for deceleration in a speed target profile is often very short. Therefore, the speed change in the periodic interrupt unit becomes extremely large compared to the low speed region. Therefore, if the same speed prediction as the speed prediction in the low speed region is performed as described in the first embodiment, the control becomes different from the speed target profile. Would.
[0031]
In other words, if the speed prediction coefficient in the deceleration region is the same as the control coefficient in the low speed region, sufficient speed control cannot be performed in the deceleration region.
[0032]
Therefore, by providing a suitable speed prediction means (speed prediction coefficient) in the deceleration area separately, stable deceleration control can be performed, and low-speed control can be stabilized. FIG. 4 shows this control flow. The description of the same parts as in FIG. 1 described in the first embodiment will be omitted (additional parts are surrounded by dotted lines for easy understanding).
[0033]
In this control flow, in (4-4), it is determined whether the region is a low speed region, a deceleration region, an acceleration region or a constant speed region. In the deceleration region, speed prediction for the deceleration region (speed prediction for overspeed, speed prediction for underspeed) is performed, and in the low speed region, speed prediction for the low speed region having different coefficients (speed prediction for overspeed). , Speed prediction for underspeed).
[0034]
As described above, by changing the speed prediction method depending on the currently driven area, more optimal speed control is performed, and the accuracy of the transporting means is improved.
[0035]
【The invention's effect】
As described above, according to the present invention, when a low-resolution encoder is used to control the DC motor at a low speed, the control at the low speed of the first target speed and the second target speed By controlling the speed by providing the speed, the transfer accuracy of the transfer motor can be increased.
[Brief description of the drawings]
FIG. 1 is a flowchart illustrating a procedure for performing speed prediction according to a first embodiment.
FIG. 2 is an explanatory diagram of a speed target profile.
FIG. 3 is a perspective view of a recording apparatus.
FIG. 4 is a flowchart showing a procedure for performing speed prediction in the second embodiment.

Claims (1)

A motor for transporting the recording medium,
Encoder means for outputting a signal as motor speed information;
Setting means for setting the motor to a first target speed and a second target speed;
Speed prediction means for calculating a speed prediction value to maintain the target speed based on the speed information,
A recording apparatus comprising: a motor control unit that controls driving of the motor based on a predicted speed value signal calculated by the speed prediction unit.

Images