JP4182795B2 - Paper feed mechanism of printing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a paper feeding mechanism of a printing apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a paper feed mechanism of an ink jet printer apparatus, a stepping motor that is rotationally controlled by a pulse signal is used as a rotation drive motor for a paper feed roller. In recent printer apparatuses, DC motors have been adopted instead of stepping motors because of the demand for higher printing speed. At the same time, it is strongly desired to improve the printing quality, and this demand is met by increasing the printing resolution.
[0003]
In order to increase the printing resolution, it is indispensable to increase the accuracy of the paper feed stop position. However, it is generally difficult to control the rotation of the DC motor more accurately than the stepping motor. It is difficult to stop the paper feed roller. Therefore, a conventional printer using a DC motor detects the rotation of the paper feed roller using an analog rotary encoder, and increases the resolution of the AD conversion of the analog signal output from this encoder. The rotation of the motor is accurately detected, and the timing for applying the brake to the DC motor is accurately controlled.
[0004]
FIG. 5 shows a waveform of a signal output from the analog rotary encoder described above. The waveform of the analog signal is obtained by amplifying an electric signal obtained by photoelectrically converting the optical signal received by the light receiving unit of the rotary encoder. The analog signal having the waveform shown in the figure is converted into a digital signal by the AD converter, and this digital signal is input to the motor control circuit. In an analog type rotary encoder, at the time of AD conversion, for example, the analog signal from the bottom value to the peak value of the waveform is divided into 10 parts to increase the resolution of AD conversion. It is possible to accurately detect the rotation.
[0005]
By the way, in the time recorder, the DC motor is rotated at a low speed in a certain section before the stop target position, and then the DC motor is stopped to improve the stop position accuracy and durability of the DC motor. It is known (see, for example, Patent Document 1). Further, there is known a motor control device that performs a drive chopping operation of an H-type drive circuit based on a pulse signal obtained from an encoder, and further switches a drive chopping operation to perform a brake chopping operation (for example, Patent Document 2). reference). Furthermore, the developing device counts the time from the start of driving of a plurality of developing devices until the predetermined process speed is reached, and controls the start-up of each developing device based on the time, thereby developing regardless of the driving load. A device configured to prevent the apparatus from shifting is known (for example, see Patent Document 3).
[0006]
[Patent Document 1]
JP-A-11-149318 [Patent Document 2]
JP 2001-275374 A [Patent Document 3]
Japanese Patent Laid-Open No. 2003-5488
[Problems to be solved by the invention]
In the above-described printer using a conventional DC motor, an AD converter for converting an analog signal into a digital signal and firmware for controlling the AD converter are necessary, so that the apparatus becomes expensive. Even if the AD conversion resolution is increased and the brake start timing of the DC motor can be accurately controlled, there is no guarantee that the roller can be stopped at an accurate stop position.
[0008]
Further, when the technique related to the time recorder disclosed in Patent Document 1 is applied to a printer device, the accuracy of the stop position of the DC motor can be increased to some extent as compared with the case where the DC motor is stopped at a stroke from the normal rotation speed. Although it is possible, the accuracy cannot be increased to the extent that it can be applied to a high-resolution printer. Furthermore, even if the techniques disclosed in Patent Document 2 and Patent Document 3 are applied, the above-described problems cannot be solved.
[0009]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. A paper feed mechanism for a printer apparatus that can increase the accuracy of a stop position of a print paper with an inexpensive configuration while using a DC motor for feed driving. The purpose is to provide.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention provides a paper feed roller for feeding a printing paper, a DC motor for rotationally driving the paper feed roller, an encoder for detecting the rotation of the paper feed roller, In a paper feeding mechanism of a printing apparatus including a motor control unit that controls a DC motor based on an output signal, the encoder outputs a predetermined digital signal corresponding to the rotation angle of the paper feeding roller, and the motor control unit prints When the device is turned on, the drive voltage of the DC motor is gradually increased to detect the minimum drive voltage when the paper feed roller starts to rotate, the minimum drive voltage is stored, and the predetermined drive higher than the minimum drive voltage When driving the DC motor with voltage and stopping the printing paper feed, the brake voltage is applied to the DC motor before the fixed stop position, and the rotation of the paper feed roller After that, the DC motor is driven with the lowest drive voltage, the paper feed roller is rotated at the lowest speed, and when it is detected from the digital signal output by the encoder that the printing paper has reached the stop position, the lowest The driving of the DC motor by the driving voltage is stopped to stop the rotation of the paper feed roller.
[0011]
In this configuration, when the feed is stopped, the rotation of the paper feed roller is temporarily stopped before a predetermined stop position, and then the DC motor is driven with the minimum drive voltage detected in advance when the power is turned on. As a result, the paper feed roller is rotated at the minimum speed in preparation for stopping at the stop position, and when it is detected that the printing paper has reached the stop position, the paper feed roller can instantaneously feed the paper if the driving of the DC motor is stopped. Stopped. In addition, since the minimum drive voltage is detected and stored in advance when the power is turned on, even if the rotational characteristics of the DC motor change over time, the DC motor is driven with the minimum drive voltage at that time. Therefore, the accuracy of the stop position of the paper described above is maintained satisfactorily. The digital signal output from the encoder is input to the motor control circuit and processed without going through the AD converter.
[0012]
According to a second aspect of the present invention, a paper feed roller that feeds printing paper, a DC motor that rotationally drives the paper feed roller, an encoder that detects rotation of the paper feed roller, and a DC motor based on an output signal of the encoder In the paper feeding mechanism of the printing apparatus including the motor control unit for controlling the rotation of the paper feeding roller, the motor control unit applies a brake voltage to the DC motor before the stop position determined when the printing paper feed is stopped. After that, the DC motor is driven at the lowest drive voltage at which the DC motor rotates, the paper feed roller is rotated at the minimum speed, and it is detected from the encoder output signal that the printing paper has reached the stop position. At this time, the driving of the DC motor by the minimum driving voltage is stopped to stop the rotation of the paper feed roller.
[0013]
In this configuration, when the feed is stopped, the rotation of the paper feed roller is temporarily stopped before a predetermined stop position, and then the DC motor is driven with the minimum drive voltage. As a result, the paper feed roller is rotated at the minimum speed in preparation for stopping at the stop position, and when it is detected that the printing paper has reached the stop position, the paper feed roller can instantaneously feed the paper if the driving of the DC motor is stopped. Stopped.
[0014]
According to a third aspect of the present invention, in the paper feeding mechanism of the printing apparatus according to the second aspect, the motor control unit gradually increases the driving voltage of the DC motor when the power of the printing apparatus is turned on, and the paper feeding roller Detects the minimum driving voltage when the motor starts to rotate, and stores the minimum driving voltage. In this configuration, since the minimum drive voltage is detected and stored in advance when the power is turned on, the DC motor is driven at the minimum drive voltage at that time even if the rotational characteristics of the DC motor change over time. Therefore, the accuracy of the stop position of the paper described above is maintained satisfactorily.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An ink jet printer apparatus provided with a paper feed mechanism according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an ink jet printer apparatus. The printer apparatus 1 receives the output of the DC motor 2 and feeds a printing paper P placed on the paper feed tray 3 into the apparatus main body, and a motor control circuit for PWM-controlling the rotation of the DC motor 2. 5 (motor control unit), an ink cartridge 7 having a head 6 for ejecting ink onto the fed paper P1, a carriage 8 for detachably storing the ink cartridge 7, and the like. The carriage 8 is supported by a shaft 9 so as to be slidable in the scanning direction, and is driven to slide by a head drive motor 10. The output of the head drive motor 10 is transmitted to the carriage 8 via the belt 11.
[0016]
The paper feed mechanism 4 includes paper feed rollers 21, 22, 23 for feeding the paper P 1, press rollers 24, 25 for bringing the paper P 1 into close contact with the paper feed rollers 22, 23, and a gear 26. The DC motor 2 that drives the feed roller 23, a disk-shaped rotor 27 that is mounted on the paper feed roller 23, an encoder 28 that detects the rotation of the rotor 27, and the like. The paper P1 is initially sent out by the paper feed roller 21. When the paper P1 is fed to the position where it contacts the paper feed roller 22, the paper feed roller 21 moves backward, and thereafter the paper P1 is fed by the paper feed roller 22 or the paper feed roller 23 in synchronization with the scanning of the head 6. The
[0017]
The motor control circuit 5 controls the DC motor 2 by PWM control. By increasing the drive voltage of the DC motor 2, the PWM duty increases and the rotational speed of the DC motor 2 increases. Conversely, by lowering the drive voltage of the DC motor 2, the PWM duty is reduced and the rotational speed of the DC motor 2 is lowered.
[0018]
By the way, in order to increase the resolution of the print image of the printer apparatus 1, the ink nozzles formed on the head 6 are miniaturized and gathered at a high density, and the paper P <b> 1 is aligned with the feed stop position when the head 6 is scanned. It is essential to stop it accurately. In the printer apparatus 1, the rotation angle of the paper feed roller 23 is detected by a signal output from a rotary encoder constituted by the rotor 27 and the encoder 28, and the motor control circuit 5 controls the rotation of the DC motor 2, The paper P1 is stopped at a predetermined stop position.
[0019]
FIG. 2 shows a rotary encoder. The diameter of the rotor 27 is about four times the diameter of the paper feed roller 23 in order to increase the detection accuracy of the rotation angle of the paper feed roller 23, and the light is emitted from the light emitting unit 31 of the encoder 28 in the vicinity of the outer periphery of the rotor 27. Slits 32 for transmitting the emitted light are formed at equal intervals in the circumferential direction. The encoder 28 includes a light emitting unit 31 for emitting light, a light receiving unit 33 that receives light emitted from the light emitting unit 31 and transmitted through the slit 32, and performs photoelectric conversion. The light emitting unit 31 and the slit 32 are arranged at positions facing each other with the slit 32 interposed therebetween. When the paper feed roller 23 rotates, the light emitted from the light emitting unit 31 is intermittently transmitted through the slit 32 and received by the light receiving unit 33. The electrical signal photoelectrically converted by the light receiving unit 31 is output from the encoder 28 as a digital signal via a comparator.
[0020]
In general, the resolution of the encoder 28 is determined by the density of the slits 32 and the diameter of the rotor 27. Therefore, when the rotation angle of the paper feed roller 23 is detected using the digital signal output from the encoder 28, in order to stop the rotation of the paper feed roller with high accuracy, the density of the slits 32 is increased and the diameter of the rotor 27 is increased. Must be increased. Increasing the density of the slits 32 causes an increase in the manufacturing cost of the rotor 27, and increasing the diameter of the rotor 27 hinders downsizing of the printer device 1. The paper feed mechanism 4 of this embodiment guarantees the accuracy of the stop position of the paper feed roller 23 by controlling the DC motor 2 so as to rotate the paper feed roller 23 at the minimum speed from before the stop position. High-resolution printing is possible while suppressing the manufacturing cost and size of the apparatus 1.
[0021]
FIG. 3 shows the waveform of the digital signal output from the encoder 28 during the time from the middle of feeding the paper P1 to the stop. This digital signal is directly input to the motor control circuit 5 without going through a signal conversion circuit such as an AD converter.
[0022]
Hereinafter, a feed operation during printing by the paper feed mechanism 4 of the printer apparatus 1 will be described with reference to FIG. At the start of printing, the paper P1 is fed at a constant speed by the paper feed roller 23, and a square wave pulse signal having the same period is output from the encoder 28. By counting this pulse signal, the rotation angle of the paper feed roller 23 is detected, and the position of the paper P1 is detected.
[0023]
The motor control circuit 5 counts a predetermined number of pulse signals and then detects that the pulse signal has switched from low to high at time T1, so that the paper P1 is a predetermined distance before the determined stop position. Can be reached. At this time, the motor control circuit 5 applies a brake voltage to the DC motor 2 to decelerate the rotation of the paper feed roller 23. As a result, as shown in FIG. 3, the cycle of the pulse signal output from the encoder 28 gradually increases, and the rotation of the paper feed roller 23 stops at time T2.
[0024]
Thereafter, the motor control circuit 5 drives the DC motor 2 at the minimum drive voltage at time T <b> 3, and the paper feed roller 23 is rotationally driven at the minimum speed of the DC motor 2. Along with this, a pulse signal with a long cycle is output from the encoder. Here, the minimum drive voltage refers to a voltage at which the paper feed roller 23 starts to rotate when the drive voltage of the stopped DC motor 2 is gradually increased. It is detected when power is turned on (at the time of initial operation) and stored in a memory in the motor control circuit 5. The time T3 may be simultaneous with the time T2.
[0025]
When the motor control circuit 5 counts a predetermined number of pulse signals after time T1 and detects that the pulse signal has switched from low to high (time T4), it detects that the paper P1 has reached the stop position. Then, the driving of the DC motor 2 by the minimum driving voltage is stopped. After time T3, the paper feed roller 23 rotates at the minimum speed. Therefore, when the driving of the DC motor 2 is stopped, the rotation of the paper feed roller 23 is instantaneously stopped, and the paper P1 is accurately positioned at the determined stop position. Stop.
[0026]
Next, processing of the motor control circuit 5 from power-on to printing end will be described with reference to FIG. When the printer apparatus 1 is turned on (# 1), the voltage of the DC motor 2 is gradually increased to detect the minimum PWM duty (# 2), and the minimum PWM duty is stored (# 3). When a print start command is input to the printer 1 (YES in # 4), the DC motor 2 is driven to feed the paper P1 (# 5). When the paper P1 reaches the position just before stopping (YES in # 6), the driving of the DC motor 2 is temporarily stopped (# 7). Thereafter, the DC motor 2 is driven with the lowest PWM duty stored in # 3, and the paper feed roller 23 is rotated at the lowest speed (# 8). When it is detected that the paper P1 has reached the stop position (# 9), the DC motor 2 is stopped to stop feeding the paper P1 (# 10), and the head driving motor 10 is driven to scan the head 6. And print for one stroke (# 11). The processes of # 4 to # 11 are repeated until the end of printing (YES in # 12). If NO in # 6, the process returns to # 5, and if NO in # 9, the process returns to # 8.
[0027]
According to the paper feed mechanism 4 of the printer apparatus 1 operating as described above, the motor control circuit 5 temporarily stops the rotation of the paper feed roller 23 before the determined stop position, and then turns the paper feed roller 23 off. Since the rotation of the DC motor 2 is stopped when the rotation is made at the lowest speed and the stop position is reached, the sheet P1 stops accurately at the determined stop position. As a result, the paper P1 can be accurately fed in correspondence with printing with an increased resolution, and the printing quality of the printer apparatus 1 can be improved.
[0028]
In addition, since the minimum drive voltage for rotating the paper feed roller 23 at the minimum speed is detected and stored in advance when the power is turned on, even if the rotational characteristics of the DC motor 2 slightly change due to long-term use, the paper P1 The accuracy of the stop position is maintained well.
[0029]
Further, since the encoder 28 that outputs a digital signal is used, an AD converter that is required in a paper feeding mechanism driven by a conventional DC motor is not necessary, and the firmware of the motor control circuit 5 is simply configured. The manufacturing cost of the printer apparatus 1 can be reduced.
[0030]
The present invention is not limited to the configuration of the above-described embodiment, and various modifications are possible. For example, the minimum drive voltage is not limited to a form that is detected and stored when the power is turned on. It may be set at the time of shipment. Further, an encoder that outputs an analog signal may be adopted, and the encoder may be used in combination with an AD converter. In FIG. 3, the time T1 and the time T4 are not limited to the time when the pulse signal switches from low to high, but may be the time when the pulse signal switches from high to low. Furthermore, the paper feed mechanism 4 is not limited to the ink jet printer apparatus 1 and can be widely applied to printing apparatuses that require high resolution such as laser printer apparatuses and image copying apparatuses.
[0031]
【The invention's effect】
As described above, according to the first aspect of the present invention, the rotation of the paper feed roller is temporarily stopped before the determined stop position, and then the paper feed roller is rotated at the minimum speed. Since the drive of the motor is stopped, the printing paper is accurately stopped at the determined stop position. Accordingly, it is possible to accurately feed the paper in correspondence with printing with an increased resolution, and it is possible to improve the printing quality of the printer apparatus. Moreover, since the minimum drive voltage for rotating the paper feed roller at the minimum speed is detected and stored in advance when the power is turned on, the accuracy of the paper stop position is good even if the rotational characteristics of the DC motor change over time. Maintained. In addition, since an encoder that outputs a digital signal is used, an AD converter that is required for a paper feed mechanism driven by a conventional DC motor is not required, and the firmware of the motor control circuit is simplified. This can reduce the manufacturing cost of the printer device.
[0032]
According to the second aspect of the present invention, the rotation of the paper feed roller is temporarily stopped before the determined stop position, and then the paper feed roller is rotated at the minimum speed. When the stop position is reached, the DC motor is driven. Since the printing paper is stopped, the printing paper accurately stops at a predetermined stop position. As a result, paper can be fed in correspondence with printing with an increased resolution, and the print quality of the printer apparatus can be improved.
[0033]
According to the third aspect of the present invention, since the minimum driving voltage for rotating the paper feed roller at the minimum speed is detected and stored in advance when the power is turned on, even if the rotational characteristics of the DC motor change over time, the paper The accuracy of the stop position is maintained well.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an ink jet printer apparatus including a paper feeding mechanism according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a rotary encoder of the same mechanism.
FIG. 3 is a view showing a waveform of a digital signal output from the encoder.
FIG. 4 is a flowchart showing the operation of the motor control circuit of the mechanism.
FIG. 5 is a diagram illustrating a waveform of an analog signal output from an encoder of a conventional paper feed mechanism.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Printer apparatus 2 DC motor 4 Paper feed mechanism 5 Motor control circuit (motor control part)
23 Paper feed roller 27 Encoder

Claims (3)

A paper feed roller for feeding printing paper, a DC motor for rotationally driving the paper feed roller, an encoder for detecting the rotation of the paper feed roller, and a motor control for controlling the DC motor based on an output signal of the encoder In a paper feeding mechanism of a printing apparatus provided with a section,
The encoder outputs a predetermined digital signal corresponding to the rotation angle of the paper feed roller;
The motor controller is
When the printer is turned on, the DC motor drive voltage is gradually increased to detect the minimum drive voltage when the paper feed roller starts to rotate, and the minimum drive voltage is stored.
When the DC motor is driven at a predetermined driving voltage higher than the minimum driving voltage to stop feeding the printing paper, a brake voltage is applied to the DC motor before a predetermined stop position, and the paper feed roller Once stopped,
Thereafter, the DC motor is driven with the minimum driving voltage, the paper feed roller is rotated at the minimum speed,
When it is detected from the digital signal output from the encoder that the printing paper has reached the stop position, the driving of the DC motor by the minimum drive voltage is stopped to stop the rotation of the paper feed roller. Paper feed mechanism of printing device. A paper feed roller for feeding printing paper, a DC motor for rotationally driving the paper feed roller, an encoder for detecting the rotation of the paper feed roller, and a motor control for controlling the DC motor based on an output signal of the encoder In a paper feeding mechanism of a printing apparatus provided with a section,
The motor controller is
When stopping the feeding of the printing paper, a brake voltage is applied to the DC motor before a predetermined stop position, and the rotation of the paper feeding roller is temporarily stopped.
Thereafter, the DC motor is driven at the lowest drive voltage at which the DC motor rotates, and the paper feed roller is rotated at the lowest speed.
When detecting that the printing paper has reached the stop position from the output signal of the encoder, the driving of the DC motor by the lowest driving voltage is stopped to stop the rotation of the paper feed roller. Paper feeding mechanism. The motor control unit gradually increases the driving voltage of the DC motor when the printing apparatus is turned on, detects the lowest driving voltage when the paper feed roller starts to rotate, and stores the lowest driving voltage. The paper feeding mechanism of the printing apparatus according to claim 2.

Images