JP4550667B2 - Inkjet printer - Google Patents

Description

  The present invention relates to an ink jet printer that prints on paper by using a DC motor to reciprocate a carriage on which a print head is mounted in a main scanning direction.

  Conventionally, as one of output devices such as computers and workstations, a DC motor is used to reciprocate a carriage mounted with a print head in a main scanning direction orthogonal to the sub-scanning direction in which the paper is conveyed. Inkjet printers that print on the printer are used. In such an ink jet printer, in general, in order to stabilize the recording position on the paper by the print head, the carriage speed is detected, and the DC motor is feedback-controlled based on the detected value, thereby controlling the movement of the carriage. Things have been done.

  As an ink jet printer as described above, for example, as disclosed in Patent Document 1, there is a printer that controls a DC motor using control parameters such as a proportional control constant and an integral control constant. In such control, appropriate control parameters are used in accordance with conditions such as the configuration and state of the controlled object such as the characteristics of the DC motor. When appropriate control parameters are not used, control cannot be performed satisfactorily, and problems such as vibrations occurring in the operation of the DC motor and poor print quality may occur. In order to satisfactorily perform control using appropriate control parameters, various proposals have been conventionally made. For example, Patent Document 1 discloses a control parameter by estimating the weight of a carriage that is a load of a DC motor. Describes a technique for obtaining good control characteristics even when the load of the DC motor changes, such as by changing the amount of ink mounted on the carriage. For example, Patent Document 2 describes a technique of reading out motor information stored in a motor and automatically setting parameters from the information.

By the way, even if it is the inkjet printer of the same model, the manufacturer of the DC motor mounted may differ according to the difference in a manufacturing lot etc. Even if DC motors have substantially the same rating and the like, torque characteristics and the like differ depending on the manufacturer, so that appropriate control parameters for controlling the DC motor also differ. Conventionally, when there are a plurality of types of DC motors that may be mounted on an ink jet printer, as described above, intermediate values of control parameters corresponding to these individual DC motors are used as control parameters. Control may be performed. In this case, by using the intermediate value as described above as a control parameter, it is possible to perform control at a constant level regardless of which DC motor is mounted.
Japanese Patent Laid-Open No. 6-91977 JP-A-7-75364

  However, as described above, for example, when an intermediate value or the like is used as a control parameter, if the DC motor manufacturer is different and the torque characteristics are different, it is not an appropriate control parameter suitable for the actually mounted DC motor. Therefore, there is a problem that the control cannot be performed satisfactorily due to the occurrence of vibration as compared with the case where an appropriate control parameter is used. If the control is not performed satisfactorily, the print quality deteriorates and the accuracy of the operation for controlling the carriage to stop decreases. In order to avoid this, an appropriate control parameter may be selected and set according to the DC motor actually mounted in the manufacturing stage of the ink jet printer, but the cost increases due to an increase in the manufacturing process. . Such a problem cannot be solved by the technique described in Patent Document 1 or Patent Document 2 described above.

  The present invention has been made in view of the above problems, and by identifying the manufacturer of the mounted DC motor from its internal resistance value and performing control with appropriate control parameters corresponding to the DC motor, It is an object of the present invention to provide an ink jet printer that can operate stably even if the manufacturer of the DC motor actually mounted is different, with good control, good print quality and carriage stop accuracy.

  In order to achieve the above object, the invention according to claim 1 is provided with a paper transport mechanism for transporting paper in the sub-scanning direction and a print head for printing on the paper, and reciprocating in the main scanning direction perpendicular to the sub-scanning direction. A carriage that is driven, a DC motor that drives the carriage, a motor driver that controls the DC motor, and an encoder strip that is attached to the carriage and has a predetermined resolution according to the reciprocating movement of the carriage. An encoder that outputs a pulse signal; a CPU; and a control unit that includes a ROM and a RAM that are communicable with the CPU and in which predetermined Kp / Ki parameters are set. When loaded, the DC motor is driven to move the carriage to the printer home position. The carriage home position is set in contact with the disk portion, and the carriage speed is calculated based on the pulse signal output from the encoder during the normal printing operation, and the carriage speed is set as a target. In the inkjet printer configured to drive the DC motor in a pulse width modulation (PWM) method by feedback controlling the motor driver using the Kp / Ki parameter so as to achieve speed, the ROM includes A table in which internal resistance values and Kp / Ki parameter information for DC motors of a plurality of manufacturers, which may be mounted on the printer as the DC motor, is recorded corresponding to each other is stored in advance. And the CPU of the control unit turns on the printer and turns on the carriage. When setting the current position, a drive voltage is applied to the DC motor for a predetermined time with a predetermined duty ratio while the carriage is in contact with the stopper portion, and the current flowing through the DC motor is detected to detect this current. The internal resistance value of the DC motor is calculated from the value, the Kp / Ki parameter corresponding to the calculated internal resistance value is read with reference to the ROM table, and the feedback control is performed based on this value.

  According to a second aspect of the present invention, there is provided a paper transport mechanism that transports paper in the sub-scanning direction, a print head that prints on the paper, and a carriage that reciprocates in the main scanning direction perpendicular to the sub-scanning direction, A DC motor that drives the carriage; a motor driver that controls the DC motor; an encoder that outputs a pulse signal in accordance with the operation of the DC motor; a CPU; and a ROM and a RAM that can communicate with the CPU; In the inkjet printer provided with a control unit that drives the DC motor by feedback-controlling the motor driver using a predetermined control parameter based on the pulse signal output from the encoder, the ROM has the There are several manufacturers of DC motors that may be installed in this printer as DC motors. The internal resistance value and the control parameter information used for the feedback control are recorded corresponding to each other, and the CPU of the control unit has a predetermined duty applied to the DC motor while the DC motor is locked. A drive voltage is applied at a ratio for a predetermined time, a current flowing through the DC motor is detected, an internal resistance value of the DC motor is calculated from this current value, and the calculated internal resistance value is obtained by referring to the ROM table. The corresponding control parameter is read, and the feedback control is performed based on this value.

  According to a third aspect of the present invention, in the second aspect of the present invention, when the printer is powered on, the control unit drives the DC motor to stop the carriage at a stopper portion provided at the home position of the printer. A carriage home position is set by contacting the carriage, and at this time, the carriage is brought into contact with the stopper portion to lock the DC motor.

  According to the first aspect of the present invention, the drive voltage is applied while the DC motor is locked to determine the internal resistance value of the DC motor, and the Kp / Ki parameter corresponding to the internal resistance value is read from the ROM table. Since feedback control is performed based on the Kp / Ki parameter, the manufacturer of the DC motor that is actually mounted is discriminated, and an appropriate Kp / Ki parameter is used. The quality and the stopping accuracy of the carriage are good, and it becomes possible to operate stably. Also, such Kp / Ki parameter setting is performed by locking the DC motor by bringing the carriage into contact with the stopper during the home position setting operation of the carriage when the power is turned on. The operation for obtaining the internal resistance value can be easily realized without requiring a special mechanism for locking.

  According to the second aspect of the present invention, the drive voltage is applied while the DC motor is locked to determine the internal resistance value of the DC motor, the control parameter corresponding to the internal resistance value is read from the ROM table, and this control is performed. Since the feedback control is performed based on the parameters, the control is performed satisfactorily as described above, the print quality and the carriage stop accuracy are improved, and the operation can be stably performed.

  According to the third aspect of the present invention, at the time of the carriage home position setting operation when the power is turned on, the control parameter is set by locking the DC motor by bringing the carriage into contact with the stopper portion. The operation for obtaining the internal resistance value can be easily realized without requiring a special mechanism for locking the motor.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of an ink jet printer according to this embodiment. The ink jet printer 1 is reciprocated in a main transport direction (black arrow direction in the figure) perpendicular to the sub-scan direction and a paper transport mechanism 2 that transports the paper P in the sub-scan direction (white arrow direction in the figure). A carriage 3, a DC motor 4 for driving the carriage 3, a motor driver 4 a for driving the DC motor 4, and an encoder strip 5 a arranged along the main scanning direction on the frame of the printer are attached to the carriage 3 so as to be able to scan. The encoder 5 and the control unit 6 are provided.

  A print head (not shown) for printing on the paper P is mounted on the carriage 3. In this ink jet printer 1, the carriage 3 is driven by a DC motor 4 to reciprocate in the main scanning direction, and the print head drops and prints ink or the like on the paper P transported by the paper transport mechanism 2 by a predetermined width. By doing so, an image is recorded on the paper P.

  The encoder 5 and the encoder strip 5a are used for controlling the movement of the carriage 3, as will be described later. The encoder strip 5a has a resolution of 150 dpi with slits equally spaced at 1/150 inches, for example. The encoder 5 scans the encoder strip 5a according to the reciprocating movement of the carriage 3, and outputs two-phase pulse signals whose phases are shifted from each other according to the moving direction and speed of the carriage 3.

  The control unit 6 is an application specific integrated circuit (ASIC) configured for an ink jet printer, and includes a CPU 6a, and a ROM 6b and a RAM 6c that can communicate with the CPU 6a. The CPU 6a is configured to control various operations of the ink jet printer 1 such as control of the moving speed of the carriage 3 and operation of detecting the home position of the carriage 3 by operating the firmware by communicating with the ROM 6b. Yes.

  The control unit 6 controls the speed at which the carriage 3 moves, for example, by PI control as shown below. The control unit 6 is set with a control parameter Kp (proportional coefficient) / Ki (integral coefficient) parameter. The CPU 6a of the control unit 6 calculates the speed of the carriage 3 by using the pulse signal output from the encoder 5 in order to stabilize the recording position on the paper P by the print head. Based on the calculated speed, feedback control is performed using the above-described Kp / Ki parameter so that the driving speed of the carriage 3 becomes the target speed. Then, a pulse waveform voltage is output from the control unit 6 to the motor driver 4a, and the motor driver 4a is controlled by a pulse width modulation (PWM) method. The motor driver 4a drives the DC motor 4 at a speed corresponding to the pulse wave voltage, whereby the speed of the carriage 3 is controlled.

  Further, the control unit 6 performs the home position detection process of the carriage 3 when the ink jet printer 1 is turned on. When the power of the printer 1 is turned on, the controller 6 gradually increases the duty ratio of the PWM control voltage for driving the DC motor 4 to drive the DC motor 4 to move the carriage 3 to move the printer 1. It is brought into contact with a stopper portion (not shown) provided at the home position.

  FIG. 2 shows the relationship between time and the duty ratio of the voltage of PWM control for driving the DC motor 4 during the home position detection process. For example, it is assumed that the carriage 3 is in contact with the stopper portion at time t1. At this time, as shown in the figure, the duty ratio is gradually increased, and is increased in a pulse waveform for several msec per one time within a range of about 50% to 90%. During this time, if it is confirmed that the carriage 3 is not moved, the position of the carriage 3 at that time is detected as the home position.

  Here, in the present embodiment, the CPU 6 a of the control unit 6 performs home position detection processing, then measures the internal resistance of the DC motor 4 to determine the manufacturer of the DC motor 4, and corresponds to the DC motor 4. A process for determining an appropriate Kp / Ki parameter is performed. The ROM 6b of the control unit 6 has information on internal resistance values and appropriate Kp / Ki parameters for DC motors of a plurality of manufacturers that may be mounted as the DC motor 4 in the inkjet printer 1 in advance. Corresponding to each other, they are recorded as a table. That is, the CPU 6a determines the manufacturer of the DC motor 4 by referring to the table of the ROM 6b based on the measured internal resistance value, and determines an appropriate Kp / Ki parameter.

  FIG. 3 shows a process for determining an appropriate Kp / Ki parameter corresponding to the mounted DC motor 4. First, when the power of the inkjet printer 1 is turned on, the home position detection process is performed as described above (S0). When the home position detection process is completed, the CPU 6a of the control unit 6 applies a drive voltage with a duty ratio of 90% (predetermined duty ratio) to the DC motor 4 while the carriage 3 is in contact with the stopper at the home position. Application is performed for 10 msec (predetermined time) (S1). At this time, since the carriage 3 is in contact with the stopper portion and cannot move, the DC motor 4 is locked. FIG. 4 shows the relationship between time and the duty ratio of the drive voltage during the operation in which the drive voltage is applied in this way. As shown in the figure, the home position detection process is started after the power is turned on, the carriage 3 comes into contact with the stopper at time t1, and then the duty ratio of the PWM control is increased on the pulse wave. At this time, if it is confirmed that the carriage 3 is not moved, the home position is detected. Then, the duty ratio of the drive voltage is set to 90% only for 10 msec from time t2 to time t3 after the home position is detected. Here, the duty ratio and the voltage application time are not limited to this, but the DC motor 4 is locked, so that the temperature of the DC motor 4 is not excessively increased.

  As described above, when a driving voltage having a duty ratio of 90% is applied, a current flows through the DC motor 4. At this time, since the DC motor 4 is locked, this current flows through the internal resistance of the DC motor 4. The control unit 6 detects the current value flowing at this time and performs A / D conversion, and the CPU 6a determines the internal value of the DC motor 4 based on the current value value and the voltage value applied to the DC motor 4 at this time. A resistance value is calculated (S2). Since the internal resistance value of the DC motor 4 varies by about 3Ω depending on the manufacturer, the manufacturer of the DC motor 4 can be determined based on the internal resistance value thus obtained. When the internal resistance value is calculated, the CPU 6a of the control unit 6 refers to the table stored in the ROM 6b and determines the Kp / Ki parameter corresponding to the internal resistance value (S3). Then, the Kp / Ki parameter is read and feedback control is performed based on this value (S4). Note that the process of determining the Kp / Ki parameter in this manner may be performed every time the power is turned on. For example, the process for determining the Kp / Ki parameter may be performed once when the ink jet printer 1 is first turned on. It may be configured to be performed only at a predetermined opportunity.

  Thus, since the CPU 6a of the control unit 6 sets the Kp / Ki parameter, the manufacturer of the DC motor 4 actually mounted is discriminated and an appropriate Kp / Ki parameter is used for feedback control. As a result, the feedback control is performed well, the printing quality is improved, and the ink jet printer 1 can be stably operated, for example, the accuracy of the operation of stopping the carriage 3 is increased.

  Further, in the present embodiment, during the home position setting operation of the carriage 3 when the power is turned on, the DC motor 4 is locked by bringing the carriage 3 into contact with the stopper portion, and an appropriate Kp as described above is obtained. Since the / Ki parameter is set, an operation for obtaining the internal resistance value can be easily realized without requiring a special mechanism for locking the DC motor 4.

  In addition, this invention is not limited to the structure of the said embodiment, A various deformation | transformation is possible suitably in the range which does not change the meaning of invention. For example, the control parameter determined by referring to the ROM 6b table from the internal resistance value of the DC motor 4 is not limited to the Kp / Ki parameter used for PI control, but is a parameter used for other feedback control. Also good. In the above-described embodiment, the speed of the carriage 3 is calculated by the linear encoder type encoder 5. However, this encoder may be a rotary encoder provided in the DC motor 4, for example. The speed of the carriage 3 may be controlled by calculating and performing feedback control.

  Further, the operation of locking the DC motor 4 when obtaining the internal resistance value of the DC motor 4 is not limited to the operation of bringing the carriage 3 into contact with the stopper portion at the home position as described above. For example, a mechanism (not shown) that rotates and transmits the operation of the DC motor 4 to the carriage 3 to be driven is temporarily fixed by using a stopper or the like automatically / manually. It may be locked.

1 is a block diagram of an ink jet printer according to an embodiment of the present invention. The figure explaining the operation | movement at the time of the home position detection process of an inkjet printer same as the above. The flowchart which shows the procedure of the process which determines the Kp / Ki parameter of an inkjet printer same as the above. The figure explaining the operation | movement which calculates | requires the internal resistance value of DC motor of an inkjet printer same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printer 2 Paper conveyance mechanism 3 Carriage 4 DC motor 4a Motor driver 5 Encoder 5a Encoder strip 6 Control part 6a CPU
6b ROM
6c RAM
P paper

Claims (3)

A paper transport mechanism for transporting paper in the sub-scanning direction;
A carriage mounted with a print head for printing on the paper, and reciprocally moved in a main scanning direction orthogonal to the sub-scanning direction;
A DC motor for driving the carriage;
A motor driver for controlling the DC motor;
An encoder that is attached to the carriage and outputs a pulse signal by scanning an encoder strip having a predetermined resolution in accordance with the reciprocating movement of the carriage;
A CPU and a control unit having a ROM and a RAM capable of communicating with the CPU and set with predetermined Kp / Ki parameters;
When the printer is powered on, the controller drives the DC motor to bring the carriage into contact with a stopper provided at the printer home position to set the carriage home position. ,
During normal printing operation, the carriage speed is calculated based on the pulse signal output from the encoder, and the motor driver is controlled using the Kp / Ki parameter so that the carriage speed becomes a target speed. In an inkjet printer configured to drive the DC motor in a pulse width modulation (PWM) system with feedback control,
A table in which internal resistance values and Kp / Ki parameter information for DC motors of a plurality of manufacturers are recorded in correspondence with each other in advance in the ROM as the DC motor. Is stored,
When the printer power is turned on and the carriage home position is set, the control unit CPU drives the DC motor with a predetermined duty ratio for a predetermined time while the carriage is in contact with the stopper unit. Apply a voltage, detect the current flowing through the DC motor, calculate the internal resistance value of the DC motor from this current value,
An ink jet printer, wherein a Kp / Ki parameter corresponding to the calculated internal resistance value is read with reference to the ROM table, and the feedback control is performed based on the value. A paper transport mechanism for transporting paper in the sub-scanning direction;
A carriage mounted with a print head for printing on the paper, and reciprocally moved in a main scanning direction orthogonal to the sub-scanning direction;
A DC motor for driving the carriage;
A motor driver for controlling the DC motor;
An encoder that outputs a pulse signal in accordance with the operation of the DC motor;
Control which has CPU, ROM and RAM which can communicate with this CPU, and drives the DC motor by feedback controlling the motor driver using a predetermined control parameter based on the pulse signal output from the encoder In an inkjet printer having a section,
In the ROM, information on internal resistance values and control parameters used for the feedback control for the DC motors of a plurality of manufacturers, which may be mounted on the printer as the DC motors, is recorded corresponding to each other in advance. Has been
The CPU of the control unit applies a driving voltage to the DC motor at a predetermined duty ratio for a predetermined time while the DC motor is locked, detects a current flowing through the DC motor, Calculate the internal resistance value of the DC motor,
An ink jet printer, wherein a control parameter corresponding to the calculated internal resistance value is read with reference to a table in the ROM, and the feedback control is performed based on this value. When the printer is powered on, the controller drives the DC motor to bring the carriage into contact with a stopper provided at the printer home position to set the carriage home position;
3. The ink jet printer according to claim 2, wherein the DC motor is locked by bringing the carriage into contact with the stopper portion.

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