JP2006248104A - Control method and controller of motor, and inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller and a control method of a motor for detecting the predetermined state of a driven body (e.g. home position of a carriage) accurately over the use period without increasing the number of components or the manufacturing cost, and to provide an inkjet printer. <P>SOLUTION: When operation of a carriage 13 is controlled by rotary driving a carriage motor 26, a threshold drive current value of the carriage motor 26 for detecting the fact that the carriage 13 is positioned at a home position is set for the drive current value of the carriage motor 26 during normal operation (scanning) of the carriage 13, and the threshold value is varied depending on variation in drive current value during scanning operation incident to increase in the number of accumulated scanning times of the carriage 13. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention sets the threshold value of the driving current of the DC motor for detecting that the driven body is in a predetermined state with respect to the driving current value of the DC motor during the normal operation of the driven body. The present invention relates to a motor control method for detecting a predetermined state of a driven body, a motor control device, and an ink jet printer.

  Among various printers that perform printing on a printing medium such as paper, cloth, and film, a printer that performs printing by discharging ink onto the printing medium is called an inkjet printer.

  In such an ink jet printer, a control system controls a motor that drives a carriage (driven body) on which a print head that ejects ink and an ink container that stores ink to be supplied to the print head are mounted. In general, printing is performed by ejecting ink from a print head toward a printing medium while moving (scanning).

  Therefore, in order to perform high-quality printing on the printing medium, it is necessary to control the motor that drives the carriage with high accuracy.

  Therefore, in order to determine the landing position of the ink droplet on the printing medium with high accuracy, the carriage position is determined based on the position where the carriage waits on one end side (for example, one digit side) in the carriage scanning direction, that is, the position of the home position. Ink ejection is controlled in accordance with the movement distance.

  Further, in a printer (serial printer) in which the carriage is driven in the scanning direction by the rotation of the motor, a driving pulley fixed to a rotating shaft of a DC motor (DC motor) and a pair of the driving pulley are elastically supported. The timing belt is stretched to a predetermined tension by the driven pulley, and a carriage is attached to the timing belt. In the printer having such a configuration, when the carriage comes into contact with the frame (per degree) and the drive current value of the DC motor exceeds a predetermined current value (threshold), it is detected as the home position.

  As described above, when the home position is detected, the transmission torque from the drive pulley acting on the timing belt changes suddenly due to the inertial force of the carriage that stops suddenly or the like. When the motor is driven, looseness occurs between the timing belt and the driving pulley, and there is a possibility that abnormalities such as tooth skipping (the timing belt teeth and the pulley are misaligned) and belt disengagement may occur. .

  Therefore, a stopper that restricts the amount of movement of the driven pulley has been proposed as means for preventing the occurrence of an abnormality such as belt detachment (see, for example, Patent Document 1).

Japanese Utility Model Publication No. 05-74848

  By the way, the driving current when the carriage (driven body) is normally scanned by the motor varies depending on the driving resistance of the carriage. The carriage drive resistance varies depending on individual printer differences, and also changes depending on the cumulative drive amount (for example, the number of scans) of the carriage. For this reason, the threshold value for detecting the home position of the carriage is set based on various variations and fluctuations of the driving resistance. When the driving resistance is relatively small, the above-mentioned tooth is set before the driving current reaches the threshold value. There is a situation in which abnormalities on the driven side such as jumping and belt detachment are likely to occur. Even if no abnormality occurs, it is impossible to detect that the driven body is in a predetermined state until an excessive load is applied to the driven side if the threshold is too large for the driving resistance. It is also conceivable that the mechanical fatigue is likely to accumulate and the life is shortened.

  Further, when the occurrence of abnormality such as belt detachment is prevented by mechanical means as in Patent Document 1, the number of parts increases and the manufacturing cost of the printer increases, which is not preferable.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a motor capable of accurately detecting a predetermined state of the driven body (for example, the home position of the carriage) over the period of use without increasing the manufacturing cost by increasing the number of parts. A control method, a motor control device, and an inkjet printer.

  The motor control method according to the present invention, which can solve the above-described problems, provides a driving current for the DC motor during normal operation of the driven body when controlling the operation of the driven body by rotational driving of the DC motor. The threshold value of the drive current of the DC motor for detecting that the driven body is in a predetermined state is set with respect to the value, and the normal that changes as the cumulative driving amount of the driven body increases The threshold value is changed according to a change in the drive current value during operation.

  According to the motor control method having such a configuration, even when the cumulative driving amount of the driven body increases and the driving resistance of the driven body changes, the threshold value is changed according to the change in the driving current value during the normal operation. By changing, it is possible to always accurately detect that the driven body is in a predetermined state. Further, since it is possible to prevent an excessive load from being applied to the driven side, it is possible to prevent the occurrence of mechanical fatigue and abnormality and to improve the life of the device. Further, it is not necessary to prevent occurrence of abnormality on the driven side by mechanical means, and the manufacturing cost is not increased by increasing the number of parts.

  In the motor control method of the present invention, it is preferable that the threshold is set between the drive current value during the normal operation and an overload current value when an abnormality occurs on the driven side.

  According to the motor control method having such a configuration, the threshold value is always set to a value lower than the overload current value, and the occurrence of abnormality on the driven side can be reliably prevented.

  Further, in the motor control method of the present invention, the driven body is a carriage having a print head for ejecting ink onto the printed body, and the threshold value is a home position at an end of the scanning direction of the carriage. It is preferable that the threshold is changed by increasing the number of scans as the cumulative driving amount of the carriage.

  According to the motor control method having such a configuration, when the carriage stops at the home position, it is detected that the drive current of the motor has increased to reach the threshold value and reached the home position. The carriage drive resistance is such that a part of the ink ejected by the print head along with the scanning of the carriage does not adhere to the printing surface of the printing medium and becomes a minute ink mist, and the ink mist adheres to the guide rail of the carriage. However, the home position can always be accurately detected by changing the threshold according to the change in the drive current value during the normal operation due to the increase in the number of carriage scans.

  In the motor control method of the present invention, it is preferable that the threshold is changed when the number of scans reaches a predetermined value.

  According to the motor control method having such a configuration, since the threshold value is changed when the number of carriage scans increases and reaches a predetermined value, the threshold value changes step by step, and the process of changing the threshold value is performed. Can be simplified.

  In addition, a motor control device according to the present invention that can solve the above problems includes a direct current motor, a driven body that operates by rotational driving of the direct current motor, and a control system that controls rotational driving of the direct current motor. The control system detects that the driven body is in a predetermined state with respect to the driving current value of the DC motor during normal operation of the driven body. And a threshold value of the drive current of the DC motor is set for changing the drive current value in the normal operation that changes with an increase in the cumulative drive amount of the driven body. It is characterized by doing.

  According to the motor control apparatus having such a configuration, even when the cumulative driving amount of the driven body increases and the driving resistance of the driven body changes, the threshold value is set according to the change in the driving current value during the normal operation. As a result of the change, it is possible to always accurately detect that the driven body is in a predetermined state. Further, since it is possible to prevent an excessive load from being applied to the driven side, it is possible to prevent the occurrence of mechanical fatigue and abnormality and to improve the life of the device. Further, it is not necessary to prevent occurrence of abnormality on the driven side by mechanical means, and the manufacturing cost is not increased by increasing the number of parts.

  In the motor control device of the present invention, it is preferable that the threshold is set between the drive current value during the normal operation and an overload current value when an abnormality occurs on the driven side.

  According to the motor control apparatus having such a configuration, the threshold value is always set to a value lower than the overload current value, and the occurrence of abnormality on the driven side can be reliably prevented.

  In the motor control device of the present invention, it is preferable that the driven body is a carriage including a print head for ejecting ink onto the printed body.

  According to the motor control device having such a configuration, when the carriage is in a predetermined state (for example, at the home position and stopped), the drive current of the motor increases and reaches a threshold value to reach the predetermined state. It is detected. The carriage drive resistance gradually increases as the ink ejected by the print head adheres to the carriage guide rail and the like as the carriage scans, but as the cumulative drive amount (for example, the number of scans) of the carriage increases, By changing the threshold according to the change in the drive current value during normal operation, the carriage can always detect the predetermined state accurately.

  Further, an ink jet printer according to the present invention that can solve the above-described problems is characterized by including the motor control device according to the present invention.

  According to the ink jet printer having such a configuration, the threshold value for detecting the state of the carriage is changed with an increase in the cumulative driving amount of the carriage without increasing the number of parts and the manufacturing cost, and the predetermined carriage A state (for example, a home position) can always be accurately detected. In particular, in a printer that is durable and used for a long period of time, the carriage drive resistance may change greatly during the period of use, so the carriage state detection function is maintained by appropriately changing the threshold value. It becomes important.

  According to the present invention, control of a motor that can accurately detect a predetermined state of a driven body (for example, a home position of a carriage) over a period of use without increasing manufacturing cost by increasing the number of parts. A method, a motor control device, and an inkjet printer can be provided.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a motor control method, a motor control device, and an inkjet printer according to embodiments of the invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic perspective view showing a main configuration of an ink jet printer capable of carrying out the motor control method of the present embodiment, and FIG. 2 shows a state in which a paper discharge tray and an upper case of the ink jet printer shown in FIG. 1 are removed. FIG. 3 is an enlarged perspective view of the carriage scanning portion shown in FIG.

An ink jet printer 1 according to the present embodiment is a front feed / discharge type printer, and as shown in FIG. 1, a cassette opened at the front center of an apparatus case 4 composed of an upper case 3 and a lower case 2. A substantially box-shaped sheet cassette 5 in which sheets are stacked and accommodated is detachably inserted into the accommodating portion 9.
Further, a paper discharge tray 6 for receiving the printed paper is provided so as to cover the open top portion of the paper cassette 5. Further, a display unit 7 such as an indicator and an operation unit 8 such as a power switch are arranged on the left and right sides of the front surface of the device case 4.

  As shown in FIG. 2, the apparatus case 4 is fed one by one from the paper cassette 5 by a pickup roller of a paper feed unit connected by a paper feed motor 12 via a plurality of transmission gears (not shown). Mounted on the carriage 13, a conveyance mechanism that conveys the sheet to be conveyed along the U-shaped conveyance path, a belt drive device 14 that supports the carriage 13 so as to be reciprocally movable in a direction orthogonal to the conveyance direction of the sheet by the conveyance mechanism. The print head 52 (see FIG. 4) that performs printing by ejecting fine particles of recording ink onto the paper, the ink tanks 15 and 16 that store the recording ink supplied to the print head, and the paper by the transport mechanism And a control system (see FIG. 4) for controlling the carriage speed, the movement speed of the carriage 13, the ink ejection operation of the print head, and the like.

As shown in FIG. 2, the carriage 13 is supported by a pair of carriage shafts 53 extending in the sheet width direction so as to be movable in the sheet width direction, and is fixed to a timing belt 35 driven by a carriage motor 26. Thus, it is reciprocated in the paper width direction according to the travel of the timing belt 35.
This ink jet printer 1 controls the ink ejection from the print head mounted on the carriage 13 with the paper transport direction as the sub-scanning direction and the movement direction of the carriage 13 as the main scanning direction. Image recording (printing).

  As shown in FIGS. 2 and 3, the belt driving device 14 is rotationally driven by a base frame 24 that is fixed to the casing of the printer body and a carriage motor (DC motor) 26 that is disposed on the base frame 24. A drive pulley 28, a pulley holder 31 disposed with respect to the base frame 24 so as to be movable back and forth toward the drive pulley 28, a driven pulley 33 rotatably supported by the pulley holder 31, and a drive pulley 28. A timing belt 35 wound around the driven pulley 33 and a driven body fixed on the timing belt 35 and reciprocatingly moved between the driving pulley 28 and the driven pulley 33 as the timing belt 35 travels. Carriage 13.

  Next, the electrical configuration of the motor control device including the control system of the inkjet printer 1 will be described with reference to FIG. FIG. 4 is a block diagram showing an electrical configuration of the inkjet printer 1.

  The ink jet printer 1 includes a main control circuit 102, a CPU 104, and various memories (ROM 110, RAM 112, EEPROM 114) connected to the main control circuit 102 and the CPU 104 via a bus. Connected to the main control circuit 102 are an interface circuit 120 that transmits and receives signals to and from an external device such as a personal computer, a paper feed motor drive circuit 130, a head drive circuit 140, and a CR motor drive circuit 150. ing.

  The paper feed motor 12 is driven by the paper feed motor drive circuit 130 to rotate the transport roller 14 and thereby move the paper P in the sub-scanning direction. The paper feed motor 12 is provided with a rotary encoder 32, and an output signal of the rotary encoder 32 is input to the main control circuit 102.

  A print head 52 having a plurality of nozzles (not shown) is provided on the bottom surface of the carriage 13. Each nozzle is driven by a head drive circuit 140 and ejects ink droplets toward a paper P or a printing material such as paper, cloth, or film.

  The carriage motor 26 is driven by a CR motor drive circuit 150. The ink jet printer 1 includes a linear encoder 70 for detecting the position and speed of the carriage 13 along the main scanning direction. The linear encoder 70 includes a linear code plate 72 provided parallel to the main scanning direction and a photo sensor 74 provided on the carriage 13. The output signal of the linear encoder 70 is input to the main control circuit 102.

  The main control circuit 102 has a function of supplying control signals to the three drive circuits 130, 140, and 150, respectively, decodes various print commands received by the interface circuit 120, and print data It also has a function of executing control related to adjustment and monitoring of various sensors. On the other hand, the CPU 104 has various functions for assisting the main control circuit 102, and executes control of various memories, for example.

  Next, the configuration of the drive control device for the carriage motor 26 will be described with reference to FIGS. FIG. 5 is a block diagram showing the configuration of the drive control device for the carriage motor 26. FIG. 6 is an explanatory diagram showing the relationship between the motor drive signal Sdr and the characteristics of the carriage motor 26.

  The drive control device for the carriage motor 26 includes a CR motor control circuit 200 and a CR motor drive circuit 150. The CR motor control circuit 200 is a part of the main control circuit 102 shown in FIG.

  The output signal Sen of the linear encoder 70 is input to the position calculation circuit 230 and the speed calculation circuit 232 in the CR motor control circuit 200. These circuits 230 and 232 obtain a current rotational position Pc and a current rotational speed Vc of the carriage motor 26 based on an A phase signal and a B phase signal (not shown) of the output signal Sen of the encoder 70, respectively. The current rotation position Pc is input to the target rotation speed generation circuit 204. The target rotational speed generation circuit 204 is preset with a target rotational speed Vt corresponding to the rotational position Pc, and generates a target rotational speed Vt corresponding to the target rotational position Pc.

  The subtractor 206 obtains a deviation ΔV between the target rotational speed Vt and the current rotational speed Vc, and calculates the rotational speed deviation ΔV from a proportional element (proportional means) 210, an integral element (integral means) 212, and a differential element (differential means). And 214. The calculation results QP, QI, and QD of these three calculation elements 210, 212, and 214 are added by an adder 216 to calculate an addition result ΣQ.

  The outputs QP, QI, QD of the respective arithmetic elements 210, 212, 214 and their addition result ΣQ are given by, for example, the following equations (1) to (4).

QP (j) = ΔV (j) × Kp (1)
QI (j) = QI (j−1) + ΔV (j) × Ki (2)
QD (j) = {ΔV (j) −ΔV (j−1)} × Kd (3)
ΣQ (j) = QP (j) + QI (j) + QD (j) (4)
Here, j is time, Kp is a proportional gain, Ki is an integral gain, and Kd is a differential gain.

  The duty adjustment circuit 220 adjusts the level of the duty signal Dt supplied to the drive circuit 150 by adjusting the integration element 212 or the target rotation speed generation circuit 204 according to the addition result ΣQ (also referred to as “PID output”). adjust. The duty signal Dt is a signal proportional to the addition result ΣQ and is a signal indicating the duty of the carriage motor 26.

  The CR motor drive circuit 150 includes a DC-DC converter 154 configured with a transistor bridge and a base drive circuit 152. The base drive circuit 152 generates a base signal to be applied to the base of the transistor of the DC-DC converter 154 in accordance with the duty signal Dt supplied from the CR motor control circuit 200. The DC-DC converter 154 generates a motor drive signal Sdr according to the base signal and supplies it to the carriage motor 26.

  FIG. 6A shows a signal change of the motor drive signal Sdr. The duty of the motor drive signal Sdr is a value obtained by dividing the period Ton at the on level by one cycle Tp of the drive signal. In the present embodiment, the duty of the motor drive signal Sdr is also referred to as “carriage motor duty”.

  When a brushed DC motor is used as the carriage motor 26, the torque / rotational speed characteristic is proportional to the duty as shown in FIG. The CR motor drive circuit 150 generates the drive signal Sdr so that the duty of the drive signal Sdr is proportional to the duty signal Dt. As a result, the carriage motor 26 generates a driving force corresponding to the duty signal Dt given from the CR motor control circuit 200 to drive the carriage 13. That is, the drive current value of the carriage motor 26 is proportional to the duty signal Dt.

  In order to perform high-quality printing on the printing medium, it is particularly important to determine the landing positions of the ink droplets on the printing medium with high accuracy, and it is necessary to accurately position the positions where ink is ejected. is there. For this reason, in this embodiment, not only the position of the carriage 13 is detected by the linear encoder 70 but also the position where the carriage waits on one end side (for example, one digit side) of the carriage 13 in the main scanning direction, that is, the position of the home position. As a reference, the position of the carriage 13 is controlled.

  In order to detect the position of the home position, the carriage 13 is brought into contact with the frame on one end side in the main scanning direction (per degree), and the carriage motor 26 is stopped when the carriage 13 is stopped against the drive signal Sdr. The value (that is, duty) increases according to the driving load. When it is detected that the drive current value of the carriage motor 26 has become equal to or greater than a predetermined current value (threshold value), the carriage 13 stops at a certain time, that is, stops at the home position ( The position is stored in the RAM 112 as a home position. At the start of the printing operation, the ink ejection timing can be determined by the amount of movement from the home position. The drive current value of the carriage motor 26 can be detected by the main control circuit 102 detecting the duty of the drive signal Sdr generated by the CR motor drive circuit 150. The threshold value is stored in the ROM 110 as an initial set value, and is compared with the drive current value by the main control circuit 102.

  The driving current value of the carriage motor 26 is a value that varies depending on the driving load of the carriage 13, and the driving load varies depending on the use conditions of the inkjet printer 1. The main factor that changes the driving load as a use condition of the ink jet printer 1 is that a minute ink droplet ejected by a printing operation becomes a mist and floats inside the ink jet printer 1 to guide the movement of the carriage 13. This is because the sliding resistance between the carriage 13 and the carriage shaft 53 is increased.

  As described above, the driving load of the carriage 13 changes within the usage period of the ink jet printer 1, but the threshold value for detecting the home position is predetermined with respect to the driving current value when the carriage 13 is scanned (during normal operation). Therefore, the difference between the drive current value and the threshold value during normal operation is preferably constant. Therefore, in this embodiment, the threshold value is changed according to the change of the drive current value during the normal operation.

  For example, the change in the threshold value is detected by the main control circuit 102 by the main control circuit 102 and is calculated by the CPU 104 based on the initial threshold value stored in the ROM 110 in accordance with the change, and the new threshold value is written in the EEPROM 114. Is done. Then, the latest threshold value read from the EEPROM 114 is compared with the drive current value by the main control circuit 102.

Next, an example in which the threshold value is changed according to the change in the drive current value of the carriage motor 26 during the use period of the inkjet printer 1 will be described with reference to FIG.
In FIG. 7, the drive load (torque) and drive current value of the carriage motor 26 during normal operation are indicated by broken lines, and the drive load (torque) and drive current value of the carriage motor 26 when an abnormality occurs on the driven side are indicated by a one-dot chain line. The threshold in the example of the present embodiment that changes stepwise according to the change during the normal operation is indicated by a solid line, and the drive current value of the carriage motor 26 during the normal operation is a predetermined value throughout the use period. The conventional threshold value set as a constant value so as to be larger than the value is indicated by a two-dot chain line.

  The drive load and drive current value (broken line) of the carriage motor 26 during normal operation increase in proportion to the number of scans of the carriage 13, and along with this increasing trend, tooth skipping of the timing belt 35, belt slippage, etc. The drive load and the drive current value (one-dot chain line) at the time of the overload state where the abnormality occurs are changed.

  The conventional threshold value (two-dot chain line) is set as a constant value that is larger than the drive current value at the end of the use period in which the drive current value becomes the largest. When this threshold value is used, the drive load is relatively high. When the carriage 13 stops at the home position and the drive current value rises at the beginning of a small use period, the overload current value is exceeded before the threshold is reached, and an overload condition occurs and abnormalities such as belt detachment occur. Resulting in.

  On the other hand, the threshold value in this example is always larger than the drive current value during normal operation and is always larger than the overload current value when an abnormality occurs (that is, always between the broken line and the alternate long and short dash line). In addition, it changes according to the change of the drive current value during the normal operation. By setting the threshold value to a value that is always lower than the overload current value, the occurrence of abnormality on the driven side can be reliably prevented.

In addition, the threshold value in this example is a normal operation when the number of scans reaches a predetermined value (initially 500,000 times, and thereafter accumulated every 500,000 times) with respect to the initial value when the number of carriage scans is zero. It changes so as to increase by a predetermined value (50 amperes in this example) with respect to the driving current value at the time, and changes stepwise throughout the use period. The cumulative number of scans of the carriage 13 is counted by the main control circuit 102, and is written and updated in the EEPROM 114 every time one printing operation is completed.
The threshold value may be continuously changed according to the continuous change of the drive current value during the normal operation without depending on the increase of the cumulative number of scans. However, the threshold value is changed every predetermined number of scans. By doing so, it is possible to simplify the process of changing the threshold value by reducing the number of times the threshold value is calculated.

  According to the motor control method, motor control apparatus, and inkjet printer 1 of the embodiments described above, even when the cumulative scanning number of the carriage 13 increases and the driving resistance (driving load) of the carriage 13 changes. Since the threshold value changes in accordance with the change in the drive current value during the normal operation, it is possible to always accurately detect that the carriage 13 is located at the home position throughout the period of use. Since it is possible to prevent an excessive load from being applied to components such as the driven pulley 28 and the timing belt 35 on the driven side that drives the carriage 13, it is possible to prevent occurrence of abnormalities such as mechanical fatigue and belt detachment. The life of the printer 1 can be improved. Moreover, it is not necessary to prevent the occurrence of abnormality on the driven side by mechanical means, and the manufacturing cost is not increased by increasing the number of parts.

  Since the motor driving load and the driving current value are proportional to the output QI of the integration element 212 shown in the above embodiment, the motor driving load and the driving current value are changed according to the change in the output QI of the constant speed moving section during the scanning of the carriage 13. The threshold can also be changed.

In the above embodiment, the control for detecting the home position of the carriage has been described. However, the motor control method, the motor control device, and the ink jet printer of the present invention detect other states of the carriage. It can also be applied to.
For example, when a paper jam occurs due to the paper being caught by the carriage during scanning of the carriage, an increase in the driving load at the initial stage of the occurrence is detected by a threshold value to stop the carriage driving and prevent a more severe paper jam state. More accurate paper jam detection can be performed by changing the threshold according to the change in the drive current value during the normal operation. In addition, the threshold for detecting the reference home position in the vertical direction, which is the reference in the vertical movement of the carriage for optimizing the distance of the print head with respect to the printing medium, is also changed. Therefore, the home position can be accurately detected without generating an excessive driving load.

Moreover, although the printing paper has been described as an example of the printing material, a film, a cloth, a thin metal plate, or the like may be used as the printing material.
Further, although an example of an off-carriage printer in which the ink tank is not mounted on the carriage has been described as an example, an on-carriage printer in which the ink tank is mounted on the carriage may be used.

  In addition to the printer according to the above embodiment, a computer system including a computer main body, a display device such as a CRT, an input device such as a mouse or a keyboard, a flexible drive device, and a CD-ROM drive device can be realized. The computer system realized in this way is a system superior to the conventional system as a whole system.

  In the motor control method and apparatus of the above embodiment, an ink jet printer has been exemplified. However, the present invention is not limited to this as long as it is a printing apparatus that can perform printing processing on a printing medium. It may be applied.

It is a schematic perspective view which shows the main structures of the inkjet printer which can implement the motor control method of this embodiment. FIG. 2 is a perspective view of a state where a paper discharge tray and an upper case of the ink jet printer shown in FIG. 1 are removed. FIG. 3 is an enlarged perspective view of a carriage scanning portion shown in FIG. 2. FIG. 2 is a block diagram illustrating an electrical configuration of a printer. It is a block diagram which shows the structure of the drive control apparatus of a carriage motor. It is explanatory drawing which shows the relationship between a motor drive signal and the characteristic of a carriage motor. It is the graph which showed an example of the change of a threshold.

Explanation of symbols

1: ink jet printer, 12: paper feed motor, 13: carriage (driven body), 14: transport roller, 26: carriage motor, 28: drive pulley, 32: rotary encoder, 33: driven pulley, 35: timing belt, 52: Print head, 53: Carriage shaft, 70: Linear encoder, 102: Main control circuit, 104: CPU, 110: ROM, 112: RAM, 114: EEPROM, 120: Interface circuit, 130: Paper feed motor drive circuit, 140: head drive circuit, 150: CR motor drive circuit, 200: CR motor control circuit, 210: proportional element, 212: integral element, 214: differential element

Claims (8)

When controlling the operation of the driven body by the rotational drive of the DC motor,
For the drive current value of the DC motor during normal operation of the driven body, a threshold value of the drive current of the DC motor for detecting that the driven body is in a predetermined state is set.
A method for controlling a motor, comprising: changing the threshold value in accordance with a change in the drive current value during the normal operation that changes with an increase in an accumulated drive amount of the driven body. A motor control method according to claim 1, comprising:
The motor control method, wherein the threshold value is set between the drive current value during the normal operation and an overload current value when an abnormality occurs on the driven side. The motor control method according to claim 1 or 2,
The driven body is a carriage having a print head for ejecting ink onto the printed body,
The threshold value is a threshold value for detecting that the carriage is positioned at the home position at the end in the scanning direction, and the threshold value is changed by increasing the number of scans as the cumulative driving amount of the carriage. The motor control method. The motor control method according to claim 3,
The motor control method, wherein the threshold value is changed when the number of scans reaches a predetermined value. A motor control device having a DC motor, a driven body that operates by rotational driving of the DC motor, and a control system that controls rotational driving of the DC motor,
The control system includes a driving current of the DC motor for detecting that the driven body is in a predetermined state with respect to a driving current value of the DC motor during normal operation of the driven body. A threshold is set,
The motor control device according to claim 1, wherein the threshold value changes in accordance with a change in the drive current value during the normal operation that changes with an increase in the cumulative drive amount of the driven body. The motor control device according to claim 5,
The motor control apparatus, wherein the threshold value is set between the drive current value during the normal operation and an overload current value when an abnormality occurs on the driven side. The motor control device according to claim 5 or 6,
The motor control device according to claim 1, wherein the driven body is a carriage including a print head that discharges ink to the printed body.   An ink jet printer comprising the motor control device according to claim 7.

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