JPH03136884A - Recording apparatus - Google Patents

Abstract

PURPOSE:To restrict the change of the speed and vibration of a carriage motor by setting the pitch of a motor cogging to be agreed with the pitch of a timing belt to offset the change of the torque by the motor cogging and timing belt through a pulley. CONSTITUTION:The belt pitch of a timing belt 6 is agreed with the pitch of coggings proper to a carriage driving motor 1. For example, supposing that the carriage driving motor 1 is a 48-step stepping motor having 24 coggings per round, a pulley 3B is formed with 24 coggings, thereby making the pitch of the cogging agreed. Moreover, in order to offset the change of the speed, the mounting position of the pulley 3B is set so as to hold a predetermined positional relation between a cycle of the cogging torque of the step motor 1 and the position of a groove of the pulley 3B. D indicates a waveform obtained by overlapping the torque change of waveforms A and C. In the waveform D, waveforms A and B are offset, thereby making small the torque change.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to various recording devices that record characters, etc. on a recording material such as paper, and in particular, the present invention relates to various recording devices that record characters, etc. on recording materials such as paper, and in particular, the present invention relates to various recording devices that record characters, etc. on recording materials such as paper, and in particular, a recording device that uses a step motor as a drive source to drive a recording head. The present invention relates to a recording device that moves for scanning.

(Prior Art) In conventionally known serial type recording devices, the carriage motor that drives the carriage that transports the recording head for recording scanning is generally a hybrid type or a PM type (permanent magnet type) stepper motor. A motor is used.

In addition, in order to reliably transmit the displacement caused by the rotation of the carriage motor to the carriage without slipping or backlash,
The output shaft of the step motor and the carriage are coupled by a timing belt. In addition, a pulley with a groove that accurately engages the protrusion of the timing belt is connected to the output shaft of the motor, and the amount of rotation of the step motor and the movement of the carriage depend on the diameter of the pulley. The relationship with quantity is determined.

Additionally, the stepper motor employs closed-loop control. This closed-loop control suppresses the vibration noise and speed unevenness associated with the step drive of the step motor, prevents step-out and resonance, and makes it possible to increase torque (which the invention aims to solve). However, in the conventional example as described above, there are the following problems to be solved.

(2) Since a step motor is used as a carriage motor, the cogging torque inherent in the step motor becomes a load on the motor, which causes periodic speed fluctuations in the carriage. Here, the cogging torque is a load that is generated when the rotor shaft of an unexcited stepper motor is rotated, and the magnitude of the load changes periodically. Such periodic fluctuations are caused by the positional relationship between the rotor magnetic poles and stator magnetic poles of the step motor, and a PM step motor with 48 steps per revolution generally has a cogging torque of 24 cycles or 4a cycles. There is a cycle.

■ Also, since a timing belt is used, when the protrusions on the timing belt engage with the grooves on the motor pulley, or when they separate, they may get caught or become stuck.
The rubbing occurs and becomes a disturbance load on the motor, causing speed fluctuations in the pitch period of the timing belt in the step motor.

■ Furthermore, if the frequency of the speed fluctuation of the cogging torque period of the step motor described above and the frequency of the speed fluctuation of the belt pitch period are close to each other, a new period of speed fluctuation will occur due to the so-called "beating" phenomenon. do.

For example, the step motor is a PMM motor with 48 steps per revolution, the occurrence of cogging is 24 per revolution, the timing belt has a pitch of 87,100 inches, and the number of bouncing is 1.
Assume that the circumference is 20 teeth, and the carriage speed is 380 mm.
Consider the case where it is set to /s. With the above settings, the rotational speed of the step motor is 582 rpm, so the frequency of the cogging torque is 225 Hz.

The belt pitch frequency is 187 Hz, and the difference between the two frequencies, 38 Hz, is the beat frequency.

As explained above, the conventional step motor rotates with speed fluctuations at these frequencies, so the carriage connected by the timing belt also
It is moving with velocity fluctuations of these frequency components. On the other hand, a recording head on a carriage (for example, a thermal transfer recording head).

(inkjet recording heads, etc.) perform recording operations at regular intervals, so if the carriage body scans for recording while having speed irregularities (spots), the recording of characters, images, etc. (referred to as printing) will not be at the predetermined recording position. It is carried out at a different time. If the speed fluctuation of the carriage is a periodic speed fluctuation, the printing deviation will also be periodic, and for example, if equally spaced vertical lines are recorded, moiré fringes will appear. In the case of the above-mentioned specific example, the moiré fringes of the cogging pitch are 1.69m.
The moire fringes of the belt pitch are 2.03 m and 5 pitches, and the moire fringes of both "beats" are seen at a pitch of 10.0 mm.

SUMMARY OF THE INVENTION In view of the above problems to be solved, an object of the present invention is to provide a recording apparatus that can suppress speed fluctuations of a carriage drive motor and improve recording accuracy and recording quality.

Means for Solving Cadi) To achieve the above object, the present invention provides a recording apparatus in which the recording head is rotated eight times in the scanning direction using a step motor as a driving source and a timing belt as a transmission means. The pitch of the timing belt is set to match the pitch of the cogging torque unique to the step motor, and the groove position of the pulley around which the timing belt is wound varies in speed in accordance with the period of the cogging torque. Features [Function] The present invention is characterized in that the recording head is positioned at a predetermined position to offset each other.The present invention provides a recording apparatus in which the recording head is moved six times for recording scanning using a step motor as a drive source.
There is a detection means for detecting the rotational angular position of the rotor of the step motor, and the drive of the step motor is controlled in a closed loop according to the detection result of the detection means. In order to offset the speed fluctuations of the step motor, the pitch of the motor cogging matches the pitch of the timing belt, and the pulleys are positioned so that they have a predetermined positional relationship, thereby suppressing the speed fluctuations of the step motor. Therefore, the recording accuracy and recording quality of the recording device can be improved.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

2 to 4 show the structure of main parts of a serial type inkjet printer according to an embodiment of the present invention.

First, FIG. 2 shows the structure of the carriage drive mechanism that drives the carriage on which the recording head is mounted, as the main part of the printer of this embodiment.In the six figures, 1 is the carriage drive motor, and 2 is the carriage. be. Carriage 2
is equipped with an inkjet recording system recording pad 4, which is mounted in the axial direction on guide shafts 5^, 5B installed parallel to a platen (not shown) that serves as a recording platform for recording paper (sheets) in the printer. It is slidably supported. The carriage 2 also has a timing belt 6.
The belt 6 is stretched between the pulleys 3 and 38, and one of the pulleys 3B is connected to the output rotation shaft of the carriage drive motor 1.

In addition, the timing belt 6 runs as the pulley 3B is rotationally driven by the carriage drive motor 1.
In conjunction with this, the carriage 2 moves the guide shafts 5A, 5
The recording paper slides on B in the direction of arrow F or R in this figure along the recording paper. By driving the recording head 4 while the carriage 2 moves once in the F or R direction,
Dot recording of the line is performed, and when the recording of one line is completed, the recording paper 7 is sent upward in the figure by one line and a line feed is performed. By repeating this process, recording is performed one line at a time. The printing position of the recording head 4 (recording position 5) and the 6th movement position of the carriage 2 are set to "0" when the shielding plate 8 fixed to one end of the carriage 2 overlaps with the slit 9^ of the photosensor 9; The determination is made by counting the output signal of the encoder of the drive motor l. The above-mentioned encoder is provided within the motor 1 as described later.

3 and 4 show the internal structure of the carriage drive motor 1 according to the embodiment of the present invention, which is driven under the above-mentioned driving conditions, in which lO is the casing, 13 is the rotor shaft, and 14 is the rotor. , 15^ and 15B are coils, 16^
and 16B are stators. 17 is a detection disk, 18 is a photointerrupter, and 17 and 18 constitute an encoder 26 that detects the rotational angular position of the rotor 14 of the motor 1. 19 is a rotor magnet. Rotor 14. The rotor magnet 19 and the detection disk are fixed to the rotor shaft 13 and rotated around the body.

FIG. 5 shows a circuit configuration of a motor drive control system according to an embodiment of the present invention that performs closed loop control of the carriage drive motor 1 described above.

In this figure, 20 to 25 constitute the control means of the present invention, and 26 corresponds to the detection means of the present invention. First, 20 is an MPU (microprocessor unit) that controls the entire printer. MPH 20 uses a RAM (random access memory) 22 as a data processing work area according to a control program stored in a ROM (read-on memory) 21. The MP020 uses hardware (not shown) to control the drive sources of other printer mechanisms (not shown), as well as the carriage drive motor 1 that drives the carriage 2 described above. The output pulse 2 of the encoder 26 consisting of the detection disk 11 and the photointerrupter 18 is detected using an internal counter configured by hardware or software.
7, the position of the carriage 2 is detected.

Furthermore, the MP020 controls the rotational speed of the carriage drive motor 1 by the motor drive circuit 25 via the pulse width modulation (PWM) signal generator 23, and switches the excitation current of the coils 15^ and 15B of the carriage drive motor 1. The motor drive circuit 25 controls the start, stop, and rotational direction of the carriage drive motor 1 via the current switching circuit 24 that performs the following:
Control the direction of movement.

This kind of motor drive control is performed by carriage drive motor 1.
Encoder 26. MPII20. PWM signal generator 2
3 and a motor drive circuit 25.

Next, features of the present invention will be explained with reference to the waveform diagram of FIG.

In the embodiment of the present invention, first, the belt pitch of the timing belt 6 is made to match the cogging pitch inherent to the carriage drive motor 1.

For example, if the carriage drive motor 1 is a 48-step stepping motor with 24 cogging cycles per revolution, the pulley 3B is also formed to have 24 teeth per revolution to match the pitch of the cogging. Therefore, if a belt with a pitch of 87,100 inches is used as the timing belt 6, the diameter of the pulley 3B will be 15.5a+a+. Even in the case of other types of rotors, the number of teeth on the pulley may be made to match the number of cogging cycles per revolution of the motor in the same way as described above.

Second, in the embodiment of the present invention, in order to offset speed fluctuations, the period of the cogging torque of the step motor l and the groove position of the pulley 3B are set to have a positional relationship as shown in FIG. Determine the mounting position of pulley 3B.

In this figure, A represents the load fluctuation of the cogging cycle of the step motor 1, B represents the position of the groove (teeth) of the pulley 3B attached to the carriage drive motor l, and C represents the groove of the pulley 5B and the timing belt 6. It shows the load fluctuation caused by the protrusion. The horizontal axis indicates a time axis, and represents temporal changes accompanying the rotation of the motor 1. In addition, D in Figure 1 is a waveform in which the torque fluctuation in A in the same figure and the torque fluctuation in C in the same diagram are overlapped, and in this waveform, the waveform in A and the waveform in B cancel each other out, and the torque fluctuation is It's getting smaller.

As mentioned above, in order to match the period of torque fluctuation to the opposite phase as shown by the waveforms A and B, in this embodiment, first, the grooves of the unmagnetized rotor 14 and the timing belt 6 are cut in advance. The pulley 3B which is attached to the pulley 3B is integrally connected to the pulley 3B.

The connection at this time may be by D-cut (processing to make the cross section of the shaft D-shaped) or by press-fitting. Next, the rotor magnet 19 is magnetized. At this time, the rotor 14 in the magnetizer is adjusted so that the period of the cogging torque generated when the step motor 1 is installed in the recording device and the groove of the pulley have a waveform relationship of opposite phase as shown in ^ and B in Fig. 1. The rotor magnet 19 is magnetized by positioning the rotor magnet 19.

Alternatively, in another embodiment, in order to align the magnetized position of the rotor 14 with the groove of the pulley 3B, a D cut is first made on the rotor shaft 13 of the unmagnetized rotor 14, and the D cut position is Then, the pulley 3B is coupled to the rotor shaft 13 so that the rotor magnet 19 is magnetized in a predetermined relationship. At this time, the shaft hole of pulley 3B is D-cut.
The groove position and its D cut position are as follows:
The positions are determined in advance so that the positional relationship as shown in ^ and B in Fig. 1 will be achieved when the parts are combined with each other.

(Effects of the Invention) As explained above, according to the present invention, the pitch of the motor cogging and the pitch of the timing belt are made to match, and the torque fluctuations due to the motor cogging and the timing belt are offset through the pulley. Since this setting is made, it is possible to obtain the effect of suppressing speed fluctuations and vibrations of the carriage motor without using any special members or mechanisms.

Therefore, the present invention provides low noise, high speed, and high precision (high quality)
A recording device capable of recording can be provided at a relatively low cost.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing load torque cancellation, which is a feature of the embodiment of the present invention. FIG. 2 is a perspective view of the carriage drive mechanism of the embodiment of the present invention. FIG. 3 is the configuration of the carriage motor of the embodiment of the present invention. FIG. 4 is a sectional view of FIG. 3, and FIG. 5 is a block diagram showing a circuit configuration of a motor drive control system according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Carriage drive motor, 2... Carriage, 38, 3B-... Pulley, 4... Recording head, 6... Timing belt, 9... Photo sensor, 13... Rotor shaft , 14... Rotor, 16^, 16B... Stator, 17... Detection disk, 18... Photo interrupter, 19... Rotor magnet, 20... MPU. 25...Motor drive circuit, 26...Encoder. body

Claims (1)

[Claims] 1) In a recording device that moves a recording head in a scanning direction using a step motor as a drive source and a timing belt as a transmission means, the pitch of the timing belt is unique to the step motor. The timing belt is set to match the pitch of the cogging torque, and the groove position of the pulley around which the timing belt is wound is positioned at a predetermined position where speed fluctuations are offset in accordance with the period of the cogging torque. Recording device.