JPH02155778A - Recording apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printing apparatus, and more particularly to a printing apparatus that uses a step motor as a drive source for moving a carriage on which a printing head is mounted.

(Prior Art) In conventionally known serial type recording devices, a hybrid type or PM type (permanent magnet type) step motor is used as a carriage drive motor for moving a recording head for recording scanning. , closed-loop control has been applied to motors.

The reason for this is that if the step motor is driven using interloop control, (1) When the carriage is driven, especially in the case of a hybrid type, a harsh "squeak" noise will be generated due to the vibration of the rotor of the step motor. do.

(2) When the carriage starts, stops, and reverses, the motor vibrates and moves, causing a loud "clank" noise.

This is due to the problem of noise generation.

(Problem to be solved by the invention) By the way, in order to perform closed-loop control of a step motor, an encoder is required to detect the rotational position of the rotor. ) must be aligned when assembling the motor.The reason this alignment is necessary is to synchronize the motor phase switching with the encoder output pulse, and to ensure accurate alignment. Otherwise, the motor may not rotate or the speed may vary depending on the direction of rotation.

Therefore, if the resolution per pulse is increased by increasing the number of output pulses per rotation of the encoder, alignment will become largely unnecessary. For example, an I rotates in 48 steps per revolution.
``In an M-type step motor, the magnetic poles of the rotor are 24, but if the encoder output pulses are 288 pulses per rotation, 12 pulses will be output per rotor magnetic pole, so When the encoder is attached to the rotor shaft, the deviation between the center of the rotor magnetic pole and the center of the encoder magnetic pole is at most half the pulse interval, which is within the range of ±4.2%. The deviation becomes negligible.

However, it is first necessary to decide which magnetic pole of the encoder should correspond to the rotor magnetic pole.To do this, first, a current is applied to the motor coil for a predetermined period of time or more, and then the rotor is slightly When the encoder rotates and comes to a standstill, the magnetic pole of the encoder that directly faces the encoder must be selected.The rest can be selected every 12 pulses from the initially determined one.

Furthermore, the initialization of the encoder pulses described above needs to be performed before moving the motor. That is, when such a motor is used as a carriage drive motor of a serial printer, it is necessary to perform an initial operation when the main body is powered on.

However, since the position of the printer's carriage is unknown after the power is turned off, there is a risk that the initial operation may not be performed correctly.For example, if the carriage is located at the left or right end of its movable range, If
Because of the initial operation, even if a certain phase is excited, the carriage does not move any further, so the motor cannot rotate, or the rotor reaches the hit point (the electrical angle is 180 degrees off from the normal position), and the torque If the motor was stopped at zero), the rotor position would not be set correctly and would be initialized, which could cause the motor to stop moving or run out of control.

An object of the present invention is to provide a recording device that enables smooth closed-loop control, paying attention to the above-mentioned points.

In a recording device in which recording is performed by reciprocating a carriage carrying a head using a step motor, there is provided a rotational position detection means for detecting the rotational position of the rotor of the stepmotor, and a rotational position detection means for detecting the rotational position of the rotor of the stepmotor. control means for closed-loop control of the drive speed of the step motor and the switching timing of the excitation current to the coil of the step motor, and an operation of confirming whether the initial drive and switching timing of the step motor are normal through the control means. It is characterized by the fact that it is possible.

(Function) According to the present invention, it is possible to reliably perform closed-loop control of a step motor that achieves quiet high torque and high responsiveness, and it is possible to obtain a safe and highly reliable recording device.

[Means to solve the problem]

In order to achieve this object, the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the invention. Here, 1 is, for example, an inkjet recording head, 2 is a carriage on which the recording head 1 is mounted and moves along guide shafts 3A and 3B, 4 is connected at both ends to the carriage 2, and pulley 5A
, 5B, 6 is a carriage drive motor that drives the carriage 2 via the timing belt 4, and 7 is a recording sheet held by a platen (not shown) at a position facing the recording head 1. .

Further, the carriage 2 is equipped with a scattering plate 8, and when the carriage 2 moves in the R direction, that is, to the left in FIG.
The position is detected by overlapping the Nishiya scattering plates 8,
An encoder (not shown) provided coaxially with the carriage drive motor 6 is initialized as "0". Then, as it moves from this initial position in the F direction, that is, in the right direction, the position is sequentially detected by counting signals from the encoder, and recording is performed on the recording sheet 7. Further, after the travel corresponding to the recording of the negative digit is completed, the recording sheet 7 is fed by one digit.

An example of the driving conditions required of the carriage drive motor 1 during such a recording operation is when the recording density is 3.
In the case of 60 dots/inch, the rotational speed of the carriage drive motor 1 corresponding to the recording speed is approximately 800 rpm in the high speed mode and approximately 40 Orpm in the low speed mode. Furthermore, in high-speed mode, the time from startup to constant speed running (rotation speed 800 rpm) is approximately 60a+sec.
The constant speed running time is about 1 second, and the time from constant speed running to stopping is about 60 m5ec.

FIGS. 2A and 2B show an example of the configuration of the carriage drive motor 6 described above. Here, lO is the rotor,
11 is a rotor shaft, 12A and 12B are stators disposed around the rotor lO, 13^ and 13B are coils, a detection disk 14 is coaxially mounted on the rotor shaft 11, and a photo sensor is mounted on the stator side. An interrupter 15 is attached. Thus, the rotational position of the motor 6 can be detected by counting the output pulses from the rotary encoder 16, which is composed of the detection disk 14 and the photointerrupter 15.

Therefore, next, referring to FIG. 3, the carriage drive motor 6
A motor drive control system that performs closed-loop control will be explained.

In FIG. 3, 20 is an M which controls the entire printer.
PU (microprocessor unit) and ROM
According to a control program stored in a read-only memory (read-only memory) 21, a RAM (random access memory) 22 for processing recorded data is used to drive and control the drive sources of each of the other printer mechanisms (not shown), and the carriage described above. For this purpose, the MPU 20 includes a counter configured by hardware or software (not shown), and by counting the output pulses 23 from the rotary encoder 16 described above, Carriage 2
Detect the position of.

The MPti 20 also controls the rotational speed of the carriage drive motor 6 to the above-mentioned high speed mode or low speed mode via the motor speed control circuit 24, and switches the excitation current to the coils 13^ and 13B of the carriage drive motor 6. Starting, stopping, and rotational direction of the carriage drive motor 6 are controlled via a current switching circuit 25 for starting, stopping, and moving the carriage 2.

Further, the motor speed control circuit 24 controls the rotational speed of the carriage drive motor 6 in a closed loop according to the detection output of the encoder 16, and specifically, the interval time of the output pulses 23 from the encoder 16 is set in advance. The time is compared with a reference time, and the control output 26 to the carriage drive motor 6 is adjusted according to the comparison result so as to eliminate the time difference.

Therefore, when the MPII 20 now instructs the rotational speed of the carriage drive motor 6 to the motor speed control circuit 24, the motor speed control circuit 24 selects a reference time for comparison corresponding to the instructed speed. death,
Using this, a comparison is made with the pulse interval, and it is selected whether the rotational speed of the carriage drive motor 6 is set to, for example, a predetermined high speed mode or a predetermined low speed mode.

On the other hand, the current switching circuit 25 starts the excitation current switching operation described above in response to the activation signal 27^ input from the MPU 20, starts the carriage drive motor 6, and also starts the MP
The carriage drive motor 6 is stopped by a stop signal 27B manually inputted from U20.

Further, as a point related to the present invention, the current switching circuit 25 switches the carriage drive motor 6 according to the detected output of the encoder 16.
The coil excitation [current switching timing is controlled in a closed loop. For this purpose, the current switching circuit 25 has a counter 28, which counts the output pulses from the encoder 16, and when the counted value matches a predetermined value, the excitation current is switched at that point.

Here, it is assumed that the current switching circuit 25 of the carriage drive motor 6 is of a two-phase excitation force type and is switched, for example, 48 times per rotation of the rotor 10, and the number of output pulses from the encoder 18 is 288 pulses per rotation. The rotor IO rotates by an equal angle every time one pulse is output, so if we assume that the excitation current is switched every time 6 pulses (288÷48) are counted, it always rotates by an equal angle. At this timing, the magnetic poles of the rotor 10 and the stator 12A.

The excitation current is switched while the relative position of the magnetic pole 12B is maintained in the same predetermined relationship. Therefore, it is assumed here that the excitation current is switched every time six pulses are counted.

Next, referring to FIG. 4, the procedure for controlling the carriage drive motor 6 by the MPU 20 during recording will be described.

Note that the explanation of the control operations of other mechanisms by the MPU 20 will be omitted here. Further, it is assumed that a control program corresponding to such a control operation procedure is stored in the ROM 21.

Now, when the power of the printer is turned on, in step S1, the position of the rotor lO and the current switching circuit 25 described above are determined.
An initialization operation is performed to obtain a correct correspondence with the count value of the counter. The initialization operation will be described in detail later, including the initial confirmation operation that is a feature of the present invention.

In this way, following the initialization operation, in step S2, it is determined whether the carriage 2 is at the home position at the left end in FIG. In step S3, the carriage drive motor 6 is driven to move the carriage 2 to the home position, and if it is determined that the carriage 2 is at the home position, the process directly proceeds to step S4. Furthermore, whether or not the carriage 2 is at the home position is determined. Detection of the position is performed using a detection signal from the photosensor 9.

Next, in step S4, the rotational speed of the motor 6 is adjusted according to the recording mode instructed by the host system (not shown).
Then, the rotation direction is determined, and the number of drive pulses for the carriage drive motor 6 is determined based on the number of prints per line.

Then, a signal instructing the motor rotation speed is output to the motor speed control circuit 24, and the carriage drive motor 6 is started by driving the current switching circuit 25 in step S5. That is, the carriage 2 is started. Also, at the same time as the carriage drive motor 6 is started, the MPU 2
0 starts counting the output pulses from encoder 16.

Next, in step S6, it is determined whether the carriage 2 has reached the recording start position based on the count value of the output pulses from the encoder 16, and when the carriage 2 has reached the recording start position, the recording head 4 is driven in step S7 to start recording. .

Next, in step S8, it is determined whether the carriage 2 has reached the end position of one line of recording from the count value of the output pulses from the encoder I6, and if it has reached the end position, step S9
At this point, the recording operation of the recording head 4 is stopped, and recording for one line is completed. Then, in step S10, a stop signal 27B is output to the current switching circuit 25, and the current switching circuit 25 short-circuits both ends of the coil of the carriage drive motor 6 in response to this signal 27B, thereby stopping the carriage drive motor 6.

Next, in step Sll, it is determined whether all printing has been completed based on the presence or absence of a remaining amount of recording data.

If all recording has been completed, the process moves to step 513, and the carriage drive motor 6 drives the carriage 2.
is moved to the home position and the process ends.

If it is determined that all recording has not been completed, there is recording data for the next line, so the process moves to step 512, and the carriage drive motor 1 is driven to move the carriage 2 to the recording start position for the next line. , returns to step S7 and repeats the following process.

Note that when performing reciprocating printing, the above-mentioned recording start position of the next line is set to the right end position of the recording width of the next line. Also,
When the carriage drive motor 6 is reversed to move the carriage 2 in the opposite direction (direction R in FIG. 1), the position of the carriage 2 can of course be detected by subtracting and counting the output pulses of the encoder 16. be.

Next, the above-mentioned initialization operation will be explained.

FIG. 5 shows the flow of initialization operation. As described above, since it is not known where the carriage is located when the current is turned on, the carriage must first be moved to a range where the initial operation can be reliably executed.

In addition, in the serial printer to which the present invention is applied, the step motor 6 is treated as a multipolar brushless motor and is controlled in a closed loop, so that it does not function as an original step motor. Since it is visible, in order to move the carriage 2, a step motor drive pattern generation circuit (not shown) is held inside the current switching circuit 25, and the motor 6 can be driven in synchronization with the signal from the MPII 20. Alternatively, the MPII 20 may send a drive pattern to the current switching circuit 25 for driving. In this way, by using the operation as a step motor in combination, it is possible to move the carriage 2 to a position with a necessary initial margin even before the initial processing of motor control.

Next, an initialization procedure for aligning the rotor magnetic poles and the encoder magnetic poles will be described.

Note that although the conditions for alignment have not been described so far, it is actually desirable that the relative positions be appropriate so that the motor 6 can be driven smoothly and favorably. Therefore, in this example, the excitation current switching operation is performed, for example, when the center of each magnetic pole in the rotor IO (where the magnetization is strongest) coincides with the center of one of the poles of the stators 128 and 12B, i.e. The above initial processing is preferably carried out when the drive torque is 0 as follows.

That is, in FIG. 5, first, in step 5IOI, one cycle or two cycles (1
In the case of phase excitation, the motor 6 is driven by 4 steps (one cycle corresponds to 4 steps). This serves to release the carriage 2 when it is stopped at the put point of the motor 6.

When the last step drive is completed in step 5102, the excitation state is maintained for a while in steps 5103 and 104, and then the process proceeds to step 5lO5, where the value of the above-mentioned counter that controls the excitation current switching timing is set to O. to cut off the excitation current. Note that the reason why the wait time is set between the final step and the counter clearing as described above is to suppress the vibration of the rotor and enable correct positioning. Further, these processes may be performed using two-phase excitation or 1-2 phase wJ magnetization. In that case, the initial value of the counter is set to a predetermined value.

Such initialization establishes correspondence between the rotor magnetic poles and the encoder magnetic poles, and also prepares for excitation current switching timing generation processing. Note that this correspondence relationship is maintained after initialization unless the power of the printer is turned off.

However, it cannot be said that the initialization of the motor 6 has been confirmed by the above steps alone, and normal operation is not guaranteed.
It is as stated earlier. Therefore, the initial confirmation operation, which is a feature of the present invention, is performed according to the following procedure.

That is, first, in step 5106, a constant voltage is applied to a motor drive circuit (not shown) built in the motor speed control circuit 24 in a closed loop control state to drive the motor 6 and drive the carriage in the direction F in FIG. 1. Note that the speed in this case does not need to be controlled, because the speed of the motor 6 is determined by the motor drive voltage and loads such as carriage friction, like a general OC motor. Therefore, the carriage speed (
When the rotational speed of the motor 6 becomes constant (step 5107), the rotational speed of the motor 6 is measured (step 5107).
The rotational speed of is detected from the time interval of encoder pulses input from the encoder 16.

Next, in step 5108, the carriage 2 is driven in the R direction with the same driving voltage as before, and in the same way, in step 510
9 measures the rotational speed of motor 6 0 Normal carriage 2
Since the coefficient of friction between the motor 6 and the guide shafts 3^, 3B is constant regardless of the direction of movement, the load on the motor 6 does not change depending on the direction of rotation, and its speed should be constant regardless of the direction of rotation. . Therefore, in step S10, the motor speeds in the F direction and the R direction are compared, and if the speed difference between them is within a predetermined value range, it is determined that the current switching is performed normally, and the next step 5itt is performed. Start the recording operation. If it is determined in step 5110 that the motor speed differs significantly depending on the rotational direction, it is assumed that an initial error has occurred and the process returns to step 5101 to redo the initialization process for the motor 6.

As described above, according to this embodiment, the initial operation of the carriage drive motor 6 can be performed reliably, and stable closed-loop control can be performed.

Therefore, carriage control without vibration and speed unevenness can be realized with a simple circuit.

Note that the speed of the motor 6 may be measured by measuring the time interval of the encoder pulses as described above, but it can also be measured by counting the encoder pulses within a certain period of time. Next, a second embodiment of the present invention will be explained with reference to FIG.

In this embodiment, a resistor 31 for current detection is provided in connection with the motor drive circuit 30. In the previous embodiment, it was determined whether the current switching was normal or not by utilizing the fact that even if the motor 6 was rotated without control, its speed was determined by the drive voltage and load.

However, in this embodiment, the initial state is determined based on the fact that when the motor 6 is controlled to a certain constant speed, a constant current flows if the load is the same.

In other words, if the excitation current switching timing differs depending on the rotation direction, the motor 6 will not be initialized correctly.
That is, if the excitation switching is performed earlier than normal, the motor will try to rotate faster, and if the excitation switching is slower than normal, the motor will try to rotate slower. Therefore, in order to rotate at the same speed in different rotational directions, if the current switching is slow, a large amount of current should be passed through the motor 6, and conversely, if the current switching is fast, a small amount of current can be passed through the motor 6. The value 32 is taken out and input to MP020 via the A/D converter 33.

Therefore, the MPt 120 compares the current values in both rotational directions and determines that if the current values are within a predetermined value range, the current switching is being performed normally regardless of the rotational direction. Furthermore, if the current value does not fall within a predetermined range depending on the direction of rotation, initialization is performed again.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, highly reliable closed-loop control is possible, so it is possible to provide an excellent recording device that is capable of high-speed recording with low noise and is highly durable. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the structure of a carriage drive mechanism according to the present invention, FIG. 2A is a perspective view showing the structure of a carriage motor according to the present invention, FIG. 2B is a sectional view thereof, and FIG. 4 is a block diagram showing the configuration of the drive control system; FIG. 4 is a flowchart showing the procedure for controlling the carriage motor according to the present invention; FIG. 5 is a flowchart showing the procedure for the initial processing operation for the carriage motor according to the present invention; FIG. 6 is a block diagram of a motor speed control circuit according to a second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Recording head, 2... Carriage, 6... Carriage drive motor, 8... Scattering plate, 9... Photo sensor, lO... Rotor, 12^, 12B... Stator, 13^, 13B... φ coil, 14... detection disk, 15... photo interrupter, 20. MPIJ. 21...ROM. 22...RAM. 24... Speed control circuit, 25... Current switching circuit, ! 28... Counter, 30... Motor drive circuit, 31... Resistor. Introduction 1: Rigid force motor, 15th section gravity bone elevation 0 Pro 1 diagram Figure 3

Claims (1)

[Scope of Claims] A recording apparatus in which recording is performed by reciprocating a carriage carrying a recording head by a step motor, comprising: rotational position detection means for detecting the rotational position of a rotor of the step motor; and the rotational position detection means. control means for closed-loop control of the drive speed of the step motor and the switching timing of the excitation current to the coil of the step motor based on a detection signal from the step motor; A recording device characterized in that it is capable of confirming whether or not switching timing is normal.