JPH1127986A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the stop of ration of a DC motor electrically, without providing a mechanism by performing a control for maintaining the duty of the pulse signal to a predetermined value in maintaining the stop of rotation of a DC motor. SOLUTION: Outputs from a speed compensation processing section 203, start PWM value installation section 204, and position compensation processing section 205 in the software configuration are inputted to PWM output circuit 300, respectively. From the PWM output circuit 300, pulse signal of predetermined duty for driving a DC motor 2 is output, based on each data of respective PWM output circuit. This pulse signal is input to the DC motor via a flow- through current prevention circuit 304, a current control circuit 305 and a driver circuit 306. That is, the DC motor 2 will be made to rotate at a rotating speed, corresponding to the duty of the pulse signal output from the PWM output circuit 300. Thus, if it is controlled for maintaining the duty of PWM signal to 50%, the stop state of the DC motor can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for controlling the driving of a DC motor by a pulse signal having a predetermined duty.

[0002]

2. Description of the Related Art Conventionally, in an apparatus such as an ink jet printer using a direct current motor (hereinafter, referred to as a "DC motor"), it is usually to prevent dust from adhering to the ink jet or to prevent the ink from drying. The print head and the ink tank are on standby outside the print area, and are covered with a cover or the like so as not to be easily touched by the user.

[0003] When such a print head or ink tank is replaced, the print head waiting outside the print area is moved to a position where the user can easily work.

At this time, since the DC motor has no ability to hold the motor itself as compared with the stepper motor, it is necessary to hold the position by using some mechanism. As the holding mechanism, a mechanical mechanism for holding the print head with a claw or an electrical mechanism for stopping by an inertia force by turning off an amplifier when a set threshold value is reached (Japanese Patent Publication No. 7-1167)
No. 4 gazette) has been considered.

[0005]

However, in the mechanical mechanism for holding the DC motor by hooking the claw as described above, it is necessary to separately provide a drive mechanism for driving the claw, and it is also necessary to provide a space for disposing the claw and the like. It is necessary to secure a moving space. In the case of an electric mechanism in which the amplifier is turned off when the set threshold value is reached and stopped by inertia, D
Although the C motor can be stopped, it cannot be held at that position, so that the print head moves during the replacement work of the print head and the ink tank, which causes a problem that the workability is deteriorated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a motor control device which can electrically stop the rotation of a DC motor without providing a mechanical mechanism.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a motor control device for solving such a problem. That is, the motor control device of the present invention includes a pulse width modulation unit that outputs a pulse signal having a predetermined duty, and a DC motor that rotates in a predetermined direction through a bridge circuit based on the pulse signal output from the pulse width modulation unit. And control means for performing control to maintain the duty of the pulse signal in the pulse width modulation means at a predetermined value in maintaining the rotation stop of the DC motor.

According to the present invention, in maintaining the rotation stop of the DC motor, the duty of the pulse signal output from the pulse width modulation means is maintained at a predetermined value under the control of the control means. , A pulse signal having a duty corresponding to the above is continuously transmitted, and the stopped state of the DC motor can be maintained.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a motor control device according to the present invention. FIG. 1 is a block diagram illustrating a motor control device 1 according to the present embodiment, FIG. 2 is a diagram illustrating an example of application to an ink jet printer 10, and FIG. 3 is a diagram illustrating a speed profile of a print head.

For example, the motor control device 1 according to the present embodiment includes an ink jet printer 10 as shown in FIG.
Is used to control the print head 5 of FIG. The print head 5 is attached to a belt 4 hung on a pulley 2a, and the pulley 2a is rotated by a DC motor 2.

That is, the pulley 2a is rotated by rotating the DC motor 2 in a predetermined direction, and the print head 5 is translated by moving the belt 4 (see arrow A in the figure).

The rotation speed of the DC motor 2 is detected by a rotation detector 3 comprising a rotary encoder or a linear encoder. The motor control device 1 in the present embodiment controls a signal applied to the DC motor 2 based on the detection result output from the rotation detection unit 3 to control the rotation direction and the rotation speed.

That is, as shown in FIG. 3, the print head increases its moving speed in order to perform predetermined printing, and performs printing when the speed reaches a constant speed (print section). Then, for example, after printing for one line is completed, the print head moves in the opposite direction and returns to the start position (return section).

The motor control device 1 of the present embodiment controls the rotation of the DC motor 2 for moving the print head and the like as described above. It is characterized by electrical control for maintaining the rotation stop of the motor.

As shown in FIG. 1, the motor control unit 1 comprises hardware of a one-chip (1 CHIP) CPU and software (Software) for compensating rotation control for the DC motor 2.

Hereinafter, each component will be described. First, the encoder I / F 101 in the hardware configuration
Receives a signal detected by the rotary encoder or the linear encoder 3a, removes a noise component, and outputs the signal.

The rotation direction detection circuit 102 detects the rotation direction of the DC motor 2 based on a plurality of phase pulse signals output from the encoder I / F 101 using, for example, a flip-flop.

The inter-edge detection circuit 103 detects, for example, a rising interval of a pulse signal output from the encoder I / F 101. The counter circuit 104 counts the number of Fast clocks between one edge detected by the edge detection circuit 103. The Fast clock generation circuit 105 uses the Fas used in the counter circuit 104.
Generate a t clock.

The memory 106 stores the number of Fast clocks counted by the counter circuit 104. The timer circuit 107 sets a period for performing sampling.

The target speed setting section 201 in the software configuration sets a target speed for the rotation of the DC motor 2 to be controlled. The speed data calculation unit 202 calculates the actual rotation speed of the DC motor 2 by performing the calculation of calculated speed data = Fast clock / capture.

The speed compensation calculation unit 203 calculates the actual rotation speed calculated by the speed data calculation unit 202 into the target speed setting unit 2.
A compensation value for achieving the target speed set in 01 is calculated. The starting PWM value setting unit 204 sets a PWM (phase width modulation) value when the rotation of the DC motor 2 is started.

The position compensation calculation section 205 calculates a position compensation value based on the speed error accumulated value 206 and the target position in the target position setting section 207.

Outputs from the speed compensation calculation unit 203, the starting PWM value setting unit 204, and the position compensation calculation unit 205 in the software configuration are input to the PWM output circuit 300, respectively. The PWM output circuit 300 outputs a pulse signal of a predetermined duty for driving the DC motor 2 based on each data.

The pulse signal output from the PWM output circuit 300 is supplied to the through current prevention circuit 304 and the current control circuit 30.
5. Input to the DC motor 2 via the driver circuit 306. That is, the DC motor 2 is connected to the PWM output circuit 3
The rotation is performed at a rotation speed corresponding to the duty of the pulse signal output from 00.

The circuit enable signal 301 outputs an enable signal to the through current prevention circuit 304 when any trouble occurs in the rotation control so as to prevent breakage of each circuit.

The above software configuration is based on the ROM 302
This is realized by reading the program processing stored in the RAM 303 into the RAM 303 and executing it.

FIG. 4 is a diagram for explaining the rotation of the DC motor 2 based on the PWM signal. The DC motor 2 is connected to a bridge circuit 306a.
06a input to the PWM signal (Dut)
The rotation direction of the DC motor 2 is controlled by y).

That is, P is applied to the bridge circuit 306a.
By inputting the WM signal, the High level of the PWM signal is input.
Two sets of two diagonal transistors centering on the DC motor 2 corresponding to the level (hereinafter, referred to as “H”) and the Low level (hereinafter, referred to as “L”) The groups are turned on alternately, and the direction of the current flowing through the DC motor 3 is alternately switched.

That is, the direction and magnitude of the effective current flowing to the DC motor 2 are determined by the switching ratio of the current direction according to the duty of the PWM signal, and the rotation of the DC motor 2 can be controlled.

For example, as shown in FIG.
When the duty of the signal is 50 to 100%, the DC motor 2 rotates clockwise, and as shown in FIG.
When the duty of the PWM signal is 0 to 50%, DC
The motor 2 rotates counterclockwise. Further, as shown in FIG. 4C, when the duty of the PWM signal is 50%, the speed is 0, that is, the motor is stopped.

The motor control device 1 according to the present embodiment shown in FIG.
Then, in maintaining the rotation stop of the DC motor 2, P
By controlling the duty ratio of the PWM signal output from the WM output circuit 300 to be 50%, the stopped state of the DC motor 2 can be maintained.

In this embodiment, the PWM output circuit 300, such as the through current prevention circuit 304, the current limiting circuit 305, and the driver circuit 306 shown in FIG.
The duty of the PWM signal for maintaining the rotation stop of the DC motor 2 is corrected in consideration of the signal delay due to various circuits up to this point.

FIG. 5 is a diagram showing a signal delay in the through current prevention circuit 304. That is, the duty 50.0
The PWM signal input in% is delayed by an internal circuit as shown by, and has a duty of 51.0%.

FIG. 6 is a diagram showing a signal delay in the current limiting circuit 305. In the through current prevention circuit 304 (see FIG. 5) described above, the PWM signal input with a 50% duty has a duty of 51.0%, and finally has a duty of 51.5%, and the current limiting circuit 305
Is input to

Then, this PWM signal passes through the current limiting circuit 305 and is input to the DC motor 2 with a duty of 52.0%.

The motor control device 1 of the present embodiment shown in FIG.
Thus, when the duty of the PWM signal is set to 50%, the signal delay causes a change in the duty when finally given to the DC motor 2, or the ink tank replacement by the user. When the print head 5 (see FIG. 2) is moved by the operation such as
The rotation of the C motor 2 is detected by a rotary encoder or a linear encoder 3a, and PW
The duty of the M signal is changed to control the rotation speed of the DC motor 2 to be zero.

At this time, the rotation direction of the DC motor 2 is
Is determined by the rotation direction detection circuit 102 shown in FIG. FIG.
3 is a diagram illustrating an example of a rotation direction detection circuit 102. FIG. The rotation direction detection circuit 102 uses a flip-flop, and is configured to use a rotary encoder or a linear encoder 3a.
The A and B phases output from FIG. 1 (see FIG. 1) are input to a flip-flop to obtain the rotation direction.

The truth table of this flip-flop is shown in Table 1 below.

[0039]

[Table 1]

That is, the A-phase signal output from the rotary encoder or the linear encoder 3a (see FIG. 1) is input to the D input of the flip-flop, and the B-phase signal is input as Clock.

FIG. 8 is a timing chart for input and output of the flip-flop. Clo of flip-flop
When ck, that is, the B phase is at the High level, and the A phase which is the D input of the flip-flop is already at the High level, the output Q outputs the High level.

On the other hand, when the phase B, which is the clock of the flip-flop, is at the high level, and the phase A, which is the D input of the flip-flop, is already at the low level, the output Q outputs the low level. You.

Since the phase shift between the A and B phases output from the rotary encoder or the linear encoder 3a (see FIG. 1) is determined according to the rotation direction of the DC motor 2, such a flip-flop is used. The rotation direction of the DC motor 2 can be determined by detecting the phase difference between the A and B phases at the High level and the Low level of the output Q.

The signal from the output Q of this flip-flop is input to the CPU interrupt detection (see FIG. 7),
This is reflected in the duty of the PWM signal output from the output circuit 300.

Further, while the rotation of the DC motor 2 is stopped, the motor control device 1 performs such duty correction of the PWM signal. May occur.

Therefore, in this embodiment, when the rotation of the DC motor 2 is stopped, if the duty of the PWM signal greatly exceeds a predetermined threshold value due to a circuit failure or the like,
When the circuit enable signal 301 shown in FIG.
The WM signal is prevented from being input to the DC motor 2.

As shown in FIG. 9, the PWM signal and the enable signal are input to the AND gate G, and the circuit enable signal 301 shown in FIG.
The WM signal is prevented from being input to the bridge circuit 306a.

FIG. 10 is an operation flowchart for duty correction. First, as shown in step S101, the PWM signal is transmitted with the duty (Duty) set to 50%. Next, as shown in step S102,
Detect the number of encoder edges per unit time.

In step S103, the detected number of edges is compared with a predetermined threshold value, and if the number of edges does not exceed the predetermined threshold value, the result is Yes, and step S103 is performed.
Proceed to 104.

In step S104, it is determined whether the number of edges is greater than zero. If it is larger, it is determined that the DC motor is rotating, and the process proceeds to step S105. If No in step S104, the process ends, assuming that the DC motor is not rotating.

When the DC motor is rotating, the rotation direction of the DC motor is detected in step S105 by detecting the level of the Q output of the flip-flop circuit described above.

Then, in step S106, it is determined whether or not the detected rotation direction of the DC motor is counterclockwise.
Proceed to 7. In step S107, a correction value is calculated by multiplying the detected number of edges of the encoder by a predetermined coefficient K.

On the other hand, if the rotation of the DC motor is not counterclockwise, the determination in step S106 is No, and the process proceeds to step S108. In step S108, a correction value is calculated by multiplying the detected number of edges of the encoder by -1 and by a predetermined coefficient K.

In step S109, the duty (50%) of the PWM signal is changed to step S107 or step S107.
A calculation for adding the correction value calculated in 108 is performed, and thereby the rotation control of the DC motor is performed.

Thereafter, the flow returns to step S102. If the DC motor is still rotated even if the DC motor is controlled with the corrected duty, steps S103 to S109 are repeated again, and the duty of the PWM signal is repeated until the DC motor stops. Make corrections.

If the number of edges of the encoder exceeds a predetermined threshold value in step S103,
Then, the process proceeds to step S110 to turn off the enable signal. By this processing, the PWM signal is not input to the DC motor, and the device can be protected. Then, in step S111, a failure is sent to inform the user that an error has occurred.

By correcting the duty of the PWM signal in this manner, even if there is a circuit delay, or even if the print head is moved by the work of replacing the ink tank by the user, the DC motor is adjusted by the duty in consideration of the movement. Rotation stoppage can be maintained. Also,
If the corrected duty greatly deviates for some reason, the PWM signal becomes DC by turning off the enable signal.
In addition to controlling the motor so that it is not input to the motor, a failure can be sent to notify an error.

[0058]

As described above, the motor control device of the present invention has the following effects. That is, since the rotation stop state can be maintained by maintaining the duty of the pulse signal from the pulse width modulation means to be given to the DC motor at a predetermined value, it is possible to accurately perform only the electrical signal processing without providing a mechanical holding mechanism. Thus, the rotation stop of the DC motor can be maintained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a motor control device according to an embodiment.

FIG. 2 is a diagram illustrating an example of application to an ink jet printer.

FIG. 3 is a diagram illustrating a speed profile of a print head.

FIG. 4 is a diagram for explaining rotation of a DC motor by a PWM signal.

FIG. 5 is a diagram illustrating a signal delay in a through current prevention circuit.

FIG. 6 is a diagram illustrating a signal delay in the current limiting circuit.

FIG. 7 is a diagram illustrating an example of a rotation direction detection circuit.

FIG. 8 is an input / output timing chart of a flip-flop.

FIG. 9 is a circuit diagram illustrating input of an enable signal.

FIG. 10 is an operation flowchart in duty correction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Motor control device, 2 ... DC motor, 300 ... PWM
Output circuit, 306a ... bridge circuit

Claims (4)

[Claims] 1. A pulse width modulation means for outputting a pulse signal having a predetermined duty, a DC motor rotating in a predetermined direction via a bridge circuit based on the pulse signal output from the pulse width modulation means, A motor control device comprising: control means for performing control to maintain the duty of a pulse signal in the pulse width modulation means at a predetermined value when the rotation stop of the DC motor is maintained. 2. The control means, when maintaining the rotation stop of the DC motor, adjusts a duty of the pulse signal to a delay of a signal sent from the pulse width modulation means to the DC motor via the bridge circuit. 2. The motor control device according to claim 1, wherein the control is performed to a value that takes into account. 3. The control means according to claim 1, wherein, when controlling the duty of the pulse signal to a predetermined value, when the value exceeds a predetermined threshold value, the control means performs control to cut off the output of the pulse signal. The motor control device according to claim 1, wherein 4. A printhead is driven by the DC motor, and when a user performs maintenance while the printhead is stopped at a predetermined position, the printhead is maintained when the user performs maintenance work. When the DC motor is moved, the encoder detects rotation of the DC motor corresponding to the movement with an encoder, detects the direction of rotation with a flip-flop, and passes the information to the control means. The motor control device according to claim 1, wherein: