JP3503429B2 - Motor control device - Google Patents

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 with 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 necessary to prevent dust from adhering to the ink jet or ink from drying. The print head and the ink tank are placed outside the print area, and are covered with a cover or the like so that they cannot be easily touched by the user.

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

At this time, since the DC motor is not capable of holding the motor itself as compared with the stepper motor, it is necessary to hold its position by using some mechanism. As a holding mechanism, a mechanical mechanism for holding the print head by hooking it, or an electric mechanism for stopping by an inertial force by turning off the amplifier when a set threshold value is reached (Japanese Patent Publication No. 7-1167).
No. 4) is considered.

[0005]

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

Therefore, it is an object of the present invention to provide a motor control device that can electrically maintain the rotation stop of a DC motor without providing a mechanical mechanism.

[0007]

SUMMARY OF THE INVENTION The present invention is a motor control device designed to solve such problems. That is, the motor control device of the present invention is a DC motor that rotates in a predetermined direction via a bridge circuit based on a pulse width modulation unit that outputs a pulse signal having a predetermined duty and a pulse signal output from the pulse width modulation unit. In order to maintain the rotation stop of the DC motor,
The presence or absence of rotation and its rotation direction are based on the encoder output.
And a control means for performing control for correcting the duty of the pulse signal in the pulse width modulation means based on the detection result .

According to the present invention, in maintaining the rotation stop of the DC motor, the presence or absence of rotation of the DC motor and the rotation thereof are maintained.
The direction is detected based on the output of the encoder, and this detection result
Since the control means corrects the duty of the pulse signal output from the pulse width modulation means based on the above, the pulse signal of the duty corresponding to the rotation stop of the DC motor is continuously sent, and the stopped state of the DC motor can be maintained. Like

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a motor control device of the present invention will be described below with reference to the drawings. FIG. 1 is a block configuration diagram illustrating a motor control device 1 according to the present embodiment, FIG. 2 is a diagram illustrating an application example to an inkjet printer 10, and FIG. 3 is a diagram illustrating a speed profile of a print head.

For example, the motor control device 1 in this embodiment is an ink jet printer 10 as shown in FIG.
It is used to control the print head 5 of FIG. The print head 5 is attached to a belt 4 that is wound around a pulley 2a, and the DC motor 2 rotates the pulley 2a.

That is, the pulley 2a is rotated by rotating the DC motor 2 in a predetermined direction, and the print head 5 is moved in parallel 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 which is composed of a rotary encoder and a linear encoder. The motor control device 1 in the present embodiment controls a signal given to the DC motor 2 based on the detection result output from the rotation detection unit 3 to control its rotation direction and rotation speed.

That is, as shown in FIG. 3, the print head increases its moving speed in order to perform a predetermined print, and prints at a certain speed (print section). Then, for example, after the printing of one line is completed, the print head is moved in the opposite direction to return 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 or the like in this way, and particularly when the print head or the like is replaced, the DC motor 2 is controlled. It is characterized by electrical control that keeps the rotation stopped.

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

Each component will be described below. 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 is a circuit that detects the rotation direction of the DC motor 2 based on pulse signals of a plurality of phases output from the encoder I / F 101 using a flip-flop, for example.

The edge-to-edge detection circuit 103 detects, for example, the rising interval of the 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 t clocks.

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

The target speed setting unit 201 in the software configuration sets the 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 a calculation of calculation speed data = Fast clock / capture.

The speed compensation calculation unit 203 uses the actual rotation speed calculated by the speed data calculation unit 202 as the target speed setting unit 2.
The 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 unit 205 calculates a position compensation value based on the speed error cumulative value 206 and the target position set by the target position setting unit 207.

The outputs from the speed compensation calculation unit 203, the start 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 a through current prevention circuit 304 and a current control circuit 30.
5, input to the DC motor 2 via the driver circuit 306. That is, the DC motor 2 has the PWM output circuit 3
The pulse signal output from 00 rotates at a rotation speed according to the duty.

Further, the circuit enable signal 301 outputs an enable signal to the through current prevention circuit 304 when some trouble occurs in the rotation control to prevent damage to each circuit.

The above software configuration is stored in 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. A bridge circuit 306a is connected to the DC motor 2, and the bridge circuit 3
The duty (Dut) of the PWM signal input to 06a
The rotation direction of the DC motor 2 is controlled by y).

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

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 signal duty 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 stopped state.

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

Further, in the present embodiment, the PWM output circuit 300, such as the shoot-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.

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

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

The motor control device 1 of this embodiment shown in FIG.
Then, even though the duty of the PWM signal is set to 50% in this way, when the duty is changed when it is finally given to the DC motor 2 due to the signal delay, or the ink tank is replaced by the user. If the print head 5 (see FIG. 2) moves due to work such as
The rotation of the C motor 2 is detected by a rotary encoder or a linear encoder 3a, and the PW is detected according to the operating speed.
The duty of the M signal is changed to control the rotation speed of the DC motor 2 to zero.

At this time, the rotation direction of the DC motor 2 is as shown in FIG.
The rotation direction detection circuit 102 shown in FIG. Figure 7
FIG. 3 is a diagram showing an example of a rotation direction detection circuit 102. A flip-flop is used in the rotation direction detection circuit 102, and a rotary encoder or a linear encoder 3a is used.
The A and B phases output from (see FIG. 1) are input to the 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 at the input / output of the flip-flop. Flip-flop Clo
When ck, that is, the B phase becomes 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 contrary, when the B phase, which is the clock of the flip-flop, becomes the High level, and the A phase, which is the D input of the flip-flop, is already at the Low level, the output Q outputs the Low level. It

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 rotating 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 shift 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) and the PWM
It is reflected in the duty of the PWM signal output from the output circuit 300.

Further, while the rotation stop of the DC motor 2 is maintained, the motor control device 1 corrects the duty of the PWM signal as described above. During that time, the circuit continues to be energized and a failure such as a circuit failure occurs. May occur.

Therefore, in the present embodiment, when the rotation stop of the DC motor 2 is maintained, if the duty of the PWM signal greatly exceeds a predetermined threshold value due to a circuit failure or the like,
Turn off 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, by inputting the PWM signal and the enable signal to the AND gate G and turning off 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 duty of the PWM signal is set to 50% and transmitted. Then, as shown in step S102,
Detects the number of encoder edges per unit time.

In step S103, the detected number of edges is compared with a predetermined threshold value. 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 0. 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 DC motor is not rotating and the process ends.

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

Then, in step S106, it is determined whether or not the detected rotation direction of the DC motor is counterclockwise, and if it is counterclockwise, Yes is determined in step S10.
Proceed to 7. In step S107, the correction value is calculated by multiplying the detected number of encoder edges by a predetermined coefficient K.

When 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, the detected edge number of the encoder is multiplied by -1 and a predetermined coefficient K is calculated to calculate a correction value.

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

After that, returning 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 until the duty of the PWM signal is stopped until the DC motor is stopped. Make a correction.

If the number of edges of the encoder exceeds the predetermined threshold value in step S103, No
Then, the process proceeds to step S110 and the enable signal is turned off. By this processing, the PWM signal is not input to the DC motor, and the device can be protected. Then, in step S111, a fail is transmitted to inform the user that an error has occurred.

By correcting the duty of the PWM signal in this way, even when there is a circuit delay and when the print head moves due to the work such as the ink tank replacement by the user, the duty is added to the DC motor by the duty. Will be able to maintain the rotation stop. Also,
If the corrected duty is greatly deviated for some reason, the PWM signal becomes DC when the enable signal is turned off.
In addition to controlling not to input to the motor, it becomes possible to send a fail to notify the error.

[0058]

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

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a motor control device of the present embodiment.

FIG. 2 is a diagram showing an example of application to an inkjet printer.

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

FIG. 4 is a diagram illustrating rotation of a DC motor according to a PWM signal.

FIG. 5 is a diagram showing a signal delay in a shoot-through current prevention circuit.

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

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

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

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

FIG. 10 is an operation flowchart of duty correction.

[Explanation of symbols]

1 ... Motor control device, 2 ... DC motor, 300 ... PWM
Output circuit, 306a ... Bridge circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-56-157293 (JP, A) JP-A-9-47056 (JP, A) JP-A-8-223986 (JP, A) JP-A-8- 126374 (JP, A) JP 5-137370 (JP, A) JP 4-307609 (JP, A) JP 4-90013 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 5/00-5/26 H02P ^7/ 00-7/34

Claims (4)

(57) [Claims] 1. A pulse width modulation means for outputting a pulse signal having a predetermined duty, a DC motor which rotates in a predetermined direction via a bridge circuit based on the pulse signal output from the pulse width modulation means, Upon maintaining the rotation stop of the DC motor, the straight
Encoder for the presence or absence of rotation of the flow motor and its direction
And a control means for performing control for correcting the duty of the pulse signal in the pulse width modulation means on the basis of the detection result of the motor control device. 2. The control means sets the duty of the pulse signal to maintain the rotation stop of the DC motor by delaying the signal sent from the pulse width modulation means to the DC motor via the bridge circuit. The motor control device according to claim 1, wherein the motor control device controls to a value that takes into consideration. 3. The control means, when controlling the duty of the pulse signal to a predetermined value, controls the output of the pulse signal when the value exceeds a predetermined threshold value. The motor control device according to claim 1. 4. A pulse signal having a predetermined duty
A pulse width modulation means for outputting, and the pulse signal output from the pulse width modulation means
DC motor that rotates in a predetermined direction via a bridge circuit based on
In order to maintain the rotation stop of the DC motor and the DC motor,
Predetermine the duty of the pulse signal in the pulse width modulation means
Motor control having control means for maintaining the value of
Control device for driving the print head by the DC motor, and when the user performs maintenance with the print head stopped at a predetermined position, the printing is performed during maintenance work by the user. When the head is moved, it is provided with a rotation detecting means for detecting the presence or absence of rotation of the DC motor corresponding to the movement by an encoder, detecting the rotation direction by a flip-flop, and passing the information to the control means. Motor control characterized by
Equipment .