JPH0984376A - Dc motor drive mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an abnormal load on a drive mechanism depending on whether the moving distance of a control object is within the predetermined range or not when the predetermined constant current is applied to a DC motor for the predetermined period, in view of detecting an abnormal load for the entire range of the moving distance by reapeating this operation for a plurality number of times. SOLUTION: In a drive mechanism for converting the rotating movement of a DC motor 1 into a reciprocal movement of a carriage 9 along a guide shaft 10, a load measuring mode is set to DPU6 to change over a mode changeover switch 15. A load measuring means 14 applies a constant current to the DC motor 1 via a DC drvier 4 for the constant period. Here, a sensor 3 detects rotation of a slit disc 2 and this slit pulse is counted by a position detecting means 11 to calculate the moving distance of the carriage 9. If this value is not in the predetermined range, it is judged as an abnormal load. An abnormal load can be detected for the entire length of a guide shaft 10 by repeating this operation for a plurality of times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive mechanism of a DC motor for moving a print head at high speed in a printer or the like, and more particularly to detection of an abnormal friction load on a carriage portion of the print head.

[0002]

2. Description of the Related Art FIG. 7 is a perspective view showing details of a carriage portion which supports a print head. In the figure, 9 is a carriage that supports the print head 9a, 10 is a guide shaft that guides the movement of the carriage 9, and 10a is a sub-shaft that guides the movement of the carriage 9 together with the guide shaft 10. In the above structure, the guide shaft 1
0 and the sliding surface 10b of the carriage 9 are provided with a minute gap, and lubricating oil is applied to reduce the friction load.

[0003]

In the above configuration,
The frictional load on the sliding part increases due to small scratches on the sliding part, unevenness due to dimensional errors, lack of lubricating oil application, running out of lubricating oil due to dust, etc., resulting in a load on the print head drive system. In some cases, the speed becomes large and the DC motor speed control and positioning control become unsuccessful. However, the abnormal load is not detected, the cause of the control failure of the DC motor is unknown, and maintenance and inspection are difficult to perform.

[0004]

In order to solve the above-mentioned problems, the present invention converts the rotational movement of a DC motor into the reciprocating movement of a controlled object, and feeds back the output of a rotary encoder that works with the DC motor. In a DC motor drive mechanism having a control unit for performing speed control and positioning control of an object to be controlled, the control unit moves the object to be moved when a predetermined constant current is applied to the DC motor for a certain time. Is calculated from the output of the rotary encoder, and the abnormality of the load of the mechanism for driving the controlled object is detected depending on whether the moving distance is within a predetermined range, and Is repeated a plurality of times to detect an abnormal load over the entire moving range of the controlled object.

[0005]

1 is a block diagram of a DC motor drive mechanism showing a first embodiment of the present invention. In the figure, 1 is a DC motor, 2 is a rotating shaft of the DC motor 1 or a slit disk which is provided in the middle of a drive transmission mechanism (not shown) and rotates in conjunction with the DC motor 1, and 3 is a slit of the slit disk 2. Of the slit pulse output from the sensor 3 by counting and managing the slit pulse output from the sensor 3 by a sensor including a light emitting / receiving element that detects the presence or absence of a slit pulse and outputs a slit pulse. D that controls the DC motor 1 according to
A C motor control unit 6 is a CPU that controls the DC motor control unit 5.

Reference numeral 7 is a pulley, 8 is a belt wound around the pulley 7, 9 is a carriage attached to the belt 8, 10 is a guide shaft for guiding the movement of the carriage 9, and the rotational movement of the DC motor 1 is the pulley. 7. The belt 8 converts the carriage 9 into a reciprocating motion along the guide shaft 10. Next, details of the DC motor control unit 5 will be described. Reference numeral 11 denotes a position detection unit, which is composed of a counter or the like for counting the input of slit pulses, counts the input pulses, and outputs the count value as position information to the CPU 6. Reference numeral 12 is a speed detection unit, and this speed detection unit 12 temporally counts the intervals of slit pulses input in time series using a counter such as a clock (not shown) to calculate the speed. The speed v is calculated by the following equation (1).

[0007]

[Equation 1]

Where T _n is the slit period (time), L
₀ is the movement distance of the carriage 9 that moves each time one slit pulse is output. The calculated speed information is stored in the CPU 6
And output to the speed control unit 13. Based on the target speed command value (v ₀ ) output from the CPU 6 and the speed information (v _n ) output from the speed detection unit 12 at that time, the speed control unit 13 calculates the following equation (2). ~
Information (I _n ) of the drive current necessary to control the DC motor 1 to the target speed by performing the calculation shown in the equation (5).
Is output to the DC motor driver unit 4.

[0009]

(2) I _n = K ₁ · F ₁ (v _n ) + K ₂ · F ₂ (v _n ) + K ₃ · F ₃ (v _n ) ... (2) F ₁ = v ₀ −v _n ···・ (3) F ₂ = ΣF ₁ (4) F ₃ = v _n −v _n-1 (5)

Here, K ₁ , K ₂ , and K ₃ are preset constants. The DC motor driver unit 4 is configured by a transistor or the like (not shown) so that the duty of the DC motor drive current becomes I _n / T _PWM based on the drive current command I _n and the preset chopping cycle T _PWM. Turn on / off the driver to control the current. Reference numeral 14 denotes a load measuring unit. The load measuring unit 14 sets a combination of a constant current value I and a time t for driving the DC motor 1 at the constant current value I in advance, and controls the (I , T) for controlling the DC motor driver unit 4.

The output section of the load measuring section 14 is connected to the mode changeover switch 15, and the changeover signal of the mode changeover switch 15 is connected to the CPU 6, and the output of the load measuring section 14 (A
Either the contact) or the output of the speed controller 13 (contact B) is switched to output to the DC motor driver 4.

The operation of the first embodiment of the present invention will be described below. Normally, the mode changeover switch 15 is connected to the B contact side by the CPU 6, and the DC motor driver section 4 is controlled by the speed control section 13 to drive the DC motor 1. Next, the case of operating in the load measurement mode will be described. In the load measurement mode, the CPU 6 causes the mode selection switch 15 to
It is connected to the A contact side. When the CPU 6 selects the load measurement mode, the load measuring unit 14 outputs a drive signal to the DC motor driver unit 4 so that the preset constant current value I ₀ and the constant current drive time t ₀ are achieved. To do. D
When the C motor 1 is driven, a slit pulse is generated,
It is counted by the position detection unit 11, and the movement distance L is counted by the position detection unit 11.

FIG. 2 shows the drive current value of the DC motor and the carrier.
It is a graph which shows the relationship of the movement distance of J. Constant current value
I₀, Constant drive time t₀To drive the DC motor 1
Then, the moving distance L of the carriage 9 is naturally determined.
You. If the load is normal, I ₀, T₀By
, Α₀<L <β₀(FIG. 2 (a)). Where α
₀, Β₀Is determined in advance from the measured value of normal load.
Keep it. When the load is abnormally heavy, L <α₀Next to
(FIG. 2B), it becomes possible to detect an abnormal load.

The CPU 6 controls the load measuring section 14.
Then, the fixed time I described above₀, Drive time t₀DC motor at
By repeating the operation of drive 1 multiple times,
Accurate detection of abnormal load over the entire shaft length
It becomes possible. FIG. 3 shows that the driving is repeated a plurality of times in this way.
Of drive current value and time and speed and movement distance
It is a graph which shows a relationship and time₀After driving, carry
When the drive moves due to inertia and the speed becomes zero, the next drive is started.
Try to do it. Furthermore, the above (I₀, T₀)The value of the
And change (I₁, T₁), (I₂, T ₂) ...
By changing the conditions so that it reciprocates over the entire length of the guide shaft.
By operating it, the abnormal load can be reliably detected. This
In case of (I_n, T_n), Depending on (α_n, Β_n) Also changed
You. The detection result should be displayed on the display or
Print it on and notify the operator.

As described above, according to the first embodiment of the present invention, D is determined by the constant current value I _n and the driving time t _n.
Since the upper limit value and the lower limit value of the carriage movement distance when the C motor 1 is driven are managed, and the DC motor 1 is driven a plurality of times with the constant current value I _n and the driving time t _n . It becomes possible to detect an abnormal load on the sliding surface of the carriage system over the entire length of the guide shaft, and it is possible to greatly improve quality.

FIG. 4 shows a second embodiment D of the present invention.
It is a block diagram of a C motor drive mechanism. In the figure, 1
Reference numeral 6 denotes a measurement mode speed control unit. The measurement mode speed control unit 16 receives a command from the CPU 6 to drive the DC motor 1 at a preset constant speed, and then performs control for cutting off the drive current. Is. The output of the measurement mode speed control unit 16 is input to the mode changeover switch 15, and the mode changeover switch 15 is operated by the control signal of the CPU 6, so that D
The output of the measurement mode speed control unit 16 is input to the C motor driver unit 4. Then, the CPU 6 detects an abnormal load by detecting the movement distance of the carriage 9 due to inertia after the drive current is cut off. The position detecting unit 11, the speed detecting unit 12, and the speed controlling unit 13, which are other components of the DC motor control unit 5, are the same as those described in FIG.

Next, the operation of the second embodiment of the present invention will be described. In the load measurement mode, the CPU 6 connects the mode changeover switch 15 to the A contact side. Then, the CPU 6 inputs the preset target speed v ₀ to the measurement mode speed control unit 16 as a command value. The measurement mode speed control unit 16 controls the DC motor 1 at a constant speed at the set target speed v ₀ . In addition,
The constant speed control method is performed by obtaining the control current from the above equations (2) to (5). Here, during normal speed control performed by the speed control unit 13, braking is performed by applying a reverse rotation current so that the carriage 9 stops at the shortest distance during deceleration, but the measurement mode speed control unit 16
In the speed control by, the deceleration operation is started at the time of moving the fixed distance L ₀ , and the current is cut off during the deceleration. During acceleration, the constant speed control is performed by the speed control unit 13
Is the same as the control of.

By cutting off the current during deceleration, the carriage 9 which has been moving at a constant speed until just before moves due to its inertia and then stops, but the moving distance depends on the load on the sliding surface. The position detection unit 11 detects the moving distance L due to inertia from the time when the current is cut off, and it is managed whether or not α <L <β, as in the first embodiment, to detect an abnormal load. I do. FIG. 5 is a graph showing the relationship between speed, current and moving distance in the second embodiment. The moving distance L from the start of deceleration to the stop is α <L _a <β (see FIG. a): Here, α and β are determined in advance from measured values of a normal load), but during an abnormal load, L _b <α (FIG. 5B). As in the first embodiment, the presence or absence of an abnormal load is detected over the entire length of the guide shaft by repeating the operation of driving at the target speed v ₀ and the moving distance L ₀ until the start of deceleration / deceleration a plurality of times.

Further, the combination of (v ₀ , L ₀ ) is (v
₁ , L ₁ ), (v ₂ , L ₂ ), etc. are changed to reciprocate over the entire length of the guide shaft, whereby the abnormal load can be detected more accurately. At this time, (v _n, L _n) is predetermined according to (α _n, β _n) also changes. As described above, according to the second embodiment of the present invention, after the constant speed control of the DC motor 1 is performed at the target speed v ₀ , the DC motor 1 of the DC motor 1 is moved when the moving distance reaches L ₀ . By disconnecting the drive current and managing the movement distance after the drive current is interrupted, which is determined by the inertia of the carriage 9 and the friction load on the sliding surface, an abnormality in the friction load on the sliding surface can be detected. At this time, by utilizing the movement distance of the carriage 9 due to the inertia, it is possible to detect an abnormal load that is canceled by the driving force of the motor, and it is possible to detect the abnormal load more reliably. Here, in the above-described first and second embodiments of the present invention, the moving distance of the carriage is measured to detect the abnormal load, but the arithmetic expression of the speed control unit in the normal operation mode is used. An abnormal load can also be detected by managing I _n in (Equation (2)).

FIG. 6 is a graph showing the relationship between speed and time and drive current and time in the third embodiment. When constant speed control is carried out, a normal load is assumed from the given target speed. The constant speed region is calculated by a predetermined calculation method, and the drive current command value I _n in this constant speed region is calculated.
If the value of is a normal load, as shown in FIG.
I _n <β, where α and β are determined in advance from measured values of normal load. However, if there is an abnormal load location, the drive current command value I _n must be increased in order to perform constant speed control, and I _n > β as shown in FIG. The abnormal load can be detected. Further, since this position can be managed by the slit pulse, the location of the abnormal load can be specified.

[0021]

As described above, the present invention manages the upper limit value and the lower limit value of the movement distance of the carriage when the carriage is moved under a certain predetermined condition, and the above operation is performed in plural. Since the process is repeated, it is possible to detect an abnormal load on the sliding surface of the carriage system over the entire length of the guide shaft. As described above, the abnormal load on the sliding surface of the carriage system can be detected, so that the maintenance becomes easy and the improvement of the printing quality can be greatly improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a DC motor drive mechanism showing a first embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the drive current value of the DC motor and the movement distance of the carriage in the first embodiment.

FIG. 3 is a graph showing a relationship between a driving current value and time, and a speed and a moving distance when driving a plurality of times.

FIG. 4 is a block diagram of a DC motor drive mechanism showing a second embodiment of the present invention.

FIG. 5 is a graph showing the relationship between speed, current and moving distance in the second embodiment.

FIG. 6 is a graph showing the relationship between speed and time and drive current and time in the third embodiment.

FIG. 7 is a perspective view showing details of a carriage unit that supports a print head.

[Explanation of symbols]

 1 DC Motor 2 Slit Disk 3 Sensor 5 DC Motor Control Section 6 CPU 9 Carriage 10 Guide Shaft 11 Position Detection Section 12 Speed Detection Section 13 Speed Control Section 14 Load Measurement Section 15 Mode Switch

Claims (4)

[Claims] 1. A control unit for converting rotational motion of a DC motor into reciprocating motion of a controlled object and feeding back an output of a rotary encoder that works in conjunction with the DC motor to control speed and positioning of the controlled object. In the DC motor drive mechanism, the control unit calculates a moving distance of a controlled object from an output of the rotary encoder when a predetermined constant current is applied to the DC motor for a predetermined time, and the moving distance is predetermined. The abnormality of the load of the mechanism for driving the controlled object is detected depending on whether or not it falls within the specified range, and the control unit repeats the above-mentioned operation a plurality of times to detect an abnormality in the entire moving range of the controlled object. A DC motor drive mechanism characterized by detecting a load. 2. A control unit for converting rotational motion of a DC motor into reciprocating motion of an object to be controlled, and feeding back an output of a rotary encoder which works in conjunction with the DC motor to perform speed control and positioning control of the object to be controlled. In the DC motor drive mechanism, the control unit controls the D speed at a preset target speed.
After the C motor is controlled at a constant speed, the drive current is cut off, and the distance at which the controlled object moves due to inertia is calculated from the output of the rotary encoder, and whether the moved distance falls within a predetermined range. The abnormality of the load of the mechanism for driving the controlled object is detected by the above, and the control unit repeats the above operation a plurality of times to detect the abnormal load over the entire moving range of the controlled object. DC motor drive mechanism. 3. A control unit for converting rotational motion of a DC motor into reciprocating motion of a controlled object, and feeding back an output of a rotary encoder that works in conjunction with the DC motor to control speed and positioning of the controlled object. In the DC motor drive mechanism, the control unit controls the D speed at a preset target speed.
The C motor is controlled at a constant speed, and an abnormality in the load of the mechanism for driving the controlled object is detected depending on whether or not the drive current value in this constant speed region falls within a predetermined range. DC motor drive mechanism. 4. The DC motor drive mechanism according to claim 1, 2, or 3, wherein the control unit manages the position of the controlled object from the output of the rotary encoder and detects the load abnormality when the rotary encoder is used. A DC motor drive mechanism characterized in that the abnormal load position is specified from the output of the DC motor.