JP2543600B2 - Printer - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer, and more particularly to a printer that drives a printer mechanism section such as a carrier mechanism and a paper feed mechanism using a pulse motor as a drive source.

[Prior Art] Conventionally, in a printer, in particular, a serial impact printer, a pulse motor is used as a drive source for driving a carrier mechanism (a generic term for a print head and a frame to which the print head is attached) and a paper feed mechanism. Pulse motors generally use a constant voltage drive circuit that controls the voltage applied to the motor to be constant, or a constant current drive circuit that controls the current supplied to the motor winding to be constant. Is driven. The constant current drive circuit has a complicated structure, but recently has been widely used for driving a pulse motor because it has characteristics suitable for high-speed drive of a motor.

Further, the carrier mechanism is a mechanism capable of reciprocating the carrier frame held and guided by the carrier shaft and the carrier auxiliary shaft via a timing belt by a pulse motor. Further, in the paper feeding mechanism, the paper feeding roller is driven by a paper feeding motor via a timing belt.

[Problems to be Solved by the Invention] In such a conventional printer, a carrier mechanism uses a carrier metal in which oil is impregnated in a fitting portion between a carrier shaft and a carrier auxiliary shaft and a carrier frame. In printers, dust mainly composed of paper and ink from the ink ribbon adhere to the carrier shaft and carrier auxiliary shaft, which increases the sliding resistance of the carrier frame and causes the pulse motor to malfunction. There is. If this kind of step-out occurs, serious problems such as misalignment of printing positions and missing prints,
Alternatively, an abnormal situation such as inability to drive the pulse motor may occur.

Further, in the paper feed mechanism, many bearing metal impregnated with oil is used as the bearing of the transport roller shaft, and sliding resistance increases due to aging and dirt, and similarly, step out of the pulse motor and print misalignment occur. There was a problem of causing.

With these mechanisms, variations in the adjustment of the belt tension,
Due to factors such as variations in finish quality of metals and shafts, variations in sliding resistance generally exist even immediately after assembly in a factory. Further, the load torque generated in these printer mechanism units includes an initial load torque of the printer mechanism unit and an increase in the load torque due to a change over time. Therefore, it is necessary for the pulse motor of the printer to use not only the initial load torque of the printer mechanism but also the drive torque including an increase in the load torque due to aging and a predetermined operation margin.

Increasing the output torque of the pulse motor reduces the possibility of malfunction even if the load torque increases to some extent, but increasing the output torque of the motor increases the cost and is disadvantageous in terms of mounting. Since there is a limit to the increase in torque, there is a problem that a large operating margin cannot be set.

Therefore, the present invention has been made to solve such a problem, and a printer capable of absorbing a malfunction without increasing the output torque and capable of quickly detecting a decrease in an operation margin due to an increase in load torque. The task is to provide.

[Means for Solving the Problem] In order to solve such a problem, in the present invention, in a printer that drives a printer mechanism unit using a pulse motor as a drive source, a means for reducing the drive torque of the pulse motor is provided. The drive torque of the pulse motor is reduced, and an increase in load torque is detected by checking the operation margin corresponding to the difference between the drive torque of the pulse motor and the load torque of the mechanism at that time.

[Operation] In such a configuration, by reducing the drive torque of the pulse motor, the operation margin corresponding to the difference between the drive torque of the pulse motor and the load torque of the mechanism is checked. For example, when the load torque is in the initial state,
Even if the drive torque of the pulse motor is reduced, there is sufficient operation margin and no abnormality occurs in the drive of the pulse motor. However, if the load torque abnormally increases due to changes over time or dust in the sliding parts, reducing the drive torque of the pulse motor will reduce the operating margin and limit the operation of the pulse motor. Reach the value. When such a limit value (usually, where the operation margin becomes almost 0) is reached, the pulse motor stops and cannot reach the position where it should originally stop. Therefore, it is possible to detect that the load torque has increased and the operation margin has decreased by decreasing the drive torque of the pulse motor.

[Examples] The present invention will be described in detail below with reference to the examples shown in the drawings.

FIG. 1 shows a printer according to an embodiment of the present invention, and in FIG. 1, a carrier mechanism as a printer mechanism portion is shown in detail. In this carrier mechanism,
A print head 2 is mounted on the carrier frame 1. The carrier frame 1 is configured to be held and guided by a carrier shaft 3 and a carrier auxiliary shaft 4, and reciprocally moved by a pulse motor 5 via a timing belt 7 hung on an idle pulley 6.
Position sensors 10 and 11 are attached to the respective end positions to detect the left and right home positions of the carrier frame. Moreover, in such a carrier mechanism,
A carrier metal 12 impregnated with oil is used in a fitting portion between the carrier shaft 3 and the carrier auxiliary shaft 4 and the carrier frame 1.

FIG. 2 shows a drive circuit for the pulse motor 5. In the figure, the control signal input unit 20 generates signals R1 and R2 that determine the excitation state of the motor, these signals are input to the excitation signal generation circuit 21, and the excitation signals R1 to R4 that are out of phase are formed. It These signals are input to the driver 23 and drive the pulse motor 5 by, for example, two-phase excitation. The driver 23 is driven by a power supply 24 and a holding power supply 25.

The drive circuit of the pulse motor is provided with a constant current control unit shown by a dotted line in order to control the motor current to a constant current. This constant current control is composed of a constant current control circuit 26 and a resistor 27 for detecting the motor current. The constant current control circuit 26 has a comparator 30 as shown in FIG. 3, and receives the signals T and M from the control signal input section 20. The signal T puts the motor drive circuit in a constant current drive state, and constant current control is performed only when this signal is on, and when it is off, the signal from the comparator 30 is invalidated and the voltage from the holding power supply 25 drives the driver. Applied to. The signal M is
This signal is a key point of the present invention and is a signal for reducing the motor current.

Here, the operation of the constant current control circuit shown in FIG. 3 will be described based on the signal waveform diagram of FIG.

During t1, the constant current control signal T is on, and the motor current I
Is sufficiently small, the + terminal of the comparator 30 has a voltage higher than the feedback signal F, and the output terminal Co of the comparator 30 is in the off state. Output 0 of constant current control circuit 26
Is turned on due to the inverted signal of Co, drives the driver,
It works in the direction of passing current to the motor. As a result, the motor current gradually increases. When the motor current increases, the terminal voltage of the current detection resistor 27 (the voltage of the feedback F is equal to the motor current x resistor 27) rises and exceeds the voltage of the comparator + terminal 30a.

The output terminal Co of the comparator 30 is turned on, the output 0 of the constant current control circuit 26 is turned off, and the driving of the driver is stopped. Therefore, the motor current starts to decrease. At this time, the output Co of the comparator 30 pulls down the voltage of the comparator + terminal to 30b through the resistor Rc.

In the period of t2, the motor current decreases and the voltage of the feedback signal F is lowered.
Below 30b, the comparator turns off again. The output of the constant current control circuit 26 turns on to increase the motor current, and the comparator + terminal returns to the voltage of 30a.

On the other hand, in the section of t3, since the condition for increasing the motor current is satisfied as in the section of t1, the motor current increases.

Since the average value of the motor current is fixed to I by repeating the above section of t2 and t3, a constant current can be supplied to the motor.

When the margin check signal M is turned on at the time t, the comparator + terminal is at the voltage level 30b shown at t4.
The voltage is further lowered to 30c by the action of the resistor 28.

Therefore, the feedback signal F (and hence the motor current) is controlled to be equal to the voltages 30c and 30d, and the average of the motor current is lowered to I '. In addition,
In the block diagram of the motor drive circuit shown in FIG. 2, a total of two circuits are used for the φ1 and φ3 windings and the φ2 and φ4 windings, which will be described later with respect to the circuits surrounded by dotted lines.

Next, the operation of the printer thus configured will be described.

FIG. 2 Two excitation signals R1 and R2 are input to the excitation signal generation circuit 21 from the control signal input section 20 and constantly drive two of the four motor windings of the pulse motor 5. As shown in the first and second stages from the top of FIG. 5, by combining the excitation signals R1 and R2 with “1” and “0”, as shown in the lower part of FIG. The pulse motor 5 is driven by the so-called two-phase excitation. In this case, the signal T is turned on, the constant current control circuit 26 is driven, the current flowing in the motor is detected by the resistor 27 so that the current I becomes constant, and at time t, when the signal M is turned on, the motor current is Control is performed so that I'is decreased. The change of the step of the pulse motor 5 at this time is shown by H in FIG. Within the illustrated range, the motor torque is normal until time t, and after t, the motor torque decreases.

Here, the carrier mechanism uses a carrier metal 12 in which the fitting portions of the carrier shaft 3 and the carrier auxiliary shaft 4 and the carrier frame 1 are impregnated with oil. In the printer, dust mainly composed of paper and ink from the ink ribbon adhere to the carrier shaft and the carrier auxiliary shaft, so that the sliding resistance of the carrier frame increases with the lapse of time, causing so-called aging. Similarly, in the paper feed mechanism, a large number of bearing metal impregnated with oil is used as the bearing of the transport roller shaft, and the sliding resistance increases due to aging and dirt.

This state is shown in FIG. 6, and it can be understood that the load torque F of the printer drive mechanism unit increases as the number of operations increases, that is, as time passes. In this case, the drive torque G of the pulse motor is assumed to be substantially constant regardless of the passage of time. At the initial stage, the load torque F of the mechanical portion is sufficiently smaller than the drive torque G of the motor, and the operation margin corresponding to the difference between the drive torque G and the load torque F has a large value.

Next, when the time elapses and the point Y is reached, the drive torque of the motor and the load torque F of the mechanical portion match, and the operation margin becomes 0, so the pulse motor loses step and malfunctions. Therefore, in the embodiment of the present invention, in order to detect the state L in which the operating margin of X and Y is insufficient, the drive torque of the motor is reduced from G to G'to create a state in which malfunction easily occurs. As shown in FIG. 5, the drive torque is reduced by setting the operation margin signal M to a low level at time t to lower the reference signal (+ terminal) of the comparator 30 and reducing the motor current by i. ing. As a result, the phase current changes from the normal operating current I to the operating margin current I '(fifth
Figure).

For example, at the time of X, the driving torque G of the pulse motor
On the other hand, since the load torque F of the mechanical portion is smaller by g and a slight operation margin remains, the printer is operating normally, and the user does not notice the fact that the operation margin is reduced. However, since the operation margin is checked at time t, the driving torque of the pulse motor is reduced to G ', and the operation margin becomes almost zero at X. Therefore, the pulse motor or the carrier mechanism or the paper feeding mechanism driven by the pulse motor. It is possible to recognize that a malfunction occurs in the mechanical part such as.

To recognize this malfunction, the position sensors 10 and 11 for detecting the end position of the carrier may be used to judge whether or not the carrier frame 1 is at the correct position, or it is possible to visually confirm that the operation is not normal. It is also possible to do so. In addition, a display may be made such as issuing an alarm when such a malfunction occurs.

It should be noted that the amount of decrease in the motor current is set in consideration of the characteristics of change over time so that the absent state L of the operating margin includes at least the number of days during which repair and maintenance can be started.

The operation margin may be checked at the time of factory shipment or maintenance adjustment, but may be checked at the start of printing operation.

In the embodiment described above, the motor current is reduced in the constant current drive circuit in order to reduce the drive torque of the pulse motor, but it goes without saying that the constant voltage drive circuit is used to reduce the motor voltage. The drive torque can also be reduced.

[Effects of the Invention] As described above, according to the present invention, the operating torque corresponding to the difference between the driving torque of the pulse motor and the load torque of the mechanism section is checked by reducing the driving torque of the pulse motor. Therefore, the load torque abnormally increases due to changes over time or when dust enters the sliding portion, and it is possible to detect a condition that causes a malfunction by a simple method and at an early stage.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a printer, FIG. 2 is a block diagram showing a configuration of a pulse motor drive circuit, and FIG. 3 is a circuit diagram showing details of a constant current control circuit.
FIG. 4 is a signal waveform diagram for explaining the operation of the constant current control circuit of FIG. 3, FIG. 5 is a signal waveform diagram for explaining the operation of the printer, and FIG. 6 is an explanatory diagram for explaining the operation margin check. is there. 1 ... Carrier frame 5 ... Pulse motor 21 ... Excitation signal generation circuit 26 ... Constant current control circuit F ... Load torque G, G '... Driving torque

Claims (4)

(57) [Claims] 1. A printer for driving a printer mechanism section using a pulse motor as a drive source, comprising means for reducing the drive torque of the pulse motor, the drive torque of the pulse motor being reduced, and the drive torque of the pulse motor at that time. A printer characterized by detecting an increase in load torque by checking an operation margin corresponding to a difference in load torque between the mechanical section and the mechanical section. 2. The printer according to claim 1, wherein the operation margin is checked depending on whether or not the pulse motor malfunctions. 3. The printer according to claim 1, wherein the drive torque of the pulse motor is reduced by reducing the motor current or voltage. 4. The printer according to claim 1, wherein the driving torque of the pulse motor is reduced immediately after the printer starts to operate.