JPH03130176A - Printer - Google Patents

Abstract

PURPOSE:To make it possible to detect the deterioration of operation margin due to increase in load torque by reducing the drive torque of a pulse motor and checking the operation margin corresponding to the difference between the drive torque of the pulse motor and the load torque of a mechanical part. CONSTITUTION:An operation margin corresponding to the difference between the drive torque of a pulse motor 5 and the load torque of mechanical parts 1 to 4, 6, 7, 12 is checked by reducing the driving torque of the pulse motor 5. Consequently, it is possible to detect the diminution of the operation margin subsequent to an increase of the load torque by reducing the drive torque of the pulse motor 5. Thus an abnormal increase of load torque due to a temporal change or dust settlement in a sliding part can be detected as a possible caused for erroneous operation by a simple and quick way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printer, and more particularly to a printer that uses a pulse motor as a drive source to drive printer mechanisms such as a carrier mechanism and a paper feed mechanism.

[Prior Art] Conventionally, in printers, particularly serial impact printers, a pulse motor is used as a drive source for driving a carrier mechanism (general term for a print head and a frame to which the print head is attached) and a paper feeding 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 that controls the current flowing to the motor windings to be constant. It is driven using a circuit. Although the constant current drive circuit has a complicated configuration, it has recently been widely used for driving pulse motors because it has characteristics suitable for high-speed motor drive.

Further, the carrier mechanism is such that a carrier frame held and guided by a carrier shaft and a carrier auxiliary shaft can be reciprocated by a pulse motor via a timing belt. Further, in the paper feed mechanism, a paper conveyance roller is driven by a paper feed motor via a timing belt.

[Problems to be Solved by the Invention] In such a conventional printer, the carrier mechanism uses a carrier metal impregnated with oil at the fitting portion between the carrier shaft and the carrier auxiliary shaft and the 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 malfunctions such as the pulse motor stepping out. There is. If such a tax adjustment occurs, there is a risk that serious troubles such as misalignment of the printing position or after printing may occur, or abnormal situations such as the pulse motor not being able to be driven may occur.

Furthermore, in the paper feeding mechanism, many oil-impregnated bearing metals are used as bearings for the conveyance roller shaft, and sliding resistance increases due to aging and dirt, which can also cause pulse motor loss of synchronization and printing misalignment. The problem was that it caused

In these mechanisms, it is common for there to be variations in sliding resistance even immediately after assembly at the factory due to factors such as variations in the tension adjustment of the belt and variations in the finishing quality of the metal and shafts. Further, the load torque generated in these printer mechanisms includes an initial load torque of the printer mechanism and an increase in the load torque due to changes over time. Therefore, the pulse motor of the printer needs to have a driving torque that includes not only the initial load torque of the printer mechanism (in addition to the increase in load torque due to changes over time and a predetermined operating margin).

If you increase the output torque of the pulse motor, the possibility of malfunction will decrease even if the load torque increases to a certain extent, but
Increasing the output torque of the motor increases the cost and is also disadvantageous in terms of implementation, and since there is a limit to the increase in the output torque of the motor, there is a problem that a large operating margin cannot be set.

Therefore, the present invention has been made to solve these problems, and provides a printer that can absorb malfunctions without increasing the output torque and can quickly detect a decrease in the operating margin due to an increase in load torque. The task is to provide the following.

[Means for Solving the Problems] In order to solve such problems, the present invention provides a printer that uses a pulse motor as a drive source to drive the printer mechanism, and includes means for reducing the driving torque of the pulse motor. reducing the driving torque of the pulse motor;
We explored a configuration that detects an increase in load torque by checking the operating margin corresponding to the difference between the drive torque of the pulse motor and the load torque of the mechanism at that time. By reducing the drive torque of the motor, the operating margin corresponding to the difference between the drive torque of the pulse motor and the load torque of the mechanical section 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 operating margin and no abnormality will occur in the drive of the pulse motor. However, if the load torque increases abnormally due to changes over time or when dust gets into the sliding parts, reducing the drive torque of the pulse motor will reduce the operating margin and reach the limit where the operation of the pulse motor is no longer guaranteed. reach the value. When such a limit value is reached (usually where the operating margin is approximately O), 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 operating margin has decreased by decreasing the drive torque of the pulse motor.6 [Actual Example] The details of the present invention will be explained below according to the embodiment shown in the drawings. Explain.

FIG. 1 shows a printer according to an embodiment of the present invention, and the carrier mechanism is shown in detail as a printer mechanism section. In this carrier mechanism, a print head 2 is mounted on a carrier frame l.

The carrier frame 1 is held and guided by a carrier shaft 3 and a carrier auxiliary shaft 4, and is configured to be reciprocated by a pulse motor 5 via a timing belt 7 hooked around an idle pulley 6. In order to detect the left and right home positions of this carrier frame, position sensors 1O111 are attached to the respective terminal positions. Also.

In such a carrier mechanism, a carrier metal 12 impregnated with oil is used at the fitting portion between the carrier shaft 3 and the carrier auxiliary shaft 4 and the carrier frame l.

FIG. 2 shows a drive circuit for the pulse motor 5. As shown in FIG. In the figure, signals R1 and R2 that determine the excitation state of the motor are generated from a control signal input section 20, and these signals are manually inputted to an excitation signal generation circuit 21 to form phase-shifted excitation signals R1 to R4. Ru. These signals are input to the driver 23 and drive the pulse motor 5, for example, with two-phase excitation. The driver 23 is driven by a power source 24 and a holding power source 25.

The drive circuit of the pulse motor is provided with a constant current control section shown by a dotted line in order to control the current of the motor to a constant current. This constant current control is composed of a constant current control circuit 26 and a resistor 27 that detects the motor current. The constant current control circuit 26 has a comparator 30 as shown in FIG. 3, and receives 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. 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 is applied to the driver. is applied to

Signal M is a key point of the present invention, and is a signal that reduces the motor current.

Here, the operation of the constant current control circuit shown in FIG. 3 will be explained based on the signal waveform diagram of FIG. 4.

When the constant current control signal T is on, the motor current ■
is sufficiently small, the + terminal of the comparator 30 is at a higher voltage than the feedback signal F, and the comparator 30
The output terminal Go of is in an off state. Constant current control circuit 26
Output 0 of is turned on because of the inverted signal of co, and it works in the direction of driving the driver and causing current to flow through the motor. As a result, the motor current gradually increases. As the motor current increases, the voltage at the terminals of the current sensing resistor 27 (the voltage at feedback F is equal to the motor current x resistance 27) rises and exceeds the voltage at the comparator + terminal 30a.

Since the output terminal co of the comparator 30 is turned on and the output 0 of the constant current control circuit 26 is turned off, the driving of the driver is stopped, so that the motor current decreases.

At this time, the output Co of the comparator 3o lowers the voltage at the + terminal of the comparator by 30 rays through the resistor Rc.In the section 6ti, the motor current decreases, and when the voltage of the feedback signal F falls below the lowered voltage 30b at the 10th terminal of the comparator. , the comparator turns off again.

The output of the constant current control circuit 26 is turned on and the motor current is increased, and the comparator + terminal returns to the voltage of 30a.

On the other hand, in the interval t3, the conditions for increasing the motor current are satisfied, similar to the interval tl, so the motor current increases.

By repeating the above sections ti and t3, the average value of the motor current is fixed to ■, so that a constant current can be passed through the motor.

When the margin check signal M turns on at time t, the comparator + terminal reaches the voltage level 30 shown at t4.
The voltage 30c is lowered by the action of the resistor 28 to a voltage 30c that is even lower than the voltage 30c.

Therefore, the feedback signal F (and therefore the motor current) operates to be equal to the voltages 30c and 30d, and the average of the motor's low current is reduced to 1'. In the block diagram of the motor drive circuit shown in FIG. 2, the circuits surrounded by dotted lines are for φ1 and φ3 windings and for φ2. φ
A total of two circuits are used for four windings.

Next, the operation of the printer configured as described above will be explained.6 The control signal input section 20 in FIG.
R2 is manually supplied to the excitation signal generation circuit 2I, and two of the four motor windings of the pulse motor 5 are constantly driven. Fifth
As shown in the first and second rows from the top of the diagram, the excitation signal R1
, R2 “1”.

By the combination of rOJ, φ
Two phases l to φ4 are excited, and the pulse motor 5 is driven by 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 through the motor is detected by the resistor 27, and the current ■ is kept constant.
Further, at time t, when the signal M is turned on, control is performed so that the motor current I' is decreased. The change in step of the pulse motor 5 at this time is illustrated by H in FIG. Within this illustrated range, the motor torque is normal until the specified time, and thereafter 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 I are impregnated with oil. In printers, 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 passage of one hour, resulting in so-called aging. Similarly, many bearing metals impregnated with oil are used as bearings for the conveyor roller shafts in the paper feed mechanism, and sliding resistance increases due to aging, dirt, and the like.

This state is illustrated in FIG. 6, and it can be seen that the load torque F of the Bunonta drive mechanism increases as the number of operations increases, that is, as time passes. In this case, it is assumed that the drive torque G of the pulse motor is approximately constant regardless of the passage of time. At the initial stage, the load torque F of the mechanical section is sufficiently small with respect to the drive torque G of the motor, and the operating margin corresponding to the difference between the drive torque G and the load torque F has a large value.

Next, one hour passes, and when the point Y is reached, the drive torque of the motor and the load torque F of the mechanical section match, and the operating margin becomes O, causing the pulse motor to step out and malfunction. Therefore, in the embodiment of the present invention, in order to detect a state where the X and Y operating margins are insufficient, the drive torque of the motor is reduced from G to Go to create a state where malfunction is likely to occur. This reduction in driving torque is caused by the operating margin signal M as shown in FIG.
is set to low level at time t, and the reference signal of the comparator 30 (
This is done by lowering the voltage (+ terminal) and decreasing the motor current by i.

As a result, the phase current changes from 1 normal operating current ■ to an operating margin current I° (FIG. 5).

For example, when X, the drive torque of the pulse motor G
On the other hand, the load torque F of the mechanical section is less by g, and a slight operating margin remains, and the printer is operating normally, so the user does not notice the fact that the operating margin has decreased. However, since the operating margin is checked at time t, the driving torque of the pulse motor decreases to Go, and the operating margin becomes almost 0 at X. It is possible to recognize when a malfunction occurs in the mechanical part of the machine.

This malfunction may be recognized by determining whether or not the carrier frame 1 is in the correct position using a position sensor to, it that detects the end position of the carrier, or by visually confirming that the operation is not normal. It is also possible to do this by doing 2. When such a malfunction occurs, an alarm or other display may be provided.

Note that the amount by which the motor current is reduced is set in consideration of aging characteristics so that the length of the operation margin shortage includes at least the number of days in which repair and maintenance can be started.

Furthermore, the operating margin may be checked at the time of factory shipment or during maintenance and adjustment, but it may also be performed at the start of the printing operation).

In the embodiments described above, the drive torque of the pulse motor is reduced by reducing the motor current in the constant current drive circuit.

Of course, the drive torque can be reduced by using a constant voltage drive circuit and reducing the motor voltage.

[Effects of the Invention] As explained above, according to the present invention, by reducing the drive torque of the pulse motor, the operating margin corresponding to the difference between the drive torque of the pulse motor and the load torque of the mechanism section is checked. Figure 1 shows the schematic configuration of the printer. A perspective view shown,
Figure 2 is a block diagram showing the configuration of the pulse motor drive circuit, Figure 3 is a circuit diagram showing details of the constant current control circuit, and Figure 4 shows the operation of the constant current control circuit in Figure 3. FIG. 5 is a signal waveform diagram for explaining the operation of the printer, and FIG. 6 is an explanatory diagram for explaining checking of the operating margin.

1...Carrier frame 5...-Pulse motor 21...Excitation signal generation circuit 26-・Constant current control circuit F...-Load torque G, G'...Driving torque

Claims (1)

[Claims] 1) In a printer that uses a pulse motor as a drive source to drive a printer mechanism, a means for reducing the drive torque of the pulse motor is provided, and the drive torque of the pulse motor is reduced, and the pulse motor at that time is A printer characterized in that an increase in load torque is detected by checking an operating margin corresponding to the difference between the drive torque of the machine and the load torque of the mechanism. 2) The printer according to claim 1, wherein the operation margin is checked based on whether or not the pulse motor malfunctions. 3) The printer according to claim 1 or 2, wherein the drive torque of the pulse motor is reduced by reducing the motor current or voltage. 4) The printer according to any one of claims 1 to 3, wherein the drive torque of the pulse motor is reduced immediately after the printer starts operating.