JPS6211759B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheet reading device that reads characters, etc. on a sheet while transporting a sheet-like material, and is provided with a control circuit that prevents sheet position shift that occurs during transport of the sheet.

In image input devices and the like, reading processing is performed for one line or several line areas on a sheet at a time by so-called incremental operation in which a sheet-like material is sent a fixed distance at a time by a step motor-driven transport mechanism.

Drive control of a step motor (also referred to as a pulse motor) is well known, but a brief explanation will be provided to facilitate understanding of matters related to the present invention.

FIG. 1 is an example of a control circuit block diagram of a commonly used step motor.

In the figure, when a start signal issued from a circuit not shown is input to the control unit 1, a corresponding control signal is output to the counter circuit 2.
The clock pulse CLK supplied from the clock generator 11 to the counter circuit 2 is subjected to frequency division or multiplication processing as required and is output to the decoder 3.
Decoder 3 inputs the clock pulse CLK,
The clock pulse CLK converted into the control signal used by the driver 4 is output to the driver 4. The driver 4 includes an input signal circuit 5 that outputs a clock pulse CLK converted by a predetermined number of steps in response to an increment operation command signal output from the decoder 3, and an input signal circuit 5 that inputs the output CLK and converts the clock pulse CLK to a desired magnetic pole. It consists of a distribution circuit 6 that controls the excitation circuit 7 so that the excitation current of the required excitation phase flows, and an excitation circuit 7 that causes the required excitation current to flow at a predetermined timing to the excitation winding wound around the magnetic pole of the step motor 8. There is.

The step motor 8, which is supplied with DC excitation currents φ1, φ2, and φ3 of three phases from the driver 4 in this example, drives the sheet transport mechanism 12, which is the object to be driven in this example.

The method of supplying excitation current to the step motor 8 to drive it is called an excitation method, and this excitation method is generally one to four-phase excitation method (or more).
(multiphase excitation) and 1-2 phase alternate excitation to n- (n+
1) There is a phase alternating excitation method. As an example, 1
Phase, two-phase, and 1-2 phase alternate excitation systems will be explained.

Figure 2 is an explanatory diagram of each of the above excitation methods, and Figure 1 is a sequence comparison diagram of 1-phase excitation, 2-phase excitation, and 1-2 phase excitation, and the timing is shown in Figure 2.
This corresponds to the step state diagrams in FIGS.

In FIG. 1, in order to facilitate the explanation of the three types of excitation, one clock corresponds to a half step in the case of 1-2 phase excitation. Therefore, it should be noted that for one-phase excitation and two-phase excitation, two clocks such as R-1, 2-3, 4-5, . . . are used instead of the usual one clock.

Now considering one-phase excitation, as shown in the one-phase excitation sequence in Fig. 2, first, the first phase excitation is performed by applying an excitation current φ1 to the mutually corresponding magnetic poles P1 and P1'.
flows in response to the Rth and 1st clocks, and thereafter the exciting currents φ2 and φ3 flow to the magnetic poles P2, P2' and P3, P3' at clocks 2 to 3 and 4 to 4, respectively.
It flows in response to 5.

The stepping states of the rotor and stator corresponding to the above-described excitation sequence are shown in FIG. 2 for a step motor with a 6-pole stator and a 4-pole permanent magnet rotor.

In FIG. 2-R, the step state at the moment when the third phase excitation current φ3 is cut off and the first phase excitation current φ1 (hereinafter simply abbreviated as φn instead of the nth layer excitation current φn) starts flowing. Therefore, the magnetic pole P
3, P3' (hereinafter, the magnetic poles will be omitted and simply referred to as P1, P2
The two poles of the rotor are located facing each other. Then, the lines of magnetic force due to φ1 act on the other two poles of the rotor, which are different from the two poles mentioned above, and draw them toward P1 and P1'. The rotation state of the rotor is counterclockwise (hereafter counterclockwise is CCW).
counter clock wise.CW clock wise
) by a rotation angle of 30° to P1, P
At 1', two poles forming a pair of rotors are held facing each other. A similar operation is performed using the excitation current φ of the second phase.
2. It also occurs when the third phase excitation current φ3 flows, and occurs every two clocks in the double clock of the normal excitation sequence shown in FIG. to 30
Rotate in degrees.

Next, we will explain the two-phase excitation sequence shown in the second row of Figure 1 and the corresponding relationship between the rotor and stator.
Looking at this, the excitation current consists of three types, φ1, φ2, and φ3, as in the case of one-phase excitation. First φ
In the latter half of the excitation period of P3 and P3' by 3, excitation of P1 and P1' by φ1 is performed by clocks R and 1 in 3-R and 3-1, and by clock R, 3-R is first in its previous state. Some φ2 and φ3
From the relationship between the rotor and stator in the balanced state (stopped phase) reached by excitation, P1 and P3,
P1' and P3' each form a pair to attract the rotor (starting phase). In this example, φ1 is reversed with respect to φ2 and φ3 so that a magnetic path is closed between the excitation poles of two adjacent phases. Next, at clock 1, at 3-1, the rotor rotates 30 degrees due to the rotor suction force from φ1 and φ3, and a balanced state is reached (stop phase).
The rotor is rotated by sequentially generating an excitation state for 2 clocks at φ2 and φ3. Therefore φ1, φ2, φ
3 are energized for 4 clocks each.

Next, if we look at the excitation sequence of the 1-2 phase alternate excitation method shown in the third row of Fig. 2 1 and the corresponding relationship between the rotor and stator with reference to Fig. 2 and 3, so first, in clock R, φ3 and φ1
4-R shows a state in which the two-phase excitation of φ1 has ended and the one-phase excitation state of only φ1 has begun.

That is, the rotor poles corresponding to P3 and P3' advance 15 degrees in the rotor rotation direction, and the rotor poles corresponding to P1 and P1' lag 15 degrees in the rotor rotation direction, and one-phase excitation by φ1 is started. .

Next, in 4-1, at clock 1, φ
At the start of the two-phase excitation state by 1 and φ2, P1 and P1' indicate a stop phase state in which they face the corresponding rotor, and from that state, the rotor is attracted by φ1 and φ2, and the starting phase begins. be done. Thereafter, similar operations continue from 4-2 onward to realize an increment operation of the step motor.

The one-phase, two-phase, and 1-2 phase excitation described above each have the following characteristics.

(1) The 1-phase excitation method has good stopping position accuracy.

(2) Two-phase excitation reduces rotor vibration and provides smooth operation.

(3) 1-2 phase excitation is called half step drive, and the step angle is 1/2 of the original.
It is possible to reduce vibration, provide good braking, and have good stopping position accuracy.

Conventionally, the excitation method of the step motor used in the sheet transport mechanism is a multi-phase method (2, 4, 6...
(phase) was common, and the start-up sequence was the same as previously described.

Such reading devices are increasingly required to perform reading at high speed and with high accuracy, but in the event that a failure occurs, it is always necessary to read a new sheet after the failure is removed. It needs to be done correctly. Obstacles during reading operations are when the sheet does not have the specified dimensions or thickness,
Or, it refers to a situation in which a transport error occurs between the operation of the sheet transport mechanism and the amount of sheet transport when a person touches the sheet during transport. Such an abnormality in sheet transport is detected by a detection means.

In conventional devices, when such an abnormality is detected, a fault signal is issued and the device is shut down. In this case, the device will be stopped regardless of the timing of the start pulse or stop pulse to the step motor, and when reading a new sheet, the operator will need to make adjustments to start the reading operation. If the operator forgets to remove the sheet that caused the problem and starts up the device again, a new problem will occur.

The present invention provides a sheet reading device that is driven by applying a series of drive control pulses formed by alternating start and stop pulses to a step motor, and is capable of restarting when a failure occurs. However, it is an object of the present invention to make it possible to automatically remove a sheet without requiring readjustment of a reading device, and even when an operator forgets to remove an obstructing sheet.

Therefore, in the present invention, when a failure is detected, the supply of excitation pulses to the step motor is temporarily stopped, and after the pulse supply is stopped, an even number of pulses starting from the start pulse is supplied to the step motor in response to a predetermined start command. By performing a predetermined amount of idling operation, the device can be brought into a normal startup state, and even if a sheet remains, it can be removed.

During this idling operation, all functions other than sheet conveyance and paper detection by the paper sensor, such as reading and printing, are suspended.

The amount of idle rotation can be determined by dividing the conveyance length from the sheet supply section to the discharge section by the paper conveyance speed to find the required conveyance time t, and then adding a margin to absorb errors to this time and multiplying it by the stability rate. The idle time is calculated and is said to be selected to be about 1.5 times t.

In this case, the number of pulses n is determined by the idling time t
(sec) and one pulse is to(sec), then n=
t/to, and n should be an even number close to n'.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is an explanatory diagram of a 1-2 phase excitation circuit in an embodiment of the present invention. For ease of explanation, this example uses a 3-phase excitation method, with a 6-pole stator and a 4-pole rotor.
The step motor explained in the figure is used.

In the figure, the a-phase excitation current flows through the excitation windings (hereinafter simply referred to as coils) 51 provided on the two opposing stator magnetic poles P1 and P1', returns to the ground, and flows through the b-phase and c-phase. Similarly, the corresponding coils 51 are excited to rotate the rotor 52.

FIG. 3 shows a time chart of the excitation current and various signals.

In the figure, time charts a, b, and c express the states of the excitation currents of the corresponding phases, with the upper part being on and the lower part being off, and the passage of time changing from the left to the right.

In the figure, the flow of operation is that first, the C-phase excitation current is on, the A-phase excitation current is turned on, then the C-phase excitation current is turned off, then the B-phase excitation current is turned on, and then the C-phase excitation current is turned on.
Furthermore, the a-phase excitation current is sequentially turned off, the c-phase excitation current is turned on, and the b-phase excitation current is turned off, and then returns to the initial a-phase excitation current on.

If we look at the above state from the clock pulses shown in the figure CLK that turn on and off these excitation currents, the pulses alternately start, end, start, and end the excitation of adjacent phases in sequence. As described above, after a plurality of c-phases and a-phases have been excited, the c-phase, which was excited earlier, has finished being excited.

Due to this excitation operation, an abnormal seat position occurs due to sheet jam etc. in the step motor driven by the same excitation current, and a failure stop signal (normal stop signal) is generated by a conventional failure detection device (not shown). ) is 〓〓〓〓〓
Once the call is made, the fault handling sequence begins as follows.

The following explanation will be given with simultaneous reference to the time chart in FIG. 3 and the circuit block diagram in FIG.

In this example, a three-phase excitation type step motor is used, so three J-
A clock pulse CLK is input to K flip-flop circuits (hereinafter referred to as FF) 101 to 103, and excitation signals of each phase of a, b, and c are sequentially input to AND gates 111 to 113. or gate 221
Each phase excitation signal is output from each of the AND gates 111 to 113 under the condition that a control signal to be output from the AND gates 111 to 113 is input.

These excitation signals are a, as shown in FIG.
b and c are sent out from the AND gates 111 to 113 in the order of two phases, that is, a start pulse and a
Phase only state, ie stop pulse is clock pulse
It is switched every time CLK is output. This excitation signal is connected to an excitation circuit (not shown) (corresponding to 7 in Figure 1).
Excitation current (φ1, φ2, φ in Figure 1)
3) is supplied to the step motor.

Since the outputs of Q 102 and Q 103 of J-KFF 101 are sequentially input to the AND gates 121 to 123 in two sets, the output signal Q ₁
is the clock pulse as shown in the time chart.
"ON" and "OFF" are repeated for each CLK, and "ON" indicates two-phase excitation, and "OFF" indicates one-phase excitation.

This two-phase excitation signal Q ₁ is input to an OR gate 142 and an AND gate 161 .

First, to explain the start-related circuits, a start signal is input from a circuit not shown to the latch circuit 151, and the output of the latch circuit 151 is input to the AND gate 161 together with the signal _Q1 mentioned above, so two-phase excitation is generated. At this time, the activation signal is sent from the AND gate 161 to the J-KFF 192 via the OR gate 142.
is applied to the clock terminal T of the clock.

Since the J and K terminals of J-KFF192 are constantly supplied with a voltage indicating a logical value "1" by a signal, the terminal Q indicates a logical value "1" as shown on the left side of time chart Q ₃ in Figure 3. Signal _Q3 is sent out at the time of startup, becomes a control signal via OR gate 221, and operates the step motor by opening AND gates 111 to 113 and passing excitation signals a, b, and c. The control signal is also input as a reset signal to the latch circuit 151, and the output of the AND gate 161 is set to "0". However, the signal Q ₃ from the Q terminal remains logic until "1" is inputted from the circuit (not shown) by the stop signal or failure stop signal' to the clock terminal T of the J-KFF 192 via the OR gate 142. The value will be kept as "1".

Next, the idle operation circuit will be described.

When the stop signal or the fault stop signal' occurs at the time shown in the time chart, this signal is applied to the J-KFF 192 through the OR gate 142, which falsely inverts the output signal of the J-KFF 192, so that the output signal is as shown in the time chart. Stop signal′
Subsequently, Q ₃ and are turned “OFF”. Therefore, the AND gates 111 to 113 block passage of the excitation signals of each phase of a, b, and c, thereby stopping the step motor.

A stop signal or a failure stop signal' is also input to the timer control circuit 171, and a signal _Q5 is output when the operator of the sheet reading device notices an abnormality and cancels it, then restarts the device. On the other hand, the signal transmitted in the two-phase excitation state
The output of the circuit 181 for differentiating the rising edge of Q ₁ is input to the AND gate 201 together with this signal Q ₅ . As a result, timer 2 is activated by the rising edge of signal _Q1 .
11 is activated and sends the signal Q ₄ to the OR gate 221
output as a control signal via. Therefore, the AND gates 111, 112, 113 start supplying each phase excitation current φ1, φ2, φ3 to the coil 51 in synchronization with the timing of two-phase excitation. timer 21
1 is set according to the setting. When an integer of the period of the two-phase detection signal Q ₁ has elapsed, the sending of the signal Q ₄ is stopped, and therefore the sheet feeding of the sheet reading device is stopped in the 1-phase excitation state, and its position accuracy is I'm trying to make it higher. Thereafter, sheet feeding accompanied by reading is started in response to a start signal from a control device (not shown) or the like.

When performing the above control, the power supply 9 for the excitation circuit shown in FIG. It can be achieved.

As described above, according to the present invention, a step motor can be controlled by using a simple logic circuit and an inexpensive power supply circuit.
By operating the machine in a half-step drive that follows a fixed starting order, it is possible to smoothly transport sheets with high accuracy, so processing can be performed reliably even during normal startup and idling operation after a stop due to sheet jamming, etc. Therefore, the operating efficiency and reliability of the equipment can be improved overall.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an example of a step motor control circuit, and Figure 2 shows one-phase excitation, two-phase excitation, one-phase excitation, and one-phase excitation.
3 is an explanatory diagram of an excitation operation in an embodiment of the present invention, and FIG. 4 is a circuit block diagram. In the figure, 1 is a control unit, 2 is a counter, 3 is a decoder, 4 is a driver, 5 is an input control circuit, and 6
1 is a distribution circuit, 7 is an excitation circuit, 8 is a step motor, 9 is a power supply, 10 is a timer, 11 is a clock generation circuit, 12 is a sheet transport mechanism, 51 is a coil (stator pole excitation winding), 52 is a rotor, 101 ，
102, 103, 192 are J-KFF (flip-flop), 111, 112, 113, 121,
122, 123, 161, 201 are AND gates, 131, 142, 221 are OR gates, 15
1 is a latch, 171 is a timer control circuit, 211 is a timer, 181 is a rising differential circuit, 192 is J-
KFF is a start signal, is a stop signal, ' is a fault stop signal, is a control signal, is "1" CLK clock pulse (clock), a, b, c are excitation phases,
φ1, φ2, φ3 are exciting currents, Q ₁ , Q ₂ , Q ₃ ,
Q ₄ and Q ₅ are signals, GND is grounding, and t is idle time. 〓〓〓〓〓

Claims (1)

[Claims] 1. Among start pulses and stop pulses that are alternately included in a given series of pulses, the start pulse starts excitation of adjacent phases sequentially, and the stop pulse starts excitation of the first phase among multiple simultaneously excited phases. A sheet reading device equipped with a sheet transport mechanism that transports sheets using a step motor that terminates phase excitation, and a detection means that detects sheet transport abnormalities according to an error between the operation of the sheet transport mechanism and the amount of sheet transport. In this step, the supply of pulses following the start pulse to the step motor is stopped by the output of the detection means, and after the pulse supply is stopped, an even number of pulses starting from the start pulse are supplied to the step motor by a predetermined starting command. A sheet reading device characterized by performing a fixed amount of idling motion.