JPS5833982A - Control device for scanning drive motor - Google Patents

Abstract

PURPOSE:To enable to smoothly transfer to equal speed control irrespective of the speed locus after starting of a drive motor by discriminating the magnitude of the rotating speed of the motor when the motor transfer from starting to equal speed control and controlling an input timing circuit based on the speed. CONSTITUTION:A scanning drive motor 8 for a copying machine or the like is driven through a phase comparator 1, a charge pump circuit 2 and a loop filter 3, and a switch SW is switched by a switching circuit 5 after starting, thereby transferring to an equal speed control. At this time a circuit 10 which discriminates whether the rotating speed of the motor 8 at the transferring time is larger than the specified speed or not is provided, thereby controlling an input timing controller 14 in response to the result, and previously inputting one of the reference pulse or rotating synchronizing pulse to the signal of a phase comparator 1 prior to the other. Accordingly, the equal speed control can be always smoothly transferred irrespectively of the speed locus or the transfer timing until the equal speed control is started.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a scanning drive motor used to repeatedly scan an object such as an exposure mirror of a copying machine, an image reading head of a facsimile machine, or a recording head of a printer.

In a scan drive motor, it is desirable that the time from startup to stabilization at a constant speed be extremely short.

In general motor control, phase-locked loop (PLL)
) type of constant velocity control is known, but because there is a delay in the loop filter, it takes a relatively long time to enter the constant velocity control mode.

Therefore, when starting the motor, a certain level of voltage is applied to the motor drive circuit as an energizing signal to start the motor, and the loop filter is charged so that its output voltage reaches the constant speed command level during constant speed control, and the motor speed or start It has been proposed that when the energization time reaches a predetermined value, the output of the loop filter is switched and applied to the motor drive circuit (Japanese Patent Laid-Open No. 54-3
(See Publication No. 5312).

By doing this, startup up to a predetermined speed is quick, there is no problem such as large hunting occurring when switching to constant speed mode, and the start-up time from startup to constant speed control is shortened.

However, if, for example, several speed specifications are specified, and a reference pulse with a period corresponding to each specified speed is selected, and a rotation synchronization pulse synchronized with the motor rotation is compared with this, before entering constant velocity control, It is necessary to set the voltage of the loop filter to a value corresponding to the specified speed, and an initial voltage setting circuit corresponding to the number of speed stages that can be specified is installed between the loop filter or its input section or between the loop filter and the motor drive circuit. A selection circuit for specifying one of them is required, and the circuit configuration becomes complicated.

Therefore, in order to solve such problems, the present inventor previously proposed the following scanning drive motor control device.

To briefly explain this using FIG. 1, the phase comparator 1
．． Charge pump circuit 2. Loop filter 3. Motor drive circuit 4. and a switching circuit for starting and constant speed control5. and switches SWI, SW whose opening and closing are controlled by the switching circuit 5.
2. Equipped with SWa etc.

Then, at startup, switch SW1 is turned on, switch S
Turn off W2, apply a constant voltage generated by the starting voltage generation circuit 6 to the motor drive circuit 4, start the scan drive motor (hereinafter simply referred to as "motor") 8 by the servo amplifier 7, and enter constant speed control. Switch S when transitioning
Turn off Wl, turn on switch SW2, apply the output of loop filter B to motor drive circuit 4, and phase comparator 1 generates a rotation synchronization pulse ( The phase of (hereinafter referred to as "comparison pulse") and the reference pulse R having a cycle corresponding to the designated speed is compared, and the motor 8 is increased or decreased in accordance with the phase difference to control the motor 8 at a constant speed.

Note that the switching signal C from the switching circuit 5 is at low level "L" at startup, and becomes high level "H" when shifting to constant velocity control. Therefore, until shifting to constant velocity control, the switching signal C from the switching circuit 5 ;SW3 is turned on and the output of the loop filter 6 is set to zero level.

When the phase of the comparison pulse V lags behind the reference pulse R, the phase comparator 1 outputs a delay signal U that becomes low level with a pulse width corresponding to the delay phase difference, and the comparison pulse V
If the phase of is leading, a leading signal which becomes low level with a pulse width corresponding to the leading phase difference is outputted (see FIGS. 6 and 4). Note that when one of the signals is being output, the other signal is not output.

The charge pump circuit 2 outputs a negative constant level voltage -Vcc while the delay signal U is at a low level, and outputs a positive constant level voltage +Vcc while the advance signal U is at a low level.
is output, and the output is set to zero level while both the delay signal U and the lead signal U are at high level (when there is no phase difference).

In this way, when there is no phase difference in constant velocity control,
That is, when the motor 8 is rotating at the designated speed, the output voltage of the charge pump circuit 2 and the output voltage of the loop filter 3 that integrates it are also at zero level, regardless of the designated speed.

Therefore, by simply turning on switch SW3 and setting the output of loop filter O to zero level until switching from starting mode to constant velocity mode, switching from starting to constant velocity control can be achieved at any specified speed. can be switched stably.

However, in order for this circuit to smoothly transition from startup to constant velocity control, the switching signal C must be
Immediately after switching from L" to "H", the output of loop filter O is a signal to increase the motor speed if the motor speed at that time is slower than the specified speed, and a signal to increase the motor speed if it is faster than the specified speed. It is necessary for the signal to decelerate.

The point in time when the transition to constant velocity control starts (when the switching signal C is “L”)
When switching from " to "H", motor 8 from )tx
If the speed locus of is like the curve ■ in Figure 2, and the motor speed υ never exceeds the specified speed v8, the frequency of the reference pulse R is always higher than the frequency of the comparison pulse V. , the phase comparator 1 outputs only the delayed signal U.

Therefore, the output of loop filter B immediately after the transition to constant velocity control becomes a signal for increasing the speed of the motor 8, and the transition to constant velocity control is performed smoothly.

However, when the curve ■ in Fig. 2 is reached, the motor speed υ exceeds the specified speed vs, so the frequency of the comparison pulse V becomes higher than the frequency of the reference pulse R, but the phase comparator 1 The output of the signal U changes from the delayed signal U to the advanced signal only after the comparison pulse V arrives twice during one period of the reference pulse R, as shown in FIG. is outputting.

Therefore, when the switching signal C changes from "L" to "H" at the timing shown in Fig. 6, the output of the loop filter B immediately after that becomes a signal that increases the speed of the motor, and the motor speeds up at a smooth constant speed. This was an obstacle to the transition to control.

In addition, when the curve ◯ in Fig. 2 is above, the frequency of the comparison pulse V once becomes higher than the frequency of the reference pulse R, and then becomes lower; however, contrary to the above case, the output of the phase comparator 1 In order for the leading signal to change to the delayed signal U, the reference signal R must arrive twice during one cycle of the comparative pulse V, as shown in FIG. is outputting.

Therefore, when the switching signal C changes from "L" to "H" at the timing shown in Fig. 4, the output of the loop filter 3 immediately after that becomes a signal that decelerates the motor, and in this case as well, the output is smooth. This hindered the transition to constant velocity control.

This problem becomes more serious when the accuracy of detecting the rotational position of the motor by a rotary encoder or the like is poor (the number of pulses per rotation is small), or when the frequency of the reference pulses is lower.

This invention was made to solve such problems, and in the control circuit of the scanning drive motor as described above, regardless of the speed trajectory after startup and the timing of transition to constant speed control, The purpose is to enable a smooth transition to constant velocity control.

Therefore, the control circuit for the scan drive motor according to the present invention includes a determination circuit that determines whether the rotational speed of the motor at the time of transition to constant velocity control is greater than a designated speed, and a phase comparator that is equipped with an input timing control circuit that inputs either a reference pulse or a rotation synchronization pulse (comparison pulse) before the other, and when the motor speed is greater than the specified speed, the comparison pulse is input first and the specified speed is input. When the pulse is small, the above object is achieved by inputting the reference pulse to the phase comparator first.

The present invention will be explained in detail below with reference to FIGS. 5 to 7 of one drawing.

FIG. 5 is a circuit diagram showing an embodiment of the present invention, and parts corresponding to those in FIG. 1 are designated by the same reference numerals, and a description of those parts will be omitted.

In FIG. 5, 10 is the motor 8 at the time of transition to constant velocity control.
This determination circuit determines whether the rotational speed of is greater than the specified speed, and is comprised of a comparator 11 and a D-type flip-flop circuit (hereinafter abbreviated as "D-FFj") 12.

The comparator 11 inputs a signal VF obtained by converting the comparison voltage V generated in synchronization with the rotation of the rotary encoder P-9K motor 8 into a voltage by the F/V conversion circuit 16. Compare it with the reference voltage signal vR corresponding to the designated speed, and if VF > VR, the output is set to high level 2H, and if VF≦VR, the output is set to low level “L”.

D-FF12 switches the switching signal C from 2L" to "H",
The input signal of the D terminal, that is, the output level of the comparator 11 at the time of switching, that is, the time of starting the transition from the startup mode to the constant velocity control mode, is stored and output to the Q terminal.

Therefore, if the rotational speed of the motor 8 is greater than the specified speed at this time, the judgment signal a of the judgment circuit 10 is at a high level 2.
If the speed is below the designated speed, the determination signal a becomes low level "L". This state is maintained while the switching signal C is 1H".

Note that the clear signal is generated between the end of constant velocity control and the start of the next constant velocity control, and clears the memory contents of the D-FF 12.

Reference numeral 14 denotes an input timing control circuit that inputs either the reference pulse R or the comparison pulse to the phase-y-comparator 1 before the other, depending on the determination result of the determination circuit 100.

Now, the judgment signal a of the judgment circuit 10 is at the low level V″L″
(The rotational speed of the motor is less than or equal to the designated speed), the operation will be explained with reference to FIG. 6 as well.

When the determination signal a becomes "L", gate Gl is opened and the reference pulse R is outputted as it is as the reference signal R'.

On the other hand, the gate G2 remains closed, but the arrival of the first reference pulse R immediately after the switching signal C switches from 'L' to 'H' opens the gate G3, and the comparison pulse V changes to the comparison signal V. ′ is output.

In other words, if the speed of the motor 8 at the moment when the switching signal C switches from L" to 'H" is smaller than the specified speed, the input signal to the phase comparator 1 is always inputted from the reference pulse R first, After that, comparison < pulse V will be input.

Therefore, the output of the phase comparator 1 always becomes the delayed signal U as shown in FIG. Therefore, a smooth transition to constant velocity control is performed.

When the judgment signal a of the judgment circuit 10 is 7.1H (the rotational speed of the motor is less than the specified speed), when the judgment signal a becomes X''H, G2 opens and the seventh As shown in the figure, the comparison pulse V is directly output from the input timing control circuit 14 as the comparison signal V'.

On the other hand, gate G1 remains closed, but gate G4 opens due to the arrival of the first comparison pulse V immediately after switching signal C switches from V"L" to "H", and reference 2 reference pulse R becomes the reference. It is output as signal R'.

That is, in this case, the input signal to the phase comparator 1 is always inputted from the comparison pulse V first, and then the reference pulse R is inputted.

Therefore, the output of the phase comparator 1 is always a leading signal as shown in FIG. Therefore, in this case as well, a smooth transition to constant velocity control is performed.

As described above with respect to the embodiments, the scanning drive motor control device according to the present invention always has the following advantages: It is possible to smoothly shift to constant velocity control.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of the control device for the scanning drive motor proposed earlier and is the object of this invention. FIG. 6 and 4 are timing diagrams for explaining the operation thereof. FIG. 5 is a circuit diagram showing an embodiment of the present invention, and FIGS. 6 and 7 are for explaining the operation. FIG. 1... Phase comparator 2... Charge pump circuit 6... Loop filter 4...
・Motor drive circuit 5... Switching circuit for starting and constant speed control 7... Servo amplifier 8...
Scanning drive motor 9...Rotary encoder I
J]...Judgment circuit 11...Comparator 12...D type flip-flop circuit (D
-FF)14...Input timing control circuit R・
...Reference pulse ■...Rotation synchronization pulse (comparison pulse) U...
...Delayed signal D...Advanced signal Applicant - Riko Co., Ltd. ---- Figure 6 Reference pulse R-Cho11[-]-]1Cho1-r--No.7

Claims (1)

[Claims] 1. A phase comparator, a charge pump circuit, a loop filter, a motor drive circuit, a switching circuit for starting and constant speed control, and a switch means for setting the output of the loop filter to zero level until shifting to constant speed control. When the motor starts and shifts to constant speed control, the output of the loop filter is applied to the motor drive circuit, and the phase comparator outputs a rotation synchronization pulse synchronized with the rotation of the motor and a periodicity corresponding to the designated speed. Compare the phase with the reference pulse,
In a control device for a scanning drive motor that controls a motor at a constant speed by increasing or decelerating the motor according to the phase difference, a determination circuit that determines whether the rotational speed of the motor at the time of transition to the constant speed control is greater than a specified speed; and an input timing control circuit for inputting either the reference pulse or the rotation synchronization pulse to the phase comparator before the other according to the determination result.