JPS6159323A - Control method of optical system of copying machine in speed abnormality - Google Patents

Abstract

PURPOSE:To brake a motor automatically by comparing the driving current value of the motor with a reference value, and decreasing the rotating speed of the motor and stopping it when the time or frequency of the generation of an abnormal current is larger than a specific value. CONSTITUTION:A current flowing through transistors (TR) 71-76 constituting the driving circuit of the motor 38 is converted by a resistance 78 into a voltage, which is compared by a comparator 77 with a reference value VZ and outputted as a signal A5 to SCPU51. When the current is abnormal on the basis of the reference value VZ, an FF60 is reset forcibly. When the signal A4 goes up to 'H', the SCPU51 knows that the motor driving current becomes abnormal. The theta output of the FF60 goes down to 'L' by its resetting and the motor driving current is ceased. When the abnormal current flows continuously for longer than a specific time or at higher than a specific frequency, it is decided that the speed of the optical system becomes abnormal, and the setting and resetting of the FF60 are controlled to stop the motor 38 gradually, braking the motor automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method of controlling a speed abnormality in an optical mobile copying machine.

<Prior art and its disadvantages> In a copying machine with a moving optical system, the feed speed of the optical system must be kept constant. The moving speed of the optical system is detected, and the motor drive current is controlled so that the detected moving speed remains constant. However, in the past, the motor drive current was unconditionally controlled by the feedbank system at any point during the feed or return of the optical system, so if the optical system locked for some reason, the motor The problem was that the load torque suddenly increased, causing a large current to flow and burning out the motor coil.

<Objective of the Invention> The object of the present invention is to eliminate the above-mentioned drawbacks, and to automatically brake the motor to prevent the optical system from running out of control when the motor is overloaded due to a locked state of the optical system, etc. An object of the present invention is to provide a method for controlling the speed of an optical system of a copying machine when the speed is abnormal.

<Configuration and Effects of the Invention> The present invention controls the rotational speed of the motor that drives the optical system by controlling the pulse width of the motor drive current, and detects whether or not there is an abnormal current by comparing the motor drive current value with a reference value. The present invention is characterized in that the motor rotation speed is gradually reduced and the motor is stopped when the abnormal current occurrence time or number of occurrences is equal to or greater than a predetermined value.

”- According to this invention, by configuring as shown below,
When the optical system locks or the motor load becomes extremely large due to abnormal friction, the motor drive current is detected to suddenly increase and the motor rotation speed is gradually reduced and stopped. Abnormalities can be detected easily and reliably, and burnout of motor coils and destruction of electronic components due to overcurrent can be prevented. In addition, the time and number of occurrences of abnormal current are set to a specified value.
Since the abnormal stop is made only when -, malfunctions due to noise etc. can be prevented. Furthermore, if the motor control current is suddenly turned off when an abnormality is detected in the motor, the inertia of the motor and optical system causes the optical system to run out of control, exceed the normal movement range, and collide with the holding member at the end (not shown) of the rail 32.35. However, in this invention, when a speed abnormality is detected, the motor rotation speed is gradually reduced and stopped, so there is a risk of double failure due to runaway of the motor and optical system. can be prevented from occurring.

<Embodiment> FIG. 2 is a schematic structural diagram of a copying machine in which the abnormal speed control method according to the present invention is implemented. A photosensitive drum 2 is arranged approximately in the center of the copying machine main body 1, and a charger, a developing section, a transfer device, a static eliminator, etc. are arranged around it. Further, an optical system 3 including a zoom lens 30 that moves horizontally according to the set magnification is arranged above the photoreceptor drum 2, and on the right side of the photoreceptor drum 2 there is a paper feeder including a paper feed l/ray and a cassette mounting section. On the left side, a conveyance section 5 for conveying the paper after transfer and a fixing section 6 consisting of two rollers are arranged. A document cover 7 is rotatably attached to the top of the copying machine body 1, and by setting a document under this cover, the optical system 3
An image corresponding to the original is formed on the photosensitive drum 2 by the feed scanning. The drive timing of the paper feed roller 40, which conveys the paper from the paper feed unit 4 toward the photosensitive drum 2, is controlled by a paper start clutch PSC in order to align the leading edge of the paper with the leading edge of the image on the drum 2. The on/off timing of this paper start clutch PSC is performed by a slave CPU for controlling the optical system, which will be described later.

FIG. 3 is a perspective view of essential parts of the optical system 3 of the copying machine. An optical system scanning section 31 that scans a document in the optical system 3 supports a mirror base MBI that integrates a light source 31a and two mirrors 31b and 31c, and a mirror 31d that reflects light reflected from the document onto the mirror 31b. It is composed of a mirror base MB2. These mirror base MBI, MB2
is supported slidably in the horizontal direction by two wooden rails 32 and 33. One side 34 of mirror base M131
is fixed to a wire 35, and as the wire 35 moves in the A or B directions, mirror bases MBI and MB2 both move in the A direction (feed direction) and B direction (return direction). Wire 35 connects pulleys 3G, 37 and brushless DC
The mirror bases MBI and MB2 are wound around the rotating shaft of the motor 38 and reciprocate as the motor 38 rotates forward and backward.

The wire fixing side portion 34 of the mirror base MBI has a vertical piece 34a, and a home position sensor HP for detecting the vertical piece 34a is provided in the stopping area of the mirror base MBI.
S is placed. The stopping area of the mirror base MHI is the range from when the rear end C of the vertical piece 34a cuts the optical path of the home position sensor HPS until it moves in the B direction (return direction) by about 10 mm. The mirror base MBI, that is, the stop position of the optical system is located at a position where the rear end C of the vertical piece 34a moves about ten millimeters past the set position of the home position sensor HPS.In the copying machine of this embodiment, the control unit is the master. It consists of a CPU and a slave 7' CPU. The slave CPU receives signals from the home position sensor HPS, a rotary encoder RE (not shown) connected to the motor 38, and other sensors to control the rotational speed of the motor 38 and the paper start clutch PSC. FIG. 4 is a schematic block diagram of the control section. CPU is master CPU (MCPU) 50
and a slave CPU (SCPU) 51,
The CPU 50 sends a mirror start command and a mirror initial command to the 5 CPU 51.
sends status etc. to the MCPU 50. MCPU
50 is an input key 2 which receives signals from various sensors, etc.
5 CPU according to the program predefined in 52
It sends commands to the CPU 51, receives status from the CPU 51, and controls various other solenoids, main motors, etc. 5CPU 51 receives a command sent from MCPU 50 and receives signals from sensor) (PS, rotary encoder RE, etc.) and starts paper start clutch P according to a program predefined in ROM 53.
Controls the on/off timing of the SC and the rotation speed of the main motor 38. It also monitors whether the drive current of the motor 38 is an abnormal current, and when the abnormal current continues for a predetermined period of time or more or occurs a predetermined number of times, it is determined that an abnormal speed of the optical system has occurred, and the rotation of the motor 3B is stopped. Stop gradually. Furthermore, after performing a predetermined operation, it transmits status etc. to the MCPU 50.

FIG. 1 is a peripheral circuit diagram of a slave CPU.

The motor circuit is a three-phase DC brushless motor 38. Sensor S1 attached to rotary encoder RE and each phase detection sensor S2 of u, v, w
It consists of S4.

The outputs of the sensors S1 to S4 and the home position sensor HPS are input to the 5cpU51 as signals A6 to A8. Signals AI and A2 from the 5cpU 51 are input to the set terminal S and reset terminal R of the flip-flop 60, respectively. These signals At and A2 define the set time and reset time of the flip-flop 60, thereby controlling the pulse width of the motor drive current. Signal A3
is input to the gate 61 as a signal for determining whether to enable or disable the Q output of the flip-flop 60. Further, the signal A4 constitutes a code that determines the energization timing of each phase of u, v, and w, and includes gates 62 to 64 and gates 68 to 7.
Enter 0. Transistors 71-76 constitute a motor drive circuit, and are controlled to be turned on or off according to the outputs of gates 65-70. During the period when transistors 71, 74, 72.75 are on, the U phase and ■ phase are energized, and during the period when transistors 72, 75, 73.76 are on, V
Phase 2w phase is energized. These transistors are switched on and off by the code determined by the signal A4, and are energized in the order of uv-+vw→wu-... to form a rotating magnetic field.The comparator 77 converts the current flowing through each transistor into a resistor. At step 78, the voltage is converted and compared with the reference value V2, and outputted to the 5CPU 51 as a signal A5. Furthermore, the flip-flop 60 is forcibly reset in the case of abnormal current. When the signal A5 becomes "H", the CPU 51 knows that the motor drive current has become abnormal for some reason. Also, by resetting the flip-flop 60, the Q output becomes "L", and the motor drive current immediately becomes 0.
The operation of the PU 51 will be explained. This figure is a flowchart showing the rotational speed control operation of the motor 38.

When the motor 38 receives a mirror start command etc. from the MCPU 50 and enters the rotation start mode, the signal A3 is set to H'' in step nl (hereinafter step n+ is simply referred to as ni). The Q output becomes valid and is guided to the motor drive circuit. Next, n2 reads the outputs of sensors S2 to S4 and detects the rotor position. Based on the results, n3 changes the output of each phase of U, V, and W. Calculate the on/off combination and output the code of the combination as signal A4.Next, at n4, wait for the motor drive current off time TB calculated by interrupt processing to be described later to elapse, and when that time has elapsed. At n5, the signal AI is set to "H".Next, at n6, wait for the morph drive signal on time TA calculated by interrupt processing to be described later to elapse;
Furthermore, during that time, the signal A5 is tested at n7, and the time TA
When elapses, the signal A2 is set to "H" at n8.

When the signal AI is set to "H" at n5, the flip-flop 60 is turned on and the on/off state of the transistor determined by the signal A4 is maintained during the set period. Furthermore, when the signal A2 is set to "■(" at n8, the flip-flop 60 is reset, and all transistors remain off during the reset period. In the test of the signal A5 at n7, the signal A5 is set to "■(").
Determine whether the level is H”.

If it is "H", that is, if the motor drive current is greater than or equal to the reference value, the internal counter is incremented.

After completing the above operations, it is determined in step n9 whether or not the vehicle has moved a predetermined distance. This judgment is made by the home position sensor H
This is done by determining whether or not the vehicle has moved a predetermined distance to the stop position after receiving the output signal A6 of the PS.

In nlo, signal A5 is “H” due to the test performed in n7.
It is determined whether the number is greater than or equal to a predetermined number. If it is less than K, steps n2 to n9 are repeated, and the motor is rotated without causing the flip-flop 60 to operate in reverse.

When the signal A8 is input manually from the sensor S1 attached to the low-resolution encoder RE while the above operation is being executed, the mode shifts to the interrupt mode and the steps from n20 onwards are executed. First n20
The number of revolutions of the motor is calculated from the pulse period of signal A8. Subsequently, in n21, the difference between the actual rotation speed and the target rotation speed is calculated. Note that the target rotational speed (target speed of the optical system) is stored in the ROM 53 in advance. When a difference is detected in n21, the process proceeds to n22, calculates the on time TA and off time TB of the motor drive current to achieve the target rotation speed, and returns. These TA and TB are the above n4. It is used in n6 to control the rotational speed of the motor to the target rotational speed.

When it is detected in the above nlo that the number of times the signal A5 becomes 'H' exceeds a predetermined value, steps n11 to n13 are executed and an abnormal stop is performed.First, in n11, the immediately preceding motor drive current on time TA is It is set shorter by ΔT.

Subsequently, at n12, the flip-flop 60 is set and reset controlled. As a result, the rotational speed of the motor 38 is forcibly reduced a little. The nil and n12 processes are continuously executed until a certain period of time has elapsed, and the motor is stopped when the rotational speed of the motor reaches approximately O. MCPU
50 has already received the status indicating that an abnormal speed has occurred from the 5 CPU 51 at this stage, so it takes abnormality processing such as displaying to the operator that an abnormal speed has occurred when the motor 38 stops. I do.

By the above operation, when a speed abnormality occurs, the motor rotation speed can be gradually reduced and stopped.

Note that if n1oT: the number of times A5 becomes "H" is less than or equal to the number of times that signal A5 becomes "H", the process does not proceed to nil and normally stops.Therefore, the case where signal A5 becomes "H" due to noise or the like can be ignored. In other words, it is possible to perform control that does not cause an abnormal stop due to noise or momentary abnormal current.Furthermore, in this embodiment, the number of times the abnormal current occurs is counted, and whether the number of times the abnormal current occurs is equal to or greater than a predetermined value. However, since the execution time from n2 to n9 is extremely short, nlo also determines whether the abnormal current generation time is greater than or equal to a certain value. Therefore, abnormal stop processing can be performed both when abnormal current occurs for a long time or when instantaneous abnormal current occurs many times after a long interval.
In this embodiment, a three-phase DCC brushless morph is used, but a normal DC motor can also be used.

[Brief explanation of the drawing]

Figure 1 shows a slave CPU of a copying machine in which this invention is implemented.
The peripheral circuit diagram is shown. Figure 2 is a schematic diagram of the copying machine;
FIG. 3 is a partial external perspective view of the optical system, and FIG. 4 is a schematic block diagram of the control section. Further, FIG. 5 is a flowchart showing the motor rotation speed control operation of the 5 CPUs. 2-photosensitive drum, 3-optical system, HPS-home position sensor, RE-rotary encoder, 38-motor. 77 - comparator, v2 - reference voltage.

Claims (1)

[Claims] (1) The rotation speed of the motor that drives the optical system is controlled by the pulse width of the motor drive current, and by comparing the motor drive current value with a reference value, it is detected whether or not there is an abnormal current. A method for controlling a speed abnormality in an optical system of a copying machine, characterized in that when the number of occurrences exceeds a predetermined value, the motor rotational speed is gradually reduced and stopped.