JP2001157494A - Apparatus and method for driving/controlling stepping motor of electrophotographic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the phase current of a constant current stepping motor variably and appropriately depending on the load torque using an operating means, e.g. a microcomputer, or a hard logic signal. SOLUTION: A low vibration, low noise, power saving drive control system for constant current stepping motor is achieved in an electrophotographic apparatus by controlling the motor phase current correctly depending on the increase/ decrease of load torque in a load system using a constant current stepping motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for mechanically driving an electrophotographic apparatus using a stepping motor.

[0002]

2. Description of the Related Art In recent years, in the POD market, high image quality and high speed printing have been promoted, while demands for power saving and low noise have been increasing. Conventionally, as a power source of an electrophotographic printing apparatus, an AC motor, a DC motor, a DC
Brushless motors and stepping motors have been used. In particular, the stepping motor rotates at a predetermined step angle in synchronization with the drive pulse, and therefore has the excellent feature that speed control and position control can be easily performed by open loop control. It is used. Further, as a driving method of the stepping motor, there are a constant voltage driving method and a constant current driving method having excellent torque characteristics in a high speed range, and a winding specification and a driving circuit suitable for the application are combined. On the other hand, due to the structure that the motor rotates in synchronization with the drive pulse, a step-out phenomenon occurs when a load torque higher than the output torque is applied.
It was necessary to select a motor capable of extracting an output torque that was about twice to 2.5 times or more.

As one form of the electrophotographic printing apparatus, there is known a laser beam printer that prints a document (double-sided printing) on each side of a sheet-shaped recording member (hereinafter, referred to as a sheet). First, paper transport in a general laser beam printer will be described with reference to FIG. As shown in FIG. 3, the sheet feeding unit includes a first hopper 42 having a similar structure,
The second hopper 41, the third hopper 40, the manual feed tray 46, and the fourth hopper 39 are composed of five types. As an example,
A case where paper is fed from the first hopper 42 will be described. The paper loaded on the first hopper 42 is transported by driving the pick roller 43, and when the vertical transport sensor 47 detects the paper, the driving of the pick roller 43 is stopped and transported to the timing roller 49 by the vertical transport roller 48. You. The sheet conveyed by the timing roller 49 is then conveyed by the registration roller 51. The toner that has formed an image on the photoconductor 53 is transferred onto the sheet conveyed by the registration roller 51. The sheet is transported to the fixing device 55 by the transport belt 54 with the toner on which the image is formed, and the toner having the image formed on the sheet is thermally fixed by the heat roll 56 of the fixing device 55.

Next, the operation of the sheet feeding unit will be described with reference to FIG. Since the first hopper 42, the second hopper 41, the third hopper 40, the manual feed tray 46, and the fourth hopper 39 have substantially the same structure, the case of the hopper 142 will be described as a representative. The first hopper 42 includes a pick roller 43, an upper separation roller 44, a lower separation roller 45, and a vertical conveyance roller 4.
8. These rollers are driven by one constant current stepping motor, and only the pick roller 43 is driven via a pick clutch. First hopper 42
Is set with multiple sheets, and is turned ON /
Pick roller 43 linked to pick clutch that turns off
The paper is picked and transported at equal intervals. Pick roller 4
3 is carried out by friction between the pick roller 43 and the sheet. Also, frictional force is generated between the sheets,
When the pick operation is performed by the pick roller 43, the paper
It often happens that not only sheets but also a plurality of sheets are conveyed.
A plurality of sheets conveyed at a time are separated by the upper separation roller 44 and the lower separation roller 45 and are conveyed by one sheet. The load torque of the constant current stepping motor in the sheet feeding unit varies due to the ON / OFF operation of the pick clutch. During printing, the pick clutch of each paper supply unit
Table 1 shows the time ratio of N. The phase current of the constant current stepping motor is set according to the maximum load when the pick clutch is ON, regardless of the magnitude of the load torque, and is always used at a constant current.

[0005]

[Table 1]

[0006]

As in the above prior art, the phase current of the constant current stepping motor in the paper feeding unit is set in accordance with the maximum load torque when the pick clutch is ON, and is always used at a constant current. However, the actual load torque fluctuates due to the generation of the acceleration torque accompanying the acceleration / deceleration operation and the ON / OFF operation of the pick clutch. The surplus torque becomes a source of vibration / noise and has the problem of accelerating wear of gears. The time ratio during which the pick clutch is ON is a short time of 13.5% in the case of duplex printing on the manual feed tray 46. In other words, it can be said that the constant current stepping motor always consumes an unnecessarily large current for a short time during which the pick clutch is turned on.

It is an object of the present invention to provide a low-vibration, low-noise, low-power, constant-current stepping motor drive control system that appropriately controls the phase current of a constant-current stepping motor in accordance with an increase or decrease in load torque. .

[0008]

According to the present invention, a microcomputer or a hard logic signal is used in a conventional drive control system including a microcomputer, a constant current driver IC and a constant current stepping motor. Current driver I for determining the phase current of a constant current stepping motor
A circuit has been added that allows the reference voltage of C to be varied in two or multiple stages. Since the output torque of a constant current stepping motor increases and decreases in proportion to the phase current, when the load torque is large, the reference voltage is high (phase current is high), and when the load torque is small, the reference voltage is low (phase current is low). ) Set and enable appropriate phase current variable control according to load torque.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a diagram schematically showing a constant current stepping motor phase current variable drive circuit according to the present invention. This circuit includes a microcomputer 1 that outputs a motor control signal, a constant current driver IC 2, and a constant current stepping motor 4. The constant current driver 2 includes a motor drive signal 6, a motor rotation direction signal 7, a motor drive pulse signal 8, a motor phase current control signal 9, and a Q1 transistor 1 from the microcomputer 1.
5, a constant current stepping motor 4 based on a reference voltage 14 composed of an R1 resistor 11, an R2 resistor 12, and an R3 resistor 13.
Is driven at a constant current. The following relational expression holds between the reference voltage 14 and the motor phase current 5 of the stepping motor 4.

Motor phase current 5 = reference voltage 14 / current detection resistance The reference voltage 14 is set in two stages by a motor phase current control signal 9 from the microcomputer 1. When the motor phase current control signal 9 is Lo, the Q1 transistor 15 is turned off,
The reference voltage 14 is set high as in Equation 1.

[0012]

(Equation 1)

When the motor phase current control signal 9 is Hi, the transistor Q115 is turned on, and the reference voltage 14 is set low as shown in equation (2).

[0014]

(Equation 2)

Next, a specific control example will be described with reference to FIG.

FIG. 2 shows an example of a control sequence of a constant current stepping motor for carrying a paper pick in a paper feeding unit. This figure shows the relationship among the motor drive pulse signal 24, the pick clutch drive signal 25, the motor phase current control signal 26, and the motor phase current 28.

The paper pick motor is driven by a motor drive pulse signal 24 to increase the acceleration section 21, the constant speed section 22, and the deceleration section 23.
The pick clutch drive signal 25 controls ON / OFF 31 of the pick clutch. The motor phase current control signal 26 becomes Lo33 when the motor drive pulse signal 24 requires acceleration torque in the acceleration section 21 and deceleration section 23 and when the pick clutch drive signal 25 is ON30 and the load torque is increasing, The phase current 28 is set at power-up 27. On the other hand, when the pick clutch is OFF 31 in the constant speed section 22, the motor phase current control signal 26 is set to Hi because the load torque is small.
32, and the motor phase current 28 is set to 29 at the time of power down.

[0018]

As described above, according to the present invention, it is possible to appropriately and variably control the phase current of the constant current stepping motor in response to the increase and decrease of the load torque. Up to 67.
It is possible to save 5%. Further, it is possible to provide a constant current stepping motor drive control system excellent in noise and vibration.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a constant current stepping motor phase current variable drive circuit of the present invention.

FIG. 2 is a time chart showing one embodiment of a constant current stepping motor phase current control sequence of the present invention.

FIG. 3 is a schematic view showing an outline of a general electrophotographic apparatus.

FIG. 4 is a schematic view of a sheet feeding unit according to the present invention.

[Explanation of symbols]

1: microcomputer, 2: constant current driver IC, 3: motor drive power supply Vcc1, 4: constant current stepping motor, 5: motor phase current, 6: motor drive signal, 7: motor rotation direction signal, 8: motor drive pulse signal , 9: motor phase current control signal, 10: logic power supply Vcc2, 11: resistor R1,
12: resistance R2, 13: resistance R3, 14: reference voltage Vre
f, 15: transistor Q1, 21: acceleration section, 22: constant speed section, 23: deceleration section, 24: motor drive pulse signal, 25: pick clutch drive signal, 26: motor phase current control signal, 27: at power up Phase current, 2
8: motor phase current, 29: phase current at power down, 3
0: Pick clutch ON, 31: Pick clutch OF
F, 32: motor phase current control signal Hi, 33: motor phase current control signal Lo, 38: laser beam printer, 3
9: fourth hopper, 40: third hopper, 41: second hopper, 42: first hopper, 43: pick roller, 44: upper separation roller, 45: lower separation roller, 46: manual tray, 47: vertical conveyance Sensor, 48: vertical transport roller, 49:
Timing roller, 50: Timing sensor, 51:
Registration roller, 52: Registration sensor, 53: Photoreceptor, 54: Conveying belt, 55: Fixing device, 56: Heat roll, 57: Flip roller, 58: Flip sensor, 6
0: discharge roller, 61: discharge sensor, 62: switchback roller, 63: switchback sensor, 65: return roller, 66: return sensor, 67: stacker.

Continuation of the front page F term (reference) 2C362 CB47 DA47 5H580 AA05 BB01 BB02 FB03 FC03 HH33

Claims (4)

[Claims] 1. An electrophotographic apparatus having a constant current stepping motor and a driving device for the stepping motor, wherein a circuit for varying a phase current of the constant current stepping motor is provided. apparatus. 2. The stepping motor drive control device for an electrophotographic apparatus according to claim 1, wherein the phase current of the constant current stepping motor is variably controlled according to the load torque. 3. A stepping motor drive control device for an electrophotographic apparatus having a sheet feeding unit constituted by a constant current stepping motor and a pick clutch, and performing a picking operation of a sheet-like sheet by ON / OFF of the pick clutch. The stepping of the electrophotographic apparatus is characterized in that the motor phase current is set high when the motor accelerates / decelerates and needs an acceleration torque, and the motor phase current is set low when the motor rotates at a constant speed and the load torque is small. Motor control method. 4. A stepping motor drive control device for an electrophotographic apparatus having a sheet feeding unit constituted by a constant current stepping motor and a pick clutch, and performing a picking operation of a sheet-like sheet by ON / OFF of the pick clutch. A stepping motor control method for an electrophotographic apparatus, wherein the motor phase current is set high when the load clutch is turned on and the load torque is large, and the motor phase current is set low when the pick clutch with a small load torque is turned off.