JPH10161467A - Image forming device and starting method of stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a stepping motor at a low cost, without affecting operation in a normal environment by changing a pattern for slowing up control at the time of starting the stepping motor, with the result of the calculation of a calculating means. SOLUTION: The heater of a fixing heater 8a is turned on to detect temp. by a thermistor 204 and when the rising of the temp. per unit hour (temperature rising gradient dT/dt) exceeds a previously set fixed value, the stepping motor is started with the slowing up control with a prescribed slowing up pattern. Further, when the temperature rising gradient dT/dt is the previously set fixed value or below, it is decided that the grease 205 of the heater 8a is not sufficiently melted and the stepping motor is started by the slowing up control with a different slowing up pattern. Thus, the stepping motor at a lower cost can be used without affecting a first printing time in the normal environment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a stepping motor and a method for starting the stepping motor.

[0002]

2. Description of the Related Art In recent years, in an image forming apparatus of a type in which a toner is thermally fixed, a stepping motor is used as a motor for driving all load systems including a rotation drive of a fixing heater in order to reduce costs.

In this stepping motor, normal driving is performed using an escape torque (pull-out torque) capable of obtaining a large output.

Here, when starting the stepping motor, a pull-in torque (pull-in torque) is required. Since the pull-in torque is smaller than the pull-out torque at the same frequency, when starting the stepping motor, it starts from a lower frequency than the normal use frequency, obtains a large torque, gradually increases the speed (frequency) to the range of the normally used pull-out torque. Acceleration slow-up control is performed.

[0005] If this slow-up is exponentially accelerated over time, it is possible to start a larger load torque than to accelerate linearly in a short time.

[0006]

However, when a ceramic heater is used as a fixing heater, grease applied between the ceramic heater and the fixing film and grease applied to each drive gear are solidified at a low temperature, and the load is reduced. There is a problem that the torque becomes heavy, and it is necessary to use a higher-cost, higher-output motor that matches the load torque at a low temperature. In addition, if the slow-up is performed exponentially for a sufficiently long time to start a larger load, an unnecessarily long slow-up time is required even when printing in a normal environment. There is a problem that it affects the time until printing starts.

[0007] The present invention has been made under such circumstances, without affecting the operation in a normal environment.
It is an object of the present invention to provide an image forming apparatus and a stepping motor activation method that enable use of a low-cost stepping motor.

[0008]

In order to achieve the above object, according to the present invention, a method for starting an stepping motor is described in the following (1) to (3).
Configure as follows.

(1) A fixing heater, a stepping motor for rotationally driving the fixing heater, a temperature sensor for detecting the temperature of the fixing heater, and a temperature rise per unit time of the fixing heater based on an output of the temperature sensor An image forming apparatus comprising: a calculating unit that calculates a gradient; and a control unit that changes a pattern of slow-up control when the stepping motor is started based on a calculation result of the calculating unit.

(2) The image forming apparatus according to (1), wherein the control means re-executes the slow-up control when the stepping motor is started, depending on the calculation result of the calculation means.

(3) A scanner motor consisting of a stepping motor having a fluid bearing, rotation speed detection means for detecting the rotation speed of the scanner motor, and a start-up time of the scanner motor based on an output of the rotation speed detection means. And a control means for changing a pattern of the slow-up control at the time of startup according to the start-up time.

(4) A stepping motor starting method for changing a pattern of slow-up control at the time of starting based on an operating state at the time of starting the stepping motor.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is hereinafter referred to as a "laser printer".
Examples will be described in more detail. Note that the present invention is not limited to a laser printer, but can be embodied in the form of an image forming apparatus such as various copying machines and printers, and in the form of a stepping motor starting method.

[0014]

FIG. 1 shows a "laser printer" according to a first embodiment.
It is sectional drawing which shows a structure of. In FIG. 1, 1 is a laser printer, 2 is recording paper, 3b and 3c are conveyance means, 4 is a transfer roller, 5 is an optical system for generating a laser beam, 6 is a photosensitive drum, 7 is a process cartridge, and 8 is a fixing device. ,
9 is a paper discharge roller, 10 is a paper discharge tray, and 11 is a printer controller.

As shown in FIG. 1, the laser printer 1 irradiates a light image based on image information from an optical system 5 according to a control command of a printer controller 11 to cause a photosensitive drum 6 serving as an image carrier to have a developer ( (Hereinafter referred to as toner). Then, in synchronization with the formation of the toner image, the recording paper 2 is transported from the cassette 3a by transporting means including a paper feed roller 3b, a pair of registration rollers 3c, and the like. The toner image formed on the photosensitive drum 6 is transferred to the recording sheet 2 by applying a voltage to a transfer roller 4 as a transfer unit, and the recording sheet 2 is fixed to a fixing heater 8.
is transferred to a fixing device 8 having a built-in portion, and the transferred toner image is fixed on the recording paper 2. Then, the recording paper 2 is discharged to a paper discharge roller 9.
And is discharged to the paper discharge tray 10.

As shown in FIG. 2, the fixing heater 8a in the fixing device 8 includes a ceramic heater 201, a plastic stay 202, a fixing film 203, and a thermistor 20.
4, the grease 205 is rotated by a stepping motor (not shown), and the printer controller 11 obtains temperature information of the fixing heater 8a by the thermistor 204.

The operation of the present embodiment will be described below with reference to FIG. 3 showing a flowchart and FIG. 4 showing a slow-up pattern of a stepping motor for rotating and driving the fixing heater 5a. The processing of this flowchart is performed by a CPU (not shown) in the printer controller. The heater of the fixing heater 8a is turned on (S302), and the thermistor 20 is turned on.
4 (S303), and if the temperature rise per unit time (temperature rise gradient dT / dt) exceeds a predetermined constant value, stepping is performed by the slow-up control of the slow-up pattern 1 in FIG. Start the motor,
If the temperature rise gradient dT / dt is equal to or less than a predetermined value, it is determined that the grease 205 of the fixing heater 8a is not sufficiently melted, and the slow-up pattern 2 shown in FIG.
The stepping motor is started by slow-up control.

As described above, according to this embodiment,
By changing the pattern of the slow-up control in accordance with the temperature rise gradient of the fixing heater, it is possible to use a lower-cost stepping motor without affecting the first print time in a normal environment.

(Second Embodiment) In the first embodiment, the printer controller 11 obtains temperature information of the fixing heater 8a by the thermistor 204. If the temperature rise per unit time (temperature rise gradient dT / dt) exceeds a predetermined constant value, the fixing heater 8a does not rotate because the stepping motor is not rotating, and the pressure roller 8b
It is determined that the temperature rise is fast because there is little heat escaping through the motor, the slow-up control of the stepping motor is executed again, and the motor is started again. This example will be described as a second embodiment with reference to the flowchart in FIG.

S501 in the flowchart of FIG.
The operations in S506 to S506 are the same as the operations in S301 to S306 in FIG. In steps S505 and S506, the stepping motor is started in the slow pattern 1 or the slow pattern 2, and the temperature of the fixing heater 8a is detected by the thermistor 204 (S507). (S50
8) Restart with slow-up pattern 2 (S50)
9). If the temperature rise gradient does not reach the predetermined value in S508, it is determined that the startup is successful, and the startup is continued. Thereafter, as soon as the rotation is normal (S510), the printing operation is started (S511).

As described above, according to this embodiment,
After the initial slow-up control, if the temperature rise gradient of the fixing heater 8a is equal to or more than a predetermined value, it is determined that the stepping motor is not rotating (startup has failed), and the slow-up operation is performed again. Thus, it is possible to prevent the stepping motor from being poorly started due to the increase in the load torque, and to reliably start the stepping motor.

(Embodiment 3) FIG. 6 is a flowchart showing the operation of Embodiment 3, FIG. 7 is a sectional view of a scanner motor using an oil lubricated bearing, and FIG. 8 is an electric block diagram. FIG. 9 and FIG. 10 are diagrams illustrating the rotation state of the scanner motor.

At present, a contact type ball bearing is often used as a bearing for an optical scanning motor of an image forming apparatus. However, in recent years, precision processing has become possible, and the cost, noise and cost are lower than those of a ball bearing. Oil-lubricated bearings capable of uneven rotation have been adopted. In this oil-lubricated bearing, the viscosity of the lubricating oil used has temperature dependence. FIG.
In the figure, reference numeral 702 denotes a shaft, and the polygon mirror 7
03, fixed to the rotor 705. Reference numeral 709 denotes a spring member for fixing the polygon mirror 703. 70
Reference numeral 7 denotes a bearing bracket. The gap between the shaft 702 and the bearing bracket 707 is filled with lubricating oil 708, and is kept out of contact during rotation. Reference numeral 706 denotes a metal plate made of a silicon steel plate, and a circuit (not shown) for driving the motor is also mounted on the metal plate 706. 704 is a stator core, 710 is an amateur coil, and 711 is a rotor magnet.

FIG. 8 is a block diagram illustrating an electrical configuration. In FIG. 8, reference numeral 804 denotes a sequencer and a driver for controlling the printer. Reference numeral 803 denotes a scanner motor including a polygon mirror, which rotates in the direction of an arrow at the time of printing. Irradiation is performed on the surface of the photosensitive drum 802 to form a toner image. Reference numeral 806 denotes a photodetector for detecting a writing position of an image, and sends out a BD signal 807. According to the timing from the BD signal 807,
The image data VDO shown in 808 is transferred, and the laser is turned on / off by the VDO signal. A scanner motor 803 and a sequencer 804 including a driver are combined with information on the number of rotations and a rotation signal.

FIG. 9 shows the relationship between the number of rotations of the scanner motor and time in a normal state. When the power is turned on, the scanner motor 803 starts to rotate, and after reaching a predetermined number of rotations, a slight overshoot occurs, and then t
In one hour, it enters the range 906 of the predetermined number of revolutions.

FIG. 10 shows the relationship between the number of rotations of the scanner motor 803 and time at low temperatures. When the power is turned on, the scanner motor 803 starts rotating, and converges to a predetermined rotation speed range 1008 while vibrating due to the viscosity of the oil.

FIG. 6 is a flowchart showing the operation of this embodiment. Here, the control flow will be described with reference to FIG. 8, FIG. 10, and FIG.

When a print signal is received in step S602, the scanner motor 803 is rotated in step S603.
In step S604, the number of rotations 1002 is increased to a predetermined number of rotations 1007.
If the time t2 within the range exceeds an arbitrarily set constant value, it is determined that the device is in a low temperature environment and the load torque is heavy, and the slow-up pattern 2 in FIG. Performs slow-up control (S606). t
If 2 is equal to or less than the predetermined value, slow-up control (S605) is performed in slow-up pattern 1 assuming a normal state. Thereafter, the printing operation starts as soon as the normal rotation starts (S60).
8).

As described above, according to the present embodiment,
Due to the change in the startup time of the fluid bearing scanner motor,
By detecting the low temperature environment and changing the pattern of the slow-up control to increase the load torque due to the solidification of the grease applied to each drive gear, it is possible to lower the speed without affecting the first print time in the normal environment. It is possible to use a costly stepping motor.

[0030]

As described above, according to the present invention,
A low-cost stepping motor can be used without affecting the operation in a normal environment. According to the second aspect of the present invention, the start-up can be performed more reliably.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a first embodiment.

FIG. 2 is a cross-sectional view illustrating a configuration of a fixing heater.

FIG. 3 is a flowchart illustrating the operation of the first embodiment;

FIG. 4 is a diagram showing a slow-up pattern of a stepping motor.

FIG. 5 is a flowchart showing the operation of the second embodiment.

FIG. 6 is a flowchart illustrating the operation of the third embodiment.

FIG. 7 is a sectional view of a scanner motor used in a third embodiment.

FIG. 8 is a block diagram of a main part of a third embodiment.

FIG. 9 is an explanatory view of the third embodiment (at normal time).

FIG. 10 is an explanatory view of the third embodiment (at a low temperature).

FIG. 11 is a diagram showing a slow-up pattern of a scanner motor.

[Explanation of symbols]

 8a Fixing heater 11 Printer controller 204 Thermistor

Claims (4)

[Claims] 1. A fixing heater, a stepping motor that rotationally drives the fixing heater, a temperature sensor that detects a temperature of the fixing heater, and a temperature rise gradient of the fixing heater per unit time based on an output of the temperature sensor. An image forming apparatus comprising: a calculating unit that calculates a value of the stepping motor; and a control unit that changes a pattern of the slow-up control when the stepping motor is started based on a calculation result of the calculating unit. 2. The image forming apparatus according to claim 1, wherein the control means re-executes a slow-up control when the stepping motor is started, depending on a calculation result of the calculation means. 3. A scanner motor comprising a stepping motor having a fluid bearing, rotation speed detection means for detecting the rotation speed of the scanner motor, and a start-up time of the scanner motor based on an output of the rotation speed detection means. And control means for changing the pattern of the slow-up control at startup according to the start-up time. 4. A method for starting a stepping motor, comprising changing a pattern of a slow-up control at the time of starting based on an operation state at the time of starting the stepping motor.