JPH0624033A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object is to provide an image forming apparatus capable of improving both performances of rise time and current consumption. An image printing unit that records image information on a recording medium by using an electrophotographic process, a conveying unit that conveys the recording medium to record the image information on the recording medium, and a plurality of printings without changing the conveying speed. In an image forming apparatus having a printing unit capable of printing with high density, a motor current detection resistor 22 for controlling acceleration of a scanner motor rotation driving unit
2a and 222b are formed in the scanner motor rotation driving means, and the dpi switching circuit 236 switches the resistance so that the resistance is low during high density printing and high during low density printing.

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, for example, an image in which a host computer develops information transferred through an interface circuit into image information and prints the image information on a recording sheet by using an electrophotographic process or the like. The present invention relates to a forming device.

[0002]

2. Description of the Related Art In a conventional image forming method, print information is created by a host computer, transferred through an interface circuit, developed by a video controller into image information, and the developed image information is used by an electrophotographic process or the like. To print on recording paper. In the electrophotographic process, the photosensitive drum is primarily charged before it is exposed to light, the laser element is blinked in accordance with the horizontal data line (main scanning direction) of the image information, and the obtained laser beam is horizontally swung to move the photosensitive drum. To expose a latent image on the exposed portion.

Image information is printed by developing the latent image on the photosensitive drum with toner, transferring the developed toner onto recording paper, and fixing the transferred toner onto recording paper using heat fixing or the like. . An image forming apparatus for printing the image information includes a host interface circuit section that receives the print information from a host computer, a video controller section that expands the print information into the image information, and a laser necessary for performing an electrophotographic process. It is equipped with an engine composed of elements, scanner motor, main motor for paper conveyance, high voltage control circuit, various sensors of fixing heater, low voltage power supply for supplying voltage to these.

The main motor driver in the engine section is
It controls a paper conveyance roller for conveying the recording paper, a photosensitive drum required for the electrophotographic process, and a main motor for rotating the fixing roller. The laser driver adjusts the amount of light emitted from the laser element according to the image signal, and blinks the laser element according to the image information. The scanner motor driver controls a scanner motor that rotates a polygon mirror (polyhedral mirror) for reflecting laser light in the main scanning direction of the photosensitive drum.

A fiber is used to synchronize the main scanning direction, a laser beam is guided, and the laser beam is converted into an electric signal by a light receiving element for beam detection. The fixing heater is a heat source of the fixing device for fixing the toner by heat fixing. In order to control the temperature, the temperature is detected by the thermistor and converted by an electric signal. The high-voltage control circuit generates and controls the high voltage necessary for performing the primary charger, development, transfer, and separation of the electrophotographic process.

The paper presence / absence sensor detects the presence / absence of recording paper in the paper feed tray, the paper feed sensor detects the leading edge of the paper at the time of paper feeding, and the paper ejection sensor detects the paper ejection state. The paper feed solenoid is a clutch for feeding the recording paper on the paper feed tray. A print sequence for controlling these various functions is performed by a program stored in the ROM in the DC controller. The video controller and the DC controller are connected by a video interface.

The basic printing operation will be described below. After expanding the image information, the video controller instructs the DC controller to prepare for printing based on the print request signal of the video interface. The DC controller rotates the main motor and scanner motor, controls the laser driver to adjust the laser light amount, warms the fixing heater to a fixable temperature, and generates the primary charging voltage, developing voltage, and transfer voltage of the high-voltage control circuit. Then, the paper feeding solenoid is turned on to feed the recording paper. A signal is generated to the video controller when the leading edge of the recording paper reaches the paper feed sensor. The video controller generates an image signal based on this signal.

The DC controller is a light-receiving element provided at a predetermined point in the main scanning direction for detecting the laser light reflected by the polygon mirror rotated by the scanner motor, and generates a beam detection signal by detecting it through the fiber. next,
The DC controller blinks the laser element with an image signal to form a latent image on the photosensitive drum. The image developed with toner is transferred onto a recording sheet and the toner is fixed by a fixing device. After the fixing, the recording paper passes through the paper discharge sensor, whereby the DC controller recognizes that the paper is normally discharged. The DC controller ends the print control when the trailing edge of the sheet passes the sheet discharge sensor.

An image forming apparatus having a function of switching the density of an image to be printed by a host computer using an operation panel or the like, changes the image density in the main scanning direction by changing the width of an image signal, and convey speed or a scanner motor. The image density in the sub-scanning direction is switched by switching the rotational speed or both (changing the process speed), and the image is output at a predetermined print density.

[0010]

However, in the image forming apparatus for switching the image density to high definition by increasing the number of rotations of the scanner motor while keeping the sheet conveying speed constant as in the above-described conventional example, the image density switching function is provided. When outputting a high-definition image, the rotation speed of the scanner motor becomes high, and there are the following drawbacks.

That is, since the scanner motor is started up from the stopped state to the high speed state, the higher the speed, the longer the rising time until the specified number of revolutions is reached. As a result, it takes a long time until the printable state is reached, and it takes a long time to print out the first sheet. In order to solve the above-mentioned drawbacks, the current detection resistance of the acceleration control motor connected to the motor driver IC that drives the scanna motor (generally a brushless motor is often used) to rotate at a constant speed is reduced so that the voltage is applied at the time of rising. The voltage was increased and the rise time was shortened.

However, in this way, the rise time is shortened for high speeds, and the drawback is solved, but on the other hand, at the time of low rotation at low density, there is a drawback that the current consumption is increased by the amount corresponding to the reduction of the current detection resistance. is there.

[0013]

The present invention has been made for the purpose of solving the above-mentioned problems, and has the following structure as one means for solving the above-mentioned problems. That is, an image printing unit that records image information on a recording medium using an electrophotographic process, a conveying unit that conveys the recording medium to record the image information on the recording medium, and a plurality of printing densities without changing the conveying speed. An image forming apparatus having a printing means capable of printing by means is provided with a switching means for switching the motor current detection resistance for acceleration control of the scanner motor rotation driving means according to the printing density.

For example, the switching means has a small resistance during high-density printing and a resistance during low-density printing, and the switching means is formed in the scanner motor rotation driving means.

[0015]

With the above structure, both the rise time and the current consumption can be improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail below with reference to the drawings. 1 and 2 are block diagrams showing the configuration of an embodiment according to the present invention. The configuration of this embodiment will be described below with reference to FIGS. Host I / F
The circuit 121 controls delivery to and from an external device such as a host computer, and is connected to the external device by a known interface suitable for a partner connection device such as RS232C specification or Centronics specification.

The video controller unit 120 for expanding the print information into image information converts the print information sent from the external device into image information and controls the print of the engine unit 130. The CPU 120a, the RAM 120b, the RO.
An M120c, a buffer 120d for storing image information, and a video I / F circuit 120e. Operation panel 122
Is for displaying the operation state of the image forming apparatus and for the user to set the operation mode.

The VIDEO I / F 11 is used to print the image information output by the video controller section 120 on a recording sheet.
The engine unit 130 is controlled through 9. Engine part 1
30 is composed of the following units. That is, a main motor for rotationally driving various rollers (not shown) such as a transport roller for performing an electrophotographic process while transporting a sheet, a primary power failure roller, a photosensitive drum, a developing sleeve, a fixing roller, and a pressure roller. 128, a main motor driver 127 for driving and controlling the same, a scanner motor 126 for rotating a polygon mirror (not shown) for reflecting laser light in the main scanning direction, and a scanner motor driver 125 for driving and controlling the same.

Furthermore, a laser element 124 for generating a laser beam for writing an image on the photosensitive drum and this is turned on.
ON / OFF and a light amount control laser driver 123, a light receiving element 115 and a beam detection signal generation circuit 115a for generating a beam detection signal which is a synchronization signal in the main scanning direction,
A paper presence / absence sensor 105 for detecting the presence / absence of recording paper, a paper feed sensor 110 for detecting the leading edge of the paper and generating a synchronization signal in the sub-scanning direction, and monitoring that the recording paper after printing has been ejected A sheet discharge sensor 112, a pickup solenoid 107 for feeding a sheet, a fixing heater 108 serving as a heat source for thermal fixing, a thermistor 109 for detecting the temperature of the fixing heater 108, a primary charger / developing
It is composed of a high voltage control circuit 117 for generating a high voltage necessary for transfer / separation, a fan motor 113 and a fan motor driver 114 for reducing a temperature rise inside the apparatus.

The DC controller 118 for controlling each unit of the engine unit 130 having the above-mentioned configuration is a CP controller.
The configuration includes a U 118a, a RAM 118b, a ROM 118c, a video I / F circuit 118d and the like. Further, a low voltage power source 104 for supplying a voltage required for each unit of the image forming apparatus, a primary power failure roller, a photosensitive drum, a developing sleeve, a charging roller, and a toner cartridge 116 in which toner is integrated are provided.

In the image forming apparatus constituted by the unit as described above, when the power source SW is turned on, the low voltage power source 1
A specified voltage is supplied to each unit from 04 to control the start-up. The video controller 120 performs a self-diagnosis process and confirms that each function operates normally.

On the other hand, the engine unit 130 first has D
Self-diagnosis of the C controller 118 is performed, and if normal, the state of each sensor of the engine unit 130 is judged, and it is checked whether or not the paper remains on the paper conveyance path. Then, the temperature control of the fixing heater 108 is started, and the temperature adjustment control is performed based on the standby temperature. At the same time, communication is performed with the video controller 120 in order to confirm that the interface with the video controller 120 is normal.
When these controls are normally performed, the DC controller 118 of the engine unit 130 notifies the video controller 120 that printing is possible through the video I / F circuit 118d.

When the image forming apparatus is in a printable state, it becomes possible to receive print information from the host I / F circuit 121. When print information is sent from the host I / F circuit 121, the print information is received, and the video controller 120 develops it into image information. Video controller 12
When 0 finishes developing the image, 0 issues a print request signal via the VIDEO I / F 119.

When the engine section 130 receives the print request signal, it starts the paper print start control, controls the temperature of the fixing heater 108 with respect to the printable state, and the main motor 12.
8 rotation control, high voltage control circuit 117 control, and the like. Also, the light amount adjustment control of the laser element 124 is performed until the start of printing. In addition, the scanner motor 126 and the scanner driver 12
In No. 5, the rotation speed is controlled to a specified rotation speed corresponding to the print density and keeps constant rotation.

When the printing is enabled by the above control, the engine unit 130 feeds the paper. When the timing of the leading edge of the paper is detected, a beam detection signal of a synchronizing signal in the sub-scanning direction and a synchronizing signal in the main scanning is generated. On the other hand, the video controller unit 120 outputs the image signal in synchronization with the synchronization signal in the main scanning direction and the sub scanning direction.

The engine section 130 blinks the laser element 124 according to the image signal from the video controller section 120. The laser light reflected by the polygon mirror (not shown) forms an image on the photosensitive drum through an imaging lens (not shown). The latent image on the photosensitive drum is developed with toner, transferred to a sheet, and fixed by a fixing device including a fixing heater 108 to print. Then, the process proceeds to the process of ejecting the paper.

When the discharge sensor 112 detects the trailing edge of the sheet, the engine section 130 controls the temperature of the fixing heater 108, the high-voltage control circuit 117, the rotation control of the main motor 128, and the scanner motor 126 to finish the printing operation. The rotation control of is ended. In the engine section, 10
Reference numeral 1 is a noise filter, 102 is a power switch, 103 is a user control circuit, 106 is a door sensor, and 111 is a cartridge sensor.

Next, a three-phase brushless motor drive circuit used in the scanner motor 126 and scanner motor driver 125 will be described with reference to FIG. The hall elements 203, 204, 205 detect the position of the rotor of the brushless motor, and detect the resistors 201, 202 and the low voltage power source 1 described above.
A voltage determined by the voltage Vcc supplied from 04, the magnetic flux from the rotor and the sensitivity of the Hall element is generated.

The differential amplifiers 206, 207 and 208 amplify the Hall voltage and input it to the LOGIC circuit 209. The LOGIC circuit 209 includes differential amplifiers 206 and 20.
The optimum excitation pattern is output to the output drivers 210, 211 and 212 corresponding to the outputs of 7 and 208. The output drivers 210, 211 and 212 continuously excite the stator coil 216 of the motor according to the output of the LOGIC circuit 209. This causes the rotor of the motor to rotate.
A frequency 235 proportional to this rotation is generated, and the generated AC voltage is input to the differential amplifier 230 through the capacitor 234. The AC voltage amplified by the differential amplifier 230 is input to the hysteresis converter 231 to remove noise chattering near the zero cross and output a pulse output.

The pulse output of the hysteresis comparator 231 is input to the speed disk circuit 232. In the speed disk circuit 232, the DC controller 1 described above is used.
Hysteresis converter 23 based on the frequency signal (B signal) corresponding to the image density from CPU 118a in 18
The period of the pulse output outputted from 1 is measured, and when it is judged to be slow, the acceleration pulse is outputted, and when it is judged to be fast, the deceleration pulse is outputted in proportion to the difference.

The frequency deviation information from the speed disk circuit 232 is obtained by the operational amplifier 224, the reference voltage 225 and the resistor 2.
26, 229 and capacitors 227, 228 are output as analog voltage. The output from the operational amplifier 224 is
A resistor 222a proportional to the motor current in the operational amplifier 220
Alternatively, the voltage is compared with the voltage across 222b, and the acceleration is controlled.

The output of the operational amplifier 220 is connected to a capacitor 223 for preventing oscillation of the acceleration loop. If the motor ON / OFF signal (A signal) from the CPU 118a in the DC controller 118 and the thermal shutdown circuit (TSD) 221 are in the motor ON state, the gate 219 outputs the output of the operational amplifier 220 to LOG.
It is sent to the IC circuit 209. The LOGIC circuit 209 is
At the same time as the phase switching operation described above, the output drives 210, 2
Through 11 and 212, the voltage across the stator coil 216 is controlled according to the output of the operational amplifier 220.

As a result, the motor rotates at a constant speed corresponding to the image density. Capacitors 213, 214, 215 connected to the stator coil 216 are for absorbing spike voltage due to an inductance component when the stator coil 216 is phase-switched in accordance with the position information of the Hall elements 203, 204, 205. Is.

The resistances 222a, 22 peculiar to this embodiment
2b is the CPU 118 in the DC controller 118 described above.
The resistance is switched by the image density switching signal (C signal) from a through the dpi switching circuit. The purpose is to increase the rise time by switching to the resistor 222a having a small resistance value at the time of high image density, and to switch to the resistance value 222b having a larger resistance value than that of the resistor 222a at the time of low image density, and to consume even if the rise time is somewhat slower. We are trying to achieve a reduction in current.

Although only two resistors 222a and 222b are described in the present embodiment, it is also possible to connect a plurality of resistors corresponding to all modes of image density switching and switch them. Also, the image density switching signal (C signal)
It is also possible to switch the detection by detecting from the frequency signal (B signal) corresponding to the image density.

As described above, according to this embodiment, high-speed printing (high-speed rotation) is achieved by switching the motor current detection resistance for acceleration control connected to the scanner motor driver IC in accordance with the image density. Since the rise time is prioritized, the resistance is made small, and the consumption current is prioritized at the time of low-density printing (low-speed rotation), so that the resistance is made large, and both the rise time and the consumption current performance are improved.

[0037]

[Other Embodiments] FIG. 4 is a diagram showing a three-phase brushless motor drive circuit used for a scanner motor 126 and a scanner motor driver 125 of another embodiment according to the present invention, in which a dpi switching circuit 236 is used as a scanner driver. It is built in the IC. Since the basic operation is substantially the same as the above description, it will be omitted.

Also in the other embodiments, the resistors 222a, 222a
Although only 22b are described as 22b, as in the previous embodiment, it is possible to increase the number of terminals of IC0 and switch by connecting a plurality of terminals for all image density switching modes.
Further, the image density switching signal (C signal) can be detected and switched from the frequency signal (B signal) corresponding to the image density, which leads to a reduction in the number of IC terminals.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can also be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0040]

As described above, according to the present invention, both the rise time and the consumption current can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a scanner motor driver circuit of the present embodiment.

FIG. 4 is a diagram showing a configuration of a scanner motor driver circuit used in another embodiment according to the present invention.

[Explanation of symbols]

 101 Noise Filter 102 Power Supply SW 103 Fusage Control Unit 104 Low Voltage Power Supply 105 Paper Presence Sensor 106 Door Switch 107 Pickup Solenoid 108 Fixing Heater 109 Thermistor 110 Paper Feed Sensor 111 Cartridge Sensor 112 Paper Ejection Sensor 113 Fan Motor 114 Fan Motor Driver 115 Photosensitive Element 115a Beam detection signal generation 116 Toner cartridge 117 High-voltage control circuit 118 DC controller 118a CPU 118b ROM 118c ROM 118d Video I / F circuit 119 VIDEO I / F 120 Video controller 120a CPU 120b RAM 120c ROM 120d Buffer 120e Video I / F circuit 121 Host I / F circuit 122 Operation panel 123 Laser driver 1 24 Laser Element 125 Scanner Driver 126 Scanner Motor 127 Main Motor Driver 128 Main Motor 130 Engine Section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaharu Tsukada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (3)

[Claims] 1. An image printing means for recording image information on a recording medium using an electrophotographic process, a conveying means for conveying the recording medium for recording the image information on the recording medium, and a plurality of conveying means without changing the conveying speed. An image forming apparatus having a printing unit capable of printing at a printing density of 1., comprising a switching unit for switching a motor current detection resistance for acceleration control of the scanner motor rotation driving unit according to the printing density. 2. The image forming apparatus according to claim 1, wherein the switching means is formed in the scanner motor rotation driving means. 3. The image forming apparatus according to claim 1, wherein the switching means has a small resistance during high density printing and a resistance during low density printing.