JPS6060635A - Image forming device - Google Patents

Abstract

PURPOSE:To eliminate the need to replace a motor even when a frequency is varied by rectifying electric power from an AC power source directly without passing it through a transformer, and driving a platen by a DC brushless motor according to the rectified DC voltage. CONSTITUTION:A reference clock is outputted from a microprocessor 154 and supplied to a phase comparator 111. Consequently, a switching circuit 100 is controlled with the signal corresponding to the phase difference between the reference clock from a PLL circuit 110 and a rotation detection signal to apply a specific voltage to a motor driving circuit 71. A motor driving circuit 71, therefore, drives, the DC brushless motor 35 at the speed corresponding to the supplied voltage value. Consequently, even when the frequency is varied, the need to replace the motor is eliminated, the weight per output is reduced, and the size and weight of the motor are reduced; and the space is utilized efficiently, the efficiency of the motor is improved, and the heating value is reduced, thereby forming an excellent image without any cooling device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image forming apparatus such as a copying machine with a movable document table.

[Technical background of the invention and its problems]

Conventional copying machines use induction or synchronous AC motors. For this reason, the efficiency was poor, heat was generated, and a cooling means was required. Furthermore, when the frequency was switched between 50 Hz and 60 Hz when used in Japan, the AC motor had to be replaced. Furthermore, the weight and size of the AC motor are large per output, making the device heavy and large.

[Purpose of the invention]

This invention was made in view of the above circumstances, and its purpose is to eliminate the need to replace the motor even if the frequency is changed, to reduce the weight of the output unit, to make the motor compact, and to reduce the weight of the output unit.
It is an object of the present invention to provide an image forming apparatus that is lightweight, can use space efficiently, has a highly efficient motor, generates little heat, and does not require a cooling device.

[Summary of the invention]

This invention directly rectifies a commercial AC power source without passing it through a transformer, and operates a DC brushless motor that drives a document table or the like in accordance with the rectified DC voltage.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

1 to 3 show the external appearance of an electronic copying machine according to the present invention, in which 1 is a main body of the copying machine with a built-in copying mechanism, and 2 is a paper feed cassette attached to the right side of the main body 1 of the copying machine. , 3 is a paper discharge tray attached to the left side of the copying machine main body 1. Further, on the top surface of the copying machine main body 1, there is provided a document table 4 that can freely move back and forth in the left-right direction (direction of arrow a), and on the front edge of the top surface of the copying machine main body 1, a display 5 and a numeric keypad 6 are provided. ..., an exposure setting volume 7, a print key 8, etc., and an operation panel 10 on which input keys 9, etc. are arranged.

As shown in FIG. 2, the document table 4 has a structure including a document placing plate (glass plate) 12 on which a document 1 is placed and a document cover 13 covering the upper surface thereof.

Further, the cassette cover 14 of the paper feed cassette 2 has a third
As shown in the figure, there is a manual paper feed tray 15 for manually feeding paper p as appropriate. In addition, 16 shown in Figure 2
is the power switch.

Next, the internal mechanism of the electronic copying machine will be explained with reference to FIG. In the figure, reference numeral 20 denotes a drum-shaped photoreceptor disposed approximately in the center of the copying machine main body 1, and the photoreceptor 20 is driven in the direction of the arrow in synchronization with the document table 4 by a drive mechanism (not shown). First, a document image uniformly charged by a charger 21 and uniformly irradiated by an exposure rung 22 is imaged onto a photoreceptor 20 by a focusing light transmitter (trade name SELFOC lens array) 23. It is designed to form an electrostatic latent image. The formed electrostatic latent image is transferred to D by the developing device 24.
The toner image is sent to the transfer charger 25 side.

A sheet P or P' that is automatically or manually fed is fed by a sheet feeding device 26, and a toner image previously formed on a photoreceptor 20 is transferred onto the sheet P or P' by a transfer charger 25.

Furthermore, the toner image is peeled off from the photoreceptor 20 by a peeling charge 27 caused by AC corona discharge, passes through a conveyance path 28, is fused and fixed onto the paper p (p') by a fixing device 29, and is then transferred to a discharge roller 230. The paper is discharged onto a removable tray 3.

On the other hand, residual toner remaining on the photoconductor 20 after transferring the toner image onto the paper P (P') is cleaned by the cleaning device 3, and the electric potential on the photoconductor 20 is lowered to a certain level by the static eliminating lamp 32. The next saw is ready for operation.

Further, a fan 33 serves as a cooling device, and exhausts heat generated by the heat generating part exposure lamp 22 and the fixing device 29 inside the machine.

Inside the copying machine main body 1, an upper frame and a lower frame (not shown) are pivotally supported at one end via a support shaft 37, and the other ends of both frames are configured to be opened at a desired angle, for example, 30°. ing. The upper frame includes a charger 21, a focusing light transmitter 23, an exposure run f22, a developing device 24, a cleaning device 3, and the like around the photoreceptor 20.
Each device such as a static elimination lamp 32 is attached to the upper unit by appropriate means, and a fan 33 as a cooling device, a paper feed roller 38 of a paper feed device 26, and a document table 4 are also attached to the above frame. It consists of The frame includes a paper feed cassette 2, a transfer charger 25, a peeling charger 26, a conveyance path 28, a forming guide plate 39, a fixing device 29, a pair of ejection rollers, a 30° tray 3, and other mechanisms, as well as a main motor (DC brushless motor) 35, power supply section 34
etc. are attached by appropriate means to the lower unit IB.
It consists of After the front cover 1a of the copying machine main body 1 is rotated and removed, it can be opened and closed approximately along the transport path 28 of the paper p (p') via a housing opening/closing device (not shown). Therefore, even if the paper p (p') becomes jammed on the conveyance path 28, it can be easily ejected.

In addition, 50.50 in FIG. 4 is an operation for correcting the inclination of the leading edge of the paper P that is automatically fed from the paper feed cassette 2 or the paper P' that is manually fed, and also for forming a toner image on the photoreceptor 20. There are two pairs of registration rollers that feed the paper P or P' toward the transfer charger 25 in synchronization with the timing, and 51 is a manual feed detection switch disposed just before the pair of registration rollers 50 and 50.

52 is a paper discharge switch, 53 is a total counter, 54 is an E24-encity switch that detects when the paper P in the paper feed cassette 2 is empty, and 55 is a developing device 2.
4, a doctor regulating the thickness of the developer layer; 56, a toner hopper; 57, a toner-out detection switch; 58, a toner concentration detector; 59, a lid for the Hori iR-; It is not supposed to move.

Further, 60 is a high voltage transformer, 61 is a static eliminating brush, 62 is a handle formed for opening and closing the upper unit A, 63 is a reflector surrounding the back of the exposure lamp 22, and 64 is an auxiliary reflector.

Further, 65 is a weight for bringing a cleaning blade 66 of the cleaning device into contact with the photoreceptor 20 at a constant pressure, and a solenoid (not shown) causes the blade to move towards and away from the photoreceptor.

Note that the reflector 63, the auxiliary reflector 64, and the convergent light transmission body 23 are assembled as one unit.

Further, the paper feed device 26 provided at the lower right side of the copying machine main body 1 includes a paper feed cassette 2 and a cassette that covers the upper surface side of the paper feed cassette 2 leaving an opening for taking out paper provided with a separating claw. A manual paper feed tray 15 formed on the cover, and a paper feed roller 3 that takes out and supplies paper P from the paper feed cassette 2.
8.

5 and 6 show the structure of the motor 35. FIG. That is, 81 is a casing, and an annular rotor 82 is provided within this casing 81, and a rotating shaft 83 of this rotor 82 is rotatably supported by the casing 81 via a bearing (not shown). ing. The rotor 82 has permanent magnets 8 magnetized into eight poles in the circumferential direction.
4 is included. A stator 85 having 12 slots is disposed inside the rotor 82, and the rotor 82 rotates around the stator 85. The windings 86 wound around the stator 85 are arranged in four poles and three phases (U, V, W) as shown in FIG. One end is connected inside, forming a so-called star connection as shown in FIG.

The above windings 86U, 86V, 86W are star connected, so
It is excited by a combination of two phases each, and there are six shapes in that combination, and the appearance of the poles in each case is shown in Figure 8 (
As shown in a) to (f), they are shifted by one slot. Now, in FIG. 8, if the excitation is performed in the order of (a) to (f), the rotor 83 will rotate clockwise by one slot due to the action of the magnetic field from the winding 86 and the magnetic field from the permanent magnet 84. However, in the -strokes (a) to (f), it rotates 90 degrees. However, if we excite in the reverse order of (f) to (,),
The direction of rotation is opposite to the above case.

On the other hand, in positions close to the stator 850 and the rotor 83, three Hall elements 8 are placed at intervals of one slot.
7U, 87V, and 87W are installed. Here, each Hall element 87U, 87V when the rotor 83 is rotated clockwise.

The output voltage (Hall voltage) of 87W becomes an AC voltage whose phase is shifted by IA period as shown in FIG. Therefore, when the rotor 83 rotates once, each Hall voltage changes four times. In other words, one period of the Hall voltage is the rotor 83
This corresponds to a rotation angle of 90 degrees. Therefore, the rotor 83 can be rotated by switching the excitation direction of the windings 86U, 86V, and 86W according to each Hall voltage. For example, when rotating clockwise, the Hall element 8
7H Hall voltage is negative (-), Hall element 87V
If the Hall voltage of the Hall element 87W is zero (0) and the Hall voltage of the Hall element 87W is glass (+), the rotor 83 is
It will be in the position shown in Figure (f). Here, when the excitation phase is switched in the U-+W direction, the rotor 83 rotates 15 degrees clockwise and attempts to settle into the position shown in FIG. 8(,). However, when the rotor 83 reaches this position,
Hall voltage of Hall element 87U is zero, Hall element 87
The Hall voltage of V changes to negative, the Hall voltage of Hall element 87W changes to positive, and the excitation phase changes accordingly to U −+
Switching to the V direction, the rotor 83 is further rotated 15 degrees, and the 8th
It works to rotate it to the position shown in Figure (b). In this way, the rotor 83 continues to rotate clockwise by sequentially switching the excitation phase according to each Hall voltage, and the switching of the excitation phase is performed by the motor drive circuit 71, which will be described next. be exposed.

FIGS. 10 and 11 are block diagrams of the copying machine of the present invention. 58,150,52,51゜54.151.1
52 is various switches, and various data are sent from these switches to the microprocessor 154 via a data selector 153. 58 is a sensor for detecting the concentration of toner in the developing unit; 150 is a switch for detecting that the toner collection bag is full of toner collected by the cleaning device; 52 is a switch for discharging the paper out of the conveyance path 51 is a switch for checking whether the manual feed paper P'
54 is a switch that detects that the paper P in the cassette is gone. 151 is a switch that detects the position of the original platen. 152 is a switch of the copying machine. This is a switch that sets the operating mode.

Reference numeral 9 denotes an input key, which consists of a cylinder switch for starting the copying operation, a numeric keypad for setting the number of copies, a clear/stop key for correcting the manual input of the numeric keypad or stopping the copying operation, and a zolium exposure adjustment key. Input data from input key 9 is input to microprocessor 154 via data selector 153. At the same time, a key manual scan signal is input from the microprocessor 154 to the input key 9. A reset circuit 155 outputs a reset signal and a clock signal to the microprocessor 154.

Furthermore, from the microprocessor 154, driver 1
A signal for displaying necessary information on the display 5 is outputted via the display 56, and at the same time, a scan signal for dynamic lighting is outputted to the display 5.

On the other hand, from the microprocessor 154, the driver 157
Various control signals are transmitted to the heater control circuit 158 via the
Lamp control circuit 159, driver 1601 high voltage power supply 16
1.162, Document platen clutch 163, Paper feed roller solenoid 120, Registration roller solenoid 124, Toner replenishment solenoid 164, Cleaner platen Lenoid 6
5 and counter 53.

The heater control circuit 158 controls the fixing heater 1 of the fixing device 29.
The power supply to 65 is controlled to maintain the temperature at a fixing temperature. Lamp control circuit 159 controls energization of exposure lamp 22 . The driver 160 controls the on/off operation of the main motor 35 and the static elimination runno 32. The high voltage power supply 161 supplies necessary voltages to the transfer charger 25, peeling charger 27, and development bias circuit 166 in accordance with the control signal. High voltage power supply 161 supplies high voltage to charger 21 . The document table clutch 163 selectively transmits the driving force for reciprocating the document table. Paper feed roller solenoid 1
20. The registration roller solenoid 124 operates or stops the spring clutch between the drive source and each roller in order to stop the rotation of the paper feed roller and the registration roller. The toner replenishment solenoid 164 is operated when the toner concentration detector 58 detects that the toner concentration is below a specified value, and replenishes toner from the toner source into the developing device.

The cleaner blade lens 172 presses the cleaning blade against the photoreceptor and separates it from the photoreceptor. The counter 53 counts the number of copies. Further, the fan 33 cools the inside of the copying machine.

Note that a signal indicating the temperature of the fixing heater 165 is sent from the heater control circuit 158 to the microprocessor 154 via the data selector 153.

Still, 104 is a main power source (AC power source), which is connected to a DC power source 171 etc. via a switch 16. In addition, the first
In the block diagram in Figure 0, "→" indicates the flow of signals, "1" indicates the flow of AC voltage supply, and "
-'' indicates the flow of DC voltage supply, and r匡pJ indicates the flow of high voltage supply.

The main power source 104 is still rectified by the rectifier circuit 103. This rectifier circuit 103 is composed of, for example, a bridge circuit of diodes 105, 106, 107, and 108, and a smoothing capacitor 109. The DC voltage of the rectifier circuit 103 is applied to the motor drive circuit 71 (described in detail later) via the switching circuit 102. The switching circuit 102 is composed of, for example, a transistor 100 and a diode 101, and by turning the transistor 100 on and off in accordance with the output from a PLL circuit 11θ, which will be described later, the output of the rectifier circuit 103 is turned on and off. It outputs according to the duty ratio. The above PLL (phase
The locked loop) circuit 110 is a rotation detection circuit (described in detail later) 7 that detects the rotation of the main motor 35.
The rotation detection signal from 0 and the microprocessor 154
It outputs a signal corresponding to the phase difference with the reference clock according to the speed from the clock, and is composed of a phase comparator 111, a triangular wave generating circuit 112, and a comparator 113. For example, if the phase difference between the base wall clock and the rotation detection signal is large, the output voltage of the phase comparator 111 becomes large, the output of the comparator 113 has a large proportion of "L# level", and the on-time of the transistor 102 increases. increases, and the effective value of the voltage supplied to the motor drive circuit 71 increases.In this way, the outputs of the reference clock and the rotation detection signal are balanced at a certain phase difference, and at this time, the frequency of the reference clock and the rotation detection signal are balanced. The signal frequencies match.

Note that in a platform where the speed of the main motor 35 is constant, the reference clock may be generated not by the microprocessor 154 but by another oscillator.

FIG. 12 shows the rotation detection circuit 70 and motor drive circuit 71. First, in the motor drive circuit 71, the Hall elements 87U, 87V, 87W
The respective output signals are sent to comparators 88U and 81j, respectively.
V and 88W, and their waveforms are shaped. The outputs of the connographs 88U, 88V, and 88W are supplied to a rotational direction VJ switching circuit 89, respectively. This rotation direction switching circuit 89 is connected to the microprocessor 1.
The rotation direction of the rotor 83 can be determined using 54 rotation direction signals! For example, there are three exclusions.
When the rotation direction signal is at the "°1" level, the comparator 8B11, 88V, 88W (D output is inverted and sent to the current switching circuit 90. This current switching circuit 9θ is connected to the rotation direction switching circuit 89. Each output 89U, 89V
, 89W, excitation phase switching signals U, l U, l
It outputs V, l VLI W, , W, respectively, and its truth table is as shown below.

Therefore, the outputs UH and V□ of the current switching circuit 90.

WH is an NPN type transistor 91U.

Powered by 91V, 91W pace. This toe-y7s
) Su 191U, 91V, 91”wV (7) Each emmi.

The terminals are connected to the collectors of NPN transistors 92, and the emitters of transistors 92 are grounded. A rotation control signal from the microprocessor 154 is supplied to the pace of the transistor 92. In addition, the above transistors 91U, 91V, 91W (
7) Each collector is a PNP type transistor 93
U.

Connected to 93V, 93W pace. - Outputs UL, V, and WL of the current switching circuit 90 are NPN transistors 94U, 94V, and 94W, respectively.
supplied to the base of Then, the transistor 93
The collectors U and 94U are commonly connected, and the connection point thereof is connected to the other end of the winding 86U of the motor 35. Further, the collectors of the transistors 93V and 94V are connected in common, and the connection point is connected to the winding 86 of the motor 35.
Connected to the other end of V. Still, the above transistor 93W
.

The respective collectors of 94"vV are connected in common, and the connection point thereof is connected to the other end of the winding 886W of the motor 35. Note that the transistor 93U.

The emitters of 93V and 93W are respectively connected to a DC power supply VC, and the transistor 94U.

The emitters of 94V and 94W are each grounded.

In such a configuration, the rotation control signal is
When the voltage reaches the + level, the transistor 92 turns on, and as a result, the transistor 91U and 91V.

91W are also turned on, and the output UH of the current switching circuit 90
, VH, WH are transistors 93'TJ, 93V.

Tell each to 93W. On the other hand, the rotation control signal is +to
``When it reaches level, transistor 91U.

91V, 91W, and 92 are cutoffs, respectively, so that transistors 93U and 93V are connected.

93W is also the cutoff. For example, if the Hall voltages of the Hall elements 87U, 87V, and 87W are negative, zero, and f-plus, respectively, if the rotational direction signal is at the level 0''0'', the rotational direction switching circuit 89 outputs 89U.

89V, 89W are I Q #, 'Q II, I
As a result, from the truth table, the output of the current switching circuit 90 has UH and WL at the "1" level, and the others at the "0" level. Therefore, if the rotation control signal is at the °′1” level, the trunk
3U and 94W are each turned on, and the current flows from transistor 931J → winding 86U → winding 86W → transistor 9
It flows as 4W. This corresponds to FIG. 8(,).

Next, in the rotation detection circuit 70, the AND circuit 95U receives the outputs of the converters 88U and 88V, and the AND circuit 95V receives the outputs of the converters 88U and 88V. The outputs of the converters 88U and 88W are connected to the AND circuit 95W, and the outputs of the converters 88V and 88W are
Each output is supplied respectively. The AND circuits 95U, 95V, 95W (D outputs are respectively supplied to an OR circuit 96, and a rotation detection signal (/'P pulse) is obtained from the output of the OR circuit 96.
A timing chart of this rotation detection circuit 70 is shown in FIG.

Next, the operation in such a configuration will be explained. For example, when the number of copies is entered using the numeric keypad 6, the set number of copies is displayed on the display 5. When the print key 8 is further operated, a copying operation is started.

First, the microprocessor 154 operates the cleaner blade solenoid 172 via the driver 157 to press the cleaning blade against the photoreceptor.
The static elimination run fsz is operated via the transfer charger 26.60, and the high voltage power supply 161 is operated. Voltages are applied to the peel & [t charger 27, respectively. At this time, a reference clock is output from the microprocessor 154 and supplied to the phase comparator 111.

Then, the switching circuit 100 is controlled by a signal corresponding to the phase difference between the reference clock and the rotation detection signal from the PLL circuit 110, and a predetermined DC voltage is applied to the motor drive circuit 7.
) is applied to Accordingly, the motor drive circuit 71 drives the DC brushless motor 3 at a speed according to the supplied voltage value.
Drive 5.

Next, data from the document table switch 151 is read through the data selector 153, and the microprocessor 154 checks whether the document table 4 is at the start position. When the document table 4 is not at the start position, the document table clutch 163 is operated to move the document table 4 back and return it to the start position. Next, the paper feed roller solenoid 12
0 is operated to rotate the paper feed 4-ra a predetermined amount to feed the paper P from the paper feed cassette, and at the same time, the exposure lamp 22 is turned on.

Next, the document table 4 is moved forward to start exposure, and
High voltage power supply 161 is operated to apply voltage to charger 21 . The document table 4 continues to move forward, and the document table switch 16
When it is detected that the document table 4 is at the paper start position based on the signal from the microprocessor 154
operates the registration roller renoid 124 via the driver 157 to rotate the registration roller 50;
Feed the paper P to the transfer section.

Next, when it is detected that the document table 4 is at the limit position based on the signal from the document table switch 163, the microprocessor 154 controls the power supply 162 to stop the operation of the charter 21 and operate the document table clutch 163. At the same time, the lamp control circuit 15
9 to turn off the exposure lamp 22.

Then, based on the signal from the document table switch 151, the microprocessor 154 detects that the document table 4 is in the home position. Furthermore, it is determined whether the number of copies is equal to the set number of copies, and if the set number of copies has not been completed, the above-mentioned operation is repeated.

When copying is completed, the document table 4 is stopped at the home position. Next, when the sheet passing signal from the manual feed switch 51 is input via the data selector 153, the microprocessor 154 turns on the high voltage power supply 16.
1 to stop the operation of the transfer charger 25.

Furthermore, when the paper ejection signal from the paper ejection switch 52 is input, the microprocessor 154 considers that paper ejection is complete, and
Controls the high voltage power supply 161, dry/J160 and motor drive circuit 71, peeling charger 27, static elimination lamp 32
After stopping the operation of the main motor 35, the cleaner blade solenoid 172 (not shown) is controlled to separate the blade from the drum and end the copying operation.

〔Effect of the invention〕

As detailed above, according to the present invention, there is no need to replace the motor even if the frequency is changed, the weight of the output unit is small, the motor is small and lightweight, space can be used efficiently, and the motor High efficiency, low heat generation,
It is possible to provide an image quality forming device that does not require the use of a cooling device.

[Brief explanation of drawings]

The drawings show one embodiment of the invention, and FIGS. 1 to 3 are external views of an electronic copying machine, FIG. 4 is a sectional view showing the structure of the electronic copying machine, and FIG. 5 is a DC brushless motor. 6 is a plan view showing the structure of the rotor and stator of the motor, FIG. 7 is a diagram showing the connection state of the windings of the motor, and FIG. 8 is a plan view showing the structure of the rotor and stator of the motor. A diagram showing the relationship between the rotor and stator to explain the operation, Figure 9 is a waveform diagram showing the Hall voltage of the Hall element, Figures 10 and 1.
1 is a block diagram showing the overall configuration, FIG. 12 is a configuration diagram of a rotation detection circuit and a motor drive circuit, and FIG. 13 is a timing chart for explaining the operation of the rotation detection circuit. 4... Original table, 11... Original, 35... Main motor (DC brushless motor), 70... Rotation detection circuit, 71... Motor drive circuit, 100... Switching circuit, 104... ... AC power supply, 103 ... rectifier circuit, 110 ... PLL circuit.

Claims (1)

[Claims] In an image forming apparatus that scans information on a document by moving the document table on which the document is placed, there is a DC brushless motor that drives the document table, a rectifier circuit that directly rectifies commercial AC power, and this rectifier. An image forming apparatus comprising: a driving means for driving the DC brushless morph according to an output of a circuit.