JPS58126553A - Copying device - Google Patents

Abstract

PURPOSE:To obtain copied picture images having less photographic fogs and good contrast in the stage of automatic exposure and to copy the contents of an original faithfully in the stage of manual exposure by providing control means which control gamma characteristics (original density-coopying density characteristics) selectively in a manual exposure mode and an automatic exposure mode. CONSTITUTION:An exposure operating system consists of a variable resistor 76 and an exposure mode selecting switch 77 relating to gamma characteristics and selects the gamma characteristics according to exposure modes. In the case of an automatic exposure mode, the 2nd contact 772 of an exposure mode selecting switch 77 is closed to an NC contact side, by which always specified optimum exposure set with the variable resistor 76 of a manual reference voltage generating circuit 185 is obtained. On the other hand, in case of an automatic exposure mode, the 2nd contact 172 of the switch 77 is closed to an NO contact side, and an exposure lamp 3 is controlled by the output voltage of an automatic reference voltage generating circuit 186. Thus, always the optimum exposure is obtained automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a copying apparatus which has a manual exposure mode and an automatic exposure mode and which performs development processing using a -component developer.

(Technical background of the invention and its problems) Generally known electronic copying devices, most of which use two-component developers consisting of toner and carrier, are used for development processing. Developers and materials that perform development using high-resistance magnetic toner have been developed and are being put into practical use. However, something like this-
An electronic copying apparatus that uses a high-resistance magnetic toner as a developer and has a manual exposure mode in which an optimum exposure amount is manually provided and an automatic exposure mode P in which an optimum exposure amount is automatically provided has the following problems.

That is, during automatic exposure, since the exposure amount is controlled using a value that integrates the density of the entire document, its main application is so-called line-to-document. i.e. normal characters,
This is a large manuscript that mainly contains numbers, etc., and the background density of the manuscript changes (newspaper, paper manuscript, paperback manuscript, etc.), so the copy density of the background must be kept low. Ideally, the contents of the original should be printed at a high copy density so that a copy image with no fog and good contrast can be obtained, but this has been difficult. On the other hand, documents that must be manually exposed include documents with a small density ratio between the document background and the document content (so-called diazo copy documents, low-density color documents such as spine, green, yellow, etc.), ', and originals with a wide density distribution (photographs, multicolor originals, etc.). but,
For such thin manuscripts, tonality is particularly problematic, and it is difficult to faithfully copy the contents of the manuscript.

(Objective of the Invention) The present invention has been made in view of the above circumstances, and its purpose is to obtain a copy image with very little capri and very good contrast during automatic exposure, and to obtain a copy image with very high contrast when using 11F and manual exposure. It is an object of the present invention to provide a copying apparatus capable of faithfully copying contents, having little fading or density unevenness in the copied image, and obtaining a copied image with good gradation.

(Summary of the invention) The present BA has a manual exposure mode and an automatic fog light mode,
- In a copying apparatus that performs development processing using a component developer, it is not necessary to provide an r-characteristic control means for switching and controlling the r-characteristic (original density-copy chain characteristic) between the manual exposure mode and the automatic exposure mode. It is something. This rI! ! #Gravity Control Hand Film Control Means To put it concretely, switching control is performed to reduce the rate of change in r4I characteristics during manual exposure mode, and to increase the rate of change in Lr characteristics during automatic exposure mode. It is something to do.

(Embodiment of the Invention) Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an electronic copying apparatus according to the present invention.

In the figure, reference numeral 1 denotes a main body of a copying apparatus, and a manuscript table 2 is provided on the upper part of the main body 1 so as to be able to reciprocate in the direction of arrow a. Although not shown, the document table 2 is provided with a document holding cover. When the document table 2 moves forward, the document is illuminated by the exposure rung 3 provided at a predetermined position below, and the reflected light is guided onto the photoreceptor drum 5 via the convergent light transmitter 4. Then, the image of the original is imaged (exposed) on the surface of the photosensitive drum 5. The photosensitive drum 5 rotates in the direction indicated by the arrow. First, the surface is charged by a charger 6, and then the image of the original is exposed to light to form an electrostatic latent image. A one-component high-resistance magnetic toner is applied to the toner by the imager 2 to make it visible, and the toner passes through a static eliminator 8 for neutralizing the toner.

Sixth, a part of the reflected light from the original is guided by a light condenser 9 to a photodetecting element (for example, a photodiode) 10,
It is converted into an electrical signal. The output signal of this photodetector element 10 is used for automatic exposure control, which will be described later.

On the other hand, the paper P is fed from the paper cassette 11 (El-')
12, and is sent to the transfer section by an aligning roller 14 via a guide path 1B, where it is removed from the surface of the photoreceptor drum 5 in close contact with the photoreceptor drum 5. The toner image is transferred. The paper P after the transfer is peeled off from the surface of the photosensitive drum 5 by the action of the peeling charger 16, and transferred to the heat roller 21 as a fixing device by the conveyance path 12.
8, the transfer portion is fixed at ζ, and then the paper is discharged to the paper discharge tray 2° by the paper discharge roller 19. After the transfer, the photosensitive drum 5 is neutralized by a static eliminator 2, residual toner on the surface is removed by a cleaner device 22, and finally the image of the electrostatic latent image is erased by a static eliminator 23. It is set to return to the initial state.

Note that 2B is a manual feed guide body that manually feeds the paper;
Reference numeral 5 denotes a feeding roller that feeds the paper fed from the manual feed guide body 24, and 26 a guide path that guides the paper fed by the feeding roller 25 to the aligning row 514.

27 is a cooling fan that cools the heat roller 18 and the like;
29 is an electromagnetic clutch that controls the reciprocation of the original gantry 2. FIG. 2 shows the document table 2 and its drive mechanism in detail. That is, the document table 2 is made of reinforced transparent glass, and its -
The side edge (rear side in the drawing) is a slide rail 32 formed by bending the upper part of one frame s1 into a U-shape.
It is slidably fitted inside. 1+, the other side edge (front side in the drawing) of the document table 2 includes a support rail 35, a guide rail 36, and a support member provided on the upper folded portion 34 of the other frame 33. 7.37. That is, the support rail J6 is connected to the frame 33.
It is a U-shaped member fixed on a bent part 34, and has a sliding smooth member 38 in its recess, and an inverted U-shaped guide rail 36 is slidably fitted above it. ing. A U-shaped support member S1°3 is attached to the side of the guide rail S6.
7 is fitted, and the side edges of the document table 20 are fitted into the recesses of the support members 31 and 37. Further, a document table drive mechanism 39 is provided on the 7th frame S3 side. This drive mechanism 19 includes the motor 28 and the electromagnetic clutch 2 to which the rotation of the motor 21 is transmitted via a timing belt.
g, a gooley 40 fixed to the rotating shaft of the electromagnetic clutch 29 and located on the front page side of the frame 33, and a frame S3.
The gooley 41 located on the front side of the document table 2 near the bottom, and these! - 40.41VC wound once,
One end is fixed to the support member 37 on the right side of the figure, and the other end is fixed to the support member srK on the left side of the figure through a coil strip ring 42.The motor 28 rotates forward or backward. Electromagnetic clutch 2 for
j, and the document table 2 moves in the direction of arrow a (horizontal direction in the figure).
It is designed to move back and forth.

Next, a position detection mechanism for detecting the moving position of the document table 2 will be explained with reference to FIGS. 2 and 3. As shown in FIG. 2, a magnet 44 is provided at a predetermined position on the back surface of the document table 2 (in the figure, the middle position is also a position on the right side), and a magnet 44 is provided at the top of the main body 1 near the back surface of the document table 2. Three reed switches 45, 46 and 47 are provided at predetermined intervals, and these constitute a position detector. Note that each output signal line of the reed switch 45, 46, 41 is sent to a control system, which will be described later, and is used as a control signal for the document table drive mechanism 39 or the paper feeding mechanism for paper P, etc. Here, an example of the positional relationship between the magnet 44 and the reed switches 45, 46, 41 will be described.
For example, as shown in FIG.
The distance between the reed switch 44 at the right end of the box and the reed switch 46 at the middle part should be set to the maximum size (for example, B5 size), so that the longitudinal length of the document (3t or B4 size) is slightly longer. The length of the document in the longitudinal direction is also slightly longer, and when the main body 1 and the document table 2 are aligned (stop position f), the magnet 44 is moved slightly to the right of the position of the Y-do switch 46. It is set to maintain a biased distance in the direction.

The reed switch 46 at the right end is a movement start position detection switch (hereinafter referred to as table start switch).
The reed switch 46 in the middle part is a stop position detection switch (
The reed switch 47 on the left end is used as a movement limit position detection switch (hereinafter referred to as a table home switch), and the reed switch 47 is used as a movement limit position detection switch (hereinafter referred to as a table!Jjy switch). It has become. Although not shown, a reed switch for starting the Eno motherboard is provided at a predetermined position between the switches 45 and 46.

A switch (referred to as a lower start switch) is provided.

FIG. 4 shows the developing device r using one-component high-resistance magnetic toner.
This shows the configuration of In the case, 51 is a main body frame, which includes a first casing 52 and a second casing 5.
3 are arranged facing each other, and seven side frames s4. ss (only the frame 54 is shown), a toner supply opening 56 for supplying toner is formed in the upper part thereof, and a developing opening 57 is formed in the lower left side. has been done. Inside the main body frame 51 configured in this way, there are a toner storage section 58, a developing roller storage section 59, a toner temporary storage section 60, and a toner receiving section 61.
are formed respectively. Note that a doctor blade 62 is integrally formed at a corner portion of the first casing 52. The doctor blade 62 is for making uniform the amount of magnetic toner conveyed by a developing row yesIfc, which will be described later. Further, a developing roller 63 is housed in the developing roller housing section 59 . This current 26 droplets is made of a non-magnetic material such as aluminum or stainless steel, and has a nine cylindrical rotating body (
(hereinafter referred to as a sleeve) 64, and a nine magnet (A-266) provided within this sleeve 64. Both the sleeve 64, the magnet, and the magnet (O-265) are connected to the side 7 through a bearing (not shown). The sill is rotatably supported on the frame 54955 so that it can rotate freely.

Next, a method of applying a bias voltage to the developing device r configured as described above, conveyance of magnetic toner, etc. will be explained with reference to FIG. As shown in the figure, the madanet roller 65 is formed into a plurality of circular poles in which N poles and eight poles are alternately spaced at cape intervals. It is now possible to do so. The sleeve 64 of the developing roller 63 rotates in the direction of arrow C with respect to the photosensitive drum 5 rotating in the direction of arrow A, and the magnet row 265 rotates in the direction of arrow d in the opposite direction. E) A gear lug G is partially exposed from the developing opening 51 formed in the frame 51 of the main body 7, and a predetermined slight gear lug G is formed between the photoreceptor drum 5 and the outer peripheral surface of the sleeve 64. It will be done. This is K.
The magnetic toner stored in the toner storage section 58 is transferred to the sysleep 6 by receiving the magnetic force of the madanet roller 65.
The magnetic toner 66 is attracted to the outer circumferential surface of the sleeve 64 in the form of a soft 11 ridge standing upright, and the attracted magnetic toner 66 is conveyed in the direction of arrow C as the sleeve 64 rotates. This magnetic toner 66 is the gear.

fG, and is attracted to the electrostatic latent image formed on the surface of the photoreceptor drum 50 and developed.

In this embodiment, the gap 7#G between the tip of the doctor blade 62 and the sleeve 64 is about 0.35 wa diameter, and the gap fG between the photosensitive drum 5 and the sleeve 64 is about 0.40 wa. , the thickness of the magnetic toner 66 at the pole position after being made uniform by the doctor blade 62 are set to about 0.50 to 0.55 W, respectively. Finally, the gear between the photosensitive drum 5 and the sleeve 64.

At the position fG, the magnetic toner 66 is slightly in contact with the surface of the photosensitive drum 50. Furthermore, in FIG. 5, a power supply blade 61 is in sliding contact with the non-developing portion of the sleeve 64, and an AC bias voltage (approximately 800 Hz) from a development bias power supply circuit 68 is applied to this blade 61. . Note that the portion other than the developing roller 63, that is, the portion of the casing 52.153 is electrically insulated from the main body 7 frame 51 and the developing roller 63.

FIG. 6 shows an operating control, which is provided on the front upper surface of the main body 1. In the figure, 11 is Nononel's main body, and this main body 11! Lint key 12, clear strike for correcting setting data or performing strug operation, f key 73, numeric keypad 74 for setting the number of copies, etc., number display 15 for displaying the set number of copies or number of copies, in manual exposure mode. Sliding variable resistor 76 for adjusting exposure amount, fog light mode selection switch for selecting exposure mode, chia r1 operation status display section 78, ready (R)
j:ADY) display rung 19, and weight (WA
IT) Display knobs 7 and 80 are provided respectively.

The exposure mode selection switch yyII'i is used to select and set the exposure mode to manual (MANUAL) or automatic (AUTO).
When set to automatic, it is turned on. The status display section 78 also includes a paper jam display rung 188.
, cleaner cleaning display rung 78. , )ner replenishment display run frB, and paper replenishment display rung 784.

FIG. 7 schematically shows the control system, which mainly includes a group of various switches 81, a microprocessor 82 that performs overall control and various data processing, and controls each food based on signals and data from this microprocessor 82. A driver 83 that creates signals, an AC drive system 85 driven by a commercial AC power source 84, a DC drive system 86 driven by a DC power source, and a display system 8 that displays various statuses.
1.

Each of the switch groups 81 includes an exposure operation system 92 consisting of the print key 72, clear/stop key 13, variable resistor 76, and exposure mode selection switch 77;
Detects the end of paper feeding by the paper feed roller 212 - Δ end switch (P-0-5W), the feed roller 25
The sheet switch (SIl) that detects manual paper
[EET-SW), and an electronic switch (P-SW) that detects no paper in the paper feed cassette 11.
ENP-8W), etc., a key switch 94 that detects insertion of a key counter (not shown), and the table start switch (T-gTR-8W) 45
, table home switch (T-HOME-8W)
4 g, table limit switch, f (T-LIM
IT-8W) 47, paper start switch C
Document platen position detection system 9 consisting of P-8TR-8W), etc.
5. Toner 7 detecting whether the cleaning device 22 is full of recovered toner; 7. A, CH (T-FULL-8W
), a cleaner cleaning switch that detects the cleaning timing in the cleaning device 22, and a toner empty switch (r-mNP) that detects the absence of toner in the developing device r.
-8w), etc., and a paper ejection switch (EX
It is configured by a transport system 97 consisting of, for example, IT-8W. The signals from each of these switches, except for the exposure operation system 92, are input to the microprocessor 82 via the data selector 911-*fcVi buffer 99. A temperature control circuit 101 , an exposure control circuit 102 and an AC control circuit 103 to which power is supplied from an AC power source 84 , a fixing heater 104 controlled by the temperature control circuit 101 and provided on the heat roller 18 , and a fixing heater 104 provided on the heat roller 18 . It is composed of a thermistor 105 that detects temperature and inputs the detection signal to the temperature control circuit 101. The exposure control circuit 102 includes the photodetector element 10. The exposure rung 3 is controlled according to signals from a variable resistor 76 and an exposure mode selection switch 77. Further, the AC control circuit 103 controls on/off of the static eliminator 2-7#zs, the cooling 7-amp 21, the motor 28, and the like.

The DC drive system 86 includes a DC power supply circuit 111 that converts an AC voltage from an AC power supply 84 into a DC voltage (for example, a DC voltage of 24°C), a high-voltage transformer 112 to which power supply voltage is supplied from the power supply circuit 111, and a charging transformer 11J1. Original table drive circuit 114, solenoid drive circuit JJj, )-
It is composed of a tall counter 116 and the current bias power supply circuit 68. Note that the high voltage transformer 11
2 is the static eliminator 8, the transfer charger 15, and the peeling charger 1.
The charging transformer 113 drives the charger 6, and the document table driving circuit 114 drives and controls the electromagnetic clutch 29.

The solenoid drive circuit 116 also includes a paper start solenoid (
P-STR-SQL) 11B, a paper feed solenoid (p-F
EED-sot, ) J J #, sheet solenoid (8HEET-8) that controls the feeding roller 25
OL) J J O1 Cleaner solenoid (C-8OL) J J that controls the cleaning device 22
J, a fixing solenoid that controls the heat ruler 18 (
N-8OL) J x x etc. are driven and controlled as necessary.

The display system 81 includes a display driver 131 . which receives signals from the key operation system 91 . and microphone of processor 8
Latch driver 132 that temporarily latches data from 2
Consisted of. In addition, each of the above drivers IS1, 1
82 is the sheet number display 15, the operating state display section rti,
Ready display run f79 and wait display 2nde80
Control the lighting of each as necessary.

Next, in the above configuration, the overall operation is
This will be explained with reference to the flowcharts shown in FIGS. First, when the AC power supply 114 is turned on, the output in the microphone grosser 82 is set to one, the RAM (random access memory) area, etc. are cleared, and then "0" is displayed on the sheet number display 16 and a wait time is displayed. Display rung 80 is lit. Next, the status of the 1 cleaner cleaning switch is checked, and if it is on, an error (ERR) is displayed;
8. lights up, and if it is in the OFF state, a check is made to see if a predetermined time (approximately 44 seconds) has elapsed, and this process is repeated until that time elapses. The remaining paper will be forcibly ejected. Then, after a predetermined period of time has passed, the sensor 111B detects -)E! -') By checking the temperature of 1 g, the state becomes copyable state 11, and it is checked whether or not it is ready for copying. When the state becomes ready for copying, "1" is displayed on the number of sheets display 75. Next, the status of the 1 key switch 94, the toner full switch, and the paper engagement switch are checked in sequence, and when these switches are in the IFf state, the ready display rung r9 is turned off. If the switch is in good condition, ready display run f1
9 is lit.

Copy processing is possible in this state.

That is, after setting the number of copies using the numeric keypad 74, the copying operation is started by pressing the print key 12. That is, by pressing the print key 12, the ready-to-use indicator lamp 19 goes out, and the cleaner solenoid 1 turns off.
2 is turned on. After that, the motor 28 is driven after a predetermined time (about 0.1 seconds) has elapsed, and then, after a predetermined time (about 0.1 seconds) has elapsed, the fixing solenoid 1
22 and high voltage transformer 112 are turned on. Next, the state of the exposure mode selection switch 11 is checked,
If it is in the off state (manual exposure mode), the developing bias power supply circuit 68 is not turned on, and an alternating current bias voltage, which will be described later, is applied to the sleeve 64 of the developing device 7. On the other hand, if the exposure mode selection switch 21 is in the on state (automatic exposure mode), the sleeve 64 of the developing device 7 remains connected to the ground and potential (Ov) as described later. After a predetermined period of time (approximately 0.31 seconds) has elapsed, the process proceeds to a multiple copy continuous copying (MULT) flow as shown in FIG.

In the continuous copying of multiple sheets 7a-, first, it is checked whether the table start switch 45 is in the OFF state, and when it is in the OFF state, the original platen backward clutch of the electromagnetic clutch 29 is turned on, and the original platen 2 moves backward. Btlb. Then, after a predetermined period of time (approximately 0.1 seconds) has elapsed, the total kakunta 11g is turned on, and the number of nine sheets is subtracted by "1" from the set number of sheets on the nine sheet number display r5 for counting, and the nine sheet number is displayed. In this state, start the E/G.

If the table start switch 45 is in the on state, it is checked whether the table start switch 45 is in the on state or not, and if it is in the off state, after a predetermined period of time (approximately 0.4 seconds) has elapsed, it is checked again whether the table start switch 45 is in the on state. If the paper start switch is in the on state, it is checked again, and if it is in the off state, the paper start switch is checked again for a predetermined period of time (approximately 0.
An error message will be displayed after 75 seconds) have elapsed. On the other hand, if the table start switch 45 and the -e-pastart switch are in the on state, the vapor feed solenoid 119 will not be turned on after a predetermined period of time (approximately 0.1 seconds) and the paper feed roller 12 will not operate. Paper is fed from within the paper feed cassette 11. Then, a predetermined time (about 0.83 seconds)
When the time has elapsed, the page/4 feed solenoid 119 is turned off and paper feeding ends. After that, for a predetermined period of time (approximately 0.1
When the exposure ramp 'j is turned on], exposure is started. At this time, when the exposure mode selection switch 77 is off, exposure is performed with the exposure amount set by the variable resistor 16, and when it is on, the photodetection element 1o
Exposure at the optimum exposure amount for the original density detected by (
automatic exposure) is performed. Therefore, the predetermined time (approximately 0.1
1 second), turn the table start switch 45 again.
It is checked whether or not the switch is in the on state, and if it is in the off state, a step 2 - display is performed after a predetermined time (about 0.06 seconds) has elapsed. On the other hand, if the table start switch 45 is in the on state, the document table forward clutch of the electromagnetic clutch 2g is turned on after a predetermined time (approximately 0.05 seconds) and the document table 2 starts moving forward.

Thereafter, after a predetermined period of time (approximately 0.18 seconds) has elapsed, the charging transformer 113 is turned on and charging processing is performed. Next K
It is checked whether the s'- quantity start switch is in the on state, and if it is in the on state, the mother start solenoid 118 is turned on and the paper ejected by the paper feed 1: l-912 is checked. P is fed by the 7 lining rollers 14 and advances to 70- in FIG. On the other hand, if the (-)-start switch is in the off state, the predetermined time (approximately 0.73 seconds)
An error message will be displayed after the time has elapsed.

As described above, when the paper P is fed by the aligning roller 14 and the trailing edge of the paper P is detected by the vapor end switch, the charging transformer 113 is activated after a predetermined time (approximately 0.04 seconds) has elapsed. is turned off, the charging process ends.

On the other hand, if the trailing edge of the paper P is not detected, the document table 2 will continue to move forward), and eventually the magnet will move.

44 is a reed switch (table limit switch)
47 is turned on, so if it is determined that this limit switch 47 is turned on, the limit switch 47 is turned on for a predetermined period of time (
After approximately 0.7 seconds have elapsed, the 2-display will be displayed. Further, even if the limit switch 41 is in the OFF state, an error display is performed after a predetermined period of time (approximately 3 seconds) has elapsed.

When the charging process is completed as described above, it is checked whether the size of the original set on the original platen 2 is 85 or less, and if it is not less than B5 size, it is checked for a predetermined time (approximately 0.03 seconds). ), the document table forward clutch is turned off and the movement of the document table 2 is stopped. Thereafter, when a predetermined time (approximately 0.1 seconds) has elapsed, the document table back clutch is turned on and the document table 2 starts moving backward, and when a predetermined time (approximately 0.06 seconds) has elapsed, the exposure lamp 3 is turned on. It turns off. As the document table 2 continues to move backward, the magnet 44 eventually turns on the reed switch (table home switch) 46, so that when it is determined that the home switch 46 is turned on, is the first
Proceed to the flow shown in Figure 1. On the other hand, the home switch 4
6 is in the off state, an error display is performed after a predetermined period of time (approximately 0.48 seconds) has elapsed.

As described above, when it is determined that the table home switch 46 is in the on state, the state of the clear/stop key 73 is checked, and if it is in the off state, then it is checked whether or not the continuous copying mode is set. When the continuous copying mode is selected, the state of the key switch 94 is checked and cleared.
When it is on, the next step is PΔempty switch.

The state of the toner full switch is checked, and when it is on, the state of the toner full switch is checked, and when it is off, the process again proceeds to the continuous copying process of FIG. 9. However, if the clear/stop key 73 is on and the continuous copy mode is not on,
If the key switch 94 is off, the vapor engine switch is off, and the toner full switch is on, the process advances to the next step 70-, and the document platen reverse clutch and E/4 starton renoid 118 become O7. . At this stage, the number of copies is restored on the sheet number display 25, and then it is determined whether or not paper ejection has been completed by checking the state of the paper ejection switch. The time is about 1.
4 seconds), the high voltage transformer 112 and the developing bias power supply circuit 68 are turned off. After that, for a predetermined period of time (approximately 3.
07 seconds), the fixing solenoid P122 is turned off, and after a further predetermined time (approximately 0.7 seconds) the motor 28 is turned off], and after a further predetermined time (approximately 0.1 seconds), the cleaner solenoid 121 is turned off. is turned off, and this completes the series of copy processing operations.

The copying machine described above saves various data by interrupting the program at predetermined intervals while the program is being processed, in order to retain the program settings in the microprocessor 82. is configured to perform reconfiguration.

Next, with reference to FIG. 12, a brief description will be given of M filling in development using a one-component high-resistance magnetic toner according to the present invention. In FIG. 12, the magnetic toner (2) is transported in the direction of arrow C by the action of the rotating magnetic field of a magnet roller 66 with a plurality of poles that rotates in the direction of arrow d and the sleeve 64 that rotates in the direction of arrow C. be done. At this time, the magnetic toner (2) has a constant thickness due to the doctor blade 62. In addition, positive charges are stored in the photoconductor layer 51 of the photosensitive drum 51 in a state corresponding to the original, and a latent image (2) is formed.

Then, the conductive layer (aluminum #) 5 of the photoreceptor drum 5
b is grounded], and the sleeve 64 on the developing device r side is also grounded via a developing bias power supply circuit 68. When the positive charge stored in the photoconductor layer 5a reaches the development point X, the conductive layer 5b has a negative charge [F] of the opposite polarity corresponding to the positive charge. is induced. However, this negative charge [F] is applied to the surface of the sleeve 640 via the development bias power supply circuit 68, and development is performed by injecting the negative charge into the magnetic toner [F].

Here, regarding the principle of development at the development point X, the first
This will be explained in more detail with reference to FIGS. 3 to 15. 13 and 14 are simplified model diagrams of development, and FIG. 15 shows its equivalent circuit. 13 and 14, 66 is a magnet roller, 64 is a sleeve) 66 is a magnetic toner layer, Jm is a photoconductor layer, and 5b is a conductive layer. First, in FIG. 15, C2 represents the capacitance 1 of the photoconductor layer 51, C0 represents the equivalent capacitance of the single magnetic toner layer 66, and RT represents the equivalent resistance of the single magnetic toner layer 66.

As mentioned above, the positive charge Qo is accumulated and the latent image ■
FIG. 13 shows the state immediately before the charge approaches the magnetic toner layer 66 and the charge is transferred to the magnetic toner layer 66.

In FIG. 13, more positive charge Qo is stored in the photoconductor layer 6a, and the potential on its surface has a value of V. Generally, in the case of high-resistance magnetic toner, since the resistance value of the magnetic toner layer 66 is large, when the surface potential V of the photoconductor layer 6a is low, the magnetic toner layer 66
The time constant (the development time) also increases. Therefore, sufficient charge is not transferred to the magnetic toner layer 66, and sufficient charge is not induced at the tip of the magnetic toner layer 66. However, when the surface potential V is high, the magnetic toner layer 66
Since the equivalent resistance BT is small due to the electric field dependence of the resistance, a sufficient charge is induced at the tip of the magnetic toner dust 66. That is, as shown in FIG. 14, the developing current! , and the charge Q is transferred from the photoconductor layer 5a to the magnetic toner layer 66. At this time, the force exerted on the charged particles at the tip of the magnetic toner layer 66 is the force exerted by the magnetic roller 65.
the magnetic surface binding force F in that direction due to the photoconductor layer 5
An electrostatic attractive force F acts in the direction of a. And if we consider the diameter of the above particles to be constant, then magne.

The magnetic binding force Fm in the direction of the troller 65 is constant,
The electrostatic attractive force F in the direction of the photoconductor layer 5a is proportional to the surface potential V. Therefore, when the surface potential To exceeds a certain value, the relationship CF,<F, ) is established], and the tip particles of the magnetic toner layer 6d are attracted to the photoconductor layer 5a and adhere to the photoconductor layer 5a. (Toner O in FIG. 12) Development is performed by doing the following.

Next, the development source circuit 68 will be explained in detail with reference to FIG. 16. In FIG.
1 is a well-known voltage control IC (for example, μA723 manufactured by Texas Fist Instruments), and as shown in FIG.
2. It is mainly composed of a constant current circuit 143, an impedance conversion amplifier 144, an error amplifier f (differential amplifier) 146, an output control transistor 146, and the like. Further, 141 is a power terminal to which a power supply voltage VCC is supplied from the DC power supply circuit 111 (see FIG. 7), and 148 is a ground terminal connected to the ground line of the power supply circuit 111. Therefore, resistors 149, 160 and PNP)
The synister 151 constitutes an on-off control circuit for the developing bias voltage. That is, the resistors 149 and 150 are connected in series, one end of which is connected to the power supply terminal 147, and the other end of which is connected to the first contact y of the exposure mode selection switch.
It is connected to the NC (normal cross) contact of r1, and the CO (common) contact of this first contact 77 is connected to the remote signal terminal 1.
52. The connection point between the resistors 149 and 150 is connected to the pace of a transistor 151, the emitter of this transistor 151 is connected to the power supply terminal 147, and the collector is connected to the power supply terminal O of the voltage control IC 141 and the output control transistor 146. are respectively connected to the collector terminals ◎. The remote signal terminal 152 is supplied with an output signal from the AND circuit 11r (see FIG. 7).

On the other hand, resistors 153 and 154 are connected in series between the reference voltage generation terminal ■ of the voltage control ICI 41 and the ground terminal 148, and the connection point between the resistors 153 and 154 is connected to the voltage control IC 141 (D non-inverting input terminal A capacitor 155 is connected between this terminal ■ and the ground terminal 148 to provide voltage stabilization and soft start functions.In addition, the inverting input terminal ■ of the voltage control IC 141 is connected to
A capacitor 156 for frequency compensation and a diode 151 of the polarity shown are connected in series between the terminal O for frequency compensation and the terminal O for frequency compensation. connected to. Furthermore, the output terminal O of the voltage control IC 141 has a resistance of 159°1g.
NPN ) transistor 16 for oscillation control via O in series.
The emitter of the common transistor 161 is connected to the ground terminal 148, and the collector of the common transistor 161 is connected to the power supply terminal 147 via the primary winding 163 of the step-up transformer 162. Then, the resistors 159 and 1
The connection point with 60 is the oscillation winding 16 of the step-up transformer 162.
A voltage clamp is connected between the other end of this oscillating winding M164 and the ground terminal 148. diode 1
65 and an oscillation capacitor 166 are connected in parallel. Further, one end of the output winding 1m16F of the external pressure transformer 162 is connected to the bias voltage output terminal 168, and the other end is connected to the ground terminal 110 via a short-circuit protection resistor 169. Here, the output terminal 168 is the power supply plate of the developing device 7. 6F (see FIG. 5) is connected, and the ground terminal 1ro is connected to the ground terminal 148 and grounded to the main body 1 (see FIG. 1). moreover,
One end of the output voltage detection winding 111 of the step-up transformer 162 is connected to a ground terminal 170, and the other end is connected to a ground terminal 1710 via a rectifying diode 172 and a smoothing capacitor 113 in series.

The connection point between the diode 111 and the capacitor 113 is connected to one end of the variable resistor 158 via a resistor 114, and the other end of the variable resistor 158 is connected to the resistor 17.
6 to the ground terminal 170. For this,
The output voltage of the detection winding a171 is converted to DC by a diode 172 and a capacitor 173, and this DC voltage is divided by resistors 174, 115 and WJ variable resistor 158, and the slider voltage of variable resistor @15g is Appropriate feedback voltage vf
b is applied to the inverting input terminal (2).

The operation shown in FIG. 16 in such a configuration will be briefly explained. Now, the remote signal terminal 152 is at low level],
And in the case of manual exposure mode (exposure mode selection switch, first contact F7 of cheerer 1 is closed), the transistor 151 is not on, and the power supply voltage +vcc is supplied to each terminal ◎ and O of the voltage control IC 141, respectively. and voltage control IC14
1 starts operation. Therefore, the voltage control IC 14
A reference voltage vr*f is outputted to the reference voltage generation terminal (2) of No. 1, and after being divided by the resistors 15B and 154, is applied to the non-inverting input terminal (2).

When the voltage is at the non-inverting input terminal ■, the voltage at the capacitor 15 is
5, the voltage gradually rises with a certain time constant until it reaches a voltage corresponding to the partial voltage of the resistors 158 and 164.

It should be noted that the feedback voltage vfb is at zero immediately after the remote signal terminal 152 becomes low level. Therefore, the voltage at the inverting input terminal ■ is lower than the voltage at the non-inverting input terminal ■ of the voltage control IC 141, and the voltage at the output terminal O is at a high level. ), current flows through the primary winding 163 and a predetermined voltage is generated at the output winding 162. The transistor 161 works to repeat the on-off operation by the feedback voltage of a predetermined constant period generated by the oscillation winding 164 and the capacitor 1. Therefore, the output winding 161
An alternating current developing bias voltage V□7 is output. These developing bias voltages v and v are adjusted to the error anzo 145 and the output control transistor so that the feedback voltage vfb obtained from the detection winding 1m171 and the like is equal to the voltage of the non-inverting input terminal (i.e., the operating reference voltage). 146' (see FIG. 17), the voltage value is always constant.

The effects of the developing bias voltage vDllY outputted from the developing bias power supply circuit 68 in this manner, particularly the relationship between the document density and the copying degree, will be described with reference to FIGS. 18 and 19. FIG. 18 Surface potential on the whirling photoconductor layer 6a and developing bias voltage (frequency is 800 Hz) V
FIG. 19 shows experimental data showing the relationship between the original density and the copy density when the developing bias voltage V 7 is varied.

First, although the principle of development has been described above, here we will discuss changes in development conditions when a development bias voltage is applied. In FIG. 18, when an AC developing bias voltage of V□7 is applied to the sleeve 64 of the developing device 7, the strength of the electric field applied to the magnetic toner layer 661/C is synchronized with the bias voltage V□7. Change. In other words, 0 in the diagram
At point f (a positive voltage is applied to the sleeve 64), the electric field strength is weaker than when the developing bias voltage VD, v is not applied, and at point f (a negative voltage is applied to the sleeve 64), it is the opposite. become stronger. Therefore, at point f, the electric field is strengthened, so that the charge is more likely to be transferred to the magnetic toner layer 66 even when the developing bias voltage V□7 is not applied. Also, at the 0 point, the charge transfers in the opposite direction, negative ←)
A force acts to attract the charged toner to the sleeve 64. In this way, when the developing bias voltage V□7 is applied, the action of promoting development and the action of inhibiting it work alternately depending on the state in which the voltage is applied.

Since FIG. 19 shows experimental data when the amount of exposure to the original is held constant, there is a proportional relationship between the density of the original and the surface potential V of the photoconductor layer 5&. As shown in the figure, the developing bias voltage Vゎ.

As the voltage is gradually increased from zero, the characteristic curve shifts to the left as a whole, and when a voltage of approximately 500s is applied, it shifts to the left at the 9th o'clock. That is, in this state, even if the original density is the same, the copy density will be higher if the developing bias voltage V□7 is applied. When the developing bias voltage VD,v is increased to 500° or more, the rate of change of the characteristic curve gradually becomes K. here,
In FIG. 19, Is fla A is when the developing bias voltage is zero, song @B is when lOO melt, and song @C is when 2
At 00 porto, song @D is 500 gelt, curve E is 80
(1? silt, curve F shows each characteristic at 1000 t? temperature. From the above data, the following can be said. Until the developing bias voltage V□7 is about 500 volts, the rate of change of the characteristic curve is tb Overall shift to the left without change.

This is very similar to the case where the exposure amount is changed by a small amount without applying the developing bias voltage vDlv. Also, set the developing bias voltage vDKv to 500? When the voltage is set higher than the default value, the rate of change of the characteristic curve changes depending on the voltage value. In other words, the gradation with respect to the density of the original becomes better. As explained above, when the developing bias voltage V□7 is changed, approximately 500? Up to a voltage of 9.500 gelt, the effect of promoting development by the negative voltage (point f) in Figure 18 is strong, and at a voltage of 9.500 gelt or higher, there is an effect of negative voltage, but rather, development is caused by a positive voltage (point). It also works together to prevent the change in the characteristic curve.

Next, the exposure control circuit 102 (see FIG. 7) will be explained. FIG. 20 schematically shows the overall configuration, in which the exposure run f3 is connected to the AC power source 14 via a bidirectional thyristor 181. Maroku, above power supply 84
A pseudo load circuit 182 is connected to. This pseudo load circuit 182 applies a voltage corresponding to the terminal voltage of the exposure rung 3 to the pseudo load when the thyristor 1111 is turned on, and outputs the voltage across the pseudo load. The output voltage of this pseudo load circuit 182 is supplied to a waveform shaping circuit 183. The waveform shaping circuit 181 shapes the output voltage of the pseudo load circuit 182 into a voltage corresponding to the effective value voltage of the exposure rung 3 and outputs it. Here, the above pseudo load circuit 1B! and waveform shaping circuit 18
3 constitutes a voltage generation circuit 184 that generates a voltage corresponding to the terminal voltage of the fog light rung 3.

On the other hand, 185 is a manual reference voltage generation circuit which generates an arbitrary DC voltage by manual setting. In addition, 18# is an automatic reference voltage generation circuit, and the photo F diode (photo detection element)
The voltage is proportional to the current signal output from 10 and is subtracted from the preset voltage and output. Each output voltage of these two reference voltage generation circuits 185 and 186 is selected by the second contact 71 of the exposure mode selection switch 1r, and then the voltage ! I! It is supplied to the l adjustment circuit 187.

The voltage adjustment circuit 181 includes an exposure mode selection switch 7
The output voltage of the manual reference voltage generation circuit 185 or the automatic reference voltage generation circuit 186 selected in step 7 is adjusted to the optimum voltage level by taking into account the difference in the optimum exposure amount due to variations in the optical system and process system of the copying machine. Make adjustments. The output voltage of this voltage adjustment circuit 181 is supplied via a limiting circuit 188 to a comparator, for example, an error amplifier 189, and the output voltage of the waveform shaping circuit 183 is also supplied to this error amplifier 189. The limiting circuit 188 includes the error amplifier 1
The output voltage of voltage adjustment circuit 187 supplied to voltage regulator 89 is limited so as not to exceed a predetermined voltage level.

The error amplifier 189 also compares the output voltage of the waveform shaping circuit 183 and the output voltage of the voltage generation circuit 187 supplied via the limiting circuit 188, and if there is a difference between the two voltages, the magnitude of the difference is determined. Outputs a signal according to the The output signal of the error amplifier 189 is transmitted to the trigger pulse generation circuit 19.
0. This trigger pulse generation circuit 1110
outputs a trigger signal synchronized with the frequency of the power supply 84, and uses the error layer @Gl to determine the generation phase of the trigger signal.
It is controlled according to the output signal of tt9, and the controlled trigger signal is supplied to the dart of the thyristor 181.

FIG. 21 specifically shows each circuit in FIG. be done.

Between the DC output terminals P and N of the rectifier 192, there is a series circuit of a diode 193 and a capacitor 194! & continued. A series circuit of a resistor 195 and a Zener diode 195 is connected between the output ends P and N, and a series circuit of a diode 197 and a capacitor 198 is connected in parallel to the diode P196. The connection point between the diode 197 and the capacitor 198 is the relay contact 1.
Connected to one end of 99. Furthermore, the output terminals P, N-
A series circuit of a resistor 200 and a Zener diode 201 is connected between them, and the connection point 2 (Hl) between the resistor 200 and the diode 201 is set at K so that a trapezoidal wave voltage synchronized with the power supply 84 is generated. , the above condenser 1
94 includes a resistor 203 that constitutes the pseudo load circuit 182;
A series circuit of a unidirectional thyristor 204 and a resistor 205 serving as a pseudo load is connected in parallel. A connection point 206 between the cathode of the thyristor 204, which is the output end of the pseudo load circuit 182, and the resistor 205 is connected to one end of the resistor 210 via a diode 207 and resistors 208 and 209 in series. A capacitor 211 and a resistor 212 are connected in series between the connecting point of the resistors 208 and 209 and the output terminal N, and a capacitor is connected between the connecting point of the resistors 209 and 210 and the output terminal N. 213 is connected.

Here, the diode 207, resistors 208 to 210 .
212 and content 9211. IN is waveform shaping circuit 1
It consists of 83. The other end of the resistor 210 is connected to the base of an NPN transistor 2140, and the collector of this transistor 214 is connected to the other end of the relay contact 199 via a resistor 215. Furthermore, a series circuit of a capacitor 216 and a resistor 211 for preventing oscillation is connected between the base and collector of the transistor 2140. The emitter of the transistor 214 is commonly connected to the emitter of another NPN transistor 218, and this connection point is connected to the output terminal N via a resistor 219. 9. The collector of the transistor 218 is connected to the connection point 220 between the relay contact ipe and the resistor 215. In particular, the transistor 21
4, 218, etc. constitute an error amplifier 189. The transistor 2180 is connected to the collector of the NPN transistor 221, and the transistor 221 is connected to the collector of the NPN transistor 221.
The output terminal NKi is connected to the output terminal NKi. Further, the base Id of the transistor 221 is connected to the connection point 220 via a resistor zzz, and is also connected to the output terminal N via a resistor 223. Here, the transistor 221 and the resistors xxx and zxs are a limiting circuit 188.
It consists of First, a series circuit consisting of the variable resistor 16 and resistors 225 and 226 is connected between the connection point 220 and the output terminal N, and these constitute a manual reference voltage generation circuit 185. .

Also, the transistor 2 serving as the output terminal of the error amplifier 189
The connection point between the collector 14 and the resistor 216 is the resistor 221
is connected to the base of an NPN transistor 228 through the connection point 2, and the collector of this transistor 228 is connected to the connection point 2
Connected to 02. The transistor 228 is connected to the output terminal N via a capacitor 22jl, and is connected to the output terminal P via a resistor It is connected to the anode of JIKPUT (abbreviated as JIKPUT) 231. The cathode of the PUT 2 J 1 is connected to the output terminal NK via a /4 transformer 2320 primary coil and an NPN transistor J'JJ in series.

The base of the transistor 233 is connected to the connection point 220 via a resistor 234 and to the output terminal N via a resistor 235. Nine, PUT!
The cathode 310 is connected to f-) of the thyristor 204 through a resistor 33g and a diode 231 in series, and this connection point is connected to the connection point 2061 through a resistor 238.
1C connected. On the other hand, the dart of PUTJJZ is connected to the output terminal N via a resistor 2S9 and to the connection point 202 via a diode 240 and a resistor 241 in series. Further, a connection point between the diode 240 and the resistor 241 is connected via a diode 242 to a connection point between the base of the transistor 228 and the resistor 22F. Therefore, the above Δ Rustzuns 232 2
The next coil is a thyristor 1g via a diode Z43.
IC)')'-) and the seventeenth node.

In particular, the transistor 228, the capacitor 22m,
PUT231, delta transformer 2S2, transistor 233, etc. are trigano! This constitutes a pulse generation circuit 1j10.

On the other hand, the anode of the photodiode 10 is connected to a resistor 2.
44 to the connection point 220, and a resistor 245 to the output terminal N. The resistor 244.degree. 14511 is used to divide the power supply voltage to obtain a predetermined set voltage. Also, the anode of the diode 10 is the non-inverting input terminal of the operational amplifier 246←)
, and its cathode is connected to the inverting input terminal ←) of the operational amplifier 246. And the above operational amplifier 246
A variable resistor 247 and a capacitor 248 are connected in parallel between the inverting input terminal and the output terminal of the variable resistor 247 and the capacitor 248. Note that the operational amplifier 246, variable resistor 247, and capacitor 24
8 constitutes a current-voltage conversion circuit.

The output terminal of the operational amplifier 14g is connected to the second contact 17. of the exposure mode selection switch yyo via a resistor 249. N of
o (normal oven) connected to 11 points. Here,
The resistors 144, 141, operational amplifier f246, etc. constitute an automatic reference voltage generation circuit 18186. In addition,
The NC contact of the second contact rr is connected to the slider of the variable resistor 76 in the manual reference voltage generating circuit 185.

Also, the second g of the exposure mode selection switch 11! Point 11.
The CO contact of is connected to the non-inverting input terminal of the operational amplifier fxsb, and the inverting input terminal of the operational amplifier fxsa is connected to the output terminal N via a resistor 25. A variable resistor 252 and a capacitor 253 are connected in parallel between the inverting input terminal and the output terminal of the operational amplifier 250. Note that the above operational amplifier f211el, resistor 1111, variable resistor 252, and capacitor txsz constitute a positive phase amplifier, variable resistor @IS;! By changing the gain at , variations in the optical system and gloss system of the copying machine are corrected, and impedance conversion to the next stage circuit is performed. However, the above opean f 211
The output terminal of 0 is connected to the transistor 2 via a resistor 254.
Connected to 180 base. ζKoni1 above opean f2
60, variable resistor 252, capacitor 253, and resistors 261 and 214 constitute voltage adjustment circuit 111.

Next, the operation in the above configuration will be explained. First, we will discuss the case of manual exposure mode, which always provides a constant optimum exposure amount despite fluctuations in power supply voltage. In this case, the second contact yr1 of the exposure mode selection switch 71 is closed to the NC contact side, so that the automatic reference voltage generation circuit 186 becomes irrelevant to the exposure control described below. Now, when the exposure rung lighting signal is turned on and the relay contact 199 is closed, a voltage obtained by dividing the voltage at the connection point 220 by the resistor 234I235 is applied to the base of the transistor 2SS, and this transistor 233 is turned on. Also, transistor 2
On the 280 base, the voltage at the connection point zze is the resistance 215.2
27 and turns on this transistor 2284. With this, the capacitor 229 is connected to the transistor 2
21. Due to this charging, F), P'UT
What is the 7 node voltage of 131? -) If the voltage exceeds the PUT
J J I Fi Ontonashi, / Dorus Trans 21
A Δlus current flows through the 201st coil. therefore,/
A pulse is generated in the secondary coil of the 4-rus transformer 232,
This becomes the trigger t4 pulse and r- of thyristor 1#1.
) is applied to When this happens, the thyristor 181 is turned on and the exposure rung 1 is turned on.

At this time, the trigger pulse is also applied to the thyristor zo401'-) via the resistor gig and the diode 231, so the thyristor 204 is turned on according to the pulse, and the voltage corresponding to the exposure rung 30 voltage is applied. is generated across the resistor 2050. This generated voltage is converted into a DC voltage corresponding to the effective value voltage of the exposure rung S by the waveform shaping circuit 18B including the diode 207, the resistors 2os to xi (1,111, and the capacitors 9211, 213). , this voltage is
140 base. Tonoto Food, Transistor 2
If the 140 pace voltage is lower than the transistor 2180 pace voltage, the collector voltage of transistor 214 will not be high, and therefore the base voltage of transistor 2280 will also be high, and the charging speed of capacitor f229 will be faster. As a result, j6, PUTjJJ generate a fast tie ζ blow monorus], the conduction angle of the thyristor 181 increases, and in the exposure run f3, the applied voltage increases and the amount of light increases. The increase in the conduction angle of thyristor 181 is due to the increase in the conduction angle of thyristor 2.
04, which causes the transistor 2140 base voltage to increase and balance at 9, which is equal to the transistor 218 pace voltage. A reference voltage is applied to the base of the transistor 2180, which is adjusted to a voltage level that satisfies the characteristic surface line G shown in FIG. Since the reference voltage is held constant against voltage fluctuations in power supply 84, the base voltage of transistor 2140 is also kept constant.
It operates so that the O applied voltage to the exposure run f8 is constant.

In this way, control is performed so that the voltage applied to the exposure run fJ is always constant as a whole, and this allows the variable resistor of the manual reference voltage generation circuit 1815 to be controlled regardless of the fluctuation K of the stain source voltage. The constant optimum exposure amount set by the device r6 can be obtained. In this case or characteristic F
The characteristic curve K is like the characteristic curve G shown in Fig. 22.

Next, a description will be given of the automatic N light mode which automatically provides the optimum exposure amount in accordance with the fluctuations in the power supply voltage and the fluctuations in the document reflectance O. In this case, the exposure mode selection switch rr
The second contact point 7F.

is closed on the NO contact side, and therefore the exposure run fl is controlled by the output voltage of the automatic reference voltage generating circuit 1a6. That is, the light from the exposure rung 1 is irradiated onto the original on the original platen 2, and the amount of reflected light proportional to the reflectance of the original is guided to the photoreceptor drum 5, but some of the reflected light is photosensitive. The light enters the diode 10 and is converted into a current. At this time, the current-voltage conversion circuit mainly composed of the operational amplifier F246 converts the output current of the diode 10 into a voltage,
The voltage obtained by subtracting the voltage from the voltage set by the resistor 244 and 245 is transmitted to the voltage adjustment circuit 111 via the second contact rr.
Output to. The output voltages of the voltage adjustment circuit 1avB and the automatic 1 quasi-voltage generation circuit 186 are adjusted to the optimal voltage level, taking into account the difference in the optimal exposure amount due to variations in the optical system and 7# palm processing system of the copying machine, as described above. and is applied to the base of transistor 2180 forming error amplifier 189. At this time, the pseudo load circuit 182 and the waveform shaping circuit 183 operate as described above, and supply a voltage corresponding to the voltage across the exposure run fz to the base of the transistor 2140.

and ζ, and assuming that the output voltage of the automatic reference voltage generation circuit 186 becomes high when the amount of light incident on the photodiode 10 is small, for example, if the original has a thick background and low reflectance, then the amount of reflected light from the original is 0. Less, 7*) Dio-Pl
Since the amount of light incident on O is also small, the output voltage of the operational amplifier 24σ is high (), and accordingly, the output voltage of the voltage adjustment circuit 111F and the base voltage of the tr transistor 211 are also high. When the base voltage of the transistor 2140 is lower than the base voltage of the transistor 2180, the voltage applied to the exposure run fl is increased by increasing the conduction angle of the thyristor 181 as described above, and the amount of light is controlled to increase. Through this control, the increase in the amount of light and the increase in the conduction angle of the p-thyristor 1111 are fed to the thyristor 104 in the same way as described above, thereby increasing the pace voltage of the transistor 214 and increasing the base voltage of the transistor 218. Balance is achieved when they become equal.On the other hand, if the voltage of the power supply 84 fluctuates in the ζO state, the transistor; tt
14 vjlilo Since the base voltages are no longer equal, the voltage applied to the exposure rung 3 is operated to be constant so that the pace voltages of the transistors 214 and 218 become equal again as described above. . As a result, the voltage applied to the exposure lamp 3 remains constant even if the power supply voltage fluctuates, and the exposure lamp 3 remains constant even if the power supply voltage fluctuates.
Control is performed so that the amount of light 3 changes automatically and the amount of light directed to the photoreceptor drum 5 remains constant. In this way, control is performed so that the voltage applied to the exposure rung 3 is always constant as a whole, and the amount of light reflected from the document is always constant. The optimal exposure amount can always be automatically obtained regardless of changes in reflectance (original density). The γ characteristic in this case becomes a characteristic curve H shown in FIG.

Note that the limiting circuit 188 performs the following operation. When the pace voltage of the transistor 218 (collector voltage of the transistor 221) exceeds the voltage set by the resistors 222 and 223 (the pace voltage of the transistor 221), a current flows through the transistor 221, which lowers the pace voltage of the transistor 218. The voltage is controlled so that the pace voltage of the transistor 218 does not exceed the set voltage.

That is, transistor 221 is transistor 2180
The base voltage is forcibly flagged so that it does not exceed the voltage set by the resistors 222 and 123. Therefore, the pace voltage of transistor 218 does not exceed the preset voltage, which results in thyristor 181
The maximum conduction angle is suppressed, and the voltage applied to the exposure rung 3 is automatically limited to a predetermined voltage or less (rated voltage or less).

In this way, the limiting circuit 188 is configured as the manual reference voltage generating circuit 1.
85 or by limiting the reference voltage from the automatic reference voltage generation circuit 186 to the error amplifier 189.
This limits the voltage applied to the ring 3 so that it does not exceed the rated voltage. The reason why such a limiting circuit 188 is provided is that when using an exposure rung whose rated voltage is lower than the commercial AC voltage, for example, it is necessary to prevent the applied voltage of the exposure 27 from exceeding the rated voltage from the viewpoint of lifespan. This is for the purpose of

Next, FIGS. 22 and 23 show the characteristics when the 1% sensitivity (original density - copy density characteristics) is switched depending on the exposure mode (manual or automatic), which is the gist of the present invention.
This will be explained with reference to the figures. First, in FIG. 22, the characteristic curve G is the developing bias voltage "nmv" during manual exposure.
is 80 (1% characteristic when the engine is at low temperature), and the rate of change of the characteristic curve is small. On the other hand, the characteristic curve (2) shows the Or.gamma. characteristic when the developing bias voltage VD, v during automatic exposure is zero, and the rate of change of the characteristic curve is large.

As is clear from the figure, the r characteristic curve H during automatic exposure shows that when copying is performed using the standard density test chart for automatic exposure, when the original density is approximately 0.50, the copy density is approximately 0.
．． The variable resistor 247 in FIG. 21 is adjusted so that the value becomes 75, so that the Orγ characteristic curve during manual exposure intersects with the point indicated by each of the density values above. i, 23rd
The figure shows the γ characteristic curve in automatic exposure mode.Characteristic curve J is the γ characteristic that represents the copy density relative to the density when the entire original is uniform, and is the operating standard in automatic exposure mode. It is what it is. That is, this characteristic surface lsJ
When copying an actual original, the expression represents the copy density relative to the background density of the original.

The exposure amount during automatic exposure is determined by the photodetection element 10 described above.
is controlled by the density integrated over the entire manuscript. Therefore, the γ characteristic at that time becomes the characteristic curve shown in FIG. 23 or the curve L. Here, the characteristic curve is based on the reference concentration test chart mentioned above (background concentration is α1).
The characteristic curve with 1% characteristic (about 0.15 character-based chart) is the gamma characteristic of newspapers and the like with relatively high background density. In this way, the Or% characteristic during automatic exposure is determined by the r characteristic curve K, based on the background r% characteristic curve J.
This is something that shifts in the left and right direction depending on the ground density.

According to the above-described copying apparatus, the r-characteristic control performs switching control such that the rate of change in r-toughness is increased in automatic fog light mode, and the rate of change in r-characteristic is decreased in manual exposure mode. By providing the means, the following effects can be obtained.

During automatic exposure, as described above, the density of the entire document is controlled by an integrated value, and the main application is line-to-document. In other words, this is a document that mainly consists of ordinary letters and numbers, and the density of the background changes, so the copy density of the background should be kept low.
Ideally, the original content should have a high copy density so that a copy image with no capri and good contrast can be obtained. Therefore, in the present invention, during automatic exposure, rather than increasing the rate of change of the r characteristic, the O
The copying density is controlled to be very low, and when the density is higher than that, the copying density is increased], thereby obtaining a copying image with very good contrast and no pigmentation.

Approximately 80 to 90 degrees of normal originals can be covered with automatic exposure, but the originals that must be exposed manually even after recovery are those with a small density ratio between the original back brown and the original content, and For originals with a wide density distribution, good delamination tonality becomes a problem. Therefore, in the present invention, by reducing the rate of change of the r characteristic during manual exposure, the linearity is significantly improved, and the content of the original can be faithfully copied. Copied images with less fading or density unevenness and good gradation can be obtained.

(Effects of the Invention) As detailed above, according to the present invention, by providing the r-characteristic control means, it is possible to obtain a copy image with very little capri and very high contrast during automatic exposure, and during manual exposure, it is possible to obtain a copy image with very high contrast. It is possible to provide a copying apparatus that can be expected to have various effects, such as faithfully copying the contents of a document, reducing blurring or density unevenness in a copied image, and obtaining a copied image with good gradation.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Fig. 1 is a side view showing a schematic configuration of an electronic copying device, Fig. 2 is a perspective view showing details of the document table and its drive mechanism, and Fig. 3 is a side view showing the schematic configuration of an electronic copying device. A schematic side view for explaining the moving position detection mechanism of the document table, FIG. 4 is a side view showing the structure of the developing device in detail, and FIG. 5 is for explaining the method of applying bias voltage to the developing device and the state of conveying magnetic toner. 6 is a plan view showing details of the operation channel, FIG. 7 is a block diagram schematically showing the control system, and FIGS. 8 to 11 are 70 diagrams for explaining the operation. −
The chart, FIG. 12 is a schematic side view for explaining the principle of development using a one-component high-resistance magnetic toner, and FIGS. 13 to 15 are for explaining the principle of development in more detail. Figures 13 and 14 are simplified development model diagrams, Figure 15 is its equivalent circuit diagram, Figure 16 is a configuration diagram showing the development bias power supply circuit in detail, and Figure 17 is the voltage control in Figure 16. 18 and 19 are schematic diagrams of the rc for use in explaining the effects of the developing bias voltage, and FIG. 18 is a diagram showing the relationship between the surface potential of the photoreceptor drum and the developing bias voltage. Figure 19 is an experimental characteristic a diagram showing the relationship (r characteristic) between original density and copy density when the developing bias voltage is changed, and Figure 20 is a diagram showing the schematic configuration of the exposure control circuit. 21 are block diagrams specifically showing each circuit in FIG. 20, and FIGS. 22 and 23 are characteristic curve diagrams for explaining the r characteristic according to the present invention. 2... Original table, J-... Exposure 2 ring, 5-- Photosensitive drum, 6- Band holder, 7... Developing device, P... Paper, 1
0... Photodetection element, 15-- Charger for transfer, 18...
・Heat roller (fixer), 63...Developing roller, 6
4... Sleeve, ttS-... Magnet roller, 6
7... Power supply blade, 68... Developing bias power supply circuit, 71... Operation panel main body, :tX-・Glint key, 76... Sliding variable resistor for adjusting exposure jt, 17
... Exposure mode selection switch, 82 ... Microprocessor, 102 ... Exposure control circuit, 181 ... Thyristor, 184 ... Voltage generation circuit, 185 ... Manual reference voltage generation circuit, 186 ... - Automatic reference voltage generation circuit, 189... error amplifier (comparator), 190-) trigger pulse generation circuit.

Claims (2)

[Claims] (1) Copying is performed through various processes such as charging, fogging, development, and transfer, and the exposure process has a manual exposure mode that manually provides the optimum exposure amount and an automatic exposure mode that automatically provides the optimum exposure amount. Further, the developing flRf process includes an r-characteristic control means for switching and controlling original density-copy density characteristics (hereinafter referred to as γ-characteristics) between the medium dynamic exposure mode and the automatic exposure mode in a copying apparatus that uses one batch of developer. A copying device characterized by being provided with. (2) The r% characteristic control means is characterized in that it performs switching control so as to reduce the rate of change of 7% characteristic during manual exposure mode, and to increase the rate of change of r characteristic during automatic exposure mode. A copying apparatus according to claim 1.