JPS61198174A - Image forming device - Google Patents

Abstract

PURPOSE:To check the operation state of a device precisely by operating part of an image forming means at different levels in the 1st and the 2nd modes. CONSTITUTION:The DC regenerated voltage of a surface potential detecting circuit is inputted to uninverted input terminals of comparator COMs 1-5 and voltages V1-V5 for comparison are inputted to inverted input terminals. Controllers V1-V5 are so controlled that only a light emitting diode LED 3 illuminates. A different surface potential is controlled only by the illumination of the same light emitting diode and a mode switch is capable of driving some of plural processing means for image formation selectively. This command means like this is provided to check the operation state of part of an image forming device such as a copying machine without driving the whole device, measure the surface potential in a desired mode easily because a load is driven selectively when the surface potential on a drum in a different mode by a surface electrometer, and also displays surface potential detection outputs by levels.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for forming an image on a recording medium, and more particularly to an image forming apparatus capable of checking the operating state of an image forming means.

2. Description of the Related Art Conventionally, some image forming apparatuses such as copying machines are capable of individually driving chargers and the like to check whether or not they operate. However, with only such a function, even if one process means is operating, it is not checked whether the output is appropriate or not.

The present invention has been made in view of the above points, and an object of the present invention is to provide an image forming apparatus that can check the operating state of the apparatus with high accuracy.

That is, the present invention provides an image forming means for forming an image on a recording medium, a command means for inputting first mode and second mode signals, and a method according to the first and second mode signals outputted from the command means. and a control means for controlling the operation of the image forming means, the control means operating a part of the image forming means at different levels in the first mode and the second mode. A forming device is provided.

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

FIG. 1 is a sectional view of a copying apparatus to which the present invention can be applied.

The surface of the drum 11 is made of a three-layer photoreceptor using a CdS photoconductor, is rotatably supported on a shaft 12, and starts rotating in the direction of an arrow 13 in response to a copy command.

When the drum 11 rotates at a fixed speed, the platen glass 1
4 is irradiated with an illumination lamp I6 integrated with a first scanning mirror 15, and its reflected light is scanned by the first scanning mirror 15 and the second scanning mirror X7. The first scanning mirror 15 and the second scanning mirror 17 move at a speed ratio of l;%, so that the original is scanned while the optical path length in front of the lens 18 is always kept constant.

The reflected light image above is the lens 18. After passing through the third mirror 19, the light passes through the fourth mirror 20 and is imaged onto the drum 11 at the exposure section 21.

The drum 11 is charged (for example, +) by a negative charger 22.
After that, in the exposure section 21, the image illuminated by the illumination lamp 16 is subjected to slit exposure.

At the same time, a static eliminator 23 is used to remove static electricity of the opposite polarity (for example, -) to the AC or - next page, and then the entire surface exposure lamp 2
4, a high-contrast electrostatic latent image is formed on the drum 11. The electrostatic latent image on the photosensitive drum 11 is then visualized as a toner image by the developing device 25. Although acid development, magnetic brush development, etc. can be used as a developing method, magnetic blank development is used in this embodiment.

Transfer paper 27-I in cassette 26-1 or 26-2
Alternatively, 27-2 is the paper feed roller 28-1. Or 2
8-2 into the machine, and the No. 1 Lujistar roller 29-1
Alternatively, rough timing is determined by 29-2, accurate timing is determined by second register roller 30, and the recording material is sent toward the photosensitive drum 11.

Next, the transfer paper 27 is passed between the transfer charger 31 and the drum 11.
The toner image on the drum 11 is transferred onto the transfer paper while the drum 11 passes through the transfer paper.

After the transfer is completed, the transfer paper is guided to the conveyor belt 32 and further to the pair of fixing rollers 33-1, 33-2, where it is fixed by pressure and heat, and then discharged onto the tray 34.

After the transfer, the surface of the drum 11 is cleaned by a cleaning device 35 composed of an elastic blade, and the process proceeds to the next cycle.

In order to control the above-described image forming cycle at each point in time, a drum clock pulse DCK is generated by a sensor Ilb that optically detects the clock point of the tarmac board 11a which rotates with the rotation of the drum II.

Reference numeral 50 denotes a surface electrometer for detecting the surface potential on the drum 11, which is attached to the developing device 21.

The surface electrometer 50 will be explained. FIG. 2 is a cross-sectional view showing the mounting position of the surface electrometer 50 and the drum 11, FIG. 3 is a side sectional view of the electrometer 50, FIG. 4 is a surface potential detection circuit, and FIG. 5 is a surface to be measured. FIG. 5 is a perspective view of a squirrel-cage chopper 53 that shields the antenna and the measurement electrode.

In FIGS. 2, 3, and 4, reference numeral 52 denotes a conductive outer cylinder made of brass or aluminum, and the outer cylinder 52 has a surface charge detection window 65. 55 is a sensor motor as a driving means for rotating the chopper 53; 53 is a cylindrical chopper having a potential measurement window 64; 54 is a surface potential measuring electrode, and 56 is a preamplifier printed board on which a detection circuit for detecting the output of the electrode 54 is formed.

The surface electrometer 50 is placed 2 mm from the surface of the drum, which is the surface to be measured.
The potential measurement window 65 is installed at a remote location so as to face the drum surface, and a preamplifier printed board 56 for amplifying the voltage detected by the electrode 54 is built into the surface electrometer 50. is formed. When the sensor motor drive signal SMD is output from the CPU 201 of the control circuit shown in FIG.
4.

The potential measurement windows 64 are provided at four locations on the chopper 53 at equal intervals. What is induced in the electrode 54 is an alternating voltage as shown in FIG. 7-1 because the chopper 53 rotates and the drum surface l intercepts the electrode 54 at equal intervals. The period T of this AC voltage and the voltage amplitude Vp-1) are:
It is proportional to the difference between the drum potential Vp and the sensor bias voltage VBIAS, which serves as a reference voltage for the potential outer cylinder 52, chopper blade 53, and preamplifier board 56. Therefore vp-p
=VBIAS, the AC voltage becomes 0. An internal circuit provided in the preamplifier board 56 receives a sensor power supply of 5Vc superimposed on the aforementioned sensor bias voltage VBIAS.
Ql, which is driven by C and performs impedance conversion of the AC conversion signal detected by the electrode 54, is a junction type F.
A minute alternating current signal induced in the electrode 54 by the ET is received by the high input resistance of the gate and converted into a low impedance signal. R3 and R4 are protective resistors.

7-2 shows the relationship between the drum potential Vp and the peak value of the output 62 from the preamplifier using the sensor bias VBIAS as a parameter.
The difference between the drum potential Vp and the sensor bias VBIAS is faithfully detected. Furthermore, the drum potential Vp is V p
If it changes in either the range ≧VBIAS or Vp≦VBIAS (7), the AC detection voltage has the characteristic of monotonically increasing or monotonically decreasing depending on the drum potential Vp, so a new detection voltage is required for polarity determination. There is no need to add a synchronous rectifier circuit. In Figure 7-2, VBIAS is 150V (
7) When the drum potential Vp is in the range of vp≦150V, the detected voltage increases monotonically in the range of -nV to +150V, and the magnitude relationship in both the positive and negative directions can be determined. However, the positive range is +150Vmax, and -nv is the preamplifier board 5.
6 is limited by the saturation voltage of the circuit provided within the circuit.

As described above, by applying a constant positive or negative bias to the electrometer housing and the internal circuit built into the electrometer, It is now possible to determine the polarity of the potential on the surface to be measured.With this configuration, there is no need to newly install a synchronization detection circuit, etc., and it also prevents external noise from affecting the electrometer's internal circuit and causing fluctuations in the measured potential. It has also become possible.

By the way, in a type of copying machine that applies light to a photoreceptor to eliminate static charges, the output voltage VpLA of the primary charger 22 is
When copies are made continuously while keeping the output voltage of the C static eliminator 23 VSL and the exposure light amount of the exposure lamp 16 constant,
The previous latent image creation affects the photosensitive characteristics in the next latent image creation. In other words, the photosensitive plate has memory characteristics.The memory characteristics vary depending on the conditions for making the photosensitive plate.
As shown in the figure, when the sensitivity of the photosensitive plate becomes faster (2-c)
In some cases (2-b), the light intensity is slower than the standard light intensity Eo (here, EO is the amount of reflected light when the exposure lamp shines light on a standard white original with the light emission adjustment dial (not shown) set to 5). The surface potential of the photosensitive plate fluctuates.

In addition, the potential especially after AC static elimination changes due to changes in the environment such as temperature and humidity. Fluctuations in AC static elimination particularly affect bright areas of the document. FIG. 9 shows the characteristics of the photosensitive plate when the AC static elimination varies.

In this way, image conditions such as dark area density, halftone density, and bright area fogging of the original may change due to continuous copying or changes in the environment, but in order to make good copies, it is possible to suppress fogging, especially in the bright areas of the original. is an important element.

A control method for controlling the bias voltage of the developing device in order to suppress fog in bright areas will be described in detail below.

In this embodiment, the original exposure lamp 10 is used instead of the document illumination lamp 16 to detect the drum surface potential in the bright area. The blank exposure lamp 10
is irradiated onto the drum surface during forward rotation and backward movement of the optical system. The surface potential of the drum surface at this time is measured as a bright area surface potential, and the developing bias applied to the developing device 25 is controlled according to this detected voltage. At this time, the amount of light that the blank exposure lamp 10 irradiates onto the drum surface is the same as the light reflected from the document illumination lamp 16 when a white document is placed with the light emission amount adjustment dial (not shown) on the operation section set to 5. The amount of light is adjusted by a variable resistor VR3. Therefore, detecting the surface potential of the drum due to irradiation with the blank exposure lamp IO is the same as the surface potential generated on the drum surface by the document mill during copying, and a certain positive voltage is added according to the detected voltage. By applying a developing bias,
Even if the photosensitive characteristics of the drum 11 fluctuate and the bright area potential fluctuates, it is possible to prevent copies from being fogged.

In this embodiment, the bright area surface potential measurement using the blank exposure lamp 10 measures the potential of the non-image area during the aforementioned pre-rotation and the non-image area between successive electrostatic latent images, and the measurement output is This serves as a reference voltage for applying a developing bias during development of the latent image following .

In the timing charts of FIGS. 6 and 15,
When a copy start signal is input from the key manual means 208, a motor drive signal MD is output from the CPU 201, and the high-voltage AC static eliminator 23, high-voltage blower 22, full-surface irradiation lamp 24, blank exposure lamp IO, and sensor motor 55 are activated. ONL, perform the aforementioned forward rotation. At this time, the sensor motor 55 is driven by a sensor motor drive circuit. The above-mentioned constant sensor bias VBIAS (+150V) is applied to the potential outer cylinder 52 and the chopper 53, and the constant sensor power supply 5Vcc is applied to the circuit inside the preamplifier board 56.
(+175V) is applied from the developing bias control circuit 207 through lead wires 60 and 61, respectively.

The AC signal detected by the electrometer 50 is amplified by the AC amplifier 204 through the lead 62, and further amplified by the rectifying and smoothing circuit 20.
5 to regenerate to DC. This DC reproduction voltage is input to the sample hold circuit 206, and the DC reproduction voltage when the STB signal is "H" output from the CPU 201 is input to the sample hold circuit 206.
6 is stored. When the pre-rotation is completed, the paper feed and exposure lamp 16 lights up, and the lamp 16 and mirror 15. The optical system consisting of 17 scans the document according to its size, and the developer motor rotates to perform development. Development bias control circuit 20
Reference numeral 7 switches between the above-mentioned DC reproduction signal and a constant value using a developing unit drive signal 1) Vf input from the CPU 201 through a lead wire 74. Therefore, a developing bias corresponding to the detected bright area potential is applied to the developing device 25 only when the developing device motor is rotating and developing the latent image. In the case of multiple copies, the strobe signal STB is sent to the CPU each time during the optical system backward movement (SCRV) of each copy.
The bright area potential is measured and stored by irradiating blank light while the optical system is moving backward, and the developing bias control circuit 207 is similarly controlled. In other words, when forming latent images continuously, an electrostatic image is formed by projecting a predetermined amount of light onto a non-image area between two consecutive latent images, and the potential of the electrostatic image is measured. Since the latent image following the electrostatic image is controlled, changes in the output of the charger due to changes in the characteristics of the photoreceptor due to continuous image formation and changes in the environment as described above can be avoided by controlling the developer. By controlling the developing device, it is possible to compensate and to form a stable image, which is particularly effective in preventing fog in bright areas. Furthermore, by detecting every time a latent image is formed, it is effective because fluctuations in bright area potential can be faithfully followed.

Figure 10 shows the sensor motor drive circuit 203 of Figure 6.
, the motor drive signal MD is “T”.
-I", the open collector inverter output becomes "L" and the voltage across capacitor C1 supplies the voltage determined by R7 and R8 of the constant voltage circuit consisting of Q3 and Q6 to the motor winding. 11 shows the AC amplifier 2
04, rectification smoothing circuit 205, sample hold circuit 20
6 is a detailed circuit diagram of FIG. The AC voltage waveform detected by the electrometer 50 is input from Jl to the coupling capacitor C3, and is AC amplified by the amplifier Q6 to become an amplified AC signal centered on +12V. VR6 is a detection gain adjustment volume.

The rectifier circuit 205 includes an operational amplifier Q7 and a diode D3°D.
4. Consisting of a resistor R20, it constitutes a linear detection circuit that linearly amplifies only the positive component around +12V. When the input voltage at the inverting input terminal of operational amplifier Q7 is positive with respect to the input voltage at the non-inverting input terminal, the point becomes negative, turning diode D4 off and diode D3 on. Since the negative input terminal of Q7 becomes +12V when D3 is turned on, the output (point B) becomes ++2V. Also, when the input voltage of the inverting input terminal is negative with respect to the input terminal of the non-inverting input terminal, the 0 point becomes positive and the diode D
4 is on and diode D3 is off, so the gain is -17
The signal is then linearly amplified and detected. Since such a linear detection circuit is used, the linearity of the DC reproduction voltage characteristic with respect to the surface potential of the drum has been improved, and compensation for temperature has also become sufficient.

The detected signal passes through a buffer amplifier consisting of an operational amplifier Q8 and is smoothed by a smoothing capacitor C6.

It is further amplified by a Q9 buffer amplifier. The signal here is outputted to the outside as a check terminal J5 for potential setting via a voltage follower Q13. The relationship between the output of J5, that is, the integral output, and the potential on the drum surface is shown in Figure 12 (
As shown in A), it has symmetrical characteristics around the sensor bias VI31AS. The sensor bias compensation signal COMP of J2 is inputted to the inverting input terminal of the summing amplifier QIO via the developing bias control circuits 207 to 71, and the voltage is extracted from the sensor bias VBIAS by dividing it with a resistor. standards). The polarity of the sensor bias compensation signal VCOMP is inverted by operational amplifier Q14, and QI is set at -1V (+12 reference).
It becomes one input of the O summing amplifier. The output of QIO exhibits the characteristics shown in FIG. 12(B). Therefore, the sensor bias compensation signal VCOMP is equal to the sensor bias VBI.
By applying AS, when the surface potential of the drum is Ov, the DC reproduced detection output is level shifted and offset to Ov (+12V reference).

Furthermore, the variation in VBIAS acts to offset the variation in the above-mentioned DC regenerated detection output.

In other words, by adding a voltage obtained by resistance-dividing the bias voltage applied to the electrometer casing to the measured output of the electrometer that has been regenerated with direct current, the fluctuations in the bias voltage are offset, making stable measurement possible.

In this case, it is applicable not only to the squirrel-cage electrometer of this embodiment but also to all No. 2 potential models that extract the potential of the surface to be measured as an AC signal and reproduce it as a DC signal.

By the way, the output of the summing amplifier QIO is the junction type FET QII.
, an amplifier Q12, a capacitor C7 with low leakage current, and a resistor R'44. At this time, the strobe signal input from J3] is “H”.
”, transistor Q15 is OFF and junction type F
The gate and source of ETQIl are reverse biased and the FET
Since Qll is OFF, the output of amplifier QIO is not stored in capacitor C7. ■When 1 is “L”, transistor Q15 is turned on, and the gate and source of FET QII becomes Ov, and the gate and source are forward biased.
The output of IO is charged to capacitor C7. Next, when the voltage 1 becomes "H" again, the FET Qll is turned off and one terminal of the capacitor C7 becomes in an oven state, so that the charged electric charge is held. With the above operation, the sample-and-hold circuit can sample and hold the output of the QIO when the voltage is low. Further, since the gain is multiplied by 1/2 by R41 and R44, the characteristic shown in FIG. 12(C) is shown. This signal is sent from J4 to the developing bias control circuit 207 via 72 in FIG. FIG. 13 is a detailed circuit diagram of the developing bias control circuit 207 shown in FIG. block 6
-1, 6-2 are high voltage generation circuits, respectively. Block 6-2 will be explained. When +24V power is supplied to the inverter transformer T2, either transistor Q24 or Q25 turns ON. Transistor Q24
is ONL, the collector current of Q24 increases, and a back electromotive force corresponding to the increase in collector current is generated in the transformer T2, which is brought to the base of Q25 (D,
Then, the collector current of Q24 further increases. This positive feedback saturates Q24 with a time constant determined by resistors R86, R88 and the inductance of transistor T2. When the collector current of Q24 is saturated, the back electromotive force of coil T2 becomes 0, and Q24 is turned off L/, transformer T2
A back electromotive force is generated according to the decrease in collector current,
Turn on Q25. By similar positive feedback, transformer Q2
4. Q25 continues to oscillate. Dll, DI2 is Q24
．． The protective diode resistor R89 of Q25 is connected to the transistor Q24°Q25. This prevents the collector current from varying due to variations in hFE, and reduces the oscillation duty to 1:l.
This is a resistance to prevent the current from disappearing. The oscillation amplitude will be approximately twice the voltage supplied to T2. This oscillation voltage is boosted to a voltage determined by the turns ratio of 1゛2, and then DI4゜C1
5, it is rectified and smoothed and a DC high voltage is output. block 6
-1 also outputs high voltage in the same manner, but it is a variable high voltage output in which the voltage supplied to I changes according to the output voltage of Q17.Developer drive signal port 1 input from terminal J7
to "H" or "L" to set the input of operational amplifier Q17 to the above-mentioned sample-and-hold voltage value, or change the variable resistor V
The voltage determined by RIO is selected. Old 1 is “
When it is "H", transistors Q16 and Q19 are turned off, and the gate of FET Q18 becomes the same potential as the source via R62, and the source and gate are forward biased, so FET QI8 is turned on.Therefore, operational amplifier Q1
The voltage input to 7 is determined by the variable resistor VRIO. ] When ■ is “L”, all (16 by reverse operation)
The sample and hold voltage input from Q17 becomes the input of Q17. The signal input to Q10 is connected to variable resistor VR8 and VR
Q20.9 is compared with the inverted input voltage determined by Q20.9 and amplified. Consists of Q21. It is supplied as power to the transformer TI via a current booster.

As the voltage applied to the transformer TI increases, the oscillation amplitude increases, and the negative high voltage on the secondary side of the transformer T2 becomes even more negative. This voltage is superimposed on the positive fixed output of block 6-2 and applied to the relay as developing bias DBIAS.
is added to the developing device via. Q17 input is terminal J6
In the case of the sample hold voltage, the characteristics of the developing bias DBIAS with respect to the drum potential are as shown in Figure 12. Here, the variable resistor VR8 is Y in the 12th diagram.
The axis intercept is determined and the resistor VR9 determines the slope. Therefore, if the drum bright area potential is 150V or less, the developing bias voltage DBIAS becomes the bright area potential +75V.

The signal MODE input to the terminal J8 becomes "H" when setting the potential described later, and the sample hold voltage from J6 is selected as the input to Q17. Furthermore, the relay Kl is opened, and the developing bias voltage DBIAS is applied to the developing device. The motor drive signal MD at terminal J9 applies 2 to the relay and the developing bias voltage DBIAS to the ONL developer 25.The sensor bias switching signal S
VCH is “H” when setting the potential.

"L""" is switched to select the sensor bias switching summer AS between the voltage 225V between resistors R76 and R77 or the voltage 150V between R77 and R78. For normal copying, use SV
CH is "H" and +150v is supplied to VBTAS. The sensor power supply 5Vcc is connected from the independent winding Ll of the transformer T2 to D15. The voltage rectified and smoothed by C10, R9, C17, and C18 is used as a power supply, and +24V is added to the sensor bias voltage VBIAS, so VBT
Even if AS is switched, 5Vcc always becomes +24V.

Further, as shown in the time chart of FIG. 15, in this embodiment, the signal BE indicating the light amount of the blank exposure lamp 10 is
When measuring the potential of XP, the light is adjusted to a predetermined amount of light, and after the recording of an image on the recording medium is completed, the light amount is switched to the predetermined amount or more. In other words, when measuring the surface potential, the light intensity of the blank exposure lamp is adjusted to a light intensity within the dynamic range in which the surface potential changes with respect to the light intensity, and after recording is completed, the light intensity of the blank exposure lamp is adjusted to a high intensity to expose the photosensitive layer. It has become possible to eliminate the non-uniform electric field caused by carriers generated within.

Next, regarding the mode switch as a drum potential setting.
The explanation will be given according to FIG. 6 and Table 1.

To set the appropriate potential for the drum when replacing the drum or adjusting the image when assembling the machine, as shown in Table 1, the dark area potential VD, bright area saturation potential VSL, and bright area potential V of a standard white original are set.
IMAGE, etc., and when the developing bias is controlled, the bright area potential Vl due to the weak blank must be set appropriately.

At this time, by providing a switch that can select each setting mode as shown in the mode switch 202 in FIG.
Just by pressing a switch, you can select the load driving conditions that will cause each set potential to occur on the drum. mode switch s
wl is for turning off the blank exposure lamp and setting the dark potential VD, which corresponds to the dark potential of the original, to the target potential +450V, and adjusting the output of the surface electrometer and the wires of the three primary chargers to set the target potential. Set to potential.

The mode switch SW2 strongly lights up the blank exposure lamp to set the bright area side saturation potential VSL of the photosensitive drum to the target potential -15.
This is to set the potential to 0V, and adjust the output of the AC static eliminator while detecting the output of the surface electrometer to set the target potential.

The mode switch SW3 is for lighting the blank exposure lamp weakly and setting the bright area potential VL corresponding to the bright area of the photosensitive drum to a target potential of -75V.The blank exposure lamp is turned on while detecting the output of the surface electrometer. The bright area potential VL is set to the target potential by adjusting the variable resistor VR3 for adjusting the amount of light.

The mode switch SW4 is controlled by the bright area potential VL due to the blank dimming set by SW3 and the bright area due to the reflected light when a standard white document is illuminated by the halogen lamp at the position of the light emission amount adjustment dial 5 of the halogen lamp for document exposure. Potential VIM
This switch is used to adjust the aperture of the halogen lamp so that the AGE matches the AGE. Before pressing the mode switch SW4, place a standard white original on the platen 14, set the light emission amount adjustment dial on the operation unit to position 5, and then press the mode switch SW5 to drive the optical system forward clutch and expose the original. An optical system consisting of a lamp and a mirror is stopped at a position where the white original is irradiated with light from the original exposure lamp.

Thereafter, by pressing the mode switch SW4 and adjusting the aperture of the halogen lamp fMi while detecting the surface electrometer output, the VIMAGE and the bright area potential VL are made to match. In this way, the light intensity of the blank exposure lamp for developing bias control measurement (blank weak) is matched with the reflected light intensity when a standard white document is illuminated with light from a 710 gen lamp at position 5 of the light-emitting adjustment dial, and the developing bias is This makes control more accurate. Furthermore, the CPU 201 in FIG. 6 outputs the sensor bias voltage VBIA according to each mode.
, S to set the difference between the target drum potential shown in Table 1 and the sensor bias voltage V r31 A S to a constant value, the adjuster can set different potentials.
Each adjustment can be made to match a single value without having to memorize various values. When the mode switch SWI is pressed, pre-programmed outputs are output from the CPU 201 and sent via the driver DR to the main motor drive signal MD, high voltage charger on signal HVI,
A high voltage AC static eliminator on signal HV2 is output. Furthermore, the signal MD is also supplied to the sensor motor drive circuit 203 and the developing bias control circuit 207 via 76 and 75, respectively, so that the sensor motor rotates and the potential detection signal is sent to the AC amplifier 204, the DC regeneration circuit 205, the sample The signal path from the hold circuit 206 to the developing bias control circuit 207 is closed. At this time, the strobe signal S
Since TB also becomes "H", STB becomes "L", the analog switch FETQII in FIG. 11 in the sample hold circuit 206 turns on, and the sensor bias switching signal 5
Since vCH is "L", SVCM becomes "L", and contact 3 of the relay in FIG. 12 is connected to the +150V side, and is supplied to the sensor housing, chopper and internal circuit as developing bias voltage VBIAS. When the mode switch 202 is pressed, a judgment signal MODE indicating whether or not the mode switch is pressed
becomes "H", transistor Q19 and relay Kl in FIG. 13 are turned on, the input of operational amplifier Q17 is selected by the signal J6, and the developing bias DBIAS going to the developing unit is cut off. On the other hand, in FIG.
4 are ONL and other exposure irradiation is not performed, so the surface potential of the drum measured by the electrometer 50 is the dark area potential VD corresponding to the dark area of the document.

At this time, the check terminal J5 exhibits the characteristics shown in FIG. 12(A), so when the target dark potential is 450V, the adjuster
Adjust VRI of the next phase electric wire and set terminal J5 to 2V (
12V standard). Similarly, when the potential setting mode switches SW2 to SW3 shown in Table 1 are pressed, the surface potential of the drum detected by the electrometer 50 changes to bright area saturation potential VSL and blank dimming according to the pre-programmed load drive conditions. The bright area potential VL is caused by the light reflected from the halogen of the standard white document, and the potential VrMAGE is caused by the reflected light from the halogen of the standard white original.Furthermore, the mode switch SW3.4 switches the sensor bias VBIAS to 225■, and as is clear from Fig. 12 (A), the setting Mode switch SW at target potential
Even though I, 3゜4 are different, check terminal J5 is set to 2V (12V standard) using high-voltage AC output regulator VR2 and blank exposure lamp light intensity regulator VR3.
, it is only necessary to adjust the halogen aperture adjuster VR4. By providing this mode switch 202, the electrometer 50 not only has the role of simply controlling the developing bias and preventing fog, but also serves as a built-in electrometer for setting the potential. . Furthermore, there is an advantage that the adjuster can adjust only one value without having to memorize the value of each set potential.

Further, by using a comparison circuit as shown in FIG. 14, it is possible to display the surface potential detection output by level.

The DC reproduction voltage of the surface potential detection circuit is input to the non-inverting input terminal of the comparator COMI-COM5, and the comparison voltage Vl-V5 is input to the inverting input terminal. Comparison voltage vl~v
5 magnitude 1tVl>V2>V3>V4. >V5 is set. The regulators VRI to VR4 are adjusted so that only the light emitting diode LED3 lights up. In this way, it has become possible to adjust different surface potentials just by lighting the same light emitting diode. Further, the mode switch can selectively drive some of the plurality of processing means for image formation. By providing such a command means, when checking the operating state of an image forming apparatus such as a copying machine, it has become possible to closely examine the operating state of a part of the apparatus without driving the entire apparatus. Furthermore, when measuring the surface potential of different modes (bright area potential, dark area potential, etc.) on the drum using a surface electrometer, it is effective because the load can be selectively driven so that the surface potential of the desired mode can be easily measured.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a copying apparatus to which the present invention can be applied;
The figure is a cross-sectional view showing the mounting position of the surface electrometer and the drum, Figure 3 is a side sectional view of the electrometer, Figure 4 is a surface potential detection circuit diagram, Figure 5 is a perspective view of the squirrel cage chopper, and Figure 6 is a cross-sectional view showing the mounting position of the surface electrometer and drum. The figure is a control circuit diagram of the copying machine shown in Figure 1, Figure 7-1 is an output waveform diagram of the electrometer, and Figure 7-2 is the drum potential Vp and the peak value of the output 62 from the preamplifier using the sensor bias VBIAS as a parameter. Figure 8 is a diagram showing the photosensitive characteristics of the photosensitive plate, Figure 9 is a diagram showing changes in the characteristics of the photosensitive plate due to environmental changes, Figure 10 is a rotation control circuit diagram of the sensor motor, and Figure 11 is a diagram showing the characteristics of the photosensitive plate. 6 is a detailed circuit diagram of the amplifier circuit 204, rectifier smoothing circuit 205, and sample hold circuit 206. FIG. 12 is a diagram showing the relationship between the surface potential Vp and the output of each part in FIG. 14 is a comparison display circuit diagram, and FIG. 15 is a timing chart of the copying apparatus of FIG. 1. In the figure, 10 is a blank exposure lamp, 11 is a photosensitive drum, 16 is an original exposure lamp, 22 is a primary charger, 23 is a static eliminator, 24 is a full exposure lamp, 25 is a developer, 50 is a surface electrometer, and 52 is an electric potential 53 is a cage type chopper, 54 is a measurement electrode, Ql is a junction type FET, VBIAS is an electrometer bias voltage, Vcomp is a compensation voltage, SW1~
SW6 indicates a mode switch.

Claims (1)

[Scope of Claims] An image forming means for forming an image on a recording medium, a command means for inputting first mode and second mode signals, and a method according to the first and second mode signals output from the command means. and control means for controlling the operation of the image forming means, the control means operating a part of the image forming means at different levels in the first mode and the second mode. Image forming device.