Electrophotographing apparatus having a toner empty discriminating unit

A toner near empty discriminating unit discriminates a near empty indicating that the toner approaches an empty state on the basis of a detection value of a toner sensor. When the toner near empty is determined, a toner supply amount calculating unit calculates a toner supply amount (w) per time as w=W/X from the number (X) of toner supplying times of a toner supply counter and a specified toner filling amount (W) when a toner cartridge is set. On the basis of the calculated toner supply amount (w) of one time, a correction processing unit corrects a rotational speed of a supply roller of a toner supply control unit and an operation time of the supply roller, or the number of discriminating times of the toner empty and the number of discriminating times of a replacement of an expendable item.

BACKGROUND OF THE INVENTION 
The invention relates to an electrophotographying apparatus which is used 
in a printer, a copying apparatus, a facsimile apparatus, or the like such 
that after an electrostatic latent image formed onto a photosensitive drum 
was developed by a two-component developing agent composed of toner and 
carrier, the developed image is transferred onto a paper. More 
particularly, the invention relates to an electrophotographying apparatus 
in which a toner supply amount is obtained on the basis of the number of 
supplying times of the toner from a toner hopper provided for a developing 
unit, thereby discriminating a toner near empty, a toner empty, a 
replacement of an expendable item, and the like. 
Hitherto, in an electrophotographying apparatus which is used in a printer, 
a copying apparatus, a facsimile apparatus, or the like, an electrostatic 
latent image is formed onto a photosensitive drum by a scan of a light 
beam, a toner image is developed by a developing unit by using a 
two-component developing agent composed of toner and carrier, and the 
developed toner image is transferred and fixed onto a paper which is 
conveyed, thereby obtaining a clear print image. A toner hopper filled 
with toner is attached to the developing unit. When the toner in the 
developing unit is consumed by the development, a toner supply roller 
provided for the toner hopper is driven, thereby supplying a predetermined 
amount of toner. The toner contained in the toner hopper is monitored, a 
toner near empty slightly before the toner becomes empty or a toner empty 
when the toner is empty is detected, and such a state is displayed to the 
user, thereby promoting the user to fill the toner by setting a toner 
cartridge. In the detection of the near empty or empty of the toner in the 
electrophotographying apparatus as mentioned above, since a toner supply 
amount of one time is determined by a rotational speed of a toner supply 
roller and a supply rotation time, the number of supplying times of the 
toner is counted, and when it reaches a specified number of times to 
discriminate a predetermined near empty or empty, the near empty or empty 
is displayed, thereby requesting the user to exchange the toner cartridge. 
In the conventional discrimination of the near empty or empty of the toner 
based on the number of toner supplying times as mentioned above, however, 
since a variation of the toner supply amount of one time is large, there 
is a problem such that the toner state cannot be correctly discriminated. 
That is, a fluidity of the toner largely fluctuates due to an influence by 
an environmental humidity of the apparatus and a variation of the toner 
supply amount of one time which is supplied from the toner hopper is 
large. Therefore, when the near empty or empty of the toner is detected by 
the predetermined number of supplying times of the toner, a difference 
between the detected toner amount and an actual remaining toner amount 
increases and a detecting precision deteriorates. Therefore, in the case 
where a large quantity of toner remains in the toner hopper because the 
toner empty is detected too early, when the toner cartridge is set and the 
toner is filled, there is possibility such that the toner overflows and 
makes the inside of the apparatus dirty. Particularly, when a paper 
conveying path is made dirty by the toner, a stain of the print occurs. 
Moreover, in case of getting extremely dirty, there is a case where not 
only the inside of the apparatus but also the floor or the user becomes 
dirty. When the detection of the toner empty is delayed, the toner is 
insufficient and a print density decreases during the use of the 
apparatus. Further, since the carrier is agitated in a state in which the 
toner density of the two-component developing agent in the developing unit 
decreases, a stress is given to the carrier and there is a problem such 
that a life of the developing agent is shortened or the like. Further, in 
the electrophotographying apparatus, with respect to expendable items such 
as desmoke filter of an apparatus using a cleaning blade, a cleaning 
brush, and a flash fixing unit, a toner collection filter of an apparatus 
using a cleaning blower, and the like in which lives are largely concerned 
with a toner consumption amount, a replacement timing is determined on the 
basis of the number of supplying times of the toner. In this case, in 
consideration of a variation of the toner supply amount, the number of 
supplying times of the toner until the replacement is set to be slightly 
small. Therefore, there are problems such that the replacement period of 
the expendable item is shorter than it is necessary, a load of the 
replacing work by the operator increases, and the running costs rise. 
In order to decrease the variation by the counting of the number of 
supplying times of the toner, on the other hand, a construction in which a 
toner sensor is attached to the toner hopper and the toner near empty and 
toner empty are detected is also considered. However, even when the toner 
sensor is attached, there is a variation in a sensor detection signal. A 
sensor discrimination value for detecting early the toner near empty or 
toner empty is set in order to prevent the variation. Therefore, the near 
empty or empty is detected early by the toner sensor and there is a fear 
such that the toner overflows at the time of the setting of the toner 
cartridge and makes the inside of the apparatus dirty. There is a case 
where the toner sensor erroneously detects the toner near empty or toner 
empty due to a noise, a failure of the sensor, or the like. There is also 
a problem such that a detecting stability lacks as compared with the case 
of the counting of the number of supplying times of the toner. 
SUMMARY OF THE INVENTION 
According to the invention, there is provided an electrophotographying 
apparatus which can correctly discriminate a near empty or empty of a 
toner and, further, a replacement timing of an expendable item by 
calculating an actual toner supply amount on the basis of a count value of 
the number of supplying times of the toner. 
According to the invention, there is provided an electrophotographying 
apparatus in which an electrostatic latent image formed on a 
photosensitive drum (photosensitive material) is developed and, 
thereafter, is transferred onto a paper, comprising: a developing unit for 
developing the electrostatic latent image on the photosensitive drum by a 
two-component developing agent composed of toner and carrier; a toner 
density sensor for detecting a toner density of the 2-component developing 
agent in the developing unit; a toner hopper containing the toner to be 
supplied to the developing unit by receiving a filling of a specified 
amount (W) of toner by the setting of a toner cartridge; and a toner 
supplying mechanism for supplying the toner from the toner hopper to the 
developing unit by the driving of a toner supply roller. The control unit 
comprises: a toner supply control unit for supplying a specified amount w0 
of toner from the toner hopper to the developing unit by driving a toner 
supply roller; each time the detection density of the toner density sensor 
is equal to or less than a specified value, a toner sensor for detecting 
the toner contained in the toner hopper; a toner near empty discriminating 
unit for discriminating a toner near empty indicating that the toner 
approaches an empty state on the basis of a detection value of the toner 
sensor; a toner supply counter which is reset when the toner is filled by 
the setting of a toner cartridge and counts the number (X) of toner 
supplying times by the toner supply control unit; and a toner empty 
discriminating unit for discriminating a toner empty state on the basis of 
the count value (X) of the toner supply counter. 
The invention is characterized in that there is provided a toner supply 
amount calculating unit for calculating a toner supply amount (w) per time 
as w=W/X from the number (X) of toner supplying times of the toner supply 
counter and a specified toner filling amount (W) when the toner cartridge 
is set in the case where a toner near empty state is discriminated by the 
toner near empty discriminating unit and that the actual toner supply 
amount per time can be recognized by the apparatus itself. Further, a 
correction processing unit is provided. The correction processing unit can 
correct control parameters of the toner supply control unit on the basis 
of the toner supply amount (w) of one time calculated by the toner supply 
amount calculating unit so as to keep a predetermined specified toner 
supply amount w0 of one time. For example, when a rotational speed (R) and 
a supply operation time (T) of the toner supply roller of a toner 
supplying mechanism to determine the toner supply amount of one time have 
been preset as control parameters of the toner supply amount control unit, 
the correction processing unit obtains a ratio (w0/w) between the 
specified toner supply amount w0 and the toner supply amount (w) 
calculated by the toner supply amount calculating unit as a correction 
coefficient (K), thereby correcting to a correction rotational speed 
(K.multidot.R) in which the roller rotational speed (R) is multiplied by 
the correction coefficient (K). Therefore, the toner supply amount per 
time for a period of time from a timing when the toner is filled by the 
setting of the cartridge to a timing when a next toner near empty state is 
detected can be adjusted so as to be the specified toner supply amount w0. 
The discrimination about the toner empty based on the number of toner 
supplying times can be more accurately performed. 
The correction processing unit corrects to a correction operation time 
(T.multidot.R) by multiplying a supply operation time (T) of the toner 
supply roller by the correction coefficient (K) obtained as a ratio (w0/w) 
between the specified toner supply amount w0 and the calculated toner 
supply amount (w). In this case as well, a toner supply amount per time 
for a period of time from a timing when the toner is filled by the setting 
of the cartridge to a timing when a next toner near empty state is 
detected can be adjusted so as to be equal to the specified toner supply 
amount w0. The discrimination about the toner empty based on the count 
value of the number of toner supplying times can be more accurately 
performed. Further, toner empty discriminating unit discriminates the 
toner empty state in which the number (X) of toner supplying times counted 
by the toner supply counter reaches a predetermined number N1 of 
discriminating times of the toner empty. In this case, the correction 
processing unit obtains the ratio (w0/w) between the specified toner 
supply amount w0 and the toner supply amount (w) calculated by the toner 
supply amount calculating unit as a correction coefficient (K), thereby 
correcting to a correction number of discriminating times (K.multidot.N1) 
obtained by multiplying the number N1 of toner empty discriminating times 
by the correction coefficient (K). Therefore, the number of toner empty 
discriminating times is corrected to the number of discriminating times 
according to a change in actual toner supply amount (w) without needing to 
correct the rotational speed (R) or supply operation time (T) of the toner 
supply roller so as to set the toner supply amount per time to the 
specified toner supply amount w0. The toner empty state can be more 
accurately detected. As a method of correcting the number of toner empty 
discriminating times by the correction processing unit, it is corrected to 
a value (A.multidot.K.multidot.N1) in which the correction value 
(K.multidot.N1) is further multiplied by a specified delay coefficient (A) 
(A&gt;1) to delay the discrimination about the toner empty. Thus, the toner 
empty is detected early, thereby certainly preventing that the toner 
overflows due to the filling of the toner by the setting of the toner 
cartridge. The control unit further comprises: a life counter of an 
expendable item which is reset at the time of replacement of the 
expendable item and counts the number (Y) of toner supplying times by the 
toner supply control unit; and an expendable item replacement 
discriminating unit for discriminating a replacement of the expendable 
item when the number (Y) of toner supplying times counted by the life 
counter reaches a predetermined number N2 of discriminating times about 
the replacement of the expendable item. In this case, the correction 
processing unit obtains the ratio (w0/w) between the specified toner 
supply amount w0 and the toner supply amount (w) calculated by the toner 
supply amount calculating unit as a correction coefficient (K), thereby 
correcting to a correction number of discriminating times (K.multidot.N2) 
obtained by multiplying the number N2 of replacement discriminating times 
by the correction coefficient (K). Therefore, the number of discriminating 
times about the replacement of the expendable item is corrected to the 
value according to the actual change in toner supply amount (w) without 
needing to correct the rotational speed (R) or supply operation time (T) 
of the toner supply roller so as to set the toner supply amount per time 
to the specified toner supply amount w0. A timing to replace the 
expendable item can be more accurately discriminated. The expendable item 
replacement discriminating unit discriminates timings to replace, for 
example, a cleaning blade, a cleaning brush, a desmoke filter of a flash 
fixing unit, a toner collecting filter of a cleaning blower, and the like. 
Another embodiment of the invention is characterized in that only a toner 
empty discriminating unit for discriminating a toner empty state of a 
toner hopper on the basis of a detection signal of a toner sensor without 
performing a discrimination about a toner near empty state based on a 
detection value of the toner sensor is provided and that, when the toner 
empty is discriminated, a toner supply amount (w) per time is calculated 
by a toner supply amount calculating unit from the number (X) of toner 
supplying times of a toner supply counter and a predetermined toner 
filling amount w0 of the toner cartridge. That is, the actual toner supply 
amount (w) per time is calculated from the specified toner filling amount 
(W) by the setting of the toner cartridge and the number (X) of toner 
supplying times until the discrimination of the toner empty sate based on 
the toner sensor and is recognized by the apparatus. In this case, the 
correction of the rotational speed (R) or supply operation time (T) of the 
toner supply roller in the toner supply control or the correction of the 
number N2 of discriminating times about the replacement of the expendable 
item is substantially the same as that in the fundamental embodiment. 
The above and other objects, features, and advantages of the present 
invention will become more apparent from the following detailed 
description with reference to the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Construction and functions of apparatus! 
FIG. 1 shows an embodiment of an electrophotographing apparatus to which 
the invention is applied and relates to a page printer as an example. 
According to a page printer 10, a continuous paper 13 is enclosed in a 
hopper 12. The continuous paper pulled out from the hopper 12 passes 
through a paper conveying path 14 and is sent to a stacker 15. A 
photosensitive drum unit 16 is provided in the middle of the paper 
conveying path 14. An optical unit 20 and a developing unit 22 are 
provided for the photosensitive drum unit 16. Further, a control unit 24 
is provided, thereby performing a print control of the page printer 10. 
The photosensitive drum unit 16, optical unit 20, and developing unit 22 
construct a main portion of the electrophotographying apparatus according 
to the invention. The photosensitive drum unit 16 forms an electrostatic 
latent image by a scan of a light beam from the optical unit 20 onto a 
photosensitive drum. The developing unit 22 develops the electrostatic 
latent image on the photosensitive drum by using a developing agent. After 
that, the image is transferred onto the continuous paper which is fed 
along the paper conveying path 14 and is fixed by a fixing unit 35, 
thereby printing. 
FIG. 2 shows a detailed structure of the photosensitive drum unit 16 and 
developing unit 22 in FIG. 1. A photosensitive drum 18 is rotated 
counterclockwise at a predetermined speed by a motor (not shown). Two 
pre-charging units 26-1 and 26-2 are installed around the photosensitive 
drum 18 on the right side of the upper portion, thereby uniformly charging 
the surface of the photosensitive drum 18. Subsequently, an LED print head 
28 is provided. An LED array in which a number of LEDs are arranged in the 
longitudinal direction of the drum is used as an LED print head 28. A 
print pattern is exposed by a light emission driving of the LED array 
according to print information, thereby forming an electrostatic latent 
image onto the photosensitive drum 18. The electrostatic latent image 
formed on the photosensitive drum 18 is developed by toner components of a 
2-component developing agent containing carrier and toner at the position 
of the developing unit 22 and becomes a toner image. On the other hand, 
the continuous paper to print is sent to a transfer position of the 
photosensitive drum 18 by a paper conveying unit 30. A transfer charging 
unit 32 is arranged at the transfer position so as to face the 
photosensitive drum 18. The toner image on the photosensitive drum 18 is 
transferred onto the paper by the transfer charging unit 32. The toner 
image transferred onto the paper is fixed by the fixing unit 35 shown in 
FIG. 1. A thermal fixing unit for fixing by a heat, a flash fixing unit 
for fixing by the light, a pressure fixing unit for fixing by a pressure, 
or the like can be used as a fixing unit 35. The residual toner remaining 
without being transferred exists on the photosensitive drum 18 after 
completion of the transfer of the toner image onto the paper by the 
transfer charging unit 32. A cleaning brush 34 is provided to remove the 
residual toner, thereby mechanically removing the residual toner on the 
photosensitive drum 18. Subsequently, a discharging LED 38 is provided, 
thereby performing a discharging process to return an electric potential 
on the photosensitive drum 18 to a zero volt in an initial state. A 
two-component developing agent comprising a toner component consisting of 
a fine particles of a coloring resin and a magnetic component consisting 
of fine magnetic carrier is contained in the developing unit 22. The 
2-component developing agent comprising the toner component having a mean 
diameter of, for example, 10 .mu.m and the magnetic carrier having a mean 
diameter of 80 .mu.m is used. The toner is supplied from a toner hopper 42 
to the developing unit 22. For example, by setting a toner cartridge 44 to 
an upper portion, the toner of a specified amount, for example, 600 g can 
be filled into the toner hopper 42. As will be obviously understood from 
the following description, when a detection value of a toner density 
sensor provided for the developing unit 22 is equal to or less than a 
specified value, the toner is supplied from the toner hopper 42 to the 
developing unit 22 by driving a toner supply roller provided for the toner 
hopper 42 at a specified rotational speed for a specified time. 
FIG. 3 is a detailed structure of the developing unit 22 in FIG. 2. The 
inside of a container of the developing unit 22 is divided to right and 
left portions by a partition wall 52 at the center of a bottom portion. 
Pre-stirring rollers 46 and 48 and a screw roller 50 are arranged on the 
right toner supplying side. The toner is supplied to installing portions 
of the pre-stirring rollers 46 and 48 from a toner supply roller 80 
provided for the toner hopper 42 installed on the right side. The toner 
supplied from the toner hopper 42 is sent to the screw roller 50 side by 
the clockwise rotations of the pre-stirring rollers 46 and 48 and is sent 
in the axial direction by the counterclockwise rotation of the screw 
roller 50 and is fed to the left side of the partition wall 52 at an axial 
end. A screw roller 54 is arranged on the left side of the partition wall 
52. The screw roller 54 is rotated clockwise in the reverse direction for 
the screw roller 50, thereby feeding the toner in the axial direction 
opposite to that of the screw roller 50. The 2-component developing agent 
is circulated in the developing unit 22 by the rotation in the reverse 
directions of the screw rollers 50 and 54. The toner component and the 
magnetic carrier component are mutually frictionally charged by stirring. 
A magnet roller is used for a conveyer roller 55. The magnetic carrier is 
adsorbed around the conveyer roller 55, thereby forming a magnetic brush. 
The toner component is electrostatically adhered to the ears of the 
magnetic brush, thereby supplying the toner component to each of a first 
development magnet roller 58, a second development magnet roller 60, and a 
third development magnet roller 62 arranged around the photosensitive drum 
18 in the upper portion, respectively. A length of each ear of the 
developing agent of the magnetic brush which is formed on the conveyer 
roller 55 is restricted by a pre-doctor blade 56. The supply of the 
developing agent to the conveyer roller 55 by the screw rollers 50 and 54 
is restricted by a flow guide plate 74. A length of each ear of the 
magnetic brush formed on each roller is restricted by scrapers 66, 68, 70, 
and 72. Further, a doctor blade 64 is arranged around the first developing 
magnet roller 58. A length of each ear of the toner component by the 
magnetic brush of the first magnet roller 58 is restricted by the doctor 
blade 64, thereby uniforming a developing density of the toner image for 
the photosensitive drum 18. The first to third development magnet rollers 
58, 60, and 62 are rotated counterclockwise in the same direction as that 
of the photosensitive drum 18 and a peripheral speed of each of them is 
set to a speed that is, for example, twice as high as a peripheral speed 
of the photosensitive drum 18. For the movement of the electrostatic 
latent image by the rotation of the photosensitive drum 18, the 
development is sequentially performed in accordance with the order of the 
third development magnet roller 62, second development magnet roller 60, 
and first development magnet roller 58. Finally, a collecting magnet 
roller 65 is provided, thereby removing the unnecessary toner component of 
the developed toner image. A toner density sensor 76 is arranged in the 
lower portion of the screw roller 50 of the bottom portion of the 
developing unit 22. The toner density sensor 76 detects a toner density of 
the 2-component developing agent in the developing unit 22 and generates a 
detection signal. 
FIG. 4 shows the toner density sensor 76 in FIG. 3. According to the toner 
density sensor 76, input windings 98 and 100 are wound on both sides 
around a core 96 and are serially connected and an output winding 102 is 
wound between them. The operation of the toner density sensor 76 is 
performed by applying a specified DC voltage Vin to a portion between 
input terminals 150 and 152. When the input voltage Vin is applied, 
divided voltages V1 and V2 are applied to the input windings 98 and 100, 
respectively, and a specified input current flows. Therefore, a magnetic 
flux 105 passing through the portion of the output winding 102 is formed 
by the input winding 98. At the same time, a magnetic flux 104 passing in 
a developing agent 106 is formed by the input winding 100. An intensity of 
the magnetic flux 104 passing in the developing agent 106 is changed by 
carrier 108 serving as a magnetic component of the developing agent 106 
and toner 95. That is, when a quantity of toner 95 is large, a 
permeability decreases. When the quantity of toner 95 is small, the 
permeability is raised. When the permeability is low because the quantity 
of toner 95 is large, a sensor output voltage Vout from output terminals 
154 and 156 by the output winding 102 is low. On the contrary, when the 
quantity of toner 95 decreases and the permeability is raised, the output 
voltage Vout of the output winding 102 rises. That is, the toner density 
sensor 76 generates a detection output according to a ratio between the 
carrier 108 and toner 95 constructing the developing agent 106 as a toner 
density detection signal. 
FIG. 5 shows a detailed structure of the toner hopper 42 in FIG. 2. The 
toner hopper 42 has a cartridge attaching portions 92 and 93 in the upper 
portion. When the toner cartridge 44 is attached to the cartridge 
attaching portion 92 and 93 as shown in the diagram and a seal 90 which 
closes the lower portion of the toner cartridge 44 is peeled off, a 
predetermined specified amount (W) (for example, W=600 g) of toner 95 can 
be filled into the toner hopper 42. Agitators 82, 84, and 86 are laterally 
arranged in the toner hopper 42 into which the toner 95 was filled from 
the toner cartridge 44. The toner supply roller 80 is arranged in the 
portion of a toner supply port 88 opening in the lower portion of a 
projecting portion on the left side. A plurality of grooves in the axial 
direction are formed on the outer periphery of the toner supply roller 80. 
The toner supply amount from the toner hopper 42 to the developing unit 
can be determined by a rotational speed and a rotating time. Rotational 
radii of the agitators 82, 84, and 86 are sequentially set to be smaller 
from the right side to the left side. When the toner is supplied by the 
rotation of the toner supply roller 80, the agitators 82, 84, and 86 are 
rotated counterclockwise, thereby feeding the toner 95 to the toner supply 
roller 80 side. A specified value w0 of the toner supply amount of one 
time of the toner that is fed to the developing unit by the driving of the 
toner supply roller 80 is determined to, for example, w0=0.5 g. A toner 
sensor 94 is arranged to the bottom portion of the agitator 82 provided 
for the toner hopper 42. A transmitting type sensor or a piezoelectric 
sensor can be used as a toner sensor 94. The toner sensor 94 is used to 
discriminate a toner near empty state when the toner 95 filled in the 
toner hopper 42 approaches a state in which it is extinguished or a toner 
empty state in which the toner is extinguished. 
FIG. 6 is a block diagram of the control unit 24 in FIG. 1. A controller 25 
using an MPU is provided for the control unit 24. The toner density sensor 
76 provided for the developing unit 22 in FIG. 3 and the toner sensor 94 
provided for the toner hopper 42 in FIG. 5 are connected to the controller 
25. A toner supply motor 110 to drive the toner supply roller 80 provided 
in FIG. 5 is connected. The optical unit 20, developing unit 22, paper 
conveying unit 30, or the like shown in FIG. 1 are also connected. 
Further, the controller is connected to an upper host computer through a 
host interface 112 and can receive print information. A display unit 114 
and an operation panel unit 122 are provided for the controller 25. In the 
invention, a toner near empty display 116, a toner empty display 118, and 
an expendable item replacement display 120 are provided for the display 
unit 114. Display lamps such as independent LEDs or the like can be also 
used as such displays. Messages indicative of a toner near empty, a toner 
empty, and an expendable item replacement can be also displayed onto the 
liquid crystal display by characters. Further, numbers indicative of the 
toner near empty, toner empty, and expendable item replacement can be also 
displayed. Various operation switches necessary for the operation of the 
page printer 10 in FIG. 1 are provided for the operation panel unit 122. 
FIG. 7 is a functional block diagram for a detection discriminating process 
about the number of toner supplying times in the electrophotographying 
apparatus of the invention which is realized by the controller 25 in FIG. 
6. First, a register 124, a toner density discriminating unit 126, and a 
toner supply control unit 128 are provided for the controller 25 for the 
purpose of a control of the toner supply motor 110 to supply the toner to 
the developing unit 22 by driving the toner supply roller 80 provided for 
the toner hopper 42 in FIG. 5. A toner density detection value of the 
toner density sensor 76 provided for the developing unit 22 in FIG. 3 is 
stored into the register 124. The toner density discriminating unit 126 
compares a predetermined discrimination reference value of a decrease in 
toner density with the toner density detection value stored in the 
register 124. When the detection value is equal to or less than the 
discrimination value of the decrease in toner density, the toner density 
discriminating unit 126 determines the reduction of the toner density and 
activates a toner supply control unit 128. A rotational speed (R) and a 
supply operation time (T) of the toner supply motor 110 for supplying the 
specified toner supply amount w0 (for example, w0=0.5 g) of toner which 
has been predetermined by a constant storing unit 135 by one time are set 
in the toner supply control unit 128. Therefore, when the discrimination 
output of the reduction of the toner density is received from the toner 
density discriminating unit 126, the toner supply control unit 128 drives 
the toner supply motor 110 at the specified rotational speed (R) and for 
the specified operation time (T), thereby supplying the preset specified 
toner supply amount (w0=0.5 g) of toner to the developing unit 22 by one 
time. However, the actual toner supply amount is not always equal to the 
specified toner supply amount w0=0.5 g. There is a variation time is in 
the toner supply amount of one time is increased or decreased in 
accordance with an environmental humidity of the apparatus. A register 132 
and a toner near empty discriminating unit 134 are provided for the 
controller 25. The toner detection value of the toner sensor 94 provided 
for the toner hopper 42 in FIG. 6 is stored into the register 132. The 
toner near empty discriminating unit 134 compares a predetermined 
specified discrimination value of the toner near empty with the detection 
value stored in the register 132. When the detection value is equal to or 
less than the discrimination value, the toner near empty discriminating 
unit 134 determines a toner near empty state in which the toner in the 
toner hopper approaches an empty state, thereby allowing the toner near 
empty display unit 116 to display a message to promote a replacement of 
the toner cartridge. On the other hand, the number of times of the toner 
supply which is performed by activating the toner supply control unit 128 
when the toner density discriminating unit 126 discriminates the decrease 
in toner density is counted by a toner supply counter 130. It is now 
assumed that a count value of the toner supply counter 130 is set to (X). 
As shown in FIG. 5, when the toner cartridge 44 is set into the toner 
hopper 42 and the toner is filled therein, the toner supply counter 130 is 
reset to X=0. After that, the counter 130 is counted up each time the 
decrease in toner density for the toner supply is discriminated by the 
toner density discriminating unit 126. The count value (X) of the toner 
supply counter 130 is sent to a toner empty discriminating unit 140. A 
specified number N1 of discriminating times to discriminate the toner 
empty state is set into the toner empty discriminating unit 140 from the 
constant storing unit 135. Therefore, when the count value (X) of the 
toner supply counter 130, namely, the number (X) of toner supplying times 
reaches the specified number N1 of toner empty discriminating times, the 
toner empty discriminating unit 140 decides the toner empty state, 
generates a discrimination output, and drives the toner empty display unit 
118 so as to display a replacement, thereby requesting for the operator to 
replace the toner cartridge. The number of toner supplying times based on 
the reduction of the toner density discriminated by the toner density 
discriminating unit 126 is also counted by a life counter 142 provided to 
discriminate a life of an expendable item. A count value of the life 
counter 142 now assumes (Y). The count value (Y) of the life counter 142 
is sent to an expendable item replacement discriminating unit 144. A 
number N2 of discriminating times of replacement of an expendable item to 
decide an expandable item replacement period which has been preset by the 
constant storing unit 135 is set in the expandable item replacement 
discriminating unit 144. Therefore, when the count value (Y) of the life 
counter 142 reaches the number N2 of replacement discriminating times, the 
expendable item replacement discriminating unit 144 determines the 
replacement of the expendable item and generates a discrimination output. 
The discriminating unit 144 drives the expendable item replacement display 
unit 120 so as to display, thereby requesting for the operator to replace 
the expendable item. As expendable items to be discriminated by the 
expendable item replacement discriminating unit 144, there are the 
cleaning brush 34 and a cleaning blade 36 which are provided for the 
photosensitive drum unit 16 in FIG. 3 and in which each life depends on 
the toner supply amount. Further, there are a toner collecting filter, a 
desmoke filter in case of using the flash fixing unit, a toner collecting 
filter in case of using a cleaning blower, and the like. Various constants 
necessary for the detection discriminating process about the number of 
toner supplying times of the invention have previously been stored in the 
constant storing unit 135. A non-volatile memory which can hold storage 
contents even if a power supply of the apparatus is shut off is used as a 
constant storing unit 135. 
FIG. 8 shows the storage contents in the constant storing unit 135 in FIG. 
7. The toner cartridge filling amount (W), the specified toner supply 
amount w0 of one time by the driving of the toner supply roller, the toner 
supply operation time (T) and toner supply rotational speed (R) as control 
parameters by the toner supply control unit 128, the number N1 of toner 
empty discriminating times, and the number N2 of expendable item life 
discriminating times are determined in the constant storing unit 135. For 
example, in this case, W=600 g, w0=0.5 g/time, T=600 msec, R=6 rpm, 
N1=1200 times, and further, N2=6000 times have been stored as constants. 
Referring again to FIG. 7, a toner supply amount calculating unit 136 and a 
correction processing unit 138 are provided subsequent to the constant 
storing unit 135. When the toner near empty is determined from the 
detection value of the toner sensor by the toner near empty discriminating 
unit 134, the toner supply amount calculating unit 136 is activated and 
fetches the number (X) of toner supplying times of the toner supply 
counter 130 at that time. On the basis of the filling amount (W) of the 
toner cartridge which is given from the constant storing unit 135, the 
toner supply amount calculating unit 136 calculates the toner supply 
amount (w) of one time so far when the toner near empty is decided by the 
following equation. 
EQU w=W/X 
For example, when the number (X) of toner supplying times of the toner 
supply counter 130 when the toner near empty is determined in case of the 
toner filling amount (W=600 g) is equal to X=1000 times, the toner supply 
amount (w) of one time at that time is 
EQU w=W/X=600/1000=0.6 g/time 
The correction processing unit 138 obtains a correction coefficient (K) as 
a ratio (w0/w) between the specified toner supply amount w0 of one time 
which is given from the constant storing unit 135 and the actual toner 
supply amount (w) of one time calculated by the toner supply amount 
calculating unit 136. The toner supply rotational speed (R) and toner 
supply operation time (T) serving as control parameters of the toner 
supply control unit 128, the number N1 of discriminating times which is 
set to the toner near empty discriminating unit 140, or the number N2 of 
discriminating times which is set to the expendable item replacement 
discriminating unit 144 is corrected by using the correction coefficient 
(K). There are two modes of a correction mode 1 and a correction mode 2 
for the correction by the correction processing unit 138. In the 
correction mode 1, the toner supply rotational speed (R) or toner supply 
operation time (T) serving as a control parameter set in the toner supply 
control unit 128 is corrected so as to make the actual toner supply amount 
(w) coincide with the specified toner supply amount w0 set in the constant 
storing unit 135. On the other hand, in the correction mode 2, the toner 
supply rotational speed (R) and toner supply operation time (T) of the 
toner supply control unit 128 are not corrected but each of the number N1 
of discriminating times for the toner empty discriminating unit 140 and 
the number N2 of discriminating times for the expendable item replacement 
discriminating unit 144 is corrected. In the correction mode 1 to correct 
the control parameter of the toner supply control unit 128, either one of 
the toner supply rotational speed (R) and the toner supply operation time 
(T) is corrected. That is, in case of correcting the toner supply 
rotational speed (R), the specified supply rotational speed (R) stored in 
the constant storing unit 135 at that time is multiplied by the correction 
coefficient K=(w0/w), thereby correcting to (K.multidot.R). For example, 
when the specified toner supply amount w0=0.5 g/time and the calculated 
toner supply amount w=0.6 g/time, the correction coefficient K=5/6 is 
obtained. By multiplying it by the present supply rotational speed R=6 
rpm, the correction rotational speed R=5 rpm is obtained and is set into 
the toner supply control unit 128. Therefore, in the subsequent toner 
supply control, the number of toner supply rotational speed is reduced 
from 6 rpm so far to 5 rpm. The toner supply amount of one time, namely, 
0.6 g/time is corrected to w=0.5 g/time serving as a specified toner 
supply amount. Even in case of correcting the toner supply operation time 
(T) in the correction mode 2, similarly, for example, when the correction 
coefficient K=5/6, by multiplying it by the specified toner supply 
operation time T=600 msec, 500 msec is obtained as a corrected toner 
supply operation time and is set into the toner supply control unit 128. 
Therefore, in the subsequent toner supply control, the toner supply 
operation time 600 msec so far decreases to 500 msec. The toner supply 
amount can be adjusted from 0.6 g/time so far to 0.5 g/time that is 
coincident to the specified toner supply amount. On the other hand, in the 
process such that the rotational speed (R) and supply operation time (T) 
of the toner supply control in the correction mode 2 are not corrected 
each of the number N1 of discriminating times of the toner empty and the 
number N2 of discriminating times of the expendable item replacement in 
the constant storing unit 135 is multiplied by the correction coefficient 
(K), thereby correcting. For instance, assuming that the correction 
coefficient K=w0/w=5/6, the number N1 of toner empty discriminating times 
(N1=1200 times) set by the constant storing unit 135 is multiplied by the 
correction coefficient K=5/6, thereby correcting to N1=1000 times. As for 
the correction of the number N1 of toner empty discriminating times, it is 
apprehended that if the discrimination of the toner empty is too early, 
the toner overflows to the outside due to the filling of the toner by the 
setting of the toner cartridge and the inside of the apparatus is made 
dirty. Therefore, the correction value is further multiplied by a 
predetermined delay coefficient (A), thereby setting the corrected number 
of toner empty discriminating times to a larger value. For instance, the 
delay coefficient (A) is set to a value larger than 1. If it is set to 
A=1.2, by multiplying the value (1000 times) as a corrected number of 
toner empty discriminating times by the delay coefficient (A), it is 
corrected to, for example, 1200 times. When the number N2 of 
discriminating times of the expendable item replacement is equal to, e.g., 
N2=6000 times, by multiplying it by the correction coefficient K=5/6, it 
can be corrected to the number of discriminating times of the expendable 
item replacement of 5000 times. That is, the number N1 of toner empty 
discriminating times and the number N2 of discriminating times of the 
expendable item replacement are corrected to the values adapted to the 
actual toner supply amount w0 per time calculated by the toner supply 
amount calculating unit 136. Thus, even if there is a variation in the 
toner supply amount of one time, the discrimination of the timing of the 
toner empty and the timing for replacing the expendable item can be more 
accurately realized. 
Calculation of toner supply amount by toner near empty detection! 
FIGS. 9A and 9B are flowcharts for the detection discriminating process of 
the toner supply amount of the invention according to the functional block 
diagram of FIG. 7. First in step S1, a setting process of constants having 
the contents of FIG. 8 is executed. Specifically speaking, the constants 
at that time when they are stored in the constant storing unit 135 as a 
non-volatile memory are read out at the time of turn-on of a power supply 
of the page printer and set into the corresponding control unit or 
discriminating unit, respectively. In step S2, the detection signal of the 
toner density sensor 76 provided for the developing unit 22 is fetched as 
shown in FIG. 3. In step S3, a check is made to see whether it is a 
predetermined specified density or less or not. When the detection density 
by the detection signal of the density sensor is equal to or less than the 
specified density, step S4 follows. The toner supply motor 110 is likewise 
driven at the supply rotational speed (R) and set supply time (T) which 
have been set at that time, thereby supplying a specified amount of toner 
to the developing unit 22 from the toner hopper 42. In step S5, the count 
value (X) of the toner supply counter 130 and the count value (Y) of the 
life counter 142 of the expendable item are counted up, respectively. In 
step S6, the detection signal of the toner sensor provided for the toner 
hopper 42 in FIG. 5 is fetched and compared with the specified near empty 
discrimination value, thereby checking whether the toner is near empty or 
not. If N0, a replacement discriminating process of the expendable item in 
step S8 is executed. The processing routine is again returned to step S2. 
The processes in steps S2 to S6 are repeated. When the near empty is 
determined in step S7, step S9 follows and a check is made to see if the 
toner near empty has been displayed. In the discrimination of the first 
near empty, since the near empty is not displayed, step S10 follows. The 
toner supply amount (w) of one time until the detection of the toner near 
empty is calculated from the filling amount (W) by the toner cartridge and 
the count value (X) of the toner supply counter 130. In step S11, the 
correction coefficient (K) is calculated. Step S12 in FIG. 9B follows and 
a correcting operation of the set value is performed. The correcting 
operation is executed in either the correction mode 1 to correct either 
one of the toner supply time (T) and toner supply rotational speed (R) or 
the correction mode 2 to correct the number N1 of toner empty 
discriminating times and the number N2 of life discriminating times. In 
step S13, the toner near empty is displayed. In the discrimination of the 
toner near empty of the second and subsequent times in step S9 in FIG. 9A, 
steps S10 to S12 are skipped and the processing routine advances to step 
S14 in FIG. 9B. In step S14, a check is made to see if the toner cartridge 
is replaced in response to a replacement request of the toner cartridge to 
the operator by the display of the toner empty in step S12. When the toner 
cartridge is replaced in response to the display of the toner empty, step 
S19 follows and the display of the toner near empty is reset. The count 
value (X) of the toner supply counter 130 is reset to X=0. After that, the 
processing routine is again returned to step S2 in FIG. 9A and the 
processes are repeated. When the toner cartridge is not replaced in step 
S14, step S15 follows and a discriminating process of the toner empty is 
performed. In the discrimination of the toner empty, the corrected number 
of toner empty discriminating times is used in case of the correction mode 
in step S12. In step S15, when the count value (X) of the toner supply 
counter 130 reaches the number N1 of toner empty discriminating times, 
step S16 follows and the toner empty is displayed, thereby requesting the 
replacement of the toner cartridge. For the display of the toner empty, 
the replacement of the toner cartridge is monitored in step S17. The 
processing routine is interrupted until the cartridge is replaced. When 
the operator replaces the toner cartridge in response to the display of 
the toner empty, the processing routine advances from step S17 to step S18 
and the display of the toner empty is reset. After that, the display of 
the toner near empty is reset in step S19. Further in step S20, the toner 
supply counter (X) is reset. The processing routine is returned to step S2 
in FIG. 9A and the processes are repeated. 
FIG. 10 shows the details of the discriminating process of the replacement 
of the expendable item shown in step S8 in FIG. 9A. In the expendable item 
replacement discriminating process, the count value (Y) of the life 
counter 142 of the expendable item is compared with the set number N2 of 
life discriminating times of the expendable item in step S101. When the 
number (Y) of toner supplying times of the life counter reaches the number 
N2 of discriminating times, step S102 follows. The replacement of the 
expendable item is displayed, thereby requesting for the operator to 
replace the expendable item. In step S103, the replacement of the 
expendable item is checked. When the expendable item is replaced, the 
display of the replacement of the expendable item is reset in step S104 
and the count value (Y) of the life counter 142 is reset. The processing 
routine is returned to the main routine in FIG. 9A. 
Calculation of the toner supply amount by the detection of toner empty! 
FIG. 11 is a functional block diagram of another embodiment of the 
detection discriminating process of the number of toner supplying times in 
the electrophotographying apparatus of the invention. The embodiment is 
characterized in that the toner empty is discriminated from the detection 
signal of the toner sensor 94 provided for the toner hopper 42 in FIG. 5, 
thereby calculating the toner supply amount of one time and correcting the 
constants. That is, the register 124 for the toner supply motor 110, toner 
density discriminating unit 126, toner supply control unit 128, toner 
supply counter 130 for counting the number of toner supplying times based 
on the detection of the reduction of the toner density by the toner 
density discriminating unit 126, life counter 142 of the expendable item, 
expendable item replacement discriminating unit 144 for the expendable 
item replacement processing unit 120, further, constant storing unit 135, 
toner supply amount calculating unit 136, and correction processing unit 
138 are the same as those in the embodiment of FIG. 7. On the other hand, 
in the embodiment of FIG. 11, the register 132, toner near empty 
discriminating unit 134, and toner near empty display unit 116 in FIG. 7 
are removed and a register 146, a toner empty discriminating unit 148, and 
the toner empty display unit 118 are provided in place of them. The toner 
empty discriminating unit 148 compares the toner detection value from the 
toner sensor 94 in FIG. 5 stored into the register 146 with a 
predetermined specified value for the toner empty discrimination. When the 
detection value is equal to or less than the specified value, the toner 
empty discriminating unit 148 generates a toner empty discrimination 
output and drives the toner empty display unit 118, thereby requesting the 
operator to replace the toner cartridge. At the same time, the toner 
supply amount calculating unit 136 is activated by the discrimination 
output of the toner empty discriminating unit 148, thereby calculating the 
actual toner supply amount (w) of one time as w=W/X from the count value 
(X) of the toner supply counter 130 at that time and the toner filling 
amount (W) from the constant storing unit 135. A calculation result of the 
toner supply amount is sent to the correction processing unit 138. In a 
manner similar to the embodiment of FIG. 7, in the correction mode 1, 
either one of the toner supply rotational speed (R) and toner supply 
operation time (T) which were set in the toner supply control unit 128 is 
corrected by the correction coefficient (K) obtained as K=w0/w. In the 
correction mode 2, the number N2 of replacement discriminating times of 
the expendable item set in the expendable item replacement discriminating 
unit 144 is corrected. 
FIGS. 12A and 12B are flowcharts for the detection discriminating process 
of the number of toner supplying times according to the embodiment of FIG. 
11. In the flowcharts, although steps S201 to S206 are the same as S1 to 
S6 in the flowchart of FIG. 9A, the toner empty is discriminated in step 
S207 instead of the toner near empty. When the toner empty is 
discriminated, so long as the toner empty is not displayed yet in step 
S209, the toner supply amount (w) of one time is calculated in step S210. 
After that, the correction coefficient (K) is obtained in step S24. A 
correcting operation of the set value is performed in step S212 in FIG. 
12B. The toner empty is displayed in step S213. In step S214, the 
processes are interrupted until the toner cartridge is replaced. When the 
toner cartridge is replaced, it is discriminated. The display of the toner 
empty is reset in step S215. Further in step S216, the count value (X) of 
the toner supply counter 130 is reset to X=0. After that, the processing 
routine is returned to step S202 in FIG. 12A and similar processes are 
repeated. The expendable item replacement discriminating process in step 
S208 in FIG. 12A is the same as that in the flowchart of FIG. 10. 
According to the invention as mentioned above, on the basis of the 
discrimination value of the toner near empty or the discrimination value 
of the toner empty, the actual toner supply amount per time is calculated 
from the count value of the number of toner supplying times so far and the 
first toner filling amount by the toner cartridge and the apparatus can 
recognize it. By correcting the toner supply amount per time to the 
predetermined specified value or by correcting the discrimination value of 
the number of toner supplying times without changing the toner supply 
amount, the toner empty or the life timing of the expendable item can be 
more accurately discriminated. The overflow of the toner due to the 
filling of the toner when the toner cartridge is set can be certainly 
prevented. The timing to replace the expendable item such as cleaning 
blade, cleaning brush, toner collecting filter, or the like can be 
properly set, the replacement frequency can be reduced, and the running 
costs of the apparatus can be reduced. 
The invention is not limited by the numerical values shown in the above 
embodiments. Many proper modifications are possible within a scope of the 
invention without departing from the objects of the invention.