JPH04293070A - Wet type image forming device - Google Patents

Abstract

PURPOSE:To prevent the clogging of a density sensor such as dust or sludge-like toner is stored in a gap between the light emitting element and the light receiving element of the density sensor from occurring. CONSTITUTION:The light receiving element 31 is fitted to a rotary bracket 36a which is freely rotated with a fulcrum 34 as a center and the light emitting element 30 is fitted to a fixed bracket 36b so as to be faced to the element 31. A spring 32 and a solenoid 33 are engaged with the upper end part of the bracket and constituted so that the gap between both elements can be changed by turning on or off the solenoid 33. Then, the prescribed quantity of the gap is kept by turning on the solenoid 33 in the course of copying operation or copying preparation. On the other hand, at a time other than it, in a period when the main power source of the device is turned off, for example, or at a standby time, the gap between both elements is enlarged by turning off the solenoid 33. Thus, the gap between both elements is prevented from being clogged by the dust or the like.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a wet image forming apparatus such as a copying machine, a printer, or a facsimile machine that performs wet development, and more particularly, to preventing contamination of a developer concentration detection device in a developer tank. It is something.

0002

2. Description of the Related Art Conventionally, in this type of wet image forming apparatus, in order to maintain a constant concentration of the developer in the developer tank that stores the developer used in the apparatus, a device is provided in the developer tank. Detect the developer concentration with the developer concentration detection device,
Based on this detection output, toner is replenished into the developer tank as needed from a toner container that is attached to the developer tank and contains high-concentration developer (hereinafter referred to as toner) for replenishing the developer tank. do. FIG. 7 shows an example of a developer concentration detection device (hereinafter referred to as a concentration sensor) in a conventional wet image forming apparatus. This concentration sensor is
Light emitting elements 30 facing each other with a predetermined gap L1
and a light-receiving element 31, the density sensor detects the concentration of the developer by detecting the light transmittance of the developer interposed in the gap between the two elements, and the bracket has a U-shape. The light-emitting element 30 and the light-receiving element 31 are respectively fixed to the mutually opposing arm parts of 36, and an elastic force is applied to the arm part in the direction in which the amount of the gap L1 changes, and A gap adjustment screw 35 is inserted between the tips of each arm. Usually, the gap L1 between the light emitting element 30 and the light receiving element 31 is about 0.3 to 0.7 mm. Since the gap L1 is very narrow, dust 38, dirt, etc. in the developer may get caught between the gaps and remain stuck between the gaps. Then, the toner in the developer becomes dusty.
The sludge-like toner that adhered to the surface of the toner, etc. and later grew to become sludge-like toner got stuck in the gap and caused a blockage in the density sensor. As a result, when the density sensor detects the light transmittance of the developer, the light transmittance is reduced by dust, sludge-like toner, etc. accumulated in the gap, and the concentration of the developer cannot be detected correctly. That is, since the toner is attached between the gaps, the light receiving element 31 cannot receive the light from the light emitting element 30, resulting in an erroneous detection in which the light is determined to be darker than the actual density. As a result, even though the density of the developer is actually lower than the set value range, the density sensor detects that the developer is darker than the set value range, and copying operations are repeated without replenishing toner to the developer. There is a problem in that the density of the developer becomes thinner each time, and the quality of the copied image continues to deteriorate. Since the density sensor jam described above does not recover by itself, when a density sensor jam is discovered due to the copy image quality, a service person has to remove the density sensor from the machine and clean it in order to remove the density sensor jam.

0003

[Problems to be Solved by the Invention] The present invention has been made in view of the above problems, and its purpose is to:
It is an object of the present invention to provide a wet image forming apparatus capable of preventing clogging of a density sensor due to accumulation of dust or sludge-like toner in the gap between a light emitting element and a light receiving element of the density sensor.

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a developer solution that detects the concentration of a developer solution in a developer tank using a light emitting element and a light receiving element that face each other with a predetermined gap. In a wet image forming apparatus equipped with a density detection device, the light emitting element and the light receiving element are supported so that the light emitting element and the light receiving element can selectively take the predetermined gap and a gap larger than the predetermined gap. A supporting means and a gap widening means for maintaining the gap between the light emitting element and the light receiving element at a gap larger than the predetermined gap during a period when the developer concentration detection device is not detecting the developer concentration. It is characterized by:

[0005]

[Operation] In the present invention, during a period when the developer concentration detection device is not detecting the developer concentration, the gap enlargement means increases the gap between the light emitting element and the light receiving element to a gap larger than a predetermined gap for detecting the developer concentration. This releases dust temporarily trapped between both elements during the period when the gap is maintained at a relatively narrow predetermined gap, and also during the period when the developer concentration detection device is not detecting the developer concentration. This prevents new dust etc. from getting caught between the two elements.

[0006]

[Embodiment] An embodiment in which the present invention is applied to a copying machine will be described. First, the overall outline of the copying machine will be explained using FIGS. 1 and 2. The document on the contact glass 60 is irradiated with the illumination device 61, and the reflected light is sent to the scanning mirror 62,
Through the lens 63, an image is formed and projected onto the drum-shaped photoreceptor 1, which is a latent image carrier, which has already been uniformly charged by the corona discharger 2 for uniform charging. Forms an electrolatent image. This electrostatic latent image is turned into a toner image by supplying a developer with a developer 5 provided on the right side of the photoreceptor 1. This toner image is conveyed from a paper feeding section and is controlled by a registration roller 16 at a timing. A transfer charger 6 transfers the image onto a transfer paper which is taken and conveyed to the surface of the photoreceptor 1. The transfer paper on which the toner image has been transferred is separated from the photoreceptor 1 by a separation roller 7, and is discharged outside the machine as copy paper through a fixing device 64. On the other hand, the residual toner on the photoconductor 1 after the transfer is removed by a cleaning device 8 provided on the left side of the photoconductor 1, and the residual charge on the photoconductor 1 after the removal of the residual toner is eliminated by a static elimination lamp 9. Prepare for the next charging by the corona discharger 2. FIG. 3 shows a block diagram of the electrical components of this copying machine. The copying machine's operation key switch unit 50, internal machine state detection unit 51, pulse generator 52 synchronized with the photosensitive drum, etc. are connected to the CPU 53 via buffers. The CPU 53 is connected to a ROM 54, a RAM 55, and input port buffers 56 and 57 via an address bus, a control bus, a data bus, etc.
7 is connected via a driver 58 to loads such as driving and display.

Next, using FIG. 2, handling the developer,
The developing device 5, developer tank 10, cleaning device 8, etc. will be described in detail. In the developing device 5, first and second developing rollers 13 and 14 are disposed within the casing, respectively, with a micro distance of 0.1 to 0.2 mm from the surface of the photosensitive drum 1, and a squeeze roller 25 is arranged between the photosensitive drum 1 and the surface of the photosensitive drum 1. They are arranged on the surface of the body drum 1 at minute intervals of 0.05 mm. The first and second developing rollers 13 and 14 are rotationally driven by a drive device in the direction of the arrow in the opposite direction to the photoreceptor drum 1 and at a faster circumferential speed than the photoreceptor drum 1. In the upper part of the casing,
A liquid supply pipe 12 from a developer tank 10 storing developer
The upper end portion of is provided as a developer supply nozzle. The developer supplied from the nozzle into the casing is stored between the developing rollers 13 and 14 and a scraper that comes into contact with the surface thereof, and is uniformly carried to the surface of the photoreceptor drum 1 by the rotation of the developing rollers 13 and 14. , after developing the latent image on the photoreceptor drum 1, the developing solution tank 10 is passed through a recovery pipe 15 whose upper end is attached to the lowest part of the casing.
returned to the factory and reused.

This developer tank 10 has a toner container 65 for storing toner in the upper lid and a mother liquid container 66 for storing a developer such as Isopar (trade name), which are installed upside down so that their outlets are at the bottom. (see FIG. 1), and a pump drive motor 26 is also attached. Inside, there is a pump 11 which is driven by the drive motor and which supplies developer to the developing device 5 and cleaning device 8 and generates an agitating flow of the developer in the tank. Concentration sensor 24 installed in a position that is submerged inside
is provided. Using the detection signal from the concentration sensor 24, toner from the toner container is replenished into the developer tank 10 based on a well-known toner replenishment control method, and the toner is mixed and agitated by the stirring flow by the pump 11 in the developer tank 10. The developer is stored in the developer tank 10 as a developer. This developer is supplied by the pump 11 to the developing device 5 and the cleaning device 8 through the developer supply pipes 12 and 22, and used for development and cleaning. The developer is circulated by being collected into the developer tank 10 via developer recovery pipes 15 and 23 whose upper ends are connected to the lowest part of the developer tank 10 . As shown in FIG. 5, a toner replenishing device 40 consisting of a solenoid or the like is also provided on the upper lid of the developer tank 10, and when the developer concentration falls below a set value based on a detection signal from the concentration sensor 24, The solenoid is driven by suction, and the valve of the toner container 65, which is normally closed by a spring, is opened by pushing with a lever, and the toner in the toner container 65 is replenished into the developer tank 10. As shown in FIG. 4, when the developer level in the developer tank 10 falls below the reference level, the mother liquid container 66 has a discharge port that communicates with the atmosphere, and the developer in the container is replenished into the tank. It is a feed valve type.

The cleaning device 8 includes a liquid supply hole 18 at the top of the casing, a liquid recovery hole 21 at the bottom of the casing, a liquid diffusion plate 19, a cleaning foam roller 16, and a squeezing roller 20 inside the casing. 18
The developer in the developer tank 10 is supplied through a supply pipe 22 whose upper end is connected to the developer tank 10 , and the developer is supplied to the developer tank 10 through a recovery pipe 23 whose upper end is connected to the solution recovery hole 21 . has been recovered.

Next, the concentration sensor 24 in this embodiment will be explained in detail. FIG. 6 shows the configuration of the detection element section of the concentration sensor 24. As shown in FIG. The light receiving element 31 is attached to a swing bracket 36a, and the swing bracket 36a is rotatable about a fulcrum 34. A spring 32 and a solenoid 33 are engaged with the upper end of the swing bracket 36a. The light emitting element 30 is attached to the fixed bracket 36b so as to face the light receiving element 31. A pillar 37 is provided on the upper part of the fixed bracket 36b to restrict rotation of the swing bracket 36a in a clockwise direction about the fulcrum 34 beyond a predetermined value.
Further, a screw 35 is provided at the lower part of the swing bracket 36a for restricting the swing bracket 36a from rotating more than a predetermined amount in a counterclockwise direction about the fulcrum 34. This screw 35 is for adjusting the gap between the light emitting element 30 and the light receiving element 31, as in the prior art shown in FIG. When the solenoid 33 is OFF, the bracket 36 is abutted against the pillar 37 due to the tensile force of the spring 32, and the gap between the light emitting element 30 and the light receiving element 31 becomes L2. When the solenoid 33 is turned ON, the bracket 36 is turned on by the screw 35.
The gap length becomes L1. The gap L1 at this time is set in advance to 0.3 to 0.7 mm. FIG. 8(a) is an electrical circuit diagram of this concentration sensor. In the figure, 38 is a variable resistor for output adjustment. Figure 8 (
b) is a graph showing changes in the output from the concentration sensor. In this example, when the output reaches a level corresponding to the upper limit of the concentration setting range (the developer concentration corresponds to the lower limit of the thinner side), the developer concentration control circuit sends the solenoid in the toner replenishment mechanism shown in FIG. The drive signal is output, toner is replenished into the developer tank 10, the developer concentration increases, and as a result, the output decreases. Then, as the toner is consumed, the output increases again, and when the above-mentioned upper limit level is reached, toner is replenished. The above steps are repeated to control the developer concentration within the set range.

In this embodiment, the error output of the density sensor due to toner in the developing solution adhering to dust temporarily caught between the light emitting element 30 and the light receiving element 31 and forming a sludge-like state is prevented. In order to prevent this, the solenoid 33 that is engaged with the swing bracket 36a is turned off as appropriate.
By enlarging the gap between both elements 30 and 31, it is made difficult for dust to get caught there, and dust that is already caught can be removed. Below, both elements 3 are controlled by the drive control of the solenoid 33.
Gap control between 0 and 31 will be explained. First, when the detection output from the concentration sensor 24 is read into the developer concentration control circuit to determine whether or not toner replenishment is necessary, it is assumed that both elements 30 and 31 are facing each other with a predetermined gap. Since the level for determining the necessity of toner replenishment is set in , it is necessary to turn on the solenoid 33 and keep the swing bracket 36 a against the tip of the screw 35 . In this example, after the developer is set to a concentration within a certain range, the concentration changes (becomes thinner) when copying is started and the developer is being used, and the density sensor Since it is necessary for the copying machine to utilize the developer concentration value measured in step 24 during the copying operation and when preparing for the copying operation, the determination using the detection output from the concentration sensor 24 is Perform this while working and preparing for copying. Here, during copying work, for example, after the operator presses the copy start button, the final transfer paper (1
In the case of a copy of only one sheet, that one sheet of transfer paper corresponds to
In the case of continuous copying, this is until the last transfer sheet (corresponding to the last transfer sheet) is ejected from the machine. Further, preparing for copying means, for example, after the main power of the apparatus is turned on, the temperature of the fixing device 64 is raised to a predetermined temperature, the developer is circulated, and the surface of the photoreceptor, the developing device 5, and the cleaning device 8 are heated. If it is detected that the developer concentration has fallen below a predetermined level during idling or at the end of a copying operation, it will be executed continuously after the end of the copying operation in preparation for the next copy. This is a period during which developer concentration control (toner replenishment is performed as necessary using the detection output from the concentration sensor 24). Therefore, in this embodiment, the solenoid 3 is
Solenoid 3 is kept in the ON state to maintain the gap between both elements 30 and 31 at a predetermined amount, while at other times, for example, when the main power of the device is turned off or when the device is in standby mode, the solenoid 3 is turned on.
3 is turned off, and the gap between both elements is made wider than the predetermined gap. FIG. 9 is a timing chart of an example of such gap control between the elements 30 and 31. In the figure, immediately after the power switch is turned on, the main motor is not rotating as it waits for the temperature of the fixing heater of the fixing device 64 to rise. After the first copy is completed, the liquid concentration is within the set value range, so the solenoid 33 and the main motor are turned off immediately after the first copy is completed. After the second copy is completed, the liquid concentration is out of the set value range, so the liquid concentration is adjusted in preparation for the next copying operation. To prepare for copying immediately after turning on the power switch, the liquid concentration is measured, and if it is within the set value range, a copy ready display is displayed, and if it is outside the set value range, preparations are continued until the liquid concentration is within the range. However, if the liquid concentration does not fall within the range even if the preparation continues for a certain period of time, the preparation is ended and a copy permission display is displayed.

According to the gap control between the elements 30 and 31 in this example, during the copying operation and during copy preparation,
Although the gap between both elements 30 and 31 is maintained at the above-mentioned predetermined gap, both elements 30 and 3
There is no risk of dust etc. getting caught between the two. That is, during this period, the concentration of the developer must be measured and the concentration of the developer must be set and maintained within a predetermined range. The pump 11 inside is operating. In addition to supplying liquid to the developing device 5 and cleaning unit 8, this pump 11 also supplies liquid to the concentration sensor 24 to prevent the concentration sensor 24 from clogging.
Liquid is also applied between the gaps in No. 4 from time to time. Therefore, during this period when the pump 11 is operating, the liquid is flowing between the gaps, so even if dust or the like is temporarily trapped, the force of the liquid will quickly remove the dust or the like.

Next, a modification of the gap control between both elements 30 and 31 will be explained. As mentioned above, the pump 11 in the developer tank not only supplies the developer to the developing device 5 and the cleaning device 8, but also agitates the developer in the developer tank 10 by rotating when supplying the developer. As a result, when the pump 11, which is an agitation device in the developer tank 10, is being driven (during operation), the toner and developer are sufficiently mixed and the concentration of the developer is averaged. Correct concentration measurement is possible with 24. Furthermore, almost no measurement error is observed during measurement. And pump 1
1 is stopped (such as when the copying machine is on standby) and the developer is not stirred, toner precipitation occurs in the developer, resulting in an error in the value measured by the concentration sensor 24. That is,
The amount of precipitate changes with the elapsed time after the pump 11 (stirring device) is stopped, and the measured value changes with time. Therefore, when the pump 11 in the developer tank 10 is stopped, it is impossible for the concentration sensor 24 to accurately measure the developer value.
Since the measurement data of No. 4 cannot be used, the concentration sensor 24 cannot be used while the pump 11 is stopped, even during preparation for copying.
The necessity of toner replenishment is not determined based on the measured data. Therefore, in this example, the solenoid 33 is turned ON only during the period when the pump 11 is being driven, which is the period when the measurement data of the concentration sensor 24 used for determining whether or not toner replenishment is necessary is being detected. , 31 is maintained at a predetermined gap, while during other periods, the gap between both elements 30, 31 is enlarged to prevent the concentration sensor 24 from clogging. FIG. 10 shows both such elements 30
, 31 is a timing chart for an example in which gap control is performed. In the figure, immediately after the power switch is turned on, the main motor does not rotate for a while to wait for the temperature of the fixing heater of the fixing device 64 to rise. When preparing for copying immediately after turning on the power switch, the rise in fixing temperature and liquid concentration are measured, and if they are within the set range, the copy ready display is displayed, and if they are outside the set value range, preparations are continued until the liquid concentration is within the range. continue. Here, in the above-mentioned gap control between both elements, at the same time as this power switch is turned on, that is,
The solenoid 33 is turned on at the same time as the preparation for copying is started, and the gap between both elements is set to a predetermined gap, but in this example, the solenoid 33 remains off at this stage. During preparation for copying, the pump 11 is turned on at the same time as the main motor starts moving, and at the same time as stirring of the developer starts, the solenoid 33 is also turned on.
Begin adjusting the liquid concentration. After the first copy is completed, the liquid concentration is within the set range, so the solenoid 33, main motor, and pump 11 are turned off immediately after the first copy is completed. After the second copy is completed, the developer concentration is adjusted to prepare for the next copying operation since the developer concentration is outside the set value range. During this time, the main motor, pump 11, and solenoid 33 are turned on.

[0014]

According to the present invention, during a period when the developer concentration detection device is not detecting the developer concentration, the gap enlarger increases the gap between the light emitting element and the light receiving element from a predetermined gap for developer concentration detection. This also allows the developer concentration detection device to detect the developer concentration. This prevents new dust etc. from getting caught between the two elements during the period when they are not being used.
It is possible to prevent the density sensor from clogging, and it is possible to form an image with an appropriate density based on accurate detection of the developer concentration. Further, the burden of cleaning the concentration sensor by a service person can be significantly reduced compared to the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the entire copying structure according to an embodiment.

FIG. 2 is a schematic configuration diagram of a device arranged around a photoreceptor of the copying machine.

FIG. 3 is a block diagram schematically showing the electrical equipment of the copying machine.

FIG. 4 is an explanatory diagram showing the structure of the outlet of the mother liquor container on the developer tank of the copying machine.

FIG. 5 is an explanatory diagram showing the structure of the outlet of the toner container on the developer tank of the copying machine.

FIG. 6 is a schematic diagram of a detection element section of a density sensor of the copying machine.

FIG. 7 is a schematic diagram of a detection element section of a density sensor of a conventional wet-type copying machine.

[Fig. 8] (a) is an electrical circuit diagram of the concentration sensor in Fig. 6, (b)
) is a graph showing the output of the same concentration sensor.

FIG. 9 is a timing chart of gap control of the same concentration sensor.

FIG. 10 is a timing chart of gap control of the concentration sensor according to a modification.

[Explanation of symbols]

10 Developer tank
, 11 pump 24 concentration sensor
, 30 light emitting element 31 light receiving element
, 32 Spring 33 Solenoid
, 34 fulcrum 36a swing bracket
, 36b fixed bracket

Claims (3)

[Claims] Claims: 1. A wet image forming apparatus comprising a developer concentration detection device that detects the concentration of a developer in a developer tank using a light emitting element and a light receiving element that face each other with a predetermined gap, the light emitting element and the light receiving element. A support means for supporting the light emitting element and the light receiving element, and the developer concentration detection device detects the developer concentration so that the element can selectively take the predetermined gap and a gap larger than the predetermined gap. 1. A wet-type image forming apparatus comprising: a gap enlarging means for maintaining a gap between the light emitting element and the light receiving element at a gap larger than the predetermined gap during a period when the light emitting element and the light receiving element are not in use. 2. The gap enlarging means maintains the gap between the light emitting element and the light receiving element at a gap larger than the predetermined gap when the apparatus is powered off and on standby for copying operation. 1 wet image forming apparatus. 3. A wet image forming apparatus comprising a stirring means for stirring the developer in the developer tank in the developer tank, wherein the gap enlarging means is configured to control the light emission while the stirring means is inactive. 2. The wet image forming apparatus according to claim 1, wherein a gap between the element and the light receiving element is maintained at a gap larger than the predetermined gap.