JPH03182784A - Wet developing device of image forming device - Google Patents

Abstract

PURPOSE:To always maintain correctly the quantity of a solvent adhering to transfer paper even in the case a temperature variation and a change with the lapse of time are generated by correcting automatically a driving speed of a squeeze roller in accordance with a variation of viscosity of a developer. CONSTITUTION:By detecting viscosity of a developer 21 utilized actually for development by a viscosity detecting means 52, and reflecting a variation of a result of its detection as a variation of a rotating speed of a squeeze roller 15, a variation of an actual solvent adhesion quantity caused by a variation of viscosity of the developer 21 is compensated automatically. In such a way, even in the case a variation of an ambient temperature and a change with the lapse of time of the developer are generated, the solvent adhesion quantity is always maintained correctly even if an operator does not execute a special operation for the compensation.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an image forming apparatus such as a copying machine,
In particular, the present invention relates to development in an image forming apparatus that performs wet development. [Prior art] As a prior art related to the present invention, Japanese Patent Application Laid-Open No. 63-1
One disclosed in Japanese Patent No. 78277 is known. In this type of image forming apparatus, the quality of the developing process is one of the major factors that influences the quality of recorded images, and in particular, the amount of solvent attached to the photoreceptor has a large effect on image quality. In the case of a wet-type developer, the developer contains colored toner and a solvent, which adhere to the photoreceptor according to the image and are then transferred to transfer paper, but in the transfer process, a large amount of solvent adheres. Sometimes, toner migration from the photoreceptor to the transfer paper is performed efficiently and the transfer efficiency is high, so that recording ii! (ii) The image density is high and the solid uniformity of the nine images is also good. When the amount of attached solvent is small, the image quality deteriorates. Thus, in terms of recorded image quality, it is generally desirable to increase the amount of solvent. However, increasing the amount of solvent also brings the following disadvantages. In other words, in the fixing process, it is desirable to remove the solvent from the developer transferred onto the transfer paper and bind the toner to the transfer paper, so the thermal energy required to remove, or evaporate, the solvent is increases with increasing amount of solvent. Furthermore, since the amount of solvent that adheres to the transfer paper and is consumed increases, the amount of developer consumed increases. Furthermore, since the odor generated as the solvent evaporates may cause discomfort to humans, an increase in the amount of solvent evaporation leads to an increase in discomfort. From the above points of view, it is necessary to set the amount of attached solvent to an appropriate value that is neither too large nor too small. The amount of this solvent attached is generally constant, but
In Japanese Patent No. 8277, the operator can arbitrarily change the smoothness in consideration of the change in the smoothness of the transfer paper actually used.

Issue 1111 to be Solved by the Invention Conventionally, the rotational speed of a squeeze roller provided in a developing device has been considered as a factor in determining the amount of attached solvent. In other words, for example, when the amount of solvent deposited is to be constant, the rotational speed of the squeeze roller is set in advance to match that condition. However, the actual amount of solvent deposited varies depending on other factors, particularly changes in the viscosity of the developer. Further, the viscosity of the developer is affected by the temperature of the developer, and it has been confirmed that when the developer is used for a long period of time, the resin component constituting the toner dissolves in the carrier liquid and increases its viscosity. Therefore, even when the rotational speed of the squeeze roller is fixed constant, the actual amount of solvent deposited may deviate from the target value due to temperature changes or changes over time. JP-A-63-1
When the rotational speed of the squeeze roller is made variable as in Japanese Patent No. 78277, it is possible to correct the amount of solvent adhesion based on the operator's judgment based on the state of the recorded image. However, this kind of judgment is difficult unless you are an expert, and the operation is cumbersome. Therefore, it is an object of the present invention to maintain an appropriate amount of solvent adhesion without requiring special operator operations even when environmental conditions and the like change. [Means for Solving the Problems] In order to solve problem a above, the present invention provides: a moving charge carrier on whose surface an electrostatic latent image is formed; a developing means for supplying the charge carrier to the charge carrier; a squeeze roller that is arranged close to the charge carrier at a position downstream of the developing means and rotates in a direction opposite to the moving direction of the charge carrier; the squeeze roller viscosity detection means for detecting the viscosity of the developer passing through the development means; and electronic control means for automatically adjusting the rotational speed of the squeeze roller according to the viscosity detected by the viscosity detection means. establish. [Function] According to the present invention, the viscosity of the developer actually used for development is detected by the viscosity detection means, and the change in the detection result is reflected as a change in the rotational speed of the squeeze roller, so the viscosity of the developer is It is possible to automatically compensate for changes in the actual amount of solvent deposited due to changes in the amount of solvent applied. Therefore, even if there is a change in the ambient temperature or a change in the developer over time, the amount of solvent adhesion can always be maintained at an appropriate level without the operator having to perform any special compensation operations. By the way, when the rotational speed of the squeeze roller is changed, the amount of solvent attached changes accordingly, and the density of the recorded image changes. Therefore, if the speed of the squeeze roller is changed in the middle of the developing process, two types of areas with different recording conditions are formed on one recorded image, resulting in deterioration of image quality due to sudden density changes. Therefore, in the embodiment described later, the electronic control means adjusts the rotational speed of the squeeze roller based on the viscosity of the developer detected during the cleaning process in which the image forming area on the charge carrier is included in the recording process. However, the rotation speed of the squeeze roller is controlled to be fixed at least during the development process included in the recording process. Incidentally, the developing solution supplied to the developing device is generally stored in a relatively large tank. In addition, a float switch is provided in the tank to detect the remaining amount of developer.
When the remaining amount of developer becomes low, developer is replenished from a predetermined bottle. When the developer in the bottle becomes empty and the amount of developer remaining in the tank decreases, the developer is not replenished and recording operations are prohibited. If the device is left in that state, the part that is below the liquid surface will normally be exposed above the liquid surface, so that part will dry out.For example, if the viscosity detection means dries, the dried toner will stick to it. death. Errors occur in subsequent detection results. Therefore, in the embodiment described later, the viscosity detection means is arranged below the liquid level at which the float switch detects a low remaining amount. Thereby, there is no risk that the developer present near the viscosity detection means will dry out, so that detection errors can be prevented from occurring. [Example] Fig. 1 shows a schematic configuration of an image forming section of a type of wet type copying machine that implements the present invention. First, the configuration and operation of this device will be briefly explained with reference to Fig. 1. . Photoreceptor drum
is rotated at a constant speed in the direction of the arrow, that is, clockwise. In the image forming process, first the main charger 2
Due to the discharge, the surface of the photoreceptor drum 1 is uniformly charged to a predetermined high potential. This surface is irradiated with light reflected from the original in the exposure section IO, and as a result, a potential distribution corresponding to the density distribution of the image to be recorded, that is, an electrostatic latent image, is formed on the surface of the photoreceptor drum 1. Ru. Immediately after the exposure step, the non-image area on the photosensitive drum 1 is neutralized by the eraser 3. After the static elimination step, the electrostatic latent image formed on the photoreceptor drum 1 is developed by the developing device 4, and a visible image is formed with toner. Since the developing device 4 performs wet development, a liquid developer composed of toner and a solvent, that is, a developing solution is supplied into the developing device 4 . That is, the developer pumped up by a pump (not shown) from a tank 51 filled with the developer 21 is supplied into the developing device 4 from the supply nozzle 23 through the supply pipe 22, and this developer is used to form the electrostatic latent image. By adhering to the surface of the photoreceptor drum 1 according to the potential distribution, a toner image corresponding to the electrostatic latent image is formed. On the other hand, the transfer paper S supplied from a paper feeder (not shown) is
It passes through the guide plate 5 and is conveyed by the registration rollers 6, and is sent onto the surface of the photoreceptor in synchronization with the timing of image formation on the photoreceptor drum 1 so as to overlap the toner image. Then, a toner image (@image liquid) is transferred from the photoreceptor drum to the transfer paper by the transfer charger 7 located downstream from that position. separated from the body drum 1,
The paper is further transported by a transport belt 9, and after the image is fixed in a fixing device (not shown), it is discharged outside the copying machine. When the transfer process is completed, the developer remaining on the surface of the photoreceptor drum is removed by a cleaning roller lla provided in the cleaning unit 11 in preparation for the next image formation.
and removed by the cleaning blade 11b. By the way, two developing rollers 13 and 14 and a squeeze roller 15 are provided in the container 19 of the imager 4. The developing rollers 13 and 14 are each arranged to face the surface of the photoreceptor drum 1 with a minute gap of about 0.1 mm, and rotate clockwise at a peripheral speed faster than that of the photoreceptor drum 1. Driven scrapers 16 and 17, one end of which is fixed to the developing container 19, abut the developing rollers 13 and 14, respectively, and scrape off the toner on each developing roller to clean them. The developer supplied from the supply nozzle 23 into the developing device 4 is
It remains in the space between each of the developing rollers 13, 14 and the scraper 16[deg.]7, and is carried to the surface of the photosensitive drum as each developing roller rotates. This developer flows through the gap between the photoreceptor drum 11 and the developing roller and develops the electrostatic latent image on the surface of the photoreceptor. The developer that has returned to the developer container 19 without adhering to the photoreceptor drum is
It is collected into the tank 51 through the collection pipe 24 and reused. The squeeze roller 15 is arranged to face the surface of the photoreceptor drum with a predetermined gap therebetween, and is driven to rotate in a direction opposite to the direction of movement of the surface of the photoreceptor. Also squeeze roller 15
The method scrapes off excess developer on the photoreceptor drum 1 and controls the thickness of the developer film on the photoreceptor surface before transfer. The developer on the surface of the squeeze roller 15 is scraped off and collected by the scraper I8. FIG. 2 shows changes in the amount of solvent contained in the developer that adheres to the transfer paper. The horizontal axis of the graph shows the rotational speed (rotational speed: rp■) of the squeeze roller 15, and the vertical axis of the graph shows the amount of solvent attached (amount attached to A4 size transfer paper: mg). The diameter is 22mm,
The gap between the roller and the photoreceptor was 50±5 μm. The viscosity of the developer used was 1.65 cps, and the smoothness of the transfer paper was about 100-120 sec. The three types of curves shown in FIG.
The characteristics obtained under the conditions of m m /5ec) are shown. Referring to FIG. 2, it can be seen that the amount of solvent that adheres to the photoreceptor changes depending on the driving speed of the photoreceptor drum and the squeeze roller. The reason why such a phenomenon occurs can be understood based on the following principle. Referring to FIG. 3, in this example, the thickness of the developer liquid on the photoreceptor l after development reaches several hundred μm due to surface tension, and it moves at a speed U. - side, squeeze roller 1
5, a developer flow Dl having a velocity V is occurring. Therefore, at the closest portion between the photosensitive drum 1 and the squeeze roller 15, there is a difference in flow velocity of w (w=u+v), and the developer liquid is torn into two flows D1+D2. Here, if the speed 2 of the squeeze roller 15 increases, the speed V increases, the thickness of the flow Dl of the removed liquid increases, and the thickness of the flow Dl remaining on the surface of the photoreceptor decreases. Further, when the relative speed between the photoreceptor speed v1 and the squeeze roller speed V2 exceeds a certain level, the change in the thickness of the flow Dl becomes small. In addition to these speeds, the thickness tl of the flow Dl depends on the viscosity of the developer. It changes depending on the surface tension, the smoothness of the photoreceptor surface, the surface condition of the squeeze roller, etc. Among these factors, the viscosity of the developer in particular changes due to changes in the temperature of the developer and changes over time due to long-term use.
During use of a copying machine, the development characteristics may change, which may adversely affect the quality of recorded images. Therefore, in this embodiment, the viscosity of the developer is detected,
The driving speed of the squeeze roller 15 is automatically compensated according to the change in viscosity. Figure 4 shows two types of developer A with different viscosities. This shows the characteristics of B, but the same can be considered when the viscosity of the same developer changes due to temperature changes, etc., so let's consider it with reference to the example in Figure 40. If the goal is to minimize the viscosity of developer A, the squeeze roller is driven at a speed of ηA when the viscosity of developer A changes, and when the viscosity changes to developer B,
The drive speed of the squeeze roller may be changed to ηB. This allows the amount of solvent deposited to be always kept at a minimum. In addition, if the control objective is to keep the amount of solvent attached constant, for example, the target value is set in advance to mb, and when the viscosity matches the characteristics of developer B, the drive speed of the squeeze roller is set to ηB. When the viscosity changes to the characteristics of developer A, the rotational speed may be set to be slightly smaller than ηB. Note that the thickness of the developer film on the surface of the photoreceptor immediately after development needs to be larger than the gap T between the photoreceptor and the squeeze roller. slip occurs, tl increases, and the amount of solvent adhesion increases. Referring to FIG. 1 again, a viscometer 52 and a float switch 53 are provided in a tank 51 that stores a developer. The viscometer 52 includes a rotor 52a,
Viscosity is detected by its rotation. The float switch 53 is normally turned off and turned on when the level of the developer in the tank 51 becomes low, that is, when the remaining amount of the developer becomes small. Normally, when the float switch 53 detects that the remaining amount of developer is low, developer is replenished into the tank from a bottle (not shown) and the liquid level rises again. However, when the bottle is empty, the float switch 53 detects that the remaining amount of developer is low. Since it remains detected, it is not possible to form an image of normal quality in that case, and the operation of the copying machine is prohibited. Therefore, the liquid level does not drop further than the state in which the float switch 53 detects that the remaining amount of developer is low. For example, if the developer remaining inside the viscometer 52 dries, the toner will stick, and even if a sufficient amount of developer is replenished, the stuck toner will prevent the rotor of the viscometer from rotating. , a viscosity detection error occurs. In order to prevent such a situation from occurring, in this embodiment, the viscometer 52 is arranged below the liquid level where the float switch 53 detects a low amount of developer applied. As a result, even if the tank 51 is left with an insufficient amount of developer remaining, there is no fear that the toner will stick inside the viscometer 52.
Viscosity can be detected accurately at all times. Referring to FIG. 5, which shows the configuration of an electric circuit that controls the rotation of the squeeze roller 15, the squeeze roller 15 is driven by an electric motor 170. Electric motor 170 is controlled by motor driver 160. Motor driver 160 controls the driving speed of electric motor 170 to match the speed information output from CPU 150. In addition to the motor driver 160, the CPU 150 includes a timing pulse generator 110. Viscometer 52° Process controller 130. and ROM 140 are connected. The process controller 130 controls the entire process of the copying machine whose main parts are shown in FIG.
:A start signal y is given to the PU 150 as a synchronization signal when starting the copy process. The timing pulse generator 110 is a sensor that outputs a pulse every minute rotation of the photoreceptor drum 1 . After the start signal appears, the CPU 150 counts the number of pulses obtained from the timing pulse generator 110, and determines the progress of the copy process based on the counted value. Inside the ROM 140, the relationship between the viscosity of the developer and the rotational speed of the squeeze roller after compensation is stored in advance in the form of a table. A part of the processing by the CPU 150 is shown in FIG. In FIG. 6, step 1 checks the progress of the copy process. In terms of equipment, the counted number of pulses is compared with a predetermined value to determine whether the leading edge of the transfer paper has reached the cleaning roller lla of the cleaning unit. When it is time to start cleaning, proceed from step 1 to step 2, step 2
Now, the viscosity of the developer in the tank is detected by the viscometer 52. In the next step 3, the adhesion amount target value set at that time is input. In this embodiment, it is possible for the operator to adjust the developer adhesion amount in order to adapt the amount of developer adhesion to the quality of the transfer paper used, for example, and the target value after adjustment is set at step 3. In step 4, which is the zero-order input, the viscosity of the developer input in step 2 and the adhesion amount target value input in step 3 are used as parameters, and the ROM1 is
40, and input the compensated squeeze roller drive speed target value. Changing the driving speed of the squeeze roller 15, that is, updating the speed information applied to the motor driver 160, is executed in step 6. In this embodiment, the progress status of the copying process is checked in step 5, and if the development process is started, the process does not proceed to step 6; if the development process is not yet started,
Since the process advances from step 5 to step 6, the drive speed of the squeeze roller is changed. Note that as the viscosity detection means, any device other than the viscometer of the above embodiment can be used as long as it can detect the viscosity of the developer. Furthermore, in the above embodiment, the driving speed of the squeeze roller is changed by adjusting the speed of the electric motor.
This type of speed change can also be effected, for example, by a transmission means such as a torque converter or a clutch. [Effect] As described above, according to the present invention, the viscosity of the actual developer is detected and the squeeze roller (
Since the drive speed in step 15) is corrected, the amount of solvent attached to the transfer paper can always be maintained at an appropriate level even when environmental changes (temperature changes) or changes over time occur. Therefore, deterioration of recorded image quality and consumption of developer more than necessary can be prevented. Further, as in the above embodiment, the speed N1j of the squeeze roller
By executing 1 at the timing of the cleaning process and prohibiting (fixing the speed) at the timing of the developing process, it is possible to prevent the influence of the speed change from having an adverse effect on the recorded image (such as a rapid change in density). Furthermore, as in the embodiment described above, when the viscosity detection means (52) is arranged below the liquid level at which the float switch (53) detects a low remaining amount, a detection error of the viscosity detection means due to drying of the developer may occur. can be prevented from occurring.

[Brief explanation of drawings]

FIG. 1 is a front view showing the main mechanical parts of one type of copying machine embodying the present invention. FIGS. 2 and 4 are graphs showing the relationship between the rotational speed of the squeeze roller and the amount of solvent deposited. 3 is a partially enlarged front view showing the vicinity of the squeeze roller of the copying machine shown in FIG. 1. FIG. FIG. 5 is a block diagram showing the configuration of an electric circuit for controlling the speed of the squeeze roller of the copying machine shown in FIG. FIG. 6 is a flowchart showing a portion of the operation of the CPU shown in FIG. 1: Photoconductor drum (@carrier special leave) 2: Main charger 4: @equipment 11: Cleaning unit 13. 14: Developing roller (developing means) 15 Nix squeeze roller (squeeze roller) 21: Developing solution 22: Supply pipe 23 : Supply nozzle 5
1: Tank 52: Viscometer (viscosity detection means) 53: Float switch 140: ROM 150: CPU (electronic control means) 160: Motor driver 170: Electric motor S: Transfer paper

Claims (3)

[Claims] (1) A moving charge carrier with an electrostatic latent image formed on its surface; A developing means arranged close to the charge carrier and supplying a developer to the charge carrier; A position downstream from the developing means a squeeze roller disposed close to the charge carrier and rotating in a direction opposite to the moving direction of the charge carrier; means for driving the squeeze roller; viscosity detection means for detecting the viscosity of the developer passing through the developing means. and electronic control means for automatically adjusting the rotational speed of the squeeze roller according to the viscosity detected by the viscosity detection means. (2) The electronic control means adjusts the rotational speed of the squeeze roller based on the viscosity of the developer detected during the cleaning process in which the image forming area on the charge carrier is included in the recording process, and 2. The wet developing device for an image forming apparatus according to claim 1, wherein the rotational speed of the squeeze roller is fixed during implementation of a developing process included in the process. (3) A float switch for detecting the remaining amount of developer is provided in a tank for storing developer to be supplied to the developing means, and the viscosity detecting means is lower than the liquid level at which the float switch detects a low remaining amount of developer. 2. The wet developing device of the image forming apparatus according to claim 1, wherein the wet developing device is disposed below.