JPH05165379A - Cleaning device for image forming device - Google Patents

Abstract

PURPOSE:To prevent a cleaning blade and an image carrier from being damaged by controlling the press-contact force of the cleaning blade to the image carrier by detecting ambient temperature and humidity. CONSTITUTION:The cleaning blade 3 is supported by a supporting member 3', and the member 3' is connected to a solenoid 7 energized by a control circuit 6. A temperature and humidity detecting sensor 9 to detect the ambient temperature and humidity is arranged at a proper spot in a device and detects the temperature of the blade 3, and the solenoid 7 is energized by the control circuit 6 through a CPU 8. When the temperature is low, the blade 3 is turned in a direction shown by an arrow B so as to increase its entering amount in the image carrier 1. When the temperature is high, the blade 3 is turned in a direction shown by an arrow C so as to decrease its entering amount in the image carrier 1. Therefore, the change of the elasticity of the blade 3 caused by temperature change is compensated, and uniform cleaning function is always achieved.

Description

Detailed Description of the Invention

[0001]

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus utilizing an electrostatic transfer process, and more particularly to a cleaning apparatus therefor.

[0002]

2. Description of the Related Art In a known image forming apparatus, which repeats the step of transferring a toner image formed on a surface of a moving image carrier to a transfer material such as paper, all toner is completely removed during transfer. It is difficult to transfer the toner to the transfer material, and it is inevitable that some toner remains on the surface of the image carrier even after the transfer.

Therefore, it is an essential requirement for obtaining a high quality image that the residual toner is thoroughly cleaned before the next image forming step, and as a cleaning means therefor, an elastic material such as urethane rubber is used. A cleaning blade that comes into contact with the surface of the image carrier to remove the residual toner that did not contribute to the transfer.
Since it has a simple structure, a small size, and an excellent toner removing function, it has been widely used in the past.

Incidentally, what should be considered in order to preferably remove the residual toner from the surface of the image bearing member is that the contact pressure of the cleaning blade to the image bearing member is appropriate and that the residual toner is removed. There are two main conditions that the cleaning action of the blade must overcome the adhesion to the image bearing member, and therefore these will be examined first.

First, the pressure contact force of the cleaning blade with the image carrier will be considered. The degree to which the cleaning blade is pressed against the image carrier is the distance between the position in the natural state of the contact edge of the blade with the image carrier and the position of the corresponding contact edge when this is pressed and displaced to the image carrier. δ (referred to as the amount of penetration). If it is too small, the toner slips through and sufficient cleaning cannot be performed. It causes inconvenience such as occurrence of.

As a material of the cleaning blade, as described above, urethane rubber is suitable and widely used from the viewpoint of wear resistance, moldability, mechanical strength, etc. On the other hand, the urethane rubber is shown in FIG. As shown in Fig. 6, when the temperature rises, the impact resilience also rises, and even if the intrusion amount is the same, the contact pressure to the image carrier increases when the temperature is low, and the temperature change is required to achieve a stable cleaning function at all times. It is necessary to change the contact pressure according to.

Further, the toner adhering to the surface of the image bearing member and reaching the cleaning portion is electrostatically driven by van der.
Adhesion is caused by various forces such as whirl force and mechanical force, but in the case of a general-purpose toner having irregularities on the surface and having a particle size of about 10 μm, it can be said that the adhesion is mainly caused by electrostatic force.

Therefore, the larger the amount of charge (referred to as tribo) obtained by the toner before reaching the cleaning portion, the greater the adhesive force to the image carrier and the more difficult the cleaning becomes. However, since the toner tribo greatly changes depending on the environmental temperature and humidity, it is necessary to adjust the amount of invasion of the cleaning blade depending on the environment. Generally, non-magnetic resin-based toner used in a color image forming apparatus tends to raise tribo when the temperature and humidity are low.

FIG. 6 shows the relationship between the humidity, the amount of tribo, and the appropriate amount of penetration when such a toner is used. When the absolute humidity is H ₁ , the amount of tribo is q ₁ and the optimum amount of penetration is δ ₁ . The combination of these is shown in quadrant c, and the blade penetration amount at absolute humidity H ₁ is δ ₁ . Similarly, when the absolute humidity is H ₂ , the optimum penetration amount is δ ₂ , and it is understood that the smaller the absolute humidity is, the larger the penetration amount needs to be.

From the above, it is usual to set the blade penetration amount so that cleaning can be sufficiently performed even at low temperature and low humidity.

However, in such a method, the impact resilience of the cleaning blade is increased in a high temperature environment, and the tribo amount of the toner is increased in a low humidity environment to deteriorate the cleaning function. Absent.

The present invention has been made to cope with such a situation, and detects the environmental temperature and humidity to change the pressure contact force of the cleaning blade with respect to the image carrier, thereby always providing stable and good cleaning. It is an object of the present invention to provide a cleaning device that can obtain a function.

[0013]

[Constitution of the invention]

In order to achieve the above object, the present invention provides a cleaning device for an image forming apparatus equipped with a cleaning blade that comes into contact with an image carrier, in response to changes in the cleaning blade or the environment. And a means for changing the amount of penetration of the cleaning blade into the image carrier.

With such a configuration, it is possible to always perform stable cleaning regardless of changes in the cleaning blade or environmental temperature and humidity.
It is also effective in preventing damage to the cleaning blade, the image carrier, and the like.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS "FIG. 1" is a side sectional view of a cleaning device showing an embodiment of the present invention, in which a cleaning device 2 is arranged in the vicinity of an image carrier running in the direction of arrow A. .. The cleaning device includes a cleaning blade 3
Was attached, and one edge of its free edge was pressed against the image carrier, and when the residual toner generated at the transfer portion (not shown) reached the position of this blade 3, it was scraped off and scraped off. The toner is guided by the scooping sheet 14 to a toner storage site in the cleaning device, and is further transported by a transport screw 5 to a separately provided waste toner storage container or the like.

In such a cleaning device, in the case of the illustrated device, the cleaning blade 3 is supported by a supporting member 3'rotatably arranged around the pivot point D, and The member 3'is connected to a solenoid 7 which is energized by a control circuit 6. A temperature / humidity sensor 9 for detecting the temperature and humidity of the environment is arranged at a proper place in the apparatus to detect the temperature of the cleaning blade, and the control circuit 6 via the CPU 8 deenergizes the solenoid 7, and when the temperature is low, By rotating the blade 3 in the direction of the arrow B in the figure to increase the amount of penetration thereof into the image carrier 1, and when the temperature is high, the blade 3 is rotated in the direction of arrow C to reduce the amount of penetration of the blade. Therefore, it is possible to always obtain a uniform cleaning function by compensating for the change in repulsion elasticity of the blade due to the temperature change.

It is a matter of course that the detecting means for detecting the temperature of the cleaning blade is preferably such that the sensor is directly attached to the blade, but in the case of a normal use condition in which there is no sudden temperature change. For example, a temperature / humidity sensor for controlling the humidity of the toner or the like can be used, and the present invention can also be applied to the case where the contact pressure of the blade is adjusted by the tribo amount of the toner described below.

Next, a case will be described in which the contact pressure of the cleaning blade with the image carrier is changed depending on the amount of toner charge. In the above cleaning device, reference numeral 9
Is a sensor for detecting the temperature and humidity of the environment. When the temperature and humidity are measured by this and the absolute humidity is low and the adhesion of the toner to the image carrier is strong, the blade 3 is rotated in the direction of arrow B. By increasing the contact pressure, and when the absolute humidity is high, by rotating the blade 3 in the direction of arrow C to weaken the contact pressure, even if the adhesion force of the toner to the image carrier changes due to the amount of tribo It is possible to obtain a cleaning function sufficient to remove

A method of obtaining the absolute humidity will be described with reference to the flow chart of FIG. A temperature / humidity sensor 9, whose main purpose is to determine the moisture absorption state of the toner, is arranged in a suitable place near the developing device, and the average value of temperature and humidity is measured for 1 to several times in 30 minutes for 8 hours. It is stored in a buffer in the minute memory 10.

In step 1 of "FIG. 2", the amount of water in the air, which is considered to affect the charge amount of the toner, the absolute humidity, or a value (for example, a mixing ratio) corresponding thereto is calculated.

In step 2, it is judged whether or not the absolute humidity has been calculated for 8 hours, and after the calculation for 8 hours, in step 3, the average values x, y, of the absolute humidity of 2 hours, 4 hours and 8 hours are calculated. Find z. These values are variables when calculating the amount of tribo and the amount of penetration of the cleaning blade.

In step 4, the 2-hour average value x is the mixing ratio 1
It is determined whether or not it is 6.5 gr or more, and if it is 16.5 g or more, a signal (hereinafter referred to as a flag) is set to TRIB 1. This means that the high humidity condition continues for 2 hours or more.

In step 5, it is judged whether the present value W is 16.5 g or more, and if it is 16.5 g or more, the flag is set to T.
RIB 2 This suggests that it was low humidity for 2 hours but is now heading towards high humidity.

Next, in step 6, the 8-hour average value z is 9 g.
If it is 9 r or more, the flag is set to T
Set to RIB 3. As a result, it is determined that the humidity is in the medium humidity for 8 hours or more.

Next, in step 7, the 4-hour average value y is 9 g.
If it is 9 gr or more, the flag is set to TRIB 4 depending on whether it is r or more. It can be seen that this is going from low humidity to medium humidity. When the 4-hour average value is less than 9 gr, the flag is set to TRIB 5.

The above-described processing is performed because the moisture absorption and dehumidification speeds of the toner are different, and the tribo amount of the toner depends not on the ambient humidity but on the moisture amount of the toner.

Next, at step 8, the variable H for tribo calculation is determined by the flag. For example, in the case of TRIB 1, since the humidity is sufficiently high, the variable becomes the 2-hour average value x.
Further, in the case of TRIB 2, since it is an intermediate state between low humidity and high humidity, the average value of the 2-hour average value x and the current value W is (x + w) / 2.

The quadrant a in FIG. 3 is a graph showing the relationship between the variable H obtained as described above and the toner tribo amount, and the quadrant b is the relationship between the toner tribo amount and the optimum penetration amount of the blade. It is a graph shown. By combining these, as shown in the quadrant c, the relationship between the variable H and the optimum penetration amount of the blade can be set. In practice, the graph in the quadrant c is approximated by an appropriate calculation formula, and the coefficient of the calculation formula is stored in the memory 10.

The flag obtained in "FIG. 2" causes the CPU 8 in "FIG. 1" to read the coefficient of the calculation formula from the table in the memory 10, and the intrusion of the blade by this coefficient and the variable H obtained in "FIG. 2". Calculate the amount.

As an example, when the blade penetration amount δ and the variable H are approximated by a linear expression with the line of the c quadrant as a straight line,
δ = a ₁ −b ₁ H. Here, a ₁ and b ₁ are the values at the position where the coordinate axes are cut, the inclination of the straight line, and the symbol “−” is the inclination direction.

The data of the penetration amount thus set is input to the control circuit 6 of FIG. 1, the solenoid 7 is actuated, and the contact pressure of the blade 3 to the image carrier is changed to an appropriate value. Can carry out cleaning.

In the embodiment described above, the blade pressure is controlled according to the history of humidity. If the device is operating steadily, the desired effects can be expected in this way, but if the device is suddenly moved to a place where the environment has changed at the beginning of installation, the sensor will In the case of a failure, data may not exist in the buffer area or data that is different from the actual data may be contained, which may cause cleaning failure. For example, when the device is installed, the temperature and humidity at that time are detected immediately after the power is turned on, and the data is stored for 8 hours assuming that this continues steadily. When there is no replacement, the operation shown in "FIG. 2" may be performed to perform a normal copy sequence.
The time data contains high humidity data, and if a new toner is added in this condition, the toner is adjusted to a lower humidity, so there is a discrepancy with the data, and cleaning failure may occur. There is.

In order to avoid such a situation, by setting the humidity data in the service mode to be rewritable by a key switch, humidity data rewriting means, or the like, good cleaning can be secured from the beginning of installation.

FIG. 4 is a schematic side view showing the configuration of a color image forming apparatus to which the present invention is applied. As shown in the drawing, of the conveyor belt 19 stretched in the image forming apparatus,
Four image forming portions P _a in the drawing the upper, P _b, P _c, is P _d are then columns set along the running direction C of the belt 19. Since the image forming units are all provided with a same configuration, the image forming section P _a will be described below.

The cylindrical image carrier 1a is rotated in the direction of arrow A so as to be in contact with the conveyor belt 19 so as to run synchronously with the belt, and its surface is uniformly charged by the primary charger 17a. The image signal giving means 16a gives an image signal of the black component color of the document to form an electrostatic latent image.

When this latent image arrives at the developing portion where the image carrier 1a and the developing device 13a face each other, black toner is supplied from the developing device to form a black toner image, and this toner image is further carried on the image. Body 1a and transfer charger 14a
When and reach the transfer site facing each other, a transfer material (not shown) is transported to the transfer site by the transport belt 19 by this time, and the transfer bias applied to the transfer charging device 14a causes the transfer material (black) to operate. The toner image is transferred to the transfer material. At this time, the residual toner remaining on the image carrier 1a without being transferred to the transfer material reaches the cleaning device 15a and is scraped off by the cleaning blade 18a.

[0037] The transfer material reaches the transfer portion of the image forming portion P _b, in a manner similar to the case of the image forming portion P _a by this time, the image bearing member 1 _b of the image forming portion P _b Forms a magenta toner image in the magenta component color of the document, and this toner image is transferred onto the transfer material in a superimposed manner.

Similarly, in the image forming portions P _c and P _d , the yellow toner image and the cyan toner image are further superimposed and transferred onto the transfer material, and then the transfer material is operated by the separation charging device 61. The toner images of the respective colors are fixed and fixed, and the color image is completed, and then the toner images are discharged to the discharge tray 23.

In the image forming apparatus having the above structure, the same cleaning blade as the cleaning blade 18a of the image forming section P _a is arranged in each of the image forming sections P _{a to} P _d .

In such a color image forming apparatus, when a well-known fixing device utilizing a pair of heating and pressing rollers is used, toner of each color is used in order to improve image quality characteristics such as saturation, brightness and hue of an image. There is a tendency to use a fixing device having a large heat capacity because it needs to be sufficiently melt-mixed.

Therefore, the temperature distribution in the vicinity of each image forming portion is as shown in the lower graph of FIG.
It is unavoidable that a temperature gradient as shown in the figure is generated between the temperature x _d of the cleaning blade on the side closer to 0 and the temperature x _a of the blade on the far side. For this reason, the cleaning blade used in each cleaning device also has a difference in temperature, and thus in repulsion elasticity, depending on the distance of each image forming unit from the fixing device due to this effect, and thus in cleaning function. There is a risk of defective cleaning of the blade.

In order to avoid such a problem, as shown in FIG. 1, the cleaning device for each of the image forming portions P _{a to} P _d is provided with a means for changing the amount of penetration into the image carrier in response to temperature. With this arrangement, it is possible to preferably prevent the occurrence of a difference in the cleaning function due to the temperature difference between the image forming units and the deterioration of the image quality due to the difference.

The temperature responsive means as shown in FIG. 1 is, of course, optimal to be provided in each image forming section, but from the viewpoint of cost, the graph in the lower part of FIG. As can be seen from the figure, the blade temperature changes monotonically as the distance from the side closer to the fixing portion increases, so temperature responsive means is provided for the blade closest to the fixing portion and the blade farthest from the fixing portion, and Alternatively, it may be estimated by proportional calculation or the like.

Further, even if the blade temperature detecting means and the blade moving means are arranged only on the blades of one or two image forming portions near the fixing portion, a certain effect can be obtained. It is possible.

By the way, in the case of the image forming apparatus having the above-mentioned structure, not only the temperature rise in the vicinity of the fixing portion, but also when the transfer material, especially the frequently used transfer paper passes through the fixing portion, the transfer paper is heated. Since the water contained in the water vaporizes, the atmosphere near the fixing portion is likely to be in a high humidity state when a large number of copies are dried.

Therefore, the amount of moisture absorbed by the toner, that is, the amount of tribo, varies depending on the position of the image forming portion, the adhesive force to the image carrier varies, and the cleaning function of the cleaning blade also varies, resulting in a difference in image quality. May have an impact.

Therefore, by using the above-mentioned temperature and humidity sensor, by providing means for determining the amount of invasion of the blade into the image bearing member in response to the amount of tribo of the toner, the image caused by the internal structure of the apparatus can be obtained. It is possible to prevent the cleaning function from fluctuating due to an environmental difference between the forming parts, particularly a humidity difference.

In the case of an apparatus using a plurality of types of toner as shown in FIG. 4, the relationship between the variable H and the amount of tribo varies depending on the toner. By providing a sensor and a blade moving means for each blade of _{a to} P _d and setting the blade pressure separately, it is possible to determine the intrusion amount in consideration of the difference in toner. Further, the humidity change is also generally reduced from the side closer to the fixing portion to the side farther from it, as in the case of the temperature change described above. It is also possible to simplify the configuration and reduce the cost by setting or controlling only one or two blades near the fixing portion.

[0049]

As described above, according to the present invention, in the cleaning device for cleaning the image bearing member by using the cleaning blade, the characteristics of the cleaning blade are changed due to the change of environment, and the toner on the image bearing member is changed. Since the change in the adhesive force is detected to change the contact pressure of the blade with respect to the image carrier, it is possible to always perform cleaning with the optimum contact pressure, and the life of the cleaning blade is extended. It has a remarkable effect in obtaining a high quality image.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a configuration of a cleaning device according to the present invention.

FIG. 2 is a flow chart for determining the humidity control amount in the same as above.

FIG. 3 is a graph showing the relationship between absolute humidity and the amount of tribo of toner.

FIG. 4 is a schematic side view of a color image forming apparatus suitable for applying the present invention.

FIG. 5 is a graph showing temperature characteristics of a cleaning blade.

FIG. 6 is a graph showing the relationship between the contact pressure of the cleaning blade and the amount of penetration into the image carrier.

[Explanation of symbols]

 1 image carrier 2 cleaning device 3 cleaning blade 6 control circuit 7 solenoid 8 CPU 9 temperature and humidity detection sensor 10 memory

Claims (3)

[Claims] 1. A cleaning device for an image forming apparatus, comprising a cleaning blade for contacting an image carrier,
A cleaning device provided with a means for changing the amount of the cleaning blade or the amount of penetration of the cleaning blade into the image carrier according to changes in the environment. 2. The cleaning device according to claim 1, wherein the means for changing the amount of penetration is a means for detecting the temperature of the cleaning blade and a movable means for the cleaning blade. 3. The cleaning apparatus according to claim 1, wherein the means for changing the amount of invasion are means for detecting environmental temperature and humidity and movable means for the cleaning blade.