Patent Application
20190049880
The present invention relates to control of an amount of discharge of ultra fine particles that are discharged from an image forming apparatus.
Image forming apparatuses such as copying machines and printers have a heat-type fixing apparatus that causes an image to be fixed to a sheet. It is known that ultra fine particles (hereinafter abbreviated to UFP) may be produced from such a fixing apparatus. UFPs are produced by wax comprised in a developer evaporating. Japanese Patent Laid-Open No. 2014-92718 has proposed reducing the fixing temperature and reducing the printing medium conveyance speed in accordance with the UFP discharge amount in order to suppress the UFP discharge amount.
In general, measurement devices for measuring a UFP discharge amount are expensive. Accordingly, it is difficult to provide an image forming apparatus with a measurement device. Accordingly, image forming apparatuses predict the UFP discharge amount. However, if the predicted discharge amount is less than the actual discharge amount, a large number of UFPs will be discharged. If the predicted discharge amount is larger than the actual discharge amount, the sheet conveyance speed will be slower than necessary, and image formation productivity will be reduced.
The present invention may provide an image forming apparatus comprising the following elements. A fixing device is configured to, by adding heat and pressure to a toner image formed on a sheet, fix the toner image to the sheet. A temperature sensor is configured to detect a temperature of an end of the fixing device in a direction perpendicular to a sheet conveyance direction. A cooling device is configured to cool the end of the fixing device. A cooling controller is configured to control a cooling level by the cooling device in accordance with the temperature of the end of the fixing device detected by the temperature sensor. A prediction unit is configured to, based on a parameter depending on the cooling level, predict a discharge amount of ultra fine particles that are discharged from the image forming apparatus. An image formation controller is configured to control an image forming operation by the image forming apparatus such that the discharge amount of ultra fine particles is reduced in accordance with the discharge amount predicted by the prediction unit.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Exemplary embodiments of the present invention will be described hereinafter, with reference to the drawings. Note, the following embodiments are examples and the present invention is not limited to the content of the embodiments.
As illustrated in
The fixing apparatus 13, while conveying the sheet S, adds heat and pressure to the sheet S and the toner image. Thereby, the toner image is fixed to the sheet S. The fixing apparatus 13 comprises a fixing roller 14 and a pressure roller 15. Because the fixing roller 14 is hollow, it is also referred to as a fixing film. In the inside of the fixing roller 14, a fixing heater 30 and a temperature sensor 31 for detecting the temperature thereof are provided. The fixing heater 30 is controlled so that the temperature of the fixing heater 30 becomes a target temperature.
On the left side of the fixing apparatus 13 in
As
The image forming apparatus 100 conveys the sheet S, centering it in the conveyance path. If the width of the sheet S is narrow, the left end and the right end of the fixing roller 14 do not contact the sheet S. Specifically, only the central portion of the fixing roller 14 contacts the sheet S. Heat is stolen from the central portion by the sheet S, but heat tends not to be stolen from the left end and the right end of the fixing roller 14. For this reason, the cooling mechanism 50 must cool the left end and the right end of the fixing roller 14. Note that the central portion is also referred to as a sheet passing portion and the left end and right end are referred to as a non-sheet passing portion. As
<Control Section>
A print controller 102 is connected to the engine controller 101 and a host computer 103. The print controller 102 converts image data into bitmap data in accordance with a print job inputted from the host computer 103, executes image processing such as tone correction, and generates an image signal. The print controller 102 transmits an image signal to the engine controller 101 in synchronization with a TOP signal transmitted from the engine controller 101.
A cooling control section 120 controls an air flow amount and opening amount of the cooling mechanism 50. A temperature prediction section 121 predicts an ambient temperature of the fixing apparatus 13. A UFP prediction section 122 predicts a UFP discharge amount. A UFP control section 123 controls a UFP discharge amount. This may be implemented as hardware such as an ASIC, and may be implemented by the CPU 104 executing a control program. ASIC is an abbreviation for application specific integrated circuit.
<Cooling Control Section Operation>
By the foregoing control, it is possible to maintain the temperature in the central portion of the fixing apparatus 13 at a target temperature, and cool the ends.
<Temperature Prediction Section Operation>
The temperature prediction section 121 predicts an ambient temperature C(t) of the fixing apparatus 13 and provides it to the UFP prediction section 122 or the like. Below, this prediction process is described in detail.
In the present embodiment, an increasing curve and a decreasing curve of the ambient temperature C(t) in the case where the image forming apparatus 100 is caused to operate, and the convergence temperature Cx at which the temperature increase stops are measured by experimentation in advance under various conditions. The following prediction equation is obtained from the measured curves and convergence temperature Cx. t is an integer type variable indicating time, and its unit is seconds. This means that C(t) is predicted every second.
C(t)=C(t−1)+k(Cx−C(t−1)) (1)
Here, C(t−1) is the ambient temperature predicted the previous time (one second previous). Cx is the convergence temperature corresponding to the current operation state of the image forming apparatus 100 obtained by experimentation in advance. k is a temperature curve coefficient.
As
<UFP Prediction Section Operation>
In the present embodiment, the UFP discharge amount Us(t) is treated as a unit-less relative value.
The following two reasons can be considered for the UFP discharge amount Us(t) being influenced by the opening amount x of the shutter 53. The first is that the flow of air in the periphery of the fixing apparatus 13 differs between the case where the shutter 53 is closed and the case where it is open, and for the UFPs produced by the fixing apparatus 13, the amount that stops inside the image forming apparatus 100 and the amount that are discharged to the outside differs. The second is that the ambient temperature C(t) tends not to rise when the shutter 53 is open and outside air is supplied to the periphery of the fixing apparatus 13. The reasons that the ambient temperature C(t) influences the UFP discharge amount Us(t) are that when the ambient temperature C(t) increases by a certain amount, the UFPs tend to adhere to members in the periphery of the fixing apparatus 13, and the amount of UFPs that are discharged to the outside is reduced. Also, UFPs become integrated with each other, the particle size of the UFPs becomes larger, and the number of UFPs per unit volume decreases.
In this way, the UFP discharge amount Us(t) is greatly influenced by the opening amount x of the shutter 53 and the ambient temperature C(t). Accordingly, the UFP prediction section 122 predicts the UFP discharge amount Us(t) by using the opening amount x of the shutter 53 and the ambient temperature C(t). Thereby, the prediction accuracy for the UFP discharge amount Us(t) improves.
In the present embodiment, by experimentation in advance, the UFP discharge amount per sheet S is obtained, and the UFP discharge amount is determined to be a reference value. The UFP discharge amount at that time may be normalized to 1. The experimentation is started in a state in which the shutter 53 is closed and the ambient temperature C(t) is substantially corresponding to the room temperature. The size of the sheet S was A4. The conveyance speed was full speed. Also, the experimentation was performed with different combinations of the opening amount x of the shutter 53 and the ambient temperature C(t) when measurement starts. The ratios Rx and Rc for the UFP discharge amount in relation to the reference value were obtained.
In a case where the conveyance speed is set to half speed, the target temperature of the fixing heater 30 decreases, and the toner wax volatile matter decreases. Accordingly, the UFP discharge amount at half speed is lower than the UFP discharge amount at full speed. Accordingly, in the present embodiment, to simplify control, the UFP discharge amount in the case where the conveyance speed is half speed is assumed to be 0. In the present embodiment, the target temperature of the fixing heater 30 at full speed is 180° C., and the target temperature at half speed is 160° C.
An equation for predicting the UFP discharge amount Us(t) that uses the parameters obtained by the above experimentation is as follows.
Us(t)=Us(t−1)+N×Rc×Rx (2)
Here, Us(t−1) indicates the discharge amount predicted the previous time (one second previous). N indicates the number of sheets subjected to image formation that was performed in the most recent 1 second, and is obtained by the N determination section 133. Rx is the UFP discharge ratio obtained by the Rx determination section 135 based on the combination of the air flow amount y and the opening amount x from the table illustrated in
<UFP Control Section Operation>
When the image forming condition is changed, the UFP discharge amount is substantially 0. Accordingly, it becomes possible to reduce the UFP discharge amount Us(t) to be less than or equal to the threshold Uth. Note that the threshold Uth is determined from the reference value for the UFP discharge amount per one A4 sheet of the image forming apparatus 100 and the absolute value of the UFP discharge amount which is made to be the upper limit.
In this way, in the first embodiment, the UFP discharge amount Us(t) is predicted based on the ambient temperature C(t) and the cooling level of the cooling mechanism 50. Since the UFP discharge amount Us(t) is predicted taking into consideration the influence of the cooling mechanism 50 on the UFP discharge amount Us(t), the prediction accuracy improves. In conditions in which the UFP discharge amount Us(t) is large, a UFP reduction operation is executed. Thereby, the amount of UFP discharge is reduced. In conditions in which the UFP discharge amount is small, normal image formation is executed. Accordingly, image formation productivity is maintained.
In the first embodiment, the cooling level of the cooling mechanism 50 is controlled in accordance with the end temperature Te of the fixing apparatus 13. In the second embodiment, control for cooling the end of the fixing apparatus 13 in which the UFP discharge amount Us(t) is also taken into consideration is employed. This is advantageous in maintaining the conveyance speed. In the second embodiment, description of matters that are common to or similar to the first embodiment is omitted.
In the second embodiment, a control mode in which an increase in the end temperature Te is reduced by controlling the conveyance interval between two adjacent sheets S is added to the UFP control section 123. Below, the control mode in which the cooling mechanism 50 is used that is described in the first embodiment is referred to as the first mode, and the control mode in which an increase in the end temperature Te is reduced by controlling the conveyance interval is referred to as the second mode.
<Second Mode>
The UFP discharge amount Us of the second mode converges to a value that is lower than the UFP discharge amount Us of the first mode. Since the shutter 53 is always closed in the second mode, the UFP discharge ratio Rx is smaller. Furthermore, since the convergence temperature C(t) becomes high quickly, the UFP discharge ratio Rc is small. Formula (2) indicates that if Rx and Rc become smaller, the UFP discharge amount Us(t) becomes smaller.
In the first mode, since the UFP discharge amount Us(t) exceeds the threshold Uth when approximately 150 seconds have elapsed from when the image formation starts, the productivity falls from 60 ppm to 30 ppm due to reduction of the UFP discharge amount. Since the UFP discharge amount Us(t) converges at less than the threshold Uth in the second mode, a reduction in the conveyance speed does not occur. However, since the conveyance interval is widened in accordance with the cooling level, the productivity falls gradually (60 ppm=>40 ppm=>30 ppm=>24 ppm). The productivity may be compared by the number Ns of sheets S on which an image is formed. At the point in time when 180 seconds have elapsed, the number of sheets Ns in the first mode is 159. The number of sheets Ns in the second mode is 118. Accordingly, the productivity of the first mode is higher than the productivity of the second mode.
In this way, the first mode has the merit of maintaining high productivity. The second mode has the merit of reducing the UFP discharge amount. In the second embodiment, either the first mode or the second mode is selected based on the UFP discharge amount Us(t).
<Cooling Control Taking UFP Discharge Amount into Consideration>
In the second embodiment, the temperature prediction section 121 and the UFP prediction section 122 execute the same processing as in the first embodiment. The threshold Uth of the UFP control section 123 is 120.
The first mode region a is a region in which the UFP discharge ratio Rc becomes small since the ambient temperature C(t) is high. In this region, the UFP discharge amount Us converges without exceeding the threshold Uth regardless of which of the first mode and the second mode are used. Accordingly, by selecting the first mode, the productivity is kept high. In accordance with the selection formula Td, the region in which Us<40 and Us+45≤C is satisfied falls in the first mode region a. Also, the region in which Us≥40 and 0.56×Us+62.6≤C is satisfied falls under the first mode region a.
The first mode region b is a region in which the UFP discharge ratio Rc becomes large since the ambient temperature C(t) is small. Specifically, in the first mode region b, the UFP discharge amount Us exceeds the threshold Uth regardless of which of the first mode and the second mode are used. Accordingly, the first mode is selected, and the conveyance speed is reduced so that the UFP discharge amount Us becomes less than or equal to the threshold Uth. In accordance with the selection formula Td, the region in which Us<40 and 1.5×Us≥C is satisfied falls in the first mode region b. Also, the region in which Us≥40 and 0.88×Us+24.8≥C is satisfied falls under the first mode region b.
The region in which Us<40 and Us+45>C>1.5×Us is satisfied falls in the second mode region. Also, the region in which Us≥40 and 0.56×Us+62.6>C>0.88×Us+24.8 is satisfied falls in the second mode region. In the second mode region, the UFP discharge amount Us may exceed the threshold Uth when the first mode is executed, but the UFP discharge amount Us converges without exceeding the threshold Uth when the second mode is executed. Accordingly, by selecting the second mode, the UFP discharge amount Us is reduced to less than or equal to the threshold Uth. In a case where the second mode is transitioned into from the first mode, the second mode is maintained until the ambient temperature C(t) becomes the threshold Cth (example: 130° C.) or more. Thereby, the effect of reducing the UFP discharge amount Us is enhanced.
Note that in the case where the number of sheets on which an image is formed is small, the print job will likely end up being completed prior to the ambient temperature C(t) becoming high in a case where the second mode is selected in accordance with the determination formula Td. In such a case, the effect of reducing the UFP discharge amount caused by the ambient temperature C(t) becoming high is not achieved much. There is the possibility that in spite of this productivity will greatly decrease. Accordingly, configuration may be taken such that if the number of sheets subject to image formation N designated by the job data of the print job is a predetermined value or less (example: 120 sheets), the first mode is selected. Thereby, high productivity should be maintained.
Flowchart
In the first embodiment, the first mode is always selected. When 60 seconds has elapsed from the start of image formation, the cooling level becomes 1 or higher, and the shutter 53 opens. For that reason, the UFP discharge amount Us continues to increase. At the point in time when approximately 150 seconds have elapsed, the UFP control section 123 switches the conveyance speed to half speed.
In the second embodiment, the second mode is selected when the cooling level becomes 1 or higher. Accordingly, the conveyance interval widens, and productivity decreases. Meanwhile, a UFP discharge amount UsII is reduced to be lower compared to the UFP discharge amount UsI. When the ambient temperature C(t) exceeds the threshold Cth at the point in time when approximately 150 seconds has elapsed, the control mode switches to the first mode, and the productivity returns to what it was. At that point in time, the UFP discharge amount UsII has converged. Also, the UFP discharge amount UsII is reduced to be lower than the UFP discharge amount UsI. Around where the total number of sheets subjected to image formation Ns exceeds 200 sheets (at the point in time when approximately 250 seconds has elapsed), the productivity of the second embodiment exceeds the productivity of the first embodiment. After that, the productivity of the second embodiment is higher than the productivity of the first embodiment. Accordingly, in the case where the number of sheets on which images are to be formed is large, the second embodiment is advantageous in that the UFP discharge amount Us is reduced and high productivity can be achieved.
In this way, in the second embodiment, in a case of a condition in which the UFP discharge amount Us is large, the control mode is switched from the first mode to the second mode. Consequently, it becomes possible to reduce the UFP discharge amount US. The first mode is selected in the case where the condition is the same for the UFP discharge amount Us regardless of which of the first mode and the second mode is selected. Thereby, high productivity is maintained. In the second embodiment, the method of widening the conveyance interval is employed as the second mode. In the case of an image forming apparatus 100 that has a conveyance speed that is between full speed and half speed (example: ¾th speed), the conveyance speed may be reduced to ¾th speed together with widening the conveyance sheet interval.
Also, a simple formula for determining using only the ambient temperature C or only the UFP discharge amount Us may be used for the determination formula Td. For example, in the case where only the ambient temperature C is used, the first mode region is determined if the ambient temperature is 85° C. or more, and the second mode region is determined otherwise, and in the case where only the UFP discharge amount Us is used, the first mode region is determined if the UFP discharge amount Us is 65 or more and the second mode region is determined otherwise.
In the third embodiment, the UFP discharge amount is reduced by starting image formation after raising the ambient temperature C(t) prior to the start of image formation. In the third embodiment, description of matters that are common to or similar to the first and second embodiments is omitted.
<Control of Fixing Temperature Taking into Consideration UFP Discharge Amount>
The first mode region a of the determination formula Td illustrated in
Experimental Results
Also, the determination formula Td may be a simple formula for determining by using only the ambient temperature C. For example, the first mode region a is determined if the ambient temperature C is 85° C. or more and the second mode region is determined otherwise.
In this way, in the third embodiment, in a case where image formation is started in a state where the UFP discharge amount Us is large, image formation is started after raising the ambient temperature C(t) in advance. Accordingly, since a reduction in the conveyance speed does not occur, the UFP discharge amount Us is reduced and high productivity is achieved.
[Conclusion]
The fixing apparatus 13 functions as a fixing device that, by adding heat and pressure to a toner image formed on a sheet S, fixes the toner image to the sheet S. The temperature sensor 32 functions as a temperature sensor that detects a temperature of an end of the fixing roller 14 in a direction perpendicular to a sheet conveyance direction. The cooling mechanism 50 functions as a cooling device that cools the end of the fixing roller 14. The cooling control section 120 functions as a cooling controller that controls a cooling level by the cooling mechanism 50 in accordance with the temperature of the end of the fixing roller 14 detected by the temperature sensor 32. The cooling level is a term that can be substituted with the control state of the cooling mechanism 50. The temperature prediction section 121 functions as an obtaining unit that obtains the ambient temperature C(t) of the fixing apparatus 13 based on an environmental temperature of the environment in which the image forming apparatus 100 is installed or an initial value based on the ambient temperature of the previous time and an operation time of the image forming apparatus 100. The ambient temperature of the previous time is an ambient temperature obtained when the power of the image forming apparatus 100 is off or an energy saving mode is transitioned into. For example, the power of the image forming apparatus 100 being turned off and on prior to the ambient temperature decreasing to the environmental temperature can be considered. In such a case, the ambient temperature when the power of the image forming apparatus 100 was turned on is closer to the ambient temperature predicted the previous time than the environmental temperature. In such a case, the ambient temperature C(t) may be predicted based on the ambient temperature predicted the previous time and the elapsed time (operation time) from when the power was turned on. The UFP prediction section 122 functions as a prediction unit that, based on a parameter depending on at least one of the cooling level and the ambient temperature C(t), predicts the discharge amount Us(t) of ultra fine particles that are discharged from the image forming apparatus 100. Note that the temperature prediction section 121 may predict the ambient temperature C(t) based on the cooling level. The UFP control section 123 functions as an image formation controller that controls an image forming operation by the image forming apparatus 100 such that a discharge amount of ultra fine particles is reduced in accordance with the discharge amount Us(t). By virtue of the embodiments, the prediction accuracy of the UFP discharge amount Us(t) improves since at least the cooling level is taken into consideration.
The cooling fan 51 and the duct 52 or the like function as a blower unit that supplies air to the end of the fixing roller 14. The UFP prediction section 122 may predict the discharge amount Us(t) for ultra fine particles by using the air flow amount y of the cooling fan 51 as the parameter depending on the cooling level. The cooling mechanism 50 may further comprise the shutter 53 which is provided at the exit of the duct 52 and can be opened/closed. The UFP prediction section 122 may predict the discharge amount by using the opening amount x of the shutter 53 as the parameter depending on the cooling level.
The Rx determination section 135 is one example of a first determination unit that determines a first discharge coefficient (example: discharge ratio Rx) based on the air flow amount y and the opening amount x. The UFP prediction section 122 may predict the discharge amount by using the first discharge coefficient as the parameter depending on the cooling level. The Rc determination section 134 is one example of a second determination unit that determines a second discharge coefficient (example: discharge ratio Rc) based on the ambient temperature C(t). The UFP prediction section 122 may predict the discharge amount by using the second discharge coefficient as the parameter depending on the ambient temperature C(t). The UFP prediction section 122 may predict the discharge amount based on the number of sheets subjected to image formation per unit time N in addition to these parameters. According to Formula (2), Rx, Rc, and N are all used, but configuration may be such that one or more of these is used.
The temperature prediction section 121 may be configured to obtain the ambient temperature C(t) at regular intervals. The temperature prediction section 121 may obtain the ambient temperature C(t) by multiplying the temperature coefficient k with the difference between the convergence temperature Cx obtained based on the opening amount x of the shutter 53 and the ambient temperature C(t−1) obtained the previous time, and then adding the ambient temperature C(t−1) thereto.
The k determination section 131 may function as a selection unit that selects a first temperature coefficient (example: k1) if the ambient temperature C(t−1) is exceeding the convergence temperature Cx. Also, the k determination section 131 may function as a selection unit that selects a second temperature coefficient (example: k2) that is smaller than the first temperature coefficient if the ambient temperature C(t−1) is not exceeding the convergence temperature Cx, and passes it to the temperature prediction section 121.
The UFP control section 123 may reduce the discharge amount Us by controlling the conveyance speed of the sheets S conveyed through the fixing apparatus 13 in accordance with the discharge amount Us. Note that the target temperature of the fixing apparatus 13 decreases when the conveyance speed decreases.
As described in the second embodiment, the UFP control section 123 may have a first mode in which the discharge amount Us is reduced by controlling the conveyance speed of the sheets S and a second mode in which the discharge amount Us is reduced by controlling the conveyance interval of the sheets S. The UFP control section 123, based on at least one of the ambient temperature C(t) and the discharge amount Us(t) of ultra fine particles predicted by the UFP prediction section 122, selects one of the first mode and the second mode. When the second mode is selected, the cooling mechanism 50 stops. Thereby, the discharge amount Us(t) is reduced. The UFP control section 123 may select the second mode when at least one of the ambient temperature C(t) and the discharge amount Us(t) predicted by the UFP prediction section 122 satisfies a predetermined condition, and the cooling level is a predetermined level or more. The UFP control section 123 may select the second mode when at least one of the discharge amount Us(t) and the ambient temperature C(t) satisfies a predetermined condition and the cooling level is a predetermined level or more, and the number of remaining sheets to which image formation is to be performed is a predetermined number or more.
As described in the third embodiment, when a print job is inputted into the image forming apparatus 100, there are cases in which at least one of the ambient temperature C(t) and the discharge amount Us(t) predicted by the UFP prediction section 122 does not satisfy the predetermined condition. In such a case, the UFP control section 123 may heat the fixing apparatus 13 until at least one of the discharge amount Us(t) and the ambient temperature C(t) satisfies the predetermined condition. Thereby, the amount of UFP discharge is reduced.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as anon-transitory computer-readable storage medium′) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2017-154731, filed Aug. 9, 2017, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-154731 | Aug 2017 | JP | national |
