JP2024127120A - Image forming device - Google Patents

Abstract

To provide an image forming apparatus in which optimal linear interpolation of a fixing temperature is conducted based on a use environment and rotational speed.SOLUTION: An image forming apparatus includes: a fixing device for fixing a toner image on a recording material; an environment detection unit which detects an environment temperature of the image forming apparatus, and is capable of detecting a low environment temperature and a high environment temperature; a prediction unit for calculating a predicted value of a temperature of the fixing device; a speed control unit which controls conveyance speed to a second speed when the low environment temperature and the predicted value attain a first threshold, and controls conveyance speed to a second speed when the high environment temperature is detected and the predicted value attains a second threshold being larger than the first threshold; and a temperature control unit which conducts linear interpolation of a fixing temperature at a prescribed environment temperature, and determines the temperature to be used for linear interpolation based on the conveyance speed controlled by the speed control unit, in a state that the predicted value is at the first threshold and the second threshold.SELECTED DRAWING: Figure 6

Description

It relates to an image forming device that forms an image on a recording material.

In general, fixing devices that fix toner images onto recording media by applying heat and pressure are widely used in various devices, including image forming devices such as copiers, laser beam printers, and facsimiles.

The fixing device described above uses a heating rotor and a pressure rotor to form a nip, which fixes the toner image to the recording material. When fixing, heat and pressure are applied to the toner image and recording material to fix the toner image.

When fixing paper with a width smaller than the maximum width that the fixing device can fix, a non-paper passing area is created. The recording material does not pass through this non-paper passing area. As a result, heat is not removed from the heating rotor, and the temperature rises compared to the paper passing area. This is called non-paper passing area temperature rise. Many countermeasures against this non-paper passing area temperature rise have been proposed (Patent Document 1). For example, one countermeasure against non-paper passing area temperature rise is to reduce the rotation speed of the heating rotor and pressure rotor when the temperature of the fixing device rises, thereby reducing the amount of heat generated per unit time, thereby suppressing the temperature rise in the non-paper passing area.

The degree of temperature rise in the non-paper passing areas varies depending on the environment in which the image forming device is used. When the image forming device is used in a high-temperature environment, the amount of heat taken away by the heating rotor when the recording material passes through the nip is small. On the other hand, in a low-temperature environment, the amount of heat taken away by the heating rotor when the recording material passes through the nip is greater than in a high-temperature environment. Therefore, the timing for slowing down the rotation speed of the heating rotor and pressure rotor is shifted between high-temperature and low-temperature environments. The rotation speed of the heating rotor and pressure rotor is slowed down earlier in a low-temperature environment than in a high-temperature environment. When the rotation speed is slowed down, the fixing temperature is also lowered accordingly, so the fixing temperature is set lower than before the rotation speed is slowed down. This makes it possible to deal with temperature rise in the non-paper passing areas due to differences in the intended use environment.

JP2004-212769

Measures against temperature rise in non-paper passing areas are taken by shifting the timing for correcting the rotation speed and fixing temperature in low-temperature and high-temperature environments. Here, linear interpolation is performed to correct the fixing temperature in environments between low-temperature and high-temperature environments. Specifically, linear interpolation is performed using the fixing temperatures in the low-temperature and high-temperature environments. However, the fixing temperatures in the low-temperature and high-temperature environments are set based on the rotation speed. Therefore, in a device that performs control to shift the timing for correcting the rotation speed in low-temperature and high-temperature environments, optimal linear interpolation is not performed when linear interpolation of the fixing temperature in environments between low-temperature and high-temperature environments is performed.

The image forming device of the present invention aims to perform optimal linear interpolation of the fixing temperature based on the usage environment and rotation speed.

In view of the above problems, the present invention provides an image forming apparatus comprising: a fixing device that fixes a toner image onto a recording material;
a speed control unit that controls a conveying speed of the recording material in the fixing device, the speed control unit controls the conveying speed to a first speed and a second speed lower than the first speed, and a temperature control unit controls a fixing temperature of the fixing device, an environment detection unit that detects an environmental temperature of the image forming apparatus, the environment detection unit can detect a low environmental temperature and a high environmental temperature higher than the low environmental temperature, predicts a temperature of the fixing device, and calculates a predicted value of the temperature of the fixing device, and the speed control unit, when the environment detection unit detects the low environmental temperature and the predicted value reaches a first threshold value, , controls the conveying speed to the second speed, and when the environment detection unit detects the high environmental temperature and the predicted value reaches a second threshold value that is greater than the first threshold value, controls the conveying speed to the second speed, and the temperature control unit linearly interpolates the fixing temperature using the fixing temperature of the low environmental temperature at a predetermined environmental temperature between the low environmental temperature and the high environmental temperature, and the temperature control unit determines the fixing temperature to be used for linear interpolation based on the conveying speed controlled by the speed control unit when the predicted value is between the first threshold value and the second threshold value.

According to the present invention, the fixing temperature can be optimally corrected according to the usage environment and rotation speed, thereby improving image quality.

FIG. FIG. FIG. 1 is a block diagram showing a configuration of an image forming apparatus. 13 is a diagram showing the case where the process speed variable threshold is the same in the environment. 11 is a diagram showing a case where the process speed variable threshold differs depending on the environment (before measures are taken). 13 is a diagram showing a case where the process speed variable threshold differs depending on the environment (after measures are taken). A diagram showing the operating environment temperature. A diagram showing how the device heats up. 13 is a diagram showing the case where the process speed variable threshold is the same in the environment. 11 is a diagram showing a case where the process speed variable threshold differs depending on the environment (before measures are taken). 13 is a diagram showing a case where the process speed variable threshold differs depending on the environment (after measures are taken).

Example 1
As a measure to avoid temperature rise at the edges when small size paper is passed through, the process speed is reduced to half speed (second speed) (second speed). In this case, the aim is to devise a method of linear interpolation for the target temperature control temperature for fixing and to perform optimal settings.

<Image forming apparatus>
Before describing the characteristic features of this embodiment, the overall configuration of the image forming apparatus will be described.

Figure 2 is a schematic diagram showing an example of the cross-sectional configuration of an image forming apparatus. Image forming apparatus 1 is an apparatus that forms an image in an image forming section that uses an electrophotographic process, transfers the formed image to recording material P in a transfer section, and fixes the image to recording material P by heating recording material P to which the image has been transferred in a fixing section. The image forming apparatus described in this embodiment is a four-color full-color multifunction printer (color image forming apparatus) that uses an electrophotographic process. It will be described in detail below.

The image forming device 1 is equipped with a controller 100 that controls each component within the device. The controller 100 functions as a control unit that performs various controls, and plays a role in comprehensively controlling the various components within the device and executing image forming operations based on input print information signals (e.g., image data, paper information, etc.).

The recording material P used in the description is a recording material on whose surface an image is formed. Examples of recording materials P include plain paper, thick paper, overhead projector paper, coated paper, medical bands, label paper, perforated paper, etc.

The image forming apparatus 1 forms a multi-color image by overlapping four colors of developer (hereinafter referred to as toner), namely, yellow (Y), magenta (M), cyan (C), and black (K). For this purpose, it is provided with an image forming station 10 that forms a toner image of each color. Although the reference numerals in the figure are given the suffixes YMCK, the image forming stations 10 of each color have the same basic configuration. Therefore, in the specification, when the description applies to the image forming stations of all colors, the suffixes are omitted. The image forming station 10 has a rotating drum-type electrophotographic photosensitive member 11 (hereinafter referred to as the photosensitive drum 11) as an image carrier on which an image is formed. It also has a cleaning member (not shown: hereinafter referred to as the photosensitive drum cleaning member) as a process means acting on the photosensitive drum 11, a charging roller 12 as a charging device, and a developing unit 14 as a developing device. The toner storage chamber of the developing unit 14 is basically configured to store toner of each color that is negatively charged.

A laser scanner unit 13 is disposed adjacent to the image forming station 10 as an exposure means for the drum 11, and a cassette 2 for storing recording material P is disposed below. Furthermore, a transfer belt unit 20 (hereinafter referred to as the transfer unit) is provided above the image forming station 10.

The transfer unit 20 has an intermediate transfer belt 21 and a drive roller 22 that drives it. In addition, four primary transfer rollers 15 (first to fourth) that serve as primary transfer devices are arranged in parallel inside the intermediate transfer belt 21. Each primary transfer roller 15 is disposed opposite the drum 11 of each image forming station.

The upper surface of the drum 11 of each color in the image forming station 10 contacts the lower surface of the intermediate transfer belt 21 at the position of each primary transfer roller 15. This contact area is called the primary transfer section.

The drive roller 22 is a roller that rotates and drives the intermediate transfer belt 21, and a secondary transfer roller 25, which is a secondary transfer device, is disposed outside the portion of the intermediate transfer belt 21 that is backed up by the drive roller 22. The intermediate transfer belt 21 contacts the secondary transfer roller 25, which is a transfer means, and this contact portion is called the secondary transfer nip portion T2. An intermediate transfer belt cleaning member 23 is disposed outside the portion of the intermediate transfer belt 21 that is backed up by the tension roller.

As a result, the remaining toner has a positive polarity, which is opposite to normal. As a result, in the primary transfer section where a positive voltage is applied, normal negatively charged toner is transferred to the intermediate transfer belt 21, while the remaining positively charged toner is collected on the photosensitive drum 11. The toner collected on the photosensitive drum 11 is collected by a cleaning member for the photosensitive drum.

The image forming apparatus 1 is equipped with a paper transport device. A paper transport path Q (indicated by a dashed line in the figure) is provided to transport the recording material P picked up from the cassette 2 upward. On the paper transport path Q, a feed roller 3, a pair of separation rollers 4, a pair of registration rollers 5, a secondary transfer roller 25, a fixing unit 30, and a pair of discharge rollers (not shown) are arranged in this order from upstream, and transport the recording material P to a discharge tray 9. A speed control is provided to control the transport speed of the recording material. This speed control also controls the transport speed in the fixing device 30. The speed control section mainly controls the transport speed of the recording material in the fixing device 30 to a first speed and a second speed. The first speed and the second speed will be described later.

The fixing unit 30, which is a fixing device, has a pair of rotating bodies, a heating rotating body and a pressure rotating body. The pair of rotating bodies form a nip portion, where heat and pressure are applied to the recording material to fix the toner image to the recording material. Since heat is required to fix the recording material, the heating rotating body in this embodiment is heated by a heater. A voltage is applied to the surface of the fixing unit 30 to electrically prevent the toner from adhering to the pair of fixing rollers.

It has a temperature control unit that controls the temperature of the heater. The temperature control unit controls the temperature of the heater of the heating rotor. By controlling the temperature of the heater, it is possible to perform fixing at a predetermined fixing temperature for a predetermined recording material P. The temperature control unit controls the temperature by feeding back the value detected by the temperature detection unit that detects the temperature of the heating rotor.

The image forming device 1 is equipped with an image reader 40. The image reader 40 has a function of reading an image of an original document with an optical sensor and converting it into an image signal. The image reader 40 is equipped with an original document feeder 41. The original document feeder 41 has a function of multi-traying original documents set face up on an original document tray 42 one by one in order from the first page, and reading the original document image with a reader scanner 43. The read original document is discharged to a current discharge section 44. The reader scanner 43 has a light irradiation section (not shown) and an image sensor (not shown), and converts the original document into an image signal by forming an image on the imaging surface of the image sensor. The reader scanner 43 extends in the main scanning direction (a direction perpendicular to the original document transport direction), so it is possible to read the image of the entire page by transporting the original document.

When reading a document without using the document feeder 41, the user first lifts the document feeder 41 and places the document on the platen glass 45, and then scans the reader scanner 43 from left to right to read the document.

It also has a UI (user interface) unit 50 that displays the status of the image forming device 1 and receives input from the user.

[Image formation control unit]
3 is a block diagram showing the schematic configuration of the image forming apparatus 1. Note that in this figure, the parts necessary for explaining the operation of this embodiment are mainly described, and other parts already known as image control are omitted.

First, the controller 100 that controls the printing will be described in detail. The controller 100 is an electric circuit board equipped with a calculation unit such as a CPU 101 and storage units (memories) such as a ROM and RAM 102. The controller 100 functions as a control unit that performs various controls by having the CPU circuit unit 101 read out programs stored in the ROM and RAM 102. The controller 100 is also electrically connected to various components such as an external information terminal such as a personal computer (not shown), an input device such as an image reader 40, and an operation panel 50, and is capable of exchanging signal information. The controller 100 performs image formation operations by comprehensively controlling various components within the device based on print information signals (e.g., image data, paper information, etc.) input from the input device.

Next, we will explain the details of what the CPU circuit unit 101 controls for each block.

The UI unit 50 exchanges information with the CPU circuit unit 101. It outputs key signals corresponding to the operation of each key of the input unit 502 to the CPU circuit unit 101, and displays corresponding information on the display unit 501 based on the signal from the CPU circuit unit 101.

The image forming unit includes an environment detection unit 600. Information from the environment detection unit is transmitted to the CPU 101, and the CPU 101 reflects the information from the environment detection unit in various controls.

The CPU 101 controls the high-voltage power supply 151 that applies voltage to the primary transfer roller 15 of the image forming unit. At the same time, the CPU 101 also obtains the measurement results from the measuring device 152.

The paper transport device 8 also has cassette size detection and multi-size detection, and inputs paper size information to the CPU 101, which then performs control according to the paper size.

<Image formation sequence>
The image formation sequence will be described with reference to the cross-sectional view of FIG.

When the image forming apparatus 1 performs an image forming operation, the controller 100 executes the following control for each component involved in the image forming operation to form a full-color image on the recording material P.

First, the controller 100 starts to rotate the drum 11 in the image forming station 10 and the drive roller 22 in the transfer belt unit 20 at a predetermined speed in accordance with the image formation timing. Specifically, the drum 11 is rotated in a clockwise direction in the figure, and the intermediate transfer belt 21 is rotated relative to the drive roller 22 in a forward direction (counterclockwise in the figure) relative to the rotation direction of the drum 11.

Next, the image forming station 10 executes operational control to develop an image on the drum 11 of each color. First, the charging roller 12 uniformly charges the surface of the drum 11 to a predetermined potential with negative polarity. Next, the laser scanner unit 13 scans and exposes the surface of the drum 11 using a laser beam modulated according to the image information signals of each color of Y, M, C, and K, to form an electrostatic latent image of each color. Next, the developing unit 14 electrostatically attaches toner to the electrostatic latent image formed, forming (developing) a toner image on the drum 11.

Next, the controller 11 performs an operation control to superimpose the toner images formed on the drums 11 of each color onto the intermediate transfer belt 21. In detail, a predetermined positive voltage is applied to the primary transfer roller 15, which faces the drum 11 via the intermediate transfer belt 21, and the toner image on the drum 11 is electrostatically transferred onto the intermediate transfer belt 21 at the primary transfer section. By performing this operation for each color, a full-color (Y+M+C+K) unfixed toner image is formed on the intermediate transfer belt 21. This unfixed toner image is carried to the secondary transfer nip section T2 by the rotational drive of the drive roller 22. Note that any toner remaining on the drum 11 that could not be transferred to the intermediate belt 21 at the primary transfer section is cleaned by a photosensitive drum cleaning member (not shown).

In addition, in parallel with the operation of forming an unfixed toner image on the intermediate transfer belt 21, an operation of feeding paper from cassette 2 is performed. Specifically, in accordance with the image formation timing, recording material P is fed one sheet at a time by a feed roller 3 and a separation roller pair 4 and transported to a registration roller pair 5. After that, in synchronization with the unfixed toner image on the intermediate transfer belt 21, the recording material P is transported to the secondary transfer nip portion T2.

Next, the operation control is performed to transfer the unfixed toner image on the intermediate transfer belt 21 onto the recording material P. In detail, when the unfixed toner image and the recording material P are transported to the secondary transfer nip portion T2, a secondary transfer bias is applied to the secondary transfer roller 25 with a positive polarity opposite to the negative polarity of the toner charge. This causes the unfixed toner image to be electrostatically transferred from the intermediate transfer belt 21 to the recording material P (secondary transfer). In other words, the unfixed toner image is transferred to one side of the recording material P as the recording material P is nipped and transported at the secondary transfer nip portion T2. Note that any toner remaining on the intermediate transfer belt 21 that could not be transferred to the recording material P at the secondary transfer portion is cleaned by the intermediate transfer intermediate transfer belt cleaning member 23.

The image forming device of this embodiment calculates a predicted value that indicates the state of the main body, that is, how it warms up. The image forming device has a prediction unit. This prediction unit calculates a predicted value of the state of the main body. Values used in the calculation include a thermistor that detects the surface temperature of the heating rotor, the ambient temperature, and the number of pages that have been printed on a job. Using these elements, the prediction unit predicts the state of the main body.

The process speed variable threshold for the predicted value representing how the main body will warm up differs depending on the environment. For example, in this embodiment, a first threshold and a second threshold are used. In a low temperature environment, the first threshold is used, and in a high temperature environment, the second threshold is used. In such a case, linear interpolation is performed on the controlled temperature for the predicted value representing how the main body will warm up. Furthermore, linear interpolation is performed on the controlled temperature at full speed (first speed) and the controlled temperature at half speed (second speed). This results in inappropriate temperature control, which may cause poor fixing or high temperature offset.

The above content will be explained in detail below using Figure 4 and Figures 5(a) and (b) as an example of passing small size paper.

Figure 4 is a graph showing the predicted value representing how the main body will warm up against the variable process speed threshold when the threshold is the same in a high temperature environment (N environment) and a low temperature environment (L environment).

A low temperature environment is a state in which the environmental detection unit detects a low temperature. This is referred to as the low temperature environmental temperature. A high temperature environment is a state in which the environmental detection unit detects a high temperature. This is referred to as the high temperature environmental temperature.

The horizontal axis of Figure 4 shows how the main body heats up, the vertical axis (left) shows the temperature control temperature of the fixing unit, and the vertical axis (right) shows the process speed. (The same applies to Figures 5, 6, 9, 10, and 11 below.)

As shown in Figure 4, if linear interpolation is performed on the temperature control temperatures of the N environment actual thin line and the L environment actual thick line with respect to the predicted values that represent how the main body will warm up, the result will be a dashed line, and appropriate temperature control will be obtained at full speed (first speed) and half speed (second speed).

Figures 5(a) and 5(b) are graphs (before countermeasures were taken) showing the predicted value representing how the main body will warm up versus the variable process speed threshold value when it is different in the N environment and the L environment.

The reason for changing the process speed variable threshold between the N environment and the L environment is that all other conditions are the same and small size paper is passed through. In this case, the amount of heat absorbed by the paper is greater in the L environment than in the N environment, and the same amount of heat is also applied to non-paper passing areas. This results in severe temperature rise at the edges.

To prevent temperature rise at the ends, the threshold for switching from full speed (first speed) (first speed) to half speed (second speed) is made earlier in the L environment.

It is also possible to consider a method of speeding up the threshold for switching from full speed (first speed) (first speed) to half speed (second speed) in the N environment to match the L environment, but this would also reduce the productivity of the N environment.

In this embodiment, FIG. 5(a) shows an environmental temperature of 17°C, which is included in the N environmental setting, and the process speed variable threshold is a predicted value of 280 that indicates how the main body will warm up.

When linear interpolation is performed on the temperature control temperatures of the N environment thin line and the L environment thick line against the predicted values that represent how the main body will warm up, it becomes the dotted line. In part A in the figure, 185°C is required to ensure fixability at full speed (first speed), but linear interpolation with the temperature control temperature at half speed (second speed) results in 150°C, and fixability is not ensured.

In this embodiment, FIG. 5(b) shows an environmental temperature of 16°C, which is included in the L environmental setting, and the process speed variable threshold is a predicted value of 180 that indicates how the main body will warm up.

When linear interpolation is performed on the temperature control temperatures of the N environment thin line and L environment thick line against the predicted values that represent how the main body will warm up, it becomes the dotted circle line. In part B in the figure, 130°C is appropriate to ensure fixability at half speed (second speed), but it is interpolated with the temperature control temperature at full speed (first speed) to become 143°C, and because an excessive temperature is applied, the latitude for high temperature offset is reduced.

<Example 1-(a)>
The predicted values indicating how the main body will warm up are those that represent the temperature of the pressure source R, which increases as printing progresses, and the temperature transition of the cleaning member for the photosensitive drum, and are shown in FIG.

The horizontal axis of Figure 8 shows the number of pages printed, and the vertical axis shows the predicted value indicating how the main body will warm up.

As the number of printed sheets increases, the predicted value that represents the warming of the main body increases, and decreases from 1,500 sheets, when printing stops. In this embodiment (a), as shown in Figure 6 (a), we will describe the linear interpolation method when the environmental temperature is 17°C (belonging to the N environmental setting).

The solid thin line in FIG. 6(a) shows the controlled temperature relative to the predicted value representing how the main body will warm up in the N environment. The solid thick line shows the controlled temperature relative to the predicted value representing how the main body will warm up in the L environment. The thick dotted line shows the controlled temperature when the process speed variable threshold in the L environment is matched to the process speed variable threshold in N.

The dotted line shows the linear interpolation of the temperature trend in the N environment and the temperature trend in the L environment after the change.

In this way, by matching the process speed variable threshold of the L environment to the process speed variable threshold of the environment to which the set temperature belongs (in this example, the N environment to which 17°C belongs), the temperature control down at full speed (first speed) as occurred in Figure 5(a) is eliminated, and the fixing failure is resolved.

By taking the above measures, we can ensure the productivity and stability of the N environment.

Next, the flow of linear interpolation shown in FIG. 6(a) will be explained using FIG. 1. The user sets the paper to be used. (S020) The paper size is detected by cassette size detection. (S030) In the case of small size, if it is smaller than A4 size in this embodiment, it is recognized as small size. In the case of small size, follow the flow on the left side of FIG. 1. (S040) The paper type, number of prints, and single-sided or double-sided printing are determined based on the user's print command. (S050) The environment detection unit (600) of the main body grasps the environmental temperature in which the image forming device 1 is placed. (S060) Based on the information on the paper size (S040), paper type, single-sided or double-sided (S050), and environmental temperature (S060), the process speed variable threshold (S070) is determined. This determines the intersection α of the dashed line in FIG. 6(a) and the predicted value that represents the warming of the main body.

In this implementation, the process speed variable threshold of the L environment is adjusted to the process speed variable threshold (280) of the environment to which the set temperature belongs (in this example, the N environment to which 17°C belongs). With the process speed variable threshold of the N environment adjusted to the process speed variable threshold of the L environment, linear interpolation of the temperature control temperature is performed (S080). This determines the dotted line in Figure 6(a). The state of how the main body (fuser) is warming up is confirmed (S090). This information makes it possible to confirm where it is located on the horizontal axis of Figure 6(a), and the print speed (S100) and temperature control temperature (S110) are determined.

For example, when the predicted value indicating how the main body will warm up is 200, it can be seen that the temperature control is performed at full speed (first speed) at point β in the diagram, with the temperature control temperature being 185°C. In this case, the temperature control at full speed (first speed) in the N environment and the temperature control at full speed (first speed) in the L environment are linearly interpolated to calculate the appropriate temperature control, so no fixing problems will occur. Next, image formation (S120), fixing (S130), and paper discharge (S140) are performed, and the process of checking the main body status (S090) to paper discharge (S140) is repeated until the number of pages specified in the print command is reached. When the number of pages specified in the print command is reached, the JOB ends. (S150) By taking the above measures, productivity and fixability in the N environment can be ensured.

<Example 1-(b)>
In this embodiment 1-(b), as shown in Fig. 6(b), a linear interpolation method will be described for the case where the environmental temperature is 16°C (belonging to the L environment setting). The solid thin line in Fig. 6(b) indicates the controlled temperature for the predicted value representing the way the main body will warm up in the N environment. The solid thick line indicates the controlled temperature for the predicted value representing the way the main body will warm up in the L environment. Also, the thin dotted line indicates the controlled temperature when the process speed variable threshold value for the N environment is changed to the process speed variable threshold value for the L environment.

The dotted circle line shows the linear interpolation of the temperature change in the N environment and the temperature change in the L environment after the change.

In this way, linear interpolation is performed by matching the process speed variable threshold of the N environment to the process speed variable threshold of the environment to which the set temperature belongs (in this example, the L environment to which 16°C belongs). This eliminates the temperature increase at half speed (second speed) that occurred in Figure 5(b), and resolves the concern about high temperature offset.

By taking the above measures, it is possible to avoid temperature rise at the edge of the L environment and high temperature offset.

Next, the linear interpolation flow shown in Figure 6(b) will be explained using Figure 1.

The user loads the paper to be used. (S020) The paper size is detected by cassette size detection. (S030) In the case of small size, in this implementation, if it is A4 size or smaller, it is recognized as small size. In the case of small size, follow the flow on the left. (S040) The paper type, number of prints, and single-sided or double-sided printing are determined based on the user's print command. (S050) The environmental detection unit of the main body detects the environmental temperature in which the image forming device is placed. (S060) The process speed variable threshold (S070) is determined based on information on the paper size (S040), paper type, single-sided or double-sided (S050), and environmental temperature (S060).

This determines the intersection point γ of the dashed dotted line in Figure 6(b) and the warm air prediction value.

In this implementation, the process speed variable threshold of the N environment is adjusted to the process speed variable threshold (180) of the environment to which the set temperature belongs (in this example, the L environment to which 16°C belongs). (S070) With the process speed variable threshold of the L environment adjusted to the process speed variable threshold of the N environment, linear interpolation of the temperature control temperature is performed. (S080) This determines the dotted line in Figure 6(b). The state of how the main body is warming up is confirmed. (S090) This information makes it possible to confirm where it is located on the horizontal axis in Figure 6(b), and the print speed (S100) and temperature control temperature (S110) are determined.

For example, if the predicted value representing how the main body will heat up is 240, it can be seen that the temperature will be controlled at point ε on the diagram at half speed (second speed) and a controlled temperature of 120°C.

Next, image formation (S120), fixing (S130), and paper discharge (S140) are performed, and the process of checking the status of the main unit (S090) through paper discharge (S140) is repeated until the number of pages printed is reached. When the number of pages printed is reached, the job ends. (S150) By taking the above measures, it is possible to avoid edge temperature rises in the L environment and high-temperature offset.

Furthermore, from the results of Figures 6(a) and 6(b), it is possible to perform appropriate linear interpolation while maintaining productivity in the N environment, and while avoiding temperature rise at the edge in the L environment.

If the document is detected as large size in (S040) of FIG. 1 (in this embodiment, A4 size or larger), the flow on the right side of FIG. 1 is followed. The case where the document is detected as large size is explained in the following Example 2-(a) and Example 2-(b).

Example 2
The image forming apparatus, image forming control unit, and image forming sequence of this embodiment 2 are similar to those of this embodiment 1. Here, only the differences from this embodiment 1 will be described. In this embodiment 2, the process speed is reduced to half speed (second speed) as a measure to avoid the occurrence of curling of the cleaning member of the photosensitive drum when the cleaning member of the photosensitive drum of the image forming station 10 rises in temperature due to continuous feeding of large size paper. The purpose is to devise a method of linear interpolation regarding the target temperature control temperature of fixing in this case and to perform optimal setting. Details will be described below.

<Example 2-(a)>
The case where a large size is detected (S030) will be described as Example 2-(a).

If a large size is detected (A4 size or larger in this implementation) (S040), the flow on the right side of Figure 1 is followed. For large sizes, as with small sizes, if the process speed variable threshold differs from the predicted value that represents how the main body will warm up in the environment, linear interpolation is performed on the controlled temperature for the predicted value that represents how the main body will warm up. This results in inappropriate temperature control, as linear interpolation is performed on the controlled temperature at full speed (first speed) and the controlled temperature at half speed (second speed), which may result in poor fixing or high temperature offset.

As with the small size, the explanations will be given in the following order.

Figure 9 shows the case where the process speed variable threshold is the same depending on the environment. Figure 10 (before measures) shows the case where the process speed variable threshold differs depending on the environment. Figure 11 (after measures) shows the case where the process speed variable threshold differs depending on the environment. Figure 9 is a graph showing the predicted value indicating how the main unit will warm up versus the case where the process speed variable threshold is the same in the N environment and the H environment.

As shown in Figure 9, if linear interpolation is performed on the temperature control temperatures of the thin solid line in the N environment and the thick halftone line in the H environment for the predicted values that represent how the main body will warm up, the result will be the dotted line, and appropriate temperature control will be obtained at full speed (first speed) and half speed (second speed).

Figures 10(a) and 10(b) are graphs (before measures were taken) showing the predicted value representing how the main body will warm up versus the variable process speed threshold value when it is different in the N environment and the H environment.

The reason for changing the process speed variable threshold between the N environment and the H environment is that when large-size paper is fed continuously under the same conditions other than the environmental conditions, a larger amount of heat accumulates inside the main body in the H environment than in the N environment. This is also because problems such as the cleaning member of the photosensitive drum turning over can occur. For this reason, the threshold for switching from full speed (first speed) to half speed (second speed) is made faster in the H environment.

It is also possible to consider a method of speeding up the threshold for switching from full speed (first speed) to half speed (second speed) in the N environment to match the H environment, but this would also reduce the productivity of the N environment.

In this embodiment, FIG. 10(a) shows an environmental temperature of 24°C, which is included in the N environmental setting, and the process speed variable threshold is a predicted value of 5600 that indicates how the main body will warm up.

When linear interpolation is performed on the temperature control temperatures of the N environment thin solid line and the L environment thick halftone line with respect to the predicted values that represent how the main body will warm up, it becomes the dotted line, and in the figure, in part A', 165°C is required to ensure fixability at full speed (first speed), but linear interpolation with the temperature control temperature at half speed (second speed) results in 143°C, and fixability is not ensured.

In this embodiment, FIG. 10(b) shows an environmental temperature of 27° C., which is included in the H environmental setting, and the process speed variable threshold is a predicted value of 3600, which represents how the main body will warm up.

When linear interpolation is performed on the temperature control temperatures of the N environment thin solid line and the H environment thick halftone line with respect to the predicted values that indicate how the main body will warm up, it becomes the circle dotted line, and in part B' in the figure, 80°C is appropriate to ensure fixation at half speed (second speed), but it is interpolated with the temperature control temperature at full speed (first speed) to become 103°C, and because an excessive temperature is applied, the latitude against high temperature offset and curling of the cleaning member of the photosensitive drum is reduced.

Next, we will use Figure 11 to explain the countermeasure, which is to "perform linear interpolation according to the process speed variable threshold value for the predicted value that represents how the main unit will warm up in the environment to which the set temperature belongs."

As shown in FIG. 11(a), we will describe the linear interpolation method when the environmental temperature is 24°C (belonging to the N environmental setting).

The solid thin line in FIG. 11(a) shows the controlled temperature relative to the predicted value representing how the main body will warm up in the N environment. The halftone thick line shows the controlled temperature relative to the predicted value representing how the main body will warm up in the H environment. The thick halftone dotted line shows the controlled temperature when the process speed variable threshold in the H environment is matched to the process speed variable threshold in the N environment.

The dotted line shows the linear interpolation of the temperature change in the N environment and the temperature change in the H environment after the change.

In this way, the process speed variable threshold of the H environment is adjusted to the process speed variable threshold of the environment to which the set temperature belongs (in this example, the N environment to which 24°C belongs). This eliminates the temperature control down at full speed (first speed) that occurred in Figure 10(a) and resolves the fixing failure.

By taking the above measures, we can ensure the productivity and stability of the N environment.

Next, the linear interpolation flow shown in Figure 11(a) will be explained using Figure 1.

The user sets the paper to be used. (S020) The paper size is detected by cassette size detection. (S030) In the case of large size, in this embodiment, if it is A4 size or larger, it is recognized as large size. In the case of large size, the flow on the right side of Figure 1 is followed. (S040) The paper type, number of prints, and single-sided or double-sided printing are determined based on the user's print command. (S1050) The environmental detection unit of the main body grasps the environmental temperature in which the image forming device is placed. (S1060) The process speed variable threshold is determined based on the information on paper size (S040), paper type, single-sided or double-sided (S1050), and environmental temperature (S1060). This determines the intersection α' of the dashed line in Figure 11 (a) and the predicted value that represents the warming of the main body.

In this embodiment, the process speed variable threshold of the H environment is adjusted to the process speed variable threshold (5600) of the environment to which the set temperature belongs (in this embodiment, the N environment to which 24°C belongs). (S1070) With the process speed variable threshold of the H environment adjusted to the process speed variable threshold of the N environment, linear interpolation of the temperature adjustment temperature is performed (S1080). This determines the dotted line of linear interpolation in Figure 11 (a).

The state of the main body (fuser) warming up is checked (1090). This information allows you to check where it is located on the horizontal axis of Figure 11(a), and then the print speed (S1100) and temperature control temperature (S1110) are determined.

For example, when the predicted value representing how the main body will heat up is 4000, it can be seen that at full speed (first speed), the temperature will be adjusted to 150°C, at point β' on the diagram.

In this case, the temperature control at full speed (first speed) in the N environment and the temperature control at full speed (first speed) in the L environment are linearly interpolated to calculate the appropriate temperature control temperature, so poor fixing does not occur.

Next, image formation (S1120), fixing (S1130), and paper discharge (S1140) are performed, and the process of checking the status of the main unit (S1090) through paper discharge (S1140) is repeated until the commanded number of pages is printed. When the commanded number of pages is printed, the job ends (S1150). By taking the above steps, the productivity and fixation of the N environment can be ensured.

<Example 2-(b)>
In this embodiment, as shown in FIG. 11B, a linear interpolation method will be described for the case where the environmental temperature is 27° C. (belonging to the H environmental setting).

The solid thin line in FIG. 11(b) shows the controlled temperature relative to the predicted value representing how the main body will warm up in the N environment. The halftone thick line shows the controlled temperature relative to the predicted value representing how the main body will warm up in the H environment. The thin dotted line shows the controlled temperature when the process speed variable threshold in the N environment is changed to the threshold in the H environment.

The dotted circular line shows the linear interpolation of the temperature trends in the N environment and the H environment after the change.

In this way, linear interpolation is performed by matching the process speed variable threshold of the N environment to the process speed variable threshold of the environment to which the set temperature belongs (in this embodiment, the H environment to which 27°C belongs). This eliminates the temperature increase at half speed (second speed) that occurred in Figure 10(b), and resolves concerns about high temperature offset and peeling of the cleaning member of the photosensitive drum.

By taking the above measures, it is possible to prevent the cleaning member of the photosensitive drum from turning over in the H environment.

Next, the linear interpolation flow shown in Figure 11(b) will be explained using Figure 1.

The user sets the paper to be used. (S020) The paper size is detected by cassette size detection. (S030) In the case of large size, if it is A4 size or larger in this embodiment, it is recognized as large size. In the case of large size, follow the flow on the right. The paper type, number of prints, and single-sided or double-sided printing are determined based on the user's print command. (S1050) The environment detection unit of the main body grasps the environmental temperature in which the image forming device is placed. (S1060) The process speed variable threshold is determined based on the information on the paper size (S040), paper type, single-sided or double-sided (S1050), and environmental temperature (S1060). This determines the intersection γ' of the dashed line and the warm air prediction value in Figure 11 (b). In this embodiment, the process speed variable threshold of the N environment is adjusted to the process speed variable threshold (3600) of the environment to which the set temperature belongs (in this embodiment, the H environment to which 27°C belongs). (S1070) Linear interpolation of the temperature control temperature is performed with the process speed variable threshold of the H environment and the process speed variable threshold of the N environment aligned. (S1080) This determines the dotted line in FIG. 11(b). The state of how the main body is warming up is confirmed. (1090) This information allows you to confirm where you are located on the horizontal axis of FIG. 11(b), and the print speed (S1100) and temperature control (S1110) are determined. For example, in the case of a predicted value of 4800 that represents how the main body is warming up, it is understood that the temperature control is performed at half speed (second speed), with a temperature control temperature of 80°C, and at point ε' in the figure. Next, image formation (S1120), fixing (S1130), and paper discharge (S1140) are performed, and the process of checking the main body state (S1090) to paper discharge (S1140) is repeated until the number of sheets specified in the print command is reached.

When the number of puddings specified in the command is reached, the job ends (S1150).

By taking the above measures, it is possible to avoid temperature rise at the edge of the L environment, high temperature offset, and curling of the cleaning member of the photosensitive drum.

Furthermore, from the results of Figures 11(a) and 11(b), it is possible to ensure productivity in the N environment, while avoiding high temperature offset and curling of the cleaning member of the photosensitive drum in the H environment.

1 Image forming apparatus 2 Paper feed cassette 3 Paper feed roller 4 Separation roller 5 Registration roller 6 Multi-tray 9 Discharge tray 10 Image forming station (YMCK for each color)
11 Electrophotographic photoreceptor (YMCK for each color)
12 Charging device (YMCK for each color)
13 Exposure means (YMCK for each color)
14 Developing device (YMCK for each color)
15 Primary transfer device (YMCK for each color)
151 Primary transfer power supply 152 Primary transfer measurement device 20 Transfer belt unit 21 Intermediate transfer belt 22 Drive roller 23 Intermediate transfer belt cleaning member 231 Belt cleaning member power supply 232 Belt cleaning member measurement device 25 Secondary transfer device 251 Secondary transfer power supply 252 Secondary transfer measurement device 30 Fixing device 301 Fixing power supply device 302 Fixing measurement device 40 Image reader 41 Document feeder 42 Document tray 43 Reader scanner 44 Document discharge unit 50 User interface unit 501 Display unit 502 Input unit 600 Environment detection unit 100 Controller 101 CPU
102 Memory section T2 Secondary transfer nip section Q Paper transport path P Paper M Main thermistor

Claims (1)

a fixing device that fixes the toner image onto the recording material;
a speed control section for controlling a conveying speed of the recording material in the fixing device;
the speed control unit controls the conveying speed to a first speed and a second speed lower than the first speed,
a temperature control unit for controlling a fixing temperature of the fixing device;
an environment detection unit that detects an environmental temperature of the image forming apparatus;
The environment detection unit can detect a low environment temperature and a high environment temperature higher than the low environment temperature,
a prediction unit that predicts a temperature of the fixing device and calculates a predicted value of the temperature of the fixing device;
the speed control unit controls the conveying speed to the second speed when the environment detection unit detects the low environmental temperature and the predicted value reaches a first threshold, and controls the conveying speed to the second speed when the environment detection unit detects the high environmental temperature and the predicted value reaches a second threshold that is higher than the first threshold;
the temperature control unit linearly interpolates the fixing temperature at a predetermined environmental temperature between the low environmental temperature and the high environmental temperature, using a fixing temperature at the low environmental temperature;
an image forming apparatus characterized in that the temperature control unit determines the fixing temperature to be used for linear interpolation based on the conveying speed controlled by the speed control unit when the predicted value is between the first threshold value and the second threshold value.

Images