JP7786136B2 - Image forming apparatus and image forming method - Google Patents

Description

The present invention relates to a fixing device, an image forming apparatus, and an image forming method.

Images have traditionally been formed on a variety of paper types using image forming devices that use electrophotographic two-component development technology and thermal fixing technology.

With conventional technology, when continuously forming images on various types of paper, there is a chance that the fixing temperature will need to be adjusted when switching between paper types. Furthermore, after fixing, there is a chance that the post-processing device finisher will need to wait for stapling, punching holes, saddle stitching, and binding to complete. In this case, the toner image formation process (development process) will wait, meaning that the device will run idle, while waiting for these processes to complete.

When this waiting period occurs, for example in two-component development where carrier and toner are mixed, the toner continues to rotate without a toner balance, causing the toner to deteriorate. Examples of toner deterioration include additives that should be present on the surface of the toner matrix becoming embedded in the toner matrix, or additives being missing from the surface of the toner matrix. Toner deterioration can cause uneven transfer and lead to image degradation.

Patent Document 1 discloses that the driving of the developing device is stopped when there is a gap between pages, and that the driving of the developing device is resumed after the paper feed signal is turned ON. Furthermore, the timing for resuming the development drive of the developing device that was stopped in the non-image area between the image areas of two pages is determined based on the image pattern of the image area of the subsequent page. Patent Document 1 claims that it is possible to set an appropriate restart timing depending on the image pattern of the image area of the subsequent page, thereby eliminating unnecessary restart margins. This reduces the stress on the developer caused by development drive unnecessary for image formation, and minimizes the stress on the developer.

In Patent Document 1, if the paper gap (image gap) when switching between papers is large, the developing unit is shut down and restarted after the paper feed signal is turned ON. Generally, the paper feed signal is considered to be turned ON after the fixing means is ready to allow paper to pass through.

However, when the developing unit is started up after the paper feed signal is turned ON in this way, the paper is not transported to the fixing unit even though the fixing unit is ready to pass paper, which causes the job time to increase. On the other hand, if the developing unit is left running when raising the fixing temperature of the fixing unit, the job time can be prevented from increasing, but toner degradation may occur. Prior art has not been able to solve both of these problems at the same time.

The present invention therefore aims to provide a fixing device that can shorten the time required for continuous jobs and suppress toner degradation.

In order to solve the above problem, the image forming apparatus of the present invention includes an image carrier that carries a latent image, a developing roller that develops the latent image with a developer to form a visible image, transfer means that transfers the visible image to a recording medium, and fixing means that fixes the visible image on the recording medium, and in a continuous job in which images are formed on a plurality of recording media, when N is an integer of 2 or more and is a job number, and the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, after fixing the N-1th recording medium, when the fixing temperature of the fixing means is raised or lowered to fix the Nth recording medium, before the fixing means becomes ready to pass paper, a notification is given to start driving the developing roller to perform the Nth development, and the Nth development is started. When a notification is given to start the Nth development, the notification to start the Nth development is a notification to start driving the developing roller, and after the notification to start driving the developing roller to perform the Nth development, driving of the developing roller to perform the Nth development is started, and if, in the continuous job, the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium and it takes a predetermined time after fixing of the N-1th recording medium to raise the fixing temperature of the fixing means to the fixing temperature of the Nth recording medium, driving of the developing roller that was being driven to perform the N-1th development is stopped from the time the N-1th development is completed until the notification to start driving the developing roller to perform the Nth development is given.

This invention provides a fixing device that can shorten the time required for continuous jobs and suppress toner degradation.

1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention. 1 is a schematic diagram illustrating an example of a fixing device according to the present invention. 4 is a time chart for explaining an example of the image forming method of the present invention, in which the fixing temperature of the fixing unit is increased. 10 is a time chart for explaining an example of an image forming method that is not included in the present invention. 5 is a time chart for explaining another example of the image forming method of the present invention. 10 is a time chart for explaining another example of the image forming method of the present invention, in which the fixing temperature of the fixing unit is lowered.

The fixing device, image forming apparatus, and image forming method according to the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments shown below, and can be modified, including other embodiments, additions, modifications, and deletions, within the scope of what one skilled in the art can conceive. Any embodiment that achieves the effects and advantages of the present invention is within the scope of the present invention.

The fixing device of the present invention is a fixing device that fixes a visible image transferred to a recording medium onto the recording medium, and is characterized in that, in a continuous job in which images are formed on multiple recording media, when N is an integer greater than or equal to 2 and the job number is an integer, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, after fixing the N-1th recording medium, when the fixing temperature of the fixing device is raised or lowered to fix the Nth recording medium, a notification is given to start driving the developing means to perform the Nth development or a notification is given to start driving the image carrier to perform the Nth image formation before the fixing device becomes ready to pass paper.

The image forming apparatus of the present invention comprises an image carrier that carries a latent image, a developing unit that develops the latent image with a developer to form a visible image, a transfer unit that transfers the visible image to a recording medium, and a fixing unit that fixes the visible image to the recording medium, wherein the fixing unit is the fixing device of the present invention, and when a notification to start the Nth development is given, the notification to start the Nth development is a notification to start driving the developing unit, and after the notification to start driving the developing unit for the Nth development, driving of the developing unit is started to perform the Nth development, or after a notification to start driving the image carrier for forming the Nth image, driving of the image carrier is started to perform the Nth image. Note that in this embodiment, the fixing device and fixing unit have the same meaning.

The image forming apparatus of the present invention is characterized in that it includes an image carrier that carries a latent image, a developing unit that develops the latent image with a developer to form a visible image, a transfer unit that transfers the visible image to a recording medium, and a fixing unit that fixes the visible image to the recording medium. In a continuous job in which images are formed on multiple recording media, where N is an integer greater than or equal to 2 and the job number is an integer greater than or equal to 2, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, after fixing the N-1th recording medium, when the fixing temperature of the fixing unit is increased or decreased to fix the Nth recording medium, the image forming apparatus starts driving the developing unit to perform the Nth development or starts driving the image carrier to perform the Nth image formation before the fixing unit becomes ready to pass paper.

The image forming method of the present invention includes a developing step in which a latent image carried by an image carrier is developed with a developer using a developing means to form a visible image; a transfer step in which the visible image is transferred to a recording medium; and a fixing step in which the visible image is fixed to the recording medium. In a continuous job in which images are formed on multiple recording media, where N is an integer of 2 or greater and the job number is the fixing temperature of the Nth recording medium, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, after fixing the N-1th recording medium, when the fixing temperature is increased or decreased in the fixing step to fix the Nth recording medium, the developing means is started to be driven to perform the Nth development, or the image carrier is started to be driven to perform the Nth image formation, before the fixing step becomes ready for paper passage.

The following describes an embodiment of an image forming apparatus of the present invention, taking as an example an electrophotographic tandem color printer (hereinafter referred to as printer 200).

Figure 1 is a diagram illustrating the general configuration of a printer 200 according to this embodiment. Figure 2 is a diagram illustrating an example of the configuration of a fixing device that can be provided in the printer 200 according to this embodiment.

As shown in Figure 1, printer 200 is a high-speed machine equipped with image forming unit 200A located at the top of the device body and paper feed unit 200B located below image forming unit 200A. Printer 200 also incorporates fixing device 100 (fixing means) in image forming unit 200A.

In image forming unit 200A, intermediate transfer belt 210 is located in the vertical center of the device body. Above intermediate transfer belt 210, a structure is provided for forming toner images corresponding to multiple colors that are complementary to the color separation colors. Specifically, photoconductors 205Y, M, C, and K are arranged along the upper transfer surface of intermediate transfer belt 210 as image carriers (latent image carriers) capable of carrying toner images of yellow (Y), magenta (M), cyan (C), and black (K), which are complementary colors.

The photoconductors 205Y, M, C, and K are drum-shaped and rotatable in the same direction (counterclockwise in the figure). Around each photoconductor 205, there are arranged charging devices 202Y, M, C, and K, developing devices 203Y, M, C, and K, primary transfer devices 204Y, M, and C, and photoconductor cleaning devices 206Y, M, C, and K, respectively.

The developing devices 203Y, 203M, 203C, and 203K contain respective color toners.
Furthermore, optical writing devices 201Y and 201M and optical writing devices 201C and 201K are arranged at the top inside the image forming section 200A.

The intermediate transfer belt 210 is looped around a drive roller and a driven roller, and is configured to be movable in the same direction as the photosensitive elements 205Y, M, C, and K at a position opposite them. A secondary transfer roller 212 is provided opposite a secondary transfer opposing roller 211, which is one of the driven rollers. The transport path for paper P (as a recording medium, also referred to as a recording material or sheet) from the secondary transfer roller 212 to the fixing device 100 is a transverse path in a substantially horizontal direction.

The paper feed unit 200B has a paper feed tray 220 that holds a stack of paper P, and a transport mechanism. The transport mechanism separates the paper P in the paper feed tray one by one, starting from the bottom, and transports them to the position of the secondary transfer roller 212.

An example of image formation in this printer 200 will be described. The surface of photoconductor 205Y is uniformly charged by charging device 202Y, and an electrostatic latent image (also referred to as a latent image) is formed on photoconductor 205Y based on image information from the image reading unit. The formed electrostatic latent image is visualized as a toner image by developing device 203Y, which contains yellow (Y) toner. This toner image is primarily transferred onto intermediate transfer belt 210 by primary transfer device 204Y, to which a predetermined bias is applied.

Similar images are formed on the other photoreceptors 205M, C, and K, except that the toner colors are different, and the toner images of each color are transferred in sequence onto the intermediate transfer belt 210 by electrostatic force and superimposed on top of each other.

The toner image that has been primarily transferred from photoreceptors 205Y, M, C, and K onto intermediate transfer belt 210 is then transferred onto paper P, which has been transported thereto, by secondary transfer opposing roller 211 and secondary transfer roller 212. The paper P onto which the toner image has been transferred is then transported to fixing device 100, where it is fixed in fixing nip N between fixing belt 51 and pressure roller 55, and is then discharged to the exit side of fixing nip N. The paper P that has been discharged from fixing nip N is then sent along the discharge path to stacker 215.

In addition, residual toner and other materials remaining on photoconductors 205Y, M, C, and K that were not primarily transferred onto intermediate transfer belt 210 are removed by photoconductor cleaning devices 206Y, M, C, and K, respectively. In addition, residual toner and other materials remaining on intermediate transfer belt 210 that were not secondary transferred onto paper P are removed by belt cleaning device 213 in preparation for the next image formation.

Figure 1 illustrates a control unit 1000. The printer 200 shown in Figure 1 may have the control unit 1000, or the fixing device 100 may have the control unit 1000. Alternatively, the printer 200 and the fixing device 100 may both have separate control units.

The control unit 1000 can be, for example, general hardware configured from an arithmetic unit having a processor such as a CPU (Central Processing Unit), and the above control is performed by the arithmetic unit executing a program. Note that the processing performed by executing the program can be performed by the arithmetic unit itself, and may include dedicated circuits (for example, FPGAs (Field-Programmable Gate Arrays) or ASICs (Application Specific Integrated Circuits)) that perform specific processing.

Next, we will explain the fixing device (fixing means) of this embodiment and an example of a fixing device (fixing means) that can be provided in the printer 200 of this embodiment.

Figure 2 is a schematic diagram of an example of the configuration of a fixing device using two belt heating methods that can be suitably equipped in the printer 200 of this embodiment. Figure 2(a) is a schematic diagram of an example in which a heater 53a, such as a halogen heater, is provided inside the heating roller 54 as the heating means for the heating roller 54. Figure 2(b) is a schematic diagram of an example in which an induction heating means 53b, which is a heating means of an IH system using electromagnetic induction, is provided as the heating means for the heating roller 54.

The only difference between the fixing device 100 shown in FIG. 2(a) and the fixing device 100 shown in FIG. 2(b) is the heating means for heating the heating roller 54. Therefore, we will first focus on the components common to the examples shown in each figure.

The fixing device 100 shown in Figures 2(a) and 2(b) (hereinafter referred to as Figure 2 as appropriate) includes a fixing roller 52, a heating roller 54, a fixing belt 51, and a pressure roller 55 inside a fixing cover 100a. The pressure roller 55 is pressed against the fixing roller 52 with the fixing belt 51 sandwiched between them, forming a fixing nip N between the fixing belt 51 and the pressure roller 55.

A fixing separation member 57 and a pressure separation member 58 are provided on the paper P discharge side of the fixing nip N.

The fixing roller 52 has a metal core 52a and an elastic rubber layer 52b made of silicone rubber or the like. The material for the elastic rubber layer 52b can be selected as appropriate, and examples include foamed silicone rubber. If foamed silicone rubber is used, it is less likely to absorb heat from the fixing belt 51, shortening the warm-up time.

The heating roller 54 can be, for example, a hollow roller made of stainless steel or a nickel alloy. In the configuration example shown in Figure 2(a), a heater 53a, which is a heating means using a halogen heater, is provided inside. In this case, the heating roller 54 is heated by the halogen heater.

On the other hand, in the configuration example shown in Figure 2(b), induction heating means 53b is provided facing the outer periphery of the fixing belt 51 that is wound around the heating roller 54. The induction heating means 53b is a heating means of an IH system that uses electromagnetic induction. In this case, the heating roller 54 is heated by the induction heating means 53b.

The fixing belt 51 is an endless belt, and its cross-sectional structure is a two-layer structure, with an elastic layer such as a silicone rubber layer formed on a base material such as polyimide. The fixing belt 51 is stretched across the fixing belt 51 and heating roller 54 with a constant tension by a heating roller tension spring fixed to the heating roller 54 and the fixing frame.

The pressure roller 55 is a hollow cylindrical roller made of aluminum or iron, with an elastic layer made of silicone rubber or the like provided on the outer periphery of the hollow roller. Inside it is a heater 59, which is a heating means using a halogen heater.

The pressure roller 55 is also configured to be switchable between a pressurized state in which it applies pressure to the fixing belt 51 and a depressurized state (separated state) in which it is separated from the fixing belt 51 and depressurized, by the pressure-releasing means 80 described below.

As shown in FIG. 2, the pressure applying/releasing means 80 has a pressure applying lever 81, a pressure applying spring 82, a pressure applying cam 83, and a pressure applying camshaft 84, and is configured to be switchable between a pressure applying state and a pressure releasing state by rotating the pressure applying camshaft 84 with a drive motor. Specifically, by rotating the pressure applying camshaft 84, it is possible to move the pressure applying roller 55 toward the fixing belt 51 to apply pressure, or to move the pressure applying roller 55 away from the fixing belt 51 to separate it and release the pressure.

In addition, by using this pressure/release means 80 and adjusting the cam position of the pressure cam 83 with a drive motor, a predetermined nip pressure can be obtained.

When the fixing device 100 is driven, for example, the fixing roller 52 is driven to rotate clockwise in Figure 2, causing the fixing belt 51 to rotate in the direction in which the paper P is discharged, and the pressure roller 55, which is in pressure contact with the fixing belt 51, rotates along with it. Note that the roller that is driven to rotate is not limited to the fixing roller 52, but may also be the pressure roller 55.

During the fixing operation, in the example shown in Figure 2(a), the heating roller 54 is first heated by the heater 53a provided inside the heating roller 54, and the heat from the heating roller 54 is transferred to the fixing belt 51. The heating roller 54 is heated until the temperature of the fixing belt 51 detected by the thermopile 56 reaches a predetermined temperature (e.g., a temperature suitable for toner fixing).

On the other hand, in the example shown in Figure 2(b), the heating roller 54 is first heated by electromagnetic induction from induction heating means 53 provided outside the heating roller 54, and the heat from the heating roller 54 is transferred to the fixing belt 51. The heating roller 54 is heated until the temperature of the fixing belt 51 detected by the thermopile 56 reaches a predetermined temperature.

In this embodiment, the fixing temperature of the fixing means is the temperature of the fixing belt 51, which is the temperature detected by, for example, the thermopile 56.

The pressure roller 55 is also heated to a predetermined temperature when necessary, such as when the temperature is increased, by the heat generated by the heater 59 located inside. While this embodiment uses a roller-type pressure roller 55 as the pressure member, this is not limited to this, and a belt-type pressure member using an endless belt stretched between two rollers may also be used.

In the fixing device 100, for example, while the fixing belt 51 and pressure roller 55 are driven to rotate, the surface of the fixing belt 51 is heated to a predetermined temperature. Then, a sheet of paper P carrying (forming) an unfixed toner image T is transported (passed through) the fixing nip N, and the unfixed toner image T is fixed to the sheet of paper P by the application of pressure and heat at the fixing nip N.

At this time, the paper P may exit wrapped around the fixing belt 51, and is therefore separated by the fixing separation member 57. Furthermore, the paper P that is discharged wrapped around the pressure roller 55 side is separated by the pressure separation member 58 and transported along the transport guide.

In the fixing device 100, the heating roller 54 is heated to a predetermined temperature, and after the fixing device 100 is ready for paper passage, the paper P is passed (transported) through the fixing nip N. Note that although the term "passing paper" is used, the recording medium is not limited to paper.

The predetermined temperature of the heating roller 54 is not particularly limited, but can be, for example, approximately 150°C. The upper and lower limits can be selected as appropriate, and can be in the range of 120°C to 200°C, for example. This can be changed as appropriate depending on the type of recording medium, and in particular the fixing temperature of the recording medium.

When paper P passes through the fixing nip N, heat is taken away from the fixing nip N, so heating is performed taking this into consideration. Particularly in the case of a continuous job in which paper P is passed through continuously, the heating roller 54 is continuously heated to compensate for the heat taken away by the paper P from the fixing nip N. The fixing belt 51, which is stretched between the heating roller 54 and the fixing roller 52, transfers heat to the fixing nip N and fixes the toner onto the paper P. At the same time, the fixing belt 51 also continuously applies heat to the fixing roller 52.

The continuous job mentioned above is not particularly limited and can be selected as appropriate. A continuous job consists of multiple jobs. When simply referred to as a job, unless otherwise specified, it means one job within a continuous job. The number of recording media on which images are formed in one job can be selected as appropriate, and may be one or multiple sheets. For example, a continuous job in which 10 or more sheets of paper P are passed through continuously in one job and multiple such jobs are performed can be cited.

The above description uses an example in which a fixing belt is used, but the present invention is not limited to cases in which a fixing belt is used. An example of a method in which a fixing belt is not used is a method in which a fixing roller and a pressure roller are used.

(First embodiment)
Next, a detailed example of image formation in this embodiment will be described.
The fixing device, image forming apparatus, and image forming method of the present embodiment have the following features, for example, in a continuous job in which images are formed on a plurality of recording media with different fixing temperatures.

In a continuous job in which images are formed on multiple recording media, where N is an integer greater than or equal to 2 and the job number is an integer, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, after fixing the N-1th recording medium, when the fixing temperature of the fixing device is raised or lowered to fix the Nth recording medium, the fixing device issues a notification to start driving the developing means to perform the Nth development or a notification to start driving the image carrier to perform the Nth image formation before the fixing device becomes ready to pass paper.

In an image forming apparatus equipped with the fixing device of this embodiment, when a notification is given to start the Nth development, the notification to start the Nth development is a notification to start driving the developing means, and after the notification to start driving the developing means to perform the Nth development, the developing means may be started to be driven to perform the Nth development, or after the notification to start driving the image carrier to perform the Nth image formation, the image carrier may be started to be driven to perform the Nth image formation.

In addition, in the image forming apparatus of this embodiment, in a continuous job in which images are formed on multiple recording media, where N is an integer equal to or greater than 2 and the job number is an integer, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, after fixing the N-1th recording medium, when raising or lowering the fixing temperature of the fixing means to fix the Nth recording medium, the image forming apparatus starts driving the developing means to perform the Nth development or starts driving the image carrier to perform the Nth image formation before the fixing means becomes ready to pass paper.

In addition, in the image forming method of this embodiment, in a continuous job in which images are formed on multiple recording media, when N is an integer equal to or greater than 2 and the job number is an integer, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, after fixing the N-1th recording medium, when the fixing temperature is increased or decreased in the fixing process to fix the Nth recording medium, driving of the developing means to perform the Nth development or driving of the image carrier to perform the Nth image formation is started before the fixing process becomes ready for paper passage.

In this embodiment, we will mainly explain starting the drive of the developing unit to perform the Nth development. Starting the drive of the image carrier to form the Nth image will be explained in the following embodiment.

An example of this embodiment will be described with reference to FIG.
3 is a time chart for explaining consecutive jobs in this embodiment. Here, an example will be described in which an image is formed on thin paper in the (N-1)th job and an image is formed on thick paper in the Nth job.

This example shows a case where an image is formed on one recording medium in one job. This has been done for ease of explanation, and the present embodiment is not limited to this example. This embodiment also includes a case where an image is formed on multiple recording media in one job. However, in this embodiment, the type of recording media on which images are formed within one job, particularly the fixing temperature, is assumed to be the same.

This example is an example of increasing the fixing temperature of the fixing means in order to form an image for the Nth job. This embodiment also includes a mode in which the fixing temperature of the fixing means is decreased in order to form an image for the Nth job.

The definitions of thick paper and thin paper in this embodiment are not particularly limited and can be selected appropriately. For example, in the Ricoh Pro C7200 series, thin paper is defined as paper with a basis weight of 105 gsm (g/m ² ) or less, and thick paper is defined as paper with a basis weight of 220 gsm or more. Note that the maximum weight for the Ricoh Pro C7200 series is approximately 360 gsm.

In Figure 3, (a) represents the image creation operation state, (b) represents the image creation drive, and (c) represents the fixing operation state. The vertical axes of (a) to (c) do not have units but are used to schematically explain the state. (d) represents the fixing temperature of the fixing means, and the vertical axis is in units of temperature. The fixing temperature of the fixing means can be selected as appropriate, and represents, for example, the temperature of the fixing member of the fixing means, and in this example, it is the temperature of the fixing belt 51. The horizontal axes of (a) to (d) represent time.

Note that, hereinafter, the image forming operation state may be referred to as "(a) image forming operation state" or "image forming operation state (a)." It may also be simply referred to as "image forming operation state." The same applies to (b) image forming drive, (c) fixing operation state, and (d) fixing temperature of the fixing means.

Image formation includes operations such as driving an image carrier, forming a latent image, developing, and transferring. Image formation may also include discharging and cleaning the image carrier.
Driving the image carrier can also be said to be the rotation of the image carrier.
The latent image formation is to form a latent image (which may also be called an electrostatic latent image) on an image carrier, using, for example, a charging means and an exposure means.
In the development, the latent image is made visible with a developer to form a visible image (toner image).
The transfer transfers a visible image to a recording medium.
After the image is formed, fixing is performed.

First, the general flow of the continuous job in this example will be explained.
In the (N-1)th job, development and transfer are performed, followed by fixing. Then, in the Nth job, development and transfer are performed, followed by fixing, in the same manner as in the (N-1)th job. Such operations are shown in (a) image formation states a1 to a4 and (c) fixing states c1 to c4.

As shown in the figure, the start timing for development and transfer in the N-1th job is indicated by a1 in the figure, and the end timing is indicated by a2. Similarly, the start timing for development and transfer in the Nth job is indicated by a3 in the figure, and the end timing is indicated by a4. Furthermore, the start timing for fixing in the N-1th job is indicated by c1 and the end timing is indicated by c2. Similarly, the start timing for fixing in the Nth job is indicated by c3 and the end timing is indicated by c4.

As mentioned above, this example is for forming an image on one recording medium in one job. Therefore, as shown in the figure, a2 is followed by c1. As will be explained later, when forming images on multiple recording media in one job, the order is a1, c1, a2, c2. In other words, after transfer of the first recording medium in the N-1th job is completed, fixing of the first recording medium is performed, but while fixing of the first recording medium is being performed, development and transfer of the second and subsequent recording media are performed.

In this example of a continuous job, the N-1th recording medium is thin paper, and the Nth recording medium is thick paper. The fixing temperature of the Nth recording medium is higher than the fixing temperature of the N-1th recording medium. Therefore, after fixing the N-1th recording medium, the fixing temperature of the fixing means (fixing device) is raised to fix the Nth recording medium.

In the figure, (d) shows the fixing temperature of the fixing means being increased. d1 is the point at which the increase in the fixing temperature of the fixing means begins, and d4 is the point at which the fixing temperature of the fixing means reaches the target temperature. In this example, the fixing temperature of the fixing means is increased to the fixing temperature of the Nth recording medium (cardboard), so d4 represents the point at which the fixing temperature of the Nth recording medium is reached.

In the example shown in FIG. 2(a) above, the heating roller 54 is heated by the heater 53a provided inside the heating roller 54, thereby raising the temperature of the fixing belt 51. In this example, the temperature of the fixing belt 51 detected by, for example, the thermopile 56 is used as the fixing temperature of the fixing means. In the example shown in FIG. 2(b) above, the heating roller 54 is heated by electromagnetic induction from the induction heating means 53 provided outside the heating roller 54, thereby raising the temperature of the fixing belt 51. Therefore, in this example, after fixing is performed on the N-1th recording medium, the temperature of the fixing belt 51 is raised to a temperature at which fixing can be performed on the Nth recording medium.

(b) Image formation drive refers to the drive of components that create images. Examples of image formation drive include the drive (rotation) of the image carrier and the drive of the developing means. Examples of the drive of the developing means include the drive (rotation) of the developing roller that the developing means has.

In this example, after the image creation operation for the N-1th job is completed (after a2 in the diagram), the image creation drive starts to shut down and stops. The point in time when the image creation drive starts to shut down is indicated by b1 in the diagram, and the point in time when the image creation drive stops is indicated by b2 in the diagram. In this example, the operations and stops in (b) image creation drive are described as the rotation and cessation of rotation of the developing roller of the developing unit. The developing roller applies toner to the image carrier by rotating near the image carrier. However, the operations and stops in (b) image creation drive may also be the rotation and cessation of rotation of the image carrier (photosensitive member).

In this embodiment, starting the operation of the image formation drive is also referred to as starting up the image formation drive or starting the startup of the image formation drive. Examples of starting up the image formation drive include starting the rotation of the developing roller and starting the rotation of the image carrier.
In addition, stopping the operation of the image formation drive is also referred to as shutting down the image formation drive or starting to shut down the image formation drive. Examples of shutting down the image formation drive include stopping the rotation of the developing roller and stopping the rotation of the image carrier.
Generally, when a developing roller or an image carrier is started to rotate from a stopped state, it takes a certain amount of time for it to reach a rotational speed at which development or image formation can be performed. Similarly, when a developing roller or an image carrier is stopped from rotating, it takes a certain amount of time for the developing roller or the image carrier to stop rotating. The time required for start-up and the time required for shut-down may be the same or different.

As mentioned above, the reason for stopping image creation drive is to reduce the drive of the developing means (or rotation of the photosensitive drum) that does not contribute to image formation; in other words, to suppress unnecessary drive of the developing means (or rotation of the photosensitive drum). While it is not necessarily necessary to stop image creation drive between image creation in the N-1th job and image creation in the Nth job, it is preferable to stop such image creation drive from the perspective of suppressing toner degradation. Therefore, in consecutive jobs, it is preferable to start shutting down the developing means and stop the developing means after transfer to the N-1th recording medium. Alternatively, in consecutive jobs, it is preferable to start stopping the drive (stopping rotation) of the image carrier and stop the image carrier (stopping rotation of the image carrier) after transfer to the N-1th recording medium.

The circumstances under which image creation drive is stopped can be selected as appropriate. Image creation drive may be stopped every time the fixing temperature of the Nth recording medium differs from the fixing temperature of the N-1th recording medium, but this may not be desirable because it would mean stopping image creation drive every time the fixing temperature is increased or decreased even slightly. Therefore, it is preferable to stop image creation drive when the fixing temperature of the Nth recording medium differs from the fixing temperature of the N-1th recording medium and when it takes a predetermined amount of time for the fixing temperature of the fixing means to reach the fixing temperature of the Nth recording medium.

That is, in the consecutive jobs, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, and if it takes a predetermined time for the fixing temperature of the fixing means to reach the fixing temperature of the Nth recording medium after fixing the N-1th recording medium, it is preferable to stop driving the developing means or the image carrier from the time the N-1th development is completed until a notification is given to start driving the developing means to perform the Nth development, or from the time the N-1th development is completed until a notification is given to start driving the image carrier to perform the Nth image formation. This prevents the developing means from running idle and further suppresses toner degradation.

Note that (b) the image creation drive is in operation before development and transfer for the N-1th job because, for example, the fixing temperature of the recording medium for the N-2th job is the same or nearly the same as the fixing temperature of the recording medium for the N-1th job. Furthermore, in this case, having the image creation drive in operation between the N-2th job and the N-1th job has the advantages of stabilizing the rotation of the photosensitive drum, stabilizing the charging potential, and stabilizing the toner charge amount.

Furthermore, after development and transfer for the Nth job are completed, (b) the image creation drive is in operation because, for example, the fixing temperature of the recording medium for the N+1th job is the same or approximately the same as the fixing temperature of the recording medium for the Nth job. In this case, having the image creation drive in operation between the Nth job and the N+1th job has the advantage of ensuring stable operation of components and preventing damage to components. For example, if only the photosensitive member stops until the intermediate transfer member stops, rubbing may occur, so it is preferable to wait for the contacting components to finish rotating.

For example, if image formation is performed on 10 sheets of thin paper in the N-1th job, and then image formation is performed on 10 sheets of thick paper in the Nth job, it is preferable to stop the image formation drive between the last thin paper and the first thick paper.

At point b1 in the figure, a determination is made to stop image formation. The determination is made, for example, by a control unit of the image forming apparatus. The determination to stop image formation is not particularly limited, but may be made, for example, when primary transfer to the recording medium has been performed, or when secondary transfer to the recording medium has been performed. Furthermore, the image formation time may be known in advance, and the determination may be made by predicting the time when image formation will end. Furthermore, image formation may also be determined when de-electrification or cleaning of the image carrier has been completed.

When an image formation shutdown determination is made, for example, a control unit in the image forming apparatus issues an instruction to the developing means or image carrier to stop image formation drive. In this example, the developing roller is instructed to stop rotation at time b1 in the diagram, and the developing roller stops rotating at time b2 in the diagram. In the diagram, the time required to shut down image formation drive, i.e., the time from b1 to b2, is shown as shutdown time t2. After the image formation operation for the (N-1)th job is completed and image formation drive stops, image formation drive remains stopped until an instruction to start image formation drive is issued.

In this example, the timing to start image creation drive for image creation in the Nth job is determined by the fixing temperature of the fixing means. As described above, after fixing the N-1th recording medium (after c2 in the diagram), the fixing temperature of the fixing means is raised to fix the Nth recording medium (d1 to d4 in the diagram). In this example, the development means for the Nth development is started to start up (b3 and d2 in the diagram) before the fixing device (fixing means) becomes ready for paper passage, i.e., before d3 in the diagram.

In the diagram, d3 represents the point in time when adjustment of the fixing temperature of the fixing means is complete, and represents the point in time when the fixing means is ready to feed recording media (paper passing state). When this state is reached, an instruction to start development and transfer for the Nth job is issued. The temperature of d3 (the temperature at which paper passing state is reached) can be determined, for example, by experimentally deriving the lower limit of the fixing success range. The temperature of d3 differs depending on the recording medium, so it can be selected as appropriate.

In an example not included in this invention, the image formation drive starts up when the fixing device becomes ready to pass paper. This example will be described later.

As shown by b3 and d2 in the diagram, in this example, image formation drive begins when the fixing temperature of the fixing means reaches point d2. Specifically, for example, the control unit of the image forming device acquires and determines the temperature of the fixing belt 51 detected by the thermopile 56, and when the acquired temperature reaches point d2, the control unit of the image forming device instructs the start of image formation drive, for example, to start rotating the developing roller.

Alternatively, as indicated by "Notification of image creation startup" in the figure, the control unit of the fixing device may obtain the temperature of the fixing belt 51 detected by the thermopile 56, make a judgment, and issue a notification. In this case, for example, when the obtained temperature reaches point d2, the control unit of the fixing device may issue a notification to start driving the developing means to perform the Nth development. The notification to start driving the developing means may be sent to, for example, a control unit of the image forming apparatus.

When an instruction to start image formation driving is issued, the developing means begins to ramp up, and ramp-up is completed at time b4. In other words, driving of the developing means begins at time b3, and the developing means enters a driving state at time b4. Note that in the diagram, the time required for the developing means to ramp up completely, i.e., the time from b3 to b4, is shown as ramp-up time t3. The ramp-up time t3 may be the same as or different from the ramp-down time t2.

Note that, because the image formation drive starts starting up when the fixing temperature of the fixing means reaches point d2, point d2 can also be described as a start-up trigger. For this reason, this description is included in the diagram.

After the development means has finished starting up, development and transfer for the Nth job are performed (a3 in the figure). The timing for starting development and transfer for the Nth job can be selected as appropriate. For example, development and transfer for the Nth job begin when the fixing temperature of the fixing means reaches d3, i.e., when the fixing means is ready to pass paper. The determination of whether the fixing means is ready to pass paper may be made by a control unit in the image forming apparatus or a control unit in the fixing device.

When the image forming unit is instructed to start developing and transferring for the Nth job, it begins developing and transferring for the Nth job (a3 in the figure). Then, at time a4 in the figure, developing and transferring for the Nth job is completed. Next, the recording medium (cardboard in this example) on which the Nth job has been developed and transferred is transported to the fixing means, where fixing is performed (c3 and c4 in the figure).

The fixing temperature of the fixing means continues to rise even while development and transfer for the Nth job are being carried out. Therefore, by the time the recording medium is transported and reaches the fixing means, the fixing temperature of the fixing means has reached a temperature at which the Nth recording medium can be fixed (c3, d4 in the figure).

In this way, in this example, after fixing the N-1th recording medium, when the fixing temperature of the fixing means is raised to fix the Nth recording medium, the development means for the Nth development starts operating before the fixing device is ready to pass paper (b3, d2 in the figure). This allows the timing for starting fixing for the Nth job to coincide with or be close to the timing for the temperature rise of the fixing means to be completed. Therefore, this example prevents the development means from running idle while waiting for the fixing temperature rise of the fixing means to be completed, even when the image creation operation is ready to begin. This makes it possible to suppress toner degradation.

Toner degradation can occur, for example, when additives that should be present on the surface of the toner matrix become embedded in the toner matrix, or when additives are missing from the surface of the toner matrix. Toner degradation can cause uneven transfer and lead to image degradation, but this example can prevent such problems. Common additives include titanium oxide and silica.

In addition, this example prevents situations where it is necessary to wait until the image creation operation can begin even though the fixing temperature of the fixing means has already been increased. In such a situation, it becomes necessary to maintain the fixing temperature of the fixing means, which not only increases power consumption, but also creates a problem where the waiting time causes the fixing temperature of the fixing means to drop and need to be increased again. This example prevents these problems from occurring and avoids situations where the fixing temperature of the fixing means needs to be increased again, thereby preventing job times from becoming longer.

In this example, when a job involves switching from thin paper, which has a low fixing temperature, to thick paper, which has a high fixing temperature, the image forming unit, including the developing means, shuts down and stops while the fixing temperature is raised during the switch. Then, before the fixing temperature of the fixing means reaches the temperature at which paper can be passed, image formation starts up and the image forming drive starts up again. This allows the image forming unit to begin recovery and start-up operations as quickly as possible.

In an example not included in the present invention, the developing means for performing the Nth development starts operating at time d3. An example of this case (comparison example) is shown in Figure 4. As shown in Figure 4, the developing means for performing the Nth development starts to start up at time d3, when adjustment of the fixing temperature of the fixing means is complete. At this time, an instruction to start development and transfer for the Nth job has also been issued, but because the start-up of the image creation drive has not yet completed (b3, b4), development and transfer wait for the start-up of the image creation drive. As a result, even though the temperature of the fixing means has completed rising, it enters a state of waiting for paper, requiring further heating and making it impossible to shorten the job time.

The value d2, which is the starting point for starting the image creation drive, can be selected as appropriate. More specifically, the fixing temperature of the fixing means is increased, and the temperature at which image creation drive starts can be selected as appropriate. For example, when increasing the fixing temperature of the fixing means to fix the Nth recording medium, it is preferable that the difference between the fixing temperature of the fixing means when the fixing means becomes ready to pass paper (d3) and the fixing temperature of the fixing means when drive of the developing means for the Nth development starts (d2) be equal to or greater than a predetermined value. In this case, there is no need to change d2 depending on the type of recording medium, preventing the process from becoming complicated.

The above-mentioned predetermined value can be selected appropriately and can be set taking into consideration the rate at which the fixing temperature of the fixing means rises and falls, the fixing temperature of the recording medium, etc. Therefore, although it cannot be generalized, a value of 10°C, for example, is preferable. In this case, time leeway for development and transfer in the Nth job can be ensured, and it becomes easier to prevent the fixing temperature of the fixing means from reaching its maximum at an early stage.

In addition to the above, d2, the starting point for starting up the image formation drive, can also be set taking into account, for example, the start-up time t3 and the rate of increase or decrease of the fixing temperature of the fixing means. For example, it is preferable to determine the rate of increase or decrease of the fixing temperature of the fixing means in advance, and then calculate the time to start up the developing means or drive the image carrier based on that rate of increase or decrease. In this case, there is no need to detect and determine the fixing temperature of the fixing means, allowing for a simpler design.

In this example, the predicted fixing temperature waiting time t1 shown in the figure can be used, for example, to determine whether or not to shut down the imaging system. Using t1 makes it possible to prevent unnecessary time being wasted by immediately starting up the imaging system after it has been shut down. The predicted fixing temperature waiting time t1 can be set to, for example, the time required to start up the imaging system after it has been turned down plus 10 seconds.

In this example, the N-1th recording medium is thin paper and the Nth recording medium is thick paper, and the fixing temperature of the Nth recording medium is higher than that of the N-1th recording medium. Whether the fixing temperature of the Nth recording medium is higher than that of the N-1th recording medium can be determined, for example, from job information held by the control unit. In addition to the above, the type of recording medium (fixing temperature) and number of sheets may be set in the device before executing consecutive jobs.

In this embodiment, as described above, the case where the fixing temperature of the fixing means is increased to fix the Nth recording medium has been described. The case where the fixing temperature of the fixing means is decreased is not particularly limited and can be selected as appropriate. For example, if the N+1th recording medium is thin paper, in other words, if the fixing temperature of the N+1th recording medium is lower than the fixing temperature of the Nth recording medium, the image creation drive is turned off and on as appropriate, taking into account the rate at which the fixing temperature of the fixing means is decreasing.

Here, we will explain an example of forming images on multiple recording media in one job. Figure 5 is a time chart to explain this example, and is similar to Figure 3. As shown, fixing begins before development and transfer in the N-1th job are completed. That is, c1 is located before a2, and the order is a1, c1, a2, c2. Similarly, fixing begins before development and transfer in the Nth job are completed. That is, c3 is located before a4, and the order is a3, c3, a4, c4.

For example, after transfer of the first recording medium in the N-1th job is completed, fixing of the first recording medium is performed, but while fixing of the first recording medium is being performed, development and transfer of the second and subsequent recording media are performed.

Next, an example of lowering the fixing temperature of the fixing means in order to fix the Nth recording medium will be described.
6 is a time chart for explaining successive jobs in this example, in which an image is formed on thick paper in the (N-1)th job and an image is formed on thin paper in the Nth job.

The example shown in Figure 6 is substantially the same as the example shown in Figure 3, except that (d) the fixing temperature of the fixing means is lowered to perform the Nth fixing. As shown in the figure, after fixing the N-1th recording medium (after c2), when the fixing temperature of the fixing device is lowered to fix the Nth recording medium, a notification is sent (d2) to start driving the developing means to perform the Nth development before the fixing device becomes ready to pass paper (before d3).

Furthermore, after fixing the N-1th recording medium (after c2), when the fixing temperature of the fixing device is lowered to fix the Nth recording medium, a notification may be sent (d2) indicating that driving of the image carrier to form the Nth image will begin before the fixing device becomes ready to pass paper (before d3).

The above notification is primarily performed by the fixing means (fixing device), but instead of being configured to send the notification, it may also be configured in the image forming device, as in the above example, to start driving the developing means or the image carrier.

There are no particular limitations on the method for lowering the fixing temperature of the fixing means; for example, a cooling means may be used, or the fixing means may be left to cool naturally.

The example shown in Figure 6, like Figure 3, is an example of forming an image on one recording medium in one job. As with the example shown in Figure 5, the example shown in Figure 6 may also be configured to form images on multiple sheets of recording medium in one job. In this case, the timing of (a) the image creation operation state and (c) the fixing operation state, etc. will be as shown in the example shown in Figure 5.

Example 1
Next, an example using a specific temperature will be described.
In this embodiment, thin paper with a fixing temperature of 140° C. is used as the (N−1)th recording medium, and thick paper with a fixing temperature of 180° C. is used as the Nth recording medium.
As shown in a1, a2, and b1 in Figure 3, after the N-1th development and transfer, the developing unit begins to stop (shut down). Also, after the N-1th development and transfer, the recording medium is transported to the fixing unit and fixed (c1). The fixing temperature of the fixing unit at this time is 140°C. After fixing for the N-1th job is completed (c2), the fixing unit begins raising the fixing temperature to fix the Nth recording medium (cardboard) (d1). Specifically, the fixing temperature of the fixing unit is raised (increased) from 140°C to 180°C as shown in d1 to d4.
The image forming drive starts to stop at b1 and is completely stopped at b2.

In this embodiment, the temperature of d2 is set to 165°C, and when the fixing temperature of the fixing means reaches 165°C, an instruction to start image creation is issued. Therefore, when the fixing temperature of the fixing means reaches 165°C, the development means begins to be driven (b3).

After passing through d2, the fixing temperature of the fixing means is further increased, and the fixing means is ready to pass paper at time d3. In this embodiment, the temperature at d3 (the temperature at which the fixing means is ready to pass paper) is set to 175°C.
Therefore, in this embodiment, the developing means can be started up 10°C earlier than the paper passing permitted temperature, thereby reducing the waiting time for changing paper. Although this differs depending on the conventional configuration, it was possible to reduce this by approximately 5 seconds compared to the conventional case.

Example 2
Next, another example using a specific temperature will be described.
Although d2 is set in the above embodiment, this is not limited to this in the present embodiment. For example, as in this embodiment, the rate of increase in the fixing temperature of the fixing unit may be obtained in advance, and the time to start the start-up of the developing unit may be calculated based on the rate of increase.

Specifically, when the fixing temperature of the Nth recording medium is A [°C], the fixing temperature of the N-1th recording medium is B [°C], the rate of rise in the fixing temperature of the fixing means is C [°C/s], the time from when the driving of the developing means starts until it enters the driving state is D1 [s], and the time from when the fixing temperature of the fixing means starts to rise until when the driving of the developing means to develop the Nth recording medium starts E1 [s], E1 can be calculated as follows:
E1=(|A-B|)/C-D1

Note that A-B is an absolute value because it takes into account cases where the fixing temperature is lowered (for example, Example 3 below).

This will be explained using specific numerical values.
In this embodiment, thin paper with a fixing temperature of 150°C is used as the N-1th recording medium, and thick paper with a fixing temperature of 180°C is used as the Nth recording medium. Furthermore, using actual measurement data from a Ricoh Pro C7200, for example, the rate of increase in the fixing temperature of the fixing means is assumed to be 2°C/s and the rate of decrease is assumed to be 0.5°C/s. Furthermore, the time from when the developing means starts to start up until development begins is assumed to be 5 seconds.

In this case, applying the above explanation, A is 180° C., B is 150° C., C is 2° C./s, and D1 is 5 s. Therefore, E1 can be calculated as follows:
E1=(|180-150|)/2-5=10 [s]

As a result, fixing is performed on the N-1th recording medium (thin paper), and the development unit starts to start up 10 seconds after point d1, when the fixing temperature of the fixing unit starts to rise. In other words, the time from d1 to d2 is 10 seconds. In this way, according to this embodiment, the time to issue the image formation start-up notification can be determined in advance, eliminating the need to determine the fixing temperature of the fixing unit each time, and providing advantages such as a simplified component configuration.

Example 3
Next, a description will be given of a case where the fixing temperature of the fixing unit is decreased in the above-described embodiment 2. As in embodiment 2, for d2, for example, as in this embodiment, the rate of decrease in the fixing temperature of the fixing unit may be obtained in advance, and the time to start the start-up of the developing unit may be calculated based on the rate of decrease.

Specifically, when the fixing temperature of the Nth recording medium is A [°C], the fixing temperature of the N-1th recording medium is B [°C], the rate of decrease in the fixing temperature of the fixing means is C [°C/s], the time from when the driving of the developing means starts until it enters the driving state is D1 [s], and the time from when the driving of the fixing means starts to decrease until when the driving of the developing means to develop the Nth recording medium starts E1 [s], E1 can be calculated as follows:
E1=(|A-B|)/C-D1

In this case, applying the above explanation, A is 150°C, B is 180°C, C is 0.5°C/s, and D1 is 5s. Therefore, E1 can be calculated as follows:
E1=(|150-180|)/0.5-5=55[s]
Therefore, it is preferable to issue the image formation start notification 55 seconds after the fixing temperature of the fixing means starts to drop.

Second Embodiment
Next, another embodiment of the present invention will be described, and a description of the same matters as those in the above embodiment will be omitted.
In the above embodiment, the driving of the developing means is started. However, the driving of the image carrier may also be started.

In this embodiment, after fixing the N-1th recording medium, when the fixing temperature of the fixing device is increased or decreased to fix the Nth recording medium, a notification is sent to the effect that the image carrier will begin to be driven to form the Nth image before the fixing device becomes ready to pass paper.

Furthermore, in this embodiment, after fixing the N-1th recording medium, when the fixing temperature of the fixing means is increased or decreased to fix the Nth recording medium, the image forming apparatus starts driving the image carrier to form the Nth image before the fixing means becomes ready to pass paper.

Furthermore, in the image forming method of this embodiment, after fixing the N-1th recording medium, when the fixing temperature is increased or decreased in the fixing process to fix the Nth recording medium, driving of the image carrier to form the Nth image is started before the fixing process becomes ready for paper passage.

In this embodiment, in the image formation drive in Figure 3(b), "operating" and "stopped" refer to the rotation and stoppage of the image carrier. Therefore, in the image formation drive in Figure 3(b), the image carrier is rotating before b1, and an instruction to stop the rotation of the image carrier is issued at b1. Then, at b2, the rotation of the image carrier stops. Next, before the fixing temperature of the fixing means reaches the fixing temperature of the Nth recording medium, an instruction to start rotation of the image carrier is issued (b3), the image carrier rises, and at point b4, the rise of the image carrier is completed and it enters a driving state.

By controlling the drive of the image carrier in this way, the same effect as in the above embodiment can be achieved.

Furthermore, in this embodiment, as in the above embodiment, it is also possible to determine the rate at which the fixing temperature of the fixing means increases or decreases in advance, and calculate the time at which to start driving the image carrier based on that rate.

Furthermore, in this embodiment, the same can be done as in Examples 1 to 3 of the above embodiment. For example, when the fixing temperature of the Nth recording medium is A [°C], the fixing temperature of the N-1th recording medium is B [°C], the rate of increase or decrease of the fixing temperature of the fixing means is C [°C/s], the time from when the driving of the image carrier starts until it is in a driving state is D2 [s], and the time from when the fixing temperature of the fixing means starts to increase or decrease until when the driving of the image carrier starts to form an image on the Nth recording medium is E2 [s], E2 is
E2=(|A-B|)/C-D2
It can be found by:

51 Fixing belt 52 Fixing roller 54 Heating roller 55 Pressure roller 56 Thermopile 100 Fixing device 200 Printer 200A Image forming section 200B Paper feeding section 203 Developing device 205 Photoconductor 210 Intermediate transfer belt 1000 Control section N Fixing nip section

JP 2017-107044 A

Claims (6)

an image carrier that carries a latent image;
a developing roller for developing the latent image with a developer to form a visible image;
a transfer means for transferring the visible image onto a recording medium;
a fixing means for fixing the visible image on the recording medium,
In a continuous job for forming images on a plurality of recording media, when N is an integer of 2 or more and is a job number, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, after fixing the N-1th recording medium, when the fixing temperature of the fixing means is increased or decreased to fix the Nth recording medium, a notification is issued to the effect that driving of the developing roller for performing the Nth development will be started before the fixing means becomes ready to pass paper;
when a notification to start the N-th development is given, the notification to start the N-th development is a notification to start driving the developing roller,
After receiving a notification to start driving the developing roller for performing the Nth development, the developing roller is started to be driven to perform the Nth development;
In the continuous job, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, and if it takes a predetermined time for the fixing temperature of the fixing means to reach the fixing temperature of the Nth recording medium after fixing the N-1th recording medium, the image forming apparatus stops driving the developing roller that was being driven to perform the N-1th development from the end of the N-1th development until a notification is received that driving of the developing roller to perform the Nth development will begin. an image carrier that carries a latent image;
a developing roller for developing the latent image with a developer to form a visible image;
a transfer means for transferring the visible image onto a recording medium;
a fixing unit for fixing the visible image on the recording medium,
In a continuous job for forming images on a plurality of recording media, when N is an integer of 2 or more and is a job number, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, after fixing the N-1th recording medium, when the fixing temperature of the fixing means is increased or decreased in order to fix the Nth recording medium, driving of the developing roller for performing the Nth development is started before the fixing means becomes ready to pass paper ;
In the continuous job, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, and if it takes a predetermined time to raise the fixing temperature of the fixing means to the fixing temperature of the Nth recording medium after fixing the N-1th recording medium, driving of the developing roller that has been driven to perform the N-1th development is stopped from the end of the N-1th development until driving of the developing roller for performing the Nth development is started.
An image forming apparatus characterized by: 3. An image forming apparatus according to claim 1, wherein when the fixing temperature of the fixing means is increased or decreased to fix the Nth recording medium, the difference between the fixing temperature of the fixing means when the fixing means is in a state where paper can be passed through and the fixing temperature of the fixing means when the driving of the developing roller to perform the Nth development is started is a predetermined value or more. An image forming apparatus according to any one of claims 1 to 3, characterized in that the rate of increase or decrease of the fixing temperature of the fixing means is determined in advance, and the time to start driving the developing roller is calculated based on the rate of increase or decrease . When the fixing temperature of the Nth recording medium is A [°C], the fixing temperature of the N-1th recording medium is B [°C], the rate of increase or decrease of the fixing temperature of the fixing means is C [°C/s], the time from when the driving of the developing roller starts until it is in a driving state is D1 [s], and the time from when the fixing temperature of the fixing means starts to increase or decrease until when the driving of the developing roller starts to develop the Nth recording medium is E1 [s], E1 is
E1=(|A-B|)/C-D1
5. The image forming apparatus according to claim 4 , wherein: a developing step in which the latent image carried by the image carrier is developed with a developer by using a developing roller to form a visible image;
a transfer step of transferring the visible image onto a recording medium;
a fixing step of fixing the visible image on the recording medium,
In a continuous job for forming images on a plurality of recording media, when N is an integer of 2 or more and is a job number, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, after fixing the N-1th recording medium, when the fixing temperature in the fixing step is increased or decreased in order to fix the Nth recording medium, driving of the developing roller for performing the Nth development is started before the fixing step becomes a paper passable state , and
In the continuous job, if the fixing temperature of the Nth recording medium is different from the fixing temperature of the N-1th recording medium, and if it takes a predetermined time to bring the fixing temperature of the fixing step to the fixing temperature of the Nth recording medium after fixing of the N-1th recording medium, driving of the developing roller that has been driven to perform the N-1th development is stopped from the end of the N-1th development until driving of the developing roller for performing the Nth development is started.
An image forming method comprising: