Image forming apparatus and image forming method

Abstract

To provide a fixing device that can reduce time for a continuous job and prevent deterioration of toner.SOLUTION: A fixing device is to fix a visible image transferred to a recording medium to the recording medium, and in a continuous job for forming images on a plurality of recording media, when an integer N of 2 or more is defined as a job number, if a fixing temperature of the N-th recording medium is different from a fixing temperature of the N-1-th recording medium, and in performing fixing to the N-1-th recording medium and subsequently increasing or decreasing the fixing temperature of the fixing device for performing fixing to the N-th recording medium, performs, before the fixing device enters a paper feedable state, a notification that drive of developing means for performing the N-th development is started or performs a notification that the drive of an image carrier for performing N-th image formation is started.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a fixing device, an image forming apparatus, and an image forming method. [Background technology]

[0002] 2. Description of the Related Art Conventionally, images have been formed on various types of paper using image forming apparatuses that use electrophotographic two-component development technology and thermal fixing technology.

[0003] In conventional technology, when continuously forming images on various types of paper, there is a need to wait for the temperature adjustment of the fixing device when switching between paper types. After fixing, there is also a need to wait for the completion of stapling, punching, saddle stitching, and bookbinding processes in the post-processing device finisher. In this case, the toner image formation process (development process) may wait, meaning that the device may idle while waiting for these processes to finish.

[0004] When the above-mentioned waiting occurs, for example, in a two-component developer in which a carrier and a toner are mixed, rotation continues 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 being buried in the toner matrix, or additives being missing from the surface of the toner matrix. When toner deteriorates, uneven transfer occurs, leading to image deterioration.

[0005] Patent Document 1 discloses that the driving of a 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 according to 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. Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, if the paper interval (image interval) 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 in a state where paper can pass through.

[0007] However, when the developing unit is started after the paper feed signal is turned ON, the paper is not conveyed to the fixing unit even though the fixing unit is ready to pass paper, which causes a problem of prolonging the job time. 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 being prolonged, but toner degradation may occur. Conventional technology has not been able to solve these problems at the same time.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a fixing device that can shorten the time required for continuous jobs and suppress toner deterioration. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention Image forming device teeth, a developing device for fixing the visible image to the recording medium, and a transfer means for transferring the visible image to a recording medium; and a fixing means for fixing the visible image to the recording medium, wherein, in a continuous job for forming images on a plurality of recording media, when N is an integer of 2 or more and a job number is a fixing temperature of the Nth recording medium, the fixing means notifies the user that the driving of the developing roller for performing the Nth development will start before the fixing means becomes ready to pass paper, when the fixing temperature of the fixing means is increased or decreased to fix the Nth recording medium after fixing the N-1th recording medium. When the N-th development is to be started, the notification to start the N-th development is a notification to start driving the developing roller, and after the notification to start driving the developing roller to perform the N-th development, driving of the developing roller to perform the N-th development is started, and if, in the continuous job, the fixing temperature of the N-th recording medium is different from the fixing temperature of the N-1-th recording medium and it takes a predetermined time to raise the fixing temperature of the fixing means to the fixing temperature of the N-th recording medium after fixing of the N-1-th recording medium, driving of the developing roller that has been driven to perform the N-1-th development is stopped from the end of the N-1-th development until the notification to start driving the developing roller to perform the N-th development is given. It is characterized by: [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a fixing device that can shorten the time required for continuous jobs and suppress toner deterioration. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention. [Figure 2] 1 is a schematic diagram illustrating an example of a fixing device according to the present invention. [Figure 3]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. [Figure 4] 10 is a time chart for explaining an example of an image forming method that is not included in the present invention. [Figure 5] 5 is a time chart for explaining another example of the image forming method of the present invention. [Figure 6] 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. DETAILED DESCRIPTION OF THE INVENTION

[0012] The fixing device, image forming apparatus, and image forming method according to the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following embodiments, and other modifications, additions, corrections, deletions, and other changes can be made within the scope of what a person skilled in the art can conceive. Any embodiment is within the scope of the present invention as long as it achieves the functions and effects of the present invention.

[0013] 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 of forming images on a plurality of 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, before the fixing device becomes ready to pass paper, a notification is given that the development means for performing the Nth development will begin to be driven, or a notification is given that the image carrier for performing the Nth image formation will begin to be driven.

[0014] The image forming apparatus of the present invention 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, 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 performing 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 performing the Nth image formation, driving of the image carrier is started to perform the Nth image formation. Note that in this embodiment, the fixing device and the fixing unit have the same meaning.

[0015] In addition, the image forming apparatus of the present invention is an image forming apparatus comprising an image carrier that carries a latent image, a developing means that develops the latent image with a developer to form a visible image, a transfer means that transfers the visible image to a recording medium, and a fixing means that fixes the visible image to the recording medium, and in a continuous job of forming images on a plurality of recording media, when 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 means is raised or lowered 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.

[0016] The image forming method of the present invention is an image forming method having 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, wherein in a continuous job in which images are formed on a plurality of recording media, when N is an integer of 2 or greater 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 in the fixing step is increased or decreased to fix the Nth recording medium, the driving of the developing means to perform the Nth development or the driving of the image carrier to perform the Nth image formation is started before the fixing step becomes ready for paper passage.

[0017] An electrophotographic tandem color printer (hereinafter referred to as printer 200) will be described as an embodiment of the image forming apparatus of the present invention.

[0018] Fig. 1 is a diagram illustrating the general configuration of a printer 200 according to this embodiment. Fig. 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.

[0019] 1, printer 200 is a high-speed machine that includes image forming section 200A located at the top of the device body and paper feed section 200B located below image forming section 200A. Printer 200 also incorporates fixing device 100 (fixing means) in image forming section 200A.

[0020] In the image forming unit 200A, an intermediate transfer belt 210 is disposed in the vertical center of the apparatus main body. A configuration for forming toner images corresponding to a plurality of colors that are complementary to the color separation colors is provided above the intermediate transfer belt 210. Specifically, photoconductors 205Y, 205M, 205C, and 205K are disposed along the upper transfer surface of the 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.

[0021] The photoconductors 205Y, 205M, 205C, and 205K are drum-shaped and rotatable in the same direction (counterclockwise in the drawing). Charging devices 202Y, 202M, 202C, and 202K, developing devices 203Y, 203M, 203C, and 203K, primary transfer devices 204Y, 204M, and 204K, and photoconductor cleaning devices 206Y, 206M, 206C, and 206K are arranged around each photoconductor 205.

[0022] 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.

[0023] Intermediate transfer belt 210 is wound around a drive roller and a driven roller, and is configured to be movable in the same direction as photoconductors 205Y, M, C, and K at a position facing them. Secondary transfer roller 212 is provided at a position facing secondary transfer opposing roller 211, which is one of the driven rollers. The transport path of paper P as a recording medium (also referred to as recording material, sheet, etc.) from secondary transfer roller 212 to fixing device 100 is a lateral path in a substantially horizontal direction.

[0024] The paper feed unit 200B has a paper feed tray 220 that stores a stack of paper sheets P, and a transport mechanism. The transport mechanism separates the paper sheets 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.

[0025] 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 containing 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.

[0026] Similar images are formed on the other photosensitive members 205M, 205C, and 205K, except that the toner colors are different, and the toner images of the respective colors are transferred in order onto the intermediate transfer belt 210 by electrostatic force and superimposed on each other.

[0027] Next, the toner images primarily transferred from the photoconductors 205Y, M, C, and K onto the intermediate transfer belt 210 are transferred onto the paper P conveyed thereto by the secondary transfer opposing roller 211 and the secondary transfer roller 212. The paper P onto which the toner image has been transferred is further conveyed to the fixing device 100, where the toner image is fixed at the fixing nip N between the fixing belt 51 and the pressure roller 55, and the paper P is discharged to the exit side of the fixing nip N. Next, the paper P discharged from the fixing nip N is sent to the stacker 215 along the discharge path.

[0028] Furthermore, residual toner and the like remaining on the photosensitive members 205Y, 205M, 205C, and 205K without being primarily transferred onto the intermediate transfer belt 210 is removed by photosensitive member cleaning devices 206Y, 206M, 206C, and 206K. Furthermore, residual toner and the like remaining on the intermediate transfer belt 210 without being secondarily transferred onto the paper P is removed by a belt cleaning device 213 in preparation for the next image formation.

[0029] 1 illustrates a control unit 1000. The printer 200 shown in FIG. 1 may have the control unit 1000, or the fixing device 100 may have the control unit 1000. Alternatively, both the printer 200 and the fixing device 100 may have separate control units.

[0030] 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 arithmetic unit executes a program to perform the above control. Note that the entity that executes the program and performs the processing may be the arithmetic unit, and may include a dedicated circuit (for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit)) that performs specific processing.

[0031] Next, an example of the fixing device (fixing means) of this embodiment and a fixing device (fixing means) that can be provided in the printer 200 of this embodiment will be described.

[0032] 2A and 2B are schematic explanatory diagrams of examples of the configuration of a fixing device using two belt heating methods that can be suitably provided in the printer 200 of this embodiment. Fig. 2A is a schematic explanatory 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. Fig. 2B is a schematic explanatory 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.

[0033] The fixing device 100 of the configuration example shown in FIG. 2(a) and the configuration example shown in FIG. 2(b) differ only in terms of the heating means for heating the heating roller 54, so we will first explain the configuration common to the configuration examples shown in each figure.

[0034] 2(a) and 2(b) (hereinafter referred to as FIG. 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 therebetween, and a fixing nip N is formed between the fixing belt 51 and the pressure roller 55.

[0035] On the discharge side of the fixing nip N from which the paper P is discharged, a fixing separating member 57 and a pressure separating member 58 are provided.

[0036] The fixing roller 52 has a metal core 52a and an elastic rubber layer 52b made of silicone rubber or the like. The material of the elastic rubber layer 52b can be selected appropriately, and foamed silicone rubber is an example. When foamed silicone rubber is used, it is less likely to absorb heat from the fixing belt 51, and the warm-up time can be shortened.

[0037] The heating roller 54 may be, for example, a hollow roller made of stainless steel or a nickel alloy. In the configuration example shown in Fig. 2(a), a heater 53a, which is a heating means using a halogen heater, is provided inside the heating roller 54. In this case, the heating roller 54 is heated by the halogen heater.

[0038] 2(b), induction heating means 53b is provided facing the outer periphery of fixing belt 51 wound around heating roller 54. Induction heating means 53b is a heating means of an IH system that uses electromagnetic induction. In this case, heating roller 54 is heated by induction heating means 53b.

[0039] The fixing belt 51 is an endless belt, and has a two-layer cross-sectional structure in which an elastic layer such as a silicone rubber layer is formed on a base material such as polyimide. The fixing belt 51 is stretched over the heating roller 54 with a constant tension by a heating roller tension spring fixed to the heating roller 54 and the fixing frame.

[0040] The pressure roller 55 is a hollow roller made of aluminum or iron, etc., and is a cylindrical roller with an elastic layer made of silicone rubber or the like provided on the outer periphery of the hollow roller. A heater 59, which is a heating means using a halogen heater, is provided inside the roller.

[0041] In addition, the pressure roller 55 is configured to be switchable between a pressurized state in which it applies pressure to the fixing belt 51 side and a depressurized state (separated state) in which it is separated from the fixing belt 51 and depressurized by the following pressure / depressurization means 80.

[0042] 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 in a direction away from the fixing belt 51 to separate it and release the pressure.

[0043] Furthermore, 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.

[0044] When the fixing device 100 is driven, for example, the fixing roller 52 is driven to rotate clockwise in FIG. 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 be the pressure roller 55.

[0045] 2(a), during the fixing operation, first, the heating roller 54 is heated by the heater 53a provided inside the heating roller 54, and the heat of 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 (for example, a temperature suitable for toner fixing).

[0046] 2(b), the heating roller 54 is first heated by electromagnetic induction of the induction heating means 53 provided outside the heating roller 54, and the heat of 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.

[0047] In this embodiment, the fixing temperature of the fixing unit is the temperature of the fixing belt 51, which is detected by the thermopile 56, for example.

[0048] Furthermore, when necessary, such as when the temperature of the pressure roller 55 is increased, the pressure roller 55 is heated to a predetermined temperature by the heat generated by the heater 59 disposed inside. In this embodiment, an example in which a roller-type pressure roller 55 is used as the pressure member is shown, but the present invention is not limited to this, and a belt-type pressure member using an endless belt stretched between two rollers may also be used.

[0049] In the fixing device 100, for example, while the fixing belt 51 and the 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.

[0050] At this time, the paper P may come out wrapped around the fixing belt 51, and is therefore separated by a fixing separating member 57. Furthermore, the paper P that comes out wrapped around the pressure roller 55 side is separated by a pressure separating member 58 and is transported along a transport guide.

[0051] In the fixing device 100, the heating roller 54 is heated to a predetermined temperature, and after the fixing device 100 is in a state where paper can be passed through, the paper P is passed (conveyed) through the fixing nip N. Although the term "passing paper" is used, the recording medium is not limited to paper.

[0052] The predetermined temperature of the heating roller 54 is not particularly limited, but can be, for example, about 150° C. The upper and lower limits can be selected as appropriate, and can be, for example, in the range of 120° C. to 200° C. The temperature can be changed as appropriate depending on the type of recording medium, and in particular, the fixing temperature of the recording medium.

[0053] When the 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 continuously passed through, the heating roller 54 is continuously heated to compensate for the amount of 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.

[0054] The continuous job 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 continuously in one job and multiple such jobs are performed can be cited.

[0055] Although the above description has been given using an example in which a fixing belt is used, the present invention is not limited to the case in which a fixing belt is used. As an example in which a fixing belt is not used, for example, a method in which a fixing roller and a pressure roller are used is given.

[0056] (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.

[0057] In the fixing device of this embodiment, in a continuous job for forming images on multiple recording media, when the job number is an integer N greater than or equal to 2, 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 device is raised or lowered to fix the Nth recording medium, before the fixing device becomes ready to pass paper, a notification is given that the development means for performing the Nth development will begin to be driven, or a notification is given that the image carrier for performing the Nth image formation will begin to be driven.

[0058] 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.

[0059] Furthermore, in the image forming apparatus of this embodiment, in a continuous job in which images are formed on a plurality of recording media, when the job number is an integer N of 2 or greater, 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 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.

[0060] Furthermore, in the image forming method of this embodiment, in a continuous job in which images are formed on a plurality of recording media, when the job number is an integer N of 2 or greater, 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 in the fixing process is increased or decreased to fix the Nth recording medium, the developing means for performing the Nth development is started to be driven, or the image carrier for performing the Nth image formation is started to be driven, before the fixing process becomes ready for paper passing.

[0061] In this embodiment, the start of driving of the developing unit for performing the Nth development will be mainly described. The start of driving of the image carrier for performing the Nth image formation will be described in the following embodiment.

[0062] 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.

[0063] This example is an example of a case where an image is formed on one recording medium in one job. This is 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, it is assumed that the type of recording media on which images are formed within one job, particularly the fixing temperature, is the same.

[0064] This example is an example of a case where the fixing temperature of the fixing unit is increased in order to form an image of the Nth job. This embodiment also includes a mode in which the fixing temperature of the fixing unit is decreased in order to form an image of the Nth job.

[0065] 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, the basis weight is 105 gsm (g / m 2 ) or less is considered thin paper, and 220gsm or more is considered thick paper. The Ricoh Pro C7200 series has a maximum thickness of around 360gsm.

[0066] In FIG. 3, (a) represents the image formation operation state, (b) represents the image formation 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.

[0067] 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.

[0068] 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.

[0069] 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 operation states a1 to a4 and (c) fixing operation states c1 to c4.

[0070] As shown in the figure, the start timing of development and transfer in the (N-1)th job is indicated by a1 and the end timing is indicated by a2. Similarly, the start timing of development and transfer in the Nth job is indicated by a3 and the end timing is indicated by a4. Furthermore, the start timing of fixing in the (N-1)th job is indicated by c1 and the end timing is indicated by c2. Similarly, the start timing of fixing in the Nth job is indicated by c3 and the end timing is indicated by c4.

[0071] As mentioned above, this example is an example in which an image is formed on one recording medium in one job. Therefore, as shown in the figure, a2 is followed by c1. As will be described later, when images are formed 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.

[0072] In this example, in the consecutive jobs, the (N-1)th 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-1)th recording medium. Therefore, after fixing the (N-1)th recording medium, the fixing temperature of the fixing means (fixing device) is raised to fix the Nth recording medium.

[0073] 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.

[0074] 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 increasing the temperature of the fixing belt 51. In this example, for example, the temperature of the fixing belt 51 detected by 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 of the induction heating means 53 provided outside the heating roller 54, thereby increasing the temperature of the fixing belt 51. Therefore, in this example, after fixing is performed on the (N-1)th recording medium, the temperature of the fixing belt 51 is increased to a temperature at which fixing can be performed on the Nth recording medium.

[0075] (b) Image formation drive refers to the drive of the components that form the image. 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 of the developing means.

[0076] In this example, after the image formation operation of the N-1th job is completed (after a2 in the figure), the image formation drive starts to shut down and stops. The time when the image formation drive starts to shut down is indicated by b1 in the figure, and the time when the image formation drive stops is indicated by b2 in the figure. In this example, the operations and stops in (b) image formation drive are described as the rotation and stop of the developing roller of the developing means. The developing roller applies toner to the image carrier by rotating near the image carrier. However, the operations and stops in (b) image formation drive may also be the rotation and stop of the image carrier (photosensitive member).

[0077] 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.

[0078] As described above, the reason for stopping the image formation drive is to reduce the drive of the developing device (or the rotation of the photosensitive member) that does not contribute to image formation, i.e., to suppress unnecessary drive of the developing device (or the rotation of the photosensitive member). While it is not necessarily necessary to stop the image formation drive between the image formation of the (N-1)th job and the image formation of the (N)th job, it is preferable to stop such image formation drive from the viewpoint of suppressing toner deterioration. Therefore, in consecutive jobs, it is preferable to start shutting down the developing device and stop the developing device after transfer to the (N-1)th recording medium. Alternatively, 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-1)th recording medium in consecutive jobs.

[0079] In addition, the circumstances under which the image formation drive is stopped can be selected as appropriate. The image formation drive may be stopped every time the fixing temperature of the Nth recording medium is different from the fixing temperature of the (N-1)th recording medium, but this may not be desirable because the image formation drive would be stopped every time the fixing temperature is increased or decreased even slightly. Therefore, it is preferable to stop the image formation drive when the fixing temperature of the Nth recording medium is different from the fixing temperature of the (N-1)th recording medium and it takes a predetermined time for the fixing temperature of the fixing means to reach the fixing temperature of the Nth recording medium.

[0080] That is, in the continuous 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 for performing the Nth development, or from the time the N-1th development is completed until a notification is given to start driving the image carrier for performing the Nth image formation. This prevents the developing means from running idle and further suppresses toner degradation.

[0081] The reason why (b) the image formation drive is in operation before the development and transfer of the (N-1)th job is that, for example, the fixing temperature of the recording medium for the (N-2)th job is the same or approximately the same as the fixing temperature of the recording medium for the (N-1)th job. Also, in this case, by having the image formation drive in operation between the (N-2)th job and the (N-1)th job, there are advantages such as stabilizing the rotation of the photosensitive drum, stabilizing the charging potential, and stabilizing the toner charge amount.

[0082] Furthermore, after development and transfer for the Nth job are completed, (b) the image formation 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. Also, in this case, having the image formation 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 rotation of the contacting member to finish.

[0083] 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.

[0084] The determination of stopping image formation is made at time b1 in the figure. The determination of stopping image formation is made, for example, by a control unit of the image forming apparatus. The determination of stopping image formation is not particularly limited, but may be made, for example, by the completion of primary transfer to the recording medium or the completion of secondary transfer to the recording medium. Also, the image formation time may be known in advance, and the determination may be made by predicting the image formation completion time. The image formation termination may also be determined by the completion of de-electrification or cleaning of the image carrier.

[0085] When the image formation stop determination is made, for example, a control unit of the image forming apparatus issues an instruction to the developing means or image carrier to stop image formation drive. In this example, at time b1 in the figure, an instruction to stop rotation is issued to the developing roller, and rotation of the developing roller stops at time b2 in the figure. In the figure, the time required to stop image formation drive, i.e., the time from b1 to b2, is shown as stop time t2. After the image formation operation for the (N-1)th job is completed and image formation drive is stopped, image formation drive is stopped until an instruction to start image formation drive is issued.

[0086] In this example, the timing to start image formation drive for forming an image for 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 figure), the fixing temperature of the fixing means is raised to fix the Nth recording medium (d1 to d4 in the figure). In this example, before the fixing device (fixing means) becomes ready to pass paper, that is, before d3 in the figure, start-up of the developing means to perform the Nth development is started (b3 and d2 in the figure).

[0087] In the figure, d3 represents the point in time when the adjustment of the fixing temperature of the fixing means is completed, and represents the point in time when the fixing means is ready to feed a recording medium (a paper-passable 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 is passable) 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, and can be selected as appropriate.

[0088] In an example not included in the present invention, the start-up of the image forming drive is started when the fixing device is in a state where paper can be passed through. This example will be described later.

[0089] As shown by b3 and d2 in the figure, in this example, image formation drive is started when the fixing temperature of the fixing means reaches point d2. Specifically, for example, the control unit of the image forming apparatus 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 apparatus issues an instruction to start image formation drive, for example, to start rotation of the developing roller.

[0090] Alternatively, as indicated by "notification of image formation start" 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 issues a notification to start driving the developing means for performing the Nth development. The notification to start driving the developing means is sent to, for example, a control unit of the image forming apparatus.

[0091] When an instruction to start image formation driving is issued, the developing means starts to start up, and the start-up is completed at time b4. In other words, the driving of the developing means starts at time b3, and the developing means is in a driving state at time b4. In the figure, the time required for the developing means to complete the start-up, i.e., the time from b3 to b4, is indicated as start-up time t3. The start-up time t3 may be the same as or different from the fall-down time t2.

[0092] Note that, since the start-up of the image forming drive starts when the fixing temperature of the fixing means reaches the point d2, the point d2 may be described as a start-up trigger, etc. Therefore, such a description is given in the figure.

[0093] After the start-up of the developing means is complete, 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, that is, 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 included in the image forming apparatus or a control unit included in the fixing device.

[0094] The image forming unit starts developing and transferring for the Nth job when instructed to do so (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 development and transfer for the Nth job has been performed is transported to the fixing means, where fixing is performed (c3 and c4 in the figure).

[0095] The fixing temperature of the fixing means continues to rise even while development and transfer are being performed for the Nth job, so that when 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).

[0096] Thus, 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 developing means for the Nth development is started to be driven 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 approach the timing when the temperature rise of the fixing means is completed. Therefore, this example prevents the developing means from running idle while waiting for the temperature rise of the fixing means to be completed, even when the image creation operation is ready to start. This suppresses toner degradation.

[0097] Toner deterioration can occur, for example, when additives that should be present on the surface of the toner matrix are buried in the toner matrix, or when additives are missing from the surface of the toner matrix. When toner deterioration occurs, uneven transfer occurs, leading to image deterioration, but this example can prevent such problems. Titanium oxide and silica are commonly used as additives.

[0098] Furthermore, this example can prevent a situation in which the image forming operation must wait until it is ready to start even though the fixing temperature of the fixing unit has already been increased. In such a situation, it becomes necessary to maintain the fixing temperature of the fixing unit, which increases power consumption. In addition, the waiting time causes the fixing temperature of the fixing unit to drop, requiring it to be increased again. This example can prevent these problems from occurring and avoids the need to increase the fixing temperature of the fixing unit again, thereby preventing job times from becoming longer.

[0099] In this example, when 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 unit, shuts down and stops when the fixing temperature is increased during the switchover. Then, before the fixing temperature of the fixing unit reaches the paper passing temperature, image forming start-up begins and the image forming drive starts up again. This allows the image forming unit to start up and return to normal operation as quickly as possible.

[0100] In an example not included in the present invention, the developing unit for performing the Nth development starts operating at time d3. An example of this case (comparison example) is shown in FIG. 4. As shown in FIG. 4, the start-up of the developing unit for performing the Nth development starts at time d3, when the adjustment of the fixing temperature of the fixing unit is completed. At this time, an instruction to start development and transfer for the Nth job is also issued, but because the start-up of the image formation drive has not yet completed (b3, b4), development and transfer wait for the start-up of the image formation drive. As a result, even though the temperature rise of the fixing unit has completed, the fixing unit enters a paper waiting state, requiring further heating, and the job time cannot be shortened.

[0101] The value d2, which is the starting point for starting the image formation drive, can be selected as appropriate. More specifically, the fixing temperature of the fixing unit is increased, and the temperature at which the image formation drive is started can be selected as appropriate. For example, when increasing the fixing temperature of the fixing unit to fix the Nth recording medium, it is preferable that the difference between the fixing temperature of the fixing unit at the time (d3) when the fixing unit becomes ready to pass paper and the fixing temperature of the fixing unit at the time (d2) when the drive of the developing unit to perform the Nth development is started is 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, and the process can be prevented from becoming complicated.

[0102] 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 increases and decreases, the fixing temperature of the recording medium, etc. Therefore, although it cannot be generalized, it is preferable to set it to, for example, 10°C. In this case, it is possible to ensure time leeway for development and transfer in the Nth job, and it becomes easier to prevent the fixing temperature of the fixing means from being completed at an early stage.

[0103] In addition to the above, d2, which is the starting point for starting up the image formation drive, may be set taking into consideration, for example, the start-up time t3 and the rate of increase or decrease of the fixing temperature of the fixing unit. For example, it is preferable to obtain the rate of increase or decrease of the fixing temperature of the fixing unit in advance and calculate the time to start up the developing unit or drive the image carrier based on the rate of increase or decrease. In this case, there is no need to detect and determine the fixing temperature of the fixing unit, which simplifies the design.

[0104] 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 image forming system. By using t1, it is possible to prevent unnecessary time from being wasted by immediately starting up the image forming 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 image forming system after it has been turned down plus 10 seconds.

[0105] This example corresponds to a case where 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 the fixing temperature of the N-1th recording medium. A method for determining whether the fixing temperature of the Nth recording medium is higher than the fixing temperature 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 the number of sheets may be set in the device in advance before executing consecutive jobs.

[0106] In this embodiment, as described above, the case where the fixing temperature of the fixing unit is increased to fix the Nth recording medium has been described. The case where the fixing temperature of the fixing unit 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 formation drive is stopped and started as appropriate, taking into account the rate at which the fixing temperature of the fixing unit is decreasing.

[0107] Here, an example of forming images on multiple recording media in one job will be described. Fig. 5 is a time chart for explaining this example, and is similar to Fig. 3. As shown in the figure, fixing starts before development and transfer in the (N-1)th job are completed. That is, c1 is located before a2, and the order is a1, c1, a2, c2. Similarly, fixing starts 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.

[0108] For example, after the transfer of the first recording medium in the N-1th job is completed, the first recording medium is fixed, but while the first recording medium is being fixed, development and transfer of the second and subsequent recording media are carried out.

[0109] 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 consecutive 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.

[0110] The example shown in Fig. 6 is substantially the same as the example shown in Fig. 3, but (d) the fixing temperature of the fixing means is lowered to perform the Nth fixing. As shown in the figure, after the N-1th recording medium has been fixed (after c2), when the fixing temperature of the fixing device is lowered to perform the Nth recording medium, a notification is made (d2) to start driving the developing means to perform the Nth development before the fixing device becomes ready to pass paper (before d3).

[0111] 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 given (d2) to start driving the image carrier to form the Nth image before the fixing device becomes ready to pass paper (before d3).

[0112] The above notification is mainly performed by the fixing means (fixing device), but instead of a configuration that performs the notification, it may be a configuration of the image forming device, as in the above example, that starts driving the developing means or starts driving the image carrier.

[0113] The method for lowering the fixing temperature of the fixing means is not particularly limited, and for example, a cooling means may be used, or the fixing means may be left to cool naturally.

[0114] The example shown in Fig. 6 is an example of forming an image on one recording medium in one job, similar to Fig. 3. As with the example shown in Fig. 5, images may be formed on multiple recording media in one job in the example shown in Fig. 6. In this case, the timing of (a) the image forming operation state and (c) the fixing operation state, etc., will be as shown in the example shown in Fig. 5.

[0115] 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 FIG. 3, after the N-1th development and transfer, the developing means begins to stop (shut down). Also, after the N-1th development and transfer, the recording medium is transported to the fixing means and fixed (c1). The fixing temperature of the fixing means at this time is 140°C. After fixing for the N-1th job is completed (c2), the fixing means begins to raise the fixing temperature (d1) to fix the Nth recording medium (cardboard). Specifically, the fixing temperature of the fixing means is raised (increased) from 140°C to 180°C as shown in d1 to d4. The image formation drive starts to stop at b1 and is completely stopped at b2.

[0116] In this embodiment, the temperature of d2 is set to 165° C., and an instruction to start image formation driving is issued when the fixing temperature of the fixing means reaches 165° C. Therefore, when the fixing temperature of the fixing means reaches 165° C., driving of the developing means starts (b3).

[0117] After passing through d2, the fixing temperature of the fixing means is further increased, and at d3, the fixing means is ready to pass paper. 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 start up 10°C earlier than the paper passing permitted temperature, 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 method.

[0118] <Example 2> Next, another example using a specific temperature will be described. In the above embodiment, d2 is set, but this embodiment is not limited to this. 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 starting up the developing unit may be calculated based on the rate of increase.

[0119] Specifically, if 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 development means starts to operate until it enters the operating state is D1 [s], and the time from when the fixing temperature of the fixing means starts to increase until the development means starts to operate to develop the Nth recording medium is E1 [s], E1 can be calculated as follows: E1=(|AB|) / C-D1

[0120] The reason why AB is an absolute value is that a case where the fixing temperature is lowered (for example, Example 3 below) is taken into consideration.

[0121] This will be explained using specific numerical values. In this example, thin paper with a fixing temperature of 150°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. Furthermore, 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, using actual measurement data from a Ricoh Pro C7200, for example. Furthermore, the time from when the developing means starts up until development begins is assumed to be 5 seconds.

[0122] In this example, applying the above explanation, A is 180°C, B is 150°C, C is 2°C / s, and D1 is 5s. Therefore, E1 can be calculated as follows: E1 = (|180 - 150|) / 2 - 5 = 10 [s]

[0123] Therefore, after fixing is performed on the N-1th recording medium (thin paper), the start-up of the developing means begins 10 seconds after the time d1 when the fixing temperature of the fixing means 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 means each time, and providing advantages such as a simplified component configuration.

[0124] Example 3 Next, a description will be given of the case where the fixing temperature of the fixing unit is lowered in the above-mentioned Example 2. As in Example 2, for d2, for example, as in this example, 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.

[0125] 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=(|AB|) / C-D1

[0126] In this example, 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] For this reason, it is preferable to issue the image formation start notification 55 seconds after the fixing temperature of the fixing means starts to drop.

[0127] (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.

[0128] In this embodiment, after fixing the N-1th recording medium, when the fixing device raises or lowers the fixing temperature of the fixing device to fix the Nth recording medium, the fixing device notifies the user that it will start driving the image carrier to form the Nth image before the fixing device becomes ready to pass paper.

[0129] Furthermore, in the image forming apparatus of 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 carrier is started to be driven to form the Nth image before the fixing means is ready to pass paper.

[0130] Furthermore, in the image forming method of this embodiment, after fixing the N-1th recording medium, when the fixing temperature in the fixing process is increased or decreased 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.

[0131] In this embodiment, in the image formation drive of Figure 3(b), "operating" and "stopped" refer to the rotation and stop of rotation of the image carrier. Therefore, in the image formation drive of 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), and the image carrier rises up, and at point b4, the rise of the image carrier is completed and the image carrier enters a driving state.

[0132] By controlling the driving of the image carrier in this way, it is possible to obtain the same effects as in the above embodiment.

[0133] Furthermore, in this embodiment, as in the above embodiment, it is also possible to determine the rate of increase or decrease of the fixing temperature of the fixing means in advance, and calculate the time to start driving the image carrier based on the rate of increase or decrease.

[0134] Furthermore, in this embodiment, the same procedures as in Examples 1 to 3 of the above embodiment can be carried out. 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=(|AB|) / C-D2 It can be found by: [Explanation of symbols]

[0135] 51 Fixing belt 52 Fuser roller 54 Heating roller 55 Pressure roller 56 Thermopile 100 Fixing device 200 printers 200A Image forming unit 200B Paper feed section 203 Developing device 205 Photoreceptor 210 Intermediate transfer belt 1000 control section N Fixing nip [Prior art documents] [Patent documents]

[0136] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-107044

Claims

1. 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 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 a notification is given that the driving of the developing roller for performing the Nth development will start. An image forming apparatus characterized by:

2. 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. 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 ready to pass paper and the fixing temperature of the fixing means when the driving of the developing roller to perform the Nth development is started is equal to or greater than a predetermined value.

3. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

4. The rate of increase or decrease of the fixing temperature of the fixing means is obtained in advance, and the time to start driving the developing roller is calculated based on the rate of increase or decrease.

4. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

5. 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:

6. 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:

Images