JP2014178574A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which can appropriately set fixing conditions depending on the type of a transfer material.SOLUTION: The image forming apparatus includes: a fixing device which heats a toner image on the basis of a set fixing temperature to fix the image on a recording medium; an optical sensor 50 which detects a smoothness degree of the recording medium; and a heat source control circuit which determines a set fixing temperature in accordance with a sensor value of the optical sensor 50. When a recording medium having a smoothness degree detected is denoted by a recording medium P as well as a recording medium to be conveyed next to the recording medium P is denoted by a recording medium Q, the heat source control circuit determines a set fixing temperature on the recording medium Q in accordance with sensor values of a plurality of recording medium P (1 to n sheets) detected by the optical sensor 50.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, a printer, or a complex machine of these.

  A so-called electrophotographic image forming apparatus such as a digital copying machine or a laser printer transfers a toner image to a recording medium such as recording paper, and heats and presses the toner image under a predetermined condition to record the toner image on a recording medium such as recording paper. To form an image.

  In such an image forming apparatus, it is necessary to consider conditions such as a heating amount and a pressure when fixing a toner image. In particular, when forming a high-quality image, it is necessary to individually set conditions for fixing the toner image according to the type of the recording medium.

  This is because the image quality recorded on the recording medium is greatly influenced by the material, thickness, humidity, smoothness, coating state, and the like of the recording medium. For example, there is smoothness as an index representing smoothness. The smoothness is expressed by the time [sec] in which a certain amount of air flows between the paper surface and the test plate when they are brought into close contact with each other. The term “coating” means that ink or paint is coated or printed.

  Here, there is a very high correlation between the smoothness of the recording medium and the fixing quality. This is because the toner fixing rate in the recesses changes depending on the degree of unevenness in the recording medium. Therefore, when fixing is not performed under fixing conditions that take smoothness into account, not only a high-quality image can be obtained, but also an abnormal image such as fixing failure may be caused in some cases.

  On the other hand, with the recent progress of image forming apparatuses and diversification of expression methods, there are several hundred types of recording papers that serve as recording media, and the basis weight, thickness, etc. for each type of recording paper There are various brands due to the difference. Therefore, in order to form a high-quality image, it is necessary to set detailed fixing conditions and the like according to the type and brand of a recording medium such as recording paper.

  For example, the types of recording media include plain paper, gloss coated paper, matte coated paper, coated paper such as art coated paper, OHP sheets, etc., as well as special paper with a paper surface embossed. ing. These special papers are increasing in recent years. Note that recording media other than recording paper and the like exist as recording media.

By the way, in the current image forming apparatus, it is very general that the fixing condition is set according to the basis weight of the recording material. For example, paper with a basis weight of 60 to 90 g / m ² is plain paper, 91 to 105 g / m ² is medium thick paper, 106 to 200 g / m ² is thick paper, and so on. The fixing temperature, the recording medium conveyance speed, and the like are changed every time.

  The basis weight information of the recording material is generally described in a recording material package or the like, and can be grasped by the user. This basis weight information can be recognized by selecting it on the operation unit (operation panel) if it is a copier, or on the printer driver displayed on the PC display if it is a printer.

  In general, the user needs to set the basis weight information by himself / herself. In addition to being troublesome when performing printing or the like, the user may not be able to obtain a desired high-quality image if set incorrectly.

  Therefore, conventionally, a technique relating to an image forming apparatus that is equipped with a sensor that detects the thickness of a recording medium, for example, and that can automatically select the recording medium to form an image has been studied.

  On the other hand, the smoothness of the recording medium is usually not printed on the recording material package, and it is extremely difficult for the user to know the smoothness information. For this reason, the smoothness of the recording medium has to be obtained using a sensor or the like.

  As described above, there is a high correlation between the smoothness and the fixing quality, but the smoothness is the time during which a certain amount of air flows between the recording material and the test piece, so that it is difficult to detect in a short time. . Therefore, conventionally, as a substitute characteristic of smoothness, a sensor that measures surface roughness and light reflected light quantity highly correlated with smoothness has been studied.

  Conventionally, as a method for detecting such smoothness, reflection is performed by irradiating a recording medium with light emitted from a light source such as a light emitting diode (LED) and detecting the smoothness of the recording medium based on the amount of reflected light from the recording medium. An optical system is known. According to this reflected light method, since the smoothness can be detected without contact with the recording medium, there is an advantage that there is no damage to the recording medium.

  As this type of reflected light smoothness detection method, for example, the amount of reflected light in the regular reflection direction of light irradiated on the surface of the recording medium is detected, and the smoothness of the recording medium is detected based on the detected amount of light in the regular reflection direction. A method of detecting the degree is known (for example, see Patent Document 1).

  In addition, it has a plurality of light amount detection units, detects not only the amount of reflected light in the regular reflection direction of the light irradiated on the surface of the recording medium but also the amount of scattered reflected light, and based on these two amounts of light, A method for identifying smoothness is also known (see, for example, Patent Document 2).

  The smoothness detected by such a detection method is used, for example, for setting fixing conditions such as fixing temperature and image forming conditions. Further, a predetermined time is required from the start of image formation to transfer onto transfer paper and until the actual fixing temperature reaches the target fixing temperature.

  Therefore, in an image forming apparatus that uses the detected smoothness of the recording medium for setting the fixing conditions and the image forming conditions, it is necessary to detect the smoothness in advance in consideration of the predetermined time as described above. In particular, the arrangement and detection timing of the sensor for detecting the smoothness are particularly important.

  Some image forming apparatuses include a paper thickness detection sensor for detecting the thickness of the recording medium, and the fixing conditions are changed according to the thickness of the recording medium. Even in such an image forming apparatus, arrangement and detection timing of a paper thickness detection sensor and the like are important for setting appropriate fixing conditions.

  However, in the image forming apparatuses described in Patent Documents 1 and 2, the time from the start of image formation to the transfer onto the transfer paper and the time until the actual fixing temperature reaches the target fixing temperature are taken into consideration. Therefore, no consideration is given to arranging a sensor for detecting the smoothness at an optimal position or performing detection at an optimal timing.

  Further, not only the smoothness sensor but also the paper thickness detection sensor, like the smoothness sensor, its arrangement and detection timing in consideration of the time until the actual fixing temperature reaches the target fixing temperature. Must be set appropriately.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of appropriately setting fixing conditions according to the type of transfer material.

  In order to achieve the above object, an image forming apparatus according to the present invention forms an image forming means for forming a toner image on a transfer material, and heats the toner image formed on the transfer material on the basis of a target fixing temperature. Fixing means for fixing on the transfer material, detection means for detecting the type of the transfer material used when setting the target fixing temperature, and fixing control for determining the target fixing temperature according to the detection value of the detection means A transfer material whose type is detected by the detection means is a transfer material P, and a transfer material conveyed next to the transfer material P is a transfer material Q. The target fixing temperature for the transfer material Q is determined according to the detected values of the plurality of transfer materials P detected by the means.

  According to the present invention, it is possible to provide an image forming apparatus capable of appropriately setting fixing conditions according to the type of transfer material.

1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention. It is a schematic front view of the optical sensor which concerns on embodiment of this invention. 1 is a functional block diagram of an image forming apparatus according to an embodiment of the present invention. It is a time chart for demonstrating the fixing process of the conventional fixing device. FIG. 4 is a diagram showing a relationship between a recording medium S and a recording medium Q in a fixing process of the fixing device according to the embodiment of the present invention. It is a figure which shows an example of the fixing process which concerns on embodiment of this invention. 6 is a time chart for explaining a fixing process of the fixing device according to the embodiment of the present invention. It is a figure which shows the modification of the detection method of the smoothness of the recording medium by the optical sensor which concerns on embodiment of this invention. 6 is a time chart illustrating an example in which the fixing process of the fixing device according to the embodiment of the present invention is applied when print jobs are different.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically illustrating an example of an internal configuration of a general electrophotographic image forming apparatus. The image forming apparatus 1 includes an image forming apparatus main body 100, an image reading apparatus 200, and a duplex unit 300.

  The image forming apparatus main body 100 includes an intermediate transfer belt 11, image forming devices 12c, 12m, 12y, and 12k, an exposure device 13, a paper feeding device 14, a recording medium conveyance path 16, a paper feeding roller 17, and a cylinder. An internal paper discharge unit 18 and a paper discharge device 23 are provided. The image forming apparatus main body 100 includes primary transfer devices 25c, 25m, 25y, and 25k, an optical sensor 50, and a fixing device 60.

  The intermediate transfer belt 11 is an endless belt that is stretched around a plurality of rollers provided in the image forming apparatus main body 100 and stretched almost horizontally, and is configured to run in the counterclockwise direction in the drawing. ing. Here, the endless shape means a state in which both ends of the belt are joined and no joint exists.

  The image forming devices 12c, 12m, 12y, and 12k correspond to cyan, magenta, yellow, and black colors, and are arranged in a quadruple tandem manner along the traveling direction of the intermediate transfer belt 11 below the intermediate transfer belt 11. Is provided.

  The image forming devices 12c, 12m, 12y, and 12k include a drum-shaped image carrier that rotates clockwise in the drawing, a charging device, a developing device, a transfer device, a cleaning device, and the like provided around the image carrier. It is comprised by.

  The exposure device 13 is provided below the image forming devices 12c, 12m, 12y, and 12k. The exposure device 13 writes a latent image corresponding to each color toner image of the original image read by the image reading device 200 on the image carriers of the image forming devices 12c, 12m, 12y, and 12k charged by the charging device.

  The paper feeding device 14 is provided below the exposure device 13 and has a plurality of paper feeding cassettes 15 that store recording media S as transfer materials in a stacked manner. In FIG. 1, two paper feed cassettes 15 are provided. However, this is an example, and the present invention is not limited to this.

  The recording medium conveyance path 16 is formed on the right side in the image forming apparatus main body 100 and directed vertically upward. The in-cylinder discharge section formed between the image forming apparatus main body 100 and the image reading apparatus 200. Leading to 18.

  In the recording medium conveyance path 16, a conveyance roller 19 that conveys the recording medium S in order from the upstream side to the downstream side in the conveyance direction of the recording medium S, a secondary transfer device 21 that faces the intermediate transfer belt 11, and fixing. A device 60 and a paper discharge device 23 are provided. Further, a re-feed conveyance path to the duplex unit 300 is branched and provided in the recording medium conveyance path 16 on the downstream side of the fixing device 60 in the recording medium conveyance direction.

  The sheet feeding roller 17 is provided at the upper right of each sheet feeding cassette 15 in FIG. 1, and feeds the recording medium S in each sheet feeding cassette 15 one by one and feeds it to the recording medium conveyance path 16.

  The in-body discharge unit 18 is formed between the image forming apparatus main body 100 and the image reading apparatus 200, and the recording medium S discharged from the discharge apparatus 23 is stacked.

  The primary transfer devices 25c, 25m, 25y, and 25k are provided so as to be in contact with both the image carrier of each of the image forming devices 12c, 12m, 12y, and 12k and the intermediate transfer belt 11. The primary transfer devices 25c, 25m, 25y, and 25k sequentially transfer the toner images on the image carriers of the image forming devices 12c, 12m, 12y, and 12k onto the intermediate transfer belt 11 in sequence, thereby transferring the toner onto the intermediate transfer belt 11. To form a desired color image.

  The optical sensor 50 is provided on the downstream side of the transport roller 19 and calculates the smoothness of the recording medium S transported to the recording medium transport path 16 from the paper feed cassette 15 or the manual paper feeder 36. The optical sensor 50 detects the type of the recording medium S used when setting the fixing conditions including the fixing setting temperature (target fixing temperature) described later, from the calculated smoothness of the recording medium S. The optical sensor 50 in the present embodiment constitutes detection means.

  As the detection means for detecting the type of the recording medium S, in addition to the optical sensor 50, for example, a paper thickness sensor that detects the thickness of the recording medium S and detects the type of the recording medium S based on the detection result. Can be used. As the paper thickness sensor, for example, the paper thickness is specified from the conveyance time of the recording medium S between a plurality of sensors, or the image at the front end of the recording medium S is read and generated in proportion to the thickness of the recording medium S. Paper that specifies the paper thickness from the change in the shadow area of the recording medium S or irradiates light on one side of a paper bundle made up of a plurality of recording media and detects the leaked light from the side of the paper bundle. Paper thickness sensors having various configurations such as those for specifying the thickness can be used.

  By providing the optical sensor 50 on the downstream side of the conveying roller 19, the image forming apparatus 1 can set the recording medium conveying path 16 without installing the optical sensor 50 in each of the sheet feeding cassettes 15 and the manual sheet feeding device 36. The smoothness of all the recording media S that pass through can be calculated.

  As a method of mounting the optical sensor 50 in the image forming apparatus, a method of detecting the surface of the recording medium S by installing it in the vicinity of the uppermost recording medium S loaded in each paper feed cassette 15 can be considered. In such a case, the number of optical sensors 50 increases and the cost increases. Further, when the recording medium S is set in the paper feeding cassette 15, the distance between the optical sensor 50 and the recording medium S is short, so that the operation is disturbed and the sensor release synchronized with the opening / closing of the paper feeding cassette 15 The mechanism is also required to be separated from the recording medium S), and the mechanism becomes complicated. For this reason, in this Embodiment, the said malfunction is eliminated by providing the optical sensor 50 in the downstream of the conveyance roller 19 as above-mentioned. Details of the optical sensor 50 will be described later.

  A paper feed path 37 is provided on the upstream side of the conveyance roller 19 in the recording medium conveyance direction. The paper feed path 37 is used to re-feed the recording medium S once formed and fixed on the surface from the duplex unit 300 to the recording medium transport path 16 again, or across the duplex unit 300 and the manual feed apparatus 36. Is provided for manually feeding the recording medium S. The paper feed path 37 joins the recording medium transport path 16.

  The secondary transfer device 21 transfers the toner image formed on the intermediate transfer belt 11 to the recording medium S at the secondary transfer position formed between the intermediate transfer belt 11 and the secondary transfer device 21. The primary transfer devices 25c, 25m, 25y, and 25k and the secondary transfer device 21 in the present embodiment constitute an image forming unit that forms a toner image on the recording medium S.

  The fixing device 60 heats and fixes the toner image formed on the recording medium S on the recording medium S based on a fixing set temperature (target fixing temperature) described later. Specifically, the fixing device 60 includes a heating member that applies heat to the recording medium S and a pressure member that applies pressure to the recording medium S. The fixing device 60 heats and pressurizes the recording medium S at a nip portion formed between the heating member and the pressure member, and fixes an unfixed toner image on the recording medium S to the recording medium S. The fixing device 60 in the present embodiment constitutes a fixing unit.

  Next, an image forming operation when the image forming apparatus 1 takes a copy will be described.

  First, the image forming apparatus 1 supports the image forming apparatuses 12c, 12m, 12y, and 12k, in which the latent images corresponding to the color toner images of the original image read by the image reading apparatus 200 are uniformly charged by the charging device. Writing is performed on the body using the exposure device 13.

  Next, the image forming apparatus 1 forms a toner image by applying each color toner from the developing device to each color toner latent image on the image carrier of each of the image forming apparatuses 12c, 12m, 12y, and 12k.

  Next, the image forming apparatus 1 sequentially transfers the respective color toner images formed on the image carrier onto the intermediate transfer belt 11 by using the primary transfer apparatuses 25c, 25m, 25y, and 25k. A desired color image is formed on the belt 11.

  On the other hand, the image forming apparatus 1 selectively rotates one of the sheet feeding rollers 17 in the two-stage sheet feeding cassette to feed the recording medium S from the corresponding sheet feeding cassette 15 or from the manual sheet feeding apparatus 36. The manual recording medium S is fed out to the paper feed path 37.

  Next, the image forming apparatus 1 carries the recording medium S fed from the paper feeding cassette 15 or the manual paper feeding apparatus 36 into the recording medium conveyance path 16.

  Next, the image forming apparatus 1 performs the secondary transfer of the recording medium S conveyed to the conveying roller 19 through the recording medium conveying path 16 with the timing of the toner image formed on the intermediate transfer belt 11 by the conveying roller 19. It is sent to the secondary transfer position of the apparatus 21.

  Here, the image forming apparatus 1 calculates the smoothness of the recording medium S by the optical sensor 50, and transfers the color image on the intermediate transfer belt 11 to the recording medium S by the secondary transfer apparatus 21.

  Next, the image forming apparatus 1 transports the recording medium S on which the color image has been transferred to the fixing device 60, and heats and presses the recording medium S at the nip portion of the fixing device 60, thereby fixing the color image on the recording medium S.

  Here, when an image is also formed on the back surface of the recording medium S, the image forming apparatus 1 re-uses the recording medium S on which the color image is fixed on one side using a switching claw (not shown) for switching the conveyance path. The paper is carried into the paper feed conveyance path 24 and conveyed to the duplex unit 300.

  When the recording medium S passes through the duplex unit 300, the front surface and the back surface of the recording medium S are reversed, and then the recording medium S is carried into the paper feed path 37, and is re-supplied to the recording medium conveyance path 16 through the paper feed path 37. Paper.

  After the recording medium S is re-fed, the image forming apparatus 1 secondarily transfers the color image for the back surface formed on the intermediate transfer belt 11 to the recording medium S as in the case of the front surface, and the fixing device. The color image secondarily transferred by 60 is fixed.

  When all the fixing of the color image to the recording medium S is completed, the image forming apparatus 1 discharges the recording medium S on which the color image is fixed by the paper discharge device 23 onto the in-body paper discharge unit 18, and the recording medium S Are stacked, the image forming operation is completed.

  FIG. 2 is a diagram illustrating the configuration of the optical sensor 50.

  The optical sensor 50 includes a light source 51, a collimating lens 52, a regular reflection light detector 53 as a light detector, an aperture 54, and a control unit 55.

  The light source 51 is configured by a surface emitting laser (VCSEL: Vertical Cavity Surface Emitting Laser). Therefore, the light source 51 can suppress FFP (Far Field Pattern) and form a more accurate optical system than a case where a general LED or an end face LD (Laser Diode) is used as a stable light source. Can do. Here, FFP is a value that means the beam divergence angle. The light source 51 is not limited to a surface emitting laser, and may be configured by various light sources such as LEDs.

  The collimating lens 52 is a convex lens that is provided between the light source 51 and the irradiation surface of the recording medium S and converts light emitted from the light source 51 into collimated light. Here, the collimate means that the laser light emitted from the light source is made into a bundle of parallel light that is not diffused and converged, and the collimated light means the laser light adjusted to be in a parallel state.

  The optical sensor 50 increases the detection sensitivity of the smoothness of the recording medium S by adjusting the incident angle of the laser light irradiated from the light source 51 by the collimating lens 52 and the parallelism of the collimated light. Can do.

  The regular reflection light detector 53 is provided on the downstream side of the reflection surface of the recording medium S in the direction of the laser light emitted from the light source 51, and detects a light regularly reflected by the recording medium S. Etc.

  The regular reflection light detector 53 detects the intensity of the light regularly reflected by the recording medium S as a voltage, and outputs the detected result to the control unit 55 as an output signal. Thereby, the optical sensor 50 can calculate the smoothness of the recording medium S by the control unit 55.

  The aperture 54 is provided between the irradiation surface of the recording medium S and the regular reflection light detector 53, and limits the incident angle of light entering the regular reflection light detector 53. By providing the aperture 54, the optical sensor 50 can limit the scattered light mixed in the reflected light while ensuring the amount of reflected light emitted from the light source 51 and reflected by the irradiation surface of the recording medium S. It can prevent that the precision of smoothness detection falls.

  The control unit 55 is connected to the regular reflection light detector 53 and calculates the smoothness of the recording medium S from the sensor value (detection value) detected by the regular reflection light detector 53. The function of the control unit 55 will be described later.

  The optical sensor 50 configured in this manner detects the smoothness of the surface of the recording medium S by detecting the intensity of the regular reflection light in the regular reflection direction of the light irradiated to the recording medium S by the light source 51. It is like that. The optical sensor 50 in the present embodiment constitutes a smoothness detecting means.

  FIG. 3 is a functional block diagram showing each configuration of the image forming apparatus 1.

  In FIG. 3, the image forming apparatus 1 is connected to each element via a bus, and the CPU 101 controls each element so that the functions of the image forming apparatus 1 can be exhibited.

  The CPU 101 includes a paper feed cassette 15, a recording medium conveyance path 16, a secondary transfer device 21, a paper discharge device 23, a manual paper feed device 36, a fixing device 60, a memory unit 102, and an A / D. A conversion unit 106, a voltage detection unit 107, and an interface 108 are connected. The CPU 101 is connected to the image reading apparatus 200 and the duplex unit 300.

  The fixing device 60 includes a heat source control circuit 61 that determines an amount of heat (hereinafter referred to as “supplied heat amount”) supplied from the heat source 62 to the heating member, that is, a fixing set temperature (target fixing temperature), and temperatures of the heating member and the pressure member. And a thermistor 64 for detecting.

  Here, in order to obtain a high-quality image as described above, it is necessary to determine the fixing setting temperature (target fixing temperature) in consideration of smoothness having a very high correlation with the fixing quality. Accordingly, the heat source control circuit 61 according to the present embodiment fixes the fixing set temperature (target fixing temperature) according to the sensor value of the optical sensor 50 described above, that is, the smoothness of the surface of the recording medium S detected by the optical sensor 50. To decide. The heat source control circuit 61 in the present embodiment constitutes a fixing control means.

  Further, the fixing device 60 includes an A / D conversion unit 63 that performs A / D conversion into a digital value and notifies the CPU 101 of the analog value detected by the thermistor 64 for processing by the CPU. Further, the fixing device 60 includes a pressure control circuit 65 that controls the force for pressing the pressure member against the heating member and the width of the nip portion.

  Further, the control unit 55 of the optical sensor 50 is connected to the fixing device 60, and when the fixing device 60 receives a signal transmitted from the control unit 55, the heat source control circuit 61 and the pressure control circuit 65. Control is executed.

  The memory unit 102 includes a ROM (Read Only Memory) 103 and a RAM (Random Access Memory) 104. The ROM 103 stores program codes executed by the CPU 101 and a fixing control pattern. In addition, the detection voltage is temporarily stored in the RAM 104.

  The CPU 101 reads out the program code stored in the ROM 103, expands it in the RAM 104, executes the program defined by the program code while using the RAM 104 as a data buffer, and controls each element.

  The current control circuit 105 is an element that receives a signal transmitted from the control unit 55 of the optical sensor 50 and controls a transfer current value when the secondary transfer device 21 transfers the toner image to the recording medium S.

  The A / D conversion unit 106 converts the analog voltage detected by the voltage detection unit 107 that performs voltage detection in order to perform control in a stable power state into a digital value for processing by the CPU 101 and notifies the CPU 101 of the analog voltage. It is.

  The interface 108 functions as a connection unit that connects to an external storage element 109 such as a hard disk device or an external communication device 110 such as a personal computer, and takes in image data into the image forming apparatus 1 from the outside.

  Next, with reference to FIG. 4, a fixing process in a conventional image forming apparatus provided with an optical sensor for detecting smoothness similar to the optical sensor 50 according to the present embodiment will be described.

  As shown in FIG. 4, in the conventional fixing process, when the leading edge of the recording medium S reaches the optical sensor, the optical sensor starts detecting the smoothness of the recording medium S (time T0). Here, the time T0 means the time when the leading edge of the recording medium S reaches the surface facing the optical sensor.

  Thereafter, the optical sensor detects the recording medium S conveyed at the process linear velocity (conveyance speed) v from time T0 to time T1. That is, the detection of the recording medium S ends at time T1. In this process, the optical sensor irradiates the print surface of the recording medium S with laser light emitted from the light source through the collimator lens until time T1.

  Then, the specularly reflected light that has been specularly reflected on the printing surface of the recording medium S and passed through the aperture enters the specularly reflected light detector. The time T1 means a time sufficient to start the calculation of the smoothness of the recording medium S conveyed by the optical sensor at the process linear velocity (conveyance speed) v from the time T0 and complete the calculation. The end of detection by the optical sensor may be the time when the trailing edge of the recording medium S reaches the optical sensor, or may be a predetermined time point during conveyance of the recording medium S.

  Next, at time T2, the sensor value detected by the optical sensor up to time T1 is determined by the control unit. Here, the determination of the sensor value may be, for example, an average value of voltages detected by the regular reflection light detector during a period from time T0 to time T1, or may be a minimum value. The time T2 means a time sufficient for the control unit of the optical sensor to determine the sensor value measured by the optical sensor until the time T1.

  When the sensor value is determined, at time T3, the heat supply control circuit determines the amount of heat supplied to the fixing device according to the determined sensor value, that is, the fixing set temperature (target fixing temperature) at the nip portion of the fixing device.

  Here, the fixing set temperature (target fixing temperature) is the voltage value stored in the storage unit such as a memory and the fixing set temperature based on the correlation between the smoothness of the recording medium S and the fixing set temperature obtained experimentally in advance. It can be determined by referring to the relationship table. Further, the fixing set temperature (target fixing temperature) is detected by using a mathematical formula stored in a storage unit such as a memory based on the correlation between the smoothness of the recording medium S and the fixing set temperature, which are experimentally obtained in advance. It is also possible to calculate from the smoothness.

  When the fixing setting temperature (target fixing temperature) is determined, supply of heat from the heat source to the heating member is started so that the nip portion of the fixing device reaches the fixing setting temperature (target fixing temperature) at time T4. Thereafter, at time T5, the temperature of the nip portion of the fixing device reaches the fixing setting temperature (target fixing temperature).

  On the other hand, the recording medium S is conveyed at the process linear velocity (conveying speed) v through the conveying distance L to the nip portion of the fixing device after the leading edge reaches the optical sensor at time T0, and time T6 (= T0 + L / v). ) To reach the nip.

  However, in such a fixing process in the conventional image forming apparatus, the recording medium S reaches the nip portion of the fixing device at a time T6 before the time T5 when the fixing device reaches the fixing set temperature (target fixing temperature). It was. For this reason, the conventional image forming apparatus has a problem that the recording medium S cannot be fixed at the determined fixing set temperature (target fixing temperature).

  Therefore, in the image forming apparatus 1 according to the present embodiment, the fixing device 60 reaches the fixing set temperature (target fixing temperature) before the recording medium S reaches the nip portion of the fixing device, that is, time T6> time. It was set as the structure which satisfy | fills the relationship of T5.

  Here, in satisfying the relationship of time T6> time T5, the recording medium S in which the smoothness is detected and the recording medium to be fixed at the fixing set temperature (target fixing temperature) determined in accordance with the detected smoothness. It is desirable that S is the same. In this case, for example, if the distance between the optical sensor 50 and the fixing device 60 is long, the relationship of time T6> time T5 can be satisfied. However, in consideration of the recent demand for downsizing of the apparatus and problems due to the arrangement of the optical sensor 50 in the paper feed cassette 15 as described above, the relationship of time T6> time T5 is satisfied for the same recording medium S. It is difficult to meet.

  Therefore, in the present embodiment, as will be described below, the recording medium S for detecting the smoothness and the recording medium for fixing at the fixing set temperature (target fixing temperature) determined according to the detected smoothness. By making S different from S, the relationship of time T6> time T5 is established. Here, the time T5 corresponds to the time Ta in the present invention, and the time T6 corresponds to the time Tb in the present invention.

  In this embodiment, in order to set a more appropriate fixing set temperature (target fixing temperature), the smoothness of the plurality of recording media S is detected, and the smoothness of the plurality of recording media S is obtained. Accordingly, the fixing set temperature (target fixing temperature) is determined. The fixing setting temperature (target fixing temperature) is determined by the heat source control circuit 61 as described above.

  Hereinafter, the fixing process according to the present embodiment will be described with reference to FIG.

  In FIG. 5, the recording medium whose smoothness is detected by the optical sensor 50 is described as a recording medium P, and the recording medium conveyed next to the recording medium P is described as a recording medium Q. In the present embodiment, there are a plurality (for example, 1 to n) of recording media P.

  In the present embodiment, a case will be described in which both the recording medium P and the recording medium Q are recording media in the same print job.

  As shown in FIG. 5, the optical sensor 50 detects the smoothness of the first to nth recording media P and transmits the sensor values of these recording media P to the heat source control circuit 61.

  The heat source control circuit 61 determines a fixing setting temperature (target fixing temperature) for the recording medium Q according to the sensor values of the first to nth recording media P detected by the optical sensor 50.

  Here, the fixing set temperature (target fixing temperature) determined in accordance with the sensor value of the first to nth recording media P is the mth sheet that is sequentially conveyed after the first recording medium Q. It may be reflected for all of the recording media Q up to, or the fixing set temperature (target fixing temperature) may be sequentially changed for each recording medium Q that reaches the nip portion. In the latter case, the fixing set temperature (target fixing temperature) determined according to the sensor value of the first to nth recording media P is reflected in the first recording medium Q, and the second to n + 1th recording media. It is preferable that the fixing set temperature (target fixing temperature) determined according to the sensor value of the recording medium P of the eye is reflected on the recording medium Q of the second sheet.

  FIG. 6 shows an example in which the fixing set temperature (target fixing temperature) is determined according to the sensor value of the first to third recording media P.

  As shown in FIG. 6, the first to third recording media P are sequentially conveyed, pass through the optical sensor 50, and according to the sensor values of the first to third recording media P. A fixing set temperature (target fixing temperature) is determined. At this time, the fourth recording medium on which the fixing set temperature (target fixing temperature) determined in accordance with the sensor values of the first to third recording media P is reflected, that is, the first recording medium. Q is located in front of the optical sensor 50. Accordingly, the distance A between the leading edge of the third recording medium P and the nip portion of the fixing device 60 at this time is equal to the nip of the fourth recording medium (first recording medium Q) and the nip of the fixing device 60. It is shorter than the distance B with the part. That is, the fourth recording medium (first recording medium Q) reaches the nip portion of the fixing device 60 later than the third recording medium P.

  Therefore, before the fourth recording medium, that is, the first recording medium Q reaches the nip portion of the fixing device 60, the fixing device 60 may be raised to the fixing set temperature (target fixing temperature). it can. In this case, after determining the fixing set temperature (target fixing temperature), the optical sensor 50 causes the fixing device 60 to set the fixing set temperature before the fourth recording medium (first recording medium Q) reaches the nip portion. It is necessary to secure the distance A and the distance B that can reach (target fixing temperature). That is, the optical sensor 50 is disposed at an appropriate position in consideration of the above.

  Therefore, in the present embodiment, as shown in FIG. 7, after the leading end of the first recording medium P among the plurality of recording media P is detected by the optical sensor 50, the fixing device 60 is determined by the heat source control circuit 61. When the time until the fixing set temperature (target fixing temperature) is reached is T5 and the time until the recording medium Q reaches the fixing device 60 is T6, the optical sensor 50 is set so that the relationship of time T6> time T5 is established. Is arranged.

  Here, the fixing set temperature before the change is a predetermined temperature after the warm-up of the fixing device 60 is completed. Therefore, the time T5 is a time until the fixing device 60 that has completed the warm-up reaches the fixing setting temperature (target fixing temperature) set for the recording medium Q.

  In this embodiment, the sensor values of the plurality of recording media P used when determining the fixing set temperature (target fixing temperature) are the average of the sensor values of the plurality of recording media P detected by the optical sensor 50. Value. That is, the heat source control circuit 61 performs a plurality of recordings detected by the optical sensor 50 within a predetermined period (in the present embodiment, for example, a period in which the first to nth recording media P pass through the optical sensor 50). The fixing setting temperature (target fixing temperature) is determined using the average value of the sensor values of the medium P. Thereby, the amount of information regarding the smoothness of the recording medium P can be increased, and the average smoothness of the recording medium P used can be detected more accurately.

  Here, the sensor value of the recording medium P may be a sensor value obtained by one detection at an arbitrary detection timing for each recording medium P, or as shown in FIG. It may be an average value of sensor values obtained by performing the detection a plurality of times every time and performing the detection a plurality of times.

  That is, in the latter case, as shown in FIG. 8, the optical sensor 50 is configured to detect the smoothness a plurality of times for each of the plurality of recording media P. Further, the heat source control circuit 61 uses an average value of a plurality of smoothness values detected by each of the plurality of recording media P by the optical sensor 50 as a sensor value of each recording medium P. In this case, for example, even if a minute bending or distortion occurs in the recording medium P being conveyed, fluctuations in the sensor value due to these can be suppressed. For this reason, an accurate sensor value can be acquired, and the sensor value of the recording medium P can be stably obtained.

  As described above, the image forming apparatus 1 according to the present embodiment fixes the recording medium Q conveyed next to the recording medium P according to the sensor values of the plurality of recording media P detected by the optical sensor 50. The set temperature (target fixing temperature) is determined. For this reason, since the optimum fixing set temperature (target fixing temperature) is determined according to the sensor values of the plurality of recording media P, the fixing conditions can be appropriately set according to the type of the recording media.

  As a result, the image forming apparatus 1 according to the present embodiment is supplied with an optimum amount of heat corresponding to the smoothness of the recording medium P, and can efficiently fix an unfixed image on the recording medium Q.

  Further, in the image forming apparatus 1 according to the present embodiment, from the time T5 until the fixing device 60 reaches the fixing set temperature (target fixing temperature) after the leading edge of the first recording medium P is detected by the optical sensor 50. In addition, the optical sensor 50 is arranged so that the time T6 until the recording medium Q reaches the fixing device 60 is increased. Therefore, the fixing temperature of the nip portion can be raised to the fixing setting temperature (target fixing temperature) before the recording medium Q reaches the fixing device 60.

  Accordingly, it is possible to supply an appropriate amount of heat to the recording medium Q, and it is possible to prevent a fixing defect from occurring on the recording medium Q. Further, since an excessive amount of heat is not supplied to the recording medium Q, power consumption can be reduced.

  In the present embodiment, the optical sensor 50 is arranged in the direction to detect the surface on which the image of the recording medium S is fixed. However, the present invention is not limited to this, and for example, when the layout is difficult, the recording medium S is difficult. The image may be arranged in a direction for detecting the back surface of the surface on which the image is fixed.

  In the present embodiment, the optical sensor 50 is configured to detect the smoothness of the recording medium S until time T1. However, the present invention is not limited to this. For example, the rear end of the recording medium S is connected to the optical sensor 50. You may detect until the arrival time.

  In the present embodiment, as described above, the fixing set temperature (target fixing temperature) is obtained using the average value of the sensor values detected by the optical sensor 50 for each of the first to nth recording media P. I decided to decide. On the other hand, the image forming apparatus according to the present invention may determine the fixing set temperature (target fixing temperature) using, for example, a sensor value detected on one recording medium P.

  In this case, the optical sensor 50 is configured to detect the smoothness multiple times for one recording medium P. Further, in this case, the heat source control circuit 61 determines the fixing set temperature (target fixing temperature) by using the average value of the plurality of smoothness values detected on one recording medium P as the sensor value of the recording medium P. preferable. Even in such an example, as in the present embodiment, the optical sensor 50 is arranged so that the relationship of time T6> time T5 is satisfied.

  In the image forming apparatus configured as described above, the amount of heat supplied to the recording medium Q can be quickly changed by shortening the detection period of the smoothness of the recording medium P as compared with the present embodiment. Can do.

  Further, in the present embodiment, the example in which the image forming apparatus according to the present invention is applied when the recording medium P and the recording medium Q are both recording media in the same print job has been described. On the other hand, the image forming apparatus according to the present invention can be applied to a case where the recording medium P and the recording medium Q are recording media in different print jobs, as shown in FIG. .

  FIG. 9 shows recordings in the print job A having the same fixing set temperature (target fixing temperature) for the recording medium Q determined according to the smoothness of the 1 to n recording media P detected in the print job A. The case where it cannot reflect in the medium Q is shown. For example, this is the case where the print job A has only a very small number (for example, n or less) of recording media P.

  In this case, the fixing set temperature (target fixing temperature) determined in print job A is stored in a storage unit such as a memory, so that the fixing setting temperature (target target) determined in print job A in the next print job B (target). The fixing temperature can be used as it is. That is, it is possible to use supply heat amounts determined across different print jobs A and B.

  For this reason, in the print job B, it is not necessary to detect the smoothness again, and an appropriate amount of supplied heat can be applied from the time of return, and fixing can be performed at the fixing set temperature (target fixing temperature) at an early stage. . As a result, temperature control related to the fixing process can be performed without waste.

1 Image forming apparatus 21 Secondary transfer apparatus (image forming means)
25c, 25m, 25y, 25k Primary transfer device (image forming means)
50 Optical sensor (detection means, smoothness detection means)
Reference Signs List 51 light source 53 specular reflection light detector 55 control unit 60 fixing device (fixing means)
61 Heat source control circuit (fixing control means)
62 Heat source 100 Image forming apparatus main body 101 CPU
200 Image reading device 300 Duplex unit S, P, Q Recording medium (transfer material)

JP-A-10-160687 JP 2006-062842 A

Claims (11)

Image forming means for forming a toner image on a transfer material;
Fixing means for heating and fixing the toner image formed on the transfer material on the transfer material based on a target fixing temperature;
Detecting means for detecting a type of the transfer material used in setting the target fixing temperature;
Fixing control means for determining the target fixing temperature according to a detection value of the detection means,
When the transfer material whose type is detected by the detection means is a transfer material P, and the transfer material conveyed next to the transfer material P is a transfer material Q,
The image forming apparatus, wherein the fixing control unit determines the target fixing temperature for the transfer material Q in accordance with detection values of a plurality of transfer materials P detected by the detection unit. After the leading edge of the first transfer material P among the plurality of transfer materials P is detected by the detection means, the time until the fixing means reaches the target fixing temperature determined by the fixing control means is Ta, the transfer When the time until the material Q reaches the fixing means is Tb,
The image forming apparatus according to claim 1, wherein the detection unit is arranged so that a relationship of Tb> Ta is established.   The detection means is constituted by a smoothness detection means for detecting the smoothness of the surface of the transfer material by detecting the intensity of the regular reflection light in the regular reflection direction of the light irradiated to the transfer material by a light source. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 3, wherein the fixing control unit determines the target fixing temperature using an average value of detection values detected within a predetermined period by the smoothness detection unit.   The fixing control means uses the average value of the detected values detected by each of the plurality of transfer materials P by the smoothness detecting means as the average value of the detected values detected within the predetermined period. The image forming apparatus according to claim 4, wherein the temperature is determined. The smoothness detecting means is configured to detect smoothness a plurality of times for each of the plurality of transfer materials P,
6. The fixing control unit according to claim 5, wherein an average value of a plurality of smoothnesses detected by each of the plurality of transfer materials P by the smoothness detection unit is used as a detection value of each transfer material P. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the transfer material P and the transfer material Q are both transfer materials in the same print job.   The image forming apparatus according to claim 1, wherein the transfer material P and the transfer material Q are transfer materials in different print jobs. Image forming means for forming a toner image on a transfer material;
Fixing means for heating and fixing the toner image formed on the transfer material on the transfer material based on a target fixing temperature;
Smoothness detecting means for detecting the smoothness of the surface of the transfer material by detecting the intensity of the light of the regular reflection light in the regular reflection direction of the light irradiated to the transfer material by a light source;
Fixing control means for determining the target fixing temperature according to the detection value of the smoothness detection means,
When a transfer material whose smoothness is detected by the smoothness detecting means is a transfer material P, and a transfer material conveyed next to the transfer material P is a transfer material Q,
The smoothness detecting means is configured to detect smoothness for the transfer material P a plurality of times,
The fixing control unit determines the target fixing temperature for the transfer material Q according to an average value of a plurality of detection values of the transfer material P detected by the smoothness detection unit. . After the leading edge of the transfer material P is detected by the detection means, Ta is the time until the fixing means reaches the target fixing temperature determined by the fixing control means, and the transfer material Q reaches the fixing means. Tb is the time until
The image forming apparatus according to claim 9, wherein the detection unit is arranged so that a relationship of Tb> Ta is established.   The time Ta is a time required for the fixing unit that has completed warm-up to reach a target fixing temperature set for the transfer material Q, according to claim 1. The image forming apparatus described.

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