Pressurization mechanism, belt drive device, and image forming apparatus

Abstract

This reduces the variation in applied pressure time caused by differences in the drive stop timing of one stepping motor and the other stepping motor. [Solution] The pressurizing mechanism 60 includes a first pressurizing member 61a that operates one end of the member to be pressed, a second pressurizing member 61b that operates the other end of the member to be pressed, a first stepping motor 63a that drives the first pressurizing member 61a, and a second stepping motor 63b that drives the second pressurizing member 61b. The number of input pulses input to the first stepping motor 63a and the number of input pulses input to the second stepping motor 63b are different, so that at least one of the drive pulse frequencies and drive start timings of the first stepping motor 63a and the second stepping motor 63b during pressurizing operation is different.

Description

Technical Field

[0001] The present invention relates to a pressurizing mechanism, a belt drive device, and an image forming apparatus.

Background Art

[0002] In an image forming apparatus such as a copying machine or a printer, a technique for pressurizing a pressure-applying member such as a roller against a mating member is known.

[0003] For example, in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2023-46220), as a pressurizing mechanism for pressurizing a secondary transfer roller against a secondary transfer opposing roller, a configuration is described in which both ends of the secondary transfer roller are pressurized against the secondary transfer opposing roller using a pair of arm members driven by separate stepping motors.

[0004] However, in a pressurizing mechanism such as that of Patent Document 1, if the number of pulses of the stepping motor is individually adjusted to adjust the pressurizing force of the secondary transfer roller, a difference occurs in the drive stop timing of the two stepping motors, so variations occur in the timing of completion of the pressurizing operation on one end side and the other end side of the secondary transfer roller. In that case, a time when the pressurizing force is different occurs between one end side and the other end side of the secondary transfer roller.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, an object of the present invention is to reduce the variation time of the pressurizing force caused by a difference in the drive stop timing of one stepping motor and the other stepping motor.

Means for Solving the Problems

[0006] To solve the above problems, the present invention provides a pressurizing mechanism for pressurizing a member to be pressed against a mating member, comprising: a first pressurizing member that operates to pressurize a portion of the member to be pressed that is on one end side of the longitudinal center of the member to be pressed against the mating member; a second pressurizing member that operates to pressurize a portion of the member to be pressed that is on the other end side of the member to be pressed that is opposite to the one end side of the longitudinal center of the member to be pressed against the mating member; a first stepping motor for driving the first pressurizing member; and a second stepping motor for driving the second pressurizing member, wherein the number of input pulses input to the first stepping motor so that the portion of the member to be pressed that is on one end side of the member to be pressed against the mating member is in a predetermined pressurized state and the number of input pulses input to the second stepping motor so that the portion of the member to be pressed that is on the other end side of the member to be pressed against the mating member is in a predetermined pressurized state and the drive pulse frequencies and drive start timings of the first stepping motor and the second stepping motor are different during the pressurizing operation for pressurizing the member to be pressed against the mating member. [Effects of the Invention]

[0007] According to the present invention, it is possible to reduce the variation time of applied pressure caused by a difference in the drive stop timing of one stepping motor and the other stepping motor. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of an image forming apparatus according to the first embodiment of the present invention. [Figure 2] This is a hardware configuration diagram of an image forming apparatus according to the first embodiment of the present invention. [Figure 3] This is a perspective view of a pressurizing mechanism according to the first embodiment of the present invention. [Figure 4] This is a perspective view showing the secondary transfer device supported by the pressurization mechanism according to the first embodiment of the present invention. [Figure 5] This figure shows the pressurizing operation by one arm member of the pressurizing mechanism according to the first embodiment of the present invention. [Figure 6] This is a schematic diagram showing the pressurizing operation of the pressurizing mechanism according to the first embodiment of the present invention. [Figure 7] This is a schematic diagram showing the pressurizing operation of the pressurizing mechanism according to the second embodiment of the present invention. [Figure 8] This is a schematic diagram showing the pressurizing operation of the pressurizing mechanism related to the comparative example. [Figure 9] This is a block diagram showing an example of a control unit that controls the first stepping motor and the second stepping motor. [Modes for carrying out the invention]

[0009] The present invention will be described below with reference to the attached drawings. In each drawing used to explain the present invention, components such as members and parts having the same function or shape will be denoted by the same reference numerals as far as possible to distinguish them, and their description will be omitted after they have been described once.

[0010] <Overall configuration of the image forming apparatus> First, with reference to Figure 1, the overall configuration of the image forming apparatus according to the first embodiment of the present invention will be described.

[0011] Figure 1 is a schematic diagram of an image forming apparatus according to the first embodiment of the present invention.

[0012] As shown in Figure 1, the image forming apparatus 1000 according to the first embodiment of the present invention includes an image forming section 1 in which four image forming units 10Y, 10M, 10C, and 10K are arranged to form toner images of Y (yellow), M (magenta), C (cyan), and K (black). The four image forming units 10Y, 10M, 10C, and 10K each have a photoreceptor module 20Y, 20M, 20C, and 20K, a charging module 30Y, 30M, 30C, and 30K, a developing module 40Y, 40M, 40C, and 40K, and a cleaning module 50Y, 50M, 50C, and 50K, and are configured to be detachable from the main body of the image forming apparatus. The photoreceptor modules 20Y, 20M, 20C, and 20K each include drum-shaped photoreceptors 21Y, 21M, 21C, and 21K. The charging modules 30Y, 30M, 30C, and 30K are equipped with a charging device. The developing modules 40Y, 40M, 40C, and 40K are equipped with a developing device that develops using a two-component developer containing toner and a magnetic carrier. The cleaning modules 50Y, 50M, 50C, and 50K are equipped with a cleaning device that cleans the photoreceptors 21Y, 21M, 21C, and 21K.

[0013] Furthermore, an exposure unit 2 is positioned above the image forming unit 1. Above the exposure unit 2, a bottle mounting section 3 is positioned where toner bottles 11Y, 11M, 11C, and 11K, which contain the developing toner for each color, are mounted. The toner bottles 11Y, 11M, 11C, and 11K are configured to be detachable from the bottle mounting section 3. Therefore, if any of the toner bottles 11Y, 11M, 11C, or 11K becomes empty, the empty toner bottle can be removed from the bottle mounting section 3 and replaced with a new toner bottle.

[0014] Furthermore, an intermediate transfer device 4 having an intermediate transfer belt 12 is positioned below the image forming unit 1. The intermediate transfer belt 12 is an endless belt consisting of one or more layers, formed from materials such as vinylidene fluoride, ethylene-tetrafluoroethylene copolymer, polyimide, and polycarbonate. The intermediate transfer belt 12 is stretched across a plurality of rollers. At least one of the plurality of rollers rotates as a drive roller, causing the intermediate transfer belt 12 to move in a circular motion in the direction of the arrow in Figure 1.

[0015] Furthermore, four primary transfer rollers for Y, M, C, and K are arranged inside the intermediate transfer belt 12. These primary transfer rollers come into contact with each photoreceptor 21Y, 21M, 21C, and 21K via the intermediate transfer belt 12, causing the outer surface (outer surface) of the intermediate transfer belt 12 to come into contact with the outer surfaces of each photoreceptor 21Y, 21M, 21C, and 21K, forming a primary transfer nip. In the primary transfer nip, a primary transfer bias is applied to the primary transfer rollers, thereby forming a primary transfer electric field.

[0016] Furthermore, a secondary transfer device 5 is positioned below the intermediate transfer device 4. The secondary transfer device 5 comprises a secondary transfer belt 13 consisting of an endless belt and a secondary transfer roller 14 positioned inside the secondary transfer belt 13. The secondary transfer roller 14 is positioned to face a secondary transfer opposing roller 15 via the secondary transfer belt 13 and the intermediate transfer belt 12. The secondary transfer opposing roller 15 is one of a plurality of rollers that tension the intermediate transfer belt 12. When the secondary transfer roller 14 is pressed against the secondary transfer opposing roller 15 via the secondary transfer belt 13 and the intermediate transfer belt 12, a secondary transfer nip is formed between the outer circumferential surface of the secondary transfer belt 13 and the outer circumferential surface of the intermediate transfer belt 12. In addition, when a secondary transfer bias is applied to the secondary transfer roller 14 from a power supply provided in the image forming apparatus body, a secondary transfer electric field is formed between the secondary transfer roller 14 and the electrically grounded secondary transfer opposing roller 15 (secondary transfer nip).

[0017] On the left side in the figure of the secondary transfer device 5, a fixing device 6 for fixing the toner image transferred onto the recording sheet is arranged. The fixing device 6 has a heating roller provided with a heating element inside. Also, between the secondary transfer device 5 and the fixing device 6, a conveyance belt 7 for conveying the recording sheet after toner image transfer toward the fixing device 6 is arranged.

[0018] Further, at the lower part of the image forming apparatus 1000, a sheet feeding device 8 for feeding out the recording sheet to the secondary transfer device 5 is arranged. Also, on the left side in the figure of the fixing device 6, a sheet discharging device 9 for conveying the recording sheet that has passed through the fixing device 6 out of the machine or toward the duplex unit 16 is arranged.

[0019] When the image forming apparatus 1000 receives image data from a scanner unit or an external personal computer or the like, it starts a print job and starts driving the intermediate transfer belt 12 and the like. Then, in the image forming unit 1, the surfaces of the respective photoreceptors 21Y, 21M, 21C, 21K that are rotationally driven are uniformly charged to a predetermined charging potential by the charging devices of the respective charging modules 30Y, 30M, 30C, 30K. On the surfaces of the charged respective photoreceptors 21Y, 21M, 21C, 21K, electrostatic latent images for Y, M, C, K are formed by the exposure unit 2 performing optical scanning based on the image data. After the electrostatic latent images are developed as toner images by the respective developing modules 40Y, 40M, 40C, 40K, they are sequentially primary transferred onto the intermediate transfer belt 12 so as to overlap, resulting in a four-color superimposed toner image. Also, the transfer residual toner remaining on the surfaces of the respective photoreceptors 21Y, 21M, 21C, 21K after transfer is removed from the surfaces of the respective photoreceptors 21Y, 21M, 21C, 21K by the cleaning devices of the respective cleaning modules 50Y, 50M, 50C, 50K.

[0020] Also, in parallel with the formation of the toner image, a recording sheet is fed out from the sheet feeder 8. The fed-out recording sheet hits the timing roller pair 17 on the way to the secondary transfer nip, and the conveyance is temporarily stopped. Then, the timing roller pair 17 starts rotating in accordance with the timing when the toner image on the intermediate transfer belt 12 reaches the secondary transfer nip, and the recording sheet is conveyed to the secondary transfer nip. Then, the toner image on the intermediate transfer belt 12 is transferred onto the recording sheet conveyed to the secondary transfer nip. Also, the residual transfer toner remaining on the intermediate transfer belt 12 after transfer is removed from the surface of the intermediate transfer belt 12 by the belt cleaning unit 18.

[0021] The recording sheet onto which the toner image has been transferred is conveyed to the fixing device 6 by the conveyance belt 7. In the fixing device 6, the toner image on the recording sheet is fixed to the recording sheet by heating and pressurization. Then, the recording sheet is conveyed to the sheet discharge device 9, and the recording sheet is conveyed to either outside the machine or the duplex unit 16 by the sheet discharge device 9. In the case of single-sided printing, the recording sheet is conveyed outside the machine and discharged onto the discharge tray. In the case of duplex printing, the conveyance path is conveyed to the duplex unit 16, and the recording sheet is reversed front and back by the duplex unit 16 and conveyed to the secondary transfer nip again. Then, after the toner image is transferred onto the back surface of the recording sheet at the secondary transfer nip, the toner image on the back surface is fixed to the recording sheet by the fixing device 6. Then, the recording sheet is discharged to the discharge tray outside the machine by the sheet discharge device 9. In this way, a series of image forming operations are completed.

[0022] <Hardware Configuration> Next, while referring to FIG. 2, the hardware configuration of the image forming apparatus according to the first embodiment of the present invention will be described.

[0023] FIG. 2 is a hardware configuration diagram of the image forming apparatus according to the first embodiment of the present invention.

[0024] As shown in Figure 2, the image forming apparatus 1000 according to the first embodiment of the present invention includes a controller 910, a short-range communication circuit 920, an engine control unit 930, an operation panel 940, and a network interface 950.

[0025] The controller 910 includes the main components of the computer: the CPU 901, system memory (MEM-P) 902, northbridge (NB) 903, southbridge (SB) 904, ASIC (Application Specific Integrated Circuit) 906, local memory (MEM-C) 907 (storage unit), HDD controller 908, and HD 909 (storage unit). The NB 903 and ASIC 906 are connected by an AGP (Accelerated Graphics Port) bus 921.

[0026] The CPU901 is a control unit that performs overall control of the image forming apparatus. The NB903 is a bridge that connects the CPU901 to the MEM-P902, SB904, and AGP bus 921. The NB903 has a memory controller that controls reading and writing to the MEM-P902, as well as a PCI (Peripheral Component Interconnect) master and an AGP target.

[0027] MEM-P902 consists of ROM902a, which is a memory for storing programs and data that realize the various functions of the controller 910, and RAM902b, which is used for program and data deployment, and for drawing during memory printing. The programs stored in RAM902b may be configured to be provided as installable or executable files recorded on a computer-readable recording medium such as a CD-ROM, CD-R, or DVD.

[0028] SB904 is a bridge for connecting NB903 to PCI devices and peripheral devices. ASIC906 is an integrated circuit (IC) for image processing applications that has hardware elements for image processing and acts as a bridge connecting the AGP bus 921, PCI bus 922, HDD controller 908, and MEM-C907, respectively. This ASIC906 consists of a PCI target and AGP master, an arbiter (ARB) that forms the core of the ASIC906, a memory controller that controls the MEM-C907, multiple DMACs (Direct Memory Access Controllers) that perform image data rotation using hardware logic, and a PCI unit that performs data transfer between the scanner unit 931 and the printer unit 932 via the PCI bus 922. Note that the ASIC906 may be connected to a USB (Universal Serial Bus) interface or an IEEE1394 (Institute of Electrical and Electronics Engineers 1394) interface.

[0029] MEM-C907 is local memory used as a copy image buffer and code buffer. HD909 is storage for storing image data, font data used during printing, and forms. HD909 controls data reading or writing to it according to the control of CPU901. The AGP bus 921 is a bus interface for graphics accelerator cards proposed to speed up graphics processing, and by directly accessing MEM-P902 with high throughput, the graphics accelerator card can be made faster.

[0030] Furthermore, the short-range communication circuit 920 is equipped with an antenna 920a for the short-range communication circuit. The short-range communication circuit 920 is a communication circuit such as NFC or Bluetooth (registered trademark).

[0031] The engine control unit 930 also includes a scanner unit 931 and a printer unit 932. The operation panel 940 includes a panel display unit 940a, such as a touch panel, which displays current settings, selection screens, etc., and accepts input from the operator, as well as hard keys 940b, which consist of a numeric keypad that accepts setting values ​​for image formation conditions such as density settings, and a start key that accepts a copy start command. The controller 910 controls the entire image forming apparatus, for example, controlling drawing, communication, and input from the operation panel 940. The scanner unit 931 or the printer unit 932 includes an image processing section, such as error diffusion and gamma conversion.

[0032] In the image forming apparatus 1000 according to the first embodiment of the present invention, the document box function, copy function, printer function, and facsimile function can be sequentially switched and selected using the application switching key on the operation panel 940. When the document box function is selected, it enters document box mode; when the copy function is selected, it enters copy mode; when the printer function is selected, it enters printer mode; and when the facsimile mode is selected, it enters facsimile mode. The network I / F 950 is an interface for data communication using a communication network. The short-range communication circuit 920 and the network I / F 950 are electrically connected to the ASIC 906 via the PCI bus 922.

[0033] <Configuration of the pressurizing mechanism> Next, we will explain the configuration of the pressurizing mechanism that applies pressure to the secondary transfer roller 14 shown in Figure 1 against the secondary transfer opposing roller 15.

[0034] Figure 3 is a perspective view of a pressurizing mechanism according to the first embodiment of the present invention.

[0035] The pressurizing mechanism according to the first embodiment of the present invention is a mechanism that pressurizes the secondary transfer roller 14, which is the member to be pressurized, against the opposing secondary transfer roller 15, which is the mating member. In Figure 3, only the pressurizing mechanism 60 is shown, and the secondary transfer apparatus 5, which includes the secondary transfer roller 14, is omitted by the dashed line.

[0036] As shown in Figure 3, the pressurizing mechanism 60 includes a pair of arm members 61a, 61b, a pair of cams 62a, 62b, and two stepping motors 63a, 63b, etc.

[0037] The pair of arm members 61a and 61b are supported so as to be able to swing (rotate) in the direction of arrow A in Figure 3, around fixed pivot points 71a and 71b provided on the housing frame 64 of the pressurizing mechanism 60. Note that in Figure 3, the housing frame 64 supporting the front arm member 61a is omitted.

[0038] The pair of cams 62a and 62b are rotatably mounted at both ends of a fixed shaft 72, which is fixed to the housing frame 64. In other words, the pair of cams 62a and 62b are supported to rotate independently of each other via the fixed shaft 72.

[0039] The two stepping motors 63a and 63b function as drive sources for rotating a pair of cams 62a and 62b. When each stepping motor 63a and 63b is driven, their respective driving forces are transmitted to each cam 62a and 62b via separate power transmission mechanisms 59a and 59b. Specifically, the power transmission mechanisms 59a and 59b consist of timing belts 67a and 67b and driven pulleys 68a and 68b that transmit the rotational motion of each stepping motor 63a and 63b to the rotating shafts 66a and 66b, and timing belts 73a and 73b, a drive pulley 74a, and driven pulleys 75a and 75b that transmit rotational motion from the rotating shafts 66a and 66b to each cam 62a and 62b. Note that in Figure 3, the driven pulley 75a on the near side is hidden by the arm member 61b and is therefore not visible.

[0040] When each stepping motor 63a, 63b is driven to rotate, the timing belts 67a, 67b stretched between the rotation shafts of each stepping motor 63a, 63b and the driven pulleys 68a, 68b rotate, causing the driven pulleys 68a, 68b to rotate. As the driven pulleys 68a, 68b rotate, the rotation shafts 66a, 66b, which have the driven pulleys 68a, 68b at one end, rotate, and consequently, the drive pulleys 74a, 74b, which are provided at the other end of the rotation shafts 66a, 66b, rotate. As the drive pulleys 74a, 74b rotate, the timing belts 73a, 73b stretched between the drive pulleys 74a, 74b and the driven pulleys 75a, 75b rotate, causing the driven pulleys 75a, 75b to rotate. As the driven pulleys 75a and 75b rotate, the cams 62a and 62a rotate together with the driven pulleys 75a and 75b.

[0041] The pair of stepping motors 63a and 63b are motors in which the output shaft rotates by a predetermined angle with each pulse (cycle) of the ON / OFF state of the electrical signal input by the control unit 80. Therefore, the cams 62a and 62b rotate according to the number of pulses input to each stepping motor 63a and 63b. The control unit 80 is a microcomputer that includes a CPU, ROM, RAM, I / O interface, etc., and controls the rotation direction (forward rotation, reverse rotation), drive start and stop timing, number of input pulses, rotation speed (drive pulse frequency), etc., of each stepping motor 63a and 63b. In the first embodiment of the present invention, as shown in Figure 9, the engine control unit 930 functions as a control unit 80 that controls the pair of stepping motors 63a and 63b (the first stepping motor 63a and the second stepping motor 63b). Furthermore, even when the stepping motors 63a and 63b are not energized, a holding torque is generated by the attractive force of the rotor magnets. Therefore, when the power supply to the stepping motors 63a and 63b is terminated, the cams 62a and 62b are held in a stopped state at a predetermined rotation angle.

[0042] In the first embodiment of the present invention, the rotational motion of each stepping motor 63a, 63b is reduced and transmitted via the rotating shafts 66a, 66b and the pulleys 68a, 68b, 74a, 74b at both ends, in order to adjust the amount of rotation of the cams 62a, 62b per pulse or the required torque. However, if it is not necessary to reduce the rotational motion of the stepping motors 63a, 63b, the rotating shafts 66a, 66b and the pulleys 68a, 68b, 74a, 74b at both ends may be omitted.

[0043] Figure 4 is a perspective view showing the secondary transfer device supported by the pressurization mechanism according to the first embodiment of the present invention.

[0044] As shown in Figure 4, the secondary transfer device 5 is supported so as to be sandwiched between a pair of arm members 61a and 61b of the pressurizing mechanism 60. In this state, a portion of the secondary transfer belt 13 is exposed on the upper surface of the secondary transfer device 5. In addition, both axial ends of the secondary transfer roller 14, which is positioned inside the secondary transfer belt 13, are supported by the pair of arm members 61a and 61b. Therefore, when the pair of arm members 61a and 61b swing (rotate) around the fixed pivot points 71a and 71b, the secondary transfer roller 14 is moved in the direction in which it is pressed against the secondary transfer opposing roller 15 (see Figure 1) or in the opposite direction. In other words, in the first embodiment of the present invention, of the pair of arm members 61a and 61b, one arm member 61a functions as a first pressurizing member that operates to pressurize the portion of the secondary transfer roller 14 closer to one end than the center in the longitudinal direction (axial direction) against the secondary transfer opposing roller 15, and the other arm member 61b functions as a second pressurizing member that operates to pressurize the portion of the secondary transfer roller 14 closer to the other end than the center in the longitudinal direction against the secondary transfer opposing roller 15. Furthermore, one stepping motor 63a functions as a first stepping motor that drives one arm member 61a (the first pressurizing member), and the other stepping motor 63b functions as a second stepping motor that drives the other arm member 61b (the second pressurizing member).

[0045] <Pressurization action> Next, we will explain the pressurizing operation in which the secondary transfer roller 14 is pressed against the secondary transfer opposing roller 15.

[0046] Figure 5 shows the pressurizing operation by one arm member of the pressurizing mechanism according to the first embodiment of the present invention.

[0047] In the first embodiment of the present invention, the pressurizing operation of the pressurizing mechanism 60 is basically the same for one arm member 61a and the other arm member 61b. Therefore, in the following description, the pressurizing operation of one arm member will be explained using the arm member 61b shown in Figure 5 as an example.

[0048] As shown in Figure 5, the arm member 61b is equipped with a cam follower 65b in a position opposite to the cam 62b. The cam follower 65b is held in contact with the cam surface of the cam 62b. In this state, when the cam 62b rotates clockwise in Figure 5 by the drive of the stepping motor 63b, the cam follower 65b is pushed upward in the figure, following the shape of the cam surface, and the arm member 61b follows suit, swinging (rotating) in the direction of arrow A1 around the fixed pivot point 71b. As a result, the secondary transfer roller 14 supported by the arm member 61b is pressed against the secondary transfer opposing roller 15, and a secondary transfer nip is formed between the secondary transfer roller 14 and the secondary transfer opposing roller 15. Note that in Figure 5, the secondary transfer belt 13 and intermediate transfer belt 12 interposed between the secondary transfer roller 14 and the secondary transfer opposing roller 15 are omitted.

[0049] Furthermore, when the stepping motor 63b rotates in reverse while the secondary transfer roller 14 is under pressure against the secondary transfer opposing roller 15, the cam 62b rotates counterclockwise in Figure 5. As a result, the cam follower 65b moves downward in the figure following the cam surface, and the arm member 61b swings (rotates) around the fixed pivot point 71b in the opposite direction to the direction of arrow A1. In this way, when the stepping motor 63b rotates in reverse, the arm member 61b swings in the opposite direction to the swinging direction during the pressurizing operation, causing the secondary transfer roller 14 to move away from the secondary transfer opposing roller 15, and the pressurized state of the secondary transfer roller 14 against the secondary transfer opposing roller 15 is released.

[0050] <Challenges in pressurization mechanisms> Here, we will explain the challenges related to a pressurizing mechanism that uses the two stepping motors described above to pressurize the secondary transfer roller.

[0051] When performing a pressurizing operation to press the secondary transfer roller against the opposing secondary transfer roller, if the number of pulses input to the two stepping motors is the same, ideally the two cams should rotate by the same angle, resulting in the same pressurizing force being obtained at both ends of the secondary transfer roller. However, in reality, due to dimensional tolerances of the roller diameter of the secondary transfer roller, as well as variations in the component characteristics of the pressurizing mechanism's constituent parts, even if the same number of pulses are input to the two stepping motors, the same pressurizing force is not always obtained at both ends of the secondary transfer roller. Consequently, a pressure deviation may occur, resulting in variations in the pressurizing force at both ends of the secondary transfer roller.

[0052] To address the problem of pressure deviations, a pressurizing mechanism using two stepping motors can eliminate or reduce pressure deviations by individually adjusting the number of input pulses supplied to each stepping motor. Specifically, if the pressurizing force on one end of the secondary transfer roller is lower than that on the other end due to dimensional tolerances or variations in component characteristics, the number of input pulses for one stepping motor that moves the cam on the one end is increased compared to the number of input pulses for the other stepping motor. As a result, the cam on the one end rotates by a predetermined angle more than the cam on the other end, thus achieving the required pressurizing force on the one end and eliminating or reducing the pressure deviation.

[0053] However, if the input pulse count of one stepping motor is increased compared to the input pulse count of the other stepping motor, the stepping motor with the higher input pulse count will have a longer operating time, resulting in a difference in the timing of when the two stepping motors stop operating. In this case, variations will occur in the timing of the completion of the pressurizing operation at one end and the other end of the secondary transfer roller, resulting in different pressurizing times at each end. When such variations in pressurizing time occur, the intermediate transfer belt and the secondary transfer belt will shift to one side in the roller axis direction due to the variations in pressurizing time (pressure deviation). Since such belt shifting can cause image defects, it is necessary to reduce the pressurizing time that causes belt shifting.

[0054] Therefore, the present invention aims to reduce the variation in pressure due to the difference in the drive stop timing of one stepping motor and the other stepping motor, thereby suppressing belt misalignment. The following describes the features of the pressurizing mechanism according to the present invention.

[0055] First, before describing the characteristic features of the pressurizing mechanism according to the present invention, we will describe the pressurizing operation of a comparative example pressurizing mechanism that differs from the present invention.

[0056] <Pressurization operation of the pressurization mechanism in the comparative example> Figure 8 is a schematic diagram showing the pressurizing operation of a pressurizing mechanism according to a comparative example.

[0057] In Figure 8, (a) shows the state before the pressurization operation begins, (b) shows the state during the pressurization operation, and (c) shows the state after the pressurization operation is completed. As shown in Figure 8(a), in the state before the pressurization operation begins, the secondary transfer roller 14 is inclined with respect to the secondary transfer opposing roller 15, so that the right end of the secondary transfer roller 14 is located further away from the secondary transfer opposing roller 15 than the left end. Here, the variation in the distance between the secondary transfer roller 14 and the secondary transfer opposing roller 15 is shown as being due to the inclination of the secondary transfer roller 14 with respect to the secondary transfer opposing roller 15, but such variation in the distance between the rollers at one end and the other end may be due to differences in the roller diameter of the secondary transfer roller 14 or the secondary transfer opposing roller 15, or it may be due to variations in the characteristics of the components of the pressurization mechanism.

[0058] In this case, as shown in Figure 8(a), the right end of the secondary transfer roller 14 is further away from the secondary transfer opposing roller 15 than the left end. Therefore, if the right and left ends of the secondary transfer roller 14 are brought closer to the secondary transfer opposing roller 15 by the same distance, the pressure applied to the right end will be weaker than that applied to the left end. In such a case, in order to obtain a uniform pressure, the number of input pulses input to the right stepping motor 63b must be greater than the number of input pulses input to the left stepping motor 63a. That is, if the basic number of input pulses input to each of the left and right stepping motors 63a and 63b during the pressurizing operation is a [step], then the number of input pulses (correction pulses) n [step] (where n is a positive number) to make the pressure applied to the secondary transfer roller 14 uniform must be added to the input pulse count a [step] of the right stepping motor 63b, so that the input pulse count of the right stepping motor 63b is a + n [step].

[0059] However, increasing the number of input pulses for the right-side stepping motor 63b results in uniform pressure, but a time difference occurs between the right and left ends until the pressurizing operation is completed. This results in a period of time during which the pressure differs between the right and left ends. Specifically, if the left and right stepping motors 63a and 63b are driven simultaneously with the same drive pulse frequency X [pps] (number of pulses input per unit time) from the state shown in Figure 8(a), the right and left ends of the secondary transfer roller 14 approach the secondary transfer opposing roller 15 at the same speed. As a result, as shown in Figure 8(b), the left end of the secondary transfer roller 14 is pressed against the secondary transfer opposing roller 15 earlier than the right end. Since a certain amount of time is required from the start of pressurizing until the pressurizing operation is completed as shown in Figure 8(c), a period of time occurs during which the pressure differs between the left and right ends of the secondary transfer roller 14.

[0060] For example, if the basic input pulse count a of each stepping motor 63a and 63 on the left and right is set to 60 [steps], the correction pulse count n is set to 10 [steps], and the drive pulse frequency X of each stepping motor 63a and 63b is set to 500 [pps], then a time difference of n / X = 10 / 500 = 0.02 [sec] will occur from the completion of driving the left stepping motor 63a until the completion of driving the right stepping motor 63b. During this time difference, a pressure deviation will occur at the left and right ends of the secondary transfer roller 14.

[0061] The reason for this pressure deviation time is that, despite the input pulse count being different for each of the left and right stepping motors 63a and 63b, the drive of each stepping motor 63a and 63b was started simultaneously with the same drive pulse frequency. In other words, when two stepping motors 63a and 63b with different input pulse counts start driving at the same rotational speed (drive pulse frequency) and at the same timing, the stepping motor 63b with a higher input pulse count will take longer to complete its drive compared to the stepping motor 63a with fewer input pulses.

[0062] In contrast, in the first embodiment of the present invention, the following pressurizing operation is performed.

[0063] <Pressurization operation of the pressurization mechanism according to the first embodiment of the present invention> Figure 6 is a schematic diagram showing the pressurization operation of a pressurization mechanism according to the first embodiment of the present invention. In Figure 6, (a) shows the state before the pressurization operation is started, (b) shows the state during the pressurization operation, and (c) shows the state after the pressurization operation is completed.

[0064] As shown in Figure 6(a), in the state before pressurization begins, the right end of the secondary transfer roller 14 is positioned further from the secondary transfer opposing roller 15 than the left end. Therefore, in the first embodiment of the present invention, as in the comparative example above, the number of input pulses for the right stepping motor 63b and the left stepping motor 63a are adjusted individually. That is, the number of input pulses input to the right stepping motor 63b is set to be greater than the number of input pulses a[step] for the left stepping motor 63a, to a+n[step] (where n is a positive number).

[0065] In this first embodiment of the present invention, the drive start timing of the left and right stepping motors 63a and 63b is set to the same timing as in the comparative example when the pressurizing operation starts. However, the drive pulse frequencies of the stepping motors 63a and 63b are set to different values, unlike in the comparative example.

[0066] In this case, if we let a be the number of input pulses input to the left stepping motor 63a during pressurization, a+n be the number of input pulses input to the right stepping motor 63b during pressurization, and X be the drive pulse frequency of the left stepping motor 63a during pressurization, then the drive pulse frequency of the right stepping motor 63b during pressurization is set to a value expressed by (a+n) / a×X. This drive pulse frequency expressed by (a+n) / a×X is a value determined according to the number of additional input pulses (correction pulses) n[step] added to the right stepping motor 63b, and the larger the number of additional input pulses n[step], the larger the drive pulse frequency. In other words, the larger the number of additional input pulses n[step], the faster the motor rotation speed is set.

[0067] Thus, in the first embodiment of the present invention, the rotational speed of the right stepping motor 63b, which has a large number of input pulses, is set to be faster than the rotational speed of the stepping motor 63a, which has a small number of input pulses. As a result, as shown in Figure 8(b), the right end of the secondary transfer roller 14 approaches the secondary transfer opposing roller 15 at a faster speed (larger drive pulse frequency (a+n) / a×X [pps]) than the left end. Therefore, even if the left and right stepping motors 63a and 63b are started simultaneously (the pressurizing operation is started simultaneously), the right end of the secondary transfer roller 14 moves to catch up with the left end, thus reducing the timing difference in the completion of pressurizing the secondary transfer opposing roller 15 at the right and left ends of the secondary transfer roller 14. This suppresses the occurrence of variations in pressurizing time between one end and the other end of the secondary transfer opposing roller 15, and thus suppresses belt misalignment caused by variations in pressurizing time.

[0068] Furthermore, as in the first embodiment of the present invention, by setting the drive pulse frequency of the right-side stepping motor 63b to the value expressed by (a+n) / a×X, it is theoretically possible to make the drive stop timing of each stepping motor 63a and 63b the same. In this case, the time difference in the pressurization completion timing at the right and left ends of the secondary transfer roller 14 can be eliminated, so belt misalignment can be effectively suppressed. Therefore, in order to effectively suppress belt misalignment, it is preferable that the drive stop timings of each stepping motor 63a and 63b are simultaneous, but the drive stop timings of each stepping motor 63a and 63b do not necessarily have to be simultaneous. Even if the drive stop timings of each stepping motor 63a and 63b are not simultaneous, if the variation in these drive stop timings can be reduced, a certain effect of suppressing belt misalignment can be obtained, so it is acceptable for the drive stop timings of each stepping motor 63a and 63b to be slightly different.

[0069] Next, other embodiments of the present invention will be described. In the following description, we will mainly describe parts that differ from the first embodiment of the present invention, and descriptions of the same parts will be omitted as appropriate.

[0070] <Second Embodiment of the Present Invention> Figure 7 is a schematic diagram showing the pressurization operation of the pressurization mechanism according to the second embodiment of the present invention. In Figure 7, (a) shows the state before the pressurization operation is started, (b) shows the state during the pressurization operation, and (c) shows the state after the pressurization operation is completed.

[0071] In the first embodiment of the present invention described above, an example was described in which the variation in the drive stop timing of each stepping motor 63a and 63b is reduced by making the drive pulse frequencies (rotational speeds) of each stepping motor 63a and 63b different. In contrast, in the second embodiment of the present invention, although the drive pulse frequencies of each stepping motor 63a and 63b are the same, the variation in the drive stop timing of each stepping motor 63a and 63b is reduced by starting the drive of the right stepping motor 63b, which has an additional number of input pulses, before the other stepping motor 63a.

[0072] Specifically, in the second embodiment of the present invention, if the number of input pulses input to the left stepping motor 63a during pressurization is a, the number of input pulses input to the right stepping motor 63b during pressurization is a+n, and the drive pulse frequency of the left and right stepping motors 63a and 63b during pressurization is X, then during pressurization, the drive of the right stepping motor 63b is started a time represented by n / X before the drive start timing of the leftmost stepping motor 63a. This time represented by n / X is a value determined according to the number of additional input pulses (correction pulses) n[step] added to the right stepping motor 63b, and corresponds to the increase in drive time that occurs with the addition of the number of input pulses (correction pulses) n[step]. Therefore, here, the right stepping motor 63b is set to start driving by the amount of drive time that has increased according to the number of additional input pulses.

[0073] In this way, the right-side stepping motor 63b, which has a higher input pulse count, starts driving earlier than the stepping motor 63a, which has a lower input pulse count. As a result, as shown in Figure 7(b), the right end of the secondary transfer roller 14 starts moving before the left end and approaches the secondary transfer opposing roller 15. This reduces the timing difference between the left and right pressurizing timings of the secondary transfer roller 14, even if the other stepping motor 63a then starts driving at the same rotational speed (same drive pulse frequency X). Therefore, in the second embodiment of the present invention, belt misalignment caused by a time difference in the pressurizing timing between the right and left ends of the secondary transfer roller 14 can also be suppressed.

[0074] Furthermore, as in the second embodiment of the present invention, by starting the drive of the right stepping motor 63b earlier than the drive start timing of the left stepping motor 63a by a time represented by n / X, the drive stop timings of both stepping motors 63a and 63b can be made the same, in theory. However, in the second embodiment of the present invention, as in the first embodiment described above, the drive stop timings of each stepping motor 63a and 63b do not necessarily have to be simultaneous. That is, even if the drive stop timings of each stepping motor 63a and 63b are not simultaneous, if the variation in these drive stop timings can be reduced, a certain effect of suppressing belt misalignment can be obtained, so it is acceptable for the drive stop timings of each stepping motor 63a and 63b to be slightly different.

[0075] As described above, according to each embodiment of the present invention, even when the number of input pulses for one stepping motor (the first stepping motor) and the other stepping motor (the second stepping motor) are set to different values, by making the drive pulse frequencies of each stepping motor different from each other, or by making the drive start timings of each stepping motor different from each other, it is possible to reduce the variation in the drive stop timings of one stepping motor and the other stepping motor, thereby suppressing belt misalignment. Furthermore, during pressurization, both the drive pulse frequency and the drive start timing of each stepping motor may be made different. That is, by making at least one of the drive pulse frequencies and drive start timings of the first stepping motor and the second stepping motor different during pressurization, it is possible to reduce the variation in the drive stop timings of the first stepping motor and the second stepping motor, thereby suppressing belt misalignment.

[0076] Furthermore, the pressurizing mechanism according to the present invention is not limited to applications where a secondary transfer roller 14 is pressed against a secondary transfer opposing roller 15, but is also applicable to applications where a roller other than the secondary transfer roller 14 is pressed against the opposing roller. That is, in a belt drive device comprising a first roller, a second roller positioned opposite the first roller, and a belt interposed between the first and second rollers and stretched across either the first or second roller, there is a risk of belt misalignment due to pressure deviations between the first and second rollers. Therefore, by applying the present invention to a pressurizing mechanism used in such a belt drive device, it is possible to suppress belt misalignment in the same way as in the embodiments of the present invention described above. For example, the present invention can also be applied to a pressurizing mechanism for a primary transfer roller that pressurizes each of the photoreceptors 21Y, 21M, 21C, and 21K shown in Figure 1 via an intermediate transfer belt 12.

[0077] Furthermore, the member to be pressurized by the pressurizing mechanism according to the present invention may be a member other than a roller. Even if the member to be pressurized is not a roller, if there is a risk of variation in the pressurizing time occurring between one end and the other end in the longitudinal direction of the member to be pressurized, the present invention can be applied to reduce the variation in pressurizing time.

[0078] Furthermore, the pressurizing mechanism according to the present invention is not limited to the above-described configuration, and the shape or structure of the parts can be appropriately changed without departing from the spirit of the invention. For example, the pressurizing member that moves the secondary transfer roller 14 in the pressurizing direction is not limited to a pair of arm members 61a, 61b, but may be a cam or other pressurizing member.

[0079] Furthermore, the image forming apparatus according to the present invention is not limited to a color printer that forms a color image using multiple toners as shown in Figure 1, but may also be a copier, facsimile, printing press, or a multifunction device that combines two or more of these.

[0080] To summarize the embodiments of the present invention described above, the present invention includes at least the following embodiments.

[0081] [First aspect] The first embodiment is a pressurizing mechanism for pressurizing a member to be pressurized against a mating member, comprising: a first pressurizing member that operates to pressurize a portion of the member to be pressurized that is one end away from the longitudinal center of the member to be pressurized against the mating member; a second pressurizing member that operates to pressurize a portion of the member to be pressurized that is the other end opposite to the one end away from the longitudinal center of the member to be pressurized against the mating member; a first stepping motor for driving the first pressurizing member; and a second stepping motor for driving the second pressurizing member, wherein the number of input pulses input to the first stepping motor so that the portion of the member to be pressurized that is one end away from the mating member is in a predetermined pressurized state is different from the number of input pulses input to the second stepping motor so that the portion of the member to be pressurized that is the other end is in a predetermined pressurized state against the mating member, and the pressurizing mechanism is configured to have at least one of the drive pulse frequencies and drive start timings of the first stepping motor and the second stepping motor different during the pressurizing operation in which the member to be pressurized is pressed against the mating member.

[0082] [Second aspect] In the second embodiment, in the first embodiment, if the number of input pulses input to the first stepping motor during the pressurizing operation is a, the number of input pulses input to the second stepping motor during the pressurizing operation is a+n, and the drive pulse frequency of the first stepping motor during the pressurizing operation is X, then during the pressurizing operation, the second stepping motor starts driving at the same timing as the first stepping motor and is driven at the drive pulse frequency expressed as (a+n) / a×X.

[0083] [Third aspect] In the third embodiment, in the first embodiment, if the number of input pulses input to the first stepping motor during the pressurizing operation is a, the number of input pulses input to the second stepping motor during the pressurizing operation is a+n, and the drive pulse frequency of the first stepping motor and the second stepping motor during the pressurizing operation is X, then during the pressurizing operation, the drive of the second stepping motor is started a time represented by n / X before the drive start timing of the first stepping motor.

[0084] [Fourth aspect] A fourth embodiment is a belt drive device comprising a first roller, a second roller positioned opposite the first roller, a belt interposed between the first roller and the second roller and stretched over either the first roller or the second roller, and a pressurizing mechanism that pressurizes the first roller against the second roller, wherein the pressurizing mechanism is the pressurizing mechanism described in any one of claims 1 to 3.

[0085] [Fifth aspect] A fifth embodiment is a transfer roller in which the first roller is pressed against the second roller via the belt to form a transfer nip for transferring an image onto a recording sheet.

[0086] [Sixth aspect] The sixth embodiment is an image forming apparatus comprising a pressurizing mechanism according to any one of the first to third embodiments, or a belt drive device according to the fourth or fifth embodiment. [Explanation of Symbols]

[0087] 12 Intermediate transfer belt (belt) 13. Secondary transfer belt (belt) 14. Secondary transfer roller (pressure target component) 15. Secondary transfer opposing roller (mating member) 60 Pressurization mechanism 61a Arm member (first pressurizing member) 61b Arm member (second pressurizing member) 63a Stepping motor (first stepping motor) 63b Stepping motor (second stepping motor) 1000 Image forming apparatus [Prior art documents] [Patent Documents]

[0088] [Patent Document 1] Japanese Patent Publication No. 2023-46220

Claims

1. A pressurizing mechanism that pressurizes a target member against a mating member, A first pressurizing member is operated to pressurize the portion of the member to be pressed that is located at one end of the member to be pressed, rather than at the center in the longitudinal direction, against the mating member. A second pressurizing member is operated to pressurize the portion of the member to be pressed that is opposite to the one end of the longitudinal center of the member to be pressed, against the mating member. A first stepping motor that drives the first pressurizing member, A second stepping motor for driving the second pressurizing member, Equipped with, The number of input pulses input to the first stepping motor so that the one end of the member to be pressed is subjected to a predetermined pressure state relative to the mating member is different from the number of input pulses input to the second stepping motor so that the other end of the member to be pressed is subjected to a predetermined pressure state relative to the mating member. A pressurizing mechanism characterized in that at least one of the drive pulse frequencies and drive start timings of the first stepping motor and the second stepping motor are different during a pressurizing operation in which the member to be pressed is pressed against the mating member.

2. Let a be the number of input pulses input to the first stepping motor during the pressurizing operation. Let a + n be the number of input pulses input to the second stepping motor during the pressurizing operation. If the drive pulse frequency of the first stepping motor during the pressurizing operation is X, The pressurizing mechanism according to claim 1, wherein during the pressurizing operation, the second stepping motor starts driving at the same timing as the first stepping motor and is driven at the drive pulse frequency represented by (a + n) / a × X.

3. Let a be the number of input pulses input to the first stepping motor during the pressurizing operation. Let a + n be the number of input pulses input to the second stepping motor during the pressurizing operation. If X is the drive pulse frequency of the first stepping motor and the second stepping motor during the pressurizing operation, The pressurizing mechanism according to claim 1, wherein, during the pressurizing operation, the driving of the second stepping motor is started a time represented by n / X before the driving start timing of the first stepping motor.

4. The first Laura and, A second roller is positioned opposite the first roller, A belt interposed between the first roller and the second roller, and stretched over either the first roller or the second roller, A pressurizing mechanism that pressurizes the first roller against the second roller, A belt drive device comprising, A belt drive device characterized in that the pressurizing mechanism is the pressurizing mechanism described in any one of claims 1 to 3.

5. The belt drive device according to claim 4, wherein the first roller is a transfer roller that is pressed against the second roller via the belt to form a transfer nip for transferring an image onto a recording sheet.

6. An image forming apparatus characterized by comprising a pressurizing mechanism according to any one of claims 1 to 3.

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