Pressurization device, fixing device, and image forming device

Abstract

To reduce impact noise due to preceding rotation of a cam in a cam mechanism for pressing a pressing member to a pressurized member by rotation of the cam.SOLUTION: In a cam mechanism (35) having a pressurizing member (19), a pressurized member (20), and a pressurizing force generating member (44), a cam (51), a first member (38) for moving the pressurizing member (19) by rotation of the cam (51) and giving pressurizing force generated by the pressurizing force generating member (44) to the pressurizing member (19), and a second member (48) for varying the pressurizing force of the pressurizing force generating member (44) by rotation of the cam (51) are provided. The cam (51) has a plurality of cam outer peripheral surfaces (L1 to L5) at different positions in a rotation axis direction. A first cam outer peripheral surface (L5) among a plurality of cam outer peripheral surfaces does not act on a first member (38) even though at least part thereof is in a positional relation to overlap with the first member.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pressure device including a pressure mechanism for applying pressure from a pressure member to a pressure-receiving member, a fixing device, and an image forming apparatus. [Background technology]

[0002] A thermal roller type fixing device installed in an electrophotographic image forming device has a heating roller and a pressure roller which forms a nip portion together with the heating roller, and heats a sheet onto which a toner image has been transferred while sandwiching and transporting it in the fixing nip, thereby fixing the toner image to the recording material.

[0003] The fixing unit is provided with a mechanism for moving the heating roller toward or away from the pressure roller by the rotation of a cam, and switching between a pressurized state during fixing and transport and a pressure-released state during standby or jam processing. Conventional pressure mechanisms generally have a configuration including a pressure plate that presses the heating roller against the pressure roller by the pressure generated by a pressure spring, and a cam that moves the pressure plate by rotation.

[0004] In such a pressure mechanism, when the heat roller is in a pressurized state, the spring force of the pressure spring transmitted to the heat roller via the pressure plate is at a minimum, whereas when the heat roller is in a pressure-released state, the spring force of the pressure spring transmitted to the heat roller via the pressure plate is at a maximum.

[0005] Therefore, when the cam rotates and the heating roller transitions from a pressure-released state to a pressure-applied state, the spring force of the pressure spring is suddenly released from its maximum state. This movement causes the cam to be pushed all at once through the pressure plate, causing it to rotate ahead of the cam's driving force, resulting in a sudden collision at the input side drive unit and a banging noise.

[0006] Patent Document 1 proposes a configuration in which a pressure plate that presses the heating roller against the pressure roller with the pressure of a pressure spring, a pressure force variable plate that variably applies the pressure force to the pressure plate, and a cam that acts on the pressure plate and the pressure force variable plate are arranged. In the configuration of the pressure mechanism in Patent Document 1, the spring force (pressure force) of the pressure spring is maximum in the pressurized state. On the other hand, the spring force (pressure force) of the pressure spring is minimum in the pressure release state. Therefore, when the cam rotates and the heating roller transitions from the pressure release state to the pressurized state, the spring force of the pressure spring is not released all at once, and the generation of a knocking sound due to a collision in the drive unit caused by the preceding rotation of the cam is suppressed. Furthermore, in Patent Document 1, when the first member (pressure plate) and the second member (pressure force variable plate) are both abutted by the rotation of the cam, the rotation torque of the cam is cancelled out by the pressing force, thereby reducing the preceding rotation of the cam, thereby reducing the knocking sound due to a collision in the drive unit. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2015-87701 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the technology of Patent Document 1 has a timing when it cannot reduce the knocking noise caused by the collision in the drive unit. Specifically, it is the timing when the pressurized state of FIG. 2(b) is switched to the pressure release state of FIG. 2(a). As shown in FIG. 2, at the timing when the pressurized state transitions to the pressure release state, the cam only contacts the pressure force variable plate. Therefore, it is not possible to obtain the effect of reducing the preceding rotation of the cam by canceling out the rotational forces of the cams. Furthermore, at the above transition timing, the radius of the cam changes suddenly, and the spring force of the pressure spring is released in a flash from the maximum state. Therefore, the cam is pushed in a flash via the pressure force variable plate, and rotates in advance of the driving force of the cam. Therefore, a sudden collision occurs in the drive unit on the input side, and a knocking noise is generated.

[0009] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to reduce the impact noise caused by the advance rotation of the cam, both when transitioning from a depressurized state to a pressurized state, and when transitioning from a pressurized state to a depressurized state. [Means for solving the problem]

[0010] In order to achieve the above object, a pressurizing device according to one aspect of the present invention has a pressurizing member and a pressurized member, and is switchable between a pressurized state in which the pressurizing member presses the pressurized member and a pressure-released state in which the pressurizing member does not press the pressurized member, the pressurizing device comprising a pressurizing force generating member that generates a pressurizing force, a rotatably supported cam, and a first member that comes into contact with the cam and is displaced by rotation of the cam, the pressurizing member being moved in a direction approaching the pressurized member and a direction away from the pressurized member, and the pressurizing force generated by the pressurizing force generating member being released from the pressurizing force generating member. The pressurizing mechanism comprises a first member that applies a pressure to the pressurizing member, and a second member that abuts against the cam and is displaced by the rotation of the cam, the second member varying the pressurizing force generated by the pressurizing force generating member, the cam having a plurality of cam outer peripheral surfaces formed circumferentially at different positions in the rotation axis direction of the cam, the plurality of cam outer peripheral surfaces acting on the second member regardless of the phase of the cam, while a first cam outer peripheral surface of the plurality of cam outer peripheral surfaces does not act on the first member despite being in a positional relationship in which at least a portion of the cam outer peripheral surface overlaps with the first member. Effect of the Invention

[0011] According to the present invention, it is possible to reduce impact noise caused by anticipatory rotation of the cam both when transitioning from a pressure-released state to a pressure-applied state and when transitioning from a pressure-applied state to a pressure-released state. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a side view showing a configuration of a pressure mechanism according to a first embodiment; [Diagram 2] FIG. 1 is a side view showing a configuration of a conventional pressure mechanism. [Diagram 3] FIG. 1 is a schematic diagram showing a configuration of an image forming apparatus according to a first embodiment. [Figure 4] FIG. 1 is a perspective view showing the relationship between a pressure mechanism, a heating roller, and a pressure roller according to a first embodiment; [Diagram 5] FIG. 1 is a diagram showing a shape of a cam according to the first embodiment; [Figure 6] FIG. 1 is a diagram showing the shape of a cam contact surface-A according to the first embodiment; [Figure 7] 1 is an explanatory diagram showing a pressure release state and a state in the middle of transition to a pressure release state of the pressure mechanism according to the first embodiment; [Figure 8] FIG. 13 is an explanatory diagram showing an operation of the pressurizing mechanism according to the first embodiment, showing a pressurizing state and a state during a transition to a pressure release state; [Figure 9] FIG. 1 is a perspective view showing a pressurizing state of a pressurizing mechanism according to a first embodiment; [Figure 10] FIG. 1 is a diagram showing the positional relationship between a pressure spring and a cam of a pressure mechanism according to the first embodiment; [Figure 11] FIG. 11 is a side view showing the configuration of a pressure mechanism having a pressure spring according to another example of the first embodiment; [Figure 12] FIG. 11 is a side view showing the configuration of a pressure mechanism having a pressure spring according to another example of the first embodiment; [Figure 13] FIG. 13 is a diagram showing the shape of a cam in another example according to the first embodiment; [Figure 14] FIG. 13 is a diagram showing the positional relationship between a cam and a cam contact surface -A in another example of the pressure mechanism according to the first embodiment; [Figure 15] FIG. 11 is a side view showing another example of a pressure plate in the pressure mechanism according to the first embodiment; [Figure 16] FIG. 11 is a diagram showing the shape of a cam according to the second embodiment. [Figure 17] 11 is an explanatory diagram showing an operation of the pressure mechanism according to the second embodiment, showing a pressure release state and a state during transition to a pressure release state; [Figure 18] FIG. 11 is an explanatory diagram showing the operation of the pressure mechanism according to the second embodiment in a light pressure state and a pressure state; [Figure 19] FIG. 11 is an explanatory diagram showing a state in the middle of transition from a pressurized state to a pressure-released state of the pressurizing mechanism according to the second embodiment; [Figure 20]FIG. 11 is a side view showing the configuration of a pressure mechanism according to a third embodiment. [Figure 21] FIG. 11 is a perspective view showing a sheet feeding device according to a third embodiment from a driving side; [Figure 22] FIG. 11 is an explanatory diagram showing the operation of a pressure mechanism according to the third embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described in detail below with reference to the drawings. The preferred embodiment of the present invention is an example of the best mode of the present invention, but the present invention is not limited to the following examples, and various configurations can be replaced with other known configurations within the scope of the concept of the present invention.

[0014] First, before describing this embodiment, a conventional pressure switching device will be described with reference to FIG. 2. FIG. 2(b) is a diagram showing the state when the pressure is applied. In order to eliminate loss of pressure, the pressure plate 111 and the cam 112 secure a certain distance H without contacting each other. On the other hand, in order to stably exert the maximum pressure, it is necessary to displace the pressure spring 113 and the pressure force variable plate 114 to the maximum. Therefore, the cam shape has a minimum radius d2 in the direction toward the pressure plate 111, and a maximum radius d1 in the direction toward the pressure force variable plate 114 that exerts the pressure force. Therefore, the difference between the maximum radius d1 and the minimum radius d2 of the cam shape is the action length of the pressure spring 113, but in order to stabilize the pressure, it is desirable to set the spring factor of the pressure spring 113 low and increase the action length. The "pressure spring" used in the fixing device has a strong pressure equivalent to several tens of kg.

[0015] Increasing the operating length of the pressure spring 113, i.e., increasing the difference between the maximum radius d1 and the minimum radius d2 of the cam shape, inevitably leads to a sudden change in the cam radius when switching between the pressure state and the pressure release state. In the conventional configuration, when one cam 112 abuts against both the pressure plate 111 and the pressure force variable plate 114, the rotation torques of the cams are cancelled out and the preceding rotation of the cam is reduced. However, due to the gap H between the cam 112 and the pressure plate 111 secured to eliminate the loss of pressure force as described above, or a sudden change in the cam radius, there are times when one cam abuts against only one of the pressure plate 111 or the pressure force variable plate 114.

[0016] As shown in Fig. 2(c), at the timing of transition from the pressurized state (Fig. 2(b)) to the pressure released state (Fig. 2(a)), the cam 112 is only in contact with the pressure variable plate 114 due to the gap H between the cam and the pressure plate. Therefore, the rotational forces of the cam 112 cancel each other out, and it is not possible to obtain the effect of reducing the pre-rotation of the cam.

[0017] Furthermore, at the timing of the transition from the pressurized state (FIG. 2(b)) to the pressure-released state (FIG. 2(a)), the cam radius d changes suddenly, causing the pressure spring to try to release its maximum spring force all at once. Therefore, the cam 112 is pushed all at once via the pressure-variable plate 114, causing it to rotate before the driving force of the cam 112 (preceding rotation), causing a sudden collision in the driving section on the input side, resulting in a banging sound.

[0018] In the following embodiments, a pressurizing mechanism that applies pressure to a pressurized member by rotating a cam will be described, in which the impact noise caused by the preceding rotation of the cam is reduced in both the transition from the pressure release state to the pressurized state and the transition from the pressurized state to the pressure release state. Furthermore, a pressurizing mechanism that does not lose the pressure of the pressurizing member in the pressurized state will be described. EXAMPLES

[0019] The configuration of the pressure device according to the present invention and the image forming apparatus to which the pressure device is applied will be described with reference to Figures 1 and 3 to 10. In this description, the overall configuration of the image forming apparatus will be described first, and then the configurations of the fixing device and pressure device according to the present invention will be described.

[0020] [Overall configuration of image forming device] 3, image forming apparatus 100 is a color laser beam printer that forms an image on a sheet S, which is a recording medium. Image forming apparatus 100 forms and outputs an image on sheet S based on image information read from an original or image information input from an external device. Note that the sheet S includes, in addition to plain paper, special paper such as coated paper, recording materials in special shapes such as envelopes and index paper, and plastic films and cloths for overhead projectors.

[0021] An apparatus body 101 of an image forming apparatus 100 is provided with an intermediate transfer tandem type image forming section 3 including four image forming units 3Y, 3M, 3C, and 3K and an intermediate transfer unit 10. The image forming units 3Y, 3M, 3C, and 3K form yellow, magenta, cyan, and black toner images. Since the configuration of each image forming unit is substantially the same except for the color of the toner used for development, the configuration of the image forming units and the toner image forming operation will be described below using the yellow image forming unit 3Y as an example.

[0022] When a request is made to the image forming unit 3Y to form a toner image, the photosensitive drum 1, which is a photosensitive member, is rotated and the charging device 2 uniformly charges the surface of the photosensitive drum 1. An exposure device 9 disposed at the bottom of the apparatus main body 101 irradiates the photosensitive drum 1 with laser light based on image information to expose the drum surface, and forms an electrostatic latent image on the photosensitive drum 1. The electrostatic latent image is then visualized (developed) by toner supplied from the developing device 6, and a toner image is formed on the surface of the photosensitive drum 1.

[0023] Similarly, toner images of corresponding colors are formed in the image forming units 3M, 3C, and 3K. The toner images formed by each of the image forming units 3M, 3C, 3Y, and 3K are primarily transferred from the photosensitive drum 1 to an intermediate transfer belt 12 serving as an intermediate transfer body by a primary transfer roller 11 so as to be superimposed on each other. Adherents such as toner remaining on the photosensitive drum 1 are removed by cleaning devices provided in each of the image forming units 3M, 3C, 3Y, and 3K, and are collected in a collection container 27.

[0024] The intermediate transfer belt 12 is wound around the inner secondary transfer roller 13 and the tension roller 14, and is driven to rotate in a counterclockwise direction in the drawing. The tension roller 14 is urged in the direction of the arrow T by an urging member such as a spring, and applies an appropriate tension to the intermediate transfer belt 12. The toner image carried on the intermediate transfer belt 12 is secondarily transferred to the sheet S at a secondary transfer section formed by the intermediate transfer belt 12 and the secondary transfer roller 16 facing the inner secondary transfer roller 13. Adherents such as toner remaining on the intermediate transfer belt 12 are removed by a belt cleaning device 26 and collected in a collection container 27. The sheet S to which the toner image has been transferred is delivered to a fixing device 18. The fixing device 18 has a heating roller 19, an opposing pressure roller 20, and a heater 7 as a heat source, and applies heat and pressure to the toner image while sandwiching and transporting the sheet S. As a result, the toner melts and adheres to the sheet S, and the image is fixed to the sheet S. In addition, as will be described later, in this embodiment, the heating roller 19 is an example of a pressure applying member, and the pressure roller 20 is an example of a pressure receiving member.

[0025] In parallel with the image forming process, the sheet feeding section 25 feeds the sheet S toward the image forming section 3. The sheet feeding section 25 includes a feeding cassette 23 as a sheet storage section, and a feeding roller 24 that feeds the sheet S from the feeding cassette 23. The sheet fed by the feeding roller 24 is transported toward the registration section 17 in a state where it is separated from other sheets by a separating means such as a retard roller or a separating pad. The feeding roller 24 is an example of a sheet feeding means capable of feeding a sheet, and may be replaced with another feeding mechanism such as an air feeding system.

[0026] In addition, it is also possible to feed the sheet S stacked on the manual feed tray 74 from the feed roller 77 .

[0027] The registration unit 17 corrects skew of the sheet S and sends the sheet S toward the secondary transfer unit in accordance with the progress of the toner image formation operation in the image forming unit 3. Then, the sheet S, on which an image is formed by passing through the secondary transfer unit and the fixing device 18, is delivered to a pair of conveying rollers 28 located downstream of the fixing unit 18. A flap-shaped guide member 29 is disposed downstream of the pair of conveying rollers 28 to distribute the sheet S toward either the pair of discharge rollers 21 or the double-sided conveying unit. In the case of single-sided printing, the sheet S sent out from the pair of conveying rollers 28 is guided by the guide member 29 toward an upper conveying guide 34. The sheet S moves toward the pair of discharge rollers 21 via the upper conveying guide 34, and is discharged by the pair of discharge rollers 21 to a discharge tray 22 provided at the top of the device main body 101.

[0028] When double-sided printing is performed, the sheet S is guided to a switchback path 30 by a guide member 29. The double-sided conveying section switches the sheet S back on the switchback path 30, swaps the front side and the back side, and conveys the sheet again toward the image forming section 3 via a re-conveying path 31. Then, the sheet S, on whose back side an image has been formed by the image forming section 3, is guided by the guide member 29 to a pair of discharge rollers 21 and discharged to the discharge tray 22.

[0029] The image forming unit 3 is an example of an image forming means for forming an image on the sheet S, and may be replaced with another image forming mechanism such as a direct transfer type electrophotographic mechanism or an inkjet type.

[0030] [Double-sided conveying section] Next, the configuration of a duplex conveying unit, which is an example of a sheet conveying device, will be described. The duplex conveying unit has a switchback path 30, a re-conveying path 31, and a switchback roller pair 32. The switchback roller pair 32 provided as a reversing conveying unit is a roller pair that can be driven in a forward rotation direction and a reverse rotation direction, and reverses the received sheet by switching it back. The switchback roller pair 32 conveys the received sheet to a position where the downstream part in the conveying direction protrudes above the discharge tray 22 by rotating in the forward rotation direction.

[0031] When the trailing edge of the sheet passes the guide member 29, the guide member 29 switches to a direction for guiding to the switchback path 30, and the switchback roller pair 31 starts to rotate in the reverse direction before the trailing edge of the sheet leaves the nip portion. Here, since the guide member 29 has switched to a direction for guiding to the re-conveying path 31, the sheet conveyed by the reverse rotation of the switchback roller pair 32 is guided to the re-conveying path 31, and reverse feeding is restricted.

[0032] The re-conveying path 31 is a sheet conveying path extending in a substantially vertical direction from the switchback roller pair 32 toward the registration unit 17, and includes a re-conveying roller pair 33 disposed thereon. The re-conveying roller pair 33 conveys the sheet received from the switchback roller pair 32 toward the registration unit 17.

[0033] Next, the configuration of the fixing device and the pressure mechanism will be described.

[0034] [Fixing device] Fig. 1 is a side view showing a fixing device 18 having a pressure mechanism 35 according to the first embodiment, viewed from the non-driven side. Fig. 4 is a perspective view showing the relationship between the pressure mechanism 35, the heating roller 19, and the pressure roller 20 of the fixing device 18. The fixing device 18 is a thermal fixing type fixing device that heats an unfixed toner image transferred to a sheet S with a sleeve 36.

[0035] The fixing device 18 has a heating roller 19, a pressure roller 20, and a pressure mechanism 35. The heating roller 19 is an example of a pressure member. The pressure roller 20 is an example of a pressure-receiving member. The pressure mechanism 35 is an example of a pressure device. The fixing device 18 including the pressure mechanism 35 is an example in which the pressure device of this embodiment is applied to the fixing device 18.

[0036] The fixing device 18 has a frame 37 which constitutes the framework of the fixing device, and the heating roller 19, the pressure roller 20, and the pressure mechanism 35 are each supported by the frame 37.

[0037] The heating roller 19 has a heater 7 which is a heat generating element, and a heater holder 39 which supports the heater. The heating roller 19 further has a cylindrical sleeve 36 loosely fitted onto the outer periphery of the heater holder, and flanges 40 disposed on both ends of the sleeve in the longitudinal direction.

[0038] The heating roller 19 has a flange 40 movably supported by a frame 37 so that the sleeve 36 can be pressed against the pressure roller 20 .

[0039] The pressure roller 20 is supported to rotate by the frame 37 via bearings 41 at both ends, and is disposed so that the surface of the pressure roller 20 contacts the surface of the sleeve 36 of the heating roller 19. A gear 42 is fixed to one of the shaft portions.

[0040] The fixing device 18 of this embodiment is configured to apply pressure to the flange 40 of the heating roller 19 by the pressure plate 38, thereby pressing the sleeve 36 in a direction perpendicular to the generatrix direction of the pressure roller 20. When the flange 40 is pressed, the heater 7 is pressed against the pressure roller 20 via the sleeve 36. This causes the elastic layer of the pressure roller 20 to be crushed and elastically deformed, and a nip of a predetermined width required for heat fixing of an unfixed toner image is formed between the surface of the sleeve 36 and the surface of the pressure roller.

[0041] The heat fixing process of the fixing device 18 will be described. The driving force of a motor (not shown) provided in the device main body 100 is transmitted to the gear 42, which rotates the pressure roller 20 in the direction of the arrow. The sleeve 36 rotates following the rotation of the pressure roller 20 while the inner circumferential surface (inner surface) of the sleeve slides over the heater 7 and heater holder 39.

[0042] The sheet S onto which the unfixed toner image has been transferred is nipped and conveyed in the nip portion N while the heat of the heater 7 and the pressure of the nip portion are applied to the unfixed toner image, whereby the toner image is heated and fixed onto the sheet.

[0043] In this embodiment, as one example of the configuration of the heating roller 19, a configuration using a heater 7, which is a heat-generating element, and a sleeve 36 is given, but other configurations are also possible, such as a configuration in which a core and a wound coil are placed inside and a circulating current is passed through the sleeve itself to generate heat.

[0044] [Pressure mechanism 35] The configuration of the pressure mechanism (also called a cam mechanism) 35 will be described with reference to Fig. 1 and Fig. 4. The pressure mechanism 35 is configured to be symmetrical with respect to the center in the longitudinal direction of the heating roller 19, except that it is provided with a gear 43 on one end side in the longitudinal direction. Regarding the components of the pressure mechanism 35, the reference numerals of the drive side members provided with the gear 43 are suffixed with "d" to distinguish them from the non-drive side members. The same applies to the pressure mechanism 35 described in the second embodiment.

[0045] The pressure mechanism 35 includes a pressure spring 44d, which is a compression spring that is compressed from both ends and generates a pressure in the direction of expansion. The pressure spring 44d is an example of a pressure generating member. The pressure spring 44d is disposed substantially parallel to the moving direction of the heating roller 19 on the downstream side of the fixing nip portion in the sheet conveying direction.

[0046] The pressure plate 38d has a spring support surface 45d that presses one end of the pressure spring 44d and a fulcrum portion 46d at the other end that serves as a fulcrum for the rotational movement. The pressure plate 38d is an example of a first member that applies a pressure force from a pressure generating member to the pressure member.

[0047] The pressure plate 38d is disposed so as to face the support portion of the flange 40d in the moving direction of the heat roller 19, and presses one end of the pressure spring 44d.

[0048] The pressure plate 38d, which supports the pressure spring 44d on the spring support surface 45d, rotates around the fulcrum 46d by receiving the pressure force generated by the pressure spring 44d. This presses the protrusion of the flange 40d, and the heating roller 19 is pressed against the pressure roller 20.

[0049] The pressure mechanism 35 further includes a pressure variable plate 48d having at one end a spring support surface 47d for pressing the other end of the pressure spring 44d. The pressure variable plate 48d is an example of a second member that varies the pressure applied by the pressure generating member.

[0050] The pressure variable plate 48d is disposed so as to be slidable approximately parallel to the direction in which the pressure spring expands and contracts, and supports the other end of the pressure spring 44d on a spring support surface 47d.

[0051] With the above-described configuration, the pressure variable plate 48d is adapted to variably apply the pressure generated by the pressure spring to the pressure plate 38d by sliding.

[0052] The pressure mechanism 35 also includes a cam 51d between a cam abutment surface 49d disposed on the opposing side of the spring support surface 45d of the pressure plate 38d and a cam abutment surface 50d at the end of the pressure force variable plate 48d on the side opposite the spring support surface 47d. The cam 51d is fixedly held at the longitudinal end of a cam shaft 52 disposed along the longitudinal direction of the sleeve 36 and the pressure roller 20, respectively. The cam shaft 52 is rotatably supported by the frame 37. A gear 43 is fixedly held at one longitudinal end of the cam shaft 52, and the gear 43 is rotated by receiving a driving force from a motor (driving source) (not shown) of the device main body 100.

[0053] When the cam 51d rotates, the outer peripheral surface of the cam abuts against the cam abutment surface 49d of the pressure plate 38d and the cam abutment surface 50d of the pressure force variable plate 48d. This movement causes the pressure plate 38d to rotate about the fulcrum parts 46, 46d, pressing or separating the protrusions of the flange 40d. This movement causes the heating roller 19 to approach or separate from the pressure roller 20, switching between a pressurized state and a pressure-released state.

[0054] The pressure variable plate 48d slides while being supported by two shafts, a cam shaft 52 and a support shaft 53, and expands and contracts the pressure spring 44d. This varies the pressure applied to the pressure plate 38d. The position of the pressure variable plate 48d is restricted by the cam shaft 52 that holds the cam 51d to which a large force is applied. Therefore, the relative positional relationship between the cam 51d and the pressure variable plate 48d is configured to be less susceptible to distortion that may occur when pressure is applied.

[0055] Next, the details of the shape of the cam and the cam contact surface -A will be described.

[0056] [Cam shape in Example 1] 5(a) and 5(b), the cam 51 of the first embodiment has a plurality of circumferentially formed cam outer circumferential surfaces disposed at different positions in the rotation axis direction of the cam 51. However, the cam 51 is formed as an integral part, and the plurality of cam outer circumferential surfaces may be referred to as regions S1, S2, and S3, respectively.

[0057] Region S2 is an example of a first cam outer peripheral surface, and regions S1 and S3 are examples of a second cam outer peripheral surface. Regions S1 and S3 have the same shape of the outer peripheral surface and are composed of multiple outer peripheral surfaces described below.

[0058] The region S1 and the region S3 have outer peripheral surfaces L1 to L4. The outer peripheral surface L1 abuts against the cam abutment surface 50d of the pressure variable plate 48d in the pressurized state, and abuts against the cam abutment surface 49d in the pressure released state.

[0059] The outer circumferential surface L1 includes a region where the distance d1 from the center of the camshaft 52 to the outer circumferential surface (hereinafter referred to as the radius) is the longest.

[0060] The outer peripheral surface L2 abuts against the cam abutment surface 50d in the pressure-released state, and is disposed on the cam abutment surface 49d side in the pressure-applied state. The outer peripheral surface L2 includes a region where the radius d2 is shortest.

[0061] The outer peripheral surface L3 and the outer peripheral surface L4 are disposed between the outer peripheral surface L1 and the outer peripheral surface L2, and are regions where the radius changes suddenly from d1 to d2.

[0062] Region S2 is an example of a first cam outer peripheral surface, and is sandwiched between regions S1 and S3 in the rotation axis direction of camshaft 52. Region S2 is composed of a plurality of outer peripheral surfaces L1 and L5 described below. The cam surface in region S2 (first cam outer peripheral surface) abuts against cam abutment surface 50d of pressure variable plate 48d in the pressurized state, and abuts against cam abutment surface 49d of pressure plate 38 in the released state. Outer peripheral surface L5 includes the region with the longest radius d1.

[0063] The outer peripheral surface L5 is an area where the radius changes gradually within a range of lengths longer than d2 and shorter than d1. The outer peripheral surface L5 is an area in the same phase as the outer peripheral surfaces L2, L3, and L4. The cam outer peripheral surfaces of the areas S1 to S3 are common in that they have the cam outer peripheral surface L1. In other words, the cam 51d has a cam outer peripheral surface with a partially identical shape. [Cam contact surface in Example 1] As shown in FIG. 6, the cam contact surface 49d on the pressure plate 38d side of the first embodiment has a hole 54d in a range overlapping with the longitudinal region S2 (first cam outer peripheral surface) of the cam outer peripheral surface. The hole 54 is one form of action avoidance means described later. When the outer peripheral surface L5 rotates to a position overlapping with the cam contact surface 49d, it slips into the hole 54d. That is, although the first cam outer peripheral surface is in a positional relationship in which at least a part of it overlaps with the pressure plate 38d (first member), it does not contact the pressure plate 38d (first member). Therefore, the outer peripheral surface L5 does not act on the cam contact surface 49d of the pressure plate 38d.

[0064] [Operation of the pressure mechanism 35 in the first embodiment] Next, the operation of the pressure mechanism 35 of the first embodiment will be described with reference to Figs. 7 to 10. Figs. 7 to 10 are operation explanatory diagrams showing the operation of the pressure mechanism 35 from the non-driving side. The cam 51d rotates counterclockwise. As a result, the heating roller 19 switches to a pressure release state, State 1 in the middle of switching from the pressure release state to the pressure release state, the pressure release state, and State 2 in the middle of switching from the pressure release state to the pressure release state.

[0065] 7(a) is a diagram showing a pressure release state in which the heating roller 19 is not pressing the pressure roller 20. The pressure plate 38d rotates around the fulcrum 46d, and the pressure force variable plate 48d also slides. Due to the pressure force of the pressure spring 44d, the cam contact surface 49d of the pressure plate contacts the outer peripheral surface L1 of the cam, and the cam contact surface 50d of the pressure force variable plate 48d contacts the portion of the outer peripheral surface L5 of the cam 51d with the shortest radius d. When the outer peripheral surface L1 of the cam 51d is in contact with the cam contact surface 49d of the pressure plate 48d, the cam receives the pressure force of the pressure spring 44d, and the pressure plate 38d is in a position inclined to the left in the figure. Therefore, the heating roller 19 is in a position away from the pressure roller 20, and is in a pressure release state in which it is not subjected to the pressure force of the pressure spring 44d.

[0066] At this time, the distance R between the spring support surface 45d and the spring support surface 47d becomes the longest, and the pressure spring 44d becomes the most stretched, so that the pressure of the pressure spring 44d becomes the smallest.

[0067] In this embodiment, the pressure plate 38d and the protrusions of the flange 40d are illustrated in a separated state, but if the heating roller 19 is not applying pressure to the pressure roller 20, the pressure plate 38d and the protrusions of the flange 40d may be in contact with each other.

[0068] 7(b) is a diagram showing a state in the middle of transition from the pressure release state to the pressure applied state. The contact of the cam contact surface 49d of the pressure plate 38d with the cam outer peripheral surface switches from the outer peripheral surface L1 to the outer peripheral surface L3. The outer peripheral surface L5, which has a longer radius than the outer peripheral surface L3, slips into the hole 53d of the cam contact surface 49d, which is an example of the action avoidance means of the pressure plate 38d, and does not come into contact with or act on the cam contact surface 49d.

[0069] On the other hand, the contact of the cam contact surface 50d of the pressure variable plate 48d with the cam outer peripheral surface continues to contact the surface on the outer peripheral surface L5 where the radius d gradually increases, and then contacts the outer peripheral surface L1. At this time, along with the profile of the cam outer peripheral surface L5 where the radius d gradually increases, the distance R between the spring support surface 45d and the spring support surface 47d gradually decreases and the pressure of the pressure spring 44d gradually increases.

[0070] Since the change here is in the direction of gradually increasing pressure, the pressure spring 44d is not released all at once, and the cam 51d is not pushed all at once, so there is no knocking noise caused by a collision in the drive part due to the cam rotating in advance.

[0071] Furthermore, cam 51d abuts against both cam abutment surface 49d and cam abutment surface 50d, and the rotational force torque of the cams is cancelled out by the pressing force, thereby reducing the pre-rotation of the cam, and it is expected that this will have the effect of reducing the knocking noise caused by collision in the drive section.

[0072] 7, the cam abutment surface 49d and the outer circumferential surface of the cam 51 are still in contact with each other, so the cam 51 receives the pressure of the pressure spring 44d, and the heating roller 19 remains in a pressure-released state because it is in a position away from the pressure roller 20. As the cam 51d continues to rotate from this point, the heating roller 19 comes into contact with the pressure roller 20, the cam abutment surface 49d and the outer circumferential surface of the cam 51d move away from each other, and the heating roller 19 begins to apply pressure to the pressure roller 20.

[0073] 8(a) is a diagram showing a pressurized state in which the heating roller 19 applies pressure to the pressure roller 20. The cam abutment surface 50d of the pressure variable plate 48d abuts against the outer peripheral surface L1 of the cam 51d. As shown in FIG. 9, the cam abutment surface 49d of the pressure plate 38d has the outer peripheral surface L5 of the cam 51d recessed into the hole 53d. Therefore, the cam 51d abuts against the pressure plate 38d and receives the pressure force generated by the pressure spring 44d. This ensures that the pressure force is not insufficient to be transmitted to the heating roller 19.

[0074] Also, it is spaced a certain distance H from the outer peripheral surface L2 and is not in contact with the cam outer peripheral surface. When the outer peripheral surface of the cam is in a position spaced from the cam contact surface 49d, the pressure of the pressure spring 44d is received by the flanges 40, 40d via the pressure plate 38d, and the heating roller 19 is in a state where it is receiving the pressure of the pressure spring 44d against the pressure roller 20 (pressurized state).

[0075] At this time, the distance R between the spring support surface 45d and the spring support surface 47d becomes the shortest, and the pressure spring 44d becomes the most compressed, so that the pressure of the pressure spring 44d becomes the greatest.

[0076] 8(b) shows a state in the middle of transition from the pressurized state to the pressure released state. The cam contact surface 49d of the pressure plate is not in contact with the cam outer peripheral surface because the outer peripheral surface L5 of the cam is recessed in the hole 53d and is spaced a certain distance from the outer peripheral surfaces L2 and L4.

[0077] The cam contact surface 50d contacts the cam outer peripheral surface L5, where the radius d on the outer peripheral surface L5 gradually decreases, until it reaches the point where the radius is the shortest. At this time, the distance R between the spring support surface 45d and the spring support surface 47d gradually increases with the profile of the cam outer peripheral surface L5, where the radius d gradually decreases. Therefore, the pressure of the pressure spring 44d gradually decreases.

[0078] Although the change here is in the direction of decreasing the pressure, it is a gradual and gradual displacement. Therefore, the pressure spring 44d is not suddenly released, and the cam 51d is not suddenly pressed, so there is no knocking noise caused by a collision with the drive unit due to the cam rotating ahead of the others.

[0079] In this figure, the cam abutment surface 49d and the outer circumferential surface of the cam are still separated, and the heating roller 19 remains in a state of pressing against the pressure roller 20. As the cam 51d rotates further from here, the cam abutment surface 49d and the outer circumferential surface L4 of the cam start to abut against each other, the pressure force of the pressure spring 44d is received by the cam, and the heating roller 19 transitions to a pressure-released state with respect to the pressure roller 20.

[0080] The cam 51d shown in this embodiment has an outer peripheral surface formed into arc sections L1 to L5, so that even if a deviation occurs in the rotation angle due to a rotation angle error of the cam within the arc length range of each arc section, the positions of the pressure plate 38d and the pressure force variable plate 48d do not change. Also, it is possible to absorb errors by the distance from the motor that rotates the cam 51d, rotational play due to backlash in the drive gear train that transmits the rotation of the output shaft of the motor to the cam, slight twisting of the cam shaft 52, etc.

[0081] In this embodiment, the relative positional relationship between the pressure spring 44d and the cam 51d is such that the cam 51d is disposed within a range on the winding central axis of the pressure spring 44d as shown in Fig. 10. Therefore, the cam 51d can receive a large pressure force from the pressure spring 44d at the center of gravity. In other words, this configuration reduces the risk that the cam 51d will tilt due to the pressure force and that this will cause the frame body itself to become distorted.

[0082] [Effects of Example 1] As described above, the pressurizing mechanism 35 of the first embodiment can reduce the impact noise caused by the preceding rotation of the cam 51d both at the timing of transition from the pressure release state to the pressure state and at the timing of transition from the pressure release state to the pressure release state. Furthermore, the pressurizing mechanism 35 of the first embodiment can reduce the loss of the pressurizing force of the pressurizing member in the pressurized state.

[0083] [Explanation of other configuration examples of pressure mechanism] The same effects may be obtained even if other configurations are used for each part described in the first embodiment. This will be explained below.

[0084] [Compression spring - Tension spring] 7 to 9, the pressure mechanism 35 using the compression spring, the rockable pressure member, and the pressure variable plate 48d has been described, but the present invention is not limited to this. Another configuration example of the pressure mechanism 35 is shown in Figures 11(a) and (b).

[0085] 11(a) and 11(b), the pressure mechanism 35 includes a pressure spring 55 made of a tension spring that generates a tensile force (pressure force) in a contracting direction by pulling both ends of the tension spring 55. The pressure spring 55 is disposed parallel to the moving direction of the heating roller 19 on the downstream side of the nip portion N in the recording material conveying direction.

[0086] Also, a pressure plate 57 is provided having at one end a hook portion 56 for hooking one end of the pressure spring 55 and at the other end a fulcrum portion 46 serving as a fulcrum for rotation. Further, similar to the pressure plate 57 described above, a pressure force variable plate 60 is provided having at one end a hook portion 58 for hooking the other end of the pressure spring 55 and at the other end a fulcrum portion 59 serving as a fulcrum for rotation.

[0087] In this configuration, in the pressure released state shown in Fig. 11(a), the length Ra of the tension spring 55d is the shortest, thereby minimizing the pressure force. Also, in the pressured state (Fig. 11(a)), the length Rb of the tension spring 55d is the longest, thereby maximizing the pressure force.

[0088] In the above configuration, by using the same cam shape and cam contact surface shape as in this embodiment, the same operational effect can be obtained using this pressure mechanism 35.

[0089] [Pressure spring - Torsion spring] 7 to 9, the pressure mechanism 35 using a compression spring, a rockable pressure member, and a pressure variable plate has been described. However, the present invention is not limited to this. Another configuration example is shown in Figures 12(a) and (b).

[0090] 12A and 12B, the pressure mechanism 35 includes a pressure spring 61d that is a torsion spring that generates a pressure force in a twisting back direction. The pressure spring 61d is disposed downstream of the nip portion N in the recording material conveying direction.

[0091] The pressure plate 63d has a spring support surface 62d that abuts against and supports the pressure spring 61d at one end and a fulcrum portion 46d that serves as a fulcrum for rotation at the other end. Furthermore, similar to the pressure plate 63d, the pressure plate 63d has a slidable pressure force variable plate 65d that has a spring support surface 64d that abuts against and supports the other end of the pressure spring 61d.

[0092] In this configuration, unlike other pressure spring configurations, the pressure plate 63d and the pressure force variable plate 65d are not disposed so as to face each other across the cam 51d. Also, since the pressure force variable plate 65 can be made compact, the degree of freedom in arrangement is improved.

[0093] In this configuration, in the pressure released state shown in Figure 12(a), the pressure spring 61d, which is a tension spring, opens the most, resulting in the smallest pressure force, and in the pressured state shown in Figure 12(b), the pressure spring 61d, which is a tension spring, is twisted the most, resulting in the largest pressure force.

[0094] In the above configuration, by using the same cam shape and cam contact surface shape as in this embodiment, the same operational effect can be obtained using this pressure mechanism 35.

[0095] [Cam, spring support surface-A] 7 to 9, the pressure mechanism 35 using the spring support surface -A having the hole 54d is described, but the present invention is not limited to this. Another configuration example is shown in Figures 13(a)(b) and 14(a)(b).

[0096] [Cam shape] 13(a) and 13(b), the cam 66 has different outer circumferential surfaces in regions S4 and S5 which are different in the direction of the rotation axis. The shape of the outer circumferential surface of region S4 is composed of a plurality of outer circumferential surfaces described below.

[0097] That is, the outer peripheral surface L1 abuts against the cam abutment surface 50d of the pressure variable plate 48d in the pressurized state, and abuts against the cam abutment surface 49d of the pressure plate 38d in the pressure released state. The outer peripheral surface L1 includes a portion where the radius d1 is longest.

[0098] The outer peripheral surface L2 abuts against the cam abutment surface 50 of the pressure variable plate 48d in the pressure release state, and is disposed on the cam abutment surface 49 of the pressure plate 38d in the pressure applied state. The outer peripheral surface L2 includes a portion where the radius d2 is shortest.

[0099] The outer peripheral surfaces L3 and L4 are located between the outer peripheral surface L1 and the outer peripheral surface L2, and are outer peripheral surfaces where the radius changes suddenly from d1 to d2.

[0100] On the other hand, the shape of the outer peripheral surface of the region S5 is composed of multiple outer peripheral surfaces as described below. That is, the outer peripheral surface L1 abuts against the cam abutment surface 50 in the pressurized state, and abuts against the cam abutment surface 49 in the pressure-released state. The outer peripheral surface L1 includes the outer peripheral surface with the longest radius d1.

[0101] The outer peripheral surface L5 is a region where the radius changes gradually within a range longer than d2 and shorter than d1. The outer peripheral surface L5 is in the same phase as the outer peripheral surfaces L2, L3, and L4.

[0102] [Cam contact surface-A] 14(a) and 14(b), the cam contact surface 67 is disposed at a position that overlaps with the longitudinal region S4 of the cam outer peripheral surface, but does not overlap with the longitudinal region S5. Therefore, even when the outer peripheral surface L5 rotates toward the cam contact surface 67, it does not overlap with the longitudinal direction, and therefore the outer peripheral surface L5 does not come into contact with the cam contact surface 67 to act.

[0103] The same effect can be obtained by using the pressure mechanism 35 having the above-mentioned configuration. With this configuration, there is no need to provide an escape hole in the cam contact surface 67. Furthermore, with this configuration, the cam does not necessarily need to be configured as an integral part, and the same effect can be obtained even with a configuration in which two cams, cam-1 having the shape of the outer circumferential surface of the longitudinal region S4 and cam-2 having the shape of the outer circumferential surface of the longitudinal region S5, are provided.

[0104] [Pressure plate] In Fig. 7 to Fig. 9, the pressure plate 38d rotates around the fulcrum 46d to press and separate the protrusion of the flange 40d. This causes the heating roller 19 to slide toward and away from the pressure roller 20, switching between the pressurized state and the pressure-released state. However, the present invention is not limited to this. Another configuration example is shown in Fig. 15(a) and (b).

[0105] As shown in Figures 15(a) and (b), the heating roller 19 is supported by a pressure plate 69d via a flange 68d, and the pressure plate 69d rotates around a fixed shaft 70d of the frame 37 as a fulcrum, thereby allowing the heating roller 19 to be pressed against the pressure roller 20.

[0106] The pressure plate 69d rotates around the fixed shaft 70d. Accordingly, the heat roller 19 also rotates together with the pressure plate 69d supporting the flange 68d. As a result, the heat roller 19 moves closer to or away from the pressure roller 20, switching between a pressure-applied state (FIG. 15(b)) and a pressure-released state (FIG. 15(a)).

[0107] The same effect can be obtained by using the pressure mechanism 35 having the above-mentioned configuration. Furthermore, with this configuration, the degree of freedom to realize an optimal pressure distribution within a nip of a specified width can be increased by adjusting the position of the rotation center of the pressure plate 69d and the arrangement of the pressure springs 44d. EXAMPLES

[0108] Next, the configuration of a pressure mechanism according to Example 2 will be described with reference to Fig. 16 to Fig. 19. The pressure mechanism 35 of Example 2 differs from Example 1 in that it has a light pressure state in which the pressure is smaller than that of the pressure state, in addition to a pressure state and a pressure release state. In this example, the description of the parts common to Example 1 will be omitted.

[0109] [Cam shape in Example 2] 16(a) and 16(b), the cam 71 of the second embodiment has different regions S1, S2, and S3 in the rotation axis direction. The regions S1 and S3 have the same outer circumferential surface shape and are composed of multiple outer circumferential surfaces described below.

[0110] The outer peripheral surface L1 is an outer peripheral surface including a region with the longest radius d1, which abuts against the cam abutment surface 50 in a pressurized state and abuts against the cam abutment surface 49 in a pressure-released state. The outer peripheral surface L2 is an outer peripheral surface including a region with the shortest radius d2, which abuts against the cam abutment surface 50 in a pressure-released state and is disposed on the cam abutment surface 49 in a pressurized state. The outer peripheral surface L6 is disposed between the outer peripheral surfaces L1 and L2, and is an outer peripheral surface with a radius that changes abruptly from d1 to d2. The outer peripheral surface L7 is adjacent to the outer peripheral surface L1, and is an outer peripheral surface with a radius that gradually decreases. The outer peripheral surface L8 is adjacent to the outer peripheral surface L7, and is an outer peripheral surface including a region with a radius d3 that is smaller than the radius d1. The outer peripheral surface L9 is disposed between the outer peripheral surfaces L8 and L2, and is an outer peripheral surface with a radius that changes abruptly from d3 to d2.

[0111] On the other hand, the shape of the outer peripheral surface of the region S2 sandwiched between the regions S1 and S3 is composed of a plurality of outer peripheral surfaces described below.

[0112] The outer peripheral surface L1 is an outer peripheral surface that includes a region with the longest radius d1, which abuts against the cam abutment surface 50 in a pressurized state and abuts against the cam abutment surface 49 in a released state. The outer peripheral surface L7 is adjacent to the outer peripheral surface L1 and has a gradually decreasing radius. The outer peripheral surface L8 is adjacent to the outer peripheral surface L7 and includes a region with a radius d3 smaller than the radius d1.

[0113] The outer peripheral surface L10 is between the outer peripheral surfaces L1 and L8, and includes a region in which the radius gradually changes over a length range longer than d2 and shorter than d1. The outer peripheral surface L10 is in the same phase as the outer peripheral surfaces L2, L6, and L9.

[0114] [Cam contact surface in Example 2] Similar to the first embodiment (see FIG. 6), the cam contact surface 49 of the second embodiment has holes 54 in a range overlapping with the longitudinal region S2 of the cam outer peripheral surface. Therefore, even when the outer peripheral surface L10 rotates to a position overlapping with the cam contact surface 49, the outer peripheral surface L10 slips into the holes 54, and therefore does not come into contact with the cam contact surface 49 to act.

[0115] [Operation of the pressure mechanism in the second embodiment] The operation of the pressure mechanism 35 of the second embodiment will be described with reference to Figures 17 to 19. Figures 17 to 19 are operation explanatory views showing the operation of the pressure mechanism 35 from the non-driving side.

[0116] 17(a) shows a pressure release state in which the heating roller 19 is not pressing the pressure roller 20. The pressure plate 38d rotates around the fulcrum 46, and the pressure force variable plate 48d also slides in accordance with the rotation. Due to the pressure of the pressure spring 44d, the cam contact surface 49 of the pressure plate abuts against the outer peripheral surface L1 of the cam, and the cam contact surface 50 of the pressure force variable plate abuts against the portion of the outer peripheral surface L10 of the cam with the shortest radius d. When the outer peripheral surface L1 of the cam is in contact with the cam contact surface 49, the pressure of the pressure spring 44d is received by the cam, and the pressure plate 38d is in a position inclined to the left in FIG. 17. Therefore, the heating roller 19 is in a position away from the pressure roller 20, and is in a pressure release state in which it is not subjected to the pressure of the pressure spring 44d.

[0117] At this time, the distance R between the spring support surface 45 and the spring support surface 47d becomes the longest, and the pressure spring 44d expands to the greatest extent, so that the pressure of the pressure spring 44d becomes the smallest.

[0118] In addition, in Example 2, the pressure plate 38d and the protrusions of the flange 40d are illustrated in a separated state, but if the heating roller 19 is not applying pressure to the pressure roller 20, the pressure plate 38d and the protrusions of the flange 40d may be in contact with each other.

[0119] 17(b) shows a state in the middle of transition from the pressure release state to the light pressure state. The contact of the cam contact surface 49 of the pressure plate with the cam outer peripheral surface switches from outer peripheral surface L1 to outer peripheral surface L9. Note that outer peripheral surface L10, which has a longer radius than outer peripheral surface L9, fits into hole 53 of the cam contact surface, so it does not come into contact with or act on cam contact surface 49.

[0120] The cam abutment surface 50 abuts against the cam outer peripheral surface while continuing to abut against a surface on the outer peripheral surface L10 where the radius d gradually increases, and then abuts against the outer peripheral surface L8. At this time, along with the profile of the cam outer peripheral surface L10 where the radius d gradually increases, the distance R between the spring support surface 45 and the spring support surface 47 gradually becomes shorter, and the pressure of the pressure spring 44 gradually increases.

[0121] Since the changeover here is in the direction of gradually increasing pressure, the pressure spring 44 is not released all at once, and the cam 71 is not pushed all at once, so there is no knocking noise caused by a collision in the drive section due to the cam rotating in advance.

[0122] Furthermore, cam 71 abuts against both cam abutment surface 49 and cam abutment surface 50, and the torque of the cams is cancelled out by the pressing force, thereby reducing the pre-rotation of the cam and reducing the knocking noise caused by collision in the drive section.

[0123] 17, the cam abutment surface 49 and the outer circumferential surface of the cam are still in contact with each other, so the cam receives the pressure of the pressure spring 44, and the heat roller 19 remains in a pressure-released state because it is in a position away from the pressure roller 20. As the cam 71d continues to rotate from this point, the heat roller 19 abuts against the pressure roller 20, the cam abutment surface 49d and the outer circumferential surface of the cam move away from each other, and the heat roller 19 begins to press the pressure roller 20.

[0124] 18(a) shows a light pressure state in which the heating roller 19 lightly presses the pressure roller 20. The cam abutment surface 50 of the pressure variable plate abuts against the outer peripheral surface L8 of the cam. The cam abutment surface 49 of the pressure plate has the outer peripheral surface L10 of the cam recessed in a hole 53. Therefore, the cam abuts against the pressure plate and receives the pressure generated by the pressure spring, so that the pressure is not insufficiently transmitted to the heating roller 19. Also, it is separated from the outer peripheral surface L2 by a certain distance H, and is not in contact with the outer peripheral surface of the cam.

[0125] When the outer peripheral surface of this cam is in a position away from the cam abutment surface 49, the pressure force of the pressure spring 44 is received by the flange 40d via the pressure plate 38d, and the heating roller 19 is in a lightly pressurized state in which it is subjected to the pressure force of the pressure spring 44 against the pressure roller 20.

[0126] 18(b) is a diagram showing a pressurized state in which the heating roller 19 presses the pressure roller 20. The cam abutment surface 50 of the pressure variable plate abuts against the outer peripheral surface L1 of the cam. The cam abutment surface 49 of the pressure plate is very close to the outer peripheral surface L10 of the cam, but does not abut against it due to the presence of a hole 53. Therefore, the cam abuts against the pressure plate and receives the pressure generated by the pressure spring, so that the pressure is not insufficient to be transmitted to the heating roller. In addition, it is separated from the outer peripheral surface L2 by a certain distance H, and is not in a state of abutment with the outer peripheral surface of the cam.

[0127] When the outer peripheral surface of this cam is in a position separated from the cam abutment surface 49, the pressure force of the pressure spring 44 is received by the flange 40d via the pressure plate 38d, and the heating roller 19 is in a pressurized state in which it is receiving the pressure force of the pressure spring 44 against the pressure roller 20.

[0128] At this time, the distance R between the spring support surface 45 and the spring support surface 47d becomes the shortest, and the pressure spring 44 becomes the most compressed, so that the pressure of the pressure spring 44 becomes the maximum.

[0129] 19 shows a state in the middle of transition from a pressurized state to a pressure-released state. The cam abutment surface 49 of the pressure plate is not in contact with the cam outer peripheral surface because the cam outer peripheral surface L10 is recessed in the hole 53. The cam abutment surface 50 abuts against the cam outer peripheral surface by continuously abutting against a surface on the outer peripheral surface L10 where the radius d gradually decreases, and moves to the point where the radius is the shortest. At this time, the distance R between the spring support surface 45 and the spring support surface 47d is gradually displaced in the direction of increasing in accordance with the profile of the cam outer peripheral surface L10 where the radius d gradually decreases, and the pressure force of the pressure spring 44 is slowly reduced.

[0130] Although the change here is in the direction of decreasing the pressure, it is a gradual and gradual displacement. Therefore, the pressure spring 44 is not suddenly released, and the cam 71 is not suddenly pressed, so there is no knocking noise caused by collision with the drive unit due to the cam rotating ahead of the others.

[0131] In this figure, the cam abutment surface 49 and the outer circumferential surface of the cam are still separated, and the heating roller 19 remains in a state of pressing against the pressure roller 20. As the cam 71 rotates further from here, the cam abutment surface 49 and the outer circumferential surface L9 of the cam begin to abut, the pressure force of the pressure spring 44 is received by the cam, and the heating roller 19 transitions to a pressure-released state with respect to the pressure roller 20.

[0132] The cam 71 shown in the second embodiment has an outer peripheral surface formed of an arc portion L1-10, so that even if a deviation occurs in the rotation angle due to an error in the rotation angle of the cam within the arc length range of each arc portion, the positions of the pressure plate 38d and the pressure force variable plate 48d do not change. Also, it is possible to absorb the error by the distance from the motor that rotates the cam 71, rotational play due to backlash in the drive gear train that transmits the rotation of the output shaft of the motor to the cam, minute twisting of the cam shaft 52, etc.

[0133] As in the first embodiment (see FIG. 10), the relative positional relationship between the pressure spring 44 and the cam 71 shown in the second embodiment is such that the cam 51 is disposed within the range of the central axis of the pressure spring 44. Therefore, the cam 71 can receive a large pressure force from the pressure spring 44 at the center of gravity. In other words, this configuration can reduce the risk that the cam 71 will tilt due to the pressure force, causing the frame itself to become distorted.

[0134] [Effects of Example 2] As described above, the pressure mechanism 35 of the second embodiment can reduce the impact noise caused by the preceding rotation of the cam both when the pressure release state transitions to the pressure release state and when the pressure state transitions to the pressure release state. Furthermore, it is possible to provide a pressure mechanism and an image forming apparatus including the pressure mechanism that do not lose the pressure of the pressure member in the pressure state and the light pressure state.

[0135] Moreover, in the second embodiment, a light pressure state is provided. In the light pressure state, the pressure is smaller than in the pressurized state, so the nip width, fixability, conveying force, etc. are different. By providing a plurality of pressure positions, it is possible to select a state suitable for the conveyed sheet S.

[0136] In the second embodiment, in the two positions of the pressurized state and the lightly pressurized state, it is necessary to set the cam contact surface 49 of the pressurizing plate and the outer peripheral surface of the cam at a certain distance so as not to contact each other, thereby preventing loss of pressurizing force. Therefore, while there is little margin in each profile phase region on the outer peripheral surface of the cam, it is possible to maximize the benefits of the effect obtained from this embodiment. EXAMPLES

[0137] Third Embodiment Next, as an example using a pressing mechanism according to a third embodiment, the configurations of a sheet supplying device and a pressing mechanism will be described with reference to FIGS.

[0138] [Sheet Feeding Device] Fig. 20 is a side view of a sheet supplying device 73 having a pressure mechanism 72 according to the third embodiment, as viewed from the non-driving side. Fig. 21 is a perspective view of the sheet supplying device 73, as viewed from the driving side.

[0139] The sheet supply device 73 has a pressure mechanism 72, a manual feed tray 74, a pad (pressure member) 76 attached to a swingable tray 75 arranged downstream of the base tray, and a feed roller (pressurized member) 77. Restriction units are movably provided on both sides of the manual feed tray 74 in the sheet stack width direction to restrict the width position of the sheet stack according to the width of the sheets. Furthermore, the sheet supply device 73 has a frame 78 that constitutes the frame of the sheet supply device, and the manual feed tray 74, the swingable tray 75, the feed roller 77, and the pressure mechanism 72 are each supported by the frame 78.

[0140] The pad 76 is made of a friction material and is attached to the tray surface of the swingable tray 75 so as to be able to apply pressure to the feed roller 77. The feed roller 77 is supported for rotation by a frame 78 and is disposed so that the outer peripheral surface (front surface) of the feed roller 77 comes into contact with the pad 76. A gear 42 is fixed to one of the shaft portions.

[0141] In the sheet supplying device 73 of the third embodiment, a pressing force is applied by the swing tray 75, so that the pad 76 is pressed in a direction perpendicular to the generatrix direction of the feed roller 77. As a result, a nip pressure is generated between the pad 76 and the feed roller 77.

[0142] A description will now be given of a sheet conveying operation of the sheet supplying device 73. A driving force of a motor (not shown) provided in the apparatus main body 100 is transmitted to the gear 42, whereby the feeding roller 77 rotates.

[0143] A nip pressure is applied to the sheets S stacked on the tray, which generates a sufficient conveying force, and the sheets S are conveyed while being separated one by one by the friction of the pad 76.

[0144] [Pressure mechanism 72] 20 and 21, the configuration of the pressure mechanism 72 will be described. The pressure mechanism 72 is configured symmetrically with respect to the center in the longitudinal direction of the heat roller, except that the pressure mechanism 72 is provided with a gear 43 on one end side in the longitudinal direction.

[0145] The pressure mechanism 72 includes a pressure spring (pressure generating member) 44 which is a compression spring that generates a pressure in the expanding direction by being compressed from both ends.

[0146] The tray 75 (first member) has a spring support surface 79 for pressing one end of the pressure spring 44, and a pivot portion 80 at the other end, which serves as a pivot for pivoting, and is used to mount a large number of sheets S.

[0147] The oscillating tray 75, which supports the pressure spring 44 on a spring support surface 79, rotates about a fulcrum portion 80 due to the pressure generated by the pressure spring 44. As a result, the pad 76 attached to the tray surface is pressed by the feed roller 77.

[0148] Similar to the swingable tray 75, the sheet feeding device 73 includes a pressure variable plate 82 (second member) having a spring support surface 81 at one end for pressing the other end of the pressure spring 44.

[0149] The pressure variable plate 82 is disposed so as to be slidable approximately parallel to the direction of expansion and contraction of the pressure spring, and supports the other end of the pressure spring 44 on a spring support surface 81. The pressure variable plate 82 variably applies the pressure generated by the pressure spring to the oscillating tray 75 by sliding.

[0150] Also, a cam 51 (cam mechanism) is provided between a cam abutment surface 83 arranged on the opposite side of the spring support surface 79 of the tray and a cam abutment surface 84 at an end of the pressure force variable plate on the side different from the spring support surface 81. The cams 51 are fixed to the longitudinal ends of cam shafts 52 arranged along the longitudinal direction. The cam shafts 52 are rotatably supported by the frame 78. A gear 43 is fixed to one longitudinal end of the cam shaft 52, and the gear is rotated in the direction of the arrow by receiving a driving force from a motor (driving source) (not shown) provided in the apparatus main body 100.

[0151] As the cam 51 rotates, the outer circumferential surface of the cam comes into contact with the cam contact surface 83 of the oscillating tray and the cam contact surface 84 of the pressure variable plate. With this movement, the oscillating tray 75 rotates about the fulcrum portion 80, and the pad 76 attached to the tray surface moves closer to and away from the feed roller 77, switching between a pressurized state and a pressure-released state.

[0152] Next, the details of the shape of the cam and the cam contact surface -A according to the third embodiment will be described.

[0153] [Cam shape of Example 3] It has the same shape as in Example 1 (see Figs. 5(a) and (b)). Details are omitted.

[0154] [Cam contact surface-A in Example 3] Similar to the first embodiment (see FIG. 6), the cam contact surface 83 of the third embodiment has a hole 54 in a range overlapping with the longitudinal region S2 of the cam outer peripheral surface. Therefore, even when the outer peripheral surface L5 rotates to a position overlapping with the cam contact surface 83, the outer peripheral surface L5 slips into the hole 54, and therefore the outer peripheral surface L5 does not come into contact with the cam contact surface 83 to act.

[0155] [Operation of the pressure mechanism in the third embodiment] Next, the operation of the pressure mechanism 72 of the third embodiment will be described with reference to Figures 22(a) and (b). Figures 22(a) and (b) are explanatory diagrams showing the operation of the pressure mechanism 72 from the non-driving side, and are explanatory diagrams of the operation when the cam 51 rotates counterclockwise and switches the pressure release state of the pad 76 against the feed roller 77.

[0156] 22(a), the cam 51, the swing tray 75, and the pressure variable plates 82 and 82d are movable in the same manner as in the first embodiment (see FIG. 7(a)). As a result, the pad 76 is moved away from the feed roller 77 and is in a pressure release state where it is not subjected to the pressure of the pressure springs 44 and 44d.

[0157] In the intermediate state-1 (from pressure-released state to pressure-applied state), the cam 51, the swinging tray 75, and the pressure-adjusting plate 82 are movable in the same manner as in the first embodiment (see FIG. 7(b)). Since the changeover here is in the direction in which the pressure gradually increases, the pressure spring 44 is not suddenly released, and the cam 51 is not suddenly pressed, so that no knocking noise is generated due to a collision at the drive unit caused by the preceding rotation of the cam.

[0158] In Fig. 22(b), as in the description of the first embodiment (see Fig. 8(a)), the cam 51, the oscillating tray 75, and the pressure variable plate 82 are moved, so that the cam abutment surface 84 of the pressure variable plate abuts against the outer peripheral surface L1 of the cam. The cam abutment surface 83 of the pressure plate is such that the outer peripheral surface L5 of the cam slips into the hole 53. Therefore, the cam abuts against the pressure plate and receives the pressure generated by the pressure spring, so that the pressure is not insufficiently transmitted to the express roller.

[0159] Also, the pad 76 is spaced from the outer peripheral surface L2 by a certain distance H, and is not in contact with the outer peripheral surface of the cam. As a result, similar to the first embodiment, the pad 76 is in a pressurized state in which the pad 76 receives the pressure of the pressure springs 44, 44d against the feed roller 77, and sufficient nip force can be secured, preventing poor feeding.

[0160] In the mid-switching state (from the pressurized state to the pressure-released state), the cam 51, the oscillating tray 75, and the pressure-variable plate 82 move in the same manner as described in the first embodiment (see FIG. 8(b)). Although the switching here is in the direction in which the pressure force decreases, the displacement is gentle and slow. Therefore, the pressure spring 44 is not released all at once, and the cam 51 is not pressed all at once, so there is no knocking noise caused by a collision in the drive unit due to the cam rotating ahead of time.

[0161] [Effects of Example 3] As described above, the pressure mechanism 72 of the third embodiment can reduce the impact noise caused by the preceding rotation of the cam not only in the fixing device but also in the sheet feeding device. Furthermore, it is possible to provide a sheet feeding device in which the pressure of the pressure member is not lost in the pressurized state. [Explanation of symbols]

[0162] 1 Photosensitive drum 2. Charging device 3Y, 3M, 3C, 3K Image forming unit 6. Developing device 7 Heating element 9 Exposure equipment 10 Intermediate transfer belt unit 11 Primary transfer roller 12 Intermediate transfer belt 13 Secondary transfer inner roller 14 Tension roller 15 Secondary transfer section 16 Secondary transfer roller 17 Registration Section 18 Fixing device 19 Heating roller 20 Pressure roller 21 Discharge roller pair 21a Upper roller 21b Lower roller 22 Output tray 23 Paper feed cassette 24 Feeding roller 25 Sheet feeding section 26 Belt cleaning device 27 Collection Container 28 Transport roller pair 29 Guide member 30 Switchback Pass 31 Re-transport path 32 Switchback roller pair 33 Re-transport path 33a Drive roller 33b Driven roller 34 Upper transport guide 35 Pressurizing mechanism 36 Sleeve 37 Frames 38d Pressure plate 39 Heater holder 40, 38d flange 41, 38d Bearing 42 Gear 43 Gear 44d Pressure spring 45d spring support surface 46d Support part 47d, 45d Spring support surface 48d Variable pressure plate 49d Cam contact surface 50d Cam contact surface 51d Cam 52 Camshaft 53 Support shaft 54d Hole 55d Pressure spring 56d Hook part 57d Pressure plate 58d Hook part 59d Fulcrum part 60d Variable pressure plate 61d Pressure spring 62d Spring support surface 63d Pressure plate 64d Spring support surface 65d Variable pressure plate 66d Cam 67d Cam contact surface 68d flange 69d Pressure plate 70d fixed axis 71d Cam 72 Pressure Mechanism 73 Sheet Feeding Device 74 Manual feed tray 75 Swinging Tray 76 Pad 77 Feeding roller 78 frames 79d Spring support surface 80d Support part 81d Spring support surface 82d Variable pressure plate 83d Cam contact surface 84d Cam contact surface 100 Image forming device 101 Device body 111 Pressure plate 112 Cam 113 Pressure Spring 114 Pressure variable plate S Seat S1, S2, S3, S4, S5 Longitudinal area of ​​the cam d cam radius L1, L2, L3, L4, L5, L6, L7, L8, L9, L10 Cam outer surface H Distance between the cam contact surface and the cam

Claims

1. A pressure applying device having a pressure applying member and a pressure receiving member, the pressure applying device being switchable between a pressure applying state in which the pressure applying member applies pressure to the pressure receiving member and a pressure release state in which the pressure applying member does not apply pressure to the pressure receiving member, A pressure generating member that generates a pressure force; A rotatably supported cam; a first member that comes into contact with the cam and is displaced by rotation of the cam, the first member coming into contact with the pressing member and moving the pressing member in a direction toward the pressed member and a direction away from the pressed member, and applies a pressing force generated by the pressing force generating member to the pressing member; a second member that is in contact with the cam and displaced by rotation of the cam, and that varies the pressure generated by the pressure generating member; Equipped with The cam has a plurality of cam outer peripheral surfaces formed circumferentially at different positions in a rotation axis direction of the cam, a pressure application device, characterized in that the multiple cam outer peripheral surfaces act on the second member regardless of the phase of the cam, while a first cam outer peripheral surface among the multiple cam outer peripheral surfaces does not act on the first member despite being in a positional relationship in which at least a portion of the first cam outer peripheral surface overlaps with the first member.

2. In the step of switching the pressure member from the pressure-applied state to the pressure-released state by rotating the cam, 2. The pressure applying device according to claim 1, wherein the radius of the outer peripheral surface of the first cam at a phase where the first cam abuts against the second member while the pressure applied by the pressure applying member transitions from a position where the pressure applied by the pressure applying member is maximum to a position where the pressure applied by the pressure applying member is reduced is gradually shortened and is larger than the radii of the outer peripheral surfaces of other cams at the same phase.

3. 2. The pressure device according to claim 1, wherein the first cam outer peripheral surface and the other cam outer peripheral surfaces of the plurality of cam outer peripheral surfaces have cam outer peripheral surfaces having partially the same shape.

4. 2. The pressure device according to claim 1, wherein said cam is formed as a single piece.

5. 2. The pressure device according to claim 1, wherein the first member and the second member are disposed so as to face each other with the cam therebetween.

6. 2. The pressure device according to claim 1, wherein the pressure generating member is disposed at a position overlapping with the cam in a direction of a rotation axis of the cam.

7. 2. The pressure applying device according to claim 1, wherein the first member has an action avoiding means for avoiding an action from the outer peripheral surface of the first cam.

8. 2. The pressurizing device according to claim 1, wherein the action avoiding means is a hole or a recess provided in the first member.

9. 2. The pressure device according to claim 1, wherein the outer peripheral surface of the first cam is disposed at a position different from that of the first member in the direction of the rotation axis of the cam.

10. 2. The pressure application device according to claim 1, characterized in that in the pressurized state in which the pressurizing member is pressing the pressurized member, the second member has a plurality of different positions, and the cam acts on the second member to displace the position of the second member and change the pressure of the pressure generating member.

11. 2. The pressure device according to claim 1, wherein the first member is a pressure plate having one surface that contacts the cam and another surface that contacts the pressure generating member.

12. 2. The pressure device according to claim 1, wherein the second member is a pressure variable plate having one surface in contact with the cam and slidingly moved by rotation of the cam.

13. an image forming unit that forms an image on a sheet; a fixing device that fixes the image formed on the sheet by the image forming unit to the sheet; An image forming apparatus comprising: The image forming apparatus according to claim 1 , wherein the fixing device is provided with the pressure device according to claim 1 .

14. a sheet feeding device that feeds a sheet; an image forming unit that forms an image on the sheet fed by the sheet feeding device; An image forming apparatus comprising: The image forming apparatus according to claim 1 , wherein the sheet feeding device comprises the pressure device according to claim 1 .

Images