CN111458999A

CN111458999A - Image forming apparatus with a toner supply device

Info

Publication number: CN111458999A
Application number: CN202010044658.8A
Authority: CN
Inventors: 八木昌隆
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 2019-01-21
Filing date: 2020-01-16
Publication date: 2020-07-28
Also published as: JP2020118765A; JP7305962B2

Abstract

Provided is an image forming apparatus capable of reducing the degree to which heat energy supplied to a belt in a fixing device is wasted in a useless form. The image forming apparatus includes: an endless belt that can be circulated to convey a recording medium from upstream to downstream; a fixing pad (52) that presses the belt from the inner side of the belt at least toward the 1 st side; a slider disposed between the belt and the fixing pad; a support member (54) that supports the fixing pad (52) from the side opposite to the belt; and a roller. The roller and a fixing pad (52) sandwich the slide sheet and the belt, and the fixing pad (52) has a plurality of recesses (5) on the surface on the roller side.

Description

Image forming apparatus with a toner supply device

Technical Field

The present invention relates to an image forming apparatus.

Background

An image forming apparatus including a fixing device is known. In recent years, in a fixing device, a method using a fixing pad is sometimes adopted from the viewpoint of energy saving and cost reduction.

Such fixing devices are described in, for example, japanese patent laid-open nos. 2006-47769 and 2013-68724.

Disclosure of Invention

In the fixing device using the fixing pad system, the fixing pad is fixed in a state of being in contact with the belt (belt). In the fixing device, a fixing pad and a roller are configured to nip the belt, and the roller presses the fixing belt toward the fixing pad. Since the fixing pad is generally made of resin and has low rigidity, when it is pressed by a roller, it is easily bent if only the pad is used. In order to suppress the bending when the pressing is applied, a support member formed of a metal plate material is provided on the back surface of the gasket.

In order to increase the rigidity of the support member, a certain degree of wall thickness is required. However, when the support member is formed of a thick plate material, the heat capacity of the support member increases. Since heat is applied to the belt in the fixing device from the heat source, the belt reaches the fixing nip portion in a high temperature state. The heat is transferred to the paper as a recording medium to fuse the toner on the paper and fix it to the paper.

However, heat brought into the fixing nip from the belt is transmitted not only from the surface of the belt to the paper but also to the fixing pad located on the back side of the belt. The heat is further transferred from the fixing pad to the support member to heat the support member. Rather, the support member becomes hot and the heat energy provided to the belt from the heat source is wasted in a useless manner. The thermal energy is originally generated by electric energy for heating the heat source, and therefore the thermal energy is wasted, which becomes waste of electric energy.

Accordingly, an object of the present invention is to provide an image forming apparatus capable of reducing a degree to which thermal energy supplied to a belt in a fixing device is wasted in a useless form.

In order to achieve the above object, an image forming apparatus according to the present invention includes: an endless belt that can be circulated to convey a recording medium from upstream to downstream; a fixing pad pressing the belt from an inner side of the belt at least toward a 1 st side; a slider disposed between the belt and the fixing pad; a supporting member supporting the fixing pad from a side opposite to the belt; and a roller that sandwiches the slide sheet and the belt with the fixing pad, the fixing pad having a plurality of concave portions on a surface on the roller side.

The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description, which is to be read in connection with the accompanying drawings.

Drawings

Fig. 1 is a conceptual diagram of an image forming apparatus according to embodiment 1 of the present invention.

Fig. 2 is a conceptual diagram of a fixing device provided in an image forming apparatus according to embodiment 1 of the present invention.

Fig. 3 is a partially enlarged view of the fixing device shown in fig. 2.

Fig. 4 is a 1 st explanatory view of a method of attaching the fixing pad to the supporting member.

Fig. 5 is a 2 nd explanatory view of a method of attaching the fixing pad to the supporting member.

Fig. 6 is a perspective view of the fixing pad attached to the support member.

Fig. 7 is a cross-sectional view of a structure included in a fixing device provided in an image forming apparatus according to embodiment 1 of the present invention.

Fig. 8 is a front view of a fixing pad included in an image forming apparatus according to embodiment 1 of the present invention.

Fig. 9 is a partial perspective view of a fixing pad included in an image forming apparatus according to embodiment 1 of the present invention.

Fig. 10 is a conceptual diagram of a structure in the vicinity of a fixing pad included in an image forming apparatus according to embodiment 1 of the present invention.

Fig. 11 is a partial perspective view of a modification of the fixing pad included in the image forming apparatus according to embodiment 1 of the present invention.

Fig. 12 is a 1 st explanatory diagram of the shape of the unevenness of the fixing pad and the manner of contact of the belt.

Fig. 13 is a 2 nd explanatory view of the shape of the unevenness of the fixing pad and the manner of contact of the belt.

Fig. 14 is a front view of example 1 of an arrangement of a plurality of recesses in a fixing pad.

Fig. 15 is a front view of example 2 of the arrangement of a plurality of recesses in a fixing pad.

Fig. 16 is a front view of example 3 of the arrangement of a plurality of recesses in a fixing pad.

Fig. 17 is a front view of example 4 of the arrangement of a plurality of recesses in a fixing pad.

Fig. 18 is a front view of example 5 of an arrangement of a plurality of recesses in a fixing pad.

Fig. 19 is a front view of example 6 of the arrangement of a plurality of recesses in a fixing pad.

Fig. 20 is an explanatory view of example 1 in which a fixing nip portion is configured by using a fixing pad.

Fig. 21 is a front view of example 7 of the arrangement of a plurality of recesses in a fixing pad.

Fig. 22 is an explanatory diagram of example 2 in which a fixing nip portion is configured by using a fixing pad.

Fig. 23 is a front view of an 8 th example of an arrangement form of a plurality of recesses in a fixing pad.

Fig. 24 is a cross-sectional view of the slide plate.

Fig. 25 is an explanatory diagram of a case where the width of the concave portion of the fixing pad is large to some extent.

Fig. 26 is an explanatory diagram of a case where the width of the concave portion of the fixing pad is small to some extent.

Fig. 27 is a graph showing the experimental results.

Fig. 28 is an explanatory diagram of a model in a case where the fixing pad is pressed while overlapping the slider and the recording medium.

Fig. 29 is an explanatory diagram of the amount of bending generated in the slider.

Fig. 30 is an explanatory view of sectional moment of inertia.

Detailed Description

(embodiment mode 1)

An image forming apparatus according to embodiment 1 of the present invention will be described with reference to fig. 1 to 10.

Fig. 1 shows a conceptual diagram of an image forming apparatus 801 according to the present embodiment. The image forming apparatus 801 includes a housing 1 and a cartridge 40 disposed below the housing 1. Inside the housing 1, a photoreceptor 44, a charger 46, a transfer belt 47, an image exposure device 48, a developing roller 45, a 1 st transfer roller 42, a 2 nd transfer roller 43, a fixing device 101, and the like are disposed. In the cassette 40, 1 or more recording media 2 are accommodated. The recording medium 2 may be paper, for example, but may be a medium other than paper. The transfer belt 47 is endless and is configured to rotate cyclically.

In the image forming apparatus 801, the surface of the photoreceptor 44 is charged by the charger 46 so as to be uniformly at a predetermined potential. The image exposure device 48 performs image exposure corresponding to the document image on the charged region. Thereby, an electrostatic latent image is formed on the surface of the photoreceptor 44. The electrostatic latent image is developed by the developing roller 45 to which a developing bias is applied, and becomes a visible toner image. The 1 st transfer roller 42 is biased to attract toner, and the visible toner image on the surface of the photosensitive body 44 is transferred to the transfer belt 47.

On the other hand, the recording media 2 are taken out one by one from the cassette 40 by the paper feed roller 41 and conveyed to the 2-time transfer roller 43. The 2-time transfer roller 43 is also applied with a voltage in the same manner as the 1-time transfer roller 42. The transfer belt 47 is sandwiched between the 2-time transfer roller 43 and the pressing roller 49, and this portion becomes the 2-time transfer nip 38. When the recording medium 2 passes through the 2-time transfer nip 38, the recording medium 2 and the transfer belt 47 are nipped and pressed by the 2-time transfer roller 43 and the pressing roller 49. The visible toner image conveyed by the transfer belt 47 is transferred to the recording medium 2 at the 2-time transfer nip 38. The recording medium 2 bearing the visible toner image is sent to the fixing device 101. The detailed structure of the fixing device 101 will be described later. The fixing device 101 applies heat and pressure to fix the toner to the recording medium 2. The recording medium 2 on which the image formation is thus completed is discharged from the outlet 39.

Fig. 2 shows a case where the fixing device 101 is taken out separately. The fixing device 101 includes an endless belt 51, a roller 58 for applying pressure, and a fixing pad 52 fixedly disposed inside the belt 51. The fixing pad 52 and the roller 58 are positioned to nip the belt 51, thereby forming the fixing nip 50. The fixing pad 52 defines a path of the belt 51. The belt 51 is conveyed along the shape of the fixing pad 52.

The fixing pad 52 is supported by a support member 54. A heat source 56 is disposed inside the heating member 57. The belt 51 is bridged by a heating member 57 and a fixing pad 52. The roller 58 is rotated at a predetermined rotational speed by a motor not shown. Thereby, the belt 51 is conveyed.

The fixing pad 52 may be made of resin such as polyphenylene sulfide, polyimide, or liquid crystal polymer, for example, or the fixing pad 52 may be made of metal such as aluminum or iron, or ceramic instead of resin. The fixing pad 52 may include a fixing member made of silicone rubber, fluororubber, or the like. The fixing pad 52 may be formed by a combination of 2 or more members.

The heating member 57 is formed of metal such as aluminum or SUS, and has a substantially cylindrical shape. The roll 58 is a 3-layer construction of core metal/resilient layer/lift layer. The elastic layer is preferably formed of a material having high heat resistance such as silicone rubber or fluororubber. The core metal is preferably formed of a metal such as aluminum or iron. The core metal may be either in the shape of a conduit or a solid. The mold release layer is preferably formed of a fluorine tube or a structure to which mold release properties are imparted such as a fluorine-based coating layer.

The heat source 56 may also be a halogen heater. Alternatively, the heat source 56 may be configured to heat the heating member 57 and/or the belt 51 by IH. The following may also be used: the heating member 57 and/or the belt 51 are formed of a resistance heating element and generate heat by themselves.

The recording medium 2 to which the toner image is transferred is conveyed to the fixing nip 50 with the surface to which the toner image is transferred facing the heated belt 51, and passes through the fixing nip 50. The recording medium 2 passing through the fixing nip 50 is pressed and heated by being nipped by the belt 51 and the roller 58. Thereby, the toner image is fixed to the recording medium 2.

Fig. 3 shows a case where the vicinity of the fixing pad 52 is enlarged. In this figure, the recording medium 2 is conveyed from below to above as indicated by

arrows

91, 92, and therefore the lower side is the upstream side and the upper side is the downstream side. The roller 58 is pressed toward the left in fig. 3.

The recording medium 2 fed into the fixing nip 50 is correctly guided to the fixing nip 50 as indicated by an arrow 91. The recording medium 2 having passed through the fixing nip 50 is discharged from the fixing nip 50 as indicated by an arrow 92.

The fixing pad 52 is attached to the support member 54 as described with reference to fig. 4 to 6. Fuser pad 52 has a surface 6. A plurality of recesses 5 are provided in the surface 6. The support member 54 may also be formed of sheet metal. As shown in fig. 4 and 5, the support member 54 is provided with a hole 54a for attaching the fixing pad 52. As shown in fig. 5, a pin (pin)52b is provided on the surface of the fixing pad 52 on the side of the support member 54 in order to attach the fixing pad to the support member 54. By fitting the pin 52b into the hole 54a, the fixing pad 52 can be attached to the support member 54. Fig. 6 is a perspective view showing a state where the mounting is completed. The fixing pad 52 and the support member 54 are combined, and the slide sheet 53 is further sleeved. Thus, the fixing pad assembly 60 shown in fig. 7 is completed. The end of the slide sheet 53 may also enter between the fixing pad 52 and the support member 54.

Fig. 8 shows a state in which the fixing pad 52 is viewed from the front. In the example shown here, the recess 5 is rectangular when viewed from the front. The plurality of recesses 5 are arranged in parallel. Fig. 9 shows a state where a part of the fixing pad 52 is taken out. As shown in fig. 10, the slider 53 is disposed so as to cover the surface 6 of the fixing pad 52. The belt 51 is conveyed in the direction of arrow 90 while being in contact with the slider 53. The conveying direction of the belt 51 and the longitudinal direction of the concave portion 5 are not necessarily perpendicular, but are schematically illustrated in fig. 10 for convenience of explanation. Fig. 10 shows a cross section of the fixing pad 52 and the slider 53 cut along a plane perpendicular to the longitudinal direction of the concave portion 5, together with the belt 51. Since the entrance of the recess 5 is blocked by the slide piece 53, the inside of the recess 5 becomes a space isolated from the outside. That is, a void is generated in the recess 5.

The structure of the image forming apparatus 801 according to the present embodiment can be expressed as follows. The image forming apparatus 801 includes an endless belt 51 that can circulate to convey the recording medium 2 from upstream to downstream, a fixing pad 52 that presses the belt from inside the belt 51 at least toward the 1 st side 95, a slide sheet 53 disposed between the belt 51 and the fixing pad 52, a support member 54 that supports the fixing pad 52 from the side opposite to the belt 51, and a roller 58, wherein the roller 58 and the fixing pad 52 sandwich the slide sheet 53 and the belt 51, and the fixing pad 52 has a plurality of recesses 5 on the surface on the roller 58 side.

In the present embodiment, as shown in fig. 10, the fixing pad 52 is covered with the slide sheet 53, and the concave portion 5 is a closed space, so that the heat insulation property can be improved. In the case of the conventional art, there is a problem that heat is transferred from the belt 51 to the fixing pad 52 via the sliding piece 53 and further to the supporting member 54, but the heat insulation property in the vicinity of the surface of the fixing pad 52 is improved by the recess 5 provided as a closed space, and as a result, heat transfer from the belt 51 to the supporting member 54 is suppressed. This can improve energy saving performance. That is, it is possible to provide an image forming apparatus that can reduce the extent to which the thermal energy supplied to the belt in the fixing device is wasted in a useless form.

Since the recessed portion 5 of the fixing pad 52 is closed by the slide piece 53, grease, wear debris, and the like can be prevented from entering the recessed portion 5, and durability is also excellent.

In the example shown in fig. 10, the bottom of the recess 5 is a plane parallel to the surface 6, but the shape of the inside of the recess 5 is not limited to such a shape. For example, as shown in fig. 11, the bottom of the recess 5 may be curved.

Different examples are shown. For example, in the example shown in fig. 12, the concave portion has a V shape, and the convex portion is also pointed. Even such a shape of the fixing pad 52 can obtain a substantial effect, but is not preferable. In this case, since the slide sheet 53 is in point contact with the fixing pad 52, the slide sheet 53 itself has a shape in which irregularities are repeated along the shape of the fixing pad 52. In this case, the belt 51 is also formed in a shape having repeated irregularities by the irregularities of the slider 53. Thereby, the pressure distribution in the fixing nip 50 becomes uneven. Thus, fixing noise may occur. The "fixing noise" referred to herein includes, for example, a defect that a toner unfixed region partially remains in an image or that uneven gloss is expressed due to insufficient toner fixation.

In order to prevent such a defect, as shown in fig. 13, the surface 6, which is the upper surface of the convex portion, is preferably left as a flat surface. In this case, the slide piece 53 comes into contact with the surface 6, so that the slide piece 53 is relatively flat, and the belt 51 coming into contact with the slide piece 53 is conveyed in a relatively flat state, whereby the pressure distribution in the fixing nip 50 can be made as uniform as possible.

The plurality of recesses 5 are preferably arranged as follows: when any straight line from the upstream to the downstream is assumed on the surface of the fixing pad 52 on the roller 58 side, the arbitrary straight line passes through a portion other than the concave portion at least once regardless of where the arbitrary straight line is provided. This will be described with reference to fig. 14 to 16. Fig. 14 to 16 are views of the surface of the fixing pad 52 on the roller 58 side from the front.

For example, in a fixing pad 52z shown in fig. 14, each of the plurality of recesses 5 is arranged so that a direction parallel to the paper feeding direction is a longitudinal direction. When the plurality of concave portions 5 are arranged in this manner, the number of times and the length of the portion other than the concave portion is passed through by the arrow 81 and the arrow 82 in the fixing nip portion 50 are greatly different. At arrow 81, the sheet passes through the concave portion 5 all the time while passing through the fixing nip portion 50, and does not pass through a portion other than the concave portion at one time. On the other hand, the portion other than the recess is always passed through while passing through the fixing nip 50 at the arrow 82. In this way, the number of times and the length of the

arrows

81 and 82 passing through the portion other than the recessed portion are greatly different, which causes the degree of fixing to be non-uniform, and hence fixing noise is likely to occur, which is not preferable.

For example, in the fixing pad 52 shown in fig. 15, each of the plurality of recesses 5 is arranged so that a direction intersecting at an angle of 45 ° with respect to the paper feeding direction is a longitudinal direction. If a plurality of concave portions 5 are arranged in this way, the fixing nip portion 50 passes through the concave portions 5 and also passes through a portion other than the concave portion as indicated by an arrow 81. The recess 5 is inevitably passed more than 1 time even if the position of the arrow 81 is appropriately shifted to the left and right. In this case, the fixing degree becomes substantially uniform at any position in the longitudinal direction of the fixing pad, and the fixing noise can be prevented from occurring.

For example, in a fixing pad 52i shown in fig. 16, each of the plurality of recesses 5 is arranged so that a direction intersecting at an angle of about 20 ° with respect to the paper feeding direction is a vertical direction. In the fixing pad 52i, the plurality of recesses 5 are not rectangular but S-shaped. The recess 5 may also be of such a shape. In this case, as indicated by arrow 81, the sheet passes through the recessed portion 5 while passing through the fixing nip portion 50, and also passes through a portion other than the recessed portion. The recess 5 is inevitably passed more than 1 time even if the position of the arrow 81 is appropriately shifted to the left and right. In this case as well, the fixing noise can be prevented from occurring as in the example of fig. 15.

In fig. 15 to 16, each of the plurality of recesses 5 is groove-shaped, but is not limited to groove-shaped, and may be point-shaped. For example, in a fixing pad 52j shown in fig. 17, each of the plurality of concave portions 5 has a rectangular dot shape. The quadrangle referred to herein may also be a rhombus, for example. In this case, if attention is paid to the arrow 81, the sheet passes through the concave portion 5 and also passes through a portion other than the concave portion while passing through the fixing nip portion 50. When the position of the arrow 81 is appropriately shifted to the left and right, or when the

arrows

82, 83, 84, and 85 are assumed, the recess 5 is inevitably passed 1 or more times. In this case, the fixing noise can be prevented from occurring.

In the fixing pad 52k shown in fig. 18, each of the plurality of recesses 5 is circular. In this case, if attention is paid to the arrow 81, the sheet passes through the concave portion 5 and also passes through a portion other than the concave portion while passing through the fixing nip portion 50. In this case, the fixing noise can be prevented from occurring.

However, in the examples shown in fig. 17 and 18, among arrows 81 to 85, the distance passing through the recess 5 is long because 3 recesses 5 pass through the

arrows

81 and 85, and the distance passing through the recess 5 is short because 2 recesses 5 pass through the arrow 83. Since there is no portion crossing the recess 5 in the

arrows

82 and 84, there is almost no distance passing through the recess 5. Conversely, the distance across the surface 6, which is not the location of the recess 5, can be said to be longer in the

arrows

82, 84, shorter in the arrow 83, and shorter in the

arrows

82, 84. When such a difference is present, a difference may occur in the degree of fixing depending on the place. When the plurality of concave portions 5 are provided in a dot shape, it is preferable that the plurality of concave portions are arranged so that the difference in distance between the concave portions and the surface 6 is as small as possible. A fixing pad such as fixing pad 52m shown in fig. 19 is preferable. In the fixing pad 52m, each of the plurality of concave portions 5 is circular, and the number of concave portions 5 arranged in the paper feeding direction is equal at any position. In the fixing pad 52k shown in fig. 18, the locations where 3 recesses 5 are arranged and the locations where 2 recesses 5 are arranged are alternately arranged, but in the fixing pad 52m shown in fig. 19, 3 recesses 5 are arranged at any position in the paper feeding direction. In this way, since 3 recesses 5 are passed through at

least arrows

81, 83, and 85 at any position, the difference in distance passing through surface 6 can be reduced.

In a region where the nip pressure during the nip operation is the maximum, the fixing strength is determined, and therefore, it is preferable that no concave portion is disposed in the region. In other words, it is preferable that the plurality of concave portions 5 are disposed so as to avoid a position where the pressure distribution in the area where the roller 58 and the belt are in close contact is maximum. For example, as shown in fig. 20, when paper is fed along arrow 97 in a state where roller 58 is in contact with fixing pad 52n having a simple shape, concave portion 5 is disposed in fixing pad 52n avoiding maximum pressure position 9 as shown in fig. 21. In this example, since the fixing pad 52n has a substantially symmetrical shape on both the inlet side and the outlet side, the maximum pressure position 9 is also near the center. At the maximum pressure position 9, the recess 5 is not arranged but the surface 6 is arranged. At the maximum pressure position 9, the surface 6 extends horizontally straight.

As shown in fig. 22, in the case of the fixing pad 52r having a shape in which the outlet side protrudes more than the inlet side, the maximum pressure position 9 is located close to the outlet. In this case, as shown in fig. 23, the concave portion 5 is disposed in the gasket member 52r so as to avoid the maximum pressure position 9 located close to the outlet.

Fig. 24 shows a state where a cross section of the slide sheet 53 is enlarged, the slide sheet 53 has a surface 53a and a surface 53b, the surface 53b has irregularities, the surface 53a is a surface against which the belt 51 rubs, the surface 53b is a surface against which the fixing pad 52 abuts, the surface 53b of the slide sheet 53 on the fixing pad 52 side has irregularities, and the width of each of the plurality of concave portions 5 provided to the fixing pad 52 is preferably smaller than the width of a convex portion included in the irregularities of the slide sheet 53, which will be described with reference to fig. 25 to 26, the width of each of the plurality of concave portions 5 provided to the fixing pad 52 is L1, the width of a convex portion included in the irregularities of the slide sheet 53 is L2, in the example shown in fig. 25, L1 > L2, in this example, the convex portion of the slide sheet 53 enters the concave portion 5 of the slide sheet 53 at the positions G1, G2, G3, G4, and if this is achieved, a pressure necessary for fixing is not applied, and a defective gloss is locally generated.

In the example shown in fig. 26, L1 < L2, in this example, the convex portion of the slider 53 does not enter the concave portion 5 of the slider 53 at any position.

The slide piece 53 may be a cloth-like sheet member obtained by fluorine coating glass fibers. The thickness of the slider 53 may be 120 μm, for example.

For example, when the weaving cycle of the slide piece 53 is set to 1.2mm pitch, the width of the convex portion becomes 0.6 mm. In this case, when the width of the concave portion 5 of the fixing pad 52 is 0.9mm, the entrance into the concave portion 5 occurs.

Even if the weaving cycle of the slide sheet 53 is 1.2mm pitch, if the width of the concave portion 5 of the fixing pad 52 is 0.4mm, the width is smaller than the width of the convex portion by 0.6mm, and therefore, the entry into the concave portion 5 does not occur.

(experiment)

Regardless of whether there is an irregularity on the surface of the slide sheet 53, if the width of the concave portion 5 of the fixing pad 52 is too wide, the slide sheet 53 may be locally depressed. An experiment for verifying the relationship between the width of the concave portion 5 and the thickness of the slide piece 53 will be described.

A structure in which a plurality of recesses 5 are provided on the surface of the fixing pad 52 is prepared. The plurality of concave portions 5 are arranged so that a direction inclined by 45 ° with respect to the paper feeding direction becomes a longitudinal direction.

As the slide piece 53, the slide pieces under the conditions shown in table 1 were used.

[ Table 1]

Using an image forming apparatus including a fixing device including the fixing pad 52 and the slide sheet 53, a 3-color superimposed solid image was printed on plain paper, and the glossiness of the fixed image was measured and evaluated.

As shown in table 2, experiments were performed while varying the width of the concave portion 5 from 0.4mm to 1.4mm every 0.2 mm.

[ Table 2]

Fig. 27 shows the experimental results. As shown in the graph, it is understood that if the width of the concave portion 5 is less than 1.0mm, an extreme decrease in glossiness is not observed. The arrow 88 is generally horizontal and indicates little change in gloss. However, when the width of the concave portion 5 is 1.0mm or more, the glossiness is drastically reduced as indicated by an arrow 89. That is, fixing failure occurs. In this experiment, the thickness of the slide sheet 53 was 200 μm, and 1.0mm, which is the upper limit of the condition that the glossiness was not extremely decreased, was 5 times the thickness of the slide sheet 53.

From the above, it is preferable that the width of each of the plurality of recesses 5 provided in the fixing pad 52 is less than 5 times the thickness of the slide sheet 53.

This point will be described with reference to fig. 28 to 30.

In fig. 28, the fixing pad 52 was modeled as being pressed while overlapping the slider 53 and the recording medium 2, the width of the concave portion 5 was L, and the load W was applied to the slider 53 above the concave portion 5, and as shown in fig. 29, the amount of bending of the slider 53 in the concave portion 5 at this time was W L³W is the load, L is the length of the beam, E is the longitudinal modulus of elasticity, I is the moment of inertia in section, which can be calculated assuming the sectional shape of the beam as shown in fig. 30, h is the width of the beam when viewed in section, b is the height, h/2 is the height, E the amount of flexure of the slider 53 is proportional to the cube of the length L of the beam, i.e., the cube of the width of the recess 5, on the other hand, the amount of flexure of the slider 53 is inversely proportional to the cube of the thickness h of the slider 53, and therefore, if L/h is held constant, the amount of flexure of the slider 53 becomes a constant value.

From this conclusion, it is understood that if the width of each of the plurality of concave portions 5 provided in the fixing pad 52 is less than 5 times the thickness of the slide sheet 53 as described above, the amount of bending of the slide sheet 53 should be able to maintain a good value.

Further, a plurality of the above embodiments may be combined as appropriate.

The above embodiments disclosed herein are merely illustrative and not restrictive in all respects. The scope of the present invention is indicated by the appended claims, and includes all changes that come within the meaning and range of equivalency of the claims.

While the embodiments of the present invention have been described, it should be understood that the embodiments disclosed herein are illustrative only and not restrictive in all respects. The scope of the present invention is indicated by the claims, and is intended to include all changes which come within the meaning and range of equivalency of the claims.

Claims

1. An image forming apparatus includes:

an endless belt that can be circulated to convey a recording medium from upstream to downstream;

a fixing pad pressing the belt from an inner side of the belt at least toward a 1 st side;

a slider disposed between the belt and the fixing pad;

a supporting member supporting the fixing pad from a side opposite to the belt; and

the roll(s) are (are) rolled,

the roller and the fixing pad nip the slide sheet and the belt,

the fixing pad has a plurality of recesses on a surface on the roller side.

2. The image forming apparatus according to claim 1,

the plurality of recesses are arranged so that, when an arbitrary straight line is assumed on the surface of the fixing pad on the roller side from the upstream to the downstream, the arbitrary straight line passes through a portion other than the recess at least once regardless of the setting of the arbitrary straight line.

3. The image forming apparatus according to claim 1 or 2,

the plurality of concave portions are disposed so as to avoid a position where pressure distribution in a region where the roller and the belt are in close contact with each other is maximum.

4. The image forming apparatus according to any one of claims 1 to 3,

the fixing pad side surface of the slide sheet has irregularities, and the plurality of concave portions provided to the fixing pad each have a width smaller than a width of a convex portion included in the irregularities of the slide sheet.

5. The image forming apparatus according to any one of claims 1 to 4,

the width of each of the plurality of recesses provided to the fixing pad is less than 5 times the thickness of the slider.