JP3581588B2 - Sheet material transport device and image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is a sheet material conveying device that sandwiches and conveys a sheet material by two or more opposing rollers, and enables adjustment of a nip force without breaking a conveying speed, and furthermore, the plurality of rollers can be integrally attached and detached. And an image forming apparatus including the same.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, particularly in an image forming apparatus having an electrophotographic recording means, a fixing device for applying heat and pressure to a sheet material as a recording medium is provided. FIG. 19 shows a first example of a conventional fixing device. In FIG. 19, the fixing device 100 has a casing 101 in which a main roller 102 and a nip roller 104 are housed.
[0003]
The main roller 102 is driven to rotate by driving means (not shown), and has a heater 103 inside to heat the sheet material S. The nip roller 104 is pressed against the main roller 102 by a pressing unit 105, is rotatably supported, and follows the drive of the main roller 102. At least one of the main roller 102 and the nip roller 104 has a soft material surface layer, and the sheet material S is nipped and conveyed by these nips.
[0004]
Forming a larger nip width improves the efficiency of heat transfer to the sheet material S. Therefore, conventionally, a large pressing force has been applied to the nip roller 104. However, if a large amount of pressure is applied to the roller pair, mechanical deformation occurs in the roller itself, so that stable roller rotation is not performed, and unevenness occurs in the transport speed of the sheet material S. This uneven conveyance speed causes fixing unevenness on the surface of the sheet material in the form of a change in supplied heat energy, and as a result, the quality of a recorded image may be deteriorated.
[0005]
Therefore, conventionally, a fixing device 106 as shown in FIG. 20 has been provided in order to prevent the roller from being deformed by the pressing force and to form a predetermined nip width without applying an excessive load to the roller. The fixing device 106 of the second conventional example has two nip rollers 104 as compared with the first conventional example, each of which is pressed against the main roller 102 by the pressing means 105, and the two nip portions are Is formed.
[0006]
With this configuration, it is possible to reduce the pressing force per nip roller 104 and generate a larger nip width. Therefore, although it is effective to reduce the mechanical deformation of the roller, it is necessary to adjust the two pressing means 105 at the same time.
[0007]
[Problems to be solved by the invention]
In general, when a sheet material is conveyed by a pair of rollers facing each other, it has been experimentally confirmed that the true conveyance amount of the sheet material is different from the conveyance amount calculated from the main roller diameter and the rotation speed. Roller pressure, the main roller surface shape deformed by pressurization, the main roller hardness, sheet material hardness, the frictional resistance between the roller and the sheet material, and many other factors. By specifying the roller material (mainly hardness),
(Conveyance amount calculated from roller rotation speed) ≤ (True conveyance amount)
There is a characteristic. This property is treated as a well-known case, and many model analyzes have been made.
[0008]
For example, in the Journal of the Rubber Society of Japan, Vol. 62, No. 11, 1989, "Paper Feeder and Rubber Material" by Masataka Kawauchi, a report on this property is made as follows.
[0009]
The relationship between the load and the amount of deformation of the rubber roller is determined from the constant volume property of the rubber, and the transport error of the sheet material is calculated based on the relationship. Under the condition that no slip occurs between the roller and the sheet material, a combination of a rubber roller and a rigid roller is considered, and a transport error amount is obtained as a difference between the respective rotation amounts.
[0010]
FIG. 21 shows the analysis model. Assuming that the radius of the rubber roller 107 before deformation is r0, the thickness of the rubber portion 107a of the rubber roller 107 is b, the nip width is h, and the volume of the rubber portion 107a removed by the rigid roller 108 is ΔV, the virtual radius of the rubber roller 107 R the following equation ^{R = {r0 2 (1 +} △ V / hb)} 1/2
Can be represented by The nip width and the volume ΔV are corrected and calculated with a certain correction coefficient.
[0011]
FIG. 22 shows the relationship between the pressing force W and the rotational speed error (ratio), that is, (R-r0) / r0. Here, (I) shows a calculation result obtained from the ratio of the excluded rubber volume ΔV to the volume of the deformation region. (II) is a result obtained from the ratio of the circumference of the rigid roller to the circumference of the rubber roller in the nip portion. The circles indicate the experimental values, and it can be seen that the calculation method of (I) agrees very well with the actual one.
[0012]
Further, FIG. 23 shows the result of calculating the deformation amount δ of the rubber roller 107 and the rotational speed error (ratio), and it can be seen that the experimental result and the calculation result are consistent with each other. Thus, the transport (rotation speed) error is (transport (rotation speed) error) = (conveyance amount calculated from roller rotation speed) − (true transport amount)
It is represented by This property is actually a problem of the physical properties of rubber, the physical properties of the sheet material, and the contact points between the rubber and the sheet material: for example, the mechanism of friction transport, the rubber material such as sliding phenomenon, and the mechanical system dynamics are difficult to mix. It is a problem.
[0013]
Accordingly, in the second conventional example shown in FIG. 20, the roller material for the sheet material S to be conveyed is selected in consideration of the magnitude comparison between the roller rotation amount and the sheet material conveyance amount described above, and the roller material is further conveyed with respect to the sheet material conveyance amount. The balance of each pressurizing means 105 must be adjusted so as to satisfy the condition that the downstream side becomes faster at the nip portion located upstream / downstream of the road. If the adjustment is not properly performed, the magnitude relationship of the transport amount of the sheet material S is reversed between the two nips as shown in the figure, that is, the upstream side becomes faster, causing a jam.
[0014]
In view of the above, the present invention takes into account the condition that when the deformation amount δ increases (the pressing force W increases) as an error characteristic of the sheet conveying means constituted by the roller pair, a conveying (rotational speed) error also occurs by several percent. Provided is a sheet material transport device including a plurality of low pressure roller pairs and capable of adjusting the pressure without deteriorating the magnitude relationship (that is, the pressure balance) of the transport speed of each roller pair, and an image forming apparatus having the same. It is intended to be.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, a typical configuration of the sheet conveying apparatus and the image forming apparatus according to the present invention includes a main roller, a plurality of sub-rollers opposed to the main roller, the main roller and the plurality of sub-rollers. Roller unit means integrated by coupling means for movably supporting the auxiliary roller in the separating direction, pressure means for pressing the shaft part of the main roller, and shaft parts of the plurality of sub rollers And a case means comprising a connecting means, wherein the case means houses the roller pair unit means by connecting the pressing means and the supporting means by the connecting means. In addition to the above, the auxiliary roller on the downstream side of the main roller in the sheet material conveyance direction is configured to be pressed with a larger force than the auxiliary roller on the upstream side .
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
[First embodiment]
A first embodiment of a sheet conveying apparatus and an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a view showing a sheet conveying apparatus according to the present embodiment, FIG. 2 is a detailed view showing the structure of the sheet conveying apparatus, FIG. 3 is a view for explaining the structure of a roller, and FIG. FIG. 5 is a top view illustrating the link means, FIG. 6 is a view illustrating the distribution of the pressing force of the sheet conveying device, and FIG. 7 is a view illustrating the sheet conveying state by the sheet conveying means. FIG. 8 is a diagram illustrating a problem that occurs in a configuration that does not satisfy the present invention, FIG. 9 is a diagram illustrating a relationship between a pressing force and a conveying speed, and FIG. 10 is an overall configuration diagram of the image forming apparatus.
(overall structure)
The image forming apparatus 1 shown in FIG. 10 forms an image based on an image signal sent from a not-shown host computer or the like. First, the sheet material S stacked on the sheet cassette 2 is picked up by the feeding roller 3, and is conveyed to the recording unit by the conveying roller pair 4a. The sheet material S has a multilayer structure having a surface coat layer permeable to ink in an initial state and a holding layer capable of absorbing and holding ink under the surface coat layer. The surface coat layer is smoothed by heating the surface coat layer. It is configured to protect a person
[0017]
The recording unit is provided with an ink jet recording unit 5 which is an image forming unit. The ink jet recording means 4 is capable of reciprocating along a shaft 6 in a direction (main scanning direction) orthogonal to the transport direction, and can record an image by discharging ink from a recording head 5a. Then, the image is recorded on the entire surface of the sheet material by intermittently conveying (sub-scanning direction) the image by the conveying roller pairs 4a and 4b. A platen 7 is provided below the recording head 5a, and is configured to secure the flat surface of the sheet material S.
[0018]
A fixing device 8 as a sheet conveying means is provided downstream of the ink jet recording means 5, and details thereof will be described later. By applying heat and pressure by the fixing device 8, the coating layer of the sheet material S is melted and smoothed, the holding layer is protected, and the evaporation of the ink is promoted to secure the fixing. it can. The sheet material S that has passed through the fixing device 8 is discharged out of the apparatus by a discharge roller pair 9.
[0019]
The sheet conveying apparatus according to the present invention has versatility when a sheet material is heated and conveyed, and is not limited to dissolving a coat layer on the sheet material surface together with the ink jet recording means.
(Sheet conveying device)
As shown in FIG. 1, the fixing device 8 as the sheet conveying device according to the present embodiment is configured by housing a roller unit 16 in a unit case 10 as a case unit. Hereinafter, each will be described.
[0020]
The roller unit 16 has a main roller 17 as one main roller and a nip roller 18 as two sub rollers, and these are connected by four links 19. As shown in FIG. 3, these rollers have an outer periphery of an aluminum roller covered with a soft silicone resin. In the present embodiment, the surface thickness t of the main roller 17 is about 3 mm, the surface thickness t of the nip roller 18 is 1 mm, and the respective surface hardnesses are 60 ° and 80 °.
[0021]
As shown in FIG. 4A, the link 19 has a round hole 19a at one end and a long hole 19b at the other end. Then, as shown in FIG. 4B, by connecting the shaft portion 17a of the main roller to the round hole 19a and connecting the shaft portion of the nip roller 18 to the long hole 19b, the two nip rollers 18 are connected to the main roller 17. It has an integral structure that can be separated from and connected to the main roller 17 and can perform planetary motion independently about the main roller 17. As shown in FIG. 5, a bearing 20 is attached to the end of the shaft portion 17a of the main roller, and the round holes 19a of the two links 19 are fitted through the bearing 20. Similarly, a bearing 21 is attached to the end of the shaft portion 18a of the nip roller, and the elongated hole 19b of the link 19 is fitted through the bearing 21.
[0022]
The unit case 10 is composed of an upper case 10a and a lower case 10b as shown in FIG. 2, and these are connected to be openable and closable by a rotation supporting dowel 11, and are closed by a pressing screw 12 as a connecting means to fix the roller unit 16 to a predetermined position. It is fixedly held in the state. A heater 22 for heating the main roller 17 is supported on the unit case 10 by support means (not shown).
[0023]
The upper case 10a is provided with a pressing portion 13 as a pressing means for pressing the shaft portion 17a of the main roller, while the lower case 10b is formed with a concave corner portion 14 as a supporting means for receiving the shaft portion 18a of the nip roller. Are formed. The pressing unit 13 is formed at a predetermined angle θ at the downstream side, and presses the shaft unit 17a of the main roller by contacting the shaft unit 17a. A guide plate 15 is provided at substantially the center of the two corners 14, and guides the conveyed sheet material S to the nip on the downstream side.
[0024]
The roller unit 16 is inserted by rotating the two nip rollers 18 to the lower case 10b side and closing the upper case 10a to press the main roller 17 so that the nip is formed between the main roller 17 and the two nip rollers 18 respectively. It is formed. In this state, a driving force is transmitted from a driving unit (not shown) to the main roller 17, and the two nip rollers 18 follow the driving force. By integrally attaching and detaching the roller pair as described above, the assembling work can be simplified.
[0025]
Further, since the pressing portion 13 is inclined by the predetermined angle θ, the shaft portion 17a of the main roller receives the pressing force inclined downstream as shown in FIG. That is, the nip force on the downstream side is greater.
[0026]
Here, as described in the conventional example, in the nipping conveyance by the nip of the roller pair, a conveyance error occurs according to the pressing force. For example, in the configuration of the roller pair used in the present embodiment, it has been experimentally confirmed that when a pressure of 40 kgf is applied, a sheet conveyance error of about 3% occurs. As shown in FIG. 9, this tendency is such that as the pressing force increases, the transport error increases, and the actual sheet material transport speed becomes higher than the transport speed based on the roller rotation amount.
[0027]
Therefore, assuming that the pressing unit 13 does not have the predetermined angle θ as shown in FIG. 8, V1 and V2 may be equal or the upstream conveyance speed V2 may be higher. In this case, the sheet material S is compressed between the two nips to cause buckling, which may cause a jam.
[0028]
However, since the pressure applied to the nip roller 18 on the downstream side is higher due to the above configuration, it is possible to guarantee that the transport speed V1 of the downstream nip is faster than the transport speed V2 of the upstream nip.
[Second embodiment]
Next, a second embodiment of the sheet conveying apparatus according to the present invention will be described with reference to the drawings. FIG. 11 and FIG. 12 are configuration diagrams illustrating the sheet conveying apparatus according to the present embodiment. The same reference numerals are given to the same portions as those in the first embodiment, and the description is omitted.
[0029]
In the first embodiment, the pressing unit 13 has a configuration in which a part of the upper case 10a is simply provided with an inclination. However, the distribution of the pressing force of the two nip rollers 18 is substantially determined by the inclination angle, and a predetermined distribution of the pressing force may not be maintained due to wear due to use.
[0030]
Therefore, in the fixing device 8 according to the present embodiment, as shown in FIG. 11, a pressing member 23 separate from the upper case 10a is provided as a pressing unit instead of the pressing unit 13. The pressing member 23 has an arc-shaped slit 23a, and the slit 23a is attached to the upper case 10a by a fastening member 24. Therefore, by loosening the fastening member 24, it is possible to rotate around the shaft portion 17a of the main roller, and it is possible to adjust the angle of contact with the shaft portion 17a of the main roller.
[0031]
Further, as shown in FIG. 12, the pressing member 23 is slidably supported using locking means 25 instead of the fastening member 24, and the contact angle is adjusted using the pressing member driving means 26. May be. As a result, the contact angle can be mechanically and electrically adjusted and controlled, and it is possible to always maintain an optimal distribution of the pressing force.
[Third embodiment]
Next, a third embodiment of the sheet conveying apparatus according to the present invention will be described with reference to the drawings. FIG. 13 and FIG. 14 are configuration diagrams illustrating the sheet conveying apparatus according to the present embodiment. Parts that are the same as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0032]
In the first embodiment, the upper case 10a and the lower case 10b are simply fixed and held by the pressing screw 12 as the connecting means. However, the pressing force between the main roller 17 and the nip roller 18 is determined solely by the positional relationship between the upper case 10a and the lower case 10b.
[0033]
Therefore, as shown in FIG. 13, in the present embodiment, a gap 10 c is provided between the upper case 10 a and the lower case 10 b at the pressure screw 12 and the main roller 17 is changed by changing the fastening force of the pressure screw 12. The pressure between the nip roller 18 and the nip roller 18 can be adjusted. Even when the pressing force of the pressing unit 13 is increased or decreased in this way, since the pressing unit 13 is formed with the predetermined angle θ, the distribution that the pressing force of the downstream nip is always higher than that of the upstream nip. Can be maintained, and the pressure can be adjusted without breaking the pressure balance. Therefore, similarly to the first embodiment, it is possible to guarantee that the transport speed V1 of the downstream nip is faster than the transport speed V2 of the upstream nip.
[0034]
Further, as shown in FIG. 14, a drive connection means 27 may be arranged in place of the pressure screw 12 so that the pressure can be adjusted. As a result, the pressing force can be adjusted and controlled mechanically and electrically, and an optimum pressing force can always be obtained.
[Other embodiments]
Further, the pressure means and the connection means shown in the second or third embodiment may be arbitrarily combined. That is, FIG. 15 shows an example in which the upper case 10a and the separate pressing member 23 are provided and a gap 10c is formed between the upper case 10a and the lower case 10b. Similarly, FIG. 17 shows an example in which the pressing member driving means 26 and the gap 10c are provided, and FIG. 18 shows an example in which the pressing member driving means 26 and the driving connecting means 27 are used. With such a configuration, it is possible to easily or automatically adjust the pressing force and the distribution thereof.
[0035]
【The invention's effect】
As described above, in the sheet transporting apparatus and the image forming apparatus according to the present invention, the main roller and the plurality of sub-rollers are integrally formed by the coupling means , so that the detaching and mounting of the main roller and the plurality of sub-rollers are facilitated, and the assembling is facilitated. Simplify.
[0036]
In addition, since the pressure distribution of the plurality of sub-rollers to the main roller is determined by the angle of the pressure means provided in the case means, the distribution of the pressing force can be set easily and reliably, and the occurrence of a jam is reduced. Can be suppressed.
[0037]
Further, with this configuration, even when the pressing force is adjustable, the distribution of the pressing force can be necessarily maintained, that is, the transport speed relationship between the two nips is not broken.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a sheet conveying apparatus according to a first embodiment.
FIG. 2 is a detailed diagram illustrating a configuration of a sheet conveying device.
FIG. 3 is a diagram illustrating a configuration of a roller.
FIG. 4 is a side view illustrating a link means between a main roller and a sub roller.
FIG. 5 is a top view illustrating a link unit.
FIG. 6 is a diagram illustrating distribution of a pressing force of the sheet conveying device.
FIG. 7 is a diagram illustrating a sheet conveyance state by a sheet conveyance unit.
FIG. 8 is a diagram illustrating a problem that occurs in a configuration that does not satisfy the present invention.
FIG. 9 is a diagram illustrating a relationship between a pressing force and a transport speed.
FIG. 10 is an overall configuration diagram of an image forming apparatus.
FIG. 11 is a configuration diagram illustrating a sheet conveying apparatus according to a second embodiment.
FIG. 12 is a configuration diagram illustrating a sheet conveying apparatus according to a second embodiment.
FIG. 13 is a configuration diagram illustrating a sheet conveyance device according to a third embodiment.
FIG. 14 is a configuration diagram illustrating a sheet conveying device according to a third embodiment.
FIG. 15 is a diagram illustrating another embodiment of the sheet conveying apparatus according to the present invention.
FIG. 16 is a diagram illustrating another embodiment of the sheet conveying apparatus according to the present invention.
FIG. 17 is a diagram illustrating another embodiment of the sheet conveying apparatus according to the present invention.
FIG. 18 is a diagram illustrating another embodiment of the sheet conveying apparatus according to the present invention.
FIG. 19 is a diagram illustrating a first conventional example of a sheet conveying apparatus.
FIG. 20 is a diagram illustrating a second conventional example of a sheet conveying apparatus.
FIG. 21 is a diagram illustrating an analysis model of a rubber roller and a rigid roller.
FIG. 22 is a diagram for explaining a relationship between a pressing load and a rotational speed error (ratio).
FIG. 23 is a diagram illustrating the relationship between the amount of deformation of a rubber roller and a rotational speed error (ratio).
[Explanation of symbols]
S: sheet material 1: image forming apparatus 2: sheet cassette 3: feeding roller 4a: transport roller pair 5: ink jet recording means 5a: recording head 6: shaft 7: platen 8: fixing device 9: discharge roller pair 10: unit Case 10a ... Upper case 10b ... Lower case 10c ... Gap 11 ... Rotation support dowel 12 ... Pressure screw 13 ... Pressure section 14 ... Corner 15 ... Guide plate 16 ... Roller unit 17 ... Main roller 17a ... Shaft section 18 ... Nip roller 18a ... shaft part 19 ... link 19a ... round hole 19b ... elongated hole 20 ... bearing 21 ... bearing 22 ... heater 23 ... pressing member 23a ... slit 24 ... fastening member 25 ... locking means 26 ... pressing member driving means 27 ... Drive coupling means

Claims (8)

A main roller,
A plurality of sub-rollers opposed to the main roller;
Roller-to-unit means integrated by coupling means for supporting the main roller and the plurality of sub-rollers so as to be movable in a separating direction,
Pressing means for pressing the shaft of the main roller,
Support means for supporting shaft portions of the plurality of sub-rollers,
And a case means comprising a connecting means,
The case means can store the roller pair unit means by connecting the pressurizing means and the support means by the connecting means, and the auxiliary means on the downstream side in the sheet material conveyance direction with respect to the main roller . A sheet conveying device, wherein a roller is configured to be pressed with a larger force than an upstream sub-roller . The pressing unit has a pressing unit that presses against the shaft of the main roller, and the pressing unit is formed to be inclined to the downstream side to convey the sheet material to the main roller. 2. The sheet conveying apparatus according to claim 1, wherein the auxiliary roller on the downstream side in the direction is configured to be pressed with a larger force than the auxiliary roller on the upstream side . 3. The case means is configured such that the nip amount due to the pressurization of the main roller and the plurality of sub-rollers is such that the sub-roller on the downstream side in the sheet material conveyance direction is formed larger than the sub-roller on the upstream side . 3. The sheet conveying apparatus according to claim 1, wherein a shaft portion and a shaft portion of the plurality of sub-rollers are held. The coupling unit is a link unit, and one end of both ends of the link unit is coupled to the shaft of the main roller, and the other end is coupled to the shaft of each of the plurality of sub-rollers. The sheet conveying device according to claim 1, wherein the sheet conveying device is configured to be capable of planetary movement about a main roller. 5. The sheet conveying apparatus according to claim 1, wherein the supporting means for supporting the shaft of the sub-roller is a concave corner formed in the case means. The distribution of the pressing force between the main roller and the plurality of sub-rollers can be adjusted by changing the contact angle of the pressing unit with respect to the shaft of the main roller. The sheet conveying device according to any one of claims 1 to 5. The sheet according to any one of claims 1 to 6, wherein the pressing force between the main roller and the plurality of sub-rollers can be adjusted by changing a fastening force of the connecting unit. Transport device. A sheet conveying device according to any one of claims 1 to 7,
An image forming apparatus comprising: an image forming unit.

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