JPS58137866A - Fixing device - Google Patents

Abstract

PURPOSE:To obtain a small, lightweight fixing device excellent in durability and strength by supporting small diameter journals formed on both ends of large diameter paper passing part of a pair of fixing rolls by ball bearings. CONSTITUTION:Small diameter journals formed on both ends of large diameter paper passing parts 10a, 11a of a pair of fixing rolls 10, 11 are supported to housings 14, 15 by ball bearings 12, 13. Even when small bearings 12, 13 are used, they can bear large pressure applied to the rollers 10, 11. Accordingly, the diameter D of the paper passing part can be made smaller than conventional ones. Thus, a small lightweight fixing device excellent in durability and strength is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device which is applied to image forming apparatuses such as copying machines and electrostatic recording machines and which fixes unfixed toner particles on a sheet.

Hereinafter, a pressure fixing device will be described as an example. Figure 1 shows a conventional pressure fixing device, which includes a pair of pressure fixing rollers (
Hereinafter, simply referred to as ■-ra) 1 and 2 are paper passing portions 1a and 2a with a large diameter D0 and journal portions 1b and 1b with a small diameter D□ formed at both ends thereof, respectively.

2b, 2b. Each of the rollers 1@2 is equipped with large ball bearings 3 and 4 that can withstand the large pressure applied to the rollers by a pressing mechanism (not shown) in its journal portions 1b, 1b, 2b, 2bK, and holds the outer periphery of the ball bearings. The housings 5 and 6 are rotatably attached to the housings 5 and 6.

In the above case, the large diameter dimensions of rollers 1 and 2. Considering the outer diameter D2 of the ball bearings 3 and 4, the wall thickness of the housings 5 and 6 that hold the bearings, and the dimensional margin α of each part.

D6 wealth is determined by D2 + t + α ore. Therefore, the large diameter dimension D0 was unnecessarily large in terms of strength and durability. (The pressure fixing device is large and heavy due to the large size and weight of the pressure fixing device.) Image forming apparatuses that use this device are becoming larger, and the pressure fixing device has to be mounted on one side heavier than the other. Therefore, in order to reduce the size of the pressure fixing device, it has been considered that the bearing parts should be inserted into each other as shown in Figure 2, but in reality it is difficult to apply large pressure. In the case of pressure fixing, it is not preferable to lengthen the shaft portion 1c that connects the paper passing section 11 and the front journal section 1b, as in Row 21, since a large moment is applied to the shaft portion 1c, which is undesirable in terms of durability and strength. .

The present invention has been proposed in view of the above, and an object of the present invention is to obtain a fixing device that is small, lightweight, and has excellent durability and strength.

As shown in FIG. 3, the present invention includes a pair of rollers 10 and 11, each having a large diameter paper passing section 10a, 11m and a small diameter journal section 10b, 10b, 11b formed at both ends thereof.
- At least two or more ball bearings 12.15 are attached to each journal part of the housing 14-11b.
15. Two ball bearings 12, 12, and 13-13 are arranged side by side and press-fitted into each journal part of the illustrated example, and these ball bearings are held in wide housings 14 and 15. It may be used for installation. In this case, all ball bearings of the same shape and size can be used.

Since the present invention has the above configuration, even if a small ball bearing with a small outer diameter is used, it can withstand a large pressure applied to the roller. Therefore, as is clear from the above equation, the diameter of the paper passing portion of the roller o-11 can be made smaller than the diameter D of the paper passing portion of the conventional roller 2. Outer diameter 47~. Using a ball bearing roller with a pressure resistance of 1000 KP and supporting a roller with an outer diameter of 55 or more considering the wall thickness of the housing, the present invention uses a ball bearing roller with an inner diameter of 20 to -9 and an outer diameter of 37% and a pressure resistance of 5o.
If oKP's ball bearings can be used, a roller with an outer diameter of 45% will suffice, even considering the thickness of the housing. Therefore, the weight of the roller, which used to be 8~, has decreased to 5? This means that the entire device is approximately 409I! The weight will be reduced soon.

-! 9. As the diameter of the paper passing section of the row 20 becomes narrower, the crossing angle for applying pressure uniformly between the rollers becomes larger.

Conventionally, in order to prevent shock when the sheet 16 enters between the rollers, the entire pressure fixing device had to be tilted with respect to the sheet-row direction. This is because the intersection angle α is small, so the contact le between the upper and lower rollers 10 and 11 shown in FIG.
This is because when the angle C formed by the tip of the sheet and the tip of the sheet is electrically connected in parallel to the bottom roller, +α) becomes extremely small, and this amount alone is insufficient to prevent shock.

However, there is one pressure fixing device of the present invention! So Law 910.11
Since the t6 diameter can be configured to be small, the crossing angle that makes the pressure contact force in the longitudinal direction of the rollers 1° and 11 uniform needs to be larger than the conventional large roller diameter. To give specific figures, the horizontal feed of an A4 sheet is approximately 297ff).
Apply a pressure of 0 Kp/m to both ends of the roller.
When a force of 00KP (300jlX2) is applied, the roller with a smaller diameter is larger.If the entire device is placed parallel to the image forming device.

In the pressure fixing device of the present invention, the sheet leading edge and the upper and lower four rollers 10,
As shown in the half of the intersection angle α formed by the contact lines of No. 11, it is no longer necessary to dispose the entire unit (pressure fixing device F) obliquely within the drawing soda forming device. Therefore, roller 1
When applying the drive to the sprocket 17, a chain may be suspended in a straight line from a motor (not shown) provided on the sprocket forming lid. This is effective when the fixing device is also driven.

First, if the intersection angle α is large, the same pressure C, for example 20 kg
It is known from experience that fixing is good even in the case of /an), and this is said to be due to the fact that the sheet is squeezed; however, in the pressure fixing device of the present invention, the intersection angle can be increased as described above. The pressure can be lowered to obtain the same fixing performance as before. For a different body, the intersection angle is 1.6” and it is 0.8”.
Since the same degree of fixing performance can be obtained at 181'l/min for K, the pressure applied to the bearings 14 and 15 can also be reduced.

7 in FIG. 112 and 17t in FIGS. 6 and 4; i A sprocket attached to the roller shaft receives power from a drive source (not shown).

Although the present embodiment has been described using a pressure fixing device as an example, the present invention is not limited thereto, and can of course be applied to, for example, a heating roller fixing device.

[Brief explanation of the drawing]

FIG. 1 is a longitudinally sectional front view of a bearing portion of a conventional pressure fixing device, FIG. 2 is a longitudinally sectional front view of a bearing portion of a pressure fixing device of the present invention, FIG. 2 is a longitudinal sectional view showing another example. FIG. 4 is a front view showing the relationship between the contact line of the pressure fixing roller and the sheet. 10.11 is a roller, 10m, 11b is a paper passing section, 10b
・10b, 11b, 11゛b are journal parts, 12.1
2゜13-13 is a ball bearing, 14 and 15 are housings. Fu 2- book 3 country, li5
/7'! 87 circle collection 4th r (

Claims (1)

[Claims] (1) In a device that fixes an unfixed toner image on a core sheet by passing a sheet having an unfixed toner between a pair of fixing rollers, each of the fixing rollers has a large diameter paper passing section and both ends thereof. A fixing system characterized by having a small-diameter journal section formed therein, two or more ball bearings attached to each journal section, and the ball bearings being held in a housing for each journal! li&place.