JPH02201478A - Heat roll for heat fixing - Google Patents

Abstract

PURPOSE:To simplify a power feed constitution and to maintain power feed always well by forming the entire part in the axial direction of a cylindrical body to the same outside diameter and providing power feed brushes to both ends in the axial direction of the heating resistance layer on the outer periphery of the cylindrical body so that electric power can be fed via the brushes to the heating resistance layer. CONSTITUTION:The heating resistance layer 2 is provided on the outer periphery of the cylindrical body 1 made of a mild steel so that the cylindrical body can be heated. The cylindrical body 1 is formed to the same outside diameter over the entire part in the axial direction thereof and the outer peripheral surface thereof is roughened by blasting. This surface is subjected to plasma thermal spraying of Cr, etc., to form a bond layer. The outer peripheral surface exclusive of both ends in the axial direction of the heating resistance layer 2 is coated with 'Teflon(R)' to form a protective layer 4. The annular brushes 5 are provided in the outer peripheral parts at both ends in the axial direction of the heating resistance layer 2 where the protective film 4 is not provided so that the heating by the direct feeding from the brushes 5 to the heating resistance layer 2 is executed. The production stages are decreased in this way and the production is made advantageous; in addition, the durability of the heat roll is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heat roll for heat fixing in electronic copying machines, facsimile machines, printers, etc., and in particular, a power supply configuration for a direct heating type heat roll using a heat generating resistive layer. This is an improved version of .

[Prior Art] As a heat roll for a heat fixing device such as an electronic copying machine, a direct heating type heat roll, which has a quick temperature rise time and good thermal efficiency, has come to be used. This type of heat roll has a heating resistance layer provided on the outer periphery of a cylindrical body via an insulating layer, a protective layer further provided on the outer periphery, and a metal layer formed on the outer periphery of both axial ends of the heating resistance layer to serve as electrodes. Heating is achieved by supplying electric power to this electrode via a power supply brush (Japanese Patent Laid-Open No. 154476/1983).

In addition, both axial ends of the cylindrical body constituting the heat roll are
There is also a device that is formed on a small diameter bearing to be held in the heat fixing device main body, and a conductive wire is used to connect the heating resistance layer in the central large diameter portion and the electrode provided on the small diameter bearing.
Publication No. 572). The reason why the heat generating resistor layer and the electrode are connected by a conductive wire in this manner is that it is difficult to provide the heat generating resistor layer by thermal spraying on the side surface of the stepped portion where the axial diameter of the cylindrical body changes.

[Problems to be Solved by the Invention] Conventionally, a heat roll using a heat generating resistive layer has a metal electrode provided on its outer periphery in order to supply power to the heat generating resistive layer. However, the heating resistance layer is made by thermal spraying a mixture of ceramic and conductive material, and must be manufactured through a separate process different from that of the electrodes. This increased the number of manufacturing steps for the heat roll, which was not desirable.

In addition, the heat roll incorporated in the fixing device is kept in a heated state for a long time, so if an electrode is provided around the outer periphery of the heat-generating resistor layer, the heat-generating resistor layer or electrode may undergo thermal expansion changes, or the bonding surface may oxidize. There is a problem in that the bonding state between the two changes due to this, and the resistance at the interface increases.

Although this problem does not occur when connecting the heating resistor layer and the electrode with conductive wire, the manufacturing process increases and
This causes disadvantages for downsizing the device, such as increased axial length.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to simplify the power supply structure to the heat roll, thereby making it advantageous in terms of manufacturing, and to maintain a good power supply to the heat roll at all times.

Means for Solving E-Stress] The present invention provides a heat roll for heat fixing such as an electronic copying machine in which a heating resistance layer is provided on the outer periphery of a cylindrical body, in which the entire axial direction of the cylindrical body is formed to have the same outer diameter. The present invention is characterized in that power feeding brushes are provided at both ends in the axial direction of the heat generating resistive layer on the outer periphery of the cylindrical body, so that power can be supplied to the heat generating resistive layer via the brushes.

Both axial ends of the heat generating resistor layer where it comes into contact with the brush will wear out slightly over long periods of use, but in order to be able to supply power even in such cases, the thickness of the heat generating resistor layer in the area where it comes in contact with the brush must be increased. is thicker than the center part.

[Function] In the heat roll for heat fixing of the above means, since the power supply brush is brought into contact with both ends of the heat generating resistor layer in the axial direction, power can be supplied from the brush to the heat generating resistor layer without providing a separate electrode, and the heat roll can be heated to the temperature required for heat fixing. Furthermore, the heat roll is advantageous in terms of manufacturing since it is not necessary to provide electrodes, and there is no possibility of connection failure between the heat generating resistive layer and the electrodes.

[Example] Embodiments of the present invention will be described with reference to the drawings.

The heat roll used in the heat fixing device has a heating resistance layer 2 provided on the outer periphery of a cylindrical body l made of soft iron, so that it can be heated.

The cylindrical body l is formed to have the same outer diameter in the entire axial direction, and its outer circumferential surface is roughened by blasting, and a bonding layer (not shown) is created by plasma spraying Cr or the like on the surface, thereby forming an insulating layer to be described later. can be strongly bonded. Alumina was thermally sprayed on the outer periphery of this bonding layer to form an insulating layer 3, and a mixed material of alumina and nichrome was further thermally sprayed on the outer periphery to form a heating resistor layer 2 having a uniform thickness (approximately 60 μm). The bonding layer, the insulating layer 3, and the heating resistance layer 2 were formed on the entire outer peripheral surface of the cylindrical body l in the axial direction.

Then, the outer circumferential surface of the heat generating resistive layer 2 provided on the cylindrical body 1, except for both axial ends, was coated with Teflon to form a protective film 4, so that the transfer paper on which the toner was fixed could be smoothly peeled off.

Ring-shaped brushes 5 are provided on the outer periphery of both ends in the axial direction of the heat generating resistor layer 2 where the protective film 4 is not provided, so that power can be directly supplied from the brush 5 to the heat generating resistor layer 2 to heat it.

At both ends of the cylindrical body l of the heat roll for heat fixing having the above configuration,
A support shaft 6 is provided to rotatably hold the fixing device main body, so that the toner on the transfer paper passing between the heat roll and a pressure roll (not shown) can be heated and fixed.

In order to compare the manufacturing cost and service life of the heat roll of the above example with the conventional example, the outer periphery of the heat generating resistive layer on the outer periphery of the cylindrical body was electrodes were installed, and furthermore,
Corresponding to the heat roll of Publication No. 9-128572, metal electrodes were provided on the outer periphery of both axial ends of a cylindrical body, and these electrodes and the heat generating resistor layer on the center side were connected with a conductive wire. Power was also supplied to each electrode in the comparative example via a power supply brush.

Using the heat rolls of the above examples and comparative examples, we measured the number of sheets that passed until an abnormality occurred in the heat roll when the transfer paper was continuously fed and the toner was thermally fixed.
The results are shown in Table 1. Table 1 also shows the life ratio and
The manufacturing cost ratio is also shown.

As can be seen from Table 1, it can be seen that the heat roll of this example is more durable and has a lower manufacturing cost.

The abnormal condition that occurs in the heat roll of the comparative example is a connection failure that causes damage to the heating resistance layer on the inner circumference of the electrode, or a connection failure at the conductor connection part. It was a poor connection that caused the heating resistance layer to wear out.

In the heat roll of the above example, the thickness of the heat generating resistor layer was made almost uniform throughout the axial direction, but in order to prevent connection failure due to abrasion due to contact with the power supply brush, one heat generating resistor layer was formed on the power supply brush. It is also possible to make the wall thickness of the part that comes into contact with the thicker.

[Effects of the Invention] In the heat roll for heat fixing of the present invention, a heating resistance layer is provided on the outer periphery of a cylindrical body whose outer diameter is the same throughout the axial direction, and a power supply brush is provided at both ends of the heating resistance layer in the axial direction without intervening electrodes. Since the power is supplied directly from the heat roll, it is advantageous in terms of manufacturing because it reduces the number of manufacturing steps. Increases durability.

[Brief explanation of the drawing]

The drawing is a sectional view of a heat roll for heat fixing according to the present invention. l; Cylindrical body 2; Heat generating resistance layer 3; Insulating layer 4; Protective layer 5; Brush

Claims (2)

[Claims] (1) In a heat roll for heat fixing such as an electronic copying machine, in which a heating resistance layer is provided on the outer periphery of a cylindrical body, the entire axial direction of the cylindrical body is formed to have the same outer diameter, and the entire axial direction of the cylindrical body is A heat roll for thermal fixing, characterized in that a heating resistor layer is provided, and power feeding brushes are provided on the outer periphery of both axial ends of the heating resistor layer, so that power can be supplied to the heating resistor layer via the brushes. (2) The heat roll for thermal fixing according to claim (1), wherein the heat generating resistive layer at both ends in the axial direction in contact with the brush is formed thicker than at the center in the axial direction.