JP2000340351A - Transformer power feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transformer power feeding device with high power-feed efficiency by canceling magnetic attraction force acting between a fixing side core (a fixing yoke) and a rotating side core (a moving yoke) and eliminating the generation of vibration. SOLUTION: In this transformer power feeding device, a columnar fixing side core 1 is fixed to a shaft 10 and a rotating side core 3 rotating around the fixing side core 1 is fixed to a flange 6 of a heat roller. High frequency voltage higher than a commercial frequency is supplied to a primary winding 2, and a heater within the heat roller is connected to a secondary winding 4. A magnetic attraction force component acting to a columnar air gap G between the fixing side core 1 and the rotating side core 3 is canceled, and vibration caused by magnetic attraction force is rarely produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer power supply device, and more particularly, to a non-contact type fixing roller (heat roller) used in an electrophotographic image forming apparatus such as a copying machine or a laser beam printer. The present invention relates to a transformer power supply device for supplying power.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a fixing device including a heat roller and a pressure roller is used to fix a toner image transferred to a recording material.
Conventionally, a lamp having a built-in halogen lamp has been widely used.However, there is a problem that heat transfer efficiency is poor and it takes time to reach a predetermined temperature. A device having a built-in planar heater on the inner surface has been proposed. However, since power is supplied by bringing a carbon brush or the like into contact with the heat roller, the life of the brush becomes a new problem, and a non-contact power supply method using a transformer has been considered.

FIG. 5 shows a first example of a conventional transformer power supply device, FIG. 5 (A) is a side sectional view, and FIG.
(A) is a sectional view taken along the line YY '. This conventional transformer power supply device is configured such that a primary side and a secondary side face each other, and is provided between a heat roller and a frame of an image forming apparatus main body. The primary side is fixed to a shaft 10 provided on a frame 9 of the image forming apparatus main body, and as shown in a sectional view taken along the line YY ′ shown in FIG. In which the primary winding 2 is wound. When the primary winding 2 is energized, a current flows through the secondary winding 4 wound around the secondary rotating core 3 that rotates together with the heat roller, and is supplied to the inside of the heat roller. The heat roller has a flange 6 supported by a frame 9 via a bearing 8 and a shaft 10. The heat roller substrate 7 heated to a predetermined temperature by energization contacts a recording material such as paper to fix a toner image.

A second example of a transformer power supply device used for a fixing device is disclosed in Japanese Patent Application Laid-Open No. Hei 8-305203. This example comprises an E-shaped fixed core wound with a primary winding and a movable bobbin wound with a secondary winding. The bobbin is attached to the center leg of the E-shaped core via an air gap. The power supply device of the heat roller is fitted.

[0005]

However, the above-described first conventional transformer power supply apparatus has a transformer primary side and a secondary side.
Since the secondary side faces the thrust direction via the air gap G, the primary side (fixed side) via the air gap G when a large power of about 1 kW is supplied.
A large magnetic attraction force having a frequency twice as high as the supplied electric power acts between the motor and the secondary side (rotating side). When the vibration generated by transmitting the magnetic attraction force to the frame is transmitted in the transport direction of the paper transport system, the image quality deteriorates (banding). In addition, image quality degradation also occurs when the vibration is transmitted in the laser scanning direction, and the adverse effect is further magnified when the vibration reaches an optical system in which precise positioning is performed.

On the other hand, in the above-described second conventional transformer power supply device, since the core is constituted only by the fixed core, there is no problem of magnetic attraction, but the secondary winding rotates in the air gap portion. In addition, there is a problem that the coil supporting member (movable bobbin) that withstands the electromagnetic force generated in the coil due to the supplied electric power rotates, so that the air gap must be large, and the magnetic force between the primary side and the secondary side is increased. The coupling efficiency was poor.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the prior art, and has as its object to prevent generation of vibration based on a magnetic attraction force acting between a fixed side and a rotating side, and to improve power supply efficiency. And to provide a transformer power supply device with high power.

[0008]

According to a first aspect of the present invention, in a transformer power supply device, a primary core is a fixed yoke, and a secondary core is a movable yoke. In a transformer power feeding device for forming a magnetic path with iron and feeding power to a movable electric circuit connected to a secondary side, each direction component of magnetic attraction force acting between the fixed yoke and the movable yoke An air gap is formed between the fixed yoke and the movable yoke so that an equal magnetic attraction component acts in a substantially opposite direction to the fixed yoke.

According to a second aspect of the present invention, in the first aspect of the present invention, an air gap is provided in such a shape that a magnetic attraction component that completely cancels out each direction component of the magnetic attraction acts. And

According to a third aspect of the present invention, in the first or second aspect of the present invention, the fixed yoke fixed to the rotating shaft and the movable yoke rotating therearound face circumferentially around the rotating shaft. It is characterized by having.

According to a fourth aspect of the present invention, in the third aspect of the present invention, one end of the fixed yoke and the end of the movable yoke which oppose each other and form the air gap are either one end. The portion has a larger area than the other end.

According to a fifth aspect of the present invention, in the third aspect of the present invention, an end of the fixed yoke and an end of the movable yoke forming the air gap facing each other have the same area. It is characterized by.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, bearings are provided at both ends of the heat roller, and one of the bearings regulates the position in the thrust direction, and the other bearing is in the thrust direction. It is a freely movable structure, wherein a transformer power supply device is arranged on a bearing side for regulating the position in the thrust direction.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, it is provided inside the heat roller.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, a voltage having a frequency higher than the commercial frequency is applied to the primary side.

A ninth aspect of the present invention is characterized in that, in the eighth aspect, the frequency is higher than 20 kHz.

[0017]

FIG. 1 shows a transformer power supply apparatus according to an embodiment of the present invention. FIG.
FIG. 2B is a sectional view taken along the line YY ′ of FIG. As shown in FIG. 1, in the transformer power supply device of the present invention, a flange portion 6, a heat roller base 7, a bearing 8, a frame 9, a shaft 10, and the like are formed in the same manner as the conventional example shown in FIG. On the other hand, a fixed core (fixed yoke) 1 around which the primary winding 2 is wound is provided on the frame 9 in a substantially columnar shape with the shaft 10 as a central axis, and a secondary winding is formed around the fixed core 1. A rotating core (movable yoke) 3 around which the wire 4 is wound is provided in a substantially cylindrical shape having a concentric shaft shape (see a cross-sectional view taken along the line YY 'in FIG. 1B). (Hereinafter, referred to as circumferentially opposed). And
The rotation-side core 3 is fixed to the flange 6 of the heat roller by a support member 5, and rotates with the rotation of the heat roller.

The fixed side core 1 and the rotating side core 3 form one magnetic path via an air gap G, and the end of the fixed side core 1 opposed to the air gap G is located between the rotating side core 3 and the rotating side core 3.
The fixed core 1 is arranged such that the end of the rotating core 3 faces the substantially central portion of the end of the fixed core 1.

In the transformer power supply device having the above configuration,
When a current is supplied from the outside to the primary winding 2 of the fixed side core 1, a current is induced in the secondary winding 4 of the magnetically coupled rotating side core 3 to supply power to the electric circuit inside the heat roller. Will be At this time, in the air gap G between the fixed-side core 1 and the rotation-side core 3, a magnetic flux penetrates in the vertical direction on the paper surface in FIG. 1A, and the magnetic attraction due to this is shown in FIG. In the YY 'sectional view, it is the sum of the magnetic attraction components in the direction of the rotation center with respect to the rotation side core 3, and is always equal to the opposite side by 180 degrees for each component, and Since the component exists, the value is 0 or a value close to 0. In addition, the magnetic attraction force is 0 or a value close to 0 because the components from the center to the outside cancel each other out with respect to the fixed core 1. As a result, no or almost no vibration is generated by the magnetic attraction force, and the frame 9 does not adversely affect the outside.

When the power supply is to be heated, such as a heat roller of a fixing device, the power may be thermally expanded in the thrust direction due to a rise in temperature. At this time, the rotating core 3 moves to the left on the paper surface in FIG. 1A with respect to the fixed core 1, but the end of the fixed core 1 is the end of the rotating core 3 as described above. Since the area is larger than the area, the ends are still opposed to each other, and the state of the air gap does not change. Therefore, the sum of the magnetic attraction forces is maintained at 0, and the transformer power supply device of the present embodiment can absorb the displacement in the longitudinal direction of the rotating shaft (hereinafter, referred to as the thrust direction). Thus, the air gap G
If a margin is provided in the above configuration, it is effective against errors due to the mechanical mounting accuracy of the heat roller.

Of the bearings rotatably supported at both ends of the heat roller, one of the bearings regulates the position in the thrust direction, and the other end of the bearing is free to move in the thrust direction to absorb thrust play. By arranging it on the bearing side that regulates the position in the thrust direction, even if thermal expansion of the heat roller occurs, the position of the movable yoke hardly changes, and the change in the air gap of the transformer section does not change. Therefore, stable power supply can be performed.

If the backlash in the thrust direction is so large that there is a region where the ends do not face each other, there is a portion where the magnetic flux penetrating through the air gap goes in an oblique direction. Since the backlash in the thrust direction acts to return to the original state due to the suction force, the displacement in the thrust direction exceeding a specified value can be restricted.
Therefore, if the ends of both opposing yokes are formed so as to have the same area, and if they are set to a position where they exactly oppose each other, that is, a position where they are magnetically balanced, a shift in the thrust direction occurs. A magnetic attraction can be applied to the heat roller to return to an automatically equilibrating position. As a result, the position of the heat roller in the width direction is accurately controlled, and highly accurate paper conveyance can be realized.

Further, by providing an appropriate offset in the thrust direction from the beginning and applying a constant pressurizing force to the bearing in the thrust direction, the positional accuracy of the heat roller in the width direction can be improved.

FIG. 2 is a side sectional view of another embodiment of the present invention, showing an example of a configuration in which a transformer power supply device is housed in a heat roller. In the case of the transformer power supply device of this embodiment,
Since it is necessary to set the diameter of the heat roller to a predetermined value,
As shown in FIG. 2, the fixed side core 11 and the rotating side core 13 are preferably displaced in the axial direction and arranged alternately so as to save space so as to fit in the heat roller. Also in this embodiment, it is easily understood that the magnetic attraction force becomes 0, as in the embodiment shown in FIG.

By the way, in each of the above embodiments, it is known that when the frequency of the voltage applied to the primary windings 2 and 12 is increased, the magnetic attraction decreases in inverse proportion thereto. 3 and 4 show the relationship between the power supply frequency fs and the magnetic attractive force Fm when silicon steel is used for the fixed cores 1 and 11 and when ferrite is used, respectively. The solid line shows the case where the primary winding is 200T, and the broken line shows the case where the primary winding is 50T. 1000N at commercial frequencies such as 50Hz and 60Hz
It can be seen that a very large magnetic attraction force of the order before and after is applied. Using this relationship, each component acts on the core of the voltage applied to the primary winding of the transformer power feeding device of the present embodiment even if the magnetic attraction force is canceled out as a result. Therefore, in consideration of the influence on the durability of the core, it is desirable to apply a high-frequency voltage that can reduce the magnetic attractive force. Therefore, it is preferable that the power is not supplied directly from the commercial power supply at all, but the power supply transformer and the switching power supply transformer are also used, and the frequency is once increased through the power supply circuit. Since the frequency range below 20 kHz is the audible frequency range, from the viewpoint of preventing noise,
More preferably, the frequency of the voltage applied to the next winding is higher than 20 kHz.

[0026]

The present invention has the following effects since it has the structure described above. According to the first aspect of the present invention, the magnetic attraction force between the fixed yoke and the movable yoke includes components that cancel each other in the respective directional components. Becomes Thereby, the vibration transmitted from the secondary side to the primary side can be suppressed, and the vibration transmitted to the member fixing the primary side can be suppressed.

According to the second aspect of the present invention, since the magnetic attraction force remaining as a whole becomes zero, vibration transmitted from the secondary side to the primary side can be eliminated.

According to the third aspect of the present invention, the air gap between the two yokes is fixed by using a circumferentially opposed structure in which the movable yoke is rotated around the fixed yoke while being fixed around the fixed yoke. , And the magnetic attraction components of the same size and opposite to each other act on each magnetic attraction force component, so that a transformer power feeding device can be easily realized.

According to the fourth aspect of the present invention, when a member having an electric circuit, for example, a heat roller generates heat by being supplied with power and thermally expands in the direction of the rotation axis, or the mechanical mounting accuracy of the member If the position of the movable yoke shifts in the thrust direction, the air gap moves even if the position of the movable yoke shifts in the thrust direction because one end of both yokes has a larger area than the other end The same state as before is maintained, the magnetic flux distribution becomes constant, and stable power supply can be performed.

According to the fifth aspect of the present invention, when the heat roller is displaced in the thrust direction, for example, the ends of both ends of the two yokes having the same area become smaller, and the state of the air gap changes. At this time, a magnetic attraction force acts in a direction in which the deviation is restored by the magnetic flux penetrating the ends diagonally, so that the play in the thrust direction can be restricted, and highly accurate paper conveyance can be realized.

According to the invention of claim 6, one of the bearings of the heat roller regulates the position in the thrust direction,
Since the other bearing is a bearing that does not regulate the position in the thrust direction, and the transformer power feeding device is disposed on the bearing side that regulates the position in the thrust direction, even if thermal expansion of the heat roller occurs, The change in the air gap of the transformer section is small, and stable power supply can be performed.

According to the invention of claim 7, since the transformer power supply device is provided inside the heat roller, the heat roller can be downsized.

According to the invention of claim 8, the magnetic attraction force is 1
Since the frequency becomes lower in inverse proportion to the frequency of the voltage applied to the next side, by raising the frequency higher than the commercial frequency, the condition for the durability of the member to which the magnetic attraction force is applied is relaxed, and the manufacturing becomes easy.

According to the ninth aspect of the present invention, noise can be avoided by using a frequency range higher than the audible frequency.

[Brief description of the drawings]

FIG. 1 is a diagram showing a transformer power supply device according to an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between a power supply frequency and a magnetic attraction force when silicon steel is used for a fixed-side core.

FIG. 4 is a diagram illustrating a relationship between a power supply frequency and a magnetic attraction force when ferrite is used for a fixed-side core.

FIG. 5 is a diagram illustrating an example of a conventional transformer power supply device.

[Explanation of symbols]

1,11 ... fixed side core (fixed yoke), 2,12 ... primary winding, 3,13 ... rotating side core (movable yoke), 4,14 ... 2
Next winding, 5: Support member, 6: Flange, 7: Heat roller base, 8: Bearing, 9: Frame, 10: Shaft, G: Air gap.

Claims (9)

[Claims] 1. A primary core is a fixed yoke, and a secondary core is a movable yoke. The fixed yoke and the movable yoke form a magnetic path and are connected to the secondary side. In a transformer power supply device for supplying power to a movable electric circuit, an equal-sized magnetic attraction component acts in substantially the opposite direction to each direction component of magnetic attraction acting between the fixed yoke and the movable yoke. A transformer power supply device, wherein an air gap having such a shape is provided between the fixed yoke and the movable yoke. 2. The transformer power supply device according to claim 1, wherein an air gap having a shape in which a magnetic attraction force component that completely cancels out each direction component of the magnetic attraction force is provided. 3. The fixed yoke fixed to a rotating shaft and the movable yoke rotating therearound are circumferentially opposed around the rotating shaft. Transformer power supply. 4. An end of the fixed yoke and an end of the movable yoke which oppose each other to form the air gap have an area at one end larger than that at the other end. The transformer power supply device according to claim 3, wherein the transformer power supply device is large. 5. The transformer power supply according to claim 3, wherein an end of the fixed yoke and an end of the movable yoke which face each other and form the air gap have the same area. apparatus. 6. A bearing having bearings at both ends of a heat roller, wherein one bearing regulates a position in the thrust direction, and the other bearing has a structure capable of moving in the thrust direction, and regulates the position in the thrust direction. The transformer power supply device according to any one of claims 1 to 5, wherein a transformer power supply device is disposed on the side. 7. The transformer power supply device according to claim 1, wherein the transformer power supply device is provided inside a heat roller. 8. A voltage having a frequency higher than the commercial frequency is 1
8. The transformer power supply device according to claim 1, wherein the voltage is applied to a secondary side. 9. The transformer power supply according to claim 8, wherein the frequency is higher than 20 kHz.