JP2022163874A - heating unit - Google Patents

Abstract

To prevent the positional deviation of a heater due to repeated thermal expansion and contraction of the heater to prevent the positional deviation of a power supply terminal.SOLUTION: A heating unit 1 comprises: a substrate 11; a resistance heating element 12 that is supported by the substrate 11; a heater 10 that has a power supply terminal 18 in conduction with the resistance heating element 12, the power supply terminal 18 located at one end 11E in a longitudinal direction of the substrate 11; an endless belt that has an inner peripheral surface in contact with a nip surface of the heater 10 and rotates around the heater 10; a holder 20 that supports the heater 10; and a heat conduction member 30 that is located between the holder 20 and a rear side surface 16 on the opposite side of the nip surface of the heater 10 and has a larger thermal conductivity than that of the substrate 11. The holder 20 has a first position regulation part 23 opposite in the longitudinal direction to one end 11A in the longitudinal direction of the substrate 11. The heat conduction member 30 has a second position regulation part 32 opposite in the longitudinal direction to the other end 11B in the longitudinal direction of the substrate 11.SELECTED DRAWING: Figure 2

Description

The present invention relates to a heating unit used in a fixing device of an image forming apparatus.

2. Description of the Related Art Conventionally, a known heating unit includes a plate-shaped heater and a holder that supports the heater (see Patent Document 1). In this technique, the heater is positioned in the longitudinal direction by abutting one end of the heater against a rib formed at one longitudinal end of the holder. In consideration of thermal expansion in the longitudinal direction of the heater, a gap is provided between the other end of the heater and the other end of the holder.

JP 2018-54898 A

However, in the prior art, one end of the heater is only abutted against the rib of the holder. There is a possibility that it will shift to the other end side of the If such a phenomenon in which the position of the heater is displaced occurs, the position of the power supply terminal provided on the heater and the connector connected to the power supply terminal may be displaced, resulting in contact failure.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to suppress positional deviation of a power supply terminal by suppressing positional deviation of a heater due to repeated thermal expansion and contraction of the heater.

In order to solve the above-described problems, a heating unit according to the present invention includes a substrate, a resistance heating element supported by the substrate, and a power supply terminal electrically connected to the resistance heating element, the heating unit being provided at one longitudinal end of the substrate. an endless belt that rotates around the heater and has an inner peripheral surface that contacts the nip surface of the heater; a holder that supports the heater; a thermally conductive member located between the back surface opposite to the nip surface and the holder and having thermal conductivity higher than that of the substrate.
The holder has a first position regulating portion facing the one longitudinal end of the substrate in the longitudinal direction.
The heat-conducting member has a second position regulating portion facing the other longitudinal end of the substrate in the longitudinal direction.

According to this configuration, the position of the substrate can be regulated by the second position regulating portion of the thermally conductive member from being displaced toward the other end in the longitudinal direction due to repeated thermal expansion and contraction. Displacement can be suppressed.

Further, the heat conducting member may have a base portion that contacts the back side surface of the heater, and the second position regulating portion may protrude from the other end portion of the base portion in the longitudinal direction.

According to this configuration, compared to a structure in which a hole is formed in the other end of the heat-conducting member and a protrusion that enters the hole is provided in the other end of the substrate, the structure of the heat-conducting member and the substrate can be simplified. can.

Moreover, the length by which the second position regulating portion protrudes from the other longitudinal end portion of the base portion may be smaller than the thickness of the substrate.

According to this configuration, it is possible to prevent the second position regulating portion from interfering with the belt.

Further, the holder has a third position regulating portion for positioning the heat conducting member in the longitudinal direction, the distance from the first position regulating portion to the third position regulating portion is Lp, and the substrate Assuming that the length in the longitudinal direction is Lb, the coefficient of linear expansion of the substrate is α1, and the coefficient of linear expansion of the thermally conductive member is α2,
Lp≦{1−(α1/α2)}×Lb
Lp may be set so as to satisfy the following formula.

With this configuration, the amount of elongation of the substrate can be made equal to or less than the amount of elongation of the thermally conductive member, so that the other end of the substrate can be suppressed from being pressed against the second position regulating portion during thermal expansion. Damage to the substrate or the heat-conducting member can be suppressed.

Further, the longitudinal length of the heat conducting member may be longer than the longitudinal length of the resistance heating element.

According to this configuration, the temperature of the heater can be made uniform over the entire range in which the resistance heating element is arranged in the longitudinal direction.

Further, the substrate may be made of a ceramic made of aluminum oxide, and the thermally conductive member may be a plate member made of aluminum.

According to this configuration, since the specific heat of the substrate and the specific heat of the thermally conductive member can be made close to each other, only the coefficient of linear expansion needs to be taken into consideration regarding the positioning of the thermally conductive member in the longitudinal direction with respect to the substrate, which facilitates design. .

According to the present invention, positional displacement of the heater due to repeated thermal expansion and contraction of the heater can be suppressed, so positional displacement of the power supply terminal can be suppressed.

4 is a cross-sectional view of the heating unit; FIG. A view (a) showing the surface of the heater on which the resistance heating element is arranged, a view (b) showing the heater and the heat-conducting member from the back side of the heater, and a cross-sectional view (c) taken along the longitudinal direction of the heating unit. is. FIG. 4A is an enlarged view of one longitudinal end portion of the heating unit, and FIG. 4B is an enlarged view of the other longitudinal end portion of the heating unit. 10A to 10C are diagrams (a) to (c) exaggerating the state of the substrate and the thermally conductive member during thermal expansion and contraction.

The heating unit 1 according to the embodiment is used for a fixing device of an image forming apparatus, a device for transferring foil by heat, and the like. As shown in FIG. 1, the heating unit 1 includes a belt 3, a heater 10, a holder 20, a heat conducting member 30, and a pressure roller 40. As shown in FIG.

The pressure roller 40 sandwiches the belt 3 with the heater 10 . The pressure roller 40 has a cylindrical shaft 41 and a cylindrical roller portion 42 . The shaft 41 is made of metal, for example. The roller portion 42 is made of, for example, rubber. The roller portion 42 covers a portion of the shaft 41 . The roller portion 42 contacts the belt 3 . One of holder 20 and pressure roller 40 is biased toward the other. In the following description, the direction in which one of the holder 20 and the pressure roller 40 is biased is also called the biasing direction.

The belt 3 is endless and made of metal, resin, or the like. Belt 3 rotates around heater 10 while being guided by holder 20 . The belt 3 has an outer peripheral surface 3A and an inner peripheral surface 3B. The outer peripheral surface 3A contacts the pressure roller 40 or the sheet to be heated. Inner peripheral surface 3B contacts heater 10 .

The heater 10 has a substrate 11 , a resistance heating element 12 supported by the substrate 11 , and a cover 13 . The substrate 11 consists of an elongated rectangular plate of ceramic made of aluminum oxide. The heater 10 is a so-called ceramic heater. The resistance heating element 12 is formed on one surface of the substrate 11 by printing. As shown in FIG. 2A, in this embodiment, two resistance heating elements 12 are provided. The two resistance heating elements 12 are long in the longitudinal direction of the heater 10 (hereinafter, the longitudinal direction of the heater 10 is simply referred to as the "longitudinal direction"), and are spaced apart from each other in the short direction perpendicular to the longitudinal direction. are placed. A wire 19A is connected to one end 12A of each resistance heating element 12, and a power supply terminal 18 for supplying electric power to the resistance heating element 12 is provided at each end of the wire 19A.

The power supply terminal 18 is electrically connected to the resistance heating element 12 via a lead wire 19A. The power supply terminal 18 is positioned at one longitudinal end portion 11E of the substrate 11 .

Further, the other ends 12B of the resistance heating elements 12 are connected to each other by a conductor 19B. The number of resistance heating elements 12 is not particularly limited. In addition, there is a resistance heating element in which the amount of heat generated at the central portion in the longitudinal direction is greater than that at the ends in the longitudinal direction, and a resistance heating element in which the amount of heat generated at the ends in the longitudinal direction is greater than the amount of heat generated at the central portion in the longitudinal direction. and individually controlling each resistance heating element to adjust the heat generation distribution in the longitudinal direction.

As shown in FIG. 1 , the cover 13 covers the resistance heating element 12 . The cover 13 is made of glass, for example. The heater 10 has a nip surface 15 in contact with the inner peripheral surface 3B of the belt 3 and a back surface 16 opposite to the nip surface 15 .

The holder 20 is a member that supports the heater 10 . The holder 20 has a support portion 21 and a guide portion 22 . The support portion 21 has a plate shape corresponding to the shape of the heater 10 . The guide portions 22 are provided at both ends of the support portion 21 in the lateral direction. Each guide portion 22 has a guide surface 22G along the inner peripheral surface 3B of the belt 3. As shown in FIG. The guide portion 22 has a plurality of guide ribs 22A arranged in the longitudinal direction.

The heat conducting member 30 is a member for conducting heat in the longitudinal direction of the heater 10 to make the temperature of the heater 10 uniform in the longitudinal direction. The heat-conducting member 30 is a plate-like member and is positioned between the back side surface 16 of the heater 10 and the support portion 21 of the holder 20 . When the heating unit 1 sandwiches a sheet to be heated between the belt 3 and the pressure roller 40 , the heat conducting member 30 is sandwiched between the heater 10 and the support portion 21 . The heat conducting member 30 has a heater side surface 31A in contact with the back side surface 16 of the heater 10 and an opposite surface 31B opposite to the heater side surface 31A. The opposite surface 31B is in contact with the support portion 21. As shown in FIG.

The heat-conducting member 30 is a member whose thermal conductivity in a direction parallel to the heater side surface 31A (hereinafter, simply referred to as “plane direction”) is greater than that in the plane direction of the substrate 11. In this embodiment, , the heat-conducting member 30 is made of aluminum.

As shown in FIGS. 2(a) and 2(b), one end 12A and the other end 12B of the resistance heating element 12 are located outside the maximum width W1 of the sheet usable in the heating unit 1 in the longitudinal direction and are heat conductive. Located inside one end 30A and the other end 30B of member 30 . That is, the length of the heat conducting member 30 is longer than the length of the resistance heating element 12 in the longitudinal direction.

The length of the substrate 11 is longer than the length of the heat conducting member 30 in the longitudinal direction. One end 30A of the heat conducting member 30 is positioned inside the one end 11A of the substrate 11 in the longitudinal direction. The other end 30B of the heat conducting member 30 is located outside the other end 11B of the substrate 11 in the longitudinal direction.

As shown in FIGS. 2C and 3 , the heat conducting member 30 has a plate-like base portion 31 that contacts the back side surface 16 of the heater 10 and a second position restricting portion 32 . In FIG. 2C, illustration of the resistance heating element 12, the cover 13 and the belt 3 is omitted for the sake of convenience. Also, in FIG. 3, for the sake of convenience, illustration of the resistance heating element 12 and the cover 13 is omitted.

The base portion 31 has the heater side surface 31A and the opposite surface 31B described above. The base portion 31 has the other end portion 31C including the other end 30B of the heat conducting member 30 . The second position regulating portion 32 protrudes in the biasing direction from the other end portion 31C of the base portion 31 and faces the other longitudinal end 11B of the substrate 11 in the longitudinal direction. The second position regulating portion 32 is arranged to substantially contact the other end 11B of the substrate 11, and regulates the other end 11B of the substrate 11 from moving in the other longitudinal direction. Here, substantially contacting includes not only contacting but also a slight gap between the other end 11B and the second position regulating portion 32 .

The length by which the second position regulating portion 32 protrudes from the other end portion 31</b>C of the base portion 31 is smaller than the thickness of the substrate 11 . That is, the second position regulating portion 32 is further away from the pressure roller 40 than the surface F1 of the substrate 11 on the pressure roller 40 side in the biasing direction.

The support portion 21 of the holder 20 has a first surface 21A and a second surface 21B, which are surfaces on the heater 10 side, and a stepped surface 21C connecting the first surface 21A and the second surface 21B. The first surface 21A and the second surface 21B are orthogonal to the biasing direction. The step surface 21C is perpendicular to the longitudinal direction. The first surface 21</b>A supports the heat conducting member 30 by contacting the heat conducting member 30 . The second surface 21B supports the one end portion 11E of the substrate 11 by contacting the one end portion 11E of the substrate 11 .

The length of the first surface 21A is longer than the length of the heat conducting member 30 in the longitudinal direction. The length of the heat conducting member 30 is longer than the length of the roller portion 42 of the pressure roller 40 in the longitudinal direction. The roller portion 42 is positioned within the range of the heat conducting member 30 in the longitudinal direction.

The second surface 21B is located at a position different from the first surface 21A in the longitudinal direction. Specifically, the second surface 21B is located on one side of the first surface 21A in the longitudinal direction.

The second surface 21B is arranged closer to the heater 10 than the first surface 21A. The size of the stepped surface 21</b>C in the biasing direction is substantially the same as the thickness of the base portion 31 of the heat conducting member 30 . It is desirable that the size of the step surface 21</b>C in the biasing direction is equal to or greater than the thickness of the base portion 31 .

The holder 20 further has a first position restricting portion 23 and a third position restricting portion 24 . The first position regulating portion 23 protrudes in the biasing direction from one longitudinal end portion of the second surface 21B and faces the one longitudinal end 11A of the substrate 11 in the longitudinal direction. The substrate 11 is arranged so that one end 11A contacts the first position regulating portion 23 .

The third position regulating portion 24 is a portion for positioning the heat conducting member 30 in the longitudinal direction. The third position restricting portion 24 protrudes from the first surface 21A and enters a hole H1 formed at a predetermined position in the longitudinal direction of the base portion 31 of the heat conducting member 30 . The size by which the third position regulating portion 24 protrudes from the first surface 21A is smaller than the thickness of the base portion 31 . Alternatively, a protrusion may be formed at the end of the heat conducting member 30 in the short direction, a recess for receiving the protrusion may be formed in the holder 20, and the recess may be used as the third position regulating portion. Also, the relationship between the convex portion and the concave portion may be reversed. A projection projecting from the opposite surface 31B of the base portion 31 toward the first surface 21A may be provided, and a recess for receiving the projection may be formed in the first surface 21A, and the recess may be used as the third position regulating portion.

A distance Lp from the first position regulating portion 23 to the third position regulating portion 24 is set so as to satisfy the following equation.
Lp≦{1−(α1/α2)}×Lb
Lb: length of the substrate 11 in the longitudinal direction α1: linear expansion coefficient of the substrate 11 α2: linear expansion coefficient of the thermally conductive member 30 In the present embodiment, the linear expansion coefficient of aluminum oxide forming the substrate 11 is approximately 7.2. ×10 ⁻⁶ /K. Also, the linear expansion coefficient of aluminum constituting the heat conducting member 30 is approximately 23.9×10 ⁻⁶ /K.

By setting the distance Lp in this manner, the longitudinal extension amount ΔLb of the substrate 11 is the extension amount of the portion (Lb−Lp) of the heat conducting member 30 from the third position regulating portion 24 to the other end 30B. Δ(Lb−Lp) or less.

The heating unit 1 further comprises a connector 50 for supplying electricity to the heater 10 . The connector 50 includes a connector body 51 made of resin or the like, and two connection terminals 52 made of a conductive material such as metal.

The connection terminal 52 is made of an elastic metal plate. The two connection terminals 52 are arranged side by side in the longitudinal direction of the heater 10 at intervals. The connection terminal 52 is connected to the power supply terminal 18 of the heater 10 .

The connector main body 51 has a substantially U shape when viewed from the longitudinal direction. The connector main body 51 sandwiches one longitudinal end of the heater 10 and one longitudinal end of the holder 20 in the urging direction. Connector 50 is attached to one end of heater 10 and holder 20 from one side of heater 10 in the short direction.

Next, assembly of the heater 10, the holder 20, and the heat conducting member 30 of the heating unit 1 of this embodiment will be described. First, the heat conducting member 30 is arranged on the first surface 21A of the holder 20 . At this time, by inserting the third position restricting portion 24 into the hole H1 of the base portion 31, the heat conducting member 30 is positioned in the longitudinal direction. One end 30</b>A of the heat conducting member 30 has a gap that allows the thermal expansion of the heat conducting member 30 with respect to the step surface 21</b>C of the support portion 21 .

Next, the heater 10 is arranged on the second surface 21B of the holder 20 . At this time, the heater 10 is arranged on the second surface 21B in a state in which the one end 11A of the substrate 11 is abutted against the first position regulating portion 23, and the other end 11B of the substrate 11 is placed on one side of the second position regulating portion 32 in the longitudinal direction. to be placed. Thereby, the heater 10 and the heat conducting member 30 are assembled to the holder 20 .

Next, the states of the substrate 11 and the thermally conductive member 30 during thermal expansion or contraction will be described.
When the substrate 11 and the heat conducting member 30 thermally expand in the longitudinal direction due to the temperature rise of the heating unit 1 from the state shown in FIG. Together with the second position restricting portion 32 of 30, it moves to the other side in the longitudinal direction. At this time, the distance Lp from the first position regulating portion 23 to the third position regulating portion 24 is set such that Lp≦{1−(α1/α2)}×Lb, so that the other end of the substrate 11 is 11B moves together with the second position restricting portion 32 without being pressed against the second position restricting portion 32 .

When the temperature of the heating unit 1 decreases from the state shown in FIG. 4B and the substrate 11 and the thermally conductive member 30 contract in the longitudinal direction, as shown in FIG. may shrink closer to the center of the In this case, the one end 11</b>A of the substrate 11 in the longitudinal direction may try to move away from the first position regulating portion 23 . On the other hand, since the heat conducting member 30 is positioned in the longitudinal direction by the third position regulating portion 24, it shrinks with the position of the hole H1 as a base point. That is, both ends of the heat conducting member 30 in the longitudinal direction are shrunk so as to approach the positions of the holes H1. Therefore, the contraction of the heat-conducting member 30 moves the second position regulating portion 32, and the substrate 11 is pressed toward the first position regulating portion 23 by the moving second position regulating portion 32. 2, the one end 11A of the substrate 11 can be restrained from being separated from the first position regulating portion 23. As shown in FIG. Therefore, the position of the substrate 11 can be regulated by the second position regulating portion 32 of the heat conducting member 30 from being displaced toward the other end in the longitudinal direction due to repeated thermal expansion and contraction.

According to the above, the following effects can be obtained in this embodiment.
The second position regulating portion 32 of the heat conducting member 30 can regulate the shift of the position of the substrate 11 toward the other end in the longitudinal direction due to repeated thermal expansion and contraction, so that the position of the power supply terminal 18 can be prevented from shifting. can be suppressed.

Since the second position regulating portion 32 protrudes from the other longitudinal end portion 31C of the base portion 31, for example, a hole is formed in the other end portion of the heat-conducting member, and a protrusion that enters the hole is formed in the other end portion of the substrate. The structure of the thermally conductive member 30 and the substrate 11 can be simplified as compared with the structure in which they are provided.

As shown in FIG. 3B, the length by which the second position regulating portion 32 protrudes from the other end portion 31C of the base portion 31 is smaller than the thickness of the substrate 11. can be prevented from interfering with

By setting the distance Lp from the first position regulating portion 23 to the third position regulating portion 24 so as to satisfy the formula Lp≦{1−(α1/α2)}×Lb, the longitudinal elongation of the substrate 11 is minimized. The amount ΔLb can be made equal to or less than the extension amount Δ(Lb−Lp) of the portion (Lb−Lp) on the other end side of the heat conducting member 30 . Therefore, it is possible to suppress the other end 11B of the substrate 11 from being pressed against the second position regulating portion 32 during thermal expansion, thereby suppressing damage to the substrate 11 or the heat conducting member 30 .

Since the length of the heat conducting member 30 in the longitudinal direction is longer than the length of the resistance heating element 12 in the longitudinal direction, the temperature of the heater 10 is made uniform over the entire range in which the resistance heating element 12 is arranged in the longitudinal direction. be able to.

The specific heat of the substrate 11 and the specific heat of the heat conducting member 30 are close to each other by forming the substrate 11 from a ceramic made of aluminum oxide and forming the heat conducting member 30 from a plate member made of aluminum. Therefore, only the coefficients of linear expansion α1 and α2 need to be taken into account with respect to the positioning of the heat conducting member 30 in the longitudinal direction with respect to the substrate 11, which facilitates design.

The present invention is not limited to the above-described embodiments, and can be used in various forms as exemplified below.

In the above embodiment, the heat conducting member 30 is made of one sheet-shaped member, but may be made up of a combination of a plurality of sheet-shaped members. In this case, the plurality of sheet-like members may be different from each other in material, thermal conductivity, shape, etc., or may be the same as each other.

In the above-described embodiment, the substrate 11 of the heater 10 is made of an elongated rectangular plate made of ceramic. may The heat conducting member may be made of an aluminum alloy, copper, or the like.

Each element described in the above embodiment and modifications may be implemented in any combination.

1 Heating Unit 3 Belt 3B Inner Peripheral Surface 10 Heater 11 Substrate 11A One End 11B Other End 11E One End 12 Resistance Heating Element 15 Nip Surface 16 Rear Side 18 Power Supply Terminal 20 Holder 23 First Position Regulating Part 30 Thermal Conductive Member 32 Second Position regulatory department

Claims (6)

a heater having a substrate, a resistance heating element supported by the substrate, and a power supply terminal electrically connected to the resistance heating element and located at one longitudinal end of the substrate;
an endless belt that rotates around the heater and has an inner peripheral surface that contacts the nip surface of the heater;
a holder that supports the heater;
a thermally conductive member located between the holder and the back surface of the heater opposite to the nip surface, and having a thermal conductivity greater than that of the substrate;
The holder has a first position regulating portion that faces the one longitudinal end of the substrate in the longitudinal direction,
The heating unit, wherein the heat conducting member has a second position regulating portion facing the other longitudinal end of the substrate in the longitudinal direction. The thermally conductive member has a base portion in contact with the back surface of the heater,
2. The heating unit according to claim 1, wherein the second position regulating portion protrudes from the other longitudinal end portion of the base portion. 3. The heating unit according to claim 2, wherein the second position regulating portion protrudes from the other longitudinal end portion of the base portion to a length smaller than the thickness of the substrate. The holder has a third position regulating portion for positioning the heat conducting member in the longitudinal direction,
Lp is the distance from the first position regulating portion to the third position regulating portion, Lb is the length of the substrate in the longitudinal direction, α1 is the coefficient of linear expansion of the substrate, and α2 is the coefficient of linear expansion of the heat conducting member. As
Lp≦{1−(α1/α2)}×Lb
4. The heating unit according to any one of claims 1 to 3, wherein Lp is set so as to satisfy the following equation. 5. The heating unit according to claim 1, wherein the longitudinal length of the heat conducting member is longer than the longitudinal length of the resistance heating element. The substrate is made of a ceramic made of aluminum oxide,
6. The heating unit according to any one of claims 1 to 5, wherein the heat conducting member is a plate member made of aluminum.

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