Method of forming a hollow pole projecting on a plate and a method of manufacturing a heat sink using said method

FIELD OF THE INVENTION

The present invention relates to a method of forming a hollow pole projecting on a plate such as a metal plate to which various components are to be attached or which is to support a rotating member, and a method of forming heat dissipating fins by utilizing the aforementioned hollow poles in order to dissipate heat away from electronic components generating said heat in an effective manner by providing the heat dissipating fins in the vicinity of the electronic components.

DESCRIPTION OF THE PRIOR ART

In order to axially support a rotating part or axially affix other parts to a plate such as a metal plate, a hole is bored in the plate and a specially manufactured axial member is then passed through the hole. The axial member is then fixed using end fixing means or using a screw.

However, the number of components required when an axial member is separately made and fixed to a plate is large, as is the number of manufacturing steps, and high costs are therefore inevitable. Because of this, in Japanese Patent Laid-open Publication No. Hei. 6-26737, the present applicant proposed a method of integrally forming a cylindrical projection by utilizing plastic processing technology, which was extremely useful in practical terms.

FIG.

9

and

FIG. 10

are views showing a method of forming a cylindrical projection at a plate proposed in the related art, where

FIG. 9

is a view showing a method of forming a cylindrical projection having a bottom in the plate. First, in a first press step #

10

, a press tool

401

that is a circular column formed with a flat end surface is pushed against one surface of a plate

400

comprising a metal plate of a metal having plasticity such as iron or aluminum so as to form a hole

102

at the one side and a projection

403

at the other side.

Next, in a flat press step #

11

, the end surface of a columnar flat press tool

404

of an external diameter greater than the external diameter of the projection

403

is brought into contact with the side of the opening of the hole

402

and pressed. As a result, the metal of the pressed portion moves towards a central section

405

of the hole

402

that provides no resistance and is also moved to the projection

403

so that the projection

403

is made to project further.

In a second press step #

12

, the plate

400

that has undergone the flat press step #

11

is again pressed by the press tool

401

from the side of the opening and the height of the projection is further increased so as to form a cylindrical projection

406

at the plate

400

. The height of the cylindrical projection

406

is then two times a thickness t

1

of the plate

400

or more.

FIG. 10

is a view showing a method of forming a cylindrical projection that penetrates the plate from one side to the other. Namely, up to the flat press step #

11

, the steps shown in

FIG. 9

are gone through. Thereafter, a boring step is provided. Here, a boring tool

407

having a stem portion of a small diameter is inserted through the hole

402

and punching is carried out so as to bore a thruhole

408

. Next, in a burring step #

14

, a burring tool

409

with a tapered front end and an external diameter that is the same as the diameter of the press tool

401

is inserted from the hole

402

and passed through while broadening out the thruhole

408

so as to form a cylindrical projection

410

having a height L

02

. In the method shown in

FIG. 10

a height L

02

of the cylindrical projection

410

is also formed to be at least twice the thickness t

1

of the plate

400

.

In the methods of forming a cylindrical projection at a plate described above, the cylindrical projection

406

are integrally formed at the sheet

400

. Costs are therefore reduced and cylindrical projection having a height of twice the thickness of the plate

400

or more can be formed at the plate

400

. There is a limit on making the cylindrical projection substantially larger with respect to the thickness t

1

of the plate

400

in that the direction of the movement of the metal due to pressing by the flat press tool

404

is dispersed. There are also cases where a thick projection is required but there are limits when the thickness is increased in the related axial part forming method for the reasons state above.

As the present invention sets out to resolve the aforementioned problems of the related forming methods, it is the object of the present invention to provide a method of forming a cylindrical projection, which is substantially a hollow pole, in a plate where the hollow pole can be made substantially higher with respect to the thickness of the plate or where the thickness of the hollow pole is made thicker.

It is also a further object of the present invention to provide a method of easily and cheaply manufacturing a heatsink with superior heat dissipating effects by forming one or more heat dissipating fins utilizing the aforementioned hollow pole, and to provide a heatsink thereof.

SUMMARY OF THE INVENTION

In order to achieve the aforementioned object, according to the present invention, there is provided a method of forming a hollow pole projecting from a metal plate by plastic deformation and comprising the steps of: (a) pressing the plate from one surface of the plate using a press tool so as to form a hole on the one surface and a projection on the other surface thereof; (b) moving metal of the plate around said projection towards interior of said hole so as to gather the metal into a periphery of an opening of said hole using a tapered tool; (c) pressing said periphery of said hole using a flat press tool which is greater than said projection in an external diameter so as to move the metal gathered by said tapered tool further towards the interior of said hole and to increase a height of said projection; and (d) inserting said press tool into said hole while pressing the interior of said hole so as to increase further the height of said projection and to form the hollow pole. The projection can therefore be made substantially higher with respect to the thickness of the plate or the thickness of the hollow pole can be made thicker. Further, a heatsink utilizing the hollow poles as superior heat dissipating fins can be manufactured easily and cheaply.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a sectional oblique cross-section showing an example of a plate formed with a hollow pole of the present invention;

FIG. 2

is a process view showing steps of a method for forming a hollow pole at a plate of the present invention;

FIG. 3

is a process view showing steps of a further method for forming a hollow pole at a plate of the present invention;

FIG. 4

is a cross-section showing a modified example of a first press step of the present invention;

FIG. 5

is a process view showing steps of a method for forming a hollow pole of the present invention;

FIG. 6

is a process view showing steps of a further method for forming a hollow pole of the present invention;

FIG.

7

(A) and FIG.

7

(B) are cross-sections showing a forming method for a case when the thickness of a hollow pole with a bottom is to be made thick;

FIG.

8

A and

FIG. 8B

are cross-sections showing a forming method for a case when the thickness of a hollow pole is to be made thick;

FIG. 9

is a process view showing steps of a related method for forming a cylindrical projection at a plate;

FIG. 10

is a process view showing steps of a further related method for forming a cylindrical projection at a plate;

FIG. 11

is a sectional oblique cross-section showing a further example of a plate formed with a hollow pole of the present invention;

FIG. 12

is a process view showing steps of a method for forming a hollow pole at a plate of the present invention;

FIG.

13

(A) and FIG.

13

(B) are cross-sections showing modified examples of a first press tool of the present invention;

FIG. 14

is a process view showing steps of a method for forming a hollow pole of the present invention;

FIG. 15

is a cross-section showing a forming method of the present invention for the case where the thickness of a hollow pole having a bottom is made thick;

FIG. 16

is a cross-section showing a forming method of the present invention for the case where the thickness of a hollow pole is made thick;

FIG. 17

is a process showing the steps of a further method for forming a hollow pole of the present invention;

FIG. 18

is a view showing an embodiment of a heat sink of the present invention, with FIG.

18

(

a

) being a cross-section of a heatsink unit and FIG.

18

(

b

) being a cross-section showing a situation when electrical components are in contact with the heatsink;

FIG. 19

is a view showing steps for manufacturing a heat dissipating fin at a heatsink of the present invention;

FIG. 20

is a cross-section showing a further example of a heat dissipating fin of a heatsink of the present invention;

FIG.

21

(

a

), FIG.

21

(

b

) and FIG.

21

(

c

) are views showing arrangements of heat dissipating fins of heatsinks of the present invention;

FIG. 22

is a perspective view showing a first embodiment of a heatsink of the present invention;

FIG. 23

is an oblique view with essential parts enlarged showing the heat dissipating fins of the heatsink of

FIG. 18

;

FIG. 24

is a plan view of the heatsink of

FIG. 18

;

FIG. 25

is a cross-section of the heatsink of

FIG. 18

;

FIG. 26

is a view illustrating the operation of the heatsink shown in

FIG. 18

;

FIG. 27

is a manufacturing process view showing steps for forming a heatsink projection of the present invention;

FIG. 28

is a view showing a second embodiment of the heatsink of the present invention, where FIG.

28

(A) is a perspective view of the heat dissipating fins and FIG.

28

(B) is a cross-section of a die showing the slit forming method;

FIG. 29

is a view showing a third embodiment of the heatsink of the present invention, where FIG.

29

(A) is a perspective view of the heat dissipating fins and FIG.

29

(B) is a cross-section of a die showing the slit forming method;

FIG. 30

is a view showing a second embodiment of the heatsink of the present invention, where FIG.

30

(A) is a perspective view of the heat dissipating fins and FIG.

30

(B) is a cross-section of a die showing the slit forming method; and

FIG. 31

is a perspective view of heat dissipating fins showing a heatsink of a fifth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a detailed description with reference to the drawings of a method of forming a hollow pole in a plate of the present invention.

FIG. 1

is a sectional oblique cross-section showing a hollow pole manufactured using the method of the present invention. Here, a metal plate such as iron, copper, aluminum, or brass to which plastic deformation is applied is selected as a plate

1

. A hollow pole

2

is then formed as a single hollow circular cylindrical body with a bottom protruding from the inside of the plate by plastically deforming a part of the plate

1

. This hollow pole

2

is formed to a height that is three to five times the thickness of the plate

1

by forming method described in detail later.

A recess

3

having a prescribed internal diameter is formed at the peripheral edge of an opening at the lower side of the recess

3

. This recess

3

is thinner than the plate

1

, with the metal originally at this portion having been moved to the hollow pole

2

during plastic deformation in order to obtain the prescribed height for the hollow pole

2

. It is also possible for a plurality of hollow poles to be provided next to each other at intervals of greater than the prescribed internal diameter of the recess

3

. Further, it is preferably for the recess

3

to be circular when the hollow pole

2

is circular but a polygon shape such as a substantially quadrangular shape or triangular shape or an ellipsoidal shape is also possible.

Next, a description is given of the method of the present invention for forming a hollow pole in a plate.

FIG. 2

is a view showing the processes for forming the hollow pole

2

formed as a hollow circular cylinder with a bottom from the interior of a plate. First, in a first press step #

1

, one side of the plate

1

being a metal plate of iron or copper etc. is pressed by a press tool

10

, with a hole

4

being formed on the one side of the plate

1

and a projection

5

being formed on the other side of the plate. The press tool

10

is formed as a cylindrical column with a flat end surface and the projection

5

is formed in substantially a cylindrical shape due to pressing by the press tool

10

.

Next, in a metal shifting step #

2

, which is a principal process of the present invention, metal at the periphery of the opening for the hole

4

is gathered so as to be moved in a direction towards the inside of the hole

4

.

A tapered tool

11

used in step #

2

is formed as a cylindrical column of an external diameter greater than the external diameter of the projection

5

. The end surface of the tapered tool

11

is formed with a tapered recess

11

a

having a tapered surface recessed in a substantially conical shape from the outer periphery of the end surface towards the center of the end surface. This tapered tool

11

is pressed down so as to come into contact from the side of the hole

4

of the plate

1

. As a result, metal at the periphery of the opening of the hole

4

is gathered by the tapered recess

11

a

in the direction of a central part

6

in which no resistance is presented, and metal

7

moved to the side of the opening of the central part

6

is formed so that the projection

5

projects further.

The plate

1

that has passed through the metal shifting step #

2

is then moved to a flat press step #

3

. In the flat press step #

3

, an end surface of a flat press tool

12

in the shape of a cylindrical column with a flat end is pressed down so as to come into contact with the side of the hole

4

of the plate

1

in such a manner as to add to the pressing processing of the tapered tool

11

. The metal

7

formed on the side of the opening of the central part

6

is therefore moved in a direction towards the center of the central part

6

, the metal

7

is moved in the direction of the projection

5

and the central part

6

is made to project further. The recess

3

is then formed at the periphery of the hole

4

by the pressing of the flat press tool

12

.

Next, in a second press step #

4

, the plate

1

that has passed through the flat press step #

3

is again pressed down from the side of the opening by the press tool

10

so as to add height to the projection

5

and therefore form the hollow pole

2

that is cylindrical with a bottom shown in FIG.

1

.

A height L

10

of this hollow pole

2

can therefore be made substantially greater than the height of the forming method of the related art because the amount of metal at the periphery of the opening of the hole

4

gathered in the direction of the central part

6

and moved to the projection

5

by the tapered recess

11

a

of the tapered tool

11

is increased.

FIG. 3

is a view showing a further embodiment of the method of forming a hollow pole in a plate of the present invention, i.e. in the method shown in

FIG. 3

, pressing is carried out from the other surface of the plate

1

.

The first press step #

1

of

FIG. 3

is the same as the first press step #

1

of

FIG. 2

described previously and a description is therefore omitted. The following metal shifting step #

2

is then a process for gathering metal at the periphery of the opening of the hole

4

and moving the metal in a direction towards the interior of the hole

4

. A cylindrical tapered tool

20

used in this second step #

2

is formed in a cylindrical shape, has an internal diameter that allows insertion of the projection

5

, and a tapered part

20

a

of a substantially conical shape that is concave from the outer periphery towards the center is formed at an end surface of the cylindrical tapered tool

20

.

The cylindrical tapered tool

20

is inserted into the projection

5

formed by the first press step #

1

, and is pressed against the edge of the hole

4

from the other side with a contact member

21

that is flat at one end pressed against one side of the plate

1

. As a result, metal at the peripheral edge of the hole

4

is gathered by the tapered recess

20

a

in the direction of a central part

6

in which no resistance is presented, and metal

7

moved to the side of the opening of the central part

6

is formed so that the projection

5

projects further.

Next, in the flat press step #

3

, the periphery of the other side of the hole

4

is pushed down by a cylindrical flat press tool

22

that has a flat surface at one end and is of an internal diameter that permits the insertion of the projection

5

, with the contact member

21

pressing down. The metal of the pressed portion is therefore moved in the direction of the central part

6

of the hole

4

and the projection

5

is made to project further. At this time, an annular recess is formed at the side of the other surface of the periphery of the projection.

After this, in the second press step #

4

, height is added to the projection

5

so as to give a hollow pole

2

that is cylindrical with a bottom by again pressing down with the press tool

10

from the side of the opening with the projection

5

inserted in the cylindrical flat press tool

22

.

A height L

20

of the hollow pole

2

formed by the forming method shown in

FIG. 3

can also be made substantially greater than in related forming methods as with the method shown in

FIG. 2

because metal at the periphery of the opening of the hole

4

is gathered by the tapered part

20

a

of the cylindrical tapered tool

20

and the metal moved to the projection

5

is increased.

FIG. 4

shows a modified example of the press tool

10

used in the first press step #

1

, with FIG.

4

(A) showing an example where the end is formed so as to be hemispherical and FIG.

4

(B) showing an example where the end is at first flat and then tapered. In each of the aforementioned methods, a hollow pole

2

higher than that of the related art can also be formed using one of these press tools.

FIG. 5

is a view showing a process for forming a cylindrical hollow pole having a thruhole passing through from one side to the other side of the plate. In

FIG. 5

, a first press step #

1

, a second metal shifting step #

2

and a flat press step #

3

are the same as for FIG.

2

and are therefore omitted.

A thruhole

5

a

is then bored in the bottom of the projection

5

of the plate

1

that has passed through the flat press step #

3

by a hole boring tool

30

in a hole boring step #

5

. The hole boring tool

30

is formed in a shape that tapers off towards its end. The hole boring tool

30

then comes into contact with the bottom of the projection

5

and bores the thruhole

5

a

by pressing.

After this, a burring step #

6

is proceeded to. Here, a burring tool

31

formed in a substantially parabolic shape that tapers off towards the end of an external diameter that is the same as the diameter of the press tool

10

is inserted into the central part

6

and pressed. The thruhole

5

a

is then passed through and a cylindrical hollow pole

2

A is formed. At this time, the metal of the bottom part of the projection

5

is extended by the burring tool

31

and a height L

50

of the hollow pole

2

A can therefore be made substantially larger than the height in the related art.

FIG. 6

is a view showing a modified example of a process for forming a cylindrical hollow pole having a thruhole passing through the bottom surface of the plate. The forming process shown in

FIG. 6

is based on the forming method shown in FIG.

3

and as the first press step #

1

, metal shifting step #

2

, and flat press step #

3

are the same as for the forming method shown in FIG. #

3

, their description is omitted.

In the hole boring step #

5

of

FIG. 6

, the hole boring tool

30

is brought into contact with the bottom part of the projection

5

of the plate

1

that has passed through the flat press step #

3

and pressed down so that the thruhole

5

a

is bored in the bottom part of the projection

5

.

After this, the burring step #

6

is proceeded to and the burring tool

31

is inserted into the central part

6

and pressed so as to pass through the thruhole

5

a

and form a cylindrical hollow pole

2

B. At this time, a height L

60

of the hollow pole

2

B can be made substantially higher as in the example in

FIG. 5

because metal of the lower part of the projection

5

is extended by the burring tool

31

.

Methods for forming a projection to a substantially greater height are shown in each one of the examples described above. However, greater thickness for the same height as for the related art is also sought depending on the application. In such cases, forming can be achieved with the methods shown in FIG.

7

and FIG.

8

.

FIG.

7

(A) shows a method, based on the forming method shown in

FIG. 2

, where the thickness of the cylindrical projection having a bottom is increased. In FIG.

7

(A), the first press step #

1

, metal shifting step #

2

, and flat press step #

3

are the same as for the forming method shown in FIG.

2

and are therefore omitted. However, a point of distinction of this method from the method in

FIG. 2

is that a press tool

40

used in the first press step #

1

and second press step #

4

is smaller in diameter. The internal diameter of the central part

6

of the projection

5

therefore becomes smaller when the press tool

40

of a smaller diameter is pushed from the side of the opening of the hole

4

, with a hollow pole

2

C being formed to a greater thickness as a result.

The height of the hollow pole

2

C is substantially the same as the projection shown in the related example but a thickness t

71

is substantially greater than that of the related forming method because metal at the periphery of the opening for the hole

4

is gathered by the tapered recess

11

a

of the tapered tool

11

and moved to the projection

5

so as to increase the metal at the projection

5

.

FIG.

7

(B) is a view showing a method, based on the forming method shown in

FIG. 3

, for thickening the cylindrical projection having a bottom. The point of distinction of this method shown in FIG.

7

(B) is also that the press tool

40

used in the first press step #

1

, and the second press step #

4

is smaller in diameter. A thickness t

72

of the hollow pole

2

C can therefore also be thickened in FIG.

7

(B).

FIG.

8

(A) and FIG.

8

(B) show methods of making a cylindrical hollow pole having a thruhole passing from one side to the other side of a plate thicker. The method in FIG.

8

(A) is based on the forming method shown in FIG.

5

. The first press step #

1

, metal shifting step #

2

and second press step #

4

are therefore the same as for the forming method shown in FIG.

5

and are therefore omitted. Here, the point of distinction with

FIG. 5

is that the external dimensions of the press tool and a burring tool

50

used in the first press step #

1

and the burring step #

6

have their diameters smaller to a greater extent than the press tool

10

described previously. The internal diameter of the central part therefore becomes smaller as a result of pushing the burring tool

50

from the side of the opening of the hole

4

and a thicker cylindrical hollow pole

2

D is formed as a result.

In this example, a height L

80

of the hollow pole

2

D is substantially the same as for the projection shown in the related art. However, the projection

5

is formed to a much greater thickness than in the forming method of the related art because metal at the periphery of the opening of the hole

4

is gathered in the direction of the central part

6

by the tapered tool

11

and the tapered recess

11

a

so as to be moved to the projection

5

and increase the metal at the projection

5

.

FIG.

8

(B) is a forming method based on the forming method shown in FIG.

6

. In FIG.

8

(B), the point of distinction is that the burring tool

50

used in the first press step #

1

and the burring step #

6

is tapered. The details of this method are the same as described for FIG.

6

and are therefore omitted but the hollow pole

2

D can also be made thicker as in FIG.

8

(B).

In the above, a specific description is given based on the embodiments but the present invention is by no means limited to the above embodiments and modifications are possible that do not deviate from the essence of the invention as laid out in the patent claims. For example, rather than being cylindrical, the projection can also be a polygonal shape such as a substantially quadrilateral shape or a conical shape, or an ellipsoidal shape. The central part of the projection or the end portion etc. can also be made to be arbitrary shapes in response to various applications, such as a D-cut shape or a shape for forming a stopper etc. Further, in the above embodiments, examples of forming a single hollow pole are shown but it goes without saying that a plurality of hollow poles can also be formed in the plate.

FIG. 11

is an oblique sectional cross-section showing a hollow pole manufactured using the method of the present invention. Here, a metal plate such as iron, copper, aluminum, or brass to which plastic deformation is applied is selected as a plate

101

. A hollow pole

102

is then formed as a single hollow circular cylindrical body with a bottom protruding from the inside of the plate by plastically deforming a part of the plate

101

. This hollow pole

102

is formed to a height that is three to five times the thickness of the plate

101

by a forming method described in detail later.

Further, an annular thin section

103

is formed at the peripheral edge of the hollow pole

102

. This thin section

103

is thinner than the plate

101

and metal that was originally at the thin section

103

has been moved to the hollow pole

102

during plastic deformation in order to obtain a prescribed height for the protrusion axis

102

. It is also possible to provide a plurality of hollow poles

102

next to each other at intervals greater than a prescribed internal diameter of the thin section

103

. Further, it is preferable for the thin section

103

to be circular when the hollow pole

102

is circular but a polygon shape such as a substantially quadrangular shape or triangular shape or an ellipsoidal shape is also possible.

Next, a description is given of the method of the present invention for forming a hollow pole on a plate.

FIG. 12

is a view showing the processes for forming the hollow pole

102

formed as a hollow circular cylinder with a bottom from the interior of a plate. First, in a first press step #

1

, one side of the plate

101

comprising a metal plate of iron or copper etc. is pressed by a press tool

110

, with a hole

104

being formed on the one side of the plate

101

and a projection

105

being formed on the other side of the plate. The press tool

110

is formed as a cylindrical column with a flat end surface and the projection

105

is formed in a substantially cylindrical shape due to pressing by the press tool

110

.

Next, the metal shifting step #

2

is a process for gathering metal at the periphery of the opening of the hole

104

and moving this metal in the direction of the interior of the hole

104

. A cylindrical tapered tool

111

used in step #

2

is formed in the shape of a cylinder with an internal diameter that permits the insertion of the projection

105

. The end surface of the tapered tool

111

is formed with a tapered recess

111

a

having a tapered surface

111

a

recessed in a substantially conical shape from the outer periphery of the end surface towards the center of the end surface.

An inner hole of the cylindrical tapered tool

111

is inserted into the projection

105

formed by the first press step #

1

. On the other side, a contact member

112

with a flat surface at one end is made to come into contact with one surface of the plate

1

. The peripheral edge of the hole

4

is then pushed from the other side by the tapered recess

111

a

of the cylindrical tapered tool

111

. The tapered recess

111

a

therefore gathers metal at the peripheral edge of the hole

104

in the direction of the central part

106

that offers no resistance, the metal is moved to the side of the opening of the central part

106

and metal

107

is formed. At this time, the projection

105

is made to project further.

The hollow pole

102

that has undergone the metal shifting step #

2

then goes on to the next flat press step #

3

. In the flat press step #

3

, the periphery on the side of the other surface of the hole

104

is pressed with the contact member

112

in contact by a cylindrical flat press tool

113

with a flat front end and having an inner hole of an inner diameter that permits insertion of the projection

105

. As a result, metal of the pressed portion is moved further in the direction of the central part

106

of the hole

104

and the projection

105

is further projected. At this time, the side of the other surface of the periphery of the projection

105

is annuarly depressed and the thin section

103

is formed.

Additional height is then added to the projection

105

by pressing the press tool

110

down again from the side of the opening with the cylindrical flat press tool

113

inserted in the second press step #

4

so that a hollow pole

102

is formed.

A height L

2

of the hollow pole

102

that has been subjected to the second press step #

4

is substantially greater than that of the related forming method because in the metal shifting step #

2

, metal at the periphery of the opening of the hole

104

is gathered in the direction of the central part

106

by the tapered recess

111

a

of the cylindrical tapered tool

111

so as to be moved to the projection

105

and increase the metal of the projection

105

. The plate

101

is then transferred to a further extrusion step #

5

in order to further increase the height of the hollow pole

102

.

In the extrusion step #

5

, the thin section

103

is further extruded in the direction of projection of the hollow pole

102

by an extrusion tool

14

with a front end surface

14

a

projecting in a substantially conical shape. As a result, a height L

3

is added to the hollow pole

102

due to plastic deformation of the thin section

103

so that the hollow pole

102

is formed as the final shape. At this time, the extrusion height L

3

due to the extrusion tool

14

is set to the same extent as the thickness of the plate

101

. However, when the thin section

103

is not made to project from the surface of the plate

101

depending on the application, the height L

3

of extrusion can be set in an appropriate manner such as a setting to less than the thickness of the plate

101

.

FIG. 13

shows a modified example of the press tool

110

used in the first press step #

1

, with FIG.

13

(A) showing an example where the end is formed so as to be hemispherical and FIG.

13

(B) showing an example where the end is at first flat and then tapered. In each of the aforementioned methods, a hollow pole

102

higher than that of the related art can also be formed using one of the these press tools.

FIG. 14

is a view showing a process for forming a cylindrical hollow pole having a thruhole passing through from one side to the other side of the plate. In

FIG. 14

, a first press step #

1

, a second metal shifting step and a flat press step are the same as for FIG.

12

and are therefore omitted.

In a subsequent hole boring step #

6

, a small thruhole

105

a

is bored by a hole boring tool

20

formed tapered towards its front end pressing on the bottom part of the projection

105

of the plate

1

that has undergone the flat press step #

3

.

After this, a burring step #

7

is proceeded to. Here, a burring tool

121

, formed in a substantially parabolic shape and that tapers off towards the end and having an external diameter that is the same as the diameter of the press tool

110

shown in

FIG. 12

, is inserted into the central part

106

and pressed. The thruhole

105

a

is then passed through and a cylindrical hollow pole

102

is formed. At this time, the hollow pole

102

can be formed to a height L

4

substantially greater than that of the related art because the metal of the bottom part of the projection

105

is extended by the burring tool

121

and the plate

101

has been subjected to the metal shifting step. The plate

101

is then transferred to a subsequent extrusion step #

8

in order to make the height of the hollow pole

102

higher.

In the extrusion step #

8

, the thin section

103

is further extruded in the direction of projection of the hollow pole

102

by an extrusion tool

122

with a front end surface

122

a

formed in a substantially conical shape. As a result, a height L

5

is added to the height of the hollow pole

102

due to plastic deformation of the thin section

103

so that the hollow pole

2

A is formed as a result. At this time, the height L

5

of the extrusion due to the extrusion tool

122

is set to the extent of the thickness of the plate

101

but can be set in an appropriate manner according to use.

Methods for forming a hollow pole to a substantially greater height are shown in each one of the examples described above. However, a projection of a greater thickness is also sought depending on the application. In such cases, forming can be achieved with the methods shown in FIG.

15

and FIG.

16

.

FIG. 15

shows a method, based on the forming method shown in

FIG. 12

, where the thickness of the cylindrical projection having a bottom is increased. In

FIG. 15

, the first press step #

1

, metal shifting step, and flat press step are the same as for the forming method itself shown in

FIG. 12 and a

description thereof is therefore omitted. However, a point of distinction of this method from the method in

FIG. 12

is that a press tool

130

used in the first press step and second press step #

4

A is smaller in diameter. The internal diameter of the central part

106

of the projection

105

therefore becomes smaller when the press tool

130

of a tapered diameter is pushed from the side of the opening of the hole

104

, and a thickness t

2

can therefore be achieved. Thereafter, an extrusion step #

5

A is proceeded to, the thin section

103

is plastically deformed by extrusion by the extrusion tool

122

in the direction of projection of the projection

105

and a height L

6

is added to the projection

105

. As a result, a taller hollow pole

2

B is formed.

The hollow pole

2

B can therefore be formed to a much greater height than in the related example even when the hollow pole

2

B is subjected to the metal shifting step #

2

so as to be formed to a thickness t

2

because the projection

105

is further extruded in the extrusion step

5

A.

FIG. 16

is a view showing a method where the thickness of a cylindrical hollow pole having a thruhole passing through the sheet from front to back is formed to be thick based on the forming method shown in FIG.

14

. In the method shown in

FIG. 16

, a press tool for the first press step (not shown) and a burring tool

140

used in the burring step #

7

A are smaller in diameter. When burring is carried out using the burring tool

140

of a tapered diameter, the internal diameter of the projection

105

becomes small and a thickness t

3

is then made thick.

After this, an extrusion step #

8

A is proceeded to, and a height L

7

is added to the projection

105

as a result of plastic deformation of the thin section

103

by extrusion of the thin section

103

in the direction of projection of the projection

105

using the extrusion tool

122

so that the hollow pole

2

C is formed. The hollow pole

2

C can therefore be formed to a substantially greater height than that of the related example by this extrusion step even when the hollow pole

2

C is made thick in the extrusion step.

FIG. 17

is a view showing an example of a further method for forming a hollow pole on a plate of the present invention. The first press step #

1

is also the same as for the forming method shown in

FIG. 12

in this example and a description thereof is therefore omitted. However, the point of distinction from the method of

FIG. 12

is that the metal shifting step and the flat press step are carried out on a surface of the plate

101

on the opposite side from the projection

105

.

Namely, in a flat press step #

9

, an end surface of a cylindrical flat press tool

151

of an external diameter greater than the external diameter of a projection

150

is brought into contact with the plate

1

that has undergone the first press step (not shown) from the side of an opening of a hole

152

and is then pressed. As a result, metal of the pressed portion is moved to a central part

53

of the hole

152

which provides no resistance so as to be moved to the projection

150

so as to project. A thin section

156

is then formed at the periphery of the opening of the hole

152

pressed by the flat press tool

151

.

Next, in a second press step #

10

, the press tool

154

is again pressed against the plate

101

that has undergone the flat press step #

9

from the side of the opening and further height is added to the projection

150

. After this, the plate

101

is transferred to an extrusion step #

11

and the thin section

156

is extruded in the direction of projection of the projection

150

by an extrusion tool

155

. The thin section then undergoes plastic deformation and height is added to the projection

150

. In this way, a hollow pole

2

D is formed integrally with the plate

101

.

The extrusion tool

155

is also formed with a substantially conical protruding front end surface

155

a

that is the same external diameter as the cylindrical flat press tool

51

or can be formed with a slightly smaller diameter. The thin section

156

is then subjected to plastic deformation by pressing the extrusion tool

155

down in a state concentric with the flat press tool

151

and the hollow pole

2

D is made taller.

In the above, a specific description is given based on the embodiments but the present invention is by no means limited to the above embodiments and modifications are possible providing such modifications do not deviate from the essence of the invention as laid out in the patent claims. For example, in each of the above examples the front end surface of the flat press tool is substantially conical in shape but can also be hemispherical or have an external diameter smaller than the inner diameter of the thin section, with just the central side of the thin section than being subjected to plastic deformation. Further, in addition to being cylindrical, the projection can also be a polygon such as a quadrilateral or can be a column-shape. It also goes without saying that it is possible to form a plurality of projections in the plate.

The following is a description of a heat sink and a manufacturing method thereof formed with a plurality of heat dissipating units utilizing the aforementioned method of forming hollow poles.

FIG. 18

is a cross-section showing a heat sink unit formed by the forming method of the present invention, where FIG.

18

(

a

) is an enlarged view showing a heat sink unit and FIG.

18

(

b

) is a view showing the state when the heat sink comes into contact with electronic components generating heat.

As shown in FIG.

18

(

a

), a plurality of heat dissipating fins

203

are formed as circular hollow poles in the heat sink

201

by subjecting a base

202

a

comprised of a metal plate

202

of a metal having a superior thermal conductivity such as aluminum to plastic deformation. The heat dissipating fins

203

are formed to a height of approximately 1 to 3 times a thickness t of the base

202

a

of the metal plate.

Thruholes

204

that penetrate through from one side to the other of the metal plate

202

are provided at the center of the heat dissipating fins

203

.

Crater-shaped recesses

205

are formed at the peripheral edges of opening parts communicating with the thruholes

204

at the other surface of the metal plate

202

from which the cylindrical heat dissipating fins

203

are protruding. By forming the recesses

205

, metal originally at the metal plate

202

is moved in the direction of the heat dissipating fins

203

by plastic deformation and a required prescribed height h can be obtained for the heat dissipating fins

203

. The heat dissipating fins

203

are provided at prescribed intervals P so that the crater-shaped recesses

205

do not overlap. In addition to being circular, the heat dissipating fins

203

can also be polygonal shapes such as a quadrilateral or triangle.

Because the heat sink

201

has a plurality of heat dissipating fins

203

formed as hollow poles, surface area can be increased compared with related heatsinks having heat dissipating fins and the heat dissipating effects are therefore improved in proportion to the increase in the surface area. The surface area of the cylindrical heat dissipating fins

203

is the total surface area of the inner surfaces, outer surfaces and the upper end surfaces but in the case of the heat dissipating fins

203

, at least the surface area of the inner surface of the thruholes

204

is increased. Further, heat dissipation due to cooling air being passed through is substantially facilitated by the providing of the thruholes

204

.

As shown in FIG.

18

(

b

), both ends of the above heat sink

201

are attached to a case

208

so that the lower surface of electronic components

207

such as a CPU etc. comes into contact with the heat sink so as to be substantially face to face. When the electrical components

207

then conduct electricity via a circuit board

206

on which a prescribed wiring pattern (not shown) is formed, heat occurring due to the operation of the electrical components

207

is transmitted to the heat sink

201

coming into contact with the electrical components

207

. At this time, as a plurality of heat dissipating fins

203

are provided at the heat sink

201

, in addition to the increased surface area, heat dissipation can also be carried out in an effective manner by passing cooling air using the thruholes

204

.

Next, a description is given of a method of manufacturing the heat sink of the present invention.

FIG.

19

(

a

) to FIG.

19

(

c

) show a manufacturing process of the heat-dissipating fins

203

.

First, a press step is shown in FIG.

19

(

a

). Here, a press tool

230

formed with a front end with a flat surface and of a small diameter and gradually tapering outwards from the front end is used to press the metal plate

202

formed of a metal having a superior thermal conductivity such as aluminum. The crater-shaped recess

205

is then formed to a depth exceeding the thickness of the metal plate

202

at one surface of the metal plate

202

and a projection

221

is extruded at the other surface of the metal plate

202

.

When the crater-shaped recess

205

is formed at one side of the metal plate

202

in this press step, metal of the recess

205

is moved to the projection

221

formed at the other surface of the metal plate

202

and the metal of the projection

221

is therefore increased. The press tool in this press step can also be a press tool

230

a

with a front end formed in a substantially hemispherical shape. Further, it is not necessary to have the relatively large angled taper shown in

FIG. 19

for the shape of the front end of the press tool and this angle can also be set to a smaller angle or an arbitrary angle, etc.

Next, in a punch step, the projection

221

of the metal plate

202

that has been subjected to the press step is mounted on a die

240

and a punch

231

having a rod-shaped section of a fine diameter is passed through from the open side of the crater-shaped recess

205

and the front end of the projection

221

is punched so as to form a thruhole

222

of a small diameter.

After this, the metal plate

202

that has passed through the punch step is mounted on a die

241

and a burring tool

232

having a rod section of a diameter greater than the rod section of the punch

231

is made to penetrate from the side of the opening of the crater-shaped recess

205

in a burring step. In this burring step, the diameter of the hole

222

is broadened and the heat dissipating fins

203

are formed. As a result, the height of the cylindrical heat dissipating fins

203

formed on the other surface of the metal plate

202

can be formed to a height of approximately one to three times the thickness of the plate. When the thickness of the metal plate

202

is taken to be 1 mm to 3 mm, the height of the heat dissipating fins is 1 mm to 9 mm. In the case of these thicknesses, heat dissipating fins

203

of outer diameters of 1 mm to 5 mm are preferred for the best heat dissipating results.

In each of these steps subjecting the metal plate

202

to plastic deformation, the production can be achieved at low costs because metal patterning of a complicated structure such as casting is not necessary. These steps can be carried out one after another or can be carried out individually. Usually, a large number of heat dissipating fins are formed at the same time using a large number of press tools

230

, punches

231

and burring tools

232

but the heat dissipating fins can also be made one at a time or a plurality at a time.

By carrying out processing using the above three processes, heat dissipating fins

203

having a height of approximately one to three times the thickness of the plate can be formed at the metal plate

202

. The surface area occurring at unit intervals including a plurality of heat dissipating fins

203

can therefore be increased for the heat sink

201

provided with the cylindrical heat dissipating fins

203

and heat dissipation effects can be increased substantially because the surface area has been increased by the thruholes

204

of the heat dissipating fins

203

. Further, heat dissipation effects are increased because the surface area is substantially increased due to the crater-shaped recesses

205

being formed at the opening of the cylindrical head dissipating fin

203

. In addition, it becomes easy for hot air to flow from the crater-shaped recesses

205

and to be led into the thruholes

204

of the heat dissipating fins

203

due to the effect of the shapes of the crater-shaped recesses

205

. Convection effects are therefore increased as a result and the heat sink that dissipates heat more effectively is obtained. Typically, for integrated circuits such as CPUs etc. where cooling is particularly necessary, heat dissipation results that were about five times greater than those for a related heatsink were attained by forcibly cooling the heatsink

201

using a cooling fan or by passing cooling air within the thruholes

204

of the heat dissipating fins

203

using a cooling fan.

FIG.

21

(

a

) and FIG.

21

(

b

) are views showing examples of arranging heat dissipating fins

203

on the metal plate

202

, where FIG.

21

(

a

) shows a large number of heat dissipating fins

203

formed so as to be lined up in rows at the metal plate

202

. FIG.

21

(

b

) shows an example where a space is provided for mounting the electronic component

207

at the center of the metal plate

202

and a large number of heat dissipating fins

203

are formed randomly about the periphery of the electronic component

207

. When the electronic component

207

is then arranged in this manner, various patterns for arrangement are possible for forming the heat dissipating fins

203

such as forming the plurality of heat dissipating fins

203

in a plurality of concentric circle shapes about the periphery of the electronic component

207

or forming the plurality of heat dissipating fins

203

gathered about the side of the heat generating portion of the electronic component

207

. Alternatively, the electronic component

207

can be provided at a portion where heat dissipating fins

203

are not provided from the relationship between other neighboring structural components and the space.

In the above, a specific description is given of the present invention based on the embodiments but the present invention is by no means limited in this respect and various modifications that do not deviate from the spirit of the invention as stated in the patent claims are possible. For example, when the height of the plurality of heat dissipating fins

203

formed at the metal plate

220

is low, the punch step and the burring step can be carried out by the same implement. Further, the crater-shaped openings formed at the heat dissipating fins

203

can also be formed in the shape of an arc rather than as a straight tapered hole. Moreover, as shown in

FIG. 20

, the crater-shaped recess can be formed to a depth of less than half of the thickness of the metal plate

202

and, as shown in FIG.

21

(

c

), it is also possible to have the heights of the heat dissipating fins

203

different depending on the portion at which the heat dissipating fins

203

are formed.

The following is a description with reference to

FIG. 22

to

FIG. 25

of a further method for forming a heat sink of the present invention.

In a heat sink

301

shown in

FIG. 22

to

FIG. 25

, a large number of hollow cylindrical projections

303

as heat dissipating fins are integrally formed by taking a base

302

comprised of a metal having a superior thermal conductance such as aluminum or copper and subjecting parts of the base

302

to plastic deformation. Thruholes

304

are then provided at the axial centers of hollow cylindrical projections

303

as the heat dissipating fins, with the thruholes

304

penetrating from the bases

302

to the front ends of the projections

303

. Four slits

305

are then formed at equal spacings extending from the bases

302

to the front ends along the axial direction at the hollow cylindrical projections

303

. These hollow cylindrical projections

303

are then formed to a height greater than a thickness t of the base

302

of the metal plate and preferably to a height h two to five times greater than the height h by a forming method to be described in detail hereafter.

Further, thin sections

306

having a prescribed internal diameter w are formed at the peripheral edges at corresponding positions on the reverse side of the base

302

which is formed with the cylindrical projections

303

. These thin sections

306

are thinner than the thickness t of the base

302

, with metal that was originally at these thin sections

306

being moved to the projections

303

during plastic deformation in order to make the projections

303

of the prescribed height h. Each of the cylindrical projections

303

are provided next to each other at intervals p of greater than a prescribed internal diameter w of the thin sections

306

. The thin sections

306

are preferably made circular when the projections

303

are cylindrical but do not have to be circular, and can also be a polygon such as a quadrilateral or triangle, etc.

With the heat sink

301

constructed in this manner, surface area is increased compared with the related heatsink having heat dissipating fins because the large number of projections

303

are formed in the shape of cylinders and heat dissipating effects are therefore improved in proportion to the increase in the surface area. The surface area of the cylindrical heat dissipating fins

203

is the total surface area of the inner surfaces, outer surfaces and the upper end surfaces but in the case of the cylindrical heat dissipating fins

303

, at least the surface area of the inner surface of the thruholes

304

is increased. Further, heat dissipation due to cooling air flowing in a vertical direction from the base

302

through the thruholes is substantially facilitated by the providing of the thruholes

304

.

Further, as shown in

FIG. 26

, when cooling air

307

shown by solid lines passes through the slits

305

, the thruholes

304

are at negative pressure because of the slits

305

formed so as to extend along the axial direction of a trunk portions of the projections

303

from the base

302

to the front ends thereof. Heated air

309

generated from an accompanying element

308

that generates heat and is lined up so as to face the reverse surface side of the heatsink

301

and air

310

heated at the periphery of the element

308

is therefore drawn into the thruholes

304

from the reverse surface side of the base

302

and expelled together with the cooling air

307

. The heat dissipating effect due to the thruholes

304

is therefore multiplied so as to bring about a dramatic increase in the heat dissipation effect. Heat that has accumulated at the base

302

is also cooled by the passing of the heated air

310

and the heat dissipation effect is therefore further improved. This is to say that an almost ideal heatsink can be made by forming slits

305

in the projections

303

. It also goes without saying that heat transmitted to the heatsink

301

can be emitted as radiated heat from the surface of the heatsink

301

as with a typical related heatsink.

The following is a description of a method of forming a heatsink of the present invention.

FIG. 27

is a view showing steps for forming the hollow cylindrical projection

303

as heat dissipating fins, with the first to fifth steps being for a burring step for forming a hollow cylindrical projection penetrating the metal plate from one side to the other by plastic deformation of one surface of the metal plate. A sixth step is a slit forming step for forming a slit

305

in the outer periphery of the projection

303

.

First, in a first step, a first tool

331

with a flat front end and tapering outwards from the front end is pushed down against a surface of a metal plate

320

of a metal such as aluminum having a superior thermal conductivity, so that a depression

321

is formed at one surface of the metal plate

320

and a projection

322

is formed at the other surface of the metal plate

320

.

Next, in a second step, an end surface

332

a

of a columnar second tool

332

of a diameter a greater than the external diameter b of the projection

322

is brought into contact with the metal plate

320

that has undergone the first step from the side of the depression

321

and pressed so as to form the thin sections

306

. Metal at the portion pressed by the second tool

332

is then moved to the projection

322

while being moved towards the a central section

323

that provides no resistance and the projection

322

is further elongated.

In a third step, the metal plate

320

subjected to the second step is again pushed from the side of the depression

321

by the first tool

331

and height is added to the projection

322

. A projection

322

having a height of at least twice the thickness of the plate

320

is therefore formed by the steps undergone up to this point.

In a fourth step, a third tool

333

having a fine diameter stem portion is made to penetrate the metal plate

320

that has passed through the third step from the side of the depression

321

and a hole

324

is then made by punching out the end of the projection

322

.

In a fifth step, the hole

324

is broadened by passing a fourth tool

334

having a stem portion of a wider diameter than the stem portion of the third tool

333

through the metal plate

320

that has passed through the fourth step from the side of the opening. As a result of carrying out this fifth step, a hollow cylindrical projection

303

is formed, and a thruhole

304

passing through from the thin section

306

to the end of the projection

303

is formed at the center of the axial direction of the projection

303

formed by the penetration of the fourth tool

334

. Each of the first to fifth steps simply subject the metal plate

320

to plastic deformation. Metal patterning with complex structures such as in casting are therefore not required and production can be achieved at low cost. These steps can be carried out in a continuous sequence or can be carried out individually.

The cylindrical projection

303

formed in the above way can be formed to a height that is two to five times the thickness of the metal plate

320

. After this, a plurality of slits

335

are formed at the outer periphery of the cylindrical portion of the projection

303

in a sixth step.

A fifth tool employed in a sixth step is a slit-forming punch

335

. As shown in

FIG. 27

, four blade-shaped cutter blades

335

b are formed so as to project at equal intervals and to extend along the axial direction at the outer periphery of a circular stem section

335

a

having an outer diameter that allows insertion into the thruhole

304

formed in the projection

303

. The width of the cutter blades

335

b

is set in such a manner that the diameter of a circle formed by connecting the outer peripheries of the four cutter blades

335

b

is approximately equal to the outer diameter of the projection

303

. The front ends of the cutter blades

335

b

are formed in such a manner that overall the blades taper outwards when going from the front ends toward the base but steps

335

c

are formed at the outer ends. The ends of the circular stem sections

335

a

also taper off so as to simplify penetration through the thruhole

304

.

On the other hand, the projection

303

of the metal plate

320

is inserted into a hole formed in a metal-molded die (not shown). The fifth tool

335

is then inserted from the side of the depression

321

and the circular stem section

335

a

is made to pass through the thruhole

304

. The four cutting blades

335

b

then cut away while being pushed in the axial direction of the cylinder of the projection

303

. Four slits

305

are then formed in the cylindrical portion of the projection

303

when the cutter blades

335

b

pass the front end of the projection

303

.

The number of cutting blades

335

b

formed to project from the slit-forming punch

335

is by no means limited to four, and an arbitrary number from two to eight can be provided depending on the number of slits

305

that are necessary. In the above embodiment, steps

335

c

are formed at the end portions of the cutting blades

335

b

but this is not essential. It is preferable to form the steps

335

c

in order to form slits

305

of a suitable appearance. The shape of the end of the fifth tool

335

can also be hemispherical rather than being substantially conical. In the second an third steps, the second step was taken to be necessary in order to increase the height of the projection

3

but at least the third process can be omitted when a low height for the projection

303

is appropriate. In this case, the front end of the second tool

332

shown in the second step can be changed to being substantially a conical stand shape.

When a projection

303

having slits

305

is formed by a process comprising a burring step of forming a hollow cylindrical projection that penetrates from one side to the other of the metal plate

320

by subjecting one surface of the metal plate

320

to plastic deformation and a slit forming process of pressing the slit-forming punch

335

formed with a plurality of cutting blades

335

b

into the thruhole

304

of the projection

303

so as to form slits

305

in the outer periphery of the projection

303

, the projection

303

can easily be formed to the required height and the slits

305

can easily be formed at the outer periphery of the projection

303

.

In the above embodiment, an example is shown of a heatsink

301

formed with a plurality of slits along the axial direction at the outer periphery of the projection

303

formed as a hollow pole but the slits can also be formed in other shapes. In the examples shown in

FIG. 28

to

FIG. 30

, the body of a hollow cylindrical projection is divided up into partitions, with each partition being opened up outwards from the projection so as to form slits between the partitions.

In FIG.

28

(A), the body of a hollow cylindrical projection

350

is partitioned into eight, with each one partition

351

opening up outwards from the base of the projection

350

towards the end side so that the projection

250

looks like the petals of a flower, with slits

352

therefore being formed between the partitions

351

. As slits

352

are also formed at the front ends with this kind of projection

350

, a state of negative pressure can also be made to occur within a thruhole

353

as in the previous embodiments by having cooling air pass through the slits

352

. Hot air generated by an element that generates heat (not shown) that is surface-bonded to the rear surface of a heatsink

350

and surrounding air that is also heated is therefore drawn in and expelled together with the cooling air.

Next, a description is given of a method for forming the projection

350

shown in FIG.

28

(A). The method up to the forming of the hollow cylindrical projection

350

is the same as the process in the first to fifth steps of

FIG. 27

described for the previous embodiment and a description thereof is therefore omitted. The hollow cylindrical projection

350

formed in this manner is mounted at a slit-forming die

355

. As shown in FIG.

28

(B), the slit-forming die

355

is provided with an insertion hole

356

for insertion of the projection

350

and is formed with equally-spaced channels

357

at four places at the inner surface of the insertion hole

356

. The radius of the inner surface of the channels

357

is formed so as to be larger than the radius of the insertion hole

356

with the thickness of the projection

350

added. A slit-forming punch

358

then comprises a stem

358

a

formed with an external diameter that is capable of insertion into a thruhole

353

of the projection

350

and four opening banks

359

formed so as to protrude out from the outer periphery of the stem

358

a

at positions corresponding to the channels

357

. These opening banks

359

are tapered with their width gradually becoming greater from the front end side towards the rear.

After the projection

350

is inserted into the insertion hole

356

of the slit-forming die

355

, the slit-forming punch

358

is forcibly inserted from the front end side of the projection

350

. In this way, the outer periphery of the projection

350

positioned to correspond to the channels

357

is gradually sheared by the pressing of the opening banks

359

and, as shown by the two-dotted and dashed lines in FIG.

28

(B), one partition

351

is pushed out into each one channel

357

. As a result, as shown in FIG.

28

(A), the body of the hollow cylindrical projection

350

is partitioned into eight, with slits

352

being formed between each one partition

351

and the neighboring remaining body of the projection

350

.

In FIG.

29

(A), the body of a hollow cylindrical projection

360

is partitioned into eight, with slits

362

being formed between these partitions

361

by bending each partition

361

into an approximate L-shape so as to open up towards the outside. As with the previous embodiment, as slits

362

are formed in the projection

360

if cooling air is passed through the slits

362

, a state of negative pressure occurs within the thruhole

363

and the effect where hot air and surrounding heated air is drawn in and expelled can again be obtained.

Next, a description is given of a method for forming the projection

360

, an example of which is shown in FIG.

29

(A). The method for forming the hollow cylindrical projection

360

is the same process of the first to fifth steps of

FIG. 27

described for the previous embodiment and a slit-forming metal die is substantially the same as the die

355

shown in FIG.

28

(B), so the same numerals are given thereto and detailed descriptions thereof are omitted. On the other hand, a slit-forming punch

365

comprises a stem

366

formed with an external diameter that is capable of insertion into a thruhole

363

of a projection

360

and four opening banks

367

formed so as to protrude out from the outer periphery of the stem

365

at positions corresponding to the channels

356

of the die

355

. However, the opening banks

367

are formed of fixed dimensions continuously from tapered parts

367

a

at the ends thereof.

After the projection

360

is inserted into the insertion hole

356

of the slit-forming die

355

, the slit-forming punch

365

is inserted from the front end side of the projection

360

. In this way, the outer periphery of the projection

360

positioned to correspond to the channels

357

is gradually sheared by the pressing of the opening banks

367

and, as shown by the two-dotted and dashed lines in FIG.

29

(B), one partition

361

is pushed out into each one channel

357

. As a result, as shown in FIG.

29

(A), the body of the hollow cylindrical projection

360

is partitioned into eight, with each partition

361

being bent into an approximate L-shape so as to open out towards the outside of the projections

360

. Slits

362

are therefore formed between the neighboring remaining parts of the body of the projection

360

.

In FIG.

30

(A), as in the example in FIG.

27

and

FIG. 29

, the body of a hollow cylindrical projection

370

is partitioned into eight, with the outer diameter of a locus formed by each one of the partitions

371

being greater than the dimensions of the outer circumference of the projection

370

, so that slits

372

are formed between the partitions

371

. As with the previous embodiment, as slits

372

are formed, if cooling air is passed through the slits

372

, a state of negative pressure occurs within the thruhole

373

and the effect where hot air and surrounding heated air is drawn in and expelled can again be obtained.

Next, a description is given of a method for forming the projection

370

, an example of which is shown in FIG.

30

(A). The method for forming the hollow cylindrical projection

370

is the same as the process of the first to fifth steps of

FIG. 27

described for the previous embodiment and a slit-forming metal die is substantially the same as the die

355

shown in FIG.

28

(B), so the same numerals are given thereto and detailed descriptions thereof are omitted. On the other hand, a slit-forming punch

375

comprises a stem

376

formed with an external diameter that is capable of insertion into a thruhole

373

of a projection

370

and four opening banks

377

formed so as to protrude out from the outer periphery of the stem

376

in accordance with channels

357

. However, the opening banks

377

are formed of fixed dimensions continuously from insertions

377

a

at the ends thereof.

After the projection

370

is inserted into the insertion hole

356

of the slit-forming die

355

, the slit-forming punch

375

is inserted from the side of the metal plate

320

on the opposite side from the projection

370

. As pushing of the slit-forming punch

375

then progresses, the inserts

377

a

are pushed in from the base of the projection

370

, with the inserts

377

a

being positioned so as to correspond with channels

357

, and the projection

370

is gradually sheared by the pressing of the opening banks

367

while, as shown by the two-dotted and dashed lines in FIG.

30

(B), each one partition

371

is pushed out into each one channel

357

. The body of the hollow cylindrical projection

370

is therefore partitioned into eight, with each one partition

371

standing up from the base and with a locus being formed by each one of the partitions having an outer circumference that is larger then the outer circumference of the projection

370

. Slits

372

are therefore formed between the neighboring remaining parts of the body of the projection

370

.

In

FIG. 31

, as shown in the other embodiments, four flat partitions

381

are formed so as to stand up so as to give a projection

380

with mutually opposite partitions

381

. Here, slits

382

are formed extending in the axial direction from the base of the projection

380

to the front end thereof. If cooling air

308

is therefore passed through the slits

382

in the manner shown by the solid lines in

FIG. 31

, a state of negative pressure occurs within a thruhole

383

. Heated air

310

generated from an element lined up so as to face the rear surface of the heatsink

301

is therefore drawn in in the manner shown by the dotted lines at the rear surface of the base and is expelled together with the cooling air

308

.

Various modifications are possible for each of the above embodiments of the present invention. For example, when manufacturing the cylindrical projection

303

, the hole

324

is broadened by passing the fourth tool

334

having a large-diameter stem through from the opening side but it is also possible to form channels at the outer surface of the fourth tool

334

and push the fourth tool

334

into the hole

324

so that grooves are also formed at the inner surface of the hole

324

and the surface area of the inner surface is increased. In the further embodiments shown in

FIG. 28

to

FIG. 30

, the partitions are made substantially equal but can also be made unequal, with, for example, the width of partitions projecting out from the projection being smaller.

As described above, in the method for forming a hollow poles projecting from a metal sheet of the present invention, there is provided a method of integrally forming a projection as a hollow pole in the sheet by plastic deformation, where a thin section is formed in an extrusion step so as to increase the height of the projection. It is therefore possible to make the projections substantially higher. Further, as the amount of metal shifted to the projection is increased by a metal shifting step, the height of the projection can be increased compared with projections formed by related projection-forming methods, or alternatively, the projection can easily be made thicker. The cost of adding these steps has a minimum influence on prices and manufacture is therefore cheap.

According to the method of forming a heatsink of the present invention, a plurality of hollow poles as cylindrical heat dissipating fins can be easily formed in a metal sheet with few steps and manufacturing costs can therefore be reduced. Further, by giving the cylindrical heat dissipating fins funnel-shaped openings, metal can be shifted to the cylindrical heat dissipating fins and high-quality heat-dissipating fins can therefore be formed. Moreover, heatsinks formed by this method have a large number of heat dissipating fins having heights in excess of the thickness of the metal plate and the overall surface area of the heatsink can therefore be increased. Air can also be made to flow through because the heat dissipating fins have thruholes that penetrate through from one side of the metal plate to the other and a heat dissipating effect can therefore be substantially improved. In particular, the heat dissipating effect can be improved several times over by passing cooling air through the thruholes of the heatsink when forcible cooling is carried out using the fins.

Still further, slits extending in the axial direction from the base to the front end are formed at the body of the hollow pole as the heat dissipating fins. A state of negative pressure therefore occurs when cooling air is passed through the slits so that heated air occurring at the reverse surface of the base is drawn in and expelled together with cooling air. The heat dissipating effect due to the thruholes of the hollow pole is multiplied and is therefore dramatically increased. According to the method of forming the heatsink of the present invention, hollow poles are formed at a surface of the metal sheet by a burring step and slits are formed at the outer periphery of the hollow poles using a slit-forming punch. Heat dissipating fins having slits can therefore be easily formed in few steps.

Number	Date	Country	Kind
10-241057	Aug 1998	JP
10-259251	Aug 1998	JP

Number	Name	Date	Kind
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2308953	Brown	Jan 1943	A
2743518	Zohodiakin	May 1956	A
2898788	Baxa	Aug 1959	A
2909281	Koskinen	Oct 1959	A
2977918	Kritzer	Apr 1961	A
3080839	Fein et al.	Mar 1963	A
3131758	Kern et al.	May 1964	A
3245465	Young	Apr 1966	A
3682122	Haddon et al.	Aug 1972	A
3757718	Johnson	Sep 1973	A
4109501	Kozima	Aug 1978	A
4150556	Melnyk	Apr 1979	A
4400965	Schey	Aug 1983	A
5237849	Miyazawa	Aug 1993	A
5448832	Kanemitsu et al.	Sep 1995	A
5600992	Kanazawa et al.	Feb 1997	A
5761949	Dalessandro et al.	Jun 1998	A
5797291	Yamada	Aug 1998	A
6134783	Bargman et al.	Oct 2000	A

Method of forming a hollow pole projecting on a plate and a method of manufacturing a heat sink using said method

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (2)

US Referenced Citations (21)

Foreign Referenced Citations (1)