WO2001072089A1

WO2001072089A1 - Device for heating workpieces

Info

Publication number: WO2001072089A1
Application number: PCT/EP2001/003400
Authority: WO
Inventors: Waldemar Gezarzick; Hans-Jürgen LEISSNER; Peter Schulte
Original assignee: Elotherm Gmbh
Priority date: 2000-03-24
Filing date: 2001-03-26
Publication date: 2001-09-27

Abstract

The invention relates to a device for inductive heating of sections of metallic workpieces (W, B), in particular, for the annealing of previously hardened components (W, B), with an inductor (3, 50, 70), comprising at least one conductor piece (31-37, 52-59, 71-77), extending from the energy supply in the longitudinal direction, along the length of the section of the workpiece to be heated (W, B), in close proximity thereto and engaging with said workpiece (W, B) around, at most, a part of the circumference thereof and a second conductor piece (31-37, 52-59, 71-77) arranged in the longitudinal direction of the workpiece (W, B) and leading back to the energy source. Said device further comprises a drive arrangement for a rotating relative movement between the workpiece (W, B) and the inductor (3, 50, 70), along the longitudinal axis (X) of the workpiece (W, B) during the heating process.

Description

Device for heating workpieces

The invention relates to a device for heating workpieces, in particular for tempering previously hardened components, with an inductor.

When heating workpieces with different diameters in the axial direction, there is a requirement with inductive heating to position the conductor branches of the inductor on the workpiece in such a way that on the one hand the electromagnetic field is sufficiently induced in the workpiece and on the other hand overheating at certain exposed areas Edges is avoided. Such edges are present, for example, in the area of the transition between the individual, different-diameter shoulders of the workpiece.

In devices known from practice for heating workpieces of the type in question, inductors are used, the inductor branches of which are guided helically around the workpiece rotating during the heating. The effectiveness of the field generated by the inductor branches is determined by a suitable sheet set. In this way, an inductor is available which completely surrounds the section of the workpiece to be heated and whose output is adapted to the respective requirements.

Practical experience with known devices of the type explained above shows that the heating leads to unsatisfactory results despite the individual adaptation of the shape of the inductor to the external shape of the component to be heated. It has thus been found that even when using inductors in which the helix of the inductor branches are arranged in close proximity, there is an inhomogeneous distribution of the heat in the workpiece. This applies in particular if such a device is to be used to start a hardened workpiece consisting of solid material in the region of its pin-like projection by reheating.

Such workpieces are, for example, components from the transmission or the drive train of a motor vehicle that are provided with longitudinal teeth in the region of a pin. After the entire workpiece has been hardened beforehand, such components or the sections adjoining them are tempered in order to restore the required toughness of the material in the relevant sections.

The object of the invention is to provide a device of the type explained above, which it makes it possible to heat workpieces of the type explained above with an improved work result.

This object is achieved by a device for inductively heating sections of metallic workpieces, in particular for tempering previously hardened components, with an inductor which extends at least one starting from an energy supply in the longitudinal direction over the length of the section of the workpiece to be heated and close to this guided conductor piece, which encompasses the workpiece by at most part of its circumference, and has a second conductor piece guided back to the energy supply in the longitudinal direction of the workpiece, and is equipped with a drive device which, during heating, rotates a relative movement about the longitudinal axis of the workpiece between workpiece and inductor.

In an apparatus designed according to the invention, an inductor is used to induce the electromagnetic field, the shape of which is determined by two conductor pieces extending essentially along the workpiece to be heated. In contrast to the prior art, these conductor pieces are not wound several times around the circumference of the workpiece, but at most are guided around a partial section of the total circumference.

The inductor branches which extend essentially linearly in the axial direction of the workpiece induce an in Longitudinal direction of the workpiece uniformly formed field, which due to its limited width covers only a portion of the circumferential surface of the workpiece. The relative movement rotating about the longitudinal axis of the workpiece, however, ensures that the entire circumference of the workpiece is evenly swept by the induced fields.

As a result, the mode of operation of a device according to the invention leads to homogeneous heating of the workpiece. The heated workpiece has no dead zones that cannot be reached by the heat. The invention achieves this with an inductor which, measured on the inductors used in known devices, can be easily shaped and manufactured in a simple manner.

If the workpiece to be heated has a plurality of successive sections in the axial direction, then it is expedient if the inductor is divided in steps in accordance with the sequence of sections of the workpiece to be heated and each of the sections is extended in the longitudinal direction and extends over the length of the respective section Guide piece is closely associated with the section concerned. In this way, the shape of the inductor is optimally adapted to the shape of the workpiece to be heated. By providing appropriately designed laminations at a suitable point on the respective conductor pieces, the electro-magnetic fields can be integrated into the required areas are induced in such a way that heating which is also optimally adapted to the respective machining task is carried out.

Depending on the design of the workpiece, it may also be expedient if the conductor pieces of the inductor running in the longitudinal direction are connected to one another by a conductor piece running in the circumferential direction. This is especially true if there are pronounced shoulders between the individual sections of the workpiece that require special treatment. Such sections can be heated directly with great accuracy from the fields induced by the conductor pieces guided radially around the circumference.

The uniform generation of the heating can also be perfected in that the conductor pieces of the inductor are arranged symmetrically with respect to the axis of rotation of the workpiece. In this embodiment, the individual pieces of the inductor are of equivalent design and are equally arranged in space, so that the fields are induced into the workpiece with great uniformity. For the same reason, it is expedient if those guided in the circumferential direction jointly embrace at least half of the respective paragraph.

Depending on the size of the section to be heated, the wall thickness of the component in this area and the shape, it may be necessary, at least to guide one of the longitudinally extending conductor pieces simultaneously in the longitudinal and circumferential directions of the workpiece. In this way, larger powers can be induced over a larger area in the relevant section of the workpiece. It is essential, however, that the conductor piece encompasses only part of the circumference of the workpiece, but is never completely guided around its circumference.

A first possibility, not only to guide the respective conductor piece only axially parallel to the longitudinal axis of the workpiece, but also in the circumferential direction, is that in the conductor piece, starting from a longitudinally directed section, a loop is formed which extends along the circumference of the workpiece is. Alternatively or additionally, the conductor piece can also be guided at an angle deviating from the longitudinal direction of the workpiece along the circumference of the workpiece in order to achieve both a longitudinal and a circumferential extent of the relevant conductor piece. The conductor section can be divided into at least two sections that run towards each other at an acute angle. This configuration also makes it possible to distribute a large length of the relevant conductor piece over a small section of the workpiece circumference.

A further advantageous embodiment of the invention is characterized in that the energy supply pulsates the inductor with electrical energy in such a way that each heating interval occurs Break interval follows. In this mode of operation of the energy supply, there is sufficient time after the supply of heat that the heat generated is distributed in the workpiece by heat migration. In this way, overheating of the workpiece can be avoided with optimal energy yield and uniform, gentle heating of the workpiece can be guaranteed. In this context, practical tests have shown that it is advantageous if the ratio of the duration of the heating interval to the duration of the pause interval is 3: 4.

A device according to the invention for tempering previously hardened workpieces can be used particularly advantageously.

The invention is explained in more detail below on the basis of a drawing illustrating an exemplary embodiment. In a schematic representation:

Figure 1 shows a device for heating workpieces in a side, partial view.

FIG. 2 shows an inductor used in the device according to FIG. 1 in a perspective illustration;

3 shows another side view of another inductor intended for use in the device according to FIG. 1; FIG. 4 shows a third side view of a third inductor intended for use in the device according to FIG. 1.

The machined in the device 1, shown in Fig. 1, the rotationally symmetrical workpiece W has an elongated, pin-shaped projection Wl, in which a toothing is formed, a first paragraph W2 adjoining it in the longitudinal direction L, the diameter D2 of which is larger than the diameter Dl of the projection Wl, and a cup-shaped shoulder W3, the diameter D3 of which is in turn larger than the diameter D2 of the shoulder W2. The workpiece W has undergone hardening before being placed in the device 1.

The workpiece W sits on a turntable 2 of the device 1, which is driven to rotate about an axis of rotation X via a drive, not shown. The workpiece W is oriented so that the axis of rotation X and the longitudinal axis of the workpiece W coincide and the peg-shaped projection W1 points freely upwards.

To heat the workpiece W, an inductor 3 is provided, which is designed symmetrically with respect to the axis of rotation X of the device 1.

The inductor 3 has a first conductor piece 31 which extends axially in the longitudinal direction L of the workpiece W. The conductor piece 31 is in its lower end region 31a Direction of the projection Wl cranked so that it is guided closer to the projection Wl in this area.

A radially circumferential conductor piece 32 is connected to the cranked end region 31a and is assigned to the foot region Wla of the projection Wl of the workpiece W. The radially circumferential conductor piece 32 encompasses a quarter of the circumference of the projection W1 at a short distance from the outside thereof. In this case, the conductor piece 32 is in the state placed on the workpiece W with an equally small distance above the free upper side of the second shoulder W2 of the workpiece W.

A second conductor piece 33, which extends axially along the workpiece W, is connected to the end of the first radially rotating conductor piece 32 facing away from the first axially extending conductor piece 31. This conductor piece 33 is formed in its end section 33a assigned to the conductor piece 32 so as to be bent in the direction of the axis of rotation X in such a way that its end section 33a is placed on the top of the end of the conductor piece 32. In this way, the conductor piece 33 engages around the free edge W2a of the second paragraph W2 with a sufficient distance.

A conductor piece 34, which extends radially around the second shoulder W2 of the workpiece W, is connected to the lower end of the axially extending conductor piece 33. This second radially circumferential conductor piece 34 encompasses the second shoulder W2 by 180 °, also between the conductor piece 34 and the outer side of paragraph W2 there is only a small distance. At the same time, the length of the second axially extending conductor piece 33 is dimensioned such that the second radially extending conductor piece 34, when the inductor 3 is placed on the workpiece W, is just as close above the free upper side of the third shoulder W3 of the workpiece W.

At its end facing away from the axially extending conductor piece 33, a further axially extending conductor piece 35 is formed on the second radially circumferential conductor piece 34 opposite this conductor piece 33. The conductor piece 35 has the same shape as the conductor piece 33 and lies, encompassing the free edge W2a, with its end facing away from the radially circumferential conductor piece 34 on another radially circumferential conductor piece 36.

The conductor piece 36 is formed with respect to the longitudinal axis of the workpiece W in a point-symmetrical manner with respect to the first radially circumferential conductor piece 32 and, like the latter, engages around the foot region Wla of the projection W by 90 °.

Connected to the end of the conductor piece 36 facing away from the conductor piece 35 is a last axially extending conductor piece 37 arranged opposite the first conductor piece 31, the shape of which corresponds to the shape of the conductor piece 31.

At the end of the conductor pieces facing away from the respectively assigned, radially rotating conductor pieces 32 or 36 31 and 37 are each connected to one of the supply lines, not shown in detail, via which an energy feed, also not shown, supplies the inductor 3 with electrical energy.

The strength and orientation of the field induced by the respective conductor pieces 31-37 is adjusted by a suitable sheet metal not shown.

To start the previously hardened workpiece W arranged on the turntable 2, the inductor 3 is placed on and supplied with electrical energy via the feed, not shown. The energy supply is pulsed in such a way that a heating interval of a duration T1 is followed by a pause interval of the duration T2. The ratio of the duration T1 to the duration T2 is 3: 4. In this way it is achieved that the heat supplied during the heating interval is distributed in the workpiece W during the interval, so that there is uniform heating without the risk of overheating.

Due to the radially guided around the workpiece pieces 32, 34 and 36, the transition areas between the projection Wl and the shoulder W2 or between the shoulder W2 and the shoulder W3 of the workpiece W are included in the heating, so that not only the projection Wl , but also the relevant transition areas are left in the device 1 after the heating treatment. If the pot-shaped shoulder W3 of the workpiece W is also to be left on, the inductor 50 shown in FIG. 3 can be used for this purpose. This inductor 50 has a first conductor piece 52 connected to the first pole 51 of an energy supply (not shown), which runs in the longitudinal direction L and runs parallel to the axis of rotation X for heating the peg-shaped projection W1. This is followed by a conductor piece 53 guided radially by about a quarter of the circumference of the peg-shaped projection W1.

An axially extending conductor section 54 is connected to the conductor section 53 via a cranked end section placed on the conductor section 53. The conductor piece 54 extends in the longitudinal direction L along the contour of the pot-shaped shoulder W3, it being arranged in one plane with the axis of rotation X. A conductor piece 55 is connected to the conductor piece 54 radially in the region of the lower edge of the step W3, which piece extends around the circumference of the step W3 by approximately 180 °.

At an acute angle, starting from the end of the conductor piece 55 assigned to it, a conductor piece 56, which extends in the longitudinal direction L and at the same time runs around a partial section of approximately 150 ° of the circumference of the shoulder W3, runs in the direction of the upper edge of the shoulder W3. There, the conductor piece 56 merges into a conductor piece 57 which is guided radially by approximately 180 ° around the shoulder W2 of the workpiece W. Via a conductor piece 58 which is guided in the longitudinal direction L parallel to the axis of rotation X, the conductor piece 57 is connected to a further conductor piece 59 encompassing the peg-shaped projection W1 in its foot region by approximately 90 °. This conductor piece 59 is finally connected to the second pole of the energy supply via a conductor piece which is covered by the workpiece W in FIG. 3 and is arranged parallel to the axis of rotation X and is guided in the longitudinal direction L.

Appropriate sheet metal of inductor 50 induces heat in workpiece W at the required points. The conductor piece 56, which extends simultaneously in the longitudinal direction L and the circumferential direction, enables the uniform and precisely metered induction of an electric field into the wall of the section W3, which is relatively thin in this area.

The inductor 70 shown in FIG. 4 is particularly suitable for tempering a component B that is not rotationally symmetrical. Component B shown in FIG. 4 has a pin B1, which is followed by a pot-shaped section B3 via a shoulder B2. The component B can be, for example, a so-called "tripode", as is used in the area of the front-wheel drive of cars.

The inductor 70 has a first conductor piece 71, which extends in the longitudinal direction L along the pin Bl and the shoulder B2 and which has one end at the first pole of an energy supply, not shown, is connected. At the other end of the conductor piece 71, a conductor piece 72 guided radially by about a quarter of the foot region of the shoulder B2 is connected.

A conductor piece 73, which extends in the longitudinal direction L and extends over the length Lb3 of the pot-shaped section B3, is connected to the conductor piece 72. The conductor piece 73 is divided into three sections 73a, 73b and 73c, of which the sections 73a and 73c are guided in alignment with one another, axially parallel to the axis of rotation X of the component B. In contrast, the section 73b arranged between the sections 73a and 73c is designed in the manner of a loop and is guided in the circumferential direction by approximately 120 ° around the section B3.

At the end of the section 73c facing away from the section 73b is formed a conductor section 74 which is guided radially to the foot region of the shoulder B and which, after approximately 180.degree. A conductor piece 76 which extends radially by approximately 90 ° around the foot region of the shoulder B2 leads from the conductor piece 75 to a last conductor piece 77 which extends in the longitudinal direction L along the pin B1 and which is connected to the second pole of the energy supply.

The power induced in the wall of the pot-shaped section B3 is adjusted by means of suitably dimensioned sheets 78, which are arranged in the region of the loop-shaped section 73b. LIST OF REFERENCE NUMBERS

1 device for heating a workpiece W

2 turntables

3 inductor

31 - 37 conductor pieces

31a lower end region of the conductor piece 31

50 inductor

51 pole of energy supply

52 - 59 conductor pieces

70 inductor

71 - 77 conductor pieces

73a, 73b, 73c sections of the conductor piece 73

78 sheets

B component

Bl cones

B2 paragraph

B3 pot-shaped section

Dl diameter of the projection Wl

D2 diameter of the heel W2

D3 diameter of the heel W3

L longitudinal direction of the workpiece W

Bb3 length of the pot-shaped section B3

W workpiece

Wl cone-shaped projection

Wla foot area of the projection Wl

W2 heel of the workpiece W

W2a edge of the second paragraph W2

W3 cup-shaped heel

X axis of rotation of workpiece W and component B

Claims

P A T E N T A N S P R Ü C H E

Device for inductive heating of sections of metallic workpieces (W, B), in particular for tempering previously hardened components (W, B), with an inductor (3,50,70), which is at least one starting from an energy supply in the longitudinal direction (L ) over the length of the section of the workpiece (W, B) to be heated and extending closely to this conductor piece (31-37.52-59.71-77), which the workpiece (W, B) at most by a part of its circumference encompasses, and has a second conductor piece (31-37.52- 59.71-77) which is led back to the energy supply in the longitudinal direction of the workpiece (W, B), and with a drive device which, during heating, has a rotation around the longitudinal axis (X) of the workpiece (W, B) rotating relative movement between workpiece (W, B) and inductor (3,50,70) causes.

Apparatus according to claim 1, characterized in that the inductor (3, 50, 70) is divided in stages in accordance with the sequence of sections of the workpiece (W, B) to be heated and since each of the Sections are assigned a conductor piece (31-37,52-59,71-77) which extends in the longitudinal direction (L), extends over the length (Lb3) of the respective section (B3) and is guided closely to the section (LB3) in question.

3. Device according to one of the preceding claims, characterized in that ß extending in the longitudinal direction (L) conductor pieces (31- 37.52-59.71-77) with each other by a circumferential conductor piece (31-37.52- 59, 71-77) are connected.

4. The device according to claim 3, characterized in that ß jointly associated with a paragraph of the workpiece (W, B), running in the circumferential direction conductor pieces (31-37,52-59,71-77) together the respective paragraph (W1, W2, W3) grasp at least half of it.

5. Device according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t, d a ß the conductor pieces (31-37.52-59.71-77) of the inductor

(3,50,70) are arranged symmetrically with respect to the axis of rotation (X) of the workpiece (W, B).

6. The device according to claim 5, characterized in that ß each together a portion of the workpiece (W, B) assigned, in the longitudinal direction (L) extending conductor pieces (31-37,52-59,71-77) are arranged opposite each other in one plane.

7. Device according to one of claims 1 to 6, characterized in that ß at least one (73) of the longitudinally extending (L) extending conductor pieces (31-37,52-59,71-77) simultaneously in the longitudinal and circumferential directions of the workpiece (W, B) is performed.

8. The device according to claim 7, d a d u r c h g e k e n n z e i c h n e t, d a ß in the conductor piece (73) starting from a in the longitudinal direction (L) directed portion (73a, 73b, 73c) a loop is formed, which is guided along the circumference of the workpiece.

9. The device according to claim 7, d a d u r c h g e k e n n z e i c h n e t, d a ß the conductor piece

(56) at an angle deviating from the longitudinal direction (L) of the workpiece (31-37.52-59.71-77) along the circumference of the workpiece (W, B).

10. The device according to claim 9, d a d u r c h g e k e n n z e i c h n e t, d a ß the conductor piece

(73) is divided into at least two sections (73a, 73b, 73c) which run towards each other at an acute angle.

11. Device according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t, d a ß the energy supply pulsating the inductor (3,50,70) with electrical energy in such a way that a pause interval follows each heating interval.

12. The apparatus of claim 11, d a d u r c h g e k e n n z e i c h n e t, that the ratio of the duration of the heating interval to the duration of the pause interval is 3: 4.