WO2016037799A2

WO2016037799A2 - Series motor, and electric tool comprising a series motor

Info

Publication number: WO2016037799A2
Application number: PCT/EP2015/068783
Authority: WO
Inventors: Lothar Dietl
Original assignee: C. & E. Fein Gmbh
Priority date: 2014-09-11
Filing date: 2015-08-14
Publication date: 2016-03-17
Also published as: WO2016037799A3; DE102014113117A1

Abstract

Disclosed is a series motor (10), in particular a single-phase series motor, comprising: a stator (16) and a rotor (12) that is mounted so as to be rotatable relative to the stator (16), the stator (16) being provided with a plurality of poles (28, 30, 36, 38, 40, 42) which are magnetically coupled to one another via a stator ring (26) and are designed to transmit a magnetic field to the rotor (12); a stator winding having a plurality of windings on the stator (16) in order to generate a magnetic exciting field; and a rotor winding (14) on the rotor (12) in order to generate a magnetic rotor field. The rotor winding (14) is electrically connected to the stator winding (18) in series, and the number of turns of the stator winding (18) is smaller on a first pole (30, 38, 42) than the number of turns thereof on a second pole (28, 36, 40).

Description

Series motor and power tool with a series motor

The present invention relates to a series motor, in particular a single-phase series motor, with a stator and a rotor, wherein the rotor is rotatably mounted relative to the stator and wherein the stator has a plurality of poles, which is magnetically coupled via a stator ring and thereto are adapted to transmit a magnetic field to the rotor, a stator winding having a plurality of turns, which is arranged on the stator to produce a magnetic excitation field, and a rotor winding, which is arranged on the rotor, to a magnetic rotor field generate, wherein the rotor winding is electrically connected in series with the stator winding.

The present invention further relates to a power tool with a series motor, which can be coupled with a tool spindle for driving the tool.

From the prior art it is well known to drive small electrical appliances such as power tools with a universal motor or a series motor and in particular a single-phase series motor. In this case, the series-wound motors have a stator winding and a rotor winding which are electrically connected in series and a commutator which poles a current direction in the rotor winding accordingly, so that the series-wound motor is driven continuously in one direction of rotation. Such series-wound motors are known as universal motors from the prior art and can be driven with any input voltage for electrical power supply.

Series motors are known from the prior art, which have two poles on each of which the stator winding is arranged symmetrically with identical numbers of turns in order to enforce the rotor with a magnetic field and to drive the rotor accordingly with a torque. In order to increase the torque provided by series-wound motors, it is known for example from DE 10 2009 037 1 14 A1 to form the pole pieces of the poles of the stator with permanent magnets, whose magnetic field is superimposed on the electrical exciter field, so that the magnetic field is permanently increased to drive the rotor, in the case of AC voltage a rectifier must be used.

The disadvantage of this is that the technical complexity for the production of such series-wound motors is increased and that the stator of such series motors depending on the desired maximum torque require a fixed space, so that miniaturization of small electrical appliances not or only with increased technical effort is possible ,

To reduce the space is proposed in DE 10 2007 025 009 A1, offset the poles of the stator in the circumferential direction or arranged asymmetrically, so that the poles are formed on one side of the stator and the stator ring formed flattened on the opposite side can be so that the required space for the stand is reduced on this page.

The disadvantage here is that the technical complexity for the production of such a series motor is not significantly reduced, since the cost of producing the field winding remains the same and the torque provided can not be significantly increased.

It is therefore the object of the present invention to provide an improved series motor, which allows an individually compact design and can provide a large torque.

This object is achieved in the aforementioned series motor according to a first aspect of the invention in that a number of turns of the stator winding at a first of the poles is smaller than a number of turns at a second of the poles. The above object is achieved in the aforementioned series motor in that the stator has at least four poles to transmit the magnetic field to the rotor.

According to the invention is understood by a smaller number of turns both a numerically smaller number of windings, which may be formed on the first pole as well as that no stator winding is formed on the first pole and thus the number of turns is equal to zero and thus smaller than the number of turns the stator winding of the second pole. In other words, the turns are distributed inhomogeneously or asymmetrically at the poles, so that one of the poles can also have no exciter windings.

Characterized in that in the first aspect, the stator winding has different numbers of turns at the poles or the number of turns at one of the poles is zero, an individually adapted stator ring can be realized by the smaller number of turns in the first pole a smaller radial Has size. Further, the necessary magnetic excitation field can be generated by the remaining turns on the second pole, so that the possible torque that can be provided by the series-wound motor is not reduced.

Characterized in that the series-wound motor according to the second aspect comprises a stator with at least four poles to transmit the magnetic field to the rotor, a more uniform distribution of the magnetic field can be achieved and a larger magnetic field are transmitted to the rotor, so that a larger torque can be provided by the electric drive.

In a preferred embodiment, the stator has two poles, wherein the magnetic exciter field is generated substantially by the stator winding at one of the poles. As a result, the assembly effort for the stator winding can be reduced because the stator winding must be mounted substantially on one of the poles.

In a preferred embodiment, the stator has at least four poles, wherein the magnetic excitation field is generated substantially from the stator winding to two of the poles.

This can be significantly reduced in a four-pole stator assembly costs of the stator winding, since the winding effort is significantly reduced at two poles.

It is further preferred if in each case two of the poles form a pole pair and the stator winding is formed in each case only at one pole of each pole pair.

As a result, the assembly effort to produce the stator winding can be significantly reduced, since the stator winding must be mounted only on one of the poles of each pole pair. Poles without stator winding, which are transmitted only the magnetic exciter field on the rotor also referred to as a follower pole.

It is further preferred if at least one of the poles has a permanent magnet whose magnetic field is superimposed on the exciter field.

Thereby, in general, the torque provided by the electric drive can be increased because the magnetic field transmitted to the rotor can be increased by the permanent magnetic field.

It is preferred if the permanent magnet and the stator winding are arranged on the same pole.

As a result, an asymmetrical design of the stator ring is possible because of the stator winding and the permanent magnet are formed on a pole. It is further preferred if the permanent magnet and the stator winding are arranged at different poles.

As a result, the technical complexity for the assembly of the poles can be reduced, since the different elements are arranged at different poles.

It is generally preferred if the rotor is mounted eccentrically to the stator ring.

As a result, special applications in a compact design are possible, since the distance between the stator ring is reduced to the axis of the rotor on one side.

It is further preferred if poles are formed at the poles, which are adapted to transmit the magnetic field to the rotor, wherein the pole pieces are formed eccentrically to the stator ring.

Characterized a one-sided compact design is possible because a distance of the axis of rotation of the rotor is reduced to the stator ring.

It is further preferred if pole cores of at least two poles in the circumferential direction of the stator ring have different widths.

As a result, the pole cores can be adapted to the number of turns of the respective poles and permanent magnets, which are arranged at the poles, are dimensioned larger, whereby a total of a larger torque can be achieved and an individually compact design is possible.

In a particular embodiment, the pole cores of at least two poles have different radial lengths. As a result, the poles can be adapted to the different numbers of turns and, at the same time, a compact design can be realized.

Overall, a one-sided compact and asymmetric design can be realized by the special design of the stator winding and the special distribution of Windungszahlen to the poles and at the same time the assembly costs are reduced, so that individual designs are possible in which the rotor eccentric to the stator ring is stored. By the use of additional permanent magnets to the poles, an increased torque can be further provided, whereby the performance of the electric drive with a more compact design and reduced installation costs is possible.

It is understood that the features mentioned above and those yet to be explained not only in the combination specified, but also in other combinations or alone, without departing from the scope of the present invention.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. Show it:

Fig. 1 is a schematic view of a series motor;

Fig. 2 shows a stator and a rotor of a series motor with two

Poland;

FIG. 3 shows a stator and a rotor of a four-pole series-wound motor; FIG.

4 shows a stator and a rotor of a series motor with two

Poland and one-sided excitation development; 5 shows a stator and a rotor of a series-wound motor with two electrically excited poles and two magnetically excited poles. and

Fig. 6 is a schematic representation of a power tool in the form of a

Angle grinder with a series-wound motor according to the invention.

In Fig. 1, a circuit of a series motor or a universal motor is shown schematically, which is generally designated 10.

The series motor 10 has a rotor 12 with a rotor winding 14. The series motor 10 also has a stator 16 with a stator winding 18, which is electrically connected in series with the rotor winding 14.

The stator winding 18 is configured to generate a magnetic excitation field, which passes through the rotor and the rotor winding 14, so that the rotor 12 is driven by the electromotive force in a rotational direction 20. The rotor 12 generally has a commutator 22 which directs an electrical current I in the rotor winding 14, so that the rotor 12 is driven in the direction of rotation 20 by the magnetic excitation field of the stator winding 18.

The series-wound motor 10 is supplied from a voltage source, not shown, with a voltage U, which may be formed as a DC voltage, pulsating DC voltage or AC voltage, wherein the series-wound motor 10 may be associated with an inverter, not shown here, to the AC voltage in a pulsating To convert DC voltage.

In Fig. 2 is a schematic sectional view of an embodiment of the series motor 10 is shown. The series motor 10 has the stator 16 with the stator winding 18 and the rotor 12 with the rotor winding 14. The rotor 12 is rotatably mounted about an axis of rotation 24 relative to the stator 16 and rotates in the direction of rotation 20. The stator 16 has a stator ring 26 on which poles 28, 30 are arranged. The pole 28 has the stator winding 18 to generate a magnetic excitation field 32. The poles 28, 30 each have a pole piece, which are adapted to transmit the magnetic exciter field 32 to the rotor 12 and thereby drive it. The poles 28, 30 each have a pole core, which connects the respective pole piece with the stator ring 26, wherein the pole pieces are each formed in a circumferential direction of the stator ring 26 wider than the pole cores and correspondingly form pole horns 34.

In the embodiment shown in Fig. 2, only the pole 28, the stator winding 18, wherein the pole 28 is magnetically coupled via the stator ring 26 to the pole 30 and the pole 30 and the pole piece of the pole 30, the magnetic excitation field 32 transmits to the stand 12. The pole 30 is thus formed as a follower pole. The fact that the stator winding 18 is formed only on the pole 28, the technical complexity for mounting the stator winding 18 can be reduced, since only a pole winding must be wound, which may have a corresponding higher number of turns. Due to the stray field magnetic coupling of the poles 28, 30 so asymmetrically formed stator winding 18 has no influence on the field distribution of the magnetic exciter field 32 in the rotor 12th

In a particular embodiment, at least one permanent magnet can be arranged on one of the poles 28, 30, whose permanent magnetic field is superimposed on the magnetic field 32 and thereby amplifies the magnetic field which flows through the rotor 12. The permanent magnet is preferably formed on the pole 30, on which no stator winding is formed, so that no additional space for accommodating the permanent magnet is needed. When using alternating current, the use of a rectifier is necessary.

In Fig. 3 is a schematic sectional view of another embodiment of the series motor 10 is shown. The same elements are designated by the same reference numerals, only special features are explained here. The stator 16 has in this embodiment, four poles 36, 38, 40, 42 which are magnetically coupled together via the stator ring 26 and each transmit the magnetic field to the rotor 12 by means of a pole piece. In the embodiment shown here, the stator winding 18 is formed both on the pole 36 and on the opposite pole 40, whereas the poles 38, 42 have no stator winding and are thus formed as a follower poles. The magnetic field of the follower poles is formed by the stray fields of the two adjacent, electrically excited poles and thus has the opposite polarity of the electrically excited poles. Overall, poles 36, 38, 40 and 42 form a system of four poles of alternating polarity. For example, if the electrically excited poles each form a magnetic north pole in the direction of the rotor, then the two follower poles each form a magnetic south pole in the direction of the rotor.

One or more of the poles 36-42 may comprise a permanent magnet whose permanent magnetic field is superimposed on the magnetic excitation field 42 so that the magnetic field passing through the rotor 12 is amplified. The permanent magnets may be disposed on any one of the poles 36-42 and are preferably arranged on the poles 38, 42 which have no stator winding 18, so that no additional space is needed and in a particular embodiment, the stator ring 26 at the poles 38, 42nd can be made narrower, so that a smaller design is possible, as explained in more detail below.

By the four-pole design, a better distribution of the magnetic field can be effected and at the same time a larger magnetic field are transmitted to the rotor 12, so that in general the torque provided by the series-wound motor 10 is increased.

It is understood that the poles 30 and 38, 42 of the embodiments of FIGS. 2 and 3 may also have parts of the stator winding 18, wherein the number of turns at these poles 30, 38, 42 are smaller than the number of turns to the Poland 28, 36, 40. As a result, the necessary space can be obtained, for example, for the permanent magnet or the stator 26 may at this point be formed narrow, so that the outer dimensions of the series motor 10 can be made more compact on one side.

In Fig. 4 is a detailed sectional view of a two-pole embodiment of the series motor 10 is shown. The same elements are designated by the same reference numerals, in which case only the special feature is explained.

The stator winding 18 is formed only on the pole 28. The pole core of the pole 28 extends in the radial direction between the stator ring 26 and the pole piece of the pole 28, wherein the pole core of the pole 30 is formed in the radial direction shorter than the pole core of the pole 28. This is possible because the pole 30 no stator winding 18 has. In other words, a distance of the pole piece of the pole 30 from the stator ring 26 is less than a distance of the pole piece of the pole 28 from the stator ring 26. The rotor 12 can thus be formed eccentrically to the stator ring 26, so that a distance between the axis of rotation 24th and an outer edge of the stator ring 26 is significantly reduced in the region of the pole 30, whereby special applications, for example, drill bits with a small Eckmaß are possible. Because the pole 30 has no windings, the pole core can be made wider in the circumferential direction of the stator ring 26, so that a better magnetic coupling of the pole piece to the stator ring is possible and at the same time a particularly flat construction of the stator ring 26 in the middle of Pols 30 is possible. Thereby, the distance between the rotation axis 24 and the outer edge of the stator ring 26 can be further reduced in this area. In a particular embodiment, the pole core is formed as wide as the pole piece of the pole 30, so that no Polhörner or Polhörner are formed with small dimensions at this pole.

It is understood that the pole 30 and / or the pole 28 may each be formed with a permanent magnet whose permanent magnetic field is superimposed on the magnetic excitation field 32 in order to increase the torque provided by the series-wound motor 10. In Fig. 5 is a detailed sectional view of the series motor 10 with four poles is shown. The same elements are designated by the same reference numerals, in which case only the special features are explained.

The poles 36, 40 have the stator winding 18, wherein the poles 38, 42 are formed without stator winding 18. The poles 38, 42 each have a permanent magnet 44, 46, whose permanent magnetic field is superimposed on the electrical exciter field of the stator winding 18, so that the magnetic field, which passes through the rotor 12, is increased. The permanent magnets 44, 46 may be formed in the entire pole piece of the poles 38, 42 and / or in the entire pole piece of the poles 36, 40 in order to amplify the magnetic excitation field accordingly. In a particular embodiment, the permanent magnets 44, 46 are arranged asymmetrically on the poles 38, 42 and / or asymmetrically on the poles 36, 40, whereby an improved commutation can be achieved in a preferred direction motor.

The pole cores of the poles 38, 42 are formed in the embodiment shown in Fig. 5 in the radial direction of the stator ring 26 shorter than the pole cores of the poles 36, 40 and in the circumferential direction of the stator ring 26 formed wider than the pole cores of the poles 36, 40. Due to the radially shorter design, the stator ring 26 can be made narrower in the X-direction shown here, whereby a more compact design in this direction is possible. As a result of the more accurate design of the pole cores of the poles 38, 42, the magnetic excitation field 32 can be better supplied to the pole shoes and the permanent magnets 44, 46 can be made larger, so that overall a larger torque can be provided. As shown in Fig. 5, the pole horns 34 of the poles 38, 42 are formed very small, whereby the stray magnetic field can be reduced.

Characterized in that only two of the poles 36, 40 have the stator winding 18, the assembly effort of the stator winding 18 is not increased compared to a conventional two-pole series motor and the fact that the poles 38, 42 have no stator winding, the design compared to a conventional Series motor not enlarged. Thus, with little technical effort, a series-wound motor can be provided, which has a compact design and can simultaneously provide an increased torque.

In principle, all possible combinations of the permanent magnets 44, 46 with the poles 38, 42 without stator winding 18 or with stator winding 18 are conceivable and variants are also conceivable in which one of the poles 36-42 or three of the poles 36-42 the Have stator winding 18 and corresponding to one, two, three or four of the poles have a permanent magnet. A corresponding list of variants for a four-pole stand is shown below:

wherein poles with stator winding 18 are denoted by E, poles without stator winding 18 are denoted by F and poles with permanent magnets are denoted by PM.

Overall, the provision of the magnetic field and the dimension of the stator ring can thus be designed or adjusted individually depending on the application.

In Fig. 6, a power tool 50 is shown in the form of an angle grinder in a schematic representation as an application example. The power tool 50 has a series-wound motor 10 according to the present invention, resulting in an asymmetric or eccentric arrangement of the axis of rotation 24. It is understood that the power tool 50 is formed by way of example only as an angle grinder and the series motor 10 can also be used in other power tools such as drills or the like.

Claims

claims

A series motor (10), in particular a single-phase series motor, comprising: a stator (16) and a rotor (12), wherein the rotor (12) is rotatably mounted relative to the stator (16), and wherein the stator (16) has a plurality of poles (28, 30, 36, 38, 40, 42) which are magnetically coupled via a stator ring (26) and adapted to transmit a magnetic field to the rotor (12),

- A stator winding (18) having a plurality of turns, which is arranged on the stator (16) to generate a magnetic excitation field, and a rotor winding (14) which is arranged on the rotor (12), to a magnetic rotor field wherein the rotor winding (14) is electrically connected in series with the stator winding (18), characterized in that a number of turns of the stator winding (18) at a first one of the poles (30, 38, 42) is smaller than a number of turns a second of the poles (28, 36, 40).

A series motor according to claim 1, characterized in that the stator (16) has two poles (28, 30), wherein the magnetic excitation field (32) is generated substantially by the stator winding (18) on one of the poles (28).

A series motor according to claim 1 or 2 or according to the preamble of claim 1, characterized in that the stator (16) has at least four poles (36-42) for transmitting the magnetic field to the rotor (12).

4. A series motor according to claim 3, characterized in that the magnetic exciter field (32) substantially of the stator winding (18) to two of the poles (36, 40) is generated.

5. A series motor according to one of claims 1 to 4, characterized in that in each case two of the poles form a pole pair and wherein the stator winding (18) in each case only at one of the poles (28, 36, 40) of each pole pair is formed.

6. A series motor according to one of claims 1 to 5, characterized in that at least one of the poles has a permanent magnet (44, 46) whose magnetic field is superimposed on the excitation field (32).

7. A series motor according to claim 6, characterized in that the permanent magnet (44, 46) and the stator winding (18) are arranged on the same pole.

8. A series motor according to claim 6, characterized in that the permanent magnet (44, 46) and the stator winding (18) are arranged at different poles.

9. series motor according to one of claims 1 to 8, characterized in that the rotor (12) is mounted eccentrically to the stator ring (26).

10. A series motor according to one of claims 1 to 9, characterized in that at the poles pole pieces are formed, which are adapted to transmit the magnetic field to the rotor (12), wherein the pole shoes eccentrically to the stator ring (26) are.

1 1. A series motor according to any one of claims 1 to 10, characterized in that Polkerne of at least two poles in the circumferential direction of the stator ring (26) have different widths.

12. A series motor according to one of claims 1 to 1 1, characterized in that Polkerne of at least two poles have different radial lengths.

13. Power tool (50) with a series motor (10) according to one of claims 1 to 12, which can be coupled with a tool spindle for driving the tool (50).