Power tool having a motor shaft and a fan wheel, wherein there is a magnetic coupling between the motor shaft and the fan wheel

Abstract

A power tool is provided having a motor and a motor shaft, wherein a fan wheel in the power tool is designed to generate an air flow for cooling the motor. The power tool provides a coupling formed magnetically between the fan wheel and the motor shaft such that the motor shaft drives the fan wheel in a rotary movement with a speed that is less than a speed of the motor shaft. As a result of the magnetic coupling of the fan wheel and motor shaft, the movements of the two components can be decoupled from one another such that an increase in the rotational speed of the motor shaft does not also result in an increased speed at the fan wheel. As a result, fan losses can be considerably reduced and the efficiency of the motor of the power tool can be significantly improved. A method is also provided for cooling a motor of a power tool, wherein there is a magnetic coupling between a fan wheel and a motor shaft of the power tool.

Claims

1-15. (canceled)

16: A power tool comprising: a motor; a motor shaft; a fan wheel in the power tool to generate an air flow for cooling the motor; and a coupling formed magnetically between the fan wheel and the motor shaft such that the motor shaft drives the fan wheel in a rotary movement with a speed less than a speed of the motor shaft.

17: The power tool as recited in claim 16 wherein the fan wheel includes magnetic regions for creating the magnetic coupling between the fan wheel and the motor shaft.

18: The power tool as recited in claim 16 wherein a plurality of permanent magnets are integrated in the fan wheel.

19: The power tool as recited in claim 16 wherein the fan wheel has a first sprocket including magnetic regions for creating the magnetic coupling between the fan wheel and the motor shaft.

20: The power tool as recited in claim 19 wherein the motor shaft has a second sprocket, wherein the second sprocket is magnetic in a manner corresponding to the first sprocket of the fan wheel.

21: The power tool as recited in claim 16 further comprising an electromagnet bringing about the magnetic coupling between the fan wheel and motor shaft.

22: The power tool as recited in claim 16 wherein the electromagnet has a basic body and a coil for generating a magnetic field.

23: The power tool as recited in claim 22 wherein the basic body includes a ferromagnetic material.

24: The power tool as recited in claim 22 wherein the basic body has a first region surrounded by the coil, and a second region having an opening, a first sprocket of the fan wheel and a second sprocket of the motor shaft being arranged in the opening so as to be rotatable with respect to one another.

25: A method for cooling a motor of a power tool as recited in claim 16 comprising magnetically coupling the fan wheel and the motor shaft of the power tool.

26: A cooling unit for a motor of a power tool, the cooling unit comprising: a motor shaft; a fan wheel for generating an air flow for cooling the motor of the power tool; and a coupling formed magnetically between the fan wheel and the motor shaft such that the motor shaft drives the fan wheel in a rotary movement with a speed that is less than a speed of the motor shaft.

27: The cooling unit as recited in claim 26 further comprising an electromagnet bringing about the magnetic coupling between the fan wheel and motor shaft.

28: The cooling unit as recited in claim 27 wherein the electromagnet has a basic body and a coil for generating a magnetic field.

29: The cooling unit as recited in claim 28 wherein the basic body includes a ferromagnetic material.

30: The cooling unit as recited in claim 28 wherein the basic body has a first region surrounded by the coil, and a second region having an opening, a first sprocket of the fan wheel and a second sprocket of the motor shaft being arranged in the opening so as to be rotatable with respect to one another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Identical and similar components are denoted by the same reference signs in the figures, in which:

[0030] FIG. 1 shows a side view of a cooling unit with a motor shaft and fan wheel

[0031] FIG. 2 shows a view of a possible arrangement of magnetic regions

[0032] FIG. 3 shows a view of a possible configuration of a sprocket

[0033] FIG. 4 shows a side view of a cooling unit with a motor shaft, fan wheel and electromagnet

DETAILED DESCRIPTION

[0034] FIG. 1 shows a side view of a motor shaft 2 and of a fan wheel 3, which together form a cooling unit for a power tool (100, shown schematically). The motor shaft 2 is connected to the motor 1 (illustrated solely schematically) and, during operation of the power tool, rotates preferably at the same speed, i.e. rotational speed, as the motor 1 itself. Between the fan wheel 3 and the motor shaft 2 there is a magnetic coupling, which, according to a first configuration of the invention (FIGS. 1 to 3), can be generated by magnetic regions 4 or permanent magnets 5. According to a second configuration of the invention (FIG. 4), the magnetic coupling can be brought about by an electromagnet 8. In this configuration of the invention, the cooling unit also comprises the electromagnet 8, which is provided to generate the magnetic coupling between the fan wheel 3 and motor shaft 2.

[0035] The magnetic regions 4 or the permanent magnets 5 can be arranged for example in the fan wheel 3. However, for the purposes of the invention, it may also be preferred that the magnetic regions 4 or the permanent magnets 5 are arranged in a sprocket 6, wherein the sprocket 6 is connected to the fan wheel 3. For the purposes of the invention, it is very particularly preferred that the fan wheel 3 has a first sprocket 6, wherein the first sprocket 6 comprises magnetic regions 4 and/or permanent magnets 5, which can bring about the magnetic coupling with the motor shaft 2. The motor shaft 2 can also comprise a sprocket 7, which is referred to as second sprocket 7 for the purposes of the invention. It is preferred, for the purposes of the invention, that the second sprocket 7 of the motor shaft 2 is configured so as to correspond magnetically to the first sprocket 6 of the fan wheel 3. This preferably means, for the purposes of the invention, that the arrangement of the magnetic regions 4 or of the permanent magnets 5 on the second sprocket 7 is similar or identical to the arrangement of the magnetic regions 4 or of the permanent magnets 5 on the first sprocket 6. The sprockets 6, 7, or their magnetic regions 4 and/or their permanent magnets 5, interact with one another such that a movement of the motor shaft 2 is transmitted to the fan wheel 3. The inventors have recognized that, as a result of the provision of a magnetic coupling between the fan wheel 3 and the motor shaft 2, a direct transmission of the movement between the components 2, 3 can be prevented. Instead, a movement of the motor shaft 2 with high rotational speeds is converted preferably into a movement of the fan wheel 3 with a lower rotational speed. As a result, losses of cooling performance, as can occur in the case of a rigid connection between the fan wheel 3 and motor shaft 2, can be considerably reduced.

[0036] FIG. 2 shows a possible arrangement of magnetic regions 4 on the fan wheel 3 or on the first sprocket 6 of the fan wheel. The magnetic regions 4 can be formed by small permanent magnets 5, which can be introduced for example into the material of the fan wheel 3 or of the first sprocket 6. The magnetic regions 4 or the permanent magnets 5 can be arranged in an outer region of the fan wheel 3 or of its first sprocket 6, wherein in each case a south pole and a north pole of two permanent magnets 5 are arranged opposite one another. In other words, the magnetic regions 4 or the permanent magnets 5 are arranged with respect to one another such that in each case a north pole and a south pole are oriented toward one another.

[0037] FIG. 3 shows a possible configuration of a sprocket 6, 7. The sprocket can be either the first sprocket 6 of the fan wheel 3 or the second sprocket 7 of the motor shaft 2. The sprockets 6, 7 have teeth 14, wherein in particular the teeth 14 of the second sprocket 7 form preferably yoke-like magnetic bridges to the permanent magnets 5 or the magnetic regions 4 in the fan wheel 3 or its sprocket 6.

[0038] FIG. 4 shows a second configuration of the invention, in which the magnetic coupling is created by means of an electromagnet 8. In particular, FIG. 4 shows a cooling unit with an electromagnet 8. The electromagnet 8 comprises a basic body 9 and a coil 10, wherein the coil 10 is designed to generate a magnetic field. The coil 10 is preferably wound around a first region 11 of the basic body, while a second region 12 of the basic body 9 has an opening 13 in which the sprockets 6, 7 of the fan wheel 3 and of the motor shaft 2 can be arranged. In particular, FIG. 4 shows a motor shaft 2 with a fan wheel 3 and electromagnet 8.

[0039] For the purposes of the invention, it is preferred that a coupling between the fan wheel 3 and the motor shaft 2 is formed magnetically such that a dependence of the movement of the fan wheel 3 on the movement of the motor shaft 2 can be considerably reduced. In a second configuration of the invention, the cooling unit comprises an electromagnet 8, which can bring about the magnetic coupling between the fan wheel 3 and motor shaft 2. To this end, the electromagnet 8 comprises a basic body 9 and a coil 10 for generating a magnetic field, wherein the basic body 9 can comprise a ferromagnetic material. The basic body 9 has a first region 11, which is surrounded by the coil 10, and a second region 12, which has an opening 13 in which a first sprocket 6 of the fan wheel 3 and a second sprocket 7 of the motor shaft 2 are arranged so as to be rotatable with respect to one another.

LIST OF REFERENCE SIGNS

[0040] 1 Motor [0041] 2 Motor shaft [0042] 3 Fan wheel [0043] 4 Magnetic regions [0044] 5 Permanent magnets [0045] 6 First sprocket of the fan wheel [0046] 7 Second sprocket of the motor shaft [0047] 8 Electromagnet [0048] 9 Basic body [0049] 10 Coil [0050] 11 First region of the basic body [0051] 12 Second region of the basic body [0052] 13 Opening in the basic body [0053] 14 Teeth of the sprockets [0054] 100 Power tool