Machine tool with an electrical generator for passive power generation

A machine tool with a generator for generating electrical power is disclosed. The generator has a rotor and a stator. A coil and a magnet are arranged on the stator. The rotor is capable of moving relative to the stator and has a first region and a second region. The rotor is configured in such a way that, during a movement of the rotor relative to the stator, a magnetic flux in the coil is changed due to differences between the first and second regions in terms of their magnetic permeability and/or in terms of their geometric configuration, and an electrical voltage is induced.

This application claims priority under 35 U.S.C. §119 to German patent application no. 10 2010 002 182.2, filed Feb. 22, 2010, the disclosure of which is incorporated herein by reference in its entirety.

Cross Reference is made to copending U.S. patent application Ser. No. 13/031,483, entitled “Machine Tool with an Active Electrical Generator for Power Generation,” filed on Feb. 21, 2011.

The present disclosure relates to a machine tool with an electrical generator for passive power generation.

BACKGROUND

When working with electric tools, auxiliary means are often required for optimizing the performance of work. For example, illumination of the working area by means of light-emitting means may be useful.

DE 10 2006 045 157 A1, for example, has disclosed tools in which the light-emitting means are integrated in the tool. However, the supply of energy to the light-emitting means can pose a problem.

SUMMARY

An object of the present disclosure can therefore be considered that of providing an improved machine tool which enables a supply of energy to additional elements.

This object can be achieved by the subject matter of the present disclosure. Advantageous embodiments of the present disclosure are described herein.

Features, details and possible advantages of an apparatus in accordance with the embodiments of the disclosure will be discussed in detail below.

In accordance with a first aspect of the present disclosure, a machine tool, such as a handheld machine tool, for example, with a generator which generates electrical energy or power is described. The generator has a stator and a rotor which is capable of moving in relation thereto. At least one coil, for example an induction coil, and at least one magnet, for example a permanent magnet or an electromagnet, are arranged on the stator. The rotor has at least one first and at least one second region. The first region has a first magnetic permeability and a first geometric configuration. The second region has a second magnetic permeability and a second geometric configuration. The first permeability and the second permeability are in this case different and/or the first geometric configuration and the second geometric configuration are different. Depending on whether the first or second region of the rotor is located closer to the stator, the magnetic lines of force emanating from the magnet can propagate differently. During a movement of the rotor relative to the stator, the position of the first and second regions of the rotor with respect to the stator changes continuously. As a result, the magnetic flux changes and a voltage in the coil of the stator is induced.

The first and second regions of the rotor can be configured, for example, as a profile in the rotor. That is to say that the first region can correspond to elevations and the second region can correspond to cutouts in the rotor. Optionally, different materials, in particular with different magnetic permeability, can be used for the different regions.

With the aid of the generator according to the disclosure, it is possible to provide voltage or electrical energy for machine tool-internal components, such as light sources for illuminating the working area, for example. This electrical energy is advantageously independent of a mains or battery voltage of the machine tool. Therefore, no additional elements for rectification and transformation of the mains current need to be installed in the machine tool. This may be advantageous in particular in the case of handheld machine tools since a weight saving can also be made. In addition, the electrical circuit of the generator according to the disclosure can be designed for operation on a low voltage (for example less than 50 V) and is therefore not subject to the requirements for mains-operated machines, such as the maintenance of insulation gaps, for example. This provides greater freedom in terms of the structural design of the machine tool.

In addition, the generator according to the disclosure is preferably designed without any movable magnets. During operation of the machine tool, only the rotor moves, while both the coil and the magnet are arranged immovably on the stator. This makes it possible for already existing machine tools to be subsequently modified in a simple manner. In addition, this enables simple, space-saving and inexpensive implementation of an energy source for machine-internal components of newly produced machine tools, such as light sources, for example.

In accordance with one exemplary embodiment of the disclosure, the stator and the rotor comprise ferromagnetic materials. That is to say the relative permeability μ of the materials is equal to, greater than or preferably substantially greater than 1 (μ>>1). Such materials can be, for example, steel, iron, cobalt, nickel and combinations thereof. The stator and the rotor can for the most part or completely consist of these materials.

In accordance with one exemplary embodiment, the rotor can be coupled to the output drive, for example to an output shaft, of the machine tool mechanically in a force-fitting, form-fitting and/or frictionally engaged manner or can be formed as part of the output drive or integrated therein. This can take place, for example, by the change of existing parts of the output drive and can thus be implemented in a cost-saving manner. The rotor can also be connected to the output drive cohesively, such as by means of an adhesive, for example. The output drive can be part of the machine which outputs power and can be, for example, a spindle, a ring gear, an accommodating flange or a tool receptacle, a motor shaft or the protrusion thereof.

In accordance with a further exemplary embodiment, the generator can have a second circuit which is electrically isolated from or independent of the first circuit of the machine. The first circuit is connected, for example, to a mains supply or a rechargeable battery supply. The second circuit can generate a voltage which is different from the first circuit by the operation of the generator. As a result, for example, a machine-internal light source, for example, can be supplied with energy without a mains voltage needing to be transformed and rectified. It is thus possible to dispense with additional components and therefore to save installation space and considerable additional costs.

In accordance with further exemplary embodiments, the machine tool can have one or more light sources. The light source is supplied with energy by the generator according to the disclosure and is connected thereto, for example directly or via an electrical transducer. In addition, the light source can be integrated directly into the machine or arranged thereon and can be a light source which enables possibly continuous illumination of a working area during operation of the machine. An additional light source can output a light signal, for example by means of changing color or by means of a change in intensity and therefore indicate a present rotation speed of the rotor. For example, the signal can be a blinking signal. It is thus possible to signal that specific rotation speeds are being passed through, exceeded and/or undershot, for example in the event of an overload, and an overtravel of the rotor or the motor even once the machine has been disconnected. In addition, for example, an additional light source can be configured as a laser light source for labeling the working area and guiding the machine.

In accordance with a further exemplary embodiment, the machine tool has an electrical energy store, such as a capacitor and/or a rechargeable battery, for example. By virtue of the electrical energy store, it is possible, for example, for the persistence time and intensity of the light source to be improved. The electrical energy store can be integrated, for example, in electronics of the machine. In the electronics, the electrical voltage generated can be matched to the requirements of the light source.

In accordance with a further exemplary embodiment, the coil or a plurality of coils of the stator is or are arranged at or on a yoke which intensifies the magnetic flux. The yoke can connect the magnet(s) to one another and/or to the coil(s). The yoke can have a higher magnetic permeability than the material of the stator housing, for example, and can contribute to targeted guidance of the magnetic lines of force and intensify the magnetic flux. Owing to this intensification of the flux, a sufficient voltage, for example for operation of light sources, can also be generated at low operating speeds.

In accordance with a further exemplary embodiment, the rotor can perform a rotary or linearly oscillating movement. The machine tool can therefore be configured as, for example, an angle grinder or straight grinder, screwdriver, drill, circular saw or in the form of a saw, for example a jigsaw, a saber saw, a crosscut saw or precision saw.

All of the figures are merely schematic illustrations of devices according to the disclosure or parts thereof. In particular, distances and size relationships have not been reproduced true to scale in the figures. Corresponding elements have been provided with the same reference numerals in the various figures.

DETAILED DESCRIPTION

FIGS. 1 to 7illustrate the machine tool with a rotating rotor using the exemplary embodiment of an angle grinder, andFIGS. 8 to 10illustrate the machine tool with a linearly oscillating rotor using the example of a jigsaw.

FIG. 1shows a schematic illustration of a cross section through an angle grinder1. The angle grinder1has the conventional components such as motor housing25, motor27, fan29, pinion31, gear housing33, protective cover35, two-hole nut37, spindle39, ring gear41, bearing flange43and accommodating flange47. A light source15can illuminate a working region45or the working area45. The light source15can be integrated, for example, in the bearing flange43. In the case of the angle grinder1, the ring gear41, the accommodating flange47or the spindle39can be used as the rotor7.

FIGS. 2A and 2Brepresent the mode of operation of the generator3of the machine tool1. In this case,FIGS. 2A and 2Bshow cross sections through the generator3in different movement phases of the rotor7. A coil11and two magnets13with different polarity are arranged on the stator5. The magnets13and the coil11are arranged on a yoke23for intensifying the magnetic flux.

Owing to the movement63(indicated by the arrow) of the rotor7with respect to the stator5, the magnetic field in which the coil11is located changes. As a result, a voltage is induced in the coil11, it being possible for the voltage to be passed on to a light source15, for example via the electronics21, which can comprise an electrical energy store19. A change in the magnetic field can be achieved, for example, by the change in the resistance (also referred to as reluctance) of the magnetic circuit.

InFIG. 2A, a first region51of the rotor7is located opposite the coil11of the stator5. Second regions53of the rotor7are located opposite the magnets13of the stator5. In the exemplary embodiment, the first region51and the second region53have different geometric configurations. The first region51has an elevation in the direction of the stator5. The second region53, on the other hand, is set back with respect to the stator5in comparison with the first region51, with the result that the air gap9between the stator5and the rotor7in the second region53is greater than in the first region51.

During a movement63of the rotor7, the magnetic flux emanating from the permanent magnet13changes. The magnetic lines of force17therefore change as illustrated inFIG. 2and a voltage11is induced in the coil.

The regions51,53of the rotor7can comprise different materials with different magnetic permeability given the same or different geometric configuration. In this case, the rotor7can be realized by virtue of changes to existing parts of the output drive49of the machine tool1. For example, the rotor7can be provided with grooves. During a movement of the rotor7, the reluctance changes as follows: in a position of the grooves51with respect to the magnets13, a high reluctance is brought about by the large air gap9; in a position of webs51with respect to the magnets, a low reluctance is brought about.

FIGS. 3A,3B,3C,3D illustrate a generator3with an accommodating flange47as the rotor7.FIGS. 3A and 3Bshow different perspectives of the generator3.FIGS. 3C and 3Dillustrate cross sections through the generator3. Webs51and grooves53are arranged in the accommodating flange47. When the magnets13are positioned with respect to webs51of the flange47, the magnetic flux can develop both tangentially (FIG. 3C) and radially (FIG. 3D) thanks to the low reluctance. This is indicated by the magnetic lines of force17inFIGS. 3C and 3D.

As shown inFIG. 3B, additional grooves55can be arranged, for example, on that side of the flange47which faces the spindle39. As a result, the fluctuation in the magnetic flux can be increased in the different positions of the rotor7. As a result, higher voltages can be induced in the coil11of the stator5. In this case, the stator can be integrated in the bearing flange43.

FIGS. 4A,4B,4C illustrate possible embodiments of the stator shown inFIGS. 3A-3D. As is shown inFIG. 4A, the stator5can be in the form of a ring and have a plurality of magnets13and coils11connected by a yoke23. Alternatively, for example if there is not sufficient installation space or the induced voltage is sufficient, the stator5can consist of a yoke section and a coil11, as shown inFIGS. 4B and 4C. In this case, the yoke23can consist of solid material or of strips of sheet metal. An embodiment of the stator with only one magnet13is also possible. This is shown inFIG. 4C.

FIGS. 5A and 5Billustrate different perspectives of a generator3with a ring gear41as the rotor7. The lower side of the ring gear can be provided with teeth in order to realize the different regions51,53of the rotor7.

FIGS. 6A,6B illustrate possible configurations of the rotor7.FIG. 6Ashows an intensifying yoke50with a high relative permeability in comparison with the materials of the rotor. The intensifying yoke50can reduce the reluctance. When seen individually, it can be used as the rotor7, as shown inFIG. 6A. Alternatively, the intensifying yoke50can be integrated in other parts of the output drive49such as the ring gear41or the accommodating flange47, as shown inFIG. 6B, and make the desired reluctance profile possible. In addition, it is possible to integrate the desired material properties directly in the parts of the output drive49. For example, this can be performed by the simultaneous or successive processing of a plurality of materials during the production of the components in a sintering process.

FIGS. 7A,7B,7C illustrate the configuration of the stator5with magnet coils57.FIG. 7Ashows a magnet coil57with a permanent magnet13and a coil11wound around the core59. As is shown in cross section through the generator3inFIG. 7C, the magnet coil57is aligned axially and perpendicular to the ring gear41and the accommodating flange47, respectively. The magnetic lines of force17are closed via the rotor7(in this case: ring gear41) and the core59of the magnet coil57.

As is shown inFIG. 7B, the magnet coils57can be integrated in the bearing flange43. The magnet coils57can also be integrated in an additional element, such as the magnet coil former61. The coils11or the magnet coils57can be connected in series, for example, in such a way that the output power is maximized. The number and position of the magnet coils57can be selected differently. For example, they can be arranged rotationally symmetrically.

FIG. 8shows a schematic illustration of a cross section through a machine tool1, in the form of a jigsaw. The jigsaw1has a lifting rod65, which can move linearly up and down. The stator5is arranged around the lifting rod65. The light source15illuminates a working area45during operation of the rotor7. The lifting rod65and the saw blade67arranged thereon perform a linearly oscillating movement63(indicated by an arrow).

FIGS. 9A,9B,9C illustrate embodiments of the generator3with a linearly oscillating rotor7.FIG. 9Ashows a plan view of the generator3.FIGS. 9B and 9Cshow the generator3in cross section in different positions of the rotor7. The stator5with the coil11and the magnet13surrounds the lifting rod65in the form of a ring. In addition, a magnetic return disk69with a relative magnetic permeability which is preferably high is arranged on the stator. The rotor7consists of the lifting rod65and a magnetic return yoke71, which is in the form of a disk and is moved along with the lifting rod65. The magnetic return yoke71remains below the stator5in the exemplary embodiment shown inFIG. 9.

InFIG. 9B, the rotor7is located in a lower position, with the result that the magnetic return yoke71of the rotor7is so far removed from the stator5that the magnetic lines of force17(indicated by dashed lines) do not pass through the yoke71and are relatively weak. InFIG. 9C, the rotor7is in an upper position, with the result that the magnetic lines of force17run via the magnetic return yoke71of the rotor7and the magnetic lines of force17are more pronounced. In this case, the magnetic return yoke71can be considered to be a first region51of the rotor7with a high permeability. The remaining regions of the lifting rod65can be considered to be a second region53with a low permeability.

FIGS. 10A,10B,10C,10D,10E illustrate alternative embodiments of the generator3shown inFIGS. 9A,9B,9C.FIG. 10Ashows a plan view of the generator3.FIG. 10Billustrates an enlarged detail ofFIG. 10A;FIGS. 10C,10D and10E illustrate cross sections of the generator in different movement phases of the rotor7. The stator5inFIGS. 10A-10Eis formed with one magnetic return disk69above the magnet13and one below the magnet. The rotor7with the magnetic return yoke71can move completely through the stator5in the exemplary embodiment inFIGS. 10A-10E. In comparison with the exemplary embodiment inFIG. 9, this has the advantage that a movement of the lifting rod59is not impaired and that higher voltages can be induced in the coil11, as a result of a higher possible frequency of the fluctuation of the magnetic lines of force17. As is shown inFIGS. 10A-10E, a cylindrical configuration of the components of the rotor7and the stator5can be advantageous.

By virtue of the magnetic return yoke71, it is possible to realize the regions51,53of different geometric configuration or different magnetic permeability on the rotor7. The magnetic return yoke71can consist of a material with a high magnetic permeability. In addition, the magnetic return yoke71can be realized as part of the lifting rod59. By virtue of the movement63of the alternately tapered magnetic return yoke71, the reluctance of the magnetic circuit changes. As a result, the magnetic flux varies and a voltage is induced in the coil11. The rotor7can be considered to be a “magnetic valve”, which can inhibit the development paths of the magnetic flux in the manner of a bar.

By way of conclusion it should be noted that expressions such as “having” or the like are not intended to rule out the possibility of further elements or steps being provided. Furthermore, the use of “one” or “a” is not intended to rule out a greater number. In addition, features described in connection with the various embodiments can be combined with one another as desired.