Integrated motor braking resistor

Abstract

The invention relates to an electric motor, in particular as a drive for a machine tool, containing: an energy supply means; a stator having a laminated stator core and at least two coil windings; a rotor which is rotatable relative to the laminated stator core; and a controller. At least one recess for accommodating at least one resistor element is formed in an outer lateral surface of the laminated stator core, with the at least one resistor element being designed to convert an electric voltage, which can be generated by means of the coil windings of the stator during a braking operation of the rotor, into heat.

Description

[0001] Integrated motor brake resistor

[0002] The present invention relates to an electric motor, in particular as a drive for a machine tool, comprising a power supply, a stator with a stator laminated core and at least two coil windings, a rotor rotatable relative to the stator laminated core, and a control device.

[0003] Furthermore, the present invention relates to a stator for an electric motor.

[0004] Furthermore, the present invention relates to a machine tool with an electric motor.

[0005] Electric motors (particularly as drives for machine tools) are known from the prior art. These motors essentially comprise a stator and a rotor rotatable relative to the stator to generate torque. For the electric motor to function properly, and in particular for selectively generating a magnetic field, the stator must have a plurality of coil windings around the respective pole teeth or stator teeth. To produce a coil or coil winding, a winding wire is wound in several layers around the pole tooth or stator tooth. The pole tooth or stator tooth serves as a carrier for the coil winding.

[0006] Motor brakes are often necessary and an integral part of the motor in order to slow down the motor as quickly as possible or to stop the rotation of the rotor relative to the stator.

[0007] Engine brakes currently available on the market, especially those known from the state of the art, often have the problem that they are relatively large and also have a certain degree of complexity.

[0008] It is therefore an object of the present invention to solve the problem described above.

[0009] The problem is solved by the subject matter of independent patent claims 1, 9 and 10.

[0010] Further advantageous embodiments of the subject matter of the invention are contained in the corresponding dependent patent claims.

[0011] The object is achieved in particular by an electric motor, in particular as a drive for a machine tool, comprising a power supply, a stator with a stator laminated core and at least two coil windings, a rotor rotatable relative to the stator laminated core and a control device.

[0012] According to the invention, at least one recess for receiving at least one resistance element is contained on an outer circumferential surface of the stator laminated core, wherein the at least one resistance element is designed to convert an electrical voltage, which can be generated by the coil windings of the stator during a braking process of the rotor, into heat.

[0013] According to an advantageous embodiment, it may be possible for the at least one recess to extend substantially axially to a stator axis.

[0014] According to a further advantageous embodiment, it may be possible for the at least one recess to be positioned in a radial alignment with a pole tooth of the stator.

[0015] According to a further advantageous embodiment, it may be possible for a recess to be positioned in radial alignment with each pole tooth.

[0016] According to a further advantageous embodiment, it may be possible for the at least one recess to be at least partially filled with a connecting material.

[0017] According to a further advantageous embodiment, it may be possible for the connecting material to be at least partially designed as a thermosetting plastic or ceramic mortar.

[0018] According to an alternative embodiment, it may be possible to include at least one ventilation device for generating at least one ventilation flow, wherein the resistance element is positioned at least partially in the ventilation flow for dissipating heat from the resistance element.

[0019] According to an alternative embodiment, it may be possible for the at least one resistance element to be designed as a high-load resistor.

[0020] Furthermore, the task is solved by a stator for an electric motor.

[0021] Furthermore, the object is achieved by a machine tool with an electric motor. Further advantages will become apparent from the following description of the figures. The figures illustrate various embodiments of the present invention.

[0022] The figures, the description, and the claims contain numerous features in combination. The skilled person will also expediently consider the features individually and combine them into further meaningful combinations.

[0023] They show:

[0024] Figure 1 is a schematic side view of a machine tool according to the invention according to an exemplary embodiment with an electric motor;

[0025] Figure 2 is a perspective view of a stator core with recesses and resistance elements;

[0026] Figure 3 is a plan view of a stator and rotor;

[0027] Figure 4 shows a detailed view of the stator laminated core with a recess and a resistance element according to a first embodiment;

[0028] Figure 5 shows a detailed view of the stator laminated core with a recess and a resistance element according to a second embodiment;

[0029] Figure 6 shows a detailed view of the stator core with a recess and a resistance element according to a third embodiment; and

[0030] Figure 7 is a detailed view of the stator laminated core with a recess and a resistance element according to a fourth embodiment.

[0031] Examples of implementation:

[0032] Figure 1 shows a machine tool 1 according to an exemplary embodiment. The machine tool 1 is designed as a battery-powered drill.

[0033] According to an alternative embodiment, the machine tool can also be designed in the form of a saw, a grinder, a hammer drill or the like.

[0034] The machine tool 1 designed as a drilling machine essentially contains a housing 2, a handle 3, a tool holder 4 and a power supply 5.

[0035] The housing 2 has a front end 2a, a rear end 2b, an upper end 2c and a lower end 2d.

[0036] The tool holder 4 is positioned at the front end 2a of the housing 2. The tool holder 4 serves to receive and hold a tool. The tool is not shown in the figures.

[0037] In the present embodiment, the tool can be designed in the form of a drill. A first end 3a of the handle 3 is positioned at the lower end 2d of the housing 2. A battery interface 7 is provided at the second end 3b of the handle 3.

[0038] As shown in Figure 1, the handle 3 has an activation switch 8 with which the machine tool 1 can be set to an activation state or a deactivation state.

[0039] The power supply 5 can be releasably attached to the battery interface 7. In the present embodiment, the power supply 5 is designed in the form of a rechargeable battery. The power supply 5 serves to supply the machine tool with electrical energy.

[0040] According to an alternative embodiment, the power supply 5 can also be configured as a power cable for connecting the machine tool 1 to a mains power source (socket). The power supply 5 configured as a power cable is not shown in the figures.

[0041] Inside the housing 2 there is essentially positioned an electric motor 9 as a drive, a transmission device 10, a drive shaft 11, a ventilation device 6 and a control device 12.

[0042] The electric motor 9, the gear device 10, the drive shaft 11 and the tool holder 4 are arranged in relation to one another inside the housing 2 in such a way that a torque generated in the electric motor 9 can be transmitted to the gear device 10, the drive shaft 11 and finally to the tool holder 4 or to the tool.

[0043] The control device 12 is connected to the activation switch 8, the battery interface 7 and the electric motor 9 by means of corresponding lines L.

[0044] The electric motor 9 is designed in the form of a brushless electric motor and essentially contains a stator 16 and a rotor 17, see Figure 2.

[0045] At a rear end of the stator 16, the ventilation device 6 in the form of a fan wheel 6a is positioned such that the fan wheel 6a is driven by the rotor 17. As indicated in Figure 1, ventilation inlets LA1 are provided at the front end 2a of the housing 2, and ventilation outlets LA2 are provided at the rear end 2b of the housing 2. When the fan wheel 6a is driven by the rotor 17, a ventilation flow F is generated through the housing 2 to dissipate waste heat from the surface of the stator 16.

[0046] The power supply 5, designed as a rechargeable battery, can be detachably connected to the machine tool 1 to supply the machine tool 1 with electrical energy. The rechargeable battery 5 essentially contains a battery housing 20, a number of energy storage cells 13, a battery interface 14, and a control device 15.

[0047] The energy storage cells 13 can also be referred to as battery cells and are arranged inside the battery housing 20.

[0048] The battery housing 20 essentially contains a cover element 20a, four side walls 20b and a base element 20c.

[0049] The battery interface 14 is arranged on the outside of the cover element 20a and serves for the electrical or electronic as well as mechanical connection of the battery 5 to the machine tool 1 or a charging device.

[0050] The charging device is used to charge the accumulator 5 with electrical energy and is not shown in the figures.

[0051] For electrical or electronic connection, the battery interface 14 has a positive contact, a negative contact, and a communication contact. The positive and negative contacts serve to create an electrical circuit when the battery 5 is connected to a machine tool 1 or a charging device. The communication contact serves to send and receive data and information in the form of electrical signals.

[0052] Alternatively or additionally, the accumulator 5 can also incorporate radio communication (e.g., Bluetooth) or wireless communication. The energy storage cells 13 serve to absorb, store, and re-release electrical energy. The energy storage cells 13 are cylindrical in shape and are designed based on lithium-ion technology. Each energy storage cell 13 contains a contact device at one end, which serves to transmit electrical energy. The individual contact devices are connected to the control device 15 of the accumulator 5 via corresponding lines.

[0053] Alternatively, the energy storage cells 13 may also be based on another suitable technology.

[0054] The cylindrical shape of the energy storage cells 13 is also optional, so any other suitable shape or geometry can be selected. In particular, it is also possible for the energy storage cells 13 to be designed as pouch cells.

[0055] It is also possible for the accumulator 5 to contain both cylindrical energy storage cells 13 and pouch cells. In particular, it is possible for the accumulator 5 to contain only a single cylindrical energy storage cell 13 and a single pouch cell.

[0056] The control device 15 regulates and controls various functions of the accumulator 5. These functions include, among others, controlling the absorption and release of electrical energy into and from the energy storage cells 13. Furthermore, the control device 15 controls the amount of electrical energy to be absorbed or released by the energy storage cells 13.

[0057] As indicated in Figure 3, the rotor 17 is positioned inside the stator 16 and is also designed to be rotatable relative to the stator 16.

[0058] As shown in Figure 2, the stator 16 contains a stator laminated core 18 with four radially inwardly directed pole teeth 19. The stator laminated core 18 essentially consists of a number of profiled sheets stacked one above the other.

[0059] Two pole teeth 19 are positioned opposite each other. According to an alternative embodiment, more than four pole teeth 19 can also be provided. The pole teeth 19 serve to respectively accommodate a coil wire 21 to create a coil 24. The coils 24 are connected to the power supply 5 via the control device 12 in order to apply an electrical voltage to the coils 24. In other words, the coils 24 are energized. With the help of the coils 24, an alternating magnetic field is generated, which rotates the rotor 17.

[0060] A number of recesses 22 extending axially to a stator axis SA are positioned on an outer surface 23 of the stator core 18. Figure 2 shows a stator core 18 according to a first embodiment with four recesses 22. The recess 22 can also be referred to as a depression, groove, groove, or cavity.

[0061] According to a second embodiment, the stator laminated core 18 has six recesses 22, see Figure 3.

[0062] According to an alternative embodiment, the stator core 18 may contain more than six pole teeth 19 and more than six recesses 22. The number of pole teeth 19 and recesses 22 need not be the same.

[0063] As can be seen in Figures 2 and 3, the recesses 22 according to the first and second embodiments on the outer surface 23 are aligned with the pole teeth 19. In other words, a recess 22 is radially aligned with a pole tooth 19.

[0064] As described below, a recess 22 can also be positioned radially between two adjacent pole teeth 19. According to the illustrated embodiments, the recesses 22 extend over the entire length L of the stator core 18. The length of a recess 22 thus corresponds to the length of the stator core 18.

[0065] According to an alternative embodiment not shown in the figures, it is also possible for one or more recesses 22 to be shorter than the stator laminated core 18, whereby one or more recesses 22 do not extend over the entire length of the stator laminated core 18.

[0066] As indicated in the figures, a recess 22 serves to accommodate a resistance element 25, which is connected via corresponding lines to the control device 12 and to the coils 24 of the stator 16. Figure 3 shows the connections between the coils 24 and the respective resistance elements 25. In the embodiment in Figure 2, the resistance element 25 is designed as a current-conducting wire in the shape of a curve or an arc.

[0067] If the rotational speed of the rotor 17 relative to the stator 16 is to be reduced or the rotor 17 is even to be stopped completely, the rotor 17 must be braked by means of a braking process. When the rotor 17 is braked, an electrical voltage is induced at the coils 24 of the stator 16. By connecting the coils 24 via lines L to the respective resistance elements 25, the induced electrical voltage can be converted into heat in the resistance elements 25. Furthermore, a recess 22 also serves as a flow channel through which a ventilation current F generated by the ventilation device 6 can flow.

[0068] As already described above, the fan wheel 6a, driven by the rotor 17, generates a ventilation flow F, which flows over the outer surface of the stator 16 or stator core for cooling. The recesses 22 increase the outer surface area 23 of the stator core, thereby enabling better heat dissipation. Furthermore, the recesses 22 direct the ventilation flow F like channels along the resistance elements 25, effectively cooling them.

[0069] According to a further alternative embodiment, it is also possible for a resistance element 25 not to be located in every recess 22. Preferably, a resistance element 25 is located in each of two opposite recesses 22.

[0070] Figure 4 shows a detailed view of the stator core with a recess 22 and resistance element 25 according to a first embodiment. As can be seen, the recess 22 with a resistance element 25 is located between two adjacent pole teeth 19.

[0071] Figure 5 shows a detailed view of the stator core with a recess 22 and resistance element 25 according to a second exemplary embodiment. As can be seen, the recess 22 with a resistance element 25 is radially aligned with a pole tooth 19.

[0072] Figure 6 shows a detailed view of the stator core with a recess 22 and resistance element 25 according to a third exemplary embodiment. As can be seen, the recess 22 with a resistance element 25 is located between two adjacent pole teeth 19. The recess 22 is almost completely filled with a thermoset resin as the bonding material 26. As indicated in Figure 6, the filling height FH of the bonding material 26 is less than the depth of the recess 22.

[0073] According to an alternative embodiment, the filling height FH of the connecting material 26 can correspond to the depth AT of the recess 22.

[0074] Figure 7 shows a detailed view of the stator core with a recess 22 and resistance element 25 according to a fourth exemplary embodiment. As can be seen, the recess 22 with a resistance element 25 is radially aligned with a pole tooth 19. The recess 22 is almost completely filled with a thermoset as the connecting material 26. As indicated in Figure 7, the filling height FH of the connecting material is less than the depth of the recess 22. According to an alternative embodiment, the filling height FH of the connecting material 26 can correspond to the depth AT of the recess 22.

[0075] Reference symbol

[0076] 1 machine tool

[0077] 2 housings

[0078] 2a front end of the housing

[0079] 2b rear end of the housing

[0080] 2c upper end of the housing

[0081] 2d lower end of the housing

[0082] 3 Handle

[0083] 3a first end of the handle

[0084] 3b second end of the handle

[0085] 4 tool holder

[0086] 5 Energy supply

[0087] 6 Ventilation system

[0088] 6a Fan wheel

[0089] 7 Battery interface

[0090] 8 activation switches

[0091] 9 Electric motor

[0092] 10 Gear device

[0093] 11 Drive shaft

[0094] 12 Control device

[0095] 13 Energy storage cell

[0096] 14 Battery interface

[0097] 15 Control device

[0098] 16 Stator

[0099] 16a upper end of the stator

[0100] 16b lower end of the stator

[0101] 17 Rotor

[0102] 18 Stator laminated core

[0103] 19 Pole tooth

[0104] 20 battery housing 20a cover element

[0105] 20b side wall

[0106] 20c floor element

[0107] 21 Coil wire 22 Recess

[0108] 23 Outer surface of the stator laminated core

[0109] 24 coil

[0110] 25 resistance element

[0111] 26 Connecting material

[0112] LA1 ventilation inlet

[0113] LA2 ventilation outlet

[0114] F Ventilation flow

[0115] Lsb Length of the stator core L Line

[0116] SA stator axis

[0117] FH Filling level of the connecting material

[0118] AT Depth of the recess

Claims

Patent claims 1. Electric motor (9), in particular as a drive for a machine tool (1), comprising a power supply (5), a stator (16) with a stator laminated core (18) and at least two coils (24), a rotor rotatable relative to the stator laminated core (18) (17) and a control device (12), characterized in that on an outer surface (23) of the stator laminated core (18) at least one recess (22) for receiving at least one resistance element (25) is contained, wherein the at least one resistance element (25) is designed to convert an electrical voltage, which can be generated by the coils (24) of the stator (16) during a braking process of the rotor (17), into heat.

2. Electric motor (9) according to claim 1, characterized in that the at least one recess (22) extends substantially axially to a stator axis (SA).

3. Electric motor (9) according to claim 1 or 2, characterized in that the at least one recess (22) is positioned in a radial alignment with a pole tooth (19) of the stator (16).

4. Electric motor (9) according to claim 1 or 2, characterized in that a recess (22) is positioned in radial alignment with each pole tooth (19).

5. Electric motor (9) according to at least one of claims 1 to 4, characterized in that the at least one recess (22) is at least partially filled with a connecting material.

6. Electric motor (9) according to claim 5, characterized in that the connecting material (26) is at least partially designed as a thermosetting plastic or ceramic mortar.

7. Electric motor (9) according to at least one of claims 1 to 6, characterized in that at least one ventilation device (6) is included for generating at least one ventilation flow (F), wherein the resistance element (25) is positioned at least partially in the ventilation flow (F) for dissipating heat from the resistance element (25).

8. Electric motor (9) according to at least one of claims 1 to 7, characterized in that the at least one resistance element (25) is designed as a high-load resistor.

9. Stator (16) for an electric motor (9) according to at least one of claims 1 to 8.

10. Machine tool (1) with electric motor (9) according to at least one of claims 1 to 8.

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