Integrated temperature measurement on a laminated stator core

Abstract

Disclosed is an electric motor, in particular as a drive for a machine tool, containing a power supply, a stator having a laminated stator core and a rotor which is rotatable relative to the laminated stator core, a memory unit and a controller having a device for measuring voltage values and a device for measuring current-intensity values. At least one recess for accommodating at least one temperature-dependent resistor element is formed in an outer lateral surface of the laminated stator core, wherein the at least one resistor element is connected to the power supply for selectively applying an electric voltage, and at least one voltage value can be measured by the device for measuring voltage values, and at least one current-intensity value can be measured by the device for measuring current-intensity values, so that at least one resistance value of the resistor element can be ascertained, and can be used to determine at least one temperature value by comparing said resistance value with reference values stored in the memory unit.

Description

[0001] Hilti Corporation in Schaan

[0002] Principality of Liechtenstein

[0003] Integrated temperature detection on the stator core

[0004] 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 a rotor rotatable relative to the stator laminated core, a storage unit and a control device with a device for detecting voltage values ​​and a device for detecting current values.

[0005] Furthermore, the present invention relates to a stator for an electric motor.

[0006] Furthermore, the present invention relates to a machine tool with an electric motor.

[0007] Furthermore, the present invention relates to a method for determining a temperature value on an electric motor comprising a power supply, a stator with a stator laminated core and a rotor rotatable relative to the stator laminated core, as well as a control device with a device for detecting voltage values ​​and a device for detecting current values, wherein at least one recess for receiving at least one coil winding is contained on an outer circumferential surface of the stator laminated core.

[0008] Electric motors (particularly as drives for machine tools) are known from the prior art. They essentially comprise a stator and a rotor rotatable relative to the stator to generate torque. A temperature sensing device is usually provided on the stator of the electric motor to detect temperature values.

[0009] Temperature detection devices currently available on the market, and particularly 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.

[0010] It is therefore an object of the present invention to solve the problem described above.

[0011] The object is achieved by the subject matter of independent patent claims 1, 9, 10 and 11. Further advantageous embodiments of the subject matter according to the invention are contained in the corresponding dependent patent claims.

[0012] 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 a rotor rotatable relative to the stator laminated core, as well as a control device with a device for detecting voltage values ​​and a device for detecting current values.

[0013] According to the invention, at least one recess for receiving at least one temperature-dependent resistance element is contained on an outer circumferential surface of the stator laminated core, wherein the at least one resistance element is connected to the power supply for selectively applying an electrical voltage and at least one voltage value can be detected by the device for detecting voltage values ​​and at least one current value can be detected by the device for detecting current values, so that at least one resistance value of the resistance element can be determined, which resistance value can be used to determine at least one temperature value by comparison with reference values ​​stored in the memory unit.

[0014] A temperature-dependent resistance element is an electrical resistor whose resistance value changes reproducibly with temperature. The temperature-dependent resistance element can also be referred to as a thermistor. The temperature-dependent resistance element can also be designed as a thermistor, which has a negative temperature coefficient (NTC) and conducts electricity better at high temperatures than at low temperatures.

[0015] Alternatively, the temperature-dependent resistance element can also be designed as a PTC thermistor, which has a positive temperature coefficient (PTC) and conducts electricity better at low temperatures than at high temperatures.

[0016] According to an alternative embodiment, it may be possible for the at least one temperature-dependent resistance element to be designed in the form of a coil winding.

[0017] According to a further alternative embodiment, it may be possible for the at least one recess to extend at least partially axially to a stator axis.

[0018] According to a further alternative 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. According to a further alternative embodiment, it may be possible for a recess to be positioned in radial alignment with each pole tooth.

[0019] According to a further alternative embodiment, it may be possible for the at least one recess to be at least partially filled with a connecting material.

[0020] According to a further alternative embodiment, it may be possible for the connecting material to be at least partially designed as a thermoset or ceramic mortar.

[0021] According to a further alternative embodiment, it may be possible for the at least one temperature-dependent resistance element to be designed as a high-load resistor.

[0022] Furthermore, the task is solved by a stator for an electric motor.

[0023] In addition, the task is solved by a machine tool with an electric motor.

[0024] Furthermore, the object is achieved by the method for determining a temperature value on an electric motor comprising a power supply, a stator with a stator laminated core and a rotor rotatable relative to the stator laminated core, a storage unit and a control device with a device for detecting voltage values ​​and a device for detecting current values, wherein at least one recess for receiving at least one temperature-dependent resistance element is contained on an outer circumferential surface of the stator laminated core.

[0025] According to the invention, the following process steps are included

[0026] - Applying an electrical voltage to the resistance element through the power supply;

[0027] - detecting a voltage value by the device for detecting voltage values;

[0028] - detecting a current value by the current detection device;

[0029] - Determining a resistance value as a quotient of the voltage value and the current value; and

[0030] - Determining a temperature value by comparing the resistance with reference values ​​stored in the memory unit. Further advantages will become apparent from the following description of the figures. The figures illustrate various embodiments of the present invention.

[0031] The figures, the description, and the claims contain numerous features in combination. The skilled person will expediently consider the features individually and combine them into further meaningful combinations.

[0032] They show:

[0033] Figure 1 is a schematic side view of a machine tool according to the invention according to an exemplary embodiment with an electric motor;

[0034] Figure 2 is a perspective view of a stator core with recesses and resistance elements;

[0035] Figure 3 is a top view of a stator and rotor;

[0036] Figure 4 shows a detailed view of the stator laminated core with a recess and a resistance element according to a first embodiment;

[0037] Figure 5 shows a detailed view of the stator laminated core with a recess and a resistance element according to a second embodiment;

[0038] Figure 6 shows a detailed view of the stator core with a recess and a resistance element according to a third embodiment; and

[0039] Figure 7 is a detailed view of the stator laminated core with a recess and a resistance element according to a fourth embodiment.

[0040] Examples of implementation:

[0041] Figure 1 shows a machine tool 1 according to an exemplary embodiment. The machine tool 1 is designed as a battery-powered drill.

[0042] 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.

[0043] 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.

[0044] The housing 2 has a front end 2a, a rear end 2b, an upper end 2c and a lower end 2d.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] The energy storage cells 13 can also be referred to as battery cells and are arranged inside the battery housing 20.

[0057] The battery housing 20 essentially contains a cover element 20a, four side walls 20b and a base element 20c.

[0058] 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.

[0059] The charging device is used to charge the accumulator 5 with electrical energy and is not shown in the figures.

[0060] 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.

[0061] 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.

[0062] Alternatively, the energy storage cells 13 may also be based on another suitable technology.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] As shown in Figure 2, the stator 16 contains a stator core 18 with four radially inwardly directed pole teeth. The stator core 18 essentially consists of a number of profiled sheets 19 stacked one above the other.

[0068] Two pole teeth 19 are positioned opposite one another. 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 generate 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 MF is generated, by which the rotor 17 is rotated. On an outer circumferential surface 23 of the stator laminated core, a number of recesses extending axially to a stator axis SA are positioned. Figure 2 shows a stator laminated core according to a first exemplary embodiment with four recesses.

[0069] According to a second embodiment, the stator core has six recesses, see Figure 3.

[0070] According to an alternative embodiment, the stator core 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.

[0071] As can be seen in Figures 2 and 3, the recesses 22 according to the first and second embodiments on the outer circumferential surface 23 are correspondingly aligned with the pole teeth 19. In other words, a recess 22 is radially aligned with a pole tooth 19. As described below, a recess 22 can also be positioned radially between two adjacent pole teeth 19. According to the embodiments shown, 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 Lsb of the stator core 18.

[0072] 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 Lsb of the stator laminated core 18.

[0073] As indicated in the figures, a recess 22 serves to accommodate a temperature-dependent resistance element 25. In the present embodiment, the temperature-dependent resistance element 25 is designed in the form of a coil winding.

[0074] Alternatively, the temperature-dependent resistance element 25 can also be designed in the form of a sheet resistor, foil resistor, ground resistor, wire resistor or potentiometer.

[0075] Each resistance element 25 configured as a coil winding is connected to the power supply 5 via the control device in order to apply an electrical voltage to the coil winding. Alternatively, the resistance element 25 configured as a coil winding is also connected directly (i.e., immediately) to the power supply 5.

[0076] In addition, each resistance element 25 designed as a coil winding is connected to a device for detecting voltage values ​​27 and serves to detect voltage values ​​at the respective resistance element 25. Furthermore, each coil winding is connected to a device 28 for detecting current values ​​and in turn serves to detect current values ​​at the respective resistance element 25. As already mentioned above, the control device 12 is connected to the device 27 for detecting voltage values ​​and the device 28 for detecting current values ​​such that the values ​​(volts or amperes) detected by the respective devices can be sent to the control device 12.

[0077] To carry out the method for determining a temperature value on the casing surface of the stator 16, an electrical voltage is first applied to at least one temperature-dependent resistance element 25 with the aid of the energy supply 5.

[0078] The device 27 for detecting voltage values ​​detects a voltage value at the resistance element 25. Furthermore, the device 28 for detecting current values ​​detects a current value at the resistance element 25. Both the detected voltage value and the detected current value are transmitted to the control device 12. Multiple voltage values ​​and current values ​​can be detected at regular or irregular intervals and sent to the control device 12. The time interval for detecting voltage values ​​and current values ​​can be, for example, ten seconds. Alternatively, the time interval can also be more or less than ten seconds.

[0079] Using the transmitted voltage and current values, the control device 12 can determine a resistance value for the temperature-dependent resistance element 25. Reference values ​​in the form of look-up tables are stored in a memory unit 29, which represent the relationship between the electrical resistance and the temperature of the respective material used for the resistance element 25. By comparing the determined resistance value with the reference values, the respective temperature of the resistance element 25 is determined. Since the resistance element 25 is located in the immediate vicinity of or in contact with the outer surface 23 of the stator laminated core 18, the temperature of the resistance element 25 also corresponds to the temperature of the outer surface 23 of the stator laminated core 18.

[0080] 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 coil winding is located in each of two opposite recesses. Figure 4 shows a detailed view of the stator core 18 with a recess 22 and a 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.

[0081] Figure 5 shows a detailed view of the stator core 18 with a recess 22 and a 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.

[0082] Figure 6 shows a detailed view of the stator core 18 with a recess and a resistance element 25 according to a third exemplary embodiment. As can be seen, the recess with a resistance element 25 is located between two adjacent pole teeth 19. The recess 22 is almost completely filled with a thermoset as the connecting material 26. As indicated in Figure 6, the filling height FH of the connecting material 26 is less than the depth AT of the recess 22.

[0083] According to an alternative embodiment, the filling height FH of the connecting material 26 can correspond to the depth AT of the recess 22.

[0084] Figure 7 shows a detailed view of the stator core 18 with a recess 22 and a 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 6, the filling height FH of the connecting material 26 is less than the depth AT of the recess 22.

[0085] According to an alternative embodiment, the filling height FH of the connecting material 26 can correspond to the depth AT of the recess 22.

[0086] Reference symbol

[0087] 1 machine tool

[0088] 2 housings

[0089] 2a front end of the housing

[0090] 2b rear end of the housing

[0091] 2c upper end of the housing

[0092] 2d lower end of the housing

[0093] 3 Handle

[0094] 3a first end of the handle

[0095] 3b second end of the handle

[0096] 4 tool holder

[0097] 5 Energy supply

[0098] 6 Ventilation system

[0099] 6a Fan wheel

[0100] 7 Battery interface

[0101] 8 activation switches

[0102] 9 Electric motor

[0103] 10 Gear device

[0104] 11 Drive shaft

[0105] 12 Control device

[0106] 13 Energy storage cell

[0107] 14 Battery interface

[0108] 15 Control device

[0109] 16 Stator

[0110] 16a upper end of the stator

[0111] 16b lower end of the stator

[0112] 17 Rotor

[0113] 18 Stator laminated core

[0114] 19 Pole tooth

[0115] 20 battery housing 20a cover element

[0116] 20b side wall

[0117] 20c floor element

[0118] 21 coil wire

[0119] 22 recess

[0120] 23 Outer surface of the stator laminated core

[0121] 24 coil

[0122] 25 resistance element

[0123] 26 Connecting material

[0124] 27 Device for detecting voltage values

[0125] 28 Device for recording current values

[0126] 29 Storage unit

[0127] LA1 ventilation inlet

[0128] LA2 ventilation outlet

[0129] F Ventilation flow

[0130] Lsb length of the stator lamination stack

[0131] L Line

[0132] SA stator axis

[0133] FH Filling level of the connecting material

[0134] AT Depth of the recess

Claims

Patent claims 1. An 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 a rotor (17) rotatable relative to the stator laminated core (18), a storage unit (29), and a control device (12) with a device (27) for detecting voltage values ​​and a device (28) for detecting current values, characterized in that at least one recess (22) for receiving at least one temperature-dependent resistance element (25) is contained on an outer circumferential surface (23) of the stator laminated core (18), wherein the at least one resistance element (25) is connected to the power supply (5) for selectively applying an electrical voltage, and at least one voltage value can be detected by the device (27) for detecting voltage values ​​and at least one current value can be detected by the device (28) for detecting current values,so that at least one resistance value of the resistance element (25) can be determined, which can be used to determine at least one temperature value by comparing it with reference values ​​stored in the memory unit (29).

2. Electric motor (9) according to claim 1, characterized in that the at least one temperature-dependent resistance element (25) is designed in the form of a coil winding.

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

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

5. Electric motor (9) according to at least one of claims 1 to 4, characterized in that a recess (22) is positioned in radial alignment with each pole tooth (19).

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

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

8. Electric motor (9) according to at least one of claims 1 to 7, characterized in that the at least one temperature-dependent 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 an electric motor (9) according to at least one of claims 1 to 8.

11. A method for determining a temperature value on an electric motor (9) comprising a power supply (5), a stator (16) with a stator laminated core (18) and a rotor (17) rotatable relative to the stator laminated core (18), a storage unit (29) and a control device (12) with a device (27) for detecting voltage values ​​and a device (28) for detecting current values, wherein at least one recess (22) for receiving at least one temperature-dependent resistance element (25) is contained on an outer circumferential surface (23) of the stator laminated core (18), characterized by the method steps: - applying an electrical voltage to the resistance element (25) by the power supply (5); - detecting a voltage value by the device (27) for detecting voltage values; - detecting a current value by the current value detecting device (28); - Determining a resistance value as a quotient of the voltage value and the current value; and Determining a temperature value by comparing the resistance with reference values ​​stored in the memory unit (29).

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