electrical appliance

Abstract

Electrical device (1) with an electric motor (2), a switch (5) having a switch housing (13) for switching the electrical device on and / or off, a microcontroller (9) arranged in the switch housing (13) for controlling the electric motor (2) and with a voltage supply (14) formed by a mobile energy store (8) for operating the electrical device, wherein the energy store (8) is composed of several individual cells (18), wherein the electrical device (1) further comprises monitoring electronics (15) arranged in the switch housing (13), which are designed to measure electrical intermediate voltages (19) at the individual cells (18) and the total electrical voltage (16) of all cells (18) and to supply these to the microcontroller (9), and wherein the microcontroller (9) is designed to switch off the electrical device (1) or at least the electric motor (2) if at least one individual voltage (19) of the voltage supply (14) falls below and / or exceeds a limit value.

Description

[0001] The invention relates to an electrical device with an electric motor.

[0002] The electrical device may be a power tool, specifically a cordless and / or mains-powered power tool, in particular a drill, grinder, saw, planer, angle grinder, or similar. The electrical device may also be a household appliance, such as a kitchen appliance, a vacuum cleaner, or similar, or a portable lamp.

[0003] Such power tools contain an electric motor. For proper operation, the power tool is equipped with a power supply. In particular, a load within the power tool, such as the electric motor, is powered by energy from the power supply. It has been shown that changes in the supply voltage outside of certain limits can lead to damage to the power tool. This can lead to the destruction of the battery, especially when using a rechargeable battery to power the power tool.

[0004] State-of-the-art electrical devices and aspects of such electrical devices are known in particular from the documents DE 10 2008 000 704 A1, EP 2 051 315 A1 and DE 10 2005 000 139 A1.

[0005] The invention is based on the object of preventing damage to electrical devices due to voltage fluctuations in the supply voltage. In particular, it is the object of providing a very simple solution to the problems described.

[0006] This object is achieved in an electrical device having the features of claim 1.

[0007] In the electrical device according to the invention defined by the main claim, the operation of the electrical device is shut down if at least one individual voltage of the power supply falls below and / or exceeds a limit value. Preferably, in this case, the load in the electrical device driven by the supply voltage is shut down. The invention thus provides, in particular, supply voltage monitoring for a power tool. Further embodiments of the invention are the subject of the dependent claims.

[0008] Typically, the electrical device can be manually switched on and / or off by the user using a switch, whereby the switch may have a switch housing. A microcontroller is often assigned to the switch, which is controlled by software and is expediently located in the switch housing. The microcontroller is used as electronics in the switch to control the electric motor. For example, the microcontroller controls the electric motor so that it runs at a preselected speed. For the sake of compactness, it is advisable to also install monitoring electronics for measuring the voltage and / or the individual voltages of the power supply in the switch housing. This creates supply voltage monitoring for a power tool in the switch.

[0009] This eliminates the need for special electronics in the energy storage system, which performs monitoring and disconnects the load using a switching element or at least sends a shutdown signal to the switch, which then carries out the disconnection. Such a system would consist of several separate electronic modules, resulting in redundancies that, while desirable, are difficult or impossible to sell from a commercial perspective. Rather, this development according to the invention creates a combination of switch and monitoring electronics, thereby reducing costs. In particular, the switching element already present in the switch is used to disconnect the load, eliminating the need for the otherwise additional switching element.

[0010] The individual voltages measured by the monitoring electronics are fed to the microcontroller. The evaluation of whether the measured voltage and / or the measured individual voltages are within the specified limits is then carried out by the microcontroller, which can optionally be operated with appropriate software. Preferably, the load is then switched off by a switching element of the switch depending on the previous evaluation by the microcontroller. The switching element can expediently comprise a semiconductor switch, which is in particular a power transistor, such as a MOSFET. In a compact manner, the switching element is also located in the switch housing.

[0011] The electrical device is powered by a supply voltage from a mobile energy storage device, similar to a battery. The energy storage device, in turn, consists of several cells. The monitoring electronics measures the intermediate electrical voltages at the individual cells and the total electrical voltage of all cells in the energy storage device.

[0012] By monitoring each intermediate voltage as well as the total voltage, individual cells are prevented from being subjected to greater stress than others in the energy storage system. Otherwise, an unbalanced discharge of the energy storage system could cause damage. This is prevented by the invention, which allows the power tool switch to disconnect the load from the source, i.e., the energy storage system, early on.

[0013] The following can be observed for a particularly preferred embodiment. Typically, the electrical system of the power tool is supplied with electrical energy from a connected, mobile energy storage device. For example, this can be a rechargeable battery with a nominal voltage of 14.4 V direct current (DC), 18.0 V DC, or similar. All intermediate voltages are then fed from the energy storage device used to the electronics of the power tool switch. The electronics of the power tool switch measure the intermediate voltages and the total voltage of the energy storage device. In further developments, the evaluation of whether the voltages are within the specified limits can be carried out using a microcontroller and software. The load can be switched off using a switching element in accordance with the previous evaluation by the microcontroller.

[0014] The advantages achieved by the invention are, in particular, that the electronics in the power tool switch can be designed in such a way that the monitoring function according to the invention does not require any component configuration variations. If a microcontroller is used in the switch, the software can additionally control the voltage evaluation and the switch's shutdown behavior, so that no damage to the energy storage device is caused by fluctuating voltage. Only electrical connections from the energy storage device to the switch are then required, but no additional monitoring electronics, especially not those in the energy storage device.

[0015] On the one hand, electronic modules can be developed for power tools that comprehensively monitor and protect the energy storage device during discharging. On the other hand, using a microcontroller, the software can control both the behavior of the electronics, the monitoring, and the shutdown. The same electronic module can be produced for several different voltage variants of the energy storage device, with the software determining the corresponding behavior of the electronic module, for example, by setting the respective limit values.

[0016] An embodiment of the invention with various developments and refinements is shown in the drawings and is described in more detail below. Fig. 1 schematically shows a power tool, with the housing of the power tool partially broken away, and Fig. 2 a block diagram for the power tool.

[0017] In Fig. 1 shows a power tool 1 with an electric motor 2 for driving a tool 3. This can be a cordless and / or mains-powered power tool.

[0018] An example is Fig. 1 shows a cordless drill as a power tool 1, which is operated with a supply voltage from a mobile energy storage device 8 in the form of a battery. Of course, the power tool 1 can also be a grinder, a saw, a planer, an angle grinder, or the like.

[0019] A switch 5 with a switch housing 13 is arranged in the housing 4 of the power tool 1. The switch 5 is accommodated in the housing 4 in such a way that an actuating element 6 of the switch 5, which can be moved manually by the user, protrudes from the housing 4. The switch 5 has a contact system 7, which the actuating element 6 acts on to switch over, so that the voltage supply 14 (see Fig. 2) from the energy storage device 8 for the power tool 1, in particular for operating the electric motor 2, can be switched on and / or off by the user by means of the actuating element 6. Finally, the switch 5 comprises an electrical circuit arrangement for controlling and / or regulating the electric motor 2. The circuit arrangement serves as control electronics 9 for changing the speed of the electric motor 2 according to the position of the actuating element 6 moved by the user. The electronics 9 comprises a microcontroller for controlling the electric motor 2, as can be seen from Fig. 2 of . The microcontroller 9 is controlled by software and is conveniently located in the switch housing 13.

[0020] How to continue in Fig. As can be seen in Figure 1, a work area illumination 10 is arranged on the housing 4, with the aid of which the work area for the tool 3 can be illuminated to assist the user. The voltage supply for the work area illumination 10 also comes from the energy storage device 8, specifically in this case via the control electronics 9, which operates as a pulse-width modulation circuit. The work area illumination 10 is thus operated via a pulse-width modulation signal 11 fed by the supply voltage from the energy storage device 8, whereby the brightness of the light-emitting diode (LED) 10 can be adjusted accordingly as desired.

[0021] As mentioned, the microcontroller 9 is used to control the electric motor 2. As can be seen from Fig. 2, the microcontroller 9 operates the electric motor 2 by means of a pulse-width modulation signal 12 according to the speed set by the user using the actuating element 6. A direction of rotation switch 20 is used by the user to select the direction of rotation of the electric motor 2. The operation of the power tool 1, specifically of the electric motor 2 acting as an electrical load, is switched off by the microcontroller 9 when the voltage 16 and / or an individual voltage 19 of the power supply 14 falls below and / or exceeds a limit value.

[0022] How the Fig. 2, is located in switch 5, in particular in switch housing 13 (see Fig.1) Monitoring electronics 15 are arranged for measuring the voltage 16 of the power supply 14. The voltage 16 measured by the monitoring electronics 15 is fed to the microcontroller 9. The microcontroller 9 then evaluates, using appropriate software, whether the measured voltage 16 is within the specified limits. If, according to the previous evaluation by the microcontroller 9, the voltage 16 lies outside the specified limits, the electric motor 2 representing the load is switched off by means of a switching element 17. The switching element 17 comprises a semiconductor or a semiconductor switch and is also located in the switch housing 13. This is the power transistor, such as a MOSFET, which simultaneously serves to supply voltage to the electric motor 2 according to the pulse width modulation.

[0023] The energy storage device 8 is composed of several individual cells 18. The monitoring electronics 15 also conveniently measures the intermediate voltages 19 across the cells 18. As already mentioned, the total voltage 16 of all cells 18 of the energy storage device 8 is also measured by the monitoring electronics 15. The microcontroller 9 then checks whether the intermediate voltages 19 and / or the total voltage 16 are within the specified respective limits. If this is not the case, the electric motor 2 is shut down to prevent damage to the energy storage device 8.

[0024] The invention can be used preferably on all power tool switches for power tools with single- or multi-cell energy storage devices, in particular on a power tool switch for Li-ion batteries. However, the invention is suitable not only for direct current (DC) power tools but also for alternating current (AC) power tools that contain a microcontroller for control. Such mains-powered AC power tools operate by means of a leading-edge and / or trailing-edge phase control for speed adjustment. Furthermore, the invention is explained using a power tool but is not limited to the described and illustrated embodiment. Rather, it also encompasses all expert developments within the scope of the invention defined by the patent claims.Thus, a load shutdown in the event of a voltage and / or individual voltages of the power supply that are outside specified limits can also be used on other electrical devices, for example on household appliances, portable lamps, etc. List of reference symbols 1 power tool 2 electric motor 3 tools 4 Housing (of power tool) 5 Switches / Power tool switches 6 Actuating element 7 contact system 8 energy storage 9 Control electronics / electronics / microcontrollers 10 Work area lighting / LED 11 Pulse width modulation signal (for work area illumination) 12 Pulse width modulation signal (for electric motor) 13 Switch housing 14 Power supply 15 Monitoring electronics 16 Voltage (from power supply) / Total voltage 17 Switching element 18 cells (from energy storage) 19 Intermediate voltage 20 direction switch

Claims

[1] Electrical device (1) with an electric motor (2), a switch (5) having a switch housing (13) for switching the electrical device on and / or off, a microcontroller (9) arranged in the switch housing (13) for controlling the electric motor (2) and with a voltage supply (14) formed by a mobile energy store (8) for operating the electrical device, wherein the energy store (8) is composed of several individual cells (18), wherein the electrical device (1) further comprises monitoring electronics (15) arranged in the switch housing (13), which are designed to measure electrical intermediate voltages (19) at the individual cells (18) and the total electrical voltage (16) of all cells (18) and to supply these to the microcontroller (9), and wherein the microcontroller (9) is designed to switch off the electrical device (1) or at least the electric motor (2) if at least one individual voltage (19) of the voltage supply (14) falls below and / or exceeds a limit value. [2] Electrical device according to claim 1, further comprising a switching element (17), wherein the microcontroller (9) is designed to switch off the electric motor (2) by means of the switching element (17) in accordance with the preceding evaluation by the microcontroller (9). [3] Electrical device according to claim 2, characterized by that the switching element (17) comprises a semiconductor switch. [4] Electrical device according to one of the preceding claims 2 or 3, wherein the switching element (17) is located in the switch housing (13).

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