EP3363597B1 - Protection contre la surcharge d'une machine-outil électrique fonctionnant sur accumulateur - Google Patents

Protection contre la surcharge d'une machine-outil électrique fonctionnant sur accumulateur Download PDF

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Publication number
EP3363597B1
EP3363597B1 EP18154744.9A EP18154744A EP3363597B1 EP 3363597 B1 EP3363597 B1 EP 3363597B1 EP 18154744 A EP18154744 A EP 18154744A EP 3363597 B1 EP3363597 B1 EP 3363597B1
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EP
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Prior art keywords
electric machine
machine tool
overload protection
voltage
supply voltage
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German (de)
English (en)
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EP3363597A1 (fr
Inventor
Frank Matheis
Tobias Beck
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Metabowerke GmbH and Co
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Metabowerke GmbH and Co
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25F—COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR
    • B25F5/00—Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for

Definitions

  • the invention relates to a method for overload protection of a battery-operated power tool.
  • the invention also relates to a battery-operated power tool with an overload protection device and a computer program with program code means for carrying out a method for overload protection of a power tool.
  • power tools are understood to mean both hand-held power tools, such as drills, angle grinders and the like, and machines that are stationary in operation, i.e. stationary or semi-stationary devices, such as table saws or the like.
  • Methods for detecting an overload situation in an electric power tool are already known from the state of the art.
  • the aim is to prevent one or more components of the electric power tool from failing due to excessive current flow, for example connecting cables, the electric motor, soldered connections, a battery pack or controlled switches.
  • Overload situations can occur, for example, if the electric motor of the electric power tool blocks. In this state, very high currents can flow through the windings of the electric motor; from the perspective of a battery pack, such a stationary motor behaves similarly to a short circuit. The thermal load on the components of the electric power tool can therefore quickly rise to a critical level.
  • the EN 10 2005 038 225 A1 a method for detecting an overload situation of an electric machine tool with an electric motor, wherein a Operating current of the electric motor is determined, whereby a difference between the value of the operating current and at least one stored current value is determined and a thermal overload of the power tool is concluded from the difference.
  • the WO 2012/079936 A2 proposed that a thermal model be taken into account, whereby during operation of the power tool a current thermal energy content of the component is determined from a current energy inflow and a current energy outflow, and the power tool is operated in at least one operating range depending on the thermal energy content. This ultimately means that a relatively short current peak cannot automatically lead to the power tool being switched off.
  • thermal model Although the inclusion of such a thermal model can increase the accuracy of overload protection, it still cannot create thermal models suitable for all operating or fault situations and for all critical components. In addition, the computational effort required to implement the method is relatively high.
  • Another problem is that the currently known overload protection methods cannot take into account whether the power tool is operated with a faulty battery pack or a battery pack with outdated technology, for example with a high internal resistance. Because there are usually different types of battery packs on the market, which should preferably remain compatible with newer power tools in order to increase user-friendliness and customer loyalty, already damaged or old battery packs can potentially be damaged before the overload protection of the power tool can intervene, because the overload protection device assumes a fault-free (modern) battery pack.
  • the problem is exacerbated when using battery packs with different internal resistances, as high internal resistances can cause the supply voltage of the battery pack to drop to such an extent when the power tool has a high power requirement that electrical components, in particular the power control of the electric motor, can no longer be adequately supplied, causing the electronics to assume an undefined state. Due to the subsequent undefined situation, damage to the power tool may occur even sooner and/or the overload protection device may fail due to insufficient supply.
  • the generic US 2016/049636 A1 relates to a method in which the electrical output power of a battery pack supplied to a power tool is reduced or switched off when an irregularity is detected in the battery pack.
  • the present invention is based on the object of providing a method for overload protection of a battery-operated power tool that is improved compared to the prior art and in which the known disadvantages can at least be reduced.
  • the present invention is also based on the object of providing a power tool with an overload protection device that is improved compared to the prior art.
  • overload protection according to the invention is based on the detection of a voltage drop and not on a current measurement results in several advantages.
  • the overload protection according to the invention is therefore compatible with any battery cell arrangement or independent of a battery cell arrangement used, and can be used without restriction even if the battery cell arrangement is damaged.
  • overload protection according to the invention can react more quickly than the known overload protection methods of the prior art. This is because long-term current measurements no longer have to take place. A high current requirement can be detected directly via the connection with the supply voltage of a battery cell arrangement, which results from the internal resistance of the battery cell arrangement.
  • Controllers or control devices within the power tool as well as drivers of the electric motor can be supplied with sufficient voltage at any time or the voltage supply can be switched off completely (in a controlled manner) to protect them.
  • Detecting a supply voltage means that the voltage currently being used to supply the power tool or its components (power electronics, electric motor, etc.) is detected.
  • the voltage measurement can be carried out directly on the battery cell arrangement or the power tool's supply terminals and/or at any point within the power tool.
  • the supply voltage refers in particular to the numerical value of the supply voltage or another value that mathematically correlates with the supply voltage.
  • the reference value can be a reference voltage or a numerical value that is calculated analogously to a numerical value that represents the supply voltage or is mathematically correlated with the supply voltage.
  • the actual supply voltage can then either be calculated mathematically from this or the reference value can be selected or scaled accordingly, taking into account that only half the supply voltage was measured.
  • the battery cell arrangement can be designed as a battery pack in which several battery cells are connected to one another in series and/or in parallel. A group connection of battery cells is also possible.
  • a battery pack can be an accumulator with a single battery cell (also called a secondary cell) or a connected pack with several battery cells.
  • a battery pack can also be a storage device for electrical energy that is not or not exclusively electrochemically constructed, for example a capacitor.
  • batteries or battery packs i.e. non-rechargeable storage devices for electrical energy, are also included in the term “battery pack” or “battery cell”.
  • the battery cell arrangement can be designed as a single battery pack or as multiple battery packs, for example two battery packs, three battery packs, four battery packs or more battery packs, wherein the multiple battery packs can be electrically connected in any way in a series circuit, parallel circuit or group circuit.
  • the battery cell arrangement or the battery packs do not have to be arranged directly on the power tool, but can also be connected to the power tool via an adapter arrangement and/or a cable connection.
  • the energy supply of the electric machine tool is immediately limited as soon as the detected supply voltage is lower than the reference value.
  • the power supply to the power tool can therefore be limited as quickly as possible, within the technical possibilities, as soon as the detected supply voltage is lower than the reference value. For example, no intentional delays are provided.
  • the power tool can thus be protected particularly quickly from an overload situation.
  • the energy supply of the power tool is limited if the detected supply voltage is lower than the reference value, wherein a delay between the limiting of the energy supply and the supply voltage falling below the reference value can in particular be smaller than a triggering delay of a deep discharge protection.
  • the method according to the invention for overload protection reacts faster than an existing deep discharge protection, whereby a False triggering of a deep discharge protection of the battery cell arrangement due to the voltage drop can also be avoided.
  • the reference value is determined on the basis of a minimum voltage which is required for the error-free operation of safety-critical electrical components or electrical components of the power tool.
  • the reference value can be stored in a volatile or non-volatile data memory of an electrical circuit of the power tool.
  • a safety-critical component is a component that has a major influence on the power requirement of the power tool. This can, for example, be parts of the power electronics for controlling the electric motor, which can trigger and/or amplify a fault in the undefined conditions caused by an undersupply.
  • the safety-critical components within the meaning of patent claim 1 are semiconductor components, for example transistors, in particular (power) MOSFETs.
  • MOSFETs are used as analog components within the electronics of the power tool, in particular as controlled resistors, a reference voltage that is too low can lead to an unspecified or undesirable output resistance of the transistor, which can cause the MOSFET to heat up disproportionately when there is a high current flow on the output side or can cause such a current flow in the first place due to the too low output resistance.
  • MOSFETs are used as controlled switches within a digital circuit of the power tool, defined voltage levels must be maintained to distinguish between the defined digital signal levels “low” (logical '0') and “high” (logical '1') so that no undefined signals occur within the digital circuit that can spread through the entire switching network.
  • threshold voltage should be avoided, as this is the voltage at which the MOSFET switches on the output side. If the supply voltage is too low, the switching times or signal edges can also be delayed in an unfavorable way.
  • parts of the digital signal processing and/or control for example a state machine (finite state machine, FSM), can assume unwanted states and/or states that are excluded from the outset.
  • FSM finite state machine
  • the problem of undersupplied (power) electronics in the power tool can be avoided. This is primarily because the voltage drop that leads to the undersupply and thus to the undefined state of the electronics and possibly a chain reaction that leads to the (thermal) destruction of the power tool or its components can no longer occur. The voltage drop is detected and the problem of excessive current consumption is immediately counteracted by limiting the power supply to the power tool before a critical supply voltage is reached (e.g. the reference value).
  • the reference value is smaller than a final discharge voltage of the battery cell arrangement.
  • the discharge end voltage refers to the limit value of the battery cell arrangement voltage for deep discharge. It is well known that deep discharge of the battery cell arrangement should be avoided, as otherwise the battery cell arrangement can be destroyed or lose its service life. The provision of deep discharge protection is not within the scope of the task of this invention. In the event of a load-induced voltage drop or an overload of the power tool the supply voltage of the battery cell arrangement typically drops significantly below the final discharge voltage. However, this is only a short-term dip that is not related to a deep discharge of the battery cell arrangement, but rather to excessive current consumption due to overload. After limiting the power supply to the power tool, a supply voltage that is above the final discharge voltage of the battery cell arrangement will immediately return (unless the battery cell arrangement is actually deeply discharged).
  • a deep discharge protection device In order to avoid false detection, a deep discharge protection device must therefore monitor the supply voltage of the battery cell arrangement over a relatively long period of time (for example, over several seconds). A deep discharge protection device is therefore unsuitable for detecting an overload of the power tool - and vice versa.
  • the power tool can be equipped with an inventive method for overload protection and at the same time with deep discharge protection.
  • the method for overload protection can quickly eliminate an overload-induced voltage drop
  • the deep discharge protection can also be implemented in a technically simple manner, since false detection due to the overload-induced voltage drop can be virtually ruled out.
  • the reference value is less than 75% of a nominal voltage of the battery cell arrangement, preferably less than 65% of the nominal voltage, particularly preferably less than 55% of the nominal voltage, for example less than 45% of the nominal voltage.
  • the battery cell arrangement comprises lithium-ion battery cells that have a nominal voltage of approximately 3.6 volts.
  • Battery packs that are composed of a series connection of five lithium-ion battery cells are often used to operate power tools, resulting in a nominal voltage of the battery pack of approximately 18 volts - or 36 volts for, for example, ten lithium-ion battery cells connected in a series connection.
  • the reference value is approximately 10 volts (or approximately 20 volts for the ten lithium-ion battery cells), while the final discharge voltage of the battery pack is approximately 12.5 volts (or 25 volts for ten lithium-ion battery cells).
  • the battery cells can also be nickel-metal hybrid battery cells, nickel-cadmium battery cells or lead battery cells.
  • the invention is not limited to use with a specific type of battery pack/battery cells or a specific type of battery cell arrangement.
  • the nominal voltages and final discharge voltages in particular are different.
  • the supply voltage is continuously detected during operation of the electric power tool and compared with the reference value, preferably by using asynchronous circuit technology and/or by using synchronous circuit technology with a clock frequency greater than 1 Hz, preferably greater than 1 kHz, particularly preferably greater than 1 MHz, for example greater than 10 MHz.
  • a controlled switch can be provided that opens automatically when the detected supply voltage is lower than the reference value.
  • a MOSFET can be provided whose threshold voltage is selected or set accordingly. As soon as the supply voltage of the battery cell arrangement is regenerated (because the controlled switch has switched off due to insufficient supply), the switch is automatically closed again and the power tool continues to be supplied. This makes it possible to provide a self-regulating system using the simplest of means.
  • the supply voltage of the battery cell arrangement is recorded at regular time intervals and compared with the reference value. Preferably, short time intervals are selected.
  • the supply voltage of the battery cell arrangement can be measured at intervals of less than 1 s, ⁇ 100 ms, ⁇ 10 ms, ⁇ 1 ms, ⁇ 100 ⁇ s, ⁇ 10 ⁇ s, ⁇ 1 ⁇ s or at even shorter time intervals.
  • the energy supply of the electric machine tool is limited by interrupting the energy supply of the electric machine tool, preferably for a defined time interval.
  • the energy supply of the electric machine tool is limited by a method for power limitation or current limitation, preferably by a pulse modulation method.
  • the device for detecting the supply voltage is designed as a voltage measuring device and/or is designed to read out a numerical value of the supply voltage of the battery cell arrangement from a data interface of the battery cell arrangement (analog and/or digital).
  • the supply voltage can be detected using a voltage measuring device at any point within the power tool and/or within the battery cell arrangement. It can also be provided that a voltage value dependent on the supply voltage, for example a voltage at a node within a voltage divider, etc., is measured and then converted to the actual numerical value of the supply voltage.
  • a modern battery pack usually includes an integrated battery management system (BMS) and a data interface.
  • BMS battery management system
  • the BMS is used to monitor and/or regulate the battery pack, is sometimes also referred to as a "power management system” (PMS), and usually transmits data in analog and/or digital form about the status (e.g. charge level or supply voltage and/or temperature status) and/or the design or characteristic parameters (e.g. nominal voltage, final charging voltage and/or identification data) of the respective battery pack.
  • the device for recording the supply voltage evaluate or use such data signals to detect the supply voltage.
  • the switching device is designed as a controlled switch and/or comprises a controllable current limiter. More than one controlled switch can also be provided, for example two, three, four, five, six, seven, eight or more controlled switches can be provided, which are connected together to form a switching bridge, for example.
  • the switching device can interrupt the energy supply to the power tool for a defined time interval, for example by opening a controlled switch, or limit it in another way, for example by means of a pulse modulation method, in particular a pulse width modulation method.
  • the overload protection device and/or at least one component of the overload protection device is or are designed as a digital circuit, for example as a microprocessor, as an application-specific integrated circuit (ASIC), as a programmable digital circuit, for example as a "Field Programmable Gate Array” (FPGA) or programmable logic arrangement (PLA) and/or in the manner of electrical components arranged on a circuit board and connected to one another, in particular discrete electrical components.
  • ASIC application-specific integrated circuit
  • FPGA Field Programmable Gate Array
  • PDA programmable logic arrangement
  • Discrete electrical components include, for example, resistors, capacitances or capacitors, inductances or coils and/or diodes, as well as active components such as transistors, up to integrated circuits.
  • the method for overload protection according to the invention can be carried out completely digitally, using existing devices for monitoring the supply voltage and existing switching devices, for example circuit breakers.
  • the method according to the invention can be implemented, for example, in an existing microprocessor and, for example, subsequently integrated into an existing power tool as a software update.
  • the overload protection device is designed to carry out several parallel methods for overload protection in accordance with the above description, in particular to detect more than one supply voltage and/or to use more than one reference value.
  • the supply voltage can be monitored separately at several points within the power tool.
  • monitoring can be provided directly on the battery cell arrangement, directly on the electric motor and/or on power electrical components.
  • the invention also relates to a computer program with program code means for carrying out a method according to the above description when the program is executed on a microprocessor as part of an overload protection device of a battery-operated power tool.
  • the method for overload protection according to the invention is preferably carried out in a battery-operated power tool or implemented within the battery-operated power tool. Alternatively, however, it can also be provided that the method for overload protection is carried out within the battery cell arrangement and is implemented, for example, on the BMS of a battery pack.
  • the method for overload protection is implemented in an adapter, wherein the adapter accommodates the battery cell arrangement on the input side and is connected to the power tool on the output side in order to supply the power tool via the battery cell arrangement.
  • Figure 1 a flow chart of the method according to the invention is shown, as it can be implemented, for example, on a state machine (finite state machine), for example for execution on a microprocessor 1 or another digital circuit.
  • a state machine finite state machine
  • the method for overload protection of a battery-operated power tool 2 according to the invention comprises at least the three steps (a), (b) and (c).
  • the method can be implemented on the basis of asynchronous and/or synchronous circuit technology.
  • a the supply voltage U of a battery cell arrangement 3 (cf. Figures 2 to 4 ) which is connected to the power tool 2 to supply energy to the power tool 2.
  • a second step (b) the measured supply voltage U is compared with a reference value U REF in order to detect a load-induced voltage drop ⁇ U (cf. Figures 5a and 5b ) of the supply voltage U. If it is detected that the supply voltage U is greater than or equal to the reference value U REF , the method can start again from the beginning or the supply voltage U can be detected again in step (a). The method can thus be carried out cyclically or the supply voltage U can, for example, be detected continuously during operation of the electric machine tool 2 and then compared with the reference value U REF .
  • the energy supply to the electric machine tool 2 is limited in a third step (c).
  • the reference value U REF can therefore be a threshold value or a threshold voltage that serves as an execution condition for limiting the energy supply to the electric machine tool 2 in step (c). The method can then start again from the beginning - with step (a).
  • Steps (a) and (b) may also be implemented in a common step. Likewise, steps (b) and (c) or all steps (a), (b) and (c) may be implemented in a common step.
  • the reference value U REF can be stored in a volatile or non-volatile data memory of the power machine tool 2 and/or (re)calculated if necessary.
  • the reference value (U REF ) is determined on the basis of a minimum voltage (U MIN ) which is required for the fault-free operation of safety-critical electrical components of the power machine tool 2, wherein the safety-critical components are semiconductor components.
  • the minimum voltage U MIN can be the threshold voltage of MOSFETs in the power electronics 4 (cf. Figures 2 to 4 ) of the power tool 2.
  • the reference value U REF can be smaller than a final discharge voltage of the battery cell arrangement 3.
  • the final discharge voltage can, for example, be approximately 70% of the nominal voltage (e.g. 12.5 volts at a nominal voltage of approximately 18 volts).
  • the reference value U REF can be less than 75% of a nominal voltage of the battery cell arrangement 3, for example less than 65% of the nominal voltage, less than 55% of the nominal voltage or less than 45% of the nominal voltage.
  • Figure 2 shows a circuit diagram in a first embodiment. Shown are the circuit diagram of a battery-operated power tool 2 and a circuit diagram of a battery cell arrangement 3.
  • the battery cell arrangement 3 is designed as a single battery pack 3.1 in which several battery cells 5 are connected in series.
  • the nominal voltage of the battery pack 3.1 therefore essentially corresponds to the sum of the nominal voltage of the individual battery cells 5.
  • Lithium-ion battery cells 5 are preferably used.
  • the nominal voltage of the battery pack 3.1 is, for example, 18 volts (e.g. with five lithium-ion battery cells 5 connected in series) or 36 volts (e.g. with ten lithium-ion battery cells 5 connected in series).
  • any battery cell arrangement 3 can be provided, for example a group consisting of several battery packs 3.1.
  • the illustrated power tool 2 comprises a consumer M, in this case an electric motor M, which is operated or controlled by a power electronics unit 4.
  • a user can switch the power tool on or off by means of an operating switch 6. 2 as required, whereby the electrical circuit between the battery pack 3.1 and the electric motor M can be closed.
  • the power tool 2 further comprises an overload protection device 7 according to the invention for carrying out a method for overload protection.
  • the overload protection device 7 has a device 8 for detecting a supply voltage U of the battery pack 3.1 connected to the power tool 2 for energy supply.
  • the device 8 for detecting the supply voltage U is designed as a voltage measuring device V and measures the supply voltage U of the battery pack 3.1 between the terminals or nodes U DD and GND at a battery pack interface 9 of the power tool 2.
  • the overload protection device 7 also has a comparator circuit 10 for comparing the detected supply voltage U with the reference value U REF .
  • the comparator circuit 10 is implemented in a microprocessor 1.
  • the overload protection method is thus operated using synchronous circuit technology with a defined clock frequency.
  • the clock frequency is determined by the clock signal CLK.
  • the clock frequency can basically be arbitrary, but is preferably greater than 1 Hz, for example greater than 1 kHz, greater than 1 MHz or greater than 10 MHz.
  • the device 8 for detecting the supply voltage U detects the supply voltage U asynchronously in this case.
  • the detected supply voltage U is then used for comparison at certain times, for example every millisecond, according to the timing of the comparator circuit 10.
  • the overload protection device 7 has a switching device 11 for limiting the energy supply of the power tool 2.
  • This can be a controllable current limitation or power limitation.
  • a pulse width modulation method can be used.
  • the switching device 11 for limiting the energy supply is arranged in the supply path of the electric motor M and is able to limit or switch off the current flow to the electric motor M in the event of an overload of the electric machine tool 2, for example if the electric motor M is stationary.
  • the battery cell arrangement 3 is designed as a single battery pack 3.1.
  • the battery pack 3.1 already includes a voltage measuring device V for detecting the supply voltage U.
  • a battery management system (BMS) is usually provided in a battery pack 3.1 in order to evaluate and/or regulate parameters of the battery pack 3.1.
  • the BMS can also carry out the voltage measurement.
  • the supply voltage U measured within the battery pack 3.1 is then transferred to the power tool 2 via a data interface 12 of the battery pack 3.1.
  • the device 8 for detecting the supply voltage U of the overload protection device 7 is thus designed to read a numerical value of the supply voltage U of the battery pack 3.1 from the data interface 12 of the battery pack 3.
  • the supply voltage U recorded in the battery pack 3.1 is recorded as before between the nodes U DD and GND (or at the corresponding nodes within the battery pack 3.1).
  • the supply voltage U can also be determined by measuring at the terminals of the battery cells 5, e.g. by measuring all the individual voltages of the battery cell 5 and then summing them. It can also be provided that only one individual voltage a battery cell 5 or a part of the individual voltages is determined, after which the supply voltage U is approximately determined.
  • the comparator circuit 10 is here formed by asynchronous circuit technology. No clock signal CLK is provided. As soon as the detected supply voltage U falls below the reference value U REF , a digital control signal y is generated in order to cause the switching device 11 to limit the energy supply to the electric machine tool 2.
  • the switching device 11 is designed as a controlled switch 13 and can be controlled directly by the control signal y.
  • the energy supply to the electric machine tool 2 is therefore limited in this case by interrupting the energy supply to the electric machine tool 2 - at least until the supply voltage U of the battery pack 3.1 has regenerated to a value that is above the reference value U REF .
  • the energy supply of the power tool 2 is interrupted for a defined time interval, which is, for example, longer than the time that the supply voltage U of the battery pack 3.1 requires to regenerate. This can prevent disproportionate stress or excessive switching operations of the overload protection device 7.
  • FIG 4 A further embodiment of the invention is shown as a highly schematic circuit diagram. It is basically the simplest implementation of the method or the overload protection device 7 of the power tool 2.
  • this embodiment shows two battery packs 3.1, which are accommodated in two battery pack interfaces 9 of the power tool 2 and connected in series.
  • the supply voltage U relevant for the operation of the power tool 2 is therefore again between the nodes or terminals U DD and GND.
  • a parallel connection of the battery packs 3.1 would of course also be possible.
  • the battery cell arrangement 3 can, in particular when using two or more battery packs 3.1, also be connected to the power tool 2 via an adapter arrangement and/or a cable connection via a single battery pack interface 9.
  • the device 8 for detecting the supply voltage U, the comparator circuit 10 for comparing the detected supply voltage U with the reference value U REF and the switching device 11 for limiting the energy supply are designed as one piece or functionally combined.
  • the overload protection device 7 in the embodiment of the Figure 4 can be an electrical component that carries out a switching operation, in particular a switch-off operation, when a certain (defined) input voltage is undershot. As soon as its input voltage, in this case the supply voltage U, falls below a defined threshold value (e.g. the reference value U REF ), the circuit is interrupted; as soon as the supply voltage U has sufficiently regenerated, the supply is resumed - immediately or with a delay. This can also take place in several stages, e.g. using several reference values, or continuously or in an analogous manner.
  • the overload protection device 7 and/or at least one component of the overload protection device 7 can be designed as a digital circuit, for example as a microprocessor 1, as an application-specific integrated circuit (ASIC), as a programmable digital circuit and/or in the form of electrical components arranged on a circuit board and connected to one another.
  • a mixed analog and digital circuit can also be provided.
  • the supply voltage U can basically be detected at any point within the power tool 2 or within the battery cell arrangement 3 or the at least one battery pack 3.1.
  • the detection of the supply voltage U does not necessarily have to be provided at the supply terminals U DD , GND of the battery pack interface 9 of the power tool 2.
  • the overload protection device 7 is designed to carry out several of the above-mentioned methods. For example, it can be provided that more than one supply voltage U is detected and/or compared with more than one reference value U REF .
  • Figure 5a the curve of the supply voltage U and the supply current I of an electric machine tool 2 over time t with a conventional overload protection is shown.
  • Figure 5b shows corresponding exemplary curves when the method according to the invention is used.
  • the system or the power tool 2 is in idle mode or is still switched off. No supply current I is consumed by the power tool 2 - apart from negligible standby current. Due to the idle mode, the supply voltage U is above the nominal voltage of a battery pack 3.1 used. In this case, the nominal voltage is 18 volts, for example.
  • the power tool 2 is put into operation and undergoes a start-up process until time t 2 . Subsequently, until time t 3 , the power tool 2 is used in normal operation or work is carried out with the power tool 2.
  • the supply current I and the supply voltage U have settled on a stable value corresponding to the complexity of the work performed with the power tool 2.
  • the supply voltage U drops sharply depending on the internal resistance R IN of the battery pack 3.1.
  • the supply voltage U has already fallen below the end-of-charge voltage (in this case, for example, 12.5 volts) and also below a minimum voltage U MIN (in this case, for example, 10 volts), which would just be necessary for error-free operation of the electrical components of the power tool 2, in particular its power MOSFETs.
  • the voltage drop ⁇ U is over 11 volts.
  • the supply voltage U has dropped to approx. 8 volts, causing analog and/or digital circuits, for example the power electronics 4, which controls the electric motor M, to change to an undefined state.
  • the inventors have recognized that the current overload protection methods regularly react too late, since they have to monitor the supply current I over a certain period of time in order to detect short-term current peaks (see, for example, current peak 14 of the Figure 5b ), which would be basically harmless, to trigger false alarms. Accordingly, the electric motor M or its supply circuit is only switched off relatively late, namely at time t 5 . In particular, since at this time the supply voltage U is already so low that the functionality of none of the circuits of the power tool 2 can be reliably guaranteed, this may already be too late. It is also possible that the common Overload protection procedures are also no longer functional at this point because their minimum operating voltage has also been exceeded.

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Claims (13)

  1. Procédé de protection contre la surcharge d'une machine-outil électrique (2) alimentée par accumulateur comportant les étapes suivantes :
    a) Mesure d'une tension d'alimentation (U) d'un agencement de cellules d'accumulateur (3), relié à la machine-outil électrique (2) pour l'alimentation en énergie de la machine-outil électrique (2) ;
    b) Comparaison de la tension d'alimentation (U) mesurée avec une valeur de référence (UREF), afin de détecter un chute de tension (ΔU) provoquée par la charge ;
    c) Limitation de l'alimentation en énergie de la machine-outil électrique (2), lorsque la tension d'alimentation (U) mesurée est inférieure à la valeur de référence (UREF),
    dans lequel la valeur de référence (UREF) est déterminée sur la base d'une tension minimale (UMIN) requise pour le fonctionnement sans défauts de composants électriques de la machine-outil électrique (2) critiques pour la sécurité, dans lequel les composants critiques pour la sécurité sont des composants à semiconducteurs.
  2. Procédé de protection contre la surcharge selon la revendication 1, caractérisé en ce que,
    l'alimentation en énergie de la machine-outil électrique (2) est limitée immédiatement dès que la tension d'alimentation (U) mesurée est inférieure à la valeur de référence (UREF).
  3. Procédé de protection contre la surcharge selon l'une des revendications 1 à 2, caractérisé en ce que,
    la valeur de référence (UREF) est inférieure à une tension de fin de décharge de l'agencement de cellules d'accumulateur (3).
  4. Procédé de protection contre la surcharge selon l'une des revendications 1 à 3, caractérisé en ce que,
    la valeur de référence (UREF) est inférieure à 75% d'une tension nominale de l'agencement de cellules d'accumulateur (3), de préférence inférieure à 65% de la tension nominale, de manière particulièrement préférée inférieure à 55% de la tension nominale, par exemple inférieure à 45% de la tension nominale.
  5. Procédé de protection contre la surcharge selon l'une des revendications 1 à 4, caractérisé en ce que,
    la tension d'alimentation (U) est mesurée en continu lors du fonctionnement de la machine-outil électrique (2) et est comparée à la valeur de référence (UREF), de préférence au moyen d'une technologie de circuit asynchrone et/ou au moyen d'une technologie de circuit synchrone avec une fréquence d'horloge supérieure à 1 Hz, de préférence supérieure à 1 kHz, de manière particulièrement préférée supérieure à 1 MHz, par exemple supérieure à 10 MHz.
  6. Procédé de protection contre la surcharge selon l'une des revendications 1 à 5, caractérisé en ce que,
    l'alimentation en énergie de la machine-outil électrique (2) est limitée par l'interruption de l'alimentation en énergie de la machine-outil électrique (2), de préférence pour un intervalle de temps défini.
  7. Machine-outil électrique (2) alimentée par accumulateur pourvue d'un dispositif de protection contre la surcharge (7) pour la mise en oeuvre d'un procédé de protection contre la surcharge selon l'une des revendications 1 à 6, dans laquelle la protection contre la surcharge (7) comprend au moins les composants suivants :
    - un dispositif (8) pour la mesure d'une tension d'alimentation (U) d'un agencement de cellules d'accumulateur (3) relié à la machine-outil électrique (2) pour l'alimentation en énergie de celle-ci ;
    - un circuit comparateur (10) pour comparer la tension d'alimentation mesurée (U) à au moins une valeur de référence (UREF) ; et
    - un circuit de commutation (11) pour limiter l'alimentation en énergie de la machine-outil électrique (2).
  8. Machine-outil électrique (2) selon la revendication 7,
    caractérisée en ce que,
    l'agencement de cellules d'accumulateur (3) est réalisé sous la forme d'un bloc d'accumulateurs (3.1) dans lequel plusieurs cellules d'accumulateur (5) sont connectées entre elles en série et/ou en parallèle.
  9. Machine-outil électrique (2) selon l'une des revendications 7 ou 8,
    caractérisée en ce que,
    le dispositif (8) pour la mesure de la tension d'alimentation (U) est réalisé sous la forme d'un appareil de mesure de la tension (V) et/ou est agencé pour lire une valeur numérique de la tension d'alimentation (U) de l'agencement de cellules d'accumulateur (3) depuis une interface de données (12) de l'agencement de cellules d'accumulateur (3).
  10. Machine-outil électrique (2) selon l'une des revendications 7 à 9,
    caractérisée en ce que,
    le dispositif de commutation (11) est réalisé sous la forme d'un commutateur commandé (13) et/ou comprend une limitation de courant commandable.
  11. Machine-outil électrique (2) selon l'une des revendications 7 à 10,
    caractérisée en ce que,
    le dispositif de protection contre la surcharge (7) et/ou au moins un composant du dispositif de protection contre la surcharge (7) est ou sont réalisés sous la forme d'un circuit numérique, par exemple sous la forme d'un microprocesseur (1), sous la forme d'un circuit intégré spécifique à l'application, sous la forme d'un circuit numérique programmable et/ou sous la forme de composants électriques disposés sur un circuit imprimé et reliés entre eux.
  12. Machine-outil électrique (2) selon l'une des revendications 7 à 11, caractérisée en ce que,
    le dispositif de protection contre la surcharge (7) est agencé pour réaliser en parallèle plusieurs procédés selon l'une des revendications 1 à 8, en particulier pour mesurer plus d'une tension d'alimentation (U) et/ou pour utiliser plus d'une valeur de référence (UREF).
  13. Programme informatique avec des moyens de code de programme pour la réalisation d'un procédé selon l'une des revendications 1 à 6, si le programme est exécuté sur un microprocesseur (1) faisant partie d'un dispositif de protection contre la surcharge (7) d'une machine-outil électrique (2) alimentée par accumulateur selon l'une des revendications 7 à 12.
EP18154744.9A 2017-02-15 2018-02-01 Protection contre la surcharge d'une machine-outil électrique fonctionnant sur accumulateur Active EP3363597B1 (fr)

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DE102017103005.0A DE102017103005A1 (de) 2017-02-15 2017-02-15 Überlastschutz einer akkubetriebenen Elektrowerkzeugmaschine

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6629047B1 (en) * 2000-03-30 2003-09-30 Intel Corporation Method and apparatus for flash voltage detection and lockout
DE102006000439A1 (de) * 2006-09-04 2008-03-13 Hilti Ag Verfahren zur Steuerung eines Motors eines akkubetriebenen Werkzeuggerätes

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050073282A1 (en) 2003-10-03 2005-04-07 Carrier David A. Methods of discharge control for a battery pack of a cordless power tool system, a cordless power tool system and battery pack adapted to provide over-discharge protection and discharge control
EP2978100A4 (fr) 2013-03-22 2016-10-19 Hitachi Koki Kk Bloc de piles et dispositif électrique

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6629047B1 (en) * 2000-03-30 2003-09-30 Intel Corporation Method and apparatus for flash voltage detection and lockout
DE102006000439A1 (de) * 2006-09-04 2008-03-13 Hilti Ag Verfahren zur Steuerung eines Motors eines akkubetriebenen Werkzeuggerätes

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