ELECTRIC DRIVE UNIT FOR AN ELECTRIC HAND TOOL MACHINE AND ELECTRIC HAND TOOL MACHINE WITH AN ELECTRIC DRIVE UNIT

Description

AREA OF INVENTION

[0001] The present invention relates to an electric drive unit for an electric hand tool and an electric hand tool with an electric drive unit.

[0002] A drill bit of an electric power tool, such as a drill, can become wedged in the substrate while drilling. To prevent the drill from rotating on its axis at the moment of this wedged movement, potentially injuring the operator, a mechanical safety device in the form of a slip clutch is conventionally installed. This clutch disconnects the drive from the drill bit, cuts off the power supply to the electric motor, and allows the motor to coast to a stop without endangering the operator. If an electronic safety device were to perform this function, high braking currents would be required to complete this process within milliseconds, thus ensuring operator safety.

[0003] To generate a high braking current using an electronic circuit, the voltage at the rotor winding of an electric motor is reversed. This reversal is conventionally achieved in an electric motor by using a bridge circuit with TRIACs (bidirectional thyristor triodes) operated with an alternating voltage. With this use of TRIACs, the reversal can only occur during a zero crossing of the alternating current, as TRIACs can only change their state, specifically switch off, at this time. This can result in a time delay of up to 10 ms during braking (with a mains half-cycle period of 50 Hz). To stop the motor within a predetermined time, the braking current must be increased in this case. However, this leads to significantly higher carbon brush wear in brushed electric motors.Furthermore, when using TRIACs, the currents occurring in the electric motor cannot be regulated during rotor voltage reversal. A circuit for braking a shunt-wound motor is disclosed in US 5828194 A.

[0004] Against this background, one object of the present invention is to propose an improved drive unit for an electric hand-held power tool. REVELATION OF THE INVENTION

[0005] According to a first aspect, an electric drive unit for an electric hand tool is proposed. The electric drive unit comprises an electric motor with a stator winding and a rotor winding, a control circuit for controlling the electric motor, and a connection unit for coupling a power source to drive the electric motor. The stator winding is connected via a first node to a stator-side first half-bridge comprising a first semiconductor device and a second semiconductor device, and is connected via a second node to the rotor winding. The rotor winding is connected to a third node, which is connected to the connection unit via a conductive component. The control circuit comprises a third semiconductor device, which is connected via the second node to both the rotor winding and the stator winding, and which is directly connected to the connection unit via a fourth node.

[0006] By means of the control circuit of the electric drive unit, the respective semiconductor components can be advantageously controlled in such a way that, during a braking process of the electric motor, the rotor and stator current of the electric motor can be precisely and independently adjusted.

[0007] This allows the rotor current to be advantageously limited to a predetermined current level, while the stator current can be regulated independently. This makes it possible to decelerate the electric motor within a specified time period, albeit with high braking torque, in a way that protects the carbon brushes. Simultaneously, the limited rotor current and the adjustable stator current reduce brush arcing and the heating of the electric motor. This, in turn, reduces carbon brush wear. As a result, the electric motor's maintenance intervals are extended, leading to a longer service life for the electric motor in the power tool.

[0008] Another advantage of the electric drive unit is that its control circuitry uses a small number of semiconductor components, especially compared to conventional drive units. As a result, manufacturing costs can be reduced, while the low number of semiconductor components increases the reliability of the electric drive unit.

[0009] When a semiconductor device is in a conducting state, current can flow through it. When a semiconductor device is in a non-conducting state, no current can flow through it.

[0010] The electric motor comprises a brushed electric motor, preferably a universal motor or a universal motor.

[0011] The electric motor comprises, in particular, a stator with at least one stator winding and a rotor with at least one rotor winding. The stator winding can be referred to as the field winding of the electric motor, while the rotor winding can be referred to as the armature winding of the electric motor. Specifically, the stator winding exhibits ohmic resistance and inductance, and the rotor winding also exhibits ohmic resistance and inductance. The respective ohmic resistance is preferably as low as possible. When a voltage is applied to the stator winding or the rotor winding, a current flows through the respective winding. Due to the current and the inductance, a magnetic field is generated. Depending on the phase relationship between the stator and the rotor, the direction of current flow (and thus the direction of the magnetic field), and the respective direction of rotation of the motor, the rotor is driven or decelerated.Since the rotor moves within the stator's magnetic field, a voltage is induced in the rotor winding according to Lenz's law. This voltage induces a current that opposes the cause (change in magnetic flux). In other words, the induced current itself creates a magnetic field that opposes the stator's magnetic field. By controlling the current flow in the stator and rotor, it is therefore possible to switch between driving and braking the electric motor.

[0012] According to one embodiment of the electric drive unit, the control circuit further comprises another semiconductor component which is connected to the rotor winding and the stator winding via the second node and is directly connected to the connection unit via a fifth node.

[0013] The fifth node differs significantly from the fourth node. For example, the fifth node is connected to a first rail of the connection unit, which can be connected to a first pole of the energy source, and the fourth node is connected to a second rail of the connection unit, which can be connected to a second pole of the energy source.

[0014] Preferably, the second semiconductor device and / or the subsequent semiconductor device is designed as a passive device, such as a diode. This simplifies the design of the control circuit and reduces manufacturing costs compared to an active device, such as a bipolar transistor or a MOSFET. Furthermore, the third semiconductor device can be designed as a thyristor. This also reduces manufacturing costs.

[0015] According to another embodiment of the electric drive unit, the control circuit is configured to put the first semiconductor component into a non-conducting state in order to interrupt a supply current flow.

[0016] In particular, the supply current is a current flow that is generated by the energy source and can flow through the electrical drive unit via the connection unit. It flows specifically from a first pole of the energy source to the respective semiconductor component and through the respective semiconductor component, such as the first semiconductor component, towards a second pole of the energy source.

[0017] Preferably, in this embodiment, the interruption of the supply current flow does not occur as part of controlling the first semiconductor device with a PWM signal, as is used, for example, in motor operation. The duration of the interruption of the supply current flow is, in particular, many times longer than one period of the PWM signal.

[0018] The period of the PWM signal comprises at least one pulse (high level) and one zero pulse (low level). The duty cycle preferably specifies the ratio of the pulse duration or pulse of the PWM signal to the period of the PWM signal. For example, at a duty cycle of 0.550%, the pulse duration (high level) is 50% of the period. The remaining 50% of the period comprises the zero pulse (low level). This means that for a PWM signal with a duty cycle of 0.5 and a period of 100 µs, the PWM signal outputs a pulse or high level for 50 µs and a zero pulse or low level for 50 µs.

[0019] A control terminal of the respective semiconductor device, such as the first semiconductor device, is controlled, in particular, by the high level of the PWM signal or the low level of the PWM signal. If, for example, the respective semiconductor device is a bipolar transistor, the control terminal is configured as a base terminal. Alternatively, if the respective semiconductor device is configured as a MOSFET or an IGBT, the control terminal is configured as a gate terminal.

[0020] If a high level is applied to the control pin of the respective semiconductor device, the semiconductor device is switched to a conducting state. Conversely, if a low level is applied to the control pin of the respective semiconductor device, the semiconductor device is switched to a non-conducting state. It should be noted that reverse logic can also be used, in which the roles of the high and low levels are reversed.

[0021] By switching the first semiconductor component to a non-conductive state, the electric motor is preferably switched from motor operation to braking mode. Prior to the interruption of the supply current, the electric motor is operated, in particular, in motor mode. During motor operation, a work process, such as drilling into a substrate or chiseling, is preferably carried out by an operator of the electric power tool. In braking mode, the electric motor, and thus also any tool driven by it, is brought to a standstill. For the purposes of this patent application, the term "braking mode" means that the electric motor is not in motor operation.Braking operation can also include time intervals in which the electric motor is not braked with a braking torque, and can include time intervals in which a current flow through the electric motor has a driving effect. This can be the case, in particular, for a short time interval immediately after switching from motor operation to braking operation.

[0022] One advantage of the electric drive unit is that the control circuit is designed to switch the respective semiconductor components to a conductive or non-conductive state at any given time during motor operation and / or braking. Thus, if the drill bit jams during motor operation, braking can be initiated immediately. This increases safety for the operator of the electric power tool.

[0023] Preferably, the control circuit is configured to detect a predetermined operating state of the electric hand tool during operation of the electric motor. Preferably, the predetermined operating state includes at least one interruption state, in particular the jamming of a drill bit of the electric hand tool. For example, if the drill bit jams in a substrate, such as reinforcement in a reinforced concrete block, during a drilling operation with the electric hand tool, this is detected as an interruption state. The presence of the predetermined operating state is detected, for example, by means of a sensor, in particular a gyroscope, of the electric hand tool.

[0024] According to another embodiment of the electric drive unit, the control circuit is configured to put the third semiconductor component into a conductive state in order to connect the rotor winding in parallel to the stator winding.

[0025] According to a further embodiment of the electric drive unit, the control circuit is configured to bring the first semiconductor component into a conductive state in addition to the third semiconductor component in order to provide a magnetic flux, so that a voltage is induced on the rotor winding which has the opposite direction compared to a voltage applied to the rotor winding during motor operation of the electric motor.

[0026] In particular, the magnetic flux is generated by the current through the stator winding. The magnetic flux is provided in such a way that the rotating rotor moves within this magnetic flux. The magnetic flux can also be described as the magnetic field of the stator winding, which is caused by the flow of the stator current through the stator winding.

[0027] The voltage induced in the rotor winding is primarily caused by a current induced in the rotor winding according to Lenz's law. Since this current flow is directed in such a way that the magnetic field it generates opposes its cause, a braking torque is created that counteracts the rotation of the rotor. Thus, the electric motor, and especially its rotor, is slowed down.

[0028] The control circuit is specifically designed to bring the first and third semiconductor devices into a conducting state as soon as the rotor current reaches or falls below a predetermined switching threshold. Preferably, the predetermined switching threshold is 0 A. When the rotor current has reached the predetermined switching threshold, it has completely decayed and is therefore preferably 0 A.

[0029] According to a further embodiment of the electric drive unit, the electric drive unit comprises a first current measuring unit for determining a current rotor current, wherein the control circuit is configured to put the first semiconductor device into a non-conducting state depending on the determined current rotor current and a predetermined threshold value of the rotor current in order to limit the rotor current.

[0030] The rotor current is preferably limited in such a way as to the predetermined threshold value that the magnitude of the rotor current is less than or equal to the predetermined threshold value, i.e., does not exceed the predetermined threshold value.

[0031] According to a further embodiment of the electric drive unit, the conductive component comprises a fourth semiconductor component and the control circuit further comprises a fifth semiconductor component, which is connected to the rotor winding via the third node and which is directly connected to the connection unit via a fifth node.

[0032] The fifth node differs significantly from the fourth node. For example, the fifth node is connected to a first rail of the connection unit, which can be connected to a first pole of the energy source, and the fourth node is connected to a second rail of the connection unit, which can be connected to a second pole of the energy source.

[0033] According to one embodiment of the electric drive unit, the first, second, third, fourth and / or fifth semiconductor device is designed as a bipolar transistor, in particular as an IGBT, or as a MOSFET.

[0034] An IGBT is a bipolar transistor with an insulated gate electrode. Specifically, a protection diode (freewheeling diode) is arranged in parallel with the semiconductor device in reverse bias with respect to the supply current from the power source. Freewheeling diodes preferably serve to protect against overvoltage when switching off an inductive DC load, such as an electric motor. If the semiconductor device is a bipolar transistor, the freewheeling diode is connected in parallel with the collector and emitter terminals of the bipolar transistor. If, on the other hand, the semiconductor device is a MOSFET, the freewheeling diode is connected in parallel with the drain and source terminals of the MOSFET. For example, a rotor or stator current can decay across a freewheeling diode.

[0035] According to another embodiment of the electric drive unit, the control circuit is configured to put the fourth semiconductor component into a non-conducting state in order to interrupt a rotor current through the rotor winding.

[0036] One advantage of the electric drive unit is that the control circuit is designed to switch the respective semiconductor components to a conductive or non-conductive state at any given time during motor operation and / or braking. Thus, if the drill bit jams during motor operation, braking can be initiated immediately. This increases safety for the operator of the electric power tool.

[0037] According to another embodiment of the electric drive unit, the control circuit is designed to put the third and fifth semiconductor components into a conductive state to reverse the polarity of an input voltage applied to the rotor winding compared to motor operation.

[0038] The control circuit is preferably configured to connect the rotor winding in parallel with the stator winding before the polarity reversal by bringing the third semiconductor device into a conducting state. In particular, before the parallel connection, the stator and rotor windings of the electric motor are connected as in a series-wound machine, whereas after the parallel connection, the stator and rotor windings of the electric motor are connected as in a shunt-wound machine.

[0039] Reversing the polarity of the input voltage at the rotor winding U in This will be explained in more detail below. For the rotor current through the rotor winding i Armature For example, the following equation (1) applies approximately: i Armature = 1 L Armature ∫ u L Armature ⋅ dt , where L Armature the inductance of the rotor winding and u LArmature represent the rotor voltage at the rotor winding.

[0040] During motor operation before reversing the polarity, the following applies to the rotor voltage: u LArmature equation (2): u L Armature = U in − U R Armature − U IND , wobei U in the input voltage at the rotor winding, U RArmature a voltage drop across the rotor's ohmic resistance and U IND a voltage induced at the rotor winding, which can be represented by equation (3): U IND = c A ⋅ Ψ E ⋅ ω , where c A a machine constant ψ E the magnetic excitation flux generated by the stator current through the stator winding and ω to display the current rotational speed of the rotor.

[0041] By reversing the polarity of the input voltage at the rotor winding U in does it have the same sign as the induced voltage? U IND This is why the voltages are now all added together. Therefore, during braking after reversing the polarity, the following applies to the rotor voltage: u LArmature equation (4): u L Armature = − U in − U R Armature − U IND .

[0042] As a result, a current flowing in the opposite direction to the stator current through the stator winding is generated in the rotor winding. This current, in turn, creates a magnetic field that interacts with the magnetic field generated by the stator winding, resulting in a braking torque. This slows down the rotor.

[0043] According to a further embodiment of the electric drive unit, the electric drive unit comprises a first current measuring unit for determining a current rotor current, wherein the control circuit is configured to alternately switch the fourth semiconductor device and the fifth semiconductor device into a conducting state and a non-conducting state depending on the determined current rotor current and a predetermined threshold value of the rotor current in order to limit the rotor current.

[0044] The rotor current is preferably limited depending on the predetermined threshold value in such a way that the rotor current does not exceed the predetermined threshold value.

[0045] The term "alternating opposite" means in particular that two semiconductor devices, such as the fourth and the fifth semiconductor device, are switched alternately in such a way that, for example, the fourth semiconductor device is in a conducting state while at the same time the fifth semiconductor device is in a non-conducting state, or vice versa.

[0046] According to another embodiment of the electric drive unit, the control circuit is designed to alternately switch the fourth semiconductor component and the fifth semiconductor component into a conducting state and a non-conducting state depending on the determined current rotor current, the predetermined threshold value of the rotor current and a current speed of the electric motor, in order to limit the rotor current.

[0047] Here, the rotor current is also preferably limited depending on the predetermined threshold value in such a way that the rotor current does not exceed the predetermined threshold value.

[0048] According to a further embodiment of the electric drive unit, the electric drive unit comprises a second current measuring unit for determining a current stator current, wherein the control circuit is configured to alternately put the first semiconductor device into a conducting state and into a non-conducting state in order to control a stator current through the stator winding as a function of a current speed of the electric motor.

[0049] The control circuit is preferably configured to increase the stator current as the rotational speed decreases. Increasing the stator current increases the braking torque.

[0050] According to another embodiment of the electric drive unit, the control circuit is configured to alternately switch the first semiconductor component into a conductive state and a non-conductive state after a predetermined period of time has elapsed, after the third and fifth semiconductor components have been switched into a conductive state, in order to regulate a stator current through the stator winding depending on a current speed of the electric motor.

[0051] In particular, after reversing the polarity, the system waits for a predetermined period to elapse. This predetermined period is less than 5 ms, preferably less than 4 ms, preferably less than 3 ms, and preferably less than 2 ms. Once the predetermined period has elapsed, the stator winding is preferably energized depending on the state of the first semiconductor device, and the stator current can be increased. Thus, the stator current can be controlled independently of the rotor current. This measure advantageously reduces brush arcing, thereby decreasing carbon brush wear.

[0052] According to another embodiment, the electric drive unit is designed for operation on a DC voltage source, a pulsating DC voltage source or an AC voltage source with a rectifier.

[0053] Preferably, the energy source is an alternating voltage source with a rectifier, and a smoothing capacitor may also be provided.

[0054] According to another embodiment of the electric drive unit, the control circuit comprises several driver circuits, wherein each semiconductor component is assigned a driver circuit for outputting a respective control signal to control the respective semiconductor component.

[0055] By controlling the semiconductor components via the control circuit using the respective driver circuit, it is possible to precisely and independently adjust the rotor and stator currents of the electric motor during braking. The control signal is, in particular, a PWM (pulse width modulation) signal.

[0056] According to a second aspect, an electric hand-held power tool with an electric drive unit according to the first aspect is proposed.

[0057] An electric hand tool is designed, for example, as a drill, a hammer drill, a saw, a mixer, a grinder, an angle grinder, or the like. Electric hand tools are typically corded. Alternatively, they may have a compartment for a battery that powers them. BRIEF DESCRIPTION OF THE FIGURES

[0058] The following description explains the invention with reference to exemplary embodiments and figures. The figures show: Fig. 1 a schematic view of an electric hand-held power tool; Fig. 2 a schematic view of a first embodiment of a circuit topology of an electric drive unit; Fig. 2 a schematic current flow diagram in motor operation of an electric motor within the circuit topology of the electric drive unit according to Fig. 2A ; Fig. 2C a schematic current flow diagram in braking operation of an electric motor within the circuit topology of the electric drive unit according to Fig. 2A Fig. 3A A schematic view of a second embodiment of a circuit topology of an electric drive unit; Fig. 3A A schematic current flow diagram in motor operation of an electric motor within the circuit topology of the electric drive unit according to Fig. 3A ; Fig. 3C a schematic current flow diagram in braking operation of an electric motor within the circuit topology of the electric drive unit according to Fig. 3A Fig. 4 shows a schematic view of a third embodiment of a circuit topology of an electric drive unit; Fig. 5 shows a schematic view of a fourth embodiment of a circuit topology of an electric drive unit; and Fig. 6 shows a schematic diagram of a sequence of a control method for braking an electric motor.

[0059] Identical or functionally equivalent elements are indicated by the same reference symbols in the figures, unless otherwise specified. FORMS OF EXECUTION OF THE INVENTION

[0060] Fig. 1 Figure 1 shows a schematic view of an electric hand-held power tool 1, which is exemplified as a drill. The drill 1 has a tool holder 3 in which a drill bit 5 is inserted as a drilling tool. The primary drive of the drill 1 is an electric motor 7 with a stator winding 12 and a rotor winding 14. An operator can guide the drill 1 using a handle 9 and start it using a push button 11. During operation, the drill 1 continuously rotates the drill bit 5 around a working axis and can thereby drill the drill bit 5 into a substrate along the working axis.

[0061] Drilling machine 1 has in Fig. 1 An electric drive unit 100 is shown. The electric drive unit 100 comprises the electric motor 7 and a control circuit 4 for controlling the electric motor 7. The electric drive unit 100 is coupled via an electrical cable arrangement 13 to a connection terminal 15, which can be connected to a power supply (not shown) by means of a plug 17. Alternatively, the drill 1 can also be powered by a battery (not shown). The drive train includes, for example, a drive shaft and a gearbox between the electric motor 7 and the drive shaft. The gearbox can, for example, provide a speed n(t) (see Fig. 6 ) of the electric motor 7 to a desired speed of the drill 5.

[0062] Fig. 2A shows a schematic view of a first embodiment of a circuit topology of an electric drive unit 100, which is used, for example, in the electric hand tool 1 according to Fig. 1 can be used.

[0063] The electric drive unit 100 of the Fig. 2A The electric drive unit 100 has an electric motor 7, which comprises a stator winding 12 and a rotor winding 14. The electric drive unit 100 also has a control circuit 4 for controlling the electric motor 7. Furthermore, the electric drive unit 100 has a connection unit 6, 8 for coupling a power source 2 to drive the electric motor 7. The power source 2 is located in the Fig. 2A For example, the energy source 2 can be configured as an AC voltage source with a rectifier 19. It is also possible, in particular, for the energy source 2 to be configured as a DC voltage source or as a pulsating DC voltage source.

[0064] Furthermore, in the Fig. 2A The stator winding 12 is connected via a first node 10 to a stator-side first half-bridge comprising a first semiconductor device T1 and a second semiconductor device T2. Additionally, the stator winding 12 is connected via a second node 16 to the rotor winding 14. The rotor winding 14 is connected to a third node 18, which is connected via a conductive component T4 to a second terminal 8 of the connection unit 6, 8. The power source 2 has, in particular, a first pole, preferably a positive pole, which is connected to a first terminal 6 of the connection unit 6, 8. Furthermore, the power source 2 comprises a second pole, in particular a negative pole, which is connected to the second terminal 8 of the connection unit 6, 8.The control circuit 4 comprises a third semiconductor device T3, which is connected via the second node 16 to the rotor winding 14 and the stator winding 12, and which is directly connected via a fourth node 20 to the second terminal 8 of the connection unit 6, 8. Additionally, the first and third semiconductor devices T1, T3 each have a parallel-connected freewheeling diode T1D, T3D. Fig. 2A The second semiconductor device T2 is configured as a diode. One anode terminal of the diode is connected to the second terminal 8 of the terminal unit 6, 8. The diode is thus arranged in reverse bias with respect to a supply current from the energy source 2. Furthermore, in Fig. 2A The first and third semiconductor devices T1 and T3 are each designed as examples of IGBTs.

[0065] Fig. 2B shows a schematic current flow diagram of a supply current generated in the energy source 2, in the motor operation of an electric motor 7 within the circuit topology of the electric drive unit 100 according to Fig. 2A In motor operation (drive case), the conductive component T4 is permanently in a conductive state, and the third semiconductor component T3 is permanently in a non-conductive state, so that the stator winding 12 is connected in series with the rotor winding 14. The electric motor 7 is operated here as a series-wound machine. The control of the supply current through the stator and rotor windings 12, 14, and thus also the current speed n(t) (see Fig. 6 ) of the electric motor 7 is achieved in particular by alternately moving the first semiconductor component T1 into a conducting state and into a non-conducting state.

[0066] In Fig. 2B The supply current flows in the case of the electric motor 7 being driven, as shown in Fig. 2B as represented by arrows A, from the energy source 2 via a first connection 6 of the connection unit 6, 8 and via a fifth node 22 through the first semiconductor device T1, from the first semiconductor device T1 via a first node 10 through the stator winding 12, from the stator winding 12 via a second node 16 through the rotor winding 14 to a third node 18, from the third node 18 through the conductive device T4 via a fourth node 20 and via a second connection 8 of the connection unit 6, 8 back to the energy source 2.

[0067] Fig. 2C shows a schematic current flow diagram in the braking operation of an electric motor 7 within the circuit topology of the electric drive unit 100 according to Fig. 2A In braking mode, the respective semiconductor components are controlled as follows: In a first step, the first semiconductor component T1 is switched to a non-conducting state to switch the electric motor 7 from motor operation to braking mode. Switching the first semiconductor component T1 to a non-conducting state interrupts the supply current flow. In a second step, the third semiconductor component T3 is switched to a conducting state to connect the rotor winding 14 in parallel with the stator winding 12. In a third step, the first semiconductor component T1 is switched to a conducting state to provide a magnetic flux, thus inducing a voltage in the rotor winding 14 that has the opposite direction to the voltage applied to the rotor winding 14 during motor operation of the electric motor 7.In a fourth step, the first semiconductor device T1 is switched to a non-conducting state depending on a predetermined threshold IL (see . Fig. 6 ) for a rotor current IR (t) (see Fig. 6 ) through the rotor winding 14 to limit the rotor current IR(t). The rotor current IR(t) is preferably limited to a predetermined threshold value. For example, a current measuring unit (not shown) is provided for this purpose, which is configured to monitor the rotor current IR(t). In a fifth step, the first semiconductor device T1 is alternately switched to a conducting state and a non-conducting state to measure a stator current IS(t) (see Fig. 6 ) through the stator winding 12 as a function of a current rotational speed n(t) (see Fig. 6 The stator current IS(t) of the electric motor 7 is to be controlled. The stator current IS(t) is preferably regulated to a speed-dependent value. For example, an additional current measuring unit (not shown) is provided for this purpose, which is configured to monitor the stator current IR(t). When the speed n(t) of the electric motor 7 has reached a predetermined threshold value, the electric motor 7 is preferably completely disconnected from the energy source 2. The braking process is thus completed.

[0068] During braking, the third semiconductor component T3 is permanently in a conductive state. Consequently, the stator and rotor windings 12, 14 are no longer connected in series. The electric motor 7 is therefore considered a shunt-wound machine and no longer a series-wound machine (see Fig. 2B The voltage induced in the rotor winding 14, particularly during braking, is preferably caused by a rotor current IR(t) induced in the rotor winding 14 according to Lenz's law. Since this current flow is directed such that the magnetic field it generates opposes its cause, a braking torque is created that counteracts the rotation of the rotor. Thus, the electric motor 7 is braked.

[0069] During braking, a supply current flows, as indicated by arrows A in Fig. 2C As shown, the current flows from the energy source 2 via a first terminal 6 of the connection unit 6, 8 and via a fifth node 22 through the first semiconductor device T1, from the first semiconductor device T1 via a first node 10 through the stator winding 12, from the stator winding 12 via a second node 16 through the third semiconductor device T3, from the third semiconductor device T3 via a fourth node 20 and via a second terminal 8 of the connection unit 6, 8 back to the energy source 2. Simultaneously, an induced current flows in the rotor winding 14, which is indicated by arrows B in Fig. 2C The induced current has a direction opposite to the supply current. This opposing current flows from the second node 16 through the third semiconductor device T3 to a fourth node 20, from the fourth node 20 via the conductive device T4 to a third node 18, and from the third node 18 through the rotor winding 14 back to the second node 16.

[0070] Fig. 3A shows a schematic view of a second embodiment of a circuit topology of an electric drive unit 100, which is used, for example, in the electric hand tool 1 according to Fig. 1 can be used.

[0071] The electric drive unit 100 of the Fig. 3A has a similar design to the electric drive unit 100 of the Fig. 2A The following only outlines the differences to the electric drive unit 100. Fig. 2A explained. In addition to the Fig. 2A The electric drive unit 100 of the Fig. 3A A fifth semiconductor device T5 is included. This is exemplified as an IGBT with a freewheeling diode T5D connected in parallel. The fifth semiconductor device T5 is connected to the rotor winding 14 via a third node 18 and is directly connected to a first terminal 6 of the terminal unit 6, 8 via a fifth node 22. Furthermore, the conductive device T4 is included in Fig. 3A as a fourth semiconductor device T4 and also, by way of example, as an IGBT with a freewheeling diode T4D connected in parallel. The second semiconductor device T2 is also in Fig. 3 designed as an IGBT with a freewheeling diode T2D connected in parallel.

[0072] Fig. 3B shows a schematic current flow diagram of a supply current in motor operation of an electric motor 7 within the circuit topology of the electric drive unit 100 according to Fig. 3A The supply current flow during motor operation in Fig. 3B is related to the supply current flow during motor operation in Fig. 2B They are identical, therefore no further explanation is needed. It should be noted that semiconductor component T4 is permanently in a conductive state. Furthermore, during motor operation, the second and fifth semiconductor components, T2 and T5, are permanently in a non-conductive state.

[0073] Fig. 3C shows a schematic current flow diagram in the braking operation of an electric motor 7 within the circuit topology of the electric drive unit 100 according to Fig. 3A In braking mode, the respective semiconductor components are controlled as follows: In a first step, the fourth semiconductor component T4 is switched to a non-conductive state to switch the electric motor 7 from motor operation to braking mode. In a second step, the third semiconductor component T3 and the fifth semiconductor component T5 are switched to a conductive state to reverse the polarity of an input voltage applied to the rotor winding 14 compared to motor operation. In a third step, the fourth semiconductor component T4 and the fifth semiconductor component T5 are switched on or off depending on a predetermined threshold value IL (see Fig. 6 ) for a rotor current IR (t) (see Fig. 6 The rotor winding 14 is alternately switched to a conducting state and a non-conducting state to limit the rotor current IR(t). The rotor current IR(t) is preferably limited to a predetermined threshold value. For example, a current measuring unit (not shown) is provided for this purpose, which is configured to monitor the rotor current IR(t). The fourth and fifth semiconductor devices T4 and T5 form, in particular, a second half-bridge on the rotor side. In a fourth step, the first semiconductor device T1 is alternately switched to a conducting state and a non-conducting state to limit a stator current IS(t) (see Fig. 6 ) through the stator winding 12 as a function of a current rotational speed n(t) (see Fig. 6 The stator current IS(t) of the electric motor 7 is to be controlled. The stator current IS(t) is preferably regulated to a speed-dependent value. For example, an additional current measuring unit (not shown) is provided for this purpose, which is configured to monitor the stator current IR(t). When the speed n(t) of the electric motor 7 has reached a predetermined threshold value, the electric motor 7 is preferably completely disconnected from the energy source 2. The braking process is thus completed.

[0074] During braking, the third semiconductor component T3 is permanently in a conductive state. Consequently, the stator and rotor windings 12, 14 are no longer connected in series. The electric motor 7 is therefore considered a shunt-wound machine and no longer a series-wound machine (see Fig. 3B The stator current IS(t) through the stator winding 12 is controlled (as in the drive case) in particular by the stator-side first half-bridge comprising the first and second semiconductor devices T1 and T2. The rotor current IR(t) through the rotor winding 14 is controlled by the rotor-side second half-bridge comprising the fourth and fifth semiconductor devices T4 and T5. A voltage induced in the rotor winding 14 is preferably caused by a rotor current IR(t) induced in the rotor winding 14 during braking operation, according to Lenz's law. The induced rotor current IR(t) in the rotor winding 14 is caused in particular by reversing the polarity (see above, second step) of the input voltage at the rotor winding 14. Since this current flow is directed such that the magnetic field it generates opposes its cause, a braking torque is created that counteracts the rotation of the rotor.Thus, the electric motor 7 is slowed down.

[0075] During braking operation of the electric motor 7, a supply current flows, as indicated by arrows A in Fig. 3C As shown, the current flows from energy source 2 via a first terminal 6 of the connection unit 6, 8 and via a fifth node 22 through the first semiconductor device T1, from the first semiconductor device T1 via a first node 10 through the stator winding 12, from the stator winding 12 via a second node 16 through the third semiconductor device T3, from the third semiconductor device T3 via a fourth node 20 and via a second terminal 8 of the connection unit 6, 8 back to energy source 2. Additionally, the supply current flows from energy source 2 via the first terminal 6 of the connection unit 6, 8 via the fifth node 22 through the fifth semiconductor device T5 to a third node 18. Due to the reversal of the input voltage (see above, second step) at the rotor winding 14, the supply current now flows in the opposite direction through the rotor winding (compared to motor operation).Simultaneously, a current is induced in the rotor winding 14, flowing in the same direction, so that the two currents add up in magnitude. As indicated by arrow B in . Fig. 3C As shown, the induced current flows from the third node 18 through the rotor winding 14 to the second node 16.

[0076] In the Fig. 3A - 3C In particular, if, for example, the supply current through the stator-side first half-bridge becomes too high, the first semiconductor device T1 is switched to a non-conducting state and the second semiconductor device T2 is switched to a conducting state so that the supply current can decay through the latter. Conversely, if, in particular, the current through the rotor-side second half-bridge, which is composed primarily of the supply current and the induced current, becomes too high, the fifth semiconductor device T5 is switched to a non-conducting state and the fourth semiconductor device T4 is switched to a conducting state so that the current can decay through the latter.

[0077] Fig. 4 shows a schematic view of a third embodiment of a circuit topology of an electric drive unit 100.

[0078] The electric drive unit 100 of the Fig. 4 has a similar design to the electric drive unit 100 of the Fig. 2A The following only outlines the differences to the electric drive unit 100. Fig. 2A explained. The control circuit 4 of the Fig. 4 has another semiconductor component T6. The additional semiconductor component T6 is connected via the second node 16 to the rotor winding 14 and the stator winding 12 and is directly connected via a fifth node 22 to a first terminal 6 of a terminal unit 6, 8. The additional semiconductor component T6 is in the Fig. 4 in particular designed as a diode. A cathode terminal of the diode is connected to the fifth node 22, while an anode terminal of the diode is connected to the second node 16. Thus, the further semiconductor device T6, also designed as a diode, is arranged in reverse bias with respect to the supply current of the energy source 2. The second semiconductor device T2 of the Fig. 4 is like in Fig. 2A especially designed as a diode and, as in Fig. 2A explained, interconnected.

[0079] Fig. 5 shows a schematic view of a fourth embodiment of a circuit topology of an electric drive unit 100.

[0080] The electric drive unit 100 of the Fig. 5 has a similar design to the electric drive unit 100 of the Fig. 3A The following only outlines the differences to the electric drive unit 100. Fig. 3A explained. The second semiconductor device T2 of the Fig. 5 is like in Fig. 2A especially designed as a diode and, as in Fig. 2A explained, interconnected.

[0081] Fig. 6 shows a schematic diagram of the sequence of a control procedure for braking an electric motor 7 (see Fig. 1 , 2A , 2B, 2C , 3A , 3B, 3C , 4 , 5), for example, the electric motor 7 of the electric hand tool 1 according to Fig. 1 The schematic diagram of Fig. 6 The diagram comprises three graphs, 51, 52, and 53. The first graph, 51, shows the current rotational speed n of the electric motor 7 (vertical axis) as a function of time t (horizontal axis). The second graph, 52, shows the rotor current IR in the electric motor 7 (vertical axis) as a function of time t (horizontal axis). The third graph, 53, shows the stator current IS in the electric motor 7 (vertical axis) as a function of time t (horizontal axis).

[0082] Initially, the electric hand tool 1 is in motor operation (time interval between t 0 and t 1). In particular, a rotor current IR (t) (see second graph 52, time interval between t 0 and t 1) flows through a rotor winding 14 (see Fig. 1 , 2A , 2B, 2C , 3A , 3B, 3C , 4 ,5 ) depending on a target speed of the electric motor 7 and a stator current IS (t) (see third graph 53, time interval between t 0 and t 1 ) through a stator winding 12 (see Fig. 1 , 2A , 2B, 2C , 3A , 3B, 3C , 4 , 5 ) depending on the target speed of the electric motor 7.

[0083] For example, if the drill bit 5 (see) is in motor operation when working with the electric hand tool 1 Fig. 1 If the electric hand tool 1 becomes wedged in a reinforcing bar, this is detected by a sensor, such as a gyro sensor, as an operational interruption state of the electric hand tool 1.

[0084] At time t1, the interruption state is detected, in which the electric motor 7 switches from motor operation to braking operation. For this purpose, for example, the supply current flow through the stator winding 12 and / or the rotor winding 14 is interrupted. After the switchover, the system waits for the rotor current IR(t) to decay, which occurs, for example, within a few milliseconds. The rotor current IR(t) is considered to have decayed when it reaches or falls below a predetermined switching threshold. In this case, the predetermined switching threshold is 0 A, which is reached at time t2 (see second graph 52).

[0085] Subsequently, for example, an input voltage at the rotor winding 14 is reversed. This results in the rotor current IR(t) flowing in the opposite direction (compared to the time interval between t0 and t1) and increasing. The rotor current IR(t) of the rotor winding 14 is then limited as a function of a predetermined threshold IL (see second graph 52). In particular, the rotor current is limited or controlled to a constant or time-varying value, especially one dependent on the rotational speed. Fig. 6 The second graph 52 shows that, starting at time t2, the rotor current IR(t) increases to as high as -20A after the polarity reversal (corresponding in particular to the predetermined threshold IL) and is limited there. For example, the limit is set in the Fig. 3A in the illustrated embodiment by means of an alternating opposite displacement of a fourth semiconductor device T4 (see Fig. 3A , 3B , 3C ,5 ) and a fifth semiconductor device T5 (see Fig. 3A , 3B , 3C , 5 ) into a conducting state and into a non-conducting state depending on the predetermined threshold IL for the rotor current IR (t).

[0086] After the input voltage at rotor winding 14 has been reversed (see above), the system waits, for example, for a predetermined period to elapse (time interval between t2 and t3). This predetermined period is, in particular, up to 2 ms or up to 3 ms. It should be noted that waiting for this period is not strictly necessary. During this predetermined period, the first semiconductor device T1 (see Fig. 2A , 2B , 2C , 3A , 3B, 3C , 4 , 5 ) in the embodiment of the Fig. 2A , 2B und 2C , in the embodiment of the Fig. 3A , 3B und 3C , in the embodiment of the Fig. 4 and in the embodiment of the Fig. 5 preferably in a non-conducting state. After the predetermined period has elapsed, at time t 3, the stator current IS(t) through the stator winding 12 is increased depending on the current speed n(t) of the electric motor 7, in particular with a decrease in the current speed n(t). This occurs in the time interval between times t 3 and t 4 in the third graph 53 of the Fig. 6 This advantageously results in an increase in the braking torque with which the rotor is slowed down.

[0087] In other words, for example, in the initial moment after the polarity reversal of the input voltage at the rotor winding 14, the first semiconductor device T1 remains in a non-conducting state. As a result, the stator winding 12 remains unenergized and therefore does not increase with the rotor current IR(t), which rises after the polarity reversal (see the interval between t2 and t3). After the predetermined period, which is, for example, 2 ms or 3 ms, the first semiconductor device T1 is switched to a conducting state. This energizes the stator winding 12, and the stator current through the stator winding 12 can be increased, for example, by a controlled decrease in the current speed n(t) of the electric motor 7 (see the time interval between times t3 and t4 in the third graph 53 of the diagram). Fig. 6This measure allows the rotor and stator current IR (t), IS (t) of the electric motor 7 to be set independently of each other. REFERENCE MARK LIST

[0088] 1 Electric hand tool 2 Power source 3 Tool holder 4 Control circuit 5 Drill bit 6 Connection unit 7 Electric motor 8 Connection unit 9 Handle 10 Node 11 Push button 12 Stator winding 13 Cable arrangement 14 Rotor winding 15 Connection terminal 16 Node 17 Plug 18 Node 19 Rectifier 20 Node 22 Node 51 Graph 52 Graph 53 Graph 100 Electric drive unit A Arrow B Arrow IL Threshold IR (t) Rotor current IS (t) Stator current n (t) Rotational speed t Time t 0 Time t 1 Time t 2 Time t 3 Time t 4 Time T1 Semiconductor component T1D Freewheeling diode T2 Semiconductor component T2D Freewheeling diode T3 Semiconductor component T3D Freewheeling diode T4 Conductive component T4D Freewheeling diode T5 Semiconductor component T5D Freewheeling diode T6 Semiconductor component

Claims

1. Electric drive unit (100) for an electric handheld power tool (1), having an electric motor (7) with a stator winding (12) and a rotor winding (14), an actuating circuit (4) for actuating the electric motor (7) and a connection unit (6, 8) for coupling an energy source (2) for driving the electric motor (7), wherein the stator winding (12) is connected via a first node (10) to a stator-side first half-bridge comprising a first semiconductor component (T1) and a second semiconductor component (T2) and is connected via a second node (16) to the rotor winding (14), wherein the rotor winding (14) is connected to a third node (18) which is connected via a conductive component (T4) to the connection unit (6, 8), characterized in that the actuating circuit (4) comprises a third semiconductor component (T3) which is connected via the second node (16) to the rotor winding (14) and the stator winding (12) and which is connected via a fourth node (20) directly to the connection unit (6, 8).

2. Electric drive unit according to Claim 1, characterized in that the actuating circuit (4) further comprises a further semiconductor component (T6) which is connected via the second node (16) to the rotor winding (14) and the stator winding (12) and is connected via a fifth node (22) directly to the connection unit (6, 8).

3. Electric drive unit according to Claim 1 or 2, characterized in that the actuating circuit (4) is designed to move the first semiconductor component (T1) to a non-conductive state in order to interrupt a supply current flow.

4. Electric drive unit according to one of Claims 1 - 3, characterized in that the actuating circuit (4) is designed to move the third semiconductor component (T3) to a conductive state in order to connect the rotor winding (14) in parallel with the stator winding (12).

5. Electric drive unit according to Claim 4, characterized in that the actuating circuit (4) is designed to move the first semiconductor component (T1) to a conductive state in addition to the third semiconductor component (T3) in order to provide a magnetic flux, so that a voltage is induced at the rotor winding (14) in the opposite direction compared to a voltage applied to the rotor winding (14) during motor operation of the electric motor (7).

6. Electric drive unit according to one of Claims 1 - 5, characterized by a first current measuring unit for determining a current rotor current IR(t), wherein the actuating circuit (4) is designed to move the first semiconductor component (T1) as a function of the determined current rotor current IR(t) and a predetermined threshold value (IL) of the rotor current IR(t) to a non-conductive state in order to limit the rotor current IR(t).

7. Electric drive unit according to Claim 1, characterized in that the conductive component (T4) comprises a fourth semiconductor component (T4) and the actuating circuit (4) further comprises a fifth semiconductor component (T5) which is connected via the third node (18) to the rotor winding (14) and which is connected via a fifth node (22) directly to the connection unit (6, 8).

8. Electric drive unit according to Claim 7, characterized in that the actuating circuit (4) is designed to move the fourth semiconductor component (T4) to a non-conductive state in order to interrupt a rotor current IR(t) through the rotor winding (14).

9. Electric drive unit according to Claim 7 or 8, characterized in that the actuating circuit (4) is designed to move the third semiconductor component (T3) and the fifth semiconductor component (T5) to a conductive state for reversing the polarity of an input voltage applied to the rotor winding (14) compared to motor operation.

10. Electric drive unit according to one of Claims 7 - 9, characterized by a first current measuring unit for determining a current rotor current IR(t), wherein the actuating circuit (4) is designed to move the fifth semiconductor component (T5) and the fourth semiconductor component (T4) as a function of the determined current rotor current IR(t) and a predetermined threshold value (IL) of the rotor current IR(t) alternately in synchronism with opposite senses to a conductive state and to a non-conductive state in order to limit the rotor current IR(t).

11. Electric drive unit according to Claim 10, characterized in that the actuating circuit (4) is designed to move the fifth semiconductor component (T5) and the fourth semiconductor component (T4) as a function of the determined current rotor current IR(t), the predetermined threshold value (IL) of the rotor current IR(t) and a current rotation speed (n(t)) of the electric motor (7) alternately in synchronism with opposite senses to a conductive state and to a non-conductive state in order to limit the rotor current IR(t).

12. Electric drive unit according to one of Claims 7 - 11, characterized by a second current measuring unit for determining a current stator current (IS(t)), wherein the actuating circuit (4) is designed to move the first semiconductor component (T1) alternately to a conductive state and to a non-conductive state in order to regulate a stator current (IS(t)) through the stator winding (12) as a function of a current rotation speed (n(t)) of the electric motor (7).

13. Electric drive unit according to Claim 9, characterized in that the actuating circuit (4) is designed, after a predetermined period of time has elapsed after the third semiconductor component (T3) and the fifth semiconductor component (T5) have been moved to a conductive state, to move the first semiconductor component (T1) alternately to a conductive state and to a non-conductive state in order to regulate a stator current (IS(t)) through the stator winding (14) as a function of a current rotation speed (n(t)) of the electric motor (7).

14. Electric drive unit according to one of Claims 1 - 13, characterized in that it is designed for operation from a DC voltage source, a pulsating DC voltage source or an AC voltage source with a rectifier.

15. Electric handheld power tool (1) having an electric drive unit (100) according to one of Claims 1 - 14.