Power tools, methods, arrangement structures, computer program products and computer-readable media

Abstract

To provide an electric tool that achieves a good power factor when ohmic power loss is small. [Solution] An electric tool having a tool, an electric motor for driving the tool, and a control unit for controlling the electric motor, wherein the electric tool is configured to be connected to a power supply voltage and includes a rectifier device having an intermediate circuit for providing an intermediate circuit voltage based on the power supply voltage, the intermediate circuit voltage having a plurality of voltage half-waves that are successive to one another, and the control unit is configured to provide, for each voltage half-wave, each torque half-wave 36 for controlling the electric motor, the curve shape of which is flattened compared to the curve shape of the voltage half-wave.

Description

Technical Field

[0001] The present invention relates to a power tool having a tool, an electric motor for driving the tool, and a control unit for controlling the electric motor, particularly a hand-held power tool, such as a grinding device, a grinding machine and / or a chipping device. The power tool is formed to be connected to a power supply voltage and includes a rectifier having an intermediate circuit for providing an intermediate circuit voltage based on the power supply voltage.

Background Art

[0002] The intermediate circuit is, for example, a capacitor used particularly for smoothing a rectified power supply voltage. There are various approaches to the sizing of the intermediate circuit. The first approach is to size the intermediate circuit such that the intermediate circuit voltage is substantially constant. This enables, in particular, a substantially constant phase current for energizing the electric motor and thus a substantially constant torque transition of the electric motor. However, a large intermediate circuit leads to a poor power factor and a high harmonic ratio in the absorbed current. The second approach is to size the intermediate circuit small such that the intermediate circuit voltage follows the power supply voltage, particularly the rectified power supply voltage. However, usually, in such a small intermediate circuit, the ohmic loss power in the motor winding is larger, so it is necessary to design the electric motor larger. Also, with such a small intermediate circuit, in the conventional control of the electric motor, the induced reverse current of the electric motor may become higher than the intermediate circuit voltage, leading to a range where current cannot flow through the motor. In this aspect, a torque ripple having twice the power supply voltage may occur.

Summary of the Invention

Problems to be Solved by the Invention

[0003] *The problem of the present invention is to provide an improved power tool, particularly a power tool that achieves a good power factor when the ohmic loss power is small.

Means for Solving the Problems

[0004] The problem is solved by the power tool according to claim 1.

[0005] In power tools, the intermediate circuit voltage has multiple voltage half-waves that are consecutive with respect to each other. In particular, the intermediate circuit, such as a capacitor, is sized small so that the intermediate circuit voltage follows the rectified power supply voltage, thereby forming voltage half-waves. The rectified power supply voltage contains, in particular, a series of positive sinusoidal half-waves. Exemplarily, the intermediate circuit voltage follows the rectified power supply voltage over at least 50% of its amplitude. For example, the intermediate circuit voltage follows the rectified power supply voltage in the range of 140 to 320 V. A small intermediate circuit allows for a purposeful achievement of a good power factor, for example, at least 0.70 or at least 0.75.

[0006] Furthermore, in power tools, the control unit is configured to provide, in particular, calculate, a torque half-wave for controlling the electric motor for each voltage half-wave. Each voltage half-wave is assigned a torque half-wave, which has the same period and / or the same phase angle as the voltage half-wave. The curve shape of each torque half-wave is flatter than the curve shape of the (each assigned) voltage half-wave. This means that the torque half-waves are more uniformly oriented than the voltage half-waves for their intended purpose. For example, the ratio of the maximum value to the average value of a torque half-wave is smaller than the ratio of the maximum value to the average value of a voltage half-wave. Preferably, the standard deviation of each torque half-wave is smaller than the standard deviation of the respective assigned voltage half-wave.

[0007] The flattened curve shape of the torque half-wave can improve the ratio of torque to ohmic power loss. The energization of an electric motor is proportional to a given torque, i.e., the torque half-wave. Ohmic power loss is a function of the square of the energization. Therefore, greater energization leads to a disproportionate increase in ohmic power loss (with respect to the torque achieved). The flattened curve shape of the torque half-wave can avoid such a disproportionate increase in ohmic power loss. In particular, the flattened curve shape can result in less ohmic power loss when the electric motor is energized. The flattened curve shape yields less ohmic power loss when the electric motor is energized, especially at the same average torque (as in the case of an unflattened curve shape, e.g., a sinusoidal curve shape). "Average torque" (mittlerem Drehmoment) means "average torque" (Durchschnitts-Drehmemont).

[0008] A favorable developmental formation is the subject of the dependent claim.

[0009] The present invention also relates to a method for operating a power tool, particularly a handheld power tool, such as a polishing machine, grinding machine and / or sawing machine, comprising the tool, an electric motor for driving the tool, and a control unit for controlling the electric motor, the method comprising the following steps: providing an intermediate circuit voltage based on the power supply voltage to which the power tool is connected, using a rectifier having an intermediate circuit, wherein the spatial circuit voltage has a plurality of voltage half waves that are continuous with each other; and providing each torque half wave for controlling the electric motor, wherein the curve shape of each voltage half wave is flattened compared to the curve shape of the voltage half wave.

[0010] The present invention also relates to an arrangement structure including an electric motor for driving a tool and a control unit for controlling the electric motor. The control unit is configured to provide each torque half-wave for controlling the electric motor, wherein the curve shape is flatter than the curve shape of the voltage half-wave for each voltage half-wave of the intermediate circuit voltage.

[0011] Furthermore, the present invention relates to a computer program product that includes commands for causing a power tool to perform the method steps described above.

[0012] Furthermore, the present invention relates to a computer-readable medium on which computer program products are stored.

[0013] Furthermore, the present invention relates to a method that includes the step of installing a computer program product into a power tool.

[0014] Further illustrative details and exemplary embodiments are described below with reference to the drawings. [Brief explanation of the drawing]

[0015] [Figure 1] This diagram schematically shows an electric tool configured as a polishing device. [Figure 2] This is a schematic diagram showing a power tool configured as a sawing device. [Figure 3] This diagram schematically shows the rectifier, control unit, and electric motor of a power tool. [Figure 4] This figure shows the time progression of the intermediate circuit voltage. [Figure 5] This is a graph showing the time course of torque. [Figure 6] This is a block diagram of signal processing. [Modes for carrying out the invention]

[0016] Figures 1 and 2 show exemplary configurations of the power tool 1. The power tool 1 is exemplary, configured as a handheld power tool. The power tool 1 can be held, carried, and / or handled by the user. The power tool 1 can be configured in particular as a grinding machine 1A (see Figure 1) or as a sawing machine (saw) 1B (see Figure 2). The grinding machine 1A is, for example, a grinding machine, particularly a rotary grinding machine. The sawing machine 1B is, for example, a plunge circular saw. Alternatively, the power tool 1 can be configured as another power tool, for example, a grinding machine, particularly a renovation grinder.

[0017] The power tool 1 includes tool 2. Tool 2 is configured, for example, as an abrasive disc 2A or a saw blade 2B. Alternatively, tool 2 may be configured as another tool, such as a grinding disc. In particular, tool 2 is used to process a workpiece, especially when tool 2 is subjected to working motion, particularly rotational motion, by an electric motor 3.

[0018] The power tool 1 includes an electric motor 3 for driving the tool 2. The electric motor 3 can provide a driving rotational motion, on which the tool 2 is driven. The electric motor 3 is formed, for example, as an EC motor, i.e., an electronically rectified motor. The electric motor 3 is particularly a brushless motor, preferably a brushless DC motor, i.e., a BLDC motor.

[0019] The power tool 1 further includes a control unit 4 for controlling an electric motor 3. The control unit 4 includes, for example, a microcontroller and / or power electronics equipment. In particular, the control unit 4 is configured to supply a number of motor currents I1, I2, I3 that are specifically out of phase with each other in order to control the electric motor 3 so that the electric motor 3 may be used to perform driving rotational motion. The motor currents I1, I2, I3 may also be called phase currents. The control unit 4 includes an inverter for providing the motor currents I1, I2, I3 for practical purposes.

[0020] The power tool 1 additionally includes, by way of example, a gripping part 5 with which the user can manually grip, carry, and / or handle the power tool 1. The power tool 1 further includes an operating device 6, such as buttons and / or switches, via which the user can control the drive of the tool 2, in particular start and / or stop it. The operating device 6 is, by way of example, arranged on the gripping part 5.

[0021] The power tool 1 expediently includes a shaft 7, and the tool 2 is coupled to the electric motor 3 via this shaft so as to be drivable by the electric motor 3. The power tool 1 can optionally include a transmission, in particular an angle gear unit 8, via which the tool 2 is coupled to the electric motor 3. In FIG. 1, the power tool 1 includes, by way of example, a connecting shaft 9 via which the electric motor 3 is coupled to the angle gear unit 8. The angle gear unit 8 is, by way of example, coupled to the tool 2 via the shaft 7. Instead of this, the electric motor 3 can be coupled directly to the tool 2, for example via the shaft 7.

[0022] The power tool 1 includes, by way of example, an outer housing 10 in which, expediently, the electric motor 3, the control unit 4 and / or the rectifier 12 are arranged. The gripping part 5 is, by way of example, arranged on the outer housing 10. Instead of this, the gripping part 5 can be part of the outer housing 10.

[0023] The electric tool 1 is formed to be connected to a power supply voltage V1 (see Fig. 2). The power supply voltage V1 is an alternating voltage. The power supply voltage V1 is in particular sinusoidal and has, by way of example, an effective value of 230 V and / or a power supply frequency of 50 Hz. Also, the power supply voltage V1 can have an effective value of 120 V and / or a power supply frequency of 60 Hz. The electric tool 1 includes a connection part 11, for example a power plug and / or a power plug connection part, and the electric tool 1 can be connected to a power supply voltage, for example a plug connector, via this connection part.

[0024] The electric tool 1 includes, by way of example, a rectifier device 12 arranged in an outer housing 10. The rectifier device 12 is shown, for example, in Fig. 3. The rectifier device 12 is formed to provide an intermediate circuit voltage V2 based on the power supply voltage V1. The rectifier device 12 includes, by way of example, a rectifier 14 configured as a bridge rectifier. The rectifier 14 includes, for all intents and purposes, four diodes connected as a bridge, by way of example. The power supply voltage V1 is supplied to the rectifier 14, and the rectifier provides a rectified power supply voltage based on the power supply voltage V1. The rectifier device 12 further includes an intermediate circuit 15 configured as a capacitor, by way of example. The intermediate circuit 15 is connected to the outlet of the rectifier 14. The intermediate circuit 15 is used to smooth the rectified power supply voltage. The smoothed and rectified power supply voltage will also be referred to as the intermediate circuit voltage V2. The intermediate circuit voltage V2 drops across the intermediate circuit 15, in particular across the capacitor.

[0025] The intermediate circuit 15, in particular the capacitor, is, for example, smaller than 100 μF, or smaller than 50 μF, or smaller than 30 μF, or smaller than 20 μF, or smaller than 10 μF.

[0026] An exemplary temporal progression of the intermediate circuit voltage V2 is shown in Figure 4. The intermediate circuit voltage V2 includes a plurality of consecutive voltage half waves 16. Each voltage half wave 16 includes, exemplary, one sinusoidal portion 17 having a curve shape that is part of a sinusoidal half wave. One portion of the sinusoidal portion 17 specifically includes the maximum value 20 of a sinusoidal half wave. Exemplarily, the intermediate circuit voltage V2 follows the rectified power supply voltage in the sinusoidal portion 17. Exemplarily, the voltage half wave 16 further includes two transitional portions 18, each positioned before and after the sinusoidal portion 17. The transitional portions 18 include the minimum value 19 of the intermediate circuit voltage V2. The voltage half wave 16 does not exemplary have a sinusoidal half wave shape in the transitional portions 18. In particular, the intermediate circuit voltage does not drop to zero in the transitional portions 18. Exemplarily, the intermediate circuit voltage V2 does not follow the rectified power supply voltage in the transitional portions 18.

[0027] The minimum value 19 of each voltage half-wave 16 is, for the purpose, at least 20%, preferably at least 30%, of the maximum value 20. For example, the minimum value 19 of each voltage half-wave 16 is at least 90V and at least 100V. Alternatively, the minimum value 19 of each voltage half-wave 16 is, for the purpose, at most 70%, particularly at most 50%, preferably at most 40%, or at most 35%, of the maximum value 20. For example, the minimum value 19 is at most 120V or 110V.

[0028] Preferably, the control unit 4 and / or the electric motor 3 are powered from the intermediate circuit 15. The control unit 4 is configured to generate motor currents I1, I2, and I3 based on the electrical energy provided by the intermediate circuit 15, and in particular based on the intermediate circuit voltage V2, and to supply them to the electric motor 3. Exemplarily, the control unit 4 provides three motor currents I1, I2, and I3. For example, the motor currents I1, I2, and I3 flow from the intermediate circuit 15.

[0029] The electric motor 3 includes, in example, a stator 43 and a rotor 21. The rotor 21 is coupled to the tool 2. When the electric motor 3 is energized with motor currents I1, I2, and I3, the rotor 21 receives rotational motion relative to the stator 43.

[0030] The electric motor 3 is optionally equipped with a position sensor device 22, which is used to detect the position and / or motion of the rotor 21, particularly its current angle. The position sensor device 22 includes, for example, a magnetic sensor, particularly a Hall sensor. For the purpose, the control unit 4 is configured to detect the current angle of the rotor 21 using the position sensor device 22. The control unit 4 can also be configured to detect the current rotational speed of the electric motor 3 using the position sensor device 22.

[0031] Alternatively, or in addition to the above, the control unit 4 may be configured to detect the current angle of the rotor 21 and / or the current rotational speed of the electric motor 3. In this case, the position sensor device 22 is not present for practical purposes. In particular, the control unit 4 is configured to detect the reverse voltage induced in the electric motor and to calculate the current angle of the rotor 21 and / or the current rotational speed of the electric motor 3 based on the reverse voltage. Specifically, the control unit 4 is configured to calculate the current angle of the rotor 21 and / or the current rotational speed of the electric motor 3 using the Back-EMF-Prinzip principle, where "EMF" stands for "Electromotive Force".

[0032] Figure 6 shows an illustrative block diagram of the signal processing performed by the control unit 4 for controlling the electric motor 3.

[0033] For the purposes of the system, the control unit 4 is configured to perform rotational speed (closed-loop) control of the electric motor 3. In particular, the control unit 4 is configured to provide motor currents I1, I2, I3 based on a target rotational speed 23 and an actual rotational speed 24. The target rotational speed 23 is set by the control unit 4 according to user input operated, for example, by the operating device 6. Alternatively, the target rotational speed 23 can be pre-memorized in the control unit 4 and / or calculated by the control unit 4. The actual rotational speed 24 is the current rotational speed of the electric motor 3 and, for the purposes of the system, is obtained as described above, in particular using the position sensor device 22 and / or based on a sensorless principle, in particular based on an induced reverse voltage. The actual rotational speed 24 represents how fast the rotor 21 is rotating relative to the starter 43.

[0034] The control unit 4 includes a rotational speed controller 25, to which a target rotational speed 23 and an actual rotational speed 24 are supplied. Based on the target rotational speed 23 and the actual rotational speed 24, and particularly based on a comparison of the target rotational speed 23 and the actual rotational speed 24, the rotational speed controller 25 calculates a target torque value 26. The target torque value 26 sets the torque that should affect the rotor 21 by energizing the electric motor 3 in order to achieve the change in the actual rotational speed towards the target rotational speed value.

[0035] The control unit 4 further includes a torque transition calculation unit 27, which is configured to calculate a time-dependent torque transition 28 based on a torque target value 26. The torque transition 28 can also be called a torque signal. An exemplary torque transition 28 is shown in Figure 5. Exemplarily, the torque transition 28 has a trapezoidal curve shape.

[0036] The control unit 4 further includes a motor current supply unit 31, which is configured to calculate motor currents I1, I2, and I3 based on a torque transition 28. Exemplarily, the motor current supply unit 31 includes a target current setting unit 32, which is configured to calculate q (axis) current and d (axis) current, particularly based on the torque transition 28. The d current and q current are currents in a d / q (coordinate) system with respect to the rotor, rotating in accordance with the rotation of the rotor 21. The d current forms a component that forms the flow, and the q current forms a component that forms the torque. The d current can be called the d component or field weakening current, and the q current can be called the q component or torque forming current. The target current setting unit 32 calculates the q current and d current so as to achieve a torque transition 28 according to the q current and d current when the electric motor 3 is energized. Exemplarily, the temporal transition of the calculated q current corresponds to the torque transition 28. In particular, the q current has the same curve shape as the torque transition 28.

[0037] The motor current supply unit 31 further includes a current controller 33, which is configured to provide motor currents I1, I2, and I3. In particular, the current controller 33 is configured to perform current (closed-loop) control of the motor currents I1, I2, and I3. The motor currents I1, I2, and I3 are preferably pulse-width modulated. The current controller 33 provides the motor currents I1, I2, and I3 based on the q current and d current, particularly by performing a transformation from a biaxial coordinate system to a triaxial coordinate system. The current controller 33 provides the motor currents I1, I2, and I3 such that the calculated q current and calculated d current are achieved. The motor windings of the electric motor 3, particularly the stator 43, are energized with the motor currents I1, I2, and I3. The rotor 21 has, exemplary, permanent magnets and is driven rotationally by interaction with the magnetic field generated by the energization of the motor windings.

[0038] The torque transition 28 will be described in detail below. Figure 5 shows an exemplary torque transition 28 (as a solid line). The torque transition 28 has multiple torque half-waves 36 that are continuous with each other. Exemplarily, each torque half-wave 36 has a trapezoidal curve shape. Alternatively, the torque half-waves can have other curve shapes, such as a rectangular curve shape.

[0039] The control unit 4 is configured to provide, specifically calculate, a torque half-wave 36 for controlling the electric motor 3 for each voltage half-wave 16. The curve shape of each torque half-wave is flattened compared to the curve shape of the voltage half-wave 16. The flattened curve shape results in smaller ohmic power loss at the same average torque for the purpose when the electric motor 3 is energized.

[0040] The control unit 4, for its intended purpose, energizes the electric motor 3 in proportion to the torque half-wave. If the torque half-wave 36 takes a larger value, the control unit 4 increases the energization to the electric motor 3. Since the ohmic power loss is a function of the square of the energization to the electric motor 3, a larger current results in disproportionate ohmic power loss. The flattened curve shape of the torque half-wave 36 reduces the current maximum value that is important for ohmic power loss (due to its dependence on the square), so that ohmic power loss can be reduced, especially in smaller or slight torque reductions. The flattened curve shape can also be called an equalized curve shape. In particular, each torque half-wave 36 has a more equal curve shape than each voltage half-wave 16 and / or each (fictitious) sinusoidal half-wave 37 of the same period and / or area. Preferably, the standard deviation of each torque half-wave 36 is smaller than the standard deviation of each voltage half-wave 16 and / or each (fictitious) sinusoidal half-wave 37 of the same period and / or area.

[0041] In particular, the flattened curve shape has a smaller maximum value under the curve shape, especially compared to the (fictitious) sinusoidal half-wave 37, for the same area. Figure 5 shows a reference curve 38 (as a dashed line) which has the curve shape of a rectified sinusoidal curve and contains continuous sinusoidal half-waves 37. Each sinusoidal half-wave 37 has the same period as the torque half-wave 36. The integral under the area under each sinusoidal half-wave 37, i.e., the period of the sinusoidal half-wave 37, is, for the purposes of purpose, the same as the integral under the area under each torque half-wave 36, i.e., the period of the torque half-wave 36. The maximum value of each torque half-wave 36 is, for the purposes of purpose, at least 10% smaller or at least 20% smaller than the maximum value of each sinusoidal half-wave 37. The sinusoidal half-wave 37 is used here in the mathematical definition of the flattened curve shape of the torque half-wave and does not need to be provided by the power tool 1. The flattened curve shape of each torque half-wave 36 is preferably mathematically defined to have a smaller maximum value than the sinusoidal half-wave 37 at the same period and area as the (particularly hypothetical) sinusoidal half-wave 37.

[0042] For example, in a flattened curve shape, the ratio between the maximum value and the average value of the curve shape is reduced. For practical purposes, the ratio between the maximum value and the average value of the torque half-wave 36 is smaller than the ratio between the maximum value 20 and the average value of the voltage half-wave 16.

[0043] Preferably, the control unit 4 is formed to provide a torque half-wave 36 having a trapezoidal curve shape or a rectangular curve shape.

[0044] The description of one torque half-wave 36 preferably applies to each torque half-wave 36. The torque half-wave 36 has a flat region portion 39 that contains or represents the maximum value of the torque half-wave 36. The flat region portion 39 preferably has a slope of 0 and extends in particular over at least 40%, at least 50%, at least 60%, at least 70%, or at least 80% of the period of the torque half-wave 36. Exemplarily, the maximum value 42 of the sinusoidal half-wave 37 is greater than the flat region portion 39. The torque half-wave 36 further has two lateral portions 40 that surround the flat region portion 39. The lateral portions 40 have a slope (quantitatively) greater than that of the flat region portion 39, in particular greater than that of the sinusoidal half-wave 37 and / or voltage half-wave 16. According to one possible embodiment, the lateral portions 40 may be perpendicular, i.e., they can have an infinite slope (quantitatively). The torque half-wave 36 further has two torque minimums 41 for practical purposes, the torque minimums representing the beginning and end of the torque half-wave 36. Exemplarily, the torque is equal to zero at the torque minimum 41. Thus, the torque half-wave 36 includes the following portions which are temporally continuous, in particular directly continuous, in the order described above: a first torque minimum 41 (preferably equal to zero), a first lateral portion 40 (preferably with a positive slope), a flat region portion 39 (preferably with a zero slope), a second lateral portion 40 (preferably with a negative slope), and a second torque minimum (preferably equal to zero). The torque minimums 41 extend together in time over a period of at least 10%, at least 20%, or at least 30% of the period of the torque half-wave 36.

[0045] For the purpose, the control unit 4 is configured to provide a torque half-wave 36 having the same period as the period of each voltage half-wave 16. Preferably, the frequency of the torque transition 28 is twice the frequency of the power supply voltage V1. In particular, the frequency of the torque transition 28 is 100 Hz or 120 Hz.

[0046] For example, the control unit 4 detects the period of the voltage half-wave 16 and / or the time interval between adjacent zero crossings of the power supply voltage V1, and uses the detected period and / or time interval as the period for the torque half-wave 36. For the purpose, the control unit 4 synchronizes the torque half-wave 36 with the power supply voltage V1 and / or the voltage half-wave 16. For example, the control unit 4 synchronizes the minimum value of the torque transition 28 with the zero crossing of the power supply voltage V1 so that the minimum value of the torque transition 28 occurs simultaneously with the zero crossing of the power supply voltage V2. Also, the control unit 4 can synchronize the minimum value of the torque transition 28 with the minimum value 19 of the intermediate circuit voltage V2 so that the minimum value of the torque transition 28 occurs simultaneously with the minimum value of the intermediate circuit voltage V2. For example, the control unit 4 is configured to detect the phase angle 30 of the power supply voltage V1 and / or the intermediate circuit voltage V2, and in particular to provide the torque half-wave 36 according to the phase angle 30 so that the torque half-wave 36 is synchronized with the voltage half-wave 16 and / or the power supply voltage V1. The torque transition 28 has the same phase angle as the intermediate circuit voltage V2 for the purpose.

[0047] The control unit 4, in particular the torque transition calculation unit 27, is preferably configured to calculate the torque transition 28 based on a curve shape profile 29. The curve shape profile is, for the purposes of the operation, pre-stored in the control unit 4 and / or provided by the control unit 4. The curve shape profile 29 defines the flattened curve shape of the torque half-wave 36. For example, the curve shape profile 29 defines a trapezoidal curve shape or a rectangular curve shape.

[0048] For example, the control unit 4 is configured to calculate the torque transition 28 taking into account the phase angle 30. In particular, the control unit 4 is configured to calculate the period for each torque half-wave 36 based on the phase angle 30, and to extend or compress the curve shape profile 29 in time according to the calculated period so that the period of the curve shape profile 29 is the same as the calculated period.

[0049] For practical purposes, the control unit 4 is further configured to calculate each torque half-wave 36 based on the torque target value 26. In particular, the control unit 4 is configured to calculate each torque half-wave 36 such that the average value of each torque half-wave 36 is the same as the torque target value 26. Specifically, the control unit 4 is configured to calculate each torque half-wave 36 by scaling the curve shape profile 29 according to the torque target value 26. Exemplarily, the control unit 4 is configured to scale the curve shape profile 29 by the torque target value 26 or by a scaling factor dependent on the torque target value 26.

[0050] As described above, the control unit 4 is equipped with a rotational speed controller 25 for providing a torque target value 26, and based on this, the control unit 4 provides each torque half-wave 36. In particular, the control unit 4 is configured to energize the electric motor 3 according to the torque half-wave.

[0051] The provision of half-wave torque 36 can also be called torque forming. In particular, torque forming in a trapezoidal or rectangular shape, and the resulting current forming, can reduce ohmic power loss, i.e., copper loss, making it possible to construct a smaller electric motor 3.

[0052] As already mentioned above, a small intermediate circuit 15 is used, for the purpose of reducing structural space and cost, such that the intermediate circuit voltage V2 mainly corresponds to the (rectified) power supply voltage.

[0053] Copper loss is I 2*Since it is calculated by R, the flat region portion 39 of the trapezoidal torque half-wave 36 should have the smallest possible torque value. This is preferably achieved by selecting the longest possible time for each half-wave in which current can flow in the electric motor 3, that is, by selecting a large temporal extension of the flat region portion 39. For the sake of convenience, the electric motor 3 is set to a voltage smaller than the power supply voltage V1. Also, for the sake of convenience, the reverse voltage induced in the electric motor 3 due to changes in the field weakening current changes depending on the intermediate circuit voltage V2.

[0054] Preferably, the control unit 4 is configured to detect the reverse voltage 34 induced in the electric motor 3 and, in response to the reverse voltage 34 being greater than the intermediate circuit voltage V2, reduce the current torque value of the torque half-wave 36, particularly to zero, using the torque transition calculation unit 27, as an example. Exemplarily, the control unit 4 is configured to detect the induced reverse voltage 34 based on the rotational speed of the rotor 21. In particular, the control unit 4 is configured to reduce the q current and preferably the d current, particularly to zero, and preferably to zero (closed-loop) control, in response to the reverse voltage 34 being greater than the intermediate circuit voltage V2. In this way, undesirable braking moments that may occur when the induced reverse voltage 34 is greater than the intermediate circuit voltage V2 can be avoided or reduced.

[0055] In particular, the control unit 4 is configured to control the torque-generating current to zero (closed loop) when the reverse voltage 34 induced by the electric motor 3 is equal to or greater than the intermediate circuit voltage V2. The (closed loop) control of the torque-generating current remains active and is not stopped when the reverse voltage 34 induced by the electric motor 3 is equal to or greater than the intermediate circuit voltage V2.

[0056] Preferably, the control unit 4, in particular the target current setting unit 32, is configured to calculate the d current taking into account the intermediate circuit voltage V2. In particular, the control unit 4 is configured to set the d current Id according to the intermediate circuit voltage V2. For example, the control unit 4 is configured to quantitatively reduce the d current Id when the intermediate circuit voltage V2 is greater, and quantitatively increase it when the intermediate circuit voltage V2 is smaller. In particular, the control unit 4 is configured to set the d current Id based on the intermediate circuit voltage V2 such that the induced reverse voltage is reduced to less than the intermediate circuit voltage V2. The setting of the d current Id is, for example, inversely proportional to the intermediate circuit voltage V2. When the intermediate circuit voltage V2 increases, the d current Id is quantitatively reduced, and when the intermediate circuit voltage V2 decreases, the d current Id is quantitatively increased.

[0057] In particular, the control unit 4 is configured to constantly energize the electric motor according to the d current and / or q current so that braking moments are avoided and the power factor is dynamically adapted to the load.

[0058] In particular, the control unit 4 is configured to change the d current and q current depending on the intermediate circuit voltage V2 and / or the power supply voltage V1, in order to always operate the motor optimally so that it requires the smallest possible current.

[0059] The power tool 1 can be operated in accordance with the method described below. The method includes a first step of providing an intermediate circuit voltage V2 based on the power supply voltage V1 to which the power tool 1 is connected, using a rectifier 12 having an intermediate circuit 15. The intermediate circuit voltage V2 has a plurality of voltage half waves 16 that are consecutive with respect to each other. The method includes a second step of providing, for each voltage half wave 16, each torque half wave 36 for controlling an electric motor 3. The curve shape of each torque half wave is flattened compared to the curve shape of the voltage half wave.

[0060] For the purposes of this method, the method further includes energizing the electric motor 3 according to a torque half-wave 36 such that the rotor 21 receives a driving rotational motion, which in turn causes the tool 2 to receive a working motion.

[0061] For the purpose, the method includes one further step of processing the workpiece with tool 2, in particular polishing, grinding, and cutting with a saw. Furthermore, the present invention may also encompass the following embodiments: 1. An electric power tool (1), particularly a handheld electric power tool (1), such as a polishing machine (1A), a grinding machine and / or a sawing machine (1B), comprising a tool (2), an electric motor (3) for driving the tool (2), and a control unit (4) for controlling the electric motor (3), wherein the electric power tool (1) is configured to connect to a power supply voltage (V1) and includes a rectifier (12) having an intermediate circuit (15) for providing an intermediate circuit voltage (V2) based on the power supply voltage (V1), the intermediate circuit voltage (V2) comprising a plurality of voltage half waves (16) that are continuous with each other, and the control unit (4) is configured to provide each torque half wave (36) for controlling the electric motor (3), the curve shape of which is flatter than the curve shape of the voltage half wave (16). 2. The power tool (1) according to 1. above, characterized in that the control unit (4) is formed to provide a torque half-wave (36) having a curved shape with a maximum value smaller than that of the sinusoidal half-wave (37) in the same area as the sinusoidal half-wave (37). 3. The power tool (1) according to 1. or 2. above, characterized in that the flattened curved shape results in smaller ohmic power loss when the electric motor (3) is energized at the same average torque. 4. The power tool (1) according to any one of 1. to 3. above, characterized in that the control unit (4) is formed to provide a torque half-wave (36) having a trapezoidal curve shape or a rectangular curve shape. 5. The power tool (1) according to any one of 1. to 4. above, characterized in that the control unit (4) is configured to calculate a torque half-wave (36) using a curved profile (29). 6. The power tool (1) according to any one of 1. to 5. above, characterized in that the control unit (4) is configured to calculate a torque half-wave (36) based on a torque target value (26). 7. The power tool (1) according to any one of 1. to 6. above, characterized in that the control unit (4) is configured to calculate a torque half-wave (36) by scaling a curved profile (29) according to a torque target value (26). 8. The power tool (1) according to any one of 1. to 7. above, characterized in that the control unit (4) is configured to detect the phase angle (30) of the power supply voltage (V1) and / or the intermediate circuit voltage (V2) and to provide a torque half-wave according to the phase angle (V2). 9. The power tool (1) according to any one of 1. to 8. above, wherein the control unit (4) is equipped with a rotational speed controller (25) for providing a torque target value (26), and the control unit (4) provides each torque half-wave (36) based on the torque target value. 10. The power tool (1) according to any one of 1 to 9 above, characterized in that the control unit (4) is configured to energize the electric motor (3) according to a torque half-wave (36). 11. The power tool (1) according to any one of 1. to 10. above, characterized in that the control unit (4) is configured to calculate d current (Id) and q current (Iq) for the control of the electric motor (3), and to adjust d current (Id) according to the intermediate circuit voltage (V2). 12. The power tool (1) according to 11. above, characterized in that the control unit (4) is configured to quantitatively reduce the d current (Id) when the intermediate circuit voltage (V2) is greater, and to quantitatively increase it when the intermediate circuit voltage (V2) is smaller. 13. The power tool (1) according to any one of 1. to 12. above, characterized in that the control unit (4) is configured to detect a reverse voltage (34) induced in the electric motor (3), and in response to the reverse voltage (34) being greater than the intermediate circuit voltage (V2), reduce the current torque value of the torque half-wave (36), in particular to set it to zero. 14. A method for operating a power tool (1), particularly a handheld power tool (1), such as a polishing machine (1A), a grinding machine and / or a sawing machine (1B), comprising a tool (2), an electric motor (3) for driving the tool (2), and a control unit (4) for controlling the electric motor (3), the following steps: - A step of providing an intermediate circuit voltage (V2) based on a power supply voltage (V1) to which a power tool (1) is connected, using a rectifier (12) having an intermediate circuit (15), wherein the spatial circuit voltage (V2) has a plurality of voltage half-waves (16) that are continuous with each other, - A step of providing each torque half wave (36) for controlling an electric motor (3), wherein the curve shape is flattened compared to the curve shape of the voltage half wave (16) for each voltage half wave (16). A method that includes this. 15. The method according to 14., characterized in that a torque half-wave (36) having a curved shape having a smaller maximum value than the sinusoidal half-wave (37) in the same area as the sinusoidal half-wave (37). 16. The method according to 14. or 15. above, characterized in that the flattened curve shape results in smaller ohmic power loss when the electric motor (3) is energized at the same average torque. 17. The method according to any one of the above 14. to 16., characterized in that a torque half-wave (36) having a trapezoidal curve shape or a rectangular curve shape is provided. 18. The method according to any one of the above 14. to 17., characterized in that a torque half-wave (36) is calculated using a curved shape profile (29). 19. The method according to any one of items 14 to 18 above, characterized in that a torque half-wave (36) is calculated based on a torque target value (26). 20. The method according to any one of items 14 to 19 above, characterized in that a torque half-wave (36) is calculated by scaling a curve shape profile (29) according to a torque target value (26). 21. The method according to any one of 14. to 20. above, characterized in that the phase angle (30) of the power supply voltage (V1) and / or the intermediate circuit voltage (V2) is detected, and a torque half-wave is provided according to the phase angle (V2). 22. The method according to any one of 14. to 21. above, characterized in that the underlying torque target value (26) that provides each torque half-wave (36) is provided by a rotational speed controller (25). 23. The method according to any one of the above 14. to 22., characterized in that the electric motor (3) is energized according to a torque half-wave (36). 24. The method according to any one of 14. to 23. above, characterized in that a d current (Id) and a q current (Iq) are calculated for the control of the electric motor (3), and the d current (Id) is adjusted according to the intermediate circuit voltage (V2). 25. The method according to 24. above, characterized in that the current (Id) is quantitatively reduced when the intermediate circuit voltage (V2) is greater, and quantitatively increased when the intermediate circuit voltage (V2) is smaller. 26. The method according to any one of 14. to 25. above, characterized in that a reverse voltage (34) induced in an electric motor (3) is detected, and in response to the reverse voltage (34) being greater than the intermediate circuit voltage (V2), the current torque value of the torque half-wave (36) is reduced, in particular to zero. 27. An arrangement structure comprising an electric motor for driving a tool and a control unit for controlling the electric motor, wherein the control unit is formed to provide each torque half wave (36) for controlling the electric motor (3), wherein the curve shape of each voltage half wave of the intermediate circuit voltage (V2) is flatter than the curve shape of the voltage half wave (16). 28. A computer program product that includes a command to cause the power tool (1) described in item 1 above to perform a step in any one of items 14 to 26 above. 29. A computer-readable medium on which the computer program product described in item 28 above is stored. 30. A method comprising the step of installing the computer program product described in 29 above onto a power tool (1).

Claims

1. A power tool (1) comprising a tool (2), an electric motor (3) for driving the tool (2), and a control unit (4) for controlling the electric motor (3), wherein the power tool (1) is configured to connect to a power supply voltage (V1) and includes a rectifier (12) having an intermediate circuit (15) for providing an intermediate circuit voltage (V2) based on the power supply voltage (V1), the intermediate circuit voltage (V2) comprises a plurality of voltage half waves (16) that are continuous with each other, and the control unit (4) is configured to provide each torque half wave (36) for controlling the electric motor (3) for each voltage half wave (16), the curve shape of which is flatter than the curve shape of the voltage half wave (16), and the torque half waves (36) have a minimum torque value (41) that extends together over time for at least 10% of the period of the torque half waves (36).

2. The power tool according to Claim 1, characterized in that the power tool (1) is a handheld power tool, for example, a polishing machine (1A), a grinding machine and / or a sawing machine (1B).

3. The power tool (1) according to claim 1 or 2, characterized in that the control unit (4) is formed to provide a torque half-wave (36) having a curved shape with a maximum value smaller than that of the sinusoidal half-wave (37) in the same area as the sinusoidal half-wave (37).

4. The power tool (1) according to any one of claims 1 to 3, characterized in that the flattened curve shape results in smaller ohm power loss than the unflattened curve shape when the electric motor (3) is energized, at the same average torque.

5. The power tool (1) according to any one of claims 1 to 4, characterized in that the control unit (4) is formed to provide a torque half-wave (36) having a trapezoidal curve shape or a rectangular curve shape.

6. The power tool (1) according to any one of claims 1 to 5, characterized in that the control unit (4) is configured to calculate a torque half-wave (36) using a curved profile (29).

7. The power tool (1) according to any one of claims 1 to 6, characterized in that the control unit (4) is configured to calculate a torque half-wave (36) based on a torque target value (26).

8. The power tool (1) according to any one of claims 1 to 7, characterized in that the control unit (4) is configured to calculate a torque half-wave (36) by scaling a curved profile (29) according to a torque target value (26).

9. The power tool (1) according to any one of claims 1 to 8, characterized in that the control unit (4) is configured to detect the phase angle (30) of the power supply voltage (V1) and / or the intermediate circuit voltage (V2) and to provide a torque half-wave according to the phase angle (V2).

10. The power tool (1) according to any one of claims 1 to 9, wherein the control unit (4) includes a rotational speed controller (25) for providing a torque target value (26), and the control unit (4) provides each torque half-wave (36) based on the torque target value.

11. The power tool (1) according to any one of claims 1 to 10, characterized in that the control unit (4) is configured to energize the electric motor (3) in accordance with a torque half-wave (36).

12. The power tool (1) according to any one of claims 1 to 11, characterized in that the control unit (4) is configured to calculate a d current (Id) and a q current (Iq) for controlling the electric motor (3), and to adjust the d current (Id) according to the intermediate circuit voltage (V2).

13. The power tool (1) according to claim 12, characterized in that the control unit (4) is configured to quantitatively reduce the d current (Id) when the intermediate circuit voltage (V2) is greater, and to quantitatively increase it when the intermediate circuit voltage (V2) is smaller.

14. The power tool (1) according to any one of claims 1 to 13, characterized in that the control unit (4) is configured to detect a reverse voltage (34) induced in the electric motor (3) and to reduce the current torque value indicated by the torque half-wave (36) in response to the reverse voltage (34) being greater than the intermediate circuit voltage (V2).

15. The power tool (1) according to claim 14, characterized in that the control unit (4) is configured to set the current torque value to zero.

16. A method for operating a power tool (1) having a tool (2), an electric motor (3) for driving the tool (2), and a control unit (4) for controlling the electric motor (3), the following steps: - A step of providing an intermediate circuit voltage (V2) based on a power supply voltage (V1) to which a power tool (1) is connected, using a rectifier (12) having an intermediate circuit (15), wherein the spatial circuit voltage (V2) has a plurality of voltage half-waves (16) that are continuous with each other, - A step of providing each torque half wave (36) for controlling an electric motor (3), wherein the curve shape of each voltage half wave (16) is flattened compared to the curve shape of the voltage half wave (16). A method comprising a torque half-wave (36) having a torque minimum value (41) that extends together with the torque half-wave (36) over a period of at least 10% of the period of the torque half-wave (36) in time.

17. The method according to claim 16, characterized in that the power tool (1) is a handheld power tool, for example, a polishing machine (1A), a grinding machine and / or a sawing machine (1B).

18. The method according to 16 or 17, characterized in that a torque half-wave (36) having a curved shape having a smaller maximum value than the sinusoidal half-wave (37) in the same area as the sinusoidal half-wave (37).

19. The method according to any one of claims 16 to 18, characterized in that the flattened curve shape yields smaller ohm power loss than the unflattened curve shape when the electric motor (3) is energized, at the same average torque.

20. The method according to any one of claims 16 to 19, characterized in that a torque half-wave (36) having a trapezoidal curve shape or a rectangular curve shape is provided.

21. The method according to any one of claims 16 to 20, characterized in that a torque half-wave (36) is calculated using a curved profile (29).

22. The method according to any one of claims 16 to 21, characterized in that a torque half-wave (36) is calculated based on a torque target value (26).

23. The method according to any one of claims 16 to 22, characterized in that a torque half-wave (36) is calculated by scaling a curve shape profile (29) according to a torque target value (26).

24. The method according to any one of claims 16 to 23, characterized in that the phase angle (30) of the power supply voltage (V1) and / or the intermediate circuit voltage (V2) is detected, and a torque half-wave is provided according to the phase angle (V2).

25. The method according to any one of claims 16 to 24, characterized in that a base torque target value (26) that provides each torque half-wave (36) is provided by a rotational speed controller (25).

26. The method according to any one of claims 16 to 25, characterized in that the electric motor (3) is energized in accordance with a torque half-wave (36).

27. The method according to any one of claims 16 to 26, characterized in that a d current (Id) and a q current (Iq) are calculated for the control of an electric motor (3), and the d current (Id) is adjusted according to the intermediate circuit voltage (V2).

28. The method according to 27, characterized in that the d current (Id) is quantitatively reduced when the intermediate circuit voltage (V2) is greater, and quantitatively increased when the intermediate circuit voltage (V2) is smaller.

29. The method according to any one of claims 16 to 28, characterized in that a reverse voltage (34) induced in an electric motor (3) is detected, and in response to the reverse voltage (34) being greater than the intermediate circuit voltage (V2), the current torque value indicated by the torque half-wave (36) is reduced.

30. The method according to claim 29, characterized in that the current torque value is set to zero.

31. An arrangement structure comprising an electric motor for driving a tool and a control unit for controlling the electric motor, wherein the control unit is configured to provide each torque half wave (36) for controlling the electric motor (3), the curve shape of which is flatter than that of the voltage half wave (16) for each voltage half wave of the intermediate circuit voltage (V2), and the torque half wave (36) has a minimum torque value (41) that extends together over time for at least 10% of the period of the torque half wave (36).

32. A computer program product comprising a command that causes the power tool (1) described in claim 1 to perform a step according to any one of claims 16 to 30.

33. A computer-readable medium on which the computer program product described in claim 32 is stored.

34. A method comprising the step of installing the computer program product described in claim 33 into a power tool (1).

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