DE102009020116A1 - Control device for an electric drive motor and machine tool - Google Patents

Abstract

The controller (17) has a limitation device (31) limiting an output torque at a torque-maximum value depending on a motor current value (34) that represents motor current (Imot) supplied to a drive motor (12). The device has a comparison unit (37) comparing the torque maximum value with inner motor moment value (36) that depends on the current. The device decreases the inner motor moment value or increases the torque maximum value around a moment of inertia value (43) that depends on acceleration of a drive train (11) during comparison for reproduction of really provided output torque. An independent claim is also included for a machine tool comprising a temperature sensor.

Description

The The invention relates to a control device for controlling or Control of an electric drive motor of a drive train, in particular a screw-type power tool, with a limiting device for limiting a drive train provided on the drive train Output torque to a maximum torque value based on a Motor current value, which is a motor current for energizing the drive motor represents as well as a machine tool equipped therewith, in particular a hand-held machine tool.

From the German patent application DE 103 41 975 A1 is a control with a torque limiting device for an electric motor, in particular for an electric screwdriver known. On the drive train enters a torque component, which is due to the motor current of the drive motor, as well as a kinetic energy of the rotating masses. The energy of these masses is determined as a function of rotational speed, for example calculated or based on a curve. The controller or controller then sets the motor current, from which the torque component dependent only on the motor current, to a limit value, such that, taking into account the speed-dependent, kinetic torque component, the maximum permissible torque is not exceeded. Thus, therefore, for the shutdown in the drive train to existing, speed-dependent energy is predicted as one for the screws after switching still existing energy, so to speak.

It Therefore, the object of the present invention is a control device and a machine tool equipped therewith with an improved Provide torque limit.

to Solution of the problem is in a control device of the aforementioned type, that the limiting device Comparison means for comparing the maximum torque value with of having motor current dependent internal motor torque values, where in the comparison to the replica of the real provided Abgabedrehmoments the respective inner motor torque value by one dependent on an acceleration of the drive train Moment of inertia reduced by the limiting device or the torque maximum value about that of the acceleration of the Powertrain dependent inertia torque value is enlarged. To solve the task is also a equipped with such a control device Machine tool, in particular a hand-held machine tool, z. B. an electric screwdriver, provided.

The Limiting device has z. B. generating means for generating representing the actual delivered output torque Output torque values by decreasing the motor current dependent internal motor torque values of the drive motor to that of the acceleration the powertrain dependent inertia torque values of the powertrain.

The Control device according to the invention, for example Hardware and / or software components may contain one high dynamics ready. The torque limit also works at low maximum torque values.

Further can start or accelerate the machine with high acceleration, without the torque limiting unnecessary intervention. At the Acceleration of the drive train is the internal engine torque in essential to overcome the inertia of the Powertrain needed. This is done by the controller considered advantageous. The one of an acceleration powertrain dependent ratios and not a stationary, each speed-dependent Power of the powertrain forms the basis for torque limitation, so that instead of a substantially stationary operating state a dynamic operating case for torque limitation is based on.

Yet is a sensitive and timely shutdown, too in so-called hard screwdriving, that is, when spontaneous torque peaks occur, readily possible.

The comparison means compare output torque values determined on the basis of the internal engine torque, which are optimally approximated to the real output torque value, with the respectively set or predetermined torque maximum value. For this purpose, the so-called internal engine torque of the drive motor, which in itself depends only on the motor constant and the current used to energize the drive motor, is adjusted for the moment of inertia values of the drive train. The inertia torque values of the drive train contain the dynamic component in the calculation, namely the acceleration of the drive train. This acceleration occurs, for example, when switching on the machine tool or during the intermediate acceleration of a respective drive train. Because the acceleration-dependent and therefore dynamic components of the output-side output torque are taken into account, the control device according to the invention reacts very quickly and switches off when the torque maximum value is reached.

The Control device according to the invention can only with values of the motor current without associated motor voltage work.

For example, the comparison condition for limiting torque is: Mab ≥ Mmax (1) where Mab is a so-called "simulated" output torque determined by the controller, and Mmax is the torque maximum value. An internal torque Mi of the drive motor depends on the motor current Imot and on an engine constant kt of the drive motor: Mab = kt · Imot (2)

The output torque Mab then calculates the controller according to the following formula as follows: Mab = Mi - J · a (3) where J is the moment of inertia of the drive train and a its acceleration. The acceleration a determines the control device according to the following formula as a time derivative of the rotational speed ω: a = dw dt (4)

From the formula (4), the output torque Mab according to the formula (3) can be expressed as follows: Mab = kt · Imot - J · dw dt (5)

It is advantageous for the control device, also other influences of the drive train, which reduce the internal engine torque and thus the output side are not available to take into account. For example, it is provided in the limiting device that it also takes into account friction torque values of the drive train in generating the output torque values. Assuming essentially constant temperature and speed ratios, a friction torque Mr of the drive train can be set as constant: Mab = kt · Imot - J · dw dt - Mr (6)

Advantageous It is, however, when influences on the friction torque taken into account become. Influences are, for example, temperatures in the range of the drive train. For example, a temperature T has an effect square to the respective value of the friction torque Mr. An oil or a grease in the drive train, for example in a transmission, is much more viscous when the temperature drops as at higher temperature. It is therefore advantageous if the control device has an input for a temperature sensor having. In the machine tool according to the invention, For example, in an electric screwdriver, it is advantageous when the drive motor has a temperature sensor in the Near the transmission is arranged. Thus, the temperature sensor detects both the temperature of the drive motor and the transmission, what in the generation or calculation of the friction torque value or the Reibmomentwertverlaufes is advantageous.

Furthermore, a rotational speed ω of the drive motor and / or of the transmission has an effect on the friction torque Mr. This is also taken into account by the control device according to the invention. The speed ω can also be dependent on a respectively set transmission ratio u of the transmission. Mab = kt · Imot - J · dw dt - Mr (T, ω, u) (7)

It is also useful in the control device according to the invention when limitation direction to simulate the actually provided output torque Mab in response to a change in a target speed value is configured. For example, the generating means are configured to generate the output torque values in response to a change in a speed command value. Whenever an increase in the speed is desired, the motor current increases, for example because a regulation of the control device so prescribes it. However, the output side available speed of the drive train does not increase immediately, for example due to magnetic influences, due to friction influences and the like more. Acceleration values are therefore initially or insufficiently available for determining a moment of inertia value. This is taken into account in the inventive control device by a time-limited correction, which starts with an acceleration request.

Advantageously, the generating means are adapted to generate the output torque values by reducing the internal motor torque values Mi by compensation values K (t). These compensation values K (t) serve to compensate for a rise of the motor current Imot after an increase of a speed command value ωsoll for a predetermined period of time. In this period, the increase of the motor current Imot initially causes no change in the output side available speed ω and thus no acceleration of the drive train. Mab = kt · Imot - J · dw dt - Mr (T, ω, u) - K (t) (8)

Especially when the output torque values are calculated, where sensor values It may be that peak values are not plausible are, occur. Therefore, it is advantageous if the control device Plausibility check, for example Filters, integrators and the like, which are plausible the output torque values and / or these underlying sensor values. A single overshoot of, for example, the output torque values, which immediately lead to a torque limitation of the drive train would be filtered out in this way, for example.

The Plausibility check, for example, already take place on the part of the generating means, so that the generated Output torque values directly used by the comparison means become. But also on the side of the comparison means the plausibility check occur.

It it is understood that a control device according to the invention instead of reducing the internal engine torque Mi by one Acceleration of the powertrain dependent inertia torque values J · a of the drive train and / or by a friction torque Mr and / or Compensation values K (t) also correspond to the torque maximum value to depend on an acceleration of the powertrain Moment of inertia values and / or friction moments and / or compensating values could increase it before using it with the inner one Engine torque Mi compares. This procedure is equivalent.

The Torque limitation of the control device according to the invention is then particularly effective when they have a switching device for switching the drive motor to a braking mode, when the output torque values reach the torque maximum value or exceed. Thus, the powertrain goes immediately in braking mode and stops. Especially with a hard one Screwing, for example, to destroy the screw and / or a screw insert of a screwdriver could, this is beneficial. The switching device has For example, a switch for shorting the drive motor. If the drive motor is an electronically commutated drive motor is also an energizing in reverse direction to a stop the drive train done.

The Limiting device is expediently switched off. For this purpose, a separate switch is preferably provided. It understands itself, that too, for example, a switch on the maximum torque values are adjustable, usable for switching off the limiting device is.

at Switching to the braking mode feeds the drive motor expediently return electrical energy to an electrical energy store, For example, in an accumulator of a cordless screwdriver.

Either the shutdown and the braking of the drive motor or drive train by means of a short circuit of the drive motor can not suffice, for example, with a small screw that with high speed, but a small moment is screwed, a tearing off the screw head when it hits the workpiece, and / or deep penetration of the screw into the workpiece to avoid.

The Limiting device is therefore advantageous for sending control commands for driving a current supply device energizing the drive motor designed in a braking operation, in which the energizing device a drive motor decelerating, to a respective direction of rotation of the drive motor generates opposing rotating field. The limitation device controls to limit the output torque provided on the output side to the torque maximum value of the energizing device to the Braking operation under at least one braking condition. The braking condition Advantageously, that a quotient of the output torque and a present in the drive train rotational energy smaller or is equal to a maximum ratio.

One The basic idea is that the power supply to a Brake operation is controlled, whereby one to the direction of rotation of the Drive motor generates opposing rotating field. The drive motor is so actively slowed down.

One however, such braking is not in all cases of operation advantageous, for. B. because thereby the energy consumption of the power tool increases, which is undesirable, especially in a battery operation is. Furthermore, the machine would heat up, causing the cooling effort elevated.

If For example, screws with a relatively large moment, however Low speed are screwed, is such a deceleration not beneficial. If, for example, a big screw is screwed into a workpiece, the drive motor rotates usually with relatively less Speed, but generates a high moment. For example, it is rising a motor current of the drive motor when the screw is complete is screwed. The limiting device then switches the drive motor, for example, based on a comparison of the torque maximum value with a motor current value or a value derived therefrom. Even if the drive train then continues to rotate for a short time, harms not the screw.

The case is otherwise mounted on small screws, especially if they impact a hard, unyielding workpiece surface at the end of a screwing operation. Such a hard screwing is detected by the controller. The braking condition is then that the output torque in relation to the rotational energy of the drive train when screwing is relatively small, for example according to the following formula: Mab erot ≤Xmax (a) where Mab is the output torque, Erot is the driveline rotational energy, and Xmax is the maximum ratio.

The Maximum ratio Xmax is preferably chosen that the active shutdown of the drive motor, d. H. the energizing in the opposite direction of rotation of the drive motor, in particular at sensitive workpieces and / or sensitive screwed Screw damage in torque shutdown case avoids. It is possible that the maximum ratio Xmax on the control device or the machine tool adjustable is, for example by means of a suitable switch, a parameterization software or similar. Anyway, by the invention Approach takes into account that, for example, small Screw the output torque Mab relatively is small while the speed ω of the drive train is comparatively large. The speed of the powertrain For example, the speed of the drive motor, the speed a tool holder or the like, preferably gear ratios be taken into account.

The following formula (b) illustrates the relationship between the rotational energy Erot and the rotational speed ω of the powertrain: Erot = 1 2 Jω 2 (B) where J is the moment of inertia of the drive train and ω the speed of the drive train, the control device z. B. determined based on the speed of the drive motor or a tool holder.

The Control device according to the invention, for example Hardware and / or software components may contain one high dynamics ready. The torque limit also works at low maximum torque values.

Yet is a sensitive and timely shutdown, too in so-called hard screwdriving, that is, when spontaneous torque peaks occur, readily possible.

Accordingly, it is an advantageous braking condition if the output torque Mab is set in proportion to the rotational speed ω of the drivetrain, preferably to the first power of the rotational speed ω of the drivetrain. This is the case with the following formulas (c) and (d): Mab ω ≤ Y max (c) wherein Ymax is a ratio adjustable or set from the controller with respect to the rotational speed ω of the powertrain, and in the following formula (d), Zmax is a ratio with respect to the square of the rotational speed ω.

Another braking condition which is advantageous when switching over into the advantageous braking mode is when the control device or the limiting device evaluates the respective rate of increase of the output torque. If the output torque increases sharply, which is usually only the case with relatively small screws, the limiting device will suitably consider the following formula (e): DMAB dt ≥ H (e) where H is the rate of increase of the output torque Mab.

A further advantageous braking condition is that the output torque reaches or exceeds the predetermined slew rate in response to a minimum speed of the drive motor. Ie. the active braking by counter-energizing is activated by the controller only if, for example, small screws are rotated at high speed. Just then, the active braking is advantageous because there is a large rotational energy in the drive train, which could lead to damage to the screw and / or the workpiece. The corresponding braking condition, which then tests the limiting device, is represented by the following formula (f): ω ≥ ωmin (f) where ωmin is the minimum speed.

As already explained above, is the active shutdown of the drive motor by Gegenbestromung particularly advantageous if the output torque before switching off relatively small is what z. B. when screwing small screws is the case. So For example, it is advantageous if the at least one braking condition includes that a predefinable or predetermined desired maximum value Smax or the output torque Mab representing output torque values before switching equal to or less than a predetermined threshold torque value Ms is. The threshold torque value Ms is in the range, for example from 2 to 5 Nm advantageous. It is therefore taken into account that switching off and counter-current especially at small Screws that are screwed with little moment, advantageous is used.

The braking condition may also include that the maximum torque value at which the limiting device becomes active is below a threshold torque value. Mab ≤ Ms (g)

Furthermore, it is expedient if the limiting device is designed to output the control commands in response to a braking course of the drive train during braking operation by opposing current supply. If, for example, the active braking of the drive train results in the torque maximum value not being reached or being reached only slowly, the limiting device expediently reduces the braking effect and transmits corresponding control commands to the energizing device. Preferably, it is provided that the limiting device is designed to control the braking process. For example, the control device observes the maximum torque value that is actually available on the output side or that is reproduced by the control device, and sends corresponding control commands to the current supply device about the decelerating rotation Set field depending on the output torque. In any case, it is advantageous if the limiting device controls the braking course in such a way that the output torque rapidly reaches the torque maximum value but does not exceed it.

Farther it is expedient if the limiting device at the beginning of the braking operation, the energizing device to a stronger braking and then the braking decreases or regulates depending on the braking process. The reduction can be done step by step, for example. By this measure it is ensured that the maximum torque value possible is not exceeded, but at the beginning of braking is optimally braked, in any case, an excess to prevent the torque maximum value.

The Machine tool is preferably a hand-held machine tool. The Although machine tool according to the invention is expediently a screwdriver. But also in other applications, in where a fast, torque-dependent shutdown desired is, the invention can be used, for example in hedge trimmers.

following an embodiment of the invention will be explained. Show it:

1 an electrical functional diagram of a machine tool with a control device according to the invention,

2 a schematic side view of the machine tool,

3 a curve of a delivery torque of the hand machine tool according to 1 . 2 as well as other curves,

4 Characteristics of output torques in active braking by counter-energizing and

5 a field winding arrangement of the drive motor of the machine tool with current curves in a braking operation by short circuit and an active braking by counter-energization.

A powertrain 11 a machine tool 10 , For example, an electric screwdriver, includes a drive motor 12 that has a gearbox 13 a drive spindle 14 with a tool holder 15 drives. Into the tool acceptance 15 is for example a screwdriver bit 16 can be used for screwing a screw.

The powertrain 11 is from a controller 17 controlled. The control device 17 contains a microprocessor 18 for executing program code of a control module 19 and a limiting module 20 , which is an output side, on the drive train 11 available output torque Mab limited. The control module 19 and the bounding module 20 are for example in a memory 21 the control device 17 saved.

Furthermore, the control device contains 17 an energization module 22 for example, to generate a rotating field in a first direction 63 and or a second direction 64 for the drive motor 12 , The energization module 22 may also include a pulse width modulator. The drive motor 12 For example, it may be a series motor or an electronically commutated motor. Instead of in the control device 17 integrated power supply module 22 would also be one of the controller 17 separate and controllable by this energizing device possible.

Although the electrical drive energy for a machine tool according to the invention can be provided for example by a power grid. At the machine tool 10 However, it is an electrical energy storage 23 , for example, to a housing 25 the machine tool 10 bottom battery pack 24 , for providing electrical operating energy for the machine tool 10 intended. This works as follows:
An operator of the machine tool 10 can, for example, on a rotary encoder containing a rotary and / or pressure switch 26 Target speed values 27 specify a desired speed ωsoll. The control module 19 regulates the drive motor 12 based on the target speed values 27 as well as actual speed values 28 which is an actual rotational speed ω ist of the drive motor 12 represent. For example, detects a speed sensor 29 the respective actual rotational speed ω is the drive motor 12 , The speed sensor 29 can be part of the drive motor 12 form.

The control module 19 generated based on the speed values 27 . 28 Target current values 30 for the lighting module 22 , The energization module 22 represents based on the desired current values 30 a motor current Imot for energizing the motor 12 one.

The motor current Imot forms a first input value for the limiting module 20 that is a limiting device 31 for limiting a delivery torque Mab to the powertrain 11 represents. As another input value for the limiting module 20 is at a shutdown torque sensor 32 a maximum torque on the drive train 11 is to be available, adjustable, namely a torque maximum value Mmax. The shutdown torque sensor 32 For example, is a potentiometer switch to which an operator of the machine tool 10 can set a desired Abschaltmoment. It is understood that a fixed shutdown torque may be provided in a control device according to the invention, for example, an absolute value. In a screwdriver, which is prepared for predetermined applications, such as screws always the same screw type, it is even advantageous if the output side provided output torque Mab is fixed.

The energization module 22 and / or a separate current sensor 33 generate motor current values 34 representing the respective motor current Imot. The motor current value 34 forms an input value for an engine torque function 35 , which is the internal engine torque Mi of the drive motor 12 representing engine torque values 36 generated.

An exemplary course of the internal engine torque values 36 is in 3 shown. Starting at a time t1, the internal engine torque Mi rises to a time t2 correlated with an acceleration a of the drive train 11 , which starts at time t1, strong. If now a comparison means 37 forming comparative function 38 of the limiting module 20 the engine torque values 36 directly with the at Abschaltmomentgeber 32 Set torque maximum value Mmax would compare, it would already at a time t1 'detect an excess of the maximum torque value Mmax and a shutdown command 39 to the power module 22 for switching off the energizing of the drive motor 12 send. The machine tool 10 would then turn off the screwing too early. This is where the invention starts.

From the inner engine torque values 36 namely losses of the drive train 11 that are acceleration dependent subtracted. The engine torque function 35 forms part of generating means 40 with further a generating function 41 for generating output torque values 42 according to the above formula (8). The generating function receives this 41 the internal engine torque values 36 that the generating function 41 around moment of inertia values 43 diminished, that of an inertial moment function 44 based on a respective acceleration of the drive train 11 according to the formulas (3) and (4) on the basis of the actual rotational speed values 28 be generated. The moment of inertia function 44 calculates a respective acceleration-dependent moment of inertia of the drive train 11 , It goes without saying that, as an alternative or in addition to the calculation, corresponding moments of inertia in the memory 21 can be stored.

The generating function 41 reduces the internal engine torque values 36 according to the formula (7) for friction torque values 45 that of a friction torque function 46 are generated and a friction torque Mr of the drive train 11 represent.

The friction torque function 46 generates the friction torque values based on the respective actual speed values 28 of the powertrain 11 , In addition, the friction torque function takes into account 46 a gear ratio u of the transmission 13 , which is set in each case. If the transmission 13 Turning at higher speeds, this affects more on the friction of the drive train 11 out. One on the gearbox 13 arranged translation sensor 47 detects a respective shift position of the transmission 13 and accordingly transmits the gear ratio u representing gear ratios 48 to the friction torque function 46 ,

In addition, the friction torque function takes into account 46 in the generation of friction torque values 45 temperature values 49 that is a temperature sensor 50 reports. The temperature sensor 50 is suitably in a range between the drive motor 12 and the transmission 13 arranged so that it can detect the temperature of both components. The temperature sensor is advantageous 50 even a component of the drive motor 12 , For example, a sensor in the excitation windings w1, w2, w3 and other excitation windings wn of the drive motor 12 is arranged. Thus, the temperature sensor detects 50 the temperature of the drive motor 12 and at the same time of the transmission 13 , For example, the lubricant.

Finally, subtract the generation function 41 from the internal engine torque values 36 still comm pensationswerte 51 a compensation function 52 , The compensation function 52 receives as input values the target speed ωsoll and the actual speed ω ist. Based on an increase of the setpoint speed ωsoll the compensation function recognizes 52 an acceleration request. In the first moment after increasing the setpoint speed ωsoll, although the motor current Imot increases, but not the actual speed ωist. This compensates for the compensation function 52 by generating the compensation values 51 that the compensation function 52 to the generating function 41 for the output torque values 42 transmitted. This pulls the compensation values 51 from the internal engine torque values 36 so that overall the formula (8) is realized.

Furthermore, the generation function takes into account 41 expediently a respective transmission ratio u of the transmission 13 , By taking into account the gear ratio u reduces the generation function 41 a driven side on the drive motor 12 the engine output torque Mmab and generates the output torque values 42 that mimic the real existing output torque Mab.

The comparison function 38 now compares the output torque values 42 with the maximum torque value Mmax. While the internal engine torque Mi already between the times t1 and t3 exceeds the maximum torque Mmax, resulting in an early shutdown of the drive train 11 lead, the limiting device switches 31 the drive motor 12 now only at a time t4 from. Thus, the complete output side desired output torque Mab is available until time t4, and the unillustrated screw can be screwed with maximum torque and high dynamics.

The control device 17 Switches the powertrain 11 upon reaching the torque maximum value Mmax z. B. only off.

Preferably, the controller switches 17 the drive train 11 but not only off, but in a braking operation. A switching device 53 switches the drive motor 12 for example, in a short circuit. The switching device 53 has a switch 55 , For example, a relay or an electronic switch, to short-circuit the drive motor 12 , This also leads to a feeding back of electricity in the electrical energy storage 23 so the machine tool 10 works sparingly.

A stator of the drive motor 12 contains, for example, excitation windings w1, w2, w3-wn, which pass through the lighting module 22 be energized. The respective exciter windings w1wn are from the lighting module 22 , which forms an energizing device, energized with excitation currents. In 5 For example, an excitation current ID1 flowing across the excitation winding w1 is shown. The energization module is equipped to switch the excitation currents 22 via switches S11, S12, S13, S1n of a first switch group, which are connected on the input side to a supply potential Vcc and the output side to the windings b1-bn, and switches S21-S2n of a second switch group, on the input side to the exciter windings w1-wn and on the output side are connected to a ground potential Mp.

at a brake operation, for example, the switches S11-S1n closed so that in stitches K11, K12, K13-Kn over the excitation windings w1, w2, w3-wn respectively short-circuit currents I11, I12, I13 flow. It is also possible to close the switches S21-S2n, so that in Mesh K21, K22, K23-K2n short-circuit currents I21, I22, I23 can flow.

The limitation device 31 is at a switch 54 switched off.

The control device 17 receives the temperature values 49 at an entrance 56 and also has an entrance 57 for the respective translation value 48 ,

In 3 is plotted a curve of a total correction value Kges, with the course of the acceleration a of the drive train 11 essentially correlated. Between times t1 and t3, between which the internal moment Mi substantially accelerate the drive train 11 is used and the output side is not ready, a particularly strong correction or reduction of the internal engine torque Mi is required to determine the actual existing output torque Mab.

It is understood that when detecting sensor values and / or when determining the output torque Mab, the output side of the drive train 11 is available, individual measurement or calculation errors may occur. For their compensation, the generating means advantageously have plausibility check means 58 , The plausibility checker 58 For example, they contain a filter 59 which filters out implausible values of, for example, the output torque Mab. Such a value is, for example, a peak output rotation torque value 60 that exceeds the maximum torque value Mmax. This would in itself lead to an immediate shutdown of the drive motor 12 to lead. The filter 59 however, compares the instantaneous output torque value 60 with previous output torque values 61 and 62 and filters the outlier "output torque value 60 far out of range through the output torque values 61 . 62 determinable course of the output torque Mab is.

Beyond the above-mentioned short-circuit braking operation of the drive motor, the machine tool is 10 also to a kind of active braking by energizing the drive motor in the opposite sense of direction 12 designed.

The energization module 22 is for energizing the drive motor 12 , ie the excitation winding w1-wn designed in the sense of braking. The energization module 22 generates, for example, a decelerating, to a respective direction of rotation 63 of the drive motor 12 opposite rotating field 64 , In this case, for example, via the excitation winding w1 an exciting current ID2 flows, which flows opposite to the previously described exciter current ID1. The excitation currents ID1, ID2 each flow at a comparable time, but are assigned to oppositely rotating fields.

The limitation device 31 controls the energizing device 22 for the braking operation, in which the rotating field 64 the drive motor 12 decelerates, based on control commands 65 ,

The limitation device 31 sends the control commands 65 depending on the initially described braking conditions, in particular according to at least one of the formulas (a) - (g).

An in 4 drawn curve 66 shows, for example, a curve of the output torque Mab when screwing a relatively small screw. The output torque Mab is relatively low until a time t5. By that time, most of the energy needed to accelerate the powertrain is needed. The drive rotor 12 the screw rotates at a relatively high speed ω from time t5, with the torque increasing with increasing screw depth due to higher frictional effects between time t5 and time t6.

Although the output torque Mab is at the curve 66 between times t5 and t6 relatively low, the speed ω, however, high. Therefore, the drivetrain 11 existing rotational energy Erot relatively large. In this initial situation led a further rotation of the drive train 11 from the time t6 at or immediately before reaching a maximum torque value Mmax1, for example, to destroy the screw, to an excessively deep screwing the screw into the workpiece or both. To remedy this situation, the limiting device controls 31 the energizing device or the energizing module 22 to the above-mentioned braking operation based on the opposing rotating field 64 at. Namely, the output torque Mab is Erot in relation to the rotational energy present in the drive train in an operation case according to the curve 66 small, so the limiting device 31 determined on the basis of the braking condition (a) the need for active braking operation.

The situation is different with, for example, a large screw. In 4 is an example of a course 67 of the output torque Mab. At time t5, the output torque Mab increases relatively sharply. At time t6, upon reaching a maximum torque value Mmax2, the limiting device transmits 31 only the shutdown command 39 to the energizing device 22 so that the drive motor 12 is switched off. A slowing down of the drive motor 12 by means of an opposing rotating field 64 is not necessary in this case of operation and would only increase the energy consumption and thus the useful life of the energy storage 23 shorten.

It is particularly advantageous if the limiting device 31 the energizing device 22 or the Bestromungsmodul to the braking operation by means of the brake rotating field 64 controls when the output torque Mab increases particularly strong. For example, if a screw head of a small screw strikes the workpiece, so to speak enters a hard screwing, for example, a gradient 68 of the output torque Mab. Just then it is advantageous if the limiting device 31 the energization module 22 for generating the decelerating rotating field 64 controls.

Furthermore, it is expedient that the limiting device 31 the control commands 65 depending on a braking course of the drive train 11 outputs. So controls the limiting device 31 for example, at the time t6, the energizing device 22 such that it drives the drive 12 slowing down. The output torque Mab therefore decreases very sharply or no longer from time t6, what in a braking process 69 in 4 is clarified. From time t7, the limiting device controls 31 the energization module 22 to a reduced braking operation, so that the output torque Mab increases from the time t7 until it reaches the torque maximum value Mmax1 at the time t8.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 10341975 A1 [0002]

Claims (27)

Control device for controlling or regulating an electric drive motor ( 12 ) of a drive train ( 11 ), in particular a screwing machine tool ( 10 ), with a limiting device ( 31 ) for limiting one on the drive train ( 11 ) on the output side provided output torque (Mab) to a maximum torque value (Mmax, Mmax1, Mmax2) based on a motor current value ( 34 ), a motor current (Imot) for energizing the drive motor ( 12 ), characterized in that the limiting device ( 31 ) Comparison means ( 37 ) for comparing the torque maximum value (Mmax, Mmax1, Mmax2) with engine torque (Imot) dependent inner engine torque values ( 36 ), wherein in the comparison to the simulation of the actually provided output torque (Mab) the respective internal motor torque value ( 36 ) about one of an acceleration (a) of the drive train ( 11 ) dependent inertia torque value ( 43 ) by the limiting device ( 31 ) or the maximum torque value (Mmax, Mmax1, Mmax2) by that of the acceleration (a) of the drive train ( 11 ) dependent inertia torque value ( 43 ) is enlarged. Control device according to claim 1, characterized in that the limiting device ( 31 ) Generating means ( 40 ) for generating output torque values representing the actually provided output torque (Mab) ( 42 ) by reducing the motor current (Imot) dependent inner motor torque values ( 36 ) of the drive motor ( 12 ) by the acceleration (a) of the powertrain ( 11 ) dependent inertia torque values ( 43 ) of the drive train ( 11 ), and that the comparison means ( 37 ) for comparing the output torque values ( 42 ) are configured with the torque maximum value (Mmax, Mmax1, Mmax2). Control device according to claim 1 or 2, characterized in that the limiting device ( 31 ) for simulating the actually provided output torque (Mab) for reducing the respective internal engine torque value ( 36 ) by at least one friction torque value ( 45 ) of the drive train ( 11 ) or for increasing the torque maximum value (Mmax, Mmax1, Mmax2) by the at least one friction torque value ( 45 ) is configured. Control device according to claim 2, characterized in that it comprises at least one input ( 56 ) for at least one temperature value ( 49 ) of the drive train ( 11 ), and that the limiting device ( 31 ) for determining the at least one friction torque value ( 45 ) of the drive train ( 11 ) in dependence on the at least one temperature value ( 49 ) is configured. Control device according to claim 2 or 3, characterized in that the limiting device ( 31 ) for determining the at least one friction torque value ( 45 ) of the drive train ( 11 ) as a function of at least one speed value ( 28 ) of the drive train ( 11 ) is configured. Control device according to one of the preceding claims, characterized in that the drive train ( 11 ) a the drive motor ( 12 ) downstream transmission ( 13 ), and in that the control device has an input ( 57 ) for a translation value ( 48 ) or a sensor for determining the translation value ( 48 ), the translation value ( 48 ) on the transmission ( 13 ) set gear ratio (u) represents. Control device according to claim 6, characterized in that the limiting device ( 31 ) for simulating the actually provided output torque (Mab), in particular for generating the output torque values ( 42 ), depending on at least one transmission ratio (u) of the transmission ( 13 ) is configured. Control device according to one of the preceding claims, characterized in that the limiting device ( 31 ) for simulating the actually provided output torque (Mab) as a function of a change in a setpoint speed value ( 27 ) is configured. Control device according to one of the preceding claims, characterized in that the limiting device ( 31 ) for simulating the real provided output torque (Mab) by reducing the internal motor torque values ( 36 ) around compensation values ( 51 ) or increasing the torque maximum value (Mmax, Mmax1, Mmax2) by compensation values ( 51 ), the compensation values ( 51 ) an increase of the motor current (Imot) after an increase of a setpoint speed value ( 27 ) for a predetermined period of time in which the increase in the motor current (Imot) substantially no change in the output side rotational speed (ω) of the drive train ( 11 ) causes. Control device according to one of the preceding claims, characterized in that it comprises plausibility check means ( 58 ), in particular filter media ( 59 ), for checking a plausibility of the output torque values ( 42 ) and / or to determine the output torque values ( 42 ) to be evaluated sensor values. Control device according to one of the preceding claims, characterized in that the comparison means ( 37 ) for performing a plausibility check upon reaching and / or exceeding the maximum torque value (Mmax, Mmax1, Mmax2) by the output torque values ( 42 ) are configured. Control device according to one of the preceding claims, characterized in that it comprises a switching device ( 53 ) for switching the drive motor ( 12 ) in a braking operation when the output torque values ( 42 ) reach or exceed the maximum torque value (Mmax, Mmax1, Mmax2). Control device according to claim 12, characterized in that the switching device ( 53 ) at least one switch ( 55 ) for short-circuiting the drive motor ( 12 ) having. Control device according to one of the preceding claims, characterized in that the limiting device ( 31 ) for sending control commands ( 65 ) for driving a drive motor ( 12 ) energizing energizing device ( 22 ) is configured in a braking operation, in which the energizing device ( 22 ) a drive motor ( 12 ) decelerating, to a respective direction of rotation ( 63 ) of the drive motor ( 12 ) opposing rotating field ( 64 ) and that the limiting device ( 31 ) for limiting the output torque provided on the output side (Mab) to the torque maximum value (Mmax, Mmax1, Mmax2) the energizing device ( 22 ) to the braking operation under at least one braking condition, wherein the at least one braking condition comprises that a quotient of the output torque (Mab) and one in the drive train ( 11 ) is less than or equal to a maximum ratio (Xmax). Control device according to claim 14, characterized in that the at least one braking condition comprises that the output torque (Mab) in relation to a rotational speed (ω) of the drive train ( 11 ), in particular the first power of the rotational speed (ω) of the drive train ( 11 ), below or equal to a predetermined or adjustable ratio (Ymax; Zmax). Control device according to Claim 14 or 15, characterized characterized in that the at least one braking condition comprising that the output torque (Mab) has a predetermined slew rate (H) reached or exceeded. Control device according to claim 16, characterized in that the at least one braking condition comprises that the output torque (Mab) the predetermined rate of increase (H) in dependence on a minimum speed (ωmin) of the drive motor ( 12 ) reaches or exceeds. Control device according to one of claims 14 to 17, characterized in that the at least one braking condition comprises that a predefinable or predetermined desired maximum value (SMmax) and / or the output torque (Mab) representing output torque values ( 42 ) are equal to or less than a predetermined threshold torque value (Ms) before switching. Control device according to one of the claims 14 to 18, characterized in that the at least one braking condition includes that the maximum torque value (Mmax, Mmax1, Mmax2) below a threshold torque value. Control device according to one of claims 14 to 19, characterized in that the limiting device ( 31 ) for issuing the control commands ( 65 ) as a function of a braking course ( 69 ) of the drive train ( 11 ) is configured during braking operation. Control device according to claim 20, characterized in that the limiting device for controlling the braking course ( 69 ) is configured. Control device according to claim 21, characterized in that the limiting device the braking course ( 69 ) so that the output torque (Mab) sets the maximum torque value (Mmax, Mmax1, Mmax2). Control device according to one of claims 21 to 22, characterized in that the limiting device at the beginning of the braking operation, the energizing device ( 22 ) drives to a stronger braking and the braking then depending on the braking course ( 69 ) reduces or regulates. Control device according to one of the preceding claims, characterized in that the limiting device ( 31 ) can be switched off. Machine tool ( 10 ), in particular hand machine tool, with an electric drive motor ( 12 ) having drive train ( 11 ), characterized in that it comprises a control device ( 17 ) according to one of the preceding claims for controlling or regulating the drive motor ( 12 ) having. Machine tool according to claim 25, characterized in that the drive train ( 11 ) a the drive motor ( 12 ) downstream transmission ( 13 ), and that the drive motor ( 12 ) at least one on a the transmission ( 13 ) facing side of the drive motor ( 12 ) arranged temperature sensor ( 50 ), wherein the at least one temperature sensor ( 50 ) for the transmission of temperature values ( 49 ) with the control device ( 17 ) connected is. Machine tool according to claim 25 or 26, characterized in that it comprises a hand-held machine tool ( 10 ) for drilling and / or screwing.