PERCENTAGE UNIT

Description

State of the art

[0001] Impact units, in particular for a drill and / or percussion hammer, with a control unit intended to control and / or regulate a pneumatic impact mechanism are already known. Disclosure of the invention

[0002] The invention is based on a percussion unit which is designed as a non-linear, oscillatable system, in particular for a drill and / or percussion hammer, with a control unit which is intended to control and / or regulate a pneumatic percussion mechanism.

[0003] It is proposed that the control unit be provided, in at least one operating state in which an operating parameter is set as a supercritical operating value, temporarily setting the operating parameter to a starting value for a change from idle operation to percussion operation. The operating parameter is a percussion mechanism speed, and the starting value lies in a range of the percussion mechanism speed at which an amplitude frequency response of a vibrating body of the percussion mechanism has an unambiguous solution, and the supercritical operating value lies in a range of the percussion mechanism speed at which the amplitude frequency response has an ambiguous solution, and the starting value lies below the supercritical operating value. In this context, a "percussion mechanism unit" is to be understood in particular as a unit provided for operating a percussion mechanism. The percussion mechanism unit can in particular have a control unit.The percussion unit can have a drive unit and / or gear unit provided for driving the percussion mechanism. A "control unit" in this context is understood to mean, in particular, a device of the percussion unit provided for controlling or regulating, in particular, the drive unit and / or the percussion mechanism. The control unit can preferably be designed as an electrical, in particular an electronic, control unit. A "drill and / or percussion hammer" in this context is understood to mean, in particular, a machine tool provided for machining a workpiece with a rotating or non-rotating machining tool, wherein the machining tool can be subjected to impact pulses by the machine tool. The machine tool is preferably designed as a handheld power tool operated manually by a user.In this context, a "percussion mechanism" is understood to mean, in particular, a device comprising at least one component intended for generating and / or transmitting an impact pulse, in particular an axial impact pulse, to a machining tool arranged in a tool holder. Such a component can be, in particular, a striker, a firing pin, a guide element, such as, in particular, a hammer tube, and / or a piston, such as, in particular, a pot-shaped piston, and / or another component deemed appropriate by a person skilled in the art. The striker can transmit the impact pulse directly to the machining tool or, preferably, indirectly. Preferably, the striker can transmit the impact pulse to a firing pin, which transmits the impact pulse to the machining tool. "Provided" is understood to mean, in particular, specially designed and / or specially equipped.In this context, "idle operation" is understood to mean, in particular, an operating state of the percussion mechanism characterized by the absence of regular percussion pulses or in which only low percussion pulses occur. "Low" percussion pulses in this context are understood to mean, in particular, percussion pulses that have less than 50%, preferably less than 25%, and particularly preferably less than 10% of the impact strength intended for machining a workpiece. The percussion mechanism can preferably have an idle mode in which it is designed for idle operation. In this context, "impact operation" is understood to mean, in particular, an operating state of the percussion mechanism in which the percussion mechanism preferably exerts regular percussion pulses at an impact strength intended for machining a workpiece.The percussion mechanism can preferably have a percussion mode in which it is designed for percussion operation. "Regularly" in this context is understood to mean, in particular, recurring, especially at a specified frequency. An "operating state" in this context is understood to mean, in particular, a mode and / or a setting of the control unit. The operating state can depend, in particular, on user settings, ambient conditions, and other parameters of the percussion mechanism. A "change" from idle mode to percussion mode in this context is understood to mean starting the percussion mechanism from idle mode. The change to percussion mode can occur, in particular, when the percussion mechanism is switched from idle mode to percussion mode.In this context, a "starting value" is understood to mean, in particular, a stable operating parameter suitable for reliably starting the percussion mechanism. "Reliable" in this context is understood to mean, in particular, that when the percussion mechanism switches from idle mode to percussion mode, percussion operation begins in more than 90%, preferably more than 95%, and particularly preferably more than 99% of cases. "Temporary" in this context is understood to mean, in particular, a limited period of time. In particular, the period can be shorter than 30 seconds, preferably shorter than 10 seconds, and particularly preferably shorter than 5 seconds. A reliable start of percussion operation can be achieved. Percussion operation with operating parameters unsuitable for starting the percussion mechanism may be possible. Operating parameters unsuitable for starting the percussion mechanism may be permissible as a working value.Idle operation with operating parameters unsuitable for starting the percussion mechanism may be possible. Operating parameters unsuitable for starting the percussion mechanism may be permissible as idle values. The reliability of the percussion mechanism may be increased. The performance of the percussion mechanism may be increased.

[0004] In this context, a "supercritical" operating value is understood to mean, in particular, an operating parameter at which a successful transition from idle operation to impact operation is not guaranteed. In particular, with an impact mechanism in impact mode, impact operation can start in less than 50%, preferably in less than 80%, and particularly preferably in less than 95% of cases at a supercritical operating value. A relationship between an operating parameter and the impact amplitude of a striker or another component of the impact mechanism used to generate impacts can, in particular, exhibit hysteresis. A supercritical operating parameter can, in particular, be characterized by exceeding or falling below a limit value, above or below which a function of the amplitude is ambiguous depending on the operating parameter.A supercritical work value during an already successful impact operation can preferably be characterized by a stable continuation of the impact operation. The performance of the impact mechanism can be increased with a supercritical operating parameter. The performance of a machine tool equipped with the impact mechanism can be increased. Operation of the impact mechanism with a supercritical work value can be permissible. The impact mechanism can preferably be operated in idle mode with an idle value that corresponds to the supercritical start value. The impact mechanism can be operated in impact mode and in idle mode with a supercritical operating parameter.

[0005] Furthermore, an operating mode change sensor is proposed, which is provided for signaling a change in operating mode. In particular, the operating mode change sensor can signal a change from idle mode to impact mode to the control unit. The operating mode change sensor can be provided to detect contact pressure of a tool on a workpiece. It can advantageously be detected when the user begins a machining process. Particularly advantageously, the operating mode change sensor can detect a switching of the impact mechanism, in particular an opening and / or closing of idle openings and other openings of the impact mechanism that are provided for an operating mode change. The operating mode change sensor can detect a displacement of an idle and / or control sleeve that is provided for an operating mode change of the impact mechanism. The control unit can advantageously detect when an operating mode change of the impact mechanism takes place.The control unit can advantageously change the operating parameters to support and / or enable the operating mode change. Impact operation can be started reliably.

[0006] Furthermore, an impact sensor unit is proposed, which is designed to signal impact operation. In particular, the impact sensor unit can signal to the control unit that the impact mechanism is executing impact operation. A successful start of the impact mechanism can advantageously be detected by the control unit. A suspension of impact operation can advantageously be detected by the control unit. In particular, the suspension of impact operation, during which the impact mechanism continues to be in impact mode, can be detected. The control unit can restart the impact mechanism.

[0007] It is proposed that the impact sensor unit be provided to detect impact operation by evaluating at least one drive parameter. A "drive parameter" in this context is understood to mean, in particular, a rotational speed, a current consumption, and / or a voltage. The impact sensor unit can detect impact operation from the current consumption of the drive unit. An increasing current consumption can indicate impact operation. The impact sensor unit can preferably have a load estimator. A "load estimator" in this context is understood to mean, in particular, a control device known to those skilled in the art, which is provided to estimate a drive load resulting from impact operation by evaluating a rotational speed curve of the drive unit. In particular, the load estimator can estimate the drive load resulting from impact operation by evaluating periodic rotational speed fluctuations.The load estimator preferably takes into account known periodic loads during the evaluation, such as the angular dependence of a gear ratio of the eccentric gear, time-dependent fluctuations in the supply voltage of a power control of the drive unit, and loads caused by the mass inertia of the drive unit and parts of the impact mechanism driven by the drive unit. The load estimator can preferably differentiate the influences of impact operation on a speed signal from other influences, such as a load generated by a rotating tool during machining of a workpiece. Impact operation can be reliably detected. The speed signal may already be available to control the drive unit. The impact sensor unit can use the existing speed signal. Additional sensors can be avoided. A load estimator can dispense with the calculation of a dynamic model.A computing unit of the load estimator can be particularly cost-effective. The impact sensor unit can be particularly cost-effective. In a further embodiment of the invention, it is proposed that the impact sensor unit have a load observer. In this context, a "load observer" is to be understood in particular as a control device known to those skilled in the art, which is intended to estimate an output drive torque of the drive unit from a rotational speed and current consumption of the drive unit with the aid of a calculated dynamic model of the drive unit. The load observer can detect a load characteristic of impact operation in a curve of the estimated drive torque.In particular, the load observer can differentiate the influences of impact operation on the drive torque from other influences, such as a load created by a rotating tool during machining of a workpiece. Impact operation can be reliably detected. The speed signal and current consumption may already be available to control the drive unit. The impact sensor unit can use the existing speed signal and current consumption. Additional sensors can be avoided. The impact sensor unit can be cost-effective. The impact sensor unit can take dynamic loads of the drive unit into account particularly well. The impact sensor unit can be particularly reliable.

[0008] In a further embodiment of the invention, it is proposed that the impact sensor unit comprise at least one sensor for a mechanical measurement variable, which is intended to detect the impact operation. A "mechanical" measurement variable in this context is understood to be a measurement variable that represents a movement and / or a force, such as, in particular, a force, an acceleration, a speed, a pressure, a sound pressure, or a deformation, and / or, in particular, a measurement variable that deviates from a purely electrical value. In particular, the impact sensor unit may comprise an acceleration sensor. Accelerations caused by the impact pulses can be particularly well measured. The acceleration sensor can preferably be arranged close to the point where the impact occurs, for example, on a guide tube, a tool holder, or a gear housing.The acceleration sensor is particularly preferably provided to measure accelerations in the direction of impact. Reliable detection of the impact operation may be possible. It is further proposed that the impact sensor unit contain a force sensor, such as a piezo sensor, or a deformation sensor, such as a strain gauge sensor (DMS). The influence of a force and / or deformation caused by the impact pulse can be particularly well measured. The force sensor or the deformation sensor can preferably be arranged on a component and / or between components in the force flow of the impact pulse, such as in or on a tool, a tool holder, a striking pin, a guide tube and / or a striker. The force sensor or the deformation sensor is particularly preferably provided to measure forces and / or deformations in the direction of impact. Reliable detection of the impact operation may be possible.It is further proposed that the impact sensor unit contain a pressure sensor. The pressure sensor can preferably be provided to measure a pressure curve in the space between the striker and the piston. The pressure sensor can particularly reliably measure the pressure accelerating the striker in the impact direction. Impact operation can be particularly reliably detected. A brief pressure increase due to a displacement of a control and / or idle sleeve when switching from idle mode to impact mode can be detected. In addition to impact operation, the impact sensor unit can detect a change in operating mode from idle mode to impact mode.

[0009] It is further proposed that the impact sensor unit have at least one filter unit designed to isolate a signal component from a sensor signal of the sensor. In this context, a "filter unit" is understood to mean, in particular, a unit designed to modify the sensor signal spectrum. The filter unit can be part of the signal processing unit of the sensor unit. The filter unit can be at least partially a physical unit formed by components. Preferably, the filter unit can be at least partially formed by a computing algorithm that is processed by a computing unit of the sensor unit to filter the sensor signal. In particular, the filter unit can be designed to amplify and / or attenuate frequency bands and / or to attenuate unwanted signal components and / or to amplify desired signal components.In this context, "desired" signal components are understood to mean, in particular, components of the sensor signal that are suitable for detecting the impact characteristic, such as signal components that are at least substantially caused directly or indirectly by the impact pulse. "Unwanted" signal components are understood to mean, in particular, signal components that are at least only partially suitable for detecting the impact characteristic, such as signal components that are at least substantially caused by vibrations of a drive unit or a gear of the handheld power tool or by machining operations on the machining tool. "At least substantially" is understood to mean, in particular, predominantly more than 50%, preferably more than 75%, particularly preferably more than 90%. The sensor unit can detect the impact characteristic particularly reliably.Interference in the sensor signal can be reduced.

[0010] The control unit advantageously has a learning mode for determining the operating parameter. In particular, the control unit can have a learning mode for learning at least one limit parameter that delimits the range of stable impact operation from critical impact operation. Furthermore, the control unit can be provided to learn a maximum parameter that must not be exceeded during impact operation, such as the maximum speed. Preferably, the control unit is provided to define an advantageous start parameter and / or an advantageous start speed in the learning mode. The control unit can advantageously determine the operating parameter. The operating parameter, in particular the start parameter, can be optimally defined depending on environmental influences. In particular, a permissible start parameter and / or a limit parameter can be dependent on an ambient pressure and / or a temperature.Changes to the percussion mechanism during its service life can be taken into account. In particular, the operating parameters can be adjusted to suit percussion mechanism wear, percussion mechanism lubrication, and other influences. The learning mode can be initiated upon initial commissioning, each time the device is commissioned, at set intervals, each time the device switches from idle mode to percussion mode, or via a user setting. The percussion mechanism can exhibit optimal operating parameters under various environmental conditions and under various influencing factors. Setting the operating parameters by the percussion mechanism manufacturer and / or the user is no longer necessary.

[0011] It is proposed that the control unit saves the operating parameter in learning mode upon successful start-up of the impact mechanism. The control unit can select a high critical working speed when switching from idle mode to operating mode. The control unit can then reduce the speed until impact operation begins. This speed can be saved as the limit speed and / or start-up speed. The control unit can save a speed reduced by a safety factor as the start-up speed, for example 0.5 - 0.8 times the determined limit speed. Alternatively, the control unit can save a limit speed reduced by a fixed value as the start-up speed. In a further method, the control unit can learn the limit speed and / or maximum start-up speed by increasing the start-up speed by a fixed step or factor each time the impact mechanism is started, starting from a known safe start-up speed.If the impact mechanism starts successfully, the speed is saved as the permissible starting speed. If the impact mechanism fails to start for a specified period of time when switching from idle mode to impact mode, the set speed value is discarded and a previous, lower speed value is used as the starting speed for future operating changes. Furthermore, if the maximum permissible vibration is exceeded and / or impact mode is aborted, the control unit can set a maximum speed that should not be exceeded subsequently. Simple and reliable determination of the operating parameter may be possible.

[0012] It is further proposed that the control unit have at least one delay parameter which is intended to influence a time duration for a change between two values ​​of the operating parameter. The change from an idle value and / or working value to a starting value and / or from the starting value to the working value can take place by means of a setpoint jump. The change can preferably be linear and / or have a continuous course. Current consumption of the drive unit can be limited. Accelerations, driving forces and / or vibrations can be reduced. The time duration and / or the course of the change between the two values ​​of the operating parameter can preferably be determined as a function of a setting of a selector switch and / or a machining case and / or a type of material and / or a type of tool and / or ambient conditions.In particular, when impact drilling, a slow transition between the values ​​of the operating parameter may be useful; for example, the transition may take at least 1-2 seconds. When chiseling, a short time for a transition between the values ​​of the operating parameter may be useful, e.g., 0.1-0.5 seconds. Preferably, the duration and / or the course of the transition between two values ​​of the operating parameter can be dependent on a working position; in particular, the duration can be shortened if the working position is at least substantially downward and extended if the working position is at least substantially upward. In this context, a "working position" should be understood to mean, in particular, an orientation of the impact mechanism with respect to gravity.In this context, "upward" is understood to mean, in particular, a direction opposite to the force of gravity, and "downward" is understood to mean, at least essentially, the direction of gravity. The delay parameter can be provided to define at least one gradient and / or at least one curve of the function defining the change between the values ​​of the operating parameter. Advantageously, the time period for starting the percussion mechanism can be specified. "Startup" in this context is understood to mean, in particular, starting the percussion mode from a standstill of the drive unit. The percussion mechanism can start from a standstill directly to a critical working value, in particular a critical working speed. If the speed increases slowly, the percussion mechanism can start before the limit speed is reached. If the speed increases rapidly, the percussion mechanism may not start before the limit speed is reached.The speed must be temporarily set to the starting speed for a percussion mechanism start. Preferably, the control unit has a learning mode designed to learn a maximum ramp rate for a percussion mechanism start with a critical operating parameter. The control unit can gradually increase the ramp rate of the transition from standstill to the working speed during successive transitions to impact operation from standstill. If the percussion mechanism does not start, the maximum ramp rate may be exceeded. The control unit can specify a reduced ramp rate as the maximum ramp rate for a percussion mechanism start.It is also possible for the control unit in learning mode to initially set a high ramp-up speed for a percussion start from standstill. If the percussion start fails, it gradually reduces this speed during subsequent attempts to start the percussion from standstill until a reliable percussion start is achieved. If the percussion start fails, the control unit can start the percussion by temporarily switching to the starting speed. This ensures optimal operation of the percussion mechanism. Parameters can be set automatically.

[0013] Furthermore, an operating condition sensor unit is proposed. An operating condition sensor unit can be provided, in particular, to measure an air pressure surrounding the percussion mechanism. A temperature sensor of the operating condition sensor unit can be provided, in particular, to measure an air temperature surrounding the percussion mechanism and / or a temperature of the percussion mechanism, in particular of a percussion mechanism housing and / or guide tube. Other influencing factors for the operation of the percussion mechanism device can be available. A robustness reserve of the operating parameter can be small. In this context, a "robustness reserve" is to be understood, in particular, as an adjustment of the operating parameter intended to ensure reliable operation under deviating operating conditions, which can result in reduced performance under given operating conditions.

[0014] It is proposed that the control unit is provided to process a measured variable of the operating condition sensor unit. In particular, the control unit can define the limit parameter and / or the start parameter and / or the maximum parameter depending on at least one measured variable of the operating condition sensor unit. The limit parameter and / or the start parameter and / or the maximum parameter of the impact mechanism can be dependent on the ambient pressure and / or the temperature. The limit parameter and / or the start parameter and / or the maximum parameter can be stored in a memory unit depending on the ambient pressure and / or temperature. A computing unit can have functions for calculating permissible limit parameters and / or start parameters and / or maximum parameters. The control unit can define the parameters based on the measured variables.The stored parameters and / or the calculation functions can be selected so that the determined parameters include a safety margin. Controlled operation of the impact mechanism start and / or controlled adjustment of the operating parameter may be possible. In this context, "controlled operation" and / or "controlled adjustment" should be understood in particular to mean that determining successful impact operation is omitted. An impact sensor can be omitted. When changing operating modes, the control unit can use the parameters defined depending on the measured variables. Components and costs can be saved. Detection of impact operation can be omitted. Malfunctions due to incorrect detection of impact operation can be avoided. Optimization of the operating parameter depending on environmental parameters is possible.In particular, a percussion start can be ensured at high altitudes and / or at reduced ambient pressure.

[0015] Furthermore, a handheld power tool, in particular a hammer drill and / or percussion hammer, with an impact mechanism unit according to the invention is proposed. The handheld power tool can have the aforementioned advantages. drawing

[0016] Further advantages will become apparent from the following description of the drawings. The drawings illustrate four exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into further meaningful combinations.

[0017] They show: Fig. 1 is a schematic representation of a hammer drill with an impact mechanism unit according to the invention in a first embodiment in an idle mode, Fig. 2 is a schematic representation of the hammer drill in an impact mode, Fig. 3 is a schematic representation of a simulated amplitude-frequency response of a non-linear oscillatory system, Fig. 4 is a schematic representation of another simulated amplitude-frequency response of the non-linear oscillatory system, Fig. 5 is a schematic representation of the simulated impact energy of the impact mechanism unit during an impact mechanism start with a falling and rising impact frequency, Fig. 6 is a schematic representation of the simulated impact energy of the impact mechanism unit during an impact mechanism start with different ambient pressure conditions, Fig. 7 is a schematic representation of a possible definition of a start value, a limit value, a working value and a maximum value, Fig.8 a schematic representation of a filter unit of an impact sensor unit for isolating a signal component, Fig. 9 a representation of a block diagram of the impact unit, Fig. 10 a representation of a flow chart of the control unit of the impact unit when changing between an idle mode and an impact mode, Fig. 11 a representation of signals of the impact unit when changing between the idle mode and the impact mode, Fig. 12 a representation of possible setpoint curves of the impact frequency when changing from an idle value to the start value, Fig. 13 a representation of possible setpoint curves of the impact frequency when changing from the start value to the working value, Fig. 14 a schematic representation of a drilling and percussion hammer with an impact unit according to the invention with an operating condition sensor unit in a second embodiment, Fig. 15 a schematic representation of a characteristic map for determining at least one operating parameter, Fig.Fig. 16 is a schematic representation of a venting unit of a percussion mechanism of a hammer drill with a percussion mechanism unit, Fig. 17 is a further schematic representation of the venting unit, and Fig. 18 is a schematic representation of a hammer drill with a percussion mechanism unit with an impact sensor unit in a further embodiment. Description of the embodiments

[0018] Figure 1 and Figure 2show a hammer drill and percussion 12a with a percussion unit 10a and with a control unit 14a, which is intended to control and regulate a pneumatic percussion mechanism 16a. The percussion unit 10a contains a motor 48a with a gear unit 50a, which drives a hammer tube 54a in rotation via a first gear 52a and an eccentric gear 58a via a second gear 56a. The hammer tube 54a is connected in a rotationally fixed manner to a tool holder 60a, in which a tool 62a can be clamped. The tool holder 60a and tool 62a can be driven with a rotating working movement 64a via the hammer tube 54a for drilling. If a striker 66a is accelerated in a striking direction 68a in the direction of the tool holder 60a during a striking operation, it exerts an impact impulse upon impact on a striking pin 70a arranged between striker 66a and tool 62a, which impact impulse is passed on by the striking pin 70a to the tool 62a.The tool 62a exerts a percussive working movement 72a due to the impact impulse. A piston 74a is also movably mounted in the hammer tube 54a on the side of the striker 66a facing away from the impact direction 68a. The piston 74a is periodically moved in the hammer tube 54a in the impact direction 68a and back again via a connecting rod 76a by the eccentric gear 58a, which is driven at a percussion mechanism speed. The piston 74a compresses an air cushion 78a enclosed between the piston 74a and the striker 66a in the hammer tube 54a. When the piston 74a moves in the impact direction 68a, the striker 66a is accelerated in the impact direction 68a. Depending on the operating parameters 18a (described below), the piston 74a is driven in the impact direction 68a. Figure 7) impact operation can begin. Due to a rebound on the firing pin 70a and / or a negative pressure created between the piston 74a and the striker 66a by the return movement of the piston 74a against the impact direction 68a and / or due to a counterpressure in the space between the striker 66a and the firing pin 70a, the striker 66a can, likewise depending on operating parameters 18a such as impact frequency, temperature and ambient pressure, be moved back again against the impact direction 68a and then accelerated again in the impact direction 68a for a next impact pulse. In an area between the striker 66a and the firing pin 70a, ventilation openings 80a are arranged in the hammer tube 54a so that the air trapped between the striker 66a and the firing pin 70a in an impact chamber 142a can escape. In an area between striker 66a and piston 74a, idle openings 82a are arranged in the hammer tube 54a.The tool holder 60a is mounted for displacement in the impact direction 68a and is supported on a control sleeve 84a. A spring element 88a exerts a force on the control sleeve 84a in the impact direction 68a. In an impact mode 140a (. Figure 2 ), in which the tool 62a is pressed by a user against a workpiece, the tool holder 60a moves the control sleeve 84a against the force of the spring element 88a so that it covers the idle openings 82a. If the tool 62a is removed from the workpiece, the tool holder 60a and the control sleeve 84a are moved by the spring element 88a in the impact direction 68a into an idle mode 138a ( Figure 1) so that the control sleeve 84a releases the idle openings 82a. Pressure in the air cushion 78a between the piston 74a and the striker 66a can escape through the idle openings 82a. In the idle mode 138a, the striker 66a is not accelerated or is only slightly accelerated by the air cushion 78a. In idle operation, the striker 66a exerts no or only slight impact impulses on the striking pin 70a. The rotary hammer 12a has a handheld power tool housing 90a with a handle 92a and an auxiliary handle 94a, by which it is guided by a user.

[0019] The onset of impact operation when switching the impact mechanism unit 10a from the idle mode 138a to the impact mode 140a by closing the idle openings 82a depends on the operating parameters 18a. The piston 74a experiences periodic excitation by the air cushion 78a enclosed between the piston 74a and the striker 66a, with an impact frequency that corresponds to the impact mechanism speed of the eccentric gear 58a.

[0020] The striking mechanism 16a represents a non-linear oscillating system. Figure 3shows a schematic representation of a simulated amplitude-frequency response of a general non-linear oscillating system as a function of a frequency f. The amplitude A corresponds to the amplitude of an oscillating body of the system (not shown in detail here) corresponding to the striker 66a when externally excited, as occurs in the striking mechanism 16a by the piston 74a. The amplitude frequency response is non-linear; at high frequencies, the amplitude frequency response has multiple solutions. The amplitude that occurs in this range depends, among other things, on the direction in which the frequency f is changed. If, starting from a higher frequency f, a minimum frequency f 1 of the range of the amplitude frequency response with multiple solutions is undershot, the amplitude A jumps from a peak 174a with infinite gradient to a permissible solution of the amplitude frequency response with a higher level.If a maximum frequency f 2 of the range of the amplitude frequency response with multiple solutions is exceeded from a lower frequency f, the amplitude A jumps from a peak 176a with infinite slope to a feasible solution of the amplitude frequency response with a lower level. Figure 3 This behavior is indicated by arrows. In Figure 4 Another simulated amplitude-frequency response of the nonlinear oscillating system under different conditions is shown. Instead of a maximum frequency f 2 , the amplitude-frequency response exhibits a gap 178a. This occurs, for example, when the maximum frequency f 2 is higher than a possible excitation frequency with which the oscillating system can be excited. In the case of the percussion mechanism 16a, the excitation frequency can be limited, for example, by a maximum speed of the eccentric gear 58a.

[0021] The effect of the non-linear amplitude frequency response on the percussion operation of the percussion mechanism 16a is shown in Figure 5 shown. Figure 5shows a simulated impact energy E of the impact mechanism 16a when the impact mechanism starts up with a falling impact frequency 96a and with a rising impact frequency 98a. If the striker 66a is excited with an increasing impact mechanism speed or impact frequency 98a, the impact energy E increases with an increasing impact frequency 98a. If the striker 66a is excited from an idle impact mode from a high impact mechanism speed with a falling impact mechanism speed or impact frequency 96a, the impact mode only begins at a certain impact mechanism speed. This impact mechanism speed represents a limit value 104a. Above this impact frequency, the striker 66a does not begin to move with a falling impact frequency 96a, or only does so with a low amplitude and / or speed, even if the idle openings 82a are closed when switching from the idle mode 138a to the impact mode 140a.The striker 66a exerts no or only very small impact impulses on the firing pin 70a. Above a maximum value 106a, the impact energy E drops steeply. In this case, the striker 66a performs no movement in the impact direction 68a or movements with a low amplitude in the impact direction 68a, so that no or only small impact impulses with a low impact energy E are transmitted to the firing pin 70a. Depending on the ambient conditions and the design of the impact mechanism 16a, the limit value 104a lies in a range of 20 - 70 Hz. The maximum value 106a is greater than the limit value 104a and, depending on the ambient conditions and the design of the impact mechanism 16a, lies in a range of 40 - 400 Hz. Depending on the ambient conditions and the design of the impact mechanism 16a, the impact energy E reaches 1 - 200 joules at the limit value 104a and 2 - 400 joules at the maximum value 106a.

[0022] Figure 6shows the simulated impact energies E of the impact mechanism 16a when the impact mechanism starts with a falling and rising impact frequency under different ambient conditions. In this example, curve 100a shows the impact energy E at a first ambient pressure and curve 102a shows the impact energy E at a second ambient pressure that is reduced compared to the first ambient pressure. A limit value 180a of the impact frequency at the second ambient pressure occurs at a lower impact frequency than the limit value 104a of the impact frequency at the first ambient pressure. If the second ambient pressure is 10% lower than the first ambient pressure, the limit value 180a of the impact frequency is 1 - 25% lower than at the first ambient pressure, depending on other influencing factors. The temperature of the impact mechanism 16a, in particular of the hammer tube 54a, also influences the limit value 104a of the impact frequency.At lower ambient temperatures, friction of the striker 66a in the hammer tube 54a increases, particularly due to the increasing viscosity of lubricants. If the temperature of the hammer tube 54a drops by 10K, the limit value 104a of the impact frequency decreases by 1-30%, depending on other influencing factors. The limit value 104a of the impact frequency can also change by + / - 20% due to the influence of the tool 62a. The tool 62a can influence the rebound of the striker 66a from the firing pin 70a and thus affect the limit value 104a of the impact frequency.

[0023] Figure 7shows a schematic representation of a possible definition of operating parameters 18a of a control strategy according to the invention, in particular a starting value 20a, the limit value 104a, a working value 22a and the maximum value 106a. The starting value 20a is preferably selected at a percussion mechanism speed n at which the amplitude frequency response has an unambiguous solution. The starting value 20a is less than or equal to the limit value 104a. A reliable percussion mechanism start can be ensured regardless of the direction from which the starting value 20a is approached. The limit value 104a represents the transition to an ambiguous amplitude frequency response and the maximum starting value 20a. The starting value 20a is preferably selected at a distance from the limit value 104a, for example, with a 10% reduced percussion mechanism speed. Once percussion operation is ensured, the percussion mechanism 16a can be operated at a higher power at a supercritical working value 22a.In this case, a supercritical working value 22a is characterized by an ambiguous amplitude frequency response. A reliable impact mechanism start is not guaranteed with the supercritical working value 22a. Above the maximum value 106a, the impact energy drops sharply. The working value 22a is therefore selected lower than the maximum value 106a. The working value 22a can be specified by the control unit 14a or set by the user, for example, via a selector switch not shown here. The working values ​​22a are determined, among other things, depending on a machining case and / or a material type and / or a tool type. Working values ​​22a are assigned to various adjustable machining operations. A working value 22a above the limit value 104a is a supercritical working value 22a; a working value 22a below the limit value 104a and / or below the starting value 20a is a stable working value 22a.In addition to the starting value 20a and the limit value 104a, an optional idle value 108a can be specified. The idle value 108a is set particularly in idle mode 138a. The idle value 108a is advantageously set higher than the starting value 20a. A ventilation unit (not shown here) driven by the motor 48a can be operated at a higher speed than when operated with the starting value 20a. The cooling of the impact mechanism 16a in idle mode 138a is improved. The operating noise of the rotary hammer 12a is perceived by the user as more powerful than with the starting value 20a. Furthermore, the idle value 108a is advantageously set lower than the working value 22a. Noise emissions and / or vibrations can be reduced compared to operation with the working value 22a. When changing from idle mode 138a to impact mode 140a, the starting value 20a can be reached faster than from the working value 22a.

[0024] The control unit 14a is provided to temporarily set the operating parameter 18a to the starting value 20a in an operating state in which a supercritical operating value 22a is set for switching from idle operation to impact operation. In impact operation in impact mode 140a, the control unit 14a subsequently sets the operating parameter 18a to the supercritical operating value 22a. The user can safely start the impact mechanism unit 10a with a supercritical operating value 22a. In idle mode 138a, the idle value 108a is set. The idle value 108a can be identical to the operating value 22a, advantageously smaller than the operating value 22a, and larger than the starting value 20a.

[0025] In an operating state in which a stable working value 22a is selected at least below the limit value 104a or below the starting value 20a, the control unit 14a sets the operating parameter 18a directly to the working value 22a. If the idle value 108a, which corresponds to the working value 22a, is selected in idle operation, setting the operating parameter 18a when switching between idle operation and impact operation can be omitted. In the cases described here, the operating parameter 18a is a percussion mechanism speed. When switching from idle operation to impact operation, the control unit 14a temporarily reduces the percussion mechanism speed to a starting value 20a if the working value 22a of the percussion mechanism speed is selected to be higher than the starting value 20a.

[0026] An operating mode change sensor 28a is provided to signal a change in operating mode. The operating mode change sensor 28a detects the position of the control sleeve 84a. To switch between the idle mode 138a and the impact mode 140a, the user presses the tool 62a against a workpiece, causing the control sleeve 84a to be displaced counter to the impact direction 68a and close the idle openings 82a. The operating mode change sensor 28a simultaneously signals the control unit 14a that an operating mode change has occurred and that the impact mechanism 16a is now in impact mode 140a. The operating mode change sensor 28a is designed as an inductive sensor and detects when the control sleeve 84a is in a position in which it covers the idle openings 82a and the impact mechanism 16a is in impact mode 140a.Alternatively, the mode change sensor 28a may also be mounted so that it detects when the control sleeve 84a is in a position in which it releases the idle openings 82a and the striking mechanism 16a is in the idle mode 138a.

[0027] An impact sensor unit 30a is provided to signal impact operation. The control unit 14a can detect, with the aid of the impact sensor unit 30a, whether the impact mechanism 16a is in impact operation or in idle operation, in particular whether and at what time an impact mechanism start has occurred. The impact sensor unit 30a has a sensor 34a for a mechanical measurement variable, which is provided to detect impact operation. The sensor 34a is designed as an acceleration sensor and measures accelerations 190a on the gear housing 146a. A filter unit 36a of the impact sensor unit 30a is provided to isolate a signal component 38a from the sensor signal 40a of the sensor 34a for processing a sensor signal 40a ( Figure 8). The signal components 38a are particularly excited by the impact pulses. The signal components 38a typically have frequencies in a frequency band of 1 - 5 kHz. The filter unit 36a has a bandpass filter 110a, which filters out frequencies outside the range of 1 - 5 kHz of the frequencies generated by the impact pulses. The sensor signal 40a is rectified by a rectifier 112a and integrated by an integrator 114a during a time window Δt. The time window Δt is adapted to the impact mechanism speed and the duration of an impact event. A comparator 116a compares the filtered, rectified, and integrated sensor signal 40a with a comparison signal 118a and transmits the result of the comparison to the control unit 14a via a digital output 120a, thus signaling impact mode or idle mode.

[0028] Figure 9shows a block diagram of the impact mechanism unit 10a. A target speed 122a is determined by a target impact rate calculator 136a depending on a working gear selection 124a, an operating mode signal 126a of the impact sensor unit 30a, and an operating mode signal 128a of the operating mode change sensor 28a. The target impact rate calculator 136a is part of the control unit 14a. Depending on these parameters and the gear ratio of the gear unit 50a, the target speed 122a of the motor 48a is set such that the impact frequency and / or a speed of the eccentric gear 58a corresponds to the working value 22a, the idle value 108a, or the starting value 20a. The target speed 122a is passed on to a controller 130a. An actual speed 134a of the motor 48a is fed back as a controlled variable to the target stroke rate calculator 136a and the controller 130a.The controller 130a calculates a phase angle 182a as a manipulated variable for a voltage regulator 132a from a deviation between the actual speed 134a and the target speed 122a. The voltage regulator 132a transmits a voltage 184a to the motor 48a, which generates a drive torque 186a depending on the voltage 184a and the actual speed 134a and uses this torque to drive the impact mechanism 16a via the gear unit 50a. The impact sensor unit 30a detects the operating mode based on the acceleration 190a caused by the impact mechanism 16a and transmits the operating mode signal 128a to the target impact rate calculator 136a; the operating mode change sensor 28a detects the operating mode based on a control sleeve position 188a and transmits the operating mode signal 126a to the target impact rate calculator 136a.

[0029] Figure 10shows a flowchart of the operation of the impact mechanism unit 10a. In a first step 194a, the operating mode signal 126a is evaluated. This evaluation is continuously repeated as long as the idle mode 138a is detected. If the impact mode 140a is detected, an operating mode change 192a is initiated. In a step 196a, the start value 20a is set. In a step 198a, the system waits until impact mode begins. For this purpose, the operating mode signal 128a is evaluated. In a further step 200a, the working value 22a is set. The impact mechanism 16a is now in impact mode. In a step 202a, the operating mode signal 126a is again evaluated. This evaluation is continuously repeated as long as the impact mode 140a is detected. If the idle mode 138a is detected, a jump to step 194a takes place. If an idle value 108a has been defined that differs from the working value 22a, this is set when jumping to step 194a.In an extension of the in . Figure 10 In the sequence shown, in step 202a, the operating mode signal 128a can be monitored in addition to the operating mode signal 126a. If the operating mode signal 128a signals a lack of impact operation while the operating mode signal 126a continues to signal the impact mode 140a, a jump to step 196a occurs. The impact mechanism 10a can thus be restarted.

[0030] The control unit 14a has a learning mode for determining at least the operating parameter 18a. The learning mode can be activated manually, for example, when the percussion mechanism 16a is used under changed ambient conditions, such as a changed ambient pressure. The control unit 14a can also execute the learning mode, for example, upon each start-up or at specified intervals. To learn the starting value 20a, the percussion mechanism speed is continuously reduced from a specified maximum value 106a until the impact sensor unit 30a signals a percussion mechanism start. The control unit 14a stores the percussion mechanism speed at the time of the percussion mechanism start, multiplied by a safety factor of, for example, 0.8, as the starting value 20a. In an alternative learning mode, the control unit 14a can determine an optimal starting value 20a by gradually increasing the percussion mechanism speed upon repeated switching from the idle mode 138a to the impact mode 140a.If the percussion mechanism starts successfully, the percussion mechanism speed is saved as the new starting value 20a. If the percussion mechanism does not start after a further increase in the percussion mechanism speed when switching from idle mode 138a to percussion mode 140a, the starting value 20a for subsequent switches from idle mode 138a to percussion mode 140a is set to the last successful starting value 20a.

[0031] Figure 11shows a signal curve of an operation of the impact mechanism unit 10a. Diagram 206a represents a signal curve of the operation change sensor 28a, diagram 208a a signal curve of the impact sensor unit 30a and diagram 210a the curve of the target speed 122a during the time t. The target speed 122a can in particular assume the idle value 108a, the starting value 20a and the working value 22a. Diagram 212a shows the actual speed 134a. The actual speed 134a at least largely follows the target speed 122a with a delay caused by an inertia in particular of the motor 48a and the gear unit 50a. The change between different target speeds 122a takes place during a time period 44a. The time period 44a generally characterizes the time period of a change between two target speeds 122a. The time period 44a is determined by a delay parameter 42a, which determines the maximum gradient of the target speed curve.The delay parameter 42a determines how quickly the target speed 122a changes to the working value 22a when the impact mechanism starts, as detected by the impact sensor unit 30a, and in the example is the angle of the gradient of the target speed 122a during the time period 44a. The delay parameter 42a can also be learned, for example, by extending the time period 44a if the change from idle mode to impact mode was unsuccessful because the change to the working value 22a was too fast.

[0032] The transition of the target speed 122a from the idle value 108a to the starting value 20a can have different characteristics depending on the operating mode. These are shown in Figure 12shown in diagrams 12i - 12v. Diagram 12i shows a direct jump in the setpoint speed 122a from the idle value 108a to the starting value 20a. The starting value 20a can thus be reached particularly quickly. Diagram 12ii shows a linear setpoint change with a constant gradient. Accelerations that occur are lower. This can increase user comfort. Diagrams 12iii to 12v show further possible curves for a setpoint change, with the curve in diagram 12iii showing a reduced jerk. Diagrams 12iv and 12v show an overshooting curve of the setpoint change, which can have a positive influence on the starting behavior. The duration of the transitions shown here can also be variable. The impact mechanism unit 10a can select the curves shown here to suit the operating modes and conditions.

[0033] The transition of the target speed 122a from the starting value 20a to the working value 22a can also have different characteristics depending on the operating mode. These are shown in Figure 13shown in diagrams 13i - 13v. Diagram 13i shows a direct jump in the setpoint speed 122a from the starting value 20a to the working value 22a. The working value 22a can thus be reached particularly quickly. Diagram 13ii shows a linear setpoint change with a constant gradient. The delay parameter 42a determines the gradient of the setpoint change. Accelerations that occur are lower. The impact mechanism start is particularly reliable. Diagrams 13iii to 13v show further possible curves for a setpoint change, with the curve in diagram 13iii showing a reduced jerk. Diagrams 13iv and 13v show an overshooting curve of the setpoint change. The time duration 44a of the transitions shown here can also be variable. The impact mechanism unit 10a can select the curves shown here as appropriate depending on the operating modes and conditions.In particular, the impact mechanism unit 10a can adjust the progressions depending on a work cycle selection 124a. When impact drilling, a gentle increase in impact force is advantageous. The time duration 44a is set to be longer, for example, in the range of 0.8 - 1.2 seconds. When chiseling, the selected impact force should be available quickly. A short time duration 44a is set, advantageously in the range of 0.1 - 0.5 seconds. The user can also adjust the time duration 44a directly using a control element not shown here. The time duration can be adjusted depending on the working position, for example, shorter than 0.5 seconds for a downward-facing working position and longer than 1 second for an upward-facing working position.

[0034] In another operating mode, impact operation is started from standstill. The target speed 122a is increased to the working value 22a during the time period 44a. If the time period 44a is selected to be long enough, a change from idle operation to impact operation takes place before the limit value 104a is exceeded. The control unit 14a does not need to initially set the starting value 20a for an impact mechanism start. The time period 44a can be learned. If a change from idle operation to impact operation from standstill is unsuccessful, a longer time period 44a is selected the next time the change from idle operation to impact operation from standstill.

[0035] The following description and the drawings of further exemplary embodiments are essentially limited to the differences between the exemplary embodiments. Regarding components with the same designation, particularly with regard to components with the same reference numerals, reference can generally also be made to the drawings and / or the description of the other exemplary embodiments. To distinguish the exemplary embodiments, the letters b - d are placed after the reference numerals of the further exemplary embodiments instead of the letter a of the first exemplary embodiment.

[0036] Figure 14shows a percussion unit 10b for a hammer drill 12b with a control unit 14b, which is intended to control and regulate a pneumatic percussion mechanism 16b, in a second exemplary embodiment. The percussion unit 10b differs from the previous exemplary embodiment in particular by an operating condition sensor unit 46b. The control unit 14b is intended to process a measured variable of the operating condition sensor unit 46b. In particular, the control unit 14b is intended to determine a limit value 104b for a reliable percussion mechanism start ( Figure 15). The operating condition sensor unit 46b is provided to detect a temperature T and an ambient pressure P. The operating condition sensor unit 46b is integrated as a module on a circuit board of the control unit 14b. The operating condition sensor unit 46b detects an ambient temperature. The temperature influences the viscosity of lubricants and the friction of a striker 66b with the hammer tube 54b. The ambient pressure particularly influences the return movement of the striker 66b and the limit value 104b for a reliable impact mechanism start. The control unit 14b is further provided to define the operating parameter 18b of the impact mechanism 16b. The operating parameter 18b is a target impact rate and / or target impact mechanism speed. The control unit 14b defines the operating parameter, particularly depending on pressure and / or temperature.The control unit 14b can determine several target impact rates, such as a target impact rate as a working value for particularly efficient impact operation, and a target impact rate as a starting value for starting the impact mechanism. The starting value and the working value are determined depending on the limit value 104b; in particular, the working value is set higher and the starting value lower than the limit value 104b. In another operating mode, the user can set a relative working value between 0 and 1 using a rotary knob (not shown in detail here), which is then multiplied by the pressure- and / or temperature-dependent target impact rate for impact operation. The user can thus determine the percentage of the pressure- and / or temperature-dependent target impact rate at which impact operation should take place. In the present example, the control unit 14b determines the operating parameter 18b depending on a characteristic map 164b stored in the control unit 14b (. Figure 15). The characteristic map 164b shows the limit value 104b as a function of the temperature T and the ambient pressure P. Intermediate values ​​are suitably interpolated by the control unit 14b. If the working value and the starting value are not to be calculated, further characteristic maps not shown here can alternatively be provided for these values. The control unit 14b sets the starting value for the impact mechanism start if a working value is selected that is higher than the starting value at the current temperature T and the current ambient pressure P. Since the control unit 14b determines the operating parameter 18b with the aid of the operating condition sensor unit 46b, an impact sensor unit for detecting impact operation can be omitted. When an operating mode changes from an idle mode to an impact mode, impact mechanism operation takes place sufficiently reliably within the limits of the operating parameter 18b determined by the operating sensor unit 46b.

[0037] Figures 16 and 17show an alternative, non-inventive, percussion unit 10c. The percussion unit 10c differs from the preceding percussion unit 10b in that an operating parameter 18c determined by a control unit 14c is a throttle parameter of a venting unit 24c. A percussion chamber in a hammer tube is delimited by a firing pin and a striker. The venting unit 24c has venting openings in the hammer tube 54c for venting the percussion chamber. The venting unit 24c serves to equalize the pressure of the percussion chamber with the environment of a percussion mechanism 16c. The venting unit 24c has an adjustment unit 144c. The adjustment unit 144c is provided to influence the venting of the percussion chamber arranged in front of the striker in an impact direction 68c during an impact process. The hammer tube 54c of the percussion mechanism 16c is mounted in a gear housing 146c of a drilling and percussion hammer 12c.The gear housing 146c has star-shaped ribs 148c facing an outer side of the hammer tube 54c. A bearing bush 150c is pressed between the hammer tube 54c and the gear housing 146c in an end region 152c facing an eccentric gear, which bush supports the hammer tube 54c on the gear housing 146c. The bearing bush 150c, together with the ribs 148c of the gear housing 146c, forms air channels 154c that communicate with the vent openings in the hammer tube 54c. The air channels 154c form part of the venting unit 24c. The impact chamber is connected via the air channels 154c to a gear chamber 156c arranged behind the hammer tube 54c, opposite the impact direction 68c. The air channels 154c form throttle points 158c, which influence a flow cross-section of the connection between the impact chamber and the gear chamber 156c. The adjustment unit 144c is provided for adjusting the flow cross-section of the throttle points 158c.The air channels 154c forming the throttle points 158c form a transition between the striking chamber and the gear chamber 156c. An adjusting ring 214c has star-shaped, inward-facing valve extensions 162c. Depending on the rotational position of the adjusting ring 214c, the valve extensions 162c can completely or partially cover the air channels 154c. The flow cross-section can be adjusted by adjusting the adjusting ring 214c. The control unit 14c adjusts the adjusting ring 214c of the adjusting unit 144c by rotating the adjusting ring 214c with the aid of a servo drive 204c. If the venting unit 24c is partially closed, the pressure in the striking chamber created by a movement of the striker in the striking direction 68c can escape only slowly. A counterpressure is created that counteracts the movement of the striker in the striking direction 68c.This counterpressure supports a return movement of the striker against the impact direction 68c and thus a start of the impact mechanism. If a supercritical operating value is selected for the impact mechanism speed, at which a reliable start of the impact mechanism is not possible with the venting unit 24c open, the control unit 14c partially closes the venting unit 24c to switch from idle impact operation to impact operation. The start of impact operation is supported by the counterpressure in the impact chamber. After the impact mechanism has been started, the control unit 14c reopens the venting unit 24c. The control unit 14c can also use the operating parameter of the throttle characteristic of the venting unit 24c to regulate the power.

[0038] Figure 18shows a percussion unit 10d with a control unit 14d for a percussion mechanism 16d in a further exemplary embodiment. The percussion unit 10d differs from the first exemplary embodiment in particular in that an impact sensor unit 30d is provided to detect an impact operation by evaluating at least one drive parameter 32d. The impact sensor unit 30d has a load estimator 166d for this purpose. The load estimator 166d is integrated with the impact sensor unit 30d on the control unit 14d and is provided to use a measured engine speed ω an engine 48d an unknown drive load f L to estimate. The unknown drive load f L is an unknown load torque acting on the motor 48d 500 .

[0039] A total torque M denotes the sum of all torques acting on the motor 48d. M includes a drive torque of the motor 2000and the unknown load moment ML . J is the rotational inertia of all ω rotating parts of the motor 48d, a gear unit 50d with an eccentric gear 58d, whereby the gear ratios must be taken into account. The following angular momentum equation then applies: J dω t dt = ∑ M

[0040] The total moment M is the sum of a moment 2000 of the 48d engine and torques M Li of loads acting on the motor 48d: J dω t dt = M M + M L 1 + M L 2 + …

[0041] The engine speed ω can be calculated as a function of time ω(t) which result from a base speed that does not change or changes only slowly ω 0 as well as rapidly changing, highly dynamic components fi (t) and the desired drive load f L consists of: ω t = ω 0 + f 1 t + f 2 t + … + f L

[0042] The functions fi (t) describe known loads. This equation is obtained by integrating the angular momentum theorem, the functions ftherefore do not have the dimension of a torque and are therefore designated with the letter f instead of M This procedure is known to the expert. The load to be estimated f L can be calculated by subtracting the known values ​​from the measured engine speed ω(t) be determined. f M (t) is the function of the moment 2000 of the 48d engine: f L = ω t − ω 0 − f M t − f 1 t − f 2 t − …

[0043] The known load shares fi (t) describe in particular speed fluctuations caused by variable gear ratios, motor irregularities and a non-uniform voltage supply, e.g. by a motor control. A distinction can be made between time-periodic loads fi (t) and angular periodic loads fi (Φ) A time-periodic load fi (t)can be, for example, a voltage fluctuation, in particular with double mains frequency of a power supply of a drilling and percussion hammer 12d, an angular periodic load fi (Φ) For example, this can be a ratio that changes with the rotational position of the eccentric gear 58d. The specialist will store loads whose course is precisely known as a calculation rule on the control unit 14d. Impact operation is detected when f L exceeds a specified or adjustable threshold and signals the control unit 14d. The other functions and application of the impact sensor unit 30d correspond to the first embodiment.

Claims

1. Percussion mechanism unit (10a-d), which is designed as a non-linear, oscillatory system, in particular for a rotary and / or percussion hammer (12a-d), with a control unit (14a-d) that is provided to control a pneumatic percussion mechanism (16a-d) by open-loop and / or closed-loop control, characterized in that the control unit (14a-d) is provided, in an operating state in which an operating parameter (18a-c) is set as an above-critical working value (22a), to set the operating parameter (18a-c) temporarily to a starting value (20a) for the purpose of changing from an idling operating state to a percussive operating state, wherein the operating parameter (18a-c) is a percussion-mechanism rotational speed (n) and the starting value (20a) lies in a range of the percussion-mechanism rotational speed (n) in which an amplitude-frequency response of an oscillating body of the percussion mechanism (16a-d) has a single-valued solution, and the above-critical working value (22a) lies in a range of the percussion-mechanism rotational speed (n) in which the amplitude-frequency response has a multi-valued solution, and wherein the starting value (20a) lies below the above-critical working value (22a).

2. Percussion mechanism unit (10a-d) according to Claim 1, characterized in that the starting value (20a) is designed in such a way that a reliable starting of the percussion mechanism is ensured.

3. Percussion mechanism unit (10a-d) according to either one of the preceding claims, characterized by an operation change sensor (28a), which is provided to signal a change of the operating mode.

4. Percussion mechanism unit (10a-d) according to any one of the preceding claims, characterized by a percussion sensor unit (30a; 30d), which is provided to signal a percussive operating state.

5. Percussion mechanism unit (10a-d) according to Claim 4, characterized in that the percussion sensor unit (30d) is provided to identify the percussive operating state by evaluation of at least one drive parameter (32d).

6. Percussion mechanism unit (10a-d) at least according to Claim 4, characterized in that the percussion sensor unit (30a) has at least one sensor (34a) for a mechanical measured quantity, which sensor is provided to detect the percussive operating state.

7. Percussion mechanism unit (10a-d) at least according to Claim 4, characterized in that the percussion sensor unit (30a) has at least one filter unit (36a), which is provided to isolate a signal component (38a) out of a sensor signal (40a) of the sensor (34a).

8. Percussion mechanism unit (10a-d) according to any one of the preceding claims, characterized in that the control unit (14a) has a learning mode for determining the operating parameter (18a).

9. Percussion mechanism unit (10a-d) according to Claim 8, characterized in that, in the learning mode, the control unit (14a) stores the operating parameter (18a) in the case of a successful starting of the percussion mechanism.

10. Percussion mechanism unit (10a-d) according to any one of the preceding claims, characterized in that the control unit (14a-d) has at least one delay parameter (42a), which is provided to influence a time period (44a) for a change between two values of the operating parameter (18a).

11. Percussion mechanism unit (10a-d) according to any one of the preceding claims, characterized by an operating-condition sensor unit (46b).

12. Percussion mechanism unit (10a-d) according to Claim 11, characterized in that the control unit (14b) is provided to process a measured quantity of the operating-condition sensor unit (46b).

13. Hand-held power tool, in particular rotary and / or percussion hammer (12a-d), comprising a percussion mechanism unit (10a-d) according to any one of the preceding claims.