EP2855096B1 - Percussion unit and method. - Google Patents

Description

State of the art

Percussion units, in particular for a hammer drill and / or percussion hammer, with a control unit which is intended to control a pneumatic percussion unit and at least one operating condition sensor unit are already known. Such a percussion unit is from the DE 10 2008 000 973 A1 known.

Disclosure of the invention

The invention is based on a striking mechanism unit, in particular for a hammer drill and / or percussion hammer, with a control unit which is intended to control and / or regulate a pneumatic striking mechanism and at least one operating condition sensor unit.

According to the invention, the control unit is provided to determine at least one impact mechanism parameter as a function of measured values of the operating condition sensor unit. “Provided” is to be understood in particular to be specially designed and / or specially equipped. In this context, a “striking mechanism unit” is to be understood in particular to mean a unit which is provided for operating a striking mechanism. The striking mechanism unit has a control unit. The striking mechanism unit can have a motor and / or a gear unit which is and / or which is provided for driving the striking mechanism unit. In this context, a “control unit” is to be understood in particular to mean a device of the percussion mechanism unit which is provided for controlling and / or regulating, in particular, the motor and / or the percussion mechanism unit. The control unit can preferably be designed as an electrical, in particular as an electronic control unit. In this context, a “hammer drill and / or percussion hammer” is to be understood in particular to mean a machine tool which is provided for machining a workpiece with a rotating or non-rotating tool, the tool being able to apply impact pulses to the tool. The machine tool is preferably designed as a hand-held machine tool guided by a user. In this context, a “percussion mechanism” is to be understood in particular to mean a device which has at least one component which is provided for generating and / or transmitting an impact pulse, in particular an axial impact pulse, to a tool arranged in a tool holder. Such a component can be, in particular, a racket, a firing pin, a guide element, such as, in particular, a hammer tube and / or a piston, such as, in particular, a pot piston, and / or a further component that appears useful to the person skilled in the art. The club can transmit the impact pulse directly to the tool or preferably indirectly. The racket can preferably transmit the impact pulse to a firing pin, which transfers the impact pulse to the tool. In this context, an “operating condition sensor unit” is to be understood in particular to mean a measuring device which is provided to detect operating conditions of the striking mechanism. The operating condition sensor unit can comprise one or more sensors. A sensor can be arranged on a circuit board of the control unit. A sensor arrangement can be particularly inexpensive. A sensor can be arranged on an inside or an outside of a handheld power tool housing. The sensor can record measured values particularly precisely inside the handheld machine tool or outside the handheld machine tool. A sensor can be arranged on a main handle or an additional handle. A sensor can be arranged on a motor or a guide tube. In particular, the sensor can detect measurement values which are influenced by the motor and / or affect guide properties of the guide tube particularly precisely. The operating condition sensor unit can advantageously comprise one or more external sensors. In particular, the operating condition sensor unit can be connected to sensors of external devices, such as a smartphone, and / or to sensors and / or operating condition data accessible via the Internet. The operating condition sensor unit can preferably include temperature and / or ambient air pressure data obtain from external sensors. Sensors can be saved. "Operating conditions" are to be understood in particular as physical quantities which influence the operation of the striking mechanism. Operating conditions can in particular be environmental conditions of an environment of the striking mechanism. In this context, an “influence” is to be understood in particular to mean that an operating behavior of the striking mechanism can change as a result of the operating conditions, such as, in particular, an efficiency and / or a starting behavior. In this context, a “striking mechanism parameter” is to be understood in particular to mean a value of an operating parameter influencing the operation of the striking mechanism. In particular, the hammer mechanism parameter can be a pressure and / or a hammer mechanism speed and / or a hammer frequency. According to the impact mechanism parameter is a limit value of the operating parameter. The control unit can take the determined percussion mechanism parameters into account when operating the percussion mechanism. The operation of the striking mechanism can be particularly reliable. The striking mechanism can be operated with high effectiveness under different operating conditions.

It is proposed that the operating condition sensor unit be provided to detect at least one temperature. In particular, the operating condition sensor unit can be provided to detect a temperature of an impact mechanism environment. In particular, the operating condition sensor unit can be provided to detect a temperature of the striking mechanism. In this context, a “temperature of the striking mechanism” is to be understood in particular to mean a temperature of a component of the striking mechanism, in particular the guide tube and / or the striker and / or a striking mechanism and / or transmission housing. The temperature can in particular have an effect on lubrication of the striking mechanism, for example due to a changed viscosity of a lubricant. The temperature can cause components to expand and change tolerances between components. The operating behavior of the striking mechanism can change. The control unit can set operating parameters that are particularly suitable for the temperature.

According to the operating condition sensor unit is provided to detect at least one ambient air pressure. The ambient air pressure can, in particular, influence a start-up behavior of the striking mechanism and / or a return movement against the direction of the striker's striking. In particular, a return movement of the racket at low ambient air pressure can be unreliable. In particular, starting the hammer mechanism at low ambient air pressure can be unreliable. In this context, “unreliable” is to be understood in particular to mean that the striking operation fails repeatedly and / or arbitrarily, in particular at least every 5 minutes, preferably at least every minute, and / or that the striking mechanism starts up on more than every tenth attempt to start the striking mechanism , especially if more than every fifth attempt fails. The control unit can set suitable operating parameters for the ambient air pressure, which ensure reliable operation.

It is further proposed that the control unit be provided to determine at least one cut-off frequency of an amplitude-frequency response of the striking mechanism. In this context, an “amplitude-frequency response” of the striking mechanism is to be understood in particular as a striking force of the striker depending on a striking mechanism frequency and / or a striking mechanism speed. In this context, a “percussion mechanism speed” is to be understood in particular as a speed of an eccentric gear which moves a piston of the percussion mechanism. The piston can in particular be provided to generate a pressure cushion for pressurizing the racket. The racket can be moved at the stroke frequency in particular by the pressure cushion generated by the piston. The beat frequency and the hammer mechanism speed are preferably directly related. In particular, the amount of the impact frequency 1 / s can be the amount of the impact mechanism speed U / s. This is the case if the racket strikes once per revolution of the eccentric gear. In the following, the terms "frequency" and "speed" are therefore used equivalently. The person skilled in the art will adapt the following statements accordingly in the case of designs of a striking mechanism that deviate from this connection. In this context, a “limit frequency” is to be understood in particular as a frequency in which a behavior of the amplitude-frequency response changes fundamentally. The cut-off frequency can represent a transition between a continuous and a discontinuous range of the amplitude-frequency response. In particular, the cut-off frequency can represent the beginning of a frequency range by the amplitude-frequency response has a hysteresis and / or by assigning several possible amplitudes to a frequency. Operation of the striking mechanism can be unreliable and / or inadmissible at certain frequencies. The cut-off frequency can define a start or an end of such a range. It can be avoided that the striking mechanism is operated with unreliable and / or impermissible operating parameters. The reliability of the striking mechanism can be increased. The performance of the striking mechanism can be increased.

It is further proposed that the control unit be provided to define at least one operating parameter of the striking mechanism. The control unit is preferably provided to determine the operating parameter as a function of a determined percussion mechanism parameter. In particular, the control unit can be provided to set a start value for the operating parameter. Furthermore, the control unit can be provided to determine a work value and / or a minimum and / or maximum work value for the operating parameter. Furthermore, the control unit can be provided to set an idle value for the operating parameter. In this context, a “work value” is to be understood as a value of the operating parameter set by the control unit during the striking operation of the striking mechanism. In this context, an “idle value” is to be understood as a value of the operating parameter set by the control unit when the striking mechanism is idling. In this context, a “start value” is to be understood as a value of the operating parameter set by the control unit when the striking mechanism changes from idle operation to striking operation. In this context, an “idle mode” is to be understood in particular to mean an operating state of the striking mechanism which is characterized by the absence of regular impact pulses. The striking mechanism can preferably have an idle mode in which it is provided for idle operation. In this context, “striking operation” is to be understood in particular to mean an operating state of the striking mechanism in which the striking mechanism preferably exerts regular striking impulses. The striking mechanism can preferably have a striking mode in which it is provided for the striking operation. In this context, “regular” is to be understood to mean, in particular, recurring, in particular with an intended frequency. Under an "operating state" should a mode and / or a setting of the control unit should be understood in this context. The operating state can depend in particular on user settings, environmental conditions and other parameters of the striking mechanism. In this context, a "change" from idle mode to striking mode is understood to mean starting the striking mechanism from idling mode. The change to field operation can take place in particular if the striking mechanism is switched from idle mode to field mode. The control unit can advantageously determine the operating parameters. In particular, the control unit can determine the operating parameters depending on the operating conditions, in particular on a temperature and / or an ambient air pressure. The striking mechanism can be operated under various operating conditions with advantageous operating parameters. In particular, at a low ambient air pressure, operating parameters can be set in which starting the hammer mechanism at a low ambient air pressure is particularly reliable. With a high ambient air pressure, operating parameters can be set for which the striking mechanism is particularly powerful. A robustness reserve of the operating parameters can be low. In this context, a “robustness reserve” is to be understood in particular to mean an adjustment of an operating parameter which is intended to ensure reliable operation in the case of different operating conditions and which results in reduced performance under given operating conditions. The operating parameters are preferably determined such that the striking mechanism starts up reliably at a stroke frequency of 20-70 Hz at least at an ambient air pressure of 950-1050 mbar and an ambient temperature of 10-30 ° C. and / or a stroke frequency of 20-70 Hz as the starting value can be used. With known operating conditions, safe operating parameters for the operation of the striking mechanism can be defined. Sensors for monitoring the operation of the striking mechanism can be omitted. Failure of a field operation can be unlikely.

It is proposed that the operating parameter be a throttle characteristic of a ventilation unit. In this context, a “throttle characteristic” is to be understood in particular to mean a setting of the ventilation unit that changes a flow resistance of the ventilation unit, in particular a flow cross section. Under a "ventilation unit" in this Connection in particular a ventilation unit of the striking mechanism can be understood. The ventilation unit can be provided in particular for pressure and / or volume compensation of at least one space in the striking mechanism. In particular, the ventilation unit can be provided for ventilating and / or venting a space in a guide tube guiding the racket in the direction of impact in front of and / or behind the racket. The operating parameter can preferably be a throttle position of the ventilation unit of the space arranged in front of the racket in the direction of impact. If the flow cross-section in this venting unit is increased, the venting of the space in front of the racket can be improved. A counter pressure against the direction of the club can be reduced. The impact strength can be increased. If the flow cross section of this ventilation unit is reduced, the ventilation in front of the racket can be reduced. A counter pressure against the direction of the club can be increased. The impact strength can be reduced. In particular, the return movement of the racket against the direction of impact can be supported by the counter pressure. The start of the striking mechanism can be supported. The operating parameter can ensure a reliable start of the striking mechanism. The operating parameter with a reduced flow cross section can be a stable operating parameter. It can be suitable as a starting value. The operating parameter with an enlarged flow cross section can be a critical operating parameter with increased performance of the striking mechanism. It can be suitable as a work value.

In an advantageous embodiment of the invention, it is proposed that the operating parameter is the stroke frequency and / or a stroke mechanism speed. The control unit speed can be set particularly easily by the control unit. A hammer mechanism speed can be particularly suitable for a machining case. The striking mechanism can be particularly powerful at a high striking mechanism speed. The motor of the striking mechanism can be operated at a higher speed at a higher striking mechanism speed. A ventilation unit driven by the motor can also be operated at a higher speed. Cooling of the striking mechanism and / or the motor by the ventilation unit can be improved. A function of a striking amplitude of the striking mechanism can be dependent on the striking mechanism speed. At a speed above a limit speed, the function can have a hysteresis have and be ambiguous. Starting the field operation when switching from the idle mode to the field mode and / or restarting the field operation when the field operation is interrupted can be unreliable and / or impossible. A hammer mechanism speed below the limit speed can be used as a starting value and / or work value for stable hammer operation. A hammer mechanism speed above the limit speed can be used as a work value for a critical hammer operation. Above a maximum speed, impact operation may be impossible and / or unreliable. In this context, “unreliable” is to be understood in particular to mean that the striking operation fails repeatedly and / or arbitrarily, in particular at least every 5 minutes, preferably at least every minute. The control unit can be provided to determine a target percussion speed and / or frequency and / or a work value for percussion operation. The striking mechanism can be particularly efficient with this operating parameter. The control unit can also be provided to determine a limit speed, a starting speed and / or a maximum speed.

It is further proposed that the control unit be provided to determine the at least one operating parameter with the aid of a computing unit. In this context, a “computing unit” is to be understood in particular to mean a unit for calculating at least one mathematical formula. In this context, a “formula” is to be understood in particular as a calculation rule which is intended to determine the operating parameter by calculation as a function of input variables. In particular, the formula can be provided to calculate a limit frequency as a function of an ambient air pressure and / or a temperature. A suitable formula can be determined by the person skilled in the art on the basis of calculations and / or on the basis of tests. A formula can represent an approximation to a real behavior of the striking mechanism. The person skilled in the art will determine which deviations a suitable formula may have from the real behavior, for example determined in experiments. In particular, a formula can be suitable if a calculated value deviates by less than 50%, preferably by less than 25%, particularly preferably by less than 10% from a value determined in experiments with the striking mechanism. The control unit can calculate a limit parameter for an operating value above which a hammer mechanism start is unreliable. The control unit can now start one Set the operating parameter reduced by a safety margin from the limit parameter as the starting value for this operating value. The control unit can determine the operating parameters particularly easily.

It is further proposed that the control unit be provided to determine the at least one operating parameter with the aid of a storage unit for storing a characteristic curve and / or a characteristic diagram. In this context, a “characteristic curve” is to be understood as a number of value pairs which link a value with a further value of the value pair. In this context, a “characteristic map” is to be understood as a number of characteristic curves which each link a plurality of defined values to a further, variable value, the individual characteristic curves differing in the amounts of at least one of the defined values. The characteristic curves and / or the characteristic maps can be determined in experiments and / or by calculations. The control unit can determine an operating parameter by taking the values that match the measured operating conditions from the characteristic curve and / or the characteristic diagram. The control unit can advantageously be provided to suitably interpolate values between the values recorded in the characteristic curve and / or the characteristic diagram. A multitude of methods is known to the person skilled in the art how an interpolation of values is possible. The control unit can determine the operating parameters with particularly little computing effort. The values can be determined by experiments. There is no need to link the values using a functional equation.

It is further proposed that the control unit be provided to take position information and / or an operating mode and / or an application into account when determining the at least one percussion mechanism parameter and / or the at least one operating parameter. In this context, “position information” is to be understood in particular to mean a direction of a weight with respect to the striking mechanism. A position sensor can be provided to record the position information. Operating parameters of the striking mechanism can be influenced by the location. A return movement of the racket can be made more difficult by a weight force acting in the direction of impact. The control unit can determine operating parameters depending on the position. In particular, the starting value of the impact frequency for starting the impact mechanism can be increased when the working position is essentially down is directed. A starting value of the stroke frequency for the start of the striking mechanism can be lowered if the working situation is essentially directed upwards. In this context, a “work situation” is to be understood in particular as an orientation of the striking mechanism with respect to gravity. In this context, “upward” should in particular be understood to mean a direction that is opposite to gravity, and “downward” at least essentially the direction of gravity. In this context, a “use case” is to be understood in particular to mean a specific application in which special operating parameters are advantageous. An application can require a particularly low-vibration operation, a particularly high impact effect and / or a certain frequency or a particularly quick and / or frequent impact mechanism start. The control unit can determine operating parameters depending on the application. An “operating mode” can in particular be a chisel operation, a drilling operation with deactivated striking mechanism or a percussion drilling operation with activated striking mechanism and a rotating drilling movement. The control unit can determine operating parameters depending on the operating mode. At least one further sensor can be provided to detect a speed of the racket before and after the shot. A recoil number and / or the impact strength can be determined from a speed difference. The control unit can be provided to set or regulate at least one operating parameter depending on the impact strength determined. A target impact strength can be adhered to particularly precisely.

It is further proposed that the control unit be provided to take into account at least one wear parameter when determining the at least one impact mechanism parameter and / or the at least one operating parameter. A wear parameter can in particular be a wear measure of carbon brushes of the motor and / or a changing friction. The control unit can be provided to estimate the wear parameter on the basis of an operating hours counter. The control unit can contain maps and / or functions of operating parameters depending on a state of wear and / or on a number of operating hours. The control unit can have sensors which are provided to measure a wear parameter, in particular a wear measure of carbon brushes.

The control unit can determine operating parameters as a function of the wear parameters.

It is proposed that the control unit be provided to temporarily lower the impact frequency and / or the impact mechanism speed to a start frequency and / or a start speed in at least one operating state for a change from idle mode to impact mode. In this context, a “starting frequency and / or a starting speed” is to be understood in particular to mean a speed below the limit speed, which is suitable for a reliable change from idle mode to impact mode. The impact speed can in particular be reduced to the starting speed if the impact mechanism is switched from idle mode to impact mode. The impact speed can in particular also be reduced to the starting speed if the impact mode is interrupted in the impact mode. An idling speed in idling mode can preferably be identical to a working speed in impact operation. The lowering to a starting speed can preferably be omitted if the working speed is a stable operating parameter of the striking mechanism.

It is further proposed that the control unit be provided to set the operating parameter directly to the work value in at least one operating state for a change from idle mode to impact mode. In particular, the control unit can be provided to set the operating parameter directly to the work value when a user requests a work value that is a stable operating parameter under given conditions. A change from idle mode to field mode can be reliable with this labor value. The setting of the start value can be avoided. An irritation of the user by a brief change of the operating parameter at the start of the striking mechanism can be avoided. There is no need for the control unit to intervene in the operating parameters.

An operating change sensor is also proposed, which is provided to signal a change in the operating mode. In particular, the change of operation sensor of the control unit can signal a change from idle mode to beat mode. The change of operation sensor can be provided to detect a contact pressure of the tool on a workpiece. It can can advantageously be recognized when the user starts a processing operation. The change of operation sensor can particularly advantageously detect a changeover of the striking mechanism, in particular an opening and / or closing of idle openings and further openings of the striking mechanism, which are provided for a change of operating mode. The change of operation sensor can detect a shift of a control sleeve which is provided for the change of operating mode of the striking mechanism. The control unit can advantageously recognize when the operating mode change of the striking mechanism takes place. The control unit can advantageously change the operating parameter in order to support and / or enable the change of operating mode. The field operation can be started reliably.

It is further proposed that the control unit have at least one delay parameter which is intended to influence a time period for a change between two values of the operating parameter. The change from an idle value and / or work value to a start value and / or from the start value to the work value can be done by a setpoint jump. The change can preferably be linear and / or have a continuous course. Current consumption of the motor can be limited. Accelerations, driving forces and / or vibrations can be reduced. The delay parameter can be provided to determine an increase in the function defining the change between the operating parameters. In particular, the time period for starting the striking mechanism can be specified. In this context, “starting” is to be understood in particular to mean starting the impact mode from a standstill of the engine. The hammer mechanism can be started directly from a standstill to a critical working value, in particular a critical working speed. If the speed increases slowly, the hammer mechanism can start before the limit speed is reached. The control unit can allow the hammer mechanism to start at a critical operating frequency from a standstill if the speed increases slowly. There is no need to set the start value. If the speed increases rapidly, the hammer mechanism may fail to start before the limit speed is reached. The speed must be temporarily set to the start speed when the hammer mechanism starts. Optimal operation of the striking mechanism can be ensured.

A hand-held power tool with a striking mechanism unit with the properties mentioned is also proposed. The handheld power tool can have the advantages mentioned.

drawing

Further advantages result from the following description of the drawing. Three exemplary embodiments of the invention are shown in the drawings. The drawings, description, and claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations within the scope of the claims.

Fig. 1

eine schematische Darstellung eines Bohr- und Schlaghammers mit einer erfindungsgemäßen Schlagwerkeinheit in einem ersten Ausführungsbeispiel in einem Leerlaufmodus,

Fig. 2

eine schematische Darstellung des Bohr- und Schlaghammers in einem Schlagmodus,

Fig. 3

eine schematische Darstellung eines simulierten Amplituden-Frequenzgangs eines nichtlinearen schwingfähigen Systems,

Fig. 4

eine schematische Darstellung eines weiteren simulierten Amplituden-Frequenzgangs des nichtlinearen schwingfähigen Systems,

Fig. 5

eine schematische Darstellung einer simulierten Schlagenergie der Schlagwerkeinheit bei einem Schlagwerkstart bei fallender und bei steigender Schlagfrequenz,

Fig. 6

eine schematische Darstellung einer möglichen Festlegung eines Startwerts, eines Grenzwerts, eines Arbeitswerts und eines Maximalwerts,

Fig. 7

eine schematische Darstellung der simulierten Schlagenergie der Schlagwerkeinheit bei einem Schlagwerkstart bei unterschiedlichen Umgebungsluftdruckverhältnissen,

Fig. 8

ein Blockschaltbild eines Algorithmus der Schlagwerkeinheit,

Fig. 9

ein lineares Kennfeld eines Schlagwerks mit einer Schlagwerkeinheit in einem zweiten Ausführungsbeispiel,

Fig. 10

ein bilineares Kennfeld,

Fig. 11

eine schematische Darstellung einer Entlüftungseinheit eines Schlagwerks eines Bohr- und Schlaghammers mit einer Schlagwerkeinheit in einem dritten Ausführungsbeispiel und

Fig. 12

eine weitere schematische Darstellung der Entlüftungseinheit.

Show it:

Fig. 1

1 shows a schematic illustration of a hammer drill and percussion hammer with an impact mechanism unit according to the invention in a first exemplary embodiment in an idle mode,

Fig. 2

1 shows a schematic representation of the hammer drill and percussion hammer in a percussion mode,

Fig. 3

1 shows a schematic representation of a simulated amplitude-frequency response of a nonlinear oscillatory system,

Fig. 4

1 shows a schematic representation of a further simulated amplitude-frequency response of the nonlinear oscillatory system,

Fig. 5

1 shows a schematic representation of a simulated impact energy of the impact mechanism unit when the impact mechanism starts and the impact frequency falls and increases,

Fig. 6

1 shows a schematic representation of a possible definition of a start value, a limit value, a work value and a maximum value,

Fig. 7

1 shows a schematic representation of the simulated impact energy of the striking mechanism unit when the striking mechanism starts at different ambient air pressure conditions,

Fig. 8

a block diagram of an algorithm of the percussion unit,

Fig. 9

2 shows a linear characteristic diagram of a striking mechanism with a striking mechanism unit in a second exemplary embodiment,

Fig. 10

a bilinear map,

Fig. 11

a schematic representation of a ventilation unit of a hammer mechanism of a rotary and percussion hammer with a hammer mechanism unit in a third embodiment and

Fig. 12

a further schematic representation of the ventilation unit.

Description of the embodiments

Figure 1 and Figure 2 show a hammer drill and striking hammer 12a with a striking mechanism unit 10a and with a control unit 14a, which is intended to control and regulate a pneumatic striking mechanism 16a. The striking mechanism unit 10a contains a motor 36a with a gear unit 38a, which rotates a hammer tube 42a via a first gear 40a and drives an eccentric gear 46a via a second gear 44a. The hammer tube 42a is non-rotatably connected to a tool holder 48a in which a tool 50a can be clamped. The tool holder 48a and the tool 50a can be driven for a drilling operation via the hammer tube 42a with a rotating working movement 52a. If a striker 54a is accelerated in a striking operation in a striking direction 56a in the direction of the tool holder 48a, it strikes a striking pin 58a arranged between the striker 54a and the tool 50a, which is passed on from the striking pin 58a to the tool 50a . The tool 50a exerts a striking working movement 60a through the impact pulse. A piston 62a is also movable in the hammer tube 42a in the striking direction 56a facing away from the racket 54a. The piston 62a can be moved periodically in the hammer tube 42a in the impact direction 56a and back again by means of a connecting rod 64a by the eccentric gear 46a driven by a hammer mechanism speed. The piston 62a compresses an air cushion 66a enclosed between the piston 62a and the striker 54a in the hammer tube 42a. When the piston 62a moves in the striking direction 56a, the striker 54a is accelerated in the striking direction 56a. By a rebound on the firing pin 58a and / or by a negative pressure resulting from a return movement of the piston 62a against the direction of impact 56a between the piston 62a and the striker 54a and / or by a counterpressure in a striking space 100a between the striker 54a and the firing pin 58a the racket 54a is moved back against the direction of impact 56a and then accelerated again in the direction of impact 56a for a next impact pulse. In a region between the striker 54a and the firing pin 58a, vent openings 68a are arranged in the hammer tube 42a, so that the air trapped in the striking space 100a between the striker 54a and the firing pin 58a can escape. In an area between the striker 54a and the piston 62a, idle openings 70a are arranged in the hammer tube 42a. The tool holder 48a is mounted displaceably in the impact direction 56a and is supported on a control sleeve 72a. A spring element 74a exerts a force in the impact direction 56a on the control sleeve 72a. In an impact mode 76a, in which the tool 50a is pressed against a workpiece by a user, the tool holder 48a moves the control sleeve 72a against the force of the spring element 74a so that it covers the idle openings 70a. If the tool 50a is removed from the workpiece, the tool holder 48a and the control sleeve 72a are moved in an idling mode 80a by the spring element 74a in the striking direction 56a in such a way that the control sleeve 72a releases the idling openings 70a. A pressure in the air cushion 66a between the piston 62a and the striker 54a can escape through the idle openings 70a. In idle mode 80a, racket 54a is not accelerated or is accelerated only slightly by air cushion 66a ( Figure 1 ). In idle mode, the striker 54a exerts little or no impact impacts on the firing pin 58a. The hammer drill 12a has a handheld power tool housing 82a with a handle 84a and an additional handle 86a, on which it is guided by the user.

The use of a striking operation when the striking mechanism unit 10a is switched from the idle mode 80a to the striking mode 76a by closing the idle openings 70a depends on striking mechanism parameters, in particular on the striking mechanism speed and an ambient air pressure. The piston 62a is periodically excited by the air cushion 66a enclosed between the piston 62a and the striker 54a with an impact frequency which corresponds to the impact mechanism speed of the eccentric gear 46a.

The striking mechanism 16a represents a non-linear oscillatory system. Figure 3 shows for understanding a schematic representation of a simulated amplitude-frequency response of a general, non-linear oscillatory system as a function of a frequency f. The amplitude A corresponds to the amplitude of a vibrating body of the system, which is not shown here in greater detail and corresponds to the striker 54a, in the case of external excitation, such as is effected by the piston 62a in the striking mechanism 16a. The amplitude frequency response is non-linear, at high frequencies the amplitude frequency response has several solutions. The amplitude that arises in this area depends, among other things, on the direction in which the frequency f is changed. If, starting from a higher frequency f, a minimum frequency 124a of the range of the amplitude frequency response with several solutions is undershot, the amplitude A jumps from an apex 126a with an infinite slope to a permissible solution of the amplitude frequency response with a higher level. If a maximum frequency 128a of the range of the amplitude frequency response with several solutions is exceeded from a lower frequency f, the amplitude A jumps from an apex 130a with an infinite slope to a permissible solution of the amplitude frequency response with a lower level. In the Figure 3 this behavior is indicated by arrows. In Figure 4 Another simulated amplitude-frequency response of the nonlinear oscillatory system is shown under different conditions. The amplitude frequency response has a gap 132a instead of a maximum frequency 128a. This case occurs, for example, when the maximum frequency 128a is higher than a possible excitation frequency with which the oscillatable system can be excited. In the case of the striking mechanism 16a, the excitation frequency can be limited, for example, by a maximum speed of the eccentric gear 46a.

The effect of the non-linear amplitude frequency response on the striking operation of the striking mechanism 16a is shown in FIG Figure 5 shown. Figure 5 shows a simulated impact energy E of the impact mechanism 16a when the impact mechanism starts with a falling impact frequency 92a and with an increasing impact frequency 94a. If the racket 54a is excited with an increasing impact mechanism speed or impact frequency 94a, the impact energy E increases with an increasing impact frequency 94a.If the impactor 66a is excited from a high impact mechanism speed starting from an idling mode with a falling impact mechanism speed or impact frequency 92a, the impact operation only starts at one certain percussion speed. This impact mechanism speed represents a limit frequency 20a. Above this impact frequency, when the impact frequency 92a falls, the racket 54a does not begin to move or only moves at a low amplitude and / or speed, even if a switchover from idle mode 80a ( Figure 1 ) to beat mode 76a ( Figure 2 ) the idle openings 70a are closed. There are no or very little impact impulses exerted by the striker 54a on the firing pin 58a. The impact energy E drops sharply above a maximum value 90a. In this case, the striker 54a does not perform any movement in the striking direction 56a or movements with a small amplitude in the striking direction 56a, so that no or only small striking pulses with a low impact energy E are delivered to the striking pin 58a. Depending on the ambient conditions and the design of the striking mechanism 16a, the limit frequency 20a is in a range from 20-70 Hz. The maximum value 90a is greater than the limit frequency 20a and is in a range of 40-400 Hz depending on ambient conditions and the design of the striking mechanism 16a The impact energy E reaches 1 - 200 joules depending on the ambient conditions and the design of the striking mechanism 16a at the limit frequency 20a, 2 - 400 joules at the maximum value 90a.

Figure 6 shows a schematic representation of a possible definition of operating parameters, in particular a starting value 28a, the cut-off frequency 20a, a working value 30a and the maximum value 90a. The cut-off frequency 20a is preferably selected at a hammer mechanism speed n at which the amplitude frequency response has a clear solution and a reliable hammer mechanism start is possible. The starting value 28a is less than or equal to the limit frequency 20a.

A reliable percussion mechanism start can be guaranteed, regardless of the direction from which the start value 28a is approached. The limit frequency 20a represents the transition to an ambiguous amplitude frequency response and the maximum start value 28a. The start value 28a is preferably selected at a distance from the limit frequency 20a, for example with a hammer mechanism speed reduced by 10%. If the striking operation is ensured, the striking mechanism 16a can be operated with a higher output with a supercritical working value 30a. A safe hammer mechanism start is not guaranteed with the supercritical working value 30a. The impact energy E drops sharply above the maximum value 90a. The working value 30a is therefore chosen to be lower than the maximum value 90a. The working value 30a can be set by the control unit 14a or set by the user, for example using a selector switch (not shown here). The work values 30a are determined, inter alia, as a function of a machining case and / or a type of material and / or a tool type. Work values 30a are assigned to various adjustable work steps. A work value 30a above the limit frequency 20a is a supercritical work value 30a, a work value 30a below the limit frequency 20a and / or below the start value 28a is a stable work value 30a. In addition to the start value 28a and the limit frequency 20a, an idle value 140a can optionally be defined. The idle value 140a is set in particular in the idle mode 80a. The idle value 140a is advantageously set higher than the start value 28a. A ventilation unit, not shown here, driven by the motor 36a can then be operated at a higher speed than when operating with the starting value 28a. The cooling of the striking mechanism 16a in idle mode 80a improves. An operating noise of the hammer drill and percussion hammer 12a is perceived by the user as more powerful than at the starting value 28a. Furthermore, the idle value 140a is advantageously set lower than the working value 30a. Noise emissions and / or vibrations can be reduced compared to an operation with the work value 30a. When changing from idle mode 80a to blow mode 76a, the starting value 28a can be reached faster than from the working value 30a.

Figure 7 shows the simulated impact energies E of the impact mechanism 16a when the impact mechanism starts with a falling and with an increasing impact frequency under different environmental conditions. In this example, curve 134a shows the Impact energy E at a first ambient air pressure and curve 136a the impact energy E at a second ambient air pressure reduced compared to the first ambient air pressure. A cut-off frequency 138a at the second ambient air pressure occurs at a lower impact frequency than the cut-off frequency 20a at the first ambient air pressure. If the second ambient air pressure is 10% lower than the first ambient air pressure, the limit frequency 138a is 1 - 25% lower than in the first ambient air pressure, depending on other influencing factors. A temperature of the striking mechanism 16a, in particular the hammer tube 42a, also has an influence on the cut-off frequency 20a. If the ambient temperature is lower, friction of the striker 54a in the hammer tube 42a increases, in particular due to an increasing viscosity of lubricants. If the temperature of the hammer tube 42a drops by 10K, the limit frequency 20a is reduced by 1 - 30% depending on other influencing factors. The limit frequency 20a can also change by +/- 20% due to influences of the tool. The tool can influence the rebound of the striker 54a from the firing pin 58a and thus influence the limit frequency 20a of the striking frequency.

f₀ stellt dabei eine Basisfrequenz und/oder Basisdrehzahl dar, C_lin,p eine applikationsabhängige Konstante des Druckterms und P den Umgebungsluftdruck. Im vorliegenden Beispiel hat f₀ den Wert von 10 Hz und C_lin,p einen Wert von 0.05 Hz/mbar. Bei einem Umgebungsluftdruck von 1000mbar beträgt f_soll,max 60 Hz. Der Fachmann wird diese Parameter geeignet anpassen. Entsprechend können bei abweichenden Basisdrehzahlen und/oder abweichenden druck- und applikationsabhängigen Konstanten C_lin,p druckabhängige Werte für den Startwert 28a, den Arbeitswert 30a und die Grenzfrequenz 20a festgelegt werden. Wird der Arbeitswert 30a und/oder der Maximalwert 90a der Soll-Schlagwerkdrehzahl unterhalb der Grenzfrequenz 20a festgelegt, kann der Startwert 28a entfallen und das Schlagwerk 16a kann mit dem Arbeitswert 30a gestartet werden.The control unit 14a is provided to determine the impact mechanism parameters as a function of measured values from an operating condition sensor unit 18a. In particular, the control unit 14a is provided to determine the limit frequency 20a of the amplitude frequency response for a reliable percussion mechanism start. The operating condition sensor unit 18a is provided to detect a temperature and the ambient air pressure. The operating condition sensor unit 18a is integrated as a module on a circuit board of the control unit 14a. The operating condition sensor unit 18a detects an ambient temperature. The temperature has an influence on a viscosity of lubricants and on a friction of the striker 54a with the hammer tube 42a. The ambient air pressure in particular has an influence on the return movement of the striker 54a and on the cut-off frequency 20a of the amplitude frequency response for a reliable hammer mechanism start. In addition, the operating condition sensor unit 18a has a radio interface, not shown here, by means of which it can obtain temperature and ambient air pressure data from an external device, also not shown here, such as a smartphone and / or from the Internet. The control unit 14a is also provided for operating parameters of the striking mechanism 16a. The operating parameter can be determined with the aid of a computing unit 24a for calculating a formula. A possible formula for determining a pressure-dependent maximum value 90a of the target hammer mechanism speed as a function of the ambient air pressure is: $${\mathrm{f}}_{\mathrm{should},\mathrm{Max}}={\mathrm{f}}_0+{\mathrm{C.}}_{\mathrm{lin},\mathrm{p}}\ast \mathrm{P}$$

f ₀ represents a base frequency and / or base speed, C _{lin, p} an application-dependent constant of the pressure term and P the ambient air pressure. In the present example, f _{0 has} the value of 10 Hz and C _{lin, p} a value of 0.05 Hz / mbar. At an ambient air pressure of 1000 mbar, f set _{is max.} 60 Hz. The person skilled in the art will adapt these parameters appropriately. Correspondingly, in the case of deviating basic speeds and / or deviating pressure and application-dependent constants C _{lin, p,} pressure-dependent values for the starting value 28a, the working value 30a and the limit frequency 20a can be defined. If the working value 30a and / or the maximum value 90a of the desired percussion mechanism speed is set below the limit frequency 20a, the starting value 28a can be omitted and the percussion mechanism 16a can be started with the working value 30a.

C_lin,T stellt eine applikationsabhängige Konstante des Temperaturterms dar. Die weiteren Betriebsparameter werden analog festgelegt. Im vorliegenden Beispiel hat f₀ den Wert von 5 Hz, C_lin,p einen Wert von 0.05 Hz/mbar und C_lin,T einen Wert von 0.25 Hz/°C wobei die Temperatur in °C einzusetzen ist. Bei einem Umgebungsluftdruck von 1000mbar und einer Temperatur von 20°C beträgt f_soll,max 60 Hz. Der Fachmann wird diese Parameter geeignet anpassen.
Neben Umgebungsluftdruck und Temperatur können weitere Terme eingeführt werden, wie ein von einer Betriebsstundenzahl abhängiger Term, der eine Veränderung des Schlagwerks aufgrund von Verschleiß berücksichtigt. Ein hier nicht dargestellter Lagesensor der Betriebsbedingungssensoreinheit 18a erfasst eine Lage des Bohr- und Schlaghammers 12a; die Lageinformation kann in einem weiteren Term bei der Festlegung der Betriebsparameter berücksichtigt werden. Der Term für die Arbeitslage wird so gewählt, dass f_soll,max bei einer nach oben gerichteten Arbeitslage reduziert und bei einer nach unten gerichteten Arbeitslage erhöht wird. Geeignete Faktoren für diesen Term können vom Fachmann in Versuchen festgelegt werden.
In einem weiteren Betriebsmodus kann der Benutzer über ein hier nicht näher dargestelltes Drehrad einen Drehzahlfaktor (X_Dreh) 88a einstellen, der dann mit einer druck- und/oder temperaturabhängigen Soll-Schlagzahl für den Schlagbetrieb f_soll,max multipliziert wird: $${\mathrm{f}}_{\mathrm{soll}}={\mathrm{X}}_{\mathrm{Dreh}}\ast {\mathrm{f}}_{\mathrm{soll},\max }$$

Die Drehzahl f_soll wird von der Steuereinheit 14a im Schlagbetrieb eingestellt. Der Benutzer kann so ausgehend von dem für jeweilige Betriebsbedingungen optimalen Arbeitswert 30a die Schlagwerkdrehzahl nach Wunsch absenken.In an operating mode, the control unit 14a can take the temperature into account in addition to the ambient air pressure, in this case the functional equation expands as follows: $${\mathrm{f}}_{\mathrm{should},\mathrm{Max}}={\mathrm{f}}_0+{\mathrm{C.}}_{\mathrm{lin},\mathrm{p}}\ast \mathrm{P}+{\mathrm{C.}}_{\mathrm{lin},\mathrm{T}}\ast \mathrm{T}$$

C _{lin, T} represents an application-dependent constant of the temperature term. The other operating parameters are determined analogously. In the present example, f _{0 has} the value of 5 Hz, C _{lin, p} a value of 0.05 Hz / mbar and C _{lin, T} a value of 0.25 Hz / ° C, where the temperature is to be used in ° C. At an ambient air pressure of 1000 mbar and a temperature of 20 ° C, f target is _max. 60 Hz. The person skilled in the art will adapt these parameters appropriately.
In addition to ambient air pressure and temperature, other terms can be introduced, such as a term that depends on the number of operating hours and takes into account a change in the striking mechanism due to wear. A position sensor, not shown here, of the operating condition sensor unit 18a detects a position of the rotary and percussion hammer 12a; The position information can be taken into account in a further term when determining the operating parameters. The term for the working position is chosen such that f _{target, max is} reduced for an upward working position and for a downward working position is increased. Suitable factors for this term can be determined by the expert in experiments.
In a further operating mode, the user can set a speed factor (X _rotation ) 88a via a rotary wheel (not shown here), which is then multiplied by a pressure-dependent and / or temperature-dependent target number of strokes for the field operation f _{, max} : $${\mathrm{f}}_{\mathrm{should}}={\mathrm{X}}_{\mathrm{Shoot}}\ast {\mathrm{f}}_{\mathrm{should},\mathrm{Max}}$$

F _to the speed is set by the control unit 14a in the percussion mode. The user can thus lower the hammer mechanism speed as desired, starting from the optimum working value 30a for the respective operating conditions.

Figure 8 shows a block diagram of an algorithm of the striking mechanism unit 10a. Depending on the ambient air pressure P and temperature T, the maximum value 90a of the desired number of strokes is determined in a first step 142a. The speed factor 88a is multiplied in a second step 144a by the maximum value 90a in order to determine the working value 30a of the desired number of strokes. A control unit 96a controls the motor 36a with the aid of power electronics 146a. A translation of the gear unit 38a is taken into account in the determination of a speed of the motor 36a required for a target number of strokes by the hammer mechanism unit 10a. An actual speed value 148a is fed back from the control unit 96a to the control unit 96a for controlling the motor 36a.

If a supercritical working value 30a is selected as the target number of strokes, the control unit 14a is provided to temporarily set the target number of strokes to the starting value 28a in order to change from the idle mode to the field operation. After a specified period of time in which a striking mechanism start has occurred during operation of the striking mechanism 16a with the starting value 28a, the desired number of strokes is increased to the working value 30a. The time period during which the striking mechanism unit 10a sets the starting value 28a when the striking mechanism starts is determined by a delay parameter. The delay parameter is defined by a person skilled in the art or can advantageously be set by the user.

An operating change sensor 32a is provided to signal the impact mechanism unit 10a of a change in the operating mode. The change of operation sensor 32a is arranged so that it detects and signals a control sleeve position when the control sleeve 72a is shifted from idle mode 80a to impact mode 76a. The striking mechanism unit 10a now temporarily sets the desired number of strokes to the starting value 28a if a supercritical working value 30a has been selected.

The following description and the drawings of further exemplary embodiments are essentially limited to the differences between the exemplary embodiments, with reference being able to be made to the drawings and / or the description of the other exemplary embodiments with regard to components with the same designation, in particular with respect to components with the same reference symbols . To distinguish the exemplary embodiments, the letters b and c are replaced by the reference numerals of the further exemplary embodiments instead of the letter a of the first exemplary embodiment.

Figure 9 and Figure 10 show a characteristic and a map of a striking mechanism in a further embodiment. The percussion mechanism unit of the second exemplary embodiment differs from the previous one in that an operating parameter is determined with the aid of a memory unit for storing a characteristic curve and a characteristic map. The characteristic ( Figure 9 ) and the map ( Figure 10 ) serve, as described, to determine a maximum value 90b of a target number of strokes f target _{, max} . The characteristic curve defines the maximum value 90b as a function of an ambient air pressure P; the map serves to determine the maximum value 90b depending on the ambient air pressure P and a temperature T. Intermediate values of the map are suitably interpolated by the striking mechanism unit.

Figure 11 and Figure 12 show a striking mechanism unit 10c in a further embodiment. The hammer mechanism unit 10c differs from the previous hammer mechanism unit in that an operating parameter defined by a control unit 14c is a throttle characteristic of a ventilation unit 22c. A striking space in a hammer tube 42c is delimited by a firing pin and a striker. The venting unit 22c has vent openings in the hammer tube 42c for venting the impact chamber. The ventilation unit 22c serves to equalize the pressure of the impact chamber with an environment a striking mechanism 16c. The venting unit 22c has an adjustment unit 102c. The setting unit 102c is provided for influencing a venting of the striking chamber arranged in front of the racket in a striking direction 56c during a striking process. The hammer tube 42c of the hammer mechanism 16c is mounted in a gear housing 104c of a hammer drill and hammer 12c. The gear housing 104c has ribs 106c arranged in a star shape and facing an outside of the hammer tube 42c. A bearing bush 108c, which supports the hammer tube 42c on the gear housing 104c, is pressed between the hammer tube 42c and the gear housing 104c in an end region 110c facing an eccentric gear. The bearing bush 108c forms, with the ribs 106c of the transmission housing 104c, air channels 112c, which are connected to the ventilation openings in the hammer tube 42c. The air channels 112c form part of the ventilation unit 22c. The striking chamber is connected via the air channels 112c to a gear chamber 114c which is arranged behind the hammer tube 42c against the striking direction 56c. The air channels 112c form throttling points 116c, which influence a flow cross section of the connection of the impact chamber with the transmission chamber 114c. The setting unit 102c is provided to set the flow cross section of the throttle points 116c. The air channels 112c forming the throttle points 116c form a transition between the impact chamber and the gear chamber 114c. An adjusting ring 149c has star-shaped, inwardly directed valve extensions 120c. Depending on a rotational position of the setting ring 149c, the valve extensions 120c can completely or partially cover the air channels 112c. The flow cross section can be adjusted by adjusting the setting ring 149c. The control unit 14c adjusts the setting ring 149c of the setting unit 102c by rotating the setting ring 149c with the aid of a servo drive 122c. If the ventilation unit 22c is partially closed, the pressure which arises when the racket moves in the striking direction 56c can only escape slowly in the striking chamber. A back pressure directed against the movement of the racket in the direction of impact 56c is formed. This counter pressure supports a return movement of the racket against the direction of impact 56c and thus a start of the striking mechanism. If a supercritical working value has been selected for the percussion mechanism speed, in which a reliable percussion mechanism start is not possible when the ventilation unit 22c is open, the control unit 14c partially closes the ventilation unit 22c in order to switch from an idling mode to a percussion mode. Due to the counter pressure The start of the field operation is supported in the field room. After the hammer mechanism has started, the control unit 14c opens the ventilation unit 22c again. The control unit 14c can also use the operating parameter of the throttle characteristic of the ventilation unit 22c for power regulation.

Claims (15)

1. Percussion unit, in particular for a hammer drill and/or percussion hammer (12a; 12c), with a control unit (14a; 14c) which is provided for performing open-loop and/or closed-loop control of a pneumatic percussion mechanism (16a; 16c), and at least one operating condition sensor unit (18a) which is provided for sensing ambient air pressure, wherein the control unit (14a; 14c) is provided for determining at least one percussion mechanism parameter in accordance with measured values of the operating condition sensor unit (18a), characterized in that the percussion mechanism parameter is a limiting value of an operating parameter, wherein the operating parameter is an impact frequency and/or a percussion unit rotational speed and/or a throttle characteristic variable of a venting unit (22c).
2. Percussion unit according to Claim 1, characterized in that the operating condition sensor unit (18a) is provided for sensing at least one temperature.
3. Percussion unit according to one of the preceding claims, characterized in that the control unit (14a; 14c) is provided for determining at least one limiting frequency (20a) of an amplitude frequency response of the percussion mechanism (16a; 16c).
4. Percussion unit according to one of the preceding claims, characterized in that the control unit (14a; 14c) is provided for defining at least one operating parameter of the percussion mechanism (16a; 16c).
5. Percussion unit at least according to Claim 4, characterized in that the control unit (14a,c) is provided for determining the at least one operating parameter using a computing unit (24a).
6. Percussion unit at least according to Claim 4, characterized in that the control unit (14a; 14c) is provided for determining the at least one operating parameter using a memory unit for storing a characteristic curve and/or a characteristic diagram.
7. Percussion unit according to one of the preceding claims, characterized in that the control unit (14a; 14c) is provided for taking into account position information and/or an operating mode and/or an application case during the determination of the at least one percussion mechanism parameter and/or at least one operating parameter.
8. Percussion unit according to one of the preceding claims, characterized in that the control unit (14a; 14c) is provided for taking into account at least one wear parameter during the determination of the at least one percussion mechanism parameter and/or at least one operating parameter.
9. Percussion unit according to one of the preceding claims, characterized in that the control unit (14a; 14c) is provided for setting at least one operating parameter temporarily to a starting value (28a) in at least one operating state at a changeover from an idling mode into a percussion mode.
10. Percussion unit at least according to Claim 4, characterized in that the control unit (14a; 14c) is provided for setting the operating parameter to a super-critical working value (30a) in at least one operating state in the percussion mode.
11. Percussion unit at least according to Claim 4, characterized in that the control unit (14a; 14c) is provided for setting the operating parameter directly to the working value (30a) in at least one operating state at a changeover from the idling mode into the percussion mode.
12. Percussion unit according to one of the preceding claims, characterized by an operation changeover sensor (32a) which is provided for signalling a changeover of the operating mode.
13. Percussion unit according to one of the preceding claims, characterized in that the control unit (14a; 14c) has at least one delay parameter which is provided for influencing a duration for a changeover between two values of the operating parameter.
14. Hand-held machine, in particular hammer drill and/or percussion hammer (12a; 12c), with a percussion unit (10a; 10c) according to one of the preceding claims.
15. Method for determining a percussion mechanism parameter of a percussion unit (10a; 10c) according to one of the preceding claims.

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