EP3663046B1 - Screw driver assembly and method for operating same - Google Patents

Description

The present invention relates to a screwdriver assembly with a housing, a drive assembly arranged in the housing, which has a motor, in particular an electric motor, a bit holder for fixing a screw bit, which is connected to an output shaft of the drive assembly in a rotationally fixed but axially displaceable manner relative to this Resetting means which press the bit holder into an axially front starting position, a sensor which is designed and / or configured to detect an axial displacement of the bit holder from its starting position that is directed backwards into the housing against the resetting force of the elastic resetting means, and control electronics , which is coupled to the sensor and the motor to turn the motor on and off in response to output signals from the sensor. The invention also relates to a method for operating a screwdriver arrangement.

Screwdriver assemblies for tightening or loosening screws are well known. These include a housing, a motor arranged in the housing with an output shaft, a bit holder for fixing a screw bit, which is connected to the output shaft in a rotationally fixed manner, and a trigger, such as a start lever or start button. In screwdriver arrangements of this type, the motor is activated by manually actuating or pressing the respective trigger. The problem here, however, is that when the motor is activated, before a screw bit received in the bit holder is pressed sufficiently forcefully against a screw to be rotated, the screw bit is disengaged during the rotation the screw head profile of the screw jumps. This leads to damage or high wear of the screw head profile as well as incorrect or insufficient tightening torque that is exerted on the screw. As a result, a qualitative statement on the tightening torque can no longer be guaranteed.

In order to solve this problem, screwdriver arrangements are known from the prior art in which the triggering of a screwing process is force-controlled. For example, the US5701961 , US4442738 , WO2015 / 123660A1 and CN2815620Y each a screwdriver arrangement with a so-called "push-to-start" function, which enables the motor to be activated automatically as soon as a screw bit received in the bit holder is pressed with a predetermined contact pressure against a screw to be turned.

The screwdriver arrangement of the CN2815620Y comprises, like the aforementioned screwdriver arrangements without a "push-to-start" function, a housing, a motor arranged in the housing with an output shaft and a bit holder for fixing a screw bit. To implement the "push-to-start" function, the bit holder is connected to the output shaft in a rotationally fixed but axially displaceable manner relative to the output shaft. The screwdriver arrangement further comprises a helical compression spring which is arranged between the output shaft and the bit holder and which presses the bit holder into an axially front starting position, a digital Hall sensor which is arranged and formed on the housing, and which is directed backwards into the housing against the restoring force of the helical compression spring to detect axial displacement of the bit holder from its starting position, a magnetic element arranged on the bit holder and a motor control circuit, which is operationally connected to both the motor and the digital Hall sensor, to the Mo signals of the sensor on and off. When a contact force is applied to the screw head of a screw to be turned, the bit holder and thus the magnetic element move in the axial direction relative to the digital Hall sensor. As soon as the digital Hall sensor detects the presence of a magnetic field on the digital Hall sensor after a predetermined distance covered by the magnetic element, i.e. as soon as a non-zero magnetic field is measured, the digital Hall sensor outputs a digital switching signal to the motor control circuit, which then switches the motor on. As long as a magnetic field is measured, the motor remains activated. As soon as the digital Hall sensor no longer detects the presence of a magnetic field on the digital Hall sensor, ie as soon as a magnetic field is measured equal to zero, the digital Hall sensor again outputs a digital switching signal to the motor control circuit, which switches the motor off. The motor control only serves to switch the motor on or off when it receives a switching signal.

With the screwdriver arrangement of the CN2815620Y the distance covered by the magnetic element, i.e. the contact force, when reached, the digital Hall sensor detects the magnetic field of the magnetic element and the motor is switched on, cannot be varied without either replacing the Hall sensor with a more sensitive or less sensitive Hall sensor or the magnetic element with a magnetic element to exchange with a stronger or weaker magnetic field.

From the US 2007/144753 A1 discloses a rotary tool system that includes a rotary tool for driving fasteners. The rotary tool has a housing and a drive arrangement which is arranged in the housing and comprises a motor and a transmission. The transmission is operatively connected to the engine and includes an output shaft. A chuck arrangement can be connected to the output shaft in such a way that that a shaft of the chuck assembly is slidable back and forth along part of the length of the output shaft and is axially movable with respect to the remainder of the rotary tool. A receptacle for a fastening element is provided at a front end of the chuck arrangement and a ring magnet is arranged at a rear end of the chuck arrangement. In addition, a WD device in the form of a Hall sensor is provided. The shaft of the chuck arrangement is pressed by means of a spring into an axially front starting position in which the Hall sensor does not exert any tension. If the shaft is pressed backwards against the restoring force of the spring, the Hall sensor outputs a voltage that is maximum when the shaft is fully retracted backwards. The level of the magnetic field strength is proportional to the proximity of the Hall sensor to the magnet. When the magnetic field strength acting on the Hall sensor is increased, a higher voltage is output by the Hall sensor. The voltage output by the Hall sensor is used to drive the motor, with the motor rotating faster when the output voltage is increased.

In addition, the lathe tool system includes the US 2007/0144753 A1 a control which is programmable by means of a laptop using a graphical user interface under Windows with a target torque, a target speed and / or a target angle which must be reached or exceeded in order for a connection to be considered to be successfully attached. Strain gauges are also provided, which record a torque of the motor and send the recorded torque information to the controller. In this way, the controller can continuously monitor the torque. The control can be programmable in such a way that it deactivates the turning tool when a preselected cut-off torque stored in the control is reached.

The invention is therefore based on the object of providing a screwdriver arrangement of the type mentioned at the outset which allows the contact pressure exerted on the bit holder, at which the motor is triggered, to be adjusted without structural changes to the screwdriver arrangement.

1. a) an der Steuerungselektronik als Referenz ein Schaltpunkt für den Motor einstellbar ist, der einer gewünschten axialen Position/Länge des axialen Verstellwegs entspricht, die der Bithalter bei dessen nach hinten gerichteter axialer Verstellung erreicht oder überschritten haben muss, um den Motor einschalten zu können,
2. b) der Sensor ausgebildet und/oder eingerichtet ist, während der nach hinten gerichteten axialen Verstellung des Bithalters aus dessen Ausgangslage die Länge des zurückgelegten axialen Verstellwegs und/oder die axiale Position des Bithalters zu erfassen und zu der erfassten Länge/Position korrespondierende Ausgangssignale oder ein sich korrespondierend zu der erfassten Länge/Position änderndes Ausgangssignal an die Steuerungselektronik zu übermitteln und
3. c) die Steuerungselektronik dazu ausbildet und/oder eingerichtet ist, auf der Grundlage des/der vom Sensor erhaltenen Ausgangssignals/Ausgangssignale und der an der Steuerungselektronik eingestellten Referenz den Motor automatisch einzuschalten/eingeschaltet zu halten, wenn die Referenz erreicht ist oder überschritten wird, ansonsten jedoch den Motor auszuschalten/ausgeschaltet zu halten.

According to the invention, this object is achieved in a screwdriver arrangement of the type mentioned at the outset in that

1. a) a switching point for the motor can be set as a reference on the control electronics, which corresponds to a desired axial position / length of the axial adjustment path that the bit holder must have reached or exceeded during its rearward axial adjustment in order to be able to switch on the motor,
2. b) the sensor is designed and / or set up to detect the length of the covered axial displacement path and / or the axial position of the bit holder during the rearward axial adjustment of the bit holder from its starting position and output signals or output signals corresponding to the detected length / position to transmit an output signal that changes in accordance with the detected length / position to the control electronics and
3. c) the control electronics are designed and / or set up to automatically switch the motor on / keep it switched on on the basis of the output signal / output signals received from the sensor and the reference set on the control electronics when the reference is reached or exceeded, otherwise however, keep the engine off / off.

1. a) an der Steuerungselektronik als Referenz ein Schaltpunkt für den Motor eingestellt wird, der einer gewünschten axialen Position/Länge des axialen Verstellwegs entspricht, die der Bithalter bei dessen nach hinten gerichteter axialer Verstellung erreicht oder überschritten haben muss, um den Motor einschalten zu können,
2. b) der Bithalter mit einem daran fixierten Schraubbit gegen eine zu drehende Schraube gepresst und damit aus seiner axial vorderen Ausgangslage entgegen der Rückstellkraft der elastischen Rückstellmittel nach hinten in das Gehäuse axial verstellt wird,
3. c) der Sensor während der axialen Verstellung des Bithalters die Länge des zurückgelegten axialen Verstellwegs und/oder die axiale Position des Bithalters erfasst und zu der erfassten Länge/Position korrespondierende Ausgangssignale oder ein sich korrespondierend zu der erfassten Länge/Position änderndes Ausgangssignal an die Steuerungselektronik übermittelt und
4. d) die Steuerungselektronik auf der Grundlage des/der vom Sensor erhaltenen Ausgangssignals/Ausgangssignale und der an der Steuerungselektronik eingestellten Referenz den Motor automatisch einschaltet/eingeschaltet hält, wenn die Referenz erreicht ist oder überschritten wird, ansonsten jedoch den Motor ausschaltet/ausgeschaltet hält.

The aforementioned object is also achieved according to the invention by a method for operating a screwdriver arrangement of the type described above, in which

1. a) a switching point for the motor is set as a reference on the control electronics, which corresponds to a desired axial position / length of the axial adjustment path that the bit holder must have reached or exceeded during its rearward axial adjustment in order to be able to switch on the motor,
2. b) the bit holder with a screw bit fixed to it is pressed against a screw to be rotated and is thus axially adjusted backwards into the housing from its axially front starting position against the restoring force of the elastic restoring means,
3. c) During the axial adjustment of the bit holder, the sensor detects the length of the axial adjustment path covered and / or the axial position of the bit holder and transmits output signals corresponding to the detected length / position or an output signal that changes corresponding to the detected length / position to the control electronics and
4. d) the control electronics on the basis of the output signal / output signals received from the sensor and the reference set on the control electronics automatically switch the motor on / keep it switched on when the reference is reached or exceeded, but otherwise switch the motor off / keep it switched off.

The invention is therefore based on the idea of creating a motorized screwdriver arrangement in which the release force, i.e. the pressing force that has to be exerted on the bit holder so that the motor is switched on, can be set via control electronics. On the control electronics of the screwdriver arrangement according to the invention, a switching point for the motor can therefore be set as a reference, which corresponds to a desired axial position / length of the axial adjustment path that the bit holder must have reached or exceeded during its rearward axial adjustment in order to switch the motor on can. As soon as the bit holder is pressed against a screw to be rotated, it moves axially backwards into the housing from its starting position against the restoring force of the elastic restoring means, which in particular have a helical compression spring, plate spring and / or rubber spring. A set switching point corresponds to the position / length the axial displacement and the spring constant of the return means of a desired release force. During the axial adjustment of the bit holder, the sensor detects the length of the axial adjustment path covered and / or the axial position of the bit holder. In this case, the sensor can be designed and / or set up to detect the length / position continuously and / or at predetermined, preferably evenly spaced points in time. The sensor transmits output signals corresponding to the recorded length / position or an output signal that changes corresponding to the recorded length / position to the control electronics. This / these output signal / output signals can be evaluated and, in contrast to the switching signals from the prior art, allow conclusions to be drawn about the contact pressure applied to the screw. On the basis of the output signals received from the sensor and the reference previously set on the control electronics, the control electronics are now able to automatically switch the motor on / keep it switched on when the reference is reached or exceeded, but otherwise switch off the motor / to keep switched off. The control electronics therefore decide, based on a previously made user setting or user input on the control electronics, whether or not the motor is to be triggered.

As a result, with the screwdriver arrangement according to the invention, the triggering force can be set variably, for example depending on the screw bit used, without a structural change having to be made to the screwdriver arrangement. Thus, based on the type of screw bit used, sufficient contact pressure is always ensured during the screwing process, whereby the risk of the screw bit slipping out during the screwing process is considerably reduced and the quality of the screw connection is increased.

• a1) an der Steuerungselektronik als Referenz ein spezifischer Wert des/der Ausgangssignals/Ausgangssignale einstellbar und
• c1) die Steuerungselektronik dazu ausgebildet und/oder eingerichtet, die Höhe des/der Ausgangssignals/Ausgangssignale mit einem eingestellten Wert zu vergleichen und den Motor automatisch einzuschalten/eingeschaltet zu halten, wenn der eingestellte Wert erreicht ist oder übertroffen wird, ansonsten jedoch den Motor auszuschalten/ausgeschaltet zu halten,

beziehungsweise umfasst das erfindungsgemäße Verfahren die weiteren Schritte, dass

• a1) an der Steuerungselektronik als Referenz ein spezifischer Wert des/der Ausgangssignals/Ausgangssignale eingestellt wird und
• d1) die Steuerungselektronik die Höhe des/der Ausgangssignals/Ausgangssignale mit einem eingestellten Wert vergleicht und den Motor automatisch einschaltet/eingeschaltet hält, wenn der eingestellte Wert erreicht ist oder übertroffen wird, ansonsten jedoch den Motor ausschaltet/ausgeschaltet hält.

According to one embodiment of the invention

• a1) a specific value of the output signal (s) can be set as a reference on the control electronics and
• c1) the control electronics are designed and / or set up to compare the level of the output signal (s) with a set value and to automatically switch on / keep the motor switched on when the set value is reached or exceeded, but otherwise switch off the motor to keep / off,

or the method according to the invention comprises the further steps that

• a1) a specific value of the output signal (s) is set on the control electronics as a reference, and
• d1) the control electronics compares the level of the output signal (s) with a set value and automatically switches the motor on / keeps it on when the set value is reached or exceeded, but otherwise switches the motor off / off.

Setting a specific value for the output signal is advantageous because it can be compared directly, that is, without conversion, with a recorded output signal. However, a specific contact pressure, a type of screw bit, a type of screw head profile or some other operational feature can also be set on the control electronics. The control electronics can be designed and / or set up to automatically set a specific value of the output signal that corresponds to the operation-related feature set by a user.

The sensor is preferably designed as a magnetic field sensor and a magnetic element attached to the bit holder is assigned to the magnetic field sensor, wherein the magnetic field sensor is designed and / or set up to transmit a signal proportional to the magnetic flux density detected by it as an output signal to the control electronics.

The magnetic field sensor can advantageously be an analog magnetic field sensor which transmits an analog signal, such as a current or voltage signal, as an output signal to the control electronics. In contrast to the digital signals of a digital magnetic field sensor, an analog measurement signal has the greatest possible information content. The magnetic field sensor can in particular be an analog Hall sensor. In this case, the output signal proportional to the magnetic flux density is a Hall voltage signal. Another type of magnetic field sensor can also be used. For example, the magnetic field sensor can be a field plate, in particular an analog field plate.

The magnetic element is advantageously a permanent magnet, since it does not require a power supply. In principle, the magnetic element can also be an electromagnet. The magnetic element - which can be ring-shaped and then surrounds the bit holder - is preferably arranged between an axially front end of the elastic return means and a contact surface of the bit holder, the magnetic element in particular being firmly connected to the bit holder. A ring-shaped magnetic element can also be referred to as a magnetic ring. It is conceivable that the magnetic element comprises several magnets.

The sensor can also be designed as an optical sensor. A plurality of optically detectable markings arranged one behind the other on the bit holder in the axial direction are then assigned to the optical sensor. Furthermore the optical sensor is designed and / or set up to transmit a signal as an output signal to the control electronics, which signal represents a marking detected by it.

According to one embodiment of the present invention, the sensor is arranged at the axial height of the elastic return means, the sensor being separated from the magnetic element or the optically detectable markings and / or the elastic return means in the radial direction, preferably only by a cavity filled with ambient air. If a magnetic field sensor is only separated from the magnetic element by air, the magnetic field of the magnetic element is not disturbed or shielded, so that the magnetic field can be detected without any problems. Since an optical sensor is only separated from the markings by air, the optical sensor ensures a clear view of the markings and thus problem-free optical detection of the markings.

The control electronics can be internal control electronics arranged on the housing, in particular at least partially arranged within the housing, external control electronics arranged remotely from the housing and / or a higher-level controller.

The control electronics expediently comprise a memory for storing several predefined references and / or a user interface or a setting and / or input means, in particular a touch-sensitive screen, a jog wheel and / or a membrane keyboard, for setting a reference, in particular stored in the memory. In this way, a user can define an operation-related characteristic, such as a specific desired value of the output signal (s) of the sensor, a specific desired contact pressure, set a type of screw bit or a type of screw head profile via the user interface or the setting and / or input means by entering the corresponding operational feature via the user interface or the setting and / or input means or from several stored in the memory and, for example selects the choices displayed on the touchscreen. If no touch-sensitive screen is provided, which by its very nature already includes a display means, the control electronics can include any other display means. This can be, for example, an optical display means, such as a display, or an acoustic display means. An associated value of the output signal (s) can be stored in the memory in the form of a database for a large number of selectable, operationally-related features.

According to one embodiment of the invention, it is provided that the bit holder is connected to the output shaft of the drive arrangement via a coupling arrangement which comprises a coupling element which is arranged in the housing and is releasably fixed on the output shaft of the drive arrangement, and the bit holder is rotatably fixed to the coupling arrangement, but is connected axially displaceably relative to this. In a preferred configuration of this embodiment, the coupling arrangement comprises an outer coupling element which is arranged in the housing and releasably connected, in particular screwed, to the output shaft of the drive arrangement, and has an inner coupling element which is arranged in the outer coupling element and is releasably connected to it, is in particular screwed, wherein the axially rear end of the bit holder is in rotationally fixed but axially displaceable engagement with the inner coupling element. In this refinement, the bit holder is fixed to the output shaft of the drive arrangement via the coupling arrangement, and it is also attached to the drive arrangement one, preferably the inner coupling element, engages in a rotationally fixed but axially displaceable manner.

For this purpose, the bit holder can have a male coupling member at its axially rearward end, which engages with a female coupling member of corresponding design, which is formed on the coupling arrangement, preferably on a coupling element of the coupling arrangement, in particular on the inner coupling element, for a rotational movement the clutch assembly to be transferred to the bit holder. The male coupling member of the bit holder is preferably designed at its axially rear end in the form of an external hexagon, which engages with a female coupling member in the form of a receptacle formed in a corresponding manner on the coupling element. In principle, the coupling arrangement can also have only one coupling element. In principle, other suitable shaft-hub connections are also possible for connecting the bit holder to the coupling arrangement.

The elastic return means are expediently supported axially between a coupling element, in particular the inner coupling element, and the bit holder and / or a magnetic element.

The bit holder is advantageously guided axially displaceably in the coupling arrangement, in particular the outer coupling element, via a bearing, for example a slide bearing.

The sensor can be attached to the housing or the coupling arrangement, in particular the outer coupling element, preferably on the inside of the housing or a coupling element of a coupling arrangement. If, in the case of a magnetic field sensor / optical sensor, the magnetic element / the optically detectable markings are attached to the bit holder is / are, the magnetic field sensor / optical sensor is preferably attached to the coupling arrangement. It is also conceivable to attach the sensor to the bit holder and the magnetic element / the markings to the coupling arrangement or to the housing.

Advantageously, the elastic return means comprise at least one helical compression spring and / or plate spring and / or rubber spring, which preferably grips around / around the bit holder in order to be supported on the inside by this. This prevents the spring (s) from buckling while they are being compressed. In principle, of course, other known elastic restoring means can also be used. In the case of an optical sensor whose associated, optically detectable markings are provided on the bit holder, it is advisable to select and / or position the elastic return means so that the optical sensor can see the markings freely. For this purpose, the elastic restoring means can be positioned, for example, within the female coupling member which is formed on the coupling arrangement, in particular on the inner coupling element. It is also conceivable that the helical compression spring, plate spring and / or rubber spring is guided both outside the male coupling member of the bit holder and inside the female coupling member of the coupling arrangement.

Figur 1

eine erfindungsgemäße Schraubendreheranordnung gemäß einer Ausführungsform der vorliegenden Erfindung und

Figur 2

eine Detailansicht eines elektrischen Schraubendrehers der Schraubendreheranordnung nach Figur 1.

Further features and advantages of the present invention will become clear on the basis of the following description of an embodiment of a screwdriver arrangement according to the invention with reference to the accompanying drawing. It shows:

Figure 1

an inventive screwdriver assembly according to an embodiment of the present invention and

Figure 2

a detailed view of an electric screwdriver of the screwdriver assembly according to Figure 1 .

the Figures 1 and 2 show a screwdriver assembly 1 according to an embodiment of the present invention. The screwdriver arrangement 1 has an electric screwdriver 2 and external control electronics 3a connected to it. The electric screwdriver 2 comprises a housing 4, which consists of an axially front housing section 4a, a middle housing section 4b and an axially rear housing section 4c.

In addition, the electric screwdriver 2 comprises a drive arrangement 5 with a motor 5a in the form of an electric motor and a gear 5b connected to the motor 5a and a bit holder 6 which has a bit holder 7 for fixing a screw bit 8 at its front end. The bit holder 6 is connected to an output shaft (not shown) of the drive arrangement 5, here the output shaft of the transmission 5b, via a clutch arrangement 9. This comprises an outer coupling element 9a, which is essentially hollow-cylindrical and connected to the output shaft in a rotationally fixed manner, here is screwed. In the Figure 2 the through bores 10a of the outer coupling element 9a for corresponding fastening screws can be seen.

The coupling arrangement 9 also has an inner coupling element 9b, which is arranged inside the outer coupling element 9a and releasably connected to it, screwed here. In the Figure 2 the corresponding through bores 10b for the connecting screws in the peripheral wall of the outer coupling element 9a are shown.

The bit holder 6 is guided axially displaceably in the outer coupling element 9a via a bearing 11 and is axially displaceably but non-rotatably engaged with the inner coupling element 9b. For this purpose, the bit holder 6 has at its axially rear end a male coupling member 12 in the form of an external hexagon, which engages with a female coupling member 13 in the form of a correspondingly designed receptacle in the axially front end portion of the inner coupling element 9b. The bit holder 6 is pressed into an axially front starting position by elastic restoring means 14 in the form of a helical compression spring. In another embodiment, not shown here, a plate and / or rubber spring can also be used. Specifically, the helical compression spring is supported axially between the front end face 15 of the inner coupling element 9b and a rear end face of the bit holder 6, being placed on the axially rear end portion of the bit holder 6 so that it engages around it and is supported by it on the inside. A housing cap 16 is screwed onto the axially front end of the housing 4 in order to close it at the front, and the bit holder 6 extends through it. For this purpose, corresponding threaded sections 17 are formed on the housing cap 16 and the housing 4.

In addition, the electric screwdriver 2 comprises a measuring device 18 with a magnetic element 19 in the form of a permanent magnet fastened to the bit holder 6 and a sensor 20 in the form of an analog Hall sensor that is attached to the inside of the outer coupling element 9a at the axial height of the elastic return means 14 Magnet element 19 is assigned. The magnetic element 19 is ring-shaped and pushed onto the axially rear end section of the bit holder 6, it being positioned axially between the front end of the elastic restoring means 14 and an axial contact surface 21 of the bit holder 6 is. The sensor 20 is separated from the magnetic element 19 and the elastic restoring means 14 in the radial direction only by ambient air.

Furthermore, the electric screwdriver 2 comprises internal control electronics 3b, which together with the external control electronics 3a are referred to as control electronics 3 of the screwdriver arrangement 1. The internal control electronics 3b are arranged within the axially rear housing section 4c. The external control electronics 3a are located outside the screwdriver 2 and comprise a memory 22 and a user interface 23 in the form of a touch-sensitive screen. In another embodiment, not shown here, any other user interface 23 can also be used. The internal control electronics 3b are connected at the axially rear end of the housing 4 of the screwdriver 2 via a transmission line 24 to the external control electronics 3a. The control electronics 3 are coupled to the sensor 20 and the motor 5a in order to switch the motor 5a on and off as a function of output signals from the sensor 20.

According to the invention, the sensor 20 and the control electronics 3 are designed and / or set up in such a way that the screwdriver arrangement 1 according to the invention can be operated according to the method explained below.

On the external control electronics 3a, a user can use the user interface 23 as a reference to set a switching point for the motor 5a that corresponds to a desired axial position / length of the axial displacement path that the bit holder 6 must have reached or exceeded when it is axially displaced backwards in order to be able to switch on the motor 5a. The user can, for example, set a specific value of the output signal of the sensor 20, which is designed as a Hall sensor, In other words, set a specific Hall voltage value, a specific contact pressure with which the bit holder 6 is pressed against a screw to be turned, a type of screw bit, a type of screw head profile or any other operational feature via the user interface 23 by entering the corresponding operational feature or selects from a plurality of predefined selection options stored in the memory 22 of the external evaluation electronics 3a. If no Hall voltage value has been entered or selected by the user, but some other operational feature stored in memory 22 has been selected, external control electronics 3a automatically sets a Hall voltage value corresponding to the selected operational feature and stored in memory 22 as belonging to the feature.

Subsequently, the user presses the screwdriver 2 with a screw bit 8 fixed in the bit holder 6 against a screw to be turned, whereby the bit holder 6 together with the magnet element 19 attached to it from its axially front starting position against the restoring force of the helical compression spring backwards into the coupling arrangement 9 is pressed axially.

During this axial adjustment of the bit holder 6, the sensor 20 detects the length of the axial adjustment path covered and / or the axial position of the bit holder 6 and transmits an output signal that changes in accordance with the detected length / position to the internal control electronics 3b. More precisely, during the axial displacement of the magnetic element 19 relative to the sensor 20, the sensor 20 continuously measures the Hall voltage proportional to the magnetic flux density at the sensor 20 and outputs an analog measurement signal, namely an analog Hall voltage signal, as an output signal to the internal control electronics 3b. The internal Control electronics 3b converts the analog measurement signal into a digital measurement signal and forwards this via the transmission line 24 to the external control electronics 3a.

On the basis of the output signal received from the sensor 20 or the digitized output signal received from the internal control electronics 3b and the reference previously set on the external control electronics 3a, the control electronics 3 then automatically switch on the motor 5a or keep it switched on when the reference is reached or is exceeded. In the present example, the external control electronics 3a compares the level of the Hall voltage signal with the set Hall voltage value and automatically switches the motor 5a on or keeps it switched on when the set Hall voltage value is reached or exceeded. Otherwise it switches off the motor 5a or keeps it switched on.

In an alternative embodiment and if the user has set a specific contact pressure via the user interface 23, the external control electronics 3a use a Hall voltage measurement value of the digitized output signal to determine a contact force that is exerted on the bit holder 6 and with which the screw bit 8 is directed towards the screw head rotating screw is pressed. For this purpose, the axial position of the magnetic element 19 or the spring travel S is determined based on the rest position of the helical compression spring, which corresponds to the axially front starting position of the bit holder 6, i.e. the distance by which the helical compression spring has been compressed. This is done by comparing the Hall voltage measured value under consideration with a comparison curve stored in memory 22, which shows the change in the measured Hall voltage with increasing compression of the helical compression spring, starting from its rest position and thus increasing axial displacement of the Magnetic element 19 in the clutch assembly 9 reproduces. The pressing force corresponds to the spring force, ie the elastic restoring force which is brought about by the compression of the compression spring by the spring travel S when the screw bit 8 is pressed onto the screw head. Since the spring travel S has been determined and the spring constant D of the compression spring is known, the absolute contact force for a linear compression spring can be calculated using Hooke's law as follows: $${\mathrm{F.}}_{\mathrm{Contact\; pressure}}={\mathrm{F.}}_{\mathrm{feather}}=\mathrm{D.}\times \mathrm{S.}$$

The external control electronics 3a then compares the calculated or determined contact force with the specific contact force previously set on the external control electronics 3a and automatically switches the motor 5a on or keeps it switched on when the set specific contact force is reached or exceeded. Otherwise it switches off the motor 5a or keeps it switched off.

In the embodiments described above, the internal control electronics 3b can only be provided to forward the analog output signal to the external control electronics 3a without converting it. The analog output signal is then digitized for further processing only in the external control electronics 3a. The communication between the internal control electronics 3b and the external control electronics 3a can also take place wirelessly. In this case, the digitization must already take place in the internal control electronics 3b. Alternatively, either the internal control electronics 3b can be dispensed with and the analog output signal from the sensor 20 can be output directly to the external control electronics 3a or the external control electronics 3a can be dispensed with and the entire measurement data processing can be taken over by the internal control electronics 3b. In the latter In this case, the internal control electronics 3b include the memory 22 and the user interface 23, the user interface 23 then preferably being arranged on the outside of the housing 4.

In a further embodiment, not shown here, the sensor 20 is not designed as a magnetic field sensor, but as an optical sensor. In this case, instead of the magnetic element 19, a plurality of optically detectable markings arranged one behind the other in the axial direction are provided on the bit holder 6. In order not to partially cover the optical markings, it can be expedient to provide other elastic restoring means instead of the helical compression spring, which allow the optical sensor to see the markings freely. Alternatively, only the positioning of the helical compression spring can be changed in such a way that the optical sensor has a clear view of the markings. The optical sensor is designed and / or set up to transmit a signal as an output signal to the control electronics 3, which signal represents a marking detected by it. Otherwise, the mode of operation and the structural design correspond to that of the screwdriver arrangement 1 described above.

List of reference symbols

1

Screwdriver assembly

2

screwdriver

3

Control electronics

3a

external control electronics

3b

internal control electronics

4th

casing

4a

axially front housing section

4b

middle housing section

4c

axially rear housing section

5

Drive arrangement

5a

engine

5b

transmission

6th

Bit holder

7th

Bit holder

8th

Screw bit

9

Clutch assembly

9a

outer coupling element

9b

inner coupling element

10a, b

Through holes

11

camp

12th

male coupling link

13th

female coupling link

14th

elastic restoring means

15th

Face

16

Housing cap

17th

Threaded sections

18th

Measuring device

19th

Magnetic element

20th

sensor

21

Contact surface

22nd

Storage

23

User interface

24

Transmission line

Claims (15)

1. Screwdriver arrangement (1) having a housing (4), a drive arrangement (5), which is arranged in the housing (4) and has a motor (5a), in particular an electric motor, a bit holder (6) for fixing a screw bit (8), which bit holder is connected to an output shaft of the drive arrangement (5) in a rotationally fixed but axially displaceable manner relative to the latter, elastic restoring means (14) which press the bit holder (6) into an axially forward initial position, a sensor (20) which is designed and/or set up to detect an axial displacement of the bit holder (6) from its initial position, which displacement takes place counter to the restoring force of the elastic restoring means (14) and is directed rearwards into the housing (4), and control electronics (3) which are coupled to the sensor (20) and to the motor (5a) in order to switch the motor (5a) on and off as a function of output signals from the sensor (20), characterized in that

   a) a switching point for the motor (5a) can be set as a reference on the control electronics (3), which switching point corresponds to a desired axial position/length of the axial adjustment path which the bit holder (6) must have reached or exceeded during its rearward axial adjustment in order to be able to switch on the motor (5a),

   b) the sensor (20) is designed and/or set up to detect the length of the axial adjustment path covered and/or the axial position of the bit holder (6) during the rearward axial adjustment of the bit holder (6) from its initial position and to transmit output signals corresponding to the detected length/position or an output signal which changes corresponding to the detected length/position to the control electronics (3), and

   c) the control electronics (3) are designed and/or arranged, on the basis of the output signal(s) received from the sensor (20) and the reference set at the control electronics (3), to automatically switch on/keep switched on the motor (5a) when the reference is reached or exceeded, but otherwise to switch off/keep switched off the motor (5a).
2. Screwdriver arrangement (1) according to claim 1, characterized in that

   a1) a specific value of the output signal(s) can be set on the control electronics (3) as a reference, and

   c1) the control electronics (3) are designed and/or set up to compare the level of the output signal(s) with a set value and to automatically switch on/keep switched on the motor (5a) when the set value is reached or exceeded, but otherwise to switch off/keep switched off the motor (5a).
3. Screwdriver arrangement (1) according to claim 1 or 2, characterized in that the sensor (20) is designed as a magnetic field sensor and a magnetic element (19) attached to the bit holder (6) is assigned to the magnetic field sensor, the magnetic field sensor being designed and/or set up to transmit a signal proportional to the magnetic flux density detected by it as an output signal to the control electronics (3), wherein the magnetic field sensor is in particular a Hall sensor, preferably an analogue Hall sensor, and the output signal proportional to the magnetic flux density is a Hall voltage signal.
4. Screwdriver arrangement (1) according to claim 3, characterized in that the magnetic element (19) is annular and/or in that the magnetic element (19) is arranged between an axially front end of the elastic restoring means (14) and a contact surface (21) of the bit holder (6), the magnetic element (19) being in particular firmly connected to the bit holder (6).
5. Screwdriver arrangement (1) according to claim 1 or 2, characterized in that the sensor (20) is designed as an optical sensor and a plurality of optically detectable markings arranged one behind the other in the axial direction on the bit holder (6) are assigned to the optical sensor, the optical sensor being designed and/or set up to transmit a signal as an output signal to the control electronics (3) which represents a marking detected by it.
6. Screwdriver arrangement (1) according to any of the claims 3 to 5, characterized in that the sensor (20) is arranged at the axial level of the elastic restoring means (14), the sensor (20) being separated from the magnetic element (19) or the optically detectable markings and/or the elastic restoring means (14) in the radial direction preferably only by a cavity filled with ambient air.
7. Screwdriver arrangement (1) according to any of the previous claims, characterized in that the control electronics (3) are internal control electronics (3b) arranged on the housing (4), in particular arranged at least partially inside the housing (4), external control electronics (3a) arranged remote from the housing (4) and/or a higher-level controller and/or in that the control electronics (3) comprise a memory (22) for storing a plurality of predefined references and/or a user interface (23) or a setting and/or input means, in particular a touch-sensitive screen, a jogwheel and/or a membrane keyboard, for setting a reference stored in particular in the memory (22).
8. Screwdriver arrangement (1) according to any of the previous claims, characterized in that the bit holder (6) is connected to the output shaft of the drive arrangement (5) via a coupling arrangement (9) comprising a coupling element (9a) which is arranged in the housing (4) and is detachably fixed to the output shaft of the drive arrangement, and the bit holder (6) is connected to the coupling arrangement (9) in a rotationally fixed but axially displaceable manner relative thereto.
9. Screwdriver arrangement (1) according to claim 8, characterized in that the coupling arrangement (9) comprises an outer coupling element (9a), which is arranged in the housing (4) and is detachably connected, in particular screwed, to the output shaft of the drive arrangement (5), and an inner coupling element (9b) which is arranged in the outer coupling element (9a) and is detachably connected, in particular screwed, thereto, wherein the axially rear end of the bit holder (6) is in rotationally fixed but axially displaceable engagement with the inner coupling element (9b).
10. Screwdriver arrangement (1) according to claim 8 or 9, characterized in that the bit holder (6) has at its axially rear end a male coupling member (12) which is in engagement with a female coupling member (13) corresponding thereto which is formed on the coupling arrangement (9), in particular on the inner coupling element (9b), in particular the male coupling member (12) of the bit holder (6) being in the form of an outer hexagon which engages with a female coupling member (13) in the form of a correspondingly formed receptacle of the coupling arrangement (9), in particular of the inner coupling element (9b).
11. Screwdriver arrangement (1) according to any of claims 8 to 10, characterized in that the elastic restoring means (14) are supported axially between a coupling element, in particular the inner coupling element (9b), and the bit holder (6) and/or a magnetic element (19) and/or in that the bit holder (6) is guided axially displaceably in the coupling arrangement (9), in particular the outer coupling element (9a), via a bearing (11), for example a plain bearing.
12. Screwdriver arrangement (1) according to any of the previous claims, characterized in that the sensor (20) is attached to the housing (4) or the coupling arrangement (9), in particular the outer coupling element (9a), preferably on the inside of the housing (4) or the outer coupling element (9a).
13. Screwdriver arrangement (1) according to any of the previous claims, characterized in that the elastic restoring means (14) comprise at least one helical compression spring, cup spring and/or rubber spring, which preferably embrace the bit holder (6) in order to be internally supported by the latter.
14. Method for operating a screwdriver arrangement (1) according to any of the previous claims, characterized by the steps that

    a) a switching point for the motor (5a) is set on the control electronics (3) as a reference, which corresponds to a desired axial position/length of the axial adjustment path which the bit holder (6) must have reached or exceeded during its rearward axial adjustment in order to be able to switch on the motor (5a),

    b) the bit holder (6) with a screw bit (8) fixed thereto is pressed against a screw to be turned and is thus axially displaced from its axially forward initial position backwards into the housing (4) against the restoring force of the elastic restoring means (14),

    c) during the axial adjustment of the bit holder (6), the sensor (20) detects the length of the axial adjustment path covered and/or the axial position of the bit holder (6) and transmits output signals corresponding to the detected length/position or an output signal changing corresponding to the detected length/position to the control electronics (3), and

    d) the control electronics (3), on the basis of the output signal(s) received from the sensor (20) and the reference set at the control electronics (3), automatically switch on/ keep switched on the motor (5a) when the reference is reached or exceeded, but otherwise switch off/ keep switched off the motor (5a).
15. Method according to claim 14, characterized by the further steps that

    a1) a specific value of the output signal(s) is set on the control electronics (3) as a reference, and

    d1) the control electronics (3) compare the level of the output signal(s) with a set value and automatically switch on/keep switched on the motor (5a) if the set value is reached or exceeded, but otherwise switch off/keep switched off the motor (5a).

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