EP2839931A1 - Elektrischer Schrauber mit Festziehfunktion - Google Patents

Elektrischer Schrauber mit Festziehfunktion Download PDF

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Publication number
EP2839931A1
EP2839931A1 EP14181967.2A EP14181967A EP2839931A1 EP 2839931 A1 EP2839931 A1 EP 2839931A1 EP 14181967 A EP14181967 A EP 14181967A EP 2839931 A1 EP2839931 A1 EP 2839931A1
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EP
European Patent Office
Prior art keywords
torque
motor means
speed
assembly
motor
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EP14181967.2A
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English (en)
French (fr)
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EP2839931B1 (de
Inventor
Nicolas Le Du
Julien TROPEE
Benoit Allenou
Antoine Vrignaud
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Georges Renault SAS
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Georges Renault SAS
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Publication of EP2839931A1 publication Critical patent/EP2839931A1/de
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
    • B25B21/00—Portable power-driven screw or nut setting or loosening tools; Attachments for drilling apparatus serving the same purpose
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
    • B25B23/00—Details of, or accessories for, spanners, wrenches, screwdrivers
    • B25B23/14—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers

Definitions

  • the field of the invention is that of the design and manufacture of power tools screwdriving clamping.
  • the invention therefore relates to electric screwdrivers with controlled clamping, the implementation of which makes it possible to perform screwing operations in which the rotation of the element to be screwed, such as for example a screw, is never interrupted since the beginning of the screwing to the end. It does not therefore concern electric screwdrivers whose motors are powered by electrical pulses during a screwing operation, so that between two pulses of the same screwing operation, the rotation of the screw element stop.
  • Electric screwdrivers with controlled clamping are conventionally used to ensure, during a screwing operation, the tightening of an assembly, that is to say the connection of several parts for example by means of a screw tightened to a torque whose value is chosen so that the assembly is sufficiently rigid.
  • the performance of the tool reflects its ability to achieve the desired objective torque, in other words to achieve the tightening of an assembly at a predetermined torque level.
  • the productivity of the tool translates its ability to execute and chain clamps as quickly as possible.
  • the ergonomics of the tool reflect the comfort of use and the safety of use.
  • the screwdriver exerts a reaction torque in the hand of the operator.
  • the intensity of this force is equal to the tightening torque divided by the lever arm, that is to say the distance between the handle of the tool and the axis of rotation of the screw to be tightened.
  • the lower this reaction the greater the comfort of use of the tool is high. Therefore, for a given torque range, it is customary to size the distance between the handle and the axis of rotation of the screw to be tightened so that the reaction force that the operator develops to maintain the screwdriver remains moderate.
  • the level of ergonomics of a screwdriver therefore depends in particular on the reaction level of the screwdriver in the hand of the operator during a screwing operation.
  • the conventional and constant approach of the designer is therefore to size the motor and the reduction so that the output torque can reach the target torque Cobj, that is to say say the tightening torque that we set the goal to achieve.
  • the motor is supplied with electric current so that the terminal member is rotated at a generally constant fast frequency until the tightening torque reaches a threshold value of screwing corresponding in practice to the moment at which the screw docking the assembly, that is to say at the instant at which a rapid rise in the tightening torque is observed.
  • the motor is supplied with electric current so that the end member is rotated at a generally slower frequency, up to the tightening torque reaches a goal torque value Cobj.
  • This solution thus makes it possible to reduce the time during which the value of the tightening torque increases during the screwing phase, and thus to reduce the reaction of the tool in the operator's hand.
  • the ergonomics of the tool is therefore improved.
  • the body of the screwdriver is ideally not constrained in position by the operator, it is caused to rotate at an angle ⁇ around the axis of rotation of the screw, in the opposite direction to the screw under an acceleration ⁇ .
  • Frank assemblies are assemblies during the rise in torque of which the element to be screwed (for example a screw or a nut) is rotated over a low angular range (generally less than about 30 °) between the moment it hits the assembly until the target torque Cobj is reached.
  • Elastic assemblies are less rigid assemblies during the tightening of which the element to be screwed (for example a screw or a nut) is rotated over a larger angular range, between the moment when it docked the assembly and the moment when the target torque Cobj is reached.
  • the invention particularly aims to overcome these disadvantages of the prior art.
  • the object of the invention is to provide, in at least one embodiment, an electric screwdriver with controlled tightening which has a better ergonomics than the techniques of the prior art.
  • the invention aims to provide such a screwdriver which requires, in at least one embodiment, the development of a low holding effort by the operator during a clamping operation.
  • Another object of the invention is to provide such a screwdriver which has, in at least one embodiment, good ergonomics including when tightening an elastic assembly.
  • Another object of the invention is to provide, in at least one embodiment, such a screwdriver that achieves a good level of productivity.
  • the invention also aims to provide such a technique that is, in at least one embodiment, simple design and / or easy to implement and / or economic.
  • Couples Cmax and Cobj are conventionally expressed in N.m., B is expressed in meters.
  • the yield ⁇ is less than 1.
  • a screwing operation begins with a pre-screwing phase during which the motor accelerates from zero speed to the preprogrammed speed level for the completion of the tightening cycle. During this phase, the motor rotor acquires kinetic energy. Once the screw head is in contact with the part to be assembled, this kinetic energy is transferred into the assembly in the form of potential assembly energy during deceleration of the motor.
  • Ep Couple . AngleVissage / 2
  • an assembly exhibiting an evolution of the proportional torque as a function of the angle over the torque range of 0 to 60 Nm and the angle range of 0 to 60 ° (1.0472 rd) and requiring a torque of 40N.m requires to be tightened a potential energy Ep of 21 joules.
  • the kinetic energy Ec contained in a servo motor rotor rotating at a speed of 20000 rpm and whose rotor inertia is 1.4.10 -5 kg.m 2 is equal to 30 joules.
  • the kinetic energy of the rotor is therefore sufficient to ensure the tightening of an assembly.
  • the inventors have deduced that the value of the reduction ratio does not intervene as such in the return of this kinetic energy, and therefore in achieving the desired torque.
  • the inventors have found that when implementing a reduction with a low reduction ratio, the rotor is subjected to a greater deceleration torque than during the implementation. a reduction with a high ratio.
  • the inventors have deduced that the duration of the torque increase period during the tightening phase is even shorter than the ratio of the reduction is low.
  • the rotation angle of the tool body around the axis of the screw is even lower than the reduction ratio is low.
  • the effort applied by the operator to maintain the screwdriver is therefore lower as the reduction ratio is low. Therefore, the choice of a low value reduction ratio helps improve the ergonomics of the tool.
  • the inequation R. ⁇ . Cmax ⁇ B.100 reflects the fact that the transmission is designed in such a way that the output torque delivered by the screwdriver continuously is always less than the maximum effort that an operator is likely to be able to provide to maintain it at during a screwing operation, that is to say about 100 N.
  • Inequency B.100 ⁇ Cobj / 2 expresses the fact that the transmission is designed such that the objective torque Cobj to which it is desired to perform the clamping is very much greater than the output torque that can be delivered by the screwdriver by using the electromagnetic torque of the motor alone, that is to say in a prolonged tightening at low rotational speed.
  • the target torque Cobj is achieved by exploiting the kinetic energy accumulated by the transmission, which is transmitted to the assembly to achieve the screwing.
  • the implementation of the technique according to the invention thus considerably reduces the perception of the reaction of the tool by the operator, or at least limit it to a level that does not cause any inconvenience.
  • the screwdriver generates a force feedback in the hand of the operator who remains below the average threshold of tolerance from which the operator can feel discomfort or inconvenience.
  • the appearance of musculoskeletal disorders in the operator is thus avoided and the comfort of use of the screwdriver increased.
  • the kinetic energy transmitted by the rotor to the screw causes a deformation of the reduction until it reaches the necessary torque to start turn the screw and tighten.
  • a screwing phase is thus successively composed of a period of deformation of the transmission, a period of rotation of the screw, and a period of relaxation of the transmission.
  • the higher the stiffness of the transmission the greater the rotation of the tool in the hand of the operator during a screwing operation is low, which contributes to improving the ergonomics of the tool.
  • This stiffness Rd can be measured on the input shaft of the reduction when the output shaft of the tool is immobilized in rotation relative to the body of the tool.
  • the deformation of the reduction tends to absorb some of the kinetic energy accumulated by the rotor and transmission and transmitted to the assembly to ensure clamping.
  • the resistance to deformation Rd of the transmission is greater than or equal to (40.Cvmax) / R 2 .
  • said reduction contains at most one epicyclic reduction stage.
  • the inventors have responded to the dual constraint of reducing the transmission ratio of the reduction and increasing the rigidity of the transmission by reducing the number of parts in the transmission chain.
  • the continuous clamping capacity of a tool according to the invention is capped at a torque level lower than that which an operator can no longer support.
  • the low ratio reduction is designed in such a way that the target torque Cobj is reached because of the transmission of the kinetic energy accumulated by the rotor subsequently restored to the assembly and not because of the electromotive force of the rotor.
  • the electromagnetic torque of the rotor multiplied by the reduction ratio and the efficiency is much lower than the target torque Cobj.
  • the reduction ratio will be chosen so that the maximum torque A continuously deliverable by the screwdriver does not exceed the holding capacity of the screwdriver by the operator.
  • the value of the ratio R will be chosen such that R. ⁇ .Cmax ⁇ B. F
  • the reduction ratio will be chosen so that A does not exceed 10 Nm, which is compatible with the cashing capabilities of torque by the operator for this type of handle.
  • the value of the torque A may be stronger.
  • the technique according to the invention makes it possible to guarantee the attainment of a good level of productivity.
  • the reduction of the reduction ratio makes it possible to increase in proportion the pre-screwing speed of the screwdriver and thus to shorten the pre-screwing phase, which improves the productivity.
  • the Cobj value is greater than 20 Nm.
  • a screwdriver according to the invention thus offers the possibility of making screwings according to significant tightening torques while offering good ergonomics preserving the operator.
  • said screwdriver comprises at least one torque sensor for measuring information representative of the tightening torque of said assembly
  • said epicyclic reduction comprises a ring rotatably connected to the casing of the screwdriver via said torque sensor.
  • the technique discussed also relates to driving a screwdriver according to the invention, that is to say the means and the method used to ensure the steering of the screwdriver.
  • a screwdriver comprises means for parameterizing, for example as a function of the nominal stiffness of said assembly, the initial speed of said motor means before said torque is brought up in torque during a screwing operation, so that the kinetic energy Ec contained in said motor means is such that said target torque Cobj is reached while the speed of said motor means becomes zero without power supply to the motor means during the torque-up, that is to say that said objective torque Cobj is reached during the rise in torque when the speed of the motor becomes zero at the end of a period of non-feeding thereof.
  • the rotational speed of the motor is thus parameterized at the beginning of screwing according to the theoretical properties of the assembly, such as for example its theoretical stiffness, so that the attainment of the target torque Cobj results from the only transmission to the assembly of the kinetic energy accumulated by the rotor before the torque increase phase of the screwing operation.
  • the initial speed of rotation of the motor, or pre-screwing speed is set so that the objective torque is reached during the torque-up phase when the motor stops, the objective torque being reached under the effect of the momentum of the engine while the engine is no longer powered during the rise in torque.
  • the target torque Cobj is reached at the moment when the engine stops during the torque increase phase without powering the engine.
  • the determination of the value of this speed can be carried out by calculation or by tests making it possible to attribute an initial speed of rotation of the motor according to the theoretical properties of the assembly, such as, for example, its nominal stiffness, that is to say -describe the theoretical stiffness of the assembly, in order to obtain the desired result.
  • said parameterization means comprise means for selecting, depending on the type of said assembly to be clamped, the value of said initial speed of said motor means from a group of predefined standard speeds each associated with a standard assembly, the association between each typical speed and each type assembly being carried out so that the kinetic energy Ec contained in said motor means is such that said target torque Cobj is reached while the speed of said motor means becomes zero without power supply motor means during the rise in torque.
  • the operator in charge of screwing an assembly can therefore select the initial speed of rotation of the motor at the beginning of screwing by choosing from a group of predefined speeds each associated with a typical assembly, for example presented in the form of a table, abacuses or others, the one that corresponds to the assembly he is about to screw.
  • This solution makes it easier to choose the initial speed of the motor by the operator.
  • the initial speed of rotation of the motor at the beginning of screwing is defined according to the theoretical characteristics of the assembly to be screwed, for example its theoretical stiffness.
  • the actual characteristics of the assembly may be different from the characteristics it was supposed to present or other parameters such as how the operator holds the screwdriver during screwing, operating temperature of the screwdriver, its level of lubrication ... imply that the screwing operation is not realized as it should be achieved on a theoretical level. Therefore, the initial rotational speed parameterized at the start of screwing may not allow the target torque Cobj to be reached simply because of the transmission of the kinetic energy of the rotor to the assembly, or on the contrary to lead to exceeding the value of the target torque Cobj at the end of screwing.
  • the objective torque will not be achieved unless increase the speed of the engine.
  • the target torque will be exceeded unless the engine speed is reduced. In these cases, it is necessary to correct the rotational speed of the engine in real time, either by accelerating it or by braking it during the torque-up phase in order to be certain that the target torque Cobj will be reached. at the end of the torque-up phase when the engine stops at the end of a period of no power of it.
  • a screwdriver preferably comprises means for real-time correction of the value of the speed of said motor means so that the kinetic energy Ec contained in said motor means is such that said target torque Cobj is reached. while the speed of said motor means becomes zero without power supply of the motor means during the rest of the rise in torque.
  • a screwdriver preferably comprises means for evaluating the actual stiffness of said assembly, said correction means correcting the value of said speed as a function of the difference between the actual stiffness of said assembly to be tightened and its stiffness nominal (or theoretical) to ensure that said target torque Cobj is reached while the speed said motor means becomes zero without power supply of the motor means during the remainder of the rise in torque.
  • the correction of the rotational speed of the engine is thus performed as a function of the actual value of the stiffness of the assembly, which makes it possible to obtain good results.
  • Said correction means preferably comprise means for calculating in real time the potential energy remaining to be supplied to the assembly in order to reach the target torque Cobj.
  • Said correction means preferably comprise means for real-time calculation of the transfer efficiency at said assembly of the energy produced by the screwdriver.
  • the correction of the rotational speed of the motor takes into account the efficiency with which the potential energy produced by the screwdriver, in other words the kinetic energy of the rotor, is transmitted to the assembly, which allows to improve the precision of the screwing.
  • Said correction means comprise means for real-time measurement of parameters necessary for controlling the tool, such as the actual stiffness of said screw-in assembly, the torque applied to said screw-in assembly, the angular position, the rotation frequency of the rotor of said motor means, during the torque increase of the tightening torque, according to a period of time of the order of 50 ⁇ S .
  • the present invention also relates to a driving device for screwdriver according to any one of the variants described above.
  • such a device preferably comprises means for setting the initial speed of said motor means before said torque is brought into torque during a screwing operation, so that the kinetic energy Ec contained in said motor means is such that said objective torque Cobj is reached while the speed of said motor means becomes zero without power supply of the motor means during the torque rise.
  • Said setting means preferably comprise means for selecting, depending on the type of said assembly to be clamped, the value of said initial speed of said motor means from a group of predefined standard speeds each associated with a standard assembly, the association between each speed. type and each typical assembly being carried out so that the kinetic energy Ec contained in said motor means is such that said target torque Cobj is reached while the speed of said motor means becomes zero without power supply of the motor means during the rise in couple.
  • Such a device preferably comprises means for correcting in real time the value of the speed of said motor means so that the kinetic energy Ec contained in said motor means is such that said target torque Cobj is reached while the speed of said motor means becomes zero without power supply of the motor means during the remainder of the rise in torque.
  • Such a device preferably comprises means for evaluating the actual stiffness of said assembly, said correction means correcting the value of said speed as a function of the difference between the actual stiffness of said assembly to be tightened and its nominal stiffness in order to guarantee that said torque objective Cobj is achieved while the speed of said motor means becomes zero without power supply of the motor means during the rest of the rise in torque.
  • Said correction means preferably comprise means for calculating in real time the potential energy remaining to be supplied to the assembly in order to reach objective torque Cobj, said correction means correcting the value of said speed as a function of the potential energy remaining at provide.
  • Said correction means preferably comprise means for calculating in real time the transfer efficiency at said assembly of the energy produced by the screwdriver, said correction means correcting the value of said speed as a function of the transfer efficiency.
  • the present invention also relates to a driving method of a screwdriver according to any one of the variants described above.
  • such a method preferably comprises a step of setting the initial speed of said motor means before said torque is raised in torque during a screwing operation, so that the kinetic energy Ec contained in FIG. said motor means is such that said objective torque Cobj is reached while the speed of said motor means becomes zero without power supply of the motor means during the torque rise.
  • Said parameterizing step preferably comprises a step of selecting, depending on the type of said assembly to be clamped, the value of said initial speed of said motor means among a group of predefined standard speeds each associated with a standard assembly, the association between each speed. type and each typical assembly being carried out so that the kinetic energy Ec contained in said motor means is such that said target torque Cobj is reached while the speed of said motor means becomes zero without power supply of the motor means during the rise in couple.
  • Such a method preferably comprises a step of correction in real time of the value of the speed of said motor means so that the kinetic energy Ec contained in said motor means is such that said target torque Cobj is reached while the speed of said motor means becomes zero without power supply of the motor means during the remainder of the rise in couple.
  • Such a method preferably comprises a step of evaluating the actual stiffness of said assembly, said correction step correcting the value of said speed as a function of the difference between the actual stiffness of said assembly to be tightened and its nominal stiffness in order to guarantee that said torque objective Cobj is achieved while the speed of said motor means becomes zero without power supply of the motor means during the rest of the rise in torque.
  • Said correction step preferably comprises a step of calculating in real time the potential energy remaining to be supplied to the assembly in order to reach objective torque Cobj, the value of said speed being corrected as a function of the potential energy remaining to be supplied.
  • Said correction step preferably comprises a step of calculating in real time the transfer efficiency at said assembly of the energy produced by the screwdriver, the value of said speed being corrected as a function of the transfer efficiency.
  • such a screwdriver comprises a body or housing 10 having a handle 11 with a gripping zone 12 to be gripped by an operator.
  • This gripping zone 12 is distant from the axis of the end member by a distance B in a direction perpendicular to it.
  • This distance B corresponds in other words to the lever arm of the force applied by the operator to the handle to maintain the screwdriver in position relative to the axis of rotation of the terminal member (or output shaft) of the screwdriver.
  • This screwdriver comprises motor means 13.
  • These motor means 13 comprise in this embodiment a synchronous electric motor permanent magnet.
  • This motor comprises on the one hand a rotor and the other by a stator which is connected to the body 10. They are capable of delivering a constant speed output torque Cmax.
  • the screwdriver comprises a rotary terminal member 14, or output shaft, which is intended to cooperate with an assembly to be clamped such as a screw, a nut or other.
  • the output shaft 14 extends along an axis which is coaxial with the axis of the rotor of the motor.
  • Transmission means 15 connect the rotor of the motor to the end member 14.
  • These transmission means comprise a reduction 17 which in this embodiment comprises at most an epicyclic type reduction stage whose input solar is connected to the Motor rotor and the satellite gate is linked to the output shaft of the tool.
  • the screwdriver comprises a sensor for measuring information representative of the tightening torque.
  • the ring gear of the reduction planetary gear is connected in rotation with the casing via this torque sensor 18.
  • This torque sensor measures the reaction torque of the ring relative to the body of the tool whose value is proportional to the tightening torque.
  • This reduction has a ratio R and a yield ⁇ .
  • the transmission means are capable of allowing an accumulation of kinetic energy Ec when the motor means are powered then a restitution of this kinetic energy Ec to the terminal member 14.
  • the reduction is configured so that: R . ⁇ . Cmax ⁇ B .100 and B .100 ⁇ COBJ / 2
  • Cobj being the objective pair to which said assembly is to be tightened.
  • the screwdriver here comprises an angle sensor measuring the rotation angle of the rotor of the motor relative to the stator and a sensor for measuring the electric intensity consumed by the motor.
  • the screwdriver comprises control means 16 of the motor means.
  • the control means comprise means for setting the initial speed of the motor means, that is to say their pre-screwing speed at the beginning of the screwing cycle (pre-screwing phase) before the start of the period. torque rise (screwing phase), in other words before the head of the screw comes into contact with the parts to be assembled.
  • pre-screwing phase the value of this speed will be chosen so that the kinetic energy Ec contained in said motor means is such that said target torque Cobj is reached while the speed of the motor means becomes zero without power supply of the motor means during the rise in torque.
  • the control means also comprise means for correcting in real time the speed of rotation of the motor means.
  • these correction means make it possible to correct, if necessary, the value of the speed of the motor means (acceleration or braking) to ensure that the kinetic energy Ec contained in said means motors so that said target torque Cobj is reached while the speed of the motor means becomes zero without power supply of the motor means during the torque rise, for example taking into account the energy transfer efficiency and the actual stiffness of the assembly which are supposed to be constant during the rest of the rise in torque.
  • correction means iteratively corrects at a predetermined frequency, for example of the order of 20 kHz, the rotational speed the engine based on parameters measured in real time over time intervals between a start time td and an end time tf.
  • correction means comprise means for calculating the potential energy Epobj remaining to be supplied to the transmission and to the assembly so that the target torque Cobj is reached during the remainder of the rise in torque at the end of a period during which the engine is not powered and stop.
  • correction means comprise means for calculating the transfer efficiency ⁇ t at the assembly of the energy produced by the screwdriver, the sum of the electromagnetic energy produced and the variation in kinetic energy.
  • These means for calculating the transfer efficiency ⁇ t comprise means for calculating the rotation frequency of the motor Wtf, means for calculating the kinetic energy variation of the rotor ⁇ Ec between the beginning and the end of the measurement period, means for calculating the electromagnetic energy Ee supplied to the motor between the beginning and the end of the measurement period and means for calculating the potential energy produced Ep between the beginning and the end of the measurement period.
  • ⁇ td angle in radians of the rotor of the motor relative to the stator of the motor at td, comparable to the angle of the rotor with respect to an external reference system considering that the assumption is made that the body of the tool does not rotate.
  • ⁇ tf angle in radians of the rotor of the motor with respect to the stator of the motor with tf, comparable to the angle of the rotor compared to an external reference frame considering that the assumption is made that the body of the tool does not turn.
  • Wtd motor rotation frequency at td in radians per second.
  • Wtd is the Wtf value of the previous iteration.
  • Wtd corresponds to the rotation frequency at the end of the precleaning, that is to say to VP.
  • Kt torque constant of the motor (Kt is an intrinsic characteristic of each motor)
  • ⁇ td angle of the rotor of the motor with respect to the stator of the motor at td in radians
  • ⁇ tf angle of the rotor of the motor relative to the stator of the engine at tf in radian
  • microT ⁇ Ep / ⁇ Ec + Ee
  • the correction means comprise means of communication with the control means for transferring to them the value V of the corrected rotation frequency so that the control means send this instruction to the motor.
  • the screwdriver according to the invention is of the type with a bevel gearbox.
  • the screwdriver according to this second embodiment is identical to the screwdriver according to the first embodiment except that it comprises at the end of its body a bevel gear incorporating a pair of bevel gears whose axes form a angle close to 90 °.
  • the entry of this bevel gear is linked to the transmission in the extension of the axis of the motor while its output is related to the output shaft or terminal member of the screwdriver.
  • the screwdriver is first calibrated for an assembly having a given nominal stiffness (step E 1 ).
  • the calibration consists of evaluating, either by trial or by calculation, the pre-screwing speed, also called the initial speed, at which the motor must rotate at the start of the screwing in such a way that the kinetic energy accumulated by the engine and the parts in the movement of the screwdriver during the pre-screwing phase allows, when transferred to the assembly in the form of potential clamping energy, to reach the target torque Cobj during the torque-up phase (screwing phase) of the screwing operation when the motor stops at the end of a period of no power supply of the motor.
  • the pre-screwing speed also called the initial speed
  • the initial speed of rotation of the motor is set so that when it is reached by the motor, the power supply thereof is stopped and the target torque Cobj to which it is desired to tighten the screw connection is reached only by the momentum of the motor when the motor stops.
  • the objective torque is thus reached under the sole effect of the transfer in the form of potential energy screwing the kinetic energy accumulated by the engine and the transmission and not under the effect of the electromagnetic torque delivered by the engine.
  • the screwing of a given assembly with the screwdriver is made by gradually varying the initial speed of the motor to determine that which achieves the desired result. Multiple tests are thus performed for various given assemblies.
  • the operator then has a multitude of initial speeds, presented for example in the form of tables, abacuses or other, each corresponding to a given type of assembly that it is subsequently likely to screw by means of the screwdriver. He can then, at each screwing, set the initial speed by choosing the one corresponding to the assembly he screws.
  • the kinetic energy Ec that the rotor must accumulate to achieve the desired goal is firstly determined according to the theoretical characteristics of the assembly to be screwed ( eg stiffness, size, material ).
  • the initial rotation frequency V of the motor rotor can then be determined.
  • the actual situation rarely corresponds to the ideal situation in which the screw connection behaves exactly like the typical assembly taken as a reference to determine the initial speed of the motor. It may then be necessary to correct the speed of the motor in real time, either by accelerating it or by braking it, to ensure that the target torque Cobj to which it is desired to tighten the assembly to screwing is reached under the sole effect of the transfer in the form of potential energy screwing the kinetic energy accumulated by the engine and the transmission during the pre-screwing and not under the effect of the electromagnetic torque delivered by the engine.
  • the control of the screwdriver and more particularly that of the speed of rotation of the motor during screwing is based on the principle of energy conservation.
  • the electromagnetic torque motor or engine braking that are used to correct the speed of the engine in real time at any time, for example depending on the assembly stiffness and the energy transfer efficiency in the engine. assembly, so that the kinetic energy of the rotor is just sufficient on its own to complete the rise in torque. If it is the engine brake that is implemented the energy is not produced but absorbed by the engine.
  • the loop of the algorithm enchains a succession of steps implemented between two instants td (beginning) and tf (end), td and tf framing a period of time whose duration is related to the means of computation, that is to say the order of 0.05 ms.
  • this succession of steps is carried out in a repetitive manner approximately every 0.05 ms.
  • the value of the tightening torque is then compared by the correction means to that of the objective torque (step E 4 ).
  • step E 6 If the value of the tightening torque is greater than that of the objective torque (condition C 1 ), then the drive means of the screwdriver send the motor a zero speed command (step E 6 ).
  • condition C 2 the value of the tightening torque is lower than that of the objective torque (condition C 2 ), which reflects the fact that the tightening operation is not completed, then the tightening torque is compared to the torque of end of pre-screwing Cpv (step E 7 ).
  • ⁇ td angle in radians of the rotor of the motor relative to the stator of the motor at td, comparable to the angle of the rotor with respect to an external reference system considering that the assumption is made that the body of the tool does not rotate.
  • ⁇ tf angle in radians of the rotor of the motor with respect to the stator of the motor with tf, comparable to the angle of the rotor compared to an external reference frame considering that the assumption is made that the body of the tool does not turn.
  • ⁇ td angle in radians of the rotor of the motor relative to the stator of the motor to td
  • ⁇ tf angle in radians of the rotor of the motor relative to the stator of the engine at tf
  • the correction means transmit this value V to the control means (step E 18 ) which consequently regulate the supply of the motor by braking or accelerating it so that its speed becomes equal to V.
  • step E 4 The tightening torque delivered by the screwdriver is again compared with the objective torque (step E 4 ) and the algorithm is reiterated until the objective torque is reached as far as possible under the sole effect of the transmission by the rotor of its kinetic energy at assembly.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Details Of Spanners, Wrenches, And Screw Drivers And Accessories (AREA)
EP14181967.2A 2013-08-22 2014-08-22 Elektrischer Schrauber mit Festziehfunktion Active EP2839931B1 (de)

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FR1358130A FR3009803B1 (fr) 2013-08-22 2013-08-22 Visseuse electrique a serrage asservi

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023104408A1 (en) * 2021-12-10 2023-06-15 Atlas Copco Industrial Technique Ab Method of controlling an electric motor of a tightening tool

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996041701A1 (en) * 1995-06-13 1996-12-27 Ergonomi Design Gruppen Ab Portable screw or nut driver
FR2777216A1 (fr) * 1998-04-14 1999-10-15 Ass Leonard De Vinci Machine porte-outils a entrainement rotatif sans reaction de couple
US20050247459A1 (en) * 2004-05-04 2005-11-10 Mike Voigt Method for operating a disengagable screwdriver, and a disengagable screwdriver
WO2009011633A1 (en) 2007-07-13 2009-01-22 Atlas Copco Tools Ab Regulator for a power tool

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996041701A1 (en) * 1995-06-13 1996-12-27 Ergonomi Design Gruppen Ab Portable screw or nut driver
FR2777216A1 (fr) * 1998-04-14 1999-10-15 Ass Leonard De Vinci Machine porte-outils a entrainement rotatif sans reaction de couple
US20050247459A1 (en) * 2004-05-04 2005-11-10 Mike Voigt Method for operating a disengagable screwdriver, and a disengagable screwdriver
WO2009011633A1 (en) 2007-07-13 2009-01-22 Atlas Copco Tools Ab Regulator for a power tool

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023104408A1 (en) * 2021-12-10 2023-06-15 Atlas Copco Industrial Technique Ab Method of controlling an electric motor of a tightening tool

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EP2839931B1 (de) 2016-12-07
FR3009803A1 (fr) 2015-02-27
FR3009803B1 (fr) 2016-02-12

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