Optimized detorsion screwing / unscrewing device

Abstract

The present invention relates to a screwing device for an assembly, said device comprising means for managing the angular position reached by a reaction element at the end of a detorsion phase, said management means comprising means for measuring at least one operating parameter of said screwing / unscrewing device representative of the rotation of said motor rotor of the device during said detorsion phase, and means for controlling the rotation of said rotor during said detorsion as a function of said parameter. Fig. 1

Description

Title of the invention: Screwing / unscrewing device with optimized untwisting 1. Field of the invention

[0001] The field of the invention is that of the design and control of continuous tightening screwing devices enabling in particular the delivery of a high tightening torque and implementing a force absorption accessory. 2. Prior art

[0002] Continuous tightening screwing devices are commonly used in various sectors to work on tightening assemblies.

[0003] In contrast to discontinuous tightening screwing devices, which intermittently deliver a tightening torque during the performance of a screwing operation until a final tightening torque is reached, continuous tightening screwing devices continuously deliver a tightening torque, the value of this torque being able to vary during the performance of a screwing operation until a final tightening torque is reached.

[0004] A continuous tightening screwing device generally comprises a casing at the end of which is mounted a terminal member capable of being driven in rotation by means of a motor and a gear reducer housed in the casing.

[0005] To tighten an assembly to a relatively high tightening torque (in particular greater than 15 Nm, and generally greater than 100 Nm), a force-recovery accessory, such as for example a reaction bar or a reaction dog, is generally secured to the casing and pressed against a fixed element external to the screwing device. In certain cases, the casing may comprise a casing portion housing the reducer and a casing portion housing the rest of the device. These two casing portions are connected by a pivot connection capable of being locked. The force-recovery accessory is in this case secured to the casing portion housing the reducer.

[0006] When carrying out a screwing (or unscrewing) operation, the assembly formed by the terminal member, the reducer and the reaction accessory, hereinafter referred to as the reaction assembly, undergoes a mechanical stress of tensioning, under the effect of the motor, inducing an elastic deformation of the reaction assembly, the level of which depends on the stiffness of this assembly. This tensioning, when it is under stress, is an elastic potential energy.

[0007] At the end of this screwing (or unscrewing) operation, the motor stops. At this stage, the mechanical components of the reaction assembly subjected to the force of tightening, are deformed in the elastic domain, this deformation leading to storing a certain quantity of potential deformation energy in the reaction assembly.

[0008] This potential deformation energy is released after stopping the screwing (or unscrewing) operation by driving the motor rotor in the opposite direction to the screwing (or unscrewing) operation.

[0009] This release of energy occurs in two phases: - a phase of tension release: untwisting strictly speaking, that is to say the transfer of potential torsional energy to kinetic energy in the engine less voluntary losses such as braking or incurred losses such as friction; - a phase of release of the force recovery accessory: It is the kinetic energy remaining in the system following the untwisting phase which moves the force recovery accessory away from its support point.

[0010] This release of energy takes place until the potential deformation energy is absorbed by the resistive torque of the motor in the form of braking energy.

[0011] This resistive torque can be generated by the internal friction of the motor or by possible electromagnetic braking.

[0012] If this resistive torque is too low, the release of the potential deformation energy can cause the rotor of the motor to acquire a certain speed inducing a rotation of the casing of the screwdriver in the direction of the screwing (or unscrewing) operation, this rotation of the casing tending to move the force-recovery accessory away from the point of contact against which it was resting during the screwing (or unscrewing) operation.

[0013] This distance of the force-recovery accessory from the point of contact against which it was resting during the screwing (or unscrewing) operation is significant.

[0014] Indeed, if this distance is zero, the untwisting phase has not allowed sufficient release of the torsional stress of the mechanical chain so that the screwing device remains blocked on the assembly so that it is difficult, or even impossible, for the operator to dissociate the screwing / unscrewing device from the assembly.

[0015] On the contrary, if this distance is too great, the recoil of the force-recovery accessory from the point of contact against which it was resting during the screwing (or unscrewing) operation may have the following effects, which differ depending on the type of force-recovery accessory used.

[0016] In the case where the force-recovery accessory is an accessory with indirect grip on the assembly which is the subject of a screwing operation (such as for example a "long bar", an "S bar", or a "blade" in English): - rotation of the force-recovery accessory in the opposite direction to the completed screwing operation may cause it to bear against another mechanical element (such as another part of the assembly) and consequently cause a risk of damage (weakening or breakage) to this mechanical element (thread of another screw) which the force-recovery accessory could strike during its movement; - rotation of the force-recovery accessory in the opposite direction to the completed screwing operation may cause it to pinch an operator whose hand, or another part of his body, could be between the force-recovery accessory and a neighboring mechanical element which could block the movement of the force-recovery accessory.

[0017] In the case where the force-recovery accessory is an accessory with direct grip on the assembly undergoing a screwing / unscrewing operation (such as for example a "sliding bar", a "square bar" or a "square cup", in English) or with indirect grip against a mechanical element very close to the assembly undergoing a screwing operation, a rotation of the force-recovery accessory in the opposite direction to the completed screwing operation will cause it to come into direct contact with the assembly or a mechanical element very close to the assembly and induce: - the application to the assembly of a torque opposite to the tightening torque applied during the completed screwing operation (and therefore going against the screwing operation carried out), - the generation of a mechanical shock in the assembly as well as its perception by the operator, - a risk that the force recovery accessory will get stuck on the assembly in the opposite direction to the operation which was completed.

[0018] Consequently, releasing any brake opposing the rotation of the rotor would cause the constituent parts of the reducer and the rotor of the motor to move, which would transform the elastic potential energy accumulated during a screwing (or unscrewing) operation into kinetic energy which accumulates as the untwisting progresses, this kinetic energy causing the force-recovery accessory to rotate in the opposite direction to the direction of the screwing (or unscrewing) operation.

[0019] Conversely, braking / blocking the rotation of the motor would prevent the generation of kinetic energy. However, this blocking would prevent untwisting and would not allow the elastic potential energy to be dissipated; any subsequent release of the braking would then generate kinetic energy which would drive the recovery accessory. of force in the opposite direction to the direction of the screwing (or unscrewing) operation.

[0020] There is therefore a need to identify a solution which would ensure controlled untwisting leading to avoiding: - that the screwing device does not remain blocked on the assembly at the end of a screwing (or unscrewing) operation; - that the mechanical environment of the assembly is not damaged by rotation of the force-recovery accessory at the end of the screwing (or unscrewing) operation; - that an operator is injured by rotation of the force-recovery accessory at the end of the screwing (or unscrewing) operation. 3. Objectives of the invention

[0021] The invention aims in particular to provide an effective solution to at least some of these different problems.

[0022] In particular, according to at least one embodiment, an objective of the invention is to provide a screwing device equipped with a force-recovery accessory whose untwisting at the end of the screwing operation is optimized.

[0023] In particular, the invention aims, according to at least one embodiment, to provide such a device which can be easily dissociated from an assembly at the end of the screwing operation.

[0024] Another objective of the invention is, according to at least one embodiment, to provide such a device which avoids damaging the environment of the assembly at the end of the screwing operation.

[0025] Another objective of the invention is, according to at least one embodiment, to provide such a device which avoids injuring an operator at the end of the screwing operation.

[0026] Another objective of the invention is, according to at least one embodiment, to provide such a device which is reliable and / or economical and / or simple in design. 4. Presentation of the invention

[0027] For this, the invention proposes a device for screwing an assembly, said device comprising:

[0028] - a casing;

[0029] - a rotary terminal member placed at one end of said casing;

[0030] - a reducer housed in said casing;

[0031] - a motor housed in said housing, said motor comprising a rotor and a stator and being capable of rotating said terminal member via said reducer;

[0032] - means for controlling said device;

[0033] - a reaction element capable of bearing against an element external to said as assembly in order to absorb forces transmitted to the casing during an operation screwing;

[0034] said terminal member, said reducer and said reaction element forming a reaction assembly capable of storing energy during said screwing operation, said energy being capable of being restored by said reaction assembly during an untwisting phase, at the end of said screwing operation, inducing a rotation of said rotor in the opposite direction to its direction of rotation during said screwing operation.

[0035] According to the invention, said device comprises means for managing the angular position reached by said reaction element at the end of said untwisting phase, said management means comprising means for measuring at least one operating parameter of said screwing / unscrewing device representative of the rotation of said rotor during said untwisting phase and means for controlling the rotation of said rotor during said untwisting as a function of said parameter.

[0036] Thus, the invention proposes to manage the rotation of the rotor during untwisting, as a function of the value of at least one operating parameter of the screwing / unscrewing device, so as to control the angular position reached by the rotor at the end of the untwisting.

[0037] Such management of the position of the rotor at the end of the untwisting makes it possible to avoid in whole or in part: - that the screwing device does not remain blocked on the assembly at the end of a screwing (or unscrewing) operation; - that the mechanical environment of the assembly is not damaged by rotation of the force-recovery accessory at the end of the screwing (or unscrewing) operation; - that an operator is injured by rotation of the force-recovery accessory at the end of the screwing (or unscrewing) operation.

[0038] According to a preferred characteristic, said operating parameter is the rotation frequency of said rotor.

[0039] In this case, the device preferably comprises means for braking said rotor, said control means being capable of actuating said braking means during said untwisting phase.

[0040] Said control means are preferably configured to activate said braking means, during said untwisting phase, when the rotation frequency of said rotor in the opposite direction to the screwing direction reaches a predetermined braking actuation threshold.

[0041] Said control means are preferably configured to deactivate said braking means, during said untwisting phase, when the rotation frequency of said rotor in the opposite direction to the screwing direction reaches a pre-threshold. determined braking deactivation.

[0042] Said braking actuation threshold is preferably higher, in absolute value, than the braking deactivation threshold.

[0043] Said braking means are preferably at least partly of the passive type.

[0044] Said braking means are preferably at least partly of the active type and capable of exerting braking of an amplitude whose value depends on the rotation frequency of said rotor.

[0045] According to a preferred characteristic, said operating parameter is the angle of rotation of said rotor relative to said stator.

[0046] In this case, reaction assembly having an elastic stiffness, said device preferably comprises means for determining, as a function of said elastic stiffness of said reaction assembly, a theoretical final angular position of said rotor after total restitution of said energy by said reaction assembly at the end of the remainder of said untwisting phase, said control means being configured to control the position of said motor in such a way that said rotor is stopped at the end of said untwisting phase at a stopping position determined as a function of said theoretical final angular position.

[0047] The device may comprise means for determining the stiffness of the reaction assembly during the screwing / unscrewing operation and / or at the start of the untwisting phase.

[0048] Said device preferably comprises means for measuring the torque delivered by said device and means for determining in real time the angular position of said rotor relative to said stator, said means for determining said theoretical final angular position being capable of determining, at a given time t during said untwisting phase, said theoretical final angular position as a function of the torque measured by said torque measuring means and the angular position determined by said means for determining in real time said angular position.

[0049] Which instant t preferably corresponds to the moment when said torque measured during said untwisting phase is equal to the product of a final tightening torque reached at the end of said screwing operation by a predetermined coefficient R, said theoretical final angular position being determined so that the angular displacement of said rotor between the end of said screwing operation and said theoretical final angular position is equal to the angular displacement of said rotor between the end of said screwing operation and said instant t divided by (1-R) ​​R being between 0 and 1.

[0050] Said coefficient R is preferably equal to 0.5.

[0051] Said stop position is preferably equal to said final angular position. theoretical.

[0052] Said stop position is preferably equal to said theoretical final angular position added to or reduced by a predetermined angle.

[0053] The invention also relates to a method for screwing / unscrewing an assembly by means of a screwing device, said device comprising:

[0054] - a casing;

[0055] - a rotary terminal member placed at one end of said casing;

[0056] - a reducer housed in said casing;

[0057] - a motor housed in said housing, said motor comprising a rotor and a stator and being capable of rotating said terminal member via said reducer;

[0058] - means for controlling said device;

[0059] - a reaction element capable of bearing against an element external to said as assembly in order to absorb forces transmitted to the casing during a screwing operation;

[0060] said method comprising:

[0061] - a phase of carrying out a screwing / unscrewing operation during which said terminal member is driven in rotation by said motor and said reducer, said terminal member, said reducer and said reaction element forming a reaction assembly storing energy during said screwing / unscrewing phase,

[0062] - an untwisting phase, at the end of said screwing / unscrewing operation, during from which said energy is restored by said reaction assembly inducing a rotation of said rotor in the opposite direction to its direction of rotation during said screwing / unscrewing operation,

[0063] - a phase of managing the angular position reached by said reaction element at the outcome of said untwisting phase, said management phase comprising a measurement of at least one operating parameter of said screwing / unscrewing device representative of the rotation of said rotor during said untwisting phase and a control of the rotation of said rotor during said untwisting phase as a function of said parameter.

[0064] Said operating parameter is preferably the rotation frequency of said rotor.

[0065] Such a method preferably comprises a braking phase of said rotor during said untwisting phase.

[0066] Said braking phase is preferably actuated, during said untwisting phase, when the rotation frequency of said rotor in the opposite direction to the screwing direction reaches a predetermined braking actuation threshold.

[0067] Said braking phase is preferentially deactivated, during said untwisting phase, when the rotation frequency of said rotor in the opposite direction to the screwing direction reaches a predetermined threshold for deactivating the braking.

[0068] Said braking actuation threshold is preferably higher, in absolute value, than the braking deactivation threshold.

[0069] Said braking is preferably at least partly of the passive type.

[0070] Said braking is preferably at least partly of the active type and capable of exerting braking of an amplitude whose value depends on the rotation frequency of said rotor.

[0071] Said operating parameter is preferably the angle of rotation of said rotor relative to said stator.

[0072] Said reaction assembly has an elastic stiffness, said untwisting phase preferably comprising a phase of determining, as a function of said elastic stiffness of said reaction assembly, a theoretical final angular position of said rotor after total restitution of said energy by said reaction assembly at the end of the remainder of said untwisting phase, said untwisting phase comprising a phase of piloting said motor in position such that said rotor is stopped at the end of said untwisting phase at a stopping position determined as a function of said theoretical final angular position.

[0073] A method according to the invention may preferably comprise a step of determining the stiffness of the reaction assembly during the screwing / unscrewing operation and / or at the start of the untwisting phase.

[0074] Such a method preferably comprises a phase of measuring the torque delivered by said device and a phase of determining in real time the angular position of said rotor relative to said stator, said phase of determining said theoretical final angular position comprising the determination, at a given time t during said untwisting phase, of said theoretical final angular position as a function of the measured torque and the angular position determined in real time.

[0075] The instant t preferably corresponds to the moment when said torque measured during said untwisting phase is equal to the product of a final tightening torque reached at the end of said screwing operation by a predetermined coefficient R, said theoretical final angular position being determined so that the angular displacement of said rotor between the end of said screwing operation and said theoretical final angular position is equal to the angular displacement of said rotor between the end of said screwing operation and said instant t divided by (1-R) ​​R being between 0 and 1.

[0076] Said coefficient R is preferably equal to 0.5.

[0077] Said stop position is preferably equal to said theoretical final angular position.

[0078] Said stop position is preferably equal to said theoretical final angular position added to or reduced by a predetermined angle. 5. Description of figures

[0079] Other characteristics and advantages of the invention will appear on reading the following description of particular embodiments, given as a simple illustrative and non-limiting example, and the appended drawings among which:

[0080] [Fig-1] [Fig.l] illustrates a perspective view of an example of a device of screwing / unscrewing according to the invention;

[0081] [Fig.2] [Fig.2] illustrates the device of [Fig.l] installed on an assembly;

[0082] [Fig.3] [Fig.3] illustrates a longitudinal sectional view of the device of [Fig.l];

[0083] [Fig.4] [Fig.4] illustrates a front view of the device of [Fig.2];

[0084] [Fig.5] [Fig.5] illustrates the device of [Fig.4] whose recovery accessory effort is far from its support point;

[0085] [Fig.6] [Fig.6] illustrates curves illustrating the operation of a mode of rea lization implementing a power brake;

[0086] [Fig.7] [Fig.7] illustrates curves illustrating the operation of a mode of rea lization implementing engine position control;

[0087] [Fig.8] [Fig.8] illustrates a flowchart of a process implementing a brake assisted;

[0088] [Fig.9] [Fig.9] illustrates a flowchart of a process implementing a control in engine position.

[0089] 6. Description of particular embodiments 6.1. General architecture

[0090] An example of a screwing / unscrewing device according to the invention is presented in relation to Figures 1 to 5.

[0091] Such a screwing device 1 comprises a casing 10 provided with a handle 11.

[0092] A rotary terminal member 12 is placed at one end of the casing 10.

[0093] In this embodiment, the handle 11 is a pistol-type handle forming an angle with the axis of the terminal member. In variants, the handle could extend along the axis of the terminal member.

[0094] The casing 10 houses a reducer 13 as well as a motor 14.

[0095] The motor 14 comprises a stator 140 and a rotor 141. It may be an electric motor or a pneumatic motor.

[0096] The reducer 13 comprises a plurality of gears. It comprises an input connected to the rotor shaft 141 and an output connected to the terminal member 12.

[0097] The motor 14 and the reducer 13 are thus capable of driving the terminal member 12 in rotation.

[0098] The screwing device comprises control means 15 for the motor 14. These control means 15 can be integrated into control means 16 of the device, which are conventionally embodied in the form of a controller, which controller can be remote from the casing 10 of the device or can house completely or partially in the casing 10.

[0099] The screwing / unscrewing device comprises means for measuring the tightening torque 17. Such measuring means are known per se to those skilled in the art. They may, for example, be torque sensors with a deforming element equipped with strain gauges. They may also be indirect measuring means such as, for example, a motor current sensor for an electric screwing / unscrewing device, or a pressure sensor for a pneumatic screwing / unscrewing device.

[0100] The screwing / unscrewing device is of the continuous tightening type. It allows high torque screwing operations to be carried out at the end of which the final tightening torque installed in the assembly is preferably greater than or equal to 15 Nm, and preferably greater than or equal to 100 Nm.

[0101] Achieving such a tightening torque with a continuous tightening screwing device requires, to enable the screwing / unscrewing device to develop its tightening torque on the screw, the use of a force-recovery accessory 18, also called a reaction element.

[0102] Such an accessory is fixedly secured to the casing and bears on a fixed element external to the screwing device so as to take up the reaction forces transmitted to the casing, in particular the reaction torque, generated during the performance of a screwing operation. In the example illustrated, the reaction accessory 18 bears, during the tightening of a nut, against a nut 19 located close to the nut being tightened (see figures 2, 4).

[0103] The reaction element 18 and, to a lesser extent, the terminal member 12 and the reducer 13, form a reaction assembly capable of storing potential elastic deformation energy during the performance of a screwing (or unscrewing) operation. Indeed, during the performance of such an operation, the gears of the reducer as well as the terminal member and the force-recovery accessory deform elastically under the effect of the transmission by the screwing device of a tightening torque to the assembly.

[0104] At the end of the screwing (or unscrewing) operation, this potential elastic deformation energy is likely to be restored by the reaction assembly during a detorsion phase during which the reaction assembly relaxes elastically (like a spring). This relaxation tends to induce a rotation of the rotor of the motor in the opposite direction to its direction of rotation during the screwing (or unscrewing) operation and consequently a rotation of the reaction accessory which tends to move away from the nut 19 against which it is supported during the screwing / unscrewing operation (see fig. 5).

[0105] The invention aims to optimize the untwisting phase, in particular to avoid in whole or in part: - that the screwing device does not remain blocked on the assembly at the end of a screwing operation if the rotation of the reaction accessory with respect to the element against which it comes to bear during the screwing / unscrewing operation is too low; - that the mechanical environment of the assembly is not damaged by rotation of the force-recovery accessory at the end of the screwing operation, leading to a risk of it striking the environment; - that an operator is injured by the rotation of the force-recovery accessory at the end of the screwing operation, leading to a risk of it hitting the operator.

[0106] To this end, the screwing / unscrewing device comprises means 20 for managing the angular position reached by the force-recovery accessory at the end of the untwisting phase. These management means 20 comprise means for measuring at least one operating parameter of the device representative of the rotational movement of the rotor during the untwisting phase and means 21 for controlling the rotational movement of the rotor of the motor during the untwisting as a function of the measured parameter.

[0107] As will become more clear later, the operating parameter preferably belongs to the group comprising: - the rotation frequency of the rotor; - the angle of rotation of the rotor relative to the stator.

[0108] 6.2. First embodiment: assisted braking 6.2.1. Structure

[0109] When the operating parameter taken into consideration is the rotation frequency of the rotor, then the screwing / unscrewing device implements an assisted brake to optimize the untwisting phase.

[0110] In this embodiment, the screwing / unscrewing device; and more precisely the means for measuring at least one operating parameter of the device representative of the rotational movement of the rotor, comprise means 21 for measuring in real time the rotational frequency of the rotor of the motor. Such measuring means are known per se to those skilled in the art. By way of illustration, it may for example be a mechanical or optical encoder, a Hall effect sensor. It may also be an indirect measurement such as for example a motor current sensor for a screwing / unscrewing device with an electric motor, or a pressure sensor for a screwing / unscrewing device with a pneumatic motor.

[0111] The screwing / unscrewing device, or more precisely the means for managing the angular position of the rotor, comprise means 22 for braking the rotor. Such braking means are known per se to those skilled in the art. For a device screwing / unscrewing with an electric motor, this can for example be passive braking. Passive braking consists of short-circuiting the three phases of the polyphase motor, the currents self-generated by the motor generating a braking torque. It can also be active braking, in which the motor is controlled in the opposite direction to limit its rotation frequency. Braking can also be generated by external mechanical means such as pads or other friction elements.

[0112] The control means 16 of the device are capable of actuating the braking means 22 during the untwisting phase, i.e. after the completion of the screwing operation by the tightening torque reaching a predetermined objective tightening torque threshold.

[0113] The end of a screwing operation is materialized by the tightening torque reaching a predetermined objective tightening torque threshold. When the control means 16 of the tool detect the reaching of this threshold, the control means 16 act on the motor control means 15 in such a way that they stop the power supply to the motor. After this stoppage of the power supply to the motor, the rotor tends to rotate in the opposite direction to the completed operation under the effect of the relaxation of the reaction assembly which releases the potential elastic deformation energy accumulated during the operation.

[0114] During the untwisting phase during which the rotor rotates in the opposite direction to the completed operation, the control means 16 are capable of detecting the achievement by the rotation frequency of the rotor: - a predetermined brake actuation rotation frequency threshold; - a predetermined rotation frequency threshold for brake deactivation.

[0115] The brake actuation threshold is higher, in absolute value, than the brake deactivation threshold. In other words, the brake actuation threshold corresponds to a rotor recoil speed faster than the brake deactivation threshold.

[0116] The control means are configured to: - activate the braking means, during the untwisting phase, when the rotation frequency of the rotor in the opposite direction to the screwing direction reaches the predetermined brake actuation threshold; - deactivate said braking means, during the untwisting phase, when the rotation frequency of the rotor in the opposite direction to the screwing direction reaches the predetermined brake deactivation threshold.

[0117] The braking means may be of the passive type. In this case, the amplitude of the braking is substantially equal each time the braking means are actuated. In the case of passive braking, the amplitude of the braking is preferably substantially equal to a given threshold of braking activation speed.

[0118] The braking means may alternatively be active. In this case, the braking means are capable of exerting braking of an amplitude varying according to the rotor rotation frequency according to a predetermined control law.

[0119] Passive braking can consist of short-circuiting the motor phases and using its own ohmic resistance to transform the motor's kinetic energy into heat (Joules effect). The disadvantage of passive braking is that the braking speed is not controlled.

[0120] Active braking can consist of controlling the motor in such a way that it produces a controlled torque in a direction opposite to that of the rotation of the tool. Active braking induces a production of energy which must be dissipated immediately or stored somewhere, in capacitors at the input of the inverter supplying the motor for example. Active braking allows control of the braking speed.

[0121] The two previous braking variants can be combined. 6.2.2. Procedure

[0122] A method according to the invention is described below.

[0123] Prior to carrying out a screwing operation, the motor of the device is stopped.

[0124] The screwing operation begins by starting the motor.

[0125] During screwing, the tightening torque is measured in real time.

[0126] During screwing, the tightening torque increases until it reaches a predetermined objective tightening torque threshold.

[0127] When the control means detect the reaching of this threshold, they act on the motor control means in such a way that the power supply to the motor in the screwing direction stops so that the rotor tends to turn in the opposite direction to the direction of the completed operation under the effect of the relaxation of the reaction assembly during the untwisting phase.

[0128] The rotation frequency of the rotor is measured in real time during the untwisting phase.

[0129] When, during the untwisting phase, the rotation frequency of the rotor in the opposite direction increases in such a way that it reaches the predetermined threshold for actuating the brake, the control means detect the reaching of this threshold and actuate the braking means accordingly.

[0130] Therefore, the rotational frequency of the rotor decreases.

[0131] When, during the untwisting phase, the rotation frequency of the rotor in the opposite direction decreases in such a way that it reaches the predetermined brake deactivation threshold, the control means detect the reaching of this threshold and deactivate the braking means.

[0132] Consequently, the rotation frequency of the rotor tends to increase again.

[0133] Several phases of actuation and deactuation of the braking means are thus successively implemented until the rotor comes to a standstill.

[0134] The curves in [Fig.6] and the flowchart in [Fig.8] illustrate this general principle.

[0135] Alternatively, several phases of actuation and deactivation of the braking means may thus be implemented successively for a predetermined duration.

[0136] 6.3. Second embodiment: engine position control 6.3.1. Structure

[0137] When the operating parameter taken into consideration is the angle of rotation of the rotor relative to the stator, then the screwing / unscrewing device implements control means 15 in the position of the motor to optimize the untwisting phase.

[0138] In this embodiment, the screwing / unscrewing device, or more precisely the means for measuring at least one parameter representative of the rotational movement of the rotor, comprise means 23 for measuring in real time the angle of rotation of the rotor of the motor relative to the stator. Such measuring means are known per se to those skilled in the art. By way of illustration, it may for example be a mechanical or optical encoder, a Hall effect sensor, etc.

[0139] The reaction assembly has an elastic stiffness. This stiffness can be evaluated empirically.

[0140] In this embodiment, the screwing / unscrewing device comprises means 24 for determining, during the untwisting phase, as a function of the elastic stiffness of the reaction assembly, a theoretical final angular position of the rotor after total restitution of the energy by the reaction assembly at the end of the remainder of the untwisting phase, the control means 16 being configured to control the position of the motor in such a way that the rotor is stopped at the end of the untwisting phase at a stop position determined as a function of the theoretical final angular position.

[0141] The screwing / unscrewing device may comprise means 25 for determining the stiffness of the reaction assembly, during the screwing / unscrewing operation and / or at the start of the untwisting phase.

[0142] More precisely, the means for determining the theoretical final angular position are capable of determining, at a given time t during the untwisting phase, the theoretical final angular position as a function of the tightening torque measured by the torque measuring means and the angular position determined in real time by the means for determining the angular position.

[0143] The instant t corresponds to the moment when the torque measured during the untwisting phase is equal to the product of the final tightening torque reached at the end of the screwing operation by a predetermined coefficient R, the theoretical final angular position being determined so that the angular displacement of the rotor between the end of the screwing operation and the theoretical final angular position is equal to the angular displacement of the rotor between the end of the screwing operation and the instant t divided by (1-R) ​​R being between 0 and 1.

[0144] Thus, during the untwisting phase, the instant t is detected at which the tightening torque measured in real time reaches a value corresponding to a predetermined percentage between 0 and 100 of the final tightening torque reached at the end of the screwing operation. At this instant t, the angle of rotation remaining to be covered by the rotor until the tightening torque is zero is determined as a function of the rotation angle traveled by the rotor between the end of the screwing operation and the instant t.

[0145] The coefficient R, which is between 0 and 1, will preferably be equal to 0.5.

[0146] In a variant, the stop position of the rotor is equal to the final angular position theoretical so that the motor is driven in position such that at the end of the untwisting phase, the rotor stop position is the theoretical final angular position.

[0147] According to another variant, the stop position is equal to the theoretical final angular position plus or minus a predetermined angle. Thus, the motor is controlled in position such that at the end of the untwisting phase, the stop position of the rotor is the theoretical final angular position plus or minus a predetermined angle value.

[0148] In this case, a predetermined safety angle is added or subtracted, for example empirically, to be certain that all the constraints in the reaction assembly are indeed released at the end of the untwisting or to be certain that the force-recovery accessory has not moved back. 6.3.2. Procedure

[0149] A method according to the invention is described below.

[0150] Prior to carrying out a screwing operation, the motor of the device is stopped.

[0151] The screwing operation begins by starting the motor.

[0152] During screwing, the tightening torque and the rotation angle of the rotor are measured. in real time.

[0153] During the screwing operation, the tightening torque increases until it reaches a predetermined objective tightening torque threshold.

[0154] When the control means detect the reaching of this threshold, they act on the motor control means in such a way that the power supply to the motor in the screwing direction stops so that the rotor tends to turn in the opposite direction to the direction of the completed operation under the effect of the relaxation of the reaction assembly during the untwisting phase.

[0155] The control means measure in real time with the means for measuring the angle of rotation of the rotor, the angular position of the rotor during the screwing phase and the untwisting phase.

[0156] The means for determining the theoretical final angular position determine, at a given time t during the untwisting phase, the theoretical final angular position as a function of the tightening torque measured by the torque measuring means and the angular position determined in real time by the means for determining the angular position.

[0157] The instant t corresponds to the moment when the torque measured during the untwisting phase is equal to the product of the final tightening torque reached at the end of the screwing operation by a predetermined coefficient R, the theoretical final angular position being determined so that the angular displacement of the rotor between the end of the screwing operation and the theoretical final angular position is equal to the angular displacement of the rotor between the end of the screwing operation and the instant t divided by (1-R) ​​R being between 0 and 1.

[0158] The coefficient R, which is between 0 and 1, will preferably be equal to 0.5.

[0159] In a variant, the stop position of the rotor is equal to the final angular position theoretical so that the motor is driven in position such that at the end of the untwisting phase, the rotor stop position is the theoretical final angular position.

[0160] The curves in [Fig.7] and the flowchart in [Fig.9] illustrate this general principle.

[0161] According to another variant, the stop position is equal to the final angular position theoretical added or reduced by a predetermined angle. Thus, the motor is controlled in position so that at the end of the untwisting phase, the rotor stop position is the theoretical final angular position plus or minus a predetermined angle value.

[0162] In this case, the control means may add or subtract a predetermined safety angle from the theoretical angle to be certain that all the constraints in the reaction assembly are indeed released at the end of the untwisting or to be certain that the force-recovery accessory has not moved back. 6.4. Variants

[0163] The embodiments with assisted braking and engine position control can be combined.

[0164] The methods which have just been described relate to screwing operations. A method according to the invention can also be implemented during unscrewing.

Claims

Claims

1. Device for screwing an assembly, said device comprising: - a casing; - a rotary terminal member placed at one end of said casing; - a reducer housed in said casing; - a motor housed in said casing, said motor comprising a rotor and a stator and being capable of rotating said terminal member via said reducer; - means for controlling said device; - a reaction element capable of bearing against an element external to said assembly in order to take up forces transmitted to the casing during a screwing operation;said terminal member, said reducer and said reaction element forming a reaction assembly capable of storing energy during said screwing operation, said energy being capable of being restored by said reaction assembly during an untwisting phase, at the end of said screwing operation, inducing a rotation of said rotor in the opposite direction to its direction of rotation during said screwing operation, characterized in that said device comprises means for managing the angular position reached by said reaction element at the end of said untwisting phase, said management means comprising means for measuring at least one operating parameter of said screwing / unscrewing device representative of the rotation of said rotor during said untwisting phase and means for controlling the rotation of said rotor during said untwisting as a function of said parameter.;

2. Device according to claim 1 wherein said operating parameter is the rotation frequency of said rotor.

3. Device according to claim 2 comprising means for braking said rotor, said control means being capable of actuating said braking means during said untwisting phase.

4. Device according to claim 3 wherein said control means are configured to activate said braking means, during said untwisting phase, when the rotation frequency of said rotor in the opposite direction to the screwing direction reaches a predetermined braking actuation threshold.

5. Device according to claim 4 in which said means of control are configured to deactivate said braking means, during said untwisting phase, when the rotation frequency of said rotor in the opposite direction to the screwing direction reaches a predetermined threshold for deactivation of the braking.

6. Device according to claim 5 wherein said braking actuation threshold is greater, in absolute value, than the braking deactivation threshold.

7. Device according to any one of claims 3 to 6 wherein said braking means are at least partly of the passive type.

8. Device according to any one of claims 3 to 6 in which said braking means are at least partly of the active type and capable of exerting braking of an amplitude whose value depends on the rotation frequency of said rotor.

9. Device according to claim 1 wherein said operating parameter is the angle of rotation of said rotor relative to said stator.

10. Device according to claim 9, said reaction assembly having an elastic stiffness, said device comprising means for determining, as a function of said elastic stiffness of said reaction assembly, a theoretical final angular position of said rotor after total restitution of said energy by said reaction assembly at the end of the remainder of said untwisting phase, said control means being configured to control the position of said motor in such a way that said rotor is stopped at the end of said untwisting phase at a stopping position determined as a function of said theoretical final angular position.

11. Device according to claim 10 comprising means for determining the stiffness of the reaction assembly during the screwing / unscrewing operation and / or at the start of the untwisting phase.

12. Device according to any one of claims 9 to 11 in which said device comprises means for measuring the torque delivered by said device and means for determining in real time the angular position of said rotor relative to said stator, said means for determining said theoretical final angular position being capable of determining, at a given time t during said untwisting phase, said theoretical final angular position as a function of the torque measured by said torque measuring means and the angular position determined by said means for determining in real time said angular position.

13. Device according to claim 12 in which the instant t corresponds to the moment when said torque measured during said untwisting phase is equal to the product of a final tightening torque reached at the end of said screwing operation by a predetermined coefficient R, said theoretical final angular position being determined so that the angular displacement of said rotor between the end of said screwing operation and said theoretical final angular position is equal to the angular displacement of said rotor between the end of said screwing operation and said instant t divided by (1-R) R being between 0 and 1.

14. Device according to claim 13 wherein said coefficient R is equal to 0.

5.

15. Device according to any one of claims 10 to 14 in which said stop position is equal to said theoretical final angular position.

16. Device according to any one of claims 10 to 14 in which said stop position is equal to said theoretical final angular position added to or reduced by a predetermined angle.

17. Method for screwing / unscrewing an assembly by means of a screwing device, said device comprising: - a casing; - a rotary terminal member placed at one end of said casing; - a reducer housed in said casing; - a motor housed in said casing, said motor comprising a rotor and a stator and being capable of driving said terminal member in rotation via said reducer; - means for controlling said device; - a reaction element capable of bearing against an element external to said assembly in order to take up forces transmitted to the casing during a screwing operation;said method comprising: - a phase of carrying out a screwing / unscrewing operation during which said terminal member is driven in rotation by said motor and said reducer, said terminal member, said reducer and said reaction element forming a reaction assembly storing energy during said screwing / unscrewing phase, - a detwisting phase, at the end of said screwing / unscrewing operation, during which said energy is restored by said reaction assembly inducing a rotation of said rotor in the direction; reverse of its direction of rotation during said screwing / unscrewing operation, - a phase of management of the angular position reached by said reaction element at the end of said untwisting phase, said management phase comprising a measurement of at least one operating parameter of said screwing / unscrewing device representative of the rotation of said rotor during said untwisting phase and a control of the rotation of said rotor during said untwisting phase as a function of said parameter.

18. The method of claim 17 wherein said operating parameter is the rotational frequency of said rotor.

19. Method according to claim 18 comprising a braking phase of said rotor during said untwisting phase.

20. Method according to claim 19 in which said braking phase is actuated, during said untwisting phase, when the rotation frequency of said rotor in the opposite direction to the screwing direction reaches a predetermined braking actuation threshold.

21. Method according to claim 20 in which said braking phase is deactivated, during said untwisting phase, when the rotation frequency of said rotor in the opposite direction to the screwing direction reaches a predetermined threshold for deactivating the braking.

22. A method according to claim 21 wherein said braking actuation threshold is greater, in absolute value, than the braking deactivation threshold.

23. A method according to any one of claims 19 to 22 wherein said braking is at least partly of the passive type.

24. Device according to any one of claims 19 to 23 in which said braking is at least partly of the active type and capable of exerting braking of an amplitude whose value depends on the rotation frequency of said rotor.

25. The method of claim 17 wherein said operating parameter is the angle of rotation of said rotor relative to said stator.

26. Method according to claim 25, said reaction assembly having an elastic stiffness, said untwisting phase comprising a phase of determining, as a function of said elastic stiffness of said reaction assembly, a theoretical final angular position of said rotor after total restitution of said energy by said reaction assembly at the end of the remainder of said untwisting phase, said untwisting phase comprising a phase of piloting in position said motor so as to such that said rotor is stopped at the end of said untwisting phase at a stopping position determined as a function of said theoretical final angular position.

27. Method according to claim 26 comprising a step of determining the stiffness of the reaction assembly during the screwing / unscrewing operation and / or at the start of the untwisting phase.

28. Method according to any one of claims 25 to 27 comprising a phase of measuring the torque delivered by said device and a phase of determining in real time the angular position of said rotor relative to said stator, said phase of determining said theoretical final angular position comprising the determination, at a given time t during said untwisting phase, of said theoretical final angular position as a function of the measured torque and the angular position determined in real time.

29. Method according to claim 28 in which the instant t corresponds to the moment when said torque measured during said untwisting phase is equal to the product of a final tightening torque reached at the end of said screwing operation by a predetermined coefficient R, said theoretical final angular position being determined so that the angular displacement of said rotor between the end of said screwing operation and said theoretical final angular position is equal to the angular displacement of said rotor between the end of said screwing operation and said instant t divided by (1-R) R being between 0 and 1.

30. A method according to claim 29 wherein said coefficient R is equal to ns

31. d V,J. Method according to any one of claims 27 to 30 in which said stop position is equal to said theoretical final angular position.

32. A method according to any one of claims 27 to 30 wherein said stop position is equal to said theoretical final angular position plus or minus a predetermined angle.

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