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: Optimized detorsion screwing / unscrewing device 1. Scope of the invention

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

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

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

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

[0005] To tighten an assembly to a relatively high torque (particularly above 15 Nm, and generally above 100 Nm), a force-response accessory, such as a reaction bar or a reaction stop, is generally attached to the housing and supported against a fixed element external to the tightening device. In some cases, the housing may comprise a portion housing the gearbox and a portion housing the rest of the device. These two housing portions are connected by a pivot joint that can be locked. The force-response accessory is thus attached to the portion of the housing housing the gearbox.

[0006] During a tightening (or loosening) operation, the assembly formed by the end member, the reducer, and the reaction accessory, hereinafter referred to as the reaction assembly, undergoes a mechanical tensioning stress under the effect of the motor, inducing an elastic deformation of the reaction assembly, the extent of which depends on the stiffness of this assembly. This tensioning, when under stress, constitutes 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, deformed in the elastic range, this deformation leading to the storage of a certain amount of potential deformation energy in the reaction assembly.

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

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

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

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

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

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

[0014] Indeed, if this distance is zero, the detorsion phase has not allowed sufficient release of the torsional stress of the mechanical chain so that the screwing device remains stuck 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 significant, the recoil of the force-recovery accessory from the point of contact against which it was supported during the screwing (or unscrewing) operation can have the following effects, which differ according to the type of force-recovery accessory used.

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

[0017] In the case where the load-bearing accessory is an accessory with direct contact with the assembly undergoing a screwing / unscrewing operation (such as, for example, a "sliding bar", a "square bar" or a "square cup") or with indirect contact against a mechanical element very close to the assembly undergoing a screwing operation, a rotation of the load-bearing 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: - applying to the assembly 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 within the assembly, as well as its perception by the operator, - a risk that the force recovery accessory may get stuck on the assembly in the opposite direction of the operation that has been completed.

[0018] Consequently, releasing any brake opposing the rotation of the rotor would cause the constituent parts of the reducer and the motor rotor 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 motor's rotation would prevent the generation of kinetic energy. However, this blocking would prevent detorsion and would not allow to dissipate the elastic potential energy, any subsequent release of braking would then generate kinetic energy which would cause the force recovery accessory to move in the opposite direction to the direction of the screwing (or unscrewing) operation.

[0020] There is therefore a need to identify a solution that would ensure controlled detorsion, leading to the avoidance of: - that the screwing device does not remain stuck on the assembly at the end of a screwing (or unscrewing) operation; - that the mechanical environment of the assembly is not damaged by a rotation of the force-retaining accessory at the end of the screwing (or unscrewing) operation; - that an operator is injured by a rotation of the force recovery accessory at the end of a 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 detorsion 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 a 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] To this end, the invention proposes a device for screwing an assembly, said device comprising:

[0028] - a crankcase;

[0029] - a rotating terminal element placed at one end of said housing;

[0030] - a reducer housed in said casing;

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

[0032] - means of controlling said device;

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

[0034] said terminal organ, said reducer and said reaction element forming a reaction assembly capable of storing energy during said screwing operation, said energy being capable of being released by said reaction assembly during a detorsion 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 includes means for managing the angular position reached by said reaction element at the end of said untwisting phase, said management means including 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 rotor position at the end of the detorsion makes it possible to avoid, in whole or in part: - that the screwing device does not remain stuck on the assembly at the end of a screwing (or unscrewing) operation; - that the mechanical environment of the assembly is not damaged by a rotation of the force-retaining accessory at the end of the screwing (or unscrewing) operation; - that an operator is injured by a rotation of the force recovery accessory at the end of a screwing (or unscrewing) operation.

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

[0039] In this case, the device preferably includes braking means for said rotor, said control means being capable of actuating said braking means during said unwinding 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 predetermined braking deactivation threshold.

[0042] Said braking actuation threshold is preferably greater, 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 force of an amplitude whose value depends on the rotational frequency of said rotor.

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

[0046] In this case, reaction assembly having an elastic stiffness, said device preferably includes 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 detorsion phase, said control means being configured to pilot said motor in position such that said rotor is stopped at the end of said detorsion phase at a stopping position determined as a function of said theoretical final angular position.

[0047] The device may include means for determining the stiffness of the reaction assembly during the screw-in / screw-out operation and / or at the beginning of the untwisting phase.

[0048] Said device preferably includes 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 instant t during said detorsion phase, said theoretical final angular position as a function of the torque measured by said torque measurement 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 such 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 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 stopping position is preferably equal to said theoretical final angular position.

[0052] Said stopping position is preferably equal to said theoretical final angular position plus or minus a predetermined angle.

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

[0054] - a crankcase;

[0055] - a rotating terminal element placed at one end of said housing;

[0056] - a reducer housed in said casing;

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

[0058] - means of controlling said device;

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

[0060] said process comprising:

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

[0062] - a detorsion phase, following said screwing / unscrewing operation, at during 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 for managing the angular position reached by said reaction element at the end of said untwisting phase, said management phase including 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 rotational frequency of said rotor.

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

[0066] Said braking phase is preferentially activated, during said detorsion phase, when the rotation frequency of said rotor in the opposite direction to the screwing direction reaches a predetermined braking activation threshold.

[0067] Said braking phase is preferentially deactivated, during said detorsion 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 activation threshold is preferably greater, 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 rotational frequency of said rotor.

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

[0072] Said reaction assembly has an elastic stiffness, said detorsion 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 detorsion phase, said detorsion phase comprising a phase of piloting said motor in position such that said rotor is stopped at the end of said detorsion phase at a stopping position determined as a function of said theoretical final angular position.

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

[0074] Such a method preferably includes 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 including 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 corresponds preferably 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 stopping position is preferably equal to said theoretical final angular position.

[0078] Said stopping position is preferably equal to said theoretical final angular position plus or minus a predetermined angle. 5. Description of the figures

[0079] Other features and advantages of the invention will become apparent from the following description of particular embodiments, given by way of simple illustrative and non-limiting example, and the accompanying drawings, among which:

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

[0081] [Fig.2] [Fig.2] illustrates the device of [Fig.1] set up on an assembly;

[0082] [Fig.3] [Fig.3] illustrates a longitudinal cross-sectional view of the device of [Fig.1];

[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 retrieval accessory the effort is moved away from its point of support;

[0085] [Fig.6] [Fig.6] illustrates curves showing the operation of a mode of implementation using an assisted brake;

[0086] [Fig.7] [Fig.7] illustrates curves showing the operation of a mode of implementation involving position control of the engine;

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

[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 housing 10 equipped with a handle 11.

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

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

[0094] The housing 10 contains a reducer 13 and a motor 14.

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

[0096] The reducer 13 comprises a plurality of gears. It includes 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 able to drive the terminal member 12 in rotation.

[0098] The screwing device includes control means 15 for the motor 14. These control means 15 can be integrated into control means 16 of the device, classically taking the form of a controller, which controller can be remote from the housing 10 of the device or housed totally or partially in the housing 10.

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

[0100] The screwing / unscrewing device is of the continuous tightening type. It allows for high-torque screwing operations, 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, in order to allow the screwing / unscrewing device to develop its tightening torque on the screw, the implementation of a force recovery accessory 18, also called a reaction element.

[0102] Such an accessory is fixedly attached to the housing and bears against a fixed element external to the screwing device so as to absorb the reaction forces transmitted to the housing, in particular the reaction torque, generated during the tightening operation. In the illustrated example, the reaction accessory 18 bears against a nut 19 located near the nut being tightened during the tightening of a nut (see Figures 2, 4).

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

[0104] At the end of the screwing (or unscrewing) operation, this elastic deformation potential energy is likely to be restored by the reaction assembly to during a detorsion phase during which the reaction assembly relaxes elastically (like a spring). This relaxation tends to induce a rotation of the motor rotor 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 figure 5).

[0105] The invention aims to optimize the detorsion phase, in particular to avoid, in whole or in part: - that the screwing device does not remain locked onto the assembly at the end of a screwing operation if the rotation of the reaction accessory with respect to the element against which it rests during the screwing / unscrewing operation is too small; - that the mechanical environment of the assembly is not damaged by a rotation of the force-retaining accessory at the end of the screwing operation, inducing a risk that it may come into contact with the environment; - that an operator is injured by a rotation of the force recovery accessory at the end of the screwing operation, inducing a risk that it may hit the operator.

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

[0107] As will become clearer later, the operating parameter preferentially belongs to the group comprising: - the rotor's rotational frequency; - 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 rotational 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 specifically the means for measuring at least one operating parameter of the device representing the rotational displacement of the rotor, include means 21 for real-time measurement of the rotational frequency of the motor rotor. Such means The measurement methods are known to those skilled in the art. For example, they might be a mechanical or optical encoder, or a Hall effect sensor. They could also be indirect measurements, such as a motor current sensor for an electric motor-driven screw-driving / unscrewing device, or a pressure sensor for a pneumatic motor-driven screw-driving / unscrewing device.

[0111] The screwing / unscrewing device, or more precisely the means for managing the angular position of the rotor, includes means 22 for braking the rotor. Such braking means are known to those skilled in the art. For a screwing / unscrewing device with an electric motor, this may, 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 may also be active braking, in which the motor is driven in the opposite direction to limit its rotational speed. Braking may 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 reaching a predetermined objective tightening torque threshold.

[0113] The end of a screwing operation is marked by the tightening torque reaching a predetermined target tightening torque threshold. When the tool's control means 16 detect that this threshold has been reached, the control means 16 act on the motor control means 15 in such a way as to stop the motor's power supply. Following this interruption of the motor's power supply, the rotor tends to rotate in the opposite direction to the completed operation due to the release of the reaction assembly, which releases the potential elastic deformation energy accumulated during the operation.

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

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

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

[0118] The braking means can alternatively be active. In this case, the braking means are capable of exerting braking force with an amplitude varying according to the rotational frequency of the rotor, following 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 (Joule effect). The disadvantage of passive braking is that the braking speed is not controlled.

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

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

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

[0129] When, during the untwisting phase, the rotational frequency of the reverse-direction rotor increases in such a way that it reaches the predetermined threshold for brake activation, the control means detect the reaching of this threshold and activate the braking means accordingly.

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

[0131] When, during the untwisting phase, the rotational frequency of the reverse-direction rotor decreases to such an extent that it reaches the predetermined threshold for brake deactivation, the control means detect the attainment of this threshold and deactivate the braking means.

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

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

[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 can thus be successively implemented over a predetermined period.

[0136] 6.3. Second embodiment: motor 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 motor position 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 rotor's rotational displacement, includes means for measuring the rotation angle of the motor rotor relative to the stator in real time. Such measuring means are known to those skilled in the art. By way of illustration, they could, for example, be a mechanical or optical encoder, a Hall effect sensor, etc.

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

[0140] In this embodiment, the screwing / unscrewing device includes means 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 energy restitution by the reaction assembly at the end of the rest of the untwisting phase, the control means 16 being configured to control 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 include means for determining 25 the stiffness of the reaction assembly, during the screwing / unscrewing operation and / or at the beginning of the untwisting phase.

[0142] More specifically, the means for determining the theoretical final angular position are capable of determining, at a given instant 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 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 tightening operation is detected. At this instant t, the remaining angle of rotation to be traversed by the rotor until the tightening torque is zero is determined as a function of the angle of rotation traversed by the rotor between the end of the tightening operation and instant t.

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

[0146] In one embodiment, the rotor's stopping position is equal to the final angular position theoretical so that the motor is controlled in such a position that at the end of the untwisting phase, the rotor's stopping position is the theoretical final angular position.

[0147] According to another embodiment, the stopping position is equal to the theoretical final angular position plus or minus a predetermined angle. Thus, the motor is driven into position such that, at the end of the untwisting phase, the rotor's stopping position 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 ensure that all stresses in the reaction assembly are released at the end of the detorsion or to ensure that the force recovery accessory has not recoiled. 6.3.2. Process

[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 rotor's angle of rotation are measured in real time.

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

[0154] When the control means detect that this threshold has been reached, they act on the motor control means in such a way that the motor supply in the direction of screwing stops so that the rotor tends to rotate in the opposite direction to the direction of the operation completed under the effect of the relaxation of the reaction assembly during the unwinding 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 one embodiment, the rotor's stopping position is equal to the final angular position theoretical so that the motor is controlled in such a position that at the end of the untwisting phase, the rotor's stopping position is the theoretical final angular position.

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

[0161] According to another embodiment, the stopping position is equal to the final angular position The theoretical angle is added or subtracted by a predetermined angle. Thus, the motor is controlled in such a position that, at the end of the untwisting phase, the rotor's stopping 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 to the theoretical angle to ensure that all the constraints in the reaction assembly are released at the end of the detorsion or to ensure that the force recovery accessory has not recoiled. 6.4. Variants

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

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

Claims

Demands

1. A screw-fastening device for an assembly, said device comprising: - a housing; - a rotating end member located at one end of said housing; - a gearbox housed in said housing; - a motor housed in said housing, said motor comprising a rotor and a stator and being capable of rotating said end member via said gearbox; - control means for said device; - a reaction element capable of bearing against an element external to said assembly in order to absorb forces transmitted to the housing during a screw-fastening operation;said terminal organ, said reducer and said reaction element forming a reaction assembly capable of storing energy during said screwing operation, said energy being capable of being released by said reaction assembly during a detorsion 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 includes means for managing the angular position reached by said reaction element at the end of said detorsion phase, said management means including means for measuring at least one operating parameter of said screwing / unscrewing device representative of the rotation of said rotor during said detorsion phase and means for controlling the rotation of said rotor during said detorsion as a function of said parameter.;

2. Device according to claim 1 in which said operating parameter is the rotational frequency of said rotor.

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

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

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

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 a passive type.

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

9. Device according to claim 1 wherein said operating parameter is the angle of rotation of said rotor with respect 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 detorsion phase, said control means being configured to pilot said motor in position such that said rotor is stopped at the end of said detorsion 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 beginning of the untwisting phase.

12. A device according to any one of claims 9 to 11, wherein 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 of determining said theoretical final angular position being capable of determining, at a given instant t during said detorsion phase, said theoretical final angular position as a function of the torque measured by said torque measurement means and the angular position determined by said means of determining said angular position in real time.

13. Device according to claim 12 wherein 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 such 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 wherein said stop position is equal to said theoretical final angular position.

16. Device according to any one of claims 10 to 14 wherein said stop position is equal to said theoretical final angular position plus or minus a predetermined angle.

17. A method for screwing / unscrewing an assembly using a screwing device, said device comprising: - a housing; - a rotating end member located at one end of said housing; - a gearbox housed within said housing; - a motor housed within said housing, said motor comprising a rotor and a stator and being capable of rotating said end member via said gearbox; - control means for said device; - a reaction element capable of bearing against an external element of said assembly in order to absorb forces transmitted to the housing 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 detorsion phase, at the end of said screwing / unscrewing operation, during which said energy is released by said reaction assembly inducing a rotation of said rotor in the opposite direction to its direction of rotation during said screwing / unscrewing operation, - a phase of managing the angular position reached by said reaction element at the end of said detorsion 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. Method according to 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 detorsion phase.

20. Method according to claim 19 wherein said braking phase is activated, during said untwisting phase, when the rotational frequency of said rotor in the opposite direction to the screwing direction reaches a predetermined braking activation threshold.

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

22. Method according to claim 21 wherein said brake actuation threshold is greater, in absolute value, than the brake deactivation threshold.

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

24. A method according to any one of claims 19 to 23, wherein said braking is at least partly of an active type and capable of exert braking of an amplitude whose value depends on the rotational frequency of said rotor.

25. Method according to claim 17 wherein said operating parameter is the angle of rotation of said rotor with respect 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 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.

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 beginning of the untwisting phase.

28. A 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 detorsion phase, of said theoretical final angular position as a function of the measured torque and the angular position determined in real time.

29. A method according to claim 28 wherein 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. Method according to claim 29 wherein said coefficient R is equal to 0.

5.

31. A method according to any one of claims 27 to 30 wherein 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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