EP0577444A1 - Control device of a vibrator with variable imbalance - Google Patents

Abstract

The device according to the invention brings into play a phase shifter controlled by a dual-action hydraulic actuator which includes a phase-shifting chamber (16) connected to the output of the distributor (21) via a circuit comprising a non-return valve (20) and a hydraulic accumulator (31), the charging pressure of which can be limited by virtue of a limiter (D) and a chamber (18) for shifting the phase back, the pressure of which is controlled by a pressure regulator (26) so that a defined phase shift corresponds to each control value of the regulator (26). The invention applies especially to the ramming of objects such as piles or sheet piles into the ground. <IMAGE>

Description

The present invention relates to a device for controlling a variable-time vibrator such as, for example, that described in patent application No. 91 09253, of July 15, 1991, in the name of the Applicant.

It is known that vibrators of this kind which are used, for example, for driving objects such as piles or sheet piles into the ground, involve at least a couple of eccentric rotating weights, or even two sets of weights driven in opposite direction to each other, at the same speed of rotation.

In order to adjust the amplitude of the vibrations generated by the vibrator, in particular to avoid harmful transient phenomena during the starting or stopping phases, and to take account of the mechanical characteristics of the soil, proposals have been made devices making it possible to generate an angular offset between the two counterweights of the pair or between the two sets of counterweights.

Such devices can involve a planetary gear train, of the Pecqueur type, such as described in patent No. 1,566,358, in the name of the Applicant, or even a rotary link involving a hydraulic phase shifter, for example of the type comprising two rotary elements movable axially with respect to each other and against the action of a spring, under the effect of a pressurized fluid.

• une position de repos dans laquelle il interrompt l'alimentation de l'une ou l'autre ou des deux chambres de l'actionneur en fluide sous pression, et
• une position de travail dans laquelle le distributeur oriente le fluide sous pression vers l'une des susdits chambres, par l'intermédiaire d'un premier circuit de distribution.

The invention more particularly aims a control device which allows to fully exploit all the advantages of the principle of the variation of the moment by a phase shift of the flyweight train. It more particularly proposes a device for controlling a variable-time vibrator of the type comprising at least two eccentric rotary counterweights driven in rotation at the same speed and a phase shifter capable of generating an angular offset between these weights during their rotation, the phase shifter being controlled by means of a double-acting hydraulic actuator comprising a rephasing chamber and a phase shift chamber separated by a piston, the supply of this actuator with pressurized fluid delivered by a pump being effected by a hydraulic circuit comprising a distributor having at least:

• a rest position in which it interrupts the supply of one or the other or of the two chambers of the actuator with pressurized fluid, and
• a working position in which the distributor directs the pressurized fluid towards one of the above-mentioned chambers, via a first distribution circuit.

According to the invention, this device is characterized in that said first distribution circuit comprises first limiting means making it possible, thanks to a control member, to vary the pressure which it applies to said chamber within a predetermined range, and in that the other chamber is connected to a second distribution circuit comprising means making it possible to modulate the pressure which it applies to this second chamber, according to an appropriate counter-profile, so that the actuator applies to the phase shifter a motor force in relation to the resistance force which results from the amplitude of the movement of the vibrator and that thus, to each value displayed on the control member, corresponds a determined amplitude of the vibrations.

According to another characteristic of the invention, the distributor is put in the rest position when starting the engine associated with the auxiliary hydraulic pump which supplies the phase shifter and then in the rephasing position when certain conditions are met, for example when the flow rate of the main hydraulic pump which supplies the vibrator reaches a predetermined minimum value (for example a flow rate corresponding to a minimum frequency of the vibrator). A vibration start is thus obtained at a given frequency without first generating undesirable vibrations at low frequency.

Of course, before stopping the vibrator and, more generally, prior to a reduction in the speed of the flyweights below a threshold value, it will be necessary to bring the distributor back into the phase shift position. This process can be carried out automatically as soon as the conditions of flow of the pump and therefore of frequency are no longer met, but so as to be completed before undesirable vibrations at low frequency can again occur.

Another advantage of the device described above consists in that it makes it possible to get rid of nuisances due to decreases in frequency of the vibrator resulting for example from an evacuation of part of the flow by the triggering of a high pressure valve. safety device in the hydraulic circuit and / or a reduction in the flow rate of the hydraulic pump, following an excessive pressure rise compared to the safety pressure of the circuit or compared to the power that can deliver the thermal engine driving the hydraulic transmission.

This result is in fact obtained by one of the following two methods, both controlling their triggering by measuring a pressure of the hydraulic fluid just below the pressure triggering the reduction in flow rate, or even by detecting conditions requiring a reduction. amplitude of the vibrations to be corrected.

• i) agir directement sur l'alimentation du circuit de rephasage en basculant le distributeur à la position de repos ;
• ii) prévoir, en dérivation de la sortie du rephasage, un second distributeur qui, déclenché, met la chambre de rephasage en communication avec un limiteur de pression préréglé à la pression correspondant à la réduction d'amplitude souhaitée.

These two methods consist in:

• i) act directly on the power supply of the rephasing circuit by tilting the distributor to the rest position;
• ii) provide, bypassing the rephasing output, a second distributor which, when triggered, puts the rephasing chamber in communication with a pressure limiter preset to the pressure corresponding to the reduction in amplitude desired.

These actions make it possible to generate both a drop in the pressure of the hydraulic fluid and, due to the improvement in yields in the hydraulic transmission and a lower load on the main thermal engine, an accumulation of the rotation speed of the weight trains, with an increase in the kinetic energy of the latter.

The perception of the pressure drop below the critical pressure leads to a reverse tilting of the main distributor (method i)), of the second distributor (method ii)), and, consequently, a phase shift of the phase shifter and a redeployment of the moment. For a moment, the vibrator then has both the power delivered by the hydraulic motors and the kinetic energy accumulated in the flyweights.

This transient phase continues until the pressure of the hydraulic fluid again reaches its critical value or until the conditions requiring the reduction in amplitude of the vibrations reappear.

This creates a pulsating (pumping) operating regime which is particularly effective in difficult soils, while avoiding going below the frequencies which generate undesirable disturbances.

Adjustment of the pumping period can be obtained by adjusting the switching thresholds for high pressure and / or exhaust pressure (method ii)).

Another advantage of the device described above is that it allows the control of the amplitude control, either at a sound level measured on the site, or at a vibratory amplitude level measured in the ground or on a structure. .

• Les figures 1 et 2 sont deux coupes schématiques, respectivement axiales et transversales, d'un vibrateur à moment variable selon l'invention ;
• La figure 3 est un schéma hydraulique du circuit d'alimentation énergétique et de commande du vibrateur représenté figures 1 et 2 ;
• La figure 4 est un schéma du circuit électrique associé au circuit hydraulique représenté figure 3 ;
• La figure 5 est un schéma hydraulique d'une variante d'exécution du circuit d'alimentation d'un vibrateur à moment variable selon l'invention ;
• La figure 6 est un schéma du circuit électrique associé au circuit hydraulique représenté figure 5.

Embodiments of the invention will be described below, by way of nonlimiting examples, with reference to the appended drawings in which:

• Figures 1 and 2 are two schematic sections, respectively axial and transverse, of a variable moment vibrator according to the invention;
• Figure 3 is a hydraulic diagram of the power supply circuit and control of the vibrator shown in Figures 1 and 2;
• Figure 4 is a diagram of the electrical circuit associated with the hydraulic circuit shown in Figure 3;
• Figure 5 is a hydraulic diagram of an alternative embodiment of the supply circuit of a variable-time vibrator according to the invention;
• FIG. 6 is a diagram of the electrical circuit associated with the hydraulic circuit shown in FIG. 5.

In the example shown in Figures 1 and 2, the vibrator comprises two trains 1, 2 of eccentric weights rotatably mounted by means of shafts A₁, A₂, A _n - A'₁, A'₂, A ' _n parallel to a transverse axis X, X 'and the ends of which engage in bearings carried by two parallel flanges 3, 4 constituting the two lateral sides of a housing 5.

Each of the weights M, M ′ is associated with a pinion P arranged and dimensioned so that the pinions P associated with the same train 1, 2 of weights M mesh with each other, in successive pairs.

In this example, each set of counterweights M comprises a pair of sets of counterweights M / pinion P shown in solid lines, the set partially represented in broken lines indicating the mode of implantation of another pair.

The two flywheel trains are driven in rotation by means of a motorization, comprising two hydraulic motors H₁, H₂ mounted on the flange 3 at one end of the housing 5.

These two motors H₁, H₂ drive two respective parallel shafts passing through bearings integral with the flanges 3, 4 and which each carry two coaxial pinions P₁, P₂ - P₅, P₆.

The pinions P₁ and P₆ respectively mesh with the pinions P associated with the flyweights M 'and M to carry out the rotational drive of the trains 2 and 1.

The pinion P₅ is arranged so as to mesh with a pinion P₃ secured to the driven shaft 6 of a phase shifter 7 with hydraulic control. This phase shifter 7 further comprises a driving shaft 8, coaxial with the driven shaft 6, which carries a pinion P₄ engaged with the pinion P₂ driven by the motor H₁.

In the example illustrated in Figure 3, the phase shifter control device has been shown schematically in the form of a double-acting hydraulic cylinder 11 whose rod 12 which is integral with the piston 13 actuates a phase shift mechanism which may include a planetary gear train of Pecqueur or even a rotary link comprising two rotary elements axially movable relative to each other. In the latter case, at least one of these elements has a helical groove which cooperates with a part of the other element so that an axial displacement of one of the two elements relative to the other, for example under the effect of the rod 12 generates a relative rotation of these two elements.

• une chambre de déphasage 16 traversée par la tige 12 et connectée à un circuit de déphasage 17,
• une chambre de rephasage 18 connectée à un circuit de rephasage 19.

The piston 13 delimits inside the cylinder 14 of the jack 11 two chambers, namely:

• a phase shift chamber 16 traversed by the rod 12 and connected to a phase shift circuit 17,
• a rephasing chamber 18 connected to a rephasing circuit 19.

• un déplacement du piston 13 tendant à réduire le volume de la chambre de déphasage 16, sous l'effet d'un fluide hydraulique sous pression injecté dans la chambre de rephasage 18 provoque un rephasage du déphaseur jusqu'à ce qu'en fin de course du piston 13, les trains de masselottes se trouvent en phase et, qu'en conséquence, l'amplitude des vibrations soit maximale, et
• un déplacement du piston 13 tendant à réduire le volume de la chambre de rephasage 18, sous l'effet d'un fluide hydraulique sous pression injecté dans la chambre de déphasage 16, provoque un déphasage pouvant atteindre 180° (opposition de phase) et, en conséquence, une réduction, voire une annulation pure et simple des vibrations.

The transmission between the rod 12 of the piston 13 and the control of the phase shift mechanism is designed in such a way that:

• a displacement of the piston 13 tending to reduce the volume of the phase shift chamber 16, under the effect of a pressurized hydraulic fluid injected into the rephasing chamber 18 causes a rephasing of the phase shifter until at the end of its travel of the piston 13, the counterweight trains are in phase and, consequently, the amplitude of the vibrations is maximum, and
• a displacement of the piston 13 tending to reduce the volume of the rephasing chamber 18, under the effect of a pressurized hydraulic fluid injected into the phase shifting chamber, causes a phase shift which can reach 180 ° (phase opposition) and, consequently, a reduction or even an outright cancellation of vibrations.

The phase shift circuit 17 which comprises a non-return valve 20 is connected to one S₁ of the three outputs S₁, S₂, S₃ of a distributor 21 whose input E is connected to the output of a driven hydraulic pump 22 by a diesel engine 23 and of which an output S₃ is connected to the cover B by a return circuit to the cover 29.

In this example, the pressure of the hydraulic fluid applied to the inlet E of the distributor 21 is limited to a safety value by means of a circuit for returning to the tank comprising a pressure switch 24 calibrated for example at a pressure below the maximum admissible pressure in the rest of the phase shift and / or rephasing circuit.

Likewise, the output S₁ of the distributor 21 is connected to the return circuit 29 by means of a pressure switch P₀₄ calibrated for example at a value chosen as a function of the desired low pressure in the accumulator and the phase shift chamber.

The motor 23 also drives a second, more powerful hydraulic pump P, intended to supply the hydraulic motors of the vibrator.

The rephasing circuit 19 which is connected to a second outlet S₂ of the distributor 21 comprises, in series, a distributor 25 and a pressure regulator 26 allowing, by virtue of a potentiometric control 27, to vary the pressure of the fluid injected into the chamber rephasing 18 in a pressure range [P₁, P₂].

• soit à la bâche B par l'intermédiaire du circuit de retour à la bâche 29 (position de repos indiquée figure 4),
• soit sur le circuit de déphasage 17 en mettant le circuit de rephasage 19 en communication avec la bâche B, par l'intermédiaire du circuit 29 (position 1),
• soit sur le circuit de rephasage 19 en mettant le circuit de déphasage 17 en communication avec le circuit de retour à la bâche 29.

Depending on the command (manual or automatic) applied to it, the distributor 21 directs the flow of hydraulic fluid generated by the pump 22:

• either to cover B via the return circuit to cover 29 (rest position indicated in FIG. 4),
• either on the phase shift circuit 17 by putting the rephasing circuit 19 in communication with the cover B, via the circuit 29 (position 1),
• either on the rephasing circuit 19 by putting the phase shifting circuit 17 in communication with the return circuit to the cover 29.

The phase shift chamber 16 of the cylinder 11 is, moreover, connected to a hydraulic accumulator 31 whose hydraulic pressure increases as the volume of oil present in the phase shift chamber 16 is transferred from the cylinder 11 into the accumulator 31.

Thanks to a judicious choice of characteristics, volume of gas pressure, initial loading pressure of hydraulic oil, this accumulator 31 is used in combination with the pressure regulator 26 so that at each pressure value of the hydraulic fluid supplied by the regulator 26 corresponds to a position of the piston 13 in the cylinder 11, and a corresponding phase shift of the phase shifter.

Furthermore, according to the command applied to it, the distributor 25 provides a connection between the pressure regulator 26 and the rephasing chamber 18 or between the latter and the circuit 29 for returning to the tank B, by means of a pressure switch P₀₅ calibrated for example to ensure proper braking of the oil discharged from the rephasing chamber.

To avoid any risk of premature blocking of the phase shifter due to excess pressure in the accumulator 31, the pressure admitted into the latter is clipped to a value P'02 thanks to a pressure limiter D set to a judiciously chosen value, less than P₂ (maximum value of the pressure delivered by the regulator). This limiter D short-circuits the valve 22 so as to allow, in all circumstances, a phase shift of the phase shifter and, consequently, a complete deployment of the moment of the vibrator.

• i) pour fixer la pression de déphasage et permettre l'obtention de la position complètement déphasée, lorsque la chambre de rephasage 18 du vérin 11 est en communication avec le retour à la bâche (commande de rephasage au minimum), et
• ii) pour permettre à l'accumulateur 31 de développer une pression suffisante au fur et à mesure de son remplissage pour équilibrer suffisamment la pression commandée par le régulateur 26.

Conversely, the rephasing chamber 18 is charged, periodically, for example at each stop of the vibrator, by means of a line 33 whose pressure is limited to a value P'₀₁, thanks to a pressure limiter 34 connected to the output of regulator 26 and chosen at a sufficiently high level:

• i) to fix the phase shift pressure and allow the completely phase-shifted position to be obtained, when the rephasing chamber 18 of the jack 11 is in communication with the return to the cover (minimum rephasing command), and
• ii) to allow the accumulator 31 to develop sufficient pressure as it is filled to sufficiently balance the pressure controlled by the regulator 26.

The choice of the pressure couples P'₀₁ and P'₀₂ within the range of variations P'₁ - P'₂, of the accumulator 31, in the absence of a pressure limiter, ensures a renewal of the hydraulic oil from the accumulator circuit 31 / rephasing chamber 18, thus eliminating the problems of bleeding during the charging successions in phase shifted position and complete rephasing.

As previously mentioned, the device described above makes it possible to solve in a particularly advantageous manner the operating phases which, until now, were critical, such as starting the diesel engine 23, starting the vibrations, stopping the vibrations and sinking in hard ground.

Thus, the starting of the diesel engine 23 can be carried out when empty, with the counterweight trains in phase opposition (zero moment).

In addition, to avoid having the pump 25 in charge when the diesel engine 23 is started, the automatic placing in position 1 of the distributor and, consequently, the phase shift of the phase shifter, is dependent on the launch of the diesel engine 23 For this purpose, use is made for example of a servo-control of the accelerator position or a sensor 35 of the speed of rotation of the motor 23 which acts on the distributor 21 (link 36 in dashed lines) when the speed of rotation of the motor 23 exceeds a predetermined threshold. This arrangement also makes it possible to place the counterweight trains of the vibrator in phase opposition and therefore perform a launch of this vibrator without triggering vibration.

To avoid any premature propagation of low frequency vibrations, the tilting of the distributor 21 in position 2 is electrically subordinated to the obtaining of a minimum hydraulic flow (in general, a flow which corresponds to the minimum frequency of vibration) in the hydraulic circuit main powering the hydraulic motors of the vibrator. For this purpose, one can use a flow sensor 37 placed in the main hydraulic circuit or a servo exploiting a condition associated with the generation of a sufficient flow by the main pump. This sensor or this control acts on the distributor 21 so as to prohibit the passage into position 2 as long as the detected flow is less than a predetermined threshold. Optionally, this sensor 37 can automatically switch the distributor to position 2 as soon as the above threshold is crossed or, on the contrary, automatically switch the distributor to position 1 when the flow rate falls below the above threshold and, in a more general, as soon as the frequency conditions are no longer met, in particular as soon as a reduction in the main flow is manually controlled. This process, which occurs during the shutdown phase, avoids the low frequency vibrations that usually occur during this phase.

• i) à agir directement sur l'alimentation du circuit de rephasage en basculant le distributeur 21 à la position de repos ;
• ii) à déclencher le distributeur 25 de manière à mettre la chambre de rephasage 18 en communication avec le limiteur de pression P₀₅ qui est taré à une valeur de pression correspondant à la réduction d'amplitude souhaitée.

In fact, two methods can be used to eliminate the nuisances due to these decreases in frequency of the vibrator associated with the increase in power and pressure necessary for driving, these methods consisting of:

• i) acting directly on the power supply of the rephasing circuit by tilting the distributor 21 to the rest position;
• ii) triggering the distributor 25 so as to put the rephasing chamber 18 in communication with the pressure limiter P₀₅ which is set to a pressure value corresponding to the reduction in amplitude desired.

An important feature of the device described above is that it allows the vibrator to be used in overpowering by exploiting a pumping phenomenon usually considered harmful.

It turns out, in fact, that these hydraulic transmissions, such as that used between the main pump 25 and the hydraulic motors of the phase shifter necessarily have a high pressure valve, quickly relayed by a servo reducing the hydraulic flow (reduction of the tilting of the hydraulic pump plate or removal of a body for multi-body pumps or diversion of part of the flow). This has the undesirable effect of reducing the speed of rotation of the hydraulic motors and therefore the frequency of operation of the machine and, consequently, of increasing its vibration nuisance. Controlling the tilting of the distributor 21 from position 2, rephasing, to position 1, phase shift, at the measurement of a pressure just below the pressure triggering the reduction in flow, makes it possible to avoid any loss of frequency of the vibrator , while promoting sinking. In fact, the perception of this critical pressure by the servo-control leads to reducing the moment of the vibrator, consequently its vibratory amplitude, and consequently the power consumed by the vibrator. At constant flow, this results in a drop in the hydraulic pressure in the transmission.

This results in an improvement in the hydraulic efficiency of the transmission, which tends to slightly increase the speed of rotation of the counterweights, and consequently their kinetic energy of rotation. The perception of a drop in pressure below the critical pressure causes a reverse tilting of the distributor 21 and, consequently, the redeployment of the moment.

During this transient phase, the vibrator has both the power delivered by the hydraulic transmission and the kinetic energy accumulated in the flyweights. Until the critical pressure is reached again.

This establishes a pulsating operating regime of the vibrator, particularly effective in difficult soils, avoiding going below the frequencies generating undesirable disturbances.

Figure 4 shows the block diagram of an electrical control circuit associated with the hydraulic circuit previously described.

• du circuit électrique 41 du régulateur de pression 26 permettant un réglage potentiométrique de la pression appliquée à la chambre de rephasage 18, et
• des solénoïdes 42, 43 de commande du distributeur 21.

This control circuit is supplied by a direct current source, the negative terminal 40 of which is connected to ground:

• the electrical circuit 41 of the pressure regulator 26 allowing potentiometric adjustment of the pressure applied to the rephasing chamber 18, and
• solenoids 42, 43 for controlling the distributor 21.

• à l'entrée d'un dispositif de commutation 47 associé au contact permettant le démarrage du moteur diesel 23,
• au circuit électrique 41 du régulateur de pression 26,
• à un commutateur 48 actionné en fonction du débit de la pompe principale 25.

The positive terminal 46 of the power supply is connected:

• at the input of a switching device 47 associated with the contact enabling the diesel engine 23 to start,
• to the electrical circuit 41 of the pressure regulator 26,
• to a switch 48 actuated as a function of the flow rate of the main pump 25.

The switching device 47 comprises a first switch 49 in series with a switch 50, a first output 51 of which is connected to the solenoid 43 which controls the position 1 of the distributor 21 and of which a second output 52 is connected to the switch 48.

• un interrupteur 53 qui assure une liaison interruptible entre le contact du relais 44 et le solénoide 42 permettant le passage en position 2 du distributeur 21,
• un interrupteur 54 permettant de relier le solénoïde 43 du distributeur 21 à la borne positive 46 de l'alimentation.

This switch 48 actuated as a function of the flow rate of the main pump 25 comprises two alternating operation switches 53, 54, namely:

• a switch 53 which provides an interruptible link between the contact of the relay 44 and the solenoid 42 allowing the distributor 21 to move to position 2,
• a switch 54 for connecting the solenoid 43 of the distributor 21 to the positive terminal 46 of the power supply.

The operation of the previously described circuit is then as follows:

• l'interrupteur 47 étant ouvert,
• le commutateur 50 aiguillant la sortie de l'interrupteur 47 sur le solénoide 43.

When the diesel engine 23 is stopped or is running at a speed at most equal to the idling speed, the switch 47 and the switch 51 are in the position of FIG. 4:

• the switch 47 being open,
• the switch 50 switching the output of the switch 47 on the solenoid 43.

Consequently, the distributor 21 is in the rest position. The same is true after starting when the engine is idling.

When the engine 23 is started, the detection of a speed greater than the idling speed first of all causes the switch 49 to close so that the distributor 21 moves to position 1 to enable the trains of vibrator weights to go in phase opposition.

The detection of a sufficient flow rate of the main pump P, following a flow control causing the closure of the switch 53, then causes the switch 50 to switch over on its output 51 and, consequently, the excitation of the solenoid 42 of the distributor 21 which passes to position 2 (rephasing with deployment of the moment of the vibrator).

The subsequent detection of a flow rate of the main pump P less than a threshold value will then cause the switch 48 to switch (switch 53 open / switch 54 closed) and, consequently, the passage of the distributor 21, from position 2 to position 1 (phase shift with reduction of the moment).

A pumping process of the type described above is therefore obtained, the amplitude of which can be adjusted by electronic or mechanical means acting on the difference between the threshold values of the pressure of the hydraulic fluid delivered by the hydraulic pump.

Another important advantage of the device described above is that it makes it possible to control the amplitude control, either at a noise level, or at a vibratory amplitude level measured in the ground in particular in order to comply with the standards. noise or vibration at the site boundary.

To this end, there is in the sensitive area to be protected a device 60 performing the measurement of noise or vibrations. The result of this measurement is compared with a setpoint V in a comparator. The latter acts on the pressure regulator, so as to establish an appropriate phase shift tending to cancel the difference between the measured value and the set value.

A connector network 61, for example of the PID type, can be used this time to avoid oscillations and to maintain the performance of the device at maximum compatible with the set values.

It appears from the foregoing description that the principle of controlling the amplitude of the vibratory moment is based on the association of a control pressure with a phase shift position, thanks to the stable balance obtained between the motor torque due to the control pressure on the one hand, and on the other hand the natural resisting torque of the system, modified and supplemented by a known resisting torque.

• Il est tout d'abord possible d'exploiter directement le seul couple de rephasage spontané engendré par le vibrateur, le couple à appliquer étant une certaine fonction de l'angle de rephasage.
• On peut également ajouter à ce couple celui engendré dans le déphaseur par une contre-pression constante, par exemple grâce à un accumulateur de grand volume de manière à limiter la contre-pression au minimum nécessaire pour obtenir le déphasage inverse à celui imposé par la commande.
• L'usage d'un accumulateur à pression de gaz, de volume par exemple égal au double ou au triple de la cylindrée du vérin déphaseur, et dont la pression varie sensiblement avec l'angle de déphasage offre une meilleure sensibilité à la pression. Cette solution, par un choix judicieux des caractéristiques de l'accumulateur, permet en outre de rendre monotone la fonction P = f (déphasage), lorsqu'elle ne l'est pas à l'origine et, en conséquence, de simplifier le mode de commande, en obtenant une valeur unique de déphasage (à une hystérésis près) pour une valeur de pression donnée et surtout d'assurer la stabilité du déphasage en fonction de la commande.
• L'usage d'un accumulateur mécanique dont la contre-pression est réalisée par un vérin à ressort permet de linéariser la courbe de contre-pression additionnelle en fonction de l'angle de déphasage.
• Il est également possible d'appliquer une contre-pression intermittente seulement en cas de besoin de mouvement inverse à celui imposé par la commande ou encore à un limiteur ou un réducteur de pression commandable par potentiomètre qui peut être commandé manuellement ou par un asservissement.

To achieve this balance, various methods can be considered:

• It is first of all possible to directly exploit the only spontaneous rephasing torque generated by the vibrator, the torque to be applied being a certain function of the rephasing angle.
• One can also add to this torque that generated in the phase shifter by a constant back pressure, for example thanks to a large volume accumulator so as to limit the back pressure to the minimum necessary to obtain the reverse phase shift to that imposed by the control .
• The use of a gas pressure accumulator, of volume for example equal to twice or three times the displacement of the phase shifting cylinder, and the pressure of which varies appreciably with the phase shift angle offers better pressure sensitivity. This solution, by a judicious choice of the characteristics of the accumulator, also makes it possible to make monotonous the function P = f (phase shift), when it is not the origin and, consequently, to simplify the control mode, by obtaining a single value of phase shift (to within a hysteresis) for a given pressure value and above all to ensure the stability of the phase shift as a function of the command.
• The use of a mechanical accumulator, the back pressure of which is produced by a spring cylinder makes it possible to linearize the additional back pressure curve as a function of the phase shift angle.
• It is also possible to apply an intermittent back pressure only when the opposite movement is required to that imposed by the control or to a pressure limiter or reducer controllable by potentiometer which can be controlled manually or by a servo control.

In all cases, it will be possible to use means making it possible to vary the pressure in the phase shift chamber and / or the rephasing chamber by means of a hydraulic circuit leading to different pressure limiters, by means of controlled distributors. by a selector.

In the example shown in FIG. 5, the variable moment vibrator which has been represented diagrammatically by a block in broken lines 70 comprises two hydraulic motors 71, 72 supplied by a generator of pressurized hydraulic fluid 73 comprising two pump bodies 74 , 75 driven by an engine 76, for example a diesel engine. The flow rate of this generator 73 is controlled by a servo-control device 77 controlled by a potentiometer 78.

The phase shifter 79 is controlled by a hydraulic circuit supplied by an auxiliary pump 80 driven by the motor 76.

This auxiliary pump 80 delivers on a mechanical pressure limiter 81 which maintains a pressure Pr equal to a value corresponding to the rephasing pressure. The output of this limiter 81 is connected to the rephasing chamber 82 of the phase shifter via an electromechanical distributor 83 which is in the on state, in the rest position and which diverts the flow of oil towards the tank. 84 when its coil 85 is energized.

The hydraulic fluid delivered by the auxiliary pump 80 which is moreover controlled by a pressure limiter 86 which limits the maximum control pressure to a value Pmax, is applied to a second electrically controlled pressure reducer 87, which delivers of the fluid at a pressure adjustable between a maximum phase shift pressure Pdmax and a minimum phase shift pressure Pdmin by virtue of an electronic control circuit controlled by a potentiometer 88.

The output of this reducer 87 is connected to the phase shift chamber 89 of the phase shifter 79.

Associated with the hydraulic circuit previously described is an electrical control circuit (FIG. 6) supplied by a direct current source which supplies, on the one hand, the electronic circuit 90 of the pressure regulator allowing potentiometric adjustment (potentiometer 88) of the pressure. applied to the phase shift chamber 89 as well as, on the other hand, the electromagnet 85 of the distributor 83 via a switching circuit comprising a relay 91 on which is mounted in parallel a pressure switch 92 which closes when the pressure of the fluid delivered by the two pump bodies is greater than or equal to a pressure PM.

This control circuit also involves a rotary selector 93 mechanically coupled to the potentiometer 78 and whose rotary cursor 94 scans and temporarily switches a plurality of contacts (here the contacts C₁, C₂, C₃) as it is rotated.

In this example, the cursor 94 is connected to the negative pole of the power source.

Contact C₁ is in the air (not connected to any circuit).

The contact C₂ is connected to the positive pole of the power supply via the coil KA2 of a relay 95 which controls the application of the positive pole to one of the ends of the coil KA3 of the relay 91.

Contact C₃ is connected to the other end of coil KA3 of relay 91.

Hydraulically, the operation of the device described above is as follows:

Whatever the position of the potentiometer 88 for adjusting the pressure reducer 87 (between the minimum and maximum phase shift pressures), when the coil 85 of the distributor 83 is energized and the latter passes from its rest position shown in FIG. 5 (where it was before the machine was started) in its second position, the rephasing circuit is connected to the cover 84, and only the phase shift chamber 89 is supplied (with at least the minimum phase shift pressure Pdmin) and, therefore, the vibrator 70 does not generate any vibration amplitude.

On the other hand, when the coil 85 is de-energized and, consequently, the distributor goes to rest (after a sufficient unbalance speed is reached) then the rephasing chamber 82 is supplied with fluid at the rephasing pressure (which is slightly less than the maximum phase shift pressure) imposed by the reducer 87.

The phase shift chamber 82 is, for its part, supplied with fluid, the pressure of which is between the maximum and minimum phase shift pressures.

When the phase shift pressure is at its maximum (by convention, zero position of the potentiometer 88) then the phase shifter 79 is subjected to a resultant phase shift pressure (difference between the maximum phase shift pressure and the phase shift pressure). Because the phase shifter 79 was initially in the completely phase-shifted state and the rephasing requiring a resultant rephasing pressure sufficient to overcome friction and the resistance to the creation of vibrations, no vibration is able to be established.

When then the potentiometer 88 is turned towards increasing amplitudes and, consequently, a reduction in phase shift pressure is controlled from the maximum to the minimum, then the rephasing chamber 82 is maintained at the rephasing pressure while the pressure in the phase shift chamber 89 drops below this rephasing pressure. The resulting pressure is therefore a rephasing pressure and, consequently, the phase shifter resumes rephasing the weights of the vibrator 70 until the amplitude of vibration generated by the latter dynamically generates a relative torque opposing the torque exerted. by the phase shifter 79 under the effect of the resulting pressure.

The displacements of the phase shifter 79 and the values applied are chosen so as to obtain the maximum useful amplitude for a complete rephasing of the two counterweight trains when the dephasing backpressure reaches its minimum value.

The choice of the minimum phase shift pressure is that which makes it possible to obtain a complete phase shift of the flyweights in the absence of rephasing pressure.

A pressure limiter calibrated to the maximum phase shift pressure value is mounted on the rephasing circuit to limit the pressure peaks observed when under the effect of the maximum phase shift pressure, the fluid contained in the rephasing chamber 82 is found turned back towards the tarpaulin 84.

The operation of the electronic control circuit is as follows:

The contact C₁ of the rotary selector 93 which corresponds to the zero of the potentiometer 78 and therefore to a zero flow rate, is used for starting safety (prohibition of starting the generator of hydraulic fluid under pressure 73 if the pumps 74, 75 are not at zero flow, to avoid starting the engine 76 under load and turning the weights during this start).

When the selector 93 is positioned on the contact C contact, the relays 95 and 91 are at rest, while the pressure switch 92 is open. The coil 85 of the distributor 83 is supplied and the latter is therefore at rest and returns the fluid supplied by the auxiliary pump 80 to the tank 84.

The contact C₂ corresponds to a position of the potentiometer 78 controlling a speed close to the minimum vibration speed, for example 1650 rpm below which it is desired to prohibit any vibration whose frequency would be insufficient and therefore harmful.

In the case where the selector 93 is positioned on this contact C₂, the relay 95 goes to the excited state while relay 91 remains at rest. The coil 85 of the distributor 83 therefore remains in the excited state.

Contact C₃ corresponds to a position of potentiometer 78 controlling the minimum vibration speed, for example 1800 rpm.

In this position, the relay 95 is at rest while the relay 91 goes to the excited state (with self-hold) by interrupting the supply of the coil 85 of the distributor 83, which switches ensuring the connection of the output of the limiter 81 to the rephasing chamber 82. The pressure switch 92 makes it possible to close the circuit of the distributor coil, and therefore to activate it, when the pressure of the hydraulic fluid of the two pump bodies 74, 75 reaches the maximum admissible hydraulic pressure (this pressure is associated with the maximum available power inherent in the heat engine).

Thanks to these provisions, at the start of the flow of the pump bodies 74, 75 which causes the rotation of the weights, for all the speed values lower than the minimum vibration value, the coil 85 of the distributor 83 is energized, which prohibits the establishment of the rephasing pressure and therefore of any vibration.

When the minimum vibration speed is reached and exceeded, the coil 85 is in the de-energized state and the vibration amplitude is established at the level controlled by the potentiometer 88, determining the position of the pressure reducer 87.

It is therefore possible to adjust the speed of rotation of the weights (i.e. the frequency) to any value between the maximum frequency and the minimum frequency and, for each minimum frequency value of vibration, to adjust the vibration amplitude between zero and the maximum amplitude associated with the maximum eccentricity moment (weights rotating in phase).

As soon as the speed is lowered below the value deemed critical (for the propagation of tremors in the ground and shocks towards the carrier) for example 1650 rpm (contact C₂), then the coil 85 of the distributor 83 will be excited by the return of the electromagnet 91 to the rest position. Consequently, the distributor 83 will trigger the reduction and the suppression of the vibratory amplitude, whatever the position of the potentiometer 88 for controlling the amplitude, thus allowing the machine to stop without vibrating.

When the vibrator 70 generates vibrations, that is to say when the coil 85 of the distributor 83 is isolated from the negative pole of the supply S, due to the self-maintenance of the relay 91 in the energized position, and if the pressure rises to the maximum allowable pressure, due to the closing of the pressure switch 92, the coil 85 of the distributor 83 is again excited.

In this case, the return torque towards the phase shift of the weights is all the more important as the ground resists and causes the pressure generated by the two pump bodies 74, 75 to increase. This torque is added to the only phase shift pressure controlled by the potentiometer 88. It acts on the phase shifter 79 to quickly phase shift the weights and thus reduce the amplitude of the vibrator 70 and, consequently, the power necessary for the maintenance of the vibration, therefore the pressure called by the hydraulic motors 71, 72 of the vibrator 70.

Consequently, the hydraulic efficiency of the generator 73 improves and the speed of the motor 76 increases by a few hundred additional revolutions per minute. The rotary assembly therefore accumulates kinetic energy at the same time as the pressure switch 92 which causes the switching of the distributor 83. The latter restores the supply of the rephasing pressure which will quickly put the weights back in phase. During this transient phase, the vibrator 70 delivers to the ground the maximum power delivered by the generator 73 and the power associated with the excess kinetic energy of rotation of the flyweights whose rotation speed decreases by a few hundred revolutions in a few tenths seconds until the pressure again exceeds the maximum allowable pressure. This pulsation phenomenon makes it possible to prevent the vibrator 70 working on hard floors from dropping significantly in frequency (fall limited to 10%) unlike traditional vibrators which lose up to 50% of their frequency. The performance of the machine is therefore improved.

Claims (27)

Device for controlling a variable moment vibrator of the type comprising at least two offset eccentric weights (M, M ') rotated at the same speed and a phase shifter (7) capable of generating an angular offset between these weights (M , M ') during their rotation, the phase shifter (7) being controlled by means of a double-acting hydraulic actuator comprising a rephasing chamber (18) and a phase shift chamber (16) separated by a piston ( 13), the supply of this actuator (7) with pressurized fluid delivered by a pump (20) being effected by a hydraulic circuit comprising a distributor (21, 83) having at least: a rest position in which it interrupts the supply of one or the other or of the two chambers of the actuator (11, 79) with pressurized fluid, and a working position in which the distributor (21, 83) directs the pressurized fluid towards one of the above-mentioned chambers (18, 82 - 16, 89), by means of a first distribution circuit, characterized in that said first distribution circuit comprises first limiting means (26, 87) allowing, thanks to a control member (27, 88), to vary the pressure which it applies to one of the two chambers within a predetermined range, and in that the other chamber is connected to a second distribution circuit comprising means (31, 20, P'₀₂ - 81) making it possible to modulate or fix the pressure which it applies to this second chamber, so as to obtain an appropriate profile of the pressure difference applied to the phase shifter which results in a motor torque in relation to the resisting torque which results from the amplitude of the movement of the vibrator and that, therefore, at each value displayed on the control member (27, 28), corresponds a position of the phase shifter and a determined amplitude of the vibrations. Device according to claim 1,
characterized in that the above means for modulating the pressure are mounted in the circuit connecting the distributor (21) to the phase shift chamber (16) and include a non-return valve (20) and a hydraulic accumulator (31) of which the loading pressure is limited by a limiter (D). Device according to either of Claims 1 and 2,
characterized in that the means making it possible to vary the pressure in the rephasing and / or phase-shifting chamber comprise a pressure regulator (26) and / or a hydraulic circuit leading to different pressure limiters, by means of controlled distributors by a selector. Device according to one of claims 1 to 3,
characterized in that the aforesaid non-return valve (20) is short-circuited by a first pressure relief valve (D) set to a value less than the value less than the maximum pressure value of the above range of the above-mentioned regulator (26 ). Device according to one of claims 1 to 4,
characterized in that it comprises a second pressure limiter (34) on the phase shift circuit, for fixing the phase shift pressure. Device according to one of claims 1 to 4,
characterized in that it comprises a limiter (34) adjustable at a pressure allowing the phase shift when the rephasing command is at minimum. Device according to one of claims 1 to 4,
characterized in that it comprises a pressure limiter (34) allowing the accumulator (31) to be charged at a level sufficient to determine a back pressure whose profile, as a function of the rephasing positions, ensures the stability of the positions rephasing associated with the command. Device according to one of the preceding claims,
characterized in that the calibration pressures of the above first and second distributors (D, 34) are such that there is a renewal of the hydraulic oil in the accumulator (31) / rephasing chamber (18) circuit, thus eliminating the bleeding problems, during load successions in phase shifted position and complete rephasing. Device according to one of the preceding claims,
characterized in that the above weights (M, M 'are driven by at least one hydraulic actuator (H₁, H₂) powered by a pump (P) driven by a motor (23) whose speed of rotation is detected by a sensor ( 35), and in that it comprises means enabling the above-mentioned distributor (21) to be put in the rest position when the engine (23) is started as long as the speed of rotation is below a threshold predetermined speed or acceleration. Device according to one of claims 1 to 7,
characterized in that the aforesaid weights are driven by at least one hydraulic actuator supplied by a main pump (P) driven by an internal combustion engine (23), and in that it comprises means making it possible to place the above-mentioned distributor (21 ) in the rest position when starting the engine (23) and as long as it is idling. Device according to claim 10,
characterized in that as soon as the engine (23) is started, previously idling, the distributor (21) is placed in position 1 so as to enable the weights to shift into phase-shifted position, immediately during the rotation of the weights (M , M '). Device according to one of the preceding claims,
characterized in that when the speed of rotation of the flyweights (M, M ') is taken, the distributor (21, 85) changes to position 2 when the flow rate of the main pump (P) reaches or exceeds a predetermined minimum value. Device according to one of the preceding claims,
characterized in that prior to the reduction of the speed of rotation of the weights (M, M ') below a threshold value, the distributor (21, 85) is returned to position 1. Device according to one of the preceding claims,
characterized in that the return to position 1 takes place automatically as soon as the required conditions for pump flow (P) and therefore frequency are no longer met. Device according to one of the preceding claims,
characterized in that it comprises means allowing a reduction in pressure in the rephasing chamber (18, 82) when the pressure of the hydraulic fluid delivered by the main pump (P) rises above a first value, and then cause the rephasing pressure to return to the previous value, when said pressure drops below a second value. Device according to claim 15,
characterized in that the above values are substantially equal. Device according to claim 15,
characterized in that the difference between the above values is adjustable by electronic or mechanical means, so as to be able to adjust the amplitude of the pumping. Device according to one of the preceding claims,
characterized in that the pressure delivered by the above pressure regulator (26, 88) is controlled by a noise level and / or a level of amplitude or vibrational speed measured in the ground or on a structure. Device according to one of the preceding claims,
characterized in that the nuisances due to decreases in frequency of the vibrator associated with the increase in power and pressure necessary for driving are eliminated: - by acting on the supply of the rephasing chamber (18, 82) by tilting the distributor (21) to the position of placing the chamber in the tarpaulin, - by providing, bypassing the rephasing output, a second distributor (25) which, when triggered, puts the rephasing chamber (18) in communication with a pressure limiter (P₀₅) preset to the pressure corresponding to the reduction in amplitude and speed of response of the actuator desired, and therefore the desired pulsation period. Device according to one of the preceding claims,
characterized in that the pressure for triggering the rephasing or for reducing the phase shift is adjusted so as to allow optimum demand on the available power delivered by the heat engine or by the hydraulic transmission. Device according to one of the preceding claims,
characterized in that the aforementioned accumulator (31) has a large volume so as to limit the back pressure to the minimum necessary to obtain the reverse phase shift to that imposed by the control when the latter is returned to its position associated with the minimum phase shift. Device according to one of claims 1 to 20,
characterized in that the accumulator (31) has a volume of the order of one to three times the displacement of the phase shifter and a pressure which, from a minimum pressure increases rapidly with the rephasing angle. Device according to one of claims 1 to 20,
characterized in that the accumulator (31) is designed so as to provide a pressure profile as a function of the rephasing allowing to obtain a stability of the rephasing position. Device according to one of claims 1 to 20,
characterized in that it comprises a mechanical accumulator making it possible to linearize the additional backpressure curve as a function of the phase shift angle. Device according to claim 1,
characterized in that it comprises a pressure reducer (81) supplying the rephasing chamber (82) at substantially constant pressure and a pressure reducer (87) supplying the phase shift chamber (89) with variable pressure between a minimum pressure and a maximum pressure substantially equivalent to the pressure of the rephasing chamber (82). Device according to claim 25,
characterized in that the flow rate of the pressurized hydraulic fluid generator (73) is controlled by a servo-control device (77) controlled by a potentiometer (78), and in that the control of the above-mentioned distributor is carried out by means of an electrical control circuit comprising a selector (93) mechanically coupled to the above potentiometer. Device according to claim 26,
characterized in that the aforesaid control circuit comprises a source of electric current which feeds the electromagnet (85) of the distributor (83), via a switching circuit comprising a relay (91) on which is mounted in parallel a pressure switch (92) which closes when the pressure of the fluid delivered by the pump is greater than or equal to a maximum pressure (PM), the coil of the above relay being connected, on one side, to one of the poles of the source of electric current by means of the selector and, on the other side, to the other pole of the source by means of a relay controlled by said selector.

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