EP0601916B1 - Hydraulic motor mit for driving a drilling tool - Google Patents

Description

In known manner, a drilling tool is driven by a hydraulic motor at a single speed of rotation, or in a range of speeds of rotation which are ill-suited to the various operating phases.

The object of the invention is to remedy the shortcomings observed by providing for the driving of the drilling tool over a much greater range of rotational speeds than before, and at the time of drilling, with a greater engine torque.

The invention therefore relates to a power unit comprising: a frame; a driven shaft rotatably mounted relative to the frame about an axis of rotation; a first pressurized fluid motor having a corrugated cam fixed relative to said frame; a cylinder block secured to the rotation of said driven shaft; a plurality of cylinders formed in the cylinder block and arranged radially with respect to the axis of rotation; a plurality of pistons mounted sliding in the cylinders and capable of bearing reaction pressure on said cam; the shaft being capable of being driven by the first motor at at least a first rotational speed and having a recess which constitutes a passage, which, in a configuration of the rotary coupling of a drilling tool to said shaft, conveys the drilling fluid to the drilling tool, and the cylinder block of said first engine being coaxial with the axis of rotation.

According to the invention, the following provisions are adopted: A) this motor unit comprises a second motor, which is coupled in rotation to said shaft and which is capable of driving this shaft at a second speed of rotation substantially greater than said first speed of rotation; B) a first gear pinion is integral with respect to the rotation of the shaft, surrounds said shaft and is coaxial with the axis of rotation; C) the second motor has an output shaft, of which is secured in rotation a second gear pinion which meshes with said first gear pinion; and D) the first pressurized fluid motor is of the “disengageable pistons” type and is provided for this purpose with a disengaging mechanism capable of controlling the withdrawal of said pistons from the support of the corrugated cam.

• le premier moteur à fluide sous pression possède un carter fermé contenant le bloc-cylindres, susceptible de communiquer sélectivement avec une source de fluide de débrayage, ce débrayage étant réalisé par l'effet de la pression du fluide provenant de la source de fluide de débrayage admis dans le carter, qui réalise la rentrée desdits pistons dans les cylindres;
• ladite deuxième vitesse de rotation est supérieure à cinq fois la plus petite des premières vitesses de rotation;
• les premier et deuxième pignons d'engrenage sont contenus dans un carter, qui est isolé de manière étanche du premier moteur à fluide sous pression;
• le diamètre du deuxième pignon d'engrenage est inférieur au diamètre du premier pignon d'engrenage;
• d'une part, des paliers de rotation sont interposés entre l'arbre mené et le bâti et réalisent le montage à rotation dudit arbre par rapport audit bâti, d'autre part, ces paliers de rotation réalisent également le montage à rotation du bloc-cylindres par rapport à la came ondulée du premier moteur à fluide sous pression;
• le premier moteur à fluide sous pression possède un carter, qui contient le bloc-cylindres et qui est partiellement constitué par une partie dudit bâti;
• l'arbre étant susceptible d'entraîner en rotation plusieurs outils différents ayant des vitesses de rotation également différentes, le premier moteur à fluide sous pression est un moteur possédant plusieurs cylindrées de fonctionnement, de manière à pouvoir entraîner l'arbre à plusieurs vitesses de rotation distinctes et ainsi à réaliser l'entraînement desdits outils à leurs différentes vitesses de rotation respectives;
• le deuxième moteur est un moteur à fluide sous pression;
• le premier moteur à fluide sous pression comporte un carter qui contient le bloc-cylindres, dans lequel ladite came est incorporée, et dont une section transversale externe, contenue dans un plan perpendiculaire à l'axe de rotation et intersectant la came, est susceptible d'être inscrite dans un cercle de diamètre déterminé, cependant que l'évidement constituant le passage est cylindrique et possède un diamètre interne supérieur ou égal à 0,25 fois ledit diamètre déterminé.

The following advantageous arrangements are preferably adopted:

• the first pressurized fluid engine has a closed casing containing the cylinder block, capable of communicating selectively with a source of declutching fluid, this declutching being effected by the effect of pressure fluid coming from the source of declutching fluid admitted into the casing, which re-enters said pistons into the cylinders;
• said second speed of rotation is greater than five times the lowest of the first speeds of rotation;
• the first and second gear pinions are contained in a housing, which is sealed from the first pressurized fluid motor;
• the diameter of the second gear pinion is less than the diameter of the first gear pinion;
• on the one hand, rotational bearings are interposed between the driven shaft and the frame and perform the rotational mounting of said shaft relative to said frame, on the other hand, these rotational bearings also perform the rotational mounting of the block- cylinders with respect to the corrugated cam of the first pressurized fluid engine;
• the first pressurized fluid engine has a casing, which contains the cylinder block and which is partially constituted by a part of said frame;
• the shaft being capable of rotating several different tools having equally different rotational speeds, the first pressurized fluid motor is a motor having several operating displacements, so as to be able to drive the shaft at several rotational speeds separate and thus to carry out the driving of said tools at their respective respective rotational speeds;
• the second engine is a pressurized fluid engine;
• the first pressurized fluid engine comprises a casing which contains the cylinder block, in which said cam is incorporated, and an external cross section of which, contained in a plane perpendicular to the axis of rotation and intersecting the cam, is capable of '' be registered in a circle of determined diameter, while the recess constituting the passage is cylindrical and has an internal diameter greater than or equal to 0.25 times said determined diameter.

The main advantage of the invention lies in obtaining a satisfactory permanent adaptation of the drive device, both to the various operating phases and to the various tools used.

The invention will be better understood, and secondary characteristics and their advantages will appear during the description of an embodiment given below by way of example.

It is understood that the description and the drawings are given for information only and are not limiting.

• la figure 1 est une coupe axiale d'un groupe moteur conforme à l'invention; et,
• la figure 2 est le schéma d'un circuit de commande du groupe moteur de la figure 1,

Reference will be made to the accompanying drawings, in which:

• Figure 1 is an axial section of a motor unit according to the invention; and,
• FIG. 2 is the diagram of a control circuit of the engine group of FIG. 1,

The assembly shown in FIG. 1 comprises a frame 1 for fixing, for example on the infrastructure located on the surface of an oil well, a first motor 2, a second motor 3, a casing 4 of speed reducer, and , a hollow shaft 5 for driving a drilling tool not shown in the figure, connected to the shaft 5 by a train of hollow drilling rods, allowing the circulation of drilling mud between the surface infrastructure and the drilling tool.

The shaft 5 has an inner cylindrical recess 6, of diameter D6, of axis 7, and is mounted for rotation relative to said frame 1, around the axis 7, by means of bearings 8, tapered roller bearings in the represented achievement.

• un carter en trois parties 1, 9 et 10 assemblées par des vis 11, l'une desdites parties 1 étant constituée par une partie du bâti 1;
• un bloc-cylindres 12, qui présente un alésage muni de cannelures 13, traversé par l'arbre 5 et rendu solidaire dudit arbre 5 au moyen de cannelures 14, dont est muni l'arbre 5 et qui sont imbriquées dans les cannelures 13;
• deux rangées de cylindres 15, chacune disposée transversalement par rapport à l'axe 7 et comprenant une pluralité de cylindres 15 disposés radialement par rapport à l'axe 7 et répartis angulairement autour de l'axe 7 sensiblement régulièrement;
• des pistons 16 montés coulissant dans les cylindres 15, un par cylindre, délimitant chacun dans le cylindre correspondant une chambre de travail d'un fluide 17;
• une came ondulée 18, constituée par la périphérie interne de la partie intermédiaire 9 du carter, les paliers 8 réalisant ainsi, par l'intermédiaire de l'arbre 5 et des cannelures 13-14, le montage à rotation du bloc-cylindres 12 par rapport à la came 18;
• des rouleaux 19 montés aux extrémités des pistons 16 opposées aux chambres 17, susceptibles, soit de prendre appui de réaction sur la came 18, soit au contraire dans une configuration de "débrayage" d'être écartés de la came 18, sous l'effet d'un fluide sous pression contenu dans l'enceinte 20 délimitée par le carter 1-9-10, chaque rouleau 19 étant monté rotatif à l'extrémité dudit piston autour d'un axe 21 parallèle à l'axe 7;
• une face de communication 22, plane, perpendiculaire à l'axe 7, appartenant au bloc-cylindres 12, et dans laquelle débouchent, centrés sur un cercle d'axe 7, des conduits de cylindre 23 reliés chacun à une chambre 17;
• un distributeur interne de fluide 24, dont une face axiale 25, constituée par une succession d'épaulements, a une forme complémentaire d'un logement 26 ménagé dans la partie 10 du carter, trois gorges transversales 27, 28, 29 étant ménagées dans le distributeur interne de fluide 24 et débouchant dans la face axiale 25, et, respectivement, en ce qui concerne les gorges 27, 29, dans des conduits 30, 31 ménagés dans la partie 10 du carter, ces conduits 30, 31 étant en outre raccordés à des conduits externes 32, 33;
• une face de distribution 34, plane, perpendiculaire à l'axe 7, appartenant au distributeur interne de fluide 24, maintenue en appui par des ressorts non visibles sur la figure 1 sur la face de communication 22, et dans laquelle débouchent, centrés sur le même cercle que les conduits de cylindres 23, des conduits de distribution 35, 36, 37 ménagés dans le distributeur interne de fluide 24 et appartenant à trois groupes distincts de conduits, reliés respectivement aux gorges 27, 28, 29;
• un dispositif de pions et d'encoches associées 38, disposé entre la partie 10 du carter et le distributeur interne de fluide 24, et permettant de légères oscillations du distributeur interne de fluide par rapport au carter tout en rendant le distributeur interne de fluide 24 solidaire du carter vis-à-vis d'une rotation d'axe 7;
• un alésage 39, ménagé dans la partie 10 du carter, dans lequel débouchent trois gorges 40, 41, 42 reliées aux gorges 27, 28, 29 par des conduits 45, 46, 47 respectivement, alésage dans lequel est monté coulissant un tiroir 43, lui-même muni d'une gorge 44 et susceptible d'occuper une première position (représentée sur la figure 1) dans laquelle la gorge 44 met en communication les gorges 40, 41 et isole la gorge 42 des gorges 40, 41, et, une deuxième position, dans laquelle la gorge 44 met en communication les gorges 41, 42, et isole desdites gorges 41, 42, la gorge 40;
• une chambre de pilotage 48 ménagée dans la partie 10 du carter, avec laquelle communique une extrémité 49 du tiroir 43 formant piston de pilotage, un ressort 50 étant disposé entre la partie 10 du carter et le tiroir 43 et tendant à rappeler le tiroir 43 vers sa première position, l'effet de la pression d'un fluide de pilotage contenu dans la chambre de pilotage 48 étant antagoniste de celui du ressort 50;
• deux conduits 51, 52 traversant la paroi de la partie 10 du carter, et reliant la chambre de pilotage 48 et l'enceinte 20 à des conduits externes 53, 54, respectivement.

The first motor is a slow hydraulic motor, with high motor torque, and includes:

• a casing in three parts 1, 9 and 10 assembled by screws 11, one of said parts 1 being constituted by a part of the frame 1;
• a cylinder block 12, which has a bore provided with grooves 13, traversed by the shaft 5 and made integral with said shaft 5 by means of grooves 14, which is provided with the shaft 5 and which are nested in the grooves 13;
• two rows of cylinders 15, each arranged transversely to the axis 7 and comprising a plurality of cylinders 15 arranged radially with respect to the axis 7 and angularly distributed around the axis 7 substantially regularly;
• pistons 16 slidably mounted in the cylinders 15, one per cylinder, each delimiting in the corresponding cylinder a working chamber for a fluid 17;
• a corrugated cam 18, constituted by the internal periphery of the intermediate part 9 of the casing, the bearings 8 thus realizing, by means of the shaft 5 and the grooves 13-14, the rotational mounting of the cylinder block 12 by relative to cam 18;
• rollers 19 mounted at the ends of the pistons 16 opposite the chambers 17, which are capable either of bearing reaction pressure on the cam 18 or, on the contrary, in a "declutching" configuration of being moved away from the cam 18, under the effect of a pressurized fluid contained in the enclosure 20 delimited by the casing 1-9-10, each roller 19 being rotatably mounted at the end of said piston around an axis 21 parallel to the axis 7;
• a communication face 22, flat, perpendicular to the axis 7, belonging to the cylinder block 12, and into which open, centered on a circle with an axis 7, cylinder conduits 23 each connected to a chamber 17;
• an internal fluid distributor 24, one axial face 25 of which, constituted by a succession of shoulders, has a complementary shape of a housing 26 formed in part 10 of the casing, three transverse grooves 27, 28, 29 being formed in the internal fluid distributor 24 and opening into the axial face 25, and, respectively, as regards the grooves 27, 29, in conduits 30, 31 formed in the part 10 of the casing, these conduits 30, 31 being further connected to external conduits 32, 33;
• a distribution face 34, flat, perpendicular to the axis 7, belonging to the internal fluid distributor 24, held in abutment by springs not visible in FIG. 1 on the communication face 22, and into which open out, centered on the same circle as the cylinder conduits 23, distribution conduits 35, 36, 37 formed in the internal fluid distributor 24 and belonging to three distinct groups of conduits, connected respectively to the grooves 27, 28, 29;
• a device of pins and associated notches 38, disposed between the part 10 of the casing and the internal fluid distributor 24, and allowing slight oscillations of the internal fluid distributor relative to the casing while making the internal fluid distributor 24 integral of the casing with respect to a rotation of axis 7;
• a bore 39, formed in part 10 of the casing, into which three grooves open 40, 41, 42 connected to grooves 27, 28, 29 by conduits 45, 46, 47 respectively, bore in which a drawer 43 is slidably mounted, itself provided with a groove 44 and capable of occupying a first position (shown in FIG. 1) in which the groove 44 puts the grooves 40, 41 into communication and isolates the groove 42 from the grooves 40, 41, and, a second position, in which the groove 44 connects the grooves 41, 42, and isolates from said grooves 41, 42, the groove 40;
• a pilot chamber 48 provided in part 10 of the casing, with which communicates an end 49 of the drawer 43 forming a pilot piston, a spring 50 being disposed between the part 10 of the casing and the drawer 43 and tending to return the drawer 43 towards its first position, the effect of the pressure of a pilot fluid contained in the pilot chamber 48 being antagonistic to that of the spring 50;
• two conduits 51, 52 passing through the wall of the part 10 of the casing, and connecting the pilot chamber 48 and the enclosure 20 to external conduits 53, 54, respectively.

The first motor 2 is a two-displacement motor known in itself, with disengageable pistons under the effect of the pressure of a clutch control fluid admitted into the enclosure 20 via the conduit 54, so similar to that described in FR-A-2 025 354. The first motor 2 could, as a variant, be provided with a device for disengaging its pistons comprising springs, as shown in FR-A-2 504 987. The declutching configuration obtained in all cases corresponds to reentry inside the cylinders of the pistons 16, the working chambers 17 of which are no longer supplied with pressurized fluid, the rollers 19 associated with said pistons then being out of support of cam 18.

It should also be observed that if this first motor 2 is known in its general constitution, it nevertheless has the following particularity: the diameter D6 of the recess 6 of the shaft 5 is particularly large compared to the diameter D9, external of part 9 of the casing, measured in a transverse plane P18 intersecting the cam 18. It is in particular interesting that D6 is greater than or equal to D9 x 0.25, the embodiment shown does not, however, include this advantageous characteristic.

On the part 10 of the casing of the first motor 2 is fixed, by screws 55, the casing 4 of a speed reducer comprising a large pinion 56 and a small pinion 57, which mesh with each other. The casing 4 is distinct from the casing 1-9-10 of the first engine, and is isolated from the enclosure 20 by a seal 58 interposed between the shaft 5 and a bore 59 of the part 10 of the casing of the first engine crossed by the shaft 5, and by a seal 60 interposed between the part 10 of the casing of the first motor and the removable end bottom 61 delimiting the pilot chamber 48. A ball bearing 62 is interposed between the shaft 5 and the casing 4 of the speed reducer.

On this casing 4, the casing 63 of the second motor 3 is fixed, which, in this case, is a "fast" hydraulic motor. It is advantageous to use a second hydraulic type motor because of the availability of the elements of the control circuit of the first hydraulic motor, but as a variant, this second motor could be of another type, for example electric.

This second motor 3 has an engine output shaft 64, which is integral with the second pinion 57 by means of associated splines 65, with which these two parts are provided. The first pinion 56 is itself integral with the shaft 5, which passes through it via associated grooves 66, which are provided with these two parts. The first pinion 56 is also coaxial with the axis 7. Finally, the second motor 3 is provided with two main connections 67, 68 for supplying pressurized fluid and fluid exhaust, connected to external conduits 69, 70, respectively, and is provided with a third connection 71, for leakage return, connected to an external conduit 72.

The ratio of the diameter D57 of the second pinion 57 to the diameter D56 of the first pinion 56 is less than 1, since it is a speed reducer, and is here equal to 0.25 (D57 / D56 = 0.25 ).

• les premier et deuxième moteurs 2 et 3;
• une pompe principale 73, réversible, à débit variable 73A;
• une pompe de pilotage 74;
• des premier 75, deuxième 76 et troisième 77 distributeurs de fluide, couplés 78, à chacun deux positions;
• un quatrième distributeur de fluide 79, également à deux positions;
• un clapet 80, de maintien de pression;
• un clapet 81, de maintien de pression; et,
• un réservoir de fluide 82; et,

les conduits suivants:

• le conduit 32 raccordé au premier distributeur de fluide 75;
• le conduit 33 raccordé au deuxième distributeur de fluide 76;
• le conduit 53 raccordé au quatrième distributeur de fluide 79;
• le conduit 54 raccordé au troisième distributeur de fluide 77;
• le conduit 83 d'aspiration de la pompe de pilotage 74, relié au réservoir 82;
• le conduit 84 de refoulement de la pompe de pilotage 74 relié au quatrième distributeur 79;
• un conduit 85 reliant le conduit de refoulement 84 au réservoir 82, et sur lequel sont disposés le clapet 80, et, au-delà du clapet 80 par rapport au raccord du conduit 85 au conduit de refoulement 84, le clapet 81;
• un conduit 86 raccordé au conduit 85 entre le clapet de 80 et le clapet 81;
• un conduit 87 reliant le troisième distributeur de fluide 77 au conduit 86.
• un conduit 88 reliant le premier distributeur de fluide 75 au conduit 86;
• un conduit 89 reliant le deuxième distributeur de fluide 76 au conduit 88;
• un conduit 90 reliant le troisième distributeur de fluide au réservoir 82;
• un conduit 91 reliant le premier distributeur de fluide 75 au conduit 90;
• un conduit 92 reliant le deuxième distributeur de fluide 76 au conduit 91;
• un conduit 93 reliant le quatrième distributeur de fluide 79 au conduit 92;
• un conduit 94 reliant l'un, 95, des raccords principaux de la pompe principale 73 au premier distributeur de fluide 75; et,
• un conduit 96 reliant, l'autre, 97, raccord principal de la pompe principale 73 au deuxième distributeur de fluide 76.

The control circuit of FIG. 2 comprises the following elements:

• the first and second motors 2 and 3;
• a main pump 73, reversible, with variable flow 73A;
• a pilot pump 74;
• first 75, second 76 and third 77 fluid distributors, coupled 78, each at two positions;
• a fourth fluid distributor 79, also in two positions;
• a valve 80, for maintaining pressure;
• a valve 81, for maintaining pressure; and,
• a fluid reservoir 82; and,

the following conduits:

• the conduit 32 connected to the first fluid distributor 75;
• the conduit 33 connected to the second fluid distributor 76;
• the conduit 53 connected to the fourth fluid distributor 79;
• the conduit 54 connected to the third fluid distributor 77;
• the suction pipe 83 of the pilot pump 74, connected to the reservoir 82;
• the discharge pipe 84 of the pilot pump 74 connected to the fourth distributor 79;
• a conduit 85 connecting the discharge conduit 84 to the reservoir 82, and on which the valve 80 are arranged, and, beyond the valve 80 relative to the connection of the conduit 85 to the discharge conduit 84, the valve 81;
• a conduit 86 connected to conduit 85 between the valve of 80 and the valve 81;
• a conduit 87 connecting the third fluid distributor 77 to the conduit 86.
• a conduit 88 connecting the first fluid distributor 75 to the conduit 86;
• a conduit 89 connecting the second fluid distributor 76 to the conduit 88;
• a conduit 90 connecting the third fluid distributor to the reservoir 82;
• a conduit 91 connecting the first fluid distributor 75 to the conduit 90;
• a conduit 92 connecting the second fluid distributor 76 to the conduit 91;
• a conduit 93 connecting the fourth fluid distributor 79 to the conduit 92;
• a conduit 94 connecting one, 95, of the main connections of the main pump 73 to the first fluid distributor 75; and,
• one conduit 96 connecting the other, 97, main connector of the main pump 73 to the second fluid distributor 76.

• aux mises en communications des conduits 32 et 94, des conduits 69 et 88, des conduits 33 et 96, des conduits 70 et 89, et des conduits 54 et 90; et,
• aux obturations des conduits 91, 92 et 87.

The first respective positions of the first 75, second 76, and third 77 fluid distributors correspond to:

• the communications of conduits 32 and 94, conduits 69 and 88, conduits 33 and 96, conduits 70 and 89, and conduits 54 and 90; and,
• the closures of conduits 91, 92 and 87.

• aux mises en communications des conduits 32 et 91, des conduits 69 et 94, des conduits 33 et 92, des conduits 70 et 96, et, des conduits 54 et 87; et,
• aux obturations des conduits 88, 89, et 90.

The respective second positions of the first 75, second 76 and third 77 fluid distributors correspond to:

• the connections of conduits 32 and 91, conduits 69 and 94, conduits 33 and 92, conduits 70 and 96, and conduits 54 and 87; and,
• to the closings of conduits 88, 89, and 90.

• la première position, à la mise en communication des conduits 53 et 93, et, à l'obturation du conduit 84; et,
• la deuxième position, à la mise en communication des conduits 53 et 84, et, à l'obturation du conduit 93.

The two positions of the fourth fluid distributor 79 correspond:

• the first position, when the conduits 53 and 93 are placed in communication, and when the conduit 84 is closed; and,
• the second position, when the conduits 53 and 84 are placed in communication, and when the conduit 93 is closed.

• la pression de tarage du clapet 80 est égale à 20 bars;
• la pression de tarage du clapet 81 est égale à 2 bars;
• les deux vitesses de rotation du premier moteur hydraulique 2 sont égales à 70 et 140 tours par minute;
• la vitesse de rotation de l'arbre de sortie moteur 64 du deuxième moteur 3 est égale à 2000 tours par minute.

The following numerical values are generally accepted:

• the setting pressure of the valve 80 is equal to 20 bars;
• the setting pressure of the valve 81 is equal to 2 bars;
• the two rotational speeds of the first hydraulic motor 2 are equal to 70 and 140 revolutions per minute;
• the speed of rotation of the motor output shaft 64 of the second motor 3 is equal to 2000 revolutions per minute.

As a variant, the first motor 2 could have three separate displacements, and therefore three rotational speeds, such as 70, 140 and 210 revolutions per minute.

• des premières vitesses de rotation, respectivement égales à V11 = 70 et V12 = 140 tours par minute, et,
• une deuxième vitesse de rotation égale à V2 = 500 tours par minute.

It should also be observed that with the first two-speed motor 2 and the second fast motor defined above, the rotational speeds of the shaft 5 have the following values:

• first rotational speeds, respectively equal to V11 = 70 and V12 = 140 revolutions per minute, and,
• a second rotational speed equal to V2 = 500 revolutions per minute.

et est supérieur à 5. Ceci est conforme à l'utilisation dans un même groupe moteur d'un moteur lent et d'un moteur rapide.Thus, the ratio V2 / V11 of the second speed V2 to the smallest of the first speeds is $$\text{V2 / V11 = 500/70 = 7.14}$$

and is greater than 5. This is in accordance with the use in the same engine group of a slow motor and a fast motor.

The operation obtained is briefly described below.

The fourth fluid distributor 79 makes it possible to select the displacement of the first motor 2 (the number of working chambers 17 periodically supplied with pressurized fluid) and makes it possible to place the drawer 43 in its first or in its second position. Having chosen one of the positions of this fourth fluid distributor, the speed of rotation of the first motor 2 corresponding to the cubic capacity selected is also chosen.

• de faire communiquer l'enceinte 20 avec le réservoir sans pression 82, par les conduits 54 et 90, et, donc de placer tous les pistons 16 dans leur configuration "d'embrayage" dans laquelle tous les rouleaux 19 sont en appui sur la came 18;
• de relier l'alimentation du deuxième moteur 3 à l'échappement dudit moteur, par les conduits 88-69-70 et 89, et, donc de laisser ce moteur libre de tourner sans produire de couple moteur; et,
• d'alimenter le premier moteur 2 par la pompe principale 73 et les conduits 94-32 et 33-96, et, ainsi, d'entraîner en rotation l'arbre 5 à la vitesse de rotation sélectionnée du premier moteur.

The installation of the first 75, second 76 and third 77 fluid distributors in their first respective positions allows:

• to make the enclosure 20 communicate with the pressureless tank 82, by the conduits 54 and 90, and therefore place all the pistons 16 in their "clutch" configuration in which all the rollers 19 are supported on the cam 18;
• to connect the supply of the second engine 3 to the exhaust of said engine, via the conduits 88-69-70 and 89, and therefore to leave this engine free to rotate without producing engine torque; and,
• to supply the first motor 2 by the main pump 73 and the conduits 94-32 and 33-96, and thus to rotate the shaft 5 at the selected speed of rotation of the first motor.

The shaft 5, and the drill string attached thereto, drives a drilling tool during the penetration phase of the tool into the ground. For another drilling tool, it may be appropriate to select another speed of rotation of the shaft 5, which makes it possible to select the operating displacement of the first motor 2 via the fourth distributor 79.

• de faire communiquer l'enceinte 20 du carter du premier moteur avec la pression du fluide retenu par le clapet de retenue 81, par l'intermédiaire des conduits 86-87 et 54, et ainsi de placer les pistons 16 dans leur configuration de "débrayage", dans laquelle les rouleaux 19 sont hors d'appui de la came 18;
• de relier l'alimentation du deuxième moteur 3 au raccord principal 95 de la pompe principale 73 par les conduits 94-69 et l'échappement du même moteur au raccord principal 97 de la même pompe principale par les conduits 70-96, et ainsi, d'entraîner en rotation l'arbre 5 et le train de tiges de forage qui y est attelé par l'intermédiaire du deuxième moteur 3, et des pignons 57 et 56; et,
• de relier les deux raccords principaux du premier moteur 2 au réservoir 82 par les conduits 32-91-90 d'une part, et par les conduits 33-92-91-90, d'autre part.

But it is also necessary to drill very hard rocks to be able to drive special tools such as diamond crowns which require to be effective much higher rotational speeds. Indeed, they penetrate the rock by abrasion and not by cutting. During this operating phase, the penetration force becoming low, it is useful to choose a rotation speed much higher than the previous one. To do this, the first 75, second 76 and third 77 fluid distributors are placed in their respective second positions, which allow:

• to make the enclosure 20 of the casing of the first engine communicate with the pressure of the fluid retained by the check valve 81, via the conduits 86-87 and 54, and thus to place the pistons 16 in their "disengaging" configuration ", wherein the rollers 19 are out of support of the cam 18;
• to connect the supply of the second motor 3 to the main connector 95 of the main pump 73 by the conduits 94-69 and the exhaust of the same engine to the main connector 97 of the same main pump by the conduits 70-96, and thus, to rotate the shaft 5 and the drill string which is coupled thereto via the second motor 3, and the pinions 57 and 56; and,
• to connect the two main connections of the first motor 2 to the tank 82 by the conduits 32-91-90 on the one hand, and by the conduits 33-92-91-90, on the other hand.

The selection of the speed of rotation of the first motor 2 is carried out according to the nature of the terrain and its reaction to the drilling tool. With a motor with two rotational speeds (70 and 140 revolutions per minute for example), drilling tools of a first type may be driven, the specific speeds of which for hard or soft ground are equal to or close to the two speeds of the first engine. The selection of the speed of rotation of the second motor 3 corresponds to the use of a tool of a second type whose specific speed is much higher than that of the tool of the first type. It is further observed that the adjustment (73A) of the flow delivered by the main pump 73 allows additional adjustment of the rotational speeds of the motors 2 and 3.

Thus the motor unit drives the shaft 5 at the speed of rotation always adapted to the drilling tool used and to the selected operating phase.

Finally, it should be noted that the shaft 5 being hollow allows the circulation of drilling mud, the dimension D6 of the recess 6 making this circulation free from restriction.

Claims (10)

1. Drive unit comprising: a frame (1), a driven shaft (5) mounted to rotate with respect to the frame about an axis of rotation (7); a first pressurized fluid motor (2) presenting a lobed cam (18) fixed with respect to said frame; a cylinder block (12) fast, with respect to rotation, with said driven shaft (5); a plurality of cylinders (15) arranged in the cylinder block and disposed radially with respect to the axis of rotation; a plurality of pistons (16) mounted to slide in the cylinders and capable of abutting by reaction on said cam; the shaft (5) being capable of being driven by the first motor (2) at at least one first speed of rotation and presenting a recess (6) which constitutes a passage which, in one configuration of the coupling in rotation of a drilling tool to said shaft (5), conveys the drilling fluid to the drilling tool; and, the cylinder block (12) of said first motor being coaxial to the axis of rotation (7) and is disposed about said shaft (5);
      characterized in that:

   A) this drive unit comprises a second motor (3) which is coupled in rotation to said shaft and which is capable of driving this shaft at a second speed of rotation (V2) substantially higher than said first speed of rotation (V11; V12) ;

   B) a first pinion gear (56) is fast (66), with respect to rotation, with the shaft (5), surrounds said shaft and is coaxial to the axis of rotation (7);

   C) the second motor (3) presents an output shaft (64) with which is fast in rotation a second pinion gear (57) which meshes with said first pinion gear (56);

   D) the first pressurized fluid motor is of the "disengageable piston" type and, to that end, is provided with a disengagement mechanism (54) capable of controlling withdrawal of said pistons out of abutment on the lobed cam (18).
2. Drive unit according to claim 1,
      characterized in that the first pressurized fluid motor presents a closed housing (1-9-10) containing the cylinder block (12), capable of selectively communicating (77) with a source (86) of disengaging fluid, such disengagement being effected by the effect of the pressure of the fluid coming from the source of disengaging fluid admitted into the housing, which effects entry of said pistons in the cylinders.
3. Drive unit according to any one of claims 1 to 2,
      characterized in that said second speed of rotation (V2) is higher than five times the smallest (V1) of the first speeds of rotation.
4. Drive unit according to any one of claims 1 to 3,
      characterized in that the first (56) and second (57) pinion gears are contained in a housing (4), which is hermetically (58-60) isolated from the first pressurized fluid motor.
5. Drive unit according to any one of claims 1 to 4,
      characterized in that the diameter (D57) of the second pinion gear (57) is smaller than the diameter (D56) of the first pinion gear (56).
6. Drive unit according to any one of claims 1 to 5,
      characterized in that, on the one hand, rotational bearings (8) are interposed between the driven shaft (5) and the frame (1) and effect rotational assembly of said shaft with respect to said frame, on the other hand, these rotational bearings (8) also effect rotational assembly of the cylinder block (12) with respect to the lobed cam (18) of the first pressurized fluid motor (2).
7. Drive unit according to any one of claims 1 to 6,
      characterized in that the first pressurized fluid motor presents a housing (1-9-10) which contains the cylinder block (12) and which is partially constituted by a part of said frame (1).
8. Drive unit according to any one of claims 1 to 7,
      characterized in that the shaft (5) being capable of driving in rotation a plurality of different tools having likewise different speeds of rotation (V11; V12), the first pressurized fluid motor is a motor presenting a plurality of operational cubic capacities, so as to be able to drive the shaft (5) at several distinct speeds of rotation and thus drive said tools at their respective different speeds of rotation.
9. Drive unit according to any one of claims 1 to 8,
      characterized in that the second motor (3) is a pressurized fluid motor.
10. Drive unit according to any one of claims 1 to 9,
       characterized in that the first pressurized fluid motor (2) comprises a housing (1-9-10) which contains the cylinder block (12), in which said cam (18) is incorporated and whose outer transverse section, contained in a plane (P18) perpendicular to the axis of rotation (7) and intersecting the cam (18), is capable of being inscribed in a circle of determined diameter (D9), whilst the recess (6) constituting the passage is cylindrical and presents an inner diameter (D6) greater than or equal to 0.25 times said determined diameter (D9).

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