EP2268921A1

EP2268921A1 - Converter for converting mechanical energy into hydraulic energy and robot implementing said converter

Info

Publication number: EP2268921A1
Application number: EP09724364A
Authority: EP
Inventors: Samer Alfayad; Fathi Ben Ouezdou; Fayçal NAMOUN
Original assignee: BIA SAS
Current assignee: BIA SAS
Priority date: 2008-03-26
Filing date: 2009-03-25
Publication date: 2011-01-05
Anticipated expiration: 2029-03-25
Also published as: EP2268921B1; JP5613946B2; CA2719843A1; KR101729785B1; CA2719843C; FR2929347A1; PL2268921T3; KR20110019356A; US8734123B2; CN102027234A; ATE519945T1; ES2370355T3; US20110085922A1; MY159090A; JP2011525222A; WO2009118366A1; CN102027234B

Abstract

A converter for converting mechanical energy into hydraulic energy and a robot implementing the converter are disclosed. The converter includes a shaft rotated about a first axis relative to a casing, a hub defining a bore about a second axis, the shaft rotating in the bore. The first axis is parallel to the second axis, and a distance between the first axis and second axis defines an eccentricity. At least two pistons are movably disposed in radial housings of the shaft with the at least two pistons bearing against the bore. Movement of the pistons feed a hydraulic fluid into one of two annular grooves of the casing arranged in an arc of a circle about the first axis, and the hub is configured to translate along a third axis to modify the value of the eccentricity between two extreme values.

Description

Converter of mechanical energy into hydraulic energy and robot implementing the converter

The invention relates to a mechanical energy converter in hydraulic energy and a robot implementing the converter. The invention finds particular utility in the realization of humanoid robots for which one seeks to improve the autonomy. Such robots are equipped with actuating mechanisms to move the different parts of the robot. These mechanisms connect a power source providing mechanical energy such as for example an electric motor, hydraulic or pneumatic, with a load. In other words, an actuating mechanism provides mechanical power transmission between a motor and a load.

An essential parameter of an actuating mechanism is its transmission ratio which is chosen to adapt a nominal operating point of the load to that of the motor. In a known actuating mechanism whose transmission ratio is constant, for example achieved by means of gear trains, the choice of the ratio is limited to discrete values and the gear change requires complicated devices such as a gearbox. speed to fit the transmission ratio. However, in robotic applications, the operating point of the loads is generally very variable. If the reduction ratio is constant, this leads to size the motor for the worst case of use of the load.

There are devices to vary the transmission ratio continuously but they are complicated and their performance often poor. For example, belt speed reducers whose transmission ratio varies according to the speed of the motor by means of masses of inertia are known.

The actuating devices described above are bulky, heavy and complex which is detrimental to robotic applications.

In addition, among the motors mentioned above, electric motors are only suitable for high speeds and low torques. In robotic applications, the opposite situation is frequent: low speed and high torque. The implementation of electric motors for low speed imposes significant reduction ratios so complicated to achieve.

In a known manner, in robotic applications, a central hydraulic unit is used which is connected to different links to be motorized by pipes carrying a fluid under pressure. When the robot comprises a large number of actuators, the pipeline network becomes complex. In addition, the hydraulic unit must provide all the connections with the maximum pressure imposed by the most stressed connection.

The aim of the invention is to overcome all or some of the problems mentioned above by proposing an actuating mechanism transforming the mechanical energy supplied by a motor into hydraulic energy used by a load, for example in the form of a jack allowing a part to move mobile of a robot. It is understood that the invention is not limited to the robotics field. The invention can be implemented in any field where it is sought to optimize an actuating mechanism. More specifically, the invention proposes a mechanical energy converter into hydraulic energy that can be decentralized, that is to say associated with a single load. The converter then only provides the hydraulic power required by the load.

For this purpose, the invention relates to a mechanical energy converter in hydraulic energy, comprising a shaft driven in rotation by the mechanical energy around a first axis relative to a housing, a hub having a bore formed around a second axis, the shaft rotating in the bore, the two axes being parallel and a distance between the axes forming an eccentricity, at least two pistons each able to move in a radial housing of the shaft, the housing guiding the pistons, the pistons bearing on the bore, characterized in that the displacement of the pistons causes a hydraulic fluid in two annular grooves of the casing, the grooves being arranged in an arc around the first axis, the energy hydraulic being generated by a pressure difference of the fluid present between the two grooves, and in that the hub is movable in translation along a third axis perpendicular to the two first rs axes to modify the value of the eccentricity between two extreme values, one being positive and the other being negative in order to allow a reversal of the fluid pressures in the grooves while maintaining the same direction of rotation for the shaft.

One groove forms the inlet and the other groove forms the discharge of the converter. The fact of reversing the fluid pressures between the grooves causes the exchange of roles between admission and discharge of the grooves while maintaining the same direction of rotation for the shaft.

The invention also relates to a robot comprising a plurality of independent links driven by hydraulic energy, characterized in that it further comprises as many converters according to the invention as independent links, each converter being associated with a link.

The invention will be better understood and other advantages will appear on reading the detailed description of several variant embodiments given by way of example, a description illustrated by the attached drawing in which:

FIG. 1 represents in section an exemplary embodiment of a converter according to the invention; FIG. 2 represents, for the converter of FIG. 1, elements ensuring the pumping of a hydraulic fluid; Figure 3 shows an alternative embodiment of the elements shown in Figure 2; FIG. 4 represents fluid intake and discharge ports of the converter; FIG. 5 represents means for modifying an eccentricity of the converter; Figure 6 shows a hydraulic diagram of a valve of the converter; FIGS. 7a and 7b show two positions of the means for modifying the eccentricity; Figure 8 shows a hydraulic diagram of a distributor of a first variant of the converter; Figures 9 and 10 show an embodiment of the dispenser of Figure 8; these two figures are sections in perpendicular planes; Figures 1 1 to 1 1 g represent different positions of a moving part of the distributor of the first variant; Figures 12a and 12b show a hydraulic diagram of two distributors of a second variant of the converter; Figures 13 and 14 show an embodiment of the dispensers of Figures 12a and 12b; Figures 15a to 15g show different positions of a moving part of the first distributor of the second variant; Figures 16a and 16b show different positions of a moving part of the second distributor of the second variant.

For the sake of clarity, the same elements will bear the same references in the different figures.

The converter shown in Figure 1 receives mechanical energy in the form of a rotational movement of a shaft 10 driven by a motor 1 1 for example electric DC. The motor 1 1 rotates at a constant speed of rotation which optimizes its operation. The shaft 10 and connected to the motor 1 1 by a coupling 12. It is also possible to remove the coupling 12 by directly making stator windings of the motor 1 1 on the shaft 10. The shaft 10 rotates around a axis 13 relative to a casing 14 closed at the ends of the shaft 10 by two covers 15 and 16. In each cover 15 and 16, a rolling bearing, respectively 17 and 18 provides guiding, limits friction between l shaft 10 and the assembly formed by the casing 14, and the covers 15 and 16 and seals the converter.

FIG. 2 represents elements of the converter providing the pumping of a hydraulic fluid. For this purpose, the converter comprises a hub 20 comprising a bore 21 formed around a second axis 22. The shaft 10 rotates in the bore 21. The two axes 13 and 22 are parallel and a distance between the axes 13 and 22 forms an eccentricity E.

The converter comprises at least two pistons capable of moving each in a radial housing of the shaft. It is possible to implement the invention for a converter in which the pistons are parallelepipedal pallets. In the example shown, the housings are cylinders and three pistons 23, 24 and 25 each move in a cylinder, respectively 26, 27 and 28. One end of each piston bears on the bore 21. The shaft 10 comprises at least two channels extending parallel to the axis 13. The two channels 29 and 30 appear in the plane of FIG. 2. The cylinder 26 opens on the channel 29 and the cylinders 27 and 28 are open on the channel 30. The number of pistons per channel can be increased to occupy the entire volume of the shaft 10 included within the bore 21.

Advantageously, the pistons are staggered about the axis 13. In other words, between two adjacent channels, the longitudinal position along the axis 13 of a cylinder opening into a first channel is interposed between the longitudinal positions of two adjacent cylinders of the second channel. This distribution makes it possible to increase as much as possible the number of pistons for a given bore 21. The distribution improves the dynamic balancing of the shaft 10 and its pistons when the shaft 10 rotates. The distribution also ensures a lesser variation in the radial forces on the shaft 10 as a function of the angle of rotation of the shaft 10.

The displacement of the pistons 23, 24 and 25 causes a hydraulic fluid in the channels 29 and 30. More precisely, in the relative position of the shaft 10 and the hub 20 shown in FIG. 2, the pistons 24 and 25 are in a position said top dead center and the piston 24 is in a position called bottom dead center. During the rotation of the shaft 10 about its axis 13, the pistons 23 to 25 move in their respective cylinder between their two dead spots. This displacement causes the fluid present in the portion of the cylinders 26, 27 and 28 communicating with the channels 29 and 30. Each channel 29 and 30 is closed at one of its ends by a plug 31, visible in Figure 1 and communicates with inlet and discharge ports at the other end thereof, orifices which will be described later. 3 shows an alternative embodiment of the elements shown in Figure 2, in which variant the pistons 23, 24 and 25 are replaced by balls 32 to 35. The diameter of the balls is adjusted with the inner diameter of the corresponding cylinders. In the remainder of the description, the term "piston" will be used to denote indifferently cylindrical pistons as represented in FIG. 2 or balls such as shown in Figure 3. The use of beads does not ensure such a good sealing of the fluid in the cylinders due to the lower contact area between balls and cylinders. The efficiency of the converter is reduced. Nevertheless, the variant implementing beads is much less expensive to produce.

Advantageously, the hub 20 forms an inner ring of a bearing 36, for example a needle. Thus, the hub 20 can rotate together with the shaft 10 and thus limit the friction of the pistons on the bore 21.

FIG. 4 represents inlet and fluid discharge orifices of the converter in section in a plane perpendicular to that of FIGS. 1 to 3. More specifically, the shaft 10 comprises ten longitudinal channels, the channels 29 and 30 of which. casing 14 comprises two grooves 40 and 41 annular arcuate around the axis 13 and each communicating alternately with the channels of the shaft 10. The groove 40 ensures for example the admission of the fluid to the channels facing and same, the groove 41 ensures the discharge of the fluid to the channels opposite. Each of the grooves 40 and 41 communicates with a coupling, respectively 42 and 43 for supplying a load associated with the converter either directly or through a distributor which will be described later. For a given eccentricity E, the converter operates as a constant displacement volumetric pump, assuming the rotation speed of the constant shaft 10. The hydraulic energy generated by the converter is due to a pressure difference of the fluid present between the two grooves 40 and 41. Two seals 44 and 45, visible in Figure 1 and for example lip, can be placed on both sides. other grooves 40 and 41 along the shaft 10 to seal the two grooves 40 and 41.

The hub 20 is movable in translation along an axis 46 perpendicular to the axes 13 and 22 to modify the value of the eccentricity E between two extreme values, one being positive and the other being negative. To ensure the translation of the hub 20, an outer ring 47 of the bearing 36 is integral with a carriage 48 capable of moving along the axis 46 to modify the value of the eccentricity E. Assuming the speed of rotation of the shaft 10 constant, when the eccentricity E is zero, that is to say when the axes 13 and 22 are combined, the pistons are stationary in their respective cylinders and the converter delivers no fluid flow. When increasing the value of the eccentricity E in a first direction along the axis 46, the flow rate of the converter increases. On the other hand, when the value of the eccentricity E is increased in a second direction opposite to the first one, the flow rate of the converter becomes negative. In other words, the groove 40 passes from the inlet to the discharge and vice versa for the groove 41. The fact of varying the eccentricity E between a positive value and a negative value makes it possible to reverse the inlet and outlet of the converter without thereby reversing the direction of rotation of the motor 1 1. The adjustment of the eccentricity E allows to use a motor whose control is very simple to drive the shaft 10 in rotation. This motor can rotate at almost constant speed without precise speed control, which simplifies the control of it. With this type of motor, the converter flow adjustment is done only by varying the eccentricity E. The reversal admission / discharge is much faster by reversing the eccentricity E by reversing the direction of rotation of the motor due to the very low inertia of the carriage 48 compared to that of the motor and pump assembly in the conventional case . It is of course possible when necessary to adjust both the eccentricity E of the converter and the speed of the motor in its operating range.

FIG. 5 is a sectional view of the converter by a plane parallel to the plane of FIG. 1. To move the carriage 48 in translation along the axis 46, the converter comprises two pistons 50 and 51 integral with the casing 14. The pistons 50 and 51 provide guiding and movement of the carriage 14 along the axis 46. Other of the carriage 48, between each piston 50 and 51 and the carriage 48, a chamber, respectively 52 and 53, is made. A differential pressure of a fluid between the two chambers 52 and

53 moves the carriage 48 to change the eccentricity E of the converter.

For this purpose, the converter comprises a valve 55 controlling the movement of the carriage 48 by means of a pressure difference of a hydraulic fluid. A hydraulic diagram of the valve 55 is shown in FIG. 6. The valve 55 forms a hydraulic distributor fed by the fluid displacing the carriage 48. A high pressure of this fluid is noted P and a low pressure is noted T in FIG. distributor can take three positions. In a central position 55a, neither of the two chambers 52 and 53 is powered by the fluid. In a position 55c, shown on the right in Figure 6, the chamber 53 receives the low pressure T and the chamber 52 receives the high pressure P. In a position 55b, shown on the left in Figure 6, the chamber 52 receives the bass pressure T and the chamber 53 receives the high pressure P.

Advantageously, the valve 55 is made in the carriage 48. Thus all the channels supplying the chambers 52 and 53 from the valve 55 are made in the carriage 48 which frees up space in the housing 14. The converter is thus more compact. The valve 55 comprises a bore 56 formed in the slide 48.

The bore is made along an axis 57 parallel to the axis 46. The diameter of the bore 56 is constant. The valve 55 comprises a rod 58 slidable within the bore 56. The outer surface of the rod 58 is formed of alternating cylindrical shapes of small diameter d and large diameter D extending along the axis 57. Five cylindrical shapes follow one another along the axis 57. These shapes have in the order of diameters D, D, D, D and D. The diameter D is adjusted with the inside diameter of the bore 56. Two communication chambers 59 and 60 are formed between the bore 56 and the shapes of diameter d. Five channels 61 to 65 made in the bore 56 allow the fluid to communicate with the chambers 59 and 60. The channels 61 and 65 are connected to the low pressure T of fluid. The channel 62 is connected to the chamber 52. The channel 63 is connected to the high pressure P of fluid and the channel 64 is connected to the chamber 53.

Figures 7a and 7b show two positions of the rod 58 inside the bore 56. The two chambers 52 and 53 communicate permanently with the communication chambers, respectively 59 and 60 and the displacement of the rod 58 allows connect each communication chamber 59 and 60 with the high-pressure fluid P present in the channel 63 is with the low pressure fluid T present in the channels 61 and 65.

In FIG. 7a, the position represented 55a is called the equilibrium position because neither the high pressure nor the low fluid pressure communicates with the chambers 52 and 53. In this position the eccentricity E remains constant. More precisely, the three cylindrical shapes of diameter D obstruct the low pressure channels 61 and 65 as well as the high pressure channel 63. The chambers 52 and 53 only communicate with the communication chambers, respectively 59 and 60, with neither access to the high pressure or low fluid pressure.

In Figure 7b, the rod 58 is moved to the left of the figure. This is position 55b. The central cylindrical shape of diameter D frees access to the channel 63 and the high pressure P of the fluid communicates with the communication chamber 60. Likewise, the left cylindrical shape of diameter D frees access to the channel 61. The low pressure T of the fluid communicates with the communication chamber 59 and the chamber 52. The carriage 48 moves to the left. A reverse movement of the carriage 48 is possible with a movement of the rod 58 to the right to reach the position 55c. The displacement of the rod 58 is for example ensured by means of a winding 70 supplied with an electric control current. A core 71 integral with the rod 58 moves in the winding 70 as a function of the control current.

Another advantage related to the embodiment of the valve 55 in the carriage 48 is the achievement of a servocontrol of the eccentricity E of the carriage 48 relative to the control.

More specifically, a displacement of the rod 58 of the value of the desired eccentricity E with respect to the casing 14 puts certain channels 61, 63 or 65 in communication with the corresponding communication chambers 59 and 60. When the carriage 48 reaches the desired eccentricity E, the relative position of the rod 58 relative to the carriage 48 causes the rod 58 to assume the position 55a, shown in FIG. 7a, without the need for a new command to be applied. at the winding 70.

The converter comprises a sensor 72 making it possible to determine its eccentricity E. For this purpose, the sensor 72 measures the position of the rod 58 with respect to the casing 14. When the rod 58 is in its equilibrium position, that represented in FIG. 7a, the measurement made by the sensor 72 is the position of the carriage 48. When the rod 58 is in a position of its extreme positions, such as that shown in FIG. 7b, the measurement made by the sensor 72 is the position of the carriage 48 to which is added the displacement of the rod 58 with respect to the carriage 48. The displacement of the rod 58 by relative to the trolley 48 is relatively fugitive. Indeed, the valve 55 quickly resumes its central position 55a after application of a command to the winding 70. As a first approximation, it can therefore be considered that the sensor 72 measures the eccentricity E of the converter. This eccentricity E is proportional to the flow rate of the converter and therefore to the speed of displacement of a load moved by the fluid delivered by the converter.

Moreover, the knowledge of the variation of the acceleration of the load, called jerk and well known in the English literature under the name of "jerk" is important in an application of the converter to the realization of a humanoid robot for to get closer to the functioning of the human body. Indeed, we realized that the human being tends to minimize any jerk in his movements. The knowledge of the variation of the acceleration of the load makes it possible, in a control strategy of the converter, to control the shaking and thus to get closer to the human behavior.

Advantageously, the converter comprises means for determining the acceleration of the converter flow from the control of the valve 55. More precisely, the variation of the position of the rod 58 is proportional to the control signal applied to the winding 70 So the control signal is proportional to the acceleration of the load. By deriving the control signal with respect to time, one thus obtains the acceleration of the flow of the converter or the shaking.

For example, an inductive electric displacement sensor of linear displacement well known in the English literature under the name of LVDT sensor for Linear Variable Differential Transformer is used.

The fluid used to move the carriage 48 may be from a source external to the converter. This solution makes it possible to simplify the supply of the valve 55 by using an external source in which the high and low pressures P and T have constant pressures. This solution nevertheless has the disadvantage of requiring additional pipes to supply the valve 55 with fluid. To overcome this problem, the pressure prevailing in the grooves 40 and 41 is used to move the carriage 48. This improves the independence of the converter relative to its environment.

For this purpose, the converter comprises a distributor 75 for communicating the high pressure input P of the valve 55 with the groove 40 or 41 in which the pressure of the fluid is the strongest and for communicating the low pressure input T of the valve 55 with the groove 40 or 41 in which the pressure of the fluid is the lowest.

To understand the operation of the distributor 75 it is possible to perform an electrical analogy with the hydraulic operation of the distributor 75. In this analogy, the pressure delivered by the grooves 40 and 41 is compared to an alternating voltage since the eccentricity E can be positive or negative. The distributor 75 then behaves as a voltage rectifier for supplying the valve 55 between positive and negative electrical terminals of the rectifier.

FIG. 8 represents a hydraulic diagram of the distributor 75 fed by the fluid present in the groove 40 and by the fluid present in the groove 41. The distributor 75 can take three positions. In a central position 75a, the eccentricity E is zero and the pressure of the fluid in the groove 40 is equal to the pressure of the fluid in the groove 41. In this position, the distributor 75 connects the groove 40 to the inlet P of the valve 55 and the groove 41 at the inlet T of the valve 55. A load 76 supplied by the converter is represented in the form of a double-acting cylinder comprising two chambers 77 and 78. In the central position 75a, none of the chambers the load 76 is powered. When the eccentricity E is modified so that the pressure in the groove 41 is greater than the pressure in the groove 40, the distributor 75 moves to reach a second position denoted 75b in which the groove 40 is connected to the inlet low pressure T and the groove 41 is connected to the high pressure inlet P of the valve 55. The pressure difference between the two grooves 40 and 41 is achieved by pumping means 79 of the converter comprising in particular the pistons 23 to 25 described upper. In addition, in position 75b, chamber 77 of the load 76 is connected to the groove 41 and the chamber 78 is connected to a reservoir 80 of fluid noted R ₁ On the other hand, when the eccentricity E is modified so that the pressure in the groove 40 is greater than the pressure in the groove 41, the distributor 75 moves to reach a third position denoted 75c in which the groove 41 is connected to the low pressure inlet T and the groove 40 is connected to the high pressure inlet P of the valve 55. Moreover, in the position 75c, the chamber 78 of the load 76 is connected to the groove 40 and the chamber 77 is connected to a reservoir 80 of fluid noted R in Figure 8. The distributor 75 uses no external energy source for its trips. Indeed, it is the fluid pressure present in the grooves 40 and 41 that allows the distributor to move from one position to another.

Advantageously, the converter comprises means so that when the fluid pressure is balanced between the chambers 52 and 53, the eccentricity E of the converter is not zero. These means comprise for example a spring located in one of the chambers 52 or 53 tending to exert a force between the carriage 48 and the respective piston 50 or 51. This spring is useful for starting the converter. Indeed, the central position 75a is an equilibrium position obtained for a zero eccentricity. From this position, in the absence of the aforementioned means, the displacement of the rod 58 could not cause any movement of the carriage 48. By shifting the equilibrium position of the carriage 48, this risk is avoided at startup.

Generally, in the mechanisms using hydraulic fluids, it is sought to minimize the leaks better to avoid losing fluid outside the mechanism and to improve its performance. In the present invention, it is accepted that leaks occur in the various hydraulic functions of the converter, such as, for example, the pumping means 79, the valve 55 and the distributor 75. Accepting internal leaks from the converter makes it possible to to dampen any shocks or more generally unanticipated efforts that may occur on the load 76. This damping makes it possible to approach the human behavior in the case of implementation of the converter in a humanoid robot. For this purpose, it can be provided to adjust internal leakage converter.

Advantageously, the converter comprises means for recycling any internal leakage of fluid involved in particular during the pumping. These leaks are recovered in an internal hydraulic space 82 denoted PE in FIG. 8. The internal hydraulic space 82 is located inside the casing 14, in particular on either side of the trolley 48.

For this purpose, the distributor 75 comprises means for when it leaves its central position 75a, the groove whose pressure is the lowest, in this case the groove 41, is connected to the internal hydraulic space

82 recovering internal leakage of the converter as the channels feeding the load 76 remain closed by the distributor 75.

By continuing the electrical analogy presented above, the rectifier, representing the distributor, can be illustrated as a bridge of diodes whose threshold voltages would be different. A higher threshold voltage towards the negative voltage representing a depression and lower towards the positive voltage representing an overpressure. Leak recycling is done as long as the AC voltage is lower than the threshold voltage. In the hydraulic diagram of FIG. 8, the leak recycling means are not visible since only in the central position 75a, the internal hydraulic space 82 is connected to one of the grooves. Figures 9 and 10 show an embodiment of a dispenser for both the supply of the valve 55 and the recycling of leaks. The distributor 75 comprises a movable part, called butterfly 85, free to rotate about the axis 13 inside the casing 14. The butterfly 85 has the shape of a flat washer. The rotational guidance of the throttle valve 85 is provided between an annular cavity 86 of the casing 14 and an additional annular shape of the throttle valve 85. The annular cavity 86 is limited by two faces 87 and 88 of the casing 14 perpendicular to the axis 13. The face 88 belongs to the lid 1 6. The groove 40 communicates with the orifices 90a, 90b, 90c and 9Od of the face 87 and the groove 41 communicates with the openings 91a, 91b, 91c and 91d of the face 87. The channels 61 and 65, forming the low pressure inlet T of the valve 55, communicate with an orifice 92 of the face 88 and the channel 63 forming the high pressure inlet P the valve 55, communicates with a hole 93 of the face 88 The fluid reservoir 80 communicates with an orifice 94 of the face 88. Two orifices 95 and 96 situated on the face 88 form outputs of the converter making it possible to feed the load 76. more, for recycling, leakage, the face 87 comprises an orifice 97 visible in Figures 1 1 to 1 1 g communicating with the internal hydraulic space 82.

The housing 14 comprises a stop 100 limiting the rotation of the butterfly 85. The butterfly 85 comprises an annular groove 101 whose ends 102 and 103 can bear against the stop 100. The support of one end 102 or 103 against the stop 100 depends on the pressure difference of the fluid present in the grooves 40 and 41. For example, around the central position, 75a, the butterfly 85 may cover an angular sector of + or - 22.5 ° around the axis 13.

The butterfly 85 comprises several annular countersinks in communication with the fluid from the grooves 40 and 41. On a large diameter of the butterfly 85 a countersink 105 is permanently located in front of the orifice 9Od. On a large diameter of the butterfly 85 a countersink 106 is permanently located in front of the orifice 91 d. On a small diameter of the butterfly 85 two countersinks 107 and 108 are permanently located in front of the orifices 90b and 90c. On a small diameter of the butterfly 85 two counterbore 109 and 1 10 are permanently located in front of the orifices 91 b and 91 c. The term "permanently located" means that the countersink and orifice considered are opposite for any position of the butterfly 85 in its rotational movements about the axis 13. In other words, the countersinks 105, 107 and 108 contain fluid at the pressure of the groove 40 and the counterbore 106, 109 and 1 10 contain fluid at the pressure of the groove 41.

In Figure 9, the butterfly 85 is shown in a central position

75a. In its rotation around the axis 13, the butterfly 85 allows the passage or the blocking of the fluid between the orifices of the face 87 and the orifices of the face 88. The different positions that can take the butterfly 85 and the communications between orifices are shown in Figures 11a to 11g. Figure 11a shows the butterfly 85 in central position 75a.

In this position, the orifices 95 and 96 making it possible to supply the load 76 are obstructed by solid portions 11 and 14 of the throttle valve 85 respectively located between the countersinks 107 and 108 on the one hand and 109 and 10 on the other hand. go. The orifices 92 and 93 communicate in part with respectively the countersinks 108 and 109 so as to supply the valve 55. The orifice 94 connected to the reservoir 80 communicates with the countersink 106 and the orifice 97 for recycling the leaks is completely obstructed. The end 102 is at an angular position of 22.5 ° relative to the stop 100.

FIG. 11b shows the butterfly 85 in a position in which the pressure of the fluid in the groove 41 is slightly greater than that of the fluid present in the groove 40. As in FIG. 11a, the orifices 95 and 96 allowing to feed the load 76 are obstructed by the solid parts 1 13 and 1 14 of the throttle valve 85. The orifices 92 and 93 communicate in part with respectively the countersinks 108 and 109 so as to feed the valve 55. The orifice 94 connected to the reservoir 80 communicates with the counterbore 106. The orifice 97, for recirculating leakage, communicates in part with the counterbore 105 through an orifice 120 passing through the bottom of the counterbore 105. As a result, the fluid contained in the internal hydraulic space 82 communicates with the groove 40 which is in depression. The content of the internal hydraulic space 82 is sucked by pumping the converter to the tank 80. The position of the butterfly 85 shown in Figure 11b is intermediate between the position 75a and 75c b. The end 102 is at an angular position of 26.32 ° with respect to the stop 100. FIG. 11c shows the butterfly 85 in a position in which it moves from the position of FIG. 11a to position 75b so that the orifices 97 and 120 are completely opposite and the recycling of the leaks is maximum. The position of the throttle valve 85 shown in FIG. 11c is intermediate between the position of FIG. 11b and the position 75b. The end 102 is at an angular position of 29.32 ° with respect to the abutment 100.

Figure 1 1 d shows the butterfly 85 in a position where it moves between the position of Figure 1 1 b and the position 75b so that the orifices 97 and 120 are no longer facing. Leaks are no longer aspirated. In this position, the orifices 95 and 96 making it possible to supply the load 76 are always obstructed by solid portions 11 and 14 of the throttle valve 85. It is desired to suck up the leaks as long as the converter does not supply the load 76. The end 102 is at an angular position of 33.32 ° with respect to the stop 100.

Figure 11 represents the butterfly 85 almost in position 75b. In this position, the orifices 95 and 96 making it possible to feed the load 76 enter into communication with the countersinks, respectively 107 and 1 10, and the orifice 94 comes into communication with the countersink 105 so as to feed the load between the highest pressure delivered by the converter and the reservoir 80. The end 102 is at an angular position of 37.32 ° relative to the stop 100.

In the position 75b, not shown, the end 103 comes into contact with the stop 100 and the orifices 95 and 96 for feeding the load 76 are completely in communication with the countersinks respectively 107 and 1 10. The orifice 94 is also completely in communication with the counterbore 105.

Fig. 11 shows the butterfly 85 in an intermediate position between the central position 75a shown in Fig. 11a and the position 75c. In this position, the orifices 95 and 96 making it possible to supply the load 76 come into communication with the countersinks respectively 108 and 109 and the orifice 94 remains in communication with the countersink 106 so as to feed the load 76 between the high pressure delivered by the converter and the reservoir 80. The end 102 is at an angular position of 20.5 ° relative to the stop 100. In this position, the orifices 92 and 93 are not completely obstructed in order to allow feeding of the valve 55.

In the position 75c, represented in FIG. 11g, the end 102 comes into contact with the abutment 100 and the orifices 95 and 96 making it possible to supply the load 76 are completely in communication with the countersinks 108 and 109, respectively. The orifice 94 is also completely in communication with the counterbore 106. The orifices 92 and 93 supplying the valve 55 communicate with the countersinks, respectively 110 and 107.

Advantageously, the converter comprises means for accumulating hydraulic energy in a pressure tank 119.

The accumulation can be done when the load 76 must remain stationary. In a humanoid robot application, the use of a load such as a jack to move, for example an ankle, follows a cycle of operation during which rest periods alternate with periods of work. We can simulate the robot's progress and thus predefine a cyclical relationship between periods of work and rest periods of the ankle. The accumulation of hydraulic energy is during periods of rest and it is possible to size the pressure tank 1 19 according to a duty cycle between the work periods and periods of rest of the cylinder.

Advantageously, the pressure tank 1 19 is common to several converters of the robot. It is possible to choose converters whose work periods do not overlap in time and for example converters whose cycles are opposite. This is for example the case of two ankles of the robot. Thus, when one of the converters accumulates energy in the tank 1 19, another converter associated with the same tank 1 19 uses this energy. It is thus possible to reduce the dimensions of the common tank 1 19.

A variant for illustrating an example of means for accumulating hydraulic energy is shown with reference to FIGS. 12a and 12b for a hydraulic diagram, FIGS. 13 and 14 for an exemplary embodiment, FIGS. 15a to 15g for the different positions of a throttle valve of a first distributor 120 and of FIGS. 1 6a and 16b for the different positions of a throttle valve of a second distributor 121. The distributor 120 as the distributor 75 is fed by the grooves 40 and 41 and supplies the chambers 77 and 78 of the load 76, the valve 55 by its high pressure inputs P and low pressure T. The distributor 120 can take three positions 120a , 120b and 120c. The position 120a is identical to the position 75a. In the position 120b, the pressure of the groove 41 is greater than that of the groove 40. The high-pressure inputs P and low pressure T of the valve 55 are, as for the position 75b, supplied by, respectively, the grooves 41 and 40. Similarly, as for the position 75b, the chamber 77 is fed by the groove 41. But unlike the distributor 75, in the position 120b, the chamber 78 is connected to the reservoir 80 without connection with the pumping means 79 and the groove 40 draws the fluid into the pressure tank 1 19. A valve 122 ensures that the pressure of the pressure tank 1 19 is never less than the pressure of the reservoir 80 which is for example maintained at atmospheric pressure. In the position 120c, the pressure of the groove 40 is greater than that of the groove 41. The high-pressure inputs P and low pressure T of the valve 55 are, as for the position 75c, fed by, respectively, the grooves 40 and 41. In contrast, the load 76 and the tanks 80 and 1 19 are not directly connected to the distributor 120 but through the distributor 121 whose hydraulic diagram is shown in Figure 12b.

The distributor 121 can take two positions, 121 a, said rest position and 121 b said active position. The distributor 121 is controlled by an external actuator 122, for example electric. In the absence of control of the actuator 122, the distributor 121 is returned to its rest position by means of a spring 123.

In the position 121a, the two chambers 77 and 78 of the load 76 are isolated and the pumping means 79 suck fluid into the tank 80 to raise the pressure of the pressure tank 1 19. The actuator 122 is activated when it is desired to move the load in the direction shown by an arrow 124. When the actuator 122 is activated, the distributor 121 takes the position 121 b, the chamber 77 is connected to the reservoir 80 and the pumping means 79 suck in the pressure tank 119 for supplying the chamber 78. Thus the pressure difference between the two chambers 77 and 78 is equal to the sum of the pressure difference between the two reservoirs 80 and 19 and the pressure difference obtained by the means 79. Thus, when the load 76 is at rest, energy can be accumulated by increasing the pressure of the pressure tank 1 19. This accumulated energy is restored when the load 76 is put in m opening either in the 120b position or in the 120c position, these two positions being associated with the position 121 b. When all the accumulated energy has been consumed, the pressure of the tank 1 19 becomes equal to that of the tank 80 and the operation of the converter returns to that of the variant implementing the distributor 75.

To achieve the accumulation means, the distributor 120 comprises a butterfly 130, free to rotate about the axis 13 inside the casing 14. The butterfly 130, like the butterfly 85, is guided in rotation in an annular cavity 131 of the casing 14. The annular cavity 131 is limited by two faces 132 and 133 of the housing 14 perpendicular to the axis 13. The throttle 130 is shown in different positions in Figures 15a to 15g.

As for the distributor 75, the distributor 120 makes it possible to communicate the high-pressure input P of the valve 55 with the groove 40 or 41 in which the pressure of the fluid is the strongest and to communicate the low pressure input T of the valve 55 with the groove 40 or 41 in which the pressure of the fluid is the lowest. For this purpose, the distributor comprises orifices 135 and 136 connected with the channel 63, forming the high pressure inlet P the valve 55, for the orifice 135 and with the channels 61 and 65, forming the low pressure inlet T valve 55, for the orifice 136. Depending on the rotation of the throttle 130, the orifices 135 and 136 communicate either with countersinks 137 and 138 connected to the groove 40 via the orifice 90a or with countersinks 139 and 140 to the groove 41 through the orifice 91a. The distributor 120 also makes it possible to communicate the chambers 77 and 78 of the load 76 with the grooves 40 and 41 via the distributor 121 when the latter is in its position 121 b. To simplify the description of the distributor 120, it is assumed later that the distributor 121 is in its position 121 b, that is to say without realizing the accumulation of energy.

The distributor 120 comprises an orifice 141 communicating with the counterbore 138 so that the orifice 141 communicates with the groove 40, see FIG. 15g, or with a counterbore 145 so that the orifice 141 communicates with the reservoir 80 via an orifice 146 of the casing 14, see FIG. The dispenser 120 also comprises an orifice 142 communicating with the counterbore 140 so that the orifice 142 communicates with the groove 41, see FIG. 15e, or with a counterbore 143 so that the orifice 142 communicates with the reservoir 80 via of an orifice 144 of the housing 14, see Figure 15g. The pumping of the fluid from the pressure tank 1 19 is done by putting in communication an orifice 150 of the housing 14 or with a countersink 151 of the butterfly 130 connected to the groove 40, see FIG. 15e, or with a countersink 152 of the butterfly 130 connected to the groove 41, see Figure 15g.

As for the distributor 75, the distributor 120 makes it possible to recycle the leaks contained in the internal hydraulic space 82 by suction to the tank 80. The recycling is carried out between the central position of Figure 15a and the extreme position of Figure 15e. Recycling is illustrated in the throttle positions 130 shown in Figures 15b, 15c and 15d. In these positions, the load 76 is isolated and the orifices 141 and 142 do not communicate with the grooves 40 and 41 through the counterbores 138 and 140 nor with the reservoir 80 via countersinks 143 or 145.

The positions of the throttle 130 shown in Figures 15b, 15c and 15d correspond to the central position 120a of Figure 12a. The pumping means 79 draw the fluid contained in the internal hydraulic space 82 to discharge it into the reservoir 80. The internal hydraulic space 82 is connected to the groove 40 whose pressure is lower than that of the groove 41. connection is made by communicating an orifice 157 of one of the faces of the housing 14 connected to the internal hydraulic space 82 with a counterbore 158 of the butterfly 130 connected to the groove 40. In addition, the reservoir 80 is connected to the groove 41 This connection is made by communicating an orifice 159 of one of the faces of the casing 14 connected to the groove 41 by a countersink 160 of the butterfly 130. FIG. 15b marks the beginning of the recycling of the leaks in the rotation of the throttle 130 in s away from the central position 120a. Figure 15c shows the maximum suction for leaks. In FIG. 15c, the orifice 157 completely faces the countersink 158 and the orifice 159 is completely opposite to the countersink 160. FIG. 15d shows the end of the suction of the leaks before the supply of the load 76.

The distributor 121 may be made by means of a butterfly 170 rotating about the axis 13 inside an annular cavity 171 of the housing 14. Figures 16a and 16b show two positions of the butterfly 170 respectively corresponding to the positions 121 a and 121 b defined in the hydraulic diagram of Figure 12b. The butterfly 170 comprises a plurality of ports making it possible to communicate orifices located on opposite faces closing the annular cavity 171 perpendicularly to the axis 13. The spring 123, disposed between the housing 14 and the butterfly 170, tends to bring the butterfly 170 back into position. its position in Figure 16a. In the position 121a (Figure 16a) a light 175 communicates the reservoir 80 with an outlet S1 of the distributor 120. In the position 121b, (Figure 16b) a solid portion 176 of the butterfly 170 prevents this communication. In position 121 a light 177 communicates the chamber 77 of the load 76 with an outlet S2 of the distributor 120. In the position 121 b, a solid portion 178 of the butterfly 170 prevents this communication.

In the position 121 has a light 179 communicates the chamber 78 of the load 76 with an outlet S3 of the distributor 120. In the position 121 b, a solid portion 180 of the butterfly 170 prevents this communication.

In the position 121 has a light 181 communicates the pressure tank 1 19 with an outlet S4 of the distributor 120. In the position 121 b, a solid portion 182 of the butterfly 170 prevents this communication.

In the position 121 b a light 183 communicates the pressure tank 1 19 with the outlet S3 of the distributor 120. In the position 121a, a solid portion 184 of the butterfly 170 prevents this communication.

In the position 121b a light 185 communicates the reservoir 80 with the outlet S4 of the distributor 120. In the position 121a, a solid portion 186 of the butterfly 170 prevents this communication.

The distributor 121 is controlled by the actuator 122 only in the position 120c of the distributor 120. It is possible to use the pressures P and T to rotate the butterfly 170 about the axis 13 and overcome the force of the spring 123 For this purpose, the dispenser 121 comprises a chamber 190 formed in the housing 14 allowing the fluid entering the chamber to push a finger 191 of the butterfly 170. The dispenser 121 also comprises a valve that can be disposed in a space 192 of the casing 14. The valve allows the admission of the fluid to the chamber 190.

Claims

1. Converter of mechanical energy into hydraulic energy, comprising a shaft (10) driven in rotation by the mechanical energy around a first axis (13) relative to a housing (14), a hub (20) having a bore (21) formed around a second axis (22), the shaft (10) rotating in the bore (21), the two axes (13, 22) being parallel and a distance between the axes forming an eccentricity ( E), at least two pistons (23, 24, 25) each able to move in a housing (26, 27, 28) radial shaft (10), the housing ensuring the guiding of the pistons (23, 24, 25), the pistons (26, 27, 28) bearing on the bore (21), characterized in that the displacement of the pistons (26, 27, 28, 32, 33, 34, 35) causes a hydraulic fluid in two annular grooves (40, 41) of the housing (14), the grooves (40, 41) being arranged in an arc around the first axis (13), the hydraulic energy being generated by a pressure difference of the fluid ide present between the two grooves (40, 41), and in that the hub (20) is movable in translation along a third axis (46) perpendicular to the first two axes (13, 22) to modify the value of the eccentricity (E) between two extreme values, one being positive and the other being negative so as to allow a reversal of the fluid pressures in the grooves (40, 41) while maintaining the same direction of rotation for the shaft ( 10).

2. Energy converter according to claim 1, characterized in that the piston has the shape of a ball (32 to 35) whose diameter is adjusted with an inner diameter of the corresponding cylinder.

3. Energy converter according to one of the preceding claims, characterized in that it comprises a plurality of pistons (26, 27, 28, 32, 33, 34, 35) staggered about the first axis (13).

4. Energy converter according to one of the preceding claims, characterized in that the hub (20) forms an inner ring of a bearing (36), an outer ring (47) of the bearing (36) being integral with a carriage (48) movable along the third axis (46) to change the value of the eccentricity (E).

5. Energy converter according to one of the preceding claims, characterized in that it comprises a valve (55) controlling the displacement of the carriage (48) by means of the pressure difference of the fluid existing between the two grooves (40). , 41).

6. Energy converter according to claim 5, characterized in that it comprises two chambers (52, 53) respectively located on either side of the carriage (48), each of the chambers (52, 53) containing the fluid , a differential pressure of the fluid between the two chambers (52, 53) for moving the carriage (48) to modify the eccentricity (E) of the converter, and in that the converter comprises means so that, when the pressure of fluid is balanced between the chambers (52, 53), the eccentricity (E) of the converter is not zero.

7. Energy converter according to any one of claims 5 or 6, characterized in that the valve (55) is formed in the carriage (48).

8. Energy converter according to any one of claims 5 to 7, characterized in that the converter comprises means for determining the acceleration of the converter flow from the control of the valve (55).

9. Energy converter according to any one of claims 5 to 8, characterized in that the converter comprises a distributor (75, 120) for communicating a high pressure inlet (P) of the valve (55) with the throat (40, 41) in which the fluid pressure is the highest and to communicate a low pressure inlet (T) of the valve (55) with the groove (40, 41) in which the pressure of the fluid is the lowest .

10. Energy converter according to any one of claims 5 to 9, characterized in that the distributor (75, 120) comprises means for that when leaving a central position (75a, 120a), the groove (40 , 41) whose pressure is the weakest is connected to a internal hydraulic space (82) recovering internal leakage of the converter as the channels feeding the load (76) remain closed by the distributor (75).

1 1. Energy converter according to one of the preceding claims, characterized in that it comprises means (121) for accumulating hydraulic energy in a pressure tank (1 19).

Energy converter according to one of the preceding claims, characterized in that the displacement of the pistons (26, 27, 28,

32, 33, 34, 35) drives the hydraulic fluid in channels (29, 30) made in the shaft (10) and in that the channels (29, 30) communicate alternately with each of the grooves (40, 41). of the housing (14).

13. Energy converter according to one of the preceding claims, characterized in that the housing is a cylinder (26, 27, 28).

14. A robot comprising a plurality of independent links driven by hydraulic energy, characterized in that it further comprises, as many converters, according to one of the preceding claims, as independent links, each converter being associated with a link.

15. Robot according to claim 12 implementing a converter according to claim 1 1, characterized in that the pressure tank (119) is common to several converters.