FR2699609A1 - Method and apparatus for moving or stopping a hydraulic motor driving an assembly having high inertia - Google Patents

Abstract

Method allowing the setting in motion or the stopping of the hydraulic motor driving an assembly having a great inertia which consists in placing on the pressure circuit supplying the engine (2), a valve making it possible to limit the pressure of each branch to a level predetermined pressure. It is characterized in that said valve is designed so that the pressure variation inside said engine (2) between a pressure P0 and a predetermined pressure corresponding to the value not to be exceeded, is carried out in two separate distinct phases l 'one from the other by a bearing at a pressure intermediate between the aforementioned values.

Description

METHOD AND DEVICE FOR SETTING UP OR

  STOPPING A HYDRAULIC ENGINE INVOLVING A

  ASSEMBLY HAVING GREAT INERTIA.

  The present invention relates to a method and the means for implementing it to ensure the setting in motion or stopping of a hydraulic motor driving an assembly having a high inertia, for example to ensure the rotation of a turret and the

  translation of crawler or tire machines.

  At the present time, when hydraulic motors are used to drive assemblies with high inertia, for example rotation of a turret, translation of a machine, it is necessary to provide valves on the hydraulic circuits. to limit

the pressure of each branch.

  In general, the solutions proposed to date consist, as is apparent from Figure 1 attached to dispose, on the pressure circuit (1) supplying the motor (2) of a valve consisting essentially of a valve needle (3) slidably mounted inside a chamber (4) inside which the connecting duct (5) opens to the pressure circuit (1). The needle valve is held in abutment against its seat (6). ) by the action of a calibrated spring (7) guided by a cup (8), the assembly being preferably associated with an adjusting means (9) for adjusting the pressure level not to be exceeded. During the setting in motion (or vice versa of the stop) of the assembly intended to be driven by the motor (2), one obtains a rise in pressure as schematized in the diagram of the figure (la) of which it appears that this valve design causes a steep pressure rise front with systematically a "pressure stroke" designated by the technicians by the term "overshoot", superior

  to the Po value of the valve.

  Such overshoot is due to the response time of the valve and the

  pressure gradient between O and Po, calibration value of the valve.

  Indeed, such a phenomenon results from the application of the formula according to which the acceleration (+ or -) is proportional to the pressure on the inertia. Consequently, such a type of front mounted pressure punctuated by this phenomenon "overshoot", causes the driver of the machine a sensation of brutality, shock This brutality also leads to high stresses resulting from the solicitation of structures and of the

components of the craft.

  Now we have found, and this is the object of the present invention,

  a solution that solves these problems.

  In general, the invention therefore relates to a method for setting in motion or stopping the hydraulic motor driving an assembly having a high inertia which consists in disposing on the pressure circuit feeding the motor, a valve allowing limiting the pressure of each branch to a predetermined pressure level, the method according to the invention being characterized in that said valve is designed so that the variation of pressure inside said engine between a pressure Po and a predetermined pressure corresponding to the value not to be exceeded is carried out in two distinct phases separated from each other by a bearing at a

  intermediate pressure between the above values.

  Advantageously, the duration of the pressure increase phases and those of the intermediate stage are equivalent as an indication, if the pressure variation has a cycle of a duration of three seconds, each

  phase will have a duration of one second.

  The device for carrying out the process according to the invention consists essentially of a valve mounted on each pressure circuit feeding the motor so that it rotates in one direction or the other, said valve comprising, in a similar manner to a conventional valve, a needle valve sliding inside a chamber inside which opens the connection duct to the pressure circuit and which is held in abutment on the seat via a calibrated spring guided by guide cups, the assembly being associated with an adjustment system, said valve being characterized in that: the needle valve is pierced along its length with a calibrated conduit (nozzle) and comprises a section cylindrical (A 2) lower than the section Ai of the pressing seat of the needle valve; a movable piston being disposed inside a chamber, concentric with that inside which is disposed the calibrated spring, on the other side of the latter with respect to the face acting on the needle valve, a nozzle opening into said chamber and controlling the volume of oil evacuated by said movable piston. Thanks to such a set, it is possible to have a much softer and progressive setting of the driven set

by the hydraulic motor.

  The invention and the advantages that it brings will however be better understood thanks to the exemplary embodiment described hereinafter by way of indication but not limitation and which is illustrated by the attached diagrams in which: FIGS. 1 and 1 illustrate, as previously seen, the structure of a conventional valve and the operating cycle during the setting in motion of the assembly to be driven by the hydraulic motor; FIG. 2 is a diagram illustrating the manner in which the pressure variation in the supply of a hydraulic motor is carried out according to the method according to the invention; FIG. 3 is a longitudinal sectional view of a valve that is particularly suitable for carrying out the method according to the invention; FIG. 4 illustrates how a valve according to the invention is implemented when it is mounted in a block

  "cross over" to protect a hydraulic motor.

  In the remainder of the description, the invention will be described using

  the same references as those used to describe the state of the art (Figure 1) to designate the same elements or equivalent elements. According to the invention, to ensure the setting in motion (or the stop) of a hydraulic motor (2) driving an assembly having a high inertia, one has on the pressure circuit (5) supplying said motor (2) , a valve for limiting the pressure of each branch to a determined pressure level This valve, an embodiment of which is illustrated in FIG. 3, is designed so that the variation of pressure inside said engine (2) between a pressure Po and a predetermined pressure corresponding to a value not to be exceeded, is made in two distinct phases separated from each other by a bearing at an intermediate pressure between said aforementioned values. This valve is designed in the manner illustrated in FIG. 3. It essentially comprises a needle valve (3) slidable inside a chamber inside which the circuit (5) for connection to the pressure circuit C opens. valve (3) is held in abutment against a fixed seat by means of a calibrated spring (7) guided by guide cups (8). As is apparent from FIG. 3, the needle valve (3) is pierced. along its length of a calibrated conduit (10) (nozzle) and has a cylindrical section (11) whose surface A 2 is smaller than

  that Ai seat (6) of pressing the needle valve (3).

  Furthermore, a movable piston (12) is disposed inside a chamber (13) concentric with that inside which the calibrated spring (7) is arranged. This movable piston (12) is arranged on the other side of the calibrated spring (7) with respect to the face acting on the needle valve (3); a nozzle (14) opens inside said chamber (13) and controls the volume

  oil evacuated by said movable piston (12).

  The operation of such a valve is clear from the overall diagram of Figure 4, showing the positioning of the various elements before the start of the process of setting into motion

(or stop) of the engine (2).

  If we consider that the calibration value Po of the valve corresponds to the force exerted by this pressure Po on the annular section Ai A 2, then we have the relation:

  Spring setting force Fo = Po (Ai A 2).

  The pressure level of the intermediate bearing depends on the ratio of

section A 2.

  Ai For a final calibration of the valve Po, if we want an intermediate bearing according to the invention equal to Po, it is necessary that A 2 = n- in Ai n If we assume that Po = 250 bars and that the we wish

  have a bearing at 125 bar, we have N = 2.

  It will therefore be necessary to have A 2 = 2-1 or A 2 = 1 Ai

A 1 2 2

  The duration of the step To depends on the volume of oil evacuated by the mobile piston (12), the calibrated nozzle of the needle valve (3) and the

  discharge chamber (13) of the piston.

  The operation of such a valve when mounted in a "cross-over" block to protect a hydraulic motor (2), spring

Figure 4.

  On the high pressure branch of the engine (2), as soon as the pressure acting on the section Ai reaches the setting force of the spring (7), the needle valve (3) is lifted from its seat (bearing phase) by the orifice of the nozzle (10) of the valve (3), it will reign in the spring chamber and on the underside of the movable piston (12) sufficient residual pressure (pressure of the motor branch minus (-) loss of the load created by the nozzle), which will move the movable piston When the piston (12) has finished its stroke (piston abutting on the cap), we go from a dynamic phase to a static phase; there is no more pressure drop at

  through the calibrated orifice (10) of the needle valve (3).

  Thus, the pressure of the motor branch (2) is established at the same time on Ai

  and A 2, so acts on the differential section (Ai A 2).

  The time that the piston will have to make its race will determine the time TO equal to the duration of the bearing Po It should be noted that the volume of oil evacuated by the movable piston (12) goes directly into the other branch of the motor (2) which, combined with the fact that one has a bearing, reduces the risks

  cavitation of the hydraulic motor.

  The pressure exerted on the differential section (A 1 -A 2) may eventually close the needle valve until this force

  overcomes the force of the setting force of the spring (7).

  As a result, the overshoot is damped because the starting point of the valve is no longer, as for a conventional valve O to

  Po but from Po (bearing value) to Po.

  n The evacuation chamber of the mobile piston is connected to the opposite branch of the engine to be protected (2) Thus, at rest, the piston of each

  valve is in the low position (zero stroke).

  Such an assembly can be used successfully to control the rotation of a turret and will have the following dimensions if one considers that it is necessary to have a flow of thirty liters / minute and a pressure of

  setting of the hydraulic motor of 250 bars.

  Seat diameter: 61 = 5.3 mm or Ai = 22.06 mm 2 Diameter of the cylindrical part: O E = 4 mm or A 2 = 10.99 mm 2

  At 2 = 0.5, which gives an intermediate plateau at 125 bars.

  Ai Piston diameter 10.3 mm stroke 19.5 mm or a volume of 1.62 cm 3

  The dwell time will then be: To = 0.3 seconds.

  1.62 cm 3 in 0.3 S gives a flow rate of: 1.62 x 60 = 0.3241 / min 0.3 x 1000 This flow must be calibrated by the inlet nozzle of the needle valve which

will have a diameter of 0.25 mm.

  Such a particularly simple design set gives

full satisfaction.

  Of course, the invention is not limited to the embodiment described above, but it covers all variants

realized in the same spirit.

  Thus, if it is advantageous to make a valve according to the invention, all elements of which are in line and integrated in a cartridge as illustrated, it will also be possible to envisage other types of embodiment, for example of have sets where the movable piston is either inside the cartridge or

  ring and slide outside.

Claims (3)

  1 / A method for setting in motion or stopping the hydraulic motor driving an assembly having a high inertia which consists in arranging, on the pressure circuit supplying the motor (2), a valve making it possible to limit the pressure of each branch to a predetermined pressure level, characterized in that said valve is designed so that the variation of pressure inside said engine (2) between a pressure Po and a predetermined pressure corresponding to the value not to be exceeded, is carried out in two distinct phases separated from each other by a bearing at an intermediate pressure between aforementioned values.   2 / A method according to claim 1, characterized in that the duration of the pressure rise phases and that of the intermediate bearing are equivalent. 3 / Device allowing the implementation of the method according to one   Claims 1 and 2, consisting essentially of a valve   mounted on each pressure circuit supplying the motor (2) to rotate in either direction, said valve comprising a needle valve (3) sliding inside a chamber within which opens the conduit (5) for connection to the pressure circuit and which is supported on the seat by means of a calibrated spring (7) guided by guide cups (8), the assembly being associated with an adjusting system, said valve being characterized in that: the needle valve (3) is pierced along its length with a calibrated conduit (10) (nozzle) and has a cylindrical section (A 2) smaller than the section (Ai) ) the seat (6) for pressing the needle valve (3); a movable piston (12) being arranged inside a chamber, concentric with that within which is disposed the calibrated spring (7), on the other side of the latter with respect to the acting face on the needle valve (3), a nozzle (14) opening into said chamber and controlling the volume of oil discharged by said movable piston.