FR3105310A1 - Hydraulic machine such as variable displacement axial piston pump or motor with precise neutral position - Google Patents

Abstract

The invention relates to a hydraulic machine (1) such as a variable displacement axial piston pump or motor, comprising - a variable inclination plate (2), comprising an axis of rotation (YY') connected to axial pistons ( 3), each having a variable stroke, said stroke of the axial pistons (3) depending on the inclination of the variable inclination plate (2), the variable inclination plate (2) comprising a neutral position which corresponds to a zero inclination of said variable inclination plate (2) with respect to a longitudinal axis (XX') of the hydraulic machine (1); the hydraulic machine (1) further comprising - a return mechanism (4) comprising a return spring (4) configured to return the variable tilt plate (2) to the neutral position when no tilt is applied on the variable inclination platform (2); characterized in that the hydraulic machine also comprises a locking mechanism (5) comprising a movable stop (51) so that on return to the neutral position of the variable-tilt plate (2) by means of the return spring (4 ), the movable stop (51) is configured to lock the variable-tilt plate (2) in said neutral position. Figure for abstract: FIGURE 3

Description

Hydraulic machine such as a precise neutral position variable displacement axial piston pump or motor

GENERAL TECHNICAL AREA

The invention relates to an axial piston hydraulic machine such as a motor or a pump.

Such a hydraulic machine conventionally comprises:

- a cylinder block rotatably mounted around a casing with a first axis of rotation, the cylinder block comprising a plurality of cylinders in which pistons are movable in translation parallel to the first axis of rotation;

- A tilting plate along a second axis perpendicular to the first axis of rotation.

STATE OF THE ART

The stroke of the pistons depends on the inclination of the plate and makes it possible to adjust the flow of oil circulating in the hydraulic machine. There is an angular position of the plate on the second axis of rotation which is perfectly perpendicular to the first axis of rotation of the cylinder block, that is to say that the plate defines a plane perfectly perpendicular to the first axis of rotation of the cylinder block, which means that the stroke of the pistons is zero, in other words that the pump rotates without delivering, therefore has zero cubic capacity per revolution. This position is defined as the zero tilt position of the plate, or neutral position of the hydraulic machine.

The plate with variable inclination comprises a rotation axis which can be actuated for example by a lever or a control which makes it possible to adjust the inclination of the plate to obtain the desired displacement for the hydraulic machine. This external control is therefore applied to the support shaft of the variable inclination platform. It is through this command that the user can control the displacement of the pump he wishes, for example to drive a machine where the pump carries out part of the transmission. This shaft rests on two bearings 63 which define the axis of rotation of the variable tilt plate.

On certain hydraulic machines, it is desired to have a specific control which returns to the neutral position in the absence of stress. When no inclination of the plate is required, you want it to be returned to the neutral position. To help it return to the neutral position, there are return mechanisms made up of springs. In particular for pumps with two directions of flow, a double return system in neutral position is provided

A problem often encountered is that the return to the neutral position which corresponds to zero inclination of the plate is not perfectly found. Depending on the load of the hydraulic machine, i.e. the pressure it delivers, there are significant parasitic forces at the level of the plate, and the return to neutral position requires a variable force, which can be significant. There may be jams.

More particularly in the case of pumps with two directions of flow, it is not always possible to have a spring which brings a control back to a physical stop, because the neutral point of the control is in the middle of its stroke, and also the neutral point is defined in the middle of the race by two opposing springs. At the neutral point, the effort of the two springs is minimal, while at full displacement one of the two springs has maximum tension. The closer you get to the neutral point, the more the tension of the springs decreases. The variability of the springs means that the neutral point is not exactly defined, which sometimes leads to individual adjustment operations of the pumps.

In addition, in general, axial piston pump systems develop internal forces, which are variable depending on the load of the pump, which cause jamming or parasitic forces, which cause the stop position during of the automatic return to neutral is random and dispersed around the neutral point. More particularly, antagonistic return spring systems, for pumps with two directions of flow, reciprocally cancel their thrust around the neutral point, and it is very difficult to define the point of equilibrium of two antagonistic springs. A very small effort provided by one spring vis-à-vis the other, or a small geometric deviation is enough to shift the neutral point significantly for the pump to provide a flow.

There are also systems with a single spring and two levers, but all of which have the difficulty that the tension decreases around the neutral point and that this is poorly defined geometrically because the stop position is defined by a balance of floating forces. .

In all these systems, one can try to force a better return to the neutral position by using stronger springs. But in this case, the tension to be exerted to control the displacement is excessive, and the springs become cumbersome. Mounting the control is also more difficult for the mechanic.

There are also pumps with automatic reset to neutral, and in particular those with two flow directions, equipped with an individual adjustment stop at the neutral point. However, even after this adjustment operation, a random residual flow is obtained around zero flow. A machine which would use such a pump to make its transmission, for example a construction machine or a mounted mower, would have the fault of not knowing exactly when to stop and of having a tendency to make the wheels turn, either forwards or backwards at a slow speed. The user must therefore manually request the control to find the true stopping point, or else the pump must be equipped with stop devices, such as bypass valves, which make the complex and cumbersome circuit, and which have an additional cost.

PRESENTATION OF THE INVENTION

The invention makes it possible to have a hydraulic machine in which the return to the neutral position is precisely ensured.

To this end, the invention proposes a hydraulic machine such as a variable displacement axial piston pump or motor, comprising

- a variable-tilt plate, comprising an axis of rotation connected to axial pistons, each having a variable stroke, said stroke of the axial pistons depending on the inclination of the variable-tilt plate, the variable-tilt plate comprising a neutral position which corresponds to zero inclination of said variable-inclination plate with respect to a longitudinal axis of the hydraulic machine; the hydraulic machine further comprising

- a return mechanism comprising a return spring configured to return the variable-tilt tray to the neutral position when no tilt is applied to the variable-tilt tray;

characterized in that the hydraulic machine also comprises a locking mechanism comprising a movable abutment so that on the return to the neutral position of the variable-tilt plate by means of the return spring, the movable abutment is configured to lock the plate at variable inclination in said neutral position.

The invention is advantageously completed by the following characteristics, taken alone or in any of their technically possible combination:

- the return mechanism comprises a disc connected to the variable inclination plate, the rotation of the disc around an axis of rotation perpendicular to a longitudinal axis of the hydraulic machine, depending on the inclination of the variable inclination plate, said disc comprising also a neutral position corresponding to zero inclination of the variable inclination platform;

- the locking mechanism comprises a profile formed in the disc, the movable stop penetrating into said profile to lock the variable tilt plate in the neutral position;

- the locking mechanism comprises a locking spring at the end of which the movable stopper is arranged, the movable stopper penetrating into the profile of the disc by being pushed by the locking spring as soon as the disc returns to the neutral position;

- it comprises a box to house the locking spring and the movable stop;

- the return mechanism comprises two rods projecting from the disc and two arms mounted for rotation about the axis of rotation, said arms being arranged on either side of the rods, the rotation of the disc leading to a rotation of one of the two arms in a clockwise or counterclockwise direction via one of the two rods, the return spring being connected between the two arms, the arms being configured to return the disc to its neutral position whenever no tilt is applied to said variable tilt platter;

- it comprises a shaft output coaxial with the axis of rotation of the variable-tilt plate and an external control connected to the shaft output of the variable-tilt plate, the shaft output making it possible to apply an inclination to the plate with variable inclination, the shaft output also comprising a neutral position corresponds to a zero inclination of the variable inclination plate;

- the disk is connected to the external control to control the displacement of the hydraulic machine;

- the machine has a two-way flow, such that the neutral position is located in the middle of the total stroke of the control lever;

- the locking system exerts an attractive torque on the disc towards the neutral position, complementary to the force of the springs, when the disc approaches the neutral position;

- further comprising a neutral position sensor configured to deliver an electrical neutral position signal, such that the locking system performs a position sensor function delivering an electrical neutral position signal;

- the neutral position sensor includes the locking stop and the locking spring.

The invention makes it possible to have a control for resetting the hydraulic machine to neutral which does not require cumbersome means of neutralizing the flow, which is flexible to operate, and which allows a complete, safe and repeatable stoppage of the flow.

PRESENTATION OF FIGURES

Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting, and which must be read in conjunction with the appended drawings in which:

Figure 1 illustrates a hydraulic machine comprising a return mechanism according to the invention;

Figures 2a and 2b illustrate views of a return mechanism in a hydraulic machine according to a first embodiment of the invention;

Figure 3 illustrates a top view of a hydraulic machine according to a first embodiment of the invention;

Figures 4 and 5 illustrate views of a locking mechanism of a hydraulic machine according to the invention;

Figures 6a and 6b illustrate views of a return mechanism in a hydraulic machine according to a second embodiment of the invention;

Figure 7 illustrates a locking mechanism with a position sensor in a top view;

Figure 8 illustrates a locking mechanism with a position sensor in a cross-sectional view.

In all the figures, similar elements bear identical references.

DETAILED DESCRIPTION

Figure 1 illustrates a hydraulic machine such as a hydraulic pump or a hydraulic motor.

The hydraulic machine 1 comprises a casing 10 in which is arranged a cylinder block 20 rotatably mounted around a first axis of rotation XX' which corresponds to a longitudinal axis of the hydraulic machine 1.

The cylinder block 20 comprises several cylinders 21 in which are mounted pistons 3 movable in translation, in a direction parallel to the axis of rotation XX'. The cylinder block 20 is such that the pistons are arranged around the axis of rotation XX' of the machine 1 so we speak of radial pistons 3. These pistons 3 have a variable stroke.

This machine 1 also comprises a variable inclination plate 2 which makes it possible to adjust the variable stroke of the pistons. The radial pistons 3 are connected to the variable inclination plate 2 via a spherical joint 22 and connecting rods 31. The connecting rods 31 extend from the pistons towards the spherical joints 31 which are therefore integral with the connecting rods. One end of the pistons rests on the plate via sliding shoes. The pistons driven in rotation in the cylinder block can rotate along the axis XX', while having their stroke regulated by the sliding stop on the plate. This variable inclination platform 2 comprises an axis of rotation YY' around which it can rotate.

The machine 1 also comprises a shaft 7 which constitutes the mechanical power input or output of the machine 1. This shaft 18 is rotatable around the axis XX'. The shaft 18 carried on one or more bearings 71 defines this axis of rotation.

The hydraulic machine 1 also includes an oil distributor to the pistons and oil inlet and oil outlet ports which constitute the hydraulic power input or output of the machine 1. The hydraulic machine 1 includes other elements well known to those skilled in the art which will not be further described here.

Above the variable-tilt plate 2 is advantageously provided a shaft output 6 making it possible to apply an inclination to the variable-tilt plate 2. It is through this shaft output 6 that it is possible to apply the desired inclination to the variable inclination plate 2. For example, the shaft output 6 may comprise means 61 for connecting an external control 61 such as a lever for example. Such connection means 61 are, for example, constituted by an orifice in which can be inserted the lever (not shown) which makes it possible to apply an inclination to the variable inclination plate 2. Other devices can be envisaged for applying an inclination to the variable inclination plate 2.

In Figure 1, the variable inclination plate 2 is shown in a neutral position, that is to say that no inclination is applied to the latter. The axis XX' is perpendicular to the variable inclination plate 2. Indeed, the inclination of the variable inclination plate 2 is taken with respect to the axis of rotation of the hydraulic machine 1. In this position of the plate, the pistons are supported on a sliding plane perpendicular to the axis XX ', which means that the pistons do not move in the cylinder block when the latter is rotating. This position is defined as the zero inclination of the plate, which defines the neutral position of the hydraulic machine.

As already mentioned above, the inclination of the plate makes it possible to adjust the stroke of each piston, it is the stroke of the pistons which makes it possible to adjust the quantities of oil circulating in the hydraulic machine 1 and which defines the displacement per revolution. of the hydraulic machine.

At rest, as already explained in the introduction, the variable inclination platform should return to the neutral position, i.e. with zero inclination.

To do this, the hydraulic machine includes a return mechanism 4 as shown in Figures 2a and 2b according to a preferred embodiment.

Such a return mechanism 4 makes it possible to return the plate to the neutral position when no tilt is applied to the variable tilt plate 2.

More specifically, the return mechanism 4 is positioned between the housing 10 and the shaft output 6 of the variable tilt plate 2 as can be seen in Figure 3.

To ensure a return to the neutral position, the return mechanism 4 also comprises a locking mechanism 5 in the neutral position of the variable tilt plate.

This locking mechanism 5 is positioned on the periphery of the shaft output 6 for controlling the variable tilt plate 2 (see figure 3).

Returning to Figures 2a and 2b, the return mechanism 4 comprises a disc 42 in conjunction with the variable tilt plate 2.

Advantageously, the disc 42 therefore rotates as the variable tilt plate 2 tilts. Preferably, the disc 42 is mounted fixed with the output shaft 6. Thus, the disc 42 can rotate around an axis of rotation YY' perpendicular to the longitudinal axis XX' of the hydraulic machine 1. Consequently, the disc 42 also includes a neutral position which corresponds directly to zero inclination of the variable inclination plate 2.

The return mechanism 4 advantageously comprises two rods 43 projecting from the disc 42 and two arms 44, 45 rotatably mounted around the axis of rotation YY'. Disc 42 advantageously comprises an angular amplitude of +/- 19° around the neutral position.

As can be seen, the arms are arranged 44, 45 on either side of the rods 43, preferably at two diametrically opposite ends of the disc.

Each arm 44, 45 comprises at least a first arm part 441, 451 and a second arm part 442, 452 perpendicular to the first arm part 441, 451. The first arm part 441, 451 extends radially from its rotation axis. The first arm parts and the second arm parts form, when the disc is in the neutral position (FIG. 2a), a U, the rods 43 being inside the U.

Advantageously, for reasons of mechanical strength, each arm comprises a third arm part 443, 453. The first arm parts and the third arm parts also form a U symmetrical to the U framing the rods 43.

Peripheral stops 46 are arranged on the periphery of the disc to limit the movement of the arms, the third arm parts resting against these stops 46 when the disc 42 is in the neutral position.

To ensure a return to neutral position of the disc, a return spring 44 is arranged between the arms 44, 45. More specifically, the return spring 44 is fixed between the first arm parts 44, 45. As such, the spring booster 44 includes eighth notes which are inserted into holes formed in the arms.

The operation of the return mechanism 4 is as follows.

When an inclination is applied to the variable inclination plate 2 (here by applying a torque to the shaft output 6) the disc 42 between rotation for example in the direction of clockwise materialized by the arrow in the figure 2b. the arms diverge from each other via the rods 43 which initiate movement on the arm 45. The rotation of the disc 42 is such that it applies a greater force on the arm 45 than the force of spring return 41.

When no inclination is applied to the variable inclination plate 2, nothing can contain the return force of the return spring 41 which returns the arm 45 to its original position (FIG. 2a). In particular, the arm 45 via a rod 43 (the one on the right in Figures 2a and 2b) brings the disc 42 back to its neutral position.

It will be understood that the peripheral stops 46 make it possible to limit the movement of the arm when it returns to the neutral position.

As already mentioned, an external control for controlling the pump displacement is connected to shaft output 6. The external control forces the rotation of shaft output 6 to set the desired displacement. When this control is released, the pump must return to the neutral position under the effect of the return mechanism 4.

If the shaft output is long enough, this control can be fixed on the shaft output 6 above the control disc 42, for example on a cone, a keyway, or splines made on the shaft output 6, or any other means.

Alternatively, the external control can be screwed onto the control disc 42, for example by means of two threaded holes 421 shown in Figure 5. A means for centering this attachment can be provided, for example on the output tree 6.

In relation to FIGS. 3, 4 and 5, the locking mechanism 5 comprises a movable stop 51 so that on the return to the neutral position of the variable-tilt plate by means of the return spring 41, the movable stop 51 allows to lock the variable inclination platform 2 in the neutral position.

To do this, the disc 42 comprises a profile 52, for example a notch formed in the thickness of the disc 43 and the movable stop 51 locks the disc 42 and therefore the variable tilt plate in the neutral position, when the movable stop 51 penetrates in profile 52.

The movable stop 51 is arranged at the end of a locking spring 53 whose stiffness is such that when the disc 42 is rotated when an inclination is applied to the variable inclination plate 2, the stop 51 comes out of the profile 52 by pushing the locking spring 53. It is indeed the disc 42 which pushes the locking spring 53. to cooperate with the profile.

On the other hand, when no inclination is applied to the variable inclination plate 2 (no torque is applied to the disc 42), the force applied by the disc against the locking spring 53 is such that the mobile stop 51 penetrates into the profile to lock the disc 42 in the neutral position and therefore the variable inclination plate 2. The profile cooperates with the movable stop 51 in an angular sector of +/-3°, ideally 2.5°.

It is understood that the locking system by abutment in the profile defines a very precise angular position. In addition, because of the slope of the profile, the abutment system exerts a restoring torque over a small angular range around the neutral position. From the angular position where the mobile stop enters the shape of the slope of the profile, a torque is exerted by the thrust of the mobile stop on the slope.

In particular, when the arms bring the disc back to an approximate position close to the neutral position, the locking system exerts an additional restoring force when the pusher begins to encounter the downward slope of the profile, which calls the platter to come exactly into position. neutral. In other words, when the arms and the spring system bring the platter to a position close to the neutral position, the stop system attracts the disc by an additional effort which tends to bring it exactly into the neutral position. The locking mechanism therefore exercises a function of defining the neutral position, but also a function of attraction towards the neutral position in a certain angular sector, which completes the work of the spring arms.

The shape of the profile, the diameter of the pusher can be chosen to create an appeal effect on a more or less wide angular sector. The spring force of the plunger can be chosen to create a more or less strong return or locking force.

We therefore ensure that the disc 42 is locked in the neutral position with great precision and above all with great repeatability, while having a control that does not require excessively strong return springs, and therefore remains flexible over its entire travel.

Alternatively, the recall mechanism 4 described above can also take other forms. For example, in relation to Figures 6a and 6b, it may comprise a two-arm spring 44', 45', of the clothespin spring type 41'.

This clothes peg spring is wound on the output shaft 6 and the two arms 44', 45' are arranged on either side of a lever 62. As for the return mechanism described above, a disk 42 'is arranged around the shaft outlet 6 below the clothespin spring 41', this disc 42' comprises a profile 52' in which the stop 51 of the locking mechanism 5 is capable of being inserted to lock the tray in neutral position. The 52' profile here has the shape of a V-notch on an angular sector with an angular amplitude of 3°. The clothespin spring 41' is forced to rest by a square piece 46' placed under the lever 62. During rotation, at least one of the ends of the spring bears against the square piece 46'. On this assembly, the neutral position is defined when the two ends of the spring bear substantially both on the angled piece 46', which defines the neutral position, and on the lever 62. If it is desired that only the mechanism lock defines the neutral point, it is possible to leave a certain clearance between the ends of the spring and the angled piece 46', for example a clearance corresponding to an angular range of 0.5.°. Alternatively, this assembly can be used without play.

It should be noted that depending on the load of the hydraulic machine, i.e. the pressure it delivers, the return to neutral position requires too great an effort in relation to the return spring. On the assembly with the clothespin spring, the return spring is therefore unable to return until it touches the lower bracket which makes the stop in the neutral position.

In a complementary manner and in relation to FIGS. 7 and 8, the hydraulic machine 1 comprises a neutral position sensor C0 comprising rod 56 whose contact with the locking system (stop and spring) allows an electrical unit 58 of the sensor to deliver an electric signal as long as the mobile stop 51 is not in the profile of the disc 42. The example illustrated in FIG. 8 shows an extension 57 which transmits the movement of the mobile stop 51 to the rod 56 of the sensor. Contact can be direct or reverse. For example, the absence of contact and therefore the absence of an electrical signal characterizes the neutral position.

The sensor can contain its own spring, and ensure the function of the spring 53 of the locking mechanism 5. However, to set or adjust the restoring force of the disc, it is preferable to have an additional spring. The sensor can be contact or contactless, for example a sensor capable of seeing the movement of the mobile stop 51. part 51. The body of the extension being adjusted to slide in the spring 53, and to come into contact with the sensitive part of the sensor. This defines a form of plunger forming a stop, and able to transmit its movement to the position sensor.

The neutral position sensor C0 is advantageously fixed to the box 54 by means of fixing means 57 (nuts, bolts). It is advantageously fixed with a proximity adjustment, that is to say depression, vis-à-vis the position of the locking system

The invention is also applicable to a pump with one direction of flow and variable displacement comprising a control lever and a return spring in the neutral position and a locking mechanism 5 comprising a movable stop 51 which provides an additional return torque of the spring to return the shaft output 6 to the neutral position. This assembly can be illustrated for example on the basis of figure 6 by only considering the stroke of the lever over half of its stroke, i.e. over an angular range of 0 to 19°. The angle of action of the mobile stop is then to be considered over an angular range typically of 0 to 3°.

Claims (12)

Hydraulic machine (1) such as a variable displacement axial piston pump or motor, comprising
- a plate with variable inclination (2), comprising an axis of rotation (YY') connected to axial pistons (3), each having a variable stroke, said stroke of the axial pistons (3) depending on the inclination of the plate at variable inclination (2), the variable inclination plate (2) comprising a neutral position which corresponds to zero inclination of said variable inclination plate (2) with respect to a longitudinal axis (XX') of the hydraulic machine (1); the hydraulic machine (1) further comprising
- a return mechanism (4) comprising a return spring (4) configured to return the variable-tilt plate (2) to the neutral position as soon as no tilt is applied to the variable-tilt plate (2) ;
characterized in that the hydraulic machine also comprises a locking mechanism (5) comprising a movable stop (51) so that on return to the neutral position of the variable-tilt plate (2) by means of the return spring (4 ), the movable stop (51) is configured to lock the variable-tilt plate (2) in said neutral position. Hydraulic machine (1) according to Claim 1, in which the return mechanism (4) comprises a disc (42) connected to the variable inclination plate (2), the rotation of the disc (42) about a rotation axis ( YY') perpendicular to a longitudinal axis (XX') of the hydraulic machine (1), depending on the inclination of the variable inclination plate (2), said disc (42) also comprising a neutral position corresponding to a zero inclination of the variable inclination platform (2). Hydraulic machine (1) according to Claim 2, in which the locking mechanism (5) comprises a profile (52) formed in the disc (42), the movable stop (51) penetrating in the said profile (52) to lock the plate with variable inclination (2) in the neutral position. Hydraulic machine according to Claim 3, in which the locking mechanism (5) comprises a locking spring (53) at the end of which the movable stop (51) is arranged, the movable stop (51) penetrating into the profile (52 ) of the disc (42) being pushed by the locking spring (53) when the disc (42) returns to the neutral position. Hydraulic machine according to claim 4, comprising a casing (54) to house the locking spring (53) and the movable stop (51). Hydraulic machine according to one of Claims 2 to 5, in which the return mechanism (4) comprises two rods projecting from the disc (42) and two arms (44, 45) mounted for rotation around the axis of rotation (YY'), said arms (44, 45) being arranged on either side of the rods (43), the rotation of the disc (42) leading to a rotation of one of the two arms (44, 45) in a clockwise or counter-clockwise via one of the two rods (43), the return spring (41) being connected between the two arms (44, 45 ), the arms being configured to return the disc (43) to its neutral position when no tilt is applied to said variable tilt plate (2). Hydraulic machine according to one of the preceding claims, comprising a shaft output (6) coaxial with the axis of rotation of the variable inclination plate and an external control (62) connected to the shaft output (6) of the with variable inclination (2), the shaft output (6) making it possible to apply an inclination to the variable inclination table (2), the shaft output also comprising a neutral position corresponding to a zero inclination of the variable inclination table (2). A hydraulic machine according to claim 7 when appended to claim 2, wherein the disc (42) is connected to the external drive (62) to control displacement of the hydraulic machine. Hydraulic machine according to one of the preceding claims, with two flow directions, such that the neutral position is located in the middle of the total stroke of a control lever (6). Hydraulic machine according to one of Claims 2 to 9, such that the locking system (5) exerts an attractive torque on the disc towards the neutral position, complementary to the force of the springs, when the disc approaches the neutral position . Hydraulic machine according to one of the preceding claims, further comprising a neutral position sensor (C0) configured to deliver an electrical neutral position signal, such that the locking system (5) performs the function of a position sensor delivering a signal electrical in neutral position. Hydraulic machine according to the preceding claim dependent on claim 4, in which the neutral position sensor (C0) comprises the locking stop and the locking spring.