EP0454510B1 - Control circuit for a hydraulic double acting cylinder and spool valve for such a circuit - Google Patents

Description

The present invention is in the field of controlling hydraulic cylinders.

More specifically, the invention relates to a control circuit for a double-acting hydraulic cylinder consisting of a piston connected to an outlet rod and separating a cylinder into two chambers, the circuit comprising a source of pressurized fluid, a system distribution alternately placing one of the control chambers or chamber in communication with the source of pressurized fluid and the other controlled chamber or chamber in communication with a reservoir of low pressure fluid to control the movement of the piston of the jack.

A circuit of this type is for example functionally described in US Pat. No. 4,040,439, which more specifically relates to a hydraulic buffer circuit intended to avoid the occurrence of transient pressures of significant value.

Hydraulic cylinders are well-known components which transform the hydraulic energy they receive into mechanical energy, the latter possibly being considerable. Double-acting cylinders consist of a cylinder in which slides a piston dividing the cylinder into two chambers, the piston being connected to an outlet rod.

When it is desired that the jack provide work in one direction, in a conventional manner, a distribution system is controlled to admit fluid under pressure into one of the chambers, while the fluid contained in the other chamber is discharged into a low pressure tank, from which a high pressure pump is drawn, to allow the piston to move in the cylinder.

There may be cases where the cylinder is already subjected to an external force tending to cause the piston to move in one direction, and it is also desired that the cylinder moves in this same direction. This is for example the case where, after being maneuvered, it is desired that the cylinder return to its rest position, corresponding for example to the median position of the piston in the cylinder, and where the external force to which the cylinder is subjected is supplied by piston refocusing systems. Generally, the movement of the piston is again obtained in a conventional manner by admission of pressurized fluid into one of the chambers and evacuation of the fluid from the other chamber to the reservoir.

When the external forces are resistant, it is understandable that the connection of one of the chambers with the tank is intended not to hinder the operation of the jack. However, in the cases mentioned above where the cylinder is already stressed in the sense that it is desired that produce the movement of the piston, that is to say when the external forces are driving, the chamber which conventionally is connected to the reservoir is under pressure by the very fact of the external stress. Rejecting pressurized fluid to the tank therefore clearly constitutes a loss of energy, which can be significant depending on the installation controlled by the jack.

The object of the invention is therefore to provide in the control circuit an auxiliary circuit which recovers the outlet fluid from the jack when its pressure exceeds a predetermined value, an auxiliary circuit which is simple and reliable in design and does not cause an increase. significant cost of the actuator control circuit.

According to the invention, the control circuit comprises an auxiliary circuit for prohibiting communication between the controlled chamber and the reservoir and interrupting the communication between the control chamber and the source of pressurized fluid when the pressure of the fluid in the controlled chamber reaches a predetermined value.

According to an advantageous characteristic of the invention, the auxiliary circuit makes it possible to establish communication between the controlled chamber and the control chamber when the pressure of the fluid in the controlled chamber exceeds the predetermined value.

• la Figure 1 représente un schéma théorique d'un circuit de commande d'un vérin hydraulique à double effet de l'art antérieur,
• la Figure 2 représente un schéma théorique d'un circuit de commande d'un vérin hydraulique à double effet conforme à un mode de réalisation de l'invention,

Other characteristics and advantages of the present invention will emerge from the following description of two embodiments given by way of example, given in relation to the appended drawings in which:

• FIG. 1 represents a theoretical diagram of a control circuit of a double-acting hydraulic cylinder of the prior art,
• Figure 2 represents a theoretical diagram of a circuit of control of a double-acting hydraulic cylinder in accordance with an embodiment of the invention,

Figure 3 shows a theoretical diagram of a control circuit of a double-acting hydraulic cylinder according to a second embodiment of the invention.

FIG. 1 shows a known control circuit for a double-acting cylinder 10 divided by a piston 12 into two chambers 14 and 16, of variable volume. The piston is mounted on a rod 18. The hydraulic supply is provided by a pump 20, connected to a supply line 22 through a non-return valve 24. The supply line 22 is also connected to an accumulator of pressure 26.

The control circuit comprises, for the chamber 14, a three-way solenoid valve 28, which puts a line 30 in communication, either with the high pressure line 22, or with a reservoir 25. When the solenoid valve 28 is not energized , it puts the line 30 in communication with the reservoir 25. The control circuit likewise comprises, for the chamber 16, a three-way solenoid valve 28 ′ which puts a line 30 ′ into communication, that is to say with the high pressure line 22, either with the reservoir 25. When the solenoid valve 28 ′ is not energized, it puts the line 30 ′ in communication with the reservoir 25.

The control circuit can be controlled by a computer or a microprocessor (not shown) which controls each of the solenoid valves 28,28 ′ and the pump 20 with, for example, a servo-control of the jack in position.

Line 30 is connected, through a non-return valve 32, to line 34 supplying the chamber 14. Line 34 is also connected to the reservoir via a controlled valve 36. This valve is controlled by the pressure existing in line 30 ′, symmetrical with line 30, in the circuit corresponding to the second chamber 16 of the jack. If the solenoid valve 28 ′, symmetrical with the solenoid valve 28, which controls the pressure in the second chamber 16, is controlled, the pressure in the line 30 ′ causes the valve 36 to open and the chamber 14 to be turned on. tank. Conversely, if the solenoid valve 28 is energized, the pressure in the line 30 controls the opening of a valve 36 ′ which places the chamber 16 in the reservoir. Thus, the chambers 14 and 16 are alternately one under pressure, the other at the tank. If, however, the two solenoid valves 28,28 ′ are at rest, the two chambers 14 and 16 are kept isolated by closing the valves 36,36 ′ and the non-return valves 32,32 '. In the event that, for example, during a maneuver, the pressure drops in the high-pressure line 22, this would cause the valve 36 or 36 ′ to be closed, which would be open, and therefore automatically isolate the chambers 14 and 16, and the immobilization of the piston 12 in the position it occupied at the time when the hydraulic failure occurred.

In normal operation, for example after an operation which has brought the piston 12 to the left in FIG. 1, if it is desired to bring the piston 12 to the right, it has been seen above that it suffices to excite the solenoid valve 28 to admit pressurized fluid into the chamber 14, which will be called the control chamber, and to connect the chamber 16, which will be called the controlled chamber, to the reservoir, which indeed causes the desired movement of the piston 12 to the right . However, the rod 18 can itself also be subjected to external stresses tending to make it also move to the right. These stresses can come, for example, from steering reminder systems if the jack 10 is included in a hydraulic steering control system of a power-assisted vehicle, from rebound of suspension if the jack 10 is included in a steering system. hydraulic suspension of the vehicle, or generally of the action of the external environment on the jack. In these cases, before the command, the pressure of the fluid in the controlled chamber 16 is not that of the low-pressure reservoir 25, but rises to much higher values, in particular greater than that of the fluid in the control 14. The fact of discharging pressurized fluid to the reservoir leads to unnecessary consumption of hydraulic fluid, and obviously a loss of energy.

To remedy this situation, the invention proposes to have in the control circuit an auxiliary circuit which comes into action as soon as the pressure in the controlled chamber exceeds that of the control chamber by a certain value.

Figure 2 shows a control circuit according to the invention, in which the elements identical to those in Figure 1 have the same reference numerals.

The control circuit is supplied as before by the pump 20 connected to the supply line 22 through a non-return valve 24, the line 22 being connected to a pressure accumulator 26 and supplying the solenoid valves 28 and 28 ′ through of a dispenser 50 which will be described later.

The pipe 30 at the outlet of the solenoid valve 28 is connected to the pipe 34 for supplying the chamber 14 via a controlled valve 52. This valve 52 comprises a first chamber 54, into which the pipe 34 opens, containing a ball 56 loaded by a spring 58 towards a rest position where it prohibits communication to a second chamber 60 into which the pipe 30 opens. The second chamber 60 is delimited by a piston 62 carrying on one side a needle 64 susceptible to lift the ball 56 from its seat when the pressure in a third chamber 66 on the other side of the piston 62 causes the latter to move against the return spring 58 and the pressure prevailing in the chamber 54. The section of the piston 62 is identical to that of the seat of the ball 56. The third chamber 66 is in communication with the line 30 ′ symmetrical of the line 30 in the supply circuit of the chamber 16. It can thus be seen that the valve 52 is controlled by the pressure existing in the circuit 30 'corresponding to the second chamber 16 of the jack. This latter circuit comprises a valve 52 ′ identical to valve 52, its elements bearing the same numerical references assigned a "premium" therefore do not require a detailed description.

If, for example, it is desired that the piston of the jack moves to the left, considering FIG. 2, the pump 20 is implemented, the solenoid valve 28 ′ is energized, the solenoid valve 28 is left to stand. The pressure in line 22 is therefore transmitted through the distributor 50 and the solenoid valve 28 ′ in line 30 ′ and in the second chamber 60 '. The ball 56 'lifts under the action of this pressure which is then transmitted via the line 34' to the chamber 16 of the jack. Simultaneously, the pressure in the pipe 30 ′ is transmitted to the third chamber 66 of the valve 52, which has the effect of making move the piston 62 to the left considering Figure 2 and therefore lift the ball 56 from its seat, thus establishing communication between the first and second chambers 54 and 60, and therefore between the lines 30 and 14. The solenoid valve 28 not being excited, the pipe 30 communicates with the reservoir 25, and consequently the chamber 14 of the jack is therefore connected to the reservoir. The piston 12 can therefore move to the left.

Thus, the chambers 14 and 16 are alternately one under pressure, the other at the reservoir. If, however, the two solenoid valves 28, 28 ′ are at rest, the two chambers 14 and 16 are kept isolated by closing the valves 52 and 52 ′.

It will be noted in passing that this advantageous arrangement of the controlled valves 52 and 52 ′ makes it possible to dispense with having the non-return valves 32 and 32 ′ of FIG. 1 in the conduits 30 and 30 '. In the event that, for example, during an actuation of the jack, the pressure drops in the high pressure line 22, this would cause the valve 52 or 52 ′ to be closed which would be open and, consequently, the automatic isolation of the chambers 14 and 16 , and therefore immobilization of the piston 12 in the position it occupied when the damage in the hydraulic circuit appeared.

After the maneuver which has been described above to move the piston to the left, the return of the piston to the right will be caused symmetrically by excitation of the solenoid valve 28 and does not require a detailed description.

During this maneuver to the right, the pressure in the chamber 16 may be caused to rise for the reasons mentioned above. In this case the external force is driving. It is then that the auxiliary circuit according to the invention comes into play.

The auxiliary circuit mainly comprises the distributor 50 disposed between the high pressure line 22 and the solenoid valves 28 and 28 '. The distributor 50 consists of a drawer 100 sliding in a bore 102. This drawer has a central groove 104 between two bearing surfaces 106 and 108 cooperating in sealed manner with the bore 102 to divide it into three chambers: an end chamber 110,112 on each side of the drawer and an annular central chamber 114 defined by the central groove 104. The drawer 100 is symmetrical and is held in the rest position in the middle of the bore 102 by springs 116 and 118 of the same rigidity on each side of the drawer.

The auxiliary circuit also comprises a line 120 connecting the chamber 110 with the line 34 ′, and a line 122 connecting the chamber 112 to the line 34. The high pressure line 22 opens into the central chamber 114 through an orifice which does not is never covered by staves 106 and 108.

The bearing surface 106 cooperates with two orifices 124 and 126 so that the orifice 126 is uncovered and opens into the central chamber 114 when the drawer is in its central rest position or moved to the left, and is covered when the drawer 100 moves to the right (in Figure 2), while the orifice 124 is covered by the drawer in its central rest position or moved to the left, and uncovered and opens into the chamber 110 when the drawer is moved towards the right (in Figure 2). The two orifices 124 and 126 both communicate with a line 128 connected to the solenoid valve 28.

Similarly, the bearing surface 108 cooperates with two orifices 130 and 132 so that the orifice 130 is uncovered and opens into the central chamber 114 when the drawer is in its central rest position or moved to the right, and is covered when the drawer 100 moves to the left (in Figure 2), while the orifice 132 is covered by the drawer in its central rest position or moved to the right, and uncovered and opens into the chamber 112 when the drawer is moved to the left (in Figure 2). The two orifices 130 and 132 both communicate with a line 128 'connected to the solenoid valve 28'.

In normal operation, if it is desired for example that the piston 12 of the jack moves to the right (in FIG. 2), the pump 20 is implemented and the pressure in the line 22 is transmitted to the central chamber 114 of the distributor. 50. If for example the latter is at rest at this instant, the orifices 126 and 130 are exposed, and the fluid under pressure therefore reaches the solenoid valves 28 and 28 '. If only the solenoid valve 28 is energized, the pressure is transmitted via line 30 in the second chamber 60 of the controlled valve 52. The ball 56 lifts under the action of this pressure which is then transmitted through line 34 to the chamber 14 of the cylinder. Simultaneously, the pressure in the pipe 30 is transmitted to the third chamber 66 ′ of the valve 52 ′, which has the effect of causing the piston 62 ′ to move to the right when considering Figure 2 and therefore lifting the ball 56 ′ from its seat, thus establishing communication between the first and second chambers 54 ′ and 60 ′, and therefore between the pipes 30 ′ and 34 '. Since the solenoid valve 28 ′ is not energized, the pipe 30 ′ communicates with the reservoir 25, and consequently the chamber 16 of the jack is therefore connected to the reservoir. The piston 12 can therefore move to the right. As the chamber 16 is connected to the reservoir, the same applies to the chamber 110 of the distributor 50 via the conduit 120. On the other hand, the pressure prevailing in the chamber 14 is transmitted by the conduit 122, to the chamber 112 of the distributor 50.

The pressure imbalance on the two sides of the drawer 100 causes it to move to the left. In doing so, the range 106 continues to cover the orifice 124 and to discover the orifice 126. The solenoid valve 28 therefore continues to be supplied and the supply circuit of the chamber 14 is unchanged. The range 108 when it will cover the orifice 130 and discover the orifice 132. The pressure in the chamber 14 is therefore transmitted through the line 122 and the chamber 112 to the solenoid valve 28 ′, which is closed. We see that nothing changes in the return circuit of room 16.

On the other hand, if the pressure in the chamber 16 is high, for example because the rod 18 is pushed to the right by an external force and becomes greater than the pressure in the chamber 14, the imbalance of the pressures in the chambers 14 and 16 is transmitted to the chambers 110 and 112 on each side of the drawer 100 and causes the pressure in the chamber 110 to be greater than that prevailing in the chamber 112, the drawer 100 moves to the right in FIG. 2. In doing so, if the pressure difference is sufficient to crush the spring 118, the slide covers the orifice 126, thus interrupting the possibility of supply of pressurized fluid to the solenoid valve 28 by the source of pressurized fluid through the line 22, and discovers the orifice 124, and therefore allows the fluid in the controlled chamber 16 , under a pressure higher than that of the fluid in the control chamber 14, to be reinjected towards the solenoid valve 28 then towards the chamber 14 if the solenoid valve is energized. The pressure in the chamber 16 is transmitted to the chamber 54 ′ of the valve 52 ′, the left face of the piston 62 ′ is subjected in the chamber 66 ′ to the pressure of the chamber 14 via the line 30 and the chamber 60 of valve 52, always subjected to the pressure of chamber 14 of the jack. The section of the piston 62 'being equal to the section of the seat of the ball and the pressure in the chamber 54 ′, equal to that of the chamber 16, being slightly greater than or equal to the pressure in the chamber 66 ′, equal to that of the chamber 14, the ball 56 ′ does not lift and prohibits the communication of the chamber 16 with the reservoir 25.

It can therefore be seen that, thanks to the auxiliary circuit of the invention, when the pressure in the controlled chamber 16 becomes greater than that of the control chamber 14 with a sufficient distance, not only the communication of the controlled chamber 16 with the reservoir 25 is interrupted, but in addition, the supply of fluid to the chamber 14 by the source of fluid under high pressure is interrupted to be replaced by the supply of this chamber by the fluid of the chamber 16 under a pressure higher than that of room 14.

A significant energy saving is thus obtained, since that of the fluid in the chamber 16 which is otherwise lost in the reservoir 25 is recovered, hence a reduction in the consumption of hydraulic fluid in the actuator control circuit.

There is shown in Figure 3 a second embodiment of the auxiliary circuit according to the invention. The distributor 50 is identical to that of FIG. 2, except that the surfaces 106 and 108 of the drawer 100 each cooperate with a single port 126 and 130 respectively. The range 106 cooperates with the orifice 126 so that the orifice 126 is uncovered and opens into the chamber 114 when the drawer is in its rest position or moved to the left (Figure 3) and is covered when the drawer 100 is moved to the right. Similarly, the bearing surface 108 cooperates with the orifice 130 so that it is uncovered and opens into the cavity 114 when the drawer is in the central position or moved to the right in FIG. 3 and is covered when the drawer is moved towards left. Line 120 is connected to line 128 via a non-return valve 201, just as line 122 is connected to line 128 ′ via a non-return valve 202.

In normal operation, if the difference between the pressures in the chambers 14 and 16 of the jack, and therefore in the chambers 112 and 110 respectively, is small, the slide 100 remains in the central position and the solenoid valves 28 and 28 ′ can be supplied by the high pressure line 22 via the chamber 114. If for example, the solenoid valve 28 ′ is energized and the external force is resistant, the piston 12 of the jack moves to the left under the effect of the increase in pressure in the chamber 16 as described above, which increase in pressure is also transmitted to the chamber 110 of the distributor 50. The slide 100 therefore moves to the right, the bearing 106 then covers the orifice 126, while the orifice 130 remains uncovered and allows the supply of the solenoid valve 28 '. The non-return valve 202 prevents the communication of pressurized fluid to the chamber 112 of the distributor and to the chamber 14 of the jack.

When the solenoid valve 28 is excited to move the piston of the jack to the right while an external engine force is applied to the piston rod, we have seen that then the pressure in chamber 16 is higher than the pressure in chamber 14. The pressure in chamber 110 is then greater than the pressure in chamber 112. The slide 100 moves to the right and the bearing 106 covers the orifice 126, thus interrupting the supply of the solenoid valve 28 in pressurized fluid from line 22. On the other hand, the solenoid valve 28, and therefore the chamber 14, can be supplied by the line 120 and the non-return valve 201. Thus, as long as the pressure in the chamber 16 of the jack is greater than the pressure in the chamber 14, the latter can be supplied with pressurized fluid from the chamber 16 and no longer from the high pressure line 22, the valve 52 ′ remaining closed as described above.

A non-return valve 203 can be provided on the high pressure line 22 to prevent a sudden rise in pressure in the chamber 16 from being transmitted, via the lines 120 and 128, the orifice 126 and the chamber 114, to the hydraulic supply device 20,26, before the drawer 100 has moved. The hydraulic blocking of the jack is then ensured. Likewise, the non-return valve 203 ensures the hydraulic blocking of the jack in the case where the high pressure supply system 20-26 is at rest, or is broken down.

A control circuit has therefore been produced in accordance with the invention for a double-acting cylinder of simple and reliable design and without significant additional cost. Indeed, in all cases, the movement of the piston of the jack is controlled by the excitation of a single solenoid valve 28 or 28 '. The distributor 50 is sensitive to the difference in pressures in the chambers 14 and 16 of the jack, that is to say that it detects the direction of the external forces to which the rod of the jack is subjected. Depending on the direction detected, it will allow either the supply of pressurized fluid to the control chamber by the high pressure hydraulic supply device 20,26 if the external forces are resistant or weak, or the recovery of the pressurized fluid in the controlled chamber to supply it to the control chamber if the external forces are driving. An energy recovery is therefore obtained which would otherwise be lost in the low pressure tank 25, and a reduction in the consumption of hydraulic fluid of the control circuit.

Such a device will find application in all active hydraulic systems, that is to say irreversible systems which use a clean energy source, to transform them into reactive systems according to the external conditions to which they are subjected.

Claims (7)

1. Control circuit for a hydraulic double-acting jack (10), consisting of a piston (12) connected to an output rod (18) and separating a cylinder into two chambers (14, 16), comprising a source of fluid under pressure (20, 26), a distribution system (28, 28′, 52, 52′) alternately putting one of the chambers, or control chamber, in communication with the source of fluid under pressure (20, 26) and the other chamber, or controlled chamber, in communication with a reservoir of fluid under low pressure (25), in order to control the movement of the piston (12) of the jack (10), characterized in that it comprises an auxiliary circuit (50, 120, 122) for preventing communication between the controlled chamber and the reservoir (25) and for interrupting communication between the control chamber and the source of fluid under pressure (20, 26) when the pressure of the fluid in the controlled chamber reaches a predetermined value.
2. Circuit according to Claim 1, characterized in that the auxiliary circuit (50, 120, 122) establishes communication between the controlled chamber and the control chamber when the pressure of the fluid in the controlled chamber exceeds a predetermined value.
3. Circuit according to Claim 2, characterized in that the predetermined value of the pressure of the fluid in the controlled chamber is a function of the value of the pressure of the fluid in the control chamber.
4. Circuit according to Claim 3, characterized in that the predetermined value of the pressure of the fluid in the controlled chamber is equal to the pressure of the fluid in the control chamber, plus the pressure necessary for overcoming the force exerted by a return spring (116, 118) of a slide (100) distributor (50).
5. Circuit according to Claim 1, characterized in that the auxiliary circuit (50, 120, 122) comprises a slide (100) distributor (50) arranged between the source of fluid under pressure (20, 26) and the distribution system (28, 28′, 52, 52′).
6. Circuit according to Claim 5, characterized in that the slide (100) of the distributor (50) defines in the latter a central chamber (114) and two end chambers (110, 112).
7. Circuit according to Claim 6, characterized in that the end chambers (110, 112) of the distributor (50) are connected by means of pipes (120, 122) to the chambers (16, 14) of the jack (10).

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