FR2645215A2 - LOAD INDEPENDENT CONTROL DEVICE FOR HYDRAULIC USER DEVICES - Google Patents

Abstract

A control device comprises a control unit and a multi-way valve, which can be controlled independently of the control unit. A common control line 94 is capable of being supplied by the pressure of the pump and is connected by a non-return valve 100, 96 to the control line 40 passing the charge pressure XL S, which is connected to the control side d a pressure limiting valve 60 for the circulation pressure of the pump.

Description

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  The invention relates to a load independent control device for hydraulic user devices, with a control unit and a multi-way valve, which can be controlled independently of the user. control unit which has a closed position and a passage position, in which it connects to the reservoir a control line allowing the charge pressure to pass, the control unit being produced in the form of a servo-valve which is capable of being connected, together with the multi-way valve, from the same control source, via a common control line, and the multi-way valve being controlled in such a way that it is switched from the position of

  switch to the closed position, before the servo

  valve is energized, according to patent application.

  There are known independent load control devices of this type, for hydraulic user devices, with a control unit for the user and a multi-way valve, which can be controlled independently of the control unit and which has a closed position and a control position, in which it connects to the reservoir the control line letting the pressure of the load pass. Such a control device is for example described in the document DE 25 14 624 Ai. In the known case, starting from its neutral position, the control unit is placed, by means of a separate external actuating member, in one of its working positions, in which at least one user is connected to the pump via user lines. Due to the pressure that

  is then established in a sensor line, the valve to.

  Multiple track is moved to a closed position, in which it closes the passage between a flow pipe and a return pipe. Pressure regulation in user lines

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  is carried out by means of a pressure adjustment valve

  which is arranged downstream of the control unit.

  The fact that in this case the multi-way valve can then assume its closed position when the control unit and the pressure control valve have assumed the volume flow control function, this results in reaction behavior relatively inert of the control device. This can in particular have harmful effects when switching a hydraulic system fitted with the control device described above, passing from what is called reserve operation to operation with load measurement, in which it is necessary that a hydraulic flow optimally determined for the request of the working group is made available as quickly as possible. These harmful effects occurring because an insufficient supply of hydraulic power units can occur in the initial phase

volume flow control.

  In order to counter these drawbacks, it is

  proposed in main patent application No. 88.12093.

  a control device according to the preamble of claim 1. With this control device, it is ensured that the switching indicated above of the hydraulic system from the reserve state to the state with load measurement, has already been carried out before that the volume flow adjustment function is provided for the hydraulic user. As a result of the hydraulic actuation, both of the multi-way valve and also of the control unit produced in the form of a servo valve, it is also possible to actuate these two elements of the control device at the price low expenditure and simultaneously ensure that the pump provides a sufficiently high pressure when operating the volume flow control, even if the pump has previously been operated at a very low energy level, for example in the

reserve operation.

  The present invention aims to adapt a control device of this type, independent of the

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  load, on hydraulic systems which are equipped with a constant flow pump, that is to say a constant discharge pump. In systems of this kind, with volume flow adjustment, with a constant flow pump, to obtain a reduction in power losses in the neutral position of at least one of the users and in the event of discharge of the supply line. load information, an attempt is made to obtain as low a circulation pressure as possible. In the case where an internal supply of control oil has been constituted, it can be assumed that the circulation pressure of the pump which it is desired to obtain is situated clearly below the pressure

required.

  This is why the invention aims to improve an independent load control device for hydraulic users, according to the main patent (patent application No. 88.12093, so that it can be used with a technical circuit complexity as low as possible, even for a constant flow pump hydraulic system, the pump circulation pressure of which is below the pressure

  when the user is in neutral position.

  This problem is resolved by the fact that the common command line is likely to be supplied by the

  pump pressure and is connected by a check valve

  return to the control line allowing the charge pressure to pass, which is connected to the control side of a pressure limiting valve used for the circulation pressure

of the pump.

  According to the invention, the common control pressure line, which can be supplied by the pressure of the pump via a pressure valve with preliminary control, is connected to the control line allowing the passage of the charge pressure, via a non-return valve, this control line allowing the charge pressure to pass, being connected to the control side of a pressure limiting valve

  pressure used for the circulation pressure of the pump.

  The circulation pressure of the pump can

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  way to be lowered, in the neutral position of the user, far below the pressure level of the control pressure which is necessary for the performance of the switching and control functions of the control device, i.e. control unit and multi-way valve. In detail, by controlling the pre-operated pressure valve, the pump pressure can first be increased until the above-mentioned switching and control function of the control device can begin. . The circulation losses can be adjusted by the prestressing of the control spring of the pressure limiting valve, this prestressing force being able to be suitably chosen as low as

possible.

  A further reduction in the technical complexity of switching is obtained by the improvement consisting, according to the invention, in that the control line allowing the charge pressure to pass is supplied, by means of a throttle through a line allowing the passage pump pressure. By means of this technical measure concerning switching, on the one hand, an immediate reaction of the pressure limiting valve is ensured after attack of the pressure valve with preliminary control. Simultaneously, the throttle can be advantageously requested, in conjunction with the other throttle, in order to produce the differential pressure between pump pressure and information pressure of the

  charge which is necessary to adjust the volume flow.

  The control device is constructed in such a way that it can be operated in a simple manner and provide reliable operation. A particularly simple hydraulic actuation is obtained by the fact that, according to another characteristic of the invention, the control source is a source of control pressure and that the servo valve and the multi-way valve are each hydraulically switchable by via a common control pressure line, the multi-way valve being switchable from its passage position

2645215

  to its closed position in the case of a lower control pressure than to move the servo valve from its initial position to a working position. According to this improvement. only a single, common control pressure line is necessary in order to actuate the servo valve and, temporally separate from it, that is to say at an earlier time, the multi-way valve. The technical complexity of the device can be further reduced if, according to another characteristic of the invention, the servo valve control piston and the multi-way valve control piston are arranged in a common axis of movement and are capable of '' be forcibly connected to each other at their ends facing one another, by means of a mechanical coupling member. There is thus a coupling of the respective control piston of the control valve on the one hand and the multi-way valve on the other hand. By means of a coupling member, these two control pistons are preferably located in a thrust force chain, so that the return spring of the multi-way valve can be acted on, with a return spring acting in the opposite direction to the servo valve, in order to maintain the latter in the median position mechanically centered, which is possible, according to another characteristic of the invention, by the fact that the ends of the control pistons which are turned the one towards the other is each time biased by a spring, the two springs returning the servo valve to its initial position when the control pressure acting in the common control pressure line, which biases via the member adjustment the ends of the control pistons which are turned towards each other, becomes less than

a predetermined limit value.

  According to another characteristic of the invention, provision can be made for the piston slide of the multi-way valve to cooperate with a release piston for a non-return valve, integrated in the pipe.

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  user, in order to unlock the latter when moving out of the passage position. This embodiment allows the adaptation of the independent load control device to hydraulic systems whose user line leading to the work group must be sealed at times, as is for example necessary in the case hydraulic lifters for safety reasons. According to this improvement, the piston slide of the multi-way valve is urged to mechanically release

  time controlled way the non-return valve.

  According to another characteristic of the invention, the pressure valve which is the subject of a preliminary control is formed by an electrically controlled pressure adjustment valve. The energy level of the pressure regulating valve control signal is independent of the circulation pressure of the pump, which can in this way be maintained at an optimized base value. Other purposes, advantages and features of

  the invention will appear on reading the description

  following of an embodiment of the invention, made without limitation and with reference to the accompanying drawing. The drawing represents a block diagram of a hydraulic circuit supplied by a constant flow pump in which is integrated a control device independent of

  the load, for a hydraulic user.

  In the figure, 10 denotes a constant flow pump, for example produced in the form of a gear pump, which feeds, via a pump line P, a user line A, C in hydraulic fluid. Line supply

  - of user A is carried out via a servo -

  valve 20 of type 4/3, which is represented in the figure in its neutral centered position D, in which it closes a connection of reservoir T. The servo-valve 20 of type 4/3 forms part of a valve unit 30 indicated by dotted lines, which aims to ensure an intermittent supply of the user

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  and to fulfill for this purpose a switching function and a volume flow adjustment function adapted to the

  user fluid consumption.

  For this purpose, there is a charge information line, that is to say a control line 40 allowing the charge pressure Xr. To pass, which is connected to the user line A via d a first control line part 42, in which a throttle 44 is arranged, and which is connected to a pump bypass line 50, by means of another control line part

  46, in which a second constriction 48 is arranged.

  The pump bypass line 50 can be discharged to the tank 62, via a pressure limiting valve 60, the pump circulation pressure being adjustable during the reserve operation of the hydraulic circuit, by the force of a valve spring 64. The prestressing force of the valve spring 64 is chosen to be as low as possible with regard to minimizing circulation losses, so that the pressure limiting valve 60 is already placed in passage position when there are very low pressures in the pump bypass line 50 and in a control line 66 bypassing. The pressure in the load information line 40 acts via another control bypass line 68 on the sides of the valve spring 64. In the initial position of the control device which is shown, this pressure is located at a minimum pressure level, due to the fact that a connection to the reservoir 62 is established in the switching position I via a pipe branch 72 and a discharge pipe 74, via a valve

multi-track 70 type 2/2.

  80 has been designated an electrically operated pressure relief valve, which is preferably in the form of a pressure control valve. The pressure valve 80 is controlled by an electrical control line 82 which

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  acts on an adjustment member 84. The pressure valve 80 has an inlet connection 86 supplied by the pump line P, an exhaust connection 88 connected to the discharge line 74 and an outlet connection 90 which leads the common control signal, for the servo valve 20 on the one hand and for the multi-way valve on the other hand. The line passing the control signal is designated by 94, the return line passing the control pressure on the side of the valve 80 which is opposite to the regulating member 84 is

designated by 92.

  In the neutral position of the control device which is shown, the control current i is located at such a level that the control pressure in the control line 94 is located below a reaction threshold for the valves 20, respectively 70. The pump 10 works in this operating state in what is called the reserve operation, in which the circulation pressure of the pump is maintained at a

minimum.

  If users have to be connected, the volume flow of the supply must be adjusted, the control current i of the pressure control valve 80 is increased, so that the passage between the connection

  inlet 86 and outlet connection 90 is enlarged.

  Via a connection line 96, a connection is made from the control pressure line 94 to the load information line 40. In this connection line 96 is integrated a non-return valve 100

  opening to the load information line 40.

  If thus the passage between 86 and 90 is controlled under the action of the control current i, the hydraulic fluid is supplied by the connection line 96 to the control bypass line 68 of the pressure limiting valve 60. So that this hydraulic fluid does not immediately escape to the reservoir 62 via the load information line 40 and the bypass line 72, a throttle 76 is provided in the latter. This is why when the regulating valve is energized

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  pressure 80, a pressure is established which results in the increase in the pressure in the pump line P. Due to the increase in the pump pressure in the pump line P, the pressure prevailing in the line control pressure 94 common is increased until the switching and control function of the valve unit 30 can begin. As seen in the figure, the pressure in the control pressure line 94 is supplied to an adjustment member 78 of the multi-way valve 70 and simultaneously to an adjustment member 22 of the servo-valve 20. The surface control member 78 is chosen larger than the control area of the control member 22. For this reason, when establishing the pressure in the control pressure line 94, the valve to multiple lane is first moved from the passage position I to a closed position K in which the connection of the load information line 40 going to the tank 62 is closed. The movement takes place against the force of a return spring 79 which simultaneously ensures, in cooperation with a mechanical coupling member 24 located between the piston drawers of the valves 20 and 70, that the piston drawer of the servo valve 20 is mechanically centered in neutral position D, against the force of another return spring 26. The piston slide of valves 20 and 70 are thus placed in a chain of thrust forces by means of the mechanical coupling member 24. The face of the piston slide of the servo-valve 20 which is biased by the return spring 26 is connected to the reservoir 62 via

  another control line 28.

  The volume flow control function of the control device is ensured after closing the connection to the reservoir of the load information line 40, that is to say after moving the piston slide of the multi-valve valve 70 in switching position K. The constant differential pressure which is necessary for this adjustment function, between the pressure prevailing in the pump line P and the pressure prevailing

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  in the user line A, is maintained by means of the two throttles 48 and 44. In order for the servo-valve to be able to assume the working position with a view to adjusting the volume flow rate, the pressure in the control pressure line 94 by appropriate control of the pressure control valve 80, until the force acting on the piston slide of the servo-valve 20, via the control member 22 , maintain the balance with the force of the spring 26. At this instant, the mechanical coupling between the piston slide valve 20 and 70 is already removed by

  through the mechanical coupling member 24.

  Now, by reducing the control pressure in the control pressure line 94, the servo valve 20 can assume the working position F shown on the left of the figure, due to the preponderant force of the spring 26. The control pressure, which is reduced, is chosen so that the multi-way valve 70 is maintained in the closed position K by the effect of the control pressure on the regulating member 78. By a corresponding increase in pressure in the control pressure line 94, the servo valve 20 can be placed in the other working position E, which is shown on the right in the figure. By maintaining a separation of the switching and volume flow control functions of the control device, it is thus possible to control the valves 70 and 20 using a single control signal, i.e. d '' a common control pressure line. The reciprocal determination of the forces of the springs and of the active surfaces of the adjusting members 22, respectively 78 is preferably carried out in such a way that in the two working positions E and F, of the servo-valve 20, there is a range control pressure of identical size. Thus, for example, for an overall control pressure range between 0 and 20 bar, the determination can be such that for example the multi-way valve 70 takes the closing position K at 5 bar. It is set at 12.5 bar the control pressure for which the valve piston of il 2645215 the servo valve 20 is maintained in neutral position D. A range of control pressure is thus reserved between 5 bar and 12.5 bar for regulating the volume flow in the working position E of the servo-valve 20, while the control pressure range between 12.5 bar and 20

  bar is provided for working position F della servo-

valve 20.

  In the exemplary embodiment which is represented, the valve unit composed of the servo valve 20 and the multi-way valve 70 of the 2/2 type is additionally coupled to a non-return valve 110 capable of being unlocked. The piston slide of the multi-way valve 70 cooperates with a plunger 112, by means of which, when the piston slide of the multi-way valve 70 is moved, it can be lifted from

  its valve seat the ball of the non-return valve.

  The user conduit parts A and C are then interconnected. In the reserve operation, a hermetic closure of the user line C, which can in this case lead to a hydraulic cylinder, takes place by means of the non-return valve 110, closure during which it must be assured that it does

suffers from no leakage under load.

  It is clear from the above that the load-dependent control device, for hydraulic users, is able to ensure, for a low complexity in switching technique, to carry out a switching between a reserve operation with a pressure minimized pump circulation and an operating mode in which users are supplied with volume flow adjustment. The connection of the common control line for the servo valve on the one hand and the multi-way valve on the other hand, makes it possible to keep the pump circulation pressure in the reserve operation lower than the control pressure necessary for actuation of the multi-way valve. The volume flow adjustment function is carried out by varying the control signal of a pressure control valve

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  preliminary. Unlike the embodiment -

  described above, it is then possible to work with a hydraulic control signal instead of electric, which

  acts on the pressure adjustment valve.

  The invention thus creates a load independent control device for hydraulic user devices, equipped with a control unit and a multi-way valve, which can be controlled independently of the control unit. The multi-way valve has a closed position and a passage position, in which it connects to the reservoir a control line allowing the charge pressure to pass. The control unit is designed as a servo valve which can be connected, together with the multi-way valve, from the same control source. In order to provide the transition from reserve operation to flow control operation, the multi-valve is constructed in such a way that it is switched from the shift position to the closed position before the servo valve is energized. To minimize the loss of pump circulation during the reserve operation of a constant flow pump, the common control line can be supplied by the pressure of the pump, via a pressure valve with control preliminary, and is connected to the control line allowing the charge pressure to pass, which is connected to the control side of a pressure limiting valve used for the circulation pressure

of the pump.

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Claims (9)

  1.Load independent control device for hydraulic user devices, with a control unit and a multi-way valve, which can be controlled independently of the control unit and which has a closed position and a position passage, in which it connects to the reservoir a control line allowing the charge pressure to pass, the control unit being produced in the form of a servo-valve which can be connected, jointly with the track valve multiple, from the same control source, via a common control line, and the multi-way valve being controlled such that it is switched, from the shift position to the closed position, before that the servo valve is energized, according to the main patent application, characterized in that the common control line (94) is capable of being supplied by the pres pump and is connected by a non-return valve (100,96) to the control line (40) allowing the charge pressure (Xs) to pass, which is connected to the control side of a pressure limiting valve   (60) used for the circulation pressure of the pump.   2. Control device according to claim 1, characterized in that the control line (40) allowing the charge pressure to pass is supplied, via a throttle (48) by a conduit (P.)   letting the pump pressure pass.   3. Control device according to claim 1 or 2, characterized in that the control line (40) allowing the charge pressure to pass (XLsY is connected via a throttle (44) to a line user (A).   4.Order according to one of the   claims 1 to 3, characterized in that the source of   control is a source of control pressure and the servo valve (20) and the multi-way valve (70) are each hydraulically switchable via a control pressure line (94) 14 -2645215   common, the multi-way valve (70) being switchable from its passage position (I) to its closing position (K) in the case of a lower control pressure than for passing the servo valve (20) from its initial position (D) to a working position (E, F). 5. Control device according to one of   Claims 1 to 4, characterized in that the piston   control of the servo valve (20) and the control piston of the multi-way valve (70) are arranged in a common axis of movement and are capable of being forcibly connected to each other at their ends turned towards each other by means of a mechanical coupling member (24). 6. Control device according to claim 5, characterized in that the ends of the control pistons which are turned towards each other are each time biased by a spring (26,79), the two springs recalling the servo valve (20) in its initial position (D) when the control pressure acting in the common control pressure line (94), which biases the ends of the pistons via the adjusting member (22,78) facing each other, becomes less than one predetermined limit value.   7.Order according to one of the   Claims 1 to 6, characterized in that the pressure relief valve   pressure which is the subject of a preliminary order is formed by a pressure regulating valve (80) to online order.   8.Order according to one of the   Claims 5 to 7, characterized in that the drawer   piston of the multi-way valve (70) cooperates with a release piston (112) for a non-return valve (110), integrated in the user line (A, C), in order to release the latter when moving out of the passage position (I).   9.Order according to one of the   Claims 1 to 8, characterized in that it is arranged 2645215   in a hydraulic system powered by a flow pump constant (10).