Abstract:
A valve device for a hydraulic circuit ( 10 ) divides the incoming volume flow into at least two pre-determined partial flows for supplying hydraulic consumers (V 1 , V 2 ) of the circuit ( 10 ) and has at least one pressure balance ( 16 ) and at least one orifice. Since the orifice is embodied as a variable orifice ( 32 ) controllable by a proportional magnet ( 34 ), the opening area of the orifice varies. A flow regulator is then realized and can switch the regulated volume flow and/or proportionally adjust the regulated volume flow in a defined manner.

Description:
FIELD OF THE INVENTION 
     The invention relates to a valve device for a hydraulic circuit which divides the incoming volumetric flow into at least two predetermined partial flows for the supply of hydraulic consumers of the circuit. The valve device has at least one pressure compensator and at least one orifice. 
     BACKGROUND OF THE INVENTION 
     These valve devices are also technically referred to as flow regulators or pressure-compensated flow control valves and allow the incoming volumetric flow to be divided into a regulated and an unregulated residual volumetric flow according to the throttle principle. Ultimately, they are throttle valves with an adjustable orifice (throttle) in which the flow rate remains constant, regardless of changing load pressures, by a combination with a respective pressure compensator. At the same time, the pressure compensator clears a changing cross section that is inversely proportional to the load pressure so that consequently the flow rate remains essentially constant, regardless of the load pressure. 
     Such a valve device is shown, for example, in DE 10 2006 004 264 A1, relating to a stabilization means or mechanism for a multi-axle vehicle with one hydraulic control circuit each provided for the front and the rear axles. Because in the known solution the incoming volumetric flow of at least one of the axles is controlled by the pressure-compensated flow control valve, and because at a higher capacity of the supply unit, the accompanying excess of volumetric flow can be relayed to at least one of the other axles which is unregulated, in case of an excess of the volumetric flow, the flow is kept constant on the axle controlled by the flow control valve. The excess portion travels to the respective unregulated axle. Among other things, this system causes the desired roll stabilization on the unregulated axle in terms of trigger behavior to be designed to be more highly dynamic. Under actual driving conditions, this operation confers distinct advantages compared to otherwise conventional divisions of amounts with percentage volumetric ratios that are stipulated in a defined manner for the respective partial flow amounts for the supply of the hydraulic consumers in the form of the control circuit for the indicated front and rear axles. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a valve device, regardless of how high the power demand is for the respective partial flow of the hydraulic circuit, that supplies the necessary amount of fluid the consumer needs to ensure the power demand for a safety-relevant system of the hydraulic circuit. 
     This object is basically achieved by a valve device having an orifice outfitted as a variable orifice triggerable by a proportional magnet. Its opening area then can be changed to implement a type of flow regulator switching and/or proportionally setting the controlled volumetric flow in a defined manner. This function is required, in particular, when at least two hydraulic systems are operated with hydraulic consumers that are different in terms of power demand by only one hydraulic pump as a pressure supply source. Their power demand can be at least in part very different. At the same time, one of the two systems comprises the safety-relevant system which must be supplied under all conditions. 
     Due to the variable orifice implemented by triggering with a proportional magnet, a proportionally variable opening area arises and is made such that for all trigger states a defined passage area remains opened. In any case, the flow through the orifice meets the power demand for the safety-relevant system. Even in the case of a fault, for example, the power for the proportional magnet as a trigger fails, a maximally regulated volumetric flow is supplied to the safety-relevant system and its operation is guaranteed. 
     The valve device according to the invention designed as a variable pressure-compensated flow control valve, is especially advantageous when used in vehicles of any type (passenger cars, busses, trucks, roadworthy machinery, etc.) where a hydraulic pump driven by the vehicle engine as a pressure supply source supplies both the servo-assisted steering and the roll stabilization for the axles of the vehicles. 
     For the associated power demands on the individual systems, this ability means the following based on practical circumstances. 
     When the vehicle is driving at speed, only very little steering deflection (speed) is necessary on the part of the operator, and little servo assistance is necessary. In this case, the volumetric flow in the steering circuit can be ramped down to a minimum value, while at the same time greater roll moments must be corrected. Conversely, when parking, for example, a large steering deflection (speed) with correspondingly high servo assistance is necessary, and roll compensation is less important when parking. For both system requirements, there should never be too little volumetric flow for the steering since otherwise the servo assistance for the steering deflection will fail. Modern vehicles are very difficult to manage with normal expenditure of force without the pertinent servo assistance. With the invention, for this application it is always ensured that steering does not receive too little volumetric flow relative to the indicated servo assistance. 
     It must also be ensured, in case of a fault, that, for a minimally regulated volumetric flow, servo assistance benefits the steering system. Furthermore, when the power fails, as another possible fault source for the proportional magnet, the magnet should then set the largest opening area on the orifice for the largest regulated volumetric flow available for steering. 
     Regardless of the described application, the valve device according to the invention can always be used wherever different partial flows of a hydraulic circuit must be set with connected hydraulic consumers having different power requirements and/or which, especially for safety reasons, are not to be supplied beforehand. 
     In this application, the expression “orifices” is also intended to describe and to cover the use of “throttles.” This usage also applies to the term “metering orifice” used technically below. To the extent that the expression “orifice,” “variable orifice,” “free orifice cross sections,” etc. are used, these terms generally include the terms “throttle,” “variable throttle,” “free throttle cross-sectional area,” etc. 
     In one especially preferred embodiment of the valve device according to the invention, at least the pressure compensator and the respectively used orifices and proportional magnet are components of a common valve block. This common valve block can also be retrofitted on site onto existing vehicle systems as a modular unit. 
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings which form a part of this disclosure and which are schematic and not to scale: 
         FIG. 1  is a hydraulic circuit diagram of a valve device according to a first exemplary embodiment of the invention; 
         FIG. 2  is a side elevational view in section, without the crosshatching, of the proportional magnet used in the valve device of  FIG. 1  with a connected valve housing for implementation of a variable orifice and a constant orifice; 
         FIG. 3  is a side elevational view in section, without the crosshatching, of a valve device according to a second exemplary embodiment of the present invention with a downstream pressure compensator in addition to a damping means; 
         FIG. 4  is a side elevational view in section, without the crosshatching, of the pressure compensator of  FIG. 3 , but without additional vibration damping; and 
         FIG. 5  is a perspective top view of the valve device of  FIG. 3  as a whole. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The valve device shown in  FIG. 1  as a hydraulic circuit diagram is used to supply a hydraulic circuit  10  with fluid. The hydraulic circuit  10  is supplied with fluid by a pressure supply source  12 . The pressure supply source  12  has a conventional hydraulic pump driven by an engine, for example the internal combustion engine of a motor vehicle. The volumetric fluid flow flowing in via the line  14  from the pressure supply source  12  is divided at the branch site X, one partial flow leading to a hydraulic consumer V 1  (not detailed) and the other partial flow to a hydraulic consumer V 2 . In the specific exemplary embodiment, the consumer V 1  is designed to be formed from the servo-assisted steering system, and the consumer V 2  forms a roll stabilization system for the axles of the vehicle (not shown). 
     The valve device has a conventional pressure compensator  16  shown in the non-regulating basic position and forming a 4/3-way proportional valve. The pressure compensator spool  20 , guided in the pressure compensator housing  13 , is exposed on its opposite sides to control pressures ST 1  and ST 2  acting in opposite directions. As illustrated in  FIG. 1 , the pressure compensator spool  20  has its right side supported on an adjusting spring  22  in the manner of a compression spring. One control pressure ST 2  is connected to the branch site X, which in turn is connected to the fluid inlet E 2  of the pressure compensator  16  to carry fluid via the line  24 . The other control pressure ST 1  is tapped upstream of the inlet E 1  of the pressure compensator  16  in the supplying line  26 . Supplying line  26  leads to branch site X. On the opposite side of pressure compensator  16 , fluid outlets A 1 , A 2  are connected by lines  28 ,  30  to the first hydraulic consumer V 1  and second consumer V 2 . 
     Beginning at the branch site X, a variable orifice  32  is connected in the line  26  and can be triggered by proportional magnet  34 , i.e., the free opening area of the variable orifice  32  can be dictated by the proportional magnet  34 . Parallel to the variable orifice  32  another orifice  36  is connected as a constant orifice, i.e., the free opening area of the other orifice  36  is constant. The parallel arrangement for the other orifice  36  arises from being connected in a line  38  which, viewed in the fluid direction, discharges upstream of the variable orifice  32  into the line  14  and downstream of the variable orifice  32  into the line  26 , specifically, at the connecting site  40 . As shown in  FIG. 1 , the line  38  discharges into the branch site X of the line  14 . To obtain the control pressure ST 1 , the pressure compensator  16  is connected by the control line, indicated by the broken line, to the line  26  between the connecting site  40  and the fluid inlet E 1 . The fluid pressure prevailing at E 1  is then present as the control pressure ST 1 , and the control pressure ST 2  is the fluid pressure on the fluid inlet side E 2  of the pressure compensator  16 . This control line for the control pressure ST 2  is also shown in  FIG. 1  by the broken line. 
     To trigger the whole system, the coil winding  42  of the proportional magnet  34  is connected to a computer unit (not detailed) by an electrical plug contact  44  (cf.  FIG. 2 ). For example, depending on the driving speed of the vehicle, the computer unit dictates the trigger values of the current for the proportional magnet  34 . Overall, with the solution as shown in  FIG. 1 , a valve device in the manner of a flow regulator can proportionally set in a defined manner the regulated partial volumetric flow to the consumer to be regulated. This function is required if, proceeding from the pressure supply source  12 , for example two hydraulic systems with a consumer V 1  (servo-assisted steering system) and a consumer V 2  (roll stabilization system) are operated whose power demands to some extent are distinctly different. At the same time, one of the two systems, specifically the servo-assisted steering system, is a safety-relevant vehicle system and must be supplied with the volumetric flow necessary for safe operation under all conditions. The valve representation as depicted in  FIG. 2  shows the energized and therefore connected state for the valve device, yielding a minimum volumetric flow. 
     Then, in particular, the following applies to the power requirements of the two systems. 
     When the vehicle is driving at speed, only very little steering deflection (speed) is necessary and little servo assistance is required. In this case, the regulated volumetric flow in the steering circuit can be ramped down for the consumer V 1  to a minimum value, induced by the proportional magnet  34  triggerable depending on the speed. In turn, larger roll moments must be corrected, and the consumer V 2  acquires a larger residual volumetric flow from the branch site X and the pressure compensator  16 . By contrast, when parking, for example, a large steering deflection (speed) with high servo assistance is necessary, so that the hydraulic consumer V 1  requires a large partial volumetric flow. Roll compensation is conversely less relevant during parking, so that the fluid volumetric flow required in this respect can be reduced. 
     For both described states, however, the steering system, i.e., the hydraulic consumer V 1 , should never receive too little volumetric flow. This requirement is achieved with the valve device shown in  FIG. 1 . In the case of a fault, i.e., for example when the power fails, the proportional magnet  34  is no longer energized, and the variable orifice  32  will assume its largest opening cross section, i.e., have the largest opening area. The largest regulated volumetric flow will then continue to travel to the servo-assisted steering system (consumer V 1 ). 
     In the valve device according to the invention, the arrangement of the proportional magnet  34  with a variable orifice  32  and constant orifice  36  is detailed below. As already described, the proportional magnet  34  has a coil winding  42  which can be triggered via an electrical plug contact  44  by a computer unit (on-board computer), not shown. The computer unit processes the vehicle-side data, such as, for example, the vehicle speed, steering deflection, etc. In a pole tube arrangement  46  with magnetic separation  48 , an armature body  50  with an actuating rod  52  inserted on the end side is guided to be able to move lengthwise. The proportional magnet  34  is made as an attachment part. The magnet housing  54  can be fixed on third components by a flange part  56 , for example in the form of a valve block  58  as shown in  FIG. 5 . By the electrical contact or plug  44 , the coil winding  42  can be triggered by the computer unit. Depending on the vehicle speed, the computer unit relays control pulses to the coil winding  42  to advance the armature body  50  with the actuating rod  52 . The structure of these proportional magnets  34  is known so that it need not be described further. 
     The proportional magnet  34  is connected to a valve housing  60  in which a valve spool or control spool  62  is guided. The control spool  62  on its right side, as viewed in  FIG. 2 , is triggered by the actuating rod  52  and is supported with its other left free end on a support spring  64  in the manner of a compression spring supported in the valve housing  60  by a plug  66 . Spring  64  applies a permanent resetting compressive force to the control spool  62 . The control spool  62  has an annular widening  68  and has a conically widening control surface  70  on its left free face side. 
     The surface of widening  68  is used to trigger passage openings  72 ,  74 . The passage openings  72 ,  74  are made as passage bores, are arranged in succession to one another and preferably diametrically opposite one another, and extend repeatedly through the valve housing  60 . Furthermore, the passage openings  72 ,  74 , viewed in each cross-sectional row, can have different diameters and/or a different number of holes. In particular,  FIG. 2  shows a first row of bores with passage openings  72 ,  74  arranged in succession viewed in the direction of travel of the control spool  62 , with the first row of passage openings  72  being in concert with the annular widening  68  of the control spool  62  forming the control for the variable volumetric flow portion, and therefore, forming the orifice design for the variable orifice  32 . Conversely, the constant orifice  36 , located in the bypass and in a parallel connection, is formed by the passage opening  74 . The variable orifice  32  is formed by the passage opening  72 , and the constant orifice  36  is formed by the passage opening  74 . 
     Depending on the position of the control spool  62 , the spool then regulates the variable orifice  32  by the corresponding control edge between the passage opening  72  and the cylindrical constriction  78  in the control spool  62 .  FIG. 2  also illustrates that, in the event of a power failure and in the event the coil winding  42  is no longer energized, the support spring  64  is relieved and, as viewed in  FIG. 2 , shifts the control spool  62  to the right. This shifting leads to complete opening of the passage openings  72 ,  74 . Fluid passage is such that a regulated fluid supply is ensured by the connecting site  40  for the partial fluid circuit relating to the consumer V 1  in the form of the servo-assisted steering. In this way, a fail-safe circuit is achieved for the valve device according to the invention. 
     With the valve solution as shown in  FIG. 2 , a variable metering orifice (throttle)  32  is implemented characterized by triggering with the proportional magnet  34  and consequently with a proportionally variable opening area formed by the passage opening  72 . This variable opening area is designed such that for all trigger states a defined area always remains open by the proportional magnet  34 . Here, it would be fundamentally sufficient in one basic version to provide only one row of passage openings  72  for fluid passage from the outside to the inside, where, to limit the stroke of the control spool  62 , at least part of the hole diameter which is active must then remain free. 
     As shown in practice, with only one row of bores which are only partially closed, exact adjustment of the volumetric flow in the energized end position of the magnet  34  is difficult to ensure. In particular, tolerances cannot be allowed in production and mounting. Conversely, a reliable and durable system can be achieved with an arrangement in which, in addition to the proportionally adjustable orifice (throttle)  32 , an orifice (throttle)  36  is always open. The constant orifice  36  is connected parallel to the proportionally adjustable orifice  32  so that the overall orifice ratio for the system at the connecting site  40  for the pressure compensator  16  is the product of the sum of the two opening cross sections or opening areas. 
     To be on the safe side, the control spool  62  for the variable orifice  32  is dimensioned such that it is approximately 0.1 mm in front of the assignable row of passage openings  72  in the unenergized state and, in the fully energized state, as viewed in  FIG. 2 , is 0.1 mm to the left following the row of passage openings  72 . This structural design is only exemplary and ensures that, regardless of the production tolerances, the variable orifice  32  can in any case be completely opened or closed. In this respect, defined conditions prevail, and the end values are reliably reached. The permanently open orifice  36  can be implemented in the valve block  58  ( FIG. 1 ) or, as shown in  FIG. 2 , as a second row of bores  74  which preferably cannot be crossed in its entirety or even partially by the valve spool or control spool  62 , depending on the application. 
     The variable orifice  32  always interacts with the pressure compensator  16  connected downstream in the fluid direction. This arrangement is detailed in  FIG. 3 . The pressure compensator  16  is designed as a screw-in cartridge solution, and, as shown in  FIG. 4 , can be inserted into a valve block  58  (compare the exemplary embodiment as shown in  FIG. 5 ). As viewed in  FIG. 3 , the compensator on the left side, has a screw-in part  80  and on the opposite right side another screw-in part  82 . The other screw-in part  82  in the housing  18  of the pressure compensator  16  also is used to set the spring pretensioning for the adjusting spring  22  since regulation is to take place exactly to a small Δp. In agreement with the basic circuit diagram shown in  FIG. 1 , on the pressure compensator the individual connections are designated as E 1 , E 2 , A 1 , and A 2 . Furthermore, in the embodiment as shown in  FIG. 3 , at one other branch site  84  within the lines  24 ,  26  in the secondary branch  86 , part of the pertinent partial volumetric flow is routed as the control flow ST 1 , ST 2  from the inlet side E 1 , E 2  of the pressure compensator  16  to the assigned end side  88  of the pressure valve spool  20 . In this respect the pressure compensator spool  20  in each of its positions of travel has a fluid-tight separation between the inlet sides E 1  and E 2  to the spool end sides  88  by the spool ring surfaces  90  adjoining the pressure compensator housing  18 . One identical damping orifice  92  at a time is connected to the indicated secondary branch  86 . With these damping orifices  92  in the bypass, unwanted oscillations in the operation of the pressure compensator  16  can be avoided. The respective damping orifices  92  can also be implemented in the form of damping bores in the pressure compensator housing  18 . Providing only one of the two sides of the pressure compensator  16  with damping is also possible. 
     As depicted in  FIG. 3 , the pressure compensator spool  20  is shown in its middle actuation position in which it partially overlaps the fluid outlets A 1 , A 2  leading to the hydraulic consumers V 1  and V 2 . The fluid inlets E 1  and E 2  conversely are left open by the spool  20 . By radial recesses  96 , a permanent fluid connection is between E 1  and A 1  and between E 2  and A 2 . The fluid outlets A 1 , A 2  respectively are choked by the pressure compensator spool  20 . Depending on the position of travel of the pressure compensator spool  20 , the fundamental switching possibilities for the pressure compensator  16  as shown in  FIG. 1  are achieved analogously. Since this pressure compensator structure is inherently known, it will not be described further. 
     The embodiment shown in  FIG. 4  has been altered compared to the other embodiment shown in  FIG. 3 , in that the damping orifices  92  are omitted. The pressure compensator spool  20  in this embodiment in each of its positions of travel has spool ring surfaces  90  spaced apart from the pressure compensator housing  18 . Otherwise, in terms of surface ratio, the spool ring surfaces  90  opposite one another correspond to one another for the embodiments shown in  FIGS. 3 and 4 . For both embodiments the spool  20  is then essentially symmetrical in design. In the modified embodiment shown in  FIG. 4 , the fluid travels via the inlets E 1 , E 2  as well as the radial recesses  96  and the respective annular gap  98  to the active spool ring surface  90 . 
     The valve block configuration according to  FIG. 5  shows that the entire valve device can be combined in one unit. For purposes of a compact arrangement, preferably the proportional magnet  34  projects on the top of the valve block  58  and is fixed there by the flange  56 . Then, the valve housing  60  with the different passage sites to the orifice formation  32 ,  36  projects into the valve block  58 . Transversely to this installation arrangement, the pressure compensator  16 , as viewed in  FIG. 5 , extends essentially in the horizontal position between the free end sides of the valve block  58 . The screw-in parts  80 ,  82  form the housing termination to the outside. The important connecting lines P, A 1 , and A 2  then discharge on the side of the valve block  58  facing the viewer of  FIG. 5 . Other block arrangements are possible. 
     While various embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.