Valve

A valve, which is characterized in that between a neutral position (38) of a control spool (STS) and one of its end positions (34, 42) a regeneration position (36) is provided. In the regeneration position, two utility ports (A, B) are interconnected in a fluid-conveying manner, or a floating position (40) is provided, in which these utility ports (A, B) are interconnected in a fluid-conveying manner. A further valve is characterized in that by a further motion of the control spool (STS) in the same direction, as that, in which a fluid connection is established between the utility ports (A, B) starting from the neutral position (38), this fluid connection is interrupted.

FIELD OF THE INVENTION

The invention relates to a valve having a valve housing, which has at least one pressure supply port, a first utility port, a second utility port and a return port. A control spool is guided in a longitudinally movable manner in the valve housing for controlling these individual ports. The fluid connections between the ports are interrupted in a central neutral position of the control spool. When the control spool moves from the neutral position in the direction of a first end position of the control spool, the pressure supply port is connected to the first utility port, and the second utility port is connected to the return port in a fluid-conveying manner. When the control spool moves from the neutral position in the direction of a second end position of the control spool opposite from the first end position, the pressure supply port is connected to the second utility port, and the first utility port is connected to the return port. The utility ports are separated from each other in the end positions of the control spool.

The invention further relates to a valve having a valve housing, which has a first utility port and a second utility port. A control spool is guided in a longitudinally movable manner in the valve housing for controlling these utility ports. A fluid connection between the utility ports can be established by moving the control spool from a neutral position.

BACKGROUND OF THE INVENTION

Such valves, which are used to operate hydraulic motors or differential cylinders, are known in the state of the art. In particular for differential cylinders, which lift or lower masses, it has proven to be advantageous to feed the hydraulic fluid displaced from one working chamber directly into the other working chamber when the piston moves, instead of letting the hydraulic fluid flow unused out of one working chamber in the direction of the tank and in parallel pumping it out of the tank into the other working chamber, thereby consuming a lot of energy.

For this purpose, valves have been developed in the past, which, in addition to the lift-neutral-lower positions, also feature a floating position, in which the piston of the differential cylinder can move freely, and a rapid traverse, in which the piston moves faster: DE 10 2008 008 092 A1 and DE 10 2007 054 137 A1. The rapid traverse is also called regeneration. The logic of the positions of the valve spool is lifting-neutral-lowering-regenerate-floating in DE 10 2008 008 092 A1. In the case of DE 10 2007 054 137 A1 the logic is regenerate-lifting-neutral-lowering-floating.

If the valves are additionally formed as load-sensing valves, in which a load pressure is detected in particular at one of the utility ports and is transmitted to an upstream individual pressure compensator valve and/or a hydraulic pump, it has been shown that a lot of energy is wasted during operation. Also, during parallel operation of several valves situations occur in which the valves consume a larger pump volume flow than the pump can supply. This condition is also known as undersaturation. There are two load cases during lifting and lowering loads using a differential cylinder, in which cases the behavior of the known valves is particularly energy inefficient: (1) lifting at low load and (2) lowering at high load.

In the first load case of “lifting at low load”, the valve connects a bottom side of the differential cylinder to a pump and its rod side to a tank. In that case, the pump has to provide all the hydraulic fluid needed to extend the piston, for which however only a small pressure is required. If now in a system further functions are operated in parallel, to which higher loads are applied, a pressure compensator valve has to be used to regulate the pump pressure down to a level that is appropriate for the low load. Hydraulic fluid then uselessly drains to the tank. A further problem is that in this case the valve may consume such a large pump flow that the functions operated in parallel cannot be adequately supplied, and therefore, become slower, although theoretically there is enough energy available to operate all the functions.

In the second load case of “lowering at high load,” the valve connects a highly pressurized bottom side to the tank and connects the rod side to the pump. In this case, the hydraulic fluid flows unused from the bottom side to the tank, and hydraulic fluid has to be supplied in parallel at the rod side. In this case, the self-weight of the load is usually sufficient to lower the load without requiring the support of the pump.

SUMMARY OF THE INVENTION

Based on this state of the art, the invention addresses the problem of providing an improved valve having a higher energy efficiency and a simpler structure.

This problem is basically solved by valves having, between the neutral position and one of the end positions, a regeneration position is provided, in which the utility ports are interconnected in a fluid-conveying manner, or a floating position is provided, in which the utility ports are interconnected in a fluid-conveying manner.

In this way, the more energy-efficient logics of neutral-regeneration-lifting or neutral-floating-lowering can be implemented, ensuring that the hydraulic fluid available in the differential cylinder is first used to move the load before the pump supplies additional hydraulic fluid. A very small pump volume flow is then required for the load case of “lifting at low load” and in the load case of “lowering at high load” it may even possible that no pump volume flow is required at all.

Particularly advantageously, in the regeneration position the first utility port is connected to the second utility port via the pressure supply port, preferably via at least two circumferential recesses at the control spool, in a fluid-conveying manner. Thus, compared to a conventional 4/3 directional control valve, a regeneration position can be provided by only one additional recess at the control spool. That regeneration position permits considerable savings in pump power. It is advantageous if the second utility port is exclusively connected to the pressure supply port in the regeneration position and, in that way, is separated from the return port.

In the floating position, the first utility port can be connected to the second utility port via the return port, preferably via two circumferential recesses at the control spool, in a fluid-conveying manner. Again, only one additional recess at the control spool is required to provide this functionality. The fluid can then flow from one utility port to the other utility port via the return port. It is advantageous if the second utility port is exclusively connected to the return port in the floating position and is in that way separated from the pressure supply port.

The regeneration position may be advantageously provided between the neutral position and the first end position of the control spool, in particular the end position for lifting. The floating position is provided between the neutral position and the second end position of the control spool, in particular the position for lowering. In this case the spool logic is built in such a way that the floating position and the regeneration position are arranged symmetrically around the neutral position. The pump power then can be reduced, both for lifting and for lowering.

In a particularly advantageous embodiment, the control spool can have two utility port recesses, which overlap with the utility ports and a further regeneration recess, which is located between the utility port recesses. In addition, or alternatively, the control spool may have a floating recess, which is located between a utility port recess and an adjacent free end of the control spool. In this way, the control spool does not have to be extended to form the functionalities. The recesses can be advantageously provided in an existing spool of a 4/3 directional control valve.

In the valve housing, a load-sensing line can also be provided, which is de-pressurized in the neutral position of the control spool via a recess of the control spool towards the return port. In particular, a groove in the control spool can connect a section of the load-sensing line, which opens out at the control spool, to the return port.

Advantageously, the load-sensing line is directly connected to one of the utility ports when the control spool is out of the neutral position. For this purpose, two sections of the load-sensing line between the utility ports can open out into a control spool bore. One of the sections each can be brought into connection with the assigned utility port by the control spool.

To switch the control spool to the correct positions, pressure sensors may be connected to the utility ports, which are connected to a control device that controls the motions of the control spool. In this way, the load situation can be determined before the valve is switched, i.e. whether it is possible to lift or lower the load in the regeneration position or the floating position. If this is not possible, it is immediately switched to one of the positions lifting or lowering.

The recesses of the control spool may have at least one proportional opening edge having at least one control groove. The control groove can be essentially triangular in shape. Furthermore, several control grooves may be distributed along the opening edge and arranged at the respective recess. The control grooves permit the load to move without jerking, and pressure peaks in the system are prevented.

For moving the control spool, an electromechanical actuator can be provided. This actuator permits the precise position control of the spool and a smooth transition between the control spool positions.

In a second solution of the problem, a valve is provided with a valve housing, which has a first utility port and a second utility port, and in which a control spool is guided in a longitudinally movable manner for controlling these utility ports. A fluid connection between the utility ports can be established by the motion of the control spool from a neutral position. This valve is characterized in that the fluid connection between the utility ports are interruptible by a further motion of the control spool in the same direction.

Each feature of the valve according to the invention can be used individually or in combination with others. The drawings are purely schematic and not to scale. In the Figures:

Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the drawings, discloses a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a schematic representation of a hydraulic circuit diagram of a valve10according to an exemplary embodiment of the invention as part of a hydraulic overall system12. A pump P draws hydraulic fluid14from a tank14and delivers it to an individual pressure compensator valve IDW. From the individual pressure compensator valve IDW, the hydraulic fluid gets to the 5/5-way proportional valve10according to the exemplary embodiment of the invention, in particular its pressure supply port P′. Starting from the utility ports A and B of the directional control valve10, the hydraulic fluid is delivered to a hydraulic consumer16in the form of a differential cylinder and returned. The consumer16is loaded by a mass m. Returning hydraulic fluid is routed from the valve10to a return port T and then via a return18to the tank14. A load-sensing port LS of the valve10is connected to the pressure compensator valve IDW and the pump P.

The pump P is an adjustable, in particular load-pressure controlled pump. It delivers the hydraulic fluid to the pressure compensator valve IDW, which has three switching positions20,30,32. In the image plane on the far right, a switching position is shown, in which the fluid flow is interrupted. Only the pump pressure, preferably throttled by an orifice22, is transmitted to the left control side24of the pressure compensator valve IDW, while the right control side26is pressurized by the load pressure of the consumer16and by a resetting spring28. If the pressure on the left side24of the pressure compensator valve IDW exceeds the initial pressure of the resetting spring28, the pressure compensator valve IDW is set to a central switching position30, in which the hydraulic fluid is delivered to the valve10. At the same time a pump pressure P′, which is tapped between the pressure compensator valve IDW and the valve10, is passed to the left control side24via the pressure compensator valve IDW. In the left switching position32of the pressure compensator valve IDW, the fluid connection between the pump P and the valve10is again interrupted, while however the pump pressure, as it is present upstream of the valve10, continues to be transmitted to the left side24of the pressure compensator valve IDW.

The valve10is connected to the individual pressure compensator valve IDW. The valve10has a total of five switching positions, which are explained in detail below. In the far-left image plane, a lifting position34is shown. A regeneration position36is shown on the right thereof. In the central neutral position38all fluid connections are interrupted. To the right of the neutral position38, a floating position40is provided and to the far right, the valve10has a lowering position42. At its left side44a control spool STS is centered in the central neutral position38by a spring arrangement46. At its right end48, the control spool STS can be moved by an electromechanical actuator50. The differential cylinder as the consumer16is connected to the utility ports A and B. The utility ports A, B are coupled with pressure sensors52,54, which transmit the pressure present there to a control unit ECU, which controls the motions of the control spool STS. The first utility port A of the valve10is connected to a bottom side56of the differential cylinder16. The second utility port B is coupled to the rod end58of the differential cylinder16. The differential cylinder16is finally provided to move a mass m, the self-weight of which is applied to a piston rod60.

FIG. 2shows a partial section of the valve10according to the invention. The basic structure of this valve10corresponds to a known valve device, as it was disclosed, for instance, in application DE 10 2015 015 685 A1 of the proprietor. In accordance with the solution disclosed in this document, the control spool STS is arranged, movably along an axis64, in a valve housing62. The valve housing62has in pairs longitudinal sides66and end faces68opposing each other. Furthermore, the valve housing62has a top side70and a bottom side72. On the valve housing62are also located, as usual for this type of valve device, housing ports, such as a pressure supply port P′, two utility ports A and B and a return port T.

A spring assembly46, located in the housing end region74, predetermines, in the usual way for such valves10, a neutral position or center position38for the control spool STS, such as the position taken by the control spool STS inFIG. 2. At the end78, opposite from the housing end region74and located on the right inFIG. 2, a housing end part80adjoints to the valve housing62. The housing end part80has an inner chamber82, extending coaxially to the axis64. Inner chamber82is sealed against the valve housing62by a seal84, however is regarded as a component of the valve housing62. Corresponding to the valve disclosed in DE 10 2015 015 685 A1, an end section86of the control spool STS extends into the chamber82. In a manner also corresponding to the above-mentioned known solution, the control spool end section86interacts inside the chamber82with an actuating part88of an emergency actuation and a stroke length delimiter90of the control spool STS. Because this actuator structure also corresponds to the solution, known from the document mentioned above, based on adjustment bolts, no further description of that actuator structure is required. The electric motor, serving as an actuator50, is arranged at the housing end part8in such a way that its drive axis94vertically intersects the displacement axis64of the spool piston STS. A pinion100, located at one end96of a motor shaft98, is located inside the chamber82. As shown most clearly inFIG. 3, a toothed rack102is attached to the end section of the spool piston STS. That toothed rack102meshes with the pinion100. As with the mentioned known solution, the control piston STS is guided non-rotatably in the chamber82, such that the toothed rack102remains in contact with a guiding sliding element104, which is attached to the wall of the chamber82, during axial motions caused by the pinion100. Instead of the sliding element104shown, a roller bearing or a roller could also be provided. The chamber82, which is sealed to the outside, is filled with oil from the valve housing62, such that the gear arrangement106, formed by the pinion100, the toothed rack102and the sliding element104, runs in oil. The seal against the motor housing of the electric motor is formed by the O-ring seal84, which is installed axially to the axis64.

In the embodiment shown, an electric motor in the form of a permanently excited internal-rotor synchronous motor is provided as the actuator50.

In the valve housing62the control spool STS is arranged, which is shaped according to the invention. The control spool STS has two utility port recesses108,110, which are assigned to the utility ports A and B. These utility port recesses108,110each have proportional opening edges112,114,116,118on both sides. Each proportional opening edge is provided with wedge-shaped or parabolic control grooves120. Several such control grooves120are each distributed along the circumference. A regeneration recess122is provided between the utility port recesses108,110. The regeneration recess122is interrupted by a web124, which is arranged in the estuary area126of a connecting line128of a load-sensing line130. The regeneration recess122permits the second utility port B to be connected to an annular space132of the pressure supply port P′, if the control spool STS is deflected from its central neutral position38to the right. The regeneration recess122has, on its side134facing the second utility port B, a proportional opening edge136having control grooves138, while the opposite control edge140is formed by a simple step142. There is a floating recess146arranged between the second utility port recess110and a free end144of the control spool STS, to which the rack102is attached. The floating recess also has a proportional opening edge150having this time circular segmental, in particular semicircular, control grooves152on its side148facing the second utility port B. The floating recess146can be used to establish a connection between the second utility port B and the return port T. Furthermore, the control spool STS at its left end154has a groove156running in an axial direction. The groove156permits the connection of a section of the load-sensing line130to the return port in the neutral position38of the control spool STS and preferably also in the floating position40.

FIG. 3shows a further section representation in a horizontal plane through the valve10. A bore158, in particular stepped, of the load-sensing line130, which extends from a right side160into the valve housing62, is clearly visible. Furthermore, three, preferably stepped, connection bores128,162,164, connecting to the bore166of the control spool STS, are provided. The left connection bore162is arranged in such a way that the connection to the return port T can be made via the groove156in the neutral position38shown. The remaining two connection bores164,128are covered by the control spool STS in the illustration shown, so that they cannot transmit the pressure in the utility ports A, B.FIGS. 4 to 6show in detail representations again that in the neutral position38of the control spool STS, the left connection bore162overlaps with the groove156, while the other connection bores164,128assigned to the utility ports A, B are blocked by the control spool STS.

InFIGS. 7 to 11, the valve10is shown in the regeneration position36. In this position36, a fluid connection is established from the pressure supply port P′ via the first utility port recess108to the first utility port A by the control edges120provided at the opening edge114. Furthermore, the second utility port B is connected to the pressure supply port P′ via the control groove138of the regeneration recess122and via this recess to the first utility port A. There is no connection from the second utility port B to the return port T. As can be seen inFIG. 8, in this position of the control spool STS, a fluid connection is established from the first utility port A, which is part of the supply line, to the load-sensing line only via the central connection bore164. The control spool closes the two remaining connection bores128,162. In this way, the load pressure at the first utility port A is transmitted to the load-sensing line130.

InFIGS. 12 to 16, the lifting position34of the control spool STS is shown. The control spool STS is now located in its right end position. In this position the pressure supply port P′ is still connected to the first utility port A via the first utility port recess108. There is also a fluid connection from the second utility port B to the return port T via the control grooves120on the opening edge118of the second utility port recess110. The regeneration recess122is shifted to the right in the valve housing62to such an extent that there is no longer any connection between the second utility port B and the pressure supply port P′. Consequently, the utility ports A, B are separated from each other. In this position the floating recess146is without function. As can be seen inFIGS. 13 to 16, the central connection hole164continues to transmit the load pressure at the supply line or first utility port A into the load-sensing line130.

The control spool STS still closes the connection bores128,162on the right side and the left side.

InFIGS. 17 to 21, the control spool STS is shown in the floating position40. In this position40, the control spool STS is shifted to the left, so that the connection from the first utility port A to the return port T is established via the control grooves120on the left opening edge112of the first utility port recess108. There is no connection from the pressure supply port P′ to one of the utility ports A, B. Furthermore, the second utility port B is connected to the return port T via the opening edge150of the floating recess146. The load-sensing line130is de-pressurized via the left connection bore162and the groove156in the control spool STS towards the return port T. The control spool STS blocks the two right connection bores128,162.

InFIGS. 22 to 26the lowering position42is shown finally. In the lowering position42, the control spool STS is moved to the left end position. The pressure supply port P′ is connected to the second utility port B via the control grooves120of the left opening edge116of the second utility port recess110, while the first utility port A is connected to the return port T via the first utility port recess108. The regeneration recess122and the floating recess146are ineffective. As can be seen inFIGS. 23 to 26, the right connection bore128now transmits the load pressure at the second utility port B, which in this position is part of the supply line, to the load-sensing line130. The control spool STS closes the two remaining connection bores162,164.

The valve10according to the invention can be used to implement the more energy-efficient logics of neutral-regeneration-lifting or neutral-floating-lowering, in which it is ensured that the hydraulic fluid available in the differential cylinder16is first used to move the load m before the pump supplies additional hydraulic fluid. In this way, a very small pump volume flow is required for the load case “lifting at low load” and in the load case “lowering at high load.” It may even possible that no pump volume flow is required at all. This is without parallel in the prior art.