DE10041168A1 - valve means - Google Patents

Abstract

Disclosed is a valve device for controlling a consumer, in particular a tool of a harvester head, in which a control piston is provided for controlling the pressure medium paths between a hydraulic pump and the consumer. The load pressure acting on the consumer acts on the control piston when a limit load pressure is exceeded in the closing direction, which can be moved into a pressure limiting position in which the pressure on the consumer can be reduced towards a tank and the load pressure effective on the consumer continues to act in the closing direction.

Description

The invention relates to a valve device for controlling egg nes consumer according to the preamble of claim 1.

In forestry there is a tendency towards the expensive Re replacing manual work with machine work. Thereby Maschi nenaggregate used that several sub-works of timber harvesting, such as for example, felling, delimbing, debarking, collecting, storing can. So-called harvesters are used to harvest the Separate wood from the stick, delimb, cut and cut the wood to collect long pieces of wood. Further processing then takes place via so-called processors, which take over further partial work. The ge mentioned precipitation machines are usually on an off-road Attachment attached and have a hydraulic arm on which the Be work tools, such as grippers, feed rollers, saws load-bearing processing head (hydraulically controlled harvester head) is arranged.

The tools are hydraulically actuated in the harve Directional control valves, such as those found in the WO 98/05870 A1 are described. Such directional valves have one Control piston which is guided axially displaceably in a housing and over the two with the tool - for example one Hydraulic cylinder for pressurizing a feed roller, for loading operation of a knife or for power control of a saw blade - connected working connections with a to a hydraulic pump closed pressure connection or a tank connection can be connected. The Front surfaces of the control piston are subjected to a control pressure bar so that the spool moves from a home position to a tax position for connecting a working connection to the pressure connection and the other working connection with the tank connection is. The load pressure effective at the respective consumer is determined internally Bores of the control piston led to two volumetric pistons, each in an end portion of the control piston are mounted. With a deflection  Kung the control piston runs one of the volumetric pistons with its free End section on a stop so that there is one on the control piston effective closing force in the closing direction results from the cross sectional area (measuring surface) of the volumetric flask and from the consumer pressure is true.

The problem with such solutions is that they work testify applied pressure force, for example the contact pressure of the Feed rollers or the force exerted by the grippers depending on the diameter of the trunk must be set. In which The directional valve described above is such an individual pressure limiter Not possible because the control piston rises when the pressure rises kes the consumer only from the pressure medium supply to the consumer is blocked. This can, for example, be the case with a Tree peeling machine come to pressure peaks when the feed roller hits one Branch or a similar projection of the tree trunk runs over so that damage to the rollers or other tools is not sufficient is closed.

DE 197 49 639 A1 by the applicant describes a valve device disclosed for individual pressure limitation, in which the consumption proportional control valve realizing a comparison valve is assigned, via which the effective tax on the proportional valve pressure difference is adjustable. Such a valve arrangement triggers the functional problem described above, the known valve device However, processing is very expensive and requires maintenance and requires one high space requirement, so that use with harvester heads is out of the question det.

In contrast, the invention is based, the valve to further develop the device such that a pressure limitation on the Consumers of applied load pressure with a compact design and low is possible according to the technical complexity of the device.

This object is ge by the features of claim 1 solves.  

According to the invention, a control piston of the valve device can be when a limit load pressure is exceeded in a pressure limiting position bring in, in which the load pressure leading consumer connection is connected to a tank connection and the load pressure at this Ver consumer connection continues in the closing direction, d. H. in one of the ur directional deflection opposite direction on the control column ben works. In this way, the pressure at the consumer connection can abge be built, the limit load pressure by choosing the control pressure or the magnetic force for the axial displacement of the control piston can be varied is. This individual pressure limitation can damage the Consumer can be reliably avoided by pressure peaks. A white Another advantage of the solution according to the invention is that the Pressure control and the directional valve function by a single control pistons are realized, while in the solution described above according to DE 197 49 639 A1 additional expensive valve devices conditions to limit the maximum pressure are required.

The reaction force acting in the closing direction is preferred applied with the help of a volumetric flask, which - similar to the WO 98/05870 A1 - is guided in an end section of the control piston and which is loaded by the load pressure. The free end section of the Volumetric piston is against a stop when the control piston is deflected movable so that the spool is resulting from which Area of the volumetric flask and the reaction force depending on the load pressure in Closing direction is shifted and a connection to the tank opened is controlled.

In a particularly preferred embodiment, the load pressure via a radial bore of the control opening into an axial bore butted at the work connection and on the one hand to the end face che (measuring surface) of the volumetric flask and on the other hand to a control surface guided.

The valve device according to the invention is particularly compact formed when the control piston is designed with an annular collar, whose peripheral edges as control edges for opening or closing a the control chamber assigned to the pressure connection and one to the tank connection  assigned control room. This also flows into this tax union Radial bore to the outside, through which the load pressure on the consumer finally tapped.

The distance between the radial bore and the tank control room Control edge is preferably less than the width of the Working connection assigned control room selected so that in the Spoken tax position of the work connection with the tank connection is connected and at the same time the load pressure via the radial bore can be tapped.

The control piston is preferably with another ring collar executed, via which the pressure medium flow to another Ar beitsanschluß is controllable.

The load pressure guided in the axial bore of the control piston becomes tapped via a load signaling line and to a control device led by a pump.

As mentioned at the beginning, the valve device according to the invention can particularly advantageous for operating tools of a harvester head are used.

The deflection of the control piston can either be via a suitable one Control pressure difference or via electromagnets.

The following is a preferred embodiment of the invention tion explained in more detail using schematic drawings. Show it:

Fig. 1 is a schematic view of a Ven tileinrichtung invention for controlling a consumer and

FIGS. 2a-2e different positions of a control piston of the valve device in FIG. 1.

Fig. 1 shows a circuit diagram of a valve device 1 according to the invention, with the functions of a proportional Wegeven TILs and a proportional pressure valve for controlling a brauchers Ver, in the present case of a harvester head, not shown, are realized. The valve device 1 has a proportional valve 2 indicated by dash-dotted lines, via which a hy draulic consumer 4 can be connected to a hydraulic pump 6 and to a tank T. In the illustrated embodiment, the Hy dropumpe 6 is designed as a constant pump 8 with an inlet pressure compensator 10 . Alternatively, a variable displacement pump with a pump controller could also be used to supply the pressure medium.

The pressure medium is guided by means of the hydraulic pump 6 to a pressure connection P of the proportional valve 2 , the consumer being supplied with the pressure medium via a working connection A or a second working connection B. The pressure medium flowing back from the consumer is returned to the tank T via the other working connection B or A and a tank connection S.

In the illustrated embodiment, the consumer 4 is designed, for example, as a hydraulic cylinder with a piston 5 . About this hydraulic cylinder 4 , the contact pressure of a feed roller of the harvester head is adjustable.

In the housing 12 of the proportional valve 2 , an axial bore is formed, in which a control piston 14 is axially displaceably guided. The control piston 14 has two ring ports 16 , 18 each assigned to a working port A, B, which are spaced apart by a central web 20 . The end faces 22 , 24 of the control piston 14 are acted upon by compression springs 23 , not shown in FIG. 1, so that the control piston 14 is biased into its basic position shown in FIG. 1. The control piston 14 is penetrated by a dashed line, on one side by a surface acting as a control surface 21 21 axial bore 26 which opens into the left end face 22 in FIG. 1 of the control piston 14 to the outside. In the peripheral surface of the two ring collars 16 , 18 , one or more radial bores 28 and 30 are formed, which open into the axial bore 26 .

Behind the end face 22 , a measuring piston 32 is guided in the axial bore 26 and protrudes from the control piston 14 in the axial direction. The measuring piston 32 and the bottom surface 21 of the control piston 14 can be struck through the radial bore 28 or 30 with the load pressure on the consumer. The measuring piston 32 can be secured, for example, by an annular collar in the axial direction in the bore 26 .

In the basic position shown in FIG. 1, a stop 34 fixed to the housing is formed at a distance from the free end section of the measuring piston 32 . With regard to the specific structure of the measuring piston 32 and the valve seat of the axial bore 26 , reference is made, for example, to the disclosure of the aforementioned WO 98/05870 A1, in which a measuring piston is likewise guided in a control piston.

As can also be seen in FIG. 1, the housing 2 has two tank spaces 36 , 38 connected to the tank connection S. A first control chamber 40 and a second control chamber 42 are formed in the housing 2 in the region of the two ring collars 16 , 18 , while a pressure control chamber 44 is provided in the region of the central web 20 .

The end circumferential edges of the two ring collars 16 , 18 are formed as control edges each with one or more fine control notches 46 , 48 , 50 , 52 distributed over the circumference, of which only one of the notches is shown in FIG .

In the basic position shown in FIG. 1, the connection between the first control chamber 40 and the tank chamber 36 is opened via the fine control notches 52 formed on the left annular end face of the collar 16 , so that the pressure medium from a cylinder chamber 54 of the hydrocyliners 4 designed as a differential cylinder Tank T can flow and the feed roller, not shown, is relieved. The connection between the pressure control room 44 and the two adjacent control rooms 40 , 42 is blocked off. Accordingly, the connection between the second control chamber 42 and the tank chamber 38 is closed, so that an annular space 56 of the consumer is blocked both for the tank connection S and for the pressure connection P.

The two radial bores 28 , 30 are in the basic position shown by the peripheral walls between the spaces 40 , 44 and 44 , 42 covered and thus closed on the circumference.

The control piston 14 can be actuated either hydraulically by applying a control pressure into the front control spaces 60 , 62 or via solenoid valves, the tappets of which act on the end faces 22 , 24 of the control piston 14 .

As indicated in dashed lines in Fig. 1, the pressure prevailing in the axial bore 26 is tapped via an LS channel 64 and guided via a control connection LS to the inlet pressure compensator 10 , so that pressure depends on the load prevailing in the axial bore 26 Pressure medium supply to the proportional valve 2 via the hydraulic pump 6 is adjustable.

FIG. 2 shows various axial positions of the control piston 14 of the proportional valve 2 , only one compression spring acting on the control piston 4 being shown. The Darge shown in Fig. 2a basic position corresponds to the spring biased center position of the control piston 14 shown in Fig. 1, in which the control chamber 40 is connected to the tank chamber 36 , while the rooms 40 , 44 , 42 have no connection with each other.

When the right end face section 24 in FIG. 2a is acted upon with a control pressure or the actuating force brought up by an electromagnet, the control piston 14 is moved to the left from the basic position shown in FIG. 2a. In the Fig. 2b Darge presented working or control position of the control piston 14 , he ste control chamber 40 is blocked off from the tank chamber 36 and the pressure control chamber 44 . The radial bore 28 is opened by the control edge of the first control chamber 40 , so that the load pressure prevailing at the working connection A, ie the pressure in the cylinder chamber 54 in the axial bore 26 and thus also in the LS channel 64, is present. The load pressure present in the axial bore 28 acts on the measuring surface of the measuring piston 32 and presses it against the stop 34 . Accordingly, the load pressure acts on a size corresponding to the measuring surface Bo denfläche 21 of the control piston 14 in the axial bore 26th The connec tion between the pressure control chamber 44 and the second control chamber 42 is closed by the collar 18 , while the tank chamber 38 is connected to the second control chamber 42 via the control notches 46 . That is, in the control position shown in Fig. 2b there is no pressure medium supply via the working port A to the cylinder space 54 , while the pressure medium in the annular space 56 of the consumer 4 can flow out through the working port B and the tank port S to the tank T. The control position shown in Fig 2b., In which the feed roller is biased with a pre determined pressure against the tree trunk, takes the STEU erkolben 14 each then when the 14 force generated by the control pressure on the end face 24 of the control piston or the force of the electromagnet is in equilibrium with the force generated by the load pressure of the consumer 4 on the bottom surface 21 of the control piston and the force of the compression spring - not shown - acting in the closing direction.

With an increase in the control pressure in the control chamber 60 in the directional valve function of the valve device 1 , the balance of forces is disturbed, so that the control piston 14 moves to the left in the illustration according to FIG. 2 and reaches a position according to FIG. 2c. In this position, the connection from the pressure control chamber 44 to the control chamber 40 is open and pressure medium flows to the cylinder chamber 54 . The load pressure increases when the movement of the piston 5 opposes a corresponding resistance, so that the pressure in the axial bore 26 and thus the pressure force generated on the bottom surface 21 of the control piston 14 increases. The control piston moves back towards the control position. Finally, he takes up the control position according to FIG. 2b again, with a balance of forces at a higher level now corresponding to the higher control pressure. A reduction in the control pressure in the control chamber 60, the control piston 14 moves first to the right and the control chamber 40 is connected to the tank space 36th The movement of the control piston 14 to the right is limited by the federal government of the measuring piston 32 on the control piston 14 . In this position, which is shown in FIG. 2d, pressure medium flows out of the cylinder space 54 in a throttled manner. The control piston moves to the left again and returns to the control position when the forces are at a low level.

During lowering of the load pressure in the cylinder chamber 54 of the load 4 without changing the control pressure, as in the way function in increasing the control pressure in the end-side control chamber 60 ben the Steuerkol 14 moves from the in Fig. Typically position shown 2b in the position shown in Fig. 2c, where the connection between the pressure control chamber 44 and the first control chamber 40 is controlled via the fine control notches 50 . Furthermore, the connection between the second control chamber 42 and the tank chamber 38 is opened. It is pressure medium through the working port A in the cylinder chamber 54 and the existing in the annular space 56 pressure medium is returned via the working port B and the tank port S to the tank T - the hydraulic cylinder 4 is extended and the load pressure increases to the original level again Contact pressure of the feed rollers increased.

In the case in which the feed roller runs over a branch or other radial thickening of the trunk, the feed roller is acted upon by a high contact pressure, so that the piston of the hydrocylin ders 4 is acted upon in the direction of retraction. This leads to an increase in pressure in the cylinder chamber 54 and thus to an increase in the load pressure applied to the work port A. This increased load pressure is reported in the manner described above via the radial bore 28 controlled according to FIGS . 2b and 2c into the axial bore 26 , so that the bottom surface 21 and the measuring piston 32 are pressurized with the increased load. The measuring piston 32 is supported on the stop 34 , so that the control piston is relieved of a compressive force which corresponds to the cross section of the measuring piston (measuring surface). The control piston 14 is then pushed by the load pressure acting on the floor surface 21 from its control position according to FIG. 2b to the right into the position according to FIG. 2d in which a connection between the control chamber 40 and the adjacent tank space is made via the fine control notches 52 36 is controlled. The effective distance between the control notches 52 and the radial bore 28 is selected so that in this pressure limiting function the load pressure is further accessed via the radial bore 28 , while the connection to the tank space 36 is opened via the fine control notches 52 . As a result, the pressure in the control chamber 40 and thus at the working connection A to the tank is reduced, so that the control piston 14 is moved back into the control position shown in FIG. 2b. In this pressure limiting function according to FIG. 2 d, the connection between the pressure control chamber 44 and the control chamber 40 is controlled, the control chamber 42 is also connected to the tank chamber 38 .

In general position shown in Fig. 2b, the control piston 14 is Zvi rule the two states oscillate back and forth, in which once the connection to the tank chamber 36 and at another time the connection to the pressure control chamber is placed 44 controls.

To lift the feed roller from the trunk, the left end face 22 of the control piston 14 in FIG. 2 is acted upon by a control pressure or the force of an electromagnet in the travel function of the valve device, so that the control piston 14 is moved into the position shown in FIG. 2e , The control chamber 40 is connected via the fine control notches 52 to the tank chamber 36 , while the fine control notches 48 open the connection between the pressure control chamber 44 and the second control chamber 42 , so that the pressure medium is guided through the working connection B into the annular space 56 and out the cylinder chamber 54 flows back to the tank T via the working port A. With the axial displacement of the control piston 14 to the right to pressurize the working port B, the radial bore 28 is closed, while the radial bore 30 is opened with respect to the second control chamber 42 , so that the load pressure prevailing at the working port B via the radial bore 30 and the axial bore 26 in the LS channel 64 is fed. The hydraulic cylinder is retracted and the feed rollers are moved away from the log. The volumetric flask 32 has no effect since it is held in the axial bore 26 by its collar and does not abut the stop 34 .

Due to the inventive design of the proportional valve, two basic functions are thus in an extremely compact manner:

• 1. the function of a proportional directional valve and  
• 2. the function of a proportional pressure control valve

in a single, robust and simply constructed valve device summarized. The two aforementioned; Functions are proportional executed so that precise control of the consumer

4

operated tool is enabled.

With the valve device described above, the pressure can be force regardless of the diameter of the trunk and the work phase (Saws, feed, etc.) reliably in the optimal areas, so that overloading the harvester head is practically impossible is.

A valve device for controlling a Ver is disclosed user, in particular a tool of a harvester head which a control piston for controlling the pressure medium paths between one Hydraulic pump and the consumer is provided. The consumer we kend load pressure acts when a limit load pressure is exceeded Closing direction on the control piston, this in a Druckbe Limit position is movable, in which the pressure at the consumer egg is removable and the load pressure effective on the consumer continues to act in the closing direction.

Claims (8)

1. Valve device for controlling a consumer ( 4 ), with a pressure connection (P) and at least one working connection (A, B) and a tank connection (S) and with a control piston ( 14 ) which can be moved into a position in which the Pressure connection (P) for supplying pressure medium to the consumer ( 4 ) is connected to the working connection (A, B), the load pressure acting on the consumer ( 4 ) via a control line ( 26 , 28 , 30 ) to a control surface ( 21 ) acting in the closing direction of the control piston ( 14 ), characterized in that the control piston ( 14 ) can be moved into a pressure limiting position when a limit load pressure is exceeded, in which a pressure force resultant corresponding to the load pressure acts in the closing direction on the control piston such that the connection between the the load pressure leading working connection (A, B) and a tank connection is controlled. 2. Valve device according to claim 1, wherein in the region of an end face ( 22 ) in the control piston ( 14 ) a measuring piston ( 32 ) is guided, which can be acted upon by the load pressure and is movable against a housing-side stop ( 34 ). 3. Valve device according to claim 2, wherein the control piston ( 14 ) has at least one in an axial bore ( 26 ) opening radial bore ( 28 ) through which the measuring piston ( 32 ) and the control surface ( 21 ) with the load pressure on the consumer ( 4 ) can be acted upon is and which is in the pressure limiting position with reference to the working connection (A, B) is controlled. 4. Valve device according to claim 3, wherein the control piston ( 14 ) has an annular collar ( 16 ), a control edge ( 52 ) opens the connec tion to the tank connection (S) and in which the radial bore ( 28 ) opens outwards, the hydraulic effective distance between the control edge ( 52 ) and the radial bore ( 28 ) is less than the effective width of a control chamber ( 40 ) assigned to the working connection (A). 5. Valve device according to claim 3 or 4, with a wide ren working connection (B) which can be opened via a second annular collar ( 18 ) of the control piston ( 14 ), the annular collar ( 18 ) having a further, in the axial bore ( 26 ) opens; Has radial bore ( 30 ) through which the load pressure can be tapped when the working connection (B) is opened. 6. Valve device according to one of claims 3 to 5, with a load signaling channel ( 64 ) which is connected on the one hand to an axial bore ( 26 ) and on the other hand to a control device ( 10 ) of a hydraulic pump ( 6 ). 7. Valve device according to one of the preceding claims, wherein the deflection of the control piston ( 14 ) takes place via a control pressure or via electromagnets. 8. Valve device according to one of the preceding claims, the controlled consumer being a tool of a harvester head is.