Valve subassembly having at least two pump lines for a pump

A valve subassembly includes a pump connection location, a tank connection location, and two constantly adjustable direction control valves each with first and second operating connection locations and an input connection location. A first valve group includes one direction control valve whose input is connected in parallel to two separate pump lines such that pressurized fluid is directed exclusively from the two pump lines to the control connection location. The two pump lines include a maximum of a first pump line and each remaining pump line is a second pump line. The maximum one first pump line is directly connected to the pump connection location in fluid terms, and a separate constantly adjustable pump valve is associated with each second pump line. Pressurized fluid is directed from the pump connection location via the pump valve into the associated second pump line.

This application claims priority under 35 U.S.C. § 119 to patent application no. DE 10 2015 211 704.9, filed on Jun. 24, 2015 in Germany, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

The disclosure relates to a valve subassembly, a drive system having such a valve subassembly, and a method for the operation thereof.

EP 791 754 B1 discloses a drive system having a valve subassembly which is provided for connection to two separate pumps. The two pumps are each directly connected in fluid terms to one of two pump lines, wherein the two pump lines each extend through the entire valve subassembly. Furthermore, there are provided a plurality of direction control valves which are each connected in parallel to the two pump lines in such a manner that pressurized fluid can flow exclusively from the pump lines to the direction control valves. In this instance, it is also impossible for pressurized fluid to be exchanged between the two pump lines. There is associated with each direction control valve an actuator whose movement direction and speed can be controlled using the direction control valve.

The advantage of the present disclosure is that the valve subassembly can be operated with a single pump. When the maximum delivery flow of the pump is not sufficient to supply all the actuators adequately with pressurized fluid, predetermined consumers may be supplied with pressurized fluid in a preferable manner or with higher priority.

SUMMARY

According to the disclosure, it is proposed that the at least two pump lines comprise a maximum of a first pump line, wherein each remaining pump line is a second pump line, wherein the maximum one first pump line is directly connected to the pump connection location in fluid terms, wherein a separate constantly adjustable pump valve is associated with each second pump line, wherein pressurized fluid can be directed from the pump connection location via the pump valve into the associated second pump line. Preferably, each second pump line is connected to the pump connection location in fluid terms only via the associated pump valve. The central position mentioned is preferably arranged between the first and the second operating position. In the central position, the input connection location is preferably blocked.

Advantageous developments and improvements of the disclosure are set out in the dependent claims.

There may be provision for the valve subassembly to have a housing in which the direction control valves are arranged beside each other in a longitudinal direction, wherein at least a second pump line extends through the housing in the longitudinal direction along all the direction control valves. The housing may be constructed as an integral valve block. However, it is also conceivable for the housing to be composed of a plurality of separate valve discs, wherein each direction control valve is received in a separate valve disc. The portions of the valve subassembly described below correspond in the last alternative mentioned to the valve discs. The direction control valves preferably have a sliding valve member which can be moved in a linear manner transversely relative to the longitudinal direction.

There may be provision for there to be provided precisely two pump lines which extend through the housing in the longitudinal direction along all the direction control valves. The two pump lines may be a first and a second pump line. However, it is also conceivable for two second pump lines to be provided. This is the simplest embodiment of the disclosure.

There may be provision for the first pump line to extend through the housing from a central portion in the longitudinal direction along all the direction control valves at that location, wherein another second pump line extends through the housing from the central portion counter to the longitudinal direction along all the direction control valves at that location. With this embodiment, with respect to the previous embodiment, a finer differentiation of the supply priorities of the different actuators is possible. In both embodiments, the portions of the valve subassembly which are associated with the actuators can be used in identical form.

There may be provision for a second valve group to comprise those direction control valves in which the input connection location is connected in fluid terms to a single pump line. Each direction control valve belongs either to the first or to the second valve group. It is conceivable for all the direction control valves to belong to the first valve group.

There may be provision for at least a portion of the direction control valves of the second valve group to have a load tapping location, wherein the load tapping location in the first operating position is connected in fluid terms to the first operating connection location, wherein the load tapping location is connected in fluid terms in the second operating position to the second operating connection location, wherein the load tapping location is either blocked in the central position or connected in fluid terms to one of the at least one tank connection location(s). Preferably, there is provided a separate control return line which is connected to a separate tank connection location. It is conceivable for the load tapping location to be connected in fluid terms in the central position to the control return line.

There may be provision for there to be associated with each load tapping location a pressure balance which is connected in fluid terms between the respective input connection location and the respective pump channel, wherein the pressure at the load tapping location acts on the pressure balance in the manner of an adjustment. Preferably, the pressure balance controls the difference from the pressure at the load tapping location and another pressure, which is extremely preferably tapped in the supply, to a predetermined value.

There may be provision for the load tapping location to be connected to an associated constantly adjustable pressure reduction valve. By means of adjustment of the pressure reduction valve, the force with which the associated actuator operates can be influenced.

There may be provision for there to be associated with at least one direction control valve of the second valve group a current limitation valve which is connected in fluid terms between the respective input connection location and the respective pump line. An excessive amount of pressurized fluid is thereby prevented in a simple manner from being supplied to the associated actuator, which could lead to damage to the mentioned actuator.

There may be provision for there to be associated with at least one direction control valve of the first valve group a first and a separate second non-return valve, which are connected in fluid terms between the input connection location and an associated pump line, respectively. A first orifice may be connected in series in fluid terms to the first and/or the second non-return valve. The first and the second non-return valve are preferably installed in such a manner that pressurized fluid can be directed exclusively from the two respective pump lines to the control connection location, wherein a fluid exchange between the two respective pump lines is prevented.

There may be provision for the input connection locations of two direction control valves of the second valve group to be connected to each other in fluid terms via a second orifice. The respective direction control valves preferably each control an associated hydraulic motor, which is extremely preferably installed in the left or the right travel mechanism of a mobile operating machine. The second orifice causes the production during straight-line travel of a very small deviation from the ideal linear travel movement. The second orifice preferably has a constant flow resistance.

There may be provision, during operation of a drive system having a valve subassembly according to the disclosure, for at least one pump valve to be adjusted in the direction of a smaller flow resistance when the maximum delivery flow of the pump is not sufficient to supply all the actuators with pressurized fluid in accordance with the position of the associated direction control valve or the different load pressures of the actuators with a parallel connection to the pump would lead to a standstill of the actuator with the higher load and an excess quantity of the actuator with the lower load. The direction control valves of the first valve group thereby receive more pressurized fluid than the direction control valves of the second valve group or the load pressure differences are compensated for by the pump valve and a suitable quantity distribution over the actuators is achieved. An even finer differentiation can be achieved by the above-mentioned first orifice.

Of course, the features mentioned above and those yet to be explained below can be used not only in the combination set out but also in other combinations or alone, without departing from the scope of the present disclosure.

DETAILED DESCRIPTION

FIG. 1shows a drive system10having a valve subassembly20according to a first embodiment of the disclosure. The drive system10is, for example, an integral component of a hydraulic excavator. There are provided a plurality of actuators13which may be constructed as hydraulic cylinders or hydraulic motors. In the context of the hydraulic excavator mentioned, the cylinder13amay be for the support, the two cylinders13bwhich are connected in parallel for the extension arm, the hydraulic motor13cfor the rotary mechanism, the hydraulic motor13dfor the left travel mechanism, the hydraulic motor13efor the right travel mechanism and the cylinder13ffor the shovel. The actuators13are each connected in fluid terms via a first and a second operating connection location21;22to an associated portion26a-26fof the valve subassembly20.

The housing28of the valve subassembly20may be composed of a plurality of separate valve discs, wherein the first to sixth portion26a-26fand the central portion25are each formed by a separate valve disc. However, it is also conceivable for the housing28to be constructed as an integral valve block. In the first to sixth portion26a-26f, there is arranged in each case a single associated direction control valve30by means of which the movement direction and the movement speed of the associated actuator13can be controlled.

In the central portion25, no direction control valve30is provided. At this location, the pump11and the tank12are instead connected in fluid terms to a pump connection location23or a tank connection location24. The pump11draws pressurized fluid, in particular hydraulic oil, from the tank12and conveys it under pressure to the pump connection location23. From that location, it is distributed via the central portion25to the first and second pump line51;52. The first and the second pump lines51;52extend through the housing28in the first embodiment in the longitudinal direction15along all the direction control valves30. The direction control valves30are in this instance arranged beside each other in a row in the longitudinal direction15, wherein the sliding valve members thereof can be moved in a linear manner perpendicularly to the longitudinal direction15.

Reference should further be made to the two tank lines55which are connected directly to the tank connection location23in fluid terms. The tank lines55extend through the housing28in the longitudinal direction15along all the direction control valves30. Via the tank lines55, the pressurized fluid flowing back from the actuators13can be directed into the tank12. Reference may further be made to the control supply line56and the control return line57which extend through the housing28in the longitudinal direction15along all the direction control valves30. The control oil return line57is in this instance connected to an additional separate tank connection location24which is also connected to the tank12in fluid terms. The control supply line56is supplied with pressurized fluid via a separate control supply connection location58, for example, by means of a separate control oil pump16.

There is further provided a control device14by means of which the direction control valves30can be actuated and by means of which the displacement volume or the delivery flow of the pump11can be adjusted.

The first and the separate second pump line51;52primarily serve to supply the different actuators13with pressurized fluid with different priorities. The consumers13b;13c;13dand13ehave the highest priority and are connected to the first pump line51without the first orifice (No.65inFIG. 4). The remaining actuators13a;13fhave a lower priority. The priority of the actuator13bis particularly high since it can be supplied in an unthrottled manner both via the first and via the second pump line51;52. The direction control valves30of the actuators13c;13d;13ewhich are connected to only a single pump line, in this instance the first pump line51, belong to a second valve group32.

FIG. 2shows the central portion25of the valve subassembly according toFIG. 1. The first pump line51is directly connected to the pump connection location23. The second pump line52is in contrast connected to the second pump line52in fluid terms by means of a constantly adjustable pump valve50. When the corresponding free valve cross-section is large, a large amount of pressurized fluid flows into the second pump line52so that the prioritization of the actuators13b;13c;13dand13eis reduced or eliminated. By reducing the mentioned valve cross-section surface-area, the extent of the prioritization for the above-mentioned actuators13b;13c;13dand13ecan be adjusted.

The pump valve50is in the same manner as the constantly adjustable relief valve54hydraulically actuated with a respectively associated pilot valve53. The pilot valves53are in turn actuated electromagnetically by the control device (No.14inFIG. 1). Via the relief valve54, pressurized fluid can be directed from the pump connection location23to the tank connection location24. The relief valve54is opened when none of the actuators is moved or when all the direction control valves are located in the central position. The pressurized fluid which is conveyed by the pump then flows into the tank at a low counter-pressure. In parallel, the displacement volume of the pump is preferably reduced. As soon as one of the actuators is moved, the relief valve54is closed so that pressure can build up in the first and second pump lines51;52. The last pressure mentioned is limited by the second pressure limitation valve in an upward direction to a predetermined value. Via the second pressure limitation valve27, pressurized fluid can be directed from the pump connection23to the tank connection24.

FIG. 3shows the central portion25′ of a valve subassembly according to a second embodiment of the disclosure. The central portion25′ replaces in this instance the central portion (No.25inFIG. 1) of the first embodiment, wherein the remaining first to sixth portions (Nos.26a-26finFIG. 1) continue to be used again in an identical manner.

In the second embodiment, the first pump line51no longer extends over the entire length of the housing. Instead it extends from the central portion25′ in the longitudinal direction15along all the direction control valves30at that location so that, with reference toFIG. 1, only the actuators13aand13bare supplied with pressurized fluid from the first pump line. In the opposite direction, an additional second pump line52′ extends through the housing. This second pump line52′ is formed in the third to the sixth portion (Nos.26c-26f) by the same channel which in the first embodiment formed the first pump line. The only difference is that the respective channel portion52′ is now connected to the pump connection location23by means of an additional separate constantly adjustable pump valve50′. It is thereby possible for the priorities of the different actuators to be differentiated in a finer manner in terms of the supply with pressurized fluid. In particular, the actuator13finFIG. 1is now supplied via two second pump lines52;52′ which can both be throttled with respect to the first pump line51. The corresponding supply priority is therefore between the priority of the actuators13a;13binFIG. 1and the priority of the actuators13c;13d;13einFIG. 1.

FIG. 4shows the first portion26aof the valve subassembly according toFIG. 1. In this instance, it is an end portion which is fitted to the left end of the valve subassembly inFIG. 1. The first and the second pump lines51;52, the tank lines55, the control supply line56and the control return line57terminate in the first portion26a. In contrast, the mentioned lines51;52;55;56;57extend through the second to the fifth portion (Nos.26b-26einFIG. 1) over the entire width thereof in the longitudinal direction15. The sixth portion (No.26finFIG. 1) forms another end portion of the valve subassembly.

The direction control valve30has a first and a second operating position35;36and a central position37, wherein the central position37is arranged between the first and the second operating position35;36. In the central position37, the input connection location of the direction control valve30is blocked. In the first operating position36, the input connection location33is connected in fluid terms to the first operating connection location21, wherein the corresponding valve cross-section in the direction control valve30increases constantly during a movement from the central position37into the first operating position35. In the second operating position36, the input connection location33is connected in fluid terms to the second operating connection location22, wherein the corresponding valve in the direction control valve30is also constantly adjustable.

The input connection location33is connected via a first non-return valve61to the first pump line51and in parallel therewith via a second non-return valve62to the second pump line52. The non-return valves61;62result in pressurized fluid being able to flow exclusively from the first or second pump line51;52to the control connection location33. It is not possible for pressurized fluid to be able to flow from the control connection location33back into the first or the second pump line51;52. It is further not possible for pressurized fluid to be exchanged between the first and the second pump line51;52. In place of the simple non-return valves61;62, it is also possible to use more complex valves which can also prevent the reflux of pressurized fluid. Purely by way of example, reference may be made to the valve according to the German Patent Application with the file reference 102014204070.1 or the valve according to U.S. Pat. No. 4,779,836 A1. As a result of the connection described above in relation to two pump lines51;52, the present direction control valve30belongs by definition to the first valve group31.

Between the first non-return valve61and the input connection location33, there is connected a first orifice65which results in the actuator13ainFIG. 1being supplied with pressurized fluid with a somewhat lower priority than the actuator13binFIG. 2in which the first orifice is omitted, wherein the respective second portion (No.26binFIG. 5) is further constructed to be almost identical to the present first portion26a.

In the first operating position35, the second operating connection location22is connected in fluid terms to a tank line55, wherein, in the second operating position36, the first operating connection location21is connected in fluid terms to the other tank line55. The direction control valve30is adjusted with one or two pressure regulation valves70hydraulically counter to the force of the restoring springs38. The pressure regulation valve70may, for example, be constructed in accordance with DE 10 2012 222 399 A1 so that selectively one of the two adjustment pressures71;72can control for both adjustment directions of the direction control valve30. The pressure regulation valve70is electromagnetically actuated by the control device (No.14inFIG. 1). It is connected in fluid terms to the control oil supply line56and the control oil return line57. The pretensioned restoring springs38act on the direction control valve30with the resilient force thereof in the direction of the central position33.

The first and the second operating connection location21;22are each connected to an associated first pressure limitation valve63which limits the pressure at that location in an upward direction to a predetermined value. Furthermore, the second operating connection location22is connected to a load retention valve64so that the respective actuator (No.13ainFIG. 1) does not lower as a result of its inherent weight owing to leakages. The load retention valve64can be hydraulically unlocked, wherein it is unlocked by the adjustment pressure71which acts on the direction control valve30in the direction of the first operating position35.

FIG. 5shows the second portion26bof the valve subassembly according toFIG. 1. The second portion26bis constructed in an identical manner to the first portion with the exception of the differences described below so that reference may be made in this regard to the explanations relating toFIG. 4. InFIGS. 4 and 5, identical or corresponding components are indicated with the same reference numerals.

The second portion26bis constructed as an intermediate portion which can be installed between any other two portions of the valve subassembly. InFIG. 1, it is installed, for example, between the first and the central portion. The first and the second pump lines51;52, the tank lines55, the control supply line56and the control return line57extend through the second portion26bover the entire width thereof in the longitudinal direction15so that there is a fluid exchange connection with respect to the two adjacent portions. As already discussed, the first orifice (No.65inFIG. 4) is omitted with respect to the first portion.

FIG. 6shows the third portion26cof the valve subassembly according toFIG. 1. The third portion26cis, with the exception of the differences described below, constructed in an identical manner to the second portion. Accordingly, reference may be made in this regard to the explanations relating toFIGS. 4 and 5. InFIGS. 4, 5 and 6, identical or corresponding components are given the same reference numerals.

The third portion26cis in the same manner as the second portion also constructed as an intermediate portion, which can be installed between any two other portions, wherein inFIG. 1it is installed between the central portion and the fourth portion. The present direction control valve30belongs by definition to the second valve group32since the input connection location33is connected only to a single pump line, that is to say, to the first pump line51in fluid terms. The corresponding connection is in turn carried out with a first non-return valve61. The first orifice is preferably not present.

The third portion26cis in this instance configured for the actuation of the hydraulic motor of the rotary mechanism of a hydraulic excavator. Therefore, the second pressure limitation valves and the load retention valve are omitted. The second pressure limitation valves are instead preferably located directly on the mentioned hydraulic motor.

FIG. 7shows the fourth and the fifth portions26d;26eof the valve subassembly according toFIG. 1. The fourth and fifth portions26d;26eare with the exception of the optional second orifice66constructed in an identical manner to each other. They are each constructed, with the exception of the differences described below, in an identical manner to the third portion so that reference may be made in this regard to the explanations relating toFIGS. 4 to 6. InFIGS. 4 to 7, identical or corresponding components are given the same reference numerals.

The fourth and the fifth portions26d;26eare configured for the actuation of the hydraulic motors of the left and the right travel mechanism of a hydraulic excavator. In this instance, the specific feature arises that the pump (No.11inFIG. 1) can convey a significantly greater quantity of pressurized fluid than a single one of the hydraulic motors mentioned can receive. Therefore, precautions were taken so that the hydraulic motors mentioned do not become damaged as a result of excess supply with pressurized fluid. In particular, the first non-return valve is replaced by a pressure balance60. The first pump line51is connected to the input connection location33by means of a constantly adjustable valve in the pressure balance60. In the closure direction of the valve mentioned, the pressure balance60is acted on by the force of a pretensioned spring68and by the pressure at a load tapping location34. In the opening direction of the valve mentioned, the pressure balance60is acted on by the pressure in the first pump line61. A plurality of valves are connected in the corresponding control lines in order to damp system oscillations.

The load tapping location34of the present direction control valve30is in the first operating position35connected in fluid terms to the first operating connection location21, wherein, in the second operating position36, it is connected in fluid terms to the second operating connection location22, wherein the load tapping location34is either blocked in the central position37or connected to the control return line57in fluid terms. In both operating positions35;36, therefore, the supply-side pressure is present at the load tapping location34so that the pressure balance60adjusts the difference between the above-mentioned pressure and the pressure in the first pump line51to the pressure equivalent of the spring68. Consequently, the fluid flow to the respective actuators (No.13d;13einFIG. 1) cannot increase beyond a predetermined value which is dependent on the smallest valve resistance in the direction control valve30and the pressure equivalent of the spring68.

Via the second orifice66, the input connection locations33of the direction control valves30of the fourth and fifth portions26d;26eare connected to each other in fluid terms. It is thereby possible, in the event of straight-ahead travel, for the left and the right travel mechanisms to move very precisely at the same speed so that the smallest possible deviation from a precisely linear travel line is produced.

FIG. 8shows the sixth portion26fof the valve subassembly according toFIG. 1. This is constructed, with the exception of the differences described below, in an identical manner to the first portion according toFIG. 4so that reference may be made in this regard to the explanations relating toFIG. 4. In this instance, identical or corresponding components inFIGS. 4 and 8are given the same reference numerals.

The sixth portion26fforms the end portion, which is arranged at the end of the valve subassembly opposite the first portion. It is therefore constructed in a substantially mirror-symmetrical manner with respect to the first portion.

FIG. 9shows a seventh portion26gwhich can be used together with the valve subassembly according to the first and second embodiments of the disclosure. The seventh portion26gis with the exception of the differences described below constructed in an identical manner to the fourth or fifth portion so that reference may be made in this regard to the explanations relating toFIGS. 4 to 7. In this instance, components which are identical or corresponding inFIGS. 4 to 7 and 9are indicated with the same reference numerals.

The seventh portion26gis configured to control any function of a hydraulic excavator which has not yet been addressed. It is constructed as an intermediate portion which can be installed between any two portions of the first or the second embodiment. The present direction control valve30belongs by definition to the second valve group32since it is supplied with pressurized fluid only from a single pump line, in this instance from the first pump line51.

The direction control valve30is also provided with the load tapping location34which has already been set out. However, this is additionally connected to a pressure reduction valve67. The pressure reduction valve67may be electromagnetically adjusted by the control device (No.14inFIG. 1). It brings about a selective limitation of the pressure which is applied at the load tapping location34and which acts on the pressure balance60. In this instance, it should be noted that the load tapping location34is connected to the first or second operating connection location21;22via an associated valve in the direction control valve30so that via the pressure reduction valve67only a small fluid flow flows toward the tank line55.

The additional switching position of the pressure balance60′ with respect to the pressure balance60inFIG. 7should further be noted. This position prevents the reflux of pressurized fluid from the input connection location33into the first pump line51.

As a result of appropriate adjustment of the pressure reduction valve67, the maximum force with which the actuator which is connected to the seventh portion26goperates can be limited in a selective manner.

In the same manner as with the first, the second and the sixth portions, the first and the second operating connections21;22are provided with a first pressure limitation valve63which limits the pressure at that location to a predetermined value in an upward direction.

FIG. 10shows an eighth portion26hwhich can be used together with the valve subassembly according to the first and the second embodiment of the disclosure. The eighth portion26h, with the exception of the differences described below, is constructed in an identical manner to the fourth and fifth portions. It is configured for the actuation of a hydraulic motor of a travel mechanism of a hydraulic excavator so that it can be used as a cost-effective replacement for the fourth or fifth portion.

The direction control valve30has, as in the first portion and in contrast to the fourth or fifth portion, no load tapping location. The pressure balance of the fourth or fifth portion has been replaced by a current limitation valve80. The current limitation valve80comprises a fixed orifice81and a pressure balance83which is connected in series relative thereto and which is arranged in this instance downstream with respect to the orifice81. In the closure direction, the constantly adjustable pressure balance83is acted on with pressure upstream of the orifice81. In the opening direction, the pressure balance83is acted on by a pretensioned spring82and the pressure downstream of the orifice81. The pressure equivalent of the spring82and the throttle resistance of the orifice81are selected in such a manner that the current limitation valve80seeks to adjust the volume flow flowing through to the maximum permissible volume flow for the connected hydraulic motor. During normal operation, however, the pump and the present direction control valve30are adjusted in such a manner that a smaller volume flow flows through the current limitation valve80so that the pressure balance83is completely open, wherein it does not substantially influence the control of the travel mechanism. Only when an excessive quantity of pressurized fluid exceptionally flows through the current limitation valve80is the adjustment function activated, and it limits the volume flow to the preselected value.

LIST OF REFERENCE NUMERALS