WO2008052644A1

WO2008052644A1 - Supply device

Info

Publication number: WO2008052644A1
Application number: PCT/EP2007/008863
Authority: WO
Inventors: S. Gandhi Umesh; Christian Karl Wengerek
Original assignee: Hydac Filtertechnik Gmbh
Priority date: 2006-11-03
Filing date: 2007-10-12
Publication date: 2008-05-08
Also published as: DE102006051821A1

Abstract

The invention relates to a supply device with a load indicator device for a supply pump (18) which supplies a consumer control unit (20) with at least one hydraulic consumer via a supply line (24), which control unit passes fluid on to a feed pump (12) in the return line (32). The fact that when fluid quantity is lacking in the return line (32) of the feed pump (12), a quantity balancing device (42) balances said fluid quantity via the supply line (24) of the consumer control unit (20), means that when the consumer control unit delivers no, or a too low, return quantity to the feed pump, the associated loss is completely compensated via said quantity balancing device in such a way that cavitation and a failure of the feed pump are prevented.

Description

Hydac Filtertechnik GmbH, industrial area, 66280 Sulzbach / Saar

supply

The invention relates to a supply device with a load pressure reporting device for a supply pump, which supplies a consumer control with at least one hydraulic consumer via an inlet, which forwards fluid to a feed pump in the return.

Related utilities with a load pressure signaling device are known in the art. A commonly used term for a load pressure signaling device is also the indication "load-sensing system". Appropriately equipped hydraulic supply devices allow a pressure and volume flow adjustment to the current requirements of one or more consumers, which in turn can be supplied via a separate hydraulic consumer control Load-sensing systems can be regularly implemented with so-called variable displacement pumps, whereby a so-called load-sensing controller for the supply pump maintains a constant pressure drop between a controller control line of the pump and the pump outlet.

The known supply devices, as they are freely available on the market, moreover, have a feed pump, which can be used in the so-called open circuit for better filling in the intake phase with higher speed and in a closed circuit to replace zen the leakage and flushing of the circuit is used. These feed pumps are regularly used in a so-called feed circuit, which is designed as a low-pressure circuit and has the task of constantly replacing the small volume of oil in a closed circuit with fresh oil. In a pertinent feeding circuit, at least one filter and a cooler and two check valves for feeding in addition to the feed pump and a flushing valve for removing fluid are regularly provided in addition to the feed pump. In the known solution, however, it may happen that, if the Verbrauchersteue- tion provides no or too low return flow to the feed pump, for example, due to increased fluid consumption or by leakage losses, no fluid (oil) in the return, ie in the suction line The result of the cavitation of the feed pump may be due to the failure of the entire hydraulic circuit, for example due to the associated damage to the feed pump feed pump.

Based on this prior art, the invention has the object to further improve the known utilities to the effect that the mentioned disadvantage does not appear in the prior art. A pertinent object solves a supply device with the features of claim 1 in its entirety.

Due to the fact that according to the characterizing part of claim 1 by means of a quantity compensation device in the absence of fluid in the return of the feed pump is supplied via the inlet of the consumer control, if the consumer control supplies no or too low return flow to the feed pump, the pertinent loss on the fully complied with. siert, so that cavitation and failure of the feed pump are excluded.

In a particularly preferred embodiment of the supply device according to the invention, the quantity balancing device has a pressure compensator for fluid quantity control, which produces a fluid guide between inlet and return in a passage position or blocks it in a blocking position. A downstream pressure compensator for quantity control allows accurate compensation of the potential loss due to insufficient fluid supply in the return of the feed pump from the consumer control.

Preferably, it is provided that the pressure compensator is designed as a proportional valve as a control pressure spring-centered in the direction of the passage position held and as another control pressure taps the fluid pressure in the suction line of the feed pump. The required volume flow is accordingly regulated by the proportional valve on the basis of the equilibrium of forces between said spring and the control pressure in the suction line (return). The use of the spring-centered proportional valve is inexpensive to implement and allows a timely, dynamic response.

Further advantageous embodiments of the supply device according to the invention are the subject of the other dependent claims.

In the following, the supply device according to the invention will be explained in more detail using an exemplary embodiment according to the drawing. In principle and not to scale, they show the Figure 1 in the manner of a circuit diagram of the closest prior art;

FIG. 2 shows a circuit diagram representation corresponding to FIG. 1 with the quantity compensation device according to the invention;

3 in longitudinal section formed as a proportional valve quantity compensation device;

4 shows a diagram relating to the recording of a test result profile.

The known supply device has within a supply circuit 10, a feed pump 12, which is designed as a fixed displacement pump and the input side in a so-called. Suction line 14 opens and the output side in circulation in a tank T promotes. From the said tank T takes a supply pump 18 fluid, especially in the form of hydraulic oil, and delivers this to a designated as a whole with 20 consumer control, the so-called. Working hydraulics of the hydraulic circuit forms. The structure of such consumer controls 20 is known, so that will not be discussed in more detail here at this point. The consumer controller 20 may provide fluid to a plurality of hydraulic consumers; but there is also the possibility that only one consumer is supplied or that the consumer control 20 itself is formed exclusively from a hydraulic consumer. The supply pump 18 has a so-called. Load-sensing pump adjustment unit together with load-sensing controller, to which extent a known swash plate pump with adjustment can be used. The structure of such load-sensing pumps is known, so that will not be discussed further here at this point. The load-sensing controller of the pump receives via a tap line 22 the pressure information required for the control of the load control 20. The mentioned load-sensing controller (controller) maintains a constant pressure drop between serving as a control line tapping line 22 and the inlet 24 as a pump outlet and supply for the consumer control 20 upright. When the pump speed for the supply pump 18 is reduced, the pressure in the supply 24 drops, and the load-sensing controller then drives the pump, resulting in an increased output. When using the already mentioned swash plate pump as a supply pump, the said disks are swung out; If there is an increase in the pump speed, the processes run in the opposite direction. The situation is also corresponding, if the pertinent pressure profile is caused by the load control 20 in the inlet 24. In this way, a hydraulic control system is created with pressure and volume flow adaptation to the current requirements of one or more consumers formed by the consumer control 20.

Seen in the direction of FIG. 1, a so-called traction drive 26 is connected between the feed pump 12 and the load-sensing pump for the working hydraulics serving as a supply pump 18, which consists of an adjustment pump with two flow directions. The pertinent drive is connected on the output side via spring-loaded check valves 28 in a secondary branch 30 in the output line of the feed circuit 10 of the feed pump 12. Fluid returned by the consumer control 20 passes through the return 32 in the secondary branch 34 with between D

The other parallel branch line 38 opens like the other side branch 34 behind the transition point of the return 32 into the suction line 14 in a biased by spring-loaded check valves 40 line system, the output side opens into the tank T. The pertinent basic hydraulic circuit is common and comes, for example, in hydraulic lift trucks, such as forklifts, used. Regardless of this, however, a variety of applications is conceivable in which as a supply pump 18, a load-sensing pump with a feed pump 12, preferably designed as a fixed displacement pump, cooperates and the supply pump 18 supplies a load control 20, the feed pump 12 in the return has served. Delivers in the known solution according to Fig.1 now the load control 20 no or too low return flow through the return line 32 in the suction line 14 of the feed pump 12, the feed pump 12 of the traction drive 26 is undersupplied with the result that Saugunterdruck in the suction line 14th arises and the feed pump 12 thereby "cavitates", which can lead to failure of the hydraulic circuit together with its connected consumer.

To counter this, the solution according to the invention according to the circuit diagram of Figure 2 shows a significant modification to the solution presented according to the Fig.1, wherein for the components previously described in Figure 1, which in this respect also in the Fig.2 with 2, and FIG. 2 is explained only insofar as it differs from the preceding solution by using the quantity compensation device according to the invention (designated as a whole by 42) , Said quantity compensation device 42 serves, in the case of the indicated lack of fluid in the return line 32 of the feed pump 12, to supply it directly via the inlet 24 of the consumer control 20, with a constant volume adaptation taking place in this way, that is, the lack of fluid quantity for the feed pump 12 seen in the time unit is achieved directly by the outflow of the fluid quantity required in the inlet 24 of the load control 20. For the fluid quantity control, the quantity balancing device 42 has a pressure compensator, which produces a fluid guide 44 between inlet 24 and return 32 in an open position as shown in FIG. 2 or blocks it in a blocking position. In this case, a proportional valve I 46 is used as a pressure compensator, which is held as a spring-centered control pressure in the direction of the passage position shown and, as a further control pressure, decreases the fluid pressure in the suction line 14 at the point indicated by 2. On the input side, the proportional venti I 46, as already stated, connected via the connection point 1 for outfeed into the inlet 24 and output side connected to the output 3 in the secondary branch line 38, which opens into the input side of the filter unit 36, after the passage of the filtered fluid in the suction line 14 passes. Furthermore, the proportional venti I has on its seen in the direction of the Fig.2 left spring-centered side of a leak oil port 48, which is held without pressure or opens under ambient pressure in the tank T.

If, according to the solution according to the invention, the consumer controller 20 supplies no or too low a return quantity to the return line 32, in turn no hydraulic oil would enter the suction line 14 of the feed pump 12. Using the quantity balancing device 42 with proportional venti I 46, which is designed in the manner of a spring-centered pressure compensator, however, now oil is supplied via the spring-centered open proportional venti I 46 directly from the connection point 1 to the output 3 and thus the feed pump 12 then over the filter unit 36 filtered supplied. The volume flow is thus tapped by the proportional valve 46 based on the equilibrium of forces between the compression spring 50 and the control pressure tapped at the connection point 2 in the suction line 14. In this way, a kind of reflected switched pressure balance realized for quantity control for the feed pump 12, so that the feed pump 12 can no longer cavitate with the disadvantages described. Instead of a spring-centered proportional valve 46 as a pressure compensator, such a proportional valve I could also be connected to a solenoid controller (not shown), which, however, would possibly increase the control effort.

The proportional valve 46 used in FIG. 2 as part of the quantity compensation device 42 is shown in longitudinal section in FIG. The pertinent proportional valve 46 is preferably designed in the manner of a Einschraubpatrone and has the outer peripheral side corresponding annular sealing elements with which the actual valve body housing 52 can seal against a receiving housing, not shown for the valve body. The compression spring 50 acts on a Ventilfüh- approximately body 54 centered longitudinally movable within the valve housing 52 is guided and at its free lower end end via a ball guide 56 in permanent contact with a valve closure member 58 which at its lower free end face the Control pressure at the point 2 in the suction line 14 tapers, which is biased in a preferred embodiment via the check valves 40 to a biasing pressure of 7 psi or 0.35 bar. The pertinent valve closing part 58 controls the outfeed 1 in the inlet 24 and the output 3 in the secondary branch line 38 of the return 32 together with filter unit 36 with suction line 14. Furthermore, in the ball guide 56, the valve body housing 52 on the leak oil port 48 which leads to the tank , This proportional valves are common, so that will not be discussed here at this point.

FIG. 4 shows an example of a test result, wherein the curve labeled Q1 relates to the outfeed to the traction drive 26, Q2 the

Return flow to working hydraulics 20 (load-sensing circuit) is and with Q3 is the volumetric flow, which is controlled via the proportional valve 46 of the flow control device 42. Furthermore, the curve indicated by PI represents the control pressure of the proportional vent 46. The mentioned quantities Qi, Q2 and Q3 are given in l / min, as seen in the direction of Fig. 4 at the left edge refer to the values given there Q1 and Q3 and on the far right side, the return amount Q2 in l / min , The control pressure P1 is indicated in bar and the individual curves run over different periods indicated by (1), (2) and (3). As can be seen from FIG. 4, a constant volume flow QI over time is achieved by using the quantity compensating device 42 for the outfeed to the travel drive despite the widely varying quantities Q2, Q3 and PI.

The mentioned proportional venti I 46 operates in the manner of a charge valve (boot-valve) and it is surprising for a person of ordinary skill in the field of hydraulic utilities that he by creating a low-cost leveling device 42 the previous disadvantages regarding the lack of supply of feed pumps 12 in the feed circuit 10 can avoid.

Claims

Patent claims

1. supply device with a load pressure signaling device for a supply pump (18) which supplies a consumer control (20) with at least one hydraulic consumer via an inlet (24), which forwards fluid to a feed pump (12) in the return line (32) , characterized in that by means of a quantity compensating device (42) in the absence of fluid in the return line (32) of the feed pump (12) via the inlet (24) of the load control (20) is balanced.

2. Supply device according to claim 1, characterized in that the quantity compensation device (42) has a pressure compensator for fluid quantity control, which produces a fluid guide (44) between the inlet (24) and return (32) in a passage point or locks in a blocking position.

3. Supply device according to claim 2, characterized in that the pressure compensator as proportional venti I (46) formed as a control pressure spring centered in the direction of the passage position has held and as further control pressure, the fluid pressure in the suction line (14) of the feed pump (12) picks up ,

4. Supply device according to claim 2 or 3, characterized marked, that the spring-centered proportional valve (46) on the input side (1) in the inlet (24) and the output side (3) in the return line (32) is connected.

5. Supply device according to claim 3 or 4, characterized marked, that the suction line (14) of the feed pump (12) via a filter unit (36) in the return (32) of the load control (20) opens.

6. Supply device according to one of claims 2 to 5, characterized in that the suction line (14) and the return (32) via a valve device (40) are biased by the same amount.

7. Supply device according to one of claims 1 to 6, characterized in that the load pressure signaling device of the supply pump (18) is connected to the load control (20).

8. Supply device according to one of claims 1 to 7, characterized in that in addition to the supply pump (18) and the feed pump (12), a traction drive (26) in the form of a further adjustment pump is present.

9. Supply device according to one of claims 2 to 8, characterized in that the supply pump (18) from a central supply (T) takes the required amounts of fluid for the consumer control (20) and that the feed pump (12) in this central supply (T) their pumped amount of fluid from the return (32) of the load control (20) feeds.