EP2161458B1 - Assembly for supplying a hydraulic system with hydraulic fluid - Google Patents

Abstract

The arrangement (10) has a working reservoir (12) for receiving hydraulic fluid. An auxiliary reservoir (16) is connected with the working reservoir by a hydraulic line (14) for intermediate storage of hydraulic fluid. An air conveyor (28) i.e. vacuum pump, is connected with a suction line (32) flowing into a liquid-free region (30) of the auxiliary reservoir in a low pressure side. The conveyer is connected with a control line (34) comprising control openings (36a, 36b) that is covered from the hydraulic fluid in the working reservoir before starting the conveyor.

Description

The invention relates to an arrangement for supplying a hydraulic system with hydraulic fluid. The arrangement comprises a working reservoir for receiving the hydraulic fluid intended for operation of the hydraulic system. The working reservoir is designed, for example, as a differential housing of a differential gear of an agricultural utility vehicle. Furthermore, the arrangement comprises an auxiliary reservoir communicating with the working reservoir via a hydraulic line for temporary storage of hydraulic fluid removed from the working reservoir.

In this context, in John Deere tractor series 6030 and 7030 a generic arrangement is known in which a charging oil pump continuously promotes hydraulic fluid from a formed by a differential housing working reservoir against gravity in a higher-lying auxiliary reservoir for temporary storage, the hydraulic fluid starting from the auxiliary reservoir is fed via a controllable high pressure pump in a hydraulic system for the operation of hydraulic vehicle units. Hydraulic fluid that is no longer required by the vehicle units is returned to the working reservoir. The hydraulically operated vehicle units are, in particular, a steering and braking system and optionally attachable to the tractor agricultural implements, the hydraulic actuating cylinder or the like. Depending on the hydraulic fluid consumption of the vehicle units, there may be more or less pronounced fluctuations in the fluid level in the working reservoir.

Since on the output side, a pressure of the order of a few bar is present at the charge oil pump when conveying the hydraulic fluid, there are also increased demands on the pressure load capacity of the auxiliary reservoir. These lead due the associated additional design effort at appropriate additional costs. If an increased removal of hydraulic fluid occurs during operation of the vehicle aggregates, there is also the possibility that the working reservoir will be completely emptied in the direction of the auxiliary reservoir due to the continuous operation of the charge oil pump, and therefore the charge oil pump will continue to run "dry" or unlubricated. The latter can not only adversely affect the life of the charging oil pump, but also leads to the interruption of the lubrication of the located in the differential case differential gear. Another example is in document DE 2 822 209 to find.

It is therefore an object of the invention to enable a constant supply of the hydraulic system with hydraulic fluid.

This object is achieved by an arrangement for supplying a hydraulic system with hydraulic fluid according to the features of patent claim 1.

The arrangement according to the invention for supplying a hydraulic system with hydraulic fluid comprises a working reservoir for receiving the hydraulic fluid intended for operation of the hydraulic system and an auxiliary reservoir communicating with the working reservoir via a hydraulic line for temporary storage of hydraulic fluid removed from the working reservoir.

Furthermore, an air conveying device is present, which is connected on the low-pressure side to a suction line opening into a liquid-free region of the auxiliary reservoir so that a negative pressure can be built up in the intake line and thus in the associated auxiliary reservoir relative to the atmospheric ambient pressure, and with a control line connected, the one Has control opening, which is covered at least before starting up the air conveyor of the located in the working reservoir hydraulic fluid.

If the air conveying device is put into operation, hydraulic fluid flows from the working reservoir via the hydraulic connection into the auxiliary reservoir due to the negative pressure built up in the auxiliary reservoir via the suction line. In this case, the liquid level drops in the working reservoir, wherein below a certain liquid level, the control opening is at least partially exposed in the control line, so that the negative pressure built up in the auxiliary reservoir as a result of the intake via the control line from the surrounding air drops to a dependent on the flow resistance of the control port value. Due to the pressure drop, the liquid level swings back in the direction of the control opening, so that it is again covered by hydraulic fluid. This process is repeated with decreasing intensity until a corresponding equilibrium position of the liquid level in the working reservoir has been established. In other words, the liquid columns communicating in the two reservoirs via the hydraulic line are excited to a damped oscillation, whereby, after the oscillation has subsided, an equilibrium position of the liquid level in the working reservoir which depends on the position or installation height and / or the flow resistance of the control opening is established . regulates.

The air conveying device is preferably designed as an electrically driven vacuum pump. Alternatively, it is conceivable to drive them by means of an internal combustion engine arranged in the agricultural vehicle. For this purpose, the air conveyor can be connected via a belt with the engine.

Such a vacuum pump is already present in John Deere 6030 and 7030 series tractors as part of a hydraulic supply of a vehicle transmission cooperating with the internal combustion engine, so that the arrangement according to the invention can be realized with comparatively little additional effort. Since only a slight negative pressure in the order of at most a few tenths bar in the auxiliary reservoir is built, also no special requirements are placed on the pressure capacity.

Advantageous embodiments of the arrangement according to the invention will become apparent from the dependent claims.

In order to enable a readjustment of the liquid level in the working reservoir, both in the case of supply of hydraulic fluid as well as their removal, it is advantageous if the hydraulic line between a lower portion of the working reservoir and a lower portion of the auxiliary reservoir extends, so that the hydraulic fluid between the Both reservoirs can flow freely back and forth.

Furthermore, there is the possibility that a plurality of control openings, in particular designed as throttle valves, are provided in the control line. These are preferably arranged such that they are successively exposed when the negative pressure builds up due to the liquid level falling in the working reservoir. The pressure drop in the control line is slowed down in this case, so that the excitation of a damped oscillation of the liquid columns located in the reservoirs and communicating via the hydraulic line is largely suppressed. This favors a faster adjustment or regulation of a stable equilibrium position of the liquid level in the working reservoir.

The suction line can either open directly into the control line or indirectly communicate with it. In the latter case, the control line can also open into the liquid-free region of the auxiliary reservoir, so that the intake and the control line communicate only indirectly with each other and undesired penetration of hydraulic fluid drawn in via the control line from the working reservoir into the air conveying device connected to the suction line is prevented.

Preferably, the control opening is formed in the control line as a circular or slot-shaped inlet, the latter can be oriented in the longitudinal direction of the control line. In particular, the control opening may be formed in an end region projecting into the working reservoir, for example through an open end of the control line. In the case of a plurality of control openings, these are preferably arranged one above the other in the end region of the control line.

Since during operation of the hydraulic system there is the possibility that turbulences in the hydraulic fluid occur, which can lead to an undesired ingress of air into the control line, it is advantageous if the control line is surrounded by a shielding element in the region of the control opening. The shielding element is designed or arranged such that an occurrence of turbulence in the region of the control opening is largely suppressed.

The shielding element may in particular be a cylindrical shielding tube, which is closed at its lower end by means of a liquid-permeable grid. The cylindrical shielding tube is dimensioned such that it forms, together with the control line, an annular gap open at the top, via which the control orifice communicate with the hydraulic fluid in the working reservoir can. In this case, when the liquid level falls in the working reservoir, the hydraulic fluid can flow away through the liquid-permeable grid.

In the case of excessive filling of the working reservoir with hydraulic fluid, there is the possibility that the liquid level in the working reservoir after commissioning of the air conveyor due to the limited capacity of the auxiliary reservoir can not fall sufficiently to expose the control port. In order to prevent undesired penetration of hydraulic fluid via the suction line or the control line into the air conveying device, it is advantageous if a throttle valve is arranged in the suction line and / or the control line which reduces the negative pressure built up by means of the air conveying device to uncritical values.

In principle, it is conceivable to provide a return valve instead of a throttle valve, which is blocked in the case of penetrating hydraulic fluid. The recoil valve has, in particular, a floating ball valve which, when hydraulic fluid penetrates, is pressed against a valve seat in such a way that an undesirable flow of hydraulic fluid is prevented.
At low operating temperatures and consequent increased viscosity of the hydraulic fluid, it is possible that after starting up the air conveyor located in the control line hydraulic fluid does not drain in the direction of the working reservoir and the liquid level in the working reservoir in the sequence can not assume a stable equilibrium position. This can ultimately lead to overfilling of the auxiliary reservoir and thus to an ingress of hydraulic fluid via the intake into the associated air conveyor. It is therefore advantageous in the control line in a liquid-free area Provide the working reservoir opening throttle valve, which reduces the built-up by means of the air conveyor in the suction negative pressure to non-critical values.

In addition, between the throttle valve and the air conveyor or the recoil valve and the air conveyor a pressure relief valve may be arranged such that this is permeable when a predetermined negative pressure is exceeded and produces a pressure equalization connection between the low pressure side of the air conveyor and the working reservoir. For this purpose, the pressure-limiting valve is either arranged directly in a liquid-free region of the working reservoir or connected thereto via a pressure compensation line. In the latter case, the pressure limiting valve is preferably arranged outside the working reservoir. The pressure limiting valve is in particular a conventional one-way valve.

Fig. 1

ein erstes Ausführungsbeispiel der erfindungsgemäßen Anordnung zur Versorgung eines Hydrauliksystems mit Hydraulikflüssigkeit,

Fig. 2

ein zweites Ausführungsbeispiel der erfindungsgemäßen Anordnung zur Versorgung eines Hydrauliksystems mit Hydraulikflüssigkeit, und

Fig. 3

ein drittes Ausführungsbeispiel der erfindungsgemäßen Anordnung zur Versorgung eines Hydrauliksystems mit Hydraulikflüssigkeit.

The inventive arrangement for supplying a hydraulic system with hydraulic fluid is explained in more detail below with reference to the accompanying drawings. With regard to their function, matching or comparable components are identified by the same reference numerals. Show it:

Fig. 1

A first embodiment of the inventive arrangement for supplying a hydraulic system with hydraulic fluid,

Fig. 2

A second embodiment of the inventive arrangement for supplying a hydraulic system with hydraulic fluid, and

Fig. 3

A third embodiment of the inventive arrangement for supplying a hydraulic system with hydraulic fluid.

Fig. 1 shows a first embodiment of the inventive arrangement for supplying a hydraulic system in an agricultural utility vehicle, not shown, with hydraulic fluid. The agricultural utility vehicle is, for example, a tractor, a harvesting machine, a forage harvester or a spraying machine.

The arrangement 10 accommodated in an engine compartment or in the region of a transmission assembly of the agricultural utility vehicle comprises a working reservoir 12 for receiving the hydraulic fluid intended for operation of the hydraulic system and an auxiliary reservoir 16 communicating with the working reservoir 12 via a hydraulic line 14 for temporary storage or buffering the working reservoir 12 removed hydraulic fluid.

The working reservoir 12 is designed, for example, as a differential housing of a differential gear encompassed by the agricultural utility vehicle. The hydraulic fluid in the differential housing also forms a sump for lubricating the differential gear. The hydraulic fluid is conventional hydraulic or gear oil.

In order to allow a free flow back and forth of the hydraulic fluid between the two reservoirs 12 and 16, the hydraulic line 14 extends between a lower portion of the working reservoir 12 and a lower portion of the auxiliary reservoir 16. According to the example, the auxiliary reservoir 16 is arranged elevated relative to the working reservoir 12 , where the Hydraulic line 14 is connected to a bottom of the auxiliary reservoir 16, so that the auxiliary reservoir 16 can be completely empty in the direction of the working memory 12.

The hydraulic fluid is supplied by means of a charging oil pump 18 via an intermediate oil filter 20 to an existing in the agricultural vehicle engine 22 and other power transmitting components for the purpose of lubrication. A controllable high-pressure pump 24 connected downstream of the oil filter 20 serves to supply hydraulically operated vehicle units 26, for example a steering and braking system or an attachment attachable to the agricultural utility vehicle, which has hydraulic actuating cylinders or the like. Not (more) required or excess hydraulic fluid is returned here via lines not shown in the working reservoir 12.

Furthermore, there is an air delivery device 28, which is connected on the low-pressure side to a suction line 32 opening into a liquid-free region 30 of the auxiliary reservoir 16, so that a negative pressure can be built up in the auxiliary reservoir 16 relative to the atmospheric ambient pressure, and the other side is connected to a control line 34 is, which has a plurality of similar, designed as throttle valves control openings 36a and 34b formed by a downwardly open end of the control line control opening 36b, wherein the control openings 36a and 36b at least before commissioning of the air conveyor 28, so before building the negative pressure in the auxiliary reservoir 16 of the hydraulic fluid located in the working reservoir 12 are completely covered.

This condition is in Fig. 1 indicated by the liquid level denoted by a).

If the air delivery device 28 is put into operation, hydraulic fluid from the working reservoir 12 flows against the action of gravity via the hydraulic line 14 into the auxiliary reservoir 16 due to the negative pressure built up in the auxiliary reservoir 16. In this case, the fluid level drops in the working reservoir 12, so that the control ports 36a and then successively the control port 36b are exposed and the negative pressure built up in the suction line 32 due to the air sucked in from the environment via the control line 34 to a dependent of the flow resistance of the exposed control openings 36a and 36b and for setting or adjusting a corresponding equilibrium position of the liquid level in the working reservoir 12 Value drops. This condition is in Fig. 1 indicated by the liquid level denoted by b).

According to the example, the control openings 36a and 36b are arranged one above the other in an end region 38 of the control line 34 projecting into the working reservoir 12. The control openings 36a are formed in the control line 34 as circular or slot-shaped inlets, the latter being oriented in the longitudinal direction of the control line 34. The control opening 36b formed by the open end of the control line 34 typically has a diameter of the order of 25 millimeters.

It should be noted at this point that the representation of a plurality of control openings 36a and 36b has merely exemplary character. Alternatively, it is also conceivable to provide only a single control opening 36b in the form of a downwardly open end of the control line 34.

The air conveying device 28 is a conventional vacuum pump driven electrically or by means of the internal combustion engine 22 of the agricultural utility vehicle Design type. This generates in the auxiliary reservoir 16, a negative pressure in the order of typically 50 mbar.

According to an advantageous development of the arrangement 10 according to the invention, the control line 34 is surrounded by a shielding element 40 in the region of the control openings 36a and 36b. The shielding element 40 is a cylindrical shielding tube 42, which is closed at its lower end by means of a liquid-permeable grid 44. The cylindrical shielding tube 42 is dimensioned such that it forms, together with the control line 34, an upwardly open annular gap 46, via which the control openings 36a and 36b can communicate with the hydraulic fluid in the working reservoir 12.

With excessive filling of the working reservoir 12 with hydraulic fluid, there is the possibility that the liquid level in the working reservoir 12 after commissioning the air conveyor 28 due to the limited capacity of the auxiliary reservoir 16 is unable to fall sufficiently to expose the control ports 36a and in particular the control port 36b. In order to prevent an undesired penetration of hydraulic fluid into the intake line 32 or the control line 34 and thus ultimately into the air delivery device 28, a throttle valve 48 or 50 is respectively arranged in the intake line 32 and control line 34, which controls the negative pressure built up by means of the air delivery device 28 increases upon entry of hydraulic fluid such that a arranged between the throttle valve 48 and 50 and the air conveyor 28 pressure relief valve 52 is permeable when a predetermined negative pressure is exceeded and thereby produces a pressure equalization connection between the low pressure side of the air conveyor 28 and the working reservoir 12. The pressure relief valve 52 is for this purpose directly in a liquid-free region of the working reservoir 12 arranged. The pressure relief valve 52 is a conventional one-way valve.

Fig. 2 shows a second embodiment of the inventive arrangement for supplying a hydraulic system with hydraulic fluid. This differs from the one in Fig. 1 illustrated first embodiment that instead of the two throttle valves 48 and 50, only a single throttle valve 54 is provided. Furthermore, the pressure limiting valve 52 is arranged in the present case outside the working reservoir 12 and connected thereto via a pressure equalization line 56.

At low operating temperatures and consequent increased viscosity of the hydraulic fluid, it is possible that after starting the air conveyor 28 located in the control line 34 hydraulic fluid does not drain in the direction of the working reservoir 12 and the liquid level in the working reservoir 12 in the sequence can not assume a stable equilibrium position. This can ultimately lead to overfilling of the auxiliary reservoir 16 and thus to an ingress of hydraulic fluid via the suction line 32 into the associated air conveyor 28. It is therefore provided in the control line 34 in a liquid-free region of the working reservoir 12 opening throttle valve 60, which prevents at low operating temperatures and consequent increased viscosity of the hydraulic fluid in conjunction with the pressure relief valve 52 (comparable to the throttle valve 54) that when commissioning the air conveyor 28 an excessive negative pressure in the intake pipe 32 is constructed. The flow resistance of the throttle valve 60 is dimensioned such that at normal operating temperatures, a sufficient negative pressure in the suction line 32 connected to the control line 34 and thus in the auxiliary reservoir 16 can be established.

Fig. 3 shows a third embodiment of the inventive arrangement for supplying a hydraulic system with hydraulic fluid. This differs from the one in Fig. 2 illustrated second embodiment that instead of the throttle valve 54, a return valve 58 is provided which is arranged such that it is blocked in the case of penetrating hydraulic fluid. The recoil valve 58 has a floating ball valve which is pressed upon penetration of hydraulic fluid against a valve seat such that an undesirable flow of hydraulic fluid is prevented. In contrast to the two preceding embodiments, the intake manifold 32 does not open directly into the control line 34. Rather, there is only an indirect connection between the intake manifold 32 and the control line 34. For this purpose, the control line 32 also opens into the liquid-free region 30 of the auxiliary reservoir 16. Since the Both lines 32 and 34 communicate only indirectly with each other in this case, an additional protection against undesired penetration of hydraulic fluid sucked in via the control line 34 from the working reservoir 12 into the air conveying device 28 connected to the suction line 32. According to the example, the intake line 32 and the control line 34 are connected to an upper side of the auxiliary reservoir 16.

Claims (16)

1. Arrangement for supplying hydraulic liquid to a hydraulic system, having a working reservoir (12) for accommodating the hydraulic liquid provided for the operation of the hydraulic system, and having an auxiliary reservoir (16), which is connected to the working reservoir (12) via a hydraulic line (14), for temporarily storing hydraulic liquid extracted from the working reservoir (12), wherein an air delivery device (28) is provided which is connected at the low-pressure side firstly to an intake line (32) which opens into a liquid-free region (30) of the auxiliary reservoir (16), such that a negative pressure in relation to the atmospheric ambient pressure can be built up in the auxiliary reservoir (16), characterized in that the air delivery device (28) is connected secondly to a control line (34) which has a control opening (36a, 36b) which, at least before the air delivery device (28) is started up, is covered by the hydraulic liquid situated in the working reservoir (12).
2. Arrangement according to Claim 1, characterized in that the hydraulic line (14) extends between a lower region of the working reservoir (12) and a lower region of the auxiliary reservoir (16).
3. Arrangement according to either of Claims 1 and 2, characterized in that the intake line (32) opens out directly into or is directly connected to the control line (34).
4. Arrangement according to one of Claims 1 to 3, characterized in that the control opening (36a, 36b) in the control line (34) is formed as a circular or slot-shaped inlet.
5. Arrangement according to one of Claims 1 to 4, characterized in that the control opening (36a, 36b) is formed in an end region (38), which projects into the working reservoir (12), of the control line (34).
6. Arrangement according to one of Claims 1 to 5, characterized in that a plurality of control openings (36a, 36b) are formed in that end region (38) of the control line (34) which projects into the working reservoir (12), the control openings (36a, 36b) being arranged one above the other.
7. Arrangement according to one of Claims 1 to 6, characterized in that the control opening (36a) is formed as a throttle valve.
8. Arrangement according to one of Claims 1 to 7, characterized in that the control line (34) is surrounded, in the region of the control opening (36a, 36b), by a shield element (40).
9. Arrangement according to one of Claims 1 to 8, characterized in that the shield element (40) is a cylindrical shield tube (42).
10. Arrangement according to one of Claims 1 to 9, characterized in that the cylindrical shield tube (42) is closed off at its lower end by means of a liquid-permeable grate (44).
11. Arrangement according to one of Claims 1 to 10, characterized in that the cylindrical shield tube (42) is dimensioned so as to form, together with the control line (34), an upwardly open annular gap (46) via which the control opening (36a, 36b) can communicate with the hydraulic liquid situated in the working reservoir (12).
12. Arrangement according to one of Claims 1 to 11, characterized in that a throttle valve (48, 50, 54) is arranged in the intake line (32) and/or the control line (34).
13. Arrangement according to one of Claims 1 to 12, characterized in that a check valve (58) is arranged in the intake line (32) and/or in the control line (34).
14. Arrangement according to one of Claims 1 to 13, characterized in that a throttle valve (60) which opens into a liquid-free region of the working reservoir (12) is provided in the control line (34).
15. Arrangement according to one of Claims 1 to 14, characterized in that a pressure limiting valve (52) is arranged between the throttle valve (48, 50, 54, 60) and the air delivery device (28), or between the check valve (58) and the air delivery device (28), in such a way that a pressure-equalizing connection can be produced between the low-pressure side of the air delivery device (28) and the working reservoir (12).
16. Motor vehicle, in particular agricultural utility vehicle, having an arrangement (10) for supplying hydraulic liquid to a hydraulic system according to one of Claims 1 to 15.

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