DE19813038A1 - Hydraulic circuit with hydraulic pump - Google Patents

Abstract

The user units (18,22) are arranged in series in the hydraulic circuit and parallel to at least one second user unit in a channel (38) bridging over it is a threshold pressure valve (40), which is controllable by a pressure applied to a first user unit so that with a predetermined first threshold pressure at the first user unit the threshold pressure valve opens the over-bridging channel. The first user is a servo-steering nit with a current regulator (24) pre-connected in series. The second user unit is a fan hydraulic motor for a fan (20) of a cooling circuit. The hydraulic circuit is fitted in a road vehicle and the hydraulic pump is driven from an internal combustion engine.

Description

The invention relates to a hydraulic circuit with a hydraulic pump and at least two from consumers driven by hydraulic pressure generated by the hydraulic pump, according to the preamble of claim 1. The invention further relates to a hydraulic valve, in particular for use as a threshold pressure valve in a hydraulic circuit mentioned above an upstream input, a downstream output, and one Control input, at which a control pressure can be applied, one with the input, the Output and the control input connected bore with an axially displaceable therein mounted piston is provided, according to the preamble of claim 13.

In a hydraulic circuit, one or more consumers are usually replaced by the a hydraulic pump generated and transmitted by a hydraulic fluid energy driven. If there are several consumers, all must function properly Consumers in any load state of the same, the hydraulic pump at the maximum load maximum performance of all consumers. However, this is expensive and complex and is usually disproportionate to the benefit, since an operating state with at the same time maximum power consumption of all consumers very rarely and if usually only occurs briefly.

An example of one in any motor vehicle with power steering or power steering Existing hydraulic circuit is a rack and pinion hydraulic steering, one Hydraulic pump Hydraulic fluid, such as hydraulic oil, through a rotary valve and steering cylinder pumps a steering. However, there is a constant flow of Hydraulic oil is required, such as 7 liters per minute, whereas one Internal combustion engine driven hydraulic pump depending on the speed promotes different flow rates. Therefore, the power steering is usually Drive of the hydraulic pump dimensioned such that the already at an idling speed Internal combustion engine the 7 liters per minute required for the steering aid, for example  be promoted. Furthermore, there is also a series in the hydraulic circuit in front of the steering Current regulator arranged, which has a constant flow of, for example, 7 liters per Minute guaranteed and an additional amount of hydraulic oil delivered over a Returns line to the hydraulic pump. In addition, is usually parallel to Steering arranged in the hydraulic circuit, a pressure relief valve.

However, this system has the disadvantage that that of the current regulator over the Return line derived hydraulic oil flow remains unused as a loss line. It is for example from DE 43 25 113 A1 a flow control valve for a power steering pump known which the function of the current regulator and pressure limiter in one component united, but here too the hydraulic oil flow derived from the current regulator remains unused. Did you want to use this energy by having an additional consumer grinds in, however, there is the problem that the steering and the additional Overall, consumers have a higher maximum power requirement than that Nominal output or maximum output of the hydraulic pump. However, since the function of the Power steering in no operating condition affected by the additional consumer may be, the hydraulic pump would have to be dimensioned accordingly larger. This however immediately nullifies all advantages of using the power loss of the current regulator, since then the operation of the additional consumer in its own hydraulic circuit is cheaper is.

The present invention is therefore based on the object of a hydraulic circuit and a to provide a correspondingly adapted hydraulic valve of the type mentioned above, the above disadvantages are overcome and multiple consumers in one single hydraulic circuit without functional restriction of at least one of the consumers are operable, but without adding up the hydraulic pump to a maximum Need to adjust the power requirements of all consumers.

This object is achieved by a hydraulic circuit of the above. Kind of with the in Characterized features of claim 1 and by a hydraulic valve of the above. Kind with the features characterized in claim 13 solved. Advantageous embodiments of the Invention are specified in the dependent claims.  

For this it is the above-mentioned hydraulic circuit. Art according to the invention provided that the Consumers in the hydraulic circuit are arranged in series and parallel to at least a second consumer in a channel bridging this second consumer Threshold pressure valve is arranged, which from one to at least a first Consumer pressure is controllable so that at a predetermined first Threshold pressure at the first consumer the threshold pressure valve the bypass channel opens.

This has the advantage that of a hydraulic pump in a single hydraulic circuit several consumers can be driven, with a respective first consumer at high Energy demand can turn off a respective second consumer, so that Hydraulic pump only has to be dimensioned such that it has a full load on the or can deliver to the first consumers. An interpretation of the hydraulic pump on one Full load condition, in which all consumers their respective maximum load absorption claim, is thus a primary load priority or preference of the first consumer dispensable.

In a preferred embodiment, the first consumer is a power steering and the second consumer, for example a fan motor. This is an advantageous Excess hydraulic flow running through the current regulator, which in itself is a Power loss represents, exploited by a fan motor, the power steering has priority over the fan motor. In other words, the fan motor bypasses when the power steering in a peak load the full load of the only one Hydraulic pump needed.

The hydraulic circuit is arranged, for example, in a motor vehicle and the Hydraulic pump is from a drive unit, in particular one Internal combustion engine, driven.

In an expedient development of the invention, three or more consumers are in a single hydraulic circuit with a single one, only for a full load of the first Consumer sized hydraulic pump driven by two or more second consumers are provided, the pressure at the first consumer being all respective Activates threshold pressure valves of the second consumer. With a full load on the  first consumers or at full load at one of the first consumers suddenly all second consumers switched off or bridged.

A predetermined prioritization for that available from the hydraulic pump standing drive energy in the hydraulic circuit is achieved by having two or more first Consumers and two or more second consumers are provided, each printing of each first consumer at least one threshold pressure valve of at least one controls second consumer.

A cascade-like sequence of priorities for those present in the hydraulic circuit Drive energy is achieved by providing two or more second consumers are, wherein a pressure of at least a second consumer at the same time Threshold pressure valve controls at least one other second consumer. Depending on An increase in the load status or energy requirements of the individual consumers turned off one by one with increasing priority until only the one or the top priority first consumer, which pure first consumer without Threshold pressure valve are to be supplied with hydraulic energy. Then everyone is here controlling second consumers at the same time a first consumer.

Peak loads and overloading of the hydraulic circuit, for example due to a brief or permanent blocking of a hydraulic motor of a respective second consumer thereby avoided that a hydraulic pump side input of the threshold pressure valve is simultaneously designed as an additional control input such that at one predetermined second threshold pressure at this hydraulic pump-side input Threshold pressure valve opens the bypass channel.

In a particularly preferred embodiment, is parallel to at least one second Consumer a check valve, a pressure relief valve parallel to the hydraulic pump and / or a pressure relief valve parallel to at least one first consumer arranged.

A load and / or speed control of a respective second consumer is achieved in that an electrically controllable parallel to at least one second consumer Valve is arranged.  

With a hydraulic valve the above. Art is provided according to the invention that the piston is designed such that it divides the bore into two separate rooms, wherein a first space delimited by a first piston surface with the control input is connected and a second space delimited by a second piston surface with the Input and, depending on the piston position, optionally connected to the output, whereby a The circumference of the second surface strikes against a wall of the bore and the spring Force is applied to the piston in the stop direction, the arrangement being such that that the pressure at the control input pushes the piston with a force opposite to the spring force acted upon, the first surface, the second surface and the spring being dimensioned in this way are that the piston at a first predetermined pressure at the control input and / or at a second predetermined pressure at the entrance to the second space towards the exit opens.

This has the advantage that the hydraulic valve in the manner of a threshold pressure valve Exceeding a first predetermined threshold pressure at the control input and / or at Exceeding a second predetermined threshold pressure at the inlet opens suddenly. This opening process can take place slowly or quickly. That way it stands an essentially digitally operating hydraulic valve is available, d. H. at predetermined pressure ratios, the valve is either open or closed. This is in an advantageous manner, in particular for optionally bridging a hydraulic one Suitable for consumers.

In a preferred embodiment, the first surface is on a first piston part and the second surface is formed on a second piston part, wherein the piston parts by means of a Koibenstange spaced from each other and forming the second space between them are rigidly connected to each other.

A space-saving and compact design is achieved in that in the second piston part a third space is left open at one end facing away from the piston rod is designed to accommodate the spring.  

A corresponding ventilation of the third room is achieved by the third A fluid-conducting connection to the second room and / or to a room Has hydraulic fluid tank.

A firm and tight valve seat is achieved by the wall of the bore which strikes the second surface with a predetermined angle with respect to the second surface is trained. Furthermore, this ensures that the surfaces of the piston, which the second Define space, are different sizes, so that the piston on the pressure force acting on the input does not cancel, but a predetermined force component in Direction against the spring force. This is an advantageous Triggering or opening of the valve even when the second is exceeded predetermined pressure at the input ensured so that a double function of Hydraulic valve is implemented: 1. Pressure monitoring and triggering or opening the valve at a first predetermined pressure at the control input and 2. pressure monitoring and Triggering or opening of the valve at the second predetermined pressure at the inlet.

Further features, advantages and advantageous configurations of the invention result from the dependent claims, as well as from the following description of the invention based on the attached drawings. These show in

Fig. 1 is a block diagram of a preferred embodiment of a hydraulic circuit according to the invention and

Fig. 2 is a sectional view of a preferred embodiment of a hydraulic valve according to the invention.

The preferred embodiment of a hydraulic circuit 10 according to the invention shown by way of example in FIG. 1 comprises a hydraulic pump 12 which conveys a hydraulic fluid, such as hydraulic oil, from an oil sump 14 . A pressure relief valve 16 is connected in parallel to the hydraulic pump 12 . After the hydraulic pump 12 , two consumers are connected in series, namely a steering 18 as the first consumer and a fan 20 with a hydraulic motor 22 as the second consumer. This fan 20 is part of a cooling circuit for an internal combustion engine in a motor vehicle, for example.

A current regulator 24 is inserted in series in front of the steering, which ensures a constant throughput of hydraulic oil to the steering 18 of, for example, 7 liters per minute. A volume flow going beyond this from the hydraulic pump 12 is branched off by the current regulator 24 via a return line 26 with a strainer 27 and a filter 29 and is fed back to the oil sump 14 near a suction point of the hydraulic pump 12 . This has the advantage that any kinetic energy still present in the returned hydraulic oil is used by the immediate suction again by the hydraulic pump, thus relieving the hydraulic pump 12 . Furthermore, a pressure relief valve 28 is arranged parallel to the steering 18 . Hydraulic oil is conveyed out of the steering 18 via a return line 30 back to the oil sump 14 , which has flowed through the steering 18 and has done work there. Since this hydraulic oil may be heated, it runs into the oil sump 14 at a point remote from the suction point of the hydraulic pump 12 so that it can cool down before being sucked in again by the hydraulic pump 12 . During the entire operating phase of the steering, there is therefore a more or less excessive excess flow through the return line 26 , which represents a power loss. This power loss is now at least partially used by the fan hydraulic motor 22 .

Arranged parallel to the hydraulic motor 22 of the fan 20 is an electrically controllable hydraulic valve 32 which is controlled by an electrical control means 34 such that the speed can be adjusted in the cooling circuit as required. Since the fan 20 in a motor vehicle is possibly driven by an air stream and then the hydraulic motor 22 itself possibly pumps hydraulic oil, a check valve 36 connected in parallel ensures that there are no undesirable overpressures in the hydraulic circuit 10 .

The fan hydraulic motor 22 requires, for example, a pressure of 16 bar at full load and the steering 18 a pressure of 80 bar. In addition, there are line losses and throttling losses, which are strongly temperature-dependent owing to the relevant dependence on the viscosity of the hydraulic oil and amount to 10 bar, for example. The hydraulic pump of a power steering, for example, has a maximum operating pressure of 120 bar. Thus, if the steering 18 and the fan hydraulic motor 22 operate at full load, the system pressure in the hydraulic circuit adds up to a pressure above the maximum pressure of the hydraulic pump 12 , at least in brief operating phases. However, this can lead to a restricted functionality of the steering 18 , which is to be avoided in any case.

Therefore, according to the invention, a bridging channel 38 with a threshold pressure valve 40 is arranged in the hydraulic circuit parallel to the fan hydraulic motor 22 , which is controlled via a control line 42 by a pressure prevailing at the steering. As soon as this pressure exceeds a predetermined first threshold value, that is to say when the steering 18 has a high energy requirement, for example in the event of a sudden and rapid steering maneuver, the threshold pressure valve 40 opens the bridging channel 38 , so that the fan hydraulic motor 22 is bridged and all hydraulic energy flows into the steering 18 . The fan 20 is thus switched off for the duration of the large power requirement of the steering 18 . Since such operating phases usually occur extremely rarely and briefly, there are no problems in a cooling circuit assigned to the fan 20 , since the fan 20 only has a brief drop in speed.

The hydraulic circuit shown is only shown by way of example with only two consumers 22 and 18 . According to the invention, the system can be expanded from first consumer 18 , which switches off a second consumer 22 if necessary, to three or more consumers. For example, in the manner specified above, a single first consumer, which has the highest priority, switches off all other second consumers when the first consumer has a corresponding power requirement. Alternatively, however, it is also possible that a first consumer switches off a second consumer and this second consumer in turn can switch off another second consumer as the first consumer, so that a cascade-like sequence of priorities results, the corresponding predetermined pressures or threshold pressures, each of which is switched off, are selected accordingly descending or ascending. A combination of this cascade arrangement with the aforementioned arrangement with first consumers, which each switch off a plurality of second consumers, is also possible. The expression "first consumer" designates a consumer in the hydraulic circuit which has a higher priority with respect to a hydraulic energy supply than a consumer in the hydraulic circuit labeled "second consumer". In other words, each first consumer switches off at least one second consumer when the first consumer has a high power requirement. Here, a second consumer can turn off at least one other second consumer, so that a second consumer can also be a first consumer at the same time.

Fig. 2 shows an example of a preferred embodiment of Schwelldruckventiles 40 according to the invention. This comprises a housing 44 with a bore 46 , an upstream inlet 48 , a downstream outlet 50 and a control input 52 , which are each connected to the bore 46 . These are also designated in FIG. 1 to illustrate the installation position in the hydraulic circuit 10 . The bore 46 is closed by a cover 54 .

A piston 56 with a first piston part 58 , a second piston part 60 and a piston rod 62 connecting them is axially displaceably arranged in the bore 46 . The piston 56 divides the bore 46 into a first space 64 connected to the control input 52 and a second space 66 connected to the input 48 . The piston 56 separates the first space 64 with a first surface 68 on the first piston part 58 and the second space with a second surface 70 on the second piston part 60 . The two spaces 64 and 66 are completely separated from one another by the piston 56 .

A circumference of the second surface 70 abuts an inclined wall 72 of the bore 46 in the manner of a valve seat, so that, depending on the axial displacement of the piston 56, the outlet 50 is either connected to the second space 66 or not. If the second space 66 is connected to the outlet 50 , the hydraulic valve 40 and thus the bridging channel 38 ( FIG. 1) are open. The second piston part 60 forms a third space 74 , in which a spring 76 is arranged, which is supported on the cover 54 and exerts a force on the piston 56 in the stop direction on the inclined wall 72 . The control input 52 and the first surface 68 and the second surface 70 are arranged such that the respective pressures in the input 48 and in the control input 52 exert a force on the piston 56 against the spring force. In the rest position, the piston 56 is thus pressed with the circumference of the second surface 70 against the inclined wall 72 , as a result of which the second space 66 is separated from the outlet 50 . In this state, the hydraulic valve 40 and thus the bridging channel 38 ( FIG. 1) are closed.

The inclined wall 72 results in a second surface 70 which is larger than the surface of the first piston part 58 which is correspondingly opposite in the second space 66 , so that the result at the pressure at the inlet 48 is a force component against the direction of the spring force. Furthermore, the second surface 70 is dimensioned larger than the first surface 68 , so that a threshold pressure opening the valve 40 at the inlet 48 is lower than a threshold pressure opening the valve 40 at the control inlet 52 .

During operation, the threshold pressure valve 40 opens suddenly and digitally a passage from the input 48 to the output 50 as soon as a first predetermined threshold pressure is exceeded in the control input 52 and / or a second predetermined threshold pressure is exceeded in the input 48 . The first predetermined threshold pressure is, for example, less than, equal to or greater than the second predetermined threshold pressure. This can be adjusted with a corresponding dimensioning of spring 76 and surfaces 68 and 70 . In the exemplary embodiment of the threshold pressure valve 40 shown in FIG. 2, the second triggering threshold pressure is lower than the first triggering threshold pressure.

The third space 74 is, for example, as shown in FIG. 2, connected to the second space 66 for ventilation via a hole 78 . However, it is also possible to provide a fluid-conducting connection from the third space 74 to a hydraulic oil tank or to the oil sump 14 ( FIG. 1) instead.

Reference list

10th

Hydraulic circuit

12th

hydraulic pump

14

Oil sump

16

Hydraulic pump pressure relief valve

18th

steering

20th

Fan

22

Hydraulic motor from fan

24th

Current regulator

26

Return line from current regulator

27

Sieve

28

Steering pressure relief valve

29

filter

30th

Return line from steering

32

electrically controllable hydraulic valve of the fan hydraulic motor

34

electrical control means

36

check valve

38

Bridging channel

40

Threshold pressure valve

42

Control line

44

casing

46

drilling

48

upstream entrance

50

downstream outlet

52

Control input

54

cover

56

piston

58

first piston part

60

second piston part

62

Piston rod

64

first room

66

second room

68

first area

70

second area

72

sloping wall

74

third room

76

feather

78

Hole for venting the third room

Claims (17)

1. Hydraulic circuit ( 10 ) with a hydraulic pump ( 12 ) and at least two consumers ( 18 , 22 ) driven by a hydraulic pressure generated by the hydraulic pump ( 12 ), characterized in that the consumers ( 18 , 22 ) in the hydraulic circuit ( 10 ) are arranged in series and parallel to at least one second consumer ( 22 ) in a channel ( 38 ) bridging this second consumer ( 22 ) there is a threshold pressure valve ( 40 ) which can be controlled in this way by a pressure applied to at least one first consumer ( 18 ) is that at a predetermined first threshold pressure at the first consumer ( 18 ) the threshold pressure valve ( 40 ) opens the bypass channel ( 38 ). 2. Hydraulic circuit ( 10 ) according to claim 1, characterized in that the first consumer ( 18 ) is a power steering system with a series-connected current controller ( 24 ). 3. Hydraulic circuit ( 10 ) according to claim 1 or 2, characterized in that the second consumer ( 22 ) is a fan hydraulic motor for a fan ( 20 ) of a cooling circuit. 4. Hydraulic circuit ( 10 ) according to one of the preceding claims, characterized in that the hydraulic circuit ( 10 ) is arranged in a motor vehicle and the hydraulic pump ( 12 ) is driven by a drive unit, in particular an internal combustion engine. 5. Hydraulic circuit ( 10 ) according to one of the preceding claims, characterized in that two or more second consumers ( 22 ) are provided, the pressure at the first consumer ( 18 ) actuating all respective threshold pressure valves ( 40 ) of the second consumer ( 22 ). 6. Hydraulic circuit according to one of the preceding claims, characterized in that two or more first consumers ( 18 ) are provided, each pressure of each first consumer ( 18 ) controls at least one threshold pressure valve ( 40 ) from at least one second consumer ( 22 ). 7. Hydraulic circuit ( 10 ) according to one of the preceding claims, characterized in that two or more second consumers ( 22 ) are provided, wherein a pressure of at least one second consumer ( 22 ) simultaneously a threshold pressure valve ( 40 ) at least one other second consumer ( 22nd ) controls. 8. Hydraulic circuit ( 10 ) according to one of the preceding claims, characterized in that a hydraulic pump-side input ( 48 ) of the threshold pressure valve ( 40 ) is simultaneously formed as an additional control input such that the threshold pressure valve at a predetermined second threshold pressure at this hydraulic pump-side input ( 48 ) ( 40 ) opens the bridging channel ( 38 ). 9. Hydraulic circuit ( 10 ) according to any one of the preceding claims, characterized in that a check valve ( 36 ) is arranged parallel to at least one second consumer ( 22 ). 10. Hydraulic circuit ( 10 ) according to one of the preceding claims, characterized in that a pressure relief valve ( 28 ) is arranged parallel to at least one first consumer ( 18 ). 11. Hydraulic circuit ( 10 ) according to one of the preceding claims, characterized in that a pressure relief valve ( 16 ) is arranged parallel to the hydraulic pump ( 12 ). 12. Hydraulic circuit ( 10 ) according to one of the preceding claims, characterized in that a controllable valve ( 32 ) is arranged parallel to at least one second consumer ( 22 ). 13. Hydraulic valve ( 40 ), in particular for use as a threshold pressure valve in a hydraulic circuit according to one of the preceding claims, with an upstream inlet ( 48 ), a downstream outlet ( 50 ) and with a control input ( 52 ) to which a control pressure can be applied, A bore ( 46 ) connected to the inlet ( 48 ), the outlet ( 50 ) and the control inlet ( 52 ) is provided with a piston ( 56 ) axially displaceably mounted therein, characterized in that the piston ( 56 ) is designed in this way that it divides the bore ( 46 ) into two separate spaces, a first space ( 64 ) being delimited by a first piston surface ( 68 ) and being connected to the control input ( 52 ) and a second space ( 66 ) being connected by a second piston surface ( 70 ) delimited with the inlet ( 48 ) and, depending on the piston position, optionally connected to the outlet ( 50 ), a circumference of the second surface ( 70 ) on a wall ( 72 ) de r bores ( 46 ) and a spring ( 76 ) acts on the piston ( 56 ) with force in the stop direction, the arrangement being such that the pressure at the control input ( 52 ) acts on the piston ( 56 ) with a force opposite to the spring force , wherein the first surface ( 68 ), the second surface ( 70 ) and the spring ( 76 ) are dimensioned such that the piston ( 56 ) at a first predetermined pressure at the control input ( 52 ) and / or at a second predetermined pressure at Entrance ( 48 ) opens the second room ( 66 ) towards the exit ( 50 ). 14. Hydraulic valve ( 40 ) according to claim 13, characterized in that the first surface ( 68 ) on a first piston part ( 58 ) and the second surface ( 70 ) on a second piston part ( 60 ) is formed, the piston parts ( 58 , 60 ) are spaced apart from one another by means of a piston rod ( 62 ) and are rigidly connected to one another to form the second space ( 66 ). 15. Hydraulic valve ( 40 ) according to claim 14, characterized in that in the second piston part ( 60 ), a third space ( 74 ) is recessed and open at one end facing away from the piston rod ( 62 ) for receiving the spring ( 76 ). 16. Hydraulic valve ( 40 ) according to claim 15, characterized in that the third space ( 74 ) has a fluid-conducting connection ( 78 ) to the second space ( 66 ) and / or to a hydraulic fluid tank. 17. Hydraulic valve ( 40 ) according to one of claims 13 to 16, characterized in that the wall ( 72 ) of the bore ( 46 ), on which the second surface ( 70 ) abuts, with a predetermined angle with respect to the second surface ( 70 ) is trained.