EP2251549A2 - Hydraulic assembly - Google Patents

Abstract

The assembly (1) has a pressuring medium pump (3) driven by a motor unit and comprising a load (4) with a pressurizing medium (5), where the motor unit is in form of an internal combustion engine. A pressuring medium accumulator (6) is recharged from the pressuring medium pump. A priority valve (7) controls electric charging of the pressuring medium accumulator and the pressuring medium supply unit of the load dependence of a momentary output of the motor unit. Connecting or disconnecting process of a pressuring medium supply is controlled by the load and/or another load (8) of a valve (9).

Description

The invention relates to a hydraulic system, in particular for a commercial vehicle, such as a construction machine, agricultural machine, forklift, with one of a motor unit, in particular in the form of an internal combustion engine, driven pressure medium pump.

Hydraulic systems for commercial vehicles, in particular for construction machines, agricultural machines and off-road machines including forklifts, are generally composed of several hydrostatic drive systems. In addition to the steering hydraulics, these include the cooling, control and feeding hydraulics as well as the driving hydraulics. Depending on their basic structure, these systems can work partially independently of each other and fulfill their function.

In moving construction machines, the steering system is regularly operated with a steering valve with "open center", wherein a constant pump often formed as external gear pump promotes non-actuated steering system against the pressure fluid tank of the construction machine. Through the use of a so-called. Open hydraulic circuit, for example, the functions cooling, control and supply circuit can be covered with only one pressure medium pump. This may be an external gear pump with a constant displacement volume, which is attached to a power take-off of the internal combustion engine as a motor unit. For example formed as external gear constant motor cooling motor can be provided a parallel connection of control and feed hydraulic circuit. The control pressure system is used for signal transmission of certain machine characteristics, such as the control of a disk parking brake or a swivel angle adjustment of the drive pump by means of trigger valve. Through the use of the feed system, both the supply of fresh, purified hydraulic oil and an internal leakage compensation takes place.

The design of mobile work machines has also become increasingly marked in recent years by the requirements of European emissions legislation. Since 2008, the European Emission Directive III A applies to all engine power classes of mobile machinery. After the entry into force of the already agreed exhaust emission level III B from 2010, a further reduction of nitrogen oxides by up to 94%, which is currently feasible only through the use of particulate filters. A final emissions standard IV 2014 provides for a further reduction of nitrogen oxides by up to 88% compared to Stage III B. In particular, this last emission stage IV presents the construction machinery and diesel engine manufacturers with major challenges. For installation of a selective catalyst system (SCR) together with the associated urea tank, additional installation space is required on the respective machine, which leads to a high constructive and logistical effort, especially in large-scale machine series.

Taking into account the elaborate exhaust aftertreatment systems and the associated effects, especially the engine performance class up to 56 kW by eliminating the EU emission standard IV is an interesting alternative for machine manufacturers. By means of an energetic optimization of the existing drive systems, a diesel engine power reduction to below the mentioned 56 kW power limit achievable, ie it is the so-called "downsizing" of the internal combustion engine sought.

Based on the cited prior art, the invention is therefore based on the object to provide a hydraulic system for a commercial vehicle, which allows a reduction in power (downsizing) for the internal combustion engine. This object is achieved with a hydraulic system with the features in the entirety of claim 1.

Characterized in that according to the invention power peaks of the motor unit, in particular in the form of an internal combustion engine, are compensated by the use of a pressure medium accumulator, wherein the accumulator is charged or discharged in response to a current power output of the motor unit, a constructive measure is created, the overall performance of the motor unit in the sense from downsizing to a predefinable value, for example to the statutory engine power class up to 56 kW. According to the invention, the pressure medium supply to the consumers and to the accumulator of the hydraulic system is controlled by a priority valve. A connection and disconnection of the pressure medium supply to one or more consumers is controlled by a further valve.

Preferred embodiments will be apparent from the dependent claims.

In a preferred embodiment of the hydraulic system according to the invention the energy supply of the internal combustion engine is so exploited with the help of a suitable storage charging and discharging that needs to be promoted at a Zuschaltphase the accumulator to a consumer in the ideal case of the pressure medium pump less to no pressure medium to the respective consumer and vice versa, if one or more consumers are out of service, in a kind of stationary machine phase of the internal combustion engine of the accumulator is charged. By virtue of this system structure, a short-term requirement requirement of a consumer can be covered by the accumulator independently of a current machine cycle.

A preferably so-called open basic position of the further valve for connection or disconnection of the consumer based on the accumulator guarantees that, for example, suitable construction or machinery with disconnected internal combustion engine and full accumulator Notlenkeigenschaften a steering system of the construction or working machine can be ensured.

Generally, in the hybridization concept of consumers according to the invention, there is the possibility of a hydraulic energy absorption and recovery both from the high pressure side and on the low pressure side of the pressure medium pump. The goal of supplying energy to the pump high-pressure side is mainly reflected in consumer support. In this case, a higher, short-term start-up dynamics of a consumer can be achieved or a partial discharge of a pressure medium pump designed as a variable displacement pump. In a discharge of the accumulator to a low pressure side of the pressure medium pump, a short-term reduction of the drive torque of the pressure medium pump is achieved. This also represents a possibility of a much more efficient use of energy. As stated above, not only is it possible to feed in on the high-pressure side of the pump-motor unit, but also to supply it on the low-pressure side. For an injection on the suction side of the pump is preferably an additional check valve to provide, which opens in the direction of the pump, and a tank connection to the pump necessary. The pertinent tank connection is preferably realized by a corresponding connection in Prioventil.

In general, the implementation of a parallel hybrid according to the invention can be carried out in the frame outlined on the basis of a resistance or displacement control, wherein the adaptation of the hydraulic pressure fluid storage variables - volume flow and pressure - by the interpretation of the pressure fluid accumulator discharging valve as a proportional valve is preferred. At the same time, the throttle losses incurred at the valve can be used to control the system variables.

The control of the priority valve is carried out in a particularly preferred embodiment by the use of pressure sensors, whereby the charge and discharge phase of the accumulator and a delivery volume adjustment of a pressure medium source formed as a variable pressure medium pump for the consumer and the accumulator. A first pressure sensor provides a signal reflecting the load pressure of the consumer, a second pressure sensor maps a current accumulator pressure of the accumulator, while a third pressure sensor depicts the fluid pressure on the high pressure side of the pressure medium pump. By integrating the three pressure sensors, a demand-based volume power supply can be realized as a function of the respective consumer.

Particularly preferably, the priority valve is designed as a 3/2 continuous valve whose functionality is similar to a 3-way flow control unit which preferably experiences a double-sided hydraulic actuation, for example by a pressure sensor which maps the pressure medium storage charge state and detects the fluid pressure on the high pressure side of the pressure medium pump. The accumulator can be configured in a conventional manner as a piston, bubble or diaphragm accumulator. Provided 2/2 continuous valves as conventional Priority valves are used, they can be expanded by cascading switch positions obvious. Instead of the aforementioned 3-way flow control unit can also occur another multi-way flow control unit. Overall, however, it should be noted that the priority valve is designed as a continuous valve whose functionality is similar to a multi-way flow control unit.

In a particularly preferred embodiment, the accumulator has a minimum operating pressure of about 60 bar and a maximum operating pressure of about 350 bar. Preferably, its storage volume is a total of 20 I. The solution according to the invention is further characterized in that the storage charge takes place in the fluid direction via a storage charging circuit after the priority valve and a feed via a feed valve as a further valve before the priority valve.

The consumers may be a cooling fan and / or a control drive and / or a hydraulic power steering and / or a working hydraulics, etc., depending on the machine operating phase, a repeated, short-term shutdown of the consumer or a time shift of the Zuschaltvorganges the consumer in relation to a driving hydraulics of the working machine is conceivable. The 3-way flow control valve as a priority valve provides depending on its switching or sliding position for a hydraulic power supply of the parallel-connected consumers, such as accumulator and hydraulic power steering or power steering. Depending on the hydraulic energy to be retrieved it may be expedient to provide more than one accumulator in the hydraulic system.

Fig.1

ein schematisches Schaltbild einer hydraulischen Anlage mit paralleler Hybridisierung der Druckmittelversorgung von ver- schiedenen Verbrauchern in ihrem grundsätzlichen Aufbau;

Fig.2

ein schematisches Schaltbild einer hydraulischen Anlage mit paralleler Hybridisierung der Druckmittelversorgung von ver- schiedenen Verbrauchern und einer automatischen, bedarfs- gerechten Ansteuerung des Prioritätsventils und des weiteren Ventils für die Entladung des Druckmittelspeichers;

Fig.3

ein schematisches Schaltbild einer hydraulischen Anlage ge- mäß der Darstellung nach der Fig.1 bei einem Ladevorgang des Druckmittelspeichers;

Fig.4

ein schematisches Schaltbild einer hydraulischen Anlage ge- mäß der Darstellung nach der Fig.1 beim Entladevorgang des Druckmittelspeichers und verschiedener Einspeisemethoden des Druckmittels in das System;

Fig.5

ein schematisches Schaltbild einer hydraulischen Anlage ge- mäß der Darstellung nach der Fig.1 mit Rückschlagventilen in den Verbindungsleitungen zu dem Druckmittelspeicher;

Fig.6

ein schematisches Schaltbild einer hydraulischen Anlage ge- mäß der Darstellung nach der Fig.1 mit in dem Ventil zur Ent- ladung des Druckmittelspeichers integrierter Druckwaagen- funktion;

Fig.7

ein schematisches Schaltbild einer hydraulischen Anlage ge- mäß der Darstellung nach der Fig.1 mit in dem Ventil zur Ent- ladung des Druckmittelspeichers integrierter Stromregler- Funktion;

Fig.8

ein schematisches Schaltbild einer hydraulischen Anlage ge- mäß der Darstellung nach der Fig.1 mit in dem Ventil zur Ent- ladung des Druckmittelspeichers integrierter Druckminderer- Funktion;

Fig.9

ein schematisches Schaltbild einer hydraulischen Anlage ge- mäß der Darstellung nach der Fig.1, bei der bei der Entladung des Druckmittelspeichers eine Niederdruckseite der Druck- mittelpumpe mit Druckmittel beaufschlagt ist;

Fig.10

ein schematisches Schaltbild einer hydraulischen Anlage ge- mäß der Darstellung nach der Fig.1 mit weiterer Verallgemei- nerung des grundsätzlichen Funktionsprinzips in dem Sinne, dass ein mittels einer Verbrennungskraftmaschine antreibbarer Energiewandler eine Einspeiseenergie liefert oder diese von einer angeschlossenen Komponente abrufen kann.

In the following, the hydraulic system according to the invention will be explained in more detail with reference to various embodiments according to the drawing. This show in principle and not to scale representation of the

Fig.1

a schematic diagram of a hydraulic system with parallel hybridization of the pressure medium supply of various consumers in their basic structure;

Fig.2

a schematic diagram of a hydraulic system with parallel hybridization of the pressure medium supply of various consumers and an automatic, needs-based control of the priority valve and the other valve for the discharge of the pressure fluid reservoir;

Figure 3

a schematic diagram of a hydraulic system according to the illustration of the Fig.1 during a loading process of the pressure medium reservoir;

Figure 4

a schematic diagram of a hydraulic system according to the illustration of the Fig.1 during the discharge process of the accumulator and various feed methods of the pressure medium in the system;

Figure 5

a schematic diagram of a hydraulic system according to the illustration of the Fig.1 with check valves in the connecting lines to the accumulator;

Figure 6

a schematic diagram of a hydraulic system according to the illustration of the Fig.1 with pressure compensator function integrated in the valve for discharging the accumulator;

Figure 7

a schematic diagram of a hydraulic system according to the illustration of the Fig.1 with current regulator function integrated in the valve for discharging the accumulator;

Figure 8

a schematic diagram of a hydraulic system according to the illustration of the Fig.1 with pressure reducer function integrated in the valve for discharging the accumulator;

Figure 9

a schematic diagram of a hydraulic system according to the illustration of the Fig.1 in which a low pressure side of the pressure medium pump is subjected to pressure medium during the discharge of the pressure medium reservoir;

Figure 10

a schematic diagram of a hydraulic system according to the illustration of the Fig.1 with further generalization of the fundamental operating principle in the sense that an energy converter that can be driven by means of an internal combustion engine supplies a feed-in energy or can call it from a connected component.

In Fig.1 is shown in a schematic diagram partially a hydraulic system 1 for a construction machine. The hydraulic system 1 is driven by a designed as a motor unit internal combustion engine 2 (VKM), for example in the form of a diesel engine, with a predetermined effective drive power, for example, with a drive power of 56 kW, for a drive not shown 12 of the construction machine, an energy converter (pressure medium pump, transmission, electric motor) is driven, and further an adjustable pressure medium pump 13 is driven and further usable as a pump motor unit pressure medium pump 3, with the individual consumers of the hydraulic system 1 with pressure medium. 5 be supplied. Said commercial vehicle has in the embodiments shown in all figures, several hydraulic, especially hydrostatic drive systems in the form of a steering hydraulic 4, a control and feeding 8, possibly even with the inclusion of a cooling hydraulics, and a drive hydraulics 12, which is not shown in detail and the adjustable pressure medium pump 13, as set forth, is supplied. Depending on their basic structure, these systems can, in some cases, function independently of each other.

Upstream is on the high pressure side of the pressure medium pump 3, a priority valve 7 as a continuous valve, preferably designed as a 3/2 continuous valve, interposed between the first load 4 as part of the steering hydraulic and the pressure medium pump 3. Another second consumer 8 as part of the control and supply hydraulics is connected in parallel to the first consumer 4 to the output side of the priority valve 7. A pressure fluid reservoir 6 is connected in the same way in parallel arrangement on the output side with the priority valve 7, ie in the same way as the consumer 4 and the second consumer 8. The pressure fluid reservoir 6 is required to cover short-term, dynamic power peaks to below the desired in the internal combustion engine 2 to stay within the stipulated performance limit. The multi-way flow control valve, particularly preferred as a 3/2-way flow control valve constructed priority valve 7 provides in response to its slide position for a hydraulic power supply of the parallel-connected loads 4 and 8 and the accumulator 6.

For the realization of the discharge phase of the accumulator 6 another valve 9 is used. The other valve 9 can, as the Figure 6 shows, at the same time receive an automatic, hydraulic pressure signal from the priority valve 7, depending on the load on the consumer. By means of this structure, it is possible, for example, to cover short-term requirements of the valve unit by the pressure medium reservoir 6 independently of the machine requirement cycle. In the same way, an energy-saving operation of other consumers, which are controllable with the priority valve 7, be maintained. For safety-related aspects, the steering 4 is prioritized against the accumulator 6 and the other consumer 8, ie a charge of the accumulator 6 or other non-safety-relevant consumer 8 only takes place when no steering control is made or the need for the steering operation demand on the priority valve 7 is ensured in each case.

As the Fig.2 Furthermore, it is advantageous, in response to a signal of a first pressure sensor S1, which maps a load pressure of a consumer, by a signal of a second pressure sensor S2, which maps the current accumulator pressure of the accumulator 6, and by a signal of a third pressure sensor S3 , which describes the pressure at the high pressure side of the pressure medium pump 3, via a control and / or regulating device 11 (ECU) perform the charging and discharging phase of the pressure medium reservoir 6. Figure 3 again shows an operating phase of the hydraulic system 1, in which the accumulator 6 is charged. At the same time, the various consumers are 4.8 in operation and are supplied with pressure medium 5 in the required extent. Moreover, the control device 11 (ECU) has the priority valve 7 to control its operation.

In principle, two concepts can be implemented for the discharge phase and its energy supply from the accumulator 6 into the hydraulic system 1. On the one hand, a kind of serial hybrid can be represented, ie the energy discharge takes place within the hydrostat, as is indicated by the arrow "hydraulically" in FIG Figure 4 or the energy discharge takes place under formation and conversion into mechanical energy as a so-called parallel hybrid, as the arrow labeled "mechanical" in FIG Figure 4 also clarified. In Figure 4 Incidentally, the situation in the energy supply on the pump high-pressure side is clarified, which reflects a direct consumer support and for example can cause a higher starting dynamics or supply dynamics for a consumer or leads to an at least partial relief of the variable displacement pump 3 and the internal combustion engine VKM. In principle, a discharge of the accumulator 6 on the low pressure side of the pressure medium pump 3 is possible, so that an energy supply is present on the pump suction, whereby the drive torque of the pump 3 can be reduced for a short time. The responsible for the pressure medium supply of the hydraulic system 1 pressure medium pump 3 is designed as a pump motor unit, so that at a corresponding pivoting, for example, a cam ring in the pressure medium pump 3, together with the rotatably arranged therein displacement chambers pump chambers (not shown) defined during the discharge process of the accumulator 6 mechanical energy can be obtained in order to realize such a parallel hybrid solution.

In addition to an energy feed function, this also offers the possibility of braking energy storage. The braking energy is fed into the memory, this allows the relief of the service brake.
As Figure 5 shows, check valves 14 may be provided in the supply and feed line from or to the accumulator 6, wherein the check valve 14 between the pressure medium pump. 3 and hydraulic accumulator takes over the function of the further valve 9. Furthermore, the valve 9 for discharging the accumulator 6, a pressure compensator function 10 (see. Figure 6 ), a current control function (cf. Figure 7 ) or a pressure reducing function (cf. Figure 8 ).

The consumer 4,8 mentioned in the exemplary embodiments can understandably be of a different nature, for example the first consumer 4 does not need to concern the steering hydraulics. Furthermore, both consumers 4.8 could both affect a steering circuit. Thus, the second consumer 8 could be designed as hydraulic Fremdkraftlenkurig and the consumer 4 form a conventional auxiliary steering hydraulics. Common to all solutions and of particular importance, however, is that the storage charge takes place via a storage charging circuit after the priority valve 7 and the feed via the feed valve 9 before the priority valve 7 in the respective fluid direction.

In the Figure 9 a hydraulic circuit diagram solution is shown in which during the discharge of the accumulator 6, a low pressure side of the pressure medium pump 3 is acted upon by pressure medium 5. The pertinent Figure 9 and the generalized solution according to the Figure 10 may also generally have an energy converter, such as a pressure medium pump, a transmission, an electric motor and the like instead of a traction drive 12.

Claims (18)

Hydraulic system, in particular for a commercial vehicle, such as a construction machine, with a pressure medium pump (3) driven by an engine unit, in particular in the form of an internal combustion engine (2), which supplies a first consumer (4) with pressure medium (5), characterized in that a pressure medium reservoir (6) can be charged from the pressure medium pump (3), that at least one priority valve (7) controls the charging of the pressure medium reservoir (6) and the pressure medium supply of the consumer (4) as a function of a momentary power output of the motor unit; Switching on or off of the pressure medium supply to the consumer (4) and / or a further second consumer (8) by a further valve (9) is controlled. Hydraulic system according to claim 1, characterized in that in a connection phase of the pressure medium reservoir (6) of the pressure medium pump (3) no pressure medium is promoted. Hydraulic system according to claim 1 or 2, characterized in that the charging of the pressure fluid accumulator (6) takes place during a stationary engine running phase of the engine unit. Hydraulic system according to one of claims 1 to 3, characterized in that during the discharge of the accumulator (6) a high-pressure side of the pressure medium pump (3) with pressure medium (5) is acted upon. Hydraulic system according to one of claims 1 to 3, characterized in that during the discharge of the pressure medium accumulator (6) a low pressure side of the pressure medium pump (3) is acted upon with pressure medium (5). Hydraulic system according to one of claims 1 to 3, characterized in that the pressure medium pump (3) is designed as a pump motor unit and in the discharge of the pressure medium reservoir (6) hydraulic energy is converted into mechanical energy. Hydraulic system according to one of claims 1 to 6, characterized in that the further valve (9) for controlling the discharge of the pressure medium reservoir (6) is a proportional valve which controls the volume flow and / or the pressure of the pressure medium (5). Hydraulic system according to one of claims 1 to 7, characterized in that the control of the priority valve (7) in response to a signal of a first pressure sensor (S1), which represents a load pressure of the consumer (4) and / or by a signal of a second pressure sensor (S2), which represents the accumulator pressure of the accumulator (6), and / or of a signal of a third pressure sensor (S3), which describes the pressure on the high pressure side of the pressure medium pump (3). Hydraulic system according to one of claims 1 to 8, characterized in that the priority valve (7) is designed as a continuous valve. Hydraulic system according to one of claims 1 to 9, characterized in that the further valve (9) for discharging the pressure fluid accumulator (6) comprises a pressure compensator (10). Hydraulic system according to one of claims 1 to 10, characterized in that the further valve (9) for discharging the pressure medium reservoir (6) comprises a flow control function. Hydraulic system according to one of claims 1 to 11, characterized in that the pressure fluid reservoir (6) is a piston, or bubble, or diaphragm accumulator. Hydraulic system according to one of claims 1 to 12, characterized in that the pressure medium reservoir (6) has a maximum operating pressure of 350 bar and a minimum operating pressure of 60 bar. Hydraulic system according to one of claims 1 to 13, characterized in that the further valve (9) for discharging the accumulator (6) by a control and / or regulating device (11) is controlled in dependence on the load pressure. Hydraulic system according to one of claims 1 to 14, characterized in that consumers (4.8) of the hydraulic system (1) are a steering hydraulic, working hydraulics and a control and feed hydraulics. Hydraulic system according to claim 15, characterized in that the pressure medium pump (3) is pivoted back at full accumulator (6) and when driving straight ahead of the vehicle. Hydraulic system according to one of claims 1 to 16, characterized in that the hydraulic system (1) comprises two or more accumulator (6). Hydraulic system according to one of claims 1 to 17, characterized in that seen in the fluid flow direction of the pressure medium pump (3) from the storage charge via a storage charging circuit after the priority valve (7) and the feed via a feed valve as a further valve (9) before the priority valve (7).

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