EP3077674B1 - Hydraulic arrangement - Google Patents

Description

The invention relates to a hydraulic arrangement with at least one adjustable hydraulic machine whose displacement volume is adjustable via a control cylinder of the arrangement, and with a control valve, in particular a pressure control valve for regulating the pressure at the pressure connection of the hydraulic machine, wherein the actuating cylinder can be controlled via the control valve.

From the EP 1 219 831 A2 is a hydraulic arrangement with a variable in their stroke volume over zero hydraulic pump is known, which takes positive pressure volume of a first main line and outputs in a second main line negative pressure takes the second main line and discharges pressure medium in the first main line. The stroke volume of the hydraulic pump is adjusted according to an electro-proportional (EP) control. In order not to increase the pressure in the main lines above a certain value, the EP control is superimposed on a pressure control, with a first pressure regulator for limiting the pressure in the first main line and a second pressure regulator for limiting the pressure in the second main line.

Hydraulic arrangements for powerful drive units for driving hydraulic axes are known from the prior art. Such hydraulic axes are used in a variety of industrial automation applications, such as in presses, injection molding machines or bending machines. If the hydraulic axis used for pressing, it may for example be designed as a differential cylinder, in which a piston separates a cylinder chamber from an annular space. The cylinder chamber is then driven, for example, by a hydraulic machine with a certain amount of pressure medium. In order to improve a dynamics of the adjustment of the piston, the annular space can be acted upon by an adjustable, other hydraulic machine with a constant pressure and thus hydraulically clamped. In order to keep the pressure of the annulus constant, the adjustable other hydraulic machine is adjusted in its stroke volume a hydromechanical pressure control valve so that the pressure at the pressure port of the other hydraulic machine has a specific value.

Conventional hydromechanical pressure control valves fail, however, when changing the operating mode of conveyor or pump operation on a sip or motor operation of the other hydraulic machine, since this must reverse the operating principle of the pressure control valve. in the Pump operation, for example, must be set to a higher displacement volume to deliver more fluid if the pressure in the annulus is too low. In contrast, in engine operation at too low a pressure in the annulus, the displacement volume must be reduced in order to effect a stronger accumulation of pressure medium. Conventional hydromechanical pressure control valves, however, can only control the pump operation of the adjustable, other hydraulic machine.

In the DE 198 42 534 A1 a further embodiment of a hydraulic arrangement is shown, in which a cylinder space of the differential cylinder is connected to a constant hydraulic machine, which is driven by an adjustable hydraulic machine. The latter is connected on the one hand with a tank and on the other hand via a pressure medium line with imprinted pressure with an annular space of the differential cylinder. The pressurization of the pressure medium line and the annular space via a hydraulic pump, wherein the pressure in the annular space is limited by a pressure relief valve, can be throttled over the pressure medium from the pressure medium line to the tank.

A disadvantage of this solution is not only that the pressure energy consuming construction over the hydraulic pump is lost through the pressure relief valve when it opens to the tank, but that the resulting heat must also be cooled back.

In the DE 40 08 792 A1 shows a further embodiment of a hydraulic arrangement is shown, in which a cylinder space of the differential cylinder is connected to two hydraulic machines in the form of adjustable hydraulic pumps, which are drivable via a common drive shaft. One of the variable displacement pumps is connected to a tank and the other to the annular space of the differential cylinder, whereby the piston of the differential cylinder is hydraulically clamped independently of its operating direction on both sides.

Although this solution reduces the aforementioned throttle losses, it is disadvantageous that the control of at least one of the variable displacement pumps is effected as a function of pressure values of the cylinder space and the annular space detected via pressure measuring devices, which represents an additional outlay in terms of apparatus.

In contrast, the invention has the object to provide a device engineering simpler configured hydraulic arrangement with which a hydraulic machine is energy-efficiently controlled in different modes.

The object is achieved by a hydraulic arrangement with the features of patent claim 1.

Other advantageous developments of the invention are subject of the dependent claims 2 to 15.

A hydraulic arrangement has a first hydraulic machine with adjustable displacement volume and a control cylinder with a control piston for adjusting the displacement volume. The actuating piston adjoins at least one actuating chamber of the actuating cylinder, which may be referred to below as the first actuating chamber. About the actuating piston can also be acted upon in the actuating cylinder two acted upon by pressure medium, acting in opposite directions adjusting chambers separated from each other. Furthermore, the hydraulic arrangement has a first control valve, via the control function in a first operating mode of the first hydraulic machine, a pressure medium supply into the first actuating chamber and a pressure medium discharge is controllable out of it. In this way, an operating parameter of the first hydraulic machine can be controlled via a stroke of the actuating cylinder or actuating piston and the associated adjustment of the displacement volume. According to the invention, the hydraulic arrangement to an operable, in particular switchable means on the actuation, in particular circuit, the control function of the first valve can be deactivated and a control function of a second control valve of the arrangement can be activated. In this case, via the second control valve, the pressure medium supply and pressure fluid removal of the first control chamber in a second mode of operation of the first hydraulic machine can be controlled.

The means in cooperation with the first and the second control valve offers a device-technically simple solution to regulate the first hydraulic machine in their various modes with different control functions.

There are more than two modes possible, depending on what task the first hydraulic machine has to fulfill in which mode. Each further operating mode is then preferably associated with a further control valve, which via the means or another means can be activated or deactivated according to the other operating mode. Preferably, the means is electromagnetically actuated.

Particularly preferably, the first hydraulic machine is designed as an adjustable axial piston machine in swash plate construction, the swash plate is arranged on a pivotable pivoting cradle, wherein the actuating piston or the actuating cylinder is connected to the pivoting cradle.

The hydraulic arrangement proves to be particularly advantageous in a development in which the first operating mode is a motor operation and the second operating mode is a pump operation, and a different rotational direction of a drive shaft of the first hydraulic machine is assigned to both operating modes. The necessary reversal of the operating principle of the control when changing between the two operating modes, ie the change between a motor and a pump control, then takes place by the simple operation or non-actuation of the agent.

In a particularly preferred development, the arrangement has a second hydraulic machine, wherein the arrangement is configured such that the first hydraulic machine has a different mode of operation than the second hydraulic machine. This can for example be realized that a drive shaft of the second hydraulic machine is rotatably connected to the drive shaft of the first hydraulic machine, whereby rotational directions of the two hydraulic machines are in the same direction.

In a preferred development of the arrangement, a first cylinder space of a hydraulic cylinder of the arrangement, in particular an annular space of a differential cylinder, and via the second hydraulic machine a second cylinder space of the hydraulic cylinder, in particular of the differential cylinder, can be acted upon with pressure medium via the first hydraulic machine. On the different operating modes of the two hydraulic machines thus located between the two chambers piston of the cylinder can be clamped. Advantage here is that the clamping according to the invention by the regulation of the pressure and not by throttling excessively generated pressure as shown in the prior art. As a result, the arrangement is more energy efficient operable and the cost of re-cooling the pressure medium is reduced. Such a hydraulic arrangement is particularly suitable for industrial automation applications, in particular for direct or indirect drives for presses, Injection molding machines or bending machines, the hydraulic consumer, in particular the hydraulic cylinder, speed-controlled is supplied with pressure medium.

In a preferred development, a high-pressure or working pressure of the first hydraulic machine or a pressure dependent thereon can be regulated via the pressure medium supply and the pressure medium discharge. In this case, via the actuation of the means, a valve body of the second control valve against a pressure equivalent of a setpoint generator of the second control valve with the high pressure or the pressure dependent thereon or with an auxiliary pressure of the arrangement acted upon, in particular acted upon. In addition, regardless of the operation, a valve body of the first control valve against a pressure equivalent of a setpoint generator of the first control valve with the high pressure or the pressure dependent thereon or the auxiliary pressure is applied. The activation of the control function of the second control valve thus takes place via the admission of its valve body with an actual value of the pressure to be regulated. Accordingly, the deactivation of the control function of the second control valve is effected by a non-admission of the valve body.

In a preferred, further developed variant of the arrangement, a nominal value of the setpoint generator of the first control valve is greater than a desired value of the setpoint generator of the second control valve. In this simple manner it can be ensured that when the means is actuated, ie when the valve body of the second control valve is subjected to the high pressure or the pressure dependent thereon, only the control function of the first control valve is activated. Although the valve body of the first control valve is also charged with an actual value of the variable to be controlled, but its control function can not be effective, since the second control valve with the lower setpoint will never increase the pressure so far as that the valve body of the first control valve could get into a control position.

In a preferred, further developed variant of the arrangement, the valve body of the first control valve is acted upon by the actuation, in the same effective direction as the pressure equivalent of the setpoint generator of the first control valve, with the high pressure or the pressure dependent thereon or with the auxiliary pressure. In this way, the valve body of the first control valve is acted upon on both sides by the same pressure and, apart from the pressure equivalent already mentioned, pressure balanced. The pressure equivalent now causes that the valve body of the first control valve is fixed in its initial position, whereby the control function of the first control valve is deactivated during actuation. Since only a small pressure equivalent of the setpoint generator is necessary to set, it is achieved via the pressure balanced compensation described that even a lower setpoint than the second control valve can be set at the first control valve.

In a preferred embodiment, the means is formed via a valve which has a high-pressure connection which can be fluidly connected to a high-pressure connection of the first hydraulic machine or to an auxiliary pressure medium source. Furthermore, the valve has a tank connection, which is fluidically connected to a pressure medium sink. Furthermore, the valve has a working connection, which can be fluidically connected to the first setting chamber via working connections of the control valves.

Particularly preferably, all said valves are arranged on the first hydraulic machine, so that the hydraulic arrangement is designed to be particularly compact.

The valve is preferably designed simply as a 3/2-way switching valve device or it is preferably formed via a continuously adjustable 3/3-way proportional valve with transition positions.

In a preferred development, the first control valve has a high-pressure connection, which is fluidically connected to the high-pressure connection of the valve, and a first working connection, which is fluidically connected to the first adjustment chamber.

In a preferred refinement, the second control valve has a tank connection, which is fluidically connected to the pressure-medium sink, and a first work connection, which is fluidically connected to a second work connection of the first control valve, and a second work connection, which is fluidically connected to the work connection of the valve ,

Particularly preferably, at least one of the setpoint generator, preferably both, an adjustable spring, via which the associated valve body is biased with the aforementioned pressure equivalent in its initial position in which the working ports of the associated control valve fluidly connected to each other and from the other terminal the associated control valve are fluidically separated. The working ports are then fluidly separated in the case of the first control valve from the pressure port and in the case of the second control valve from the tank port.

In a preferred development, the valve can be switched via its actuation into a switching position in which the pressure port of the valve is connected to its working port and the tank port of the valve is shut off. About this switching position, the control function of the second control valve is then activated and deactivated the first control valve.

In a preferred development, the valve has a spring-loaded starting position, in particular, in which its working connection is fluidically connected to its tank connection and its pressure connection is shut off. In this initial position, the control function of the second control valve is deactivated, as already mentioned, and that of the first control valve is activated.

The 3/3-way proportional valve is preferably designed such that in its transitional positions its working connection is throttled fluidically connected to its tank connection and pressure connection. For this purpose, the valve body of the 3/3-way proportional valve on a negative overlap with the two said ports associated pressure chambers. If a transitional position is taken, then a pressure is tapped between the pressure and the tank connection, which is then present over the working ports of the two control valves in the first control chamber.

In this case, a further development of the arrangement proves to be advantageous in which the valve body of the 3/3-way proportional valve is biased by a spring arrangement in one of the transition positions, in particular centered, and the spring assembly is in contact with a Rücckoppelungshebelanordnung, via which a position of the actuating piston or the adjusting cylinder to the valve body of the 3/3-way proportional valve is rückmeldbar. About the spring assembly and the feedback lever so a zero position of the actuating cylinder or actuator piston is durable, since each movement of the actuating cylinder or actuator piston from a zero position causes a backlash of the 3/3-way proportional valve, in which this connection from the first actuating chamber via the working ports Control valves and the working port of the valve to the pressure medium sink opens.

In a particularly preferred development, the arrangement has a pressure medium source which can be connected to the pressure connection of the valve independently of or dependent on the operating mode, preferably via a check valve opening towards the pressure connection of the valve. By means of this pressure medium source, a first increase in the displacement volume of the first hydraulic machine can be provoked by filling the first actuating chamber with pressure medium, in particular when the arrangement is depressurized.

In a preferred embodiment, a particular adjustable stop is provided on the actuating cylinder. This is preferably adjusted so that a stroke of the adjusting cylinder or the adjusting piston - depending on which is designed to adjust the displacement volume is movable - starting from a zero position in only one direction is possible. In the case of the axial piston machine in swash plate design so pivoting through the pivoting cradle is prevented and each direction of rotation clearly assigned to exactly one of the modes.

Several embodiments of a hydraulic arrangement according to the invention are shown in the drawings. With reference to the figures of these drawings, the invention will now be explained in more detail.

Figur 1

ein erstes Ausführungsbeispiel in einer Grundstellung und zu Beginn eines Ausfahrens eines Pressenkolbens,

Figur 2

das Ausführungsbeispiel gemäß Figur 1 beim Ausfahren des Pressenkolbens,

Figur 3

das Ausführungsbeispiel der vorangegangenen Figuren mit dem Pressenkolben am Anschlag,

Figur 4

das Ausführungsbeispiel der vorangegangenen Figuren zu Beginn und während eines Einfahrens des Pressenkolbens,

Figur 5

das Ausführungsbeispiel der vorangegangenen Figuren beim Halten einer Position des Pressenkolbens,

Figur 6

ein zweites Ausführungsbeispiel und

Figur 7

ein drittes Ausführungsbeispiel

Show it

FIG. 1

a first embodiment in a basic position and at the beginning of a extension of a press ram,

FIG. 2

the embodiment according to FIG. 1 during extension of the press ram,

FIG. 3

the embodiment of the preceding figures with the press ram at the stop,

FIG. 4

the embodiment of the preceding figures at the beginning and during a retraction of the press ram,

FIG. 5

the embodiment of the preceding figures in holding a position of the press ram,

FIG. 6

a second embodiment and

FIG. 7

a third embodiment

According to FIG. 1 has a hydraulic arrangement 1, a first hydraulic machine 2 and a second hydraulic machine 4, the drive shafts 6 and 8 are rotatably connected to each other. Both hydraulic machines 2, 4 are designed with adjustable displacement and arranged so that in left-handed drive shafts 6, 8, the first hydraulic machine 2 as a mode of operation of the engine and the second hydraulic machine 4 as a mode pumping operation. For right-handed drive shafts 6, 8, the hydraulic machines 2, 4 reverse modes. Both hydraulic machines 2, 4 are coupled via a drive shaft 10 with a variable speed operable electric motor 12 and driven by this. The hydraulic machines 2, 4 are operated in the open hydraulic circuit, wherein a low pressure port S of the first hydraulic machine 2 is fluidically connected to a tank T and its high pressure port P to a working port B of a designed as a differential cylinder hydraulic cylinder 14. A low pressure port S of the hydraulic machine 4 is connected to the tank T and its high pressure port P to a working port A of the hydraulic cylinder 14. The latter has a piston 16, which separates a fluidically connected to the working port cylinder chamber 18 from an annular space 20 connected to the working port B. On the piston 16 is a piston rod 22, which defines the annular space 20 radially inward and a cylinder housing of the hydraulic cylinder 14 passes through to the outside. A ratio of an annular space-side piston surface to a bottom-side piston surface of the piston 16 in the illustrated embodiment is about 1:10. About the hydraulic cylinder 14 and the piston rod 22, a punch of a hydraulic press is driven (not shown). A cylinder axis 24 is oriented vertically so that a weight of the piston 16 and the piston rod 22 on the pressure medium in the annular space 20 loads. In principle, a horizontal alignment or alignment of the cylinder axis between vertical and horizontal is possible.

In order to adjust the displacement volume of the first hydraulic machine 2, the arrangement 1 has an actuating cylinder 26 with an actuating piston 28 arranged axially displaceable therein. The actuating cylinder 26 has a first actuating chamber 30, which is separated via the actuating piston 28 by a counteracting second actuating chamber 32. A piston rod 34 attached to the actuating piston 28 passes through the second actuating chamber 32 and a cylinder housing of the actuating cylinder 26 and is coupled to an adjustable lifting element of the hydraulic machine 2 for adjusting its displacement volume. Since the first hydraulic machine 2 is designed as an axial piston machine in swash plate construction, this lifting element is a swash plate, which, because it is pivotable, is also called pivoting cradle. In the first adjusting chamber 30 is an adjustable stop 36 is provided which limits a stroke of the piston 28 such that the pivoting of the pivoting _{cradle is} adjustable only between a displacement _volume V _g0 = 0 and a maximum displacement _volume of V _gmax . Thus, a swinging through the _pivoting cradle over the displacement _volume V _{g0 is} prevented. Incidentally, the adjusting piston 28 is centered via two oppositely acting springs in the position V _g0 .

From a pressure medium line 38 opening into the high-pressure connection P of the first hydraulic machine 2 branches off a pressure medium line 40, in which a check valve 42 is arranged, which opens from the pressure medium line 38 to the pressure medium line 40. The pressure medium line 40 is connected to the second actuating chamber 32 of the actuating cylinder 26. A feed of the second actuating chamber 32 with pressure medium via the pressure medium line 40 causes a reduction of the displacement volume of the hydraulic machine 2 in the direction V _g0 . From the pressure medium line 40 branches off a pressure medium line 44, which is connected to a high pressure port P of a 3/3-way proportional valve 46. This can be actuated or switched via an electromagnet 48 from a starting position (a) or from transition positions (c) into a switching position (b). In the unactuated initial position (a) of the high pressure port P of the 3/3-way proportional valve 46 is shut off and the working port A is connected to the tank port T. To the working port A of the 3/3-way proportional valve 46, a pressure medium line 50 and to the tank port T a pressure medium line 52 is connected. In the initial position (a) thus the pressure medium line 50 is relieved via the pressure medium line 52 to the tank T out. In the switching position (b), however, the high-pressure port P is connected to the working port A of the directional proportional valve 46 and the tank port T shut off. In the transition positions (c) are the ports P and T of the 3/3-way proportional valve 46 in throttled pressure fluid connection with the working port A.

For the feedback of the position of the actuating piston 28 - and thus the displacement volume V _{g of} the hydraulic machine 2 - on the 3/3-way proportional valve 46, the piston rod 34 via a feedback lever assembly 54 and a spring assembly 56 with a valve body 58 of the 3/3-way proportional valve 46th coupled.

The valve body 58 is centered on two equally strong and opposing springs of the spring assembly 56 in a middle of the transition positions (c). In addition, pages of the valve body to which the spring assembly 56 engages relieved via each a pressure medium line 60 and a damping nozzle 62 to the tank T. Actuating forces acting on the valve body 58 are thus those of the electromagnet 48 and the spring arrangement 56 in the case of displacement volumes of V _g > V _g0 .

Furthermore, the arrangement has a first control valve 64 for regulating the pressure at the high-pressure port P of the first hydraulic machine 2 in its engine operation mode and a second control valve 66 for controlling this pressure in the operating mode pump operation. Both control valves 64, 66 each have a first working port A ₁ and a second working port A ₂ . The first control valve 64 also has a high pressure port P and the second control valve 66 a tank port T. Both control valves 64, 66 are designed as a continuously adjustable 3/2-way valve. The high pressure port P of the first control valve 64 is fluidly connected via the pressure medium line 44 to the high pressure port P of the 3/3-way proportional valve 46 and the first working port A _{1 of} the first control valve 64 is connected via a pressure medium line 68 to the first actuating chamber 30 of the actuating cylinder 26. Also in the pressure medium line 68, a damping nozzle 62 is arranged. The tank connection T of the second control valve 66 is fluidically connected to the tank T via a pressure medium line 70 and the first working connection A _{1 of} the second control valve 66 is fluidically connected to the second working connection A _{2 of} the first control valve 64. The second working port A _{2 of} the second control valve 66 is fluidly connected to the working port A of the 3/3-way proportional valve 46.

To form their respective control functions, the two control valves 64, 66, more precisely whose valve body 72, 74, as follows acted upon with pressure medium: The valve body 72 of the first control valve 64 is permanently connected via the pressure medium line 44 to the high pressure port P of the first hydraulic machine 2 or a dependent thereon pressure or pending in the pressure medium line 40 auxiliary pressure p _H , against a pressure equivalent of a designed as an adjustable spring setpoint generator 76, acted upon. The valve body 74 of the second control valve 66 is acted upon by a pending in the pressure medium line 50 pressure against a pressure equivalent of a setpoint generator 78, which is also designed as an adjustable spring. The setpoint generator 76, 78 bias the valve body 72, 74 respectively in their initial position (a), in which the working ports A ₁ , A _{2 of} the respective control valve connected to each other and the other terminal of the working ports A ₁ , A _{2 is} separated. Equivalent to the pressure equivalent acting on it Each valve body 72, 74 with the pressure in the pressure medium line 70, which is connected to the tank T, applied.

Both working ports A ₁ , A _{2 of} the first control valve 64 are connected via a bypass line 80 and a damping nozzle 62 arranged therein in permanent pressure medium connection.

The following is a description of the operation of the hydraulic arrangement 1 in different phases of the actuation of the hydraulic cylinder 14. As a starting situation, it is assumed that a speed n of the drive shaft 10 is zero and the piston 16 is in a middle position, so that a load pressure in Annulus 20 and thus at the high pressure port P of the first hydraulic machine 2 only results from the weight of the piston 16 and the piston rod 22 including a load. In this basic position, the 3/3-way proportional valve 46 is unconfirmed because the solenoid 48 is de-energized. Accordingly, the 3/3-way proportional valve 46 is in one of its transition positions (c). Furthermore, the two control valves 64, 66 are in their initial positions (a), so that the first actuating chamber 30 is connected to the working port A of the 3/3-way proportional valve 46. At the same time, the high-pressure port P of the 3/3-way proportional valve 46 is connected to the second actuating chamber 32. Due to the different piston surfaces of the piston 28 - the piston surface defining the second actuating chamber 32 is reduced by the cross-sectional area of the piston rod 34 - there is a tendency for the piston 28 to move in the direction of increasing the displacement volume V _g . However, via the feedback lever assembly 54 and the spring assembly 56, any displacement of the piston 28 is transmitted to the valve body 58 and results in a return of the 3/3-way proportional valve 46 in the starting position (a), in which the working port A is connected to the tank port T. , In this way, the 3/3-way proportional valve 46 responds to the increase in the displacement volume V _g with the connection of the first control chamber 30 with the pressure medium sink T, whereby pressure fluid from the first control chamber 30 can flow to the tank T out and the displacement volume V is held _g0 ,

It should now be an extension of the piston rod 22, wherein in the annular space 20, a pressure of 150 bar is to be adjusted to clamp the piston 16 against the force acting in the cylinder chamber 18 pressure of the second hydraulic machine 4. The speed of the piston 16 during extension is consequently via the discharge of pressure medium from the annular space 20 determined by the first hydraulic machine 2 in engine operation. To extend the speed of the electric motor 12 is increased such that the drive shafts 6, 8 and 10 turn counterclockwise. This then corresponds to the engine or sip operation of the first hydraulic machine 2 and the pumping or conveying operation of the second hydraulic machine 4. At the beginning, the control piston 28 is still at its stop 36, whereby the first hydraulic machine 2 has the displacement volume V _g0 . From the pressure medium supply into the cylinder chamber 18 results in a pressure build-up in the annular space 20 and thus at the working port B of the hydraulic cylinder 14 and the high pressure port P of the first hydraulic machine 2. During which the 3/2-way proportional valve 46 as described above is still in its transition or control positions (c) and causes V _{g0 to be} held.

If the pressure at the high-pressure connection P of the hydraulic machine 2 exceeds the pressure prevailing in the pressure medium line 40 and a pressure equivalent of the check valve 42, this and the annular space 20 opens in fluid communication with the second control chamber 32 and the pressure medium line 44th Since the 3/3-way proportional valve 46 is configured such that the switching position (b) without actuation of the electromagnet 48 from the valve body 58 is not ingestible, in this mode, only the transition positions (c) and the starting position (a) of the valve body 58 are possible. Thus, a largely unthrottled connection of the pressure medium line 50 with the pressure medium line 44, in which the pressure to be regulated is present, prevented. Accordingly, the control function of the second control valve 66 is deactivated and only the first control valve 64 can regulate the pressure. The deactivation of the control function of the second control valve 66 is therefore based on the fact that this is not acted upon by the pressure to be controlled.

As long as in the pressure medium line 44 of set at the setpoint generator 76 of the first control valve 64 value of 150 bar is not reached, the first control valve remains in its initial position (a), so that the first control chamber 30 can flow no pressure medium. Consequently, the displacement volume of the hydraulic machine 2 remains at V _g0 . From the value of 150 bar in the pressure medium line 44, the first control valve 64 responds. There follows a regulation of the displacement volume of the first hydraulic machine 2 via the latter control valve 64, which is based on FIG. 2 is described.

According to FIG. 2 result from the capacity of the second hydraulic machine 4 and the swallowing power of the first hydraulic machine 2 pressure fluid flow rates Q ₂ , Q ₁ in the cylinder chamber 18 in and out of the annulus 20 out. The second hydraulic machine 4 is thus in pump mode, the first hydraulic machine 2 in engine operation. As before, the solenoid 48 is de-energized, whereby the control function of the second control valve 66 is deactivated as described. It is now assumed that the pressure in the annular space 20 exceeds the value to be regulated of 150 bar. This is in the pressure medium line 44 to a pressure that exceeds the pressure equivalent of the setpoint generator 76 of the first control valve 64. Consequently, the valve body 72 of this control valve 64 is moved out of the starting position (a) out into a control position, in which the high-pressure port P with the first working port A ₁ in fluid communication device. Accordingly, the first actuating chamber 30 is supplied via the first working port A ₁ and the pressure medium line 68 pressure medium, which leads to the displacement of the adjusting piston 28 in the direction of the maximum displacement _volume V _gmax . At the same speed n of the electric motor 12 and constant displacement volume of the second hydraulic machine 4, a movement speed of the piston 16 remains the same, resulting in increasing displacement volume V _{g of} the first hydraulic machine 2, a pressure drop in the annular space 20 and the pressure medium line 44 results. Accordingly, the pressure in the pressure medium line 44 drops again in the direction of 150 bar einzuregelnden. During this process, the feedback of the position of the actuating piston 28 to the valve body 58 of the 3/3-way proportional valve 46 takes place permanently in accordance with the above-described mode of operation. At this point, it should be mentioned that the pressure medium volume flowing in via the control positions of the first control valve 64 of the first actuating chamber 30 is reduced by a bypass volume flow via the bypass line 80 and the damping nozzle 62. The bypass line 80 thus causes a small leakage current, which causes the valve body 72 of the first control valve 64 always performs small control movements. As a result, a breakaway force of the valve body 72 is minimized. This has a positive effect on the response of the first control valve 64.

FIG. 3 shows the extended piston 16 at the stop. Accordingly, the annulus 20 is minimally small and the cylinder space 18 is maximally large. Via a position sensor 88, this operating state is detected. The speed n of the still left-rotating electric motor 12 is then greatly reduced via a control unit 92, wherein the first hydraulic machine 2 continue to operate in the engine mode and the second hydraulic machine 4 in the pump mode. The second control valve 66 is still in its initial position (A). As before, the solenoid 48 is de-energized, so that the valve body 58 can take only the transition positions (c) and the starting position (a).

In the moment in which the piston 16 is driven to stop, resulting from the movement of the piston 16 pressure medium flow rate Q ₁ decreases according to FIG. 2 to zero. Due to leakage, the first control valve 64 can not maintain the required pressure of 150 bar, since the leakage can not be replaced due to the lack of pressure medium volume flow Q ₁ . Consequently, the pressure equivalent of the setpoint generator 76 pushes the valve body 72 of the first control valve 64 back into its initial position (a), in which from the first actuating chamber 30 pressure fluid via the working ports A ₁ , A ₂ and the initial position (a) and the transition positions (c) of the 3/3-way proportional valve 46 to the tank T flows. The displacement of the adjusting piston 28 ends with the adjustment of the first hydraulic machine 2 in its displacement volume V _g0 . The speed n of the electric motor 12 is adjusted via the control device 92 such that a leakage from the cylinder chamber 18 and the second hydraulic machine 4 connected therein is compensated out and the piston 16 is held down with a pressure acting in the cylinder chamber 18 of 100 bar.

From the in FIG. 3 shown stop situation, the piston rod 22 now according to FIG. 4 be retracted again. For this purpose, the annular space 20 has to be filled with pressure medium via the first hydraulic machine 2 and pressure medium has to be removed from the cylinder space 18 via the second hydraulic machine 4. Thus, the first hydraulic machine 2 must be switched from its first operating mode, the engine operation, to its second operating mode, the pump operation. The second hydraulic machine 4 must change to engine operation. This is done solely by the fact that the direction of rotation of the electric motor 12 is switched from left to right. Since now another mode of action of the pressure control for the first hydraulic machine 2 is to be provided in pump operation, the electromagnet 48 is energized. As a result, the pressure medium line 50 via the switching position (b) of the 3/3-way proportional valve 46 is connected to the pressure medium line 44 and the pressure applied there acts on the pressure medium line 50 to the valve body 74 of the second control valve 66. In the embodiment shown so far for the Activation of the control function of the second control valve 66 imperative that the setpoint of the setpoint generator 76 of the first control valve 64 is higher than the desired value of the setpoint generator 78 of the second control valve. This is here by the desired value of the second control valve 66 of 120 bar given. Although both valve bodies 72, 74 of both control valves 64, 66 are acted upon by the pressure present in the pressure medium line 44, the deactivation of the first control valve results from said difference of the nominal values.

At the beginning of the retraction is first assumed that both actuating chambers 30, 32 of the actuating cylinder 26 are depressurized, whereby the actuating piston 28 is in its position V _g0 . To move the piston 16 in FIG. 5 against gravity (in FIG. 4 to the left) must be promoted by the first hydraulic machine 2 pressure medium in the annulus 20. For this purpose, the first actuating chamber 30 must be filled with pressure medium in order to achieve a displacement volume V _g > 0. However, since the pressure between the working port B and the pressure medium line 44 has collapsed as described above in the stop situation of the piston 16, the first hydraulic machine 2 can not deliver the quantity of pressure medium necessary to build up pressure and to fill the first actuating chamber 30. There is a need for an external auxiliary pressure source. For this purpose, an auxiliary pump 82 is provided, whose pressure port is connected via a pressure medium line with an auxiliary pressure port P _{H of} the first hydraulic machine 2. At the auxiliary pressure port P _H , a spring-loaded check valve 84 is arranged, which is connected via a pressure medium line 86 to the pressure medium line 40 and opens to this. The auxiliary pump 82 is coupled via a drive shaft 88 with the first hydraulic machine 2 and is consequently also driven via the electric motor 12.

The auxiliary pump 82 designed as a fixed displacement pump supplies a pressure of 35 bar. At a given speed thus 35 bar with opening of the check valve 84 in the pressure medium lines 86, 40 and 44 are on. This pressure is present in the second actuating chamber 32 and is reported via the switching position (b) of the 3/3-way proportional valve 46 in the pressure medium line 50. Due to the low pressure of 35 bar, both control valves 64, 66 are still in their initial positions (a). As a result, the pressure of 35 bar is also present in the first actuating chamber 30. Since the effective piston ring surface on the control piston 28 is smaller than the piston bottom surface, there is an imbalance of forces on the control piston 28, as a result of which the displacement _volume in the direction V _{gmax is} increased. This results in a pressure build-up in the pressure medium lines 38, 40 and 44 to the second control valve 66 responsive to the set value of 120 bar.

From this point, the control of the pressure in the annular space 20 via corresponding control movements of the valve body 74 of the second control valve 66, wherein at a pressure greater than 120 bar, a flow from the first control chamber 30 via the first working port A ₁ to the tank T open and at to low pressure (less than 120 bar) is closed. If the pressure is too high, the displacement volume of the first hydraulic machine 2 is consequently reduced and increased if the pressure is too low, which corresponds to a classic pump control.

According to FIG. 5 should a middle position of the piston 16 are held. Since the hydraulic cylinder 14 is vertically aligned and the annular space 20 is loaded with the weight of the piston 16 and the piston rod 22 including a load, to hold the position, the first hydraulic machine 2 must operate in its operating mode pump operation to a lowering of the piston 16 due to in System to counteract occurring leakage. By way of the control unit 92, the rotational speed n of the electric motor 12 is kept so low in dependence on the position detected by the position sensor that only the leakage is compensated and a speed of the piston 16 is kept at zero.

Since the second hydraulic machine 4 continues to be operated in the engine mode, the pressure in the cylinder chamber 18 decreases to atmospheric pressure. So that it does not fall below it, the second hydraulic machine 4 sucks pressure medium via a check valve 86. The pressure in the annular space 20 is equal to the load pressure of the stationary piston 16 and the piston rod 22 including load and thus less than 120 bar, since this pressure value only occurs in the above-described clamped retraction of the piston rod 22. At this low pressure, both control valves 64, 66 are in their initial positions (a). Since the second control valve 66 is activated when the solenoid 48 is energized and the pressure of 100 bar is less than the target value of 120 bar set at the setpoint generator 78, the control piston 28 is extended to V _gmax .

One advantage of the first embodiment is based on the fact that the electromagnetically operable 3/3-way proportional valve 46 together with the feedback lever assembly 54 and the spring assembly 56 is often provided by default for the construction of an adjustable hydraulic machine. Such prepared hydraulic machines are then to supplement the said control valves 64, 66 with only little effort.

The following two embodiments of a hydraulic arrangement 101; 201 correspond substantially to the first embodiment of the foregoing description. Since deviations from the first embodiment are provided only in the range of the above-described valve 46 and the adjusting cylinder 26, a representation of the hydraulic cylinder 14, the second hydraulic machine 4, the electric motor 12, the hydraulic pump 82 and the periphery of the four components mentioned omitted. About the embodiments consistent components of the arrangements 1; 101; 201 are provided with the same reference numerals. To shorten the description, only the differences of the embodiments will be discussed.

Notwithstanding the first embodiment, the hydraulic assembly 101 according to FIG. 6 an actuatable means 146, which is designed as a 3/2-way switching valve. By energizing the electromagnet 48, the 3/2-way switching valve 146 can be switched to the already discussed in the first embodiment switching position (b), whereby the pressure medium line 44 connected to the pressure medium line 50 and the tank port T of the 3/2-way switching valve 146 is shut off. In this way, as already described, the second control valve 66 is activated with its control function. Via a spring 156, the valve 146 in its initial position (a), which also corresponds to the starting position (a) of the first embodiment, biased. In this state, the first control valve 64 is active with its control function and the pressure medium line 50 is connected via the pressure medium line 52 to the tank T, whereas it is shut off against the pressure medium line 44. In the initial position (a) relieves the 3/2-way switching valve 146, the first actuating chamber 30 through the working ports A ₁ , A ₂ to the tank T out. When using the device constructed simple valve 146 eliminates the need for the feedback lever assembly 54 and the spring assembly 56 according to the first embodiment. Since these two components are usually formed over a device complex assembly, the second embodiment provides according to FIG. 6 A considerable device simplification compared to the first embodiment. A further device-technical simplification brings the use of the valve 146 to a control cylinder 126 of the first hydraulic machine 2 with it. It follows that a return spring in the first actuating chamber 30, as was necessary in the first embodiment, can be dispensed with.

The third embodiment according to FIG. 7 corresponds to the second embodiment according to FIG. 6 up to a changed pressurizing of the valve body 72 of the first control valve 64. Instead of these same effect with the pressure equivalent of the setpoint generator 76 with the pressure in the pressure medium line 70, which is in pressure fluid communication with the tank T, the valve body 72 in the direction mentioned above a pressure medium line 250 with the pressure in the pressure medium line 50 loaded. Thus, it is on actuation of the 3/2-way switching valve 146 in its switching position (b), so if the second control valve 66 is to be activated in its control function, loaded on both sides with the pressure in the pressure medium line 44. In addition, since the pressure equivalent of the setpoint generator 76 in the direction of the initial position (a) of the first control valve 64 acts, the valve body 72 is biased independently of the pressure in the pressure medium line 44 in the starting position (a) and thus deactivated in its control function. The advantage here is that unlike in the previous embodiments, a setpoint at the setpoint generator 76 can be set, which is less than or equal to the setpoint of the setpoint generator 78 of the second control valve 66. This changed pressure medium loading of the valve body 72 thus increases the flexibility of the hydraulic arrangement 201 with respect to the pressure regulation in the different operating modes pump operation and engine operation of the first hydraulic machine 2.

Disclosed is a hydraulic arrangement with an adjustable hydraulic machine and a first operating mode of the hydraulic machine, in particular an engine operation associated control valve, via the control of a control chamber of a control cylinder of the hydraulic machine can be acted upon with pressure medium. In addition, the arrangement for a second operating mode of the hydraulic machine, in particular for a pump operation, a second control valve for pressure medium to the actuating chamber. By actuating an arrangement means, one of the control valves can be activated or deactivated and the other can be correspondingly deactivated or activated, so that the control can take place in the different operating modes with different operating principles and / or control parameters.

LIST OF REFERENCE NUMBERS

1; 101; 201

Hydraulic arrangement

2

first hydraulic machine

4

second hydraulic machine

6, 8, 10

drive shaft

12

electric motor

14

hydraulic cylinders

16

piston

18

cylinder space

20

annulus

22

piston rod

24

longitudinal axis

26; 126

actuating cylinder

28

actuating piston

30

First parking chamber

32

Second control chamber

34

piston rod

36

attack

38, 40

Pressure medium line

42

check valve

44

Pressure medium line

46; 146

3/3-way proportional valve

48

electromagnet

50, 52

Pressure medium line

54

Feedback lever assembly

56

spring assembly

58

plunger

60

Pressure medium line

62

damping

64

First control valve

66

Second control valve

68, 70

Pressure medium line

72, 74

valve body

76, 78

Setpoint generator

80

bypass line

82

hydraulic pump

84

check valve

86

check valve

88

position sensor

90

signal line

92

control unit

94

signal line

250

Pressure medium line

A, A ₁ , A ₂ , B

working port

P

High pressure port

P _H

Auxiliary pressure port

S

Low pressure port

T

Tank connection, tank

Claims (15)

1. Hydraulic arrangement having a first hydraulic machine (2) with adjustable displacement volume (V_g), which, for the adjustment of the displacement volume (V_g), has an actuating cylinder (26; 126) with an actuating piston (28), by means of which an actuating chamber (30) is formed in the actuating cylinder (26; 126), having a first control valve (64), by means of the control function of which a pressure medium feed into the actuating chamber (30) and a pressure medium discharge out of the actuating chamber (30) are controllable in a first operating mode of the first hydraulic machine (2), wherein an actuatable means (46; 146), by the actuation of which the control function of the first control valve (64) is deactivatable and a control function of a second control valve (66) of the arrangement, by means of which the pressure medium feed and pressure medium discharge to and from the actuating chamber (30) are controllable, is activatable in a second operating mode of the first hydraulic machine (2).
2. Arrangement according to Claim 1, wherein the first operating mode is a motor mode and the second operating mode is a pump mode, and the two operating modes are assigned a different direction of rotation of a drive shaft (6) of the first hydraulic machine.
3. Arrangement according to Claim 2, having a second hydraulic machine (4), wherein the arrangement (1; 101; 201) is configured such that the first hydraulic machine (2) has a different one of the two operating modes than the second hydraulic machine (4).
4. Arrangement according to any of the preceding claims, wherein a high pressure (p) of the first hydraulic machine (2) or a pressure dependent thereon can be controlled by means of the pressure medium feed and pressure medium discharge, and wherein, by means of the actuation, a valve body (74) of the second control valve (66) can be acted on, counter to a pressure equivalent of a setpoint value generator (78) of the second control valve (66), with the high pressure (p) or the pressure dependent thereon or with an auxiliary pressure (p_H) of the arrangement, and wherein, independently of the actuation, a valve body (72) of the first control valve (64) is acted on, counter to a pressure equivalent of a setpoint value generator (76) of the first control valve (64), with the high pressure (p) or the pressure dependent thereon or the auxiliary pressure (p_H).
5. Arrangement according to Claim 4, wherein a setpoint value of the first control valve (64) is greater than a setpoint value of the second control valve (66).
6. Arrangement according to Claim 4, wherein the valve body (72) of the first control valve (64) is, by means of the actuation, acted on equivalently in terms of effect with the pressure equivalent of the setpoint value generator (76) of the first control valve (64), with the high pressure (p) or the pressure dependent thereon, or with the auxiliary pressure (p_H).
7. Arrangement according to Claim 6, wherein a setpoint value of the first control valve (64) is less than or equal to a setpoint value of the second control valve (66) .
8. Arrangement according to any of the preceding claims, wherein the means is formed by a valve (46; 146) which has a high-pressure port (P) fluidically connectable, in particular connected, to a high-pressure port (P) of the first hydraulic machine (2) or to an auxiliary pressure medium source (82), and which has a tank port (T) fluidically connectable, in particular connected, to a pressure medium sink (T), and which has a working port (A) connectable, in particular connected, via working ports (A₁, A₂) of the control valves (64, 66) to the actuating chamber (30).
9. Arrangement according to Claim 8, wherein the first control valve (64) has a high-pressure port (P) fluidically connectable, in particular connected, to the high-pressure port (P) of the valve (46; 146), and has a first working port (A₁) fluidically connectable, in particular connected, to the actuating chamber (30).
10. Arrangement according to Claim 8 or 9, wherein the second control valve (66) has a tank port (T) fluidically connectable, in particular connected, to the pressure medium sink (T), and has a first working port (A₁) fluidically connectable, in particular connected, to a second working port (A₂) of the first control valve (66), and has a second working port (A₂) fluidically connectable, in particular connected, to the working port (A) of the valve (46; 146).
11. Arrangement according to Claim 4 or any claim referred back thereto, wherein the setpoint value generators (76, 78) each have an adjustable spring by means of which the associated valve body (72, 74) can be preloaded into an initial position (a) in which the working ports (A₁, A₂) of the associated control valve (64, 66) are fluidically connected to one another and are fluidically separated from the other port (P, T) of the associated control valve (64, 66).
12. Arrangement according to any of Claims 8 to 11, wherein the valve (46; 146) is, by means of the actuation, switchable into a switching position (b) in which the high-pressure port (P) of the valve (46; 146) is connected to the working port (A) thereof and the tank port (T) of the valve (46; 146) is shut off.
13. Arrangement according to any of Claims 8 to 12, wherein the valve has an initial position (a) in which the working port (A) of the valve (46; 146) is fluidically connected to the tank port (T) thereof and the high-pressure port (P) of the valve (46; 146) is shut off.
14. Arrangement according to any of Claims 8 to 13, wherein the valve is designed as a 3/2-way switching valve (146), or wherein the valve (46) is designed as a continuously adjustable 3/3-way proportional valve (46) with transition positions (c) in which the working port (A) of the 3/3-way proportional valve (46) is fluidically connected in throttled fashion to the tank port (T) and high-pressure port (P) thereof.
15. Arrangement according to Claim 14, wherein a valve body (58) of the 3/3-way proportional valve (46) is preloadable, in particular preloaded, into one of the transition positions (c) by means of a spring arrangement (56), and wherein the spring arrangement (56) is in contact with a lever of a feedback lever arrangement (54), by means of which a position of the actuating piston (28) or of the actuating cylinder (26) can be fed back, in particular is fed back, to the valve body (58) of the 3/3-way proportional valve (46).

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