EP2420681A2 - Hydraulic linear drive device - Google Patents

Abstract

The hydraulic linear drive (1) has a hydraulic cylinder (2) which has three pressure chambers (4,6,8) that are limited to the working surfaces (A1,A2,A3), where the pressure chambers are charged with high pressure, low pressure or tank pressure over a hydro-machine (10) and a valve arrangement. The hydro-machine has a variable drive (12). The area ratios of the working surfaces are adjusted, so that the drive is operated in the same speed range.

Description

The invention relates to a hydraulic linear drive according to the preamble of patent claim 1.

Such hydraulic linear drives can be used, for example, for actuating a press ram of a press, wherein a pressing tool is closed via the linear drive, for example, at rapid traverse, and the actual pressing operation is then carried out with comparatively great force in a so-called "power stroke". After the pressing process, the press die is then moved back into its basic position in rapid reverse direction. Of course, such linear drives are also used in other applications, such as stamping, machine tools, production lines, etc.

In the US 5,522,212 a linear drive is shown, in which the feed movement is controlled by a hydraulic cylinder with three pressure chambers. In the known solution, these pressure chambers are designed with different active surfaces, wherein for the executed with a comparatively low power rapid traverse a first active surface is acted upon by means of a variable displacement pump with pressure medium. A effective effective in the same direction effective area of a third pressure chamber is acted upon by the pressure of a hydraulic accumulator, while an effective effective in the opposite direction effective area of a second pressure chamber is relieved to a tank. The pressure medium connection to the variable displacement pump, to the hydraulic accumulator and to the tank is controlled by a valve arrangement, in which case for the power stroke, the active surfaces of the first and the third pressure chamber with the pump pressure and the effective effective direction in the opposite direction of the second pressure chamber with tank pressure is applied, the connection to the hydraulic accumulator is then shut off. In the known solution, a separate charge pump is assigned in the hydraulic accumulator, so that it is always charged to a predetermined level.

Such a solution requires a very large device complexity, since on the one hand for controlling the movements of the hydraulic cylinder, a complex variable displacement is required and on the other hand, a further pump for charging the hydraulic accumulator must be provided.

In the DE 10 2008 039 011 A1 is disclosed a similar linear actuator with a running with three active surfaces hydraulic cylinder, the pressure chambers are acted upon for adjusting via two parallel variable speed pumps and a valve assembly with pressure medium. The control of the two pumps is very expensive both in terms of control and in terms of investment costs.

In contrast, the invention has for its object to provide a hydraulic linear drive, which has a relatively simple structure and allows an optimized in terms of energy control.

This object is achieved by a hydraulic linear drive having the features of patent claim 1.

Advantageous developments of the invention are the subject of the dependent claims.

According to the invention, the hydraulic linear drive has a hydraulic cylinder, which is designed with three of each active area limited pressure chambers, which can be acted upon by a hydraulic machine, preferably a pump and a valve assembly with high pressure (pump) or a low pressure source, for example, with tank pressure to the hydraulic cylinder to move in rapid traverse or in a power stroke in one direction and in rapid traverse or in the power stroke in the other direction. According to the invention, the hydraulic motor is designed with a variable-speed drive, wherein the area ratios of the active surfaces are tuned so that the drive operates at about the same speed range in rapid traverse and in the power stroke.

This design of the area ratios and the drive, it is possible to drive the latter each in the optimal torque and speed range and thus with minimal drive power, so that the energy cost and investment costs compared to the solutions mentioned above is significantly reduced, as a smaller drive motor used can be. Essentially, regardless of whether the hydraulic cylinder with comparatively high speed and low power (rapid traverse) or at a relatively low speed and high power (power stroke) is operated, the drive always operates in its optimal torque / speed range, so that an effective control of Linear drive is possible with minimized drive power. Another advantage is that the sound development of the linear drive in both operating points (rapid traverse, power stroke) is minimal due to the constant, relatively low predetermined speed of the drive.

The hydraulic machine can be designed with a constant delivery / displacement volume. However, in principle also suitable for a four-quadrant operation designed hydraulic machines in which a reversal of direction is possible.

In one embodiment of the invention, the valve assembly has a directional control valve which connects in one position a pressure port of the hydraulic machine via a working line with a first pressure chamber and a second pressure chamber via a further working line with the low pressure source, for example the tank. In a further position, the directional control valve blocks a connection of the second pressure chamber to the low-pressure source.

According to a variant of the invention, a control valve is arranged downstream of the directional control valve, which connects in one position the first pressure chamber with the second pressure chamber acting in the opposite direction.

It is preferred if in the first position, a pressure medium connection of the third pressure chamber is blocked to the hydraulic machine.

In this case, the third pressure chamber may be connected to the low-pressure source / tank via a suction line with a non-return valve opening in the direction of the third pressure chamber.

In one embodiment of the invention, the low-pressure source is associated with a storage valve which connects in one position the low-pressure source with a suction side of the hydraulic machine and in another position the former working line in the region between the directional control valve and the control valve with the low-pressure source.

The first pressure chamber is preferably designed with a larger effective area than the second pressure space acting in the opposite direction.

It may be advantageous if in turn the second effective area is designed slightly smaller than the third effective area.

As already mentioned, it may be advantageous to carry out the hydraulic machine with reversal of the direction of rotation, so that a four-quadrant operation is possible.

The hydraulic linear drive can be carried out particularly advantageously as a press drive or as the closing axis of an injection molding machine. In principle, the inventive concept can be used wherever force and speed are needed at different times.

In a variant of the invention, the hydraulic cylinder is designed with a piston having a piston hollow rod into which a rod of the hydraulic cylinder is immersed, so that the first pressure chamber is limited by this and an inner end face of the piston piston rod, which is supplied through the rod with pressure medium.

In such an embodiment, it is preferred if a piston hollow rod-side annular end face of the piston bounds the second pressure chamber and a rod-side annular end face facing away from the third pressure chamber in sections.

• Figur 1 ein Schaltschema eines Ausführungsbeispiels eines hydraulischen Linerantriebs für eine Presse;
• Figur 2 eine Einzeldarstellung eines Hydraulikzylinders des Linearantriebs aus Figur 1;
• Figur 3 den Linearantrieb gemäß Figur 1 im Krafthub;
• Figur 4 den Linearantrieb gemäß Figur 1 bei einer Rückbewegung im Eilgang;
• Figur 5 ein gegenüber dem Ausführungsbeispiel gemäß Figur 1 vereinfachtes Ausführungsbeispiel eines Linearantriebs im Eilgang und
• Figur 6 den Linearantrieb gemäß Figur 5 im Krafthub

Preferred embodiments of the invention are explained in more detail below with reference to schematic drawings. Show it:

• FIG. 1 a circuit diagram of an embodiment of a hydraulic liner drive for a press;
• FIG. 2 an individual view of a hydraulic cylinder of the linear drive FIG. 1 ;
• FIG. 3 according to the linear drive FIG. 1 in the power stroke;
• FIG. 4 according to the linear drive FIG. 1 during a return movement in rapid traverse;
• FIG. 5 a relation to the embodiment according to FIG. 1 simplified embodiment of a linear drive in rapid traverse and
• FIG. 6 according to the linear drive FIG. 5 in the power stroke

The in FIG. 1 Linear drive shown, for example, in the stamping or forming technology, such as servo presses, tube and wire bending machines, press brakes, punching and nibbling machines, stamping and forming machines, Saugtransfer- or compact suction presses, tire presses, tire building machines, Vulkanisierpressen, drawing presses, transfer and transfer presses, Extruders, bending centers, forging presses, scrap presses, injection molding machines, blow molding or powder metal presses are used.

The linear drive 1 has a hydraulic cylinder 2, which, as will be explained in more detail below, with three pressure chambers 4, 6, 8 is executed. The pressure medium supply via a hydraulic machine 10, preferably a constant displacement pump, which is driven by a variable-speed motor 12. A suction connection of the pump is connected via a low-pressure line 14 to a low-pressure source 16, for example a hydraulic accumulator or a tank. A pressure port of the hydraulic machine 10 is connected to a pressure line 18, which leads to the input port of a directional control valve 20. In the illustrated embodiment, this is designed as a 4/2-way switching valve, wherein in a basic position shown (a), the pressure line 18 is connected to a supply line 22, which in turn leads to the input terminal of a control valve 24, which also as 4/2 ways -Switch valve is executed.

In the illustrated basic position (a) of the control valve 24, this connects the supply line 22 with a working line 26, via which the first pressure chamber 4 is supplied with pressure medium. In this switching position, a further connection of the control valve 24 is connected via a regeneration line 28 to a further working line 30, which is connected on the one hand to an output connection of the directional control valve 20 and on the other hand to the second pressure chamber 6. In the position (a) of the control valve 24, the regeneration line 28 is connected to the working line 26 and shut off in the position (b) to the first pressure chamber 4 out. In the basic position (a) of the directional valve 20, the connection of the return line to the other working line 30 is shut off. The directional control valve 20 has a return port, the is connected via a return line 32 to the low pressure line 14. In the switching position (a) of the directional control valve 20, the pressure medium connection between this return line 32 and the other working line 30 is interrupted. By switching to the position marked with (b) this pressure medium connection is opened.

According to FIG. 1 the third pressure chamber 8 is connected to a further output port of the control valve 24 via a third working line 34 shown only for illustrative reasons. This working line 34 can also be combined with the suction line 36, which will be explained below. In the switching position (a) of the control valve 24, this third working line 34 is shut off to the supply line 22, the regeneration line 28 and the working line 26 out. By switching the control valve 24 to the position (b), the third working line 34 is connected to the working line 26 and the supply line 22.

According to FIG. 1 the third pressure chamber 8 is additionally connected via a suction line 36 with a non-return valve 38 open to the third pressure chamber 8 with the low-pressure line 14.

This is connected to an output terminal of a storage valve 40, which is designed in the embodiment as a 3/2-way switching valve. In its illustrated basic position (a), the low-pressure source 16 is connected to the low-pressure line 14. By switching the accumulator valve 40, the low-pressure source 16 is connected to a line 42 opening into the supply line 22 and the connection to the low-pressure line 14 is blocked. The line 42 is shut off in the position (a) of the storage valve 40 to the low pressure source 16 out.

Details of the hydraulic cylinder 2 are based on FIG. 2 explained. Accordingly, the hydraulic cylinder 2 is designed with a piston 44 which has a piston hollow rod 46 into which a rod 50 supported on the cylinder bottom 48 dips, so that an inner end surface 52 of the piston hollow rod 46 and the end face of the rod 50 define the first pressure chamber 4. Its pressure is supplied via a extending through the rod 50 through channel 54 which is connected to the working line 26. A piston rod-side annular end face 56 of the piston 54 bounded in the axial direction of the second, penetrated by the piston hollow rod 46 pressure chamber 6 and another, rod-side annular end face 58 bounded by the rod 50 third pressure chamber 8. The effective surfaces of these pressure chambers are in FIG. 2 marked with the designations A1, A2, A3. The pressure chamber 6 is as shown FIG. 1 explained, connected to the other working line 30 and the pressure chamber 8 to the third working line 34 and 36. In the illustration according to FIG. 2 are still the pressure medium flow rates Q ₁ , Q ₂ , Q ₃ to the pressure chambers 4, 6 and 8, which are adjustable via suitable control of the hydraulic machine 10.

To set a rapid extension movement of the piston hollow rod 46 at high speed or high acceleration, the hydraulic machine is to promote a volume flow O _P at a predetermined pressure, which is to act on a comparatively small, effective in the extension direction surface of the hydraulic cylinder 2, so that with a comparatively low flow - And associated low drive power - a high extension speed of the hydraulic cylinder 2 can be effected.

To set the rapid traverse the directional control valve 20 and the control valve 24 are brought to their (a) marked positions. The storage valve 40 is also connected to the position (a), so that sucked from the low pressure source 16 via the hydraulic machine 10 pressure medium and is conveyed via the supply line 22, the working line 26 and the channel 54 in the first pressure chamber 4. In the position (a) of the control valve 24, the regeneration line 28 is connected to the working line 26, so that the two pressure chambers 4, 6 are connected to each other. The third pressure chamber 8 is in rapid traverse via the suction line 36 and the non-return valve 48 opening to the pressure chamber 8 with the Low pressure line 14 and thus connected to the low pressure source 16. The pressure chamber 4 with the active surface A ₁ , a pressure medium flow is supplied via the hydraulic machine 10, so that the piston hollow rod 46 extends in the arrow direction. In this case, the pressure medium is ejected from the decreasing second pressure chamber 6 and summed via the regeneration line 28 to the funded by the hydraulic machine 10 pressure medium flow rate Q _P. When the piston hollow rod 46 is extended at rapid traverse, the third pressure chamber 8 increases, so that pressure medium is sucked in via the check valve 48 from the low-pressure source 16. The piston hollow rod 46 thus extends at a comparatively high speed at a relatively low pressure medium volume flow. In the illustrated embodiment, the effective area A _{1 of} the first pressure chamber 4 is slightly larger than the effective area A _{2 of} the second pressure chamber executed so that for extending the piston hollow rod 46 only a small pressure medium volume flow Q _{P added} to the pendulum volume flow (from the second pressure chamber 6 ejected amount) must become. Accordingly, the pressure medium volume flow Q _{p to be delivered} by the hydraulic machine 10 is calculated from the formula $${\mathrm{Q}}_{\mathrm{P}\mathrm{.}\mathrm{EIL}}\mathrm{=}{\mathrm{Q}}_{\mathrm{1}}\mathrm{-}{\mathrm{<figure-callout\; id="2"\; label="Q"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{\mathrm{2}}$$

$$\mathrm{V}\mathrm{\cdot }{\mathrm{n}}_{\mathrm{EIL}}\mathrm{=}\mathit{x}{}_{\mathrm{EIL}}\left({\mathrm{A}}_{\mathrm{1}}\mathrm{-}{\mathrm{A}}_{\mathrm{2}}\right)$$

berechnet.The volume flows Q ₁ , Q _{2 are} calculated from the product of the extension speed x with the respective effective area A ₁ , A ₂ . The delivery volume flow Q _{p of} the hydraulic machine can be calculated from the product of the speed n of the drive 12 with the delivery / displacement volume V of the _{hydraulic machine} 10, so that the pressure medium _{volume flow} Q _{p, EIL} in rapid traverse according to the equations: $${\mathrm{A}}_{\mathrm{p}\mathrm{.}\mathrm{EIL}}\mathrm{=}\mathrm{x}\left({\mathrm{A}}_{\mathrm{1}}\mathrm{-}{\mathrm{A}}_{\mathrm{2}}\right)$$

$$\mathrm{V}\mathrm{\cdot }{\mathrm{n}}_{\mathrm{EIL}}\mathrm{=}\mathit{x}{}_{\mathrm{EIL}}\left({\mathrm{A}}_{\mathrm{1}}\mathrm{-}{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">A</figure-callout>}}_{\mathrm{2}}\right)$$

calculated.

For the power stroke, the piston hollow rod 46 is extended with comparatively low speed and great force. For this purpose, the hydraulic machine 10 according to FIG. 3 promote a pressure medium volume Q _p , force on the largest possible effective area to produce the desired large force. For this purpose, according to FIG. 3 the control valve 24 and the control valve 20 are switched to their switching positions (b). The storage valve 40 remains in position (a). Accordingly, the first pressure chamber 4 is supplied with a comparatively large effective area A ₁ with pressure medium. The acting in the same direction effective area A _{3 of} the third pressure chamber 8 is also acted upon by the pressure of the hydraulic machine 10. The acting in the opposite direction effective area A _{2 of} the second pressure chamber 6 is connected via the further working line 30, the directional control valve 20 and the return line 32 to the low pressure line 14 and thus to the suction side of the hydraulic machine 10 - the piston hollow rod 46 is x with great force at low speed extended. Corresponding to the above-explained calculation equations, the required pressure medium volume flow Q _{p, force} according to the equation then results $${\mathrm{Q}}_{\mathrm{p}\mathrm{.}\mathrm{force}}\mathrm{=}\mathit{<figure-callout\; id="3"\; label="x\; force\; A"\; filenames="imgf0002.png"\; state="\{\{state\}\}">x\; </figure-callout>}\mathrm{force}\left({\mathrm{A}}_{}\right)\left({\mathrm{}}_{\mathrm{3}}\mathrm{+}{\mathrm{A}}_{\mathrm{1}}\right)$$

Assuming that the rotational speeds n should be approximately the same in rapid traverse and in the power stroke, then the factor K of the area ratios must correspond to the reciprocal value of the speed ratio: $$\frac{n_{\mathit{eil}}}{n_{\mathit{force}}}=K\cdot \frac{x_{\mathit{Eil}}}{{\dot{x}}_{\mathit{force}}}=\frac{Q_{p.\mathit{Eil}}}{Q_{p.\mathit{force}}}$$

For fast return (rapid traverse back) is accordingly according to the illustration in FIG. 4 the direction of rotation of the motor 12 vice versa. The directional control valve 20 and the control valve 24 each remain in their switching position (b), so that the hydraulic machine 10 promotes the pressure medium volume flow Q _p , _Eil in the second pressure chamber 6 acting in the retraction direction. The two acting in the opposite direction Pressure chambers 4, 8 are connected via the directional control valve 20 and the control valve 24 and the switched to its switching position (b) storage valve 40 to the low pressure source 16, so that the pressure medium from these pressure chambers 4, 8 to the low pressure source 16 or to the suction side of the hydraulic machine 10 out can flow - the hydraulic cylinder 2 is retracted at high speed and low power.

According to the above statements, the active surfaces A ₁ . A ₂ , A ₃ designed and interconnected with each other, that the engine 12 in both the power stroke and rapid traverse (back and forth) with approximately the same speed or with approximately the same torque, in which case by suitable interconnection, the desired traversing speed x or Force (px A) is achieved.

Based on FIGS. 5 and 6 a second, compared to the previously described embodiment simplified variant is explained. The only major difference is that in the case of the FIGS. 5 and 6 illustrated embodiment, the storage valve 40 and the line 42 is omitted, so that the low-pressure line 14 opens directly into the low-pressure source 16. FIG. 5 shows the linear drive during the power stroke - just as in the embodiment described above, the directional control valve 20 and the control valve 24 are adjusted in their switching positions (a), so that the active surfaces A ₁ , A ₃ are acted upon by the pressure at the output of the hydraulic machine 10. The second pressure chamber 6 is connected via the further working line 30, the directional control valve 20, the return line 32 and the low pressure line 14 to the low pressure source 16, so that the pressure medium from the third pressure chamber 6 can be pushed out.

For the process of the piston hollow rod 46 in rapid traverse the directional control valve 20 and the control valve 24 according to FIG. 6 moved to their positions (b). Here, the first pressure chamber 4 and the second pressure chamber 6 are connected to each other, so that the ejected from the latter pressure medium on the Regeneration line 28 is summed to the pressure medium volume flow flowing to the first pressure chamber 4. During this rapid traverse pressure medium is sucked in via the suction line 36 and the check valve 38 from the low-pressure source into the enlarging third pressure chamber 8.

For retracting the piston hollow rod 46 in rapid traverse the directional control valve 20 and the control valve 24 in their positions (a) adjusted (not shown) and the direction of rotation of the hydraulic machine 10 inversely (see FIG. 4 ), so that the two pressure chambers 4, 8 are connected to the suction side of the hydraulic machine 10 and the hydraulic machine 10 promotes pressure medium in the second pressure chamber 6. The low-pressure accumulator 16 is then supplied to the pressure medium, which was previously removed.

Incidentally, this corresponds to the FIGS. 5 and 6 illustrated embodiment of the embodiment described above, so that further explanations are unnecessary.

Disclosed is a hydraulic linear drive with a running with three pressure chambers hydraulic cylinder, the active surfaces are coordinated so that in a rapid traverse and in a power stroke, a drive of the hydraulic cylinder with pressure medium supplying hydraulic machine operates in about the same speed / torque range.

LIST OF REFERENCE NUMBERS

1

linear actuator

2

hydraulic cylinders

4

pressure chamber

6

pressure chamber

8th

pressure chamber

10

hydromachine

12

engine

14

Low-pressure line

16

Low pressure source

18

pressure line

20

way valve

22

supply line

24

control valve

26

working line

28

regeneration line

30

further work management

32

Return line

34

third line of work

36

suction

38

check valve

40

memory valve

42

management

44

piston

46

Piston rod pipe

48

cylinder base

50

pole

52

Inside face

54

channel

Claims (13)

Hydraulic linear drive with a hydraulic cylinder (2), the three of a respective active surface (A ₁ , A ₂ , A ₃ ) limited pressure chambers (4, 6, 8), via a hydraulic machine (10) and a valve assembly with high pressure or low pressure , For example, be acted upon with tank pressure to move the hydraulic cylinder (2) in rapid or in the power stroke in one direction or in rapid or force stroke in the other direction, characterized in that the hydraulic machine (10) has a variable-speed drive (12) and that the area ratios of the active surfaces (A ₁ , A ₂ , A ₃ ) are adjusted so that the drive (12) operates in the same speed range during rapid traverse and in the power stroke. Linear drive according to claim 1, wherein the hydraulic machine (10) is in a machine with constant delivery / displacement. Linear drive according to claim 2, wherein the valve unit has a directional control valve (20) in a first position (b) a pressure connection of the hydraulic machine (10) via a working line (26) having a first pressure chamber (4) and a second pressure chamber (6). via a further working line (30) connects to the low pressure and in a second position (a) blocks the connection of the second pressure chamber (6) to the low pressure. Linear drive according to claim 3, wherein seen in the pressure build-up direction downstream of the directional control valve (20) a control valve (24) is arranged in one position (a) the first pressure chamber (4) with the second effective in the opposite direction pressure chamber (6) and in the other Position (b) connects the first pressure chamber with the third pressure chamber (8). Linear drive according to claim 4, wherein in the first position (a) a pressure medium connection of the third pressure chamber (8) to the hydraulic machine (10) is locked. Linear drive according to claim 5, wherein the third pressure chamber (8) via a suction line (36) and in the direction of the third pressure chamber (8) opening check valve (38) is connected to low pressure. Linear drive according to claim 4, 5 or 6, with a storage valve (40) in one position (a) a low pressure source (16) with a low pressure side of the hydraulic machine (10) and in the other position (b) the low pressure source (16) a supply line (22) between the directional control valve (20) and the control valve (24) connects. Linear drive according to one of the preceding claims, wherein the first pressure chamber (4) has a larger effective area (A ₁ ) than the effective in the opposite direction of the second pressure chamber (6). Linear drive according to claim 8, wherein the effective area A _{2 of} the second pressure chamber (6) is slightly smaller than the effective area (A ₃ ) of the third pressure chamber (8). Linear drive according to one of the preceding claims, wherein the motor (12) or the hydraulic machine (10) is designed to reverse the direction of rotation. Linear drive according to one of the preceding claims, wherein this is a drive of a forming machine or injection / blow molding machine. Linear drive according to one of the preceding claims, wherein the hydraulic cylinder (2) has a piston (44) with a piston hollow rod (46), in which a rod (50) of the hydraulic cylinder (2) is immersed, so that by an inner end face (52) of the piston piston rod (46) and the end face of the rod (50) of the first pressure chamber (4) is axially limited, which is supplied through the rod (50) through pressure medium. Linear drive according to claim 12, wherein a piston rod-side annular end face (A ₂ ) of the piston (44) limits the second pressure chamber (6) and a rod-side annular end face (A ₃ ) remote from the third pressure chamber (8) in the axial direction.

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