DE102010034610A1 - Hydraulic linear drive - Google Patents

Abstract

Disclosed is a hydraulic linear drive with a hydraulic cylinder designed with three pressure chambers, the effective surfaces of which are coordinated with one another in such a way that in a rapid traverse and in a power stroke, a drive of a hydraulic machine supplying the hydraulic cylinder with pressure medium operates in approximately the same speed / torque 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 a comparatively large 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 the active surfaces of the first and the third pressure chamber are subjected to the pump pressure and the effective effective surface in the opposite direction of the second pressure chamber with tank pressure for the power stroke, the connection to 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 arrangement has a directional control valve which in one position via a pressure connection of the hydraulic machine via a working line with a first pressure chamber and a second pressure chamber over. another working line with the low pressure source, such as the tank connects. 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.

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

1 a circuit diagram of an embodiment of a hydraulic liner drive for a press;

2 an individual view of a hydraulic cylinder of the linear drive 1 ;

3 according to the linear drive 1 in the power stroke;

4 according to the linear drive 1 during a return movement in rapid traverse;

5 a relation to the embodiment according to 1 simplified embodiment of a linear drive in rapid traverse and

6 according to the linear drive 5 in the power stroke

The in 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, extrusion; 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 . 8th is executed. The pressure medium supply takes place via a hydraulic machine 10 , preferably a constant displacement pump, with a variable speed motor 12 is driven. A suction connection of the pump is via a low-pressure line 14 with a low pressure source 16 , For example, a hydraulic accumulator or a tank connected. A pressure connection of the hydraulic machine 10 is to a pressure line 18 connected to the input port of a directional control valve 20 leads. 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 to a supply line 22 is connected, in turn, to the input terminal of a control valve 24 leads, which is also designed as a 4/2-way switching valve.

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

According to 1 is the third pressure chamber 8th about a third line of work, shown only for illustrative reasons 34 with another output port of the control valve 24 connected. This working management 34 can also with the below-mentioned suction line 36 be summarized. In the switching position (a) of the control valve 24 is this third working administration 34 to the supply line 22 , the regeneration line 28 and to work management 26 locked off. By switching the control valve 24 in position (b) becomes the third working line 34 with the work management 26 and the supply line 22 connected.

According to 1 is the third pressure chamber 8th additionally via a suction line 36 with one to the third pressure chamber 8th open check valve 38 with the low pressure line 14 connected.

This is at an output port of a storage valve 40 connected, which is executed in the embodiment as a 3/2-way switching valve. In its illustrated home position (a) is the low pressure source 16 with the low pressure line 14 connected. By switching the storage valve 40 becomes the low pressure source 16 with one in the supply line 22 opening line 42 connected and the connection to the low pressure line 14 blocked. The administration 42 is in position (a) of the accumulator valve 40 to the low pressure source 16 locked off.

Details of the hydraulic cylinder 2 are based 2 explained. Accordingly, the hydraulic cylinder 2 with a piston 44 executed, which is a piston piston rod 46 has, in the one at the cylinder bottom 48 supported rod 50 dips, leaving an inner face 52 the piston hollow rod 46 and the end face of the rod 50 the first pressure room 4 limit. Its pressure supply is via a through the rod 50 passing channel 54 , to the work management 26 connected. A piston rod-side annular end face 56 of the piston 54 bounded in the axial direction of the second, from the piston piston rod 46 interspersed pressure chamber 6 and another rod-side annular end face 58 limits that from the pole 50 interspersed third pressure chamber 8th , The active surfaces of these pressure chambers are in 2 marked with the designations A1, A2, A3. The pressure room 6 is how based 1 explained to the further working management 30 and the pressure room 8th to the third working administration 34 and 36 connected. In the illustration according to 2 are still the pressure medium flow rates Q ₁ , Q ₂ , Q ₃ to the pressure chambers 4 . 6 respectively. 8th represented by suitable control of the hydraulic machine 10 are adjustable.

For setting a quick extension movement of the piston rod 46 At high speed or high acceleration, the hydromachine is to deliver a volume flow Q _P at a predetermined pressure, which is applied to a comparatively small, effective in the extension direction surface of the hydraulic cylinder 2 should act, so that with a comparatively low flow - and thus 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 into their positions marked with (a). The storage valve 40 is also switched to position (a) so that from the low pressure source 16 over the hydraulic machine 10 Pressure fluid sucked in and over the supply line 22 , the work management 26 and the channel 54 in the first pressure room 4 is encouraged. In position (a) of the control valve 24 is the regeneration line 28 with the work management 26 connected, so that the two pressure chambers 4 . 6 connected to each other. The third pressure chamber 8th is in rapid traverse via the suction line 36 and that to the pressure room 8th opening check valve 48 with the low pressure line 14 and thus with the low pressure source 16 connected. The pressure room 4 with the effective area A ₁ , a pressure medium volume flow through the hydraulic machine 10 supplied, so that the piston rod piston 46 extends in the direction of the arrow. In this case, the pressure medium from the decreasing second pressure chamber 6 pushed out and over the regeneration line 28 to that of the hydraulic machine 10 promoted pressure medium flow rate Q _P summed. When extending the piston rod 46 at rapid speed, the third pressure chamber increases 8th , so that pressure medium via the check valve 48 from the low pressure source 16 is sucked. The piston hollow rod 46 thus proceeds at a comparatively high speed with a relatively low pressure medium volume flow. In the illustrated embodiment, the effective area A _{1 of} the first pressure chamber 4 made slightly larger than the effective area A2 of the second pressure chamber, so that for extending the piston piston rod 46 only a small pressure medium volume flow Q _P to pendulum volume flow (from the second pressure chamber 6 ejected amount) must be added. Accordingly calculated by the hydraulic machine 10 to be pumped pressure medium flow rate Q _P from the formula Q _{P, EIL} = Q ₁ - Q ₂

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} at rapid _traction according to the equations: Q _{p, EIL} = x (A ₁ - A ₂ ) V · n _EIL = X _EIL (A ₁ - A ₂ ) calculated.

For the power stroke, the piston rod becomes hollow 46 extended with comparatively low speed and great power. For this, the hydraulic machine must 10 according to 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 3 the control valve 24 and the control valve 20 switched to their switching positions (b). The storage valve 40 remains in position (a). Accordingly, the first pressure chamber 4 supplied with pressure medium with comparatively large effective area A ₁ . The acting in the same direction effective area A _{3 of} the third pressure chamber 8th also with the pressure of the hydraulic machine 10 applied. The acting in the opposite direction effective area A _{2 of} the second pressure chamber 6 is about the further work direction 30 , the directional valve 20 and the return line 32 with the low pressure line 14 and thus with the suction side of the hydraulic machine 10 connected - the piston rod 46 is extended with great force at low speed x. Corresponding to the above-explained calculation equations, the required pressure medium volume flow Q _{p, force} according to the equation then results Q _{p, force} = x _force (A ₃ + A ₁ ).

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:

For fast return (rapid traverse back) is accordingly according to the illustration in 4 the direction of rotation of the motor 12 vice versa. The directional valve 20 and the control valve 24 each remain in their switching position (b), so that the hydraulic machine 10 the pressure medium _{volume flow} Q _{p, EIL} in the second pressure chamber acting in the _{retraction direction} 6 promotes. The two pressure chambers acting in the opposite direction 4 . 8th are via the directional valve 20 and the control valve 24 as well as in its switching position (b) switched storage valve 40 with the low pressure source 16 connected so that the pressure medium from these pressure chambers 4 . 8th to the low pressure source 16 or to the suction side of the hydraulic machine 10 can flow out - 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 are} designed and connectable to each other such that the motor 12 works both in the power stroke and in rapid traverse (forward and backward) with approximately the same speed or with approximately the same torque, in which case the desired travel speed x or force (p × A) is achieved by suitable interconnection.

Based on 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 5 and 6 illustrated embodiment of the storage valve 40 and the line 42 is omitted, so that the low pressure line 14 directly into the low pressure source 16 opens. 5 shows the linear drive during the power stroke - just like the embodiment described above are the directional control valve 20 and the control valve 24 adjusted in their switching positions (a), so that the active surfaces A ₁ , A ₃ with the pressure at the output of the hydraulic machine 10 are charged. The second pressure chamber 6 is about the further work direction 30 , the directional valve 20 , the return line 32 and the low pressure line 14 with the Low pressure source 16 connected, so that the pressure medium from the third pressure chamber 6 can be ejected.

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

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

Incidentally, this corresponds to the 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 a drive of the hydraulic cylinder with pressure medium supplying hydromachine works in a rapid traverse and in a power stroke 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

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 5522212 [0003]
• DE 102008039011 A1 [0005]

Claims (13)

Hydraulic linear drive with a hydraulic cylinder ( 2 ), of the three of a respective active area (A ₁ , A ₂ , A ₃ ) limited pressure chambers ( 4 . 6 . 8th ), which via a hydraulic machine ( 10 ) and a valve arrangement with high pressure or low pressure, for example, be acted upon by tank pressure to the hydraulic cylinder ( 2 ) in rapid or in the power stroke in one direction or in rapid traverse or power stroke in the other direction to move, characterized in that the hydraulic machine ( 10 ) a variable speed drive ( 12 ) and that the area ratios of the active surfaces (A ₁ , A ₂ , A ₃ ) are adjusted so that in rapid traverse and in the power stroke of the drive ( 12 ) works in the same speed range. 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 is a directional control valve ( 20 ), which in a first position (b) has a pressure connection of the hydraulic machine ( 10 ) via a management ( 26 ) with a first pressure chamber ( 4 ) and a second pressure chamber ( 6 ) on another working line ( 30 ) connects to the low pressure and in a second position (a) the connection of the second pressure chamber ( 6 ) locks to 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, which in a position (a) the first pressure chamber ( 4 ) with the second pressure space acting in the opposite direction ( 6 ) and in the other position (b) the first pressure chamber with the third pressure chamber ( 8th ) connects. Linear drive according to claim 4, wherein in the first position (a) a pressure medium connection of the third pressure chamber ( 8th ) to the hydraulic machine ( 10 ) Is blocked. Linear drive according to claim 5, wherein the third pressure chamber ( 8th ) via a suction line ( 36 ) and one in the direction of the third pressure chamber ( 8th ) opening check valve ( 38 ) is connected to low pressure. Linear drive according to claim 4, 5 or 6, with a storage valve ( 40 ), which in one position (a) is 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 ) with 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 second pressure space acting in the opposite direction ( 6 ) Has. Linear drive according to claim 8, wherein the effective area A _{2 of} the second pressure chamber ( 6 ) slightly smaller than the effective area (A ₃ ) of the third pressure chamber ( 8th ). Linear drive according to one of the preceding claims, wherein the motor ( 12 ) or the hydraulic machine ( 10 ) is executed with reversal of direction. 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 ) a piston ( 44 ) with a piston hollow rod ( 46 ) into which a pole ( 50 ) of the hydraulic cylinder ( 2 ), so that by an inner end face ( 52 ) of the piston hollow rod ( 46 ) and the end face of the rod ( 50 ) the first pressure chamber ( 4 ) axially bounded by the rod ( 50 ) is supplied through with pressure medium. Linear drive according to claim 12, wherein a piston rod-side annular end face (A ₂ ) of the piston ( 44 ) the second pressure chamber ( 6 ) and a rod-side annular end face (A ₃ ) facing away from this, the third pressure chamber ( 8th ) is limited in the axial direction.

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