WO2011035828A1

WO2011035828A1 - Prestressed hydraulic drive with variable-speed pump

Info

Publication number: WO2011035828A1
Application number: PCT/EP2010/004578
Authority: WO
Inventors: Stefan Schmidt
Original assignee: Robert Bosch Gmbh
Priority date: 2009-09-25
Filing date: 2010-07-27
Publication date: 2011-03-31
Also published as: CN102612430B; EP2480405B1; TWI519717B; EP2480405A1; CN102612430A; DE102009043034A1; TW201115034A

Abstract

The present invention relates to a hydraulic drive with a hydraulic machine (1) activated with variable speed by an electric drive motor (2), a main cylinder (4) for carrying out a sequence of movements while building up force and a secondary cylinder (8) for carrying out a rapid sequence of movements. According to the invention, the hydraulic machine (1), mechanically activated by the drive motor (2), uses one of its pressure connections to prestress at least one piston side of the main cylinder (4) with a predetermined permanent pressure, this hydraulic machine (1) bringing about a reciprocating movement of the main cylinder (4) and of the secondary cylinder (8) on the basis of one of the two sequences of movements by selectively circulating pressure medium in a closed circuit in which the hydraulic machine (1) is included.

Description

Prestressed hydraulic drive with variable speed pump

description

The present invention generally relates to a hydraulic drive preferably for a press, plastic machine, bending machine, etc. according to the preamble of claim 1. Such drives are designed to at least two movements, namely a fast transfer movement (hereinafter referred to as "rapid traverse") and a force applying work movement (hereinafter referred to as "press gear") to realize. From the prior art, for example according to EP 0 785 861 B1, a generic hydraulic drive for a press is known. This drive consists of a driven hydrostatic machine that generates a predetermined constant pressure in a primary pressure line system and a hydraulic transformer consisting of a hydraulic motor and a hydraulic pump connected to it mechanically. The preferably adjustable hydraulic motor is connected to the primary pressure line system and is thus driven by the hydrostatic machine. The also adjustable hydraulic pump acts on a secondary pressure line system with a

Hydraulic pressure, in which a press cylinder is used, whose cylinder chambers are connected via valves to the two hydraulic connections of the hydraulic pump. Finally, the two cylinder chambers of the press cylinder are connected via a pressure line to the primary pressure line system to bias the plunger to the primary pressure (corresponding to the required bias pressure for the press cylinder).

However, it has proved to be technically difficult to put into practice the idea of arranging a hydraulic transformer having the structure described above. The design effort and the number of required hydraulic components and their coordination successive reduces namely the economy of this known hydraulic drive such that it has not found greater acceptance in the art.

In view of this state of the art, the object of the present invention

Invention is to provide a generic hydraulic drive, which manages with a reduced number of hydraulic components and is characterized in operation by a low energy consumption.

This object is achieved by a hydraulic drive having the features of patent claim 1. Further advantageous embodiments of the invention are the subject of the dependent claims.

The invention accordingly relates to a hydraulic drive with a variable speed controlled by an electric drive motor hydraulic machine, a master cylinder for performing a force-building movement sequence and a slave cylinder to perform a fast movement.

According to the invention, the master cylinder is through one, preferably both

Piston surfaces acting, further preferably pre-clamped or clamped by an external pressure source generated predetermined permanent pressure, wherein the

Hydromaschine by selected transferring pressure medium in one

closed circle, in which the hydraulic machine is interposed, one Stroke movement of the master cylinder and the slave cylinder after one of the two movements causes.

By biasing the drive preferably by means of the also for

Movements are responsible hydraulic machine or by the external

Pressure source significantly reduces the volume of compression to be delivered, the combination of bias of the drive and the servo-electric variable speed pump (hydraulic machine) as a biasing means and hydraulsiches drive means for the two cylinders represents an economical realization of an energy-saving hydraulic drive with short cycle times.

The invention will be explained below with reference to a preferred embodiment with reference to the accompanying drawings.

Show it:

1 is a schematic diagram of a hydraulic drive according to a preferred embodiment of the invention at a standstill (under bias),

2 shows the schematic diagram of the hydraulic drive according to FIG. 1 in "rapid traverse" downwards,

3 shows the block diagram of the hydraulic drive according to FIG. 1 in the "press gear",

Fig. 4 shows the block diagram of the hydraulic drive of FIG. 1 in a Re-compression phase and

Fig. 5 shows the schematic diagram of the hydraulic drive of FIG. 1 in the "rapid" up (retraction phase).

As can be seen from all the figures, the inventive hydraulic drive a pressure medium source in the form of a variable speed driven hydraulic machine 1 as a pump, which is mechanically connected thereto for an electric motor 2. The hydraulic machine 1 is at its two

Pressure ports connected to a hydraulic pressure line system, which forms a closed hydraulic pressure circuit.

Specifically, a first connection line 3 is connected to a first pressure connection of the hydraulic machine 1, which leads directly to a piston side

Pressure chamber 4a of a master cylinder 4 leads. To the second pressure port of the hydraulic machine 1, a second line 5 is connected, which is connected via a valve 6 with a piston rod-side pressure chamber 4b of the master cylinder 4 (hereinafter referred to as annular chamber 4b). The valve 6 is present as a

Directional control valve and in particular as a 3/2 way switching valve formed with a first switching position, in which only a hydraulic fluid flow from the

Annular chamber 4b of the master cylinder 4 is allowed in the direction of hydraulic machine 1, a second switching position in which a hydraulic fluid flow in both directions is possible and a third switching position in which the second line 5 is completely locked. Between the hydraulic machine 1 and the aforementioned directional control valve 6, a branch 7 is inserted into the second line 5, which leads to a

piston rod side pressure chamber 8a of an auxiliary cylinder 8 leads. The piston 8b of the auxiliary cylinder 8 is in its diameter significantly smaller than the piston 4c of the master cylinder 4, so that the stroke of the auxiliary cylinder 8 at a comparable volume flow of the hydraulic fluid is greater than the stroke of the

Further, the ring sides of the cylinders 4, 8 ideally have in sum the same area as the piston side of the master cylinder 4.

Finally, a bypass or shorting line 9 is provided which connects the piston chamber 4a of the master cylinder 4 with the annular chamber 4b. In this bypass line 9, a short-circuit valve 10 is interposed, the in the present case designed as a way switching valve and preferably as a 2/2 way switching valve. In a first switching position of this short-circuit valve 10, the bypass line 9 is fully open (ie in both directions), wherein in a second switching position only a fluid flow from the annular chamber 4b is admitted into the piston chamber 4a of the master cylinder 4 via the bypass line 9.

In the concrete embodiment of the invention, the hydraulic drive with the above structure is installed in a press. For this purpose, the piston rod 4d of the master cylinder 4 as well as the piston rod 8c of the slave cylinder 8 are connected to a displaceably mounted ram 11 to which a pressing tool 12 or a punching tool is attached.

Basically, the hydraulic pressure system according to the invention also has numerous safety devices to prevent overpressure conditions or unintentional lowering of the ram 11, which are not shown in detail in the figures. Thus, the annular chamber 8a of the auxiliary cylinder 8 can be secured via two series-monitored, monitored seat valves (not shown). Thereby, a lowering of the upper pressing tool 12 can be securely prevented. In addition, the piston chamber 4 a of the master cylinder 4 can be secured against unintentional pressurization. This can be achieved by the shown directional valves 6, 10 itself, or by a supervised release of the

electric drive motor 2 of the hydraulic machine 1.

To compensate for leakage losses in the system, a pressure accumulator 13 is connected via a valve 14 to the first pressure line 3 between the hydraulic machine 1 and the piston chamber 4a of the master cylinder 4. This valve 14 is provided by a directional control valve, preferably a 2/2 way switching valve, with a first switching position in which the connection between the external pressure source 13 and the first pressure line 3 is fully released and a second switching position in which only a fluid flow the external pressure source 13 in the first pressure line 3 is allowed. In the operating state of the hydraulic drive according to the invention, at least the piston-side pressure chamber 4 a of the master cylinder 4 is constantly on the

Pressure medium source with a predetermined approximately constant (in particular regulated) hydraulic pressure applied. The movement of the two cylinders 4, 8 is controlled by circulating pressure medium in the closed pressure circuit by means of the variable-speed driven hydraulic machine 1.

Decisive for the control of the movement sequence of both cylinders 4, 8 is the supply or discharge of pressure medium from the respective annular chambers 4b, 8a via the variable-speed driven hydraulic machine 1, wherein the complete

Movement of the working stroke of the press with participation of both cylinders by means of the valves 6, 10 and the variable speed driven (constant) pump can be controlled.

The mode of operation of the hydraulic drive according to the invention can be described as follows with reference to the attached figures:

According to FIG. 1, when the hydraulic drive is at a standstill (in the retracted position of the ram 11), the switching-off valve 6 is in that switching position in which only one fluid flow out of the annular chamber 4b of the

Master cylinder 4 is allowed and the short-circuit valve 10 in the switching position in which the bypass line 9 is fully open. The electric drive motor 2 of the hydraulic machine 1 is also switched off.

In this (static) state, the weight of the ram 11 is supported by the pressure within the piston chamber 8a of the slave cylinder 8, while in the ring and piston chamber 4a, 4b of the master cylinder 4 via the

Short-circuit valve 10 Pressure equalization prevails.

To get down from this (static) state in the rapid, is 2, the valve 6 is switched to the full blocking position and the hydraulic machine 1 driven. As a result, pressure fluid is sucked out exclusively from the annular chamber 8a of the auxiliary cylinder 8 via the line 5 and discharged into the piston chamber 4a of the main piston 4. At the same time the remains

Pressure equalization between the master cylinder chambers 4 a, 4 b obtained via the still completely open short-circuit valve 10.

Since the slave cylinder 8 is smaller than the master cylinder 4 and the pump 1 acts only on the volume of the ring side of the slave cylinder 8, the downward movement (and later the retraction movement) of the ram 11 at a predetermined volume flow at a relatively high speed, even then, if the

Hydromachine 1 is designed with a small capacity. In addition, by briefly overloading the electric drive motor 2 (permissible), the speed but also the subsequent pressing force can be further increased.

Once the pressing tool 12 has reached a workpiece to be machined 15, the short-circuit valve 10 switches to the switching position in which only one flow from the annular chamber 4b of the master cylinder 4 is allowed and the valve 6 in the switching position in which a fluid flow from the annular chamber 4b to Hydromachine 1 is allowed. In this state according to FIG. 3, the pressure within the annular chamber 4 b is now reduced by the hydraulic machine 1, since no pressure equalization between the master cylinder chambers 4 a, 4 b on the

Short circuit valve 10 takes place more, whereas the pressure within the

Piston chamber 4a of the master cylinder 4 is maintained or increased. That is, instead of a considerable compression of the piston side of the master cylinder 4, the actual pressing force is generated by pressure release of the ring sides of the cylinders 4, 8. Since no pressure equalization takes place between the main cylinder chambers 4a, 4b, furthermore, the continuous pressing movement of the master cylinder 4 at a constant volumetric flow decreases significantly to a lowering movement

Speed on than the previous rapid. To terminate the pressing operation, the valve 6 is brought into a switching position according to FIG. 4, after which a fluid flow within the connecting line 5 in both directions, ie from and to the annular chamber 4b of the master cylinder 4 is made possible. In this case, a pressure equalization between the

Main cylinder chambers 4a, 4b and the annular chamber 8a of the auxiliary cylinder 8 via the connecting line 5 and the branch 7, wherein at the same time energy can be recovered via the electric drive motor 2.

Finally, the plunger 11 can be retracted by, as shown in Fig. 5, the valve 6 is brought into the switching position, in the only one

Flow from the annular space 4a of the master cylinder 4 is allowed and the short-circuit valve 10 is switched to the switching position in which the bypass line 9 is fully open (in both directions). If the hydraulic machine 1 is driven in this state to withdraw pressure medium from the piston chamber 4 a of the master cylinder 4, the withdrawn

Pressure medium with complete pressure equalization of the two master cylinder chambers 4a, 4b pressed into the annular chamber 8a of the slave cylinder 8, which retracts the ram 11 at high speed again.

In the hydraulic drive described above, the hydraulic machine 1 can be flanged to a valve block (not shown), which the

Function or safety valves of the drive contains. In turn, the electric motor for operating the pump can be attached to these. This unit can in turn be constructed on a hydraulic cylinder, whereby a particularly compact Anstriebsachse is available. LIST OF REFERENCES

1 hydraulic machine

2 servomotor (variable speed)

3 first connection line

4 master cylinders

4a piston chamber

4b ring chamber

4c master cylinder piston

4d piston rod

5 second pressure line

6 valve

7 branch

8 secondary cylinders

8a ring chamber

8b secondary cylinder pistons

8c piston rod

9 bypass line

10 short-circuit valve

11 press punches

12 pressing tool

13 accumulator

14 valve

15 workpiece

Claims

claims

1. Hydraulic drive with one of an electric drive motor (2)

Variable-speed controlled hydraulic machine (1), a master cylinder (4) for performing a force-building movement sequence and a slave cylinder (8) for performing a fast movement sequence, characterized in that at least one side of the piston

Main cylinder (4) is acted upon by one of an external pressure source (13) and / or by the drive motor (2) mechanically controlled hydraulic machine (1) constructed at a pressure connection predetermined permanent pressure, wherein the hydraulic machine (1) further by selected Umfördern of Pressure medium in a closed circle, in which the

Hydromachine (1) is interposed, a lifting movement of the

Main cylinder (4) and the slave cylinder (8) after each one of the two movements causes.

2. A hydraulic drive according to claim 1, characterized in that the other pressure port of the hydraulic machine (1) to a piston rod side annular chamber (4b) of the master cylinder (4) and to a piston rod side annular chamber (8a) of the secondary cylinder (8) is connected.

3. A hydraulic drive according to claim 2, characterized in that in a connecting line (5) of the closed circuit between the hydraulic machine (1) and the master cylinder annular chamber (4b), a valve, preferably a directional control valve (6) is interposed.

4. A hydraulic drive according to claim 3, characterized in that the valve (6) is a 3/2 way switching valve with a first switching position in which only a hydraulic fluid flow from the master cylinder annulus (4b) is allowed towards hydraulic machine (1), a second switching position in which a hydraulic fluid flow is allowed in both directions and one third switching position in which the connecting line (5) is completely locked.

5. A hydraulic drive according to claim 3 or 4, characterized by a bypass line of the closed circuit, which the

Main cylinder piston chamber (4a) with the master cylinder annular chamber (4b connects and in which a short-circuit valve (10) is interposed.

6. Hydraulic drive according to claim 5, characterized in that the short-circuit valve (10) is a 2/2 way switching valve, in a first

Switching position, the bypass line (9) opens completely and in a second switching position only a fluid flow from the annular chamber (4b) in the piston chamber (4a) of the master cylinder (4) via the bypass line (9) permits.

7. Hydraulic drive according to one of the preceding claims, characterized

characterized in that the piston rod sides (4b, 8a) of both cylinders (4, 8) have in total the same area as the piston side (4a) of the

Master cylinder (4).