WO2011003506A1

WO2011003506A1 - Electro-hydraulic controller

Info

Publication number: WO2011003506A1
Application number: PCT/EP2010/003669
Authority: WO
Inventors: Marek Chmiel; Mirjana Ristic
Original assignee: Robert Bosch Gmbh
Priority date: 2009-07-09
Filing date: 2010-06-17
Publication date: 2011-01-13
Also published as: DE102009058408A1; CN102549273B; CN102549273A; EP2452080B1; EP2452080A1

Abstract

The invention relates to a controller for a secure electro-hydraulic axis (2) comprising a valve block (10), which has a first and a second working connection (Y2, Y1) for a hydraulic load (2) that has two supply connections (X1, X2) and comprises fluidic paths between at least one of the working connections and at least one of the supply connections, a hydraulic machine (8) that is switched between the two supply connections, a rotational speed variable electric drive (6) that is coupled to the hydraulic machine, and monitored switching valves (12, 14, 16, 18) that are arranged on the valve block and each of which have a monitoring unit for monitoring the switching positions of the valves. To this end, two monitored switching valves (12, 16, 18) are arranged in series in a path, which allows the removal of pressure medium from the first working connection (Y2), and at least two safety means (12, 14) acting independently of each other are provided, which limit the supply of pressure medium into the second working connection (Y1) in a predetermined state.

Description

Electrohydraulic control

description

The invention relates to an electro-hydraulic control for a safe electro-hydraulic axis. Such electro-hydraulic controls are used for example in presses or in injection molding machines, as well as in many other applications of industrial automation. Conventional presses are often valve-controlled. Via a proportional valve, a speed or a pressing force of a press cylinder are set. Safety requirements with regard to safety at work can be implemented, for example, by switching valves which block a hydraulic connection to the press cylinder in an unactuated position. The switching valves are also monitored by a switch which detects the switching position. The DIN EN 12622: 2001 shows in Annex C an example of a hydraulic press control circuit, are implemented in the safety requirements or occupational safety requirements.

There are currently more presses designed in which the press cylinder is controlled by a hydraulic machine directly with a predetermined amount of pressure medium. The proportional valve can be omitted accordingly. The hydraulic machine has per se a constant flow rate. However, the rotational speed of an electric drive of the hydraulic machine is varied so as to obtain a controllable flow rate of the hydraulic machine.

Such drives have advantages in energy efficiency. In addition, the hydraulic circuit diagram of the press control can be simplified.

In DE 103 29 067 A1 discloses an electro-hydraulic control for a press with a driven by a variable-speed drive hydraulic pump is disclosed. A cylinder space of a press cylinder over which a piston of the press cylinder in a press tion with a pump pressure of the hydraulic pump can be acted upon, is in direct pressure fluid connection with the hydraulic pump. An annular space of the press cylinder for pressurizing the piston against the pressing direction is connected to a hydraulic accumulator, which is charged via the hydraulic pump. To limit the pressure of the pump pressure, a pressure relief valve is provided.

The disadvantage of this solution is that an interruption of the operation of the

Press cylinder in the pressing direction, for example in an emergency situation, can be done only by stopping the hydraulic pump. The above

DIN EN 12622: 2001 is not fulfilled by this. The object of the present invention is to provide a reliable and as simple as possible or cost-effective implementation of occupational safety requirements in an electro-hydraulic control, which has a variable speed driven hydraulic machine. This object is achieved by an electro-hydraulic control according to claim 1.

According to the invention, an electrohydraulic control is provided for a safe electrohydraulic axle which comprises at least one hydraulic consumer. The control is used in particular for a press, an upper piston press or a press brake. The controller has a valve block with a first working port and a second working port for the hydraulic consumer. Furthermore, the valve block has two supply ports for a pressure medium supply and a pressure medium discharge. Fluidic paths are provided between at least one of the working ports and at least one of the supply ports. A hydraulic machine is connected between the two supply connections. This is coupled to an electric drive having an actuator for adjusting its speed. On the valve block further monitored switching valves are arranged, which is assigned to monitor their switching position in each case a monitoring device. In a fluidic path, which allows the discharge of pressure medium from the first working port, two monitored switching valves are arranged one behind the other. In addition, at least two independent mutually effective security means present, which limit a supply of pressure medium in the second working port in a predetermined state.

This solution has the advantage that it is possible with a low outlay in terms of equipment at the outset to explain occupational safety requirements. In particular, according to the invention, the valves which are flown through in the normal operating cycle - also all the monitored valves - are designed as switching valves, as a result of which throttle losses which occur with proportional valves are reduced. Preferably, the safety means comprise at least one monitored switching valve arranged in a bypass path from the second working port to a tank. Due to the arrangement in the bypass path, the switching valve is flowed through only in emergency operation of pressure medium and thus causes in normal operation substantially no flow resistance.

Advantageously, the safety means in each path, which allows a pressure fluid supply to the second working port, comprise at least one monitored switching valve.

Preferably, the security means in each path, which allows a pressure medium supply to the second working port, two monitored switching valves, whereby a high reliability is ensured. To further increase safety, the safety means comprise a safety device on the electric drive of the hydraulic machine. This safety device forces a shutdown or an operating state with reduced power of the electric drive as a function of a release signal supplied to it.

Preferably, the safety means comprise a monitored switching valve, which fluidly connects the two supply ports in an unactuated position, whereby the supply of the hydraulic consumer is stopped with pressure medium.

In a preferred solution, in each path, which allows the discharge of pressure medium from the first working port, either at least two monitored switching valves arranged one behind the other or one set above the maximum nominal pressure of the hydraulic machine pressure relief valve. Further advantageous embodiments of the invention are the subject of further subclaims. In the following, with reference to schematic drawings, an embodiment of

Invention explained in more detail. Show it:

Figure 1 in a hydraulic circuit diagram, an electro-hydraulic control according to an embodiment;

Figure 2 in a hydraulic circuit diagram, the electro-hydraulic control according to the embodiment;

Figure 3 is a hydraulic circuit diagram of the electro-hydraulic control according to the embodiment;

Figure 4 in a hydraulic circuit diagram, the electro-hydraulic control according to the embodiment; and FIG. 5 shows in a hydraulic circuit diagram the electro-hydraulic control according to the exemplary embodiment.

1 shows a circuit diagram of a hydraulic press brake 1 is shown, which is constructed as a so-called upper piston press. This means that an upper pressing tool is moved up and down by a hydraulic cylinder 2 during a machine cycle. An electro-hydraulic control of the press brake 1 has an electronic unit 4, a variable-speed controllable electric drive 6, a hydraulic machine 8 with a constant delivery volume and a hydraulic control block 10. In this switching valves 12, 14, 16 and 18 are inter alia arranged. These are each provided with a switch 20 which monitors the unactuated or - the switching valve 16 - the actuated switching position. The signals of the switches 20 are supplied to a safety controller which switches off the press brake 1 when a fault occurs or moves to a safe position. To a working port A1 of the hydraulic machine 8, a first working line 24 is connected, which connects this with a supply terminal X1 of the control block 10. Via a working line 26, a second working connection A2 of the hydraulic machine 8 is connected to a second supply connection X2 of the control block 10. The hydraulic machine 8 is driven via the electric drive 6, which can be coupled with it via a coupling 27.

The switching valve 12 has two pump ports P1 and P2, wherein the pump port P1 is connected via the first supply terminal X1 of the control block 10 with the work 24 and the pump port P2 via the second supply port X2 with the second working line 26. Furthermore, the switching valve 12 has two working ports A, B, with which the hydraulic cylinder 2 is connectable.

The hydraulic cylinder 2 has a piston 28 which separates a cylinder space 29 from an annular space 30. The annular space 30 is penetrated by a piston rod 31, which is connected to the upper pressing tool (not shown).

The working port A of the switching valve 12 is connected to a pressure line 32, which opens into a working port Y1 of the control block 10, wherein the working port Y1 is connected to a consumer port Z1 of the hydraulic cylinder 2, which in turn is in fluid communication with the cylinder space 29. In the pressure medium flow path between the working port B of the switching valve 12 and the annular space 30 of the hydraulic cylinder 2, the switching valves 16, 18 are arranged. Via a spring 33, a valve spool of the switching valve 12 is biased in a basic position a, in which the working lines 24, 26 of the hydraulic machine 8 connected and the working ports A, B are locked. Via an electric actuator 34, the valve spool of the switching valve 12 can be brought into a switching position b, in which the pump port P1 to the working port A and the pump port P2 to the working port B are connected.

The switching valve 16 has two working ports A, B, a pump port P and a tank port T. The working port B of the switching valve 16 is connected to the working port B of the switching valve 12 via a connecting passage 35. About a The lower connection channel 36 is the pressure port A of the switching valve 16 with a working port B of the switching valve 18 in fluid communication. The pump connection P of the switching valve 16 is connected via a pump channel 37 to the second supply connection X2 of the control block 10 and thus to the second working line 26 connected to the hydraulic machine 8. To the tank port T of the switching valve 16, a tank channel 38 is connected, which leads to a tank port T of the control block 10, which in turn is connected via a tank line 40 to a tank 42 in fluid communication.

A valve spool of the switching valve 16 is biased by the spring 33 in a basic position a, in which the pump channel 37 is connected to the tank channel 38 and the connecting channels 35, 36 are separated from each other. About the actuator 34, the valve spool in the switching position b can be brought, in which the connecting channels 35, 36 connected to each other and the pump channel 37 is separated from the tank channel 38. The switching valve 18 has, in addition to the working port B, a further working port A, which is connected via an annular space channel 44 to a working port Y2 of the control block 10 and via an annular space line 46 connected thereto to the annular space 30 of the hydraulic cylinder 2. A valve spool of the switching valve 18 is biased by the spring 33 in the basic position a, in which a pressure medium connection is opened in the pressure fluid flow direction from the connecting channel 36 to the annulus 44 and closed in the reverse pressure fluid flow direction. In an actuated by the actuator 34 switching position b of the valve spool of the switching valve 18 of the pressure fluid flow path between the connecting channel 35 and the annular space channel 44 can be flowed through in both pressure medium flow directions.

The switching valves 12, 16, 18 are thus successively in a path from the hydraulic machine 8 to the annular space 30 of the hydraulic cylinder 2. In the unconfirmed basic position a, the switching valves 12, 16 each interrupt this path in both pressure medium flow direction and the switching valve 18 in a pressure medium flow direction.

The switching valve 14 is arranged in a bypass path to the pressure line 32 and has a working port A, which via a pressure line 48 to a working port A of Shuttle valve 50 is connected. Via this, the pressure line 48 can be connected either to the connecting channel 32 via a first pressure port B1 of the shuttle valve 50 or to the pump channel 37 via a second pressure port B2, the pressure higher pressure port B1, B2 being connected to the working port A of the shuttle valve 50.

Via a tank connection T, the switching valve 14 is in fluid communication with the tank channel 38. To a working port B of the switching valve 14 is a branched off from the connecting channel 32 working line 52 is connected. From a control connection S of the switching valve 14, a control line 54 leads to a pilot-operated check valve 56.

A valve spool of the switching valve 14 is biased by the spring 33 in a basic position a, in which the pressure line 48 connected to the shuttle valve 50 is connected to the control line 54 and the tank line 38 to the working line 52. About the actuator 34 of the valve spool of the switching valve 14 in a switching position b can be brought, in which the pressure line 48 with the working line 52 and the tank line 38 with the control line 54 are in fluid communication. The check valve 56 which can be unlocked with a control pressure of the control line 54 is arranged between the tank 42 and the cylinder chamber 29 of the hydraulic cylinder 2. A valve body of the check valve 56 is biased by a spring on a valve seat. The check valve 56 opens in the pressure medium flow direction from the tank 42 to the cylinder chamber 29. The pressure port Z1 of the cylinder chamber 29 is disposed between the check valve 56 and the cylinder chamber 29.

In the working line 52, which branches off from the connecting channel 32 to the working port B of the switching valve 14, a in the direction of pressure fluid flow toward the switching valve 14 opening check valve 58 is arranged.

Another check valve 60 is arranged in the pressure line 48 between the shuttle valve 50 and the switching valve 14, which opens in the pressure fluid flow direction from the shuttle valve 50 to the switching valve 14. By a check valve 61 in the tank channel 38, a flow of pressure medium only in the direction of the tank 42 is possible.

About a formed in the control block 10 throttle 62, the control line 54 is throttled between the switching valve 14 and the check valve 56.

A pressure fluid flow path from the annular space 30 of the hydraulic cylinder 2 to the tank 42 is secured by a pressure limiting valve 84 which is set above the maximum nominal pressure of the hydraulic machine 8 and opens at a pressure in the annular space 30 of 350 bars, for example. This also has a small nominal size, e.g. NG 4, so that in case of release, the hydraulic cylinder 2 extends only slowly.

Parallel to the switching valve 18 between the annular space channel 44 and the connecting channel 36, a further the annular space 30 of the hydraulic cylinder 2 secures pressure limiting valve 86 which opens, for example, at a pressure in the annular space 30 of 90 bar.

To the first and second working line 24, 26 connected to the hydraulic machine 6, a pressure limiting valve 88 or 90 connected to the tank 42 is likewise arranged. Wherein the pressure limiting valve 88 opens approximately at a pressure of 315 bar in the first working line 24 and the pressure relief valve 90 approximately at a pressure of 200 bar in the second working line 24. Furthermore, each working line 24 and 26 is connected to a suction line 92 and 94, respectively, which are in fluid communication with the tank 42. In the suction lines 92, 94 in each case in the pressure medium flow direction to the hydraulic machine 8 opening check valve 96, 98 is arranged. Due to the suction lines 92, 94 pressure fluid can be sucked out of the tank 42 by the hydraulic machine 8 in the absence of pressure medium.

In the following, the operation of the electro-hydraulic control will be explained with reference to Figures 1 to 5.

The cylinder chamber 29 of the hydraulic cylinder 2 is protected by the switching valve 12 against inadvertent supply of pressure medium. In the unactuated position, the two connections A1, A2 of the hydraulic machine 8 are connected and the consumer connections A, B of the Switching valve 12 locked. In addition, the switching valve 14 in the unactuated position, a bypass connection from the cylinder chamber 29 of the hydraulic cylinder 2, via the pressure line 32, the working line 52 and the tank channel 38 to the tank 42 ago. In addition, the electric drive 6 is included in the safety concept. Of the

Drive 6 has a secure control electronics, which only after the presence of a release signal of the switch 20, the drive 6 in the normal operating state in which the drive 6 converts control signals, switches. If the release signal is not present, the drive 6 is stopped or only with low power, i. operate with low torque or low speed.

In the switching position shown in Figure 1, the press brake 1 is at a standstill. The switching valves 12 to 18 are in their unactuated currentless home position a. The first and the second working line 24, 26 of the hydraulic machine 8 are connected to each other via the switching valve 12 and the second working line 26 is in addition via the pump channel 37, the switching valve 16 and the tank channel 38 to the tank 42 in fluid communication. To illustrate this in Figure 1, these fluid flow paths have been highlighted with a dashed line having a large line width. The pressure medium flow path from the annular chamber 30 of the hydraulic cylinder 2 is also highlighted with a dashed line having a large line width and ends at the switching valve 18 and the pressure limiting valve 84, 86th

Figure 2 discloses the press brake 1 with the electro-hydraulic control, in which the piston 28 is moved with the piston rod 31 of the hydraulic cylinder 2 in a rapid downward. For this purpose, the switching valves 12, 14, 16 and 18 are each connected in the switching position b.

The pressure medium flow paths between the annulus 30 and the cylinder chamber 29 of the hydraulic cylinder 2 and each of the hydraulic machine 8 are shown with a dashed line having a large line width. The hydraulic machine 8 promotes pressure medium from the annular space 30 into the cylinder chamber 29 as a hydraulic pump. The pressure medium from the annular space 30 of the hydraulic cylinder 2 is conveyed via the annular space line 46, the annular space channel 44, the switching valve 18, the switching valve 16 and the switching valve 12 via the second Working management 26 to the hydraulic machine 8 and from there via the first working line 24, the switching valve 12, the pressure line 32 to the cylinder chamber 29 of the hydraulic cylinder 2 promoted. With additional demand for pressure medium, this can be sucked through the check valve 56 from the tank 42.

In the pressure fluid flow path between the annular space 30 of the hydraulic cylinder 2 and the hydraulic machine 8, the switching valves 12, 16, 18 are arranged, which are each monitored by the switch 20. The monitoring has the purpose that the hydraulic machine 8 promotes pressure fluid from the annulus 30 into the cylinder chamber 29 of the hydraulic cylinder 2 only when the switching valves 12, 16, 18 are in the switching position b. The switches 20 report the switching position b to the electronics 4, which controls the electric drive 6. To stop the rapid traverse, one of the switching valves 12, 16, 18 is simply switched to the initial position b without a current. Alternatively, instead of the automatic actuation of the electric drive 6 via the electronics 4, with confirmed switching position of the switching valves 12, 16, 18 via the switch 20, an operator, for example, after an optical or acoustic confirmation signal is output, the electric drive 6 start manually. The switching valves 12 and 14 serve as a safety means which limit a supply of pressure medium to the cylinder chamber 29 of the hydraulic cylinder 2 in the non-actuated state and thus interrupt a displacement of the piston 28 in the pressing direction. In the non-actuated basic position a of the switching valve 14, via the pressure line 32, the shuttle valve 50, the check valve 60, the switching valve 14 and the control line 54, the check valve 56 associated with the hydraulic cylinder 2 is opened with the pump pressure, whereby the cylinder space 29 is closed Tank 42 is relieved.

In the actuated state of the switching valve 14 in Figure 2, the control line 54 is relieved to the tank 42.

In Figure 3, the switching positions of the electro-hydraulic control for the press brake 1 for a crawl of the piston 28 of the hydraulic cylinder 2 are shown. Here, the switching valves 12, 14 and 16 are actuated and the switching valve 18 is not actuated. By the non-actuated switching valve 18 is a pressure medium flow path (having large line thickness dashed line in FIG. 3) between the annular space 30 of the hydraulic cylinder 2 and the hydraulic machine 8 only via the pressure limiting valve 86. This opens only at a certain annulus pressure in the annular space 30, for example, 90 bar, which causes this annulus pressure counteracts the working pressure in the cylinder chamber 29, whereby the adjustment speed of the piston 28 of the hydraulic cylinder 2 is reduced and this is moved in crawl.

Figure 4 shows the switching positions of the electro-hydraulic control for a decompression of the hydraulic cylinder 2 of the press brake 1. Here, only the switching valves 12 and 14 are actuated. The hydraulic machine 8 promotes hydraulic pump as pressure medium from the cylinder chamber 29 of the hydraulic cylinder 2 to the tank 42. This pressure medium from the cylinder chamber 29, via the pressure line 32, the switching valve 12, the first working line 24, the second working line 26, the switching valve 16 to the tank 42 promoted , In the machine cycle of decompression, the press brake 1 is thus relieved, since the working pressure in the cylinder chamber, 29 of the hydraulic cylinder 2 is reduced.

In the switching position of the electro-hydraulic control of the press brake 1 shown in FIG. 5, the piston 28 of the hydraulic cylinder 2 is moved upwards in rapid traverse. For this purpose, the switching valves 12 and 16 are actuated. Pressure medium is thus promoted by the cylindrical space 29 of the hydraulic cylinder 2 via the pressure line 32, the switching valve 12, the first working line 24, the second working line 26, the switching valve 12, the switching valve 16, the switching valve 18 and the annular space channel 44 to the annular space 30. In order to relieve the cylinder chamber 29 in addition to the tank 42, the check valve 56 is controlled by the pressure in the control line 54, which is connected via the switching valve 14, the shuttle valve 50 and connected to the second working line 26 pump channel 37.

The following table gives an overview of the sections of the machine cycle described above in FIGS. 1 to 5. It also indicates, by marking the respective table field, which of the switching valves 12, 14, 16, 18 are actuated in the respective cycle section.

Disclosed is an electro-hydraulic control for a safe electro-hydraulic axis. The controller comprises a valve block having a first working port and a second working port for a hydraulic consumer and having two supply ports for a pressure medium supply and a fluid discharge and having fluidic paths between at least one of the working ports and at least one of the supply ports, a hydraulic machine , which is connected between the two supply ports, an electric drive which is coupled to the hydraulic machine and which has an actuator for adjusting its speed, and has arranged on the valve block monitored switching valves, which is assigned to monitor their switching position in each case a monitoring device. In this case, in a path which allows the discharge of pressure medium from the first working port, two monitored switching valves arranged one behind the other, and there are at least two independently effective safety means which limit a supply of pressure medium in the second working port in a predetermined state.

LIST OF REFERENCES

1 press brake

2 hydraulic cylinders

4 electronics

6 electr. drive

8 hydraulic machine

10 control block

12 switching valve

14 switching valve

16 switching valve

18 switching valve

20 switches

24 work management

26 work management

27 clutch

28 pistons

29 cylinder space

30 annulus

31 piston rod

32 pressure line

33 spring

34 actuator

35 connection channel

36 connection channel

37 pump channel

38 tank channel

40 tank line

42 tank

44 annulus channel

46 Annular space line

48 pressure line

50 shuttle valve

52 work management 54 control line

56 check valve

58 check valve

60 check valve 61 check valve

62 throttle

84 pressure relief valve

86 pressure relief valve

88 Pressure relief valve 90 Pressure relief valve

92 suction line

94 suction line

96 check valve

98 check valve

A, B, A1, A2, work connection

X1, X2 supply connection P, P1. P2 pump connection

T tank connection

B1. B2 Pressure connection a Basic position b Switch position

Claims

claims

1. Electrohydraulic control for a safe electro-hydraulic axle (2), which comprises at least one hydraulic consumer (2), in particular for a press, in particular an upper-piston press, in particular a

A press brake, comprising a valve block (10) having a first working port (Y2) and a second working port (Y1) for the hydraulic consumer (2) and having two supply ports (X1, X2) for a pressure medium supply and a pressure medium discharge and which has fluidic paths between at least one of the working ports (Y1, Y2) and at least one of the supply ports (X1, X2), a hydraulic machine (8) connected between the two supply ports (X1, X2), an electric drive ( 6), which is coupled to the hydraulic machine (8) and which has an actuator for adjusting its speed up and arranged on the valve block (10) monitored switching valves (12, 14, 16, 18), which for monitoring their switching position respectively a monitoring device is assigned, characterized in that in a path which the discharge of pressure medium from the first work Its connection (Y2) allows, two monitored switching valves (12, 16, 18) are arranged one behind the other, and that at least two independently effective safety means (12, 14) are present, which in a predetermined state, a supply of pressure medium in the second Limit work connection (Y1).

2. The electrohydraulic controller of claim 1, wherein the safety means (12, 14) comprise at least one monitored switching valve (14) disposed in a bypass path (32, 52) from the second working port (Y1) to a tank (42).

3. The electrohydraulic controller of claim 1 or 2, wherein the safety means (12, 14) in each path, which allows a pressure medium supply to the second working port (Y1) comprise at least one monitored switching valve (12).

4. Electrohydraulic controller according to claim 3, wherein the safety means

(12, 14) in each path, which allows a pressure medium supply to the second working port (Y1), two monitored switching valves (12, 14).

5. Electrohydraulic controller according to one of claims 1 to 4, wherein the

Safety means comprise a safety device on the electric drive (6) and wherein this safety device in response to a release signal supplied to it a shutdown of the electric drive (6) or an operating condition with reduced power of the electric drive (6) enforces.

6. Electrohydraulic controller according to one of claims 1 to 5, wherein the safety means comprise a monitored switching valve (12), which in an unconfirmed basic position (a) fluidly connects the two supply ports (X1, X2).

7. Electrohydraulic controller according to one of claims 1 to 6, wherein in each path, which allows the discharge of pressure medium from the first working port (Y2), either at least two monitored switching valves (12, 16, 18) are arranged one behind the other or via the maximum rated pressure of the hydraulic machine (8) adjusted pressure relief valve (84) is arranged.