JPH01127118A - Drawing press for sheet metal part - Google Patents

Abstract

PURPOSE: To precisely adjust blank holding force whenever needed with high reproducibility, non-hysteresis and non-inertia by directly adjusting hydraulic pressure with which force of cushion for drawing of a press for drawing of a sheet metal parts is decided. CONSTITUTION: An underside tool 9 to a sheet metal parts 1 to be drawn is fixed on a table 3 of a press for drawing of a sheet metal parts, a press ram 4 is vertically moved with two connecting rods 8, 8' and a drawer 5 is installed inside. And, under the drawers 5, an upside tool 10 having a split construction consisting of a punch 14 for drawing which is strongly fixed to the press ram 4 and a blank holder 13 is provided, and the drawer 5 is provided with a pressing plate 6 which is vertically movable in the press ram 4. Four cushions 7-7''' for drawing are vertically arranged as a piston cylinder unit on the upside of the pressing plate 6, and each cushion has pressure chambers 15-15''' respectively and when the blank holder 13 is relatively displaced against the punch 14 for drawing, liquid in the pressure chambers is exhausted resisting the prescribed drawing resistance and a work piece 1 is drawn.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a press for drawing sheet metal parts.

[Conventional technology]

A tool divided into a wrinkle holder and a drawing punch that can move relative to the wrinkle holder, and a diaphragm having at least one punch attached to the wrinkle holder and maintaining the wrinkle holding force during the relative movement inside the tool. A press for drawing sheet metal parts, which has a processing device and in which the cutter is formed as a piston-cylinder unit that operates against a predetermined hydraulic pressure, has already been described, for example, in German Patent No. 2407864. It is publicly known.

As is known, common presses are used to manufacture different sheet metal parts over time. When converting a press from producing the first sheet metal part to producing another workpiece, not only must the press tool be replaced, but the press adjustment data must also be changed to match the new tool or new workpiece. However, changing the manufacturing data of this press is much more time consuming and expensive than replacing the original tooling. Also, a large number of test presses must be performed on the Ail where the press is run continuously with high quality and similar accuracy on new workpieces.

Even if all the data for a given workpiece or tool have been accurately and carefully recorded from the previous manufacturing process and have been adjusted accordingly for the new manufacturing process,
Many time-consuming and expensive test presses are inevitable; different factors may contribute to this, but cannot be precisely determined and are limited in scope.

[Problem to be solved by the invention]

The object of the invention is that a press of the type mentioned at the outset can be purposefully and quickly reproducibly adapted to modified production conditions after converting the press to a modified sheet metal part or corresponding tooling, in particular The aim is to form the press so that the conversion can be completed with a much smaller amount of test press work than in the past.

[Means for Solving the Problems] According to the present invention, this object is achieved by arranging a pressure transducer in the pressure chamber of each crease, in which each crease is directly energized by a controlled hydraulic pressure, and a pressure transducer is arranged in the pressure chamber of each crease, which determines the wrinkle pressing force. Or, a force transducer that detects the wrinkle pressing force component applied to the range corresponding to the wrinkle pressing force or the wrinkle pressing force is applied to the wrinkle pressing force or the wrinkle pressing force in the range corresponding to the wrinkle pressing force or the wrinkle pressing force. The pressure transducer or force transducer is attached to the In addition, each pressure or force transducer is associated with a controller that continuously compares the respective actual value with a setpoint value, and these controllers each have a controllable outflow associated with each cushion. The pressure inside each cushion is increased through a throttle (throttle valve) according to the deviation between the target value and the actual value, in the sense of adjusting the cushion pressure or wrinkle holding force to the target value.
This is achieved by reducing or holding constant.

〔Effect of the invention〕

By directly adjusting the hydraulic pressure that determines the force in the cushion, the required wrinkle holding force can be precisely adjusted in each case with high repeatability, no hysteresis, and no inertia.

Hydraulic creasing force control is very precise and reproducible with great precision, yet has such low inertia that the target value can be varied in relation to stroke or crank angle according to a pre-adjustable program within the press cycle. During the pressing process, the creasing force is selectively and temporally increased or decreased with precise reproducibility. This depends in each case on the workpiece to be pressed and must be tested on a case-by-case basis.

Advantageous embodiments of the invention are described in the embodiment section of the patent claims.

〔Example〕

The present invention will be described in detail below with reference to embodiments shown in the drawings.

The press, shown schematically in vertical section in FIG. 1, has a press stand 2 and a press table 3. A lower tool 9 for a sheet metal part l to be pressed is fixed on the press table 3. A press ram 4 is guided vertically in the press stand 2. press ram 4
can be driven up and down via symmetrically arranged connecting rods. In the embodiment shown in FIG. 4, a drawing device 5, which will be described in detail later, is provided inside the press ram 4. Furthermore, an upper tool 10 is fixed to the lower side of the press ram 4. The upper tool IO has a split structure, that is, it consists of a drawing punch 14 firmly fixed to the press ram 4 and a crease presser 13, and the crease presser 13 is connected to the drawing punch 14.
is guided perpendicularly to the drawing device and can be followed with a predetermined force under the action of the drawing device.

The drawing device 5 has a pressure plate 6 vertically movably supported in the press ram 4 (this pressure plate 6 can be omitted if the piston rod acts directly on the die). A total of four drawing cushions 7゜7', 7'', 7''' formed as a piston-cylinder unit are vertically arranged on the upper side of the cylinder 6, but in Fig. 1, they are not shown. Only two of them are visible; each cushion has pressure chambers 15°, 15', 15'', and 1t'' to which liquid is supplied, and the wrinkle presser 13 is displaced relative to the drawing punch 14. The liquid is then discharged at a predetermined pressure, ie against a predetermined throttling resistance. Each cushion is therefore provided with a connection for pressurized liquid.

The invention particularly relates to cushion control, which will be described in more detail below in conjunction with FIG.

The wrinkle presser 13 has pressure pins s, 8′, s”:
The cushions 7, 7', and 7' are in contact with the pressure plate 6 in the vertical direction by dividing them into equal parts of 7'' and 7''. If there is no pressure plate 6, the piston rod directly reaches the wrinkle retainer 13. Of course, the wrinkle presser is also held in the direction of gravity, but this is not shown in detail by four pressure pins e, s', g', s''
The distribution of can be understood from Figure 2. Four pressure pins 8,8
．． 8”.

8 correspond to wrinkle holding areas 18, 18', 18'', and 18'' located at the corners of the wrinkle holding 13. Further, each of these wrinkle suppressing areas is provided with its own cushion. In the case of the embodiments shown in FIGS. 1 to 4, each wrinkle presser area includes a wrinkle presser 1
Force transducer 18, integrated with 3, t 6′, 1
s'', 16'%<attached.

These force transducers are provided with a pair of horizontal holes 31 located next to each other in a vertical wall loaded with a force flux 34 of the squeegee 13, with a vertical hole between these holes 31. A biconcave web 3z is present and is formed by providing strain gauges 22 on both sides at its thinnest point.

Each wrinkle holding range 18.18', 18''', 18''
The vertical web 32 is deformed by the shin press force component C, and this deformation is detected by the strain gauge 22.

Generally, when the force transducer is integrated into a wall loaded by the force flux 34, the load capacity of the wall is intentionally reduced locally by a small notch effect, and strain gauges are installed at weak points. . It is also conceivable to provide strain gauges on the surface of the load-bearing cross-section, but in that case the sensitive strain gauges are placed on the surface areas that are affected by the contact, so that only surface stresses or surface deformations are detected, which may be caused by any It is advantageous to construct the force transducer from a solid body in one piece, even if the force transducer does not represent the total load on the cross section of the structural component, than to fit the force transducer snugly into a corresponding recess.

That is, in the latter case, a hysteresis component will enter the force measurement when the joint gap is loaded, and this must be avoided as much as possible.

Next, hydraulic wrinkle pressing force control will be explained with reference to the hydraulic circuit shown in FIG. 4. In the upper part of Fig. 4, various areas around the wrinkle presser are shown.
8' is attached to the pressure chamber 15. 15′, ls″, 1
s" + four hydraulic shoes 7, 7', 7I
I: 7IL is shown. Also shown are the various four force transducers 16, 16', 16'', 16'' mentioned above, which are commonly powered by one battery 35 and are each energized in parallel. force transducers 16, 16' each being a Wheatstone bridge;
16″, 11) #′ strain resistance measuring taps are derived separately for each force transducer for each individual cushion 7, 7′, ?″, ? controllers 20, 20', 20 for each force transducer.
″, 20″ force (attached and at their input end a force transducer 16. 16′, 16′, 16′1
71 measurement taps are connected. Each of the four controllers 20 described above has a target value setter 19. 19′,
19':19'''l!I< are attached, and their outputs are likewise connected to the controller input. Both the force transducer and the setpoint value setter transmit comparable electrical signals of the same type. The controller 20 compares the target value signal and the actual value of the wrinkle holding force, generates a signal corresponding to the output terminal according to the difference between the two, and detects the deviation between the confirmed target value and the actual value. The control to remove it again is performed by that signal.

For this purpose, throttle valves 21, 21', 21', and 21'' are provided for each of the four control areas.
) electrically pre-controlled via a valve. The electrohydraulic pilot valve includes a control oil pump 2 that sucks up oil from a control oil tank 25.
Pressure oil is supplied from 3. Considering the sensitivity of the electrohydraulic pilot valve, this hydraulic circuit is kept particularly clean, as indicated by the filter 24. Depending on the magnitude of the control signal, the electrohydraulic viroft valve is opened or closed, and depending on this electrohydraulic field, the throttle valve 21 is also opened or closed, thus increasing or decreasing the flow resistance. If the flow resistance of one of the throttle valves increases, the pressurized liquid will be discharged from the pressure chambers 15. During this process, the pressure within the clivia increases, and thus the crease-holding force in the problem area of the crease presser 13 also increases. If the flow resistance at the throttle valve is reduced, the holding force in the wrinkle holding area is likewise reduced. Throttle valve 21.21', 21', 2 t"'
is leaked t Run nh ha work m oil 4f137 ni flows.

In the ascending stroke of the press ram 14, in which the cutlets or all their pressure chambers open up again, the non-return valves 36, 36',
Via 36', 36'', the working oil is sucked up again from the working oil [37. All four pressure chambers 15, 15', 15'', 155 for the four separate control areas
' is the force transducer 16. 16', 16".

The pressure is controlled so that the wrinkle pressing force determined in step 16 is maintained at a predetermined target value. When the wrinkle-retaining force falls below the respectively considered setpoint value for each range, the throttle valve is moved in the direction of greater flow resistance, so that the pressure in the pressure chamber 15 increases. On the other hand, when the wrinkle holding force exceeds the predetermined target value for each range due to a failure,
Since the throttle valve 21 is moved in the direction of low flow resistance, the pressure in the force-determining pressure chamber 15 decreases. When the predetermined wrinkle pressing force is again obtained by such a control action, the throttle valve is maintained at its opening degree, its flow resistance is maintained, and the pressure in the pressure chamber 15 that determines the force is maintained. Ru. This process proceeds very quickly since the amount of control oil to be conveyed is small. The control region is very short and operates almost without hysteresis, so that the control process proceeds precisely and reproducibly. Each wrinkle pressing range i s, t
a′, t s”.

To protect against 18'% overload, each control circuit is equipped with a safety valve 26.26', 26'', 26''G to reduce the pressure in the zero-acting pipe or its pressure chamber 15.15', 15', 15''''. When exceeds its maximum value, hydraulic oil flows out of the safety valve 26. Due to the working oil flowing out under this pressurized condition,
An emergency shut-off valve 27 common to all four safety valves 26, 26', 26#, 26'' is actuated and this emergency shut-off valve 27 stops the press if necessary.

Instead of forming the force transducer integrally with the crease presser, the force transducer can be formed by a pressure pin s, as shown in FIGS. 5 to 7.
It can also be integrated into s', s'', and t''. However, in this case the integrated force transducer is
It is constructed differently from the embodiment shown in FIGS. 1 to 3. In particular, the load-bearing component cross-section is locally purposefully reduced in load capacity in the effect of small notches, and strain gauges 22 are provided at weak points. Here, the weak point is formed in the form of a pot-shaped recess 33. This recess 33 is machined on the circumference of the pressure pin 8.

Place the strain gauge 22 on the smooth and flat “bottom” of the recess 33.
is pasted. Furthermore, a small hole extends from the recess 33 to the center of the pressure pin, through which an axially extending hole passes through the center of the pressure pin 8.

The energy and measurement signal lines of the strain gauge are passed through this hole in a protected manner.

As shown in FIG. 6, an integrated strain gauge with four strain resistors can be provided, with the individual strain resistors grouped together in the form of a Wheatstone ridge. However, in both cases, the individual strain resistances of the Wheatstone bridging can be paralleled or the force flux direction 34
Note that it should be located at right angles to! In the case of the embodiments in FIGS. 5 to 7, the pressure pin 8
Three recesses 33 are provided on the circumference of the circuit, in which the tangent Vt lines of the various strain resistances of the various strain gauges must be led out individually and connected in series to form a common bridge branch circuit. The strain resistors that must be placed, in particular comparable to one another, are each connected in series in the form of a bridge branch circuit. In this way, recess 3
3 an average value of all three deformations is formed.

The embodiment of the hydraulic circuit shown in FIG. 8 differs from the embodiment in FIG. 4 in that instead of a force transducer integrated with the crease holder, individual pressure chambers 15, 15', 15'' determine the force. ,
15'' and pressure transducers 17° and 17', respectively.
17'', 17'h< these pressure transducers convert the pressure signal into a corresponding electrical signal, which electrical signal is transmitted to the corresponding controller 20, 20'.
, zcr, 20.

Note that the action of the hydraulic pressure circuit in FIG. 8 is almost similar to the action of the hydraulic pressure circuit in FIG. pressure chamber 15.15', which determines the force
The difference is that the pressures of 15'' and 15'' are regulated with respect to a presettable target value.

FIG. 8 also shows, as another embodiment, that the target value can be changed depending on the crank angle.

An angle converter 29 is connected to the schematically illustrated crankshaft 28 of the press, which generates an electrical signal corresponding to the instantaneous angular position of the crankshaft 28. This signal is transmitted to four different function converters 30. 30'
, s O'l 30''.

These function converters are connected to the target value setter 19 depending on the crank angle. 1 ta', 19'', 19'! is configured to generate various function values such as 1 ta', 19'', 19'! Due to the rapid response of the control area, this is very sensitive to the setpoint value changing during the stroke. Can follow quickly.

For example, the individual shin press areas 18, 18', 1B''.

In 1B, the wrinkle pressing force is increased or decreased in stages as necessary within the press cycle. (■ Functional converters 30. 30', 30'', 30''
can be removed (after they have been individually optimized for a given workpiece) and replaced with another functional transducer that is optimal for a different workpiece. The exchange of this function converter takes place by switching in the central control room. In the central control room, all functional converters for various workpieces are grouped and ready.

Of course, the hydraulic wrinkle pressing force control method according to the present invention is as follows:
It can be used not only for cushions with multi-segment structures, but also for simple drawing machines. FIG. 9 shows a somewhat simple example of a press in use. In this case, the drawing device 5a is integrated into the press table 3a.

The press ram 4a of this press is much simpler than the press ram 4 of the press in FIG. In order to house the drawing device 5a in the press table 3a, the lower tool 12 is divided into a drawing punch 14a and a crease presser 13a, and the upper tool 11 here has a single structure. A pressure box 6a is provided in view of the only centrally arranged cushion 7a inside the drawing device 5a. This pressure box 6a has minimal dimensions in the vertical direction in order to provide good vertical guidance.

The wrinkle presser 13g is the pressure pin 8. 8′, 8″,
The pressure box 6a is supported on the pressurizing box 6a via a pin.During the operating stroke of the press, while the wrinkle presser 13a moves relative to the drawing punch 14a, the pressurizing box 6a
moves downward against a predetermined resistance.

The force-controlled or pressure-controlled outflow resistance in the hydraulic cushion 7a determines the wrinkle holding force, most importantly
In the case of the simple press in the figure, the total force of the wrinkle press is controlled. The hydraulic circuit is constructed according to the example in FIG. 4 or the example in FIG. In that case, only one control area needs to be provided, corresponding to the arrangement of only one cushion 7a.

[Brief explanation of the drawing]

1st v! J is a schematic cross-sectional view of a press for sheet metal drawing in which a drawing device is installed in the press ram (a cross-sectional view taken along line I-1 in Fig. 2), and Fig. 2 is a cross-sectional view taken along line I-1 in Fig. 1. 3 shows an enlarged partial side view of the crease holder in the area of the force transducer; FIG. 4 shows the crease-holding force using the force transducer integrated in the rugae Hydraulic circuit diagram of the control device; FIGS. 5, 6 and 7 are respectively partial longitudinal, side and cross-sectional views of the force transducer integrated in the pressure pin; FIG. 8 is the pressure A hydraulic circuit diagram different from Fig. 4 for hydraulically controlling wrinkle pressing force using a transducer; Fig. 9 shows a drawing machine with a sole cushion and a drawing device housed in the press table. FIG. 2 is a schematic cross-sectional view of a press. 7 Cushion 7a Cushion 13 Wrinkle holder 13a Wrinkle holder 15 Pressure chamber tSa Pressure chamber 16 Force transducer 17 Pressure transducer 18 Wrinkle suppressing range 19 Target value setter 20 Controller 21 Throttle valve 22 Strain gauge 31 hole 32 Web 33 Recess 34 Force flux direction Fig, 3 ~・9

Claims (1)

[Claims] 1. A tool divided into a wrinkle holder and a drawing punch that can move relative to the wrinkle holder, and a tool that is attached to the wrinkle holder and maintains the wrinkle holding force during the relative movement inside the tool. In a press for drawing sheet metal parts, the press has a drawing device having at least one cushion, and the cushion is formed as a piston-cylinder unit that operates against a predetermined hydraulic pressure. Each cushion (7a, 7, 7', 7'', 7''') is directly biased by controlled hydraulic pressure to determine the wrinkle suppressing force. pressure chamber (
15a, 15, 15', 15", 15'") are arranged with pressure transducers (17, 17', 17", 17'") or the crease pressers (13a, 13) or crease pressers (13) ) each cushion (7, 7', 7'', 7''')
The wrinkle pressing force applied to the corresponding range (18, 18', 18'', 18''') or the wrinkle pressing force applied to the corresponding range (18, 18', 18'', 18''') of the wrinkle presser (13) Force transducers (16, 16', 16''
, 16''') are attached in the wrinkle holder (13) or its pressure pins (18, 18'), said pressure or force transducer generating an electrical signal corresponding to the value of the pressure or force, Each pressure transducer (17, 17', 17'', 17'
'') or force transducer (16, 16', 16'', 16'''
) to give the same type of signal to the target value setter (19, 1
9', 19'', 19''') are attached, and each pressure transducer (17, 17', 17'', 17''') or force transducer (16, 16', 16'', 16''') is attached. , a controller (20, 20) that continuously compares the respective actual value and target value.
', 20'', 20''') are attached, and these controllers are attached to each cushion (7a, 7, 7', 7'', 7''').
) attached to the controllable outflow throttle (throttle valves 21, 21
', 21'', 21'''), each cushion (7a, 7, 7', 7'', 7
A press for drawing sheet metal parts, which is characterized by increasing, decreasing, or keeping the pressure inside (''') constant in the sense of matching the target value of cushion pressure or wrinkle pressing force. 2. Each individual controller ( 20, 20', 20'', 20''
2. Press according to claim 1, characterized in that the setpoint value for ) can be varied in dependence on the stroke or crank angle during each press cycle in accordance with an iterative model. 3. One or more force transducers (16, 16', 16
3. Press according to claim 1, characterized in that the crease retainers (13, 13a) are integrated in the crease retainers (13, 13a). 4. The force transducer (16, 16', 16'', 16''')
4. Press according to claim 1, characterized in that it is designed in the form of a strain gauge (22) in the load-bearing wall section of the crease retainer (13, 13a). 5. Press according to claim 4, characterized in that the wall section at the strain gauge (22) has a locally purposefully reduced load capacity by means of a small notch effect. 6. A pair of horizontal holes (31) located side by side in the wall part are provided, which pair of holes (31) surrounds a biconcave web (32) standing between them in the direction of the force flux; One or more strain gauges (
6. The press according to claim 5, further comprising: 22). 7. Claim characterized in that a pot-shaped recess (33) is formed on at least one side of the wall portion, and one or more strain gauges (22) are provided on its smooth and flat "bottom". Press described in 5.