DE3710178A1 - CONTROL DEVICE FOR A PNEUMO-HYDRAULIC POWER DRIVE - Google Patents

Abstract

The control arrangement has a pneumatic-hydraulic power drive (14) with an actuating rod (17). The actuating rod (17) can be actuated pneumatically with small force over large distances by means of a working piston (40) and hydraulically with large force over small distances by means of a displacing piston (63). The displacing piston (63) can in turn be actuated pneumatically via a pressure intensifier (62/63). So that workpieces with freely programmable force/displacement profiles set in a controlled manner can be manipulated or machined, the actuating rod (17) is coupled to a displacement-measuring unit (20). The actuating pressure of the working piston (40) can be set independently of the actuating pressure of the displacing piston (63) as a function of an output signal of the displacement-measuring unit (20) (Fig. 2).

Description

The invention relates to a control device for a pneumo hydraulic power drive with an operating rod that using a working piston pneumatically with little force over long distances and by means of a displacement piston hydrau is operable with great force via small paths, whereby the displacement piston, in turn, pneu via the pressure intensifier is actuated matically.  

Such a control device is from DE-OS 28 18 337 known.

In the known control device, the power drive a front, double-acting and pneumatically operated Working piston on in a cylinder bore with ratio moderately large diameter runs and pressure from both sides air can be applied. The working piston carries an actuator supply rod, which are used for example for riveting can. The working piston is compressed on its back with compressed air charged, it travels at a relatively low speed Force forward. Increased when reaching a final position the pressure on the back of the piston. The pressure Air now flows approximately evenly onto the back of an air piston Chen cross section, which in turn is essential to the displacement piston Lich smaller cross-sectional area. The displacement piston dips into an oil reservoir in the area of the back the actuating rod is arranged. Due to the diameter ratio of air pistons and displacement pistons results a force when the displacement piston is actuated pneumatically reinforcement in the area of the oil storage and thus a high Operating force for the operating rod with little deflection kung.

In the known device, the switchover is made from express gear with low force on the slow gear (power stroke) with high force automatically because, as mentioned, the compressed air from the back of the piston when reaching a certain one Value automatically reaches the back of the air piston and the power stroke starts automatically.  

To control can also switch in the known device valves are provided, the forwarding of the compressed air done on the air piston by a pressure directional valve that is then switched when the pressure at the inlet (rear of the working piston) exceeds a predetermined amount. At the known device is also provided the possibility to use a path-dependent control with a limit switch is provided in the path of movement of the actuating rod, the when actuating from rapid to slow (power stroke) switches. However, with all of these controls only switching valves used, and the actuation of the air piston takes place via a forced sequence control in Dependence on the actuation of the working piston.

The known device has the disadvantage that the over from rapid to slow speed always occurs suddenly and the slow speed runs uncontrolled, so that the well-known Ein direction cannot be used for a large number of applications When it comes down to it, the actuating force is dependent dosing specified parameters or also depending of the respective application.

The invention is therefore based on the object of a device of the type mentioned in such a way that the Operating parameters of the facility freely definable and in particular which are regulated adjustable.

This object is achieved in that the Actuating rod is coupled to a displacement measuring unit and that the operating pressure of the working piston regardless of Operating pressure of the displacer depending on an output signal of the displacement measuring unit is adjustable.  

The object on which the invention is based is achieved in this way completely solved.

Due to the position measuring unit, which can be used continuously over a longer distance , the rapid traverse in its travel path can be freely programmed - in contrast to the known limit switch. By separating the actuation of the displacement piston from the actuation of the working piston after the rapid traverse, the slow speed (power stroke) can also be freely programmed, any force / displacement dependencies being specifiable.

These measures have the advantage that the fiction appropriate control device can be used for a variety of tasks is, and not just for relatively rough power work, like the riveting mentioned above, but also for precise Power work, for example when operating a hand a handling device and the like.

In a particularly preferred embodiment of the invention the working piston is double-acting, and the actuation pressure of the working piston is by means of an electro-pneumatic 2/2 servo valves set.

This measure has the advantage of speeding up the work piston from the start position to the end position can be set precisely because the use of electro pneumatic servo valves an exact implementation of an analog Input variable allowed in a pneumatic output variable.  

In a further preferred embodiment of the invention the displacement piston with pressure intensifier single acting, and the actuation pressure of the pressure intensifier is determined by means of a electropneumatic 2/2-way valve with pilot valve set.

This measure has the advantage that the high power of the actuator dosing rod can be adjusted precisely.

In a further preferred embodiment of the invention the working piston until a first output signal is reached the measuring unit in rapid traverse with low force and then the Displacement piston until a second signal is reached in the Slow gear can be extended with high force.

In a variant of this embodiment, the second is Signal a second output signal of the displacement measuring unit.

This measure has the advantage that tasks are carried out can where the operating rod a certain way must drive through with high force without it the actuation pressure arrives, e.g. during joining work the case is.

It is preferred in this variant if when the two are reached th signal of the actuating pressure of the displacer measured by a pressure sensor and with a given actuator supply pressure interval is compared.

This measure has the advantage that it can be monitored whether to measure the aforementioned distance in the power stroke Actuation pressure had to be applied within one  specified tolerance range. Should e.g. as part of a Joining a part to be pressed into another part, so would fall below the interval that the to joining parts were made imprecise in the sense that they fit too loosely into one another and consequently only a small amount pressure was required to travel the given distance to measure while exceeding the interval andeu tet that the parts were made too tight and therefore too high actuation pressure was required to achieve the desired one To achieve coincidence. In both cases, this can be done for the abs the intended use of the joined parts may be unacceptable, so that if the interval is exceeded or undershot, the added Parts can be declared as a committee.

In another variant of the exemplary embodiment, this is second signal an output signal of the actuation pressure of the displacer-detecting pressure sensor.

In this variant, instead of a path to be measured stretch a pressure value to be reached in the power stroke, if, for example, the joining force is part of joining work is specified.

In this embodiment, too, one can accordingly When the second signal reaches the output signal of the displacement measurement compare with a given path interval.

This variant therefore becomes a criterion for a committee partly formed by checking whether until reaching of the specified pressure value a path within a permissible  Tolerance range was measured. If they fit together too loosely the parts would e.g. when the specified pressure is applied (Actuating force) measure too large a path while around swept only a short way when the parts are too narrow could be measured.

Further advantages result from the description and the attached drawing.

It is understood that the above and the following features still explained not only in the respective specified combination, but also in other combinations or can be used alone without the scope of the to leave the present invention.

This applies in particular to the following based on an implementation Example of connection explained using electropneuma valves, which are also part of professional action can be realized in other known ways.

Embodiments of the invention are shown in the drawing represents and will he in the description below purifies. Show it:

Figure 1 is a schematic overall view of a control device according to the Invention for the application of a joining device.

Fig. 2 is a hydraulic and circuit diagram for explaining the operation of an embodiment of a control device according to the invention;

Fig. 3 is a more detailed circuit diagram for one embodiment of a Erläute tion erfindungsge MAESSEN control means;

Fig. 4 is a circuit diagram, similar to Fig. 3, but for another embodiment.

In Fig. 1, 10 denotes a total of a force unit, such as those used for pressing, embossing and the like. Like. Can be used. A U-shaped portal 11 is placed on a work table 12 which carries a workpiece 13 to be joined . A power drive 14 , the details of which are further explained below in relation to FIG. 4, is seen with valve packs 15 and 16 attached laterally. At the bottom of the power drive 14 , an actuating rod 17 protrudes, which can be moved vertically as a function of the actuation of the valve packages 15 , 16 . The actuating rod 17 can carry a tool 18 , for example an embossing stamp or the like, at its lower axial end.

The actuating rod 17 is laterally coupled to an arm 19 which interacts with a displacement measuring unit 20 for the vertical deflection of the actuating rod 17 .

Via connecting cables 21 , 22 , 23 , 24 , the displacement measuring unit 20 and the valve packages 15 , 16 are connected to a control unit 25 .

The control unit 25 has, for example, a first keyboard 26 for specifying one or more extension paths of the actuating rod 17 and a second keyboard 27 , which can serve, for example, for specifying certain actuating forces or path / force curves. A schematically indicated display unit 28 serves to display operating states, operating parameters and the like. the like

With the power unit shown in Fig. 1 you want to be able to pretend, for example, that the actuating rod 17 first in a rapid traverse measures a long way by which it was previously lifted from the workpiece 13 to handle this in the area of the work table 12 . The actuating rod 17 , possibly with a tool 18 , is then to travel a certain distance under low force at high speed (typically in the range between 10 and 500 kN). The force unit 10 should be able to be controlled in such a way that the actuating rod 17 either measures a predetermined force stroke, that is to say without influencing the actuating force, provided that this does not, of course, exceed a certain limit value, or a certain final force value is to be achieved without Taking into account the required stroke.

In the case of the specified stroke, however, one wants to be able to determine NEN whether the force required for this within a certain t tolerance range, and vice versa one would like to given operating force know whether the diameter for this Stroke is within a certain tolerance range One committee part is exceeded in each case to be able to define.

In Fig. 2, one recognizes further details of the motor drive 14 together with the associated control.

The known power drive 14 has a working piston 40 in the front part, the tion in a first cylinder bore 41 runs relatively large diameter. The working piston 40 can be pressurized with compressed air from both sides by means of a front channel 42 and a rear channel 43 . For this purpose, a first line 44 is used , which is connected to the front channel 42 and leads to a first electropneumatic 2/2-servo valve 45 . A second pneumatic line 46 is connected to the rear channel 43 and leads to a two-th electropneumatic 2/2-servo valve 47 . The servo valves 45 , 47 are connected via a third line 48 or a fourth line 49 to a common compressed air connection 50 , which is typically acted upon by a supply pressure of 5 bar.

The actuating rod 17 , which separates the working piston 40 , is provided with a second cylindrical bore 56 . In a third cylindrical bore 57 , the diameter of which corresponds approximately to that of the first cylindrical bore 41 , an oil piston 58 runs , which defines an oil space (storage space) 60 in front of it, which extends into the second cylindrical bore 56 . The oil piston 58 , which runs freely in the third cylindrical bore 57 , is connected via a helical spring 61 to an air piston 62 which also runs freely in the third cylindrical bore 57 . The air piston 62 runs forward into a displacement piston 63 , the cross-sectional area of which is substantially smaller than the cross-sectional area of the air piston 62 , the oil piston 58 and the working piston 40 . The diameter of the displacement piston 63 is slightly smaller than the diameter of the second cylindrical bore 56 .

The rear side of the air piston 62 can be acted upon by compressed air via a fifth line 65 by means of a channel 64 . The fifth line 65 leads to a 2/2-way switching valve 66 which is provided with a pilot valve in the exemplary embodiment shown.

A sixth line 67 is connected to the rear channel 43 and is used to supply compressed air to the 2/2-way switching valve 66 .

With 68 a seventh line is indicated, which opens into the space between the oil piston 58 and air piston 62 . The seventh line 68 is intended to indicate that the air piston 62 can of course also be double-acting and can be pressurized with compressed air from both sides if this should be cheaper in individual cases.

An eighth line 70 leads as a branch line from the sixth line 67 to a pressure sensor 71 . The pressure sensor 71 is in turn connected to a controller 72 which receives a further input signal via a signal line 73 from the Wegmeßein unit 20 . In addition, the controller 72 is connected to the keyboards 26 , 27 and it has output terminals 74 which lead via the connecting cables 22 , 23 to the valve packs 15 , 16 and the servo valves 45 , 47 and the switching valve 66 contained therein .

The mode of operation of the arrangement according to FIG. 2 will now be explained in more detail with reference to the circuit diagram of FIG. 3.

In the variant described below, the user of the force unit 10 prescribes a first path s _a , which the actuating rod 17 is to traverse at high speed. After measuring this path s _a , a second, smaller path s _{e should be} measured in the power stroke. During the power stroke, the pressure p which acts on the air piston 62 and which can be converted into the force of the actuating rod 17 via the force booster 62/63 is to be determined, and a statement is to be made as to whether it is for measuring the power stroke s _e required pressure p is within a predetermined tolerance between a lower pressure value p _u and an upper pressure value p _o .

In order to achieve this, the values s _a , s _e , p _u and p _{o are first} entered into the control unit 25 using the keyboards 26 , 27 .

In order to put the power unit 10 into operation, a start signal is first given to a flip-flop 76 via a terminal 75 and the flip-flop 76 is thus set. The flip-flop 76 in turn actuates the second electro-pneumatic 2/2-servo valve 47 , so that compressed air can reach the working piston 40 , from the right in FIG. 2.

The displacement measuring unit 20 is connected to a first comparator 81 , the output of which is connected to a first zero detector 82 . The zero detector 82 in turn controls the set input of a second flip-flop 83 , the output of which in turn actuates the 2/2 switching valve 66 . A second comparator 84 is connected on the output side to a second zero detector 85 , the output of which is connected to the reset input of the second flip-flop 83 .

The further inputs of the comparators 81 , 82 are formed by terminals 86 , 87 , to which setpoints, namely a value s _a for the end of the rapid traverse and a value s _e for the end of the slow traverse, are applied.

The pressure sensor 71 is connected to a third comparator 88 , the output of which is connected to a first threshold stage 89 . The output of the threshold stage 89 is again at the input of an AND gate 90 .

The pressure sensor 71 is also connected to an input of a fourth comparator 91 , the output of which is connected to a second threshold value stage 92 . Its output is in turn connected to a second input of the AND gate 90 . The further inputs of the comparators 88 , 91 are connected to terminals 93 , 94 to which setpoints can be applied, namely the lower threshold value P _u and the upper threshold value p _{u of} the pressure p . The threshold values of the threshold value stages 89 , 92 define a printing interval 95 . The output of the AND gate 90 is led to a display 96 .

The device works as follows

As soon as the working piston 40 moves to the left by setting the first flip-flop 76 in FIG. 2, the arm 19 emits a signal s with the displacement measuring unit 20 , which is fed to the controller 72 via the signal line 73 . In the controller 72 , the signal s is compared in the comparators 81 and 84 with the target values s _a and s _e specified there. As soon as the target value s _{a has been} reached, ie at the end of the overdrive range, the zero detector 82 responds and sets the second flip-flop 83 , which in turn actuates the 2/2 switching valve 66 . Since the second electropneumatic table 2/2 servo valve 47 remains switched on, air pressure can be taken from the right channel 43 via the sixth line 67 and passed via the lines 67 , 65 into the channel 64 by means of the 2/2 switching valve 66 are so that the air piston ben 62 moves to the left and the displacer 63 with appropriate force amplification ensures a pressure build-up in the oil chamber 60 . The actuating rod 17 continues in this way to the left in Fig. 2, wherein by switching the first electropneumatic 2/2-servo valve 45 on both sides of the drive piston 40, the same pressure can be set to the further movement of the actuating rod 17 finally to make dependent on the deflection of the displacer 63 .

When it is finally recognized via the second comparator 84 that the actuating rod 17 has reached the end value s _{e of} the slow power stroke, the second flip-flop 83 is reset via the zero detector 85 and the switching valve 66 switches over again.

By venting the right side of the working piston 40 while simultaneously applying compressed air via the left channel 42 , the working piston 40 can now be moved back to the starting position at high speed.

During the operation described above, in particular during the slow power stroke, the pressure p on the rear of the air piston 62 was monitored via the pressure sensor 71 . If the pressure in this range lies within the interval 95 , the display 96 responds because only in this interval the outputs of both threshold value stages 89 and 92 show a positive logic signal, while outside of the interval 95 one of the two threshold value stages shows a negative logic signal leads. This means that when the display 96 was actuated, a workpiece was processed in the target area, while a reject part was produced when the display 96 went out .

The circuit diagram recognizable in FIG. 4 largely corresponds to the circuit diagram of FIG. 3, and corresponding elements are provided with the same reference symbols. Only by adding an "a" are comparable components designated in their function.

In the embodiment shown in Fig. 4 variant, the driving through the quick passage over the elements 81 to 83 by reaching the final value S _A is monitored in the manner already described. In the slow power stroke, however, the reaching of the final value of the power stroke is not monitored via the path, but via the pressure, specifically in the second comparator 84 a , which is connected to a corresponding target value p _a . When this end value is reached, the 2/2 switching valve 66 switches over and the slow power stroke is ended.

In order to make a statement about a correctly manufactured part or a reject part in this case too, an interval 95 a is defined with comparators 88 a , 91 a and threshold value stages 89 a , 92 a , in this case, however, an interval of the path that lies between a lower limit value s _u and an upper limit value s _o . Otherwise, the logic corresponds to the elements in the lower half of FIG. 3.

Thus, while it was recognized in the variant according to FIG. 3 whether more or less than a predetermined pressure range was required to measure a predetermined path in the slow force stroke, the reverse is true in the variant in accordance with FIG. 4 because there it is in the slow force stroke reaching an end pressure value is stopped and only then is it checked whether a path has been measured to reach this pressure value, which lies within a certain tolerance.

Claims (8)

1. Control device for a pneumo-hydraulic Kraftan drive ( 14 ) with an actuating rod ( 17 ), which can be actuated by means of a working piston ( 40 ) pneumatically with low force over long distances and by means of a displacement piston ( 63 ) hydraulically with large force over short distances is, the displacement piston ( 93 ) in turn being pneumatically operable via a pressure intensifier ( 62/63 ), characterized in that the actuating rod ( 17 ) is coupled to a displacement measuring unit ( 20 ) and that the actuating pressure of the working piston ( 40 ) is independent of the actuating pressure of the displacement piston ( 63 ) can be set as a function of an output signal from the displacement measuring unit ( 20 ). 2. Control device according to claim 1, characterized in that the working piston ( 40 ) is double-acting and that the actuating pressure of the working piston ( 40 ) is set by means of electro-pneumatic 2/2 servo valves ( 45 , 47 ). 3. Control device according to claim 1 or 2, characterized in that the displacement piston ( 63 ) with pressure intensifier ( 62/63 ) is single-acting and that the actuating pressure of the pressure intensifier ( 62/63 ) by means of an electropneumatic table 2/2 switching valve ( 66 ) is set with pilot valve. 4. Control device according to one of claims 1 to 3, characterized in that the working piston (40) to the Errei chen a first output signal (s _a) of the displacement measuring unit (20) in rapid traverse with low force and then the Verdrän gerkolben (63) to to reach a second signal ( s _e , p _a ) can be extended with high force in slow gear. 5. Control device according to claim 4, characterized in that the second signal is a second output signal ( s _e ) of the displacement measuring unit ( 20 ). 6. Control device according to claim 5, characterized in that when the second signal ( s _e ) the actuating pressure ( p ) of the displacer ( 63 ) is measured by means of a pressure sensor ( 71 ) and with a predetermined actuating pressure interval ( 95 ) is compared. 7. Control device according to claim 4, characterized in that the second signal is an output signal ( p _a ) of the actuating pressure ( p ) of the displacer ( 63 ) detecting pressure sensor ( 71 ). 8. Control device according to claim 7, characterized in that when the second signal ( p _a ) is reached, the output signal ( s ) of the displacement measuring unit ( 20 ) is compared with a predetermined displacement interval ( 95 a ).