CA2107612A1

CA2107612A1 - Hydraulic device for use in a production machine

Info

Publication number: CA2107612A1
Application number: CA002107612A
Authority: CA
Inventors: Karl Hehl
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-10-14
Filing date: 1993-10-04
Publication date: 1994-04-15
Also published as: JPH0775861B2; EP0592945A1; JPH06198697A; DE4234647C1; DE59306651D1; EP0592945B1; ATE153906T1

Abstract

ABSTRACT
HYDRAULIC DEVICE FOR USE IN A PRODUCTION MACHINE
In a hydraulic device at least one control valve with at least three control positions is connected with a variable capacity pump, whereby the controlling device of the variable capacity pump is connected with the supply line downstream the control valve via a feedback line with the purpose of adjusting the pump output so as to maintain a constant operational pressure gradient. The back flow pipe is conducted over the control valve, which is connected with the consumers by connecting valves associated to mentioned consumers, whereby a transducer is associated to the back flow pipe, which together with the transducer of the supply line constitutes a regulating variable for a control unit.
This way a precise and energy saving regulation or control of the consumers in both flow directions by a control valve at a reasonable price is achieved.

Description

2107~12 i~l)R~ULIC ~EVICE F~ U~E IJi J~ UCTI~l~J Mh~C~
CR-JSSREFERENCE TC~_RELhTE~ hPPLICAI~NS

This appl ication claims the priority of German Patent Application No. 4234647.9, filed Octo~er 14, l9g2, which is incorporated herein by reference.

BAC~ JUN~ GF THE INVENTION
1. Fieid of the Invention This invention reiates to a hydraulic device for hydraulic consumers for use in a production machine, particularly in an injection molding machine for processing syntnetic materials or comparabie plastic or plastifiabie masses, comprising at least one control valve with at least three c,ont,rol positions, the control valve being regulabie by at ieast one transducing means associated to a supply line by comparison of actual values with preset nominal values programmable in a control unit, whereby a variable capacity pump feeds consumers with fluid via the supply line ieading over the control valve. The hydraulic device furthermore comprising a back flow pipe and a feedback line connecting a controlling device of the variable capacity pump with the supply line downstream of the control valve with the purpose of adjusting the pump output so as to rnaintain a constant operation~l pressure gradient, 2~7~12 2. ~.escI-iptior, of t~ Prior Art A hydraulic device of this kind is disclosed in German Patent 31 19 095. In this device the energy consumption of the variable capacity purnp is adapted to the respective power requirements of a lower limit, by chosing as a basis for the operation and the control a just sufficient constant operational pressure gradient, presettable at the controlling device of the variable capacity pump. On the other hand the known control device meets the e~tremely different operational conditions, since a quaniity - or pressure adjustment diverging from the nominal value preset of the control valve is feedbackable alternatively by rrleans of pressure transducers, distance detectors or distance potential transformers to the nominal value in the contr~l circuit. However, such an appliance only can influence the afflux side of the consumer.
A further hydraulic device is known from US
Patent 4,823,551. In this device the supply lines are alternatively in connection with a common feedback line by 2~ mean~ of a shuttle valve. The branch supply line naving an inferior pressure is provided with a controller for a fully ~tabilization of a nominal value deviation of the feeding current conditioned by a pressure asymmetry. Certainly this-way a simultaneous supply of several hydraulic consumers by the varia~le capacity pump is pos~ible, however, also in this " , . . . .

2~7~2 ca.se orlly the afflu~. side of the c-,r,sumers is influenceable, US Patent 5,1~,8~6 di~closes a hydraulic device fGr a consumer provided with a ~/4-way vaive, adapted tO
effect a differential switching, ma~ir.g possible a feeding of the pressure line with fluid ousted by the consumer via a derived circuit provided with a nonreturn valve. In fact the discharge of the fluid can be effected by a overlying pressure regulation, however, the expenditure involved is considerable, since each a separate control valve has to be associated to each consumer.
SUMMA~Y OF THE INVENTION
It is an object of the invention so to design a hydraulic device which is of the kind described first hereinbefore, so that a precise and energy saving regulation or control of the consumers in both directions of flow transferred can be effected by a control valve at a reasonable price.
That object is accomplished in accordance with the invention in that the back flow pipe is also conducted via a control valve and the consumers are connected with the control valve by means of connecting valves, each of them associated to one of said consumers. Furthermore, at least one tran~ducing means is associated to the back flow pipe, which in connection with the first transducing means of the ~upply line constitutes a regulating variable for the control unit, 2~7~12 Such an arr~ngemerlt offers the advantage th~ the r~specti~e consumers do not need a direction valve, ~ince the physical variables velocity or number of revolutions, position, pressure or force, are controlled or regulated ir.
both directions of flow transferred. The consurners are merely connected by means of connecting valves thus allowing a simple control being at the same time easy to maintain. Since nevertheless the afflux side as well as the reflux side can be controlled or regulated, an improved and more comfortable control, compared with the prior art, can be realized, in spite of the cost reduction. Thereby the disadvantage that ~ hiqher self-oscillation conduct arises, caused by the distance from the control valve to the consumer, which reduces the dynamic of the control, is consciously accepted, 1~ since these effect is compensated for by the advantages aained with it. In this arrangement no additional switching magnets are required at further valves and the loss of control dynamic can be partially compensated for by the po~sibilities to influence the afflux and the reflu~.
The reduction of the number of further valves between pump and consumer additionally leads to a diminution of the 103s of pres~ure, so that the hydraulic device still can deal economically ~ith the energy being at its disposal. Thereby the basic conditions for a central velocity -, pressure - and po~ition control for the hydraulic circuit of the iniection 2~07~1~

moldir~g rnachir,e are created by a superset electronic control - or regulation device The control valve acts together with the variable capacity pump like an afflu~
corltr-, 1 .
According to a preferred feature a respective just catching control edge of the control valve derates the fluid being ousted by the consumer in a discharge. Due to this arranaement it is possible to control acceleration and reduction of speed in case cylinders or hydromotors are applied. Especially for positioning - respectively force control according to the principle of hydraulic full bridge such a construction is necessary.
According to a preferred feature further variable capacity pumps are additionally connectable in both flow flow directions in a connection line between the first and further variable capacity pùmps by means of a further connecting valve and mentioned further variable capacity pumps together with the first variable capacity pump are associated to several control circuits with several control valves regulated by a control unit. Due to the application of several variable capacity pumps connected side by side, in such arl arrangement it is po~sible to either increase the volume flow at one control valve in case necessary or to provide several control - or regulation circuits in parallel, whereby the pump capacity of the particular variable capacity 21~7fj~2 pumps might partially b~ arranged in cascade, which rnakeg a contribution to energy saving, According to a preferred feature a reser~Gir is feedable by the variable capacity pump via a 2/~-way valve and a line, the reservoir being dischargeable over the line.
If in such an arrangement a reservoir is additionally connected, volume flows momentarily not required can be loaded in the reservoir and subsequently be discharged over one or several control - or regulation circuits. This is especially perceptible in an energetically favorable operatina method, if several control circuits are connected.
Supplementarily also a high speed can be controlled by means of the reservoir.
According to a preferred feature the control valve is a 4/4-way valve; its forth control position generates a differential switching for feeding the fluid ousted by the con~umer into a pump branch, being overbridged by the 4/4-way valve via a derived circuit provided with a nonreturn valve. In such an arrangement a high speed can be achieved ~ recirculat,ion of the ousted oil into the pump br~nch in spite of an energetically favorable operating method.

2~7~12 BRIEF DE~CRIPTION OF THE DRAWING
Figure 1 is a dia~rar~natic view of the hydraulic device.
Figure 2 shows the hydraulic device according to Figure 1 and the control unit when applied to an injection molding machine for processing plastic materiais Figure 3 shows the hydraulic device provided with several variable capacity pumps and several control circuits.
Figure 4 shows the hydraulic device with its associated reservoir.
Fiaure 5 shows the hydraulic device provided with a 4/4~way valve.
DETAILE~ ~ESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention will now be described in more detail by example with reference to the embodiments shown in the Figures. It should be kept in mind that the following described embodiments are only presented by way of exampie and should not necessarily be construed as limiting the inventive concept to any particular physical configuration.
~O The hydraulic device is meant for hydraulic consumers V. In the preferred embodiment it is used in an injection molding machine for processing synthetic materials or comparable plastic or plastifiable masses such as for e~ample ceramic masses. According to Figure 1 it is provided with a 4/3-way valve with three switching positions serving ~s control valve l5, wrlictl is at ieast ~djustable by at le~st one first transducing means by cornparison of actual vaiue~
with preset nominal values prograrnmable in a control unit ~., The variable capacity pump 18 feeds the consumers V via a supply line 19 leading over the control valve. PossiDle consumers might for example be injection cylinders, dosing motors, mold closing units, ejectors, core pullers or other aggregates.
As can be seen from Figure 1 also the back flow l~ pipe 21 is led over tne centrally arranged control valve 15.
A central arrangement of the control valve 15 is of advantage if the friction losses on the supply lines 19 should be kept as low as possible, The control valve is in connection with the consumers (Fig. ~j by rneans of connecting valves 22, each one of them assosiated to each respective consumer.
A second transducing rneans is also associated to the back flow pipe 21. As transducing means two pressure transducers 16,17 for collection of the differential pressure, a pressure transducer for acquisi ion of the maximum pressure in both 2G iines or one single or several transducers for registration of the position or veiocity can be applied. Thus a quantity is acquired that plays back the conditions on both sides of the consumer, whereby this quantity can be acquired for both sides together by means of only one transducing means. This means that the transducing means provide actual values as input quantitie~ for the control unit R. Basically pressure , ................... . . .. .

21~7~12 transducers, velocity transducers, positior csverage mean3 or the like are provided as transducing means. According ~o the position of the control valve the function of supply line 1g and back flow pipe 21 is interchanged. When the control valve is in pGsition P-A the supply line which actually reacts is the supply line 19 and when the control valve is in position P-B it is the back flow pipe 21 that actually reacts.
The fluid ousted by the consumer is always derated in the discharge by the just catching control edge B-T respectively A-T of the control valve. The middle control po~ition of the control valve is a stopping position permitting a locking for example during the dwell pressure phase of the injection molding machine. The control valve can be either directly controlled or pilot controlled and be provided with one or two control magnets 15a,15b.
The application of such two control magnets should be aspired to for safety reasons. The feedback of the actual pressure value to the controlling device 18a, 18a' of the variable capacity pump 18,18' is effected by means of a shuttle valve 23.23'. It is also possible to alternatively provide for e~ample way valves, control taps at the control valve or an e~ternal pressure feeding. The feedback as well as the adjustment of the variable displacement pump is effected in connection with the superset electronic control unit R.

_ g _ 2~076~

The reedback effect~ that the variable capacity pump 18 supplie~ a variable, impressed volume flow Ql.
Figure 3 presents an arrangement of the invention in which a further variable capacity pump 18' with a volume fiow Q2 is assigned to the variable capacity pump 18.
Basically the variable capacity pump 18 is determined for the control - or regulator circuit I and the second variable capacity pump 18' for the second control - or regulator circuit II. Both control circuits are largely structured identically, so that the reference characteristics of the first control circuit, additionally provided with an apostrophe for differentiation, are used for the elements of the second control circuit. In the second control circuit the consumer is supplied via the supply line 1g'and the back ~low pipe 21' is conducted over the control valve 15'. The pressure transducers 16',17' are connected by means of the ~huttle valve 23' with the variable capacity pump 18' over the feedback line 20'. The recycled oil gets to the tank 38 downstream of the control valves 15,15'. Both variable Z0 capacity pumps 18, 18' are interconnected by a connection line 3g In this line a further connecting valve 24 is provided. According to the application desired the complete volume flow Q2 or a partial volume flow can be additionally connected to the volume flow Q1 of the variable capacity pump 1~. Ho~lever, this additional connection is also possible 2107~12 into the otheY direction of f low tran,sferred, so that ~otrl control circuits, as the need arises, can be alwa,vs supplied with the respective volume f low required. The reflux downstream of the control valve to the tank 3~ is effected via the lines 41,41'.
In Figure 4 a reservoir is added to the control -or regulator circuits I and II. The Figure thereby presents a variable capacity pump 18, regulated by the afflu~ side, which supplies the reservoir via the line 40 and the 2/2-way valve 26. provided that the control valve 15' is in its middle position. The 2/2-way valve 27 is opened for filling the reservoir and the pressure is registered by the pressure transducer 44. As a result, if the 2/2-way valve Z7 is closed, the control circuits I and II can be supplied by the variable capacity pump in the way already described. As 2/~-way vaive for example a Cartridge valve can be applied. If the reservoir is filled, it can be discharged over the line 2~ or 40 into each of both control circuits in case necessary. That way it is for example possible to effect a high speed control. In order to avoid a reflux from the reservoir 30 to the variable capacity pump during the discharge action, a nonreturn valve 45 is provided in the pump branch 33.
In Figure 5 a 4/4-way valve, which has a forth control position, is used instead of a control valve, the 2~7~12 rest of the construction of the hydraulic device remaining largely identical. In this position a differential switching is possible for feeding the fluid ousted by the consumer into a pump branch 33, the 4/4-way valve being overbridged by a S derived circuit 32 provided with a nonreturn valve 31. In this way it is possible to achieve an approximately 30%
higher speed, if the operating method is favourable with respect tG ener~etics.
Figure 2 furthermore shows the electronic control unit R in more detail with respect to its circuits.
It works on the principle of a multivariable control system of either analog or digital construction, At least one first transducing means 16, however better a first and a second transducing means 16,17, are provided for each control valve, This transducing means transmits the actual pressure - or force values to the pressure controller 37, which determines the command variable W3 for the pressure - and force regulation. The actual values for positioning xl to Xn are ascertained in the distance potential transformer 34 and compared with the nominal positioning value, whereby the command variable w1 for positioning is determined. The velocity is compared with the nominal velocity vOOll, whereby the co~nand variable w2 for velocity is determined. The appertaining actual values are acquired analogly or 2~ digitally ~y transducing means adapted to acquire actual ,. . . . . .
, 21~7~12 values. The cor~r~and variable wz for velocity or the cor~hand varlable w is superset and the comrnand variable W3 for the pressure - and force regulation has a lirniting effect ln the limiting means 35 with regard to the actual positioning variable y respectively y ,y2. Then the positioning variables are transmitted to the comparator device 42 via the siqnal line 43, which compares the actual position of the control valve with the positioning variable and in case necessary arranues for an adjusting movement of the control valve. The iO velocity can be controlled or adjusted in the sense of automatic control technic. The control circuit is closed by the electronic control unit. If purely pressure - and force r-egulation is required, also reversible controller networks could he applied.
It will be understood that the above description of the present invention is susceptible to various modifi-cations, changes and adaptations, and the same are intended to be comprehended within the meantime and range of equivalents of the appended claims.

..

Claims

1. In a hydraulic device for hydraulic consumers for use in a production machine, particularly in an injection molding machine for processing synthetic materials or comparable plastic or plastifiable masses, comprising at least one supply line, at least one back flow pipe, a control unit programmable with preset nominal values, at least one first transducing means associated with said supply line for verifying an adjusted actual value against said preset nominal values presented by said control unit, at least one control valve with at least three control positions; said control valve being regulable by said control unit according to a comparison between said actual values and said preset nominal values, at least, one variable capacity pump feeding said consumers with fluid via said supply line leading over said control valve, a feedback line connecting a controlling device of said variable capacity pump with said supply line down-stream of said control valve; said controlling device responding to a pressure in said supply line by continuously adjusting the pump output so as to maintain a constant operational pressure gradient between said pump and said supply line downstream of said control valve, the improvement residing in that said back flow pipe is also conducted via said control valve, said consumers are connected with said control valve by means of connecting valves, each of them associated to one of said consumers and at least one second transducing means is associated to said back flow pipe, which in connection with said first transducing means of said supply line constitutes a regulating variable for said control unit.

2. The improvement set forth in claim 1, wherein said control unit acquires said actual values for ascertain-ment of the conditions on both sides of said consumers.

3. The improvement set forth in claim 1, wherein a respective just catching control edge of said control valve derates said fluid being ousted by said consumer in a discharge.

4. The improvement set forth in claim 1, wherein the middle control position of said control valve is a stopping position.

5. The improvement set forth in claim 1, wherein further variable capacity pumps are additionally connectable in both flow directions in a connection line between said first and said further variable capacity pumps by means of a further connecting valve and said further variable capacity pumps together with said first variable capacity pump are associated to several control circuits with several central control valves regulated by said control unit.

6. The improvement set forth in claim 1, wherein a reservoir is feedable by said variable capacity pump via a 2/2 way valve and a line; said reservoir being dischargeable over said line.

7. The improvement set forth in claim 1, wherein said control valve is a 4/4 way valve, its forth control position generates a differential switching for feeding said fluid ousted by said consumer into a pump branch, being over-bridged by said 4/4 way valve via a derived circuit provided with a nonreturn valve.

8. The improvement set forth in claim 1, wherein said consumers are provided with additional transducing means for acquirement of regulating variables, which are processed in a closed loop by said electronic control unit for determination of a positioning variable.

9. The improvement set forth in claim 8, wherein in said control unit a superset variable is a command variable for velocity and a command variable for pressure -and force regulation has a limiting effect with respect to said actual positioning variable

10. The improvement set forth in claim 8, wherein in said control unit a superset variable is a command variable for positioning and a command variable for pressure - and force regulation has a limiting effect with respect to said actual positioning variable.