DE3448047A1 - Hydraulic device for the injection unit of a plastics injection moulding machine - Google Patents

Abstract

Between the variable-capacity pump (2) and the consumer (23), two closed-loop control units (E1; E2') are arranged in the supply line (35). The first closed-loop control unit (E1), consisting of a proportional-action flow-/pressure-control valve (4) and a pressure sensor (5), has an open-loop feedback control line (43) allocated to it in order to maintain the operating pressure gradient and has downstream of it a second closed-loop control unit (E2'), which comprises a proportional-action flow-/pressure-control valve (9), a pressure sensor (10) for pressure-dependent closed-loop control as well as a path voltage converter (21) for path-dependent closed-loop control. After the nozzle is brought into contact with the mould, a second variable capacity pump (12) is connected up via a directional control valve (8) for further maintenance of the pressure. <IMAGE>

Description

The invention relates accordingly to a hydraulic device the preamble of claim 1.

Under the term "operating pressure gradient" in the sense of the generic term a pressure gradient is understood as the basis for operation and the control of the regulating pump is still just sufficient, i.e. at a lower limit.

In a known hydraulic device of this type (DE-PS 31 19 095) result in comparison to previous hydraulic systems based on a single proportional flow / pressure valve In one consumer line to several consumers, very diverse adaptation options to different operating requirements while maintaining a minimum drive power.

Proceeding from this, the invention is based on the object of developing a hydraulic device of the type mentioned at the beginning in such a way that that the process of putting the injection molding unit on and off by choosing alternative working methods to an even higher degree adapted to the changing, sometimes extremely different, operational requirements due to a change in the production object can be accelerated.

This task is carried out in the characterizing part of the patent claim 1 mentioned features solved.

The functional interaction of the first and the second control unit in the hydraulic system creates the basic conditions for putting the injection molding unit on and off can be effected and accelerated on the injection mold by different working methods.

The second control unit is therefore not hydraulically connected to the first control unit, but rather is connected downstream in terms of its control behavior.

The invention is illustrated below with reference to the drawing using an exemplary embodiment explained.

Fig. 1 shows the hydraulic system of the control device.

The hydraulic device enables the injection molding unit to be put on and taken off adjustable to or from the injection mold. Hydraulic consumers of the injection molding unit are supplied via supply lines from a control pump 2 relatively large delivery rate and / or a regulating pump with a lower delivery rate (pressure maintenance pump 12) is supplied with pressurized oil via pressure line 47. From the regulating pump 2, which sucks in the pressurized oil from the tank 42 via a suction filter 1, feeds a consumer line 3 with a pressure limiting valve 6 a first control unit El, which is a proportional flow / pressure valve 4 with displacement transducer 4a and a pressure sensor 5 for pressure-dependent control (pressure program control). This first control unit El is provided with a control return line 43, the control member 2a of the regulating pump 2 'with the consumer line 3 according to the proportional Amount / pressure valve 4 connects in order to maintain a constant operating pressure gradient.

The first control unit El interacts with a second control unit E2 ′, which corresponds to the first control unit El and to which a line voltage converter 21 is assigned for path-dependent control. The control unit El is in the supply lines 35, 35 'to the piston-cylinder unit (driving cylinder 23) for putting on and taking off the injection molding unit, the second control unit E2 ¹ control technology

\ Cally downstream. Of the
ί

Proportional quantities / pressure valve 9 of the control unit E2 ¹ leads a return line 35a via a return filter 13 and an oil cooler 14 to the tank 42. Through the pressure maintenance pump 12, which sucks in the pressure oil from the tank 42 via a suction filter, the travel cylinder 23 is via a control valve 8 and can be fed via the first control unit El.

_ ₅ _ 3U8047

All speeds and pressures of the hydraulic system can can be operated in a closed control loop with the lowest possible energy consumption and little effort on hydraulic components.

The structure of the hydraulic device is detailed below on the process of putting the injection molding unit on and off.

First way of working:

The control unit E2 ¹ with the proportional quantities / pressure valve 9 and the pressure sensor 10 works as a switching valve. The speed and pressure are determined by the control unit El with the proportional quantities / pressure valve 4 and the pressure sensor 5. Thanks to the return line 43, this control unit El maintains a constant operating pressure gradient. In the case of speed regulation, feedback takes place via the line voltage converter 21, which works as a displacement transducer.

Second way of working:

The speed is controlled in that the proportional quantity / pressure valve 4 of the control unit El is controlled to a predetermined geometric size. The displacement of the valve piston is recorded by a displacement transducer and fed back to the setpoint as an actual value. When a pressure value specified in the program is reached during the travel movement, pressure control is used. The actual pressure value is detected by the pressure sensor 5 and fed to the electrical amplifier. If the programmed nozzle system position is reached with the help of the voltage converter 21 and at the same time the programmed nozzle system pressure with the help of the pressure sensors 5 and 10 (as a control), the following happens: A directional valve 8, which is connected upstream of the ^{control unit E2 1, which works as a switching valve in this context, is} switched to the pressure hold pump 12. The control pump 2 is controlled to zero by the control unit El. At the same time, the proportional flow / pressure valve 9 of the control unit E2 ^{1 works} as a pressure control valve. The actual pressure value is detected by the pressure sensor 10 and on

Copy ^

the electrical amplifier returned. The latter is able to do a Sol 1-Jst comparison. The displacement transducer 21 takes place the speed feedback as well as the path positioning.

In this way of working, too, the pressure shark is tepurnpe reversed after reaching the programmed nozzle system position.

Third way of working:

Speed control, pressure control and positioning take place using the proportional flow / pressure valve 9 of the control unit E2 '. Both the control pump 2 and the pressure maintenance pump can be used 12 can be used for the pressure oil supply. For this reason, when one control pump is operated, there are parallel functions with the other Control pump possible. The actual values are used for speed control and the positioning of the nozzle on the injection mold returned to the target values with the aid of the voltage converter 21. The actual pressure value from Pressure sensor 10 detected and moved back. The control piston of the proportional flow / pressure valve 9 is designed so that over the Displacement transducer 21 both a positioning and a 'leaving' the nozzle is possible without position control via displacement transducer 21, with the proportional flow / pressure valve 9 closing. The The displacement of the valve piston is detected by a displacement transducer 9a and fed back to the setpoint as an actual value. In the from the A pressure relief valve 7 is inserted into the pressure maintenance pump 12 leading to the pressure line 47 leading to the control unit E2 '.

The term "proportional flow / pressure valve" is in a broad sense to be understood and includes servovalves.

Claims (1)

PATENT LAWYERS - - ·:. '~ DR. FRI = DkICM E. M-VTER 71Q1 DIPL-PHYS. G. FRANK WESTLICHE 24 PFORZHEIM elimination from P 34 47 605.9-16 Karl Hehl, Arthur-Hehl-Str. 32, D-7298 Loßburg 1 Hydraulic device for the injection molding unit of a plastic injection molding machine. . ':' Claims 1. Hydraulic device for the injection molding unit of a plastic injection molding machine for putting the injection mold on and off the injection mold, with one that feeds the hydraulic consumers of the injection molding unit with pressurized oil via at least one consumer line Control pump and with a control unit arranged in the consumer line, which has a proportional volume / pressure valve and a pressure sensor for pressure-dependent control (pressure program control) and which is assigned to a control return line that connects the control element of the control pump with the consumer line after the proportional volume / pressure valve in order to maintain a constant operating pressure gradient , characterized in that the first control unit (El) is followed by a second control unit (E2 ¹ ) in the supply line (35) to the piston-cylinder unit (travel cylinder 23), which has a proportional flow / pressure valve (9), a pressure sensor (10 ) for pressure-dependent control (pressure program control) and a system voltage converter (21) for path-dependent control (quantity program control), and that an additional control pump (pressure maintenance pump 12) with a lower delivery rate is provided through which the travel cylinder (23) via a reversing valve (8) and the second Control unit (E2 ¹ ) can be fed, with the putting on and taking off of the injection molding unit optionally by the first (El) Copy or the second control unit (E2 ¹ ) can be controlled and, in the case of control by the second control unit (E2 ¹ ), the driving cylinder (23) can be fed either by the control pump (2) or the pressure maintenance pump (12).