EP1457283A1 - Pressure diecasting machine with acceleremoter connected to the plunger - Google Patents

Abstract

Pressure casting device comprises a pressure casting mold forming a hollow chamber (16); and a pressing plunger (26) for pressing casting material into the chamber. A drive is assigned to the plunger and is controlled by a control unit. A sensor unit interacts with the plunger to provide the control unit with a control signal. The sensor unit has an acceleration sensor (62) coupled with the plunger. Preferred Features: The drive comprises a hydraulic system consisting of a drive unit (34) having a operating plunger (30) coupled with the pressing plunger. The operating plunger is impinged with the pressure of a hydraulic liquid.

Description

The invention relates to a die casting device with a mold cavity forming die and a press-in piston for pressing in Casting material into the mold cavity, a drive being assigned to the press-in piston is that is controllable by means of a control unit, and with which Press-in piston a sensor unit which detects the movement of the press-in piston cooperates, which provides the control unit with a sensor signal.

Such die casting devices are known from EP 0 827 794 B1. With With their help, castings can be produced, preferably as the casting material liquid metal is used, especially aluminum. In the Manufacture of such castings there is a risk that the casting material not evenly distributed when pressed within the mold cavity. In particular, there is a risk that air pockets form through which the quality of the finished casting is significantly reduced.

In order to fill the mold cavity with casting material as evenly as possible it is known to press the plunger during a first phase of the casting process to move the casting material at a relatively slow speed if possible without air pockets up to an inlet opening in the mold cavity damming. Then, during a second phase of the casting process, the speed of the press-in piston is greatly increased, around the accumulated casting material through the inlet opening, the so-called Gate to press into the mold cavity.

When the mold cavity is finally completely filled with casting material, it can the injection plunger are braked suddenly, with within the Mold cavity builds up a static final pressure, which leads to a compression of the Casting material leads by pouring liquid casting material into the solidifying and the Solidification shrinkage underlying casting areas is pressed. The Switching over of the different movement phases of the press-in piston takes place often by means of adjustable switching cams arranged on a piston rod are, at the free end of the injection piston is fixed. The positioning the switch cam is time-consuming and taken into account no changes in the physical conditions within the mold cavity, for example temperature changes in the die and Casting material, which has a significant influence on the solidification behavior of the Apply casting material.

Movement is proposed in EP 0 827 794 B1 mentioned at the beginning of the press-in piston by means of a sensor unit in the form of a displacement sensor monitor, which is coupled to a control unit of the die casting device is. The displacement sensor provides a signal that a specific one Position of the injection piston corresponds. Depending on the sensor signal can the drive piston associated drive to achieve each desired speed of the press-in piston can be controlled. While A calibration of the die casting device can change the path-dependent speed of the press-in piston can be optimized. But around castings To be able to produce the highest quality, it is also necessary here, if possible ensure constant conditions within the mold cavity.

The object of the present invention is a die casting device of the beginning mentioned type in such a way that the movement of the press-in piston to the inside of the mold cavity in a structurally simple manner prevailing physical conditions can be adapted.

This object is achieved with a die casting device of the generic type solved according to the invention in that the sensor unit rigidly with the Press-in piston coupled acceleration sensor.

The idea that changes in the physical Conditions within the mold cavity when the casting material is pressed in result in a corresponding change in the pressure forces that act on the press-in piston and the one from the acceleration sensor cause detectable change in speed of the press-in piston. The pressure of the casting material exerted on the injection piston changes during the mold filling, in particular in accordance with the geometry of the casting given flow conditions. For example, this leads Accumulation of the liquid casting material at the gate of the mold cavity a brief increase in pressure, which a corresponding sensor signal of Acceleration sensor has the consequence, so that independent of the sensor signal can be determined from the position of the injection piston to which Point in time the liquid casting material during the press-in movement accumulates at the gate. During the filling of the mold cavity, more can Pressure peaks occur due to those prevailing within the mold cavity Flow conditions are specified. The latter don't just hang on the geometry of the casting, but also on the temperature of the Die casting mold and the casting material. A change in these temperatures also leads to a change in the pressure peaks that occur of the acceleration sensor can be detected. When the mold cavity is filled finally arises in connection with the post-compression a last pressure peak, which is also detected by the acceleration sensor can. The sensor signal provided by the acceleration sensor can can be used to control the drive of the injection piston, in particular, it can be provided that the speed of the press-in piston controlled depending on the sensor signal from the acceleration sensor becomes. A change in physical conditions occurs during the casting process inside the mold cavity, this leads to a change the pressure peaks that occur and thus also a change in the sensor signal, so that the control of the press-in piston in a structurally simple Adaptable to the physical conditions within the mold cavity is.

It is advantageous if the drive comprises a hydraulic system with a drive unit, which has a working piston coupled to the press-in piston, which can be acted upon by the pressure of a hydraulic fluid, wherein the pressure of the hydraulic fluid acting on the working piston by means of one or more control or regulating valves depending on the sensor signal of the acceleration sensor is controllable. The one acting on the drive unit Hydraulic fluid pressure can thus be controlled by Control or regulating valves can be adapted to the course of the sensor signal. The working piston performs a certain movement depending on the pressure from, which is transferred to the injection piston, so that it is dependent performs a desired movement from the sensor signal.

It is advantageous here if at least one of the control or regulating valves is coupled to the control unit of the die casting device, which in turn with the acceleration sensor is in electrical connection. The control unit Here, depending on the sensor signal, a speed profile can be determined of the press-in piston are specified, the speed profile in a corresponding opening and closing movement of the at least a control or regulating valve can be implemented.

It can be provided, for example, that a control or regulating valve in an outlet line is connected via which the drive unit with a storage tank stands for hydraulic fluid in flow connection. This gives the Possibility, depending on the sensor signal hydraulic fluid from the Transfer drive unit via the outlet line in the storage tank, whereby the pressure of the hydraulic fluid acting on the working piston is lowered.

Alternatively or additionally, it can be provided that a control or regulating valve is connected in a pressure line, via which a pressurized one Hydraulic fluid absorbing pressure accumulator with the drive unit is in flow connection. This gives the possibility of being dependent From the sensor signal, the pressure acting on the working piston can be specified Way to increase by the control or regulating valve accordingly is opened and closed.

In a preferred embodiment of the invention it is provided that the Drive unit comprises a working cylinder in which the working piston is displaceable is mounted and hydraulically coupled to a pressure cylinder is, wherein the pressure cylinder is connected to the pressure accumulator via the pressure line is and wherein the working cylinder via the outlet line with the storage tank connected is.

It is advantageous if both in the pressure line and in the outlet line in each case at least one controllable depending on the sensor signal Control or regulating valve is switched, because this gives the possibility of using of the control valve connected in the pressure line the strength of the to specify the driving force exerted by the working piston on the press-in piston and at the same time by means of the control or in the outlet line Control valve the time course of the movement of the with the working piston to control the coupled plunger. The one from the working piston to the press-in piston applied driving force corresponds to the press force that the press-in piston on the casting material. For example, that during a first phase of movement of the injection piston exerted only a relatively small pressing force on the casting material which is increased during a subsequent phase of the casting process, so that especially during a final phase of the casting process Post-compression of the casting material can be achieved. At the same time the movement by means of the control valve connected in the drain line of the working piston and via this also the movement of the press-in piston to be controlled. This gives in particular the possibility of speed of the control piston again during the final casting phase to reduce. This enables the necessary clamping forces to be generated by a Mold clamping unit of the die casting device exerted on the die casting mold will be reduced.

The coupling of the acceleration sensor with the injection piston can be in advantageously done in that the acceleration sensor on a is held mechanically coupled to the injection piston carrier.

The press-in piston is preferably connected to a piston rod, and the carrier comprises a switching rod arranged parallel to the piston rod, which is rigidly coupled to the piston rod and on which the acceleration sensor is held. The shift rod thus leads according to the piston rod a movement through, occurring speed changes can be reliably detected by the acceleration sensor.

It is particularly favorable if the acceleration sensor on one end face the shift rod is arranged. It has been shown that such Arrangement of the acceleration sensor has a particularly high sensitivity against speed changes can be achieved.

In a preferred embodiment, the carrier is displaceable on a guide held. It is advantageous here if the guide on the drive unit is mounted.

Preferably, the die-casting mold includes one extending from the mold cavity Outlet duct to which a vacuum source can be connected via an outlet valve is, the outlet valve depending on the sensor signal of the Accelerometer is controllable. Such a configuration enables pressurizing the mold cavity while the Casting material is pressed. This can increase the risk of air pockets be additionally reduced in the casting. The application of one However, negative pressure is not during the entire casting process Advantage, it has been found that in many cases during different Phases of the casting process a different air pressure within of the mold cavity is advantageous. The application of negative pressure therefore takes place by means of the exhaust valve depending on the sensor signal of the Acceleration sensor. This gives in particular the opportunity to use the vacuum source for example during a final phase of the casting process detach from the mold cavity while the mold cavity during an initial phase of the casting process with a particularly large negative pressure is applied.

A simple design control of the exhaust valve is carried out in a preferred Design in that the outlet valve with the control or regulating unit is coupled, which in turn with the sensor signal of the acceleration sensor is acted upon. Depending on the sensor signal in this case, the outlet valve determines the opening valve by means of the control unit and closing movements during the injection of casting material be specified.

Figur 1:

eine schematische Darstellung einer erfindungsgemäßen Druckgießvorrichtung; und

Figur 2:

eine Veranschaulichung der Bewegung eines Einpreßkolbens der Druckgießvorrichtung während des Gießvorganges in Abhängigkeit von einem Druckverlauf in einem Formhohlraum der Druckgießvorrichtung und eines entsprechenden Sensorsignals.

The following description of a preferred embodiment of the invention serves in conjunction with the drawing for a more detailed explanation. Show it:

Figure 1:

a schematic representation of a die casting device according to the invention; and

Figure 2:

an illustration of the movement of a press-in piston of the die casting device during the casting process as a function of a pressure curve in a mold cavity of the die casting device and a corresponding sensor signal.

FIG. 1 shows schematically an overall reference number 10 Die casting device shown with a first, fixed mold half 12 and a second, movable mold half 14, which in the usual way one known per se and therefore not shown in the drawing Interact mold closing unit. The latter includes a fixed and a movable platen (not shown), on each of which two mold halves is held in a known manner and the two Exercise mold halves a predetermined clamping force. The two mold halves 12 and 14 form between them a mold cavity 16 which has the shape of a has to be cast, and in which a casting material, for example a metallic melt, can be injected. For this purpose, the mold cavity has 16 an inlet opening, which is referred to below as gate 18 is. The gate 18 is via an inlet channel 20 with a cylindrical Pouring chamber 22 in connection, which has an inlet opening 24 and in which a press-in piston 26 is slidably held.

The press-in piston 26 is held on a piston rod 28 which with its fixed the end facing away from the press-in piston 26 on a working piston 30 is in a working cylinder 32 one with the reference number 34 occupied drive unit is slidably mounted. In addition to Working cylinder 32, the working unit 34 has a hydraulic with the working cylinder 32 coupled pressure cylinder 36 in which a pressure piston 38 is slidably mounted. On its facing the working cylinder 32 The end of the pressure piston 38 carries a pressure pin 40 on the piston rod 28 opposite side of the working cylinder 32 in the working cylinder 32 dips.

The pressure cylinder 36 stands over a pressure line 42 with a known per se and therefore in the drawing, not shown, accumulator Flow connection that receives hydraulic fluid under pressure. An electrically controllable control valve 44 is located in the pressure line 42 switched in the form of a solenoid valve, with the help of which the flow connection between the pressure accumulator and not shown in the drawing the pressure cylinder 36 can be opened and closed in a defined manner.

The working cylinder 32 is connected via an outlet line 46 to a storage tank 48 for hydraulic fluid in flow connection, so that via the outlet line 46 hydraulic fluid from the working cylinder 32 to the storage tank 48 can be delivered. In the outlet line 46 is a second control valve 50 switched, which is also designed as a solenoid valve, so that by means of of the second control valve 50 the flow connection between the working cylinder 32 and the storage tank 48 either released or interrupted can be.

For the electrical control of the first and second control valves 44 and 50 The die casting device 10 comprises a control and regulating unit 52, which Control lines is coupled to the two control valves 44 and 50.

On the piston rod 28, a bush 54 is held immovably on the a support arm 56 is fixed. Aligned parallel to this on the impression cylinder 36 a guide arm 58 fixed in the region of its free end is penetrated by a switching rod 60 which is parallel to the piston rod 28 is aligned and in its front, the mold halves 12 and 14 facing End region is rigidly connected to the support arm 56. On her the Mold halves 12 and 14 facing away from the rear end carries the shift rod 60 an acceleration sensor 62 on the front side, which is connected via a sensor line 64 is in electrical connection with the control and regulating unit 52.

The die casting device 10 also has a known and therefore Vacuum source not shown in the drawing, which has a Vacuum line 66 with an outlet channel opening into the mold cavity 16 68 is in flow connection. Between the vacuum line 66 and the outlet channel 68 is an outlet valve 70 configured as a solenoid valve arranged that via a control line 72 with the control and regulating unit 52 is in electrical connection.

To produce a casting, a metallic melt is made using the Press-in piston 26 is pressed into the mold cavity 16. The injection piston 26 assumes a retracted position at the start of the casting process, in which he releases the inlet opening 24 so that the metallic melt in the Casting chamber 22 can be filled. Then the press-in piston 26 inserted into the casting chamber 22 by means of the drive unit 34. The of the distance covered by the plunger 26 as a function of time is in Figure 2 is shown schematically by the curve shape 75.

The injection of the casting material via the inlet channel 20 and the gate 18 leads into the mold cavity 16 as well as the filling of the mold cavity 16 to the fact that the pressure within the mold cavity 16 is dependent changed by the position of the injection piston 26. The course of itself within of the mold cavity 16 forming pressure depending on the Time is shown in simplified form in FIG. 2 by the curve profile 77. On the first pressure rise occurs here within the mold cavity 16 Time when when the first phase A of the casting process Casting material previously filled into the casting chamber 22 is stowed at the gate 18 is. The speed of the press-in piston 26 is then increased and the molding material spreads within the mold cavity 16, whereby depending on the shape formed by the geometry of the mold cavity Flow conditions within the mold cavity 16 in successive Set pouring phases B, C and D several more pressure increases until finally at the end of the casting process in a casting phase E the mold cavity 16 is completely filled with casting material and is now a static Ultimate pressure builds up by a recompression of the casting material Repressing the melt into the solidifying and the solidifying shrinkage underlying casting areas.

The short-term pressure increases that occur during the casting process are transferred to the injection piston 26 via the casting material, so that it brakes strongly for a short time and then accelerates again becomes. These speed changes are from the acceleration sensor 62 recorded. The one provided by this during the casting process Sensor signal as a function of time is shown in FIG. 2 as curve 79 reproduced in simplified form. The sensor signal 79 has several maxima which are each assigned to a pressure peak of the pressure curve 77 can. So the first maximum of the sensor signal 79 corresponds to itself due to the congestion of the casting material at the pressure peak forming at the gate 18. The further maxima of the sensor signal 79 also correspond to Pressure peaks of the pressure curve 77, in particular corresponds to the last maximum of the sensor signal 79 which forms within the mold cavity 16 Final pressure.

In the die casting device 10 according to the invention, this is done by the acceleration sensor 72 provided sensor signal 79 for controlling the control valves 44 and 50 are used so that these are dependent on the forming maxima of the sensor signal 79 defined open and closed can be. As a result, the speed of the press-in piston 26 can be controlled depending on the sensor signal 79. For example be provided that the speed of the injection piston 26 during a second phase B of the casting process is increased as soon as that sets the first maxima of the sensor signal 79, which is the same as when the accumulation occurs of the casting material at the pressure tip forming the gate 18 corresponds. Depending on the subsequent pressure peaks, the pressure can then increase Phases C and D of the casting process the speed of the injection piston 26th can be reduced again in a predetermined manner. When the last maxim occurs the sensor signal during the casting process, the movement of the Einpreßkolbens 26 are then brought to a standstill, but during this last phase E of the casting process a defined pressure from Press-in piston 26 is exerted on the casting material for its recompression becomes.

The control of the movement of the injection piston 26 as a function of the sensor signal 79 of the acceleration sensor 62 has the advantage that the movement of the press-in piston 26 which is located within the mold cavity 16 during of the casting process forming pressure curve 77 follows. This pressure curve is directly from those prevailing within the mold cavity 16 physical conditions, especially the temperature of the both mold halves 12 and 14 and the temperature of the casting material during the casting process. If a temperature change occurs, this leads to a change in the pressure curve and thus also a change in the movement of the press-in piston 26 without having to calibrate again Die casting device 10 is required. According to the control of the Control valves 44 and 50 can also do this via the control and regulating unit 52 Outlet valve 70 for optimizing the casting process depending on the sensor signal 79 can be controlled. This gives the opportunity during individual Phases A, B, C, D and / or E the vacuum source (not shown) with the To connect mold cavity 16, so that the negative pressure that is formed temporally can be adapted to the filling process.

Claims (12)

Die casting device with a die cavity forming a die cavity (12, 14) and a press-in piston (26) for pressing casting material into the die cavity, the press-in piston (26) being assigned a drive (34) which can be controlled by means of a control unit (52), and a sensor unit which detects the movement of the press-in piston (26) and which provides the control unit (52) with a control signal cooperates with the press-in piston (26), characterized in that the sensor unit has an acceleration sensor (62) rigidly coupled to the press-in piston (26) , Die casting device according to Claim 1, characterized in that the drive comprises a hydraulic system with a drive unit (34) which has a working piston (30) which is coupled to the press-in piston (26) and can be acted upon by the pressure of a hydraulic fluid, the pressure on the working piston (30) acting pressure of the hydraulic fluid can be controlled by means of one or more control or regulating valves (44, 50) depending on the sensor signal (79) of the acceleration sensor (62). Die casting device according to claim 2, characterized in that a control or regulating valve (50) is connected to an outlet line (46) via which the drive unit (34) is in flow connection with a storage tank (48). Die casting device according to claim 2 or 3, characterized in that a control or regulating valve (44) is connected to a pressure line (42), via which a pressure accumulator under pressure hydraulic fluid is in flow connection with the drive unit (34). Die casting device according to claim 4, characterized in that the drive unit (34) comprises a working cylinder (32) in which the working piston (30) is slidably mounted and which is hydraulically coupled to a pressure cylinder (36), the pressure cylinder (36) being above the pressure line (42) is connected to the pressure accumulator and the working cylinder (32) is connected to the storage tank (48) via the outlet line (46). Die casting device according to one of the preceding claims, characterized in that the acceleration sensor (62) is held on a carrier (60) mechanically coupled to the press-in piston (26). Die casting device according to claim 6, characterized in that the press-in piston (26) is connected to a piston rod (28) and in that the carrier comprises a switching rod (60) which is arranged parallel to the piston rod (28) and is coupled to the piston rod (28) and on which the acceleration sensor (62) is held. Die casting device according to claim 7, characterized in that the acceleration sensor (62) is arranged on an end face of the shift rod (60). Die casting device according to claim 6, 7 or 8, characterized in that the carrier (60) is held displaceably on a guide (58). Die casting device according to claim 9, characterized in that the guide (58) is mounted on the drive unit (34). Die casting device according to one of the preceding claims, characterized in that the die casting mold has an outlet channel (68) extending from the mold cavity (16), to which a vacuum source can be connected via an outlet valve (70), the outlet valve (70) depending on the sensor signal ( 79) of the acceleration sensor (62) is controllable. Die casting device according to claim 11, characterized in that the outlet valve (70) is coupled to the control unit (52).

Images