JP2021124202A - Liquid pressure type casting unit - Google Patents

Abstract

To provide a casting unit comprising a differential circuit and a pressure booster, which enables an optimal casting process with less device technology.SOLUTION: A liquid pressure type casting unit has a casting cylinder 10 formed as a differential cylinder, and a piston 11 of the casting cylinder defines a bottom space 14 on a bottom side, and an annular space 15 on a piston rod 12 side. Further, the casting unit is provided with a low voltage source 56 that can be connected to the bottom space particularly via a shutoff valve device 41. Furthermore, the casting unit is provided with a liquid pressure type booster 24 as a booster unit, and the booster is designed to support the advance movement of the casting cylinder during a pressure holding phase, especially to increase the pressure in the bottom space.SELECTED DRAWING: Figure 2

Description

The present invention relates to the hydraulic casting unit described in the superordinate concept of claim 1.

The basic structure of such a casting unit used in a primary molding machine such as an injection molding machine, a die casting machine or a thixomolding machine is, for example, a publication derived from the present applicant, German Patent Application Publication No. 1020172220836. It is disclosed in the specification. According to this, the casting unit has a double-acting casting cylinder, and the piston of the casting cylinder defines the bottom space on the bottom side of the piston, and the end face of the casting cylinder on the piston rod side. Defines an annular space. In this known configuration, during the prefilling and mold filling steps, the bottom space is first connected to the low pressure accumulator via, for example, a two-way, two-position switching seat valve formed as an active logic valve. Since the annular space of the mold cylinder is connected to the bottom space via a regulating valve, the pressure medium pushed away from the annular space shrinking during the prefilling stage is provided in the differential circuit or regenerative circuit. It is supplied to the expanding bottom space via a regulating valve. In the mold filling stage, the pressure medium connection portion leading to the tank may be open-controlled via the adjustment valve on the tank side for injection, and the adjustment valve between the piston space and the annular space may be closed. Then, in the pressure holding step, the bottom space is connected to the high pressure accumulator via another regulating valve, at which time the pressure medium connection leading to the low pressure accumulator is cut off via the active logic valve. In this pressure holding stage, the pressure medium connection between the annular space and the tank remains open via the tank-side regulating valve, so that the melt in the cavity is compressed at high pressure, resulting in a material that may occur. Shrinkage is compensated.

The basic structure of the active logic valve used in this casting unit is known from the publication German Patent Invention No. 102005035170.

The casting unit disclosed in the publication, Publication No. 102017222500 of the German Patent Application, is not provided with a differential circuit or a regenerative circuit. In the pre-filling step and the mold filling step, the low pressure accumulator supplies the bottom space via the active logic valve to open and control the outflow side regulating valve, whereby the piston of the casting cylinder advances at a predetermined speed. During the transition from the prefilling stage to the mold filling stage, the outflow side regulating valve is further open controlled, which accelerates the piston and advances at a relatively high speed. The pressure medium pushed out of the shrinking annular space flows toward the outflow accumulator through the regulating valve on the outflow side, and then when it reaches a predetermined pressure in the outflow accumulator, it goes to the tank through the check valve or throttle. And leak. This reduces the maximum volumetric flow rate to the tank and thus the associated vortex. After the end of the prefilling step, the booster (multiplier cylinder) is accelerated to introduce the pressure holding step, at which time a boost is formed in the bottom space. In this case, the acceleration of the booster is achieved by connecting the annular space of the booster to the low pressure accumulator or tank via a regulating valve.

On the other hand, an object underlying the present invention is to provide a casting unit equipped with a differential circuit and a booster, which enables an optimized casting process with a small amount of equipment technology.

This problem is solved by a casting unit having the characteristics described in claim 1.

Advantageous improvements of the present invention are described in the sub-claims.

A hydraulic casting unit according to the invention, preferably designed for use in an injection molding machine, die casting machine or thixomolding machine, has a casting cylinder formed as a differential cylinder. The piston of the mold cylinder defines the bottom space on the bottom side and the annular space on the piston rod side. Further, a low pressure source that can be connected to the bottom space, especially via a shutoff valve device, is provided. In addition, a hydraulic booster is provided as the booster unit, which is designed to support the advance movement of the casting cylinder during the pressure holding phase, especially to increase the pressure in the bottom space. ing. The casting unit further connects the annular space of the casting cylinder to the bottom space via a first pressure medium flow path in the form of a regenerative circuit, especially during the prefilling stage, especially during the mold filling stage (“injection”). Then, in the pressure holding stage in which the annular space is connected to the pressure medium tank, particularly the tank, via the second pressure medium flow path, and the pressure booster is operated, the third pressure that opens into the pressure space of the pressure booster. It has a regulating valve device designed to open and control the medium flow path. In the present invention, the valve device is divided into three switching / proportional valves that can operate independently of each other. The first switching / proportional valve is in the first pressure medium flow path, the second switching / proportional valve is in the second pressure medium flow path, and the third switching / proportional valve is in the third pressure medium. It is arranged in the flow path.

Based on this separate configuration format, the regeneration procedure, injection and boosting can be controlled or adjusted independently of each other, which makes the casting process optimized and controllable or adjustable with less equipment technology effort. ing.

In the present invention, for the realization of the basic functions of the casting unit-pre-filling stage, regeneration, mold filling stage and pressure holding stage-three switching / proportional devices that are technically simple and can operate independently of each other. A valve is provided. The regenerative procedure of the casting cylinder allows the use of smaller accumulators as a low pressure source. Due to the smaller pressure difference during the regenerative function, less cavitation and thus less wear will occur. By using a smaller first switching / proportional valve that can be better separated during prefilling, the casting cylinder can be moved with higher accuracy.

In one improvement, the booster's primary piston defines the pressure space of the booster with its larger end face acting in the increasing direction and the reverse of the booster at its smaller end face acting in the opposite direction. It defines the pressure space, especially the annular space of the booster.

In one improvement, the reverse pressure space of the pressure booster can be fluid-connected to the pressure medium tank via a third pressure medium flow path, which provides outflow control during the pressure retention stage as well as this. The pressure booster can be operated by.

On the other hand, in one variation, in one improvement, the pressure space of the booster can be fluid connected to the pressure medium source via a third pressure medium flow path, thereby holding the pressure booster. Inflow control can be controlled during the stage and thus actuated.

Preferably, the switching / proportional valve is formed with a closed position. In the closed position, each pressure medium flow path is blocked or closed.

In one improvement, a pressure release flow path leading from the bottom space of the casting cylinder to the pressure medium tank via the first and second switching / proportional valves can be provided or formed. The pressure release flow path can be open-controlled or formed via the two switching / proportional valves, particularly depending on the pressure detected in the bottom space or the temporal pressure gradient.

In one improvement, at least one of the switching / proportional valves, at least the first and second switching / proportional valves, preferably all three switching / proportional valves, as two-way switching / proportional valves, in particular. It is formed as a two-way two-position switching flow control valve. Preferably, each switching / proportional valve or the two-way two-position switching flow rate adjusting valve is pilot-controlled, and particularly pilot-controlled by an electric hydraulic system.

In one improvement, at least two of the switching / proportional valves, preferably all, are formed in the same configuration, especially the same, with respect to at least one feature. The use of the same switching / proportional valve in the same configuration, or in extreme cases, is particularly effective in terms of structure, procurement, manufacturing, maintenance and operation and especially cost.

In this case, the term "same configuration" refers to one or more switching / proportional valves, such as type, connection, number of connections, diameter of connection, connection diagram, operation type, valve body, stroke, connection time, etc. Can be related to the characteristics of.

The term same construction may also relate to nominal dimensions, either alternative or supplementarily. In this regard, it has been found that it is advantageous for the first switching / proportional valve to have a smaller nominal dimension than the second and third switching / proportional valves. This is because the volume flow rate of the pressure medium in the first pressure medium flow path is relatively small as compared with the volume flow rate of the pressure medium in the second and third pressure medium flow paths.

In one improvement, pressure adjustment in the bottom space is realized by the pressure release flow path and the first and second switching / proportional valves. Advantageously, the peak pressure or pressure overshoot in the bottom space can be adjusted and / or reduced in this way.

The pressure boost during the pressure holding stage is mainly via the booster, using the third switching / proportional valve at the adjustment position, especially from the annular space of the booster and the open position of the second switching / proportional valve. It is performed by outflow control or outflow adjustment, that is, by connecting the pressure medium between the annular space of the casting cylinder and the tank.

In one improvement, the pressure space of the booster can be connected to a low pressure source, especially a hydraulic accumulator, via a shutoff valve or the like for its acceleration. In this case, the second pressure medium flow path leading from the annular space of the pressure booster to the pressure medium tank / tank is open-controlled via the third switching / proportional valve.

In one variation of the invention, the shutoff valve device is formed as a two-way, two-position switching active logic valve with a pilot valve. The active logic valve shuts off or opens the pressure medium connection between the low pressure accumulator and the bottom space of the casting cylinder, allowing extremely quick and reliable closing control during pressure buildup during the pressure retention phase. , The mold filling step can be completed very quickly and accurately.

In one alternative configuration, the check valve device is formed with a check valve located downstream of the low pressure source instead of the active logic valve, in which case the check valve and the casting cylinder A check valve is arranged between the bottom space and the bottom space. The shutoff valve opens and closes the connection that leads to the casting cylinder. The check valve closes the connection during step III or pressure boosting during the pressure retention step.

The outflow control or outflow adjustment may be optionally performed via a valve displaceable by a servomotor.

In one improvement, the casting unit can be used as a variable displacement pump or servomotor and servoconverter to return the casting cylinder and / or booster and / or to preload the casting cylinder and / or booster. It has a hydraulic pump formed as a constant-capacity pump with a device, as a variable-capacity pump with a three-phase motor and frequency converter, or as a variable-capacity pump with a three-phase motor.

In this case, by applying a preload to the annular space of the casting cylinder, the starting impact when introducing the prefilling step is avoided.

Therefore, in one preferred improvement, the casting unit has a device that preloads the piston and / or annular sides of the casting cylinder and / or booster.

The device for applying preload is preferably formed by a hydraulic pump and correspondingly arranged shutoff / preload valves.

In one improvement, the shutoff / preload valve is such that the pressure connection of the hydraulic pump via the shutoff / preload valve is the annular space of the booster and / or the annular space of the casting cylinder and / or the bottom space of the casting cylinder. It is formed so that it can be connected to. In this case, the pressure medium is sent into the annular space of the casting cylinder in order to preload the casting cylinder or return the casting cylinder, especially with the third switching / proportional valve closed.

In one improvement, the shut-off / preload valve is formed as a 4-way 3-position switching valve with at least a shut-off position. Further, the shutoff / preload valve has a first switching position in which the annular space of the booster and the annular space of the casting cylinder are connected to the pressure connection portion of the hydraulic pump, and the first switching position is the first. The pressure medium flow path of 1 is connectable or connected to the pressure medium tank, preferably via a check valve that can be opened.

In one improvement, the shutoff / preload valve has a second switching position where the bottom space of the casting cylinder is connected to the pressure connection of the hydraulic pump, at the second switching position the first. At the switching position, a preload conduit capable of connecting the annular space of the booster and the annular space of the casting cylinder to the pressure connection portion of the hydraulic pump is connected to the pressure medium tank.

Hereinafter, one preferred embodiment of the present invention will be described in more detail with reference to a schematic diagram.

It is a principle diagram of a casting unit. It is a figure which shows the simplified hydraulic circuit of one Example of a casting unit.

FIG. 1 shows the main mechanical components of a hydraulic casting unit 1 according to the present invention of a die casting machine.

According to this, the casting unit 1 has a casting cylinder 10 formed as a differential cylinder, and correspondingly, the piston 11 is formed including a piston rod 12. The piston 11 defines the bottom space 14 on the bottom side and the annular space 15 through which the piston rod 12 passes, together with the casing 13 of the casting cylinder. A casting piston 16 that penetrates into the injection chamber 18 of the casting sleeve 17 is attached to the end of the piston rod 12 that protrudes from the casing 13. In the casting sleeve 17, a filling opening 19 is located with respect to a liquid or paste-like molding material that is intended to produce a workpiece to be molded, which is hereinafter referred to as a melt. The casting sleeve 17 is attached to the mold 20, which generally comprises a movable mold half and a fixed mold half. The two mold halves define a mold hollow chamber 21, also called a cavity, formed corresponding to the geometric shape of the workpiece to be machined. The injection chamber 18 opens into the mold hollow chamber 21 via the casting passage 22.

Such a casting unit 1 is used to bring the melt into the mold 20, in which case a high rate of filling is required due to the rapid solidification process, after which the mold 20 is completely filled. High pressure is required to adjust the material shrinkage during compression and solidification.

In one embodiment according to the present invention shown in FIG. 2, a booster 24 is arranged as a boosting unit-also called a multiplying cylinder-corresponding to the casting cylinder 10, and the booster 24 is, for example, a difference. It is formed as a moving cylinder. The primary piston 26 defines the pressure space 28 of the booster on the bottom surface, and the piston rod 30 passes through the reverse pressure space of the pressure booster in the form of an annular space 32. Since the configuration of such a booster 24 is well known, further explanation is unnecessary.

The pressure medium supply of the cast unit 1 shown in the figure is formed as a constant-capacity pump in the illustrated embodiment, and is performed via a hydraulic pump 34 driven by a rotation speed control type electric motor 36, and is electrically driven. The motor 36 is formed, for example, as a servomotor equipped with a servo converter or as a three-phase motor equipped with a frequency converter. The pressure connection portion of the hydraulic pump 34 is connected to a shutoff / preload valve 42 formed as a 4-way 3-position switching valve via a pump conduit. The shutoff / preload valve 42 shuts off the pressure medium connection between the hydraulic pump 34 and the bottom space 14 at its spring-centered basic or intermediate position, as shown. It is possible to switch to two flow positions a and b by two switching magnets and hydraulic pilot control. At the flow positions a and b, the shutoff / preload valve 42 together with the hydraulic pump 34 is a casting cylinder 10. And the preloading device of the booster 24, which will be further described below.

The annular space 15 of the casting cylinder can be connected to the bottom space 14 via the first pressure medium flow path 23 and the first switching / proportional valve 27 arranged therein. The first switching / proportional valve 27 is an electrohydraulic pilot-controlled two-way 2 formed as a flow control valve, known as 2WRCE-4X from the Applicant's portfolio in the illustrated embodiment. As a position switching / proportional valve, it is formed with a basic position or a shutoff position where a preload is applied by a spring. With the start of the electro-hydraulic pilot control, the opening cross section of the valve 27 is open-controlled in response to the adjustment signal, and the annular space 15 is connected to the bottom space 14 for the regeneration procedure.

The annular space 15 of the casting cylinder 10 can be further connected to the tank T via a second pressure medium flow path 44 in which the second switching / proportional valve 46 is arranged. The second switching / proportional valve 46 has the same configuration as the first switching / proportional valve 27, but corresponds to a valve type having a larger nominal size. This is because the volume flow rate of the pressure medium passing through the second switching / proportional valve 46 is larger than the volume flow rate of the pressure medium passing through the first switching / proportional valve 27 in the regeneration procedure. The second switching / proportional valve 46 is also formed as a two-way two-position flow rate adjusting valve pilot-controlled by an electric hydraulic type, and at its basic position, the pressure medium connection to the tank T is cut off and the electric hydraulic type is used. By starting the pilot control of the above, the opening cross section with respect to the tank T is controlled to be opened in response to the adjustment signal.

The second pressure medium flow path 44 can be fluidly connected to the preload conduit 50 via a check valve 48 that opens with respect to the second pressure medium flow path 44. The preload conduit 50 is shut off at the basic position of the check valve 48, which is preloaded by a spring.

The pump conduit 40 opens into the third pressure medium flow path 25 between the third switching / proportional valve 29 and the annular space 32 of the booster. In the pump conduit 40, a check valve 70 that opens with respect to the annular space 32 of the pressure booster is arranged between the branch portion between the pump conduit 40 and the preload conduit 50 and the opening. Both check valves 48, 70 are designed to open when the pressure in the pump conduit 40 and the preload conduit 50 is sufficient, whereby the annular space 15 of the casting cylinder 10 and the annular space 32 of the booster 24 are opened. It is supposed to be sent to. In this way, the casting cylinder 10 and the pressure booster 24 can be returned so that the reverse pressure required to apply a preload to them can be formed in the annular spaces 15 and 32, respectively. It has become. For this purpose, the shutoff / preload valve 42 has a first switching position a, and at the first switching position a, the pressure connection portion P of the hydraulic pump 34 becomes the pump conduit 40 and the preload conduit 50. The first pressure medium flow path 23 is connected and can be connected to or is connected to the pressure medium tank T via an openable check valve 72.

The pressure itself at the outlet of the hydraulic pump 34 can be limited via a pressure limiting valve that opens relative to the tank T, as is well known.

In the present invention, the booster 24 and the casting cylinder 10 are arranged corresponding to the valve device divided into three flow rate adjusting valves 27, 46 and 29 that can operate independently of each other, and the flow rate adjusting valve 27 , 46 and 29 are formed as electrically hydraulically pilot-controlled valves each having two connections and are always displaceable.

A pilot-controlled two-way two-position switching built-in seat valve is formed as an active logic valve 41. Pilot control is performed via a pilot valve 52 formed as a three-way two-position switching valve. The inlet connection portion A of the active logic valve 41 is connected to the low pressure accumulator 56 via the low pressure storage conduit 54. The active logic valve 41 may be mounted in reverse with respect to the connecting portions A and B. The outlet connection portion B of the active logic valve 41 is connected to the bottom space 14 of the casting cylinder 10.

Since one possible configuration of the active logic valve 41 is known from German Patent Application Publication No. 1020172220836 and German Patent Invention No. 102005035170 of the publications cited in the introductory part of this specification, hereby Then, only the components important for understanding the present invention will be described, and for other points, refer to the above-mentioned prior art. According to this, the active logic valve 41 has a stepped main piston 60, and the main piston 60 is the pressure applied to the surface A5 from the low pressure accumulator ND via the switching pilot valve 52, and the valve seat 58. The pressure medium connection between the connection portions A and B of the active logic valve 41 and the low pressure storage conduit 54 and the pressure conduit 59 is cut off. The pressure conduit 59 is open in the bottom space 14 of the casting cylinder 10. The main piston 60 has an inner hole from the surface A5 to the surface A3, whereby the pressure compensation of the surface A5 acting in a closed manner is guaranteed by the surface A3 acting in an open manner. The active logic valve 41 can be accurately opened and closed via the control surface A4. In this case, in order to ensure that the active logic valve 41 is opened, the surface A4 may be selected to be larger than the difference between A5-A3, or the control pressure of the accumulator ND may be adjusted to be correspondingly relatively high.

The tank conduit 62 is connected to the tank connection of the pilot valve 52, and the inlet connection of the pilot valve 52 is connected to the control pressure or low pressure accumulator ND via the conduit 64. By supplying power to the switching magnet of the pilot valve 52, the pilot valve 52 can displace the annular control space of the active logic valve 41 defined by the surface A4 to the switching position connected to the low pressure accumulator ND against the spring force. As a result, the main piston 60 is lifted from the valve seat 58 based on the pressure acting on the ring end surface A4, and the fluid connection between the connection portions A and B is opened and controlled.

The active logic valve 41 is formed so as to be able to pass through with the minimum pressure loss and to be closed extremely reproducibly through the pilot valve 52 via the pilot valve 52 when the opening is appropriately controlled. The stroke of the active logic valve 41 may be restricted in order to optimize the subsequent closure characteristics. Due to this special construction of the active logic valve 41, only a small amount of control oil flow is required to open and close the active logic valve 41 quickly and reproducibly, even with large nominal dimensions.

Further, the operation reliability is enhanced by the active opening and closing of the active logic valve 41 by the pilot valve 52 and the reliable closing of the active logic valve 41 by the accumulator pressure. In this case, the closing condition can be freely selected by actively closing the active logic valve 41. This closing may be performed according to, for example, pressure, load force, moving distance, moving speed, and the like.

As shown in FIG. 2, the low-pressure accumulator 56 is hereinafter referred to as an accumulator shutoff valve 66, and can be connected to the pressure space 28 of the booster via a two-way two-position switching seat valve pilot-controlled by the pilot control valve 68. be. The control pressure medium for this is generated from the low pressure accumulator 56 itself. In this case, at the basic position where the preload is applied to the pilot control valve 68, the pressure of the low pressure accumulator 56 is supplied to the return space of the accumulator shutoff valve 66 that acts in a closed manner, and the pressure is switched. At the position, tank pressure is supplied so that the accumulator shutoff valve 66 connects the low pressure accumulator 56 to the pressure space 28 of the pressure booster. That is, at the switching position, the pressure booster 24 is contracted in the support direction.

Next, the functional form of the casting unit 1 shown in FIG. 2 between stages I to III described at the beginning will be described.

Before opening the active logic valve 41, which is also called an accumulator shutoff valve, in order to prevent a pressure wave that causes a starting impact toward the casting cylinder 10 when the casting cylinder 10 is started in the prefilling stage. Preload is applied to the casting cylinder 10 before the introduction of I. This includes the hydraulic pump 34, the shutoff / preload valve 42 moved to the first switching position a, and the open check valves 48 and 70 when the casting cylinder 10 and the pressure booster 24 return. Through this, a preload can be applied to the annular space 15 of the casting cylinder 10 and the annular space 32 of the pressure booster 24 so as to reach the maximum pump pressure. In this procedure, since the first switching / proportional valve 27, the second switching / proportional valve 46, and the third switching / proportional valve 29 are closed, a short circuit to the tank is prevented. The shutoff / preload valve 42 is preferably formed to have a check function.

In the next step, the melt shown in FIG. 1 is filled into the injection chamber 18 of the casting sleeve 17 through the filling opening 19, and the prefilling step I is introduced. For this purpose, the hydraulic pump 34 is controlled via the ramp function, and the bottom space 14 of the casting cylinder 10 is the value of the accumulator pressure of the low pressure accumulator 56 via the second switching position b of the shutoff / preload valve 42. Is filled up to. As a result, the casting cylinder 10 advances slightly at a low speed without a starting impact against the preload in the annular space 15 until the fluid contained in the annular space 15 is compressed and the force on the piston 11 is balanced. do. What is important in this case is that this control ensures that the pressure in the low pressure accumulator 56 is matched to the pressure in the bottom space 14 of the casting cylinder 10 without impact. After that, the low pressure accumulator 56 can be connected to the bottom space 14 via the active logic valve 41 (accumulator shutoff valve), and the low pressure accumulator 56 can be connected to the pressure space 28 of the booster via the accumulator shutoff valve 66. ..

This step is not necessary if the pump 34 can generate a sufficiently high pressure. When a correspondingly high preload is applied to the annular space 15, the low pressure accumulator 56 may also be switched to the piston space 14 via the active logic valve 41.

Depending on customer requirements, one common piston accumulator for casting cylinders and boosters or a dedicated piston accumulator for each may be used.

After that, the first switching / proportional valve 27 is controlled by pilot control, whereby the pressure medium pushed away from the annular space 15 is directly supplied to the bottom space 14 in the form of a regenerative circuit. This allows the casting cylinder 10 to be started and moved softly (regeneratively controlled without impact). This accelerates the melt and moves it towards the mold hollow chamber 21 shown in FIG. This is done until the melt reaches the cut in the mold and the prefilling step I is completed.

Since a relatively small amount of pressure medium is removed from the low pressure accumulator 56 based on the regenerative procedure of the casting cylinder 10 in the prefilling step I, the low pressure accumulator 56 has a smaller volume than the conventional configuration without the regenerative procedure. It may be configured. In addition, a better analysis of casting cylinder speed is possible based on the smaller pressure drop produced by the differential circuit and the first switching / proportional valve 27, which is smaller by one or two nominal dimensions. This allows the casting cylinder 10 to move at a lower speed and with better repeatability.

Another advantage of the regeneration procedure is the relatively low pressure loss in the first switching / proportional valve 27 and the pressure medium from the annular space 15 to the pressure in the low pressure accumulator 56 rather than against the tank pressure (0 bar). Based on the fact that it spills against it, less cavitation and thus less wear will occur on the valve 46, the piston 11, the casing 13 of the casting cylinder 10 and the attached control block.

In the present invention, by controlling the first switching / proportional valve 27 and the second switching / proportional valve 46 connected in series to the first switching / proportional valve 27, the pressure in the bottom space 14 is reduced or released. Can actively influence. That is, for example, the pressure overshoot in the bottom space 14 can be easily reduced by this path.

Further, in the present invention, the pressure in the bottom space 14 is affected by the first switching / proportional valve 27 and the third switching / proportional valve 29 which can be operated completely independently of the second switching / proportional valve 46. Can exert. Based on the independent pressure medium channels 23, 44, 25 and valves 27, 46, 29 described above, a more accurate and more dynamic adjustment of the pressure in the bottom space 14 will occur.

As soon as the melt reaches the cut in the mold, the original mold filling process (step II) is introduced. If the mold filling (injection) is performed at a low mold filling force, the regeneration procedure is continued. Correspondingly, at the time when the melt reaches the cut of the mold, the first switching / proportional valve 27 is, for example, a jump function, and the pressure medium connection between the annular space 15 and the bottom space 14 is significantly increased. It is displaced to an open position, which causes the melt to be ejected into the mold 20 at a high injection rate (up to 10 m / s). In this case, the pressure medium is continuously regenerated, that is, the pressure medium pushed away from the annular space 15 is supplied to the expanding bottom space 14.

Such a regeneration procedure has an advantage that even in step II, less pressure medium needs to be taken out from the low-pressure accumulator 56 than in the case of the conventional configuration.

If the injection is carried out at a relatively high mold filling force, the first switching / proportional valve 27 is brought to its closed position, for example by a jump function, at the time the melt reaches the mold cut, thereby. , The pressure medium connection between the annular space 15 and the bottom space 14 will be interrupted. In parallel, the second switching / proportional valve 46 is opened in a predetermined opening cross section with respect to the tank T, for example, by a leap function while the second switching / proportional valve 46 is in progress. As a result, the melt is injected into the mold hollow chamber 21 at a high injection speed, but in this case, unlike the procedure in the case of a low mold filling force, the process cannot proceed to the regenerative type, so that the casting cylinder The maximum force of 10 can be utilized.

As a general rule, a mixed form is also conceivable in which the first switching / proportional valve 27 is displaced to its shutoff position for the first time during step II according to the load force.

Step II can also proceed completely regeneratively. However, this is premised on the fact that the load force required in stage II can be achieved even in the regenerative circuit. In this case, it is believed that the second switching / proportional valve 46 can be replaced by a valve that switches rapidly to release the annular space 15 in step III.

After the mold hollow chamber 21 is completely filled, the transition is performed in step III. For this purpose, at the end of the mold filling step II, the third switching / proportional valve 29 is controlled by pilot control in the direction of opening the connection portion between the annular space 32 of the booster and the tank T. At the same time, the second switching / proportional valve 46 is opened. The release of pressure flowing into the annular space 32 of the booster accelerates the primary piston 26, thereby forming a high pressure in the bottom space 14, which results in the piston 11 being pressed at high pressure to form the melt. It will be recompressed. When the desired holding pressure is achieved, the second switching / proportional valve 46 is returned to the closing direction again via the pressure control device. When the second switching / proportional valve 46 is not closed sufficiently quickly, the pressure release path, that is, the switching / proportional valves 27 and 46 leading to the tank T are opened and controlled to enter the bottom space 14. Pressure overshoot can be reduced.

By using the first two-way switching / proportional valve 27 for both pressure control and regeneration control in the bottom space 14, a three-way switching / proportional valve (connection between A and T 50%). , 50% connection between A and P), a first switching / proportional valve 27 that is at least one smaller nominal size than the three-way switching / proportional valve can be used (A and T100%). As a result of the smaller nominal dimensions, improved propulsion will result.

Compared with the conventional configuration, the described casting unit has a pressure medium pushed away from the annular space 15 based on the regeneration procedure of the casting cylinder 10 through the first switching / proportional valve 27 of the casting cylinder 10. It has the advantage that it can be supplied directly to the bottom space 14. Another feature is the active closure of the active logic valve 41 at the end of stage II.

The active logic valve can also be replaced by a shutoff valve and an external check valve.

The casting cylinder of the disclosed casting unit may be regeneratively moved in the prefilling stage via the first flow control valve. The first flow rate regulating valve also has a function of adjusting the pressure in the bottom space of the casting cylinder. Through the second flow control valve, the casting cylinder may be moved in a coordinated procedure with or without regeneration at the mold filling stage. Further, in the pressure holding stage, a booster unit formed as a pressure booster is connected via a third flow rate adjusting valve. The pressure in the bottom space can also be regulated via a third flow control valve. All of the flow control valves can operate independently of each other. Both of these flow control valves enable extremely accurate and dynamic adjustment of the pressure in the bottom space, and have an improved configuration as compared with the configuration using the three-way switching flow control valve.

Claims (12)

A hydraulic casting unit for primary molding machines, especially injection molding machines, die casting machines or thixomolding machines.
A cast cylinder (10) formed as a differential cylinder with a piston (11) defining a bottom space (14) on the bottom side and an annular space (15) on the piston rod side.
A low pressure source (56) that can be connected to the bottom space (14) for the advance movement of the casting cylinder (10).
A hydraulic pressure booster (24) configured to increase the pressure in the bottom space (14) during the pressure holding step.
The annular space (15) can be fluidly connected to the bottom space (14) via the first pressure medium flow path (23) and the pressure medium tank via the second pressure medium flow path (44). A third pressure medium flow path (25) that is fluid connectable to (T) and opens in the pressure space (32) of the pressure booster (24) to operate the pressure booster (24) is open-controlled. Possible or formable regulating valve device and
In a hydraulic casting unit equipped with
The valve device is divided into three switching / proportional valves (27, 46, 29) that can operate independently of each other, of which the first switching / proportional valve (27) is the first pressure medium flow. The second switching / proportional valve (46) is arranged in the passage (23) and the second switching / proportional valve (46) is arranged in the second pressure medium flow path (44), and the third switching / proportional valve (29). Is a hydraulic casting unit, characterized in that it is arranged in the third pressure medium flow path (25). The primary piston (26) of the booster (24) defines the pressure space (28) of the booster at its larger end face acting in the increasing direction, and the smaller one acting in the opposite direction. The reverse pressure space (32) of the pressure booster, particularly the annular space of the pressure booster, is defined by the end face, and the reverse pressure space (32) of the pressure booster is defined via the third pressure medium flow path (25). 32) is the casting unit according to claim 1, which can be fluidly connected to the pressure medium tank (T). The first switching / proportional valve (27) and the second switching / proportional valve from the bottom space (14), in particular, depending on the pressure or temporal pressure gradient detected in the bottom space (14). The casting unit according to claim 1 or 2, provided with a pressure discharge flow path that can be formed to the pressure medium tank (T) via (46). Claims 1 to 3 wherein at least one of the switching / proportional valves (27, 29, 46) is preferably formed as a two-way two-position switching flow rate adjusting valve that is pilot-controlled by an electrohydraulic method. The casting unit according to any one of the items up to. At least two of the second switching / proportional valve (46) and the third switching / proportional valve (29) or the first to third switching / proportional valves (27, 29, 46). The casting unit according to any one of claims 1 to 4, wherein all the switching / proportional valves (27, 29, 46) are preferably formed in the same configuration. The one of claims 1 to 5, wherein the pressure space (28) of the booster can be connected to one low pressure source or the low pressure source (56) via an accumulator shutoff valve (66). Casting unit. The casting unit according to any one of claims 1 to 6, wherein the shutoff valve device is formed as a two-way two-position switching active logic valve (41) provided with a pilot valve (52). Formed as a variable displacement pump or as a constant capacitance pump with a servomotor and servoconverter, as a variable capacitance pump with a three-phase motor and frequency converter, or as a variable capacitance pump with a three-phase motor The casting unit according to any one of claims 1 to 7, further provided with a hydraulic pump (34). The casting unit according to any one of claims 1 to 8, further comprising a device (34, 42) for applying a preload to the casting cylinder (10) and / or the pressure booster (24). The pressure connection portion of the hydraulic pump (34) is connected to the annular space (32) of the booster and / or the annular space (15) and / or the casting cylinder (10) of the casting cylinder (10). 9. The casting unit according to claim 9, wherein a shutoff / preload valve (42) configured to connect to the bottom space (14) is provided. In the shutoff / preload valve (42), the annular space (32) of the booster and the annular space (15) of the casting cylinder (10) are connected to the pressure connection portion (P) of the hydraulic pump (34). ), And the first pressure medium flow path (23) is connectable or connected to the pressure medium tank (T) via a check valve (72) that is preferably openable. The casting unit according to claim 10, which is formed as a 4-way 3-position switching valve having the first switching position (a). The shutoff / preload valve (42) has a second switching position (b) in which the bottom space (14) is connected to the pressure connection portion (P) of the hydraulic pump (34). In the second switching position (b), the liquid in the annular space (32) of the pressure booster and the annular space (15) of the casting cylinder (10) at the first switching position (a). The casting unit according to claim 11, wherein a preload conduit (50) connectable to the pressure connection portion (P) of the pressure pump (34) is connected to the pressure medium tank (T).

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