Hydraulic control device for the injection molding machine's injection unit

Abstract

To provide a hydraulic control device of a pouring unit for a primary molding machine.SOLUTION: In a pouring cylinder 10 having a rod-side annular chamber 15 and a bottom-side bottom chamber 14 separated by a piston 11, in a hydraulic control device of a pouring unit 1, piston force and piston speed can be controlled by selectively connecting a pressure medium source 34 and a pressure medium tank T through hydraulically operable valve devices 27, 29, 41 and 46. Control pressure medium accumulators SD1 and SD2 which can be boosted are disposed, and the control pressure medium can be utilized to hydraulically operate the valve device through the pressure medium accumulators by the hydraulic control device.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a hydraulic control device for a pouring unit of an injection molding machine in the form described in the preamble of claim 1.

[0002] The term injection molding machine preferably includes, in particular, the fields of use of die casting machines, thixo molding machines and plastic injection molding machines.

[0003] The basic structure of such a hydraulic control device is disclosed, for example, in German Patent Application Publication No. 102017220836, which is attributed to the applicant. According to the specification, the control device has a double-acting pouring cylinder, the piston surface of this pouring cylinder defines an operating chamber (bottom chamber) on the bottom side of the piston, and the annular surface on the piston rod side of this pouring cylinder defines an operating chamber (annular chamber) on the piston rod side. In the known solution, the bottom chamber is first connected to a low-pressure accumulator via, for example, a 2-port 2-position switching sheet valve configured as active logic during the preliminary filling stage and the mold filling stage, and the annular chamber is connected to the bottom chamber via an adjusting valve. Therefore, in the preliminary filling stage, the pressure medium pushed out from the shrinking annular chamber is supplied to the expanding bottom chamber via the above-mentioned adjusting valve provided in the differential circuit or the regeneration circuit.

[0004] In the mold filling stage, for injection, the pressure medium connection leading to the tank is open-controlled via an adjusting valve on the tank side, and the adjusting valve between the piston chamber and the annular chamber may be closed. Then, in the pressure holding stage, the bottom chamber is connected to a high-pressure accumulator via another adjusting valve, and at this time, the pressure medium connection leading to the low-pressure accumulator is blocked via active logic. Generally, this pressure increase can also be performed via a booster. In this pressure holding stage, since the pressure medium connection between the annular chamber and the tank remains open via the above-mentioned adjusting valve on the tank side, the melt in the cavity is compressed at high pressure, and the possible shrinkage of the material is compensated.

[0005] The basic structure of active logic is publicly known from German Patent No. 102005035170 (DE102005035170B4).

[0006] The valve operation dynamics and precision described above are important, because only with high control precision can force and speed control in the injection process result in high product quality.

[0007] If a valve is hydraulically operated or pilot-controlled, the higher the available control pressure, the better the valve's operating dynamics and precision. Therefore, the highest possible control pressure is desirable. On the other hand, the pressure medium source provided for this purpose, such as a hydraulic pump, must provide a correspondingly high nominal pressure, which makes the unit expensive.

[0008] In this regard, the fundamental problem of the present invention is to provide a hydraulic control device for a flow unit in which a high control pressure can be achieved with minimal effort for a pressure medium source available for this high control pressure.

[0009] This problem is solved by a hydraulic control device having the features described in the feature section of claim 1.

[0010] Advantageous improvements to the control device are described in claims 2 to 10.

[0011] A hydraulic control device for a injection molding machine, particularly an injection molding machine, die casting machine, or thixomolding machine, has an injection cylinder. This injection cylinder has a rod to which the injection piston of the injection unit can be coupled. The rod-side operating chamber and the bottom-side operating chamber of the injection cylinder are separated by the piston of the injection cylinder. In this case, the piston has a bottom-side operating surface to which pressure can be applied, and a rod-side operating surface that is smaller than the bottom-side operating surface and to which pressure can be applied. A hydraulically operable valve device is provided to control the piston force and piston speed during the injection stage. Through this valve device, depending on the stage, the two operating chambers can be fluidly connected to and / or to a pressure medium source and a pressure medium reservoir. At least one pressurized control pressure medium accumulator is provided, from which a control pressure medium is available for hydraulically controlling the valve device. According to the present invention, a boosting path is provided, and through this boosting path, the rod-side operating chamber can be fluidly connected to at least one control pressure medium accumulator for boosting pressure.

[0012] This allows the piston of the flow cylinder and the favorable ratio of its two operating surfaces to be used to boost the pressure of at least one control pressure medium accumulator. This ratio causes the piston to function like a pressure intensifier. Therefore, high control pressures are achievable with minimal effort for the pressure medium source available for this control pressure.

[0013] Novel Claim: Pressure boosting (Aufladung) can also be performed in combination. That is, base supply to low pressure via a pump and pressure boosting to high pressure via the solution described in the claim.

[0014] In one improved version, which enables high control dynamics, control precision, and control versatility, the valve gear is broken down into valves that can be operated independently of each other, and each of these valves can independently control one or more pressure medium connections in the control chamber from one or more other valves.

[0015] Through the first valve of the disassembled valve device, the rod-side operating chamber in particular can be connected to the bottom-side operating chamber via a first flow path. Thus, a regenerative pressure medium flow path can be formed through the first valve, which makes it possible to design and provide a primary hydraulic pump to regulate a flow cylinder having a relatively small nominal volumetric flow rate. Furthermore, the first valve and the first pressure medium flow path provide the possibility of intervention for speed control.

[0016] Through a second valve in the valve mechanism, the operating chamber, particularly on the rod side, can be fluidly connected to the pressure medium tank via a second flow path. This allows the movement of the inlet piston to be controlled so that the outflow is controlled via the second valve.

[0017] To enable a holding pressure phase during pouring, the control system, in one improved version, includes a hydraulic pressure boosting unit. This boosting unit is designed to increase the pressure in the bottom control chamber during the holding pressure phase.

[0018] A hydraulic pressure boosting unit may be designed as an additional high-pressure accumulator or pressure booster, particularly as a differential cylinder capable of applying pressure to the larger of two operating surfaces of different sizes.

[0019] In one improved configuration in which the pressure boosting unit is configured as a pressure booster, particularly as a differential cylinder, a third valve of the valve device is provided to actuate the pressure booster. Through this pressure booster, a third pressure medium flow path opening into the pressure chamber or operating chamber of the pressure booster can be controlled to open or formed. Depending on the operating chamber through which the third pressure medium flow path opens, the pressure booster can be controlled to either have an inflow or outflow.

[0020] In one improved configuration in which the pressure boosting unit is configured as a high-pressure accumulator, a proportionally operable third position control valve is provided between the high-pressure accumulator and the operating chamber at the bottom of the flow cylinder. Through this position control valve, the pressure formation in the operating chamber at the bottom can be adjusted.

[0021] For a rapid and reliable reproducible connection between the bottom operating chamber of the flow cylinder and the pressure medium source, and for a corresponding rapid and reliable reproducible separation, in one improved version, a fourth valve of the valve device is configured as an active logic valve. Thus, the bottom operating chamber can be fluidly connected, in particular to the pressure medium accumulator, without relying on a hydraulic pump.

[0022] In one improved version, at least two control pressure medium accumulators are provided, one of which is capable of supplying control pressure medium to the first, second, and third valves, and the other is capable of supplying control pressure medium to the fourth valve.

[0023] In one improved version, the boost path branches to multiple control pressure medium accumulators. Alternatively, a single control pressure medium accumulator may be provided.

[0024] Different corresponding valve configurations with respect to the control pressure medium accumulator are, of course, possible. This configuration is defined in particular depending on the control pressure level required for each valve at any given time and / or the spatial proximity of the control pressure medium accumulator to each valve. In this case, immediate proximity is advantageous because damping and elasticity are minimized both when supplying the accumulator and when withdrawing the control pressure medium. Therefore, the control pressure remains stable throughout the signal rise of the valve piston, for example, during injection of the injection cylinder, and the valve piston opens to the desired target value with maximum acceleration.

[0025] In one improvement, a shut-off valve, particularly a two-port two-position switching valve, is provided in the pressure boosting path in order to ensure reliable pressure boosting of the control pressure medium accumulator and reliable shut-off of the control pressure medium accumulator with respect to the pouring cylinder.

[0026] In one improvement, an adjustable throttle device, particularly an orifice throttle, is provided in the pressure boosting path in order to be able to influence the pressure boosting-control pressure medium volume flow rate.

[0027] In one improvement, a pressure regulating valve is correspondingly arranged for at least one of the control pressure medium accumulator or the control pressure medium accumulators. Through this pressure regulating valve, the pressure in this control pressure medium accumulator can be adjusted. In particular, this is a pressure reducing valve whose inlet is subjected to the pressure of the rod-side operating chamber or a pressure depending on the pressure in this rod-side operating chamber, and whose outlet is connected to the control pressure medium accumulator.

[0028] In one possible variation, a separate pressure boosting path is correspondingly arranged for each of the control pressure medium accumulators.

[0029] Correspondingly, the last-mentioned shut-off valve, particularly a two-port two-position switching valve, and alternatively or additionally the last-mentioned adjustable throttle device, particularly an orifice throttle, may be provided in each of the plurality of pressure boosting paths.

[0030] Alternatively or supplementarily, the control pressure of the control pressure medium accumulator may be determined via the nominal pressure in the bottom-side operating chamber and the area ratio at the piston of the pouring cylinder. [[ID=二十一]] [[ID=二十二]]

[0031] [[ID=二十三]] [[ID=二十四]]Preferred embodiments of the present invention will be described in detail below with reference to the schematic diagrams. [[ID=二十五]] [[ID=二十六]]

Brief Description of the Drawings

[0032] [[ID=三十]] [[ID=三十一]] [Figure 1] [[ID=三十二]]It is a schematic diagram of the pouring unit. [[ID=三十三]] [[ID=三十四]] [Figure 2]This figure shows a simplified hydraulic circuit diagram of the injection unit shown in Figure 1, which is equipped with a hydraulic control device according to one embodiment.

[0033] Figure 1 illustrates the key mechanical components of the hydraulic injection unit 1 according to the present invention for a die-casting machine. According to this figure, the injection unit 1 is configured as a differential cylinder and has an injection cylinder 10, which consists of a piston 11 corresponding to a piston rod 12. The piston 11, together with the casing 13 of the injection cylinder, defines a bottom chamber 14 at the bottom and an annular chamber 15 through which the piston rod 12 penetrates. An injection piston 16 is attached to the end of the piston rod 12 that protrudes from the casing 13, and enters the injection chamber 18 of the injection sleeve 17. The injection sleeve 17 has a filling opening 19 for the liquid or paste-like molding material (hereinafter referred to as molten material) on which the workpiece to be molded will be formed. The injection sleeve 17 is in contact with a mold 20, which typically consists of a movable mold half and a fixed mold half. Both halves of the mold define a mold cavity 21, also called a cavity, which is formed to correspond to the geometric shape of the workpiece to be machined. The injection chamber 18 opens into the mold cavity 21 via a pouring passage 22.

[0034] Such a pouring unit 1 helps to introduce molten material into the mold 20, and based on a rapid solidification process, a high speed is required for filling, and then high pressure is required to completely fill and compress the mold 20 and to adjust for material shrinkage during solidification.

[0035] In one embodiment of the present invention shown in Figure 2, the pouring unit 1 has a hydraulic control device. For simplicity, the pouring piston 16, pouring sleeve 17, and mold 20 are not shown.

[0036] A pressure intensifier 24, also called an amplification cylinder, is positioned in the injection cylinder 10 as an amplification unit, and this pressure intensifier 24 is configured, for example, as a differential cylinder. The bottom surface of the primary piston 26 defines the pressure chamber 28 of the pressure intensifier, and the piston rod 30 passes through the back pressure chamber of the pressure intensifier, which is in the form of an annular chamber 32. The structure of such a pressure intensifier 24 is well known, so no further explanation is needed. Of course, other amplification units without a pressure intensifier are also possible, for example, a connectable high-pressure accumulator.

[0037] The basic pressure medium supply of the illustrated feeding unit 1 is provided via a hydraulic pump 34, which is configured as a constant-displacement hydraulic machine and driven by a speed-controlled electric motor 36, in the illustrated embodiment. The electric motor 36 is configured, for example, as a servo motor with a servo converter, or as a three-phase motor with a frequency converter. The pressure connection of the hydraulic pump 34 is connected via a pump pipeline to a pre-pressure valve 42, which is configured as a 4-port 3-position selectable valve. In the illustrated, spring-centered basic or intermediate position, the pre-pressure valve 42 shuts off the hydraulic pump 34 from the feeding cylinder 10 and the intensifier 24, instead connecting at least the bottom chamber 14 to the tank T via a corresponding check valve 72, and to the annular chamber 32 of the intensifier 24 via the pump pipeline 40 and the check valve 70. The preload valve 42 can be switched between two flow positions a and b by two switching magnets and hydraulic pilot control. In flow positions a and b, the preload valve 42, together with the hydraulic pump 34, can fulfill the function of a device for applying preload to the inlet cylinder 10 and the intensifier 24, which will be further explained below.

[0038] The annular chamber 15 of the inlet cylinder is connectable to the bottom chamber 14 of the inlet cylinder 10 via a first pressure medium flow path 23 and a first position-switching proportional valve 27 located within the first pressure medium flow path 23. The first position-switching proportional valve 27, known as 2WRCE-4X based on the applicant's portfolio in the illustrated embodiment, is configured as an electrohydraulic pilot-controlled two-port two-position switching proportional valve configured as a flow control valve, having a spring-loaded base position or shut-off position. Upon initiation of the electrohydraulic pilot control, the opening cross section of the valve 27 is controlled to open in response to the adjustment signal, and the annular chamber 15 is connected to the bottom chamber 14 for the regenerative procedure.

[0039] The annular chamber 15 of the inlet cylinder 10 can be connected to a tank T via a second pressure medium flow path 44, which contains a second position-switching proportional valve 46. The second position-switching proportional valve 46 is structurally identical to the first position-switching proportional valve 27 in terms of valve type and drive control, but has a larger nominal dimension than the first position-switching proportional valve 27. This is because the volumetric flow rate of the pressure medium through the second position-switching proportional valve 46 is greater than the volumetric flow rate of the pressure medium through the first position-switching proportional valve 27 during the regeneration procedure. The second position-switching proportional valve 46 is configured as a two-port, two-position flow control valve that is electrically and hydraulically pilot-controlled. In its basic position, the second position-switching proportional valve 46 disconnects the pressure medium connection to the tank T, and upon commencement of electrically and hydraulically pilot control, it opens the opening cross section toward the tank T according to the adjustment signal.

[0040] The second pressure medium flow path 44 can be fluidly connected to a pre-loaded pipeline 50 supplied by a hydraulic pump 34 via a check valve 48 that opens to the second pressure medium flow path 44. The pre-loaded pipeline 50 is blocked in the basic position where the check valve 48 is pre-loaded by a spring.

[0041] The pump pipeline 40 opens into a third pressure medium flow path 25 between the third position switching / proportional valve 29 and the pressure intensifier annular chamber 32. Within the pump pipeline 40, a check valve 70 is positioned between the branch of the pre-pressure pipeline 50 from the pump pipeline 40 and the aforementioned opening, opening toward the pressure intensifier annular chamber 32. Both check valves 48 and 70 are configured to open when the pressure in the pump pipeline 40 and the pre-pressure pipeline 50 is sufficient, so that the pressure medium is delivered to the annular chamber 15 of the feed cylinder 10 and the annular chamber 32 of the pressure intensifier 24. This allows the feed cylinder 10 and the pressure intensifier 24 to be returned, and the necessary back pressure to pre-pressure the feed cylinder 10 and the pressure intensifier 24 can be formed in their respective annular chambers 15 and 32.

[0042] To achieve this, the pre-pressure valve 42 has a first switching position a, in which the pressure connection part P of the hydraulic pump 34 is connected to the pump pipeline 40 and the pre-pressure pipeline 50, and the first pressure medium flow path 23 and the bottom chamber 14 can be connected to the pressure medium tank T via an openable check valve 72.

[0043] The pressure at the outlet of the hydraulic pump 34 can be limited via a pressure limiting valve that opens toward the tank T, in a form known to the present day.

[0044] The pressure intensifier 24 and the flow cylinder 10 are correspondingly arranged valve devices divided into three independently operable flow control valves 27, 46, and 29. Each of these flow control valves 27, 46, and 29 is configured as an electro-hydraulic pilot-controlled valve that is always adjustable and has two connection points. The hydraulic operation and pilot control are performed by a control pressure medium held in control pressure medium accumulators SD1 and SD2, which will be described in detail below.

[0045] A pilot-controlled 2-port, 2-position position-switching built-in seat valve is formed as an active logic valve 41. Pilot control of this active logic valve 41 is performed via a switching pilot valve 52 formed as a 3-port, 2-position switching valve. The inlet connection A of the active logic valve 41 is connected to a low-pressure accumulator 56 via a low-pressure accumulator conduit 54. The outlet connection B of the active logic valve 41 is connected to the bottom chamber 14 of the inlet cylinder 10.

[0046] One possible structure of the active logic valve 41 is known based on German Patent Application Publication No. 102017220836 and German Patent Invention No. 102005035170, which are cited at the beginning of this specification. Therefore, this specification will only describe the structural elements necessary to understand the present invention, and other points will be referred to the prior art described above. According to the prior art, the active logic valve 41 has a stepped main piston 60, which is preloaded against the valve seat 58 by pressure applied to surface A5 via a switching pilot valve 52 from a control pressure medium accumulator SD1, and also blocks the pressure medium connection between connections A and B of the active logic valve 41, and consequently between the low-pressure accumulator pipeline 54 and the pressure pipeline 59. The pressure pipeline 59 opens into the bottom chamber 14 of the inlet cylinder 10. The main piston 60 has an internal bore extending from the back surface A5 to the end surface A3, thereby ensuring pressure compensation between surface A5, which acts to close, and surface A3, which acts to open. The active logic valve 41 can be intentionally opened and closed via the control surface A4 by the action of the switching pilot valve 52. In this case, surface A4 can be selected to be larger than the difference between A5 and A3, or the control pressure of the control pressure medium accumulator SD1 may be adjusted to a correspondingly higher level, thereby ensuring that the active logic valve 41 is reliably opened.

[0047] The tank pipeline 62 is connected to the tank connection of the switching pilot valve 52, and the inlet connection of the switching pilot valve 52 is connected to the control pressure medium accumulator SD1 via pipeline 64. By energizing the switching magnet of the switching pilot valve 52, the switching pilot valve 52 can be displaced against spring force to the switching position in which the annular control chamber defined by surface A4 of the active logic valve 41 is connected to the low-pressure accumulator ND1 via pipeline 64. As a result, the main piston 60 lifts from the valve seat 58 based on the pressure acting on the annular end face A4, and controls the fluid connection between connections A and B to open.

[0048] The active logic valve 41 is configured to allow flow with minimal pressure loss and to close with the shortest switching time and high repeatability when controlled via the switching pilot valve 52. The stroke of the active logic valve 41 can be limited to optimize subsequent closing behavior. This configuration of the active logic valve 41 requires only a small amount of control oil flow to open and close the active logic valve 41 quickly and with high repeatability, even when the nominal size is large.

[0049] Furthermore, operational reliability is enhanced by the active opening and closing of the active logic valve 41 by the switching pilot valve 52 and the reliable closing of the active logic valve 41 by the accumulator pressure. In this case, the active closing of the active logic valve 41 allows for the free selection of the conditions for closing. This closing can be performed, for example, according to pressure, load force, travel distance, travel speed, etc.

[0050] As illustrated in Figure 2, an additional low-pressure accumulator 57 is provided in addition to the low-pressure accumulator 56. This additional low-pressure accumulator 57 can be connected to the intensifier pressure chamber 28 via a two-port, two-position switching seat valve, hereafter referred to as the accumulator shut-off valve 66, which is pilot-controlled by a pilot control valve 68. Alternatively, and as required by the customer, both low-pressure accumulators 56 and 57 may be combined into one. In this case, in the preloaded basic position of the pilot control valve 68, the pressure of the low-pressure accumulator 56 is supplied to the dorsal chamber of the accumulator shut-off valve 66, which acts to close, and in the switching position, tank pressure is supplied, thereby connecting the accumulator shut-off valve 66 to the low-pressure accumulator 56 in the intensifier pressure chamber 28. Therefore, in the aforementioned switching position, the intensifier 24 is constricted in the support direction.

[0051] Below, we will first describe the functional configuration of the infusion unit 1 shown in Figure 2 during stages I to III as explained at the beginning, and then refer to the components necessary for providing the control pressure medium required for that purpose.

[0052] To prevent pressure waves that would generate a starting shock from being generated in the direction of the injection cylinder 10 during the pre-filling stage, the injection cylinder 10 is pre-pressurized before the start of the pre-filling stage I, before the active logic valve 41, also called the accumulator shut-off valve, is opened. This prevents such a starting shock from mixing the molten material, air, and molten material skin. This mixing would, in undesirablely, lead to pores and inclusions in the injected portion, and ultimately to poor quality or defective products.

[0053] Preloading can be performed in various forms depending on the available pressure medium source. In the illustrated embodiment, when the feed cylinder 10 and the intensifier 24 are in the retracted position, preload can be applied to the annular chamber 15 of the feed cylinder 10 and the intensifier annular chamber 32 of the intensifier 24 to the maximum pump pressure via the hydraulic pump 34 and the preload valve 42 operated to the first switching position a, and via the open check valves 48, 70. In this procedure, the first position switching / proportional valve 27, the second position switching / proportional valve 46, and the third position switching / proportional valve 29 are closed, so that a short circuit to the tank is prevented. The shut-off / preload valve 42 is preferably configured to have a check valve function.

[0054] For the preloading task, the hydraulic pump 34 may be configured as a high-pressure pump up to, for example, 420 bar.

[0055] Alternatively or additionally, intensifiers may be provided for pre-pressurizing the annular chambers 15,32, which would allow the use of less powerful hydraulic pumps. For lower pre-pressurization, the possibility arises to provide generally low-pressure hydraulic pumps or low-pressure regulating pumps.

[0056] In the next step, the molten material shown in Figure 1 is filled into the injection chamber 18 of the injection sleeve 17 through the filling opening 19, initiating the pre-filling stage I. To this end, the hydraulic pump 34 is controlled via a ramp function to pressurize the bottom chamber 14 of the injection cylinder 10 to the value of the accumulator pressure of the low-pressure accumulator 56 via the second switching position b of the shut-off / pre-pressure valve 42. This compresses the fluid contained in the annular chamber 15, causing the injection cylinder 10 to move slowly and slightly without a starting shock against the pre-pressure in the annular chamber 15 until the forces are balanced at the piston 11. Importantly, this control ensures a shock-free assimilation of the pressure in the bottom chamber 14 of the injection cylinder 10 with respect to the pressure in the low-pressure accumulator 56. Subsequently, the low-pressure accumulator 56 can be connected to the bottom chamber 14 via the active logic valve 41 (accumulator shut-off valve), and the low-pressure accumulator 56 can be connected to the intensifier pressure chamber 28 via the accumulator shut-off valve 66.

[0057] This procedure is unnecessary if the pump 34 can generate a sufficiently high pressure. If a sufficiently high preload is applied to the annular chamber 15, the low-pressure accumulator 56 can also be switched to the piston chamber 14 via the active logic valve 41.

[0058] As a result, the first proportional switching valve 27 is controlled via pilot control, so that the pressure medium pushed out of the annular chamber 15 is supplied directly to the bottom chamber 14 in the form of a regenerative circuit. This allows the pouring cylinder 10 to be started and moved softly (regeneratively and controlledly without impact). This accelerates the molten material and moves it toward the mold hollow chamber 21 shown in Figure 1. This continues until the molten material reaches the mold gate and the pre-filling stage I is completed.

[0059] Because the regenerative procedure of the injection cylinder 10 in the pre-filling stage I extracts relatively little pressure medium from the low-pressure accumulator 56, the low-pressure accumulator 56 may be configured with a smaller volume than in a conventional configuration without the regenerative procedure. Furthermore, better resolution of the injection cylinder speed is possible based on the smaller pressure drop caused by the differential circuit and the first position-switching proportional valve 27 which is one or two nominal dimensions smaller, so that the injection cylinder 10 can be moved at a lower speed and with better repeatability.

[0060] Another advantage of the regenerative procedure is that, based on the relatively small pressure loss in the first position-switching proportional valve 27 and the fact that the pressure medium flows out of the annular chamber 15 against the pressure in the low-pressure accumulator 56 rather than against the tank pressure (0 bar), less cavitation and thus less wear occurs in the valve 46, the piston 11 and the casing 13 of the inlet cylinder 10 and the associated control block.

[0061] By controlling the first position-switching proportional valve 27 and the second position-switching proportional valve 46 connected in series with the first position-switching proportional valve 27, the pressure in the bottom chamber 14 can be actively affected in the sense of reducing or releasing pressure. In other words, for example, pressure overshoot in the bottom chamber 14 can be easily reduced through this path.

[0062] Furthermore, the pressure in the bottom chamber 14 can be influenced by a third position-switching proportional valve 29, which can be operated completely independently of the first position-switching proportional valve 27 and the second position-switching proportional valve 46. Based on the independent pressure medium flow paths 23, 44, 25 and valves 27, 46, 29 described above, precise and dynamic adjustment of the pressure in the bottom chamber 14 is achieved.

[0063] As soon as the molten material reaches the mold gate, the primary mold filling process (stage II) begins. If mold filling (injection) is performed with a low mold filling force, a regeneration procedure is then performed. Correspondingly, at the point when the molten material reaches the mold gate, the first position switching proportional valve 27 is displaced, for example, by a jump function, to a position where the pressure medium connection between the annular chamber 15 and the bottom chamber 14 is greatly opened, so that the molten material is injected into the mold 20 at a high injection speed (maximum 10 m / s). In this case, a regeneration procedure is then performed, meaning that the pressure medium pushed out of the annular chamber 15 is supplied to the expanding bottom chamber 14.

[0064] This regenerative procedure has the advantage that, even in stage II, less pressure medium needs to be taken from the low-pressure accumulator 56 than in the conventional configuration.

[0065] When injection is performed with a relatively high mold filling force, the first position-switching proportional valve 27 is brought to its closed position, for example in a jump function, when the molten material reaches the mold gate, thereby interrupting the pressure medium connection between the annular chamber 15 and the bottom chamber 14. In parallel, the second position-switching proportional valve 46 is opened during the process, for example in a jump function, to a predetermined opening cross section toward the tank T. This results in the molten material being injected into the mold cavity chamber 21 at a high injection velocity, but unlike the procedure for low mold filling forces, a regenerative procedure is performed, and therefore the maximum force of the pouring cylinder 10 can be utilized.

[0066] In principle, a mixed configuration is also possible in which the first position switching / proportional valve 27 is displaced to its shut-off position only in stage II in response to the load force.

[0067] Stage II can also be carried out entirely regeneratively. However, this is contingent on the load force required in Stage II being achievable within the regenerative circuit. In this case, the second position-switching proportional valve 46 can be replaced by a valve that switches rapidly to release pressure in the annular chamber 15 in Stage III.

[0068] After the mold cavity 2 is completely filled, the process transitions to stage III for holding pressure. To this end, at the end of mold filling stage II, the third position-switching proportional valve 29 is controlled by pilot control in a direction that opens the connection between the intensifier annular chamber 32 and the tank T. Simultaneously, the second position-switching proportional valve 46 is opened. The resulting pressure release in the intensifier annular chamber 32 accelerates the primary piston 26, and consequently, high pressure is formed in the bottom chamber 14, so high pressure is applied to the piston 11 and the molten material is compressed. When the desired holding pressure is achieved, the second position-switching proportional valve 46 is returned to the closing direction via the pressure control device. If the closing of the second position-switching proportional valve 46 is not performed quickly enough, the pressure overshoot in the bottom chamber 14 can be eliminated by opening the aforementioned pressure release path, i.e., the position-switching proportional valves 27 and 46 leading to the tank T.

[0069] The active logic valve 41 can be replaced by a shut-off valve and an external check valve.

[0070] The above description has shown that, for high quality of the pour-molded product, the force control and speed control of pistons 11 and 26 must have high precision and dynamics. The valves important for this control are, in particular, the hydraulically operated valves 27, 29, 41 and 46, and control pressure medium accumulators SD1 and SD2 are provided to supply the control pressure medium to these valves 27, 29, 41 and 46. The functionality and operation of the valves 27, 29, 41 and 46 have already been described.

[0071] The control surfaces 74, 76, and 78 of valves 27, 29, and 46, respectively, can be connected to the control pressure medium accumulator SD2 via the control pressure medium pipelines 80, 82, and 84, respectively. Surface A4 can be connected to the control pressure medium accumulator SD1 via pipeline 64 and the switching pilot valve 52, as described above.

[0072] The requirements for the control pressure medium supply are as follows: In order to open the active logic valve 41 by applying a load to surface 4 as described above, a control pressure of at least 20 bar, and 30 bar in the illustrated embodiment, is required, which is above the pressure in the low-pressure accumulators 56, 57 under which stages II and III of the infusion process are controlled.

[0073] In this regard, the higher the control pressure supplied to valves 27, 29, and 46, the better the opening and closing dynamics (step response time) of these valves that can be achieved in stages I, II, and III.

[0074] In conventional solutions, the control pressure medium accumulator is pressurized via a hydraulic pump 34 or another suitable hydraulic pump. Therefore, the maximum achievable control pressure depends on the maximum pressure these hydraulic pumps can generate. Since high control pressure enables high precision and dynamics of force and speed control, these hydraulic pumps must be able to cover this high pressure, which is energy-intensive and costly.

[0075] Therefore, according to the present invention, the control pressure medium accumulators SD1 and SD2 can be pressurized in a different manner. For this purpose, according to the present invention, a pressurization path 86 is provided, and through this pressurization path 86, the annular chamber 15 of the inlet cylinder 10 can be fluidly connected to a branch 88 to the control pressure medium accumulator SD1 and a branch 90 to the control pressure medium accumulator SD2. Within the pressurization path 86, a two-position switching valve 92 and an adjustable throttling device 94 are fluidly connected in series before the branch. Each branch 88 and 90 has one pressure reducing valve 96 and 98, respectively, and through these pressure reducing valves 96 and 98, the existing pressure can be adjusted to and thus limited to the control pressure required in the respective control pressure medium accumulators SD1 and SD2. Alternatively, each control pressure medium accumulator SD1 and SD2 may be correspondingly configured with a pressurization path equipped with a two-position switching valve and an adjustable throttling device connected in series.

[0076] If the same control pressure is required in both control pressure medium accumulators SD1 and SD2, a single pressure reducing valve may be provided in the boosting path 86 instead. If it is specified that the control pressure medium can be taken individually from each of the control pressure medium accumulators SD1 and SD2, one check valve can be provided at each of the branching sections 88 and 90. Such check valves are not necessarily required if the control pressure medium is always taken simultaneously from both control pressure medium accumulators SD1 and SD2.

[0077] Therefore, according to the present invention, the pressure increase of the control pressure medium accumulators SD1 and SD2 can be achieved via the annular chamber 15 of the flow cylinder. In this case, the area ratio of the bottom operating surface to the rod-side operating surface of the piston 11 acts like a pressure intensifier, so that the relatively high pressure in the annular chamber 15, and consequently the control pressure in each of the control pressure medium accumulators SD1 and SD2, can be achieved via the relatively low pressure in the bottom chamber 14. Such an area ratio is approximately between 1.5 and 2.5-3, and the corresponding pressure increase can be caused based on this area ratio. In other words, a high control pressure can be obtained indirectly depending on the pressure in the bottom chamber by a hydraulic pump 34 that increases the pressure relatively little, and this control pressure is provided to valves 27, 29, 41 and 46 or another valve for the high dynamics and precision of the control required.

[0078] A flow cycle can be used to increase the pressure of the control pressure fluid accumulators SD1 and SD2. Multiple variations of the procedure for increasing the pressure can be used individually or in combination. -First possibility: After the above-mentioned pre-pressurization of the inlet cylinder 10 and intensifier 24, the pressure medium is supplied to the bottom chamber 14 and pressurized to a pressure that can be provided by the hydraulic pump 34. To this end, the hydraulic pump 34 delivers the pressure medium to the bottom chamber 14 via the pre-pressure valve 42, which is operated to switching position b, and via the check valve 72. As a result, the piston 11 slowly starts moving, and with the position switching valve 92 and the throttling device 94 of the pressurization path 86 open, the pressure medium flows from the annular chamber 15 of the inlet cylinder to the control pressure medium accumulators SD1 and SD2 via the pressure reducing valves 96 and 98. The control pressure thus achieved is higher than the pressure that can be provided into the bottom chamber 14 by the hydraulic pump 34, depending on the area ratio (annular surface to piston surface) in the piston 11, and can be reduced via the pressure reducing valves 96 and 98 if desired. -Another possibility is to increase the pressure of the control pressure medium accumulators SD1,SD2 via the pressure boosting path 86 during the regenerative procedure (pre-filling stage) of the inlet cylinder 10. To do this, the two-position switching valve 92 is opened, and during the regenerative procedure of the piston 11, the control pressure medium accumulators SD1,SD2 are increased in pressure via the adjustable throttling device 94 and pressure reducing valves 96,98. - Another possibility is to increase the pressure of the control pressure medium accumulators SD1,SD2 via the boosting path 86 during the mold filling or injection stage. In this case, the control pressure medium accumulators SD1,SD2 can be increased to the control pressure generated in the annular chamber 15 during injection. -Another possibility is that by controlling the (discharge) valve 46 to close, a stage is provided in which the piston 11 is braked before reaching the terminal position during "ejection". This increases the pressure in the annular chamber 15, which can boost the control pressure medium accumulators SD1,SD2 via the boost path 86.

[0079] You can also choose a combination from these possibilities.

[0080] The applicant has the right to seek a patent or establish an independent claim for such a procedure for boosting the pressure of at least one control pressure medium accumulator and / or for a method of controlling a feeding unit including such boosting.

[0081] The valve 27 allows for adjustment of the piston 11 speed during the pre-filling stage, compensating for volumetric flow rate changes when the control pressure medium accumulators SD1 and SD2 are pressurized.

[0082] Disclosed is a hydraulic control device for a casting unit for a primary molding machine, wherein the casting cylinder of the hydraulic control device is capable of controlling the force and speed during the casting phase over time via a hydraulically operable valve device. The provision of the control pressure medium is achieved via a pressurized pressure medium accumulator or a pressurized pressure medium reservoir. According to the present invention, a pressurizing path is provided from the annular chamber of the casting cylinder to the pressure medium accumulator or pressure medium reservoir, so that the pressure increase of the piston of the casting cylinder is utilized for pressurization, and the pressure medium source provided for pressurization may have a low pressure level.

Claims

1. A hydraulic control device for the injection molding machine's injection unit (1), A flow cylinder (10) having a rod-side operating chamber (15) and a bottom-side operating chamber (14) separated by a piston, wherein the piston has a bottom-side operating surface and a rod-side operating surface smaller than the bottom-side operating surface, A hydraulically operable valve device (27, 29, 41, 46) is provided, via the valve device (27, 29, 41, 46), the piston force and piston speed are controllable in multiple stages (I, II, III) of the infusion process by selective connection of the operating chamber (14, 15) to and / or to the pressure medium source (34) and the pressure medium tank (T). Equipped with, A hydraulic control device is provided with at least one pressurized control pressure medium accumulator (SD1, SD2), and the control pressure medium is available via the control pressure medium accumulator (SD1, SD2) to hydraulically operate the valve devices (27, 29, 41, 46), A hydraulic control device characterized in that the rod-side operating chamber (15) is equipped with a pressure boosting path (23, 86, 88, 90) to which the fluid can be connected to at least one control pressure medium accumulator (SD1, SD2) for the purpose of boosting pressure.

2. The control device according to claim 1, wherein the fourth valve (41) of the valve device (27, 29, 41, 46) is configured as an active logic valve (41), and the bottom operating chamber (14) can be fluidly connected to the pressure medium accumulator (56) via the active logic valve (41) without relying on the pressure medium source (34).

3. The control device according to claim 2, wherein the rod-side operating chamber (15) can be connected to the bottom-side operating chamber (14) via a first valve (27) of the valve device (27, 29, 41, 46) via a first flow path (23).

4. The control device according to claim 3, comprising at least two control pressure medium accumulators (SD1, SD2), wherein one control pressure medium accumulator (SD1) is capable of supplying the control pressure medium to the first valve (27), and the other control pressure medium accumulator (SD2) is capable of supplying the control pressure medium to the fourth valve (41).

5. The control device according to any one of claims 2 to 4, wherein the rod-side operating chamber (15) can be fluidly connected to the pressure medium tank (T) via a second valve (46) of the valve device (27, 29, 41, 46) via a second flow path (44).

6. The control device according to claim 5, comprising at least two control pressure medium accumulators (SD1, SD2), wherein one control pressure medium accumulator (SD1) is capable of supplying the control pressure medium to the second valve (46), and the other control pressure medium accumulator (SD2) is capable of supplying the control pressure medium to the fourth valve (41).

7. The control device according to any one of claims 2 to 6, comprising a hydraulic pressure intensifier (24) designed to increase the pressure in the bottom operating chamber (14) during the pressure holding phase, wherein a third pressure medium flow path opening to the pressure chamber (32) of the pressure intensifier (24) can be controlled to open or formed via a third valve (29) of the valve device (27, 29, 41, 46) for the operation of the pressure intensifier (24).

8. The control device according to claim 7, comprising at least two control pressure medium accumulators (SD1, SD2), wherein one control pressure medium accumulator (SD1) is capable of supplying the control pressure medium to the third valve (29), and the other control pressure medium accumulator (SD2) is capable of supplying the control pressure medium to the fourth valve (41).

9. The control device according to any one of claims 1 to 8, wherein a shut-off valve (92) is provided in the boosting path (86).

10. The control device according to any one of claims 1 to 9, wherein an adjustable throttle device (94) is provided in the boost path (86).

11. The control device according to any one of claims 1 to 10, wherein the boost path (86) branches to a plurality of control pressure medium accumulators (SD1, SD2) (88, 90).

12. A control device according to any one of claims 1 to 11, wherein a pressure regulating valve (96, 98) is correspondingly located on at least one of the control pressure medium accumulators (SD1, SD2), and / or the control pressure of one or two of the control pressure medium accumulators can be determined via the nominal pressure in the bottom operating chamber and the area ratio in the piston of the flow cylinder.

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