Hydraulic drive unit and forming machine

Abstract

The present invention relates to a hydraulic drive device for a molding machine, which comprises: a first hydraulic pump; a drive motor; a consumer; a hydraulic pipeline system; a control unit, which has a first switching element, through which the displacement volume of the first hydraulic pump can be adjusted between a set minimum value and a maximum value depending on a set pressure threshold and / or a set volume flow threshold, wherein a second hydraulic pump is provided, which is connected to the drive motor via a drive shaft; the hydraulic pipeline system connects the second hydraulic pump to the consumer, and the hydraulic pipeline system has a first branch pipeline connected to the first hydraulic pump, a second branch pipeline connected to the second hydraulic pump and a main pipeline, each branch pipeline leading to the main pipeline, and the control unit has a second switching element, through which the displacement volume of the second hydraulic pump can be adjusted between a set minimum value and a maximum value depending on a set pressure threshold and / or a set volume flow threshold.

Description

Technical Field

[0001] The present invention relates to a hydraulic drive for a molding machine, in particular an injection molding machine, comprising a first hydraulic pump; a drive motor connected to the first hydraulic pump via a drive shaft; at least one consumer; a hydraulic line system connecting the first hydraulic pump to the consumer; and a control unit for controlling the hydraulic drive, wherein the control unit comprises a first switching element by which the displacement volume of the first hydraulic pump can be adjusted between a set minimum value and a maximum value depending on a set pressure threshold value and / or a set volume flow threshold value. The present invention also relates to a molding machine having such a hydraulic drive.

[0002] Hydraulic drives are used for various purposes in molding machines. For example, they can be used to drive closing units, ejectors, or components of the injection system. Typically, consumers in the form of piston-cylinder units are used for this purpose. Background Art

[0003] An example of an electrohydraulic control device for controlling a hydraulic consumer is known from DE 10 2007 007 005 A1. Specifically, it involves a main control circuit and a branch circuit. The branch circuit may include a two-point controller, via which the displacement volume of an adjustable fluid pump can be adjusted between a set minimum and maximum value, depending on a set pressure threshold.

[0004] This type of system is well-suited for use with consumers in injection molding machines. However, a challenge can arise in that, depending on the size of the consumer, a matching hydraulic pump and drive motor must also be provided. The drive motor and hydraulic pump must also be capable of handling the maximum load that can be driven by the consumer. The larger the drive motor and hydraulic pump, the higher the manufacturing costs. Furthermore, they must be able to drive relatively high torques and generate relatively high pressures. This results in a cost-intensive and wear-prone design. Summary of the Invention

[0005] The object of the present invention is therefore to provide a hydraulic drive which is improved compared to the prior art, in particular to eliminate or at least reduce the aforementioned disadvantages.

[0006] This is solved by a hydraulic drive for a molding machine, which has:

[0007] First hydraulic pump;

[0008] a drive motor connected to the first hydraulic pump via a drive shaft;

[0009] at least one consumer;

[0010] a hydraulic line system connecting the first hydraulic pump to a consumer; and

[0011] a control unit for controlling a hydraulic drive, wherein the control unit comprises a first switching element, via which the displacement volume of the first hydraulic pump can be adjusted between a set minimum value and a maximum value as a function of a set pressure threshold value and / or a set volume flow threshold value,

[0012] It is characterized in that at least one second hydraulic pump is provided.

[0013] Wherein, the second hydraulic pump is connected to the drive motor via a drive shaft;

[0014] The hydraulic line system connects the second hydraulic pump to the consumer, and the hydraulic line system has a first branch line connected to the first hydraulic pump, a second branch line connected to the second hydraulic pump, and a main line, wherein the first branch line and the second branch line open into the main line, and

[0015] The control unit has a second shift element, via which the displacement volume of the second hydraulic pump can be adjusted between a set minimum value and a maximum value as a function of a set pressure threshold value and / or a set volume flow threshold value.

[0016] Therefore, according to the present invention, it is provided that the second hydraulic pump is connected to the drive motor via a drive shaft. Therefore, the second hydraulic pump is provided on the same drive shaft and is driven by the same drive motor.

[0017] Furthermore, according to the present invention, a hydraulic line system connects the second hydraulic pump to a consumer, and the hydraulic line system comprises a first branch line connected to the first hydraulic pump, a second branch line connected to the second hydraulic pump, and a main line, wherein the first branch line and the second branch line open into the main line. Thus, the second hydraulic pump is used to supply the same consumer as the first hydraulic pump.

[0018] According to the present invention, the control unit also includes a second switching element, via which the displacement volume of the second hydraulic pump can be adjusted between a set minimum and maximum value, depending on a set pressure threshold and / or a set volume flow threshold. Thus, the first and second hydraulic pumps can be switched on independently of one another. Under high loads, the first and second hydraulic pumps can jointly achieve a correspondingly higher power output for the consumers to be driven; even under low required loads, just one hydraulic pump may be sufficient.

[0019] Overall, this makes it possible to drive one (or more) relatively large consumers with relatively small drive elements (drive motor and hydraulic pump).

[0020] The minimum and maximum values of the hydraulic pumps (for example according to the size of the individual pumps) can be different. These values can also be different in equally large hydraulic pumps.

[0021] For still more diverse switching possibilities, and if there is a consumer-based requirement, a third hydraulic pump can be provided, wherein the third hydraulic pump is connected to the drive motor via a drive shaft; a hydraulic line system connects the third hydraulic pump to the consumer, and the hydraulic line system has a third branch line, which is connected to the third hydraulic pump and opens into the main line; and the control unit has a third switching element, via which the displacement volume of the third hydraulic pump can be adjusted between a set minimum value and a maximum value, depending on a set pressure threshold value and / or a set volume flow threshold value.

[0022] In order to avoid the need for relatively expensive continuous controllers, a preferred embodiment provides that the switching elements together form a two-point controller. A two-point controller is a discontinuously operating controller with two output states. Two-point controllers are used when the manipulated variable is not continuously variable but can only be switched between two states, for example, on / off or minimum / maximum.

[0023] For the hydraulic pumps, it can preferably be provided that at least one of the hydraulic pumps, preferably all of the hydraulic pumps, has a maximum delivery volume of 250 cm 3 , preferably between 25 and 200 cm 3 between 45 and 180 cm, particularly preferably between 45 and 180 cm 3 between.

[0024] It is possible that the individual hydraulic pumps are designed to be of different sizes or for different maximum delivery volumes. Thus, for example, the first hydraulic pump can be a larger main pump.

[0025] However, for the sake of simpler production and more favorable purchase, it is provided that all hydraulic pumps have the same size or exert the same power. Therefore, the hydraulic pumps are constructed to be essentially the same.

[0026] According to a preferred embodiment, it is provided that the drive motor is designed as a servomotor, preferably with a maximum power of 300 kW, particularly preferably with a power of between 40 and 250 kW.

[0027] The drive device of the present invention does not form a closed system. Accordingly, it can be provided that the hydraulic pump switches to the tank when a set minimum value.

[0028] It is possible that the consumer is designed as a hydraulic rotary motor. However, it is preferably provided that the consumer is designed as a hydraulic piston-cylinder unit.

[0029] Furthermore, it can be provided that the drive motor drives two or more consumers via the hydraulic line system with the at least two hydraulic pumps. Corresponding switching elements can then be provided here for switching between the consumers or for simultaneous driving.

[0030] For better operation and more diverse adjustment possibilities, it can be provided that a directional control valve is provided in the main line of the hydraulic line system, preferably the directional control valve also forming the control unit.

[0031] Furthermore, it is preferably provided that the control unit has a measuring device for measuring the hydraulic pressure and / or volume flow in the main line. If necessary, the measuring device can also be designed to measure the relative position of the piston of the piston-cylinder unit.

[0032] Protection is also claimed for a molding machine having a hydraulic drive according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Further details and advantages of the present invention are explained in more detail below with reference to the exemplary embodiments shown in the drawings, with the aid of the description of the drawings.

[0034] Figure 1 Schematic representation of a hydraulic drive having a drive motor, a hydraulic pump, a hydraulic line system, a control unit and consumers;

[0035] Figure 2 The drive device is shown schematically and simplified;

[0036] Figure 3 Schematically illustrates a hydraulic drive arrangement in which a hydraulic pump is switched to a tank;

[0037] Figure 4-Figure 6 showing a graph with maximum torque and effective moment; and

[0038] Figure 7-Figure 8 A volume-pressure graph with different control lines is shown. DETAILED DESCRIPTION

[0039] Figure 1 The hydraulic drive 1 is schematically shown and includes a drive motor M and a drive shaft 2 rotatably driven by the drive motor M.

[0040] The first hydraulic pump P1 and the second hydraulic pump P2 are driven via the drive shaft 2. If necessary, the third hydraulic pump P3 (and further hydraulic pumps if required) can also be connected to the same drive shaft 2.

[0041] Hydraulic pumps P1, P2, and P3 are designed as variable displacement pumps and can be adjusted between two positions (indicated by two arrows). In one position (corresponding to the maximum value), hydraulic fluid is delivered to the hydraulic line system 4. In the other position (corresponding to the minimum value), no hydraulic fluid is delivered or a volume less than the maximum value is delivered (or, if necessary, returned to the tank T). In other words, there are three possibilities for the other (second) position: a delivery volume less than the maximum value, no delivery volume at all, or delivery of hydraulic fluid to the tank.

[0042] The hydraulic pipeline system 4 has a first branch pipeline 41 branching from the first hydraulic pump P1, a second branch pipeline 42 branching from the second hydraulic pump P2 (a third branch pipeline 43 branching from the third hydraulic pump P3 if necessary) and a main pipeline 40, and each branch pipeline 41, 42 (43 if necessary) flows into the main pipeline.

[0043] On or in the hydraulic pumps P1, P2 and P3, respectively, are provided respective switching elements S1, S2 and S3 of the control unit 5. Via these switching elements S1, S2 and S3, the displacement volume V of the respectively associated hydraulic pumps P1, P2 and P3 can be adjusted between a set minimum value and a set maximum value, depending on a set pressure threshold value Ps and / or a set volume flow threshold value Vs.

[0044] A directional control valve 7 is arranged in the main line 40. In the concrete case, the directional control valve 7 is designed as a 4 / 3 valve and is in the closed position C.

[0045] The consumer 3 is designed as a piston-cylinder unit and comprises a cylinder 30, a piston 31 linearly movable in the cylinder 30, a piston rod 32, a piston-side chamber 33, and a rod-side chamber 34. A piston-side line 44 of the hydraulic line system 4 leads into the piston-side chamber 33, while a rod-side line 45 leads into the rod-side chamber 34.

[0046] If the reversing valve 7 (different from Figure 1 As shown) is in the first open position A (left part of the symbol), the hydraulic fluid is then delivered through the reversing valve 7 and the piston-side line 44 to the piston-side chamber 33 of the consumer 3, which is configured as a piston-cylinder unit, and the piston 31 moves to the right relative to the cylinder 30.

[0047] If, on the other hand, the directional valve 7 is in the second open position B (right side of the symbol), the hydraulic fluid is conveyed via the directional valve 7 and the rod-side line 45 into the rod-side chamber 34 of the consumer 3 , and the piston 31 moves to the left relative to the cylinder 30 .

[0048] A measuring device 6 is provided in the main line 40 . The hydraulic pressure p or the displacement volume V can be measured by means of this measuring device 6 . Alternatively or additionally, the measuring device 6 can be arranged in one of the lines 44 or 45 .

[0049] Figure 1 The control unit 5 is shown schematically. The signal connections between the main control components of the control unit 5 and the individual further components, such as the switching elements S1 , S2 , S3 , the directional valve 7 , the measuring device 6 , the drive motor M, etc., are not shown.

[0050] The control unit 5 can be connected to a higher-level molding machine controller (not shown) for signaling purposes or can be an integrated part thereof.

[0051] The control unit 5 has access to a set pressure threshold value Ps or a set volume flow threshold value Vs. The hydraulic pressure p measured in real time by the measuring device 6 and / or the volume flow measured in real time are compared with the matching values. If the threshold values (Ps and / or Vs) are exceeded, one of the hydraulic pumps P1, P2 and / or P3 is switched. If, for example, more volume flow is required, one of the hydraulic pumps P1, P2 or P3 is switched to the maximum value. The more volume flow is required, the more hydraulic pumps P1, P2, P3 are switched to the maximum value. If a higher hydraulic pressure is required, at least one hydraulic pump P1, P2, P3 must be switched to the minimum value. The higher the required pressure, the more hydraulic pumps P1, P2, P3 are switched to the minimum value.

[0052] Figure 2 A hydraulic drive 1 with the same operating principle is shown again in a more simplified form.

[0053] according to Figure 3 A possible expansion is to switch one (or more) hydraulic pumps P2 to the tank, while the other pumps P1 are in pressure control. This results in a lower load on the drive motor M. The amount flowing to the tank T is relatively small. Small volumes can be driven at lower speeds.

[0054] It can be seen that the present invention makes it possible to "miniaturize" the drive motor M. It is not necessary to use an overly large drive motor M. Instead, it is sufficient to connect multiple hydraulic pumps P1, P2 (P3) to the (small) drive motor M via the drive shaft 2 and form a system circuit using switching elements S1, S2 (S3). Each hydraulic pump P1, P2 (P3) forms a two-point controller with its associated switching element S1, S2 (S3). Since two hydraulic pumps P1 and P2 drive one consumer 3, a four-point controller is approximately provided by four switching positions. If a third hydraulic pump P3 with an associated switching element S3 is also provided, an eight-point controller is generated based on the eight possible switching position combinations. This allows for better utilization of the drive and adaptation to the consumer 3. For example, two (or three) smaller hydraulic pumps can be used instead of one large hydraulic pump.

[0055] This embodiment will be explained by way of example with the help of the following table:

[0056]

[0057] The first column of the diagram shows two possible pivot angles for the first hydraulic pump P1. Specifically, in the first (maximum) switching position, the first hydraulic pump P1 can deliver a maximum delivery rate (of the displacement volume V) of 100% (maximum value 100), and in the second (minimum) switching position, a minimum delivery rate (V) of 50% of the displacement volume (minimum value 50). The second hydraulic pump P2 (second column of the diagram) is designed so that it can deliver at a maximum of 100% and a minimum of 25%.

[0058] As can be seen from the first two columns, this results in a total of four combinations of switching positions. Each of these switching position combinations is particularly well suited to the specific movement of the consumer 3. The precisely required amount is achieved through speed adaptation. In other words, the ranges are selected via the four switching positions, but the precisely required amount is achieved through speed control.

[0059] If the two hydraulic pumps P1 and P2 are operated to 100% of the maximum value via their respective switching elements S1 and S2, a forming movement is performed by the hydraulically driven consumer 3, which takes place at an exemplary pressure of 40% of the maximum value and an exemplary delivery volume of 100% (compare the third, fourth and fifth columns of the table).

[0060] If the first hydraulic pump P1 is adjusted to a minimum value of 50% and the second hydraulic pump P2 is adjusted to a maximum value of 100%, metering via the consumer 3 occurs at a pressure of 65% and a delivery volume of 65%.

[0061] If the first hydraulic pump P1 is adjusted to a maximum value of 100% and the second hydraulic pump P2 is adjusted to a minimum value of 25%, injection via the consumer 3 takes place at a pressure of 80% and a delivery volume of 50%.

[0062] If the first hydraulic pump P1 is adjusted to a minimum value of 50% and the second hydraulic pump P2 is adjusted to a minimum value of 25%, high pressure generation occurs via the consumer 3 at a pressure of 100% and a delivery rate of 35%.

[0063] This results in a total of a four-point controller.

[0064] If the third hydraulic pump P3 is also switched on, an even finer division and a total of an eight-point controller are produced due to the eight possible combinations of the switching positions.

[0065] Figure 4 The maximum torque D of the drive motor M is shown max and the effective torque D of the drive motor M eff The vertical axis of the line graph is the torque in Newton meters (Nm), and the horizontal axis is the motor speed per minute (U / min). eff It can also be called continuous torque and corresponds to the sum of all operating points or the average power of the drive motor M within a cycle. Point X represents, by way of example, an operating point with a short-term maximum load. Point L high and L low Specifically, by using two hydraulic pumps P1 and P2, the load point L high Move to load point L low On the load point L high Corresponding to a specific load point in the hydraulic pump according to the prior art, the load point L low The effective torque D at the drive motor M eff As a result, the speed (U / min) increases, while the torque (Nm) decreases. In other words, one of the hydraulic pumps P1 or P2 pivots back, whereby the torque decreases and the speed increases. This change also affects the effective torque point E of the drive motor. high and E low If the effective torque point E is generated high (Load point L high This is the case), then in fact it is necessary to increase the drive motor M or extend the cycle time so that the process can be completed completely. By means of the present invention, it is possible to maintain the effective torque line D eff Next, this is done by the effective moment point E low As shown. This has a positive impact on the design, the effective moment D eff reduce.

[0066] Figure 5and Figure 6 A comparison graph is shown, both with maximum torque D max and effective torque D eff Furthermore, operating points with different geometries are shown, which correspond to different movements of the consumer. In accordance with the diagram provided and explained above, the circles correspond to the molding movement, the squares to the dosing, the diamonds to the injection, and the triangles to the high pressure generation. Figure 5 As shown, by means of the additional switching position, it is achieved when moving with a large delivery volume and a medium pressure operating point: the operating point for dosing and injection is located at the maximum torque D max Therefore, "miniaturization" is also shown here. It can be seen that the drive motor M cannot be selected using a single two-point controller. The operating point can be moved to the motor characteristic line using a four-point controller.

[0067] Figure 7 The graph also shows a comparison of a constant pump, a controlled pump, a two-point controller, a three-point controller and a four-point controller. The horizontal axis of the graph is the pressure in percentage (bar), while the vertical axis is the delivery volume in percentage (cm 3 In constant-flow pumps (not according to the invention), the maximum delivery volume and maximum pressure are always design-dependent. Controlled pumps (not according to the invention) produce relatively straight control curves, but such controlled pumps are relatively complex and cost-intensive. In contrast, a multipoint controller can be used to activate multiple switching points.

[0068] at last, Figure 8 It also shows something like Figure 7 , in which the control lines of the two-point controller and the four-point controller are linked to the explained operating point or movement of the consumer 3 .

[0069] Reference Signs List

[0070] 1Hydraulic drive unit

[0071] 2 drive shafts

[0072] 3 Consumers

[0073] 30 cylinder block

[0074] 31 Piston

[0075] 32 piston rod

[0076] 33 Cavity on the piston side

[0077] 34 Rod side cavity

[0078] 4Hydraulic piping system

[0079] 40 Main Road

[0080] 41 First branch pipeline

[0081] 42 Second branch pipeline

[0082] 43 Third branch pipeline

[0083] 44 Pipeline on the piston side

[0084] 45 Rod side piping

[0085] 5Control Unit

[0086] 6. Measuring device

[0087] 7. Directional valve

[0088] P1 First hydraulic pump

[0089] P2 Second hydraulic pump

[0090] P3 third hydraulic pump

[0091] S1 First switching element

[0092] S2 Second switching element

[0093] S3 third switching element

[0094] M drive motor

[0095] V displacement volume

[0096] Ps pressure threshold

[0097] Vs Volume flow threshold

[0098] T tank

[0099] pHydraulic pressure

[0100] AFirst open position

[0101] B Second open position

[0102] C closed position

[0103] D max Maximum torque

[0104] D eff Effective torque

[0105] X Maximum operating point

[0106] L high Point of Load

[0107] L low Point of Load

[0108] Ehigh Effective torque point

[0109] E low Effective torque point

Claims

1. A hydraulic drive device (1) for a molding machine, comprising: a first hydraulic pump (P1); a drive motor (M) connected to the first hydraulic pump (P1) via a drive shaft (2); at least one consumer (3); a hydraulic line system (4) connecting the first hydraulic pump (P1) to the consumer (3); and A control unit (5) for controlling a hydraulic drive (1), wherein: The control unit (5) has a first switching element (S1) by means of which the displacement volume (V) of the first hydraulic pump (P1) can be adjusted between a set minimum value and a maximum value depending on a set pressure threshold value (Ps) and / or a set volume flow threshold value (Vs). Characterized in that at least one second hydraulic pump (P2) is provided, The second hydraulic pump (P2) is connected to the drive motor (M) via a drive shaft (2). The hydraulic pipeline system (4) connects the second hydraulic pump (P2) to the consumer (3), and the hydraulic pipeline system comprises a first branch pipeline (41) connected to the first hydraulic pump (P1), a second branch pipeline (42) connected to the second hydraulic pump (P2), and a main pipeline (40), wherein the first branch pipeline (41) and the second branch pipeline (42) are connected to the main pipeline (40), and The control unit (5) has a second switching element (S2), by means of which the displacement volume (V) of the second hydraulic pump (P2) can be adjusted between a set minimum value and a maximum value, depending on a set pressure threshold value (Ps) and / or a set volume flow threshold value (Vs).

2. The drive device (1) according to claim 1, characterized in that The molding machine is an injection molding machine.

3. The drive device (1) according to claim 1 or 2, characterized in that There is a third hydraulic pump (P3), The third hydraulic pump (P3) is connected to the drive motor (M) via a drive shaft (2). The hydraulic line system (4) connects the third hydraulic pump (P3) to the consumer (3), and the hydraulic line system has a third branch line (43) which is connected to the third hydraulic pump (P3) and opens into the main line (40), and The control unit (5) has a third switching element (S3), by means of which the displacement volume (V) of the third hydraulic pump (P3) can be adjusted between a set minimum value and a maximum value, depending on a set pressure threshold value (Ps) and / or a set volume flow threshold value (Vs).

4. The driving device according to claim 3, characterized in that The first switching element (S1), the second switching element (S2) and the third switching element (S3) respectively form together a two-point controller.

5. The driving device according to claim 3, characterized in that At least one of the first hydraulic pump (P1), the second hydraulic pump (P2), and the third hydraulic pump (P3) has a maximum delivery volume of 250 cm 3 .

6. The driving device according to claim 5, characterized in that All of the first hydraulic pump (P1), the second hydraulic pump (P2), and the third hydraulic pump (P3) have a maximum delivery volume of 250 cm 3 .

7. The driving device according to claim 5, characterized in that At least one of the first hydraulic pump (P1), the second hydraulic pump (P2), and the third hydraulic pump (P3) has a maximum delivery volume of 25 to 200 cm 3 between.

8. The driving device according to claim 5, characterized in that At least one of the first hydraulic pump (P1), the second hydraulic pump (P2), and the third hydraulic pump (P3) has a maximum delivery volume of 45 to 180 cm 3 between.

9. The driving device according to claim 1 or 2, characterized in that: The drive motor (M) is designed as a servo motor.

10. The driving device according to claim 9, characterized in that The servo motor is a servo motor having a maximum power of 300 kilowatts.

11. The driving device according to claim 10, characterized in that: The servomotor is a servomotor having a power of between 40 and 250 kW.

12. The driving device according to claim 3, characterized in that At least one of the first hydraulic pump (P1), the second hydraulic pump (P2) and the third hydraulic pump (P3) is switched to the tank (T) at a set minimum value.

13. The driving device according to claim 1 or 2, characterized in that: The consumer (3) is designed as a hydraulic piston-cylinder unit.

14. The driving device according to claim 1 or 2, characterized in that: A reversing valve (7) is provided in the main pipeline (40) of the hydraulic pipeline system (4).

15. The driving device according to claim 14, characterized in that The reversing valve together forms the control unit (5).

16. The driving device according to claim 1 or 2, characterized in that: The control unit (5) has a measuring device (6) for measuring the hydraulic pressure (p) and / or the volume flow in the main line (40).

17. The driving device according to claim 1 or 2, characterized in that: The control unit (5) is configured such that the first switching element (S1) and the second switching element (S2) together form a two-point controller, wherein four different combinations of the switching positions of the first switching element (S1) and the second switching element (S2) are generated.

18. The driving device according to claim 3, characterized in that The control unit (5) is configured so that the first switching element (S1), the second switching element (S2) and the third switching element (S3) respectively form a two-point controller together, wherein eight different combinations of the switching positions of the first switching element (S1), the second switching element (S2) and the third switching element (S3) are generated.

19. A forming machine comprising a hydraulic drive (1) according to any one of claims 1 to 18.

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