drive unit

Abstract

A drive unit is provided for driving the stroke motion of a moving frame. The drive unit includes a first actuation device for performing rapid stroke motion, a second actuation device for performing working stroke motion, and a control device. The first actuation device includes a mechanically driven actuator. The second actuation device includes a hydraulically driven linear actuator. The mechanically driven actuator and the hydraulically driven linear actuator are coupled to each other to move as a single unit. The control device controls the first and second actuation devices.

Description

[0001] The technical field of this invention The present invention relates to a drive unit for driving stroke motion, a machine (particularly a press, bending machine or punch press) including the drive unit, and a method for operating the drive unit.

[0002] Instructions for background technology Drive units for propelling stroke motion are used in a wide variety of applications and purposes, such as presses, bending machines, or punch presses. In the context of such applications, drive units are designed to drive the stroke motion of a moving frame that holds a corresponding tool according to a specific work cycle. That is, a high-speed, low-force rapid stroke motion and a low-speed, high-force working stroke motion. Rapid stroke motion, requiring high speed and low force, is used when the moving frame and tool move onto and off the workpiece. Working stroke motion, requiring low speed and high force, is used during workpiece forming or machining.

[0003] Conventionally, hydraulic drive units are used in the above applications, utilizing hydraulic cylinders to drive the stroke motion. To meet the different requirements of rapid stroke motion and working stroke motion, at least two hydraulic cylinders with different piston surfaces are provided. Specifically, hydraulic cylinders with relatively large piston surfaces are used for working stroke motion requiring low speed and high force, while hydraulic cylinders with relatively small piston surfaces are used for rapid stroke motion requiring high speed and low force. To keep the design of such hydraulic drive units relatively simple and ensure smooth interaction between hydraulic cylinders, various hydraulic circuit designs have been proposed in the prior art (e.g., in EP 2 480 405 B1, EP 2 637 852 B1, and DE 10 2021 121 461 A1).

[0004] However, with the ongoing need to reduce costs, maintenance, and energy consumption to improve the overall efficiency of machines employing such drive units, there remains a need to reduce the complexity of these drive units while providing excellent operational characteristics.

[0005] Technical problems to be solved In view of the above, the object of the present invention is to provide a drive unit for driving stroke motion, which has reduced complexity while providing excellent operating characteristics. Summary of the Invention

[0006] This objective is achieved by a drive unit having the features of independent claim 1. A machine including a drive unit (particularly a press, bending machine, or punch press) is the subject of claim 14. A method for operating the drive unit is the subject of claim 15. Further advantageous developments are set forth in the dependent claims.

[0007] According to the present invention, a drive unit for driving the stroke motion of a moving frame includes a first actuation device for performing rapid stroke motion, a second actuation device for performing working stroke motion, and a control device. The first actuation device includes a mechanically driven actuator. The second actuation device includes a hydraulically driven linear actuator. The mechanically driven actuator and the hydraulically driven linear actuator are coupled to each other to move as a single unit. The control device is configured to control the first and second actuation devices.

[0008] In other words, according to the present invention, two different technologies are combined for driving stroke motion. A first actuation device, including a mechanically driven actuator, can be used to perform rapid stroke motion requiring high speed and low force. Because high force is not required, this allows for determining the motor size and selecting a low-power motor to drive the mechanically driven actuator. Additionally, the gear ratio can be reduced to achieve the required high speed. A second actuation device, including a hydraulically driven linear actuator, can be used to perform working stroke motion requiring low speed and high force. Because high speed is not required, this allows for determining the motor size and selecting a low-power motor to drive the hydraulically driven linear actuator. The amount of hydraulic fluid required to drive the hydraulically driven linear actuator can be minimized.

[0009] According to the present invention, the efficiency, high accuracy, and low noise characteristics of two different technologies are combined. Compared with conventional hydraulic solutions, the complexity of the hydraulic circuit can be reduced by eliminating the need for additional tanks and pre-filled valves. Furthermore, the power required for installation can be reduced.

[0010] In order to perform rapid stroke motion, the control device can be configured to control a first actuator to drive the stroke motion and to control a second actuator to follow the stroke motion driven by the first actuator while generating minimal resistance.

[0011] In order to perform the working stroke movement, the control device can be configured to control the second actuator to drive the stroke movement, and control the first actuator to follow the stroke movement driven by the second actuator, while generating minimal resistance.

[0012] The control device can be configured to control the first actuation device by means of closed-loop position control or closed-loop speed control.

[0013] The control device can be configured to control the second actuator using closed-loop force control.

[0014] The second actuation device may further include a hydraulic pump, which is controlled by a control device and drives the hydraulically driven linear actuator.

[0015] The hydraulic pump can be an electrically driven hydraulic pump.

[0016] The first actuator may further include an electric motor, which is controlled by a control device and drives the mechanical actuator.

[0017] The first actuator may further include a hydraulic motor, which is controlled by a control device and drives the mechanical actuator.

[0018] The hydraulic motor of the first actuating device can be driven by the hydraulic pump of the second actuating device.

[0019] The first actuation device may include a bypass fluid path, which includes a switching valve controlled by a control device. The bypass fluid path may connect the inlet and outlet ports of a hydraulic motor, thereby bypassing a hydraulic pump.

[0020] Mechanically driven actuators can be actuators including gearboxes, roller screws, inverted roller screws, ball screws, racks and pinions, cranks and nonlinear mechanical levers, or any combination thereof.

[0021] Mechanically driven actuators can be mechanically driven linear actuators.

[0022] A hydraulically driven linear actuator can be a hydraulic cylinder.

[0023] The second actuation device may include a bypass fluid path comprising a switching valve controlled by a control device. The bypass fluid path may connect the inlet and outlet ports of the hydraulic cylinder, thereby bypassing the hydraulic pump.

[0024] Further benefits and advantages of the present invention will become clear from the following detailed description of at least one exemplary embodiment for carrying out the invention, with reference to the accompanying drawings. Attached Figure Description

[0025] In the attached diagram: Figure 1 A schematic diagram of a drive unit according to a first embodiment of the present invention is shown.

[0026] Figure 2 A schematic diagram of a drive unit according to a second embodiment of the present invention is shown.

[0027] Figure 3 A schematic diagram of a drive unit according to a third embodiment of the present invention is shown.

[0028] Figure 4 A schematic diagram of a drive unit according to a fourth embodiment of the present invention is shown. Detailed Implementation

[0029] First Embodiment The following is for reference. Figure 1The first embodiment of the present invention is described.

[0030] like Figure 1 As shown, the drive unit 1 includes a first actuation device 100 and a second actuation device 200. Additionally, the drive unit 1 includes a control device, which is not shown in the accompanying drawings.

[0031] Drive unit 1 drives the travel motion of moving frame 2. Specifically, drive unit 1 causes moving frame 2 to reciprocate in the working direction. Moving frame 2 can be part of a machine used for pressing applications, such as metal forming, stamping, bending, sizing presses, powder metal presses, horizontal or vertical die-clamping applications. Depending on the specific type of pressing application, appropriate tools or die covers can be attached to moving frame 2 to reciprocate with it.

[0032] The first actuator 100 includes an electric motor 110 and a mechanically driven actuator 120.

[0033] The electric motor 110 can be any suitable type, such as an electric servo motor (synchronous permanent magnet, asynchronous, or reluctance type).

[0034] The mechanically driven actuator 120 may be a mechanically driven linear actuator 120. According to this embodiment, the mechanically driven actuator 120 includes a screw 121 and a nut 122 connected to a sliding rod 123. The screw 121 is rotated by an electric motor 110. Torque transmission from the motor to the screw can be achieved via a suitable gearbox, belt, chain, or a combination thereof. The nut engages with the screw to reciprocate as the screw 121 rotates. The nut 122 is connected to the sliding rod 123, which reciprocates with the nut 122 as a unit, thereby performing the stroke motion. Hereinafter, the mechanically driven actuator 120 is referred to as a screw actuator 120.

[0035] The term "mechanically driven" means that the kinetic / reciprocating motion of a mechanically driven actuator is mechanically caused, i.e., caused by parts in physical contact with each other, such as gears, racks, screws, belts, chains, cranks, nonlinear mechanical levers, etc. Specifically, the term "mechanically driven" should be understood to distinguish mechanically driven actuators from other types of linear and nonlinear actuators, in which the reciprocating motion is not mechanically caused, but rather caused, for example, by pressure differences in different fluid chambers of the actuator, such as in the case of hydraulic cylinders ("hydraulically driven") or pneumatic cylinders ("pneumatically driven").

[0036] Accordingly, the mechanically driven actuator 120 is not limited to the screw actuator 120 described above, but can be designed to combine different drive and transmission arrangements and solutions, such as gearboxes, roller screws, inverted roller screws, ball screws, racks and pinions, cranks or nonlinear mechanical levers.

[0037] The second actuation device 200 includes another electric motor 210 that drives a fluid pump 230 and a hydraulically driven linear actuator 220. The fluid pump 230 supplies hydraulic fluid to the hydraulically driven linear actuator 220 via a hydraulic circuit path 240. The hydraulically driven linear actuator 220 may be a double-acting hydraulic cylinder with two fluid inlet-outlet ports. The hydraulic cylinder 220 includes a piston 221, a piston rod 222, and two fluid chambers separated by the piston 221.

[0038] Hydraulic circuit path 240 includes bypass fluid path 250, which directly connects to the two inlet-outlet ports of hydraulic cylinder 220. Bypass fluid path 250 is equipped with a switching valve 260 controlled by a control device. Depending on the state of switching valve 260, bypass fluid path 250 selectively connects to the two inlet-outlet ports of hydraulic cylinder 220 to short-circuit the inlet-outlet ports and bypass fluid pump 230.

[0039] When the bypass fluid path 250 switch valve 260 is in the closed position and the fluid pump 230 is driven by the electric motor 210, a pressure difference is generated between the two fluid chambers, which applies a force to the piston 221, causing the piston 221 and piston rod 222 to reciprocate.

[0040] The sliding rod 123 of the screw actuator 120 is connected to the piston rod 222 of the hydraulic cylinder 220 so that they move as a unit. Specifically, both the sliding rod 123 and the piston rod 222 are connected to the moving frame 2. Therefore, the reciprocating motion of one of the sliding rod 123 and the piston rod 222 is transmitted to the moving frame 2 and to the other of the sliding rod 123 and the piston rod 222.

[0041] Exemplary operation of the drive unit 1 according to the first embodiment is described below.

[0042] At the start of the work cycle, drive unit 1 is in its initial position, which corresponds to its standby position. In the initial position of drive unit 1, the sliding rod 123 of screw actuator 120 and the piston rod 222 of hydraulic cylinder 220 are fully retracted. Typically, the initial position of drive unit 1 corresponds to the state of the machine utilizing drive unit 1, where the corresponding tool or mold cover attached to the moving frame 2 is retracted from the workpiece or the mold cavity is opened.

[0043] In the initial position, the control device actuates the electric motor 110 of the first actuation unit 100 so that it does not rotate, but instead applies a holding torque to the screw actuator 120. Alternatively, a suitable braking mechanism controlled by the control device can be used to prevent the actuators 120 and 220 from reciprocating so that the initial position is maintained as long as no stroke movement is required.

[0044] Furthermore, the electric motor 210 of the second actuation unit 200 is not actuated by the control device, and the switching valve 260 is in the closed position. Therefore, fluid is not supplied to either of the two inlet-outlet ports of the hydraulic cylinder, and the piston rod 222 remains in the retracted position.

[0045] When the control unit receives a corresponding input signal requiring a stroke movement, such as when an operator operates the machine, the control unit first actuates the drive unit to perform a rapid stroke movement. Rapid stroke movements are used, for example, to quickly bring a tool close to a workpiece or to quickly bring a mold cover close to a mold; this requires high speed and low force.

[0046] The rapid stroke movement is primarily driven by the first actuation device. This control device actuates the electric motor 110 of the first actuation device 100 to extend the sliding rod 123. Specifically, the electric motor 110 is actuated to generate torque to rotate the screw, thereby moving the nut and the sliding rod in the extension direction.

[0047] Simultaneously, the control device actuates the switching valve 260 to switch from the closed position to the open position. The open switching valve 260 allows fluid to flow with low resistance between the fluid chambers via the bypass fluid path 250. This allows the piston rod 222 to extend easily by following the stroke movement caused by the extension of the sliding rod 123.

[0048] The control device can additionally actuate the electric motor 210 of the second actuation device 200 to drive the fluid pump 230 in a direction that promotes fluid flow between the fluid chambers. This allows the resistance exerted by the hydraulic cylinder on the rapid stroke driven by the first actuation device 100 to be minimized.

[0049] The rapid stroke is followed by the working stroke. For example, the change from rapid stroke to working stroke is triggered when a tool or mold cover approaches the workpiece or mold to a threshold distance, or by operator input. The working stroke is used, for example, to machine a workpiece with a tool or compress a mold, which requires low speed and high force.

[0050] The working stroke motion is primarily driven by the second actuator 200. The control device terminates the actuation of the electric motor 110 of the first actuator 100 to stop the drive of the rapid stroke motion. The switching valve 260 is actuated to switch to the closed position. The electric motor 210 of the second actuator 200 is actuated to drive the fluid pump 230. The fluid pump 230 generates a pressure difference between the two fluid chambers of the hydraulic cylinder 220, thereby applying force to the piston 221 to further extend the piston rod 222.

[0051] Simultaneously, the control device can additionally actuate the electric motor 110 of the first actuation device 100 to drive the first actuation device 100, thereby following the movement of the second actuation device 200. Specifically, the first actuation device 100 is controlled such that the sliding rod 123 follows the stroke of the piston rod 222. This allows the resistance exerted by the screw actuator 120 on the working stroke movement driven by the second actuation device 200 to be minimized.

[0052] When the working stroke has been completed, that is, when the workpiece processing or molding has been completed, the moving frame 2 retracts from the workpiece or mold toward the initial position.

[0053] Normally, to retract the moving frame 2, the drive unit 1 performs a rapid stroke motion as described above, but in the opposite direction, i.e., away from the workpiece or mold. The reversal of the stroke motion is achieved by reversing the drive direction of the electric motor 110. Therefore, the sliding rod 123 and piston rod 222 retract together with the moving frame 2 to their initial positions, and the work cycle is completed.

[0054] Under certain conditions, the first actuator 100 and the second actuator 200 can be controlled by a control device to cooperate. For example, the first actuator 100 is controlled by closed-loop position control and / or closed-loop speed control, while the second actuator 200 is controlled by closed-loop force control. That is, the pressure in the fluid chamber of the hydraulic cylinder 220 of the second actuator 200 is controlled to unload the resistance experienced by the screw actuator 120 of the first actuator 100.

[0055] Second Embodiment The following is for reference. Figure 2 The second embodiment of the present invention is described below.

[0056] The second embodiment differs from the first embodiment in the type of motor driving the first actuation device 100. Instead of an electric motor 110, a hydraulic motor 170 is provided to rotate the screw 121 of the screw actuator 120.

[0057] The fluid pump 230 of the second actuating device 200 supplies hydraulic fluid to the hydraulic motor 170 via the hydraulic circuit path 140 of the first actuating device 100. The hydraulic circuit path 140 of the first actuating device 100 and the hydraulic circuit path 240 of the second actuating device 200 are connected in parallel. Figure 2 As shown, in order to selectively supply hydraulic fluid to one of the hydraulic circuit paths 140 and 240, each hydraulic circuit path 140 and 240 is provided with a corresponding switching valve in the corresponding supply path and return path. These switching valves are actuated by a control device to actuate a first actuation device 100 by supplying fluid to a hydraulic motor 170, or to actuate a second actuation device 200 by supplying fluid to a hydraulic cylinder 220.

[0058] The hydraulic circuit path 140 of the first actuator includes a bypass fluid path 150 that directly connects to the inlet and outlet ports of the hydraulic motor 170. The bypass fluid path 150 is equipped with a switching valve 160 controlled by a control device. Depending on the state of the switching valve 160, the bypass fluid path 150 selectively connects to the inlet and outlet ports of the hydraulic motor 170 so as to short-circuit the inlet and outlet ports and bypass the fluid pump 230.

[0059] When the switching valve 160 of the bypass fluid path 150 is in the closed position, the fluid pump 230 is driven by the electric motor 210, and fluid is supplied to the hydraulic circuit path 140 of the first actuator. The hydraulic motor 170 is driven by the fluid and generates torque to rotate the screw 121 of the screw actuator 120.

[0060] When the switching valve 160 of the bypass fluid path 150 is in the open position, the hydraulic motor 170 is not allowed to generate torque. Therefore, the sliding rod 123 is allowed to easily follow the stroke movement driven by the second actuator 200.

[0061] Third Embodiment The following is for reference. Figure 3 The third embodiment of the present invention is described below.

[0062] The third embodiment differs from the first embodiment in the arrangement of the mechanically driven actuator 120 and the hydraulically driven linear actuator 220. According to the first embodiment, the screw actuator 120 and the hydraulic cylinder 220 are arranged in parallel. That is, the screw actuator 120 and the hydraulic cylinder 220 are arranged side-by-side with respect to the stroke movement. According to the third embodiment, the screw actuator 120 and the hydraulic cylinder 220 are arranged in series. That is, the screw actuator 120 and the hydraulic cylinder 220 are arranged one behind the other with respect to the stroke movement direction.

[0063] Specifically, the screw actuator 120 and the hydraulic cylinder 220 can be arranged coaxially.

[0064] Fourth embodiment The following is for reference. Figure 4 The fourth embodiment of the present invention is described.

[0065] The fourth embodiment differs from the second embodiment in the arrangement of the mechanically driven actuator 120 and the hydraulically driven linear actuator 220. In the second embodiment, the screw actuator 120 and the hydraulic cylinder 220 are arranged in parallel. That is, the screw actuator 120 and the hydraulic cylinder 220 are arranged side-by-side with respect to their stroke movement. In the fourth embodiment, the screw actuator 120 and the hydraulic cylinder 220 are arranged in series. That is, the screw actuator 120 and the hydraulic cylinder 220 are arranged one behind the other with respect to their stroke movement.

[0066] Specifically, the screw actuator 120 and the hydraulic cylinder 220 can be arranged coaxially.

[0067] Further modifications to the embodiments In the above embodiments, it has been described that the mechanically driven actuator 120 and the hydraulically driven linear actuator 220 are connected to each other to move as a unit. However, there are no particular limitations on the type of connection.

[0068] The mechanically driven actuator 120 and the hydraulically driven linear actuator 220 can be securely connected to each other.

[0069] Alternatively, the mechanically driven actuator 120 and the hydraulically driven linear actuator 220 can be disengaged from each other. That is, the mechanically driven actuator 120 and the hydraulically driven linear actuator 220 can be disconnected, allowing the two actuators 120, 220 to move asynchronously under certain operating conditions. For example, in the event of a position jam caused by a failure of the mechanically driven actuator 120, the hydraulically driven actuator 220 can use oil previously stored in the medium-pressure / high-pressure accumulator to perform a final fail-safe stroke.

[0070] The above description is not exhaustive, and the invention is not limited to the embodiments described above. Those skilled in the art will recognize that various modifications and combinations of the above embodiments are possible within the scope of the invention. Accordingly, the scope of the invention should be determined from the appended claims.

[0071] List of reference numerals 1 drive unit 2 Mobile Frames 100 First Actuation Device 110 electric motor 120 screw actuator (mechanically driven actuator) 121 screw 122 nuts 123 sliding bar 140 hydraulic circuit path 150 bypass fluid path 160 switch valve 170 hydraulic motor 200 Second Actuation Device 210 electric motor 220 hydraulic cylinder (hydraulic-driven linear actuator) 221 Piston 222 piston rod 230 fluid pump 240 hydraulic circuit path 250 bypass fluid path 260 switch valve.

Claims

1. A drive unit (1) for driving the stroke motion of a moving frame (2), the drive unit comprising: A first actuating device (100) is used to perform rapid stroke motion; A second actuating device (200) is used to perform a working stroke motion; as well as Control device, wherein, The first actuation device (100) includes a mechanically driven actuator (120). The second actuation device (200) includes a hydraulically driven linear actuator (220). The mechanically driven actuator (120) and the hydraulically driven linear actuator (220) are connected to each other to move as a single unit, and The control device is configured to control the first actuation device (100) and the second actuation device (200).

2. The driving unit (1) according to claim 1, wherein, In order to execute this rapid stroke, the control device is configured to control The first actuating device (100) drives the stroke movement, and The second actuator (200) is controlled to follow the stroke movement driven by the first actuator (100) while generating minimal resistance; and In order to execute this working stroke movement, the control device is configured to control The second actuating device (200) drives the stroke movement, and The first actuation device (100) is controlled to follow the stroke movement driven by the second actuation device (200) while generating minimal resistance.

3. The driving unit (1) according to any one of the preceding claims, wherein, The control device is configured as follows: The first actuator (100) is controlled by closed-loop position control or closed-loop speed control, and The second actuator (200) is controlled by closed-loop force control.

4. The driving unit (1) according to any one of the preceding claims, wherein, The second actuation device (200) further includes a hydraulic pump (230), which is controlled by the control device and drives the hydraulically driven linear actuator (220).

5. The driving unit (1) according to claim 4, wherein, The hydraulic pump (230) is an electrically driven hydraulic pump.

6. The driving unit (1) according to any one of the preceding claims, wherein, The first actuation device (100) further includes an electric motor (110), which is controlled by the control device and drives the mechanically driven actuator (120).

7. The drive unit (1) according to any one of claims 1 to 5, wherein, The first actuation device (100) further includes a hydraulic motor (170), which is controlled by the control device and drives the mechanically driven actuator (120).

8. The driving unit (1) according to claim 7, wherein, The hydraulic motor (170) of the first actuator (100) is driven by the hydraulic pump (230) of the second actuator (200).

9. The drive unit (1) according to claim 7 or 8. The first actuation device (100) includes a bypass fluid path (150) which includes a switching valve (160) controlled by the control device. The bypass fluid path (150) connects the inlet and outlet ports of the hydraulic motor (170), thereby bypassing the hydraulic pump (230).

10. The driving unit (1) according to any one of the preceding claims, wherein, The mechanically driven actuator (120) is an actuator that includes one or any combination of a gearbox, a roller screw, an inverted roller screw, a ball screw, a rack and pinion, a crank and a nonlinear mechanical lever.

11. The driving unit (1) according to any one of the preceding claims, wherein, The mechanically driven actuator (120) is a mechanically driven linear actuator.

12. The driving unit (1) according to any one of the preceding claims, wherein, The hydraulically driven linear actuator (220) is a hydraulic cylinder.

13. The drive unit according to claim 12, wherein, The second actuation device (200) includes a bypass fluid path (250) which includes a switching valve (260) controlled by the control device. The bypass fluid path (250) connects the inlet and outlet ports of the hydraulic cylinder (220), thereby bypassing the hydraulic pump (230).

14. A machine, particularly a press, bending machine, or punching machine, comprising: The moving frame (2) is configured to hold the tool and perform stroke movements; as well as The drive unit (1) according to any one of the preceding claims is used to drive the travel motion of the moving frame (2).

15. A method for operating a drive unit (1) according to any one of the preceding claims, wherein, During the rapid stroke of the drive unit (1), the control device controls the first actuator (100) to drive the stroke, and controls the second actuator (200) to follow the stroke driven by the first actuator (100) while generating minimal resistance; and During the working stroke of the drive unit (1), the control device controls the second actuator (200) to drive the stroke, and controls the first actuator (100) to follow the stroke driven by the second actuator (200) while generating minimal resistance.

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