DE102017125749A1 - Electrohydraulic linear actuator - Google Patents

Abstract

The electro-hydraulic linear actuator comprises a single motor-driven pump unit P. The pump unit P is in fluid communication with the working chamber of the first hydraulic cylinder Z1 and with the working chamber of the second hydraulic cylinder Z2 to alternately supply them with hydraulic fluid. The first and second hydraulic cylinders Z1, Z2 are each disposed adjacent to the pump unit P in the axial direction opposite each other and each have a piston 12, 22 on. The pistons 12, 22 are connected to each other via a common piston rod 25. Depending on the direction of rotation of the pump unit P, the piston 12 of the hydraulic cylinder Z1 or the piston 22 of the hydraulic cylinder Z2 is moved in a controlled manner and / or subjected to a hydraulic pressure.

Description

Field of the invention

The present invention relates to an electro-hydraulic linear actuator in a compact design, which is integrally formed and with which a mechanical force and / or a linear movement can be generated and transmitted to at least one connectable output device. Furthermore, the present invention relates to a joining device with the above-mentioned linear actuator, a manufacturing method for this linear actuator and an operating method for the linear actuator.

Background of the invention

In the prior art joining devices for introducing fasteners of different types are used in a variety of applications. One field of application is automotive and vehicle construction. Since on the one hand the joints are increasingly difficult to access or only a small installation space is available in the vicinity of these joints, there is a practical interest to provide joining devices of small size and low interference contour. In addition, this interest also supports the combination of joining devices with a robotic arm. Because a joining device with low weight is advantageous for a fast movement of a robot arm and makes less demands on its design and stability. The dimensions and the weight of a joining device are decisively determined by the drive unit of the joining device. In addition to joining devices but drive units of small size are also important in other areas of mechanical and tool engineering. These reduce the space requirements of the devices and often contribute to greater energy efficiency due to their lower weight.

The prior art uses various drive concepts, for example for the operation of joining devices. So describes DE 20 106 207 U1 an actuated by electric motor, mechanical transmission and spindle drive press tool. Such Einpresswerkzeuge no longer require the provision of reservoirs of hydraulic fluid and partially long supply hoses to supply the press tool with hydraulic fluid. However, it has proved to be disadvantageous that the purely electromechanically operated drive units of such press-in tools are sensitive to a punching stroke during punch riveting. Accordingly, the spindle drive used and the transmission used require frequent maintenance operations. Discloses an alternative electric drive DE 10 2015 116 464 A1 , Here, a linear movement is generated by means of an electromagnet. It comprises a coil with a core and a linearly movable along an axis of symmetry of the core armature, which performs the linear movement.

In addition to the electrical and the electromagnetic solution for an actuator just the hydraulic actuators are important. DE 44 26 706 C1 describes, for example, a servohydraulic actuator consisting of a tandem cylinder and two hydraulically associated mechanical servo valves. These servo valves are operated synchronously and are arranged achsfluchtig opposite each other in a valve housing. Both the valve arrangement and the hydraulic cylinders to be connected to form a space-intensive construction, which is also to be supplied via an external hydraulic source and hydraulic pump.

A hydraulic drive used in combination with a hydraulic press is described DE 10 2014 218 885 A1 , This hydraulic drive is also connected to an external hydraulic reservoir. The hydraulic fluid is supplied via two counter-rotating hydraulic pumps to a first and a second differential cylinder to move the hydraulic drive. By means of directional valves, the hydraulic fluid enters the various pressure chambers of the differential cylinders. Also, this construction is due to the different built-elements and the circuit complexity to be realized space-consuming and expensive.

Another concept revealed DE 10 2008 025 054 B4 in which a hydraulic unit for providing a pressurized hydraulic fluid for driving a coupled hydraulic actuator is described. This hydraulic unit comprises a reservoir for hydraulic fluid, a hydraulic pump, a hydraulic block and a motor in the form of a uniformly manageable rigid module. The hydraulic pump is a pump operable in four-quadrant mode, which allows hydraulic fluid to be delivered in two directions, forward and reverse directions. While the hydraulic unit is a compact design, it is precisely the combination of the hydraulic unit with conventional hydraulic cylinders as an actuator that increases the space required and the weight of a hydraulic actuator resulting therefrom. In this context, both the hydraulic unit as well as the associated hydraulic cylinder require appropriate maintenance to provide a reliable hydraulic actuator can.

With reference to the prior art discussed above, it is the object of the present invention to provide a compact electro-hydraulic linear actuator as a drive unit for, for example, joining devices that is currently operable without connection to an external hydraulic reservoir and external hydraulic pump.

Summary of the invention

The above object is achieved by an electro-hydraulic linear actuator according to the independent claim 1, by a joining device with such an electro-hydraulic linear actuator according to the independent claim 14, by a manufacturing method for an electro-hydraulic linear actuator according to the independent claim 15 and by an operating method for the electro-hydraulic linear actuator according to the independent claim 20 solved. Furthermore, the above object is achieved by the use of the electro-hydraulic linear actuator as a drive unit in different device configurations according to independent claim 23. Further developments and advantageous embodiments of the present invention will become apparent from the description, the accompanying drawings and the appended claims.

The present invention discloses an electro-hydraulic linear actuator, which is integrally formed and with which a mechanical force and / or a linear movement can be generated and transmitted to at least one connectable output device. The linear actuator has the following features: a motor-rotatably driven pump unit, this pump unit is in fluid communication with a first working chamber of a first hydraulic cylinder and a second working chamber of a second hydraulic cylinder to supply them alternately with hydraulic fluid, wherein the first and the second hydraulic cylinder each adjacent to the pump unit are arranged opposite one another in the axial direction and each having a piston with a piston rod, so depending on a direction of rotation of the pump unit, the first piston of the first hydraulic cylinder or the second piston of the second hydraulic cylinder controlled movable and / or with a hydraulic pressure can be acted upon.

The electrohydraulic linear actuator according to the invention represents a compactly constructed and wear-free drive unit. This preferably results from the direct combination of a central pump unit with two hydraulic cylinders arranged directly adjacent thereto. Since, depending on the direction of rotation of the pump unit, a hydraulic fluid can be fed directly into the first working chamber of the first hydraulic cylinder or the second working chamber of the second hydraulic cylinder without a complex hydraulic circuit, without an external hydraulic source and without an external hydraulic pump, the linear actuator preferred according to the invention relates to one Depending on the direction of rotation of the pump unit of the first piston of the first hydraulic cylinder or the second piston of the second hydraulic cylinder is selectively offset or applied with force to the supply of hydraulic fluid. Accordingly, at least one output device, which is connected to the first or the second piston, selectively driven to set, for example, a joining element, to put a construction or a part thereof or to provide a connected device with mechanical energy.

Preferably, the pump unit comprises only one pump. This single pump is formed by a single internal gear pump or a single external gear pump according to various embodiments of the present invention. It is also preferable to use an axially arranged multi-stage pump unit, preferably a two-stage pump unit. According to a preferred embodiment, the first pump stage is designed for a load stroke. The second pump stage is preferably configured for a delivery or return stroke. These different pump stages are then selectively switched on and off according to the pressure range to be generated or a hydraulic volume to be provided of the pumped hydraulic fluid.

Also advantageous for the compactness of the linear actuator are arranged in the axial direction on opposite sides of the pump unit hydraulic cylinder each with a displaceable piston. The hydraulic cylinders preferably have at least the same inner diameter. This ensures that the first working chamber of the first hydraulic cylinder and the second working chamber of the second hydraulic cylinder has the same capacity or receiving volume for the hydraulic fluid. This preferred dimensioning of the two hydraulic cylinders ensures operation of the linear actuator without having to connect a hydraulic fluid reservoir to the linear actuator. In addition, the volume constancy of the pumped-back hydraulic volumes makes it possible to operate the linear actuator without valve technology for controlling inflow and outflow of hydraulic fluid to a tank or surge tank and / or to an external hydraulic pump.

According to a further preferred embodiment of the present invention, the two hydraulic cylinders are axially directly opposite each other, that is, aligned or coaxial with each other, arranged. It is also preferable to arrange the two hydraulic cylinders axially opposite each other but not coaxially with each other. In the latter case, therefore, the central axes of the two cylinders are not on a common line. In both cases, it is preferred according to another embodiment of the invention to connect the pistons of the two hydraulic cylinders via a common piston rod together. Based on the use of a continuous piston rod, we preferably offset an output rod via the piston of a hydraulic cylinder. For controlled return of the piston of a hydraulic cylinder, the piston of the other hydraulic cylinder is pressurized and displaced in the opposite direction. In this case, the common piston rod takes the associated piston with, without having to be generated for a provision of the piston, a suction state in the hydraulic cylinder.

Should it be advantageous for the operation of the two hydraulic cylinders, these are also operable with separate piston rods.

According to a preferred embodiment of the present invention, the piston rod of the first piston and the piston rod of the second piston are connected together as a common piston rod. This preferred construction ensures that the targeted displacement of only one piston by means of the pumped hydraulic fluid also the second not directly loaded with hydraulic fluid piston is displaceable. This construction thus preferably provides targeted delivery of an output device, preferably a punch of a setting device, via supplying the first hydraulic cylinder with hydraulic fluid. If the second hydraulic cylinder is specifically supplied with hydraulic fluid, the first piston of the first hydraulic cylinder is reset by displacing the second piston of the second hydraulic cylinder, since the first piston and the second piston are connected to one another via a common piston rod. This results in control advantages for the inventively preferred linear actuator without the need for a complex valve technology.

Furthermore, with respect to this construction, it is preferable to store the entire working volume of hydraulic fluid within the first and second working chambers and in the pumping space of the pump unit. As a result, it is not necessary for the preferred linear actuator according to the invention to be connected via often obstructive long hoses to an external reservoir of hydraulic fluid. For the second hydraulic cylinder preferably used for the return of the first hydraulic cylinder is used as a collecting cylinder for the hydraulic fluid discharged from the first hydraulic cylinder. Accordingly, preferably, the first and second working chambers of the first and second hydraulic cylinders together with the pump unit preferably include a closed volume of hydraulic fluid which is interchangeable between the working chambers during a pumping operation.

According to a further preferred embodiment of the present invention, the pump unit comprises an electrically driven external gear pump or an electrically driven internal gear pump, which is driven by an electric motor.

With gear pumps in general, which include the external gear pump as well as the internal gear pump, the positive displacement rotors are in driving engagement. Such pumps, which are known in their basic design concepts are specifically tuned in their size and capacity to the application. In the present invention has just proven to be an advantage that the external gear pump or the internal gear pump used has only a limited space requirement, which can be combined well with the directly connected hydraulic cylinders.

Further preferably, the external gear pump or the internal gear pump is driven by an electric direct drive, in particular a servo motor with a rotor core and a stator core as engine components. According to a preferred embodiment of the present invention, the preferred internal gear pump is concentrically surrounded by the engine components. It is equally preferable to arrange the electric direct drive axially adjacent to the pump unit. These electric motors are advantageous because they allow the control of the angular position of the motor shaft and thus preferably the pump shaft and the direction of rotation and acceleration of the pump. Accordingly, desired hydraulic pressure situations or specific supply situations of the connected hydraulic cylinders can be controlled with hydraulic fluid. This ensures that either the piston of the respectively driven working cylinder is moved in a defined manner and / or subjected to a defined force.

In a further inventive preferred embodiment of the present invention, the external gear pump or the internal gear pump comprises at least two axes of rotation of rotatably arranged gears, which are parallel to the piston rod of the first and second Hydraulic cylinder are arranged. The axis of rotation of each rotating in an external gear pump or in an internal gear pump gears can be arranged both rotating and fixed with respect to a rotation. This provides a basis for the compact design of the linear actuator of the invention. For preferably one of the gears of the internal gear pump or the external gear pump is designed as a hollow shaft with a central opening and arranged on the running through the pump chamber of the pump unit piston rod. Thus, while preferably the piston rod of the compound of the two pistons in the first and second working cylinder, it also forms a stable axis of rotation for a non-driving gear in the internal gear pump or the external gear pump. Accordingly, weight and design complexity for the inventively preferred linear actuator can be reduced.

According to a preferred embodiment of the present invention, the internal gear pump comprises a pinion, which is arranged in a rotationally driving toothed ring with internal toothing. In addition, it is preferred that the pinion is designed as a hollow shaft with a central opening and the common piston rod of the first and the second hydraulic cylinder is arranged to be linearly movable in the central opening.

As already mentioned above, the preferred continuous piston rod connecting the pistons of the first and second hydraulic cylinders forms an axis of rotation for the pinion of the internal gear pump. For this purpose, it is preferable that the pinion is provided as a hollow shaft, so that the continuous piston rod can be arranged within the central opening of the hollow shaft. In order to use this preferred construction, the internal gear toothed ring surrounding the pinion is rotatably arranged via the electric motor already discussed above, preferably a servo motor. In contrast to known design principles of internal gear pumps, the drive of the internal gear pump has proved over the ring gear with internal teeth advantageous. Because this construction makes it possible that the continuous preferred piston rod provides the axis of rotation for the central pinion and is performed simultaneously stabilizing in the pinion.

According to a further preferred embodiment of the present invention, the external gear pump used in the pump unit has a helical toothing. With regard to the external gear pump, it is also preferable to form a first gear as a hollow shaft having a central opening and to arrange the common piston rod of the first and second hydraulic cylinders in the central opening of the first gear linearly movable.

Accordingly, in the context of the external gear pump, the preferred continuous piston rod is not only a mechanical linkage between the first and the second hydraulic cylinder. Rather, an axis of rotation is defined by the continuous piston rod, on which the non-driving gear with external teeth, preferably helical teeth, is arranged. While this storage of the first gear on the continuous piston rod ensures the position of the first gear with respect to the driving second gear, a linear displacement of the continuous piston rod is ensured by the central opening of the first gear simultaneously.

According to a further preferred embodiment of the linear actuator according to the invention, the gear pump defines a pump chamber and has axially oriented hydraulic openings in this pump chamber, via which the first and the second working chamber of the first and second hydraulic cylinders can be supplied with hydraulic fluid.

Within the pump space of the gear pump, the pumping motion causing gears are arranged. Accordingly, in an external gear pump, two gears with external helical toothing preferably run in the pump chamber. In the case of an internal gear pump, the pinion already discussed above in the form of a hollow shaft, the toothed ring with internal toothing and the sealing mandrel are arranged inside the pump chamber. While the gear pump generates the actuated hydraulic pressure independently of its configuration in the pump chamber, the at least two hydraulic openings in the pump chamber ensure a targeted supply of the hydraulic fluid to the first and second hydraulic cylinders. In this context, it has proven to be advantageous to orient the hydraulic openings in the axial direction, ie in a similar course as the piston rods of the first and second hydraulic cylinders. This orientation of the hydraulic openings, which serve as inflow opening and outflow opening from the pump chamber, ensure short transport paths for the hydraulic fluid to be transported into the working chamber of the hydraulic cylinders. Of course, it is equally preferable to arrange differently oriented hydraulic openings. It is only essential that, depending on the direction of rotation of the pump within the pump chamber, a hydraulic opening on the pressure side and a hydraulic opening on the negative pressure side of the pump chamber is arranged.

According to another preferred embodiment of the present invention, the Pump unit and the first and second hydraulic cylinders of the present invention preferred linear actuator arranged in a common housing.

The present invention also comprises a joining device, in particular a rivet setting device or a clinch device, which comprises an electro-hydraulic linear actuator according to one of the embodiments described above, the first piston is connected via a driven device with a setting punch and / or a hold-down device.

Furthermore, the present invention preferably comprises a press, in particular a stamping press or a forming press or a press-in device, which is driven by the electrohydraulic linear actuator according to one of the embodiments described above. Such presses are used for processing metal, plastic or paper / cardboard. Furthermore, the electro-hydraulic linear actuator is preferably used for moving components on position-controlled feed axes. In further preferred embodiments of the present invention, the electro-hydraulic linear actuator according to one of the embodiments described above is used in metal forming machines, such as tube bending machines.

The present invention also discloses a manufacturing method for a linear actuator, with which a mechanical force and / or a linear movement can be generated, in particular an electro-hydraulic linear actuator according to one of the embodiments described above. The manufacturing method according to the invention comprises the following steps: Providing a centrally arranged, single motor-driven pump unit, connecting the pump unit on two opposite sides with a first and a second hydraulic cylinder, so that the first and the second hydraulic cylinder are arranged in the axial direction opposite to each other , and establishing a fluid connection between the pump unit and the first and the second hydraulic cylinder, so that depending on a rotational direction of the pump unit, a first piston of the first hydraulic cylinder or a second piston of the second hydraulic cylinder is controllably movable and / or acted upon by a hydraulic pressure.

Based on the method steps summarized above, the individual components of the electrohydraulic linear actuator according to the invention described in detail above are connected together to form a drive unit. In this context, it has proved to be advantageous that the pump unit is arranged centrally. In addition, the two preferred hydraulic cylinders are mounted opposite each other directly adjacent to the pump unit. This construction ensures that the hydraulic fluid can only be supplied by the pump unit over short distances to the respective working chamber of the connected hydraulic cylinder. Accordingly, fluid connections to the respective working chamber of the connected hydraulic cylinder are provided. As has already been described above, the fluid connections are in the form of hydraulic openings in the pressure region and underpressure region of the pump chamber in order to avoid expensive hydraulic lines and valve arrangements.

According to a further preferred embodiment of the manufacturing method according to the invention, a common piston rod for the first hydraulic cylinder and the second hydraulic cylinder is provided, which connects the first piston arranged in the first hydraulic cylinder and the second piston arranged in the second hydraulic cylinder. Further preferably, an electrically driven external gear pump or an electrically driven internal gear pump is provided within the pump unit. In this context, the internal gear pump has a pinion, which is designed as a hollow shaft with a central opening and in the central opening of the common piston rod is arranged to be linearly movable. Alternatively, the external gear pump has a helical toothing. A first gear is formed as a hollow shaft with a central opening, while the common piston rod is arranged linearly movable in this central opening.

The present invention also discloses an operating method for the electro-hydraulic linear actuator which is described above in its various embodiments. The method of operation includes the steps of providing a first control voltage such that an electric motor of a gear pump of the pump unit rotates in a first direction of rotation, thereby pumping hydraulic fluid into the first hydraulic cylinder, linearly displacing the first piston in the first hydraulic cylinder in a first output direction, and providing a second control voltage for the electric motor, so that the gear pump of the pump unit rotates in a second direction of rotation, to offset the first piston against the first output direction.

By means of the preferably used electric motor for operating the pump unit, it is possible to rotate the motor in dependence on the used control voltage in a defined direction of rotation. Accordingly, the engine turns the Pump unit so that the pump direction is also determined by the preselected direction of rotation. It follows that based on the targeted choice of the control voltage of the electric motor driving the pump unit, the first hydraulic cylinder or the second hydraulic cylinder is supplied with hydraulic fluid. As soon as the piston of the first hydraulic cylinder or of the second hydraulic cylinder has been displaced by means of this targeted control of the electric motor of the pump unit, the piston of the first or of the second hydraulic cylinder returns the corresponding actuating path or generates a force which can be transmitted to a connected output device. Accordingly, a corresponding second control voltage of the driving electric motor of the pump unit ensures a targeted unloading of the piston of the corresponding hydraulic cylinder or for a targeted return of the piston of the hydraulic cylinder. In this connection, it is also preferable to provide at least a third control voltage for the electric motor so that a hydraulic pressure is maintained in the first or second hydraulic cylinder. Maintaining this hydraulic pressure assures the further application of a force to the correspondingly displaced piston or a continuous displacement of the piston within the first hydraulic cylinder or the second hydraulic cylinder.

According to another preferred embodiment of the operating method according to the invention, in a further step, a detection of a hydraulic pressure in the first hydraulic cylinder and / or in the second hydraulic cylinder by means of a pressure sensor arranged in the respective hydraulic cylinder and a control of the electric motor with respect to the detected hydraulic pressure.

The present invention also includes the use of the electro-hydraulic linear actuator according to one of the preferred embodiments described above as a drive unit for a mating device or as a drive unit for a fastening device or as a drive unit for a supply or delivery device.

list of figures

• 1 eine schematische Schnittdarstellung einer bevorzugten Ausführungsform des erfindungsgemäßen elektrohydraulischen Linearstellglieds,
• 2 eine Schnittdarstellung entlang der Linie A-A aus 1,
• 3 eine Schnittdarstellung entlang der Linie B-B aus 1,
• 4 eine Schnittdarstellung entlang der Linie C-C aus 1,
• 5 eine Schnittdarstellung einer bevorzugten Ausführungsform des elektrohydraulischen Linearstellglieds in Kombination mit einer Niederhaltekonstruktion zur Bildung einer Fügevorrichtung,
• 6 eine schematische Schnittdarstellung einer weiteren bevorzugten Ausführungsform des erfindungsgemäßen elektrohydraulischen Linearstellglieds mit nicht koaxial zueinander angeordneten Hydraulikzylindern,
• 7 ein Flussdiagramm einer bevorzugten Ausführungsform eines Herstellungsverfahrens des erfindungsgemäßen elektrohydraulischen Linearstellglieds,
• 8 ein Flussdiagramm einer bevorzugten Ausführungsform eines Betriebsverfahrens des elektrohydraulischen Linearstellglieds.

The preferred embodiments of the present invention will be explained in detail with reference to the accompanying drawings. Show it:

• 1 a schematic sectional view of a preferred embodiment of the electro-hydraulic linear actuator according to the invention,
• 2 a sectional view along the line A - A out 1 .
• 3 a sectional view along the line B - B out 1 .
• 4 a sectional view along the line C - C out 1 .
• 5 a sectional view of a preferred embodiment of the electro-hydraulic linear actuator in combination with a hold-down construction to form a joining device,
• 6 a schematic sectional view of another preferred embodiment of the electro-hydraulic linear actuator according to the invention with non-coaxial with each other arranged hydraulic cylinders,
• 7 a flowchart of a preferred embodiment of a manufacturing method of the electro-hydraulic linear actuator according to the invention,
• 8th a flowchart of a preferred embodiment of an operating method of the electro-hydraulic linear actuator.

Detailed Description of the Preferred Embodiments

1 shows a schematic sectional view of a preferred embodiment of the electro-hydraulic linear actuator 1 , The linear actuator 1 consists of a central pump unit P and two attached hydraulic cylinders Z1 and Z2 , The hydraulic cylinders Z1 and Z2 are axially aligned with each other and extend from opposite sides of the pump unit P , In this arrangement, the hydraulic cylinders Z1 . Z2 shown with the same outside and inside diameters. It is also preferred according to the invention in this construction, the two hydraulic cylinders Z1 . Z2 to provide in coaxial arrangement with the same inner diameters and different outer diameters.

Compared to the embodiment of 1 are in the linear actuator 1' the 6 (same components as in 1 are denoted by the same reference numerals in FIG 6 referred to) the two hydraulic cylinders Z1 . Z2 also arranged in the axial direction opposite one another on the corresponding sides of the central pump unit P. In the embodiment of the 6 are the hydraulic cylinders Z1 . Z2 but not coaxial or aligned with each other. Rather, the center axes of the hydraulic cylinder Z1 . Z2 laterally offset and arranged parallel to each other. At the same time it is preferred, the two hydraulic cylinders Z1 . Z2 to provide the same inner diameters and preferably with the same outer diameters.

The preferred non-coaxial linear actuator 1' as it is in a possible embodiment in 6 is shown in the same way as the construction of the 5 can be combined with a joining device or a forming device, here in particular with a rivet setting device. Therefore, this description is analogous to the linear actuator 1' out 6 combined. The joining device F is about the output device 30 to the second piston 22 Coupled as related below 5 is explained in more detail.

Due to the non-coaxial arrangement of the hydraulic cylinder Z1 . Z2 is the preferred linear actuator 1' just not rotationally symmetric about its longitudinal axis. This lack of rotational symmetry ensures an anti-rotation and thus a rotationally fixed stop of the linear actuator 1' , for example by the robot arm. Because as soon as the linear actuator 1' due to its attached peripherals, such as preferably the setting head according to 5 , has to be observed a disturbing contour, positional stability is important. In this way, it is preferably ensured that an interference contour critical element feed is known in its position via a laterally projecting channel bend, this position does not change despite movement of the robot and can be considered damage-safe movements of a robot.

The hydraulic cylinders Z1 and Z2 include a cylinder 10 ; 20 in which a piston 12 ; 22 is guided. The piston 12 ; 22 is with a piston rod 14 ; 24 connected. Between the piston 12 ; 22 and an opposite housing cover 40 ; 42 the pump unit P is inside the cylinder 10 ; 20 each a working chamber of the hydraulic cylinder Z1 . Z2 with hydraulic fluid 16 ; 26 Are defined.

During operation of the pump unit P of the linear actuator 1 will this hydraulic fluid 16 . 26 between the two working chambers of the hydraulic cylinder Z1 . Z2 moved back and forth. Accordingly, one of the pistons 12 . 22 offset or applied with force via an applied pressure of the hydraulic fluid.

As in the two working chambers of the hydraulic cylinder Z1 . Z2 that is, between the pistons 12 . 22 the two hydraulic cylinders Z1 . Z2 , sufficient hydraulic fluid for the operation of the linear actuator 1 is stored, requires the inventively preferred linear actuator 1 neither an external hydraulic reservoir nor an external hydraulic pump or hydraulic pressure source or a surge tank. Because the volume of hydraulic fluid between the pistons 12 . 22 remains the same regardless of the position of the pistons. The in the linear actuator 1 stored hydraulic fluid thus preferably forms a closed volume, which consists of the partial volumes in the working chambers of the hydraulic cylinder Z1 and Z2 and in the pump room 40 the pump unit P composed. It is understood that the closed hydraulic volume can be supplemented with hydraulic fluid. This could be due to leakage in the linear actuator 1 be necessary.

The in the respective hydraulic cylinder Z1 . Z2 existing hydraulic pressure is using appropriate pressure sensors 2 . 4 detectable. In addition, a position of the piston is preferred 12 using a suitable position measuring system in the form of, for example, a position sensor 38 and a position sensor 39 detectable. It is further preferred, similar displacement sensors in the hydraulic cylinder Z2 to arrange way and / or position of the piston 22 to determine. In this context, it is also preferable, a cylinder wall of the hydraulic cylinder Z1 and / or the hydraulic cylinder Z2 made of a non-magnetic material. Because the piston 12 ; 22 is preferably made of a magnetic material, such as metal, or provided with a corresponding marker, is a position of the piston 12 ; 22 in the hydraulic cylinder Z1 ; Z2 Can be detected without contact with an external sensor through the cylinder wall. Based on this embodiment, the design effort for the arrangement and attachment of a distance measuring sensor can be reduced.

The centrally arranged pump unit P includes the between two housing covers 42 . 44 enclosed pump room 40 , Preferably, the present invention in the pump unit P comprises an electrically driven gear pump. In this connection, an external gear pump (not shown) or an internal gear pump is preferable. Referring to 1 and the derived sectional views of the 2-4 becomes the pump unit P the example of a preferred internal gear pump 50 explained.

How to use the sectional image in 3 can recognize, there is the internal gear pump 50 from a pump sprocket 52 , a pump ring gear 54 with internal toothing and a sealing sickle 56 , Preferably, the operation of the internal gear pump 50 the pump ring gear 54 driven, which is the pump pinion 52 rotates.

For this purpose, the pump ring gear 54 from a preferably concentric around the Pumpenhohlrad 54 surrounded arranged electric motor. The electric motor or direct drive 60 , preferably a servomotor, consists of a motor housing 62 , a stator package 64 and a rotor package 66 , The rotor package 66 is with the pump ring gear 54 connected to rotate this in a defined direction of rotation.

Under rotor package 66 and stator package 64 In the present case, in general, the required electromagnetic components of the electric motor 60 Roger that. These include, for example, a coil winding and / or permanent magnets for forming the rotor or the stator. It is further preferred that the electric motor 60 operate without encoder.

The internal gear pump 50 and the engine components 64 . 66 are preferably in an interior of the motor housing 62 added. The interior is also preferably limited by the lateral motor housing 62 and by the axially adjacent housing cover 42 . 44 , The rotatable parts of the internal gear pump 50 like the pump sprocket 52 and the pump ring gear 54 , are in the housing covers 42 . 44 rotatably mounted. This is in the sectional views of 2 and 4 recognizable. According to a preferred embodiment of the present invention are the pump pinion 52 over a shaft area 53 and a needle bearing ring 73 in the housing covers 42 . 44 rotatably arranged. In a similar constructive way, the pump ring gear 54 over a preferred shaft area 55 and a radially adjacent needle bearing ring 75 in the housing covers 42 . 44 rotatably arranged. It is also preferable that the pump ring gear 54 Hydrostatically via a liquid layer, here hydraulic fluid, and without a mechanical bearing construction in the housing covers 42 . 44 to keep it rotatable.

Between the two housing covers 42 . 44 is the sealant 56 arranged. This subdivides the pump chamber of the internal gear pump 50 during rotation in a known manner in a pressure range and a negative pressure range. Depending on the direction of rotation of the internal gear pump 50 is related to 3 the vacuum area at the top of the sealing sickle 56 and the overpressure area at the bottom of the sealer 56 or vice versa.

According to a preferred embodiment of the present invention, the pump ring gear 54 over the engine 60 driven. The pump ring gear 54 in turn drives the pump pinion 52 on to the known overpressure-vacuum constellation hydraulic fluid in one of the connected hydraulic cylinder Z1 . Z2 to pump. For this purpose, the hydraulic fluid is preferably via a first hydraulic opening 80 and a second hydraulic opening 82 with the hydraulic cylinders Z1 . Z2 replaced. It has proved to be advantageous, the hydraulic openings 80 . 82 or breakthroughs through the housing cover 42 . 44 adjacent to the vacuum area and the overpressure area in the pump room 40 to arrange for optimal liquid transport. This is the hydraulic openings 80 . 82 preferably in the axial direction of the linear actuator 1 oriented.

According to a further preferred embodiment of the present invention, the pump pinion 52 provided as a hollow shaft with a central opening. In addition, it is preferred, the piston rod 14 . 24 the hydraulic cylinder Z1 . Z2 to train as a common piston rod, like the 1 and 5 demonstrate. The common piston rod 25 connects the two pistons 12 . 22 rigid with each other. In addition, it preferably ensures additional stability due to the guidance and storage in the housing covers 42 . 44 and in the pump gear 52 ,

According to a preferred embodiment of the present invention, the common piston rod 25 in the central opening of the pump pinion 52 stored hydrostatically. In this way, despite a lack of physical seal between the common piston rod 25 and the pump gear 52 achieved a sufficient gap seal. Alternatively, however, it is also preferred to provide physical seals, such as between the housing covers 42 . 44 and the common piston rod 25 at the reference number 48 ,

According to another preferred embodiment of the present invention, the pump unit comprises P instead of the internal gear pump 50 an external gear pump 50 ' (Not shown). This also has two rotatably arranged gears in the pump room 40 on, which are both equipped with an interlocking external toothing.

Preferably, the axes of rotation of the gears are parallel to the common piston rod 25 arranged. Accordingly, it is also preferable to provide the non-driving gear as a hollow shaft with a central opening. In the same way as with the pump unit P with internal gear pump 50 is then preferred the common piston rod 25 arranged linearly displaceable in the central opening of the gear.

It has proved to be advantageous to equip the two gears with a straight toothing or a helical toothing. Further preferably, in both embodiments, the tooth profile comprises an involute toothing.

To realize the liquid exchange between the pump room 40 and the hydraulic cylinder connected to the pump unit P Z1 . Z2 are connecting openings in the housing covers 42 . 44 the pump unit P intended. According to a preferred embodiment of the present invention, the inlet and outlet ports are from the pump chamber 40 acting as hydraulic openings 80 . 82 in combination with the Internal gear pump are designated, axially oriented (see 2 and 3 ). This is also preferred in combination with the external gear pump.

It may be necessary due to a pumping direction of the external gear teeth that the hydraulic openings 80 . 82 laterally into the pump room 40 lead. In this case, apertures in a surrounding pump housing (not shown) conduct the hydraulic fluid to the working chambers of the hydraulic cylinders Z1 . Z2 ,

How to get by 1 can recognize, the cylinders form 10 . 20 in combination with the centrally located pump unit P, a common housing of the linear actuator 1 , It is also preferred in this context, a coherent or integral housing for the linear actuator 1 provided. In this then the hydraulic cylinders Z1 . Z2 , the internal gear pump or the external gear pump, the electric motor 60 and preferably at least a part of the output device (see below) arranged.

Depending on the direction of rotation of the pump in the pump unit P the hydraulic fluid is in the hydraulic cylinder Z1 or in the hydraulic cylinder Z2 pumped. The resulting hydraulic pressure in the corresponding working chamber causes the piston 12 ; 22 in the pressurized hydraulic cylinder Z1 ; Z2 moved away from the pump unit P. The other piston 22 ; 12 moves due to the rigid connection via the common piston rod 25 to the pump unit P to.

The hydraulic cylinders Z1 . Z2 are each with lids 18 . 28 locked. The lids 18 . 28 have a ventilation function. This ventilation function will change the volume change produced by the piston movement between the piston and the cylinder cover 18 . 28 balanced.

Due to the symmetrical arrangement of the hydraulic cylinders Z1 . Z2 and the corresponding arrangement of the pistons 12 . 22 No expansion tank is required for temporarily storing excess hydraulic fluid.

A volume expansion of the hydraulic fluid is preferably through a in one of the pistons 12 . 22 integrated compensation chamber 34 added. The compensation chamber 34 has an inlet check valve 37 and a drain check valve 36 , The two mentioned valves 36 . 37 preferably have different restoring forces. Inside the compensation chamber 34 A bellows ensures the separation of hydraulic fluid and compressible gas.

Depending on the performance of the electric motor 60 , which drives the pump unit, results in a maximum achievable hydraulic pressure on the surface of one of the pistons 12 . 22 , In accordance with the pressure that can be generated in the hydraulic fluid and the size of the piston surface of the piston acted upon 12 ; 22 results in a maximum possible force of the linear actuator 1 , This force effect can be transmitted via an output device connected to the piston, for example to a punch of a joining device. An example of an output device shows 1 at the reference number 30 in combination with the piston 22 , Using the linear actuator 1 can be via the output device 30 a force and / or movement through the linear actuator 1 via the output device 30 transferred to connected devices, such as a setting device. While the driving electric motor 60 determines the flow rate of the pump, can be about the size of the working chamber in the respective hydraulic cylinder Z1 . Z2 , the size of the piston surfaces of the hydraulic pressure piston 12 . 22 determine the adjustment speed of the pressurized hydraulic cylinder and the force generated by the pressurized piston.

5 shows a schematic embodiment of a preferred combination of the linear actuator 1 with a joining device, in particular with a rivet setting device. The joining device F is about the output device 30 to the second piston 22 coupled. The per se known construction of the joining device F includes an element feed 98 , a joining channel 96 as well as a moving through the joining channel punch 90 , Furthermore, the joining device comprises F a hold-down spring 92 and a return spring 94 in the guide tube 95 are arranged. About the hold-down spring 92 becomes the joining channel 96 pressed against the components to be joined together (not shown). After any gaps between the components to be joined have been closed, a joining element under the stamp 90 in the joining channel 96 fed. Subsequently, the electric motor starts 60 To rotate the pump of the pump unit P such that hydraulic fluid in the direction of the piston 22 is pumped. Depending on the applied hydraulic pressure and the size of the piston area of the piston 22 becomes the piston 22 and thus also the output device 30 offset in the direction of the components to be joined together. During this process, hydraulic fluid is 16 from the hydraulic cylinder Z1 in the hydraulic cylinder Z2 pumped. During this movement the stamp presses 90 the joining element in the two components (not shown).

The above-described operating method for the electro-hydraulic linear actuator 1 can be according to a preferred embodiment with reference to the flowchart in 7 sum up. First, in step I provided a first control voltage, so that the electric motor 60 the pump unit P rotates in a first selected direction of rotation. Accordingly, hydraulic fluid is introduced into the first or second hydraulic cylinders Z1 . Z2 pumped. Using the pressure sensors already mentioned above 2 . 4 is preferably the hydraulic pressure in the pressurized hydraulic cylinder Z1 or Z2 recorded and monitored. This information is for example by means of a control unit the electric motor 60 provided to the pump unit P, to the corresponding with the pump unit P the setting of a desired hydraulic pressure in the hydraulic cylinder Z1 or Z2 to achieve (step II ). According to the pumped amount of hydraulic fluid, the piston 12 or 22 in the hydraulic cylinder Z1 or Z2 offset in the desired output direction (step III ). Preferably, the offset of the punch is detected by means of a suitable displacement measurement. This information is also preferably provided to a control unit in order to control the electric motor 60 the pump unit P the linear actuator 1 to be able to drive optimally.

It is further preferred, a second control voltage for the electric motor 60 the pump unit P provide. This second control voltage is used to the acted upon by hydraulic fluid piston 12 or 22 continue to deliver or apply a larger force or reset the linear actuator to its original position. While initially the piston 12 for a feed movement with pressurized hydraulic fluid has been applied, is for a reset of the piston 12 The piston 22 now acted upon by pressurized hydraulic fluid. This is achieved by the electric motor 60 in that it provides a control signal for reversing the direction of rotation of the gear pump within the pump unit P generated. Accordingly, the piston 12 set back to its original position, that is offset against the first output direction (step IV ). It is further preferred in step V another control voltage for the electric motor 60 provide. This additional control voltage is used by means of the electric motor 60 the pump unit P in the first or second hydraulic cylinder Z1 or Z2 maintains or reduces or increases existing hydraulic pressure.

The preferred manufacturing method according to the invention for the linear actuator 1 can be explained with reference to the in 8th summarize flowchart shown. First, in step A the pump unit P provided. According to various preferred embodiments, the pump unit comprises P the electrically driven external gear pump or the electrically driven internal gear pump, as described above. The internal gear pump is preferably characterized by the pinion designed as a hollow shaft. With regard to the preferred external gear screw-toothed pump, it is also preferable to provide one of the gears as a hollow shaft. Thus, in the step A also a selection of the preferred pump included in the pump unit P should be used.

In the following step B is preferably the common piston rod 25 provided the two hydraulic cylinders Z1 . Z2 combines. After that, in step C the two hydraulic cylinders Z1 . Z2 with the pump unit P connected, with the common piston rod 25 through the pump unit P extends. It is equally preferable that the two hydraulic cylinders Z1 . Z2 without the common piston rod 25 with the pump unit P to connect. In the final step D, the fluid communication between the pump unit P and the first hydraulic cylinder Z1 and the second hydraulic cylinder Z2 manufactured. On this basis, the gear pump pumps inside the pump unit P depending on their direction of rotation hydraulic fluid in the first Z1 or the second hydraulic cylinder Z2 , Accordingly, thereby the piston 12 of the hydraulic cylinder Z1 or the piston 22 of the hydraulic cylinder Z2 controlled moves and / or acted upon by a hydraulic pressure.

LIST OF REFERENCE NUMBERS

1; 1'

Linear actuator

Z1, Z2

hydraulic cylinders

2, 4

pressure sensor

10, 20

cylinder

12, 22

piston

14, 24

piston rod

25

common piston rod

16, 26

hydraulic fluid

18, 28

cylinder cover

19

ventilation

30

output rod

32

piston Head

34

bellows

36, 37

Check valve inlet, drain

38

position sensor

39

Position sensor ring

40

pump room

42, 44

Housing cover of the pump unit

46, 48

poetry

50

Internal gear pump

52

pump pinion

53

Shaft area of the pump pinion

54

Pumpenhohlrad

55

Shank area of the pump ring gear

56

sealing sickle

60

Direct drive, servomotor

62

motor housing

64

stator

66

rotor pack

73, 75

Needle bearing ring

80, 82

hydraulic opening

F

Joining device with hold-down device

90

stamp

92

Down spring

94

Return spring

95

guide tube

96

joining channel

98

element supply

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 20106207 U1 [0003]
• DE 102015116464 A1 [0003]
• DE 4426706 C1 [0004]
• DE 102014218885 A1 [0005]
• DE 102008025054 B4 [0006]

Claims (23)

An electro-hydraulic linear actuator, which is integrally formed and with which a mechanical force and / or a linear movement can be generated and transmitted to at least one connectable output device, wherein the linear actuator has the following features: a. a motor-driven rotating pump unit, b. the pump unit is in fluid communication with a first working chamber of a first hydraulic cylinder and with a second working chamber of a second hydraulic cylinder for alternately supplying them with hydraulic fluid, c. the first and the second hydraulic cylinders are each disposed adjacent to the pump unit in the axial direction opposite each other and each have a piston with a piston rod, so that d. as a function of a direction of rotation of the pump unit, the first piston of the first hydraulic cylinder or the second piston of the second hydraulic cylinder controlled movable and / or can be acted upon by a hydraulic pressure. Linear actuator according to Claim 1 in that the piston rod of the first piston and the piston rod of the second piston are connected together as a common piston rod. Linear actuator after Claim 1 or 2 in that the first and second working chambers of the first and second hydraulic cylinders, together with the pump unit, include a closed volume of hydraulic fluid which is interchangeable between the working chambers during a pumping operation. Linear actuator according to one of the preceding claims, in which the pump unit comprises an electrically driven external gear pump or an electrically driven internal gear pump which is driven by an electric motor. Linear actuator according to Claim 4 in that the external gear pump or the internal gear pump comprises at least two axes of rotation of rotatably arranged gears, which are arranged parallel to the piston rod of the first and the second hydraulic cylinder. Linear actuator according to Claim 5 in that the internal gear pump comprises a pinion, which is arranged in a rotationally driving toothed ring with internal teeth. Linear actuator according to Claim 6 in combination with Claim 2 in that the pinion is designed as a hollow shaft with a central opening and the common piston rod of the first and the second hydraulic cylinder is arranged to be linearly movable in the central opening. Linear actuator according to Claim 5 in which the external gear pump has a helical or helical toothing. Linear actuator according to Claim 8 in combination with Claim 2 in which a first gear is designed as a hollow shaft with a central opening and the common piston rod of the first and the second hydraulic cylinder is arranged to be linearly movable in the central opening. Linear actuator according to one of Claims 5 to 7 in that the gear pump defines a pump space and has axially oriented hydraulic openings, via which the first and second working chambers of the first and second hydraulic cylinders can be supplied with hydraulic fluid. Linear actuator according to one of the preceding claims, in which the pump unit and the first and second hydraulic cylinders are arranged in a common housing. Linear actuator according to one of the preceding claims, in which the first and the second hydraulic cylinder are arranged coaxially with each other. Linear actuator according to one of Claims 1 to 11 in which the first and second hydraulic cylinders are not arranged coaxially with each other. A joining device, in particular a rivet setting device or a clinch device, which has an electro-hydraulic linear actuator according to one of the preceding claims, whose first piston is connected via a driven device with a setting punch and / or a hold-down device. Manufacturing method for a linear actuator, with which a mechanical force and / or a linear movement can be generated, in particular a linear actuator according to one of Claims 1 to 13 comprising the following steps: a. Providing (A) a centrally arranged, single motor-driven rotary pump unit, b. Connecting (C) the pump unit on two opposite sides with a first and a second hydraulic cylinder, so that the first and the second hydraulic cylinder are arranged in the axial direction opposite one another, c. Establishing (D) a fluid connection between the pump unit and the first and the second hydraulic cylinder, so that depending on a rotational direction of the pump unit, a first piston of the first hydraulic cylinder or a second piston of the second hydraulic cylinder is controllably movable and / or acted upon by a hydraulic pressure. Manufacturing process according to Claim 15 with the further step of providing (B) a common piston rod which connects the first piston arranged in the first hydraulic cylinder and the second piston arranged in the second hydraulic cylinder. Manufacturing process according to Claim 15 or 16 in which an electrically driven external gear pump or an electrically driven internal gear pump is provided in the pump unit. Manufacturing process according to Claim 17 in combination with Claim 14 in which the internal gear pump has a pinion, which is designed as a hollow shaft with a central opening and in the central opening of the common piston rod is arranged to be linearly movable. Manufacturing process according to Claim 17 in combination with Claim 14 in which the external gear pump has a helical toothing and a first toothed wheel is designed as a hollow shaft with a central opening and in the central opening of the common piston rod is arranged to be linearly movable. Operating method for the electro-hydraulic linear actuator according to one of Claims 1 to 13 in that the following steps comprise a. Providing (I) a first control voltage such that an electric motor of a gear pump of the pump unit rotates in a first direction of rotation, whereby hydraulic fluid is pumped into the first hydraulic cylinder, b. Linear displacement (III) of the first piston in the first hydraulic cylinder in a first output direction, c. Providing (V) a second control voltage to the electric motor such that the gear pump of the pump unit rotates in a second direction of rotation to offset the first piston from the first output direction. Operating procedure according to Claim 20 with the further step of: detecting (II) a hydraulic pressure in the first hydraulic cylinder by means of a pressure sensor and controlling the electric motor with respect to the detected hydraulic pressure. Operating procedure according to Claim 20 or 21 with the further step of providing (IV) at least a second control voltage for the electric motor so that a hydraulic pressure in the first or second hydraulic cylinder is maintained. Use of the electrohydraulic linear actuator as a drive unit for a joining device, a drive unit for a fastening device, a drive unit for a feed device or a drive unit in a forming device.

Images