Electromechanical Cylinder

Abstract

The present invention relates to an electromechanical cylinder having a screw drive that converts the applied motor torque of an electric motor 10 into linear motion for an actuating part 14, characterized in that at least one force acting on the actuating part 14 is detected by a sensor device 46.

Description

[Technical field]

[0001] The present invention relates to an electromechanical cylinder with a screw drive, which converts the applied motor torque of an electric motor into a linear movement of an actuating part. [Background technology]

[0002] DE 102019004690 A1 discloses a linear drive system with an actuating part that can be driven in translation by an electric motor, in which the actuating part takes a position in case of energy loss in the electric drive or in emergency operation and is coupled to a mechanical energy storage device in such a way that it exerts an actuating force during this process. In this way, a linear drive system in the form of an electromechanical cylinder is created, which performs its function without interruption even during long-term operation and is not affected by any changes in the ambient conditions, such as temperature. By using a mechanical energy storage device instead of a conventional gas storage device, a purely mechanical solution is created that in principle does not require any additional maintenance for operation, such as, for example, refilling the actuating gas in the known gas springs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] DE 102019004690 Summary of the Invention [Problem to be solved by the invention]

[0004] Based on this state of the art, the present invention is based on the object of improving the functionality of such electromechanical cylinder or linear drive systems. [Means for solving the problem]

[0005] This object is achieved by an electromechanical cylinder having the features of claim 1 in its entirety.

[0006] According to the characterizing part of claim 1, an integrated force measurement is achieved in the electromechanical actuator or cylinder, since at least one force acting on the actuating part of the linear drive system is detected by a sensor device, so that the actuating part of the cylinder in the form of an actuating rod or a so-called thrust tube can be monitored or determined with regard to the desired force transmission to the third-party component and / or the application of in some cases unacceptably high forces from the third-party component. In particular, it is possible to determine whether the force applied by the actuating part by the screw drive during a part of the extension movement and / or retraction movement is sufficient to ensure a safe operation of the third-party component, in particular whether the motor torque applied by the electric drive is sufficient for this purpose or needs to be increased accordingly by increasing the motor power. By determining the force applied to the actuating part, it is possible to directly determine the force on the actuating part, which must not exceed the specified limits for reliable operation. In particular, the screw drive comprises the components of a threaded spindle and a transmission nut.

[0007] In a preferred embodiment of the electromechanical cylinder, the sensor arrangement comprises a sensor for detecting tensile forces and / or a sensor for detecting compressive forces on the actuating part. In this way, the forces occurring in the two main feed directions "extension and retraction" can be determined, whereby one or the other feed direction is specified for a left- or right-rotating screw drive. A corresponding force determination via the sensor arrangement is possible when the actuating part acting on the third component is subjected to the respective load situation.

[0008] It has been found to be particularly advantageous to implement the respective sensors of the sensor arrangement using strain gauges suitable for detecting compressive and tensile deformations. Strain gauges of conventional design are capable of changing their electrical resistance even with small deformations and can therefore be used as strain sensors. Strain gauges are freely available on the market as standardized purchased parts and can be fixed, in particular glued, to almost any component with the aid of a suitable measuring cable; even if they only deform under minimal loads, this deformation is sufficient to detect a change in the resistance of the respective strain gauge, which can be evaluated by measurement.

[0009] In a particularly advantageous manner, the screw drive comprises a transmission unit, which couples the electric motor to a threaded spindle, which moves the guide body by means of a threaded nut in which the actuating part engages. In particular, when using a belt transmission, a traction drive is provided which can be produced cost-effectively and requires little installation space on the linear drive unit in the form of an electromechanical cylinder. In particular, this requires minimal maintenance, ensures quiet and low-noise operation, and in the event of a brief unintended overload, this can be compensated for via so-called belt slippage. Furthermore, the belt transmission requires only a minimum installation weight in implementation, which is advantageous for the handling of the electromechanical cylinder when it is transported by hand and attached to other machine parts in order to fulfill its function. Instead of a belt transmission, another type of transmission unit can also be used in implementation. It is also possible to implement a linear drive concept instead of an angular drive concept, in which the drive shaft of the electric motor is arranged concentrically on the threaded spindle and connected to it via a coupling.

[0010] In a preferred embodiment of the electromechanical cylinder, it is provided that the working part is formed of a thrust tube which at least partially surrounds the threaded spindle and is guided in a housing tube so as to be longitudinally movable by a guide device using a guide body. By means of the housing tube, the thrust tube is protected from environmental contamination. Since the thrust tube surrounds the threaded spindle on the outside in each of its movement states, the fine threads of the threaded spindle are also protected from environmental influences. The hollow design of the thrust tube allows only small masses to be moved linearly using a screw drive, which helps to reduce the drive force required by the electric motor.

[0011] In a preferred embodiment of the electromechanical cylinder, the guide device comprises a guide body, which is arranged between the threaded spindle and the working part and forms, as part of the longitudinal guide, an anti-rotation device for the working part relative to the housing tube. In this way, undesired relative rotational movements between the housing and the thrust tube are prevented, whereby the guide body is guided longitudinally in the housing tube. Depending on the direction of rotation of the threaded spindle, a respective retraction or extension movement of the working part is initiated in the form of the thrust tube.

[0012] In a further preferred embodiment of the electromechanical cylinder, the sensor device is accommodated in a bearing device that is arranged between the transmission housing and the housing tube and is passed through by a threaded spindle that is attached to the bearing device by axial and radial bearing points.

[0013] Preferably, the one sensor and / or the other sensor is accommodated between the axial bearing and the common radial bearing in the bearing arrangement, respectively. The bearing arrangement can be designed in the form of a bearing block arranged in a stationary position and can perform two different functions in a space-saving central position, i.e. provide a bearing for a rotatable threaded spindle in one case and form a receiving space for a sensor arrangement with the respective sensor.

[0014] Preferably, each sensor is formed from an annular body provided with a respective strain gauge and pierced by a threaded spindle. In a particularly advantageous manner, the annular body referred to herein forms a type of membrane that allows the recording of the load in each case in time via the strain gauge attached to the membrane under the force on the actuation part. The membrane properties of the annular body also ensure that the membrane returns to its original state when the force is removed, without the possibility of the measurement result being distorted by hysteresis phenomena.

[0015] Particularly preferred for electromechanical cylinders is that the threaded spindle is fixed on the side facing the transmission unit by means of a grooved nut in the axial displacement direction, which is supported on an adjacently arranged axial bearing, and the threaded spindle rests flat against the other axial bearing on the opposite side of the bearing device. In this way, the forces received by the respective axial bearing in the adjacent annular body of the sensor device are transmitted linearly, so that, depending on the received forces, information is provided about the functionality of the individual bearing points in the bearing block, and if necessary, if a bearing is about to fail, it can be replaced with a new bearing. This is therefore not comparable to the prior art.

[0016] In the following, the electromechanical cylinder of the invention is explained in more detail using an exemplary embodiment as shown in the figures. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 shows a perspective view, not to scale, of an electromechanical cylinder according to the invention. [Diagram 2] FIG. 2 is a partial elevational and partial longitudinal sectional view of the cylinder shown in FIG. [Diagram 3] FIG. 3 is an enlarged view of the cross section of FIG. [Figure 4] FIG. 4 shows a perspective top view of an annular body to which a strain gauge is applied as an essential component of the sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 1 shows an electromechanical cylinder, also called single-arm drive system, according to the invention, comprising an electric motor 10 and a transmission unit 12 converting the applied motor torque of the electric motor 10 into a linear movement for an actuating part 14. An electromechanical cylinder designed for this purpose is mounted for rotation about a rotation axis 20 by means of two opposing angular supports 18, via a bearing arrangement 16 in the form of a bearing block.

[0019] As can be seen from the cross-sectional view according to Figure 2, the transmission unit 12 accommodated in the transmission box 21 comprises a threaded spindle 24 which is rotatably guided in the housing tube 22 and which interacts with a guide body 26 of the guide device via a threaded nut 28 which is arranged in engagement with the threaded spindle 24. In the present embodiment, the threaded nut 28 engages with the threaded spindle 24 in that the external thread of the threaded spindle 24 permanently engages with an associated internal thread of the threaded nut 28 to form a screw drive.

[0020] Furthermore, the annular guide body 26 is connected to the free end of the threaded nut 28 facing away from the transmission unit 12, and the threaded spindle 24 passes completely through the annular guide body in its longitudinal direction while maintaining a defined gap distance. The guide body 26 is adapted at its outer periphery to the inner contour of the housing part 22 as a further part of a guide device forming an outer shell for the cylinder or spindle housing.

[0021] Both the threaded nut 28 and the guide body 26 attached thereto are therefore not rotatable about the longitudinal axis of the threaded spindle 24 but can move translationally along this longitudinal axis and are therefore guided on their outer periphery along the inner wall of the housing tube 22. For this purpose, the housing tube 22 is hollow on its inside and has a non-rotationally symmetrical, in particular polygonal, preferably rectangular or square, inner cross-section, in particular with rounded edges 30 at the transition points. The outer cross-section of the guide body 26 essentially corresponds to the selected inner cross-section of the housing tube 22.

[0022] The threaded spindle 24 is designed as a cylinder rod with an external thread on its outer circumference which engages with an internal thread on the inner circumference of the threaded nut 28. The working part 14 forms a thrust tube 32 which is rigidly connected to the free end of the guide body 26 facing the threaded nut 28 and is guided in the housing tube 22 in a rotationally fixed and longitudinally displaceable manner. In any case, in the above-mentioned configuration, even when the thrust tube 32 is extended to its maximum extent, the guide body 26 together with the associated threaded nut 28 remains in the housing tube 22, which at its free end facing the environment has a stop option in the form of an inwardly protruding annular edge 33 against which the guide part 26 can be moved as an outermost limit.

[0023] 1 and 2, the thrust tube 32 is at least partially disposed in the housing tube 22 in each of its displacement positions, partially protruding with a free end 34 and partially protruding out of the housing tube 22 in front thereof. In the opposite direction, the thrust tube 32 can be retracted in the opposite direction into the housing tube 22 until the free end face 35 of the threaded spindle 24 comes into contact or nearly comes into contact with the adjacent opposite inner wall of the thrust tube 32 at its free end 34. Another possibility for limiting the retraction movement of the thrust tube 32 is for the threaded nut 28 to come into contact or nearly adjacent contact with a part of the bearing device 16 with its free end face.

[0024] To transmit the driving force of the electric motor 10, a driven pulley 36 is used, which drives in the usual way a driving pulley 40, which is rigidly connected to the threaded spindle 24 via a belt drive 38. For this purpose, the threaded spindle 24 is reduced in diameter at its left end, as viewed in the direction of FIG. 2. The transmission housing 21 encloses the belt drive 38 and the two pulleys 36, 40. The electric motor 10 and the essential parts of the feed cylinder are fixedly arranged on one side of the transmission housing 21, protrude from the transmission housing 21 and are, for example, rigidly screwed and / or pinned into the transmission housing 21, with their respective longitudinal axes arranged parallel to one another.

[0025] As can be seen in particular from the view in Fig. 3, which is enlarged by a factor of two, the sensor arrangement 46 is accommodated in the entire bearing arrangement 16 or in the bearing block. Said sensor arrangement 46 comprises a sensor 48 for detecting a tensile force on the actuating part 14 and / or a further sensor 50 for detecting a compressive force in the opposite direction on the actuating part 14. To ensure that said tensile force can act on the actuating part 14 as shown in Fig. 2, the actuating part 14 is subjected to a force acting to the right in the orientation of Fig. 2, and in the case of a compressive force, the actuating part 14 is subjected to a corresponding force vector to the left along its longitudinal axis. To ensure that the respective sensor 48, 50 can detect the abovementioned forces on the actuating part 14, a strain gauge 52 is provided, which is shown only by way of example at one point in Fig. 4.

[0026] As can be seen from Fig. 3, the sensor 48 is supported between the adjacent axial bearing 54 and the bearing block 16. A further sensor 50 is supported between the axial bearing 58 and the bearing block 16. Each of the above-mentioned sensors 48 or 50 is supported on the face of the bearing block 16 both at the top outside and at the bottom outside, as viewed in the direction of Fig. 3, so that a flow of forces towards the centre is generated. The radial bearing 56, which is arranged between the two axial bearings 54, 58, does not come into contact with the above-mentioned sensors 48, 50 and serves only to support the threaded spindle 24 during the rotational drive.

[0027] In this case, each sensor 48, 50 of the sensor arrangement 46 has its own electrical measurement connection 64, by means of which the measurement value data can be transmitted to an electronic evaluation system, not shown in detail.

[0028] Figure 4 shows the annular structure of the sensors 48, 50 of the same design. The sensor ring 65 has an upwardly projecting edge 66 at its outer periphery, which is supported on an inner flange-like annular widening 68 of the housing wall of the bearing arrangement 16, as shown in Figure 3, forming a receiving space for flush receiving of the central radial bearing 56. In the direction of a central opening 70 passing through the threaded spindle 24, a further edge 72 is provided opposite and adjacent to the edge 66, which projects downwards as seen in the direction of Figure 4 and which is supported for each sensor 48, 50 on the rotating inner ring of the axial bearing 54, 58, as shown in Figure 3.

[0029] If pressure is applied to the working part 14, after the freedom of play has been established, a force is applied to the threaded spindle 24 via the guide body 26 or the threaded nut 28, respectively, which acts on the rotating inner ring of the axial bearing 58 arranged on the right side via the cylindrical widening 60, and a corresponding force application is applied to the further sensor 50, which causes a deformation of the strain gauge arrangement 52, the resulting deformation level of which can be evaluated as a compressive force acting on the working part 14. Since the grooved nut 62 moves slightly to the left in the direction of FIG. 3 with respect to the compressive force applied to the threaded spindle 24 and is thus relaxed, the axial bearing 54 arranged on the left side is also relaxed with respect to its inner ring and thus also the sensor 48 arranged on the left side. In this case, the above-mentioned grooved nut 62 holds the bearing assembly with the bearings 54, 56, 58 and the sensors 48, 50 firmly against the widening 60 of the threaded spindle 24.

[0030] Conversely, when a tensile force is applied to the working part 14, a force acting to the right is applied to the threaded spindle 24 via the guide body 26 of the threaded nut 28, which loads the threaded grooved nut 62 and exerts a force to the right on the components of the rotating inner ring of the axial bearing 54 arranged on the left. The inner ring part of the axial bearing 54 rotating in this way acts on a further edge 72 in the form of a peripheral edge, which is supported stationary via its outer edge 66 on the annular widening 68 of the bearing arrangement 16. This causes a deformation of the annular body 65 with a corresponding deformation of the strain gauge 52, as shown in FIG. 4, which generates a measurement signal at the connection 64 and provides information about the level of the tensile force applied to the working part 14. Due to the annular arrangement with the protruding edges 66, 72 of both sensors 48, 50, once the force is removed, a reset occurs again immediately and the strain gauge 52 is no longer deformed or displaced, providing a measurement signal of zero, in other words meaning that there is no tensile or compressive force acting axially on the working part 14. Of course, during the measurement acquisition process, a reference value other than zero can also be selected as a starting point for the measurement acquisition.

[0031] The above-mentioned edges 66 and 72 on the respective sensor ring can also be omitted on at least one side. This allows the disk of the sensor ring 65 facing the respective axial bearing 54, 58 to be designed flat. In order to ensure undisturbed membrane deformations, the centrally arranged radial bearing 56 is selected to have a diameter from the outer circumference smaller than the inner diameter determined by the edge 66, seen in the direction of the central opening 70 of the sensor ring 65. Furthermore, the sensor rings 65 arranged stationary in the bearing arrangement 16 for the tension sensor 48 and the compression sensor 50 are in a position that allows the inner rings of the respective associated axial bearings 54, 58 to slide. However, it is also possible to rotate the two sensors 48, 50 together with the threaded spindle 24, in which case the measurement connection 64 transmits the detected measured values ​​of the strain gauges 52 to the evaluation electronics in the form of a sliding contact. Furthermore, if necessary, only one sensor 48 or 50 can be used in case of monitoring only tensile or compressive forces.

Claims

1. In an electromechanical cylinder having a screw drive that converts applied motor torque of an electric motor (10) into linear motion for an actuating part (14), Electromechanical cylinder, characterized in that at least one force acting on said actuating part (14) is detected by a sensor device (46).

2. 2. An electromechanical cylinder according to claim 1, characterized in that the sensor device comprises a sensor (48) for detecting a tensile force and / or a sensor (50) for detecting a compressive force on the actuating part (14).

3. 2. An electromechanical cylinder according to claim 1, characterized in that each sensor (48, 50) detects the respective force on the actuating part (14) by means of a strain gauge (52).

4. 2. An electromechanical cylinder according to claim 1, characterized in that the transmission unit (12) has at least one transmission part (36, 38, 40) that connects the electric motor (10) via a threaded nut (28) to a threaded spindle (24) that moves a guide body (26) in engagement with the actuating part (14).

5. 2. An electromechanical cylinder according to claim 1, characterized in that the actuating part (14) is formed from a thrust tube (32) which at least partially surrounds the threaded spindle (24) and is guided in the housing tube (22) so as to be longitudinally movable by means of a guide body (26).

6. 2. An electromechanical cylinder according to claim 1, characterized in that the guide device comprises a guide body (26) which is arranged between the threaded spindle (24) and the working part (14) and which forms, as part of the longitudinal guide, an anti-rotation device for the working part (14) facing the housing tube (22).

7. 2. An electromechanical cylinder according to claim 1, characterized in that the sensor device (46) is accommodated in a bearing device (16) that is arranged between the transmission housing (21) and the housing tube (22) and is passed through by a threaded spindle (24) that is attached to the bearing device (16) by axial and radial bearing points (54, 56, 58).

8. 2. An electromechanical cylinder according to claim 1, characterized in that the one sensor (48) and the other sensor (50) are housed in the bearing arrangement (16) between the axial bearings (54, 58) and the common radial bearing (56).

9. 2. An electromechanical cylinder according to claim 1, characterized in that each sensor (48, 50) comprises an annular body (65) carrying a respective strain gauge (52) and passed through by the threaded spindle (24).

10. An electromechanical cylinder as described in any one of claims 1 to 9, characterized in that the threaded spindle (24) is fixed on the side facing the transmission unit (36, 38, 40) by an axially-displacement grooved nut (62) supported on an adjacently arranged axial bearing (54), and the threaded spindle (24) rests flat against the other axial bearing (58) with a radial extension on the opposite side of the bearing device (16).

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