Linear actuator comprising a linear drive driven by a belt drive

Abstract

Linear actuator comprising a linear drive driven by a belt drive, wherein the belt drive includes a belt drive housing part, wherein a pulley of the belt drive is non-rotatably connected to a threaded spindle of the linear drive, wherein the threaded spindle is rotatably mounted via a first bearing which is received in a bearing flange which is arranged between the belt drive housing part and a housing part of the linear drive, wherein a second bearing is accommodated in the pulley, the inner ring of which is accommodated on a protrusion formed on the belt drive housing part, the pulley is connected to the threaded spindle by friction and form locking.

Description

[0001] The invention relates to a linear actuator comprising a linear drive driven by a belt drive.

[0002] It is generally known that a belt drive drives a shaft that is connected in a rotationally fixed manner.

[0003] A shaft drive device is known from DE 20 2016 101 702 U1.

[0004] A ball screw is known from WO 2023 / 132 190 A1.

[0005] An electrical actuator is known from DE 10 2008 059 771 A1.

[0006] A suspension device is known from JP 2021-146 901 A.

[0007] A geared motor is known from DE 10 2024 104 310 A1.

[0008] A rotationally fixed clamping device is known from DE 42 09 740 A1.

[0009] The invention is therefore based on the objective of providing a safer and more compact drive.

[0010] According to the invention, the problem is solved in the linear actuator according to the features specified in claim 1.

[0011] Important features of the invention for the linear actuator are that the linear actuator has a linear drive driven by a belt drive, wherein the belt drive includes a belt drive housing part, wherein a pulley of the belt drive is non-rotatably connected to a threaded spindle of the linear drive, wherein the threaded spindle is rotatably mounted via a first bearing which is received in a bearing flange which is arranged between the belt drive housing part and a housing part of the linear drive, wherein a second bearing is accommodated in the pulley, the inner ring of which is received on and / or mounted on a protrusion formed on the belt drive housing part, in particular a bearing mounting boss, the pulley is connected to the threaded spindle by friction and form locking.

[0012] An advantage of this design is that the linear actuator is designed to be safe, as a force-fit and simultaneously form-fit connection of the pulley is achieved, and is designed to be compact, as the pulley is rotatably mounted on the one hand via the threaded spindle and on the other hand via the integrated second bearing.

[0013] The pulley is mounted in a floating bearing configuration. This means that the pulley can move axially due to thermally induced changes in length, as the outer ring of the bearing is not fixed in the axial direction relative to the pulley, but rather has one degree of freedom. However, the outer ring is frictionally bound to the pulley by means of a sealing ring, the frictional force of which must be overcome during thermally induced displacement. The frictional force generated by the sealing ring is lower, and in particular significantly lower, than the force required to overcome the frictional connection between the pulley and the threaded spindle.

[0014] Overall, this results in a compact solution for driving a spindle drive via a belt drive driven by an electric motor.

[0015] In an advantageous embodiment, the area covered for the force-fit connection of the threaded spindle to the pulley in the axial direction also includes the area covered for the positive-fit connection of the threaded spindle to the pulley in the axial direction. The advantage here is that the linear actuator is compact. This is because no additional axial installation space is required for the positive-fit connection; the installation space required for the force-fit connection is sufficient and is, in effect, used twice.

[0016] In a preferred embodiment, the raised section on the inside of the belt drive housing part projects towards the threaded spindle. An advantage of this design is that the second bearing is securely mounted on the belt drive housing part.

[0017] In a preferred embodiment, the pulley is mounted onto the threaded spindle and positively connected to it by means of a keyway connection. The advantage here is that a simple, compact, and reliable positive-locking connection can be used.

[0018] In an advantageous embodiment, the area covered by the pulley in the axial direction overlaps with the area covered by the threaded spindle in the axial direction.

[0019] In particular, the axial direction is aligned parallel to the axis of rotation of the threaded spindle, and both the radial and circumferential directions are referenced to this axis of rotation. An advantage of this design is that the pulley is mounted onto the threaded spindle and compactly connected.

[0020] In an advantageous embodiment, the pulley has two sections spaced apart in the circumferential direction by a slot, in particular one that does not extend axially but extends radially only at a single circumferential position, which are pressed radially against the threaded spindle by at least one clamping screw, in particular one tangentially oriented, the screw head of which is pressed against the first of the two sections and the threaded section of which is screwed into a threaded bore of the second of the two sections, in particular wherein the clamping screw projects through the first of the two sections, in particular in the tangential direction.

[0021] An advantage of this design is that pressing the individual sections against the threaded spindle creates a force-fit, compact, and secure connection. The slot is positioned at only one circumferential angle, meaning it runs radially from the inside to the outside at a single circumferential position and not at another circumferential position spaced 180° apart. It is important to note that the geometric shape of the slot is specified in cylindrical coordinates, where the radial direction and radial distances are referenced to the axis of rotation of the threaded spindle, and the circumferential direction is also referenced to this axis, with the axial direction being parallel to it.

[0022] In an advantageous embodiment, a keyway projecting into a keyway of the threaded spindle extends into an axially directed inner groove of the pulley, which is arranged in the first or second of the two sections of the pulley. The advantage here is that a simple and secure connection is achieved.

[0023] In an advantageous embodiment, the two sub-sections are each axially spaced from the second bearing and / or from the bearing receptacle formed in the pulley, in which the second bearing is mounted. It is advantageous that the clamping connection does not interfere with the bearing receptacle. This is because, during clamping, the sub-sections are deflected elastically, thus generating stress forces in the pulley.

[0024] In an advantageous design, the outer diameter of the pulley decreases monotonically with decreasing distance to the first bearing. The advantage here is that the pulley can be as compact as possible while still being stably supported.

[0025] In an advantageous embodiment, the area covered axially by the first sub-section includes the area covered axially by the key and / or the internal groove. It is advantageous that the keyed connection is axially shorter than the friction-fit clamping connection with the sub-sections and the threaded spindle.

[0026] In an advantageous embodiment, the area covered axially by the second sub-section includes the area covered axially by the key and / or the internal groove. It is advantageous that the keyed connection is axially shorter than the friction-fit clamping connection with the sub-sections and the threaded spindle.

[0027] In an advantageous embodiment, the pulley has external teeth. A key advantage is that the pulley can be driven by a belt, particularly a toothed belt. This belt can be driven via a pinion by an electric motor of the linear actuator. The pinion is non-rotatably connected to a rotor shaft of the electric motor.

[0028] In an advantageous embodiment, the area covered by the external teeth in the axial direction comprises - the area covered by the second bearing in the axial direction and / or - encompasses the area covered in the axial direction by the bearing support area formed in the pulley, in which the second bearing is received.

[0029] An advantage of this design is that high torques can be transmitted via the belt drive. In a preferred embodiment, the external teeth are axially spaced from the first bearing. It is advantageous that the external teeth have a larger outer diameter than the clear inner diameter of the first bearing. This decouples the pulley from the first bearing while still allowing it to rotate via the threaded spindle.

[0030] In an advantageous embodiment, an annular groove is arranged in the bearing receiving area formed in the pulley, in which the second bearing is received, and in which a sealing ring, in particular an O-ring, is received.

[0031] In particular, the sealing ring is bounded by the annular groove of the pulley and by the outer ring of the second bearing and / or elastically deformed. An advantage of this is that the outer ring of the second bearing rotates with the pulley without slippage, and yet thermally induced length compensation in the axial direction is still available.

[0032] In an advantageous embodiment, the inner ring of the second bearing is axially fixed to the raised section, and the outer ring of the second bearing is arranged to be axially displaceable within the bearing mounting area, overcoming the frictional force generated by the sealing ring, in particular static and sliding friction forces. Specifically, the inner ring abuts a step of the raised section, in particular a bearing mounting boss, and a retaining ring inserted into an annular groove of the raised section confines the inner ring on its side facing away from the step. An advantage of this configuration is that the outer ring rotates with the pulley without slippage, while still allowing for thermally induced length compensation, which results in a relative axial displacement between the pulley and the sealing ring.

[0033] The invention will now be explained in more detail with reference to schematic illustrations: In the Fig. Figure 1 is a linear drive according to the invention, comprising a linear drive unit driven by an electric motor via a belt drive with a pulley 9, shown in oblique view. In the Fig. Figure 2 shows a sectional view of an area of ​​the linear drive having the pulley 9. In the Fig. Figure 3 shows the pulley 9 in oblique view. In the Fig. Figure 4 shows a top view of the pulley 9, in which a section plane AA is drawn. In the Fig. Figure 5 shows a longitudinal section AA of the pulley 9 in which a section plane BB is drawn. In the Fig. Figure 6 shows a cross-section BB of the pulley 9.

[0034] As shown in the figures, the linear drive has an electric motor whose motor housing 12 is connected via a clamping plate 15 to a belt drive housing part 5, which is connected via a bearing flange 14 to a housing part of the linear drive.

[0035] A pinion 11 is mounted on the rotor shaft 13 of the electric motor and is connected to the rotor shaft 13 in a rotationally fixed manner.

[0036] A belt 10, in particular a toothed belt, is in engagement with the toothed pinion 11 and a pulley 9 having a toothed section 32, which has a keyway 31 into which a key projects for the rotationally fixed connection of the pulley 9 with a threaded spindle 2 of the linear drive rotatably mounted via a bearing 3 received in the bearing flange 14.

[0037] The bearing 3 is mounted on a cylindrical section of the threaded spindle 2.

[0038] A spindle nut is screwed onto the threaded spindle 2, which is rotationally fixed to the housing part 1 and can be moved back and forth in the axial direction, in particular parallel to the axis of rotation of the threaded spindle 2.

[0039] The axial direction is therefore parallel to the axis of rotation of the threaded spindle 2. The circumferential direction and the radial direction as well as the radial distances are also always referred to the axis of rotation of the threaded spindle 2.

[0040] Preferably, the housing part has an axial groove on its inner wall into which a T-nut connected to the spindle nut projects, or a radially directed projection formed on the spindle nut.

[0041] The piston rod 6 is mounted on the spindle nut and is detachably connected to it. Thus, the piston rod 6 moves back and forth axially with the spindle nut – depending on the rotational movement of the threaded spindle 2.

[0042] As described above, the pulley 9 is preferably connected to the threaded spindle in a rotationally fixed manner via the keyway connection, wherein a further bearing is inserted into the pulley 9 at the end region axially away from the threaded spindle 2, wherein the further bearing is mounted on a bearing support boss 4, which projects axially towards the threaded spindle 2 on the belt housing part 5.

[0043] The additional bearing 7 is inserted into a hollow cylindrical area of ​​the pulley 9, with an annular groove 50 arranged in the hollow cylindrical area, in which a sealing ring 8 is inserted. Thus, the outer ring of the additional bearing 7, which is received in the hollow cylindrical area, also rests against the sealing ring 8 and is therefore prevented from axially moving out and a relative rotational movement between the outer ring of the additional bearing 7 and the pulley 9 is prevented.

[0044] Thus, the pulley 9 is rotatably mounted on the bearing housing 4 via the additional bearing 7 and is also rotationally fixed to the threaded spindle 2. The pulley 9 has a clamping area in its end region axially facing the first bearing, in relation to this rotationally fixed connection with the threaded spindle 2.

[0045] For this purpose, a radially continuous slot 30 is provided in the end region at a circumferential point. However, the slot 30 is not axially continuous, but only in the end region of the pulley 9 facing axially towards the first bearing.

[0046] The slot 30 separates the end region of the pulley 9, which faces axially towards the first bearing, into two sub-regions.

[0047] A clamping screw is provided in a tangentially directed bore 33 which is divided into two parts as a result of the slot 30 and protrudes through the slot 30.

[0048] The screw head of the clamping screw rests against a first section, and the threaded section of the clamping screw is screwed into a threaded section of bore 33. When the clamping screw is screwed in, the two sections are pressed onto the threaded spindle 2, thus connecting the pulley 9 to the threaded spindle by friction in addition to the positive keyway connection, in particular by clamping.

[0049] A further clamping screw is provided in a further bore 33 for improved clamping of the two sub-areas, symmetrically to the axis of rotation of the threaded spindle 2, in particular as shown in Fig. 6. Therefore, imbalance can be reduced or prevented.

[0050] The area covered axially by the keyway of pulley 9 overlaps with the area covered axially by the two sub-areas. The positive and non-positive connection is therefore located in the same axial area.

[0051] The area covered by the toothing of the pulley 9 in the axial direction includes the area covered by the bearing mounting area, i.e. the hollow cylindrical area, of the pulley 9 in the axial direction.

[0052] The largest outer diameter of the gear teeth is larger than the largest outer diameter of the two sub-sections.

[0053] To adjust the tension of the belt 10, the tensioning plate 15 is slidably mounted. For this purpose, an eccentric shaft 16 is rotatably mounted in a through bore of the belt drive housing part 5, the eccentric end of which engages in a bore of the tensioning plate 15, so that this tensioning plate 15 is slidable depending on the rotational position of the eccentric shaft 16. The direction of movement is preferably arranged in the plane that contains the axis of rotation of the threaded spindle 2 and also the axis of rotation of the rotor shaft of the electric motor. The direction of movement is, in particular, perpendicular to the axis of rotation of the threaded spindle 2.

[0054] During displacement, the clamping plate 15 is guided by protruding projections on the clamping plate 15 that engage in elongated holes formed in the belt drive housing part 5, extending parallel to the displacement direction. The inner ring of the second bearing 7 is positioned against a step of the bearing housing boss 4 and is bounded on the side of the inner ring facing away from the step by a retaining ring 21. Thus, the inner ring is fixed to the bearing housing boss and positively locked in the axial direction. The outer ring of the second bearing 7 is received in the bearing housing area of ​​the pulley 9 and is arranged to be displaceable in the axial direction. However, during displacement, the frictional force generated by the sealing ring 8, which is received in the inner groove, in particular the annular groove 50, of the pulley 9 and presses against the outer ring, must be overcome.

[0055] In further embodiments of the invention, a chain is used instead of the belt 10, and thus a sprocket is used instead of the pinion 11. Accordingly, the toothing of the pulley 9 is then a sprocket toothing. Reference symbol list 1 Housing part of the linear gear 2 threaded spindles 3 warehouses 4 bearing mounting dome 5 Belt drive housing part of the belt drive housing 6 piston rod 7 warehouses 8 Sealing ring, especially O-ring 9 Pulley 10 belts 11 sprockets 12 Motor housings 13 Rotor shaft 14 bearing flange 15 chipboard 16 eccentric shaft 20 Cover part of the belt drive housing 30 slots 31 Keyway 32 gear teeth 33 Hole for clamping screw 50 Ring groove for sealing ring, especially O-ring

Claims

Linear actuator comprising a linear drive driven by a belt drive, wherein the belt drive comprises a belt drive housing part (5), wherein a pulley (9) of the belt drive is rotationally fixed to a threaded spindle (2) of the linear drive, characterized in that the threaded spindle (2) is rotatably mounted via a first bearing (3) which is received in a bearing flange (14) which is arranged between the belt drive housing part (5) and a housing part (1) of the linear drive, wherein a second bearing (7) is received in the pulley (9), the inner ring of which is received on and / or mounted on a projection formed on the belt drive housing part (5), wherein the pulley (9) is frictionally and positively connected to the threaded spindle (2). Linear actuator according to claim 1, characterized in that the area covered for force-fit connection of the threaded spindle (2) with the pulley (9) in the axial direction comprises the area covered for form-fit connection of the threaded spindle (2) with the pulley (9) in the axial direction. Linear actuator according to one of the preceding claims, characterized in that the protrusion on the inside of the belt drive housing part (5) projects towards the threaded spindle (2). Linear actuator according to one of the preceding claims, characterized in that the pulley (9) is mounted on the threaded spindle (2) and is positively connected to the threaded spindle (2) by means of a keyway connection. Linear actuator according to one of the preceding claims, characterized in that the area covered by the pulley (9) in the axial direction overlaps with the area covered by the threaded spindle (2) in the axial direction, in particular wherein the axial direction is aligned parallel to the axis of rotation of the threaded spindle (2) and both the radial direction and the circumferential direction are related to this axis of rotation. Linear actuator according to one of the preceding claims, characterized in that the pulley (9) has two partial areas spaced apart in the circumferential direction by a slot (30), in particular not axially continuous, which only extends radially at a single circumferential position, and which are radially pressed against the threaded spindle (2) by at least one clamping screw, in particular tangentially oriented, the screw head of which is pressed against the first of the two partial areas and the threaded section of which is screwed into a threaded bore of the second of the two partial areas, wherein the clamping screw projects through the first of the two partial areas. Linear actuator according to one of the preceding claims, characterized in that a keyway projecting into a keyway groove (31) of the threaded spindle (2) projects into an axially directed inner groove which is arranged in the first or second of the two partial areas of the pulley (9). Linear actuator according to one of the preceding claims, characterized in that the two sub-areas are each axially spaced from the second bearing (7) and / or from the bearing receiving area formed in the pulley (9) in which the second bearing (7) is received. Linear actuator according to one of the preceding claims, characterized in that the outer diameter of the pulley (9) decreases monotonically with decreasing distance to the first bearing (3). Linear actuator according to one of the preceding claims, characterized in that the area covered in the axial direction by the first partial area comprises the area covered in the axial direction by the key and / or the inner groove, and / or that the area covered in the axial direction by the second partial area comprises the area covered in the axial direction by the key and / or the inner groove. Linear actuator according to one of the preceding claims, characterized in that the pulley (9) has external teeth. Linear actuator according to one of the preceding claims, characterized in that the area covered by the external toothing in the axial direction comprises the area covered by the second bearing (7) in the axial direction and / or the area covered by the bearing receiving area formed in the pulley (9) in which the second bearing (7) is received in the axial direction. Linear actuator according to one of the preceding claims, characterized in that the external toothing is axially spaced from the first bearing (3). Linear actuator according to one of the preceding claims, characterized in that an annular groove (50) is arranged in the bearing receiving area formed in the pulley (9) in which the second bearing (7) is received, in which a sealing ring (8), in particular an O-ring, is received, in particular wherein the sealing ring (8) is bounded by the annular groove (50) of the pulley (9) and by the outer ring of the second bearing (7) and / or is elastically deformed. Linear actuator according to claim 14, characterized in that the inner ring of the second bearing (7) is axially fixed on the projection and the outer ring of the second bearing (7) is arranged to be axially displaceable in the bearing receiving area, overcoming the frictional force generated by the sealing ring (8), in particular static friction force and sliding friction force, in particular wherein the inner ring abuts a step of the projection, in particular bearing receiving dome (4) and a retaining ring embedded in the annular groove (50) of the projection limits the inner ring on its side facing away from the step axially.

Images