CN106838180B

CN106838180B - Actuator with elastic element for volume compensation

Info

Publication number: CN106838180B
Application number: CN201610993980.9A
Authority: CN
Inventors: K.默瓦斯托; M.肖尔茨
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2015-11-12
Filing date: 2016-11-11
Publication date: 2020-09-15
Anticipated expiration: 2036-11-11
Also published as: DE102015222288A1; CN106838180A

Abstract

The invention relates to an actuator (10) having a housing (20) and a carrier (30), which is mounted on the housing (20) so as to be linearly movable in the direction of a longitudinal axis (11), along which the carrier (30) projects outwardly from the housing (20), which housing and carrier together define an inner chamber (12), the volume of which changes when the carrier (30) is moved relative to the housing (20), a threaded spindle (60) which projects into a hollow chamber (31) of the carrier (30) being mounted on the housing (20) so as to be rotatable about the longitudinal axis (11) by means of a rotary bearing, the carrier (30) being provided with a nut which is arranged in the inner chamber (12) and which is in a screwing action with the threaded spindle (60). An elastic element (70; 70') is arranged in the hollow chamber (31) of the bracket (30), which element is elastically deformed when the bracket (30) is moved relative to the housing (20).

Description

Actuator with elastic element for volume compensation

Technical Field

The invention relates to an actuator according to the invention.

Background

An actuator is known from DE 102007043391 a 1. The actuator has a housing and a carrier, wherein the carrier is supported on the housing in a linearly movable manner in the direction of a longitudinal axis, wherein the carrier projects out of the housing in the direction of the longitudinal axis. The housing and the bracket collectively define an interior chamber having a volume that changes as the bracket moves relative to the housing. Furthermore, a threaded spindle is provided, which is mounted on the housing so as to be rotatable about the longitudinal axis by means of a rotary bearing, wherein the threaded spindle projects into the hollow space of the console. In addition, the bracket is provided with a nut which is arranged in the inner chamber and which is in screwing action with the threaded spindle.

The screwing action mentioned requires lubrication on the one hand, so that the actuator has a long life. In addition, heat is generated during the screwing action, which must be conducted away to the surroundings. It is conceivable to solve both problems by filling the interior with a non-compressible liquid, in particular with oil. However, the variable volume of the inner chamber does not ensure that: the screwing action comes into contact with the incompressible fluid in each position of the carriage and in each installation position of the actuator.

Disclosure of Invention

One advantage of the present invention is: a section is established in the interior chamber, the volume of which section is constant when the carriage is moved. This section can be filled with an incompressible liquid in response thereto. In this way, it is ensured in each position of the bracket and in each installation position of the actuator that the screwing action comes into contact with the incompressible fluid.

According to the invention, it is proposed that an elastic element is arranged in the hollow space of the carrier, which element is elastically deformed when the carrier is moved relative to the housing. By means of the mentioned elastic deformation of the elastic element, the volume change of the interior space is compensated for during the movement of the carriage.

The nut is preferably arranged at one end of the bracket. The rotation bearing is preferably arranged at the end of the housing facing away from the bracket. The nut is preferably designed as a separate structural component which is firmly connected to the remaining bracket. Of course, it is also conceivable for the nut to be formed integrally with the remaining bracket. The elastic element is preferably made of plastic and most preferably of elastomer.

Advantageous modifications and improvements of the invention are described in the preferred and other embodiments.

It can be provided that the elastic element separates the first and second sections of the interior space in a fluid-tight manner from one another, wherein the region of the screwing action between the nut and the spindle is a constituent of the second section of the interior space. It is thereby ensured that the incompressible fluid located in the second section of the interior chamber makes contact with the screwing action in each position of the bracket and in each installation position of the actuator.

It can be provided that the nut is provided exclusively at its end facing the rotary bearing with an end seal which is in sealing engagement with the threaded spindle in such a way that it separates the third section of the interior space from the second section of the interior space in a fluid-tight manner. In this way, the necessary elastic deformation of the elastic element during the movement of the carrier is reduced. It is to be noted here that the volume of the third section is smaller when the carriage moves in, wherein the volume increases strongly when the carriage moves out. This volume change need not be absorbed by the elastic element. At the same time, the volume of the incompressible fluid, which can fill the inner chamber, is only slightly reduced. In addition, the slightly smaller fluid volume reduces the weight of the incompressible fluid, which is carried by the elastic element in each case as a function of the installation position of the actuator.

It can be provided that the nut is open at its two opposite ends in such a way that the second section of the interior space extends through the nut. It is thereby achieved that the incompressible fluid flows through the nut when the carrier moves, so that the cooling effect during the screwing action is improved.

It can be provided that the elastic element is deformed when the carrier is moved relative to the housing in such a way that the volume of the first section is changed while the volume of the second section remains substantially constant. In the ideal case, the volume of the second section remains exactly constant. Obviously, this ideal situation is difficult to achieve in practice, since, for example, inertial forces cause undesired deformations of the elastic element. However, no significant disadvantages are obtained in this connection with regard to the lubricating and cooling effect of the incompressible fluid. It is important that the large volume changes of the inner chamber that occur in conventional actuators are significantly reduced. The volume of the third section can likewise be changed when the carrier is moved relative to the housing.

It can be provided that the second section of the interior is substantially completely filled with an incompressible fluid. In an ideal case, the second section is completely filled with the incompressible fluid. But a portion of the second section can be filled with bubbles that are difficult to avoid when filling the incompressible fluid. The incompressible fluid is, for example, oil, which is particularly suitable for lubricating and/or cooling the screwing action between the nut and the threaded spindle.

It can be provided that the threaded spindle has an end face, wherein the elastic element is arranged between the end face mentioned and a bottom face of the hollow chamber of the carrier. In this region of the inner chamber, a significant volume change takes place, which can be compensated in a simple manner directly by the elastic element.

It can be provided that the elastic element is formed by an elastically deformable membrane which is fastened at the side of the hollow chamber of the carrier. The thickness of the membrane is preferably selected such that even with large bending deformations only such small stresses occur that the membrane does not break permanently. At the same time, the thickness of the membrane is preferably selected to be so great that the membrane is dimensionally stable. With such a membrane, the elastic deformation required for volume compensation can be achieved without fear of fracture of the elastic element.

It can be provided that the membrane is designed in the form of a bellows having a plurality of flexible folds which encircle annularly about the longitudinal axis. Such a bellows can be produced particularly cost-effectively. Preferably, the bellows is manufactured in a plastic injection molding process. The pleats are preferably arranged next to one another in the direction of the longitudinal axis. The bellows is preferably configured in a pot-like manner with a closed bottom side and an open head side. Preferably, the head side is firmly connected to a side wall of the hollow chamber of the carrier, wherein the bottom side faces away from the threaded main axis.

It can be provided that the elastic element is formed from a foamed plastic with a plurality of holes, wherein the holes define a first section of the interior space. Such an actuator can be produced particularly simply and cost-effectively.

It can be provided that the foam has a fluid-tight closed surface. In this way, the incompressible fluid reaches the first section from the second section of the interior chamber.

It can be provided that the foam has a plurality of pores which are spaced apart in a fluid-tight manner. In this way, the incompressible fluid reaches the first section from the second section of the interior chamber.

It can be provided that the screwing action between the nut and the threaded spindle is facilitated by a roller provided with an outer contour or by rolling elements configured as balls or cylinders. The profiled roller with its outer profile preferably engages in a helically running groove which is arranged in the threaded spindle and in the nut, respectively. The rolling elements preferably roll in helically running groove sections which are arranged in the threaded spindle and in the nut, respectively. The rolling bodies are preferably arranged in the nut in a circulating and continuous manner.

It can be provided that the carrier has at least one ventilation opening in the region of the first section of the interior chamber. The first section of the inner chamber is preferably filled with a gas, in particular air. By means of the at least one ventilation opening, it is avoided that excessive pressure changes occur in the first section of the inner chamber during the movement of the carrier. In addition to the at least one ventilation opening and the fluid inlet opening in the desired case, the interior chamber is preferably closed in a fluid-tight manner.

It is obvious that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination, but also in the combinations specified below

Can be used in other combinations or alone without leaving the framework of the invention.

Drawings

The invention is explained in detail below with the aid of the figures. Wherein:

fig. 1 is a longitudinal section through the drive-side end of an actuator according to a first embodiment of the invention;

FIG. 2 is a longitudinal section through the bracket-side end of the actuator according to FIG. 1; and is

Fig. 3 is a longitudinal section corresponding to fig. 2 of an actuator according to a second embodiment of the invention.

Detailed Description

Fig. 1 shows a longitudinal section through a drive-side end of an actuator 10 according to a first embodiment of the invention. The actuator 10 has a housing 20 consisting of a main body 23, a first end block (21 in fig. 2 and 3) and a second end block 22. The body 23 is preferably made of aluminum in an extrusion process so that it has a constant, tubular cross-sectional shape along the longitudinal axis 11. In the second end piece 22, a pivot bearing 63 is accommodated, by means of which the threaded spindle 60 is rotatably supported about the longitudinal axis 11. The rotary bearing 63 is preferably designed as a radial rolling bearing, wherein it comprises a plurality of angular ball bearings which are tightened against one another without play. A threaded spindle 60 extends through the second end block 22, wherein the threaded spindle projects outwardly from the housing 20 by means of a drive journal 62. Via the drive journal 62, the threaded spindle 60 can be brought into a rotational movement, for example by means of an electric motor (not shown). In the interior 12 of the housing 20, the threaded spindle 60 is provided with one or more spindle groove sections 61 which run helically with respect to the longitudinal axis 11.

In the inner chamber 12 of the housing 20, a nut 50 is additionally arranged, which is in screwing action with a threaded spindle 60. The nut 50 surrounds the threaded spindle 60 in the manner of a sleeve, wherein it is provided at its inner circumferential surface with one or more nut groove sections 51 which run helically with respect to the longitudinal axis 11. Currently, a ball screw nut is presented, as it is known, for example, from EP 1132651B 1. The spherical rolling elements that contribute to the screwing action are not shown in fig. 1. The cross-sectional shapes of the nut groove 51 and of the spindle groove 61 are approximately semicircular, so that they fit with a tight contact to the spherical rolling elements. Instead of the ball screw, it is of course also possible to use a planetary nut, as is known from DE 102012212311 a 1. In this case, the screwing action is brought about by a plurality of rollers which are provided with outer contours which engage in the nut groove 51 and the spindle groove 61. It is clear that the cross-sectional shape of the nut groove 51 and of the spindle groove 61 matches the outer contour of the roller mentioned. The invention is particularly advantageous in this case, since the heat generated during the screwing action can be dissipated particularly efficiently to the outside to the surroundings.

The nut 50 is provided at its end facing the rotary bearing 63 with an end seal 52 which is in sealing action with the threaded spindle 60. End seals 52 connect the second and third sections 14 of inner chamber 12; 15 are fluid-tightly separated from each other. The second section 14 is preferably sealed with an incompressible fluid, such as oil. In this way, the screwing action between the nut 50 and the threaded spindle 60 should be lubricated on the one hand, wherein at the same time the heat generated there should be dissipated. In this case, unlike conventional actuators with two end seals, not only the inner chamber of the nut is filled with oil, but also a part of the hollow chamber 31 in the bracket 30. It is also conceivable to dispense with the end seal 52, so that the largest part of the inner chamber 12, i.e. all parts except the first section (No. 13 in fig. 2 and 3), is filled with the incompressible fluid. The latter alternative is preferred when the nut 50 is designed as a planetary screw nut, wherein, in operation, a large amount of heat should be conducted away by the incompressible fluid.

The end seal 52 is now of a very robust construction so that it can withstand the pressure of the fluid. The end seal 52 is preferably formed of an elastomer. It is fastened at the body 54 of the nut 50 with a separate seal retainer 53. Obviously, it is also conceivable for the end seal 52 to be fastened directly to the body 54. The mentioned pressure of the fluid is caused, for example, by the mass acceleration during the movement of the actuator 10 or by the weight of the fluid, in particular in the vertical arrangement of the actuator 10.

The carrier 30 has a preferably cylindrical tube 34 which surrounds the threaded spindle 60 in sections. The tube 34 is firmly connected to the nut 50 by means of a connection 37. The carrier 30 is protected against rotation relative to the housing 20, for example, by means of a rotation lock known from DE 102007043391 a1, so that it does not rotate about the longitudinal axis 11 when the threaded spindle 60 is set into rotational motion. Corresponding twisting can of course also be prevented by an enclosing structural component (not shown) into which the actuator 10 is inserted.

In addition, a first input port 26 in the housing 20 and a second input port 55 in the nut 50 are indicated. In one attitude of the carriage 20, said first and said second input ports 26; 55 are arranged in alignment in such a way that the incompressible fluid mentioned can fill the second section 14 of the inner chamber 12. Preferably, a non-return valve (not shown) is arranged in the second inlet 55, which non-return valve exclusively allows a fluid flow into the second section 14.

Fig. 2 shows a longitudinal section through the end of the actuator 10 according to fig. 1 on the carrier side. There, said first end block 21 is fastened at the main body 23 of the housing 20. The bracket 30 extends through the first end block 21, wherein it is guided therein by means of a sliding bush 24 so as to be linearly movable in the direction of the longitudinal axis 11. The sliding bush 24 is preferably provided with a gap running in the longitudinal direction 11. In addition, a carrier seal 25, which is formed of an elastic body, is disposed at the first end block 21. The carrier sealing portion 25 sealingly contacts the preferably cylindrical outer peripheral surface of the carrier 30. This prevents dirt from reaching the inner chamber 12 of the actuator 10, wherein at the same time the lubricant or the like reaches from the inner chamber 12 to the outside.

The outer end of the bracket is provided with a separate fastening part 35, at which the upper level structural components (not shown) can be fastened. The fastening part 35 is provided with a fastening element 36, which is currently configured as an external thread. The fastening element 36 can of course also be designed as an internal thread, as a fastening fork or as a ball joint.

The threaded spindle 60 has a planar end face 64 which is preferably oriented perpendicularly to the longitudinal axis. The planar bottom surface 33 of the hollow chamber 31 in the carrier 30 is parallel to the mentioned end surface 64. The bottom surface 33 is arranged at the fastening part 35. In the rest of the cases, the hollow chamber 31 in the bracket 30 is delimited by a side face 32 formed by the preferably cylindrical inner peripheral face of the tube 34.

The elastic element 70 is arranged between the end face 64 and the bottom face 33. In a first embodiment of the actuator 10, this is configured in the form of an elastic membrane 71 which is fastened at the side 32 of the hollow chamber 31. Diaphragm 71 separates first and second sections 13 of inner chamber 12; 14 are fluid-tightly separated from each other. As already explained, the second section 14 is preferably filled with an incompressible liquid. Fig. 2 shows the carriage 30 in a state of maximum displacement. A part of the incompressible fluid is located in a pot-shaped diaphragm which is designed in the form of a bellows 72, wherein the bellows 72 is compressed to the maximum. If the carrier 30 is now moved out of the housing, the bellows 72 expands, since incompressible fluid is displaced from the intermediate chamber between the threaded spindle 60 and the tube 34 into the bellows 72. The results were: the second section 14 of the inner chamber 12 retains its volume, wherein only the volume of the first section 13 is changed. When the carriage 30 is moved out to its maximum extent, the bellows 72 is in its most extended state. The above explanation applies to the nut provided with the end seal portion (No. 52 in fig. 1) as described above. In the absence of this end seal, the bellows 72 can also deform in the opposite direction when the carriage 30 is moved out.

The bellows 72 has a plurality of folds 73, which are arranged next to one another in the direction of the longitudinal axis 11, wherein the folds run annularly around the longitudinal axis 11. The bellows 72 has an open head side 75, by means of which the incompressible fluid can reach the bellows 72 and can flow out of the latter. The head side 75 is firmly connected to the side 32 of the hollow chamber 31. The head side can be pressed in there, for example. The closed bottom side 74 of the bellows 72 is arranged on the side of the bellows 72 facing away from the threaded spindle 60. The bottom side 74 is free to move within the bracket 30 within the elastic range of the bellows 72. The bellows 72 is preferably made of plastic, most preferably an elastomer.

The carrier can be provided with vents 38; 38' so as to hinder: when the carriage 30 moves, the pressure in the first section 13 of the inner chamber 12 changes excessively. According to a first alternative, the ventilation opening 38 extends through the fastening part 36 concentrically to the longitudinal axis 11. According to a second alternative, the ventilation holes 38' extend through the tube 34 of the bracket 30 radially to the longitudinal axis 11. The vent holes 38 are shown in FIG. 2; 38', wherein preferably only one of said two alternatives is used.

Fig. 3 shows a longitudinal section of an actuator 10' according to a second embodiment of the invention, corresponding to fig. 2. The drive-side end of the second embodiment of the actuator 10' is constructed identically to the first embodiment, so that reference is made in this connection to the embodiment of fig. 1. The end of the actuator 10' on the carrier side is constructed in the same way as the first embodiment, apart from the differences explained below, so that in this connection reference is made to the embodiment of fig. 2. Here, in fig. 2 and 3, the same or corresponding portions are provided with the same reference numerals.

A second embodiment of the resilient element 70' is formed from a foam 76 having a plurality of pores. The foam is preferably designed in such a way that the incompressible fluid cannot be forced from the second section 14 of the interior into the foam 76. The foam 76 can have a fluid-tight closed surface for this purpose. Of course, it is also conceivable for the foam 76 to have a plurality of pores which are spaced apart in a fluid-tight manner. Such foams are also known as closed cell. The two measures can also be combined with each other.

First section 13 of inner chamber 12 is defined by the pores of foam 76. The volume of the aperture is changed only when the carriage 30 moves relative to the housing 20. The volume of the second section 14 is accordingly kept constant or approximately constant.

Fig. 3 shows the carriage 30 in a state of maximum movement into it. A part of the incompressible fluid is now located in the free space 77 formed between the end face 64 of the threaded spindle 60 and the foam 76.

The foam 76 is in its most compressed state. If the carriage 30 is now moved out, the foam 76 is stretched. At the same time, the free space 77 will be larger, because a part of the incompressible fluid located between the threaded spindle 60 and the tube 34 is displaced into the free space 77. This is particularly applicable to the case where the nut is provided with an end seal portion (No. 52 in fig. 1) as described above. If this end seal is missing, the free space 77 can also be reduced when the carriage 30 is moved out. It is also conceivable that the foam 76 rests against the end face 64 of the threaded spindle 60 in each position of the carrier 30.

The foam 76 preferably rests directly on the bottom surface 33 of the hollow chamber 31 of the carrier 30. In addition, the foam rests in sections on the side 32 of the hollow chamber 31 mentioned.

List of reference numerals

10 actuator (first embodiment)

10' actuator (second embodiment)

11 longitudinal axis

12 inner chamber

13 first section of the inner chamber

14 second section of the inner chamber

15 third section of the inner chamber

16 region of screwing action

20 case

21 first end block

22 second end block

23 main body

24 sliding bush

25 bracket sealing part

26 first input port

30 bracket

31 hollow chamber

32 sides of the hollow chamber

33 bottom surface of hollow chamber

34 pipe

35 fastening part

36 fastener

37 connecting piece

38 vent (first alternative)

38' vent (second alternative)

50 nut

51 nut groove part

52 end seal

53 seal retainer

54 nut body

55 second input port

60 screw spindle

61 Main shaft groove part

62 drive journal

63 rotating bearing

End face of 64 screw spindle

70 elastic element (first embodiment)

70' elastic element (second embodiment)

71 diaphragm

72 corrugated pipe

73 fold

74 bottom side of bellows

75 head side of corrugated pipe

76 foam plastic

77 free space

Claims

1. Actuator (10; 10') having a housing (20) and a carrier (30), wherein the carrier (30) is mounted on the housing (20) so as to be linearly movable in the direction of a longitudinal axis (11), wherein the carrier (30) projects out of the housing (20) in the direction of the longitudinal axis (11), wherein the housing (20) and the carrier (30) together define an inner chamber (12) whose volume is changed when the carrier (30) is moved relative to the housing (20), wherein a threaded spindle (60) is mounted on the housing (20) so as to be rotatable about the longitudinal axis (11) by means of a rotary bearing (63), wherein the threaded spindle projects into a hollow chamber (31) of the carrier (30), wherein the carrier (30) is provided with a nut (50) which is arranged in the inner chamber (12) and which is in a screwing action with the threaded spindle (60),

characterized in that an elastic element (70; 70 ') is arranged in the hollow chamber (31) of the bracket, which element is elastically deformed when the bracket (30) is moved relative to the housing (20), wherein the elastic element (70; 70 ') separates the first and second sections (13; 14) of the interior chamber (12) from each other in a fluid-tight manner, wherein the region (15) of the screwing action between the nut (50) and the spindle (60) is a constituent part of the second section (14) of the interior chamber (12), and wherein the elastic element (70; 70 ') is deformed when the bracket (30) is moved relative to the housing (20) in such a way that the volume of the first section (13) is changed while the volume of the second section (14) remains substantially constant.

2. The actuator according to claim 1, wherein said actuator is a linear actuator,

the nut (50) is provided exclusively at its end facing the rotary bearing (63) with an end seal (52) which is in sealing engagement with the threaded spindle (60) in such a way that it separates the third section (15) of the interior space (12) from the second section (14) of the interior space (12) in a fluid-tight manner.

3. The actuator according to claim 1, wherein said actuator is a linear actuator,

wherein the nut (50) is open at its two opposite ends in such a way that the second section (14) of the inner chamber (12) extends through the nut (50).

4. The actuator according to any one of claims 1 to 3,

wherein the second section (14) of the inner chamber (12) is substantially completely filled with an incompressible fluid.

5. The actuator according to any one of claims 1 to 3,

wherein the threaded spindle (60) has an end face (64), wherein an elastic element (70; 70') is arranged between the mentioned end face (64) and a bottom face (33) of the hollow chamber (31) of the bracket (30).

6. The actuator according to any one of claims 1 to 3,

wherein the elastic element (70) is formed by an elastically deformable membrane (71) which is fastened at a side face (32) of the hollow chamber (31) of the bracket (30).

7. The actuator according to claim 6, wherein said actuator is a linear actuator,

wherein the membrane (71) is designed in the form of a bellows (72) having a plurality of flexible folds (73) which encircle the longitudinal axis (11) in an annular manner.

8. The actuator according to any one of claims 1 to 3,

wherein the elastic element (70') is formed from a foamed plastic (76) having a plurality of pores, wherein the pores define the first section (13) of the inner chamber (12).

9. The actuator according to claim 8, wherein said actuator is a linear actuator,

wherein the foam (76) has a fluid-tight closed surface.

10. The actuator according to claim 8, wherein said actuator is a linear actuator,

wherein the foam (76) has a plurality of pores which are spaced apart from one another in a fluid-tight manner.

11. The actuator according to any one of claims 1 to 3,

wherein the screwing action between the nut (50) and the threaded spindle (60) is brought about by rollers provided with an outer contour or by rolling bodies of spherical or cylindrical design.

12. The actuator according to any one of claims 1 to 3,

wherein the bracket (30) has at least one ventilation opening (38; 38') in the region of the first section (13) of the inner chamber (12).