Abstract
The invention relates to a hydraulic transmission unit for an actuator, which hydraulic transmission unit can be filled with a hydraulic fluid and has a first and a second chamber which are hydraulically interconnected and of which one is designed as a drive chamber and the other one is designed as an output chamber. At least in the first chamber, a piston is arranged movably along a piston axis, such that this piston subdivides the first chamber into a variable-volume working chamber and a rear-side chamber, the rear-side chamber being delimited at least partially by a bellows element having a variable axial length. The invention further relates to an actuator having such a hydraulic transmission unit.
Claims
1. A hydraulic transmission unit for an actuator device, which hydraulic transmission unit can be filled with hydraulic fluid, comprising: a first and a second chamber, which are hydraulically connected to each other and of which one is formed as a drive chamber and the other is formed as an output chamber, wherein a piston is arranged movably along a piston axis at least in the first chamber such that this piston separates the first chamber into a variable-volume working chamber and a rear-side chamber, wherein the rear-side chamber is at least partially delimited by a bellows element with variable axial length.
2. The hydraulic transmission unit according to claim 1, in which the piston comprises a piston body and a piston pin, and in which the associated rear-side chamber comprises an end plate in its axial end region facing away from the piston body, through which the piston pin protrudes into the rear-side chamber and to which the piston pin is fixedly connected.
3. The hydraulic transmission unit according to claim 1, in which the first chamber is configured such that upon a movement of the piston along the piston axis, a volume compensation is effected by the bellows element for the volume of the rear-side chamber.
4. The hydraulic transmission unit according to claim 1, in which the rear-side chamber is fluid-tightly encapsulated against the outer environment.
5. The hydraulic transmission unit according to claim 1, in which the bellows element is formed as a corrugated bellows and/or as a diaphragm bellows.
6. The hydraulic transmission unit according to claim 1, in which the first chamber is laterally delimited by a cylinder wall, wherein the associated piston is arranged axially movably in relation to the cylinder wall, and wherein a gap with a gap width below 10 μm is formed between the cylinder wall and the piston.
7. The hydraulic transmission unit according to claim 1, which is filled with a hydraulic fluid.
8. The hydraulic transmission unit according to claim 1, which additionally comprises a reservoir chamber for the hydraulic fluid, which is fluidically coupled and/or capable of being fluidically coupled to the at least one rear-side chamber.
9. The hydraulic transmission unit according to claim 8, in which the reservoir chamber can be applied with pressure.
10. The hydraulic transmission unit according to claim 1, which is formed as a pumpable transmission unit, such that a summed movement can be generated in the region of the output chamber by multiple consecutive single movements in the region of the drive chamber.
11. The hydraulic transmission unit according to claim 1, which is formed to transfer a movement of a drive body arranged in the region of the drive chamber to an output body arranged in the region of the output chamber with a transmission ratio of 1:2 or less.
12. The hydraulic transmission unit according to claim 1, which is formed to transfer a movement of a drive body arranged in the region of the drive chamber to an output body arranged in the region of the output chamber with a transmission ratio of at least 2.
13. The hydraulic transmission unit according to claim 1, in which a second piston is arranged movably along a piston axis in the second chamber such that this second piston separates the second chamber into a variable-volume second working chamber and a second rear-side chamber, wherein the second rear-side chamber is at least partially delimited by a second bellows element with variable axial length.
14. An actuator device with an actuator and a hydraulic transmission unit according to claim 1, mechanically connected in series with the actuator.
15. The actuator device according to claim 14, which comprises two partial systems, wherein each partial system comprises an actuator and a hydraulic transmission unit mechanically connected in series with the actuator, wherein the two transmission units can be mechanically coupled to a common superordinated output element in the region of their respective output chambers, such that a simultaneous control of the two actuators results in a common movement of the superordinated output element the two hydraulic transmission units.
Description
[0044] Below, the invention is described based on some preferred embodiments with reference to the appended drawings, in which:
[0045] FIG. 1 shows a schematic representation of an actuator device with a piston system according to the prior art,
[0046] FIG. 2 shows a detailed view of a possible variant of a piston from FIG. 1,
[0047] FIG. 3 shows a schematic representation of an actuator device with a bellows system according to the prior art,
[0048] FIG. 4 shows a schematic representation of an actuator device according to a first embodiment of the invention,
[0049] FIG. 5 shows a detailed view of the actuator device of FIG. 4,
[0050] FIG. 6 shows a schematic representation of an actuator device according to a second embodiment of the invention, and
[0051] FIG. 7 shows a schematic representation of an actuator device according to a third embodiment of the invention.
[0052] In the figures, identical or functionally identical elements are provided with the same reference characters.
[0053] In FIG. 1, an actuator device 1 according to the prior art is shown in a schematic longitudinal section. The actuator device comprises an actuator 3 and a hydraulic transmission unit 5 mechanically connected in series with the actuator. Correspondingly, the side a of the transmission unit illustrated at the bottom in the image can be referred to as the drive side thereof and the side b illustrated at the top in the image can be referred to as the output side thereof. A mechanical stroke SA of a drive body 21a can be generated with the actuator 3 on the drive side a. By the hydraulic transmission unit 5, this stroke SA can be transmitted into a stroke SB of the output body 21b on the output side b thereof. The ratio between the stroke SB and the stroke SA corresponds to the transmission ratio of the hydraulic transmission unit 5. Principally, it can be greater than, equal to or also less than 1.
[0054] The transmission unit 5 of FIG. 1 comprises two chambers, a drive chamber 11a and an output chamber 11b. A first working chamber 15a is provided as a part of the drive chamber 11a, and a second working chamber 15b is provided as a part of the output chamber 11b. These two working chambers are filled with a hydraulic fluid 7 and hydraulically coupled to each other via a hydraulic line 16. Thus, an overall working volume for the hydraulic fluid results, which is composed of the two working chambers and the hydraulic line. In order to convey hydraulic fluid back and forth between the two working chambers in the operation of the transmission unit 5, two pistons are provided, namely a first piston 13a (as a drive piston) and a second piston 13b (as an output piston). The first piston 13a comprises a piston pin, which here forms the drive body 21a. The transmission ratio of the transmission unit 5 is determined by the ratio of the hydraulic areas of the two pistons 13a and 13b (more precisely by the ratio of the corresponding piston bodies). Namely, the respective area is linearly included in the volumetric variation, which arises upon a corresponding axial movement of the respective piston. Since the entire working volume is constant, an axial movement of the drive piston 13a results in a correspondingly increased or decreased axial movement of the output piston 13b. In the shown example, the area of the output piston 13b is comparatively smaller such that a correspondingly increased stroke SB results on the output side b, as is here indicated by the larger length of the arrow. Here, a movement along the local longitudinal axis A is respectively to be understood by the mentioned axial direction of movement of the pistons. In the example of FIG. 1, this axis for the two pistons coincides to a common longitudinal axis A (but which is not necessarily required in other embodiments). The mechanical mass is symbolically represented at various locations and respectively denoted by 20.
[0055] As already described above, an essential disadvantage of such a piston system is in that the sealing of the two working chambers 15a and 15b against the two movable pistons 13a and 13b is difficult. The difficulty of the fluidic sealing is illustrated in more detail by FIG. 2. FIG. 2 shows a detailed view for a possible variant of the drive piston 13a of FIG. 1. The region marked by a dashed oval is approximately shown in FIG. 1. This is the region, in which the drive piston 13a slides past a cylinder wall 23 in axial direction, which delimits the drive chamber towards the outside in lateral direction. In the axial movement, the hydraulic fluid 7 is to remain within the first working chamber 15a as possible and not to get into the (often exposed) region of the piston rear side through the piston gap. The gap width of the piston gap is denoted by g in FIG. 2. This gap width cannot be arbitrarily small chosen in order that the piston 13a can be well moved within the cylinder wall 23 in axial direction. In the transmission unit of FIG. 2, however, it is locally decreased in that two additional sealing elements 25 are interposed between the piston 13a and the cylinder wall. Such sealing elements can help reducing an undesired leakage of the hydraulic fluid into the outer environment. However, they often result in an impairment in the linearity and/or in the dynamics of the transmission unit since a continuous change between static friction states and dynamic friction states between the piston 13a and the cylinder wall 23 occur in the operation. Therefore, it is advantageous to avoid such additional sealing elements 25 whenever possible.
[0056] FIG. 3 shows a schematic representation of a further actuator device 1 according to the prior art. Here too, an actuator 3 is arranged mechanically in series with a hydraulic transmission unit 5. Here too, the hydraulic transmission unit comprises a drive chamber 11a and an output chamber 11b, wherein the two working volumes of these chambers are coupled by a hydraulic line 16. In contrast to the preceding variant, here, the two working chambers 15a and 15b are delimited by two associated bellows elements, namely a drive bellows 31a and an output bellows 31b. These two drive bellows replace the two pistons from the transmission unit of FIG. 1 concerning their function. Correspondingly, the actuator 3 is coupled to an end plate of the drive bellows 31a on the drive side a. A corresponding stroke SA results in an extension or compression of the drive bellows and thus in a volumetric variation of the first working chamber 15a. By the fluidic coupling, this results in a corresponding volumetric variation in the second working chamber 15b. This results in a corresponding extension or compression of the output bellows 31b and thus in a stroke SB on the output side b, which can be transferred to an output body 35.
[0057] In such a bellows system, the risk of the leakage of the hydraulic fluid 7 is considerably reduced. However, the disadvantages described above arise, especially with respect to the reduced stiffness and dynamics of the system. Here, a temperature compensation either is not possible. Therefore, the pressure in the overall system rises upon a temperature increase.
[0058] In FIG. 4, a schematic representation of an actuator device 1 according to a first embodiment of the invention is shown. This actuator device 1 too comprises an actuator 3 and a hydraulic transmission unit 5 mechanically arranged in series therewith. The basic operating principle of this transmission unit 5 according to the invention is similar as in the transmission unit of FIG. 1: Here too, the stroke SA is transmitted from a drive side a into a stroke SB on the output side b by the hydraulically coupled cooperation of two pistons 13a and 13b. Here too, the transmission ratio is determined by the ratio of the hydraulic areas of the two piston bodies. Here too, the first working chamber 15a forms a partial region of the drive chamber 11a variable by the piston movement, and the second working chamber 15b forms a partial region of the output chamber 11b variable by the piston movement there.
[0059] In contrast to the transmission unit of FIG. 1, however, the rear-side volumes of the two chambers 11a and 11b are designed encapsulated here. In other words, each of the two chambers 11a and 11b, respectively, is separated into a working chamber 15a and 15b, respectively, and a rear-side chamber 17a and 17b, respectively, by the piston. Therein, the two rear-side chambers are each fluidically encapsulated against the outer environment. They are each at least partially delimited by a bellows element 19a and 19b, respectively, with variable axial length. In the shown example, a part of the sidewall of the concerned rear-side chamber is respectively formed by such a bellows. This bellows allows that the rear-side chamber can be encapsulated and that a volumetric compensation can nevertheless take place upon the movement of the respective piston. In the example of FIG. 4, both the drive chamber 11a and the output chamber 11b are realized by such a flexibly encapsulated rear-side chamber. However, within the scope of the present invention, it is principally sufficient if at least one of the two chambers 11a or 11b is configured in the described manner.
[0060] FIG. 5 shows a detailed view of the actuator device of FIG. 4 in the region of the drive chamber 11a to clarify the configuration according to the invention with the flexibly encapsulated rear-side chamber 17a in more detail. The first piston 13a is subdivided into a piston body 22 and a piston pin 21a. The piston pin 21a in turn forms the drive body of the transmission unit. The piston body 22 subdivides the drive chamber 11a into a working chamber 15a and a rear-side chamber 17a such that the volume of the working chamber 15a varies upon a movement of the piston. The volume of the rear-side chamber 17a would also vary with a rigid configuration of the lateral bounding wall. In the configuration according to the invention, however, the lateral bounding wall is subdivided into a straight cylinder wall 23 (in the region of the piston body) and into a laterally delimiting bellows element 19a (in the part of the rear-side chamber facing away from the piston body). This bellows element 19a is flexible such that it is variable in its axial length. Upon a variation of the axial length, the cross-sectional area of the bellows element should vary as little as possible. On the side facing away from the piston body 22, the bellows element 19a is connected to an end plate 33. This end plate 33 is in turn connected to the piston pin 21a, which is passed through it. This connection 34 between piston pin 21a and end plate 33 is designed such that it is fluid-tight on the one hand and that the two elements cannot be moved against each other in axial direction on the other hand. By this rigid connection, it is achieved that the bellows element 19 is extended upon a downward movement of the piston and is compressed upon an upward movement of the piston. This axial length compensation results in the described volumetric compensation of the rear-side chamber 17a upon a movement of the piston.
[0061] If the hydraulic area of the bellows element 19a is sufficiently well adapted to the hydraulic area of the cylinder wall 23 (wherein the area of the pin 21a is respectively hydraulically not effective) and if the purely axial flexibility of the bellows element is sufficiently high at the same time, further measures for volumetric compensation of the rear-side chamber can be omitted. However, further measures for volumetric compensation can also be taken as it is illustrated in FIG. 6 for a further embodiment: FIG. 6 shows an actuator device 1, the hydraulic transmission unit 5 of which is configured substantially similarly as in the example of FIG. 4. Here, the representation of the mechanical masses 20 has partially been omitted for the sake of clarity. In contrast to FIG. 5, however, the two rear-side chambers 17a and 17b are here fluidically coupled to a reservoir chamber 41 by an additional line 37, which is also filled with the hydraulic fluid 7. This reservoir chamber too is delimited by a bellows element 43 towards the outside such that the volume of the reservoir chamber is variable. On the side of the bellows element 43 facing away from the line 37, a cover plate 45 is here arranged, with the aid of which the stroke SR can also be adjusted at the reservoir chamber. By this configuration, it is achieved that the reservoir chamber cannot only compensate for undesired volumetric variations of the rear-side chamber, but that it also can be specifically used for preloading the system. Thus, the reservoir chamber 41 can be applied with a pressure by adjusting a preset stroke position SR in the region of the cover plate 45. If the output body 21b is applied with a corresponding counterforce at the same time, it can be effected by this preadjusted pressure that the output body 21b can be preadjusted to a certain preset stroke position SA. A counterforce on the output body 21b can in turn be adjusted for example via an additional spring or else via the stiffness of the bellows 19b.
[0062] The axially movable arrangement of the piston 13a within the cylinder wall 23 can be configured similarly as in the detailed view of FIG. 2, however here without the additional sealing elements drawn there. Thus, a piston gap with uniform gap width g in particular is to be present in the configuration according to the invention. Hydraulic fluid can leak from the working chamber 15a into the encapsulated rear-side chamber 17a through the piston gap, but not into the outer environment. Thus, the hydraulic transmission unit can overall be fluid-tightly designed.
[0063] FIG. 7 shows a schematic representation of an actuator device according to a further embodiment of the invention. The actuator device of FIG. 7 comprises two partial systems configured symmetrically to each other, which each can be configured similarly as in the example of FIG. 6. Thus, the actuator device 1 comprises two individual actuators 3, which act mechanically parallel with each other. These two actuators 3 are each mechanically connected in series with an associated hydraulic transmission unit. In the shown example, the individual hydraulic transmission units are not fluidically coupled to each other. Alternatively, however, they could principally also be fluidically coupled, for example via a coupling of the two reservoir chambers 41 or else by a configuration with a common reservoir chamber. Here, the two partial systems 71 and 72 of the actuator device are mechanically connected in parallel. The two output bodies 21b are configured such that by simultaneous and equally directed control of the two actuators, an equally directed stroke SB is generated at the two output bodies 21b at the same time. In the example of FIG. 7, the two output bodies 21b are commonly coupled to a superordinated output element 75. Thus, it can be achieved that for the movement of the superordinated output element 75, an approximately doubled mechanical energy is available compared to the movement of the individual output bodies 21b.
LIST OF REFERENCE CHARACTERS
[0064] 1 Actuator device
[0065] 3 actuator
[0066] 5 hydraulic transmission unit
[0067] 7 hydraulic fluid
[0068] 11a first chamber (drive chamber)
[0069] 11b second chamber (output chamber)
[0070] 13a first piston (drive piston)
[0071] 13b second piston (output piston)
[0072] 15a first working chamber
[0073] 15b second working chamber
[0074] 16 hydraulic line
[0075] 17a first rear-side chamber
[0076] 17b second rear-side chamber
[0077] 19a first bellows element
[0078] 19b second bellows element
[0079] 20 mechanical mass
[0080] 21a first piston pin (drive body)
[0081] 21b second piston body (output body)
[0082] 22 piston body
[0083] 23 cylinder wall
[0084] 25 sealing element
[0085] 31a drive bellows
[0086] 31b output bellows
[0087] 33 end plate
[0088] 34 connecting location
[0089] 35 output body
[0090] 37 line
[0091] 41 reservoir chamber
[0092] 43 bellows element
[0093] 45 cover plate
[0094] 71 first partial system
[0095] 72 second partial system
[0096] 75 superordinated output element
[0097] A piston axis
[0098] a drive side of the hydraulic unit
[0099] b output side of the hydraulic unit
[0100] g piston gap
[0101] SA stroke on the drive side
[0102] SB stroke on the output side
[0103] SR stroke on the reservoir chamber
