Piston and Cylinder Unit Including a Piston Position Detection Unit and a Collimator

Abstract

A piston and cylinder unit (1) of a working machine, for example a wheel loader, excavator, tipper, crane or stacker or a lifting platform serves to steer, support, extend, pivot, lift or other movements of the working machine or of a tool or a different part of the working machine. The piston and cylinder unit (1) includes a cylinder (2), a piston (7) being arranged in the cylinder (2) to be axially movable along a longitudinal center axis (54) and a piston position detection unit (28). The cylinder (2) includes a mounting bore (27) extending radially in the cylinder (2). The piston position detection unit (28) is arranged in the mounting bore (27) and detects the axial position of the piston (7) in the cylinder (2) by high frequency technology. The piston position detection unit (28) includes an antenna (46) for sending and receiving high frequency signals. A collimator (57) is arranged in the beam path of the antenna (26). The antenna (26) has a main sense of direction of radiation (63) extending parallel to the longitudinal center axis (54).

Claims

1. A piston and cylinder unit, comprising: a cylinder, the cylinder including a mounting bore extending radially in the cylinder; a piston, the piston being supported in the cylinder to be axially movable along a longitudinal center axis; a piston position detection unit, the piston position detection unit being arranged in the mounting bore and being designed and arranged to detect the axial position of the piston in the cylinder by high frequency technology, the piston position detection unit including an antenna for sending and receiving high frequency signals along a beam path, the antenna having a main sense of direction of radiation extending parallel to the longitudinal center axis; and a collimator, the collimator being arranged in the beam path of the antenna.

2. The piston and cylinder unit of claim 1, wherein the collimator includes a dielectric lens.

3. The piston and cylinder unit of claim 1, wherein the collimator is an integral part of the piston position detection unit.

4. The piston and cylinder unit of claim 2, wherein the collimator is an integral part of the piston position detection unit.

5. The piston and cylinder unit of claim 1, wherein the cylinder includes a cylinder tube and a cylinder head; the mounting bore is arranged in the cylinder head; and the piston position detection unit is arranged in the mounting bore such that its longest dimension extends radially in the cylinder head.

6. The piston and cylinder unit of claim 1, wherein the cylinder has an interior, the piston and cylinder unit further comprising a sensor signal bore extending in an axial direction, the mounting bore being operatively connected to the interior of the cylinder by the sensor signal bore.

7. The piston and cylinder unit of claim 5, wherein the cylinder has an interior, the piston and cylinder unit further comprising a sensor signal bore extending in an axial direction, the mounting bore being operatively connected to the interior of the cylinder by the sensor signal bore, and wherein the cylinder head includes a cylinder head bottom surface surrounding the sensor signal bore, a plurality of beam deflecting elements being arranged in the cylinder head bottom surface.

8. The piston and cylinder unit of claim 7, wherein the beam deflecting elements are designed as recessed elements.

9. The piston and cylinder unit of claim 7, wherein the beam deflecting elements are designed as impressions being located in the cylinder head bottom surface, the impressions being spaced apart and conical.

10. The piston and cylinder unit of claim 1, wherein the piston position detection unit includes a housing and an electronic unit being arranged in the housing.

11. The piston and cylinder unit of claim 10, wherein the collimator is at least partly arranged in the housing and partly forms the housing, respectively.

12. The piston and cylinder unit of claim 10, wherein the electronic unit includes the antenna, the antenna being designed to send and receive high frequency signals through the housing; and the antenna is arranged on the electronic unit, the antenna being arranged in the housing such that the high frequency signals are directed through the sensor signal bore.

13. The piston and cylinder unit of claim 10, wherein the housing includes a first aligning element and the electronic unit includes a corresponding second aligning element, the first aligning element and the second aligning element being coordinated in a way that the electronic unit is fully mountable in the housing only in exactly one orientation.

14. The piston and cylinder unit of claim 13, wherein the first aligning element is designed as a groove being arranged eccentrically in an axial end region of the housing and that the second aligning element is designed as a tongue being arranged equally eccentrically in a corresponding axial end portion of the electronic unit.

15. The piston and cylinder unit of claim 1, wherein the piston position detection unit includes a housing and an electronic unit being arranged in the housing, the piston position detection unit being arranged in the mounting bore and being designed such that the interior of the cylinder is sealed against the surroundings of the piston and cylinder unit and that the electronic unit is removable from the housing and insertable into the housing without cancelling the sealing effect.

16. A piston position detection unit for detecting the position of a piston in a cylinder of a piston and cylinder unit, comprising: a housing being designed to be cylindrical and having a longitudinal center axis; an electronic unit being arranged in the housing and including an antenna for sending and receiving high frequency signals through the housing along a beam path, the main sense of direction of radiation of the antenna extending perpendicularly to the longitudinal center axis of the housing; and a collimator being at least partly arranged in the housing or partly forming the housing and being arranged in the beam path of the antenna.

17. The piston position detection unit of claim 16, wherein the collimator includes a dielectric lens.

18. The piston position detection unit of claim 16, wherein the collimator is an integral part of the piston position detection unit.

19. The piston position detection unit of claim 17, wherein the collimator is an integral part of the piston position detection unit.

20. The piston position detection unit of claim 16, wherein the housing is made of a thermoplastic plastic material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In the following, the invention is further explained and described with respect to preferred exemplary embodiments illustrated in the drawings.

[0067] FIG. 1 illustrates a sectional view of a first exemplary embodiment of a new piston and cylinder unit including a new piston position detection unit.

[0068] FIG. 2 illustrates an enlarged view of a part of the piston and cylinder unit according to FIG. 1.

[0069] FIG. 3 illustrates the detail A of the piston and cylinder unit of FIG. 2.

[0070] FIG. 4 illustrates a view of a part of the piston and cylinder unit according to FIG. 1 from above.

[0071] FIG. 5 illustrates a perspective exploded view of a part of the piston and cylinder unit according to FIG. 1.

[0072] FIG. 6 illustrates a perspective view of an exemplary embodiment of an electronic unit of the piston position detection unit of the piston and cylinder unit according to FIG. 1.

[0073] FIG. 7 illustrates a perspective view of the piston position detection unit of the piston and cylinder unit according to FIG. 1 including an integrated collimator.

[0074] FIG. 8 illustrates a partly sectional perspective view of the piston position detection unit according to FIG. 7.

[0075] FIG. 9 illustrates a perspective view of the cylinder head of the piston and cylinder unit according to FIG. 1.

[0076] FIG. 10 illustrates a sectional view of a second exemplary embodiment of the new piston and cylinder unit including the new piston position detection unit.

[0077] FIG. 11 illustrates an enlarged view of a part of the piston and cylinder unit according to FIG. 10.

[0078] FIG. 12 illustrates the detail B of the piston and cylinder unit of FIG. 11.

[0079] FIG. 13 illustrates a perspective exploded view of a part of the piston and cylinder unit according to FIG. 10.

[0080] FIG. 14 illustrates a perspective view of the piston position detection unit of the piston and cylinder unit according to FIG. 10.

[0081] FIG. 15 illustrates a partly sectional perspective view of the piston position detection unit according to FIG. 14.

[0082] FIG. 16 illustrates a perspective view of the collimator of the piston and cylinder unit according to FIG. 10.

[0083] FIG. 17 illustrates a perspective view of the cylinder head of the piston and cylinder unit according to FIG. 10.

DETAILED DESCRIPTION

[0084] FIG. 1-9 illustrate different views of a first exemplary embodiment of a new piston and cylinder unit 1 as well as its parts.

[0085] In FIG. 1, the discontinuation lines indicate that the piston and cylinder unit 1 actually is designed to be longer and that only a part is illustrated. Similar discontinuation lines exist in FIGS. 2, 4 and 5. In FIG. 3, the illustration ends at the straight discontinuation lines. The same applies to FIGS. 9, 10, 11 and 12.

[0086] The piston and cylinder unit 1 includes a cylinder 2 including a cylinder tube 55, an interior 3 and a cylinder head 4. In the region of the cylinder head 4, a bearing bushing 5 for the support of the piston and cylinder unit 1 at a working machine (not illustrated) is arranged.

[0087] In the present example, since it is a hydraulic piston and cylinder unit 1, the interior 3 is filled with oil 53. For this purpose, the cylinder 2 includes an oil connection 6 and an oil connection 24. Oil lines (not illustrated) are connected to the oil connections 6, 24. A hydraulic pump (not illustrated) subjects the piston 7 by the oil 53 with pressure in a way as it is known taken in isolation such that the piston 7 and the piston rod 8 being connected therewith move in the respective sense of direction along the longitudinal center axis 54 of the piston and cylinder unit 1. In this way, oil enters through the oil connections 6, 24 into the interior 3 of the cylinder 2 and exits from the interior 3, respectively, depending on the sense of direction of the movement of the piston 7 within the cylinder 2. FIGS. 1 and 2 illustrate the position of the piston 7 all the way to the right—i.e. the retracted position of the piston and cylinder unit 1.

[0088] As it has been described above, the piston and cylinder unit 1 includes the piston 7. The piston 7 is connected to the piston rod 8, a piston rod eye 9 being arranged at one of its axial ends. The piston rod eye 9 also includes a bearing bushing 10. The bearing bushing 10 serves for the operative connection of the piston 9 with a tool (not illustrated) or a different part of the working machine.

[0089] The piston rod 8 is supported by a guiding bushing 11 to be translationally movable in an axial direction along the longitudinal center axis 54. A rod seal 12, an O-ring 13 and a supporting ring 14 are provided for supporting and sealing. Another O-ring 15, a scraper 16 and a slide bearing 17 are arranged at the other axial end of the guiding bushing 11.

[0090] The piston 7 is fixedly arranged on the piston rod 8 such that they cannot be rotated with respect to one another and it is secured by a locking nut 18. Furthermore, an O-ring 19, a piston guiding ring 20, a piston seal 21, another piston guiding ring 22 and a welding seam 23 are located at the piston 7.

[0091] In this way, the piston 7 is commonly supported with the piston rod 8 and the piston rod eye 9 to be movable back and forth within the cylinder tube 55 of the cylinder 2.

[0092] A chamber 25 in the cylinder head 4 is connected to the part of the interior 3 which is formed by the cylinder tube 55. The chamber 25 also forms a part of the interior 3 and is filled with oil 53. The chamber 25 is connected to the oil connection 24. An axially extending sensor signal bore 26 is connected to the chamber 25. The sensor signal bore 26 is also connected to the interior 3 and filled with oil 53.

[0093] The sensor signal bore 26 is connected to a mounting bore 27 extending radially in the cylinder 2. The mounting bore 27 extends to the outer surface of the cylinder head 4 and may be connected to the surroundings by a compensation bore (not illustrated).

[0094] The cylinder head 4 includes a cylinder head bottom surface 59 extending annularly around the sensor signal bore 26. A plurality of been deflecting elements 60 is arranged in the cylinder head bottom surface 59. In the illustrated case, these are recessed elements 61 being designed as a spaced apart conical impressions 62. The function of the beam deflecting elements 60 will be described below.

[0095] A piston position detection unit 28 is arranged in the mounting bore 27. The piston position detection unit 28 serves to detect the axial position of the piston 7 in the cylinder 2 by high frequency technology. The details of the piston position detection unit 28 are to be best seen in the enlarged illustration according to FIG. 3 and the exploded view according to FIG. 5. The structure of the electronic unit 30 is illustrated in FIG. 6 in greater detail. For reasons of clarity of the drawings, the components of the piston position detection unit 28 have not been designated with reference numerals in FIGS. 1 and 2.

[0096] The piston position detection unit 28 includes a housing 29 and an electronic unit 30 being arranged in the housing 29.

[0097] The piston position detection unit 28 includes a collimator 57. In the illustrated case, the collimator 57 forms a part of the housing 29. However, the collimator 57 could also be arranged in the housing 29 or outside of the house and 29. In the illustrated case, the collimator 57 is designed as a dielectric lens 58. The function of the collimator 57 will be described below.

[0098] The housing 29 is designed to be cylindrical and it is closed by a bottom 31 at its lower end (see FIG. 5). The opposite upper end is open such that the electronic unit 30 can be inserted there. The housing 29 is made of a material being permeable for high frequency signals. The material especially is a thermoplastic plastic material.

[0099] The housing 29 includes a first aligning element 32 in the region of its closed bottom 31, the first aligning element 32 being designed as a groove 33 and being arranged eccentrically in the cylindrical housing 29. A second aligning element 34 of the electronic unit 30 engages the first aligning element 32. The second aligning element 34 is designed as a tongue 35. In this way, a tongue and groove connection is formed. The second aligning element 34 is also arranged eccentrically at the electronic unit 30. In this example, the tongue 35 is formed by a board 36 of the electronic unit 30. Thus, the entire board 36 is arranged eccentrically. However, this could also be realized in a different way.

[0100] The correct alignment of the housing 29 in the mounting bore 27 is realized by a third aligning element 49. In this example, the third aligning element 49 is designed as a protrusion 50 being located at the housing 29. The mounting bore 27 includes a corresponding fourth aligning element 51 being designed as a recess 52 in this case. To improve perceptibility, this region is additionally illustrated at an enlarged scale in FIG. 4.

[0101] At its opposite axial end, the board 36 is connected to a connection element 37 for transmitting data from the electronic unit 30. The connection element 37 in its mounted position is connected to the electronic unit 30 as well as to the housing 29. The connection to the housing 29 is realized by a threaded connection 38, for example. In the present case, the connection element 37 is a M12 plug. However, it could also be a different connection element 37. The housing 30 and thus the piston position detection unit 28 are securely mounted in the mounting bore 27 by a securing ring 39.

[0102] The housing 29 includes a first channel 40, a second channel 41 and a third channel 42 at its outer circumference. A first seal 43 is arranged in the first channel 40, a second seal 44 is arranged in the second channel 41 and a third seal 45 is arranged in the third channel 42. The first seal 43 being located in the first channel 40 serves to seal against the surroundings.

[0103] The seals 44, 45 form a pair of seals and serve to seal the interior 3 of the cylinder 2 being filled with oil 53. The sensor signal bore 26 in which oil 53 is located is arranged between the first channel 40 and the second channel 41 in a radial direction—i.e. in the direction of the longitudinal center axis 47. The effective sealing surfaces of the seals 44, 45 are approximately equally great such that an arrangement of the piston position detection unit 28 in the mounting bore 27 being neutral concerning forces is attained.

[0104] A number of electronic components is arranged on the board 36. One of these components is an antenna 46 being designed to send and receive high frequency signals through the housing 29. The other components serve to determine, calculate, evaluate and transmit data in the piston position detection unit 28. Taken in isolation, they are known to the skilled person and thus not further described.

[0105] The antenna 46 is arranged on the board 36, the board 36 is arranged in the housing 29 and the housing 29 is aligned in the cylinder head 4 such that the high frequency signals of the antenna 46 are directed through the sensor signal bore 26. The main sense of direction of radiation of the antenna 46 thus extends perpendicularly to the longitudinal center axis 47 of the housing 29. Thus, the main sense of direction of radiation of the antenna 46 extends along the longitudinal center axis 48 of the sensor signal bore 26 or offset thereto in a way that the high frequency signals are directed from the antenna 46 through the collimator 57 and the signal bore 26 onto the piston 7 and that the signals reflected by the piston 7 can be received by the antenna 46.

[0106] During operation of the piston position detection unit 28, it sends high frequency signals by the antenna 46 through the collimator 57, the housing 29, the sensor signal bore 26 and—depending on the position of the piston 7—through a part of the interior 3. The signals encounter the piston 7, they are reflected by the piston 7 and they return along the same path and are received by the antenna 46.

[0107] Precision of the piston position detection unit 28 is improved in several ways by the collimator 57. The collimator 57 generates a beam path of parallel beams of previously non-parallel beams and vice versa. In the sending sense of direction, the collimator 57 thus converts the non-parallel beams originating from the antenna 46 into parallel beams. In the opposite receiving sense of direction, the collimator 57 bundles the parallel signals entering the collimator 57 that had been collected by the piston 7. The signals are bundled such that they are received by the antenna 46.

[0108] The precision of the piston position detection unit 28 is further improved by the beam deflecting elements 60. The beam deflecting elements 60 deflects signals that had already been deflected before (=false signals) intentionally such that their angle strongly deviates from the direction parallel to the longitudinal center axis 54 of the piston 7. As a result, the path of the false signals through the oil 53 is correspondingly prolonged and the dampening of the false signals is correspondingly increased. Eventually, these false signals do not reach the antenna 46 at all or with a lower probability and/or only dampened.

[0109] The electronic unit 30 with its additional electronic components and the software executed by these components carries out an evaluation and thus determines the current position of the piston 7 along the longitudinal center axis 54. This determination can be conducted permanently, in defined time intervals or at specific points in time. By the connecting element 37, the result or a command being associated with the result is transmitted to an electronic computing unit of the working machine connected therewith—a part of which is the piston and cylinder unit 1.

[0110] FIGS. 10-17 illustrate different views of a second exemplary embodiment of the new piston and cylinder unit 1 as well as its parts. FIGS. 4 and 6 also concern this embodiment. Since the first and second exemplary embodiments of the piston and cylinder unit 1 have a lot in common, it is referred to the above statements.

[0111] However, the piston position detection unit 28 and the sensor signal bore 26 have a different design. The collimator 57 is a separate component being arranged in the enlarged sensor signal bore 26.

[0112] Many variations and modifications may be made to the preferred embodiments of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of the present invention, as defined by the following claims.