Piston and cylinder unit including a radially installed piston position detection unit

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 and a piston position detection unit (28) detecting the axial position of the piston (7) in the cylinder (2) by high frequency technology. The piston position detection unit (28) includes a housing (3) and an electronic unit being arranged in the housing is arranged in a mounting bore (27) extending radially in the cylinder (2). The piston position detection unit (28) is arranged in the mounting bore (27) such that the interior (3) of the cylinder (2) is sealed from the surroundings of the piston and cylinder unit (1) by the housing (29).

Claims

1. A piston and cylinder unit, comprising: a cylinder, the cylinder having an interior, the cylinder including a mounting bore extending in a radial direction, and 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; a piston, the piston being supported in the cylinder to be movable in an axial direction; and a piston position detection unit, the piston position detection unit being designed and arranged to detect an axial position of the piston in the cylinder by high frequency electromagnetic waves, the piston position detection unit including a housing and an electronic unit being arranged in the housing, and the piston position detection unit being arranged in the mounting bore such that the interior of the cylinder is sealed from the surroundings of the piston and cylinder unit by the housing.

2. The piston and cylinder unit of claim 1, wherein the housing has a cylindrical shape, a length and a diameter; the cylinder includes a cylinder tube and a cylinder head; the mounting bore is arranged in the cylinder head; the housing is arranged in the mounting bore such that its length extends in a radial direction in the cylinder head.

3. The piston and cylinder unit of claim 1, wherein the electronic unit is sealed from the interior of the cylinder by the housing.

4. The piston and cylinder unit of claim 1, wherein the housing is made of a material selected from the group consisting of a plastic material and a ceramic material.

5. The piston and cylinder unit of claim 1, wherein the housing has a cylindrical shape and an outer circumference, the housing including a first channel and a second channel being arranged in the outer circumference, a first seal being arranged in the first channel and a second seal being arranged in the second channel.

6. The piston and cylinder unit of claim 5, wherein the sensor signal bore is arranged between the first channel and the second channel in the radial direction.

7. The piston and cylinder unit of claim 6, wherein the first seal has a first effective sealing surface and the second seal has a second effective sealing surface, the first and second effective sealing surfaces having substantially equal areas.

8. The piston and cylinder unit of claim 1, wherein the piston position detection unit includes a connection element being designed and arranged to transmit data from the electronic unit, the connection element being connected to the electronic unit and to the housing.

9. The piston and cylinder unit of claim 8, wherein the piston position detection unit, with the exception of a part of the connection element, is completely arranged in the mounting bore.

10. The piston and cylinder unit of claim 1, wherein the electronic unit includes an antenna being designed and arranged to send and receive high frequency signals through the housing.

11. The piston and cylinder unit of claim 10, wherein the antenna is arranged on the electronic unit and the electronic unit is arranged in the housing such that the high frequency signals are directed through the sensor signal bore.

12. The piston and cylinder unit of claim 1, 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.

13. The piston and cylinder unit of claim 12, 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.

14. The piston and cylinder unit of claim 1, wherein the high frequency waves have a frequency of between 20 GHz and 400 GHz.

15. The piston and cylinder unit of claim 1, wherein the high frequency waves are frequency modulated continuous wave radar signals.

16. The piston and cylinder unit of claim 1, wherein the piston and cylinder unit is designed as a hydraulic piston and cylinder unit.

17. 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 including a longitudinal center axis; and an electronic unit being arranged in the housing and including an antenna for sending and receiving high frequency electromagnetic wave signals through the housing, the sense of direction of main radiation of the antenna extending perpendicularly to the longitudinal center axis of the housing, wherein the piston position detection unit is designed to be arranged in a mounting bore in the cylinder such that an interior of the cylinder is sealed from the surroundings of the piston and cylinder unit by the housing, and the piston position detection unit is designed to be arranged in the mounting bore in the cylinder such that the high frequency electromagnetic wave signals are directed through a sensor signal bore in the cylinder, the mounting bore being operatively connected to the interior of the cylinder by the sensor signal bore, the mounting bore extending in a radial direction and the sensor signal bore extending in an axial direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. In the drawings, like reference numerals designate corresponding parts throughout the several views.

(2) FIG. 1 illustrates a sectional view of an exemplary embodiment of a new piston and cylinder unit including a new piston position detection unit.

(3) FIG. 2 illustrates an enlarged view of a part of the piston and cylinder unit according to FIG. 1.

(4) FIG. 3 illustrates the detail A of the piston and cylinder unit of FIG. 2.

(5) FIG. 4 illustrates a view of a part of the piston and cylinder unit according to FIG. 1 from above.

(6) FIG. 5 illustrates a perspective exploded view of a part of the piston and cylinder unit according to FIG. 1.

(7) 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.

DETAILED DESCRIPTION

(8) Referring now in greater detail to the drawings, FIG. 1-6 illustrate different views of an exemplary embodiment of a new piston and cylinder unit 1 as well as its parts.

(9) 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 without a discontinuation line where the dashed line in FIG. 2 (detail A) is arranged.

(10) 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.

(11) 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.

(12) 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.

(13) 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.

(14) 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.

(15) 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.

(16) 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.

(17) 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).

(18) 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.

(19) The piston position detection unit 28 includes a housing 29 and an electronic unit 30 being arranged in the housing 29.

(20) 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.

(21) 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.

(22) 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.

(23) 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.

(24) The housing 30 and thus the piston position detection unit 28 are securely mounted in the mounting bore 27 by a securing ring 39.

(25) 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.

(26) 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.

(27) 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.

(28) 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 sense of direction of main radiation of the antenna 46 thus extends perpendicularly to the longitudinal center axis 47 of the housing 29. Thus, the sense of direction of main 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 signal bore 26 onto the piston 7 and that the signals reflected by the piston 7 can be received by the antenna 46.

(29) During operation of the piston position detection unit 28, it sends high frequency signals by the antenna 46 through 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 contact the piston 7, they are reflected by the piston 7 and they return along the same path and are received by the antenna 46. 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.

(30) 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.