EP0065588B1

EP0065588B1 - Hydraulic actuator of the oscillating-vane type

Info

Publication number: EP0065588B1
Application number: EP81104040A
Authority: EP
Inventors: Shimoda Shinobu
Original assignee: Torquer Co Ltd
Current assignee: Torquer Co Ltd
Priority date: 1981-05-26
Filing date: 1981-05-26
Publication date: 1987-04-01
Also published as: EP0065588A1; DE3176067D1

Description

The invention refers to a hydraulic actuator according to the preamble of claim 1.
In DE-A-2 321 043 such a hydraulic actuator is disclosed, which is provided with strong elastic sealing rings between the inner wall of the cylindrical housing and the outer circumference of the flanges. These sealing rings between the working chamber of the actuator and the outside are supported by support rings and slide on the circumference of the flanges during rotation of the rotor shaft. Therefore, the sealing material is exposed to extreme abrasion and hinders the efficiency of the actuator because of friction of the sealing with the flanges.
Further it is known from GB-A-716 776 that the surfaces rotate with very small clearance in the cylinder of a hydraulic actuator and practically no leakage occurs.
It is the object of the invention to improve a hydraulic actuator according to the preamble of claim 1 in such a way that the efficiency of the actuator is not diminished by the friction of sealings.
This object is achieved by the features in the characterizing part of claim 1. A small clearance between the inner wall of the housing and the flanges and vanes of the rotor can be maintained by the bearings pressed into the cylinder bore from both sides. This clearance provides a barrier to the passage of hydraulic medium so that a sliding seal element can be omitted.
Claims and 3 refer to a further embodiment of the invention. In this connection reference is made to US-A-2,798,462.
The invention is explained more detailedly in connection with the drawings.

Fig. 1 shows partially a cross sectional front view of an embodiment of the invention,
Fig. 2 is a cross-section view seen from A-A line in Fig. 1,
Fig. 3 is a front view showing a making process of a rotor,
Fig. 4 is a side view showing a making process of a vane,
Fig. 5 shows partially a cross sectional front view of another embodiment of the invention, and
Fig. 6 is a cross sectional view seen from B-B line in Fig. 5.

In the embodiment according to Fig. 1 two vanes 17, 18 are provided in a cylindrical housing composed of a cylinder 1 closed at its both sides by securing end covers 2 and 3 with bolts 4, 5. The cylinder 1 is defined with holes 6 on an upper and a lower face into which core metals will be inserted. The core metal is a fastening element 7 and secured to the cylinder 1 by tightening bolts, and serves to restrain action of stoppers 8, 9 as later mentioned. The cylinder 1 is further formed with inlet/outlet ports 10, 11 around the fastening element 7 for charging and discharging hydraulic medium or oil under pressure.
The rotor to be disposed within the cylinder 1 comprises a rotor shaft 12, flanges 13, 14 parallel thereto, small diameter portions 15, 16 as outer sides of the flanges 13, 14 and the vanes 17, 18 fixed between the flanges 13, 14. The rotor shaft 12 is formed with a narrow path 21 communicating oil chambers 19 and 20 as seen in Fig. 2, and a narrow path 22 communicating oil chambers which will be gradually defined between the stopper 8 and the vane 17 and between the stopper 9 and the vane 18 by rotation of the rotor. The paths 21, 22 may be omitted, if the vane and the stopper make one pair, and those may be also omitted if the cylinder 1 is formed on its lower face with oil ports as the oil ports 10, 11.
Preferably, the rotor is made in a following manner. That is, a circular material is ready for which is in diameter the same as or a bit larger than the flange, and it is machined on respective parts. At the outset, it is processed up to size of the diameter of the small diameter portions 15, 16, leaving parts which will be the flanges 13, 14 at left and right sides, subsequently the processing is continued up to size of the diameter of the rotor shaft 12, leaving parts which will be the small diameter portions 15, 16. Thus, portions of the flanges 13, 14, the small diameter portions 15, 16 and the rotor shaft 12 are formed integrally and sequentially.
Depending upon this manner, connections at respective parts are not necessary any longer, and accordingly no attention should be paid to discrepancy or error with respect to right angle, etc. In the instant actuator, the viscosity of the oil is utilized for preventing the oil leakage without using the sealing material to the vanes 17, 18. For this purpose, there is kept a clearance of microns to the extent that the oil leakage does not occur, between the inner wall of the cylinder 1 and the circumferential faces of the flanges 13, 14. Therefore, it is preferable to manufacture the rotor as mentioned above, since such precision as microns is required to sizing and setting-up of each of the parts. For the vanes 17, 18, such cylindrical body like a doughnut is ready for which has an inner diameter equal to the diameter of the rotor shaft 12 and has an outer diameter being equal to or a bit larger than the outer diameter of the flanges 13, 14, and it is cut out at one part into a sector of small width and is kept by a bolt between the flanges 13, 14. In this case, if the outer diameters of the vanes 17, 18 are prepared as slightly larger than a determined outer diameter of the flange, it is possible to accord to the outer diameter of the flanges 13, 14 by grinding the vanes 17, 18 on protruding parts thereof from the flanges 13, 14 after having fixed the vanes 17, 18 between the flanges 13, 14. The vanes 17, 18 are secured to the flanges 13, 14 by the bolts. If the vanes 17, 18 are formed with cutouts 23, the oil smoothly penetrates between the contacting vane and stopper.
A next reference will be made to fitting of the rotor into the cylinder 1. The rotor 6 is urged into the cylinder 1 under condition that the stoppers 8, 9 are kept between the flanges 13,14 on the upper and lower parts thereof. The stoppers 8, 9 are positioned within spaces defined between the rotor shaft 12, the flanges 13, 14 and the inner wall of the cylinder 1, but are not fixed to either of them. Thereby, thrust loading acting on the rotor shaft 12 may be absorbed and at the same time the sizing error or setting-up error at each of the parts may be corrected. After the rotor has been urged into the cylinder 1, radial bearings 24, 25 are forcibly set at the both sides, outer wheel of which bearings 24, 25 are a bit larger in the diameter than the inner diameter of the cylinder. The inner wheels of the radial bearings 24, 25 are mounted on the small diameter portions 15, 16 of the rotor. The rotor is securely supported in that the radial bearings 24, 25 are used, the outer wheel of which has the diameter larger than the inner diameter of the cylinder, so that the clearance is maintained between the circumferential faces of the flanges 13, 14 and the inner wall of the cylinder. The fastening elements 7 are inserted into the holes 6 and are fixed at end portions seated within bores 26, 27 of the stoppers 8, 9.
Figs. 5 and 6 illustrate another embodiment, in which cushion mechanism is disposed. Herein, oil ports 28, 29 are prepared with a main path 30 and a subpath 31, and the main path 30 is directed to an oil chamber. The subpath 31 is communicated with the oil chamber via a path 34 which is normally closed by a ball check valve 33 acted by a spring 32, and a throttle 35. The throttle 35 is controlled in its width by a control screw 36 in the cylinder 1. The other mechanisms are the same as mentioned above.
The action of the hydraulic actuator will be referred to. If the pressure oil is supplied from the oil port 10, the oil goes between the upper stopper 8 and the vane 17, i.e., into the cutout 23, the vane 17 contacting the stopper 8 slowly separates therefrom and rotates in the counterclockwise direction in Fig. 2 until it contacts the lower stopper 9. Then, part of the oil is led via the narrow path 21 into between the vane 18 and the stopper 9 and separates the both. On the other hand, the oil charged in the oil chamber 19 passes through the narrow path 21 by the vane 17 into the oil chamber 20, and is discharged from the oil port 11 by the vane 18 together with the oil charged in the chamber 20, and the rotation of the rotor is stopped in that the vane 17 contacts the stopper 9 and the vane 18 contacts the stopper 8. When the relation of the inlet and the outlet of the oil is exchanged with respect to the respective oil ports 10, 11 the same operation as mentioned is then performed to the reverse, that is, the vanes 17, 18 rotates in the opposite direction and returns to the state shown in Fig. 2. The said normal and reverse rotations are repeated and the rotary shaft is effected with reciprocating rotation.
Herein, a reference will be made to receiving manner of the thrust load in the rotary actuator. While the rotor serves the normal and reverse rotations, the rotor is always given the thrust load which is a component force other than the radial load. As far as the component force is light, it may be sufficiently received by only supporting the rotor on the radial bearing. However, if a large thrust load were acted on while the thrust load is acted on the rotary shaft from the outside, the inner wheels of the radial bearings 24, 25 would slightly biased toward the thrust in response to the extent of such thrust load and the rotor also moves accordingly, though the outer wheels of the radial bearings are so close to the inner face of the cylinder 1 and do not move. If, at this time, the stoppers 8, 9 were fixed to the inner wall of the cylinder 1, one of the flanges would be strongly urged against the stopper at its side by the thrust load, so that not only reduction of the output torque is invited but burning is caused to obstacle the rotation of the rotor.
In view of such circumstances, the stoppers 8, 9 are not fixed to the cylinder 1 at its inner wall, whereby the stoppers 8, 9 may be moved while the rotor moves with fitting to neighbourhood to avoid occurrence of said disadvantages. Being supported under non-fixing condition, the stoppers 8, 9 move freely and fit to the adjacent members. Therefore, it is possible to adjust the sizing errors or the setting-up errors when the members are set up.
An explanation will be referred to the embodiment preparing the cushion mechanisms shown in Figs. 5 and 6. In Fig. 5, the oil from the oil port 28 flows into the subpath 31, since the main path 30 is closed with the vane 17. At this time, a part of the oil flows into the throttle 35, but its most part runs toward the check valve 33 against the spring 32, and flows into the path 34 from this opening valve 33. Since the oil goes into the cutout 23, i.e., between the vane 17 and the stopper 8 as if the both are separated, the vane 17 rotates separately from the stopper, so that a new oil chamber is defined between these two members. A part of the oil passes the narrow path 22 and goes between the vane 18 and the stopper, and also there the same service is provided. When the vane 17 advances in rotation and opens the main path 30, the oil is directly fed from the main path to the oil chamber. Further the oil filled in the oil chamber 20 is pushed out from the oil port 29 through the main path 30. The oil filled in the oil chamber 19 flows into the oil chamber 20 through the narrow path 21, and similarly it is pushed out from the oil port 29. The oil which is pushed out when the vane 18 closes the main path of the oil port 29, flows into the throttle 35 and the subpath 31, but the subpath is closed by the check valve 33 pressed by the spring 32, the oil flows bit by bit from the throttle 35 only. The throttle 35 is adjusted in its width by operating an adjusting screw 36. When the vane 18 comes to the stopper 8, the oil is reduced in the discharging amount and controls the rotation of the vane 18 to make shock moderate, generated when the vane 18 contacts the stopper 8. For providing the reverse rotation of the rotor, it is sufficient to make reverse the relation of the inlet and the outlet of the oil with respect to the oil ports 28, 29.

Claims

1. Hydraulic actuator of the oscillating-vane type comprising:

a cylindrical housing (1, 2, 3) having a pair of inlet/outlet ports (10, 11) for alternately introducing and exhausting a hydraulic medium;

a spool-like rotor (12-18) including a shaft (12), two spaced apart and radially extending flanges (13, 14) and a vane (17,18) mounted between said flanges (13, 14) and said shaft (12);

a pair of radial roller bearings (24, 25) supporting said rotor (12-18) within a cylinder bore of said housing (1, 2, 3);

and a stopper (8, mounted on the inner wall of the housing (1, 2, 3) between said ports (10, 11) by means of a fastening element (7) projecting from the inner side of the housing, and engaging between said flanges (13, 14), said stopper (8, 9) being supported by said fastening element (7) such that the stopper (8, 9) is movable in the axial direction relative to the housing (1, 2, 3) and is prevented from circumferential movement;

characterised in that

a small clearance is maintained between the radial outer surface of the flanges (13, 14) and the cylinder bore thereby providing a barrier to the passage of hydraulic medium without the use of any sliding seal element;

that the outer diameter of the bearings (24, 25) . is slightly larger than the diameter of the cylinder bore;

and that the bearings (24, 25) are pressed from both sides into the cylinder bore.

2. Actuator according to Claim 1, characterised in that the inlet/outlet ports (28, 29) are provided with cushioning means comprising a main path (30) being closed by the vane (17,18) at the end of the stroke and a sub-path (31) communicating with the respective working chamber adjacent the stopper (8) via a throttle (35) and a further path for bypassing said throttle and which is normally closed by a spring biased ball check valve (32-34).

3. Actuator according to Claim 2, characterised in that a screw (36) is provided for adjusting the cross-section of the throttle (35).