Electrohydraulic linear actuator

Abstract

An electrohydraulic linear actuator comprises a housing consisting of a tubular profile, which forms a housing shell and in which there is a plurality of cavities, and which is closed at the ends by two housing covers fitted to the ends of the housing shell. A first cavity of the tubular profile forms a cylinder which forms the hydraulic cylinder of a double-acting synchronous cylinder and a second cavity which extends parallel to the first cavity accommodates a hydraulic unit in addition to the hydraulic cylinder, and a hydraulic oil reservoir is formed in said second cavity. Two working chambers of the hydraulic cylinder are separated from each other by a piston unit. The housing has at least one through-hole for a coupling element which forms a mechanical interface with the piston unit. The electric motor of the hydraulic unit is configured as a brushless outrunner motor.

Claims

1. An electrohydraulic linear actuator wherein: the linear actuator comprises a housing (1), in which a hydraulic cylinder (8), a hydraulic unit (22) pressurizing this and a hydraulic-oil reservoir (24) are housed; relative to the axis (X) of the hydraulic cylinder (8), the hydraulic unit (22) and the hydraulic-oil reservoir (24) are disposed next to the hydraulic cylinder (8); the housing (1) consists of a profile tube, which forms a housing jacket (2), in which several cavities (5, 6) are constructed and which is closed at the ends by means of two housing covers (3, 4) fitted on the axial faces of the housing jacket (2); the hydraulic cylinder (8) is constructed as a double-acting synchronous cylinder with a piston unit (9), which is guided in a cylinder (7) and which separates two working chambers (11, 12) of equal cross section from one another; the cylinder (7) is formed by a first cavity (5) of the profile tube; the housing (1) is provided with at least one opening (16) for a mechanical interface to the piston unit (9) of the coupling element (17) forming the hydraulic cylinder (8); the hydraulic unit (22) is housed and the hydraulic-oil reservoir (24) is constructed in a second cavity (6) of the profile tube extending parallel to the first cavity (5); and the electric motor (21) of the hydraulic unit (22) is constructed as a brushless external-rotor motor.

2. The electrohydraulic linear actuator of claim 1, wherein the housing covers (3, 4) are provided with stoppers (13) projecting into the first cavity (5).

3. The electrohydraulic linear actuator of claim 1, wherein a control block (31) comprising an electronic controller is attached to one housing cover (3).

4. The electrohydraulic linear actuator of claim 3, wherein the internal stator (30) of the electric motor (21) is mounted on the control block (31).

5. The electrohydraulic linear actuator of claim 3, wherein an electrical input interface (32) is situated on the housing cover (3) to which the control block (31) is attached.

6. The electrohydraulic linear actuator of claim 1, wherein the housing (1) is provided on its outer face, spatially close to the hydraulic-oil reservoir (24), with surface profiling that increases the surface area.

7. The electrohydraulic linear actuator of claim 1, wherein the hydraulic-oil reservoir (24) has a volume of at least twice the sum of the volumes of the two working chambers (11, 12).

8. The electrohydraulic linear actuator of claim 1, wherein the profile tube consists of aluminum.

9. The electrohydraulic linear actuator of claim 1, wherein the profile tube consists of the portion of an extruded section.

10. The electrohydraulic linear actuator of claim 1, wherein the cylinder (7) of the hydraulic cylinder (8) is constructed directly in the housing (1).

11. The electrohydraulic linear actuator of claim 1, wherein the hydraulic unit (22) is reversible.

12. The electrohydraulic linear actuator of claim 1, wherein no proportional control valves are present between the hydraulic unit (22) and the hydraulic cylinder (8).

13. The electrohydraulic linear actuator of claim 1, wherein the piston unit (9) of the hydraulic cylinder (8) is operatively connected to a position sensor (35).

14. The electrohydraulic linear actuator of claim 1, wherein the at least one opening (16) of the housing (1) for the coupling element (17) is disposed on the axial face of the housing (1).

15. The electrohydraulic linear actuator of claim 1, wherein a manually actuatable way valve (19) is provided, by means of which direct hydraulic communication can be established between the two working chambers (11, 12).

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The present invention will be explained in more detail hereinafter on the basis of a preferred exemplary embodiment illustrated in partly schematic manner in the drawing. What is shown therein is a longitudinal section through an electrohydraulic linear actuator that realizes the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(2) This comprises a housing 1, which is joined together from three parts, namely from a housing jacket 2 and two housing covers 3, 4 fitted on the axial faces thereof. This housing jacket 2 is formed by a portion of a profile tube constructed as an extruded aluminum section. Several cavities 5, 6 are constructed therein and, corresponding to the manufacture of the housing jacket as an extruded section, extend continuously from one to the other housing cover 3, 4.

(3) A first cavity 5 with a circular cylindrical cross section then forms cylinder 7constructed directly in housing 1of a hydraulic cylinder 8, which further comprises a piston unit 9, which can be guided displaceably in the cylinder along the axis and has two pistons 10 guided sealingly in cylinder 7. Hydraulic cylinder 8 is constructed as a double-acting synchronous cylinder, so that piston unit 9 separates two hydraulic working chambers 11, 12 of equal cross section from one another. For sealed closure at the ends of the two working chambers 11, 12, a stopper 13 projecting sealingly into first cavity 5 is provided on each of the two housing covers 3, 4.

(4) Two piston-rod portions 14, 15, which extend through corresponding openings 16 provided in housing covers 3, 4, are connected to piston unit 9. These piston-rod portions 14, 15 respectively represent a coupling element 17, whichas the mechanical output of the linear actuatorforms a mechanical interface to piston unit 9 of hydraulic cylinder 8. To protect against dirt on piston-rod portions 14, 15 in the region of the respective penetration through the associated housing opening 16, two bellows 18 are provided (merely illustrated by way of example).

(5) A reversible hydraulic unit 22, which pressurizes hydraulic cylinder 8 and comprises a hydraulic pump 20 and a brushless electric motor 21 driving this is housed in second cavity 6 of housing jacket 2, which extends parallel to first cavity 5. This pump housing 23 is inserted sealingly in cavity 6 in question, so that it further bounds a hydraulic-oil reservoir 24 constructed in second cavity 6 and formed by it. Housing cover 4, likewise bounding hydraulic-oil reservoir 24, is provided with a filling and venting device 25 discharging into the hydraulic-oil reservoir. The two pressure outlets 26 of hydraulic pump 20 are in communication via lines 27 with respectively one port 28 of the hydraulic working chamber 11, 12 in question. Furthermore, an optionally provided way valve 19 is illustrated, which is provided fluidically between the two pressure outlets 26 of hydraulic pump 20 and ports 28 of the hydraulic working chambers 11, 12, and which is suitable, as an alternative to pressurization of hydraulic cylinder 8 by hydraulic unit 22, for establishingvia the corresponding portions of lines 27direct hydraulic communication between the two working chambers 11 and 12. Way valve 19 can be manually actuated. For this purpose, an actuating lever disposed outside housing 1 and acting on way valve 19 is provided.

(6) Electric motor 21 of hydraulic unit 22 comprises an external rotor 29 coupled with the pump rotor and an internal stator 30. The latter is mounted on a control block 31, which comprises the electronic controller and which in turn is attached to the associated housing cover 3. The electrical input interface 32 is situated on housing cover 3 in question. By the fact that hydraulic cylinder 8 on the one hand and the functional group comprising hydraulic-oil reservoir 24 and hydraulic unit 22 on the other hand are housed in two mutually parallel cavities 5, 6 of housing 1, an arrangement of hydraulic unit 22 and hydraulic-oil reservoir 24 laterally next to hydraulic cylinder 8 is obtained relative to axis X of hydraulic cylinder 8.

(7) Housing jacket 2 is provided in its region surrounding hydraulic-oil reservoir 24 with cooling ribs 33 on its outside. Via these, not only is the temperature of the hydraulic oil contained in hydraulic-oil reservoir 24 controlled but also the loss heat produced in hydraulic pump 20 is removed. As regards a favorable heat budget, circulation of the hydraulic oil present in hydraulic-oil reservoir 24 is achievedwhile avoiding a hydraulic short circuitduring pumping operation of hydraulic pump 20 by means of a tube 34, which projects into hydraulic-oil reservoir 24 and is connected to hydraulic pump 20.

(8) Finally, a device for sensing the position of the piston unit is shown. This comprises a position sensor 35 integral with the housing and a transmitter 36 fixed on piston unit 9. The position signal of position sensor 35 is switched via signal line 37 to the electronic controller.