CN102971547A - Hydrostatic actuator - Google Patents

Abstract

The invention relates to a hydrostatic actuator (1, 1 a), in particular for use in a motor vehicle, comprising a drive unit (5) having an electric motor (6) and a planetary roller gear (7) driven by the rotor of the electric motor (6), and a hydrostatic master cylinder unit (8, 8 a) driven by the planetary roller gear (7) and arranged around the planetary roller gear (7). In order to increase the efficiency and reduce the production costs, the master cylinder unit is formed from a plurality of master cylinders (10, 10a, 10 b) which are distributed over the circumference with respect to the rotational axis of the rotor and are each connected to a planetary roller gear.

Description

Hydrostatic Actuator

technical field

The invention relates to a hydrostatic actuator, especially for use in motor vehicles, comprising a drive unit with an electric motor and a planetary roller transmission driven by the rotor of the electric motor and a surrounding planetary roller transmission driven by the planetary roller transmission Hydrostatic active cylinder unit with roller drive arrangement.

Background technique

Such hydrostatic actuators are disclosed in the non-prepublished German patent applications Nr. 102009051245.4, 102010009297.5 and 102010014673.0. In this case, the drive unit is provided with an electric motor whose rotor is connected to a planetary roller gear. Arranged around the planetary roller gear is a master cylinder unit with a master cylinder whose annular piston is displaced axially by the planetary gear. Due to the large diameter of the annular piston, the sealing device for sealing the annular piston relative to the housing causes high frictional torques, high wear and unloaded stroke losses. Furthermore, the seals used are expensive. The hydrostatic actuator has to be finally tested as a complete unit and requires extensive rework in the event of defects.

Contents of the invention

It is therefore the object of the present invention to advantageously improve hydrostatic actuators, in particular with regard to higher efficiency, reduced manufacturing costs and improved testability.

This task is solved by a hydrostatic actuator, especially used in motor vehicles, which contains a drive unit with an electric motor and a planetary roller transmission driven by the rotor of the electric motor and driven by planetary rollers A transmission-driven, hydrostatic master cylinder unit arranged around a planetary roller transmission, wherein the master cylinder unit consists of a plurality of cylinders distributed on the circumference with respect to the axis of rotation of the rotor, respectively connected to the planetary roller transmission Connected active cylinders are formed.

The hydrostatic actuator can be used in all applications, especially in automobiles, where it is desired to displace a component axially relative to a stationary housing. For example, a slave cylinder remote from the hydrostatic actuator and operatively connected to the master cylinder unit by means of a pressure line, for example a slave cylinder of a friction clutch, brake or the like, can be acted upon by means of the hydrostatic actuator. In this case, for example in the case of a friction clutch, the slave cylinder acts under the pressure generated by the master cylinder unit actuated correspondingly by the driven unit against the belleville spring, the lever element or the lever spring of the friction clutch and according to the friction clutch Whether it is forced open or forced closed, it is opened or closed.

In order to improve its movement and installation space, the coaxial arrangement of the electric motor, the planetary roller transmission and the master cylinder unit in the hydrostatic actuator, wherein a plurality, preferably three master cylinders distributed on the circumference surround the planetary roller Sub drive settings. In this case, the planetary roller gear converts the rotational movement of the electric motor into an axial movement, which is transmitted via the drive plate to the piston of the master cylinder. In this case, the master cylinders are designed as units that can be tested independently of each other and independently of the drive unit, have a master cylinder housing and a piston that is axially displaceable relative to the master cylinder housing, and are accommodated in hydrostatic actuators. in the casing. By forming a separate master cylinder housing, it is possible to construct the master cylinder as a functional unit which can be tested in particular for tightness and special requirements. In this way, the main components of the hydrostatic actuator can be tested prior to assembly, whereby reworking of possibly defective hydrostatic actuators or their defect rate can be reduced.

Due to the short sealing path, friction can be reduced to such an extent that, for example, in the case of three active cylinders distributed around the circumference, at an actuating force predetermined by the drive unit, the required piston cross-sectional area can be reduced and The volume of the pressure chamber between the master cylinder housing and the piston is reduced so that the diameter of the hydrostatic actuator is the same or can even be smaller than a hydrostatic actuator with an annular piston. Especially viewed in the circumferential direction, intermediate spaces can be provided between the master cylinders, in which functional components such as sensor elements (such as displacement and/or pressure sensors for detecting the axial displacement of the master cylinder unit), hydrostatic actuators, etc. An anti-twist device between the housing parts, one or more storage volumes which can be communicated with the pressure medium volume of the at least one master cylinder, for example when the piston is in the zero position, and/or the like. Large radial installation spaces for these functional elements can be avoided in this way.

The master cylinders each have a pressure connection which connects the pressure medium volume formed by master cylinder housing and piston to a pressure line inside or outside the housing of the hydrostatic actuator. The pressure line is connected at the other end to the slave cylinder.

This pressure medium volume is formed as a pressure chamber by a master cylinder housing and a piston axially displaceable in this housing. In this case, a seal between them, such as a groove ring seal, is preferably received on the piston and comes into dynamic sealing contact with the inner wall of the master cylinder housing. In order to protect the primary seal against dry running and to seal the master cylinder to the outside, at least one master cylinder can be sealed to the outside by means of a secondary seal between the piston and the master cylinder housing. The pressure-free intermediate space between the secondary seal and the primary seal can be at least partially filled with pressure medium, so that the primary seal cannot run dry. It has proven to be advantageous here if a self-discharging opening to the storage container is provided between the primary seal and the secondary seal. In this case, during displacement of the piston, pressure medium is exchanged with the storage container according to the changing volume. If the piston moves with its primary seal over the self-relieving orifice in the zero position of the pressure relief, the pressure medium volume of the pressure chamber can also be compensated by means of a reserve container, wherein the pressure difference can be equalized and suctioned or squeezed in if necessary. The air is exhausted to the storage container.

In addition to the cost savings of the small and thus low-cost sealing device and the easily producible piston, further cost savings can be achieved in that when the hydrostatic actuator is installed in operation, for example in a motor vehicle, preferably in a topological Structurally the highest active cylinder is provided with an automatic discharge hole. By interconnecting the pressure sides of the master cylinder, the master cylinder exchanges the pressure difference and the accumulated air which collects at the highest point of the hydrostatic actuator and can thus be easily discharged at the master cylinder to a storage tank. When only one master cylinder is configured with a connection to the storage container, the master cylinder housing of the corresponding master cylinder can be configured with only one primary seal running dry on one side or be provided with a secondary seal which allows the primary The intermediate space between the seal and the secondary seal is partly filled with pressure medium or lubricant, so that the primary seal can be run wet or lubricated, wherein air compensation can be achieved during the volume change when the piston is actuated, for example by Suction and displacement of secondary seals, housing bores or similar structures.

Description of drawings

The invention is explained in more detail with the aid of the exemplary embodiment shown in FIGS. 1 and 2 . The accompanying drawings show:

Figure 1 Sectional view of a hydrostatic actuator with a master cylinder unit having a plurality of master cylinders distributed over the circumference,

FIG. 2 is a section through a slightly modified hydrostatic actuator relative to that of FIG. 1 .

Detailed ways

FIG. 1 shows a sectional view of a hydrostatic actuator 1 having a multi-part housing 2 with housing parts 3 , 4 . For the basic structure and function of the hydrostatic actuator 1 reference is made to the prior art mentioned above. The housing part 4 accommodates a drive unit 5 with an electric motor 6 and a planetary roller gear 7 driven by the motor rotor, as well as a master cylinder unit 8 . The housing part 3 serves as a closure cover for the housing part 4 .

The planetary roller gear 7 converts the rotational movement of the rotor into an axial movement and axially acts on the master cylinder unit 8 . For this purpose, a drive plate 9 is provided on the planetary roller gear 7 .

The master cylinder unit 8 is composed of master cylinders 10 , preferably evenly distributed over the circumference, which each have a master cylinder housing 11 and a piston 12 axially displaceable therein. The master cylinders are constructed as a separate structural unit and are accommodated in a stationary manner in the housing part 4 of the housing. Due to the master cylinder being configured as a separate unit, it is possible to test the master cylinder in the disassembled state and to neutralize the pressure inside the master cylinder 10 so that they can be installed without additional stress on the housing 2 , thereby avoiding corresponding damage to the housing 2 . Expansion force acting in shell 2.

A pressure medium volume 13 is formed in each case by the master cylinder housing 11 and the piston 12 , which is sealed off by means of an axial fastening by a primary seal 14 , such as a groove ring seal, accommodated on the piston 12 . The pressure outlets 15 of these pressure medium volumes 13 are each integrated in a manner not shown in a pressure connection 16, which is connected to a pressure line, wherein a connection to a remotely located slave cylinder, such as a friction clutch, is established by means of the pressure line. Pressure connection for clutch slave cylinder. Due to the low friction due to the overall small circumferential dimensions of the primary seal 14 , the area of the piston 12 and thus the radial dimension of the hydrostatic actuator 1 can be kept small. For example, three master cylinders distributed over the circumference, each having a piston area of less than 150 mm ² , are sufficient to operate a conventional friction clutch, for example 135 mm ² corresponds to a diameter of approximately 13 mm. Due to this small size, the unloaded volume of the pressure medium volume, which is necessary, for example, to move the piston 12 from the zero position with the automatic relief hole 19 active until the effective pressure is built up, can be minimized.

The master cylinder 10 also has secondary seals 17 , such as ring groove seals, which seal the master cylinder housing 11 outwardly towards the piston 12 . The supplementary volume 18 between the primary seal 14 and the secondary seal 17 each has a self-discharging opening 19 which is connected to a pressure medium storage container (not shown). Due to the pressure medium applied on both sides of the primary seal, the primary seal always runs wet and can therefore be operated with minimal wear.

FIG. 1 shows the hydrostatic actuator under load, ie when the electric motor 6 is energized, the drive plate 9 is displaced axially and the piston 12 is thereby axially loaded, the pressure medium volume 13 is under pressure. If the energization of the electric motor 6 is removed or the direction of rotation is reversed, the piston 12 is unloaded and returns in the direction of the automatic relief hole. If the primary seal 14 now passes the self-releasing opening 19 , a pressure equalization between the pressure medium volume 13 and the storage container takes place via the self-releasing opening 19 . The automatic drain openings 19 can be grouped inside or outside the housing 2 and can be connected to a remotely located storage container by means of a single compensating line. Alternatively or additionally, in a manner not shown, a storage volume for pressure medium can be provided in one or more intermediate spaces arranged in the circumferential direction between preferably three active cylinders 10 . In addition, in these intermediate spaces, an anti-twist device for the housing parts 3 , 4 or a displacement sensor element 20 , shown only in part, which is arranged here radially outside the master cylinder 10 , can be provided.

FIG. 2 shows a slightly modified embodiment of the hydrostatic actuator 1a compared to the embodiment of the hydrostatic actuator 1 of FIG. Elements are arranged in a manner not shown in the intermediate space between two circumferentially adjacent master cylinders 10b. In particular, radial installation space can thus be saved and the diameter of the housing 2a can be reduced.

In order to save manufacturing costs, in the illustrated embodiment of the hydrostatic actuator 1a the master cylinder unit 8a is designed such that only the master cylinder 10a, which is topologically arranged in the highest position, is provided with a secondary seal 17a, self-discharging Bore 19a and supplementary volume 18a. In this case, master cylinder 10 a assumes pressure compensation with the storage tank or storage volume. Here, the remaining active cylinders 10b are output via pressure

15a are interconnected, whereby the pressure equalization of master cylinder 10a is also effective for master cylinder 10b.

List of reference signs

1 hydrostatic actuator

1a Hydrostatic actuator

2 shell

2a shell

3 shell parts

4 shell parts

5 drive unit

6 electric motors

7 planetary roller transmission

8 Active cylinder unit

8a Active cylinder unit

9 driver board

10 active cylinder

10a Active cylinder

11 Active cylinder housing

12 pistons

12a Piston

13 Pressure medium volume

14 primary seal

15 pressure outlet

15a Pressure outlet

16 pressure connector

17 Secondary seal

17a Primary seal

18 Supplementary volume

18a Supplementary volume

19 Automatic drain hole

19a Automatic drain hole

20 displacement sensor element

Claims (9)

1. A hydrostatic actuator (1, 1a), especially used in automobiles, comprising a drive unit (5) with an electric motor (6) and a rotor driven by the motor (6) The planetary roller transmission (7) and the hydrostatic active cylinder unit (8, 8a) driven by the planetary roller transmission (7) and arranged around the planetary roller transmission (7), is characterized in that the The active cylinder unit (8, 8a) is composed of a plurality of active cylinders (10, 10a, 10b) distributed on the circumference relative to the rotation axis of the rotor and respectively connected to the planetary roller transmission (7). 2. The hydrostatic actuator (1, 1a) according to claim 1, characterized in that the master cylinders (10, 10a, 10b) are designed to be verifiable independently of each other and independently of the drive unit (5) unit, having a master cylinder housing (11) and a piston (12, 12a) axially movable relative to the housing and positionally housed in the housing (2, 2a) of the hydrostatic actuator (1, 1a) )middle. 3. The hydrostatic actuator (1, 1a) according to claim 2, characterized in that the active cylinders (10, 10a, 10b) are connected between the piston (12, 12a) and the active cylinder housing (11) The enclosed pressure medium volumes ( 13 ) are interconnected and lead into a common pressure line for the slave cylinders. 4. The hydrostatic actuator (1, 1a) according to claim 2 or 3, characterized in that a piston (12, 12a) is received on the piston (12, 12a) to seal the piston (12, 12a) from the active cylinder Primary sealing (14) of the pressure medium volume (13) of the active cylinder (10, 10a, 10b) between the housings (11). 5. The hydrostatic actuator (1, 1a) according to any one of claims 2 to 4, characterized in that at least one active cylinder (10, 10a) is sealed between the piston (12, 12a) and the active cylinder The housings (11) are sealed externally by means of secondary sealing devices (17, 17a). 6. The hydrostatic actuator (1, 1a) according to claim 5, characterized in that on at least one active cylinder (10, 10a) between the primary sealing device (14) and the secondary sealing device (17, 17a) is provided with an automatic drain hole (19, 19a) leading to the storage container. 7. The hydrostatic actuator (1a) according to claim 6, characterized in that in the arrangement of the hydrostatic actuator during operation at least the master cylinder (10a) which is arranged topologically highest is provided with Auto relief hole (19a). 8. The hydrostatic actuator (1, 1a) according to any one of claims 1 to 7, characterized in that the Another functional component of the hydrostatic actuator (1, 1a). 9. The hydrostatic actuator (1, 1a) according to claim 8, characterized in that the functional component is a housing ( 2. The anti-rotation device of 2 a), the displacement sensor element and/or a pressure medium storage volume which can be connected to at least one pressure medium volume of the master cylinder.

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