HYDRAULIC BLOCK FOR A HYDRAULIC POWER UNIT OF A HYDRAULIC POWER VEHICLE BRAKING SYSTEM

Abstract

A power piston in a power cylinder borehole of a hydraulic block of a hydraulic power unit of a hydraulic power vehicle braking system is only guided radially in an axially delimited guide section. The power cylinder borehole is configured with a larger diameter axially outside the guide section. A brake fluid channel extends through the guide section up to an opening of a brake fluid line.

Claims

1-9. (canceled)

10. A hydraulic block for a hydraulic power unit of a hydraulic power vehicle braking system, the hydraulic block including a power cylinder borehole in which a power piston is axially displaceably accommodated and sealed using a piston seal, the power cylinder borehole including a guide section on a pressure side of the piston seal in which it radially guides the power piston, wherein the hydraulic block includes a brake fluid channel in a circumferential surface of the power cylinder borehole, which extends through the guide section on the pressure side of the power piston up to the piston seal.

11. The hydraulic block as recited in claim 10, wherein the power piston, in a retracted basic position, rests sealingly against the piston seal.

12. The hydraulic block as recited in claim 10, wherein the power cylinder borehole includes a circumferential groove, into which a brake fluid line opens, on the pressure side of the power piston in a retracted basic position of the power piston.

13. The hydraulic block as recited in claim 10, wherein the piston seal includes a sealing ring, which is exclusively made of an elastic material and/or does not include a dedicated axial support against a pressure application in an axial direction.

14. The hydraulic block as recited in claim 10, wherein the power cylinder borehole includes two piston seals, and the guide section extends between the two piston seals.

15. The hydraulic block as recited in claim 10, wherein the guide section of the power cylinder borehole for the power piston extends only over a portion of a length of the power cylinder borehole on the pressure side of the power piston and/or not on a side, facing away from the pressure side, of the piston seal situated further away from the pressure side.

16. The hydraulic block as recited in claim 10, wherein the power cylinder borehole is connected by a check valve or by a differential pressure valve and by a controllable suction valve in the hydraulic block to a master brake cylinder borehole and/or to a brake fluid reservoir.

17. The hydraulic block as recited in claim 16, wherein the check valve or the differential pressure valve is integrated into a controllable separating valve, by which a wheel brake is connected to the power cylinder borehole.

18. The hydraulic block as recited in claim 10, wherein the hydraulic block includes a power drive configured to displace the power piston in the power cylinder borehole.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0013] The present invention is described in greater detail hereafter based on one specific embodiment shown in the FIGURE.

[0014] FIG. 1 shows a section of a hydraulic block according to an example embodiment of the present invention axially through a power cylinder borehole.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0015] Hydraulic power unit 1 according to an example embodiment of the present invention shown in FIG. 1 is provided for a brake pressure generation in a hydraulic power vehicle braking system including a slip controller. Such slip controllers are, for example, anti-lock braking units, traction control units and/or vehicle dynamics control units/electronic stability programs, for which the abbreviations ABS, TCS and VDC/ESP are common.

[0016] Hydraulic power unit 1 according to the present invention includes a hydraulic block 2 for a mechanical attachment and hydraulic interconnection of hydraulic and other components of the slip controller, such as solenoid valves, check valves, hydraulic accumulators and damper chambers. The components are situated at and in hydraulic block 1 and hydraulically connected to one another by a bore of hydraulic block 2, which is not shown, corresponding to a hydraulic diagram of the power vehicle braking system and the slip controller. Two solenoid valves 3 are shown as graphical symbols by way of example.

[0017] In the illustrated and described specific embodiment of the present invention, hydraulic block 2 is a cuboidal, flat metal block made of, for example, an aluminum alloy, which is provided with boreholes for accommodating the components of the slip controller and includes boreholes corresponding to the hydraulic diagram of the vehicle braking system and the slip controller.

[0018] Hydraulic block 2 includes a power cylinder borehole 4 in which a power piston 5 is axially displaceably accommodated. Power cylinder borehole 4 extends transversely through hydraulic block 2 and is open at one end. At another, closed end on an opposing side of hydraulic block 2, hydraulic block 2 includes an outwardly projecting, cylindrical cup-shaped molding 7, which is integral with hydraulic block 2 and coaxial to power cylinder borehole 4 and which axially elongates power cylinder borehole 4. For an axially displaceable guidance of power piston 5, power cylinder borehole 4 includes a guide section 6, which extends in the axial direction over a portion of a length of power cylinder borehole 4 and radially guides power piston 5 in power cylinder borehole 4. In guide section 6, power cylinder borehole 4 has the same diameter as power piston 5. In guide section 6, the diameter of power cylinder borehole 4 may also be slightly larger by so much that power piston 5 has play and is axially displaceable without jamming. Axially on either side outside guide section 6, power cylinder borehole 4 has a larger diameter than power piston 5, so that an annular gap 8 which encloses power piston 5 exists.

[0019] In guide section 6, power cylinder borehole 4 includes two axially spaced, circumferential sealing grooves, in each of which a piston seal 9, 10 is situated, which provide sealing between power cylinder borehole 4 and power piston 5. Piston seal 9 facing molding 7 may also be interpreted as a high pressure seal 9, and piston seal 10 facing the open end of power cylinder borehole 4 may also be interpreted as a low pressure seal 10. The two piston seals 9, 10 are sealing rings made of an elastomer or another, elastically deformable plastic or another material. Piston seals 9, 10 are made exclusively of the elastomer and include no support rings, support webs or other support elements, or the like, made of metal or, for example, a deformation-resistant plastic. In the exemplary embodiment, the two piston seals 9, 10 are lip seals including a sealing lip which extends around the inside and rests sealingly against an outer circumference of power piston 5.

[0020] In the direction of the open end of power cylinder borehole 4, guide section 6 ends at low pressure seal 10 or continues axially a short distance of preferably no more than one millimeter or several millimeters over low pressure seal 10. In the direction of molding 7, guide section 6 continues by approximately half a distance between guide piston 5 in its shown, retracted basic position from the closed end of power cylinder borehole 4 in molding 7. The retracted basic position of power piston 5 is the position which, during its operation, is situated furthest away from the closed end of power cylinder borehole 4.

[0021] The sides of power piston 5 and of high pressure seal 9 facing the closed end are their pressure sides since power piston 5, during a displacement into molding 7, generates a brake pressure in molding 7, and thus in power cylinder borehole 4.

[0022] On the pressure side of power piston 5 or of high pressure seal 9, guide section 6 includes a trench as brake fluid channel 11, which extends up to power piston 5 in the retracted basic position or up to high pressure seal 9. Brake fluid channel 11 may, as shown in the drawing, extend axially parallel or, for example, also helically (not shown). Multiple brake fluid channels 11 may be present, distributed over the circumference (not shown).

[0023] Between the two piston seals 9, 10, power cylinder borehole 4 includes a circumferential groove 12 into which a brake fluid line 13 opens, which leads to a non-illustrated brake fluid reservoir placed onto hydraulic block 2. Through brake fluid line 13 and groove 12, brake fluid reaches the circumference of power piston 5 for lubricating power piston 5 and piston seals 9, 10, power piston distributing the brake fluid in the axial direction during an axial displacement in power cylinder borehole 4 so that power piston 5 in guide section 6 of power cylinder borehole 4 and piston seals 9, 10 are lubricated.

[0024] Directly at the pressure-side end of power piston 5 in the retracted basic position, power cylinder borehole 4 includes a further, circumferential groove 14, which extends over a limited circumferential section and into which also a brake fluid line 15 opens, by which hydraulic wheel brakes, which are not shown and connected by brake lines to hydraulic block 2, are connected via solenoid valves 3 to power cylinder borehole 4. By displacing power piston 5 in the direction of the closed end, a brake pressure may be generated in power cylinder borehole 4 for an actuation of the wheel brakes. Through brake fluid channel 11, which extends through guide section 6 of power cylinder borehole 4 up to groove 14, groove 14 and brake line 15 opening into it also communicate with power cylinder borehole 4 between power piston 5 and the closed end of power cylinder borehole 4 when power piston 5 is displaced, since brake fluid channel 11 extends into a portion of power cylinder borehole 4, between guide section 6 and the closed end of power cylinder borehole 4, which has a larger diameter.

[0025] As is apparent in FIG. 1, high pressure seal 9 also provides sealing at power piston 5 in the retracted basic position thereof, and there is no displacement position of power piston 5 in which high pressure seal 9 does not provide sealing at power piston 5. In this way, dead travel is avoided and during its displacement in power cylinder borehole 4, power piston 5, proceeding from its retracted basic position, displaces brake fluid out of power cylinder borehole 4 from the start.

[0026] For the displacement of power piston 5 in power cylinder borehole 4 for generating a brake pressure using external power, hydraulic power unit 1 includes an electric motor 16, which displaces power piston 5 via a planetary gear 17 as a reduction gear and a ball screw 18 in power cylinder borehole 4. Ball screw 18 may, generally speaking, also be interpreted as a worm gear or as a rotatory/translatory conversion gear. Ball screw 18 is partially situated in power piston 5 coaxially to power piston 5 and to power cylinder borehole 4, the power piston being designed as a hollow piston for this purpose. Ball screw 18 is rotatably mounted with the aid of a ball bearing 19, which is situated with a tubular bearing holder 20 on the outside of hydraulic block 2. Planetary gear 17 is also situated coaxially to power cylinder borehole 4 and to power piston 5, between ball screw 18 and electric motor 16. Electric motor 16 includes a motor housing 21, which is also screwed to the outside of hydraulic block 2, coaxially to power cylinder borehole 4 and to power piston 5. Electric motor 16, planetary gear 17, and ball screw 18 form an electromechanical power drive 22, by which power piston 5 is axially displaceable in power cylinder borehole 4 for generating the brake pressure for the vehicle braking system using external power. Together with power cylinder borehole 4 and power piston 5, power drive 22 forms a power brake pressure generator 23 of hydraulic power unit 1 according to the present invention. The present invention does not preclude a generation of the brake pressure using external power other than the electromechanical generation.

[0027] In the illustrated and described specific embodiment of the present invention, hydraulic block 2 includes a master brake cylinder bore 24, in which a master brake cylinder piston (not shown) is situatable, which is mechanically displaceable via a piston rod with the aid of a foot brake pedal, which is not shown, or a hand brake lever in master brake cylinder borehole 24. Furthermore, hydraulic block 2 includes a simulator cylinder borehole 25 for a simulator piston, which is not shown and, for example, is acted upon by a spring. From master brake cylinder borehole 24, brake fluid is displaceable into simulator cylinder borehole 25 to be able to displace the master brake cylinder piston in master brake cylinder borehole 24 during a power actuation of the vehicle braking system. In addition to power brake pressure generator 23, the vehicle braking system may also be actuated by muscle power by the displacement of the master brake cylinder piston in master brake cylinder borehole 24, which is, in particular, provided in the event of a malfunction or a failure of power brake pressure generator 23.

[0028] Power cylinder borehole 4, master brake cylinder borehole 24 and/or simulator cylinder borehole 25 may also be created in a manner other than boring.

[0029] Power cylinder borehole 4 or power brake pressure generator 23 is connected to the hydraulic wheel brakes by one or two separating valve(s) 26 which is/are hydraulically connected in parallel, and with the aid of intake valves, not shown, which are hydraulically connected in series with separating valves 26. Moreover, power cylinder borehole 4 or power brake pressure generator 23 is connected to master brake cylinder borehole 24 or to the brake fluid reservoir, which is not shown, by separating valves 26 and suction valves 27 hydraulically connected thereto in series. A differential pressure valve 28, which limits a maximum pressure in power cylinder borehole 4, is integrated into at least one separating valve 26. In this way, an impermissibly high pressure in power cylinder borehole 4, for example also in the event of a thermal expansion of the brake fluid in power cylinder borehole 4, is prevented, without displacement of power piston 5.

[0030] Separating valves 26 and suction valves 27 are solenoid valves 3 of the slip controller of the vehicle braking system with which hydraulic block 2 is equipped. Separating valves 26 and suction valves 27 are 2/2-way solenoid valves, separating valves 26 being closed in their de-energized basic positions, and suction valves 27 being open in their de-energized basic positions. Differential pressure valve 28 is integrated, as described, into at least one of separating valves 26.