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

A hydraulic block for a hydraulic power unit of a hydraulic, slipped-controlled power vehicle braking system. A power piston of an electromechanical power brake pressure generator in a power cylinder borehole of the hydraulic block is guided radially in the power cylinder borehole with the aid of a guide bushing.

FIELD

The present invention relates to a hydraulic block for a hydraulic power unit of a hydraulic vehicle braking system, in particular a hydraulic, slip-controlled and/or power vehicle braking system.

BACKGROUND INFORMATION

German Patent Application No. DE 10 2016 202 113 A1 describes a narrow, cuboidal hydraulic block for a hydraulic power unit of a slip-controlled hydraulic power vehicle braking system, in which a master brake cylinder borehole is continuously placed from one to an opposing narrow side, and a power cylinder borehole is also placed continuously through two opposite large sides of the hydraulic block, perpendicular to the master brake cylinder borehole. In addition, the conventional hydraulic block includes a blind hole for accommodating a pedal travel simulator. A cylinder liner, which is closed at one end and protrudes from the hydraulic block on one side and in which a power piston is axially displaceably accommodated, is situated in the power cylinder bore. To generate a brake pressure using external power, the power piston is displaceable by an electric motor via a ball screw in the cylinder liner. The electric motor is situated coaxially to the power cylinder borehole on the outside of the hydraulic block, and the ball screw is situated, also coaxially to the electric motor and to the power cylinder borehole, between the electric motor and the power piston. The electric motor and the ball screw form a power drive and, together with the power piston, the cylinder liner and the power cylinder borehole, form a power brake pressure generator for the hydraulic vehicle braking system.

SUMMARY

A hydraulic power unit according to the present invention is provided for a hydraulic power unit of a hydraulic vehicle braking system, in particular, for a hydraulic power vehicle braking system and/or a slip-controlled vehicle braking system. In accordance with an example embodiment of the present invention, the hydraulic power unit includes an, in particular, cuboidal hydraulic block to which hydraulic wheel brakes of the vehicle braking system are connectable via brake lines. Slip controllers are, in particular, an anti-lock braking unit, a traction control unit and/or a vehicle dynamics control unit/electronic stability program, for which the abbreviations ABS, TCS and/or VDC/ESP are common. The latter are also colloquially referred to as “anti-skid control units.” Slip controllers are conventional and are not discussed in greater detail here.

The hydraulic block is used to mechanically attach and hydraulically interconnect hydraulic components of the vehicle braking system or its slip controller. Such hydraulic components are, among other things, solenoid valves, check valves, hydraulic accumulators, damper chambers, and pressure sensors. The hydraulic components are attached in receptacles in the hydraulic block, which are usually designed as cylindrical through-holes or blind holes, partially with stepped diameters. “Interconnected” means that the receptacles or the hydraulic components attached therein are connected by lines in the hydraulic block corresponding to a hydraulic diagram of the vehicle braking system or its slip controller. The lines are typically, but not necessarily, drilled into the hydraulic block.

Equipped with the hydraulic components of the vehicle braking system or its slip controller, the hydraulic block forms the hydraulic power unit, “equipped” meaning that the hydraulic components are fastened in the respective receptacles of the hydraulic block intended for them.

The hydraulic block according to an example embodiment of the present invention includes a power cylinder borehole in which a power piston is axially displaceable, which is often also referred to as a plunger piston. For the radial guidance of the power piston, the hydraulic block according to the present invention includes a guide bushing, which is situated in the power cylinder borehole, encloses the power piston, and guides it axially displaceably in the power cylinder borehole. The present invention enables a, for example, wear-resistant and/or low-friction guidance of the power piston made of a different material than the hydraulic block.

For a brake pressure generation using external power, the power piston is displaceable in the power cylinder borehole, for example, with the aid of an electric motor via a threaded drive or using another rotatory/translatory reverse gear unit. A mechanical reduction gear may be provided between the electric motor and the threaded drive. The electric motor and the threaded drive form an electromechanical power drive for the power piston and, together with the power piston and the power cylinder borehole, form an electromechanical power brake pressure generator, the present invention not precluding power brake pressure generators other than electromechanical power brake pressure generators.

A master brake cylinder borehole in the hydraulic block is not mandatory for the present invention, even though a master brake cylinder borehole is preferably provided in the hydraulic block. The master brake cylinder borehole is provided for one or multiple piston(s) of a master brake cylinder for a muscle power or auxiliary force actuation of the vehicle braking system, i.e., one of the pistons is mechanically displaceable in the master brake cylinder borehole with the aid of a (foot) brake pedal or a (hand) brake lever.

If the hydraulic block includes a master brake cylinder borehole, it preferably also includes a simulator cylinder borehole for a pedal travel simulator in which a simulator piston which is acted upon by a spring or gas pressure, for example, is axially displaceably accommodated. The pedal travel simulator is preferably connected to the master brake cylinder via a solenoid valve, which may also be referred to as a simulator valve, and is used to receive brake fluid from the master brake cylinder borehole when the master brake cylinder is hydraulically disconnected from the vehicle braking system during a power operation of the vehicle braking system by the closing of a separating valve, so that no brake fluid may be displaced from the master brake cylinder into the vehicle braking system. The pedal travel simulator enables a displacement of the master brake cylinder piston during a power actuation of the vehicle braking system.

Through-holes or blind holes referred to here as “boreholes” or as “cylinder boreholes” may also be created in a manner other than boring.

Refinements and advantageous embodiments of the present invention are disclosed here.

All features described herein and of the figure may be implemented in specific embodiments of the present invention either alone or in a generally arbitrary combination. Embodiments of the present invention which do not include all, but only one or multiple features of a specific embodiment of the present invention are generally possible.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Hydraulic power unit1according to an example embodiment of the present invention shown inFIG. 1is provided for a 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.

Hydraulic power unit1according to the present invention includes a hydraulic block2for 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 block1and hydraulically connected to one another by a bore of hydraulic block2, which is not shown, corresponding to a hydraulic diagram of the power vehicle braking system and the slip controller. Two solenoid valves27are shown as graphical symbols by way of example.

In the illustrated and described specific embodiment of the present invention, hydraulic block2is a cuboidal, flat metal block made up of, for example, an aluminum alloy, which is provided with boreholes for accommodating the components and includes boreholes corresponding to the hydraulic diagram of the vehicle braking system and the slip controller.

Hydraulic block2includes a through-hole perpendicular to two large, mutually opposing sides of hydraulic block2as a power cylinder borehole3, in which a power cylinder4is axially displaceably accommodated. For an axially displaceable guidance of power piston4, a guide bushing5is axially fixed in power cylinder borehole3, which radially guides power piston4in power cylinder borehole3.

In the exemplary embodiment, guide bushing5is made of plastic. On the outside, guide bushing5is sealed by a force fit in power cylinder borehole3in hydraulic block2.

On the inside, guide bushing5includes a circumferential sealing groove6in which a sealing ring is situated as first piston seal7. First piston seal7, which may also be interpreted as a high pressure seal for power piston4, provides sealing between power piston4and guide bushing5.

An annular step8of power cylinder borehole3axially adjoins guide bushing5, with the aid of which power cylinder borehole3is reduced to a smaller diameter than in the area of guide bushing5. Annular step8has an axial distance from guide bushing5, so that a circumferential groove is formed in which a second piston seal9is situated, which may also be interpreted as a low pressure seal. Second piston seal9is held axially between guide bushing5and annular step8of power cylinder borehole3. It provides sealing between power cylinder borehole3and power piston4.

Axially at the height of guide bushing5, a brake fluid line10in hydraulic block2opens into power cylinder borehole3. In the exemplary embodiment, brake fluid line10opens into power cylinder borehole3between first and second piston seals7,9. Guide bushing5includes a channel11, which leads from the opening of brake fluid borehole10to a front face of guide bushing5which faces annular step8, so that brake fluid line10communicates through channel11on a front face facing guide bushing5with second piston seal9. Channel11, as shown, may, for example, be an axially parallel groove in an outer circumference of guide bushing5or a borehole in guide bushing5extending from the outer circumference to the front face of guide bushing5which faces annular step8(not shown). Guide bushing5is situated in power cylinder borehole3rotated in such a way that its channel11communicates with brake fluid line10. Brake fluid line10communicates with a brake fluid reservoir, which is not shown, and causes a lubrication of an outer circumference of power piston4in the area of second piston seal9. During an axial movement, the brake fluid on the outer circumference of power piston4also reaches first piston seal7, so that both piston seals7,9are lubricated.

On the outside, guide bushing5includes a circumferential groove12, which is interrupted at channel11and ends on both sides at a distance from channel11, so that groove12does not communicate with channel11. Brake fluid lines13, which communicate with one another by groove12, open axially into power cylinder borehole3at the height of groove12in the outer circumference of guide bushing5at two circumferential points. In this way, the two brake fluid lines13, which connect hydraulic components of the slip controller of the hydraulic power vehicle braking system to one another, are connected to one another on the outside around power cylinder borehole3. In the shown exemplary embodiment of the present invention, the two brake fluid lines13are situated outside the section plane, which is why one of the two brake fluid lines13is shown rotated into the section plane. The other brake fluid line13is not visible in the drawing.

Power cylinder borehole3extending through hydraulic block2is closed at one end by a cup-shaped cylinder cover14, which in the exemplary embodiment is screwed into power cylinder borehole3. Fastening with the aid of a spring washer is also possible, for example, which on the outside engages in a circumferential groove on the inside of power cylinder borehole3, and on the inside engages in a circumferential groove on the outside of cylinder cover14(not shown). Cylinder cover14protrudes to the outside from hydraulic block2and extends power cylinder borehole3, and thereby a displacement travel of power piston4.

Cylinder cover14is a crown cover including an edge which includes radial slots and by which it holds guide bushing5axially in power cylinder borehole3. Brake fluid may pass through the radial slots.

Outside guide bushing5, power cylinder borehole3has a larger diameter than power piston4, so that an annular gap15exists between power piston4and power cylinder borehole3. Cylinder cover14also has a larger inside diameter than power piston4, so that an annular gap16also exists between the power piston and cylinder cover14in cylinder cover14. As a result, power piston4is exclusively radially guided in guide bushing5.

For the displacement of power piston4in power cylinder borehole3for generating a brake pressure using external power, hydraulic power unit1includes an electric motor17, which displaces power piston4via a planetary gear18as a reduction gear and a ball screw19in power cylinder borehole3. Ball screw19may, generally speaking, also be interpreted as a worm gear or as a rotatory/translatory conversion gear. Ball screw19is partially situated in power piston4coaxially to power piston4and to power cylinder borehole3, the power piston being designed as a hollow piston for this purpose. Ball screw19is mounted with the aid of a ball bearing20, which is situated with a tubular bearing holder21on the outside of hydraulic block2. Planetary gear18is also situated coaxially to power cylinder borehole3and to power piston4, between ball screw19and electric motor17. Electric motor17includes a motor housing22, which is also screwed to the outside of hydraulic block2coaxially to power cylinder borehole3and to power piston4. Electric motor17, planetary gear18, and ball screw19form an electromechanical power drive23, by which power piston4is axially displaceable in power cylinder borehole3for generating the brake pressure for the vehicle braking system using external power. Together with power cylinder borehole3, cylinder cover14, and power piston4, power drive23forms a power brake pressure generator24of hydraulic power unit1according to the present invention. The present invention does not preclude a generation of the brake pressure using external power other than the electromechanical generation.

In the illustrated and described specific embodiment of the present invention, hydraulic block2includes a master brake cylinder borehole25, 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 borehole25. Furthermore, hydraulic block2includes a simulator cylinder borehole26for a simulator piston, which is not shown and, for example, is acted upon by a spring. From master brake cylinder borehole25, brake fluid is displaceable into simulator cylinder borehole26to be able to displace the master brake cylinder piston in master brake cylinder borehole25during a power actuation of the vehicle braking system. In addition to power brake pressure generator24, the vehicle braking system may also be actuated by muscle power by the displacement of the master brake cylinder piston in master brake cylinder borehole25, which is, in particular, provided in the event of a malfunction or a failure of power brake pressure generator24.

Power cylinder borehole3, master brake cylinder borehole25and/or simulator cylinder borehole26may also be created in a manner other than boring.