HYDRAULIC UNIT, IN PARTICULAR FOR CONTROLLING THE BRAKE PRESSURE OF A WHEEL BRAKE OF AN ELECTRONICALLY SLIP-CONTROLLED BRAKE SYSTEM OF A MOTOR VEHICLE

Description

Technical background

[0001] Electronically controlled slip brake systems have a hydraulic unit as a key component, which adapts the braking pressure of the wheel brakes to the slip conditions currently prevailing at the respective wheel. The brake fluids used can release a certain amount of gas depending on the temperature and pressure. If this brake fluid is then exposed to isobaric heating, for example due to self-heating, solar radiation or engine heat and / or an isothermal pressure drop, such as during a normal reduction in brake pressure or possible cavitation, the released gas can escape from the brake fluid and lead to the accumulation of gas bubbles in the brake circuits. This behavior is influenced by various parameters, such as the water content or thethe aging state of the brake fluid, the temperature, pressure, the type of brake fluid, and the operating conditions of the braking system. Due to this property of brake fluid, a targeted design or performance prediction of a braking system over its lifetime is difficult to achieve. Likewise, no technical solutions exist to maintain brake fluids in a defined condition over time.

[0002] Gas bubbles in the brake circuits influence the functional properties of a brake system, for example by dampening pressure pulsations on the suction or pressure side of a pressure generator that generates the brake pressure, but can also amplify vibrations of the hydraulic unit or cause undesirable operating noises at the valves of the hydraulic unit for brake pressure control.

[0003] To nevertheless meet market requirements regarding the functional properties, noise, and behavior of a braking system over its service life, current braking systems incorporate components that reduce the adverse effects described above. These include, for example, flexible brake lines, elastic brackets for attaching a hydraulic unit of an electronically controlled slip brake system to a vehicle body, or pulsation damping devices installed on the hydraulic unit.

[0004] Such devices take up installation space, incur parts and assembly costs, make it difficult to predict the operating behavior of a braking system during its lifetime and ultimately make the design of a braking system more complex. State of the art

[0005] The present invention is directed to a hydraulic unit, as already known, for example, from European patent application EP 1 388 476 A2. This known hydraulic unit is designed according to the features of the preamble of claim 1 and accordingly comprises a hydraulic block with a recess for receiving a pump element, a line connection for contacting the hydraulic unit with a wheel brake, a storage chamber for supplying the pump element with brake fluid, and a channel which contacts the storage chamber with the receptacle for the pump element in a region of a suction side of the pump element inserted into the recess.

[0006] A corresponding hydraulic unit is also disclosed in WO 03 / 064229 A1. Advantages of the invention

[0007] The invention differs from this prior art in that a hydraulic cavity is provided inside the hydraulic block and is in contact with the recess in the region of the suction side of the pump element inserted into the recess, that this hydraulic cavity comprises a riser pipe which forms a blind hole ending in the interior of the hydraulic block and that the riser pipe runs from the recess for the pump element in the direction of the pipe connection.

[0008] These features solve the problems of allowing gas bubbles occurring in the braking system to collect virtually automatically in this cavity due to the effective gravimetric buoyancy, and consequently effectively reducing operating noise and pressure pulsations on the suction side of the pump element generated by the pump element. The proposed measures can be implemented on the hydraulic block of the hydraulic unit without requiring any additional components or their assembly costs. They can be implemented without requiring any additional components or their assembly during manufacture of the hydraulic block and can also be combined with known damping devices, or may even eliminate the need for such additional damping devices. Finally, the invention is distinguished by the fact that it is not subject to age-related wear and tear and remains consistently effective throughout the service life of a hydraulic unit.The invention makes the operating characteristics of the hydraulic unit more uniform over its service life and allows for more precise estimation, which in turn simplifies the design of a braking system.

[0009] Further advantages or advantageous developments of the invention emerge from the subclaims or from the following description. drawing

[0010] Various embodiments of the invention are illustrated in the drawing and are explained in detail in the following description.

[0011] The Figures 1 to 8 show, each in three-dimensional representation, a drilling pattern of a hydraulic block of a hydraulic unit of an electronically controlled slip-control vehicle brake system designed according to the invention. Figures 1 , 5 , 6 and 8 show in this context the entire hydraulic block with two brake circuits, while in the Figures 2 to 7 and7 Only one half of the hydraulic block, and thus only one of the brake circuits, is visible. Corresponding components are provided with identical reference symbols in the figures. Description of the embodiments

[0012] The hydraulic block 10 after Figure 1is often also referred to as the pump housing of a hydraulic unit. It is cuboid-shaped and accordingly has two plane-parallel, opposite outer sides per spatial axis. On these outer sides of the hydraulic block 10, a plurality of recesses are formed, which are graduated from the outside to the inside and have different dimensions. Each of these recesses is open towards one of the outer sides and ends like a blind hole in the interior of the hydraulic block 10. The recesses serve, for example, to accommodate pump elements equipped with pistons for generating brake pressure, drive elements for actuating these pump pistons, valves for regulating the brake pressure generated by the pump elements, pressure accumulators for buffering brake fluid that is released from the wheel brakes during brake pressure reduction, or damping devices for damping pulsations in the brake fluid.These hydraulic components are inserted into the recesses from the outside and secured or mounted therein. Furthermore, hydraulic connections are provided on the hydraulic block 10, via which this hydraulic block 10 can be connected to a master brake cylinder and / or to the wheel brakes of a braking system via externally routed brake lines. The recesses and connections described are interconnected via pressure fluid channels according to a known hydraulic circuit diagram of an electronically controlled vehicle brake system. For installation space and / or manufacturing reasons, the recesses and pressure fluid channels are preferably arranged orthogonally to one another on the hydraulic block 10.

[0013] In the Figure 1Two horizontally aligned recesses 12, 14 can be seen, which extend from the left and right outer sides into the interior of the hydraulic block 10 and whose inner ends open into a third recess 16 open towards the front of the hydraulic block 10. The two horizontal recesses 12, 14 are each provided to accommodate a pump element. The third recess 16 is intended to accommodate a rotatably driven eccentric element, which mechanically drives the pistons of the two pump elements, which protrude in sections from opposite sides into the third recess 16, to perform a reciprocating stroke.

[0014] Furthermore, the hydraulic block 10 shown has two storage chambers 18 below the two recesses for the pump elements. These storage chambers 18 extend from the underside into the hydraulic block 10 and, in the event of a brake pressure reduction, receive pressure fluid released from the wheel brakes. The storage chambers 18 are each hydraulically connected to one of the recesses 12; 14 for the pump elements via a vertical channel 20. The vertical channel 20 connects the storage chamber 18 to a suction side of a pump element inserted into the associated recess 12; 14, thus ensuring the supply of this pump element with brake fluid.

[0015] In addition, line connections 22 and 24 are formed on the hydraulic block 10. Four line connections 22 are arranged in a row next to one another on the top side of the hydraulic block 10. These four line connections 22 are provided for connecting the hydraulic block 10 to the wheel brakes of a vehicle braking system via external lines. Two additional line connections 24 are located in the area of ​​the top side at the front of the hydraulic block 10. These two line connections 24 contact the hydraulic block 10 with the two brake circuits of a master brake cylinder via lines.

[0016] It is assumed that the fully assembled hydraulic unit, in its installed state, is arranged on a vehicle body in such a way that the line connections 22, 24 are oriented upwards for reasons of accessibility for mechanical contact of the hydraulic unit with the external components explained, i.e., they are located on or in the area of ​​an upper side of the installed hydraulic unit. Figure 1 shows the hydraulic block 10 accordingly in its installation position.

[0017] As can be seen, the vertical channel 20 runs orthogonally to the recess 12, 14 of the pump element and, as mentioned, opens into this recess 12, 14 in the area of ​​the suction side of a pump element. This area around the opening point corresponds to the area of ​​lowest pressure within a brake circuit. As explained above, this can lead to previously dissolved gas escaping from the brake fluid in this area and accumulating to form gas bubbles. To prevent gas bubbles, once they have formed, from being sucked in by the pump element and transported further to the pump pressure side, the vertical channel 20 is extended or continued on its side opposite the opening point into the pump intake.The section of the vertical channel 20 extending over the recesses 12, 14 for the pump elements forms a riser 26, which extends, preferably in the vertical spatial direction, to the line connections 22, 24 formed on the hydraulic block 10. The riser 26 ends in the manner of a blind hole inside the hydraulic block 10 at a height below the line connections 24 for the master brake cylinder.

[0018] Any gas bubbles that may occur on the suction side of a pump element enter the riser 26 due to the effective gravimetric buoyancy and rise within this riser 26 toward its closed end. The gas bubbles accumulate there. The area from which the driven pump element draws brake fluid is thus largely free of gas bubbles, preventing gas bubbles from penetrating the pressure side of the pump element.

[0019] The riser line 26 as such is part of a hydraulic cavity 28 formed within the brake circuits, which helps to avoid pulsations on the suction side of the pump element and to reduce the operating noise of the hydraulic unit. The volume of this hydraulic cavity 28 is adjusted to the maximum pressure medium volume that flows back to the suction side of the pump element via the inlet valve that is not yet closed during the compression phase of the pump element and / or to the maximum volume of gas that can potentially outgas from the pressure medium volume contained in the brake circuits due to the brake fluid heating to its maximum operating temperature. The achievable volume of a riser line 26 alone may not be sufficient for this purpose under certain circumstances. For such cases, one or more additional hydraulic cavities 28 can be provided on the hydraulic block 10 and connected to the riser line 26.Various variants of additional cavities 28 are illustrated in the figures explained in more detail below. All of these additional cavities 28 extend from one of the outer sides of the hydraulic block 10 into the interior of this hydraulic block 10 and are connected to one another via the aforementioned riser line 26. Furthermore, the additional cavities 28 are arranged in a region of the hydraulic block 10 located between the recesses 12, 14 for the pump elements and the line connections 22, 24 of the hydraulic block 10.

[0020] In the case of the variant according to Figure 2In addition to the riser 26, the cavity 28 includes a horizontal bore 30 that opens toward the left outer side of the hydraulic block 10. This horizontal bore 30 is located at the level of the inner end of the riser 26 and crosses the riser 26 in a T-shape. The horizontal bore 30 and the riser 26 have approximately the same inner diameter, for example, but this is not mandatory.

[0021] In the variant according to Figure 3The entire cavity 28 is composed of the riser 26 and a plurality of coaxial horizontal bores 30a, 30b, 30c, which cross this riser 26 at different heights and, for example, extend on both sides of this riser 26. For example, all horizontal bores 30a, 30b, 30c originate from the left outer side of the hydraulic block 10. The openings of the horizontal bores 30a, 30b, 30c to the outside are closed by closure means in the fully assembled hydraulic unit. Known closure means include balls, which are pressed into the horizontal bores 30a, 30b, 30c, preferably in the area of ​​the openings, thereby sealing them off from the environment in a pressure-tight manner. As an alternative to balls, plugs, screw plugs, or disc-shaped covers can also be used.

[0022] Figure 4shows a cavity 28, which, in addition to the riser 26, consists of two blind bores 32a, 32b crossing at right angles. The first of these blind bores 32a runs horizontally at the level of the inner end of the riser 26 and originates from the left outer side of the hydraulic block 10, while the second blind bore 32b, coming from the top of the hydraulic block 10, runs vertically and axially parallel to the riser 26 inwards and opens into the first blind bore 32a at the end of the latter. Here, too, the respective openings of the blind bores 32a, 32b are sealed in a pressure-tight manner in the assembled hydraulic unit, for example by pressed-in and / or caulked plugs, covers, or balls.

[0023] In Figure 5The riser 26 is in contact with a chamber 34, the inner diameter of which is significantly larger than the inner diameter of the riser 26 and which has a relatively shallow depth. The opening of the chamber 34 to the environment is closed by a closure cover 36, which is caulked or otherwise positively and / or non-positively fastened to the hydraulic block 10 on the circumference. A material connection such as an adhesive or a ring weld is also conceivable in order to fasten the closure cover 36 to the hydraulic block 10 in a pressure-tight manner. Of course, any combination of the cavity variants explained is also possible. One such combination is shown as an example. Figure 6. In this embodiment, the overall cavity results from the riser 26 and several horizontal bores 30a, 30b, 30c extending from the left outer side of the hydraulic block and designed as blind holes, at least one vertical bore 38 to the top of the hydraulic block 10 and a chamber 34 opening to the front of the hydraulic block 10.

[0024] In the example according to Figure 7 For example, the opening of the chamber 34 is located on the left outside of the hydraulic block 10. A horizontal bore 30 connects the interior of the chamber 34 with the riser 26. A Figure 8The further embodiment shown comprises, for example, two chambers 34a, 34b, whose openings open on different outer sides of the hydraulic block 10. The chamber 34a is designed, for example, toward the front of the hydraulic block 10, while the opening of the second chamber 34b is located, for example, on the left outer side of the hydraulic block 10. The riser 26 crosses the first chamber 34a and opens into a blind-hole-like horizontal bore 30, which opens into the second chamber 34b. Embodiments with more than two chambers 34 are conceivable.

[0025] It is of course possible to adapt the cavities 28 disclosed in the various exemplary embodiments in any number, orientation, and combination of their individual cavities to the respective application of a hydraulic unit. Common to all cavities is that each cavity 28 comprises a riser 26 which connects to the recess 12; 14 for the pump element, and that the cavities 28, relative to the position of the pump element on the hydraulic block 10, each face the upper side of the hydraulic block 10, which has the line connections 22; 24. As already explained, any gas bubbles present can thus rise via the riser 26 toward the upper side of the hydraulic unit due to the effective gravitational force and collect at an end of the cavity 28 facing away from the pump elements.

[0026] Finally, it should be noted that the exemplary embodiments each represent the formation of a hydraulic cavity 28 comprising a riser 26 in one of the existing brake circuits. In principle, it is conceivable to provide such a hydraulic cavity 28 in only one or in each existing brake circuit. The cavities 28 of the individual brake circuits can be designed similarly or differently with regard to their total volume, the arrangement, and / or configuration of the interconnected individual cavities.

[0027] Of course, further changes or additions to the described embodiments are conceivable without deviating from the basic idea of ​​the invention claimed in claim 1.

Claims

1. Hydraulics assembly for controlling the brake pressure in a wheel brake of an electronically slip-controllable brake system of a motor vehicle, comprising a hydraulic block (10) with a recess (12; 14) for receiving a pump element, a line port (22) on the hydraulic block (10) for establishing contact between the hydraulics assembly and a wheel brake, a duct (20), opening into the recess (12; 14) for the pump element, for supplying the pump element inserted into the recess (12; 14) with brake fluid, wherein the duct (20) connects a storage chamber (18) for brake fluid on the hydraulic block (10) to an intake side of the pump element inserted into the recess (12; 14), wherein the line port (22) is arranged on or in the region of an upper side of the hydraulics assembly, characterized in that a hydraulic cavity (28), formed inside the hydraulic block (10) and in contact with the recess (12; 14) in the region of the intake side of the pump element inserted into the recess (12;14), is provided, in that the hydraulic cavity (28) comprises a riser (26) which forms a blind bore ending inside the hydraulic block (10), and in that the riser (26) runs from the recess (12; 14) for the pump element in the direction of the line port (22).

2. Hydraulics assembly according to Claim 1, characterized in that the hydraulic cavity (28) has an opening facing one of the outer sides of the hydraulic block (10) which can be sealed by a sealing element which can be anchored on the hydraulic block (10).

3. Hydraulics assembly according to Claim 1 or 2, characterized in that the hydraulic cavity (28) is arranged in a region of the hydraulic block (10) which is situated between the recess (12; 14) for the pump element and the line port (22) of the hydraulic block (10).

4. Hydraulics assembly according to Claim 1, characterized in that the riser (26) is designed as a straight extension of the duct (20) establishing contact between the storage device (18) and the recess (12; 14) for the pump element.

5. Hydraulics assembly according to Claim 4, characterized in that the duct (20), connecting the storage device (18) to the recess (12; 14) for the pump element, and the riser (26) open out on opposite sides into the recess (12; 14) for the pump element and run coaxially with respect to one another.