Hydraulic unit, in particular for generating and controlling a brake pressure in an electronically slip-controllable braking system of a motor vehicle

Abstract

The invention relates to a hydraulic unit (10), in particular for generating and controlling a brake pressure in an electronically slip-controllable braking system of a motor vehicle. Known hydraulic units (10) comprise a housing block (12) with a pump receptacle (18) in which an actuatable pump element (24) is arranged. Said pump element (24) has a pump piston (28) which can be driven to perform a stroke movement and which is guided and sealed in the pump receptacle (18) by means of a sealing / guiding device (34). According to the invention, the sealing / guiding device (34) has a dimensionally elastic positioning element (38), by which a sealing ring (343) of the sealing / guiding arrangement (34) is pressed at least indirectly against a guide element (341) of the sealing / guiding device (34) with a variable axial force.

Description

[0001] R.416135

[0002] -1 -

[0003] Disclosure of the invention

[0004] title

[0005] Hydraulic unit, in particular for generating and regulating brake pressure in an electronically slip-controlled braking system of a motor vehicle

[0006] Technical background

[0007] The invention relates to a hydraulic unit, in particular for generating and controlling brake pressure in an electronically slip-controlled braking system of a motor vehicle according to the features of the preamble of claim 1.

[0008] Electronically controlled braking systems for motor vehicles, in various technical configurations, represent the state of the art and are also known as vehicle braking systems with anti-lock braking (ABS) or with electronic stability control (ESP). The purpose of such vehicle braking systems is to prevent the wheels of a motor vehicle from locking up during operation, and especially during braking, in order to maintain the vehicle's steerability or to counteract unstable driving conditions.

[0009] The basic requirement for fulfilling this task is to adjust the brake pressures on the individual wheel brakes depending on the slip conditions currently prevailing on the assigned wheels.

[0010] For this purpose, an electronically slip-controlled braking system of a motor vehicle is equipped with a hydraulic unit that has a housing block with which the wheel brakes of the motor vehicle are hydraulically contacted. A device for modulating the brake pressure is arranged on the housing block. This device includes, among other things, a pump element received in a pump housing, with a pump cylinder and a pump piston received therein that can be driven to a reciprocating motion. Based on R.416135

[0011] -2- The provided sealing / guiding device guides the pump piston radially in the pump housing and seals it against its surroundings.

[0012] A pump element in a pump receptacle of a housing block of a hydraulic power unit is shown in Figure 1 of DE 10 2014 212 292 A1 and explained in the accompanying description.

[0013] In addition to the pump element, the aforementioned brake pressure modulation system includes, among other things, electrically controlled directional control valves assigned to the wheel brakes, as well as, where applicable, accumulators and / or pulsation dampers. These are interconnected via pressure medium connections on the housing block to form hydraulic brake circuits. An electronic control unit associated with the hydraulic unit electrically controls the aforementioned components according to a braking request and taking into account the prevailing wheel slip conditions. The braking request can be mechanically initiated by the driver by actuating a brake request detection device in the form of a pedal or lever to actuate a master brake cylinder, and then detected by sensors. Alternatively, it can be triggered electronically by vehicle electronics monitoring the driving situation after an unstable driving condition has been detected.Finally, the hydraulic unit also has a reservoir in which hydraulic pressure fluid is stored.

[0014] As mentioned above, the pump piston of the pump element is guided and sealed within the pump housing by means of a sealing / guiding device. In the prior art, this sealing / guiding device consists of a sealing ring, optionally a support ring which prevents extrusion of the sealing ring into a running gap, and a guide ring for axial and radial guidance of the pump piston in the pump housing of the hydraulic unit.

[0015] The sealing ring is an elastomer component whose sealing function depends not only on its cross-sectional shape but also on the contact pressure distribution. In this context, contact pressure distribution refers to the profile of the contact pressure with which the sealing ring is pressed against the circumferential surface of the pump housing or against the pump piston. A determining parameter for this contact pressure distribution is the radial oversize of the sealing ring cross-section relative to the associated installation space, as well as the undeformed cross-sectional area of ​​the installed sealing ring relative to its housing. R.416135

[0016] -3-

[0017] In addition, the contact pressure distribution depends on the ambient conditions, in particular the prevailing temperature conditions and any component vibrations that may occur on the pump element, the pump piston, the housing block and / or the sealing ring itself.

[0018] To ensure proper installation of a pump element equipped with this sealing / guiding device into the pump housing block, given the inherent mechanical tolerances of the individual components of the sealing / guiding device, the pump piston, and the pump housing, a mechanical tolerance compensation is required. Currently, this tolerance compensation is achieved through axial play within the available installation space for the sealing / guiding device. However, this axial play allows the rings of the sealing / guiding device, particularly the support ring and the sealing ring, to move axially within this installation space under operating conditions of the pump element. This causes the elastic sealing ring to flex and wear. With wear, the contact pressure distribution of the sealing ring changes, which can lead to leaks over time.Under unfavorable conditions, pressure fluid can therefore leak from the pump cylinder and / or gas can enter the pump cylinder. The invention aims to prevent both of these occurrences.

[0019] Advantages of the invention

[0020] In contrast, the invention according to the features of claim 1 has the advantage that it permanently enables a largely fixed positioning of the sealing ring and the support ring within the installation space of a sealing / guiding device and maintains the desired contact pressure distribution on the sealing ring. A sealing ring flexes less under operating conditions and exhibits less wear due to operating time. As a result, leaks at the pump element are avoided.

[0021] A pump element according to the invention is therefore suitable for use under higher loads, e.g., extended operating time and / or a higher pressure level, and thus particularly meets the requirements of new generations of hydraulic power units compared to standard R.416135.

[0022] -4- the technology's expanded functional scope. Ultimately, the invention saves subsequent costs in the development, maintenance, or repair of hydraulic power units without requiring compromises in the assembly of a hydraulic power unit or causing significant cost increases.

[0023] According to the invention, a hydraulic power unit has a pump element which is equipped with a sealing / guiding device which includes a form-elastic positioning element by which the sealing ring is pressed at least indirectly against a guide element of this sealing / guiding device with a variable axial force.

[0024] Further advantages or advantageous developments of the invention will become apparent from the dependent claims or from the following description.

[0025] drawing

[0026] Exemplary embodiments of the invention are shown in the drawing and are explained in detail in the following description. The drawing includes several figures in which corresponding components are consistently provided with uniform reference numerals.

[0027] Fig. 1 shows, to explain the technical background of the invention, a section of a housing block of a hydraulic power unit known from the prior art with a pump receptacle and a pump element received therein in longitudinal section;

[0028] Fig. 2a shows a section of detail X from Fig. 1 in an enlarged view;

[0029] Fig. 2b shows the section according to Fig. 2a in a possible 2nd position of the individual components;

[0030] Fig. 2c shows the section according to Fig. 2a in a possible 3rd position of the individual components;

[0031] Fig. 3a shows the section according to Fig. 2a in the invention;

[0032] Fig. 3b shows the section according to Fig. 2a in half-section and in perspective view; R.416135

[0033] -5-

[0034] Fig. 4a shows a first variant of a positioning element underlying the invention as a single component and in perspective view;

[0035] Fig. 4b shows a section of the positioning element according to Fig. 4a in cross-section;

[0036] Fig. 5a shows a second variant of a positioning element in perspective view;

[0037] Fig. 5b shows a section of the positioning element according to Fig. 5a in cross-section;

[0038] Fig. 6a illustrates the force pressure curve at the sealing ring in the prior art;

[0039] Fig. 6b illustrates the force pressure curve on a sealing ring according to the invention;

[0040] Fig. 7a shows a pump element from detail X in spatial representation, which is equipped with a 2nd embodiment for a positioning element;

[0041] Fig. 7b shows the pump element according to Fig. 7a in its installed state in longitudinal section;

[0042] Fig. 8a shows a pump element from detail X in spatial representation, which is equipped with a 3rd embodiment for a positioning element;

[0043] Fig. 8b shows the pump element according to Fig. 8a in its installed state in longitudinal section and the

[0044] Figures 9a, 9b and 9c show 3 further developed variants of positioning elements according to the 3rd embodiment in a spatial view.

[0045] Description of the exemplary implementations

[0046] Fig. 1 shows a longitudinal section of a housing block (12) of a hydraulic power unit (10) known from the prior art. On this housing block (10), a housing block (10) is formed on a first outer surface of the housing, which points downwards in the figure, and is open towards this outer surface. R.416135

[0047] -6- a drive chamber (14) extending into the interior of the housing block (10) along a vertical axis (V). A pump receptacle (18), oriented transversely to the vertical axis (V) and open towards a perpendicular, second outer surface of the housing, opens into this drive chamber (14) with its end located inside the housing block (10). An eccentric ring (20) is arranged in the drive chamber (14), which has a continuous hub (22) with which it can be pressed onto a drive shaft and connected to it in a rotationally fixed manner. This drive shaft extends into the drive chamber (14) from the outside. For clarity, this drive shaft is shown in the Fig.1 not shown, however it can be assumed that the drive shaft with the eccentric ring can be driven by an electrically controlled drive motor to a rotational movement around the vertical axis (V), wherein this drive motor can be attached externally to the downward-facing outer side of the housing in axial extension of the vertical axis (V).

[0048] A pump element (24) (detail X) is arranged in the pump receptacle (18). The pump element comprises a pump cylinder (26) and a pump piston (28) with a first piston part (281) projecting from the pump cylinder (26) and a second piston part (282) guided within the pump cylinder (26). The two piston parts (281, 282) are aligned along a longitudinal axis (L) of the pump, with a recess visible on the second piston part (282) in which the first piston part (281) is partially received. The first piston part (281) rests with a piston end face facing away from the pump cylinder (26) against the circumferential surface of the driven eccentric ring (20), thereby enabling the pump piston (28) to be driven to a reciprocating stroke relative to the pump cylinder (26).As a result of this lifting movement, a hydraulic pressure medium is conveyed by the pump element (24) from a pump inlet via a pump outlet into a brake circuit, which is contacted with the pump element (24) or the pump outlet and to which at least one wheel brake is connected.

[0049] A pump inlet is located in a region of the pump element (24) where a sleeve-shaped holder (30) is arranged on the pump cylinder (26). This holder (30) is provided along its circumference with several openings (302) (Fig. 3b) through which a pressure medium flows (not visible) to the pump inlet. The holder (30) projects axially beyond the pump cylinder (26) in the direction of the drive chamber (14) and surrounds the pump cylinder (26) with its projecting opening.

[0050] -7-

[0051] The first piston part (281) extends through an opening on the end face of the holder (30) and through a cross-sectional opening at which the pump receptacle (18) opens into the drive chamber (14). The holder (30) is attached at one of its two ends to the circumference of the pump cylinder (26) and is supported at the opposite end by an annular step (181) of the pump receptacle (18). Between the annular step (181) and the opening of the pump receptacle (18) into the drive chamber (14) extends an installation space (32) for a sealing / guiding device (34).

[0052] This sealing / guiding device (34) is designed for axial and radial guidance of the pump piston (28) or the first piston part (281) and for sealing it against the environment. Viewed from left to right in Fig. 1, the sealing / guiding device (34) comprises a guide ring (341), a support ring (342), and a sealing ring (343), each of which surrounds the section of the first piston part (281) projecting from the holder (30). The guide ring (341) has an L-shaped cross-section and rests against a step adapted to this cross-section in the opening area of ​​the pump receptacle (18) into the drive chamber (14). Further inside the pump receptacle (18) is the support ring (342), which, with its rectangular cross-section, rests flush against the guide ring (341). Finally, the sealing ring (343) of the sealing / guiding device (34) is arranged at an axial distance from the support ring.This sealing ring (343) is made of elastomer and has an approximately square cross-section. An asymmetrical sealing edge is formed on an inner flank facing the pump piston (28) of this cross-section, with which the sealing ring (343) abuts the outer circumference of the first piston part (281) of the pump piston (28) in a sealing manner.

[0053] A pin-shaped axial extension is located on the right-hand, first side flank of this sealing ring (343) facing the holder (30). This axial extension engages in a corresponding recess on an end face of the holder (30) facing the holder, thus ensuring correct positioning of the sealing ring (343).

[0054] Two radially projecting ridges are located at the corners of an outer flank of the sealing ring (343). These abut an inner wall of the pump housing (18) to form a seal. R.416135

[0055] -8-

[0056] A second side flank of the sealing ring (343), facing away from the holder (30), is designed as a straight flank. Between this straight, second side flank of the sealing ring (343) and the support ring (342) there is, as shown in Fig. 1, an air space (36) which ensures that a pump element (24) equipped with the described sealing / guiding device (34) can be installed in the pump receptacle (18) under all tolerance positions of the components involved.

[0057] A disadvantage of such an air space (36), as already mentioned, is that under operating conditions, i.e., while the pump piston (28) is driven by the rotating eccentric ring (20) into a reciprocating stroke, the sealing ring (343) and / or the support ring (342) can move within this air space (36). This causes the cross-section of the sealing ring (343) to deform, and the sealing ring (343) is prone to wear. The latter causes a change in the contact pressure distribution on the sealing ring (343) and consequently a deterioration of its sealing properties.

[0058] Figures 2a-2c illustrate various positions that the sealing ring (343) and the support ring (342) can assume relative to the guide ring (341) and the holder (30) within the installation space (32) during pump operation. According to Figure 2a, the support ring (342) rests against the guide ring (341), and the sealing ring (343) rests against the support ring (342). The air space (36) is thus formed between the right-hand, first flank of the sealing ring (343) and the facing end face of the holder (30).

[0059] Figure 2b shows again the situation already known from Fig. 1 in an enlarged view, while according to Fig. 2c the support ring (342) rests on the sealing ring (343) and this sealing ring (343) rests on the holder (30), so that the air space (36) is located between the guide ring (341) and the support ring (342).

[0060] The illustrations in Figures 2a-2c are merely examples and are intended to demonstrate the possible extreme positions of the sealing ring (343) and the associated support ring (342) within the available installation space (36). Of course, intermediate positions deviating from Figure 2 are possible, in which the air space (36) is divided into a first part between the guide ring (341) and the support ring (342) and a second part between the sealing ring (343) and the holder (30) of the pump cylinder (26). R.416135

[0061] -9-

[0062] To avoid the above-described wandering movement and / or deformation of the sealing ring (343) under operating conditions of the pump element (24), it is proposed according to the invention to subject the sealing / guiding device (34) to an axial force by means of a form-elastic positioning element (38) such that its sealing ring (343) is at least indirectly pressed against the guide ring (341) under operating conditions with a variable axial force.

[0063] In a first embodiment according to Figures 3a and 3b, the positioning element (38) is arranged between the end face of the holder (30) and the first side flank of the sealing element (343). This positioning element (38) is a one-piece ring element with a disc-shaped cross-section, made of a spring-elastic material, for example, spring steel, and can be manufactured, for example, by a stamping / bending process. This positioning element (38) is divided into a disc base (381) with a central opening through which the first piston part (281) passes, a disc wall (382) projecting radially outward from the disc base (381) at an oblique angle, and a disc rim (383) circumferentially surrounding the disc and connected to the disc wall (382). The base of the plate (381) and the edge of the plate (383) are arranged in component planes (B1 , B2) that are aligned parallel to each other and spaced axially apart from each other.This axial distance between the component planes (B1, B2) is dimensioned such that the guide ring (341) is flush against the support ring (342), the support ring (342) is flush against the sealing ring (343), this sealing ring (343) is under axial preload against the positioning element (38), and the positioning element (38) is flush against the end face of the holder (30), so that the components of the sealing / guiding device (34) occupy the entire axial extent of the installation space (32) without leaving an air space.

[0064] To center the positioning element (38) relative to the holder (30) and to prevent mechanical contact between the positioning element (38) and the circumference of the first piston part (281), a centering collar (301) projecting axially towards the drive chamber (14) is formed on the end face of the holder (30) in the embodiment shown in Fig. 3a. This centering collar (301) is arranged directly around the edge of the opening in the holder (30) and its outer diameter is matched to the inner diameter of the opening in the base plate (381) of the positioning element (38). R.416135

[0065] -10-

[0066] Positioning element (38) can be slid onto the outer circumference of the centering collar (301) without the centering collar (301) hindering the elastic deformation of the positioning element (38) when it is slid onto the positioning element (38).

[0067] Figure 3b illustrates the above-explained relationships again in a spatial representation, with the respective components or component sections being labelled accordingly.

[0068] Figures 4a and 4b show a first embodiment of a positioning element (38) as a whole and, respectively, based on a component segment, in three spatial terms.

[0069] The rim (383) of this positioning element (383) is designed as a closed ring, which runs perpendicular to a longitudinal axis (A) of the positioning element (38) in a second component plane (B2). With this rim

[0070] (383) A plurality of bending tongues (384) are integrally connected, forming the plate wall (382). The bending tongues (384) extend inwards in a star shape towards an imaginary center of the positioning element (38), with each pair of bending tongues (384) being separated from each other by a radial slot (385) extending to the edge of the plate (383) and thus being axially movable relative to each other. Each bending tongue

[0071] The (384) is double-bent in opposite directions and thus comprises a spring section running obliquely to a longitudinal axis of the positioning element (38) and a free bending tongue end. The two bends (386) of the bending tongues (384) are formed such that the bending tongue ends lie together in a first component plane (B1) oriented perpendicular to the longitudinal axis (A) of the positioning element (38), which has an axial distance (S) to the second component plane (B2) in which the plate rim (383) is located. The free ends of the bending tongues (384) are rounded and together define the inner dimension of an opening in the plate base (381) of the positioning element (38), with which the latter can be fixed to the centering collar (301) of the holder (30), as already explained in connection with the description of Figures 3a and 3b.

[0072] By selecting the cross-sectional shape of the positioning element (38), the shape and number of the bending tongues (384) or radial slots (385) formed on it, the dimensions of the bending radii of the offsets (386), the choice of material and / or the material thickness, etc., a spring stiffness R.416135 can be achieved.

[0073] -11 - of a positioning element (38) constructively determine or application-specifically define, so that the effective axial force on the sealing ring (343) and thus the contact pressure distribution on the sealing ring (343) can be defined by the positioning element (38).

[0074] Figures 5a and 5b show a second variant for the first embodiment of a positioning element (383).

[0075] In contrast to the positioning element (383) shown in Figures 4a and 4b, this element does not require spring tongues and has a flat, annular base (381), an integrally formed, ring-shaped wall (382) projecting outwards at an angle to the longitudinal axis (A) of the positioning element (38), and, also integrally formed therewith, a similarly ring-shaped, flat, and outwards projecting rim (383). Due to the inclination of the wall (382), the base (381) and rim (383) are located in two plane-parallel component planes (B1 and B2) separated by an axial distance (S).

[0076] Fig. 6a illustrates the load conditions of a sealing ring in a conventional sealing / guiding device (34) and Fig. 6b shows, in comparison, the load conditions in a sealing / guiding device which is equipped with a positioning element (38) according to the invention.

[0077] In the conventional solution shown in Fig. 6a, the radial preload of the sealing ring (343) is determined by the dimensions of this sealing ring (343), the pump piston (28), and the pump housing (18) in the area of ​​the sealing ring assembly. In the axial direction, the sealing ring (343) is unloaded, so that it can deform in this direction with increasing radial load. Corresponding to the deformation, the radial forces acting on the sealing element are at least partially reduced.

[0078] These radial forces act in the areas of the sealing ring (343) where it is in mechanical contact with the circumference of the pump piston (28) or the first piston part (281), or opposite it, where it is in contact with the wall of the pump housing (18). The wall-side area extends between the two sealing beads at the corners of the outer flank of the sealing ring (343) and is therefore significantly larger in extent than the piston-side area, which is defined by the sealing lip on the inner flank of the sealing ring (343). Accordingly, in the piston-side area of ​​R.416135

[0079] -12- the contact pressure is stronger on one side than on the opposite side, as illustrated in Fig. 6a by the distance between the force arrows (F) symbolizing the contact pressure distribution

[0080] In the embodiment according to the invention shown in Fig. 6b, axial forces, in addition to radial forces, act on the sealing ring (343) due to an existing elastic positioning element (38). These axial forces result from the axial preload with which the sealing ring (343) is pressed by the positioning element (38) against the associated support ring (342). The axial forces counteract a lateral deformation of the sealing ring (343) and thus result in higher effective radial forces and consequently a higher contact pressure distribution on the inner and outer flanks of the sealing ring (343), as illustrated by the force arrows F, which are closer together than in Fig. 6a. The sealing effect of the sealing ring (343) is thus improved. Furthermore, the axial and radial forces acting on the sealing ring (343) have a stiffening effect.

[0081] Fig. 7a shows in a spatial representation a pump element (24) equipped with a sealing / guiding device (34), in which this sealing / guiding device (34) has a form-elastic positioning element (38) which is designed according to a second embodiment of this invention.

[0082] In this second embodiment, the positioning element (38) is formed by a corrugated ring disc spring (40), or a so-called wave spring, which is arranged between an end face of the pump cylinder (26) and the facing end face of a holder (30). The latter is now mounted so as to be axially displaceable relative to the pump cylinder (26) on a tightly toleranced guide diameter (261) of the pump cylinder (26). This guide diameter (261) serves, in addition to the axial guidance of the holder (30) described above, to center the corrugated ring disc spring (40). The holder (30) is sleeve-shaped and is divided into a cylindrical section (303) with circumferential openings (302) and a neck section (304) facing the sealing / guiding element (34), the neck section having smaller outer dimensions than the cylindrical section (303).

[0083] As can be seen in Fig. 7b, the corrugated ring disc spring (40) presses the holder (30) against the R.416135 with an axial force that depends on its deformation.

[0084] -13- first side flank of the sealing ring (343) and thus places this sealing ring (343) flush against the support ring (342) and the support ring (342) against the guide ring (341). The tolerance compensation required for mounting the pump element (24) equipped with the sealing / guiding device (34) in the pump receptacle (18) is achieved by the deformability of the ring disc spring (40) in the axial direction, without an air gap, known from the prior art, forming between the individual parts of the sealing / guiding device (34) in the installed state, which allows free movement of the rings of the sealing / guiding device (34) within their installation space (32) under operating conditions.

[0085] A further, third embodiment of the invention is shown in Figures 8a and 8b. In this third embodiment, the form-elastic positioning element (38) of the sealing / guiding device is formed in one piece with the holder (30) and forms a spring sleeve (42) that is form-elastic in the direction of the longitudinal axis (L). This spring sleeve (42) is preferably made of spring steel using a stamping and bending process and is divided into a hollow cylindrical central section (421) in which several successive openings (422) are formed in the circumferential direction, which in turn are separated from one another by axial webs (423). The axial webs (423) are connected to each other on both sides of the central section (421) by closed ring ends (424).

[0086] The elastic spring sleeve (42) is fixed to the circumference of the pump cylinder (26) at one of the ring ends (424), while the material of the opposite, second ring end (424) is folded inwards section by section to form a circumferential support collar (425). With this circumferential support collar (425), the spring sleeve (42) rests flush against the first side flank of the sealing ring (343).

[0087] On the axial webs (423) of the spring sleeve (42), a bulge (426) is formed by bending, extending transversely to the longitudinal axis (H; Fig. 9) and preferably oriented radially into the interior of the spring sleeve (42). The bulges (426) give the spring sleeve (42) elasticity in the axial direction, i.e., in the direction of the longitudinal axis (H; Fig. 9). R.416135

[0088] -14-

[0089] The aforementioned elasticity of a spring sleeve (42) can be determined in an application-specific manner by the thickness of the sheet metal material of the spring sleeve (42), the number or design of the axial webs (423) or the openings (422) and / or the number or dimension or design of the bulges (426) per axial web (423), and thus the axial force with which the sealing ring (343) of the sealing / guiding device (34) is pressed at least indirectly against the guide ring (341) via the support ring (342) can be defined.

[0090] Figures 9a to 9c show spring sleeves further developed in this respect (42).

[0091] Of course, modifications or advantageous further developments of the described embodiments are conceivable without leaving the scope of protection specified by the claims.

Claims

R.416135 -15- Claims 1. Hydraulic unit (10), in particular for generating and controlling brake pressure in an electronically slip-controlled brake system of a motor vehicle, comprising a housing block (12), a pump receptacle (18) formed on the housing block (12) and a pump element (24) received in the pump receptacle (18), wherein the pump element (24) has a pump piston (28) which can be driven to a reciprocating stroke movement and which is radially guided and circumferentially sealed by a sealing / guiding device (34) in the pump receptacle (18), characterized in that the sealing / guiding device (34) comprises a form-elastic positioning element (38) which presses a sealing ring (343) of the sealing / guiding device (34) at least indirectly against a guide element (341) of the sealing / guiding device (34) with a variable axial force.

2. Hydraulic unit according to claim 1, characterized in that the positioning element (38) is arranged between a holder (30) of the pump element (24) and a flank of a sealing ring (343) of the sealing / guiding device (34) facing this holder (30). R.416135 -16- 3. Hydraulic unit according to claim 1 or 2, characterized in that the positioning element (38) is ring-shaped with a plate-shaped cross-section and has a plate base (381), a plate wall (382) projecting obliquely outwards from the plate base (381) and a circumferential plate rim (383) projecting radially outwards from the plate wall (382), wherein the plate base (381) and the plate rim (383) are arranged in each of an associated component plane (B1 ; B2) and wherein the component planes (B1 ; B2) are parallel to each other and are arranged at an axial distance (S) from each other.

4. Hydraulic unit according to claim 3, characterized in that the plate wall (382) and the plate base (381) have a plurality of spring tongues (384) projecting inwards in a star shape from an annularly closed plate rim (383), wherein two spring tongues each (384) are separated from each other by a radial slot (385).

5. Hydraulic unit according to one of claims 2 to 4, characterized in that the holder (30) of the pump element (24) defines an installation space (32) for the sealing guide device (34) in the pump receptacle (18) at one of its ends and wherein a centering device, preferably a centering collar (301), is formed on an end face of this holder (30) facing the installation space (32) for centering the positioning element (38) on the holder (30). R.416135 -17- 6. Hydraulic unit according to claim 1, characterized in that the positioning element (38) is arranged between a pump cylinder (26) of the pump element (24) and the holder (30), wherein the holder (30) is arranged axially relative to the pump cylinder (26) on a guide device, preferably a guide diameter (261) of the pump cylinder (26).

7. Hydraulic unit according to claim 6, characterized in that the positioning element (38) is a corrugated ring disc spring (40) which is held centered by the guide diameter (261) on the pump element (24).

8. Hydraulic unit according to claim 1, characterized in that the positioning element (38) is formed in one piece with a holder (30) of the pump cylinder (26) and has a flexible spring sleeve (42) with ring-shaped closed ring ends (424) and axial webs (423) between the ring ends (424) and wherein at least one opening (422) is formed along the circumference of the spring sleeve (42) between the axial webs (423).

9. Hydraulic unit according to claim 7, characterized in that at least one projection (426) is provided on each of the axial webs (423) of the spring sleeves (42), which extends transversely to a longitudinal axis L and preferably projects radially into the interior of the spring sleeve (42).

Images