Brake pressure control unit

Abstract

The invention relates to a brake pressure control unit for a motor vehicle braking system, comprising an electric motor whose rotary motion is transformed into a translational motion of a piston (6) by means of a ball screw drive (5) in order to build up a defined brake pressure in a wheel brake independently of the actuation of a master brake cylinder. The invention provides that the piston (6) is provided on its outer circumference with a sealing ring (9), the end face of which facing the working cylinder is covered by a centering element (12) that is guided along a funnel-shaped guide chamfer (14) of the working cylinder, so that the sealing ring (9) comes into contact with the guide chamfer (14) without damage.

Description

[0001] The invention relates to a brake pressure control unit for a motor vehicle braking system according to the preamble of claim 1.

[0002] A brake pressure control unit for a motor vehicle brake system of the type described is known from DE 10 2013 223 859 A1. The brake pressure control unit has an electric motor whose rotary motion is transformed into a translational motion of a piston in order to build up a defined brake pressure in a wheel brake independently of the actuation of a master brake cylinder.

[0003] The object of the invention is to design a brake pressure control device of the type specified to be particularly compact and reliable using the simplest possible design means.

[0004] This problem is solved according to the invention for a brake pressure control unit of the type mentioned by the features of claim 1.

[0005] Further features of the invention can be found in the individual patent claims as well as in the description of an exemplary embodiment with reference to three drawings.

[0006] They show: Fig. 1 a schematic diagram of the brake pressure control unit according to the invention in longitudinal section, Fig. 2 in longitudinal section the essential design of the piston used in the brake pressure control unit, Fig. 3 in a longitudinal view of the in Fig. Two pistons are shown in different pivoting positions to tolerate angular errors. Fig. 4 a top view of the back of the sealing ring to show several radial grooves, Fig. 5 in a partial view the in Fig. 2 pistons shown during the insertion process into the working chamber of the working cylinder.

[0007] In detail, the Fig. 1 a schematic structure of the brake pressure control device according to the invention in longitudinal section, with an electric motor whose rotary movement is transformed into a translational movement of a piston 6 by means of a ball screw drive 5 in order to be able to build up a defined brake pressure in a wheel brake independently of the actuation of a master brake cylinder.

[0008] To create the simplest and most reliable design possible for a brake pressure control unit, the electric motor is housed in a first housing 1 and the piston 6 in a second housing 2. The second housing 2, designed as a working cylinder, is positioned diametrically opposite the first housing 1. A third housing 3 with two diametrically opposed end faces is arranged between the first and second housings 1 and 2, to which the first and second housings 1 and 2 are attached. The third housing 3 thus serves as a central housing to which all other components of the brake pressure control unit are attached.

[0009] As further from the Fig. As can be seen from Figure 1, the third housing 3, designed as a central housing, has a through-bore 4 for guiding the ball screw drive 5 through, so that in conjunction with the piston 6 arranged in the second housing 2, the function of a linear actuator is ensured by a particularly compact design of the brake pressure control unit.

[0010] The Fig. Figure 2 shows a longitudinal section of the piston 6, which has an annular groove 7 along its surface. A back ring, hereinafter referred to as a support ring 8, is fixed in this groove without play, and a sealing ring 9, located within the annular groove 7, rests against this back ring. The support ring 8 is flush and radially elastic for easy installation in the annular groove 7.

[0011] Consequently, the support ring 8 has no slot, thus reducing gap extrusion at high hydraulic pressure. At the same time, the support ring 8 improves the guidance of the piston 6 in the cup-shaped working cylinder (housing 2). An unslotted support ring 8 can be manufactured particularly economically by omitting the slotting. The use of a stretchable material ensures that the support ring 8 can be pushed over the piston collar 11, which defines the annular groove 7, and can also spring back to its original shape to be positioned without play in the annular groove 7. This is facilitated by a corresponding design of the piston collar 11, resulting in a so-called semi-open annular groove 7, which will be described in more detail later. Fig. 2 will be explained in more detail.

[0012] According to the Fig. 2. The support ring 8 is laterally bounded by a circumferential, convexly curved piston collar 10, which is adapted to the inner diameter of the working cylinder. For this purpose, its diameter is larger than that of the aforementioned additional piston collar 11, which laterally adjoins the sealing ring 9. Conversely, the piston collar 11 adjacent to the sealing ring 9 has a relatively small diameter, which means that the support ring 8 only needs to be slightly expanded to fit over the piston collar 11 in the ring groove 7. The diameter of the piston collar 11 bounding the sealing ring 9 is advantageously adapted to the radial expansion of the support ring 8.

[0013] This further piston collar 11, adjacent to the sealing ring 9, is covered on its circumferential surface by a centering body 12, for which purpose the centering body 12 has a circumferential collar 13 that assists the piston 6 in its alignment when it is inserted into the working cylinder. As a result of the collar 13, the outer diameter of the piston 6 in the region of the piston collar 11 approaches the diameter of the convexly curved piston collar 10, so that the sealing ring 9, due to the very small radial protrusion on the piston 6, can be inserted into the working cylinder without the risk of damage.

[0014] Advantageously, the collar 13 is provided with a frustoconical outer chamfer 19, which, for simplified feeding and self-centering of the piston 6 relative to the working cylinder, is supported on a funnel-shaped insertion chamfer 14 of the working cylinder, as shown in the illustration. Fig. 5 can be seen. Furthermore, the centering body 12 has a base 15 with a pin 16 for easy attachment to the piston 6, which is fixed in a central bore 17 of the piston 6.

[0015] As shown by the Fig. As illustrated in Figure 3, the piston collar 10 adjacent to the support ring 8, due to its convex curved surface, allows for a pivotable mounting of the piston 6 in the working cylinder to compensate for small alignment errors, without risk of jamming and with a negligible risk of wear.

[0016] As from the Fig. As can be seen from Figure 4, the sealing ring 9 has several radial grooves 18 evenly distributed around its circumference on the end face facing the support ring 8, in order to be able to divert any leakage from the working cylinder (housing 2) towards the central housing (housing 3) via the radial grooves 18 in order to be able to detect and thus reliably detect any leakage in the direction of the central housing (housing 3).

[0017] Finally, the aim is to use the Fig. 5. The self-centering of the piston 6 during insertion into the working cylinder (housing 2) is illustrated. For this purpose, the outer chamfer 19 of the centering body 12 is supported against a funnel-shaped insertion chamfer 14 of the working cylinder and slides along it, so that the sealing ring 9, preferably designed as a sleeve seal, reaches the insertion chamfer 14 precisely without contacting or getting stuck on the outer edge of the working cylinder (housing 2). For this purpose, the sealing ring 9, with the exception of its sealing lip, is completely covered by the centering body 12 on its end face facing the working cylinder. This ensures that the centering body always rests against the insertion chamfer 14 before the sealing ring 9 makes contact with it, thus guiding the sealing ring 9 along the insertion chamfer 14 to the working cylinder with a perfect sealing function. Reference symbol list 1 case 2 cases 3 cases 4 through holes 5 Ball screw drive 6 pistons 7 Ring groove 8 support ring 9 Sealing ring 10 piston collar 11 Piston collar 12 centering bodies 13 collars 14 Introduction phase 15 Floor 16 cones 17 Center bore 18 Radial groove 19 Outer chamfer

Claims

[1] Brake pressure control unit for a motor vehicle braking system, comprising an electric motor whose rotary motion is preferably transformed into a translational motion of a piston in a working cylinder by means of a ball screw drive, in order to be able to build up a defined brake pressure in a wheel brake independently of the actuation of a master brake cylinder, characterized by , that the piston (6) is provided on its outer circumference with a sealing ring (9), the end face of which facing the working cylinder is covered by a centering body (12) which is guided along a funnel-shaped insertion chamfer (14) of the working cylinder before the sealing ring (9) comes to rest against the insertion chamfer (14). [2] Brake pressure control unit according to claim 1, characterized by , that the piston (6) has an annular groove (7) in which an elastic support ring (8) is fixed without play, to which the sealing ring (9) is assigned within the annular groove (7). [3] Brake pressure control unit according to claim 2, characterized by , that the support ring (8) is closed without impact and is elastically stretchable in the radial direction for mounting in the ring groove (7). [4] Brake pressure control unit according to claim 2, characterized by , that the support ring (8) is laterally limited by a circumferential piston collar (10) which is adapted to the inner diameter of the working cylinder, for which purpose the diameter of the piston collar (10) is dimensioned larger than a further piston collar (11) which laterally limits the sealing ring (9). [5] Brake pressure control unit according to claim 4, characterized by , that for the pivotable mounting of the piston (6) in the working cylinder the piston collar (10) adjacent to the support ring (8) has a convexly curved outer surface. [6] Brake pressure control unit according to claim 4, characterized by, that the further piston collar (11) adjacent to the sealing ring (9) is covered on its circumferential surface by the centering body (12), for which purpose the centering body (12) has a circumferential collar (13) which centers the piston (6) when the piston (6) is inserted into the working cylinder. [7] Brake pressure control unit according to claim 4, characterized by , that the diameter of the piston collar (11) limiting the sealing ring (9) is adapted to the radial expansion of the support ring (8). [8] Brake pressure control unit according to claim 6, characterized by , that the collar (13) is provided with a frustoconical outer chamfer (19) which is supported on a funnel-shaped insertion chamfer (14) of the working cylinder for self-centering of the piston (6) in the working cylinder. [9] Brake pressure control unit according to claim 6, characterized by, that the centering body (12) for fixing to the piston (6) has a base (15) with a pin (16) which is inserted into a central bore (17) of the piston (6). [10] Brake pressure control unit according to claim 2, characterized by , that the sealing ring (9) is provided on the end face facing the support ring (8) with several radial grooves (18) evenly distributed around the circumference. [11] Brake pressure control unit according to claim 1, characterized by , that the sealing ring (9) is designed as a sleeve seal.

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