EP2469088A2 - Eccentric drive for at least one piston of a piston pump - Google Patents

Abstract

The eccentric cam drive (10) has driven shaft (14) and shaft bearing (16) to surround the driven shaft, so that piston (12) is supported on driven shaft. The shaft bearing is a sliding type bearing comprising metallic sliding surface (18) and non-metallic sliding surface (20). The non-metallic sliding surface includes groove and eccentric ring that surrounds the driven shaft.

Description

State of the art

The invention relates to an eccentric drive for at least one piston of a piston pump with a driven shaft and a bearing surrounding the shaft, on which the at least one piston is supported radially to the shaft. Furthermore, the invention relates to a use of such an eccentric drive on a piston pump of a vehicle brake system.

In known piston pumps of vehicle brake systems, in particular radial piston pumps, at least one piston is driven by means of an eccentric. The eccentric drive is realized by means of a driven shaft and an eccentric bearing arranged thereon. The bearing is usually realized as a rolling bearing with rolling elements. As rolling elements preferably needles are used. Thus, a needle bearing is then designed in which the needles are preferably surrounded by a needle sleeve.

On the outside of the bearing, the at least one piston is arranged radially. He supports himself with his piston end face on the bearing. In this support, the driving force of the eccentric is transmitted to the piston so that it reciprocates in its longitudinal direction. Due to the installation of the piston, in particular on the needles of the bearing, a line load between piston and eccentric is formed.

Both the bearing and the piston with its piston end face are formed of metal. There is basically friction between these metals, which can be reduced by lubrication or lubrication of the piston face.

Disclosure of the invention

According to the invention, an eccentric drive is provided for at least one piston of a piston pump with a driven shaft and a bearing surrounding the shaft on which the at least one piston is supported radially to the shaft and in which the bearing is designed as a sliding bearing with a metallic sliding surface and a non-metallic sliding surface ,

With the design of the bearing according to the invention as a plain bearing with two sliding surfaces, known rolling bearings and thus the rolling elements can be omitted, especially previously used needle roller bearings can be saved. In this way, initially advantageous costs are saved. According to the invention, one of the sliding surfaces is made of metal and the other sliding surface of a non-metallic material. With this combination of materials, the frictional resistance of the created sliding bearing can be kept particularly low, at the same time the demands on the life of the bearing can be met.

Preferably, the non-metallic sliding surface is formed from plastic, more preferably from injection molding, so that a simple and cost-effective production is ensured.

With the appropriate quality of the plastic, preferably high-strength plastic with lubricating properties, it is advantageously possible even to dispense with lubricant, both between the shaft and the non-metallic sliding surface, and between the non-metallic sliding surface and the piston end surface. In this way, both the cost of the lubricant and the operation of lubricating or greasing be saved, and extends the maintenance intervals for the piston pump.

According to an advantageous development of the eccentric drive according to the invention, at least one groove is formed in the non-metallic sliding surface. This at least one groove is preferably provided for receiving lubricant. The lubricant leads to a low friction between the metallic and the non-metallic sliding surface and thus advantageously to a lower abrasion. Basically, the, in particular made of plastic, non-metallic sliding surface in comparison to the metallic sliding surface a lower hardness and thus a greater abrasion. This difference in the abrasion behavior of the two sliding surfaces is compensated with the said filling of the groove according to the invention with lubricant.

The shaft is preferably provided with an eccentric portion and the non-metallic sliding surface surrounds the eccentric portion in the form of a circular ring.

With the eccentric an eccentricity for moving the at least one piston is realized radially to the rotationally driven shaft with a portion of the shaft itself. The eccentric portion can be made in one piece with the shaft, for example by means of milling. Alternatively, it may be formed by means of an eccentric element mounted on the shaft, preferably in the form of an eccentric ring pressed onto the shaft. The eccentric ring is advantageously made particularly resistant metal.

The non-metallic sliding surface is then advantageously designed in contrast with a circular ring or a circular sleeve. It preferably surrounds the eccentric section in the form of a bushing or a hollow cylinder with wall thickness which remains constant over its circumference and which rotates with its inner circumferential surface on the eccentric section. The non-metallic sliding surface is thus formed with the inner circumferential surface of the hollow cylinder. The metallic equal area is formed with the eccentric portion and its outer surface which slidably bears against the inner circumferential surface of the hollow cylinder. It is created a so-called sliding bush.

The circular ring has an outer circumferential surface on which the at least one piston is radially supported. As explained, the piston is alternately set in a reciprocating motion by the rotation of the driven eccentric shaft. One of the movements causes the piston to move into an associated piston cylinder, as a rule against the force of a piston spring arranged there, and the other movement causes the piston to move out of the associated piston cylinder. This creates pressure forces between the piston and the outer surface of the annulus. These forces are transmitted to a comparatively large area of the annulus and from there to the eccentric section. There is a so-called area load between the circular ring and the eccentric section or eccentric. This has the advantage that the piston is not tilted on the slide bearing and also less wear the components involved, in particular the plain bearing and the shaft. In contrast, in known eccentric drives with a needle bearing, there is a higher so-called line load between piston, needle and eccentric.

Another advantage is that the eccentric drive according to the invention can be designed with its sliding bearing in the size of known drives. In this way, existing installation spaces, for example in vehicles, obtained and the advantageous material properties of the sliding bearing according to the invention with metallic and non-metallic sliding surface can still be used.

Particularly preferably, the circular ring is in turn encased with metal. As a result, a metal jacket is formed, which may preferably be stationarily positioned relative to the circular ring and forms a unit therewith. The unit then has an inner circumferential surface, which functions as a non-metallic sliding surface, and an outer circumferential surface, which is formed of metal. The outer surface of metal provides increased strength and resistance compared to a pure annulus of non-metal, especially plastic. Thus, a particularly stable outer lateral surface is advantageously created, on which the at least one piston can be supported particularly rigidly radially. Possible deformations of the outer lateral surface by the pressure load of the piston are largely avoided.

In an advantageous embodiment, the at least one piston is preferably arranged stationarily on the circular ring. The annulus then does not move relative to the piston and the piston does not slide over the annulus and, if necessary, its metal sheath. Rather, the annulus itself is held against rotation and it rotates in its interior of the eccentric drive. This has the advantage that there is no sliding friction between the piston and the annulus or between the piston and the metal sheath of the annulus. Furthermore, there is thus no sliding movement of the piston and no force transversely to the longitudinal extent, so that a possible tilting of the piston is excluded. Otherwise, at least lubrication or lubrication of the piston end face would be necessary. Thus, the friction of the piston compared to known Eccentric drives diminished. Furthermore, the high line load that otherwise prevails between the piston and the eccentric is converted into a surface load between the circular ring and the eccentric.

Particularly preferably, at least one snap-on nose is formed on the circular ring. With this snap-in nose, a mechanical locking of the circular ring on the shaft is possible. It serves to "encompass" in particular the eccentric portion and thus to fix the annulus on the eccentric portion, preferably in the axial direction. For this purpose, a groove is preferably formed on the shaft, in which engages the at least one snap-in nose. Such a lock is advantageous particularly easy to implement and serves in particular as a transport lock and at the same time to the spatial location of the components to each other during operation.

As an alternative to at least one snap-action nose, the circular ring is fixed in the axial direction by means of at least one disc, which is mounted in a clamping manner on the eccentric portion or the shaft itself, in particular by means of an interference fit.

In a further embodiment of the eccentric drive according to the invention, the non-metallic sliding surface is designed with an eccentric ring which surrounds the shaft. The eccentricity for moving the piston radially to the shaft is thus realized by means of the non-metallic sliding surface itself, which is designed as an eccentric ring which surrounds the centrally rotating shaft radially. The shaft and the eccentric ring are rotatably or torque-transmitting connected to each other, preferably by a press fit. The eccentric ring is preferably in the form of a hollow cylinder designed with a circular cross-section outer contour.

The non-metallic sliding surface is then formed with the outer circumferential surface of the eccentric ring and preferably made of plastic. The eccentric ring produced in this way from plastic is inexpensive to produce as an injection-molded part and easily adaptable to the installation situation.

Furthermore, preferably at least one groove is formed in the eccentric drive according to the invention in the metallic sliding surface, which is preferably provided for receiving lubricant. With the so held Lubricant is given a lower friction between the metallic and the non-metallic sliding surface, which advantageously leads to a lower abrasion. Particularly preferably, the at least one groove is positioned in the metallic sliding surface opposite the preferably formed at least one groove in the non-metallic sliding surface. In this way, pockets for receiving lubricant, so-called fat pockets, formed. Furthermore, the metallic sliding surface of the eccentric drive according to the invention is preferably designed with a circular sleeve which surrounds the non-metallic sliding surface. The non-metallic sliding surface is preferred as explained above as an eccentric rotationally fixed or torque transmitting mounted on the centrally rotating shaft and surrounded by the circular sleeve of metal. The metal circular sleeve slides in rotation around the eccentric ring rotating with the shaft, forming the metallic sliding surface with its inner lateral surface. The non-metallic sliding surface, however, is formed with the outer surface of the rotating with the shaft eccentric ring, which is preferably made of plastic. With the appropriate quality of the plastic as a high-strength plastic with lubricating properties, neither a groove must be formed in the non-metallic sliding surface nor in the metallic sliding surface.

In a particularly preferred manner, the circular sleeve of the eccentric drive according to the invention is formed with a wrap, in particular with a flanged metal sheath. As a result, the circular sleeve is positioned in the axial direction on the eccentric ring and guided during the rotational movement of the eccentric ring. Furthermore, the stability of the circular sleeve is advantageously increased by the design of the circular sleeve with a wrap.

The eccentric drive according to the invention is preferably used on a piston pump of a vehicle brake system. The above-mentioned advantages have a particularly advantageous effect on such a piston pump.

Fig. 1

einen Längsschnitt eines ersten Ausführungsbeispiels eines erfindungsgemäßen Exzenterantriebs,

Fig. 2

den Schnitt II gemäß Fig. 1,

Fig. 3

einen Längsschnitt eines zweiten Ausführungsbeispiels eines erfindungsgemäßen Exzenterantriebs,

Fig. 4

einen Längsschnitt eines dritten Ausführungsbeispiels eines erfindungsgemäßen Exzenterantriebs und

Fig. 5

den Schnitt V gemäß Fig. 4.

Exemplary embodiments of the solution according to the invention will be explained in more detail below with reference to the attached schematic drawings. It shows:

Fig. 1

a longitudinal section of a first embodiment of an eccentric drive according to the invention,

Fig. 2

the section II according to Fig. 1 .

Fig. 3

a longitudinal section of a second embodiment of an eccentric drive according to the invention,

Fig. 4

a longitudinal section of a third embodiment of an eccentric drive according to the invention and

Fig. 5

the section V according to Fig. 4 ,

The figures show an eccentric drive 10 for five pistons 12, a piston pump, not shown. The eccentric drive 10 comprises a driven shaft 14 and a bearing 16 surrounding the shaft 14, on which the pistons 12 are radially supported. The bearing 16 is designed as a plain bearing with a metallic sliding surface 18 and a non-metallic sliding surface 20.

In the embodiments according to Fig. 1 to Fig. 3 the shaft 14 is provided with a rotating eccentric portion 22 which is made in one piece with the shaft 14 by means of milling. The eccentric portion 22 is surrounded by a circular sleeve or a circular ring 24 in the form of a sleeve or in the form of a hollow cylinder, which slides with its inner circumferential surface 26 on the eccentric portion 22 rotating along. The eccentric section 22 comprises, with its outer surface 28, which slidably bears against the inner circumferential surface 26 of the circular ring 24, the metallic sliding surface 18. The non-metallic sliding surface 20 is formed with the inner circumferential surface 26 of the circular ring 24. The circular ring 24 has an outer circumferential surface 30.

In this case, the individual piston 12 stationary on the circular ring 24, in particular on the outer lateral surface 26 (see Fig. 3 ) can be arranged. The piston 12 then does not slide over the annulus 24. In this way, no sliding friction between the piston 12 the circular ring 24 is present, so that lubrication between the piston 12 and the annulus 24 may be omitted.

According to the embodiment Fig. 1 and Fig. 2 the circular ring 24 is in turn encased with metal, whereby a metal shell 34 is formed. The metal shell 34 is fixedly positioned to the circular ring 24, so that a unit is created with this. This unit comprises the inner circumferential surface 26, which acts as a non-metallic sliding surface 20 and an outer circumferential surface 36, which is then formed correspondingly of metal. The outer metal shell surface 36 is This makes it particularly stiff and stable, so that the piston 12 can support it radially well. Preferably, the individual piston 12 is again fixedly arranged on the metal shell 34, so that it does not slide over the metal shell 34. It results in the same, above-mentioned advantages of reduced or avoided friction.

Further, in the embodiment according to Fig. 1 to Fig. 2 at least one snap-in lug 38 formed on the circular ring 24, which engages in a groove 40 formed on the shaft 14. With the snap-action nose 38, a mechanical locking of the circular ring 24 in the axial direction on the shaft 14 on the eccentric portion 22 is accomplished.

In the embodiment according to Fig. 3 the mechanical fixation of the circular ring 24 is realized in the axial direction by means of a disc 42 which is mounted clampingly on the eccentric portion 22 by means of a press fit.

According to Fig. 3 In the non-metallic sliding surface 20, an annular, in cross-section semicircular groove 44 is formed. This groove 44 opposite is positioned in the metallic sliding surface 18 also has such a shaped groove 46. In this way, with the grooves 44 and 46, a cavity or a pocket 48 is formed for receiving lubricant. The lubricant can be distributed from the pocket 48, starting between the two sliding surfaces 18 and 20 and thus leads to a low friction between the sliding surfaces.

The embodiment according to 4 and FIG. 5 shows an alternative eccentric drive 10 with rotating shaft 14, in which the non-metallic sliding surface 20 is designed with an eccentric ring 50 made of plastic, which surrounds the shaft 14. The shaft 14 and the eccentric ring 50 are rotatably or torque-transmitting connected by a press fit. The eccentric ring 50 is designed in the form of a hollow cylinder with a circular cross-sectional outer contour. The non-metallic sliding surface 20 is thus formed by a then outer lateral surface 52 of the eccentric ring 50 rotating with the shaft 14.

The metallic sliding surface 18 is formed in this variant with an inner circumferential surface 54 of a circular sleeve 56 made of metal, which rotates the eccentric ring 50 surrounds. The circular sleeve 56 is formed with a wrap 58 (see Fig. 4 ), which is designed as a flanged metal shell. With the wraparound 58, the circular sleeve 56 is stabilized, positioned in the axial direction on the eccentric ring 50 and is guided during the rotational movement of the eccentric ring 50. On the outer circumferential surface 60 of the circular sleeve 56 are the (in 4 and FIG. 5 not shown) piston 12 radially supported.

As plastic for the non-metallic sliding surface 20, a particularly high-strength plastic with lubricating properties has been used, in this case VESTAKEEP 4000 FC30. As a result, greasing or lubrication between the two sliding surfaces 18 and 20 is dispensed with in this embodiment (as well as in the embodiment according to FIG Fig. 1 and 2 ) become.

It is thus created a cost-effective eccentric 10, in particular needles can be omitted as a bearing and otherwise necessary lubrication of the piston end face. Furthermore, an otherwise high line load, which prevails in previous eccentric drives between the piston and the eccentric, converted into a surface load between the circular ring or sliding bush and eccentric shaft.

Finally, it should be noted that all the features that are mentioned in the application documents and in particular in the dependent claims, despite the formal reference to one or more specific claims, even individually or in any combination should receive independent protection.

Claims (10)

Eccentric drive (10) for at least one piston (12) of a piston pump with a driven shaft (14) and a bearing (16) surrounding the shaft, on which the at least one piston (12) is supported radially to the shaft (14),
characterized in that the bearing (16) is designed as a plain bearing with a metallic sliding surface (18) and a non-metallic sliding surface (20). Eccentric drive (10) according to claim 1,
characterized in that in the non-metallic sliding surface (18) at least one groove (44) is formed. Eccentric drive (10) according to claim 1 or 2,
characterized in that the shaft (14) is provided with an eccentric portion (22) and the non-metallic sliding surface (20) surrounds the eccentric portion (22) in the form of a circular ring (24). Eccentric drive (10) according to claim 3,
characterized in that on the circular ring (24) of the at least one piston (12) is arranged stationary. Eccentric drive (10) according to claim 3 or 4,
characterized in that on the circular ring (24) at least one snap-in nose (38) is formed. Eccentric drive (10) according to claim 1 or 2,
characterized in that the non-metallic sliding surface (20) is designed with an eccentric ring (50) surrounding the shaft (14). Eccentric drive (10) according to one of the preceding claims,
characterized in that in the metallic sliding surface (18) at least one groove (46) is formed. Eccentric drive (10) according to one of claims 6 to 7,
characterized in that the metallic sliding surface (18) is formed with a circular sleeve (56) surrounding the non-metallic sliding surface (20). Eccentric drive (10) according to claim 8,
characterized in that the circular sleeve (56) is formed with a wrap (58). Use of an eccentric drive (10) according to one of claims 1 to 9 on a piston pump of a vehicle brake system.

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