Patent Application
20140030128
The invention relates to a piston pump for delivering fluids, having a piston which can be driven to perform a reciprocating stroke movement, and a liner in which the piston is received so that it is axially displaceable, and a displacement chamber arranged in the liner between an inlet valve and an outlet valve, wherein the outlet valve is arranged on a liner base.
Piston pumps of various designs are known. They are used in motor vehicles having vehicle hydraulic brake systems. The known piston pumps comprise an inlet valve, an outlet valve and a displacement, working or delivery chamber, which is arranged between the inlet valve and the outlet valve. The displacement chamber is arranged in a pump cylinder, which here forms a liner and is usually of a substantially cup-shaped design. A passage opening, which is opened and closed by the outlet valve, is formed in a liner base of the pump cylinder. Here the outlet valve, which is usually embodied as a non-return valve, is arranged in an outlet valve cover, which is mounted externally on the liner. An outflow into a delivery line, into which the then pressurized fluid, especially the brake fluid, is discharged, is furthermore formed in the outlet valve cover.
In the brake system the piston pump serves, for example, to return brake fluid from a wheel brake cylinder or from a plurality of wheel brake cylinders into a brake master cylinder and/or to deliver brake fluid from a reservoir into a wheel brake cylinder or into a plurality of wheel brake cylinders.
The piston pump is needed in vehicle brake systems with wheel slip control (ABS or ASR), a traction control system (TCS) and/or in a brake system serving as a steering aid (FDR) and/or in an electro-hydraulic brake system (EHB) or an electronic stability program (ESP).
DE 10 2006 027 555 A1 discloses a piston pump for delivering fluids, having a piston, a cylinder element and a delivery chamber arranged between an inlet valve and an outlet valve, wherein the outlet valve comprises a closing member, a pre-tensioning device and a disk element. The outlet valve is arranged in a cover and an outflow into a delivery line ensues via this cover. A sealing seat of the outlet valve is arranged on the disk element.
On opening of the outlet valve, unwanted noises can occur due to dimensional tolerances of the individual components. Efforts are therefore underway to optimize just such piston pumps as these, acting as ABS, ASR or ESP pump elements, with regard to their noise emissions and to improve the assembly of the individual sub-assemblies of such piston pumps.
According to the invention a piston pump is created for delivering fluids, having a piston which can be driven to perform a reciprocating stroke movement, and a liner, in which the piston is received so that it is axially displaceable, and a displacement chamber arranged in the liner between an inlet valve and an outlet valve, wherein the outlet valve is arranged on a liner base. An annular extension of the liner, which encloses an installation space for the outlet valve, is formed on the side st of the liner base remote from the displacement chamber.
According to the invention two functional units are combined in one single liner, that is to say a displacement chamber on the one hand and the fitting space for the outlet valve on the other. This simplifies the assembly of the inventive piston pump of a vehicle hydraulic brake system and also creates further space for damping measures or for a device used for damping.
This measure also makes it possible to reduce the dimensional tolerances of the components, and therefore to reduce the noise generated.
The hydraulic piston pump comprises a cylindrical piston, which in a liner of substantially cup-shaped design is supported so that it can be run into and out of a cylinder bore. The liner is inserted, in particular, into a cylinder bore of a pump housing of the piston pump in a hydraulic unit. Inside the cylinder bore of the liner a fluid-filled delivery area or delivery chamber is provided between an inlet valve and an outlet valve. When the piston runs out of the cylinder, a vacuum is built up in the delivery area and the piston sucks fluid into the delivery area via the inlet valve. When it runs in on the other hand, the piston displaces the fluid out of the delivery area via the outlet valve into the hydraulic system for performing work. A passage opening, which is opened and closed by the outlet valve, is formed in the base of the liner.
The outlet valve comprises a closing member, which is advantageously embodied as a ball or plate. The liner is preferably combined with an annular extension or the latter is subsequently formed onto the liner as a hollow cylindrical continuation on the liner, in order to then accommodate the outlet valve inside the hollow cylindrical continuation. This has the advantage that components such as the closing member, the spring and noise damping means can be arranged inside the hollow cylindrical continuation from the outlet valve-side, as part of a simple assembly process, which is performed in the opposite direction to the usual one.
Here the outlet valve, which is preferably embodied as a non-return valve, is arranged in the part of the extension joined onto the liner, and an outflow into a delivery line of an associated pump housing is furthermore formed in the extension. The outflow is advantageously formed by means of a circumferential recess and a radial duct. The circumferential recess is preferably formed on the liner on the side remote from the displacement chamber, and the radial duct preferably connects the installation space of the outlet valve to the recess. The outlet valve here advantageously comprises the closing member, a pre-tensioning device for pre-tensioning the closing member and a base element for supporting the pre-tensioning device.
Here the liner of the piston pump may be of longer design dimensions, thereby additionally affording further space in the area of the outlet valve for any damping measures.
A closure element in the form of a closure cap is advantageously attached to the annular extension. The closure element is advantageously caulked into the liner and for its part caulked in the pump housing itself. Alternatively the closure element may also just be attached to the extension of the liner and caulked only in the pump housing, in order to create a fluid-tight and force-absorbing positional safeguard for the closure element in this area. Overall the closure element is integrated into the liner and the two combined with one another to form one unit, so that unwanted noises due to opening of the outlet valve are thereby already reduced.
The integrated closure element, which is preferably designed as an outlet valve cover or as an integrated closure cap of the outlet valve, is preferably made from aluminum. This affords external protection against corrosion and secure caulking in the pump housing. The aluminum has a ductility such that the caulking of the closure element in the housing wall of the liner can easily be achieved by positive interlock and frictional connection.
An exemplary embodiment of the solution according to the invention is explained in more detail below with reference to the schematic drawings attached, of which:
The piston pump 10 comprises a piston 16, one end of which, remote from the displacement chamber 18, is guided in the pump housing 14 by a first guide ring 20 and sealed off by a sealing ring 22. The other end of the piston 16, facing the displacement chamber 18, is guided in a liner 26 of the piston pump 10 by a second guide ring 24 and sealed off by a sealing ring 28. The liner 26 is inserted with a press fit into the cylinder bore 12 of the pump housing 14. The press fit produces a seal between the inlet side and the outlet side, that is to say between the low-pressure side and the high-pressure side of the piston pump 10.
For the pump inlet an axial blind bore 30, which is crossed by transverse bores 32 close to its base, is fitted in the piston 16 from a side facing the displacement chamber 18. Through windows 34 in a peripheral wall 36 of the liner 26, the blind bores and transverse bores 30, 32 communicate with an admission bore 38, which is inserted in the hydraulic unit forming the pump housing 14 radially to the piston pump 10.
At the displacement chamber end of the piston 16, a non-return valve is fitted as inlet valve 40. As valve closing member the inlet valve 40 comprises a valve ball 42, which interacts with a tapered valve seat 44, which is inserted at an orifice of the blind bore 30 of the piston 16. A helical compression spring as valve closing spring 46 presses the valve ball 42 against the valve seat 44. The valve ball 42 and the valve closing spring 46 are accommodated in a valve housing 48, which is made from sheet metal as a cup-shaped deep-drawn part having a diameter corresponding approximately to the diameter of the piston 16, and is provided with flow passage openings 50. The valve housing 48 has an annular step 52, with which it bears on an end face of the piston 16 facing the displacement chamber 18. It comprises an integral, externally projecting radial flange 54, against which a helical compression spring serving as piston return spring 56 presses and in this way holds the valve housing 48 on the piston 16. At the same time the radial flange 54 retains the guide ring 24 and the sealing ring 28 between it and a support ring 60, resting on an annular shoulder 58 of the piston 16, on the piston 16 in an axial direction.
Via the radial flange 54 of the valve housing 48, the piston return spring presses the piston 16 in an axial direction against an eccentric 62, which can be driven by an electric motor and which serves for driving the piston 16 to perform a reciprocating stroke movement in a known manner.
On a displacement chamber side the liner 26 comprises an integral liner base 64, in which a central through-hole 66 is inserted for the pump outlet. The liner 26 is extended beyond this liner base 64 by a hollow cylindrical portion or annular extension 67 on its side remote from the displacement chamber 18. The annular extension 67 comprises an installation space 69, integral with the liner 26, for an outlet valve 72, which can be fitted in this installation space 69 on the liner 26 in reverse order.
Adjoining the annular extension 67 is a closure element 68, which has the form of a closure cap, which is integrated into the annular extension 67 by pressing in a step 73, and in so doing is inserted directly into the cylinder bore 12. The closure element 68 is positively connected by a caulking 70 to the pump housing 14 and sealed fluid-tightly. The closure element 68 is thereby additionally also secured in the liner 26.
The closure element 68 is preferably formed from aluminum. This ensures external protection against corrosion and owing to the ductility of the aluminum affords a secure connection through the caulking 70 of the closure element 68 in the pump housing 14.
The outlet valve 72 is designed with a spherical closing member 74 and a return spring 76 as pre-tensioning device, and a damping device 78 as support and base element for the return spring 76. The return spring 76 exerts a return force on the closing member 74, so that this is pressed in the direction of the central hole 66.
The liner 26 has a radial duct 79 passing through it, which leads to an annular recess 80, in particular an annular duct, formed on the outside thereof, for the fluid to flow out of the pump housing 14 through an outflow duct 82 when the outlet valve 72 is opened.
In its longitudinal extent, therefore, the liner 26 is of extended design in order to afford additional space in conjunction with the integrated closure element 68. Due to the integrated arrangement of the annular extension 67 in the form of a sleeve extension and the caulking of the closure element 68 directly in the liner 26, however, the overall length of the piston pump 10 is not necessarily extended.
The design of the piston pump 10 according to the invention with the liner 26, the annular extension 67 and the integrated closure element 68 allows the closing member 74, the return spring 76 and the damping device 78 to be easily fitted from the outlet valve-side. The liner 26 itself is machined during manufacture. The machining according to the invention for producing the liner 26 with the hollow cylindrical portion and the annular extension 67 is therefore not only feasible but also cost-neutral. In addition, the design according to the invention affords additional space for the installation of the damping device 78.
Also externally visible are the recess 80 for the outflow of fluid, which passes from inside the delivery chamber into the recess 80 through the radial duct 79 (not shown here).
All features represented in the description, the following claims and the drawings may be essential for the invention, both individually and in any combination with one another.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 064 084.0 | Dec 2010 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP11/68543 | 10/24/2011 | WO | 00 | 10/10/2013 |
