WO2016055261A1 - Fluid pump, in particular for supplying fluid and regulating pressure in a fluid circuit of a slip-controllable vehicle brake system - Google Patents

Abstract

The invention relates to a fluid pump, in particular for supplying fluid and regulating pressure in a fluid circuit of a slip-controllable vehicle brake system. Fluid pumps of this type have a working chamber, arranged between an inlet (22) and an outlet (24), the volume whereof is cyclically changeable by an actuable displacer (12). As the volume of the working chamber (20) increases over the course of such a cycle, the absolute pressure in this working chamber (20) drops and a pressure difference increases with respect to the ambient pressure. In some cases, the absolute pressure becomes so low that gas originally dissolved in the fluid is released and forms gas bubbles. Gas bubbles impair the delivery capacity of the fluid pump and endanger the functioning of a fluid circuit supplied with fluid by the fluid pump. In order to prevent this, a fluid pump is equipped, according to the invention, with means (60) which limit the pressure which can be generated by the displacer (12) on the low-pressure side of the fluid pump.

Description

 Fluid pump, in particular for fluid supply and pressure control in one

Fluid circuit of a slip-controllable vehicle brake system

Description: PRIOR ART The invention relates to a fluid pump, in particular for fluid supply and

Pressure control in a fluid circuit of a slip-controllable

Vehicle brake system, according to the features of the preamble of claim 1. Fluid pumps for slip-controllable vehicle brake systems are usually as gear pumps, both in the form of an internal gear pump or as external gear pump or piston pumps, especially as

 Radial piston pumps, formed. From DE 10 2010 040 819 AI, for example, designed as a radial piston pump fluid pump is known. All of these pump designs commonly have an inlet associated with a low-pressure side, an outlet associated with a high-pressure side, and a working space arranged between the inlet and the outlet

Volume by operation of a displacer, in gear pumps by driving one of the gears or in piston pumps by reciprocating movement of a piston, cyclically changeable.

 Piston pumps each have a valve associated with the inlet and associated with the outlet for controlling a fluid flow rate through the pump. These valves are usually designed as check valves, have a valve spring pressed by a valve spring against a valve seat and take depending on the direction of movement of the piston in the

mutual exchange their open or closed position.

If the working space increases its volume in the course of such a cycle, the absolute pressure inside this working space drops or rises

Pressure difference to an ambient pressure on. Fluid is characterized by the displacer via the low-pressure side inlet of the fluid pump in the

Workspace sucked. It may now be the case that the absolute pressure in the working space is lower than a pressure threshold value up to which the fluid can store gas in solution. This pressure threshold is also referred to as the outgassing pressure of the fluid. He is of the composition of the fluid, of which

Aging condition and environmental conditions, e.g. Pressure, temperature and humidity, depending. If the absolute pressure in the working space drops below this pressure threshold value, gas dissolved in the fluid escapes and accumulates to form gas bubbles. The latter affect the delivery of the fluid pump and can even lead in extreme cases to a total failure of a vehicle equipped with the fluid pump vehicle brake system.

 One possible circumstance that can lead to such gas bubble formation is a low ambient temperature, as a result of which the viscosity of the fluid increases. In conjunction with the available and relatively small-sized flow cross sections at the upstream of the fluid pump arranged components of a slip-controlled vehicle brake system, this can cause the highly viscous fluid can not flow quickly enough into the increasing working space of the fluid pump. Due to the perpetual movement of the repressor it comes to said

Lowering of the absolute pressure in the working space below the above-mentioned pressure threshold value or for explained gas bubble formation.

Advantages of the invention

A fluid pump according to the features of claim 1 has the advantage that by the use of suitable means of the pressure generated by the displacer on the low pressure side of the fluid pump can be limited to a minimum value at which there is no accumulation of gas bubbles. In the absence of occurring gas bubbles decreases even at low

Ambient temperatures and / or highly viscous fluid does not decrease the delivery rate of the fluid pump and, in parallel with this, the reliability of a slip-controllable vehicle brake system equipped with a fluid pump of the type described is increased.

Further advantages or advantageous developments of the invention will become apparent from the dependent claims and / or the following description. According to claim 3, the proposed means substantially an elastically deformable membrane, the front side is acted upon by the pressure on the low pressure side of the fluid pump and the back is supported on a mechanical stop. Membranes are simple and robust representable and available inexpensively in a variety of design variants. There is no significant additional effort to mount this membrane.

 Due to their compactness, the means can readily be integrated into the interior of a fluid pump and / or they can be arranged outside the fluid pump upstream of an inlet (claim 2). At one of the

Components for fluid supply and pressure control receiving

Hydraulic unit of a slip-controllable vehicle brake system is sufficient space available for such means, so that the funds can be integrated without the external dimensions or the space requirement of

To increase hydraulic power unit.

 Claims 5 and 6 seek protection for the arrangement of means according to the invention in fluid pumps, which are particularly compact and cost-effective as cyclically operating piston pumps or which due to their continuous

Fluid promotion are designed as a particularly low-noise gear pumps.

drawing

An embodiment of the invention is illustrated in the drawing and will be explained in detail in the following description.

 FIG. 1 shows a longitudinal section of a fluid pump designed as a piston pump and known from the prior art;

 FIG. 2 shows a piston of such a piston pump in longitudinal section, this piston being equipped with means according to the invention.

Description of the embodiment:

The illustrated in the figure 1 and known from the prior art

Fluid pump 10 is in the form of a piston pump and has as effective displacer a piston 12, which is composed of several parts. The piston 12 is guided axially movable in a bushing 14 and is driven by a rotating drive element 16 against the force of a return spring 18 to a reciprocating stroke H. The bushing 14 is cup-shaped and has a bushing bottom 14a and a journal shaft 14b. The latter leads the piston 12 in the radial direction. At the sleeve bottom 14a, the return spring 18 is supported with its first end. The opposite second end of the

Return spring 18 is applied to the piston 12 and pushes it against the

Drive element 16. The return spring 18 is space-saving in one

Working chamber 20 of the piston pump 10 accommodated, whose volume increases due to the lifting movement of the piston 12 in a cyclic rhythm, reduced and increased again. To control a flow of fluid through the piston pump 10, it is equipped with an inlet valve 22a associated with its inlet 22 and with an outlet valve 24a associated with its outlet 24. The inlet valve 22a is disposed on the piston 12 while the outlet valve 24a is located on the liner bottom 14a. Both valves 22a, 24a have a valve closure member 26 which is urged by a valve spring 28 against a valve seat 30 to control its passage area. The latter is formed in the case of the outlet valve 24a on a side opposite the working space 20 of the piston pump 10 side of the bush bottom 14a. The valve spring 28 and the valve closing member 26 of the outlet valve 24a are housed in a recess of a sealing plug 32, which rests with one of its end faces on the bushing bottom 14a. On the basis of the sealing plug 32, the piston pump 10 in a receiving bore of a hydraulic block, not shown, of a hydraulic unit

slip-regulated vehicle brake system anchored; In addition, the sealing plug 32 seals this receiving bore to the outside, towards the environment. Unrecognizable recesses on the bushing 14 facing end face of the sealing plug 32 and / or on the closure plug 32 facing side of the bush bottom 14a together form a channel through which fluid with open outlet valve 24a under increased pressure from the working space 20 off and one of the piston pump 10 flows supplied with fluid hydraulic circuit of a vehicle brake system. The piston 12 is composed of a cylindrical first

Piston element 40 and a second sleeve-shaped piston element 42. For cost reasons, the first piston element 40 is the use of a cylinder roll available in mass production, which can be executed solid and without bores or the like. The sleeve-shaped second piston element 42 is provided with a continuous Axialausnehmung 44, in which open from the side transverse bores 46. At his workroom 20

facing end is formed on the sleeve-shaped second piston member 42 of the valve seat 30 of the inlet valve 22a. The valve spring 28 acting on the valve closure member 26 is supported on a valve cage 48 with a molded high-pressure sealing element 50. This valve cage 48 is permeable to fluid via unrecognizable slots, which flows to the working space 20 of the piston pump 10 when the inlet valve 22a is open.

The high-pressure sealing element 50 circumferentially surrounds the second piston element 42 at its end facing the working space 20 and thereby seals this working space 20 with respect to the low-pressure region of the

Piston pump 10 from. In parallel, the high-pressure sealing element 50 of the radial guidance of the piston 12 in the bushing 14. By the

Cross bores 46 on the second piston element 42 is a hydraulic connection from the low pressure region of the piston pump 10 to the inlet valve 22a. Incoming fluid may contain impurities coming from a

Filter element 52 are filtered out. This filter element 52 is fixed in the axial extension of the piston 12 receiving the open end of the bushing 14. The filter element 52 is equipped with a sealing ring 54, which seals the low-pressure side of the piston pump 10 to the the drive element 16 receiving space of the hydraulic block back. Axial to the

Sealing ring 54 is followed by a Stüz- / guide ring 56, which in its installed state forms a lying outside of the bushing 14, second radial guide for the piston 12.

With an actuation of the piston 12 by the drive element 16, the reciprocating stroke movement H is imposed on it and the volume of the working space 20 increases or decreases in a cyclical change. Depending on this volume change causes an underpressure or an overpressure in the Working chamber 20 and on the low pressure side of the piston pump 10, so that either the inlet valve 22a opens and the exhaust valve 24a closes, whereby fluid flows into the working chamber 20, or the inlet valve 22a closes and the outlet valve 24a opens, whereby fluid from the working space 20 under increased pressure flows in a connected to the piston pump 10 hydraulic circuit. Vacuum refers to a below the

Atmospheric pressure lying pressure level, while overpressure denotes a above atmospheric pressure level.

For example, if the viscosity of the fluid increases and the fluid does not flow fast enough through the inlet valve 22a into the working space 20, the pressure generated by the displacer (piston 12) on the low pressure side of the fluid pump or in the working space 20 can take on an order of magnitude Fluid escapes dissolved gas and accumulates to gas bubbles. The latter worsen the volumetric efficiency of the fluid pump or can even trigger a delivery stop.

 In order to avoid this effect, means 60 are used according to the invention

proposed, which limit the pressure generated by the displacer on the low pressure side of the fluid pump.

 These proposed means 60 are arranged on the piston 12 as an example according to FIG. The latter still comprises a massively designed first piston element 40 without bores or the like and a sleeve-shaped second piston element 42. The second piston element 42 is provided with a circumferential collar inside which the first piston element 40 is received and fixed in sections.

 The first piston element 40 extends up to a shoulder at the end of the collar of the second piston element 42 and covers with its end face the opening cross section of the sleeve-shaped first piston member 40. An elastically deformable membrane 62 rests with its outer periphery on the shoulder of the second piston member 42 and is stuck between the two

Clamped piston elements 40,42. The membrane 62 has a the

Working chamber 20 facing and open inlet valve 22a with the pressure on the low pressure side acted upon front 64 and a rear side 66 which on the closed end face of the second piston part 42nd

mechanically supported. By the choice of the material of the membrane 62, by a possibly provided reinforcement, by the dimensioning of the membrane surface and / or by the design of the cross section or the clamping, the elasticity of this membrane 62 can be determined application-specifically.

 Depending on this structural design and depending on the negative pressure acting on its front side 64, the membrane 62 bulges inwards, i. into the hollow interior of the second piston element 42 when the piston 12 retracts from the working space 20 (dashed line in FIG. 2)

shown). Thus, the membrane 62 counteracts a further pressure reduction in the working space 20 of the fluid pump. By a design of the membrane 62 adapted to the design, the maximum negative pressure occurring in the working space 20 can be limited to a value at which this negative pressure is higher or greater than the outgassing pressure of the fluid, so that ideally no gas dissolved in the fluid escapes and none Risk of gas bubbles exists.

 The embodiment of Figure 2 shows an integrated into the piston assembly 12 solution, which is particularly by their simple and

cost feasibility and characterized by their lack of additional space requirements and extremely low installation overhead. In addition, however, embodiments are also conceivable in which inventive pressure-limiting means 60 outside the

Piston assembly 12 on the low pressure side of the piston pump 10,

preferably in the region of the inlet 22 are arranged on a hydraulic block of a slip-controlled vehicle brake system. An arrangement outside of the piston pump 10 has the advantage that the pressurized front side 64 of the membrane 62 can be dimensioned individually and thereby the characteristic of the membrane 62 easier to

can be adapted to existing requirements.

Instead of the described piston pump 10 can in slip-adjustable

Vehicle brake systems and a gear pump can be used as a fluid pump. In gear pumps, the teeth of at least two gears (displacers) interlock. One of the gears is driven. In the

Interdental spaces between the interlocking teeth of the

Gears will be a fluid from a low pressure side to a high pressure side of the Gear pump promoted. In gear pumps thus form this

This is closed on both sides of the gears by a respective pressure plate or a wall of the gear pump housing. Inventive means 60 for limiting the pressure on the low pressure side of such a fluid pump can preferably be arranged in the immediate vicinity of the inlet 22 on this pressure plate and / or on the wall of the gear pump housing.

Of course, further developments on the described embodiment are conceivable without departing from the spirit of the invention.

Claims

Claims: 1. fluid pump (10), in particular for fluid supply and pressure control in a hydraulic circuit of a slip-controlled vehicle brake system, with a low pressure side of the fluid pump associated inlet (22) through which a fluid flows into a working space (20) of the fluid pump, a high-pressure side of Fluid pump (10) associated outlet (24) through which the fluid flows from the working space (20) of the fluid pump and a working space (20) limiting displacer (12) by operating the volume of the working space (20) in a cyclic change changed, characterized  in that means (60) are provided which limit the pressure which can be generated by the displacer (12) on the low-pressure side of the fluid pump (10). 2. Fluid pump according to claim 1, characterized in that the  pressure limiting means (60) are arranged inside the working space (20) of the fluid pump (10) and / or outside the working space (20) upstream of the inlet (22) of the fluid pump (10). 3. Fluid pump according to claim 1 or 2, characterized in that the pressure-limiting means (60) an elastically deformable membrane (62) acted upon by the pressure on the low pressure side of the fluid pump (10) front side (64) and supported on a mechanical stop Have back (66). 4. Fluid pump according to one of claims 1 to 3, characterized in that the fluid pump is a piston pump (10) with a reciprocating to a reciprocating stroke (H) drivable piston (12) and that the membrane (62) with their Rear side (66) on one of the working space (20) facing the end face of this piston (12) is supported 5. fluid pump according to claim 4, characterized in that the piston (12) has a first piston member (40) and a second piston member (42) which are fixedly connected to each other, wherein the second piston member (42) is sleeve-shaped and the first Piston element (40) a  End face which covers an opening cross-section of the sleeve-shaped second piston member (42) and that the membrane (62) with its outer periphery between the two piston elements (40,42) is fixedly arranged. 6. Fluid pump according to one of claims 1 to 3, characterized in that the fluid pump is a gear pump, in particular a  Internal gear pump, and that the membrane (62) is supported with its rear side (66) in the region of the low-pressure side of the gear pump on a fluid-conveying interdental spaces laterally limiting component.