DE102009027312A1 - Multi-piston pump - Google Patents

Abstract

The invention relates to a multi-piston pump (1) as a return pump for a hydraulic vehicle brake system. The invention proposes designing the multi-piston pump with two pump pistons (2) phase-shifted by 90 ° and a compensating piston (14), which is designed as a stepped piston and is arranged phase-shifted by 135 ° to the two pump pistons (2). A piston surface (18) at the smaller-diameter end of the compensating piston (14) communicates with connected outlets (12) of the pump pistons (2), a stepped surface (15) of the compensating piston (14) communicates with connected inlets (9) of the pump pistons (2). The compensating piston (14) smooths the volume flows at an inlet (10) and at an outlet (13) of the multi-piston pump (1).

Description

State of the art

The The invention relates to a multi-piston pump with the features of the preamble of claim 1. It is as a so-called return pump in anti-lock, drive slip and / or vehicle dynamics control, hydraulic vehicle brake systems or for (operating) brake pressure build-up provided in electro-hydraulic vehicle brake systems.

piston pumps for hydraulic vehicle brake systems are known. she have structurally conditioned a pulsating flow due to its reaction to a foot brake pedal (or a hand brake lever of a service brake, for example one Motorcycle) is undesirable.

to Reduction of the pulsation of the flow on a suction side are known stepped piston pumps. A diameter gradation of a stepped piston a stepped piston pump reduces a sucked amount of fluid during a return stroke in comparison with a continuously variable pump piston and causes suction of fluid during a power stroke. During the working stroke, the pump piston displaces fluid from one Pump cylinder or a pump bore. In comparison with one unrestrained pump piston, which only during the return stroke Aspirates fluid, a stepped piston distributes the sucked flow on the working and the return stroke, so that the sucked Flow less pulsating.

Another possibility for reducing pulsations are multi-piston pumps whose pump pistons are driven out of phase. Such multi-piston pumps for hydraulic, slip-controlled vehicle brake systems disclosed in the published patent application DE 198 25 114 A1 , There, for example, two pump pistons in a V-arrangement by 90 degrees or three pump pistons in a star arrangement offset by 120 degrees to each other about a common eccentric, which drives the pump piston to a lifting movement. The angular offset arrangement of the pump piston causes a phase-shifted drive of the pump piston, which in turn causes a phase shift of the flow rates of the pump piston. The flow rates of the pump piston add up, the pressure pulsation is reduced, both on the pressure and on the suction side of the multi-piston pump. The V or star arrangement of the pump piston to a common eccentric is not mandatory, the phase-shifted drive is essential, which is possible, for example, in a series arrangement of the pump piston. The pump pistons of the known multi-piston pump are stepped pistons. It is provided for or in each brake circuit, a multi-piston pump having a common drive with an electric motor.

Disclosure of the invention

The inventive multi-piston pump with the features of claim 1 comprises two pump pistons, with a phase shift, but not driven in antiphase. Inlets of the Both pump pistons are connected to each other, their common Part forms an inlet of the multi-piston pump, for example, over an intake valve to a master cylinder of a hydraulic Vehicle brake system is connected. Point the two pump pistons a fluid control, for example in a known manner with valves (Inlet and outlet valves), in particular check valves. Except the pump piston, the inventive Multi-piston pump a balance piston without fluid control, ie without inlet or outlet valve, open. The balance piston communicates with the connected inlets of the pump piston, he will approximately in phase opposition to a mean phase shift of the two Pump piston driven. By that is meant that the balance piston in opposite phase to a superposition of the strokes the two pump pistons is driven.

By the counter-phase drive displaces the balance piston Fluid to the connected inlets of the pump piston when suck the pump piston fluid to. Conversely, the balance piston sucks Fluid from the inlets of the pump piston, if this do not suck in any fluid. Preferably, the displaced from the balance piston Fluid flow then its maximum when the sum of the pump piston sucked fluid flows has a minimum and vice versa. A pulsation of the multi-piston pump according to the invention sucked fluid flow corresponds approximately to the pulsation of a multi-piston pump with the same number of pistons, d. H. a multi-piston pump with so many pump pistons such as the multi-piston pump according to the invention and balance piston has. The advantage of the invention Multi-piston pump is that her balance piston no fluid control and their construction cost is therefore lower. Because valves always represent a flow resistance is a valve-free Balancing piston without fluid control advantageous. Especially at low Temperature and as a result of countless brake fluid can the flow rate of the invention Multi-piston pump and its pressure build-up dynamics to be improved. The is to be regarded as a further advantage of the invention.

The dependent claims have advantageous off designs and developments of the invention specified in claim 1 to the subject.

A preferred embodiment of the invention according to claim 2 provides a stepped piston as a balance piston. A stepped piston allows the connection of both the inlets as well as the outlets of the pump piston with the stepped piston (Claim 3), wherein the inlets and the outlets remain hydraulically separated, communicate either the inlets of the pump pistons with the step surface and the outlets of the pump piston with preferably the smaller piston area of the balance piston or vice versa. As a result, the pressure pulsation at the inlet and the outlet of the multi-piston pump reduced. Compared with a pump piston of a conventional Return pump designed as a stepped piston pump is, is the balance piston of the multi-piston pump according to the invention preferably arranged reversely, namely with its larger diameter side facing him driving eccentric.

claim 5 provides stepless pump pistons, the balancing piston is like said preferably formed as a stepped piston. By the multi-piston principle according to the invention bring stepped piston as a pump piston no advantage compared with stepless pump piston, in any case, reduce stepped piston than Pump piston not a pressure pulsation of the sucked fluid flow the multi-piston pump according to the invention. advantage stepless pump piston is a lesser construction cost.

When ideal is a phase shift of the two pump pistons of about 90 degrees to each other and the balance piston of about 135 degrees to both View pump piston (claim 6). This will give you the greatest possible Compensation of the pulsations of the flow rates the pumps and the balance piston at the inlet and outlet and thus one achieved low pulsation.

Regarding the compensation of the pressure pulsations of the pump and the balance piston and for a low total pressure pulsation is an area ratio of the balance piston to a pump piston of about 1: √2 ideal to view (claim 7). The larger diameter Side of the balance piston can be the same piston area as a pump piston.

claim 8 sees a star-shaped arrangement of the pump piston and of the balance piston before. The pump and balancing pistons can be in a radial plane to an eccentric, around the they are arranged and which drives them out of phase, arrange.

Short description of the drawing

The Invention will now be described with reference to a drawing Embodiment explained in more detail. Show it:

1 a schematic representation of a multi-piston pump according to the invention;

2 a flow diagram on a pressure side of the multi-piston pump 1 ; and

3 a flow diagram on a suction side of the multi-piston pump 1 ,

1 shows in schematic form a multi-piston pump according to the invention 1 , which is intended for hydraulic vehicle brake systems, for example, as a return pump a anti-lock, drive slip and / or vehicle dynamics-controlled vehicle brake system. Typical abbreviations of such regulations are ABS, ASR, FDS and / or ESP. Another possible use of the multi-piston pump 1 are electro-hydraulic vehicle brake systems (abbreviation: EHB). The latter are foreign-power brake systems in which the brake pressure required for braking with a hydraulic pump, such as the multi-piston pump 1 , which is part of a foreign energy supply device of the electro-hydraulic vehicle brake system.

The multi-piston pump 1 has two stepless pump pistons 2 on, which is 90 degrees angularly offset radially to an eccentric 3 are arranged. The eccentric 3 is with an electric motor, not shown, about its axis of rotation 4 rotatable drivable. piston springs 5 hold end faces of the pump piston 2 in contact with a circumference of the eccentric 3 , so that by rotating drive of the eccentric 3 the pump pistons 2 be driven to reciprocating strokes. In the illustrated and described embodiment of the invention, the piston springs 5 Helical compression springs attached to the eccentric 3 opposite end faces of the pump piston 2 are arranged.

The pump pistons 2 are in cylinders 6 received axially displaceable, the displacement direction is radial to the axis of rotation 4 of the eccentric 3 , In the practical embodiment is provided, the pump piston 2 To receive in axial displacement in pump bores in a so-called. Hydraulic block, not shown, in the place of the drawn cylinder 6 occurs.

The pump pistons 2 have integrated inlet valves 7 on, which are designed as check valves. About holes 8th in the pump piston 2 communicate the inlet valves 7 with inlets 9 . the inlets 9 the pump piston 2 are connected to an inlet 10 the multi-piston pump 1 ,

An outlet from the cylinders 6 done by exhaust valves 11 , which are also designed as check valves. The outlets 12 the pump piston 2 are to an outlet 13 the multi-piston pump 1 connected.

Through the lifting drive of the pump piston 2 with the rotating eccentric 3 suck the pump piston 2 in a conventional manner during a return stroke fluid, here brake fluid, through the inlet 9 . 10 and displace the brake fluid to the outlet during a power stroke 12 . 13 , This is known from piston pumps per se and will not be explained in detail here. The angular offset of the two pump pistons 2 of 90 degrees causes a phase offset of their drive also 90 degrees.

The two stepless pump pistons 2 opposite, ie to both pump piston 2 each angularly offset by 135 degrees, is a stepped balance piston 14 arranged, which also by a piston spring 5 against the circumference of the eccentric 3 is pressed. A lifting drive of the balance piston 14 takes place as the lifting drive of the pump piston 2 by rotating drive of the eccentric 3 , Due to the angular offset of 135 degrees to the pump piston 2 becomes the balance piston 14 with a phase shift of 135 degrees to the two pump pistons 2 driven. In other words, the balance piston 14 in antiphase to a mean phase shift of the pump piston 2 or driven to a superposition of their two strokes. A larger diameter end of the balance piston 14 is the eccentric 3 facing, a step surface 15 is the eccentric 3 away. The balance piston 14 is in a stepped cylinder 16 or a stepped pump bore 17 of the hydraulic block, not shown here, in place of the cylinder 16 occurs, guided axially displaceable. The direction of displacement of the balance piston 14 is radial to the axis of rotation 4 of the eccentric 3 , The total of three pistons 2 . 14 the multi-piston pump 1 namely the two pump pistons 2 and the balance piston 14 , are star-shaped around the eccentric 3 arranged, as said the angular offset between the two pump piston 2 90 degrees and from both pump pistons 2 to balance piston 14 each 135 degrees.

The balance piston 14 has no valves or other fluid control. A larger diameter part of the stepped pump bore 17 is through the balance piston 14 hydraulically from the smaller diameter part of the pump bore 17 separated. The step surface 15 of the balance piston 14 communicates with the inlets 9 the pump piston 2 and thus with the inlet 10 the multi-piston pump 1 , The smaller diameter piston surface 18 of the balance piston 14 communicates with the outlets 12 the pump piston 2 and therefore with the outlet 13 the multi-piston pump 1 , The step surface 15 of the balance piston 14 is smaller by a factor √2 than a piston area of the pump piston 2 , The larger diameter part of the balance piston 14 has the same diameter as the pump piston 2 on.

Displace the two pump pistons 2 during their working strokes brake fluid through their outlets 12 in the outlet 13 the multi-piston pump 1 , performs the balance piston 14 because of its antiphase drive a return stroke, he sucks with his piston surface 18 on the smaller-diameter side brake fluid from the outlet 13 the multi-piston pump 1 at. This reduces the through the outlet 13 emerging flow of the multi-piston pump 1 , In the reverse case, during the return strokes of the pump piston 2 displace the pump pistons 2 no brake fluid. The balance piston 14 Performs a working stroke and displaces the outlet from the outlet during the previous return stroke 13 sucked brake fluid back into the outlet 13 , so that even during the return strokes of the pump piston 2 during which the pump piston 2 do not displace brake fluid, the multi-piston pump 1 a flow from its outlet 13 having.

The flow from the outlet 13 the multi-piston pump 1 is smoothed, a pressure pulsation is reduced. The flow conditions are in the diagram of 2 illustrates that on a maximum flow of a pump piston 2 normalized. You can see the two sinusoidal and phase-shifted by 90 degrees flow rates V _I , V _{II of} the two pump pistons 2 , The flow rates V _I , V _{II of} the pump piston 2 extend only over the positive sine half-waves, because the pump piston 2 do not displace brake fluid during the return stroke. The volume flow of V _{A of} the balance piston 14 is also sinusoidal and 135 degrees out of phase with the flow rates V _I , V _{II of} both pump pistons 2 , ie the volume flow V _{A of} the balance piston 14 is in phase opposition to the sum of the flow rates V _I , V _II , the two pump pistons 2 , In contrast to the flow rates V _I , V _{II of} the two pump pistons 2 extends the flow rate V _{A of} the balance piston 14 over the entire sine wave, so also over the negative half-wave, because the balance piston 14 during half a turn of the eccentric 3 Brake fluid from the outlet 13 sucks and during the other half turn of the eccentric 3 the previously sucked brake fluid back into the outlet 13 repressed. Overall, the smoothed flow V results in the outlet 13 the multi-piston pump 1 which has a low ripple and a low pressure pulsation has.

Also in the inlet 10 the multi-piston pump 1 causes the balance piston 14 a smoothing of the here referred to as suction flow or volume flow: When the two pump piston 2 during their return strokes brake fluid from the inlet 10 suck in, performs the balance piston 14 his work stroke, so he with his step surface 15 Brake fluid in the inlet 10 displaces and thereby reduces the suction flow. If the two pump pistons 2 The brake piston does not suck in any brake fluid during its working strokes 14 his return stroke and sucks with his step surface 15 Brake fluid from the inlet 10 the multi-piston pump 1 so that the multi-piston pump 1 also during the working strokes of the pump piston 2 Aspirates brake fluid. The balance piston 14 causes in this way also a smoothing of the suction flow into the inlet 10 the multi-piston pump 1 , The volume flows in the inlet 10 the multi-piston pump 1 shows the diagram in 3 that is based on the maximum suction flow of a pump piston 2 normalized. The suction flows S _I , S _{II of} the pump piston 2 are shown negative because they are in the multi-piston pump 1 flow. On the suction side of the multi-piston pump 1 So in the inlet 10 , The same conditions arise as on the pressure side, ie in the outlet 13 : The suction flows S _I , S _{II of} the pump pistons 2 each extend over the negative sine half-wave and are 90 degrees out of phase with each other. The volume flow S _{A of} the step surface 15 of the balance piston 14 extends over the entire sine wave and equalizes the suction currents S _{I ,} S _{II of} the pump piston 2 out, so in the inlet 10 the multi-piston pump 1 the suction flow S with low waviness results.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19825114 A1 [0004]

Claims (8)

Multi-piston pump, with two pump pistons ( 2 ), which are driven with a phase shift, but not in antiphase, and their inlets ( 9 ), characterized in that the multi-piston pump ( 1 ) a balance piston ( 14 ) without fluid control, with the inlets ( 9 ) the pump piston ( 2 ) and in approximately opposite phase to a mean phase shift of the two pump pistons ( 2 ) is driven. Multi-piston pump according to claim 1, characterized in that the compensating piston ( 3 ) is designed as a stepped piston. A multi-piston pump according to claim 2, characterized in that the outlets ( 12 ) of the two pump pistons ( 2 ) and hydraulically separated from the inlets ( 9 ) with the balance piston ( 14 ) communicate. A multi-piston pump according to claim 3, characterized in that a step surface ( 15 ) of the balance piston ( 14 ) with the connected inlets ( 9 ) the pump piston ( 2 ) communicates. A multi-piston pump according to claim 1, characterized in that the pump pistons ( 2 ) are stepless. Multi-piston pump according to claim 1, characterized in that the two pump pistons ( 2 ) a phase shift of about 90 degrees and the balance piston ( 14 ) a phase shift of about 135 degrees to both pump pistons ( 2 ) having. Multi-piston pump according to claim 1, characterized in that one with the inlets ( 9 ) the pump piston ( 2 ) communicating area ( 15 ) of the balance piston ( 14 ) is smaller than a piston area of the pump pistons by about the factor √2 (in words: root of two) ( 2 ). A multi-piston pump according to claim 1, characterized in that the pump pistons ( 2 ) and the balance piston ( 15 ) are arranged in a star shape.

Images