DE102010040302B4 - Opening time of a bypass channel of a positive displacement pump - Google Patents

Abstract

Positive displacement pump, in particular a gear pump, comprising a bypass channel (18) via which fluid can be guided from a pressure side (22) of the pump to a suction side (21) of the pump and which has a first opening (19s) that can be connected to the suction side (21) and a second orifice (19d) which can be connected to the pressure side (22), wherein the positive displacement pump is designed such that the orifices (19s, 19d) from a position in which they are closed into a position are displaceable, in which one of the first opening (19s) and second opening (19d) is at least partially open and the other of the first opening (19s) and second opening (19d) is closed.

Description

The invention relates to a positive displacement pump with a bypass channel for the return of fluid from a high pressure side to a low pressure side of the pump. The bypass channel is preferably part of an adjusting device for the specific delivery volume of the pump. The pump comprises at least two rotatably mounted conveying wheels, which are in a conveying engagement with each other to promote a working fluid under pressure increase from the low pressure side of the pump to the high pressure side of the pump in a rotary drive of at least one of the conveyor wheels. The invention further relates to a pump comprising the system for the supply of an aggregate with a working or lubricating fluid. In preferred uses, the pump is used to supply an internal combustion engine with lubricating oil, i. H. it forms with this use the lubricating oil pump of the engine. The specific delivery volume is understood to mean the delivery volume of the pump [delivery volume / rotational speed] related to the rotational speed of one of the delivery wheels.

From the DE 10 2008 025 346 A1 For example, a control piston of a control oil pump is known, which is displaceable relative to a further, standing in engagement with the feed wheel together with a designed as a gear conveyor wheel for adjusting the delivery volume of the pump. Depending on the axial overlap of the conveyor wheels, the delivery volume changes. At z. B. high speeds of a cold internal combustion engine, it is necessary to minimize the flow of oil. Since the gears must always be engaged, they also overlap in the position for minimum flow with a certain degree. Since, however, even with a minimum overlap of the gears, a still high volume flow of the oil can be present, a circumferential recess in the circumferential direction is incorporated in the control piston, which connects the suction side with the pressure side at a minimum overlap of the conveyor wheels, so that a short circuit is formed between the suction and pressure side, whereby oil is led from the pressure side directly to the suction side, without a consumer, such. B. the engine to go through. As a result, the delivery volume of the pump is reduced.

How out DE 10 2005 029 086 A1 and DE 10 2008 025 346 A1 shows, the groove-shaped bypass channels on a circular arc in cross section contour, the z. B. is generated with a ball cutter when incorporating the bypass groove in the piston. When the piston is displaced, openings of the bypass groove, ie an opening for the suction side and an opening for the pressure side, are respectively pushed past an edge formed by the housing, wherein the part of the opening pushed over the respective edge forms an opening cross-section. The further the bypass groove is pushed over the edge, the larger the opening cross-section becomes. The opening for the suction side opens simultaneously with the opening for the pressure side. Due to the cross-sectionally circular wall of the bypass groove, the bypass channel opens abruptly, whereby an abrupt increase in cross-section occurs. The fluid may become unstable due to pressure drops and start to vibrate.

It is therefore an object of the invention to provide a positive displacement pump with a bypass channel, which reduces the risk of instability of the system in a shift to the minimum delivery position.

The object is solved by the features of the independent claims. Advantageous developments emerge from the dependent claims, the description and the figures.

The invention is based on a positive displacement pump, in particular a gear pump or external gear pump. In general, the pump may comprise a pump chamber and a further chamber, in particular a control or pressure chamber, wherein the pump chamber and the further chamber are separated from each other by means of a piston. In the pump chamber, a first impeller and a second impeller are arranged, wherein the impellers are preferably gears and are engaged with each other. In particular, the gears mesh at a combing point, d. H. The teeth of the gears mesh there. The gears may have an involute or cycloidal or other tooth shape known to those skilled in the art. The piston is preferably axially, d. H. slidable along the axis of rotation of one of the conveyor wheels, in particular of the feed wheel, which is displaceable together with the piston. It is possible that only a first delivery wheel and a second delivery wheel are arranged in the pump chamber, whereby in particular only a single combing point is formed. Alternatively, however, embodiments are possible in which in addition to the first impeller and the second impeller in the pump chamber, a third impeller is arranged, which is either with the first impeller or the second impeller in engagement, whereby the third impeller with the first or second conveyor wheel can form a further Kämmstelle.

The pump chamber comprises a suction chamber on a suction side and on a pressure side a pressure chamber, which are separated from each other by means of the intermeshing conveyor wheels. In the suction chamber opens a feed opening through which a fluid to be delivered from outside the pump or the suction chamber can be fed into the suction chamber. In the pressure chamber opens a discharge opening, by means of the fluid to be pumped from the pressure chamber or the pump z. B. to a consumer, in particular the lubrication points of an aggregate, or motor is eligible. During delivery operation, the pressure in the suction chamber is lower than in the pressure chamber. Each engagement of intermeshing conveyor wheels, a suction chamber and a pressure chamber can be formed.

In embodiments with only a first impeller and a second impeller they can interlock, with only a suction chamber and only one pressure chamber are formed. In embodiments with a first, second and third impeller they can interlock at two points, so that each engagement a suction chamber and a pressure chamber are formed. For example, the first feed wheel may be engaged with the second feed wheel and the second feed wheel with the third feed wheel. The two pressure chambers can be fluidly separated or connected. The same can apply to the two suction chambers. The advantage of unconnected suction chambers or pressure chambers is that the flow rate for a fluid guidance system can be increased, in particular doubled. The advantage of separate suction chambers and / or pressure chambers is that with a single pump several, in particular two fluid circuits, which can be separated from each other or connected to each other, can be supplied. The peripheral portion of the feed wheel, which is in engagement with the two other feed wheels, can open in the circumferential direction between the engagement points in a suction chamber and in a pressure chamber. This conveyor wheel may in particular have two of these sections. The suction chamber located on one side may be separated from the pressure chamber located on the same side, such. Example by means of a wall which wraps around the second conveyor wheel over part of the circumference and forms a sealing gap with this part of the circumference. As a result, fluid can be conveyed from the suction chamber with a first volume flow on the pressure chamber located on the other side and a second volume flow to the pressure chamber located on the same side.

The conveyor wheels are - relative to the respective axes of rotation - the combing point opposite over a part of its circumference. In particular, the outer diameter of the gears form a sealing gap with the walls, which partially wrap around the gears. For a promotion, the conveyor wheels are rotatable at its combing point in the direction of the suction chamber. The flowing in the suction space in the tooth spaces of the conveyor wheels fluid is taken in the tooth gaps and along the looping wall on the pressure side, in particular in the pressure chamber required. The engagement of the conveyor wheels at the Kämmstelle prevents the backflow of the fluid. As a result, on the suction side, in particular in the suction chamber, a negative pressure and on the pressure side, an overpressure, in particular based on the ambient pressure.

One of the conveyor wheels via a drive device, such. As one or the engine to be lubricated or its crankshaft rotates and takes in this case the other of the conveyor wheels. The driven by the driving conveyor wheel conveyor wheel can be moved along its axis of rotation, in particular shifted back and forth. If present, the entrained feed wheel can take another impeller, which is preferably arranged axially fixed in the pump. In such an embodiment with a first, second and third feed wheel is preferred, the feed wheel displaceable, with the other two conveyor wheels, such as. B. the first and third conveyor wheels in engagement. At maximum axial coverage of the sliding conveyor wheel with the or the conveyor wheels, the pump can promote the maximum flow. The volumetric flow can be reduced by shifting one feed wheel relative to one or the other so far that the axial overlap decreases. With minimal overlap of the conveyor wheels, the pump can promote its minimum flow. By shifting at least one of the conveyor wheels of the volume or flow rate of the pump is adjustable. The displaceable feed wheel is axially fixedly connected to the piston. A displacement of the piston causes a displacement of the feed wheel.

The pressure for the fluid in the control chamber is preferably removed on the high pressure side of or after the pump. In particular, this pressure could be removed at the pressure chamber of the pump chamber. The pressure is preferably taken off at a point on the pressure side at which the fluid pressure corresponds as accurately as possible to the fluid pressure of a consumption to be supplied by the pump with the fluid. If the consumer is, for example, the engine, in particular the reciprocating engine of a motor vehicle, then the fluid pressure is preferably the pressure of the so-called main gallery, ie. H. the channel from which branch off the channels for the individual lubrication points for the crankshaft and / or the camshaft. Preferably, the piston forms a displaceable wall for the control chamber or the pressure chamber, wherein the chamber can be acted upon with a gallery pressure. The invention is based on the positive displacement pump having a bypass channel with which the pressure side of the pump can be connected to the suction side of the pump, in particular is fluidically connectable, ie. h., that fluid from the pressure side of the pump on the suction side of the pump is feasible, depending on the operating condition of the pump.

The invention is generally based on a positive displacement pump, in particular a positive displacement pump of the type mentioned above, which comprises a bypass channel with which a suction side of the pump with a pressure side of the pump is connectable. In particular, the bypass channel can be connected to the suction chamber and / or the pressure chamber of the pump. The bypass channel has a first mouth for the suction side and a second mouth for the pressure side. The first orifice can be connected to the suction side and the second orifice can be connected to the pressure side. With the pump, the volume flow or the delivery volume can be adjusted. In the setting in which the pump delivers the maximum volume flow, the bypass channel is unconnected to at least one of the suction side and the pressure side of the pump. In a setting in which the pump delivers minimal volume flow, the bypass channel is connected to the suction side and the pressure side of the pump. The pump is designed such that the bypass channel is displaceable from one position in which it is closed by a displacement path, in particular to a position for minimum volume flow. Upon displacement of the bypass channel to the displacement of the bypass channel opens depending on the displacement to the suction side and / or to the pressure side with a magnifying measure or opening cross-section.

According to the invention, the displacement pump is designed such that the orifices, i. H. the first and the second orifice, from a position in which they are closed, are displaceable into a position in which one of the first orifice and the second orifice is at least partially open and the other of the first orifice and the second orifice is closed. In other words, the orifices are opened from a position in which they are closed, in the movement in the direction of minimum conveying position in mutually different displacement positions. During the displacement, first one of the first and second openings is opened, the further opening finally opening the second opening. In particular, the first and second orifices are displaceable into a further position in which the first orifice and the second orifice are at least partially opened. For example, in the displacement of the mouths from a position in which they are closed, first the first mouth for the suction side and then the second mouth for the pressure side are at least partially opened. Alternatively, first the second orifice for the pressure side and then the first orifice for the suction side can be at least partially opened.

The fact that the orifices are opened at different times during the displacement of the orifices or the bypass channel, prevents the system "out of gear" and becomes unstable.

Preferably, the displacement direction of the displacement from the position in which the first orifice and the second orifice are closed, in the position in which one of the first orifice and second orifice is at least partially open and the other of the first orifice and second orifice closed is equal to the direction of displacement in the further position in which the first orifice and the second orifice are at least partially open. This ensures that the bypass channel or the mouths from a position in which the mouths are closed, need to be moved in only a single direction to open both mouths in succession.

The first mouth can be closed by a particular first wall and the second mouth can be closed by a particular second wall, in particular. The wall may have an offset for the first orifice and an offset for the second orifice defining the wall closing the first and / or second orifices in the direction of displacement. The offset may have an edge, or instead of the offset, an edge may bound the wall. When the bypass duct or the orifices are moved from a position where the wall closes the orifices beyond the offset or edge, the orifice is opened. The portion of the orifice displaced beyond the offset or the edge forms an opening cross-section through which fluid can flow into or out of the bypass channel. For example, a first edge may be provided for the first orifice, with the first orifice being opened with the part pushed beyond the offset or the edge, i. H. forms a first opening cross-section. Alternatively or additionally, a second edge or a second offset may be provided for the second orifice, the second orifice being opened with the part pushed beyond the second offset or the second edge, i. H. forms a second opening cross-section. During operation in the position for minimum volume flow (minimum delivery position), fluid preferably flows from the pressure space via the second opening cross section into the bypass channel and out of the bypass channel via the first opening cross section into the suction space.

There are several ways to constructively achieve a time-delayed opening of the first and second muzzle. In a first example, the first orifice and the second orifice may be axially located at different positions with respect to the direction of displacement. First and second mouth are fixed relative to each other, ie jointly displaceable. Are the first Offset and the second offset or the first edge and the second edge mounted axially in the same position, shifts the mouth, which is arranged in the direction of displacement further forward, first over the edge, whereby this mouth is opened first and the other mouth first will be opened on further shift. In principle, the first and the second offset or the first and second edge can also be arranged on axially different positions for this example. But it should be ensured that one of the mouths is pushed over the edge, while the other mouth is still closed. In general, it can be stated that one of the first and second orifices has a smaller distance measured in the displacement direction relative to the edge assigned to it than the other orifice to its associated edge.

In a second example, the offset or the edge for the first orifice or the offset for the second orifice may be arranged axially at different positions relative to the direction of displacement. The first and second mouths can be arranged axially at the same position or optionally at an axially different position. However, here as well, the distance from one of the first and second mouth to its associated edge is smaller than the distance of the other mouth to its associated edge.

According to a third example, it would be possible to form the mouths of different sizes, wherein the edges and the mouths can each be arranged in the same axial position, wherein it is also preferred that the distance from one of the first and second mouth to its associated edge smaller than the distance of the other mouth to its associated edge.

The bypass channel can z. B. be groove-shaped and have a particular semi-circular cross-section perpendicular to the circumferential direction. Such a groove can, for. B. be generated with a ball cutter. In an advantageous, optionally supplementing the invention optionally aspect of the bypass channel may have a geometry which allows that the bypass channel does not abruptly but gradually, such. B. opens proportionally or disproportionately.

Preferably, the bypass channel is arranged so that it begins to open shortly before reaching the position for minimum flow. The bypass channel is displaceable from a position in which it has its smallest opening to the suction or pressure side, by a displacement path corresponding to the path by which the bypass channel is displaceable to the position for minimum volume flow. During the displacement, the bypass channel opens in response to the displacement with an increasing degree, d. h. that the measure is a function of the displacement. The dimension may be an area or a distance, as explained below. Upon further displacement, the bypass channel can open in the same way to the other from the suction and pressure side, in particular until the minimum delivery position is reached.

The bypass passage is preferably displaceable together with the first orifice and the second orifice. Preferably, the bypass channel is formed together with its first and second orifices on a piston which is displaceable about the displacement and with which in particular the volume flow of the positive displacement pump is adjustable. As a result, the orifice is connected to the feed wheel of the pump, that a displacement of the bypass channel or the mouths or the piston causes a displacement of the feed wheel.

The bypass channel is preferably connected to a delivery wheel of the pump such that a displacement of the bypass channel causes a displacement of the delivery wheel. In particular, the delivery wheel and bypass channel are axially fixedly connected, wherein the delivery wheel is rotatable relative to the bypass channel, for example. Preferably, the bypass channel is formed on the piston, which is displaceable by the displacement and with which in particular the delivery volume of the positive displacement pump is adjustable. Piston and impeller can be connected axially fixed and rotatable relative to each other. In the simplest case, the bypass channel may be a through-bore through the piston, which opens with a first orifice to the pressure side and / or a second orifice toward the suction side to the circumference of the piston.

Preferably, the bypass passage is a groove at least partially circumferential around the circumference of the piston, which groove is open toward the outer circumference of the piston and is sealed by a wall guiding the piston. Generally, the bypass channel is closed by a wall leading the piston, in particular sealed.

For example, at least one wall may be provided, which closes the first orifice, and / or the second orifice and / or the part of the groove-shaped bypass channel facing the outer circumference, ie. H. seal. The at least one wall can be formed by the housing.

Particularly preferably, the bypass channel is designed so that the measure depending on the displacement at least in sections, at least proportionally, ie proportionally or disproportionately increased. Proportional means that the dimension increases linearly as a function of the displacement. The gradient of the measure remains constant during a shift. disproportionately means that the measure does not change linearly in dependence on the displacement, whereby the gradient increases as a function of the displacement. This means that the measure increases more with increasing displacement.

This configuration can advantageously be achieved that the bypass channel is not abruptly but gradually opened during its displacement shortly before reaching the position for minimum flow. The gradual opening avoids instability of the fluid system and unwanted vibrations.

In the case of the prior art mentioned at the outset, which provides a semicircular groove in the cross-section for the bypass channel, the extent to which the bypass channel moves with the displacement toward the position for minimum volume flow decreases with a decreasing gradient, ie. H. disproportionately too, after the bypass channel has opened abruptly.

The design of the bypass channel for a proportional or disproportionate increase in the dimension can, for. B. be achieved in that a particular first wall portion of the preferably groove-shaped bypass channel, which is disposed between an upper edge and a bottom, in particular groove bottom of the bypass channel, transverse to the displacement and / or transverse to the vertical of the displacement. When the first wall portion is straight in a cross-sectional plane which is transverse to the channel longitudinal direction or transverse to the circumferential direction of the piston, a proportional increase in the dimension is achieved. If the first wall section is convex, d. H. From the perspective of the groove is curved convex, a disproportionate increase in the measure is achieved. A disproportionate increase in the degree would be achieved by a semicircular configuration known from the prior art, in which the first wall section is concave from the point of view of the groove. Preferably, the center axis of the piston on which the bypass passage is formed lies in the cross-sectional plane which is transverse to the channel longitudinal direction or transverse to the circumferential direction.

In developments of the invention, it is possible that a combination of straight and convex or concave wall sections is arranged between the upper edge and the bottom of the bypass channel.

Preferably, between the upper edge of the bypass channel and the first wall portion, a further, second wall portion is arranged, which is perpendicular to the displacement and preferably connects to the upper edge and / or the first wall portion. As a result, it can be achieved that the dimension increases suddenly when opening by a desired value and then increases proportionally or disproportionately, or alternatively at a lower rate.

The groove may be symmetrical in cross-section or preferably axisymmetric, wherein the axis of symmetry may be transverse to the displacement, in particular perpendicular to the displacement. Alternatively, the groove-shaped bypass channel may be asymmetric.

In preferred embodiments, the piston comprises a circular arc-shaped elongated recess. The recess is arcuate transverse to the displacement and extends along the piston. The recess thus corresponds to a part of a cylinder jacket surface. The piston has at least one such recess. In versions with two conveyor wheels, the piston has a recess. In versions with three conveyor wheels, the piston may have two such recesses.

In the circular arc-shaped elongated recess engages a correspondingly shaped, d. H. adapted to the recess wall of the positive displacement pump. The wall forms with the recess a sealing gap. The recess on the one hand causes a rotation against the housing of the positive displacement pump and on the other hand, the recess allows a displacement of the piston axially at the level of the feed wheel, since the feed wheel can rotate in the recess.

When shifting the bypass channel in the direction of its position for minimum delivery volume, either only at least one of the orifices or only the part of the groove-shaped bypass channel facing the outer circumference or at least one of the orifices and the part of the groove-shaped bypass channel pointing to the outer circumference can be opened.

If only the mouth is opened, the part of the groove-shaped bypass channel facing the outer circumference can be sealed in all displaced positions of the piston or of the bypass channel by a correspondingly shaped wall, which is preferably formed by the housing of the pump.

In embodiments in which only the outer peripheral part of the bypass passage is opened, a correspondingly shaped wall may seal one or both of the orifices in all the displacement positions of the bypass passage or the piston.

The part of the groove-shaped bypass channel facing the outer circumference and / or the at least an orifice or both mouths are opened by the part of the groove-shaped bypass channel facing the outer circumference or the at least one orifice being displaceable by a displacement so as to be displaceable from a displaced position in which it is closed opens to the suction side or to the pressure side with an at least proportionally magnifying degree.

The opening of the part of the groove-shaped bypass channel pointing to the outer circumference can be achieved by virtue of the positive displacement pump having an edge which axially delimits the wall which seals the part of the groove-shaped bypass channel facing the outer circumference. The bypass channel opens with its over the edge of the wall pushed out part.

The edge which seals the wall which defines the part of the groove-shaped bypass channel facing the outer circumference limits this wall. The edge is part of an offset or heel which opens into the suction space or the pressure space, whereby on one side of the edge the wall and on the other side of the edge is a fluid space. The bypass channel is formed between its upper edge and its bottom, in particular in its first wall section, so that the distance measured perpendicular to the displacement direction increases at least proportionally from the edge to the bypass wall, depending on the displacement path of the bypass channel.

In preferred embodiments, at least one of the circumferentially facing ends of the bypass channel may not open into the circular arc-shaped elongated recess or be separated from the recess by means of a separating section which is arranged between one end of the bypass channel and the recess. Regarding the separating section is on the DE 10 2008 025 346 A1 referenced, where the advantage of such a configuration is described, namely that the danger of hooking or jamming and the wear is reduced. For example, one of the ends can not open into a recess, while the other end of the bypass channel opens into a recess. Alternatively, both ends of the bypass channel can open into the recess or not open. Alternatively or additionally, a single circular arc-shaped elongated recess may be provided on the piston, wherein at least one end of the bypass channel opens into this recess or does not open. In embodiments with two circular arcuate elongated recesses, one end of the bypass channel may open into the one recess or not open and the other end open into the other recess or not open. In particular, two bypass channels may be provided, which are arranged circumferentially opposite each other. In particular, one end of the bypass channel may form the first mouth and the other end the second mouth.

In preferred embodiments, the bypass channel may open into the at least one recess or to the outer circumference of the piston outside the recess. For this purpose, the first orifice for the pressure side and / or the second orifice can serve for the suction side. The first orifice and / or the second orifice are configured such that when the bypass channel is displaced from a position in which the first orifice and / or the second orifice are closed by the wall assigned to it, the first orifice faces the pressure side and / or or opens the second mouth to the suction side with an opening section which increases at least proportionally.

The wall closing off the first orifice and / or the wall closing off the second orifice may each have the edge, which is preferably part of an offset or shoulder connected to the suction or pressure space. During the displacement of the mouth from a position in which the wall closes the mouth associated with it, beyond the edge, the part of the mouth, which is displaced beyond the edge, forms the opening cross-section. The opening cross-section may, for example, have a triangular or trapezoidal surface, it being preferred that this surface is bordered on at least one, preferably two sides of the wall and on one or two sides of the piston.

The invention further relates to a system for supplying an aggregate, preferably a piston internal combustion engine, with a working fluid or lubricating fluid, the system comprising the positive displacement pump and the unit.

The invention has been described with reference to several embodiments. In the following, a particularly preferred embodiment will be described with reference to figures. The features disclosed in this case further advantageously form the invention, in particular also with the features described above. Show it:

1 a schematic diagram of a positive displacement pump in an arrangement with a maximum flow rate,

2 the sketch 1 with a minimum volume flow,

3 a control unit for the device of the 1 and 2 .

4 a schematic diagram of another embodiment of a positive displacement pump in a side view and a plan view,

5 a preferred modification of the bypass channel,

6 preferred modifications of the bypass channel,

7 Another preferred modification of the bypass channel,

8th yet another preferred modification of the bypass channel,

9 Yet another preferred modification of the bypass channel and

10 an arrangement according to the invention, which allows a time-delayed opening of a bypass channel.

The 1 and 2 show an external gear pump with a first gear 7 and a second gear 6 , The first gear 7 is powered by a drive, such. B. the crankshaft of a motor driven (not shown). Because the first gear 7 with the second gear 6 in a meshing engagement, the second gear becomes 6 from the rotational movement of the first gear 7 taken. First and second gear 6 . 7 rotate in opposite directions of rotation, so that at their Kämmstelle their Wälzkreisdurchmesser roll on each other.

The first gear 7 is on both ends of a wall of the housing 15 axially framed with the housing 15 form a sealing gap. The first gear 7 is over part of the circumference of a wall of the housing 15 entwined. The outer diameter of the first gear 7 or the outer surfaces of the tooth tips form with the housing 15 a sealing gap.

The second gear 6 is also over part of its circumference from the housing 15 entwined, whereby the outer diameter of the second gear 6 , In particular the outer surfaces of its tooth tips a sealing gap with the housing 15 form. The second gear 6 is rotatably mounted on a shaft, which is a control piston 3 and a pressure piston 13 connects to each other at a defined distance, which is approximately the width of the second gear 6 plus the thicknesses of the sealing gaps, which are the end faces of the second gear 6 with the control piston 3 and the plunger 13 form, corresponds.

The housing 15 and the pistons 3 . 13 form a pump chamber 1 , Below the combing point of the two gears 6 . 7 is in the pump chamber 1 a suction chamber and above the combing a pressure chamber formed. The pump has connections for a supply of lubricating oil to the suction chamber and for a discharge of the lubricating oil from the pressure chamber in the direction of the engine.

The control piston 3 has a circular cross-section and is slidable in a control chamber 2 added. The outer circumference of the cylindrical control piston 3 forms with the corresponding cylindrical inner circumference of the control chamber 2 a sealing gap 8th , The diameter of the control piston 3 corresponds approximately to the outer diameter of the second gear 6 ,

On the control piston 3 opposite side of the second gear 6 there is a piston 13 , which is referred to below for clarity as a pressure piston. The pressure piston 13 is along the axis of rotation of the second gear 6 slidable in a pressure chamber 9 arranged. The outer circumference of the pressure piston 13 forms with the wall of the pressure chamber 9 a sealing gap 17 , The pressure piston 13 is cylindrical over most of its circumference and has an outer diameter which is approximately equal to the outer diameter of the second gear 6 equivalent. Furthermore, the pressure piston 13 a part-cylindrical recess 14 having a radius approximately equal to the radius of the outer diameter of the first gear 7 corresponds, wherein the recess 14 from the peripheral side to the center axis of the pressure piston 13 extends. The distance of the recess 14 from the central axis of the pressure piston 13 or the axis of rotation of the second gear 6 is approximately the distance between the axes of rotation of the first and second gear 6 . 7 minus the radius of the outer diameter of the first gear 7 , The recess 14 allows it in the 3 and 4 separately shown unit of pressure piston 13 , second gear 6 and control piston 3 from the in 1 shown maximum conveying position in which first and second gear 6 . 7 in complete axial overlap, in an in 2 to move shown minimum conveying position, in which the first and second gear 6 . 7 only partially overlap axially. The recess 14 forms with the in 2 shown position a sealing gap with the outer diameter or the outer surfaces of the tooth tips of the first gear 7 ,

The pressure piston 13 has in particular on its cylindrical outer diameter a groove 18 which can also be referred to as short-circuit groove, bypass groove or bypass channel. The groove 18 extends in the circumferential direction of the cylindrical portion of the pressure piston 13 , The groove 18 becomes, like in the 1 and 2 can be seen, circumferentially from the wall, with the pressure piston 13 the sealing gap 17 forms, sealed. Both sides of the groove 18 forms the cylindrical outer diameter of the pressure piston 13 with the wall a sealing gap 17 , The wall is from the housing 15 educated. The groove 18 leads to the recess 14 out with mouths 19d . 19s , The mouths 19d . 19s are arranged so that one of these mouths 19d in the pressure room and the other of the mouths 19s can move into the suction chamber. The mouths 19d . 19s are in most of the conveying positions, in particular in the maximum conveying position of the second gear 6 from the pressure piston 13 leading wall of the housing 15 sealed ( 1 ). In the position of the second gear 6 for a minimum volume flow is the pressure piston 13 moved so far that the groove 18 , in particular their mouths 19d . 19s from the seal with the housing 15 is, causing the mouths 19d . 19s to the first gear 7 open out. One of the mouths 19d flows into the pressure chamber, the other one of the mouths 19s flows into the suction chamber 21 , As a result, in the position of the pump for a minimum volume flow fluid from the pressure chamber via the groove 18 flow back into the suction chamber. Thus, the volume flow delivered by the pump can be lowered even further.

The pressure piston 13 and the control piston 3 point to their second gear 6 pointing end faces relief pockets 16 on, which provide better pressure distribution in the oil during the conveying operation.

The pressure chamber 9 is preferably applied alternately with a pressure and relieved again, which corresponds to the pressure from the main gallery of the engine. For this purpose, the main gallery of the engine is fluid leading with a feeder 10 or the pressure chamber 9 connected. That in the pressure chamber 9 contained fluid or oil exerts one of the pressure chamber 9 facing end face of the pressure piston 13 dependent force on the pressure piston 13 out.

The control chamber 2 is also acted upon by a pressure, preferably the pressure from the main gallery of the engine. Through the feeder 11 For example, the amount of fluid contained in the control chamber or the pressure can be varied. Through the feeder 11 can the control chamber 2 Fluid supplied or fluid are discharged. The fluid supply and discharge can through a valve 12 be controlled, which has 3 connections and 2 switch positions in the example shown, so it can be referred to as a 3/2-way valve. About the valve 12 is the control chamber 2 fluid leading to the main gallery ( 1 ) or connectable to a storage container ( 2 ).

When the pressure chamber 9 and the control chamber 2 are each acted upon by the pressure of the main gallery, shifts the in 3 shown unit in the in 1 shown position, as to the control chamber 2 indicative face of the control piston 3 larger than the pressure chamber 9 indicative end face of the pressure piston 13 , whereby the fluid of the control chamber 2 a greater force on the in 3 shown unit 3 . 6 . 13 exerts as the fluid of the pressure chamber 9 , Will the valve 12 switched so that the control chamber 2 instead of with the main gallery with a reservoir, as generally preferred the oil pan is fluidly connected, the permanently applied pressure of the pressure chamber 9 in the 3 shown unit in the in 2 Move the position shown, in the control chamber 2 contained oil is fed into the reservoir.

Because in the pump chamber 1 , in particular in the suction chamber, a higher pressure prevails than in the control chamber 2 gets oil from the pump chamber 1 over the sealing gap 8th in the direction of the control chamber 2 pressed. This leakage oil can be harmful to the control of the pump. Therefore, according to the invention one to the sealing gap 8th open channel into the control piston 3 brought in. The channel 4 is arranged so that between it and the end faces of the control piston 3 in each case a sealing gap is located. In particular, the channel 4 be arranged approximately in the middle between the two end faces. The channel 4 runs annular over the particular entire circumference of the cylindrical control piston 3 ,

The channel 4 is by means of a fluid guide section 5 with the pump chamber 1 , in particular connected to the suction chamber or the suction side. By means of the canal 4 that's about the sealing gap 8th trapped flowing leakage oil and the fluid guide section 5 in the pump chamber 1 guided. The in 3 shown fluid guide section 5 extends approximately parallel to the axis of rotation of the second gear 6 and is to the sealing gap 8th open. How out 3 it can be seen, the fluid guide section opens 5 advantageous in one of the discharge pockets 16 , In the particular arranged in the suction discharge pocket 16 There is a relatively constant pressure, ie that by the teeth of the rotating impeller 6 On the fluid pressure fluctuations are less strong or are reduced.

In 4 another embodiment of a pump is shown. The pump includes in addition to the first gear 7 and the second gear 6 a third gear 27 , The second gear 6 stands both with the first gear 7 as well as with the third gear 27 in a meshing engagement. As best in the side view of the 4 can be seen, a suction chamber and a pressure chamber is formed at each Kämmstelle, by means of the Kämmstelle of are separated from each other, ie lie opposite. There where the teeth of the gears 6 . 7 . 27 enter the combing point is a pressure chamber, where they leak from the combing a suction chamber. Furthermore, a pressure chamber is arranged next to the suction chamber, which are separated from each other without a comb, such. B. by means of a wall, with the circumference of the gear 6 forms a sealing gap.

From a suction chamber, fluid from the meshing gears 6 . 27 ; 6 . 7 be promoted both to the opposite pressure chamber and to the adjoining pressure chamber. For example, fluid from the suction chamber, which is at the Kämmstelle the second and third gear 6 . 27 opens, with a partial flow over the third gear 27 to the opposite pressure chamber, to the meshing point of the gears 6 . 27 opens, and with a further partial flow over the second gear 6 to the adjacent pressure chamber, which at the Kämmstelle of the first and second gear 6 . 7 flows, funded. The same principle applies to the fluid of the suction chamber, which is at the meshing point of the gears 6 . 7 opens, applicable, ie it becomes a partial flow over the first gear 7 to the at the Kämmstelle the gears 6 . 7 opening, opposite pressure chamber and a partial flow over the second gear 6 to the at the Kämmstelle the gears 6 . 27 promoted opening, adjacent pressure chamber.

The first gear 7 and the third gear 27 may be substantially axially fixedly received in the housing, while the second gear 6 relative to the first and third gears 7 . 27 is axially displaceable, as in the plan view 4 indicated by the arrow direction. For the execution 4 , in particular for the design of the control piston 3 including channel 4 and plunger 13 including groove 18 will be on the description to the 1 to 3 and 5 to 9 directed. However, the pressure piston is 13 opposite to in the 1 to 3 changed execution shown. Through the additional third gear 27 has the pressure piston 13 two mutually opposite recesses, which like the recess 14 from the 3 and 4 are designed. The pressure piston 13 has a recess 14 for the first gear 7 and on the circumference opposite another second recess for the third gear 27 on. The grooves 18 flow with their mouths 19 in the position for the minimum flow in the juxtaposed suction and pressure chambers. For example, fluid from the at the Kämmstelle 6 . 7 opening pressure chamber to the at the Kämmstelle 6 . 27 opening suction space over the groove 18 be dissipated. Fluid from the to the Kämmstelle 6 . 27 opening pressure chamber can have another groove 18 to the at the Kämmstelle 6 . 7 be discharged discharging suction. By returning the fluid of the pressure chambers, the flow rate of the pump can be reduced.

5 shows for in the 1 to 4 illustrated positive displacement pump a pressure piston 13 with a modified bypass channel 18 , 5 shows the pressure piston 13 in a position for minimum flow, wherein the pressure piston 13 has been moved by the displacement x (see arrow direction).

At the device off 5 has the pressure piston 13 a groove extending over part of the circumference 18 and a circular arc-shaped elongated recess 14 on, with the groove 18 mouths 19s for the suction side and 19d for the pressure side, the outside of the recess 14 to the outer periphery of the pressure piston 13 lead. 8th shows a similar embodiment, however, the groove 18 an estuary 19s for the suction side and 19d for the print side, with the mouths 19d . 19s into the recess 14 lead.

The groove 18 can be opened in different ways when moving in the direction of its minimum flow position. How best 6 can be seen, the pressure piston 13 on the housing 15 , in particular on the housing wall 15a be guided. The housing wall 15a closes the part of the groove-shaped bypass channel facing the outer circumference 18 when the pressure piston 13 z. B. is in a maximum conveying position. Will the pressure piston 13 shifted by the displacement x in the direction of minimum conveying position, the groove opens 18 with the part that over the edge 25d for the print side 22 and 25s for the suction side 21 was pushed. The edge 25d limits the wall 15a in the area of the pressure side 22 and the edge 25s limits the wall 15a in the area of the suction side 21 , Out of the design 6 the groove opens 18 at least proportionally. The distance h measured perpendicular to the displacement direction x between the wall section 18p that is between a top edge 18o and a groove bottom 18g the groove 18 is changed proportionally or disproportionately with increasing displacement x. The distance h between the edge 25d . 25s and the wall section 18p changes linearly when the wall section 18p is straight, as seen from the cross-sectional view 6 can be seen, and increases disproportionately with increasing displacement x when the wall portion 18p is convex shaped, as with the dashed line in 6 is indicated. This ensures that the groove 18 opens gradually and not abruptly, reducing the risk that the fluid system becomes unstable and tends to vibrate.

In the 7 The embodiment shown essentially corresponds to 6 , wherein between the direction of displacement x inclined and inclined to the vertical of the displacement direction x wall portion 18p and the top edge 18o the groove 18 a perpendicular to the direction x arranged groove portion 18v is arranged, which causes the groove 18 at the beginning depending on the length of the groove portion 18v opens suddenly and then proportionally ( 7 ) or disproportionately (dashed line off 6 ) opens.

The groove 18 is asymmetrical with respect to the vertical to the displacement direction x and has the wall portion 18p opposite a groove portion 18h on, which is arranged transversely, in particular perpendicular to the displacement direction x.

9 shows another way, like the groove 18 to the suction room 21 or to the pressure room 22 can be opened. The housing 15 has an edge 26s for the suction side and 26d for the pressure side, wherein during the displacement of the pressure piston 13 about the displacement x in the direction of minimum conveying position of the over the edges 26s . 26d pushed part of the estuary 19d for the print side and 19s forms a cross-sectional area A for the suction side, which can also be referred to as opening cross-section. The in 9 formed as an edge wall section 18p can be straight or convex, as in 6 indicated by the dashed line. As the displacement x increases, the opening cross section A increases proportionally or disproportionately. The possibility the mouth 19 as in 9 indicated to open, applies both to the remarks 5 and 8th ,

10 shows for in the 1 to 4 illustrated positive displacement pump a pressure piston 13 , which is displaceable in a position for minimum flow, with a first orifice 19s for a suction side 21 the pump in front of a second orifice 19d for the print side 22 the pump opens when the pressure piston 13 is moved to the position for minimum flow. The mouths 19s and 19d are defined by the circumferentially facing ends of the groove 18 educated. Regarding the geometry of the groove 18 out 10 will depend on the execution of the 5 to 7 directed. Basically, the groove 18 out 10 but also like in 8th . 9 specified, ausgestaltbar.

Notwithstanding the comments from the 5 to 9 is for the first estuary 19s a first edge 35s provided the tasks of the edge 25s or 26s from the 5 to 9 takes over. Further, a second edge 35d for the second estuary 19d provided the tasks of the edge 25d or 26d takes over. The first edge 35s and the second edge 35d are arranged with respect to the longitudinal axis M at different axial positions. The mouths 19s . 19d are arranged with respect to the axis M at the same axial position. During the displacement of the pressure piston 13 from a position where the first estuary 19s and the second estuary 19d from the case 15 are closed, ie sealed to the displacement X in the direction of a position for minimum flow, takes the pressure piston 13 an intermediate position in which the first muzzle 19s partly over the edge 35s being pushed, being over the edge 35s shifted part of the estuary 19s the opening to the suction side 21 forms. In this in 10 shown intermediate position is the second orifice 19d from the case 15 locked. Therefore, the groove 18 in the in 10 shown position only with the suction side 21 fluid leading connected, ie with the pressure side 22 unconnected.

In a further shift of the pressure piston 13 in the direction of its position for minimum flow becomes the mouth 19d over the edge 35d pushed, causing the over the edge 35d also shifted part of the estuary 19d an opening cross-section to the pressure side 22 forms, causing fluid from the pressure side 22 in the groove 18 and out of the groove 18 to the suction side 21 towards traceable.

Due to the different opening times of the mouths 19s . 19d an instability of the system is avoided.

Claims (15)

Positive displacement pump, in particular gear pump, comprising a bypass channel ( 18 ), via the fluid from a pressure side ( 22 ) of the pump to a suction side ( 21 ) of the pump is feasible and the first muzzle ( 19s ), which with the suction side ( 21 ) is connectable, and a second mouth ( 19d ), with the pressure side ( 22 ) is connectable, wherein the positive displacement pump is designed so that the mouths ( 19s . 19d ) are displaceable from a position in which they are closed into a position in which a first mouth ( 19s ) and second mouth ( 19d ) is at least partially open and the other from the first mouth ( 19s ) and second mouth ( 19d ) closed is. Positive displacement pump according to claim 1, characterized in that the first and second mouths ( 19s . 19d ) are displaceable in a further position in which the first mouth ( 19s ) and second mouth ( 19d ) are at least partially open. Positive displacement pump according to claim 2, characterized in that the displacement direction (X) of the displacement from the position in which the first orifice ( 19s ) and second mouth ( 19d ) are locked, in the position in which the first one Estuary ( 19s ) and second mouth ( 19d ) is at least partially open and the other from the first mouth ( 19s ) and second mouth ( 19d ) is closed, equal to the direction of displacement (X) in the further position in which the first mouth ( 19s ) and second mouth ( 19d ) are at least partially open is. Positive displacement pump according to one of the preceding claims, characterized in that the first orifice ( 19s ) from a wall ( 15 ) and / or the second mouth ( 19d ) from a wall ( 15 ), in particular sealed, and characterized by an offset or an edge ( 35s . 35d ), which (s) the mouth ( 19s . 19d ) closing wall ( 15 ), whereby the displacement of the mouths ( 19s . 19d ) from a position in which the wall ( 15 ) the mouth ( 19s . 19d ), via the offset or the edge ( 35s . 35d ), which is offset by the offset or the edge ( 35s . 35d ) shifted out part of the mouth ( 19s . 19d ) forms an opening cross-section (A, H). Positive displacement pump according to one of the preceding claims, characterized in that the first orifice ( 19s ) and the second mouth ( 19d ) are arranged axially at different positions with respect to the direction of displacement (X). Positive displacement pump according to one of the preceding claims, characterized in that the offset or the edge ( 35s ) for the first estuary ( 19s ) and the offset or the edge ( 35d ) for the second mouth ( 19d ) are arranged axially at different positions with respect to the direction of displacement (X). Positive displacement pump according to one of the preceding claims, characterized in that, when displaced, the closed first orifice ( 19s ) and / or the closed second mouth ( 19d ) to the suction side ( 21 ) or to the print side ( 22 ) opens with an enlarging opening cross-section (A, h), wherein the opening cross-section (A, h) at least in sections at least proportionally, depending on the displacement (x) at least proportionally, in particular proportionally or disproportionately increased. Positive displacement pump according to one of the preceding claims, characterized in that the bypass channel ( 18 ) together with the first mouth ( 19s ) and the second mouth ( 19d ) is displaceable. Positive displacement pump according to one of the preceding claims, characterized in that the bypass channel ( 18 ) and the mouths ( 19s . 19d ) on a piston ( 13 ) are formed, which is displaceable about the displacement path (x) and with which in particular a volume flow of the positive displacement pump is adjustable. Positive displacement pump according to one of the preceding claims, characterized in that the mouth ( 19s . 19d ) so with a conveyor wheel ( 6 ) is connected to the pump, that a displacement of the bypass channel ( 18 ) and the mouth ( 19s . 19d ) a shift of the conveyor wheel ( 6 ) causes. Positive displacement pump according to one of the preceding claims, characterized in that the bypass channel ( 18 ) around the circumference of the piston ( 13 ) is at least partially circumferential groove-shaped channel which is open to the outer periphery and by a piston ( 13 ) leading wall ( 15 ) is sealed. Positive displacement pump according to one of the preceding claims, characterized in that at least one of first and second orifices ( 19s . 19d ) transverse to the direction of the bypass channel ( 18 ), with which it extends in the circumferential direction. Positive displacement pump according to one of the preceding claims, characterized in that the piston ( 13 ) an elongated, circular arc-shaped recess ( 14 ) into which the first and / or the second orifice ( 19s . 19d ). Positive displacement pump according to one of claims 1 to 12, characterized in that the first and / or second mouth ( 19s . 19d ) to the circumference of the piston ( 13 ) and in particular not in an elongated, circular arc-shaped recess ( 14 ) of the piston ( 13 ) opens. Positive displacement pump according to one of the preceding claims, characterized in that the pump is a first delivery wheel ( 7 . 27 ) and a second conveyor wheel ( 6 ), which are in a conveying engagement with each other, wherein the second conveyor wheel ( 6 ) relative to the first conveyor wheel ( 7 . 27 ) is displaceable.

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