EP1013926B1 - Hydraulic positive displacement machine, in particular pump - Google Patents

Description

The invention is based on a hydraulic displacement machine, in particular of a positive displacement pump, which the characteristics from the Preamble of claim 1 has.

A displacement machine designed as an internal gear pump Art is shown for example in DE 43 22 240 C2. At this Known internal gear pump close the pinion and the ring gear a crescent-shaped pump chamber in which there is an approximately crescent-shaped Filler is located with which the high pressure area and the low pressure area of the pump along the tooth tips of the two Gears are sealed against each other. For an effective Sealing even with larger pressure differences between the high pressure area and the low pressure area is the filler divided longitudinally. The gap between the two filler pieces becomes like this pressurized that the two filler parts each with one small excess force pressed onto the tooth tips of the gears become.

The high pressure area and the low pressure area of a gear machine must also face each other at the front of the gears be sealed. If you want the gear machine even at higher ones Use pressure and a very effective seal have, so are also used for the sealing on the end faces of the Gears used components with a certain excess force be pressed against the gears. There is a pressure field for this on the back of the components facing away from the gears mostly referred to as axial sealing washers, with the high pressure area connected to the gear machine.

So far, the ones pressed against the gears for sealing Components materials used, especially at high speeds the internal gear machine, at high pressure or at high Temperatures of the working medium are subject to abrasive wear are. The excess force with which the components to the Gears are pressed, is essentially different by preserve large areas where the pressure acts and therefore increases with increasing pressure. High speeds and high temperatures can lead to poor lubrication between components and gears. The abrasion arrives in the hydraulic circuit and can damage and malfunction cause.

Basically, it is possible to reduce abrasion by installing a filter to be removed from the hydraulic medium. Plants of the so-called Stationary hydraulics are, as it were, standard with a filter equipped. However, there are also use cases, in particular in the automotive sector, where you don't want to use filters. such Filters gradually become clogged, thereby increasing pressure losses in the hydraulic circuit and must be replaced. Not Finally, the space for a filter and its accessibility also play would be required, and the additional cost in automotive engineering a role.

There is also wear on the components sliding against each other not always compensated for by a kind of re-adjustment, so that the internal leakages in the machine increase and Efficiency losses increase.

In order to reduce the wear of the gears, JP 08-159044 A suggested the gears from a wear-resistant To produce sintered material.

Problems with the wear of components sliding against each other a displacement machine occur regardless of certain operating parameters like high speed or high temperature then when the operating medium itself has poor lubricating properties Has. Such operating media are, for example, fuels, like gasoline or diesel for internal combustion engines. For the High-pressure delivery of such fuels are mainly piston pumps, especially radial piston pumps used.

A radial piston pump designed for high-pressure delivery Displacement machine of the generic type provided by fuel Art is known for example from DE 42 13 798 A1. at Such a radial piston pump, on the one hand, the displacement parts Piston and cylinder together. On the other hand, one of the slides two displacement parts or a slide shoe held on it on one Eccentric ring through which the movement of one displacement part is forced in the delivery stroke.

To reduce wear on the components sliding on each other, is proposed in US 3,808,659 A, in the cylinder use a cylinder sleeve made of hardened sintered material.

The invention is therefore based on the object of a hydraulic displacement machine, which has the features from the preamble of claim 1, evolve so that the wear on the sliding against each other Components is low. In particular, when using a gear pump very little wear-related in an automobile and especially in the transmission area Particles are released into the hydraulic medium and onto the Installation of a filter or at least no filter replacement can be. When using a piston pump to deliver fuel despite the poorly lubricating operating medium, wear on each other sliding components to be low, so that no abrasion particles the injection nozzles clog or make it stiff and thus a failure of the Pump by eating the displacement parts or by excessive wear on the Lifting element is avoided.

This task is performed on a positive displacement machine with the characteristics from Preamble of claim 1 solved according to the invention in that at least one of the two components is hardened at least on the surface and from Sintered material consists mainly of ferrite and an additional component contains to improve the sliding properties. By mixing curable Ferrite for component and wear resistance with one component Improvement of the sliding properties arises after sintering, hardening and a grinding process, through which the component its exact dimensions and a receives a smooth surface, a component that also lacks lubrication in operation without tolerates substantial abrasion. As a result, the wear on and the particle release very low due to the displacement machine.

Advantageous embodiments of a displacement machine according to the invention can one can see from the subclaims.

According to claim 2, an internal gear machine is preferred Component made of sintered material, which is used to seal a high pressure area from a low pressure area along the tooth tips or along the End faces of the gears.

In a hydraulic piston machine, it is favorable if according to claim 3 at least one of the two displacement parts of a displacement unit, Piston and cylinder, from the hardened at least on the surface Sintered material is made. It is also advantageous for the pair of displacement part lifting elements at least a part made of the sintered material. there be expressly pointed out that a displacement part or the lifting element can also be formed in several parts, and only one of these parts, namely the Counterpart sliding, made of sintered material.

The component consisting of the sintered material is preferred 7 hardened by nitriding, with an edge zone of the component at temperatures around 500 degrees Celsius is enriched with nitrogen by the component a nitrogen releasing medium, e.g. B. is exposed to a gas stream.

Nitriding per se is a well known method for the superficial Hardening of components so that there is no need to go into them here.

According to, the component contains components that improve the sliding properties claims 8 to 10 preferably copper, molybdenum disulfide and Graphite. The combination of these makes the requirements particularly good Components met with each other in the proportions indicated as preferred.

A first embodiment designed as an internal gear pump and a Radial piston pump designed second embodiment of an inventive hydraulic displacement machine are shown in the drawing. The invention will now be explained in more detail with reference to the figures of this drawing.

Figur 1

das erste Ausführungsbeispiel in einem Schnitt durch die von den beiden Achsen der Zahnräder aufgespannten Ebene,

Figur 2

einen Schnitt entlang der Linie II-II aus Figur 1 und

Figur 3

das zweite Ausführungsbeispiel in einem Schnitt senkrecht durch die Antriebswelle.

Show it

Figure 1

the first embodiment in a section through the plane spanned by the two axes of the gear wheels,

Figure 2

a section along the line II-II of Figure 1 and

Figure 3

the second embodiment in a section perpendicular through the drive shaft.

The internal gear pump according to Figures 1 and 2 has a housing 10, the consists of an annular middle part 11, which radially encloses a pump chamber 12, a first cover part 13 and a second cover part 14. The two cover parts 13 and 14 delimit the pump chamber 12 in axial direction. The middle part 11 engages over the two cover parts 13 and 14 in Area of an outer recess 15. The cover part 13 has one through bore 16 into which a plain bearing 17 is pressed. With the hole 16 aligns a blind hole 18 of the cover part 14, in which also a plain bearing 17 is pressed. In the two plain bearings 17 there is a drive shaft 19 of the pump stored. An externally toothed pinion 20 is inside the pump chamber 12 attached to the drive shaft 19 or made in one piece therewith. The pinion is located within an internally toothed ring gear 21, the axis of which is eccentric is arranged to the axis of the crack 20 and that on its outer circumference is mounted in the middle part 11 of the housing 10. In the area on both sides spanned by the two axes of the pinion 20 and the ring gear 21 Mid-plane 22 intermesh the two gears, between which there are otherwise a crescent-shaped free space 23 is located.

This free space 23 is approximately half filled by a filler 30. For one high efficiency of the pump is between the filler 30 and the sprockets A good seal of the pinion and ring gear is necessary. That is why Filling piece 30 in two parts from a sealing segment 31 and a segment carrier 32 built up. The sealing segment 31 is adjacent to the ring gear 21 and can with a small excess force pressed against the tooth tips of the ring gear 21 become. In addition, the sealing segment 31 becomes hydraulic when the pump is operating also pressed against a flat 33 of a stop pin 34. The segment carrier 32 is hydraulic in operation with an inside and with excess power to the ring gear of the pinion 30 and also against the flat 33 of the stop pin 34 pressed.

The segment carrier 32 and the sealing segment 31 are made by two leaf springs 35 pressed apart, which are in two axially extending and to the sealing segment 31 open grooves 36 of the segment carrier 32 are. The two grooves 36 take up a sealing roller 37 in addition to a leaf spring 35 of the respective leaf spring 35, but also in operation hydraulically to the gap between the segment carrier 32 and the sealing segment 31 is pressed. Through the two sealing rollers 37 is within between the segment carrier 32 and the Sealing segment 31 existing gap against the high pressure area P and against the low-pressure area S of the pump sealed pressure chamber, which is to be pressurized, approximately half the operating pressure corresponds to the pump. It is therefore each with a milling 38 in each the end face of the sealing segment with a pressure build-up area on the ring gear of the ring gear 21, in which there is approximately half the operating pressure. in the Operation of the segment carrier 32 and the sealing segment 31 are therefore except the leaf springs 35 in the area in front of the sealing roller 37 closest to the stop pin 34 also squeezed apart by a hydraulic pressure. This pressure corresponds between the two sealing rollers 37 a fraction of the operating pressure, while it is between the end of the sealing segment distant from the stop pin 34 32 and the one sealing roller 37 corresponds to the operating pressure.

The stop pin 34 crosses the free space 23 in the central plane 22 and is in two aligned blind holes 39 of the cover parts 13 and 14 on both sides the pump chamber 12 rotatably mounted. The axial extent of the filler 24 agrees with the axial extent of the two gear wheels 20 and 21 match.

For a high efficiency of the pump is also on the stimulated parts of the gears 20 and 21, i.e. axially, a good seal between the high pressure side P, which can be delimited by an area of the pump chamber 12 in which the filler 30 is located and in the two following the filler Gradually meshing gears, and the low pressure side S the pump is necessary. For a good axial seal is between the gears 20 and 21 and each cover part 13 or 14 an axial sealing washer 45 is arranged, that of a pressure that is in between you and the corresponding one Cover part 13 or 14 existing pressure field 46 prevails, with a certain Excess force is axially pressed against the gears 20 and 21. Every axial sealing washer 45 closely surrounds the drive shaft 19 and the stop pin 34 and is thereby in position in a plane perpendicular to the axis of the drive shaft 19 secured. A pressure field 46 is defined by a recess in the cover part 13 or 14 educated. As can be seen from the dashed line in FIG. 2, it has one semi-crescent-shaped shape and extends approximately from the foot of the filler 30 am Stop pin 34 from up to close to the central plane 22.

As can be seen from Figure 2, an axial sealing washer 45 essentially covers only the high pressure side of the pump while the low pressure side is kept clear so that there is no friction between the gears and an axial sealing washer can take place, which would lower the efficiency of the pump.

At diametrically opposite points open into the pump chamber 12 Suction channel 48 and a pressure channel 49, the diameter of the suction channel 48 is larger than the diameter of the pressure channel 49. The ring gear 21 has in the Tooth gaps radially through holes 50 through from the inside, through which a hydraulic fluid from the suction channel 48 into the free space 23 and from can get there into the pressure channel 49.

The pump shown is constructed in such a way that the pinion 20, in operation according to FIG. 2 considered, must be driven clockwise. The ring gear 21 also rotates then turn clockwise. Hydraulic fluid in the tooth gaps travels along the filler 30 with the tooth gaps and reaches the tooth meshing area of the two gears. There the hydraulic fluid through the Bores 50 of the ring gear 21 are displaced into the pressure channel 49. At the same time through other holes 50 and over the end faces of the gears hydraulic fluid is sucked away from the suction channel 48 into the free space 23.

The gears of the pump shown are hardened, especially the teeth do not wear out and a high volumetric efficiency is achieved. In order to in operation also the wear on the seal between the high pressure area P and the low pressure area S serving components, namely the Sealing segment 31, the segment carrier 32 and the axial sealing washers 45 low remains and particles do not get into the hydraulic fluid circuit Clogged flow openings or in narrow guide gaps advised and to the stiffness or failure of the brought together Could lead parts, the components mentioned are hardened on their surface. They consist of a sintered material, the starting mixture of 15% to 25% Copper, 2.5% to 3% molybdenum disulfide, about 0.4% graphite and the rest iron in Contains form of ferrite. The latter is the one component that will be hardened can. This is done primarily by gas nitriding, a well known one Method. The other components of the starting mixture are used for sintering compared to a pure ferrite mixture to improve the sliding properties of the to improve finished components. After sintering and gas nitriding the components are still ground and therefore very precisely to the shape of the counter surfaces adapted to the gears. Thus the components tolerate the sealing segment, Segment carriers and axial sealing plates also lack lubrication, in particular at high pressures, high speeds or high temperatures of the hydraulic fluid can occur without significant abrasion.

The radial piston pump according to Figure 3, which is used to deliver fuel in one Automobile is intended, has a pump housing 52 in which a central receiving space 53 for receiving a drive shaft, not shown with an axis 54 driven eccentric pin 55 on which an eccentric ring 56 is rotatably mounted. These are evenly distributed around the axis 54 three displacement units 57 assigned, each of which is in a radial bore 58 of the pump housing 52 is located. Corresponding to the three displacement units 57 is the eccentric ring 56 with three flats distributed around the circumference 59 provided, on each of which a slide shoe 60 of a displacement unit 57 is supported is. Due to the force lying on the flats 59 Sliding shoes 60, the eccentric ring 56 is held so that it rotates of the eccentric pin 55 can not follow freely, but while maintaining its orientation is moved on a circle, i.e. a translational one Circular motion. The sliding shoes 60 thus slide during operation back and forth on the flats 59.

Each displacement unit 57 has a cylinder 64 with a cylinder bore 65, in which a slide shoe 60 is pressed to the stop. Through every slide shoe pass through channels that fill the cylinder bore 65 via a suction valve Allow 66 from the recording room 53. The cylinder 64 is over a Compression spring 68 biased towards the flat 59, the compression spring on the one hand on an outer shoulder of the cylinder 64 and on the other hand on one Screw plug 70 is supported, which closes a radial bore 58.

In a central blind bore of the screw plug 70, the end section is one Piston 74 is pressed into the cylinder bore, projecting far beyond the screw plug 70 65 immersed and that together with the cylinder 64 and the sliding block 60 limits a volume-variable work space.

In operation, the cylinder 64 executes a radial stroke movement. Except the relative Sliding movement between the slide shoe 60 and the eccentric ring 56 takes place in operation, a relative sliding movement between the cylinder 64 and the Piston 74 instead.

So that the wear on each other caused by the sliding movements adjacent components remains low, is at least one of these components Made from a sintered material that is predominantly ferrite and an additional one Contains component to improve the sliding properties and at least is hardened on its surface. For example, cylinder 64 could be made from one captivate commercially available sintered material under the name Ferromoliporit, which contains special lubricant deposits and is hardenable. One on agile surface treatment of the piston 74, with which one has so far been the problems trying to control the wear is not necessary. Instead of of the cylinder 64 could also be the piston 74 or cylinder and piston from the Sintered material exist.

Just like one of the displacement parts, at least one of the parts is a sliding block and eccentric ring, in particular the eccentric ring, from the above Sintered material manufactured and at least hardened on its surface.

Ferromoliporite is the sintered material which, as described with reference to FIGS. 1 and 2, is also used for parts of the internal gear pump shown there. Accordingly, the starting mixture for this material consists of 15% up to 25% copper, 2.5% to 3% molybdenum disulfide, about 0.4% graphite and Rest composed of iron in the form of ferrite.

Claims (10)

1. Hydraulic positive-displacement machine, in particular a hydraulic positive-displacement pump, with two moving components sliding against each other, characterized in that at least one component (31, 32, 45; 56, 60, 64, 74) of the two components is at least surface-hardened and is made from a sintered material, which contains predominantly ferrite and also a constituent to improve slide characteristics.
2. Positive-displacement machine according to Claim 1, characterized in that it is an internal gear machine, in particular an internal gear pump, and comprises a housing (10), a pinion (20) with external toothing, an annulus (21) meshing with the pinion (20) and a component (31, 32, 45) for sealing a high-pressure area (P) off from a low pressure area (S) along the crests or front faces of the toothed wheels (20, 21) and that the component (31, 32, 45) is at least surface hardened and is made from a sintered material, which contains predominantly ferrite and a constituent to improve slide characteristics.
3. Hydraulic positive-displacement machine according to Claim 1, characterized in that it is a piston machine and comprises at least a piston (74) and a cylinder (64) receiving the piston (74) as the positive-displacement elements and that at least one of the two positive-displacement elements (74, 64) is at least surface hardened and made from a sintered material, which contains predominantly ferrite and a constituent to improve slide characteristics.
4. Hydraulic positive-displacement machine according to Claim 1 or 3, characterized in that it is a piston machine and comprises at least a piston (74) and a cylinder (64) receiving the piston (74) as the positive-displacement elements and an eccentric ring (56) or a lifting disk as the lifting element, against which one of the positive-displacement elements slides, and that the lifting element is at least surface-hardened and made from a sintered material, which contains predominantly ferrite and a constituent to improve slide characteristics.
5. Hydraulic positive-displacement machine according to Claim 4, characterized in that the lifting element is an eccentric ring (56) with a plurality of flattened areas (59), against each of which a positive-displacement element (64, 60) slides.
6. Hydraulic positive-displacement machine according to Claim 1 or 3, characterized in that it is a piston machine and comprises at least a piston (74) and a cylinder (64, 60) receiving the piston (74) as the positive-displacement elements and an eccentric ring (56) or a lifting disk as the lifting element against which one of the positive-displacement elements (64, 60) slides and that the positive displacement element (64, 60) sliding against the lifting element is at least hardened on the surface sliding against the lifting element and with at least this surface made from a sintered material, which contains predominantly ferrite and a constituent to improve slide characteristics.
7. Hydraulic positive-displacement machine according to a preceding Claim, characterized in that the component (31, 32, 45; 56, 60, 64, 74) made from the sintered material is nitride hardened.
8. Hydraulic positive-displacement machine according to a preceding Claim, characterized in that the sintered material contains up to preferably 15% to 25% copper.
9. Hydraulic positive-displacement machine according to a preceding Claim, characterized in that the sintered material contains up to preferably 2.5% to 3% molybdenum disulfide.
10. Hydraulic positive-displacement machine according to a preceding Claim, characterized in that the sintered material contains up to preferably 0.4% graphite.

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