ES2367969T3 - VOLUMETRIC PUMP WITH DISPLACED VOLUME ADJUSTMENT. - Google Patents

Abstract

The casing (3) contains a gear pump with two wheels (1,2). These have adjustable engagement, to vary the quantity of fluid pumped from inlet (5) to outlet (6). A piston (8) coupled to at least one of the wheels, makes the adjustment. Piston chambers (9,10) are subjected to pressures (P9, P10), which act on the piston, through connections (11,12) with the high pressure side. A spring in the first piston chamber (9) acts on the piston, against fluid pressure (P9). A controller (15) adjusts the pressure in the second chamber (10), in accordance with a control magnitude (PR) which sets the rate of delivery.

Description

The invention relates to a volumetric pump with an adjustment of its specific displaced volume. The pump comprises at least two rotating impellers housed in a rotating manner which are in displacement gear between them to move a working fluid under increasing pressure from a low pressure side of the pump to a high pressure side of the pump during a rotary drive of at least one of the travel impellers. Also, the invention relates to a system comprising the pump for feeding a group with a working fluid or lubricant. In its preferable uses, the pump serves to feed lubricating oil an internal combustion engine, that is, in this use it constitutes the engine's lubricating oil pump. A specific displaced volume means the displaced volume of the pump referred to a number of revolutions of one of the travel impellers [displaced volume / number of revolutions].

In volumetric pumps, for example cogwheel pumps, the specific displacement volume is constant and, therefore, the displacement volume is proportional to the number of revolutions of the displacement impellers, while the degree of filling of the displacement cells formed by The travel impellers are 100%.

In many cases of application this proportionality is annoying. For example, in a press, a large amount of pressurized oil supply is required for rapid running, but only a high pressure is required in the final phase of the press run, while the need for volume Oil displacement is reduced to zero. Since the number of pump drive revolutions is generally kept constant, there is an excess of oil current that is under high pressure and that recirculates to an oil tank leading to a loss of energy.

An excess of oil flow is also annoying, for example, in engine lubricant pumps and auto feed oil pumps. Although these groups, at a low engine speed and, therefore, at a low pump speed, especially at idle speed, require a minimum displacement volume, and a high number of revolutions require a minimum oil pressure, the need for fluid at a higher speed is well below the proportionality line.

The specific displacement volume of pumps should be adapted to the needs of the consumer, for example an internal combustion engine, an automatic gearbox or a press, that is, it should be adjustable. In known volumetric pumps, the specific offset volume adjustment is made by adjusting the displacement gear of the displacement impellers. A whole series of adjustment mechanisms is known for this.

Document DE 198 47 132 C2 describes an external gearwheel pump, whose specific displacement volume is regulated in such a way that from a predefined limit speed number it only increases proportionally less than the number of revolutions or even keeps constant while the number of pump drive revolutions continues to increase. The pump has two cylindrical wheels with straight teeth that are housed in a pump displacement chamber and are geared between them. The displacement gear is made by the gear of the teeth of the two cylindrical wheels. To limit the specific displacement volume of the pump, one of the two cylindrical wheels is rotatably housed on a plunger. The plunger is slidably housed within a pump housing and, for its sliding, on one side of the plunger, is subjected to a fluid transported by the pump from the high pressure side of the pump. A spring element acts against the pressure of the fluid on the opposite side of the piston. The sliding position of the plunger and, therefore, also the axial position of the cylindrical wheel housed on the plunger, with respect to the other non-sliding cylindrical wheel, results from the balance of forces of the fluid pressure and the elastic force. Therefore, the axial gear length of the two cylindrical wheels and, therefore, the specific displacement volume of the pump is modified by the sliding movement of the piston. The plunger is subjected to a high pressure side fluid, such that as the pressure of the fluid increases, the length of engagement of the two cylindrical wheels is reduced against the elastic recoil force of the spring element.

Comparable external gearwheel pumps for the specific offset volume adjustment are known from DE 41 21 074 A1, DE-A-100 43 842 and DE 35 28 651 A1.

From EP 1 182 351 an internal gear wheel pump is also known, whose specific offset volume can be adjusted. The pump has an inner wheel with external teeth and a hollow wheel with internal teeth that are rotatably housed around eccentric rotational axes in a displacement chamber of the pump housing being rotatably actuated for fluid displacement. The two displacement impellers constitute displacement cells that expand from a point of the deepest engagement of the teeth to a point of the smallest engagement of the teeth and displacement cells that are compressed from the point of the smallest engagement of the teeth to the point. of the deepest engagement of the teeth. In the area of the transport cells that expand an entry into the displacement chamber, and in the area of the displacement cells that are compressed, an exit flows into the chamber. The expanding fluid cells suck fluid from the inlet and the displacement cells that are compressed move the fluid through the outlet. To be able to adjust the specific displacement volume of the pump, the hollow wheel with internal teeth is rotatably housed in an eccentric ring. The eccentric ring is also housed in the housing rotatably around an eccentric axis of rotation with respect to the axis of rotation of the hollow wheel. By adjusting the angle of rotation position of the eccentric ring with respect to the inlet and outlet, the specific offset volume adjustment is made. To adjust the angle of rotation position of the eccentric ring, a plunger acts on the eccentric ring through a rack, turning axial movements of the plunger into rotational movements of adjusting the eccentric ring. Like the piston in pumps with known outer sprockets, the piston is subjected on one side to the fluid pressure of the high pressure side and the elastic force of a recoil spring element that acts against the fluid pressure.

Known adjustment mechanisms require high recoil forces during full pump operation. If the recoil element that acts against the fluid pressure acting on the plunger is a spring element, the spring chamber housing the spring element must be very long due to the necessary elastic forces. If necessary, the spring element must be made as a multiple spring, for example a double spring.

The invention aims to provide a volumetric pump that has a space-saving adjustment device, which is economical and stable during permanent operation, for an adjustment of the specific displaced volume of the pump.

This objective is achieved by a volumetric pump indicated in claim 1.

The invention relates to a volumetric pump, the specific displacement volume of which can be adjusted and comprising a housing with a displacement chamber, with at least two displacement impellers housed in the displacement chamber and with an adjustment device for adjusting its specific offset volume. At least one inlet and at least one outlet for a fluid to be displaced by the pump flow into the displacement chamber. The inlet is communicated with a low pressure side of the pump and the outlet is communicated with a high pressure side of the pump. Low pressure side means the complete fluid conduction system from a fluid reservoir to the entrance to the displacement chamber, that is, the complete fluid conduction system upstream from the inlet including the fluid supply channels formed inside the housing. The high pressure side means the complete fluid conduction system directly downstream from the outlet of the displacement chamber to at least one following group that is fed from the fluid by the pump. If a plurality of groups are to be fed, the high pressure side is formed by the part of the fluid conduction system that extends downstream from the outlet to include at least the last of the groups to be fed.

The at least two, preferably exactly two displacement impellers can be rotatably actuated and are in displacement gear between them to displace the fluid, under increased pressure, from the inlet to the outlet. In order to be able to adjust the specific displacement volume of the pump, the displacement impellers can be adjusted with respect to each other or with respect to the fluid inlet or with respect to the fluid outlet, or with respect to the fluid inlet and the fluid outlet

The adjusting device comprises a plunger which for the adjustment of the displacement impellers is coupled with at least one of the displacement impellers. Especially if the volumetric pump is configured as an external gearwheel pump, the coupling can consist of the fact that, as in the known external gearwheel pumps, one of the displacement impellers is rotatably housed on the piston and can slide axially along the piston and with respect to the other travel impeller. However, the coupling can also be carried out by an adjustment gear that converts an adjustment movement of the plunger into an adjustment movement of the travel impellers. An example of such a coupling for an internal gearwheel pump is known for example from EP 1 182 351 mentioned.

A first pressure chamber and a second pressure chamber are also part of the adjustment device to subject the piston to the high pressure side fluid pressure. The piston extends with a first piston surface inside the first pressure chamber and with a second piston surface inside the second pressure chamber. The fluid pressure acting on the plunger in the first pressure chamber acts against the fluid pressure acting on the plunger in the second pressure chamber. The two pressure chambers are communicated with the high pressure side respectively through a fluid communication. The fluid communication with the high pressure side can be performed respectively independently, that is, the two pressure chambers can be communicated in parallel with the high pressure side. However, the two pressure chambers can also be first communicated with each other and then communicated together with the high pressure side. Finally, the fluid communication of the high pressure side can also be carried out in such a way that one of the two pressure chambers is connected to the high pressure side and that the other of the two pressure chambers is communicated with said chamber. pressure directly connected, being communicated only in this way with the high pressure side. In the latter case, the communication can be carried out by passing inside the plunger or, preferably, outside the plunger.

In addition, the adjustment device comprises a spring element, preferably a mechanical spring that acts against the fluid pressure acting on the piston in the first pressure chamber. A spring chamber in which the spring element is arranged is preferably made by the second pressure chamber. However, in principle it would also be possible for the spring element to be disposed outside the second pressure chamber acting against the fluid pressure in the first pressure chamber.

In a starting position of the piston in which the displacement impellers already move, preferably the fluid pressures in the two pressure chambers are identical, so that, in the starting position, the spring element is not subjected to the fluid pressure However, in principle, different fluid pressures can also be chosen at the starting position. In this way, the fluid pressure in the second pressure chamber can be lower than the fluid pressure in the first pressure chamber, in order to keep the spring element under a pretension in the piston starting position. In the starting position of the plunger, the position of the displacement impellers is preferably such that the pump has its largest specific displacement volume. By means of the adjustment movement of the piston against the elastic force of the spring element, therefore, the specific displaced volume in this preferable embodiment is reduced. However, another development of the specific shifted volume along the number of revolutions is also possible, for example in such a way that as the number of revolutions increases, the specific shifted volume initially increases from a starting value corresponding to the starting position of the piston, decreasing by exceeding a number of drive revolutions corresponding to the maximum specific displacement volume.

In addition, the adjustment device has a regulator that regulates the fluid pressure of at least one of the two pressure chambers depending on a magnitude of decisive regulation for fluid displacement, so that a displacement characteristic of the pump that is advantageous in regard to the specific displaced volume. The regulation quantity is preferably taken on the high pressure side and can be, for example, the temperature of the fluid or of a group to be fed with lubricating oil by the pump, or the viscosity of the fluid. Preferably, the regulation quantity is a high pressure side fluid pressure and hereinafter referred to as fluid regulation pressure to differentiate it from other fluid pressures and to indicate its use as a regulation quantity. In particular, the fluid regulation pressure can be applied directly to a regulator configured as a fluid regulator, to influence the regulator. In alternative variants, the magnitude of regulation is the number of revolutions of an alternative motor or of another group to be fed, or, in the case of non-rotating movements, a comparable frequency. Advantageously, the magnitude of regulation can be formed synthetically, especially according to a need line or a field of lines of need characteristic of the group to be fed or of a plurality of groups to be fed. By way of example, the field of characteristic lines of need applied along the number of revolutions is also mentioned here, or just a characteristic line of necessity of an alternative motor. In particular, a motor control apparatus can generate the magnitude of regulation and apply it in the regulator electrically or optically as the magnitude of regulation. Therefore, the magnitude of regulation does not necessarily have to be a physical magnitude that results directly from the pump activity, but instead, it can also be a characteristic magnitude of a group to be fed, for example of an engine or other component that is in contact with the fluid. A regulation amount of this type is also preferably taken on the high pressure side.

In a first variant, the first pressure chamber is communicated with the high pressure side and the second pressure chamber is communicated, in the first state of the regulator, with the first pressure chamber through the regulator. In a second variant, the first pressure chamber and the second pressure chamber are communicated, in the first state of the regulator, individually or together with the high pressure side through the regulator. Therefore, in the second variant, in the first state of the regulator, the two pressure chambers are fed from the high pressure side fluid through the regulator. In both variants, in the second state of the regulator, the regulator disconnects the second pressure chamber from the high pressure side. Preferably, in both variants, in the second regulator state, the second pressure chamber communicates with the low pressure side.

While in spite of the fluid displacement, the regulation magnitude does not reach a predefined value, the pressures in the two pressure chambers are preferably always identical, so that no fluid pressure force acts on the spring element. In a first regulator state, the regulator short-circuits the at least one of the two pressure chambers, whose fluid pressure regulates, directly with the high pressure side or with the other of the two pressure chambers, so that it occurs Pressure compensation without delay. This increases the dynamics of regulation. Furthermore, in this way, in the first regulator state, the spring element does not have to compensate for differential pressures, but only guarantees a secure mechanical stop contact of the plunger in the position for maximum displacement. Therefore, the spring element can be soft and short in the direction of movement of the plunger.

Preferably, the spring element is designed in such a way that it fulfills just the 'fail safe' function, guaranteeing in this function the maintenance of a minimum pressure on the high pressure side. In preferable applications, such as feeding an alternative engine with lubricating oil, the minimum pressure is two bars or less. Therefore, the spring element is preferably conceived and installed in such a way that it yields at a force corresponding to a pressure difference of two bars or less between the pressure chambers. In the case of pressure differences lower than the value set by the design and installation, the spring element forces the plunger to the position for maximum displacement.

Preferably, the pressure of the second pressure chamber is modified by the regulator, for example,

5 reduces continuously or in one or several stages as the fluid regulation pressure, temperature or number of revolutions increases. However, instead, in principle it would also be possible to increase the pressure of the first pressure chamber as the fluid regulation pressure, temperature or the number of revolutions increases. It would also be possible to regulate the pressures in the two pressure chambers in a coordinated manner by means of the regulator to obtain the desired feeding characteristic.

Preferably, the regulator is a multi-state regulator capable of adopting various discrete regulator states, that is, switching states or positions. Which of the switch positions the regulator adopts is determined by the magnitude of regulation. If the fluid regulating pressure is used as the regulation quantity and a fluid regulator is used as regulator, especially a regulating valve, the switching position is preferably determined by the difference in the force exerted by the fluid regulating pressure and a

15 recoil force acting against fluid regulation pressure. In a simple, preferable embodiment, the regulator is a two-state regulator that in a first of two switching positions communicates the second pressure chamber with the high pressure side of the pump and, in a second switching position, communicates it with the low pressure side of the pump. Preferably, a regulating valve forms the regulator, especially preferably a multi-step valve with at least two switching positions.

In other preferable embodiments, instead of a regulator with discrete regulator states, a continuous regulator, preferably a proportional valve, is provided whose regulator states change continuously depending on the magnitude of regulation.

Instead of sending the discrete or continuous fluid regulator, in an equally preferable embodiment, the regulator can be an electromagnetic regulator that evidently also regulates a fluid pressure.

25 Preferably, the volumetric pump is made as a gearwheel pump, with both the external gearwheel pumps and the internal gearwheel pumps being preferable examples. If the volumetric pump is an external gearwheel pump, the first and second travel impeller are formed respectively by a cylindrical wheel with external gear. The displacement chamber is substantially formed by the lateral surfaces of the housing that surround the cylindrical wheels located in gear meshes, and by sealing surfaces opposite to the frontal surfaces of the cylindrical and axially oriented wheels thereof. One of the two cylindrical wheels is rotatably housed on the plunger and can slide axially straight next to the plunger inside the housing, relative to the other cylindrical wheel. The piston forms the sealing surfaces of the displacement chamber, oriented axially towards the cylindrical wheel housed with this mobility. In this embodiment, the

The first pressure chamber and the second pressure chamber are in the axial extension on both sides of the sliding cylindrical wheel. Preferable details of an external sprocket pump are described in DE 198 47 132 C2.

If the volumetric pump is an internal cogwheel pump, a set of cogwheels consisting of an inner wheel with an external gear and a hollow wheel with an internal gear, whose teeth are in mutual engagement, form the first and second travel impeller. With regard to a preferable embodiment, reference is made to claim 10.

Furthermore, as regards other especially preferable features of the invention, it also refers to the dependent claims.

Next, with the help of the figures, some preferable embodiments of the invention are described.

45 The features that are manifested in the examples of embodiment constitute, each by itself and in any combination of features, advantageous variants of the objects of the claims, as well as the configurations described above. They show:

Figure 1 an external gearwheel pump in longitudinal section,

Figure 2 an external gear wheel pump in cross section,

Figure 3 an internal gear wheel pump in a cross-section starting position,

Figure 4 an internal gear wheel pump in an end position,

Figure 5 the internal gear wheel pump in longitudinal section and

Figure 6 the internal gear wheel pump in another cross section.

Figure 1 shows in longitudinal section and figure 2 in cross section AA an external sprocket pump, whose specific displacement volume is regulated in such a way that in a lower speed range the volume displaced from the pump and, next to it , the high pressure side fluid pressure increases with the number of revolutions more strongly than in a higher range. In the exemplary embodiment, the regulation is two-stage with a constant specific shifted volume in the lower speed range up to the limit speed. When the limit speed is reached, the pump is adjusted downwards, that is, the specific displaced volume is reduced in such a way that the fluid pressure remains constant in the event of a subsequent increase in the number of revolutions.

A pump housing 3 constitutes a displacement chamber 4 in which a first displacement impeller 1 is rotatably housed around its axis of rotation D1 and a second displacement impeller 2 is rotatably housed around its axis of turn D2. The travel impellers 1 and 2 are cylindrical wheels with external teeth. The two outer teeth are designated by 1st and 2nd. The travel impellers 1 and 2 are in teeth engagement with their teeth 1a and 2a. In the gear zone of the displacement impeller 1 and 2, an inlet 5, and on the opposite side, an outlet 6, as best shown in Figure 2, opens during a rotating operation of the impeller impeller. displacement 1 and 2, by means of the teeth gear fluid is suctioned from the inlet 5 and moved through the outlet 6 under an increase in pressure. In Figure 2, this displacement process is indicated by the directional arrows for the fluid and the direction of rotation of the displacement impellers 1 and 2. The complete conduction of the fluid in and out of the pump until the pressure increase is understood by low pressure side in the sense of the invention.

The rotary drive of the travel impellers 1 and 2 is carried out through a drive shaft rotatably housed by the housing 3. The travel impeller 1 is fixed on the drive shaft being secured against torsion and sliding. The driven displacement impeller 1 can exert, with respect to the housing 3, only rotational movements around its axis of rotation D1.

The second travel impeller 2 is rotatably housed around its axis of rotation D2 between two piston bodies 7 and 8 in a joint section that joins the two piston bodies 7 and 8 therein, and cannot slide with respect to to the piston bodies 7 and 8. The two piston bodies 7 and 8 form a double-acting piston that can slide straight from side to side along the axis of rotation D2 of the travel impeller 2, within a bore of the housing 3. By means of a sliding movement exerted by the piston 7/8 next to the second travel impeller 2 with respect to the first travel impeller 1, the axial length of the tooth gear of the two displacement impeller 1 is modified and 2 and, as a consequence, the specific displaced volume of the pump.

The housing 3 forms, on one side of the piston 7/8, a first pressure chamber 9, and on the other side of the piston 7/8, a second pressure chamber 10 opposite the first pressure chamber 9 along a pivot shaft D2. The piston 7/8 sealed with its piston body 7 the first pressure chamber 9 and with its piston body 8 sealed the second pressure chamber 10. The piston 7/8 fluidly separated the two pressure chambers 9 and 10 between them . The piston surface of the piston body 7 which in the first pressure chamber 9 can be subjected to a pressure P9 is as large as the piston surface of the piston body 8 which in the second pressure chamber 10 can be subjected to a pressure P10, so that on both opposite piston sides the same pressure force acts on the piston 7/8, as long as the same pressure reigns in the two pressure chambers 9 and 10.

In the second pressure chamber 10 a mechanical compression spring is housed as a spring element 13. The spring element 13 is axially supported on a bottom of the pressure chamber 10, and on the axially opposite side it rests on a body of piston 8. When the spring element 13 is axially under pressure tension, it acts against the fluid pressure P9 acting on the piston 7/8 in the first pressure chamber 9. The second pressure chamber 10 forms at the same time also the spring chamber, that is, the installation chamber for the spring element 13.

In order to be able to pressure the pressure chambers 9 and 10, the first pressure chamber 9 communicates with the high pressure side by a first fluid communication 11. In order to be able to also communicate with the high pressure side the second pressure chamber 10, a second fluid communication 12 is provided. The second fluid communication 12 is communicated with the high pressure side through a regulating valve 15. The regulating valve 15 is a distributor valve with two switching positions. In a first switching position shown in Figure 1, the regulating valve 15 communicates the second fluid communication 12 with the first fluid communication 11 and establishes the communication of the second pressure chamber 10 with the high pressure side, avoiding the plunger 7/8. In a second switching position, it separates the second pressure chamber 10 from the high pressure side and closes the first fluid communication 11. In the second switching position, the first pressure chamber 9 remains communicated with the high pressure side or At least it's closed. In the second switching position, the regulating valve 15 communicates the second pressure chamber 10 with the low pressure side. In the exemplary embodiment, in the second switching position of the regulating valve 15, the second pressure chamber 10 is communicated with a fluid reservoir 20. In preferable uses of the pump, for example as a lubricating oil pump for a Internal combustion engine, the fluid reservoir 20 is a fluid housing. The fluid communications 11 and 12 are arranged directly near the pump, preferably being integrated in the pump housing 3, Preferably, also the regulating valve 15 is integrated in the housing 3 or at least mounted externally in the housing 3. Therefore, the first pressure chamber 9, and in the first switching position of the regulating valve 15 also the second pressure chamber 10, receive their pressurized fluid preferably from within the housing 3. However, in principle also it would be possible for them to receive their pressurized fluid from a suitable point on the high pressure side, downstream of the housing 3.

The regulating valve 15 is switched according to a fluid regulation pressure PR. It is maintained in the first switching position corresponding to a starting position of the regulating valve 15 and of the piston 7/8, by means of a backspace element 16, which in the embodiment is performed as a mechanical spring element. The recoil element 16 acts against the fluid regulating pressure PR. As soon as the fluid regulating pressure PR has reached a limit pressure, the regulating valve 15 jumps from the first switching position to its second switching position against the recoil force of the recoil element 16.

PR fluid regulating pressure is taken on the high pressure side of the pump. In principle, it can be taken directly in the displacement chamber 4, on its high pressure side, at its outlet 6, from within the housing 3 behind the displacement chamber 4 or directly near the housing 3, downstream of this, but preferably, the fluid regulating pressure PR is taken at a point on the high pressure side where the fluid pressure corresponds as accurately as possible to the fluid pressure of a consumer to be fed from the fluid . If the consumer is, for example, the alternative engine of a car, the pressure regulating fluid PR is preferably the pressure of the so-called main gallery. Accordingly, the regulating valve 15 is communicated, through a fluid communication, with the corresponding point of the high pressure side. A suitable point for taking the PR fluid regulation pressure is especially between the consumer and the last filter before the consumer.

The mode of action of the pump regulation is described below for a preferable use of the pump as a lubricating oil pump for an alternative engine, assuming that the pump is driven by the engine crankshaft directly or through a gear and, by Therefore, depending on the engine speed.

The adjustment of the throttle valve 15 is such that in a lower engine speed range that for example in a tourism can be up to 1,500 or 2,000 revolutions per minute or even higher revolutions, it adopts its first switching position in the one that communicates both pressure chambers 9 and 10 with the high pressure side and in which the same pressure P9 = P10 on the high pressure side reigns in both pressure chambers. Therefore, in the lower speed range, the pressure P10 in the second pressure chamber 10 is identical to the pressure P9 in the first pressure chamber 9. In the lower speed range, especially in the engine idle, You want a specific displacement volume as large as possible to be able to guarantee the engine's lubricating oil supply also during low revs. Therefore, in the first switching position of the regulating valve 15, the axial gear length of the two travel impellers 1 and 2 is maximum, as shown in Figure 1. The maximum gear length corresponds in the example to the length of the two travel impellers 1 and 2 having the same length. It is maintained during zero travel, especially during stopping of travel impellers 1 and 2 and, as already mentioned, in the lower engine speed range and, therefore, also in the lower engine speed range of displacement 1 and 2, up to a limit speed determined by the regulating valve 15.

The first displacement impeller 1 is rotatably driven around its axis of rotation D1 by the crankshaft and, through the tooth gear, the second displacement impeller 2 also drives around the axis of rotation D2 thereof. By lubricating teeth lubricating oil is sucked from the low pressure side, that is from the oil pan 20, through the inlet 5 to the displacement chamber 4. In the displacement chamber 4 the displacement takes place by a displacement space that is enclosed in a sealed manner by the lateral surfaces of the housing 3 around the circles of tooth heads of the travel impellers 1 and 2, as well as by axial sealing surfaces, towards the outlet 6. The surfaces of Axial sealing for the displacement impeller 1 are formed by the housing 3 and those for the displacement impeller 2 are formed by the two piston bodies 7 and 8. On the high pressure side of the pump, the oil travels to the engine through an oil filter, it is cooled in a refrigerator behind the engine and, finally, it is redirected to the crankcase 20 and reduced to the pressure of the low pressure side.

By increasing the number of revolutions of the engine and, therefore, at the same time also the number of revolutions of the pump, the pressure of regulation of fluid PR increases according to the characteristic of the pump. Once the limit speed has been reached, the fluid regulation pressure PR is also so large that under its effect the regulating valve 15 switches to its second switching position. In the second switching position of the regulating valve 15, the pressure chamber 10 is communicated with the low pressure side, namely with the crankcase 20. In the second switching state of the regulating valve 15, therefore, the first pressure chamber 9 is under high pressure P9 on the high pressure side and the second pressure chamber 10 is under pressure P10 on the low pressure side, which in comparison is negligible. The piston 7/8 and, next to it, the second rotating impeller 2 rotatably slipped axially under the effect of the pressure P9, against the elastic force of the spring element 13. The sliding reduces the length of engagement of travel impellers 1 and 2 and, consequently, the specific displacement volume of the pump. The reduction of the specific displaced volume results in a decrease in the fluid pressure on the high pressure side, that is to say the PR fluid regulating pressure. When the fluid regulating pressure PR falls below the limit value, the regulating valve 15 returns to its first switching position in which the second pressure chamber 10 communicates with the first pressure chamber 9 through the two communications fluid 11 and 12. Therefore, after reaching the limit speed, the pump is regulated to maintain the limit value of the PR fluid regulation pressure. By means of the regulation a limitation of the pressure is achieved and, consequently, also a limitation of the displaced volume of the pump. The high pressure side fluid pressure increases in the lower speed range of the first travel impeller 1 to the limit speed, substantially proportional to the number of revolutions, and when reaching the limit speed is doubled to a horizontal, that is to say that the fluid pressure of the high pressure side remains constant in the speed range above the limit speed number.

By replacing the regulating valve 15 with another regulating valve with more than two discrete switching positions or with a continuous regulating valve, for example a proportional valve, other pressure developments can also be made. For example, it may be advantageous for the described pressure development to be adjusted in the lower speed range and in a following average speed range, while in a high speed range following the average speed range, the fluid pressure of the High pressure side is increased again with the number of revolutions of the first driven impeller 1. For the realization of such a pressure development, the regulating valve 15 of the exemplary embodiment could be replaced by a regulating valve with three switching positions, the second pressure chamber 10 communicating in the upper speed range, through a pressure reducing element, with the high pressure side to support the spring element 13.

Figures 3 to 6 show an internal gearwheel pump with an adjustment according to the invention of the specific displacement volume of the pump.

Figures 3 and 4 show the internal gearwheel pump respectively in cross section. The first displacement impeller 1 of the internal gearwheel pump is formed by an internal wheel rotatably driven with an external gear 1a. The second travel impeller 2 is formed by a hollow wheel with an internal gear 2i. The outer teeth 1a has a tooth less than the internal teeth 2i. The first travel impeller 1 is placed, torsion-proof, on a rotatingly driven shaft. The second travel impeller 2 is rotatably housed inside the pump housing 3. The axis of rotation D1 of the first travel impeller 1 extends parallel to a distance, ie eccentrically with respect to the axis of rotation D2 of the second travel impeller 2. The eccentricity is designated by "e".

The first displacement impeller 1 and the second displacement impeller 2 form between them a fluid displacement space divided into displacement cells 24 closed relative to each other in a pressure-tight manner. The different displacement cells 24 are formed respectively between two successive teeth of the first displacement impeller 1 and the second displacement impeller 2. From a place of the deepest tooth gear to a place of the smallest tooth gear, the displacement cells 24 they are increasingly enlarged in the direction of rotation to decrease again then from the place of the smallest teeth gear to the place of the deepest teeth gear. The displacement cells 24 that are enlarged, that is to say expand, are communicated with the input 5 of the displacement chamber 4 and the displacement cells 24 that are reduced, that is to say compressed, are communicated with the output 6 of the displacement chamber 4. The inlet 5 and the outlet 6 are formed by reniform groove openings, located laterally following the displacement cells 25, in housing sealing surfaces 3 axially opposite to the displacement impellers 1 and 2 The opening constituting the inlet 5 covers displacement cells 24 in expansion and the opening constituting the outlet 6 covers displacement cells 24 in compression of the two displacement impellers 1 and 2. In the area of the site of the tooth gear more deep and in the area of the place of the smallest gear meshing, the housing forms sealing souls between input 5 and output 6. During the rotation drive The flow of the impeller 1 and 2 is fluid suctioned through the displacement cells 24 in expansion of the low pressure side, it is transported through the place of the smallest gear meshing and on the high pressure side it travels through the outlet 6 under a higher pressure.

In order to modify the specific offset volume, the second travel impeller 2 is housed in an eccentric ring 21 which is rotatably housed by the housing 3 and whose angle of rotation position can be adjusted with respect to the housing 3. The second impeller of displacement 2 is housed freely rotatable in the eccentric ring 21 by means of a sliding swivel bearing. Figure 3 shows the eccentric ring 21 and the travel impellers 1 and 2 in a starting position in which the specific displacement volume of the pump is the maximum. By rotating the eccentric ring 21 against the direction of rotation of the travel impellers 1 and 2, the axis of rotation D2 of the second movement impeller 2 moves from the starting position against the direction of rotation around the axis of rotation D1 of the first travel impeller 1. Figure 4 shows the eccentric ring 21 in its final position in which the specific displacement volume of the pump has reached its minimum value. The final position represented in Figure 4 is the zero position of the pump in which, ideally, no fluid is transported.

Figures 5 and 6 show an adjustment mechanism for adjusting the angle of rotation position of the eccentric ring 21. The eccentric ring 21 has a bowl shape with an annular body forming the eccentric ring itself as a bowl wall, with a bowl bottom and with a spike 22 protruding axially from the bottom of the bowl. The pin 22 is concentric with respect to the annular body of the eccentric ring 21. The pin 22 is provided with a front teeth 23. The teeth 23 are in tooth engagement with the teeth 26 of a plunger 25. The piston 25 is housed inside The pump housing 3 can slide from one side to the other, and with its teeth 26 forms a rack. The piston 25 seals on one side a first pressure chamber 9 and on the other hand a second pressure chamber 10.

As regards the loading of the piston 25 with the pressurized fluid of the high pressure side, the piston 25 of the second embodiment corresponds to the piston 7/8 of the first embodiment. Also the spring element 13 corresponds in its function to that of the first embodiment. The regulation circuit for loading the two pressure chambers 9 and 10 with the pressure fluid on the high pressure side, including the regulating valve for the pressure application depending on the fluid regulation pressure or for the pressure reduction in The second pressure chamber 10 also corresponds to the first embodiment, so that in order to avoid repetition, the descriptions relating to the first embodiment are referred to.

Due to the sliding of the piston 25 caused by the fluid pressure and the spring element 13, through the tooth gear of the two teeth 26 and 23, the eccentric ring 21 rotates about its axis of rotation D1. The rotation adjustment of the eccentric ring 21 causes, as already described, the rotation adjustment of the travel impellers 1 and 2 with respect to the inlet 5 and the outlet 6 to the displacement chamber 4 of the pump. As a result, for the internal gearwheel pump the same type of specific offset volume adjustment is obtained as for the external gearwheel pump of the first embodiment.

As regards more details of the internal gearwheel pump and its adjustment, reference is made to EP 1 182 351 of the applicant, whereby a detailed description can be dispensed with here.

List of reference signs

one

Scroll roll

1st

 Jagged

2

Scroll roll

2nd, 2nd

Jagged

3

Case

4

Scroll camera

5

Entry

6

Departure

7

Piston body

8

Piston body

9

Pressure chamber

10

 Pressure chamber

eleven

 Fluid communication

12

 Fluid communication

13

Spring element

14

 -

fifteen

Regulator, regulating valve

16

Recoil element

17

 -

18

 -

19

 -

twenty

Fluid housing

twenty-one

 Eccentric ring

22

 Spike

2. 3

 Jagged

5

24  Scroll cells

25

 Plunger

26

 Jagged

D1

Axis of rotation

D2

Axis of rotation

10

P9 Fluid pressure

P10

Fluid pressure

PR

Fluid regulation pressure

Claims (9)

1. Volumetric pump with adjustable specific offset volume with a) a housing (3) containing a displacement chamber (4) into which, at a low pressure side of the pump, at least one inlet (5) for a fluid flows, and at a high pressure side of the pump, at least one outlet (6) for a fluid, b) at least two displacement impellers (1, 2) that can be rotatably operated and that are housed in the displacement chamber (4) and that are in displacement gear between them to displace the fluid from the inlet (5) to the outlet (6), the displacement impellers (1, 2) can be adjusted in such a way that by adjusting the displacement impellers (1, 2) with respect to each other or with respect to the inlet (5) and / or the output (6), the specific displacement volume of the pump is adjusted, c) a piston (7/8; 25) which, for the adjustment of the travel impellers (1, 2), is coupled with at least one of the travel impellers (1, 2), d) a first pressure chamber (9) and a second pressure chamber (10) for loading the plunger (7/8; 25) respectively with the high pressure side fluid, a fluid pressure (P9) acting on the first pressure chamber (9), which acts on the piston (7/8; 25), against a fluid pressure (P10) of the second pressure chamber (10), which acts on the piston (7/8; 25 ). e) a first fluid communication (11) that communicates the first pressure chamber (9) with the high pressure side, and with a second fluid communication (12) that communicates the second pressure chamber (10) with the side high pressure, f) a spring element (13) acting against fluid pressure (P9) acting on the plunger (7/8; 25) in the first pressure chamber (9), and g) a regulator (15) that regulates the fluid pressure (P10) of the second pressure chamber (10) based on a magnitude of regulation (PR) of the high pressure side, decisive for the displacement of fluid from the pump , characterized because h) the regulator (15) cuts off the second fluid communication (12) when the regulation magnitude (PR) exceeds a predefined value.

2.

 Volumetric pump according to claim 1, characterized in that the regulation quantity (PR) is a high pressure side fluid regulation pressure.

3.

 Volumetric pump according to the preceding claim, characterized in that a communication conduit is connected to the regulator (15) whereby the high pressure side fluid, which is under the fluid regulation pressure (PR), can be supplied to the regulator ( 15) from outside the pump housing (3).

Four.

 Volumetric pump according to any one of the preceding claims, characterized in that the regulator

(15) is or comprises a regulating valve in which as a regulation quantity (PR) a fluid regulation pressure (PR) is applied from the high pressure side of the pump, acting against the fluid regulation pressure (PR) a recoil force of a recoil element (16). 5. Volumetric pump according to any one of the preceding claims, characterized in that the regulator (15) is a regulating valve with at least two discrete switching positions (regulator states) that are switched according to the magnitude of regulation (PR).

6.

 Volumetric pump according to any one of the preceding claims, characterized in that in a first regulator state the regulator (15) communicates the second pressure chamber (10) with the high pressure side of the pump and in a second regulator state communicates it with the low pressure side of the pump, the regulator (15) adopting the second regulator state when the value of the regulation quantity (PR) is greater than the first regulator state.

7.

 Volumetric pump according to any one of the preceding claims, characterized in that the regulator

(15) in a first regulator state communicates the second pressure chamber (10) with the first pressure chamber (9) and in a second regulator state it separates it from the first pressure chamber (9) and communicates it with the low pressure side of the pump, the regulator (15) adopting the second regulator state when the value of the regulation quantity (PR) is greater than the first regulator state.

8.

 Volumetric pump according to any one of the preceding claims, characterized in that the pump is an external sprocket pump and the at least two displacement impellers (1, 2) are cylindrical wheels with external teeth that are engaged in teeth engagement between them to displace the fluid from the inlet (5) to the outlet (6), the plunger (7/8) forming a rotating bearing for one of the travel impellers (1, 2), and

in which the axial sliding of the piston (7/8) modifies an axial gear length of the travel impellers (1, 2) and thereby adjusts the specific displacement volume of the pump.

9.

 Volumetric pump according to any one of claims 1 to 7, characterized in that the pump is an internal gearwheel pump and the at least two travel impellers (1, 2) are an inner wheel with

5 external teeth and a hollow wheel with internal teeth which, while engaged in teeth gear, form displacement cells that move the fluid from the inlet (5) to the outlet (6), the hollow wheel having at least one tooth more than the inner wheel , comprising the volumetric pump: - an eccentric ring (21) that is rotatably housed inside the housing (3) around a rotation axis (D1) of the eccentric ring and that houses one of the travel impellers (1, 2) rotatably around from his 10 axis of rotation (D2), the axis of rotation (D1) of the eccentric ring and the axis of rotation (D2) of the travel impeller (2) rotatably housed by the eccentric ring (21) being eccentric with respect to each other , -and an adjusting gear (23, 26) that couples the eccentric ring (21) with the plunger (25) and converts a plunger adjustment movement (25) into a rotating movement of the eccentric ring (21) to adjust the travel impellers (1, 2) with respect to the input (5) and the output (6).