DE2330607A1 - SWASHPLATE PUMP WITH CHANGEABLE STROKE VOLUME - Google Patents

Description

Swash plate pump with variable displacement

The invention relates to hydraulic pumps which can be changed as a function of one or more delivery pressures Stroke volume with a rotatable swash plate, the inclination of which is hydraulically supported by a bearing in a carrier of the swash plate actuated piston is adjustable, which is controlled by a valve that responds to changes in the pump delivery pressure. Such pumps are described in DT-OS 1 906 226.

The invention relates to pumps with this mode of operation, which compared to the one described in DT-OS 1 906 226 is an essential one have improved outlet means.

Pumps to which separate delivery lines are connected are being used more and more frequently: For example, you can use a pump with six pistons distribute the delivery capacity of the pump to two / ei separate delivery lines, each of which consists of three Piston is fed or, in the case of a pump with nine pistons, on three delivery lines, each of which is fed by three pistons will. It is quite evident that in these cases there is no valve which is suitable for the sum of the three lines to set the prevailing pressures in such a way that it is a function of the torque required to drive the pump.

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The outlet device described in DT-OS 1 906 226 would if the Pjmpe equipped with several delivery lines require a valve body that has as many floors as there are conveyor lines; a satisfactory function such a system could only be achieved by very complex, delicate and costly means.

Accordingly, it is the object of the invention to avoid the disadvantages outlined and furthermore to standardize the pump manufacture and a common pump head for use in different pump bodies with three or sches or with nine pistons to enable.

According to the invention, this object is achieved by a hydraulic pump of the type described above that the valve has a slide which, on the one hand, is dependent on the delivery pressures prevailing on the rear side of the actuating piston Pressure is applied and on the other hand is exposed to the opposite action of a spring and between Positions can be moved back and forth in which he has a line in which the suction pressure of the pump prevails, or a line, in which the highest of the delivery pressures prevails, connects with the working chamber of the actuating piston.

Another advantage of the pump according to the invention is that it supplies power via an axial recess in the pump body which achieves a volumetric efficiency, which can be achieved much better than with the pump described in DT-OS 1 906 226.

The invention is illustrated in the following with the aid of a schematic Drawings of exemplary embodiments described with advantageous details. It shows:

1 shows a longitudinal section through a pump with cal piston; Fig. 2 is a partial view of a longitudinal section in a to cut> -

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plane of Fig. 1 vertical plane with a single piston, which is a 1/12 turn for better understanding the figure is rotated;

3 shows a partial view of a modified embodiment of the valve according to Fig. 1;

Fig. 4 is a plan view of the swash plate in Fig. 1;

FIG. 5 is a partial view of FIG. 1 with the swash plate in a position assumed at zero delivery rate will;

Fig. 6 is a section along the line A-A in Fig. 5;

Fig. 7 is a partial view of a section along the line B-B in Fig. 6;

8 shows a partial view of a section 3 along the line C-C in FIG. 6j

9 shows a longitudinal section along the line A-A in FIG. 10 of a pump with twelve pistons which supply four delivery lines and with further improvements;

Fig. 10 is a section along the line E-B in Fig. 9;

11 shows a partial view of a longitudinal section of one of the in FIG. 9 shown similar pump in a modified AusfUhrungsform;

FIG. 12 shows a section along the line D-D in FIG.

In Fig. 1 it can be seen that the pump consists of two main parts, a pump body 1 with a pump piston 3 and a pump head 2 with a drive shaft 4, which has a rope on an axis 5

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mel disc 6 carries. If the shaft 4 of a not shown Motor is rotated, it drives the swash plate 6, which alternately pushes back the pump piston 3, which is supported by springs 7 be pressed against. The swash plate 6 is articulated on the axis; the inclination of the swash plate 6 can be changed the movement of the pump piston 3 is reduced with a reduction in the angle of the swash plate 6.

The inclination adjustment of the swash plate 6 is done by a hydraulic actuator with an actuating piston 8, the is slidably guided in a bore 8a which is axially machined into the drive shaft 4 and with a sliding sleeve 8b can be provided; during operation, the pressure of the pump piston 3 acts on one side of the swash plate and on the other Side of the pressure of the actuating piston 8.

When the number of the pumping pistons 3 is odd, for example five, the one on the front side of the swash plate 6 acting pressure generated alternately by two or three pump pistons. As a result, the pulsates on the back of the actuating piston 8 prevailing pressure at high frequency, which eliminates the friction between the various moving parts of the system will. For example, the pressure acting on the front of the swash plate varies with a pump with five pump pistons by 2.5 - 20%, which at a rotational speed of the shaft 4 of 1500 revolutions per minute a pulsation with a Frequency of 250 per second.

If the number of pump pistons 3 is even, for example six, and the pump has two delivery lines, the Swash plate 6 also pressure pulsations of high frequency, if the two delivery lines are not at the same pressure. If both delivery lines are at the same pressure, or if the pump has a delivery line, a high frequency pulsation also occurs, which is caused by that because of the occurring in the prints in question

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Compressibility phenomena the course of the Piston in relation to the fall line of the swash plate 6 is not symmetrical to the course of the pressure drop.

It can be seen from FIGS. 2 and 4 that the swash plate 6 has a central blind hole 9 which extends via a recess 10 is connected to a circular segment-shaped slot 11, via the when the swash plate rotates, sliding pieces 12 of the pump piston 3 slide. When the sliders 12 slide over the slot 11, the pump pistons 3 are in their suction phase and liquid located in a chamber around the swash plate 6 is in bores, in which the pump piston 3 slide, sucked in.

On the way of the sliders 12 during the displacement phase is passed through, a plurality of passages 14 are arranged, each of which is provided with a check valve 15 and is in communication with a central chamber 16 formed in the rear of the swash plate 6 (Fig. 2).

As shown in Fig. 4, the passages 14 are in one such a distance from each other that the central opening one slider of each group of sliders belonging to a conveying line is always in communication with a passage is.

As a result, if the pump has several delivery lines, the pressure in the chamber 16 is always the greatest of the Is the pressures prevailing in the lines connected to the pump.

From FIGS. 5 and 6 it can be seen that the axis 5 on which the swash plate 6 is articulated over its entire length has a channel 34 which communicates with the chamber 16 via a channel 35 and a groove 35a, both in the body of the Swash plate are formed. From Figs. 7 and 8 it can be seen that passages 36 and 37 ra-

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dial into bearing bushes 38 that sit in drive shaft 4 and in which the axis 5 rotates. The channels 36 are directed towards the side of the swash plate 6 on which the pump pistons 3 rest and the channels 37 are directed to the side of the swash plate 6 on which the actuating piston 8 rests. This asymmetry has the aim of at least partially compensating for the effect of the torsion that the axis 5 because of the asymmetrical effect of the Pump piston 3 is exposed to swash plate 6.

From Fig. 1 it can be seen that the chamber 13 is supplied with liquid from a storage container via a channel 17i which is recessed transversely through the pump body along the A _o hse of the pump body 1, whereby a supply of the blind hole 9 and thereby the slot 11 is favored.

This arrangement favors the supply of liquid through a channel which leads perpendicularly into the center of the chamber 13 the supply of the circular segment-shaped slot 11 by the centrifugal effect on the hydraulic fluid and reduces the disturbing influence resulting from the movement of the pistons.

The actuating piston 8 lies on the rear surface of the swash plate 6 by means of a slider 18 which closes the chamber 16.

This slider 18 has a circumferential groove 19 which touches the swash plate and a circumferential groove 20 which the spherical Head of the actuating piston 8 touches. These two grooves are with pressurized oil from the chamber 16 through a Channel 21 is supplied with a calibrated passage 22.

The actuating piston 8 is extended at its rear part by a rod 24 which slides in a bore 25 which opens into a chamber 26 closed with a stopper 27.

The rod 24 has a cylindrical extension 24a which, together with the bore 25, forms an annular calibrated passage variable length forms. / 7

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The actuating piston 8 and the rod 24 together with the bore 8a form an annular chamber 23. The actuating piston 8 carries a valve which receives high and low pressure and feeds either one or the other of the chamber 23 to the actuating piston 8 in to operate one or the other direction, the inclination of the swash plate 6 is changed and the-e supplied by the pump Delivery rate or flow rate is adjusted.

In the example shown, this valve is formed by a slide 29 which is in a bore 28 in the rod 24 and in the Adjusting piston 8 slides and works against a spring 30. The slide 29 has an annular shape in its central section Chamber 29a, into which a channel 31 opens, which is in communication with the chamber 23; the chamber 29a can by shifting the Slide 29 are connected via a channel 332 with the high pressure chamber 16 or via a channel 33 with the low pressure chamber 13.

When the shaft 4 is not moved, the individual parts are in the positions shown in FIG. 1; against it Fig. 2 shows the individual parts in an operational equilibrium position.

The swash plate 6 absorbs on one side the pressure caused by the pump piston 3, which is kept in equilibrium by the pressure of the actuating piston 8. If P. and Pp are the delivery pressures (in the case of a pump with two three pistons, which supply two independent delivery lines) and s is the total cross-section of the actuating piston 8, the equilibrium pressure ρ in the chambers 25 and 26 is determined as a function of P. and P ₂ given the following formula: P χ s β P ₁ χ S ₁ + P ₂ χ S ₂ ,

where S ,. and S _{2 are} the mean effective surfaces of the groups of pump pistons 3, that is to say the mean total surface of a piston assembly connected to a common delivery line.

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In the special case in which the pump supplies two delivery lines with identical delivery rates or, more precisely, if S. = S ₀ = S, the result is: _ς

^ P = Ix (P ₁ + P ₂ ).

This pressure ρ acts on the slide 29 against the spring 30; in equilibrium, both forces are equal.

It can be seen that the role of the check valves 15 is to apply the greater of the two pressures P. or Pp of the valve to be selected and so that with a displacement of the valve there is a constant corresponding displacement of the actuating piston 8 can go hand in hand.

If one of the pressures P. or P ₂ increases, the pressure on the swash plate 6 increases accordingly, which leads to an increase in the equilibrium pressure ρ in the chambers 23 and 26. The increase in the pressure in the chamber 26 causes the slide 29 to be pushed in , which connects the channels 32 and 31 in such a way that the large pressure prevailing in the chamber 16 is passed into the chamber 23. The actuating piston 8 then begins to move to the right, at a speed that is caused by the penetration of the slide is fixed; the penetration continues as long as the imbalance between the pressure in the chamber 26 and the action of the spring 30 continues.

'As soon as the movement of the actuating piston 8 begins, the volume of the chamber increases. The amount of liquid necessary for this volume increase per unit of time is proportional to the speed of the actuating piston 8. This liquid comes out of the chamber 23 and experiences a pressure loss in the throttle point defined by the cylindrical extension 24a, which is proportional to the flow rate, ie to the speed of the Control piston 8 is. The signal pressure in the chamber 26, which had the amount ρ in equilibrium and which has assumed the amount ρ when P- or Pp has been increased, falls in the hatred, as the slide 29 moves in and the actuating piston _{/ o}

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8 accelerated. The whole thing happens to a few hundredths of a millimeter. This lowering of the pressure in the chamber 26 reduces the imbalance on the slide 29, which stops. This stopping occurs essentially when the pressure in the chamber 26 is again ρ, because the inward movement of the slide 29 and the movement of the piston 8 take place on a few hundredths of a millimeter and the preload of the spring 30 remains essentially unaffected. The initial pressure drop along the throttle point defined by the cylindrical extension 24a is therefore almost exactly p'-p, that is to say that the initial speed of the actuating piston 8 is essentially proportional to the initial difference between p ¹ and the pressure corresponding to the tension of the spring 30 .

However, since the valve is still open, the movement of the actuating piston 8 continues. The spring 30 is compressed more and more and gradually returns the slide 29 to its equilibrium position. The speed of the actuating piston 8 is at any moment essentially proportional to the remaining difference between p ¹ and the pressure corresponding to the tension of the spring 30 at the moment in question until this difference is zero, ie between the tension of the spring and the pressure p ¹ in the chambers 23 and 26 are again in equilibrium.

In practice, the determination of the spring characteristic to achieve the desired relationship is done experimentally, Point by point. A spring of very low stiffness results in a stroke volume that is only a function of the pressure little changes - accordingly you get a pump that keeps its delivery line at almost constant pressure; In any case a spring with constant stiffness results in a drive torque on the shaft 4, the value of which decreases as the pressure increases increase, i.e. the stroke volumes decrease; a spring is necessary to achieve a constant drive torque to use, the stiffness of which decreases with their deformation.

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It should be noted that the spring as a function of the selected relationship between pressure and stroke volume or as a function Depending on the technological conditions, it can be a single spring or in the form of several separate springs or one in two groups: One between the slide 29 and the shaft 4, the spring 30, the other between the slide 29 and the rod 24, as in FIG. 3 shown, the spring 30a.

Example; It became a pump with two delivery lines with six

! Pump—

same / piston 3 built of 31.00 mm diameter that at maximum Stroke volume (maximum inclination of the swash plate 6) delivers two flow rates of 50 cm per revolution each. The piston has a diameter of 60 mm, the rod 24 has a diameter of 18 mm and the slide 29 of 6 mm.

In the equilibrium position shown in Fig. 2 and with P ^ = 350 bar and Pp = 250 bar one can easily calculate:

2
TT

P = 1.5 (350 + 250) - # »242.7 bar

2 2

The spring 30 is therefore kept in equilibrium at a pressure of 242.7 bar, which acts on the slide 29.

If, due to the increasing load in one of the pump lines, the pressure P ^ rises to 400 bar, the same calculation shows that the pressure ρ ^{rises to p 1} = 262.9 bar.

The spring 30 is no longer sufficient to hold the slide 29, which pushes in and, as explained above, the / piston 8 starts. Since the equilibrium is reached very quickly and over a very short path and the displacements of the valve are negligible it can be assumed that the balance of the spring 30 remains unchanged. The valve stops opening when the Pressure in the chamber 26 has fallen to 242.7 bar. In chamber 23 there is a temporary bridge p't, which is: / 11

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2 2 2 2 2

y (TS - Έ) χ, 242.7 + ^ (Εδ ~ - Τβ ) χ p't = 1.5. ^ 3T (400 + 250), 4 4 4

that means:

p't = 1.5 x ~ χ 650 _χ 242 _f 7 and

2 2
BÖ - TE

PH - - # **. 7 bar

2 60 2 TS - F 2 2 - 18th

The pressure loss in the calibrated bore defined by the cylindrical extension 24a is therefore 264.7-242.7 = 22 bar and the speed of the actuating piston 8 is proportional to this size.

The movement of the actuating piston 8 continues and the spring 30 compresses. When a compression is reached which establishes equilibrium, for example 260 bar, a calculation similar to the above shows that the pressure p't in the chamber 23 is 263.1 bar. The pressure loss in the calibrated bore formed by the cylindrical extension 24a is accordingly only 263.1-260.0 = 3.1 bar and it can be seen that the speed of the actuating piston 8 is reduced by more than 86% in relation to the initial speed. The actuating piston 8 becomes slower and slower and reaches zero speed when the spring keeps the pressure of 262.9 bar in equilibrium.

In order to ensure better stability of the parts, a spring 39 can be arranged in the chamber 23 it is to keep the actuating piston 8 in contact with the slide 18. The above calculation remains valid, mainly the influence, one such a spring as well as the influence of the spring 7 of the pump piston is negligible.

It can be seen that the calibrated bore defined by the cylindrical extension 24a provides very good control of the system.

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speed of the piston 8 as a function of the remaining deviation to be compensated, ie a very good attenuation of readjustments that are constantly necessary to maintain the selected relationship between stroke volume and pressure. It can also be seen that the usable length of the throttle point increases when the stroke volumes decrease. Correspondingly, a certain change in pressure causes an initial speed that is lower, the smaller the stroke volume; Experience shows that this is necessary in order to obtain the same degree of stability everywhere, especially for example when operating with a constant drive torque P ^ χ Vj + 1? 2 ^x ^ 2 ⁼ constant, where V ^ and V ~ are the stroke volumes of the label both lines.

The arrangement can also be used in cases where the separate delivery lines with pistons of different Diameter to be charged; the above calculations remain applicable without change.

FIGS. 9 to 12 relate to a modified embodiment the components for the selection of the highest delivery pressure and its line to the control valve.

In the case of the pump shown in FIGS. 1 to 8, the receives Valve the high pressure via the channel 32, which opens into the slide 18, which is the chamber 16 in which the highest of the delivery pressures prevails, concludes. In contrast, in the embodiment shown in FIGS. 9 to 12, the highest delivery pressure is selected by means of check valves 40, which are arranged in the pump body 1 immediately downstream of the piston 3.

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The pump has twelve pump pistons 3, which are combined in groups of three, so that the pump has four independent delivery lines feeds: the first delivery line is fed by the pistons 3a, the second by the pistons 3b, the third by the Piston 3c and the fourth of pistons 3d; the delivery lines of the pistons of a group are among themselves downstream of the Check valves 42, 42b, 42c, 42d through channels 41, such as 41a for the piston 3a, connected.

The promotion. group a is correspondingly removed from check valve 40a, group b from check valve 40b etc .; The check valves 40a, 40b, 40c and 40d are connected by a channel 43 downstream of the terminating part. Accordingly, the pressure in channel 43 is always the greatest of the four delivery pressures.

This pressure selected in this way is passed through a line 44, which is formed in the housing 1, 2 of the pump, to a channel 45, which is formed in the piston 8 and opens on the side of the slide 29 of the valve.

The connection between the channel 44 and the channel 45 takes place by means of a rotary seal which is formed in a ring 46 which sits under friction on the shaft 4 and through a Holding member 47 is immovable.

The chamber 29a of the slide 29 communicates via a channel 31 on the one hand with the chamber 23 on the rear side of the piston and on the other hand with the interior of the slider 18 'in connection.

This slider 18 'is preferably double conical and takes on the one hand the ball head of the actuating piston 8 and on the other hand the spherical section of a on the back of the swash plate 6 lying core 48 on. In the body of this core .48 a channel 35a is formed, which communicates with the channel 35 stands.

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233060?

This modified embodiment has two advantages over that shown in FIG. 1; On the one hand, the device for selecting the highest delivery pressure is no longer inside the swash plate, which is considerably simpler from the point of view of manufacture; ^! much better; significantly better. In the pump shown in FIGS. 1 to 8, the pressure inside the slider 18 is always the greatest of the delivery pressures, which forces one to define the contact circle between the actuating piston 8 and the slider 18 as a function of the greatest possible delivery pressure and which results in a hydraulic one Leads to imbalance in the abutment of the actuating piston on the slider; this imbalance requires an arrangement, as represented by parts 19 to 22, which allows restricted leakage flow to lubricate the sliding surfaces.

In contrast, in the embodiment according to FIGS. 9 and 10, the The pressure inside the slide is always equal to the pressure in the chamber 23 and therefore practically always equal to the pressure that acts on the actuating piston 8.

In certain cases it can prove advantageous to automatically lock the movement of the swash plate 6 to have when this takes the position with the delivery rate zero.

To this end, as shown in Figures 11 and 12, the check valves 40 are not downstream of the check valves 42, but upstream in front of the chambers of the pump piston 3.

As shown in FIG. 12, there can be a check valve 40 in each chamber or, better still, only a single check valve

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40 arrange for a delivery line, in that one preferably chooses four pistons that follow each other and their position analogous to that according to Fig. 10 is, but the channels such as 41a not shown are because they are in front of the check valves 42 in height.

In this Figure 12, reference numerals denote 3c and 3d
not the delivery pistons of the pump but the holes in which the pistons slide.

Expectations;

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Claims (18)

Expectations 1 J Hydraulic pump with depending on one or more Delivery pressures variable stroke volume with a rotatable swash plate, the inclination of which with one in a carrier of the swash plate mounted, hydraulically operated actuating piston is adjustable, which is controlled by a valve that reacts to changes of the pump delivery pressure responds, characterized in that the valve has a slide (29), which is acted upon on the one hand by the pressure prevailing on the rear side of the actuating piston (8), which is dependent on the delivery pressures and on the other hand is subjected to the opposing action of a spring (30) and is movable to and fro between positions is in which he has a line (33) in which the suction pressure of the pump prevails, or a line (32) in which the The highest of the delivery pressures prevails, connects with the working chamber (23) of the actuating piston (8). 2. Pump according to claim 1, characterized in that that the slide (29) of the valve counter-pressing spring (30) has a stiffness characteristic curve, the point for Point is determined according to the desired relationship between flow rate and pressure. 3. Pump according to one of claims 1 or 2, characterized in that the valve is inside the actuating piston (8) is arranged. 4. Pump according to claim 3, characterized in that that the actuating piston (8) for the swash plate (6) has two different cross-sections, that a chamber (23) on the Rear of the large cross-section is arranged, another chamber (26) on the rear of the small cross-section that both 308882/0575 ORIGINAL INSPECTED / 2 de chambers (23, 26) via a calibrated passage (25) in connection stand that the chamber (23) located on the rear side of the large cross-section by the interposition of the valve both is acted upon with both high and low pressure in such a way that the valve is closed in the event of equality, and the two Chambers are at the same pressure, which depends on the delivery pressure. 5. Pump according to claim 4, characterized in that that the slide (29) of the valve extends into the karat Stellmer (26) on the back of the small cross section of the piston (8) extends and is acted upon by the pressure prevailing in the chamber (26), so that every change in the delivery pressures Displacement of the slide (29) of the valve causes. 6. Pump according to claim 5, characterized in that that the slide (29) of the valve counter-pressing spring (30) with variable stiffness at a fixed stop is applied, which is formed by a partition that the two chambers (23, 26) on the back of the actuating piston (8) for the Swash plate (6) separates. 7. Pump according to claim 5, characterized in that that the slide (29) of the valve is held on the one hand by a spring (30) which rests against a fixed stop, the one separating the two chambers (23, 26) on the back of the actuating piston (8) for the swash plate (6) Partition wall is formed and on the other hand by a spring (30a) which rests on a rod (24) of the actuating piston (8). 8. Pump according to claim 4, characterized in that that the calibrated passage (25) through an annular space between the small cross-section of the actuating piston (8) forming rod (24) and an opening in the dividing wall separating the two chambers (23, 26) is formed. 9. Pump according to claim 8, characterized in that that the rod (24) has a cylindrical projection (24a) /, 309882 / 057S so that the length of the calibrated passage (25) is variable is. 10. Pump according to claim 1, characterized in that that the swash plate (6) along the path of sliders (12) for the plant of the pump piston (3) in the section, which corresponds to their promotion, has a plurality of passages (14), each of which with a check valve (15) is provided and which are in communication with a central chamber (16) incorporated in the rear of the swash plate (6), and the central chamber (16) via the interior of a slider (18) for contacting the actuating piston (8) with an in the actuating piston (8) formed, the valve opening channel (32) is in communication. 11. Pump according to claim 1, characterized in that the arrangement for selecting the highest of the delivery pressures is formed by a group of channels (43, 44, 45), which are provided with check valves (40a, 40b, 40c, 40d), are interconnected and in the housing (1, 2) of the pump downstream are arranged by the pump piston (3). 12. Pump according to claim 11, characterized in that that the check valves (40a, 40b, 40c, 40d) are arranged downstream of the check valves (42a, 42b, 42c, 42d), which sit at the exit of each of the bores in which a pump piston (3) slides. 13. Pump according to claim 11, characterized in that that the check valves (40a, 40b, 40c, 40d) upstream of the at the outlet of each bore with a pump piston (3) seated check valves (42a, 42b, 42c, 42d). 14. Pump according to one of claims 11 or 12, characterized in that all pressure sides with a check valve (40a, 40b, 40c, 4Od) are provided. / 4 309882/0575 15. Pump according to claim 11 or 12, characterized in that each delivery line has only one pressure side a check valve (40a, 40b, 40c, 40d) is provided. 16. Pump according to claim 11, characterized in that that the greatest delivery pressure is applied to the valve inside the actuating piston (8) via a channel (44) in the housing (1, 2) of the pump and is supplied via a channel (45) in the actuating piston (8). 17. Pump according to claim 16, characterized in that that the two channels (44, 45) are connected to one another by a channel in a ring (46) which is on the drive shaft (4) sits on the pump and seals it against the housing (1, 2) in which it is held in a rotationally fixed manner. 18. Pump according to claim 10 or 11, characterized in that g e k e η η ζ Make sure that the selected high pressure has a duct (34) is supplied, which is connected to two channel systems (36, 37). is the one that applies the pressure to bearing shells (38) in two diametrically opposed Forward areas of the drive shaft (4). 309882/0575