EP1715183B1 - Hydraulic axial piston pump - Google Patents

Description

Technical area

The invention relates to a hydraulic (ie suitable for conveying a liquid) axial piston pump, which is particularly suitable for use as a feed pump for a fuel oil burner.

State of the art

A pump of the type mentioned is from the EP-A1-0 180 510 known. The pump described in this document has a provided with a hollow cylinder cylinder block. A arranged outside the cylinder block swash plate moves by means of a piston rod which passes through an open base of the hollow cylinder, a delivery piston in the hollow cylinder periodically back and forth. By the movement of the delivery piston, the volume of a delivery chamber is changed periodically. The delivery chamber is bounded by the other (also referred to as the front), substantially closed base surface of the hollow cylinder, which is facing this side facing the delivery piston and a part of the lateral surface of the hollow cylinder. The delivery chamber is intended for receiving and further conveying the liquid to be conveyed or pumped, the periodic change of the delivery chamber volume causing the actual pumping process. The piston movement in the sense of an enlargement of the delivery chamber volume is referred to as a suction stroke, while the piston movement in the sense of a reduction of the delivery chamber volume is referred to as a pressure stroke. An inflow line for the liquid to be conveyed opens through the conveyor piston opposite the front base of the hollow cylinder through into the delivery chamber. In the inflow line designed as a check valve suction valve is arranged, which is pressed by means of a closing spring in its closed position. For a simplified opening of the suction valve during the suction stroke, the closing spring according to EP-A1-0 180 510 further coupled via a control linkage with the swash plate. During the pressure stroke, the liquid is conducted from the delivery chamber through an outflow line into a valve chamber formed in the cylinder block, in which a pressure valve designed as a check valve is arranged. From the valve chamber, the liquid flows past the pressure valve to an outlet opening on the outside of the cylinder block.

Another generic pump goes out of the DE-OS 1,939,242 (Corpet Louvet & Cie.). This document describes a hydraulic axial piston pump with a plurality of pistons in a cylinder block. The piston stroke in the cylinder becomes an in The liquid sucked in by the cylinder is pumped out through a discharge line. The flow is regulated by pressure valves. These are held by a respective closing spring element in the closed position. The closing spring element is formed by a helical spring which is centered on the one hand on the inside on a small cylindrical pin of the valve and on the other hand on the outside in its bearing, which is formed by the sealing plug.

The generic pumps described in the cited documents have a complicated construction and take up a considerable amount of space.

Presentation of the invention

The object of the invention is to improve a generic axial piston pump such that it has a simple construction and a small space requirement.

The solution of the problem is defined by the features of claim 1. According to the invention, an axial piston pump for conveying a liquid comprises a cylinder block which has at least one outer surface which, at least in one part, has the shape of a lateral surface of a cylinder. In the cylinder block at least one hollow cylinder is formed, in which a delivery piston is displaceably arranged such that between the walls of the hollow cylinder and an end face of the delivery piston, a delivery space for receiving the liquid to be delivered is enclosed. The axial piston pump further comprises a discharge line leading away from the delivery chamber for the liquid to be conveyed, which is designed as a channel in the cylinder block and leads from the delivery chamber to the at least one cylindrical jacket-shaped part of the outer surface of the cylinder block. The axial piston pump finally comprises a non-return valve serving as a pressure valve, the valve seat of which is arranged in a section of the channel of the discharge line which is directly adjacent to the cylindrical jacket-shaped part of the outer surface of the cylinder block. A made of an elastic material ring or C-shaped, along a circumferential line of the cylinder jacket-shaped portion of the outer surface of the cylinder block extending closing spring element is arranged such that it acts as a closing spring for the pressure valve.

In the cylinder jacket-shaped part, the outer surface of the cylinder block can in particular have the shape of a lateral surface of a straight circular cylinder. Basically, the outer surface in this game but also have another suitable cylinder jacket shape, for example, the shell shape of an elliptical cylinder. In the present context, "along a circumferential line" means either along a circumferential line (or a circumferential line section) on the outer surface of the cylinder block or along a groove along a circumferential line (or a circumferential line portion) is formed in the outer surface of the cylinder block.

The use of a ring-shaped or C-shaped elastic closing spring element allows easy manufacture and assembly of the closing spring of the pressure valve and thus a cost-effective and compact construction of the axial piston pump.

The pressure valve may either be formed as a valve seat itself adjacent to the outer surface of the cylinder block channel portion, or it may be a separate valve seat member inserted into this channel section. The arrangement of the valve seat in the immediate vicinity of the outer surface of the cylinder block allows easier access to the valve seat, which is advantageous for the assembly and for any revisions of the pump.

By the outflow line of only one side (namely, the outer surface of the cylinder block) is formed as a channel in the cylinder block, a simple production of the axial piston pump is made possible. The channel may be punctured, in particular as a straight channel, e.g. be carried out by drilling or other suitable Abtragungsverfahren in the cylinder block. In addition, the arrangement of the mouth of the discharge line in the delivery chamber (also referred to as outlet of the delivery chamber) in the immediate vicinity of the front base and thus the mouth of the inflow in the delivery chamber (also referred to as an inlet into the delivery chamber) for an extremely small dead volume. A small dead volume allows the pump to be used for comparatively high suction heights, reduces the formation of air bubbles in the fluid delivered by the pump, and ensures efficient operation of the pump.

In the present context, the volume between the suction valve and the pressure valve of an axial piston pump is referred to as the dead volume, which is in each case also filled with liquid after the completion of a pressure stroke. A suction valve is understood to be a valve which permits the liquid flow in the inflow line in the direction of the delivery chamber upstream of the delivery chamber, but in the opposite direction (ie away from the delivery chamber).

In contrast, a pressure valve is understood to be a valve which permits the liquid flow in the outflow line in the direction away from the pumping chamber downstream of the pumping chamber, but in the opposite direction (ie towards the pumping chamber). Under a channel which leads directly from the pumping chamber to the outer surface of the cylinder block, a channel is to be understood, which leads from the pumping chamber without passage through any other chambers or cavities through directly to the outer surface, in contrast, for example, to the in EP-A1-0 180 510 described discharge line, which leads from the delivery chamber initially in a valve chamber and only from this to the outside of the cylinder block.

Preferably, the channel of the discharge line is even formed such that it leads on the shortest path from the hollow cylinder to the outer surface of the cylinder block. This creates a particularly small dead volume. As an alternative, however, other variants of the invention are possible in which the channel leads to deviating paths from the shortest path, either straight or along curves, from the hollow cylinder to the outer surface of the cylinder block.

According to a preferred embodiment of the invention, the delivery piston has a circumferential reduction in an axial region in the vicinity of its front side facing the front base surface of the hollow cylinder. Under a reduction in size is understood that the circumference of the delivery piston in an axial region is smaller than the substantially corresponding to the hollow cylinder circumference in the vast remaining area of the delivery piston. By the reduction in size, an annular channel (also referred to as an annular channel) is provided for the liquid flow between the delivery piston and the lateral surface of the hollow cylinder. The circumferential reduction is arranged in an axial region of the delivery piston such that it is arranged at maximum compression (ie with minimal volume of the delivery chamber) at least partially above the mouth of the outflow channel in the lateral surface of the hollow cylinder. In the position corresponding to the maximum compression of the delivery piston, the liquid can then flow from the delivery chamber through the annular channel directly through the outlet of the delivery chamber into the discharge channel. As a result, the delivery piston in the hollow cylinder can be pushed all the way to the front during the pressure stroke, so that in the position with maximum compression, the end face of the delivery piston is arranged in the immediate vicinity of the front base of the hollow cylinder. In this foremost position of the delivery piston, its front end side can be arranged partially or even completely in front of the mouth of the outflow line. It is ensured by the annular channel that the liquid can nevertheless still flow out of the delivery chamber through the outflow channel. Overall, the annular channel allows a further reduction of the dead volume.

The circumferential reduction may be formed in the foremost axial region of the delivery piston which adjoins the front end side of the delivery piston. In principle, however, it is also possible to form the circumferential reduction in the form of a recessed from the front end of the delivery piston annular channel and further form connecting channels in the piston, which extend in the axial direction from the annular channel to the front end of the delivery piston and thereby a liquid-conducting connection between the annular channel and create the pumping room.

Preferably, a check valve serving as a suction valve, which has a shut-off body with a flat portion, arranged in the axial direction immediately before the hollow cylinder such that the flat portion forms a part of the boundary wall of the pumping chamber in the closed state of the suction valve. By the flat part of the shut-off is formed as an integral part of the delivery chamber boundary wall, there is a particularly small dead volume. The directed to the delivery chamber side of the flat portion of the shut-off can in particular be designed and arranged such that it forms a part of the front base of the hollow cylinder in the closed state of the suction valve. In principle, however, other suitable suction valves for the inventive axial piston pump can be used.

Advantageously, the cylinder block is arranged on a selectively replaceable type in a pump housing which at least partially surrounds it such that the outer surface of the cylinder block is enclosed by the pump housing in the region of the discharge line (ie in the region of the mouth of the discharge line in the outer surface) is. This creates the possibility to arrange individual components of the pressure valve in the pump housing.

The pressure valve may be arranged at least partially outside the cylinder block in the pump housing. It can e.g. the closing spring element of the pressure valve and / or a shut-off body of the pressure valve may be arranged in the pump housing outside the cylinder block. Preferably, in the pump housing outside the cylinder block pressure valve components are arranged, which are subject to a comparatively small wear during operation of the pump. This makes it possible to replace in the course of a revision of the pump, only the cylinder housing together with the parts arranged therein, which are subject to a relatively large wear, while the pump housing and the parts arranged therein can be used.

The entire cylinder block may be formed as a one-piece molding to allow a quick and easy replacement of the cylinder block. Advantageously, it is made of a comparatively wear-resistant material in order to increase its service life. In contrast, the pump housing can be made of a less wear-resistant, but better machinable material, since it is subject to a much smaller wear than the mechanically highly stressed cylinder block.

Depending on the intended use, however, variants of pumps according to the invention with multi-part cylinder blocks are also possible.

Preferably, the cylinder block is formed such that its outer surface at least in a portion which includes the mouth of the channel of the discharge line in the outer surface, the shape of a lateral surface of a right circular cylinder and in this circular cylindrical shell a parallel to the hollow cylinder axis cylinder block axis (namely, the cylinder axis of circular cylindrical lateral surface) defined. Thereby, a particularly simple production of the cylinder block is made possible by the outer surface of the cylinder block can be made by turning on a machine tool. Next can in the cylinder block for cylindrical shell surface parallel hollow cylinder can be easily produced by drilling.

If the axial piston pump has two or more pressure valves, these may be designed and arranged such that the closing spring element acts as a common closing spring for these pressure valves. The pressure valves may in particular be provided with valve seats, which are arranged substantially in the radial direction within a certain circumferential line of the cylinder jacket-shaped portion of the outer surface of the cylinder block, wherein this circumferential line is that which extends along the closing spring element. The use of a single closing spring element for a plurality of pressure valves ensures a further simplification of the construction of the axial piston pump.

Advantageously, the closing spring element is designed and arranged such that it simultaneously acts as a shut-off of the pressure valve or the pressure valves. By using a single component that acts both as a closing spring element and as a shut-off body, the construction of the axial piston pump can be further simplified. According to a structurally particularly simple embodiment of the invention, the closing spring element is even designed and arranged so that it acts simultaneously as the sole closing spring and the only shut-off for the pressure valve or valves, the valve seats are arranged radially within him in the cylinder block. These pressure valves can then be designed completely free of further closing springs and / or shut-off bodies.

A diffusion element (also referred to as a mixing element) which causes a reduction in the size of any gas bubbles present in the liquid can be arranged upstream in the inflow line immediately upstream of the suction valve.

The diffusion element ensures a mixing of the medium flowing through it. If gas bubbles are present in the liquid to be conveyed, the diffusion element ensures a mixing of these gas bubbles with the liquid and thus a reduction of the gas bubbles. Such gas bubbles, In particular, air bubbles can occur when the pressure in the inflow line is comparatively small, which is the case in particular for comparatively large suction heights (ie, large heights of the pump above the liquid level of the liquid to be suctioned by the axial flow pump through the inflow line). At suction heights of typically over three meters there is a risk that air will be released from the aspirated liquid and form bubbles in the liquid. Without a diffusion element, the bubbles can reach a size which necessitates venting of the delivery chamber, which leads to pump failure, since the delivery chamber must be vented against pressure via the suction valve.

The diffusion element may be a filter element made of a sintered material or a fine mesh screen. Such diffusion elements are particularly simple and inexpensive. In principle, however, it is also possible to use other suitable diffusion elements which ensure effective reduction of any gas bubbles which may be present in the liquid.

From the following detailed description and the totality of the claims, further advantageous embodiments and feature combinations of the invention result.

Brief description of the drawings

Fig. 1

eine Axialkolbenpumpe in einer vereinfachten Querschnittansicht;

Fig. 2

einen Ausschnitt aus einer Axialkolbenpumpe gemäss einer ersten Ausführungsart der Erfindung in einer vereinfachten Querschnittansicht;

Fig. 3

einen Ausschnitt aus einer Axialkolbenpumpe gemäss einer zweiten Ausführungsart der Erfindung in einer vereinfachten Querschnittansicht;

Fig. 4

einen Ausschnitt aus einer Axialkolbenpumpe in einer vereinfachten Querschnittansicht.

The drawings used to explain the embodiment show:

Fig. 1

an axial piston pump in a simplified cross-sectional view;

Fig. 2

a section of an axial piston pump according to a first embodiment of the invention in a simplified cross-sectional view;

Fig. 3

a section of an axial piston pump according to a second embodiment of the invention in a simplified cross-sectional view;

Fig. 4

a section of an axial piston pump in a simplified cross-sectional view.

Basically, the same parts are provided with the same reference numerals in the figures.

Ways to carry out the invention

In Fig. 1 an axial piston pump is shown in a simplified cross-sectional partial view. It serves for a better understanding of the invention, as described below in connection with the FIGS. 2 and 3 is shown.

In the Fig. 1 Axialkolbenpumpe shown serves for conveying fuel oil in a heating system for a building. It comprises a cylinder block 10 whose outer shape substantially corresponds to the shape of a straight circular cylinder and is formed by a circular cylindrical lateral surface and two circular base surfaces. By the circular cylindrical surface a cylinder block axis 12 is defined, namely the axis of the circular cylinder. The cylinder block 10 is integrally formed and made of a comparatively wear-resistant steel. It is arranged in a cylinder block 10 completely comprehensive pump housing 14, 16, which is made of Antikorrodal, a material that is less resistant to wear than steel, but better machinable than steel. The pump housing 14, 16 is composed of a first pump housing part 14 and a second pump housing part 16 optionally disassembled again. The cylinder block 10 is selectively releasably attached to the first pump housing part 14 by means of a screw bolt 18 leading through a bore along the cylinder block axis 12 such that it can be dismantled and replaced by the pump housing 14, 16 as required after disassembly. Next are in the circular cylindrical lateral surface of in Fig. 1 illustrated cylinder block 10 (ie, in its circular cylindrical outer surface) formed three each along a circumferential line circumferential grooves, in each of which a sealing ring 20, 22, 24 is received. These sealing rings 20, 22, 24 provide for a seal between the cylinder block 10 and this comprehensive pump housing 14, 16th

In the cylinder block 10, three mutually identical hollow cylinders 26, 28 are formed, which are each arranged at the same radial distance between the lateral surface of the cylinder block 10 and the cylinder block axis 12. They each have the shape of a straight circular cylinder with parallel to the cylinder block axis hollow cylinder axis 30, 32. Each hollow cylinder 26, 28 is each with respect to the cylinder block axis 12 by 120 degrees offset from the other two hollow cylinders 26, 28 are arranged. In the presentation of Fig. 1 the cross-sectional plane passes through the one of these hollow cylinder 26 (the upper in Fig. 1 ). For better clarity, in the presentation of Fig. 1 another of these hollow cylinders 28 (the lower in Fig. 1 ), which is offset in the cross-sectional plane (ie offset by 60 degrees with respect to the cylinder block axis 12).

The hollow cylinders 26, 28 are each bounded by a first base surface (also referred to as a front base surface) and a circular cylindrical lateral surface. In each hollow cylinder 26, 28 each a delivery piston 34, 36 in the direction of the associated hollow cylinder axis 30, 32 slidably disposed such that between the first base of the hollow cylinder 26, 28, one of these facing end side of the delivery piston 34, 36 (as a front end side the delivery piston 34, 36) and a part of the lateral surface of the hollow cylinder 26, 28 a delivery chamber 38, 40 is included for receiving the fuel oil to be delivered. The three each formed by a hollow cylinder 26, 28 and a slidably received therein delivery piston 34, 36 formed piston-cylinder assemblies are identical to each other and arranged with respect to the cylinder block axis 12 rotationally symmetrical to each other.

The drive device for an axial piston pump of Fig. 1 shown type is known per se and is therefore described only briefly. A coaxial with the cylinder block axis 12 and arranged in the second pump housing part 16 rotatably mounted drive shaft 42, at the cylinder block 10 facing the longitudinal end an inclined to the shaft axis arranged swash plate 44 is fixedly mounted, is not one of shown drive means rotated. The rotating together with the drive shaft 42 swash plate 44 which is arranged in the pump housing 14, 16 outside of the cylinder block 10, thereby cyclically actuates the delivery piston 34, 36 in the axial direction back and forth by against the spring force of return springs 46, 48 on the from the delivery chambers 38, 40 facing away from the longitudinal ends of the delivery piston 34, 36 presses. The delivery pistons 34, 36 are designed as piston rams 50, 52 in the region of these longitudinal ends, which projects out of the cylinder block 10 in the axial direction through the open second base surfaces of the hollow cylinders 26, 28. Instead of a drive device based on a swashplate 44, just as well any other suitable drive device for driving the delivery pistons 34, 36 could be used.

In the presentation of Fig. 1 the upper delivery piston 34 is shown in its maximum compression position. In this position, with minimal delivery chamber volume 38, it is pushed completely forward in the hollow cylinder 26, so that its front end side is arranged in the immediate vicinity of the front base surface of the hollow cylinder 26. In contrast, the lower one in Fig. 1 illustrated delivery piston 36 shown in its position with minimal compression. In this position with maximum delivery chamber volume 40, it is displaced completely in the hollow cylinder 28 to the rear, so that its front end side is arranged at a considerable distance relative to the front base surface of the hollow cylinder 28.

Each piston-cylinder arrangement further comprises one each through the first (front) base surface of the hollow cylinder 26, 28 into the delivery chamber 38, 40 inflowing inflow line 54, 56 and an out of the delivery chamber 38, 40 leading outflow line 58, 60 for that promoting fuel oil.

The region of the pump arranged in front of the delivery chamber 38, 40 with respect to the direction of flow of the fuel oil to be delivered is referred to as the low-pressure region or the suction region of the pump. In this area, the fuel oil is under a comparatively low pressure, which is between the vapor pressure of the heating oil and the atmospheric pressure in the vicinity of the pump. The in terms of the Flow direction downstream of the pumping chamber 38, 40 arranged pump region is referred to as the high-pressure region of the pump, wherein prevail in this range Heizöldrücke between the atmospheric pressure and about 700 bar. During a suction stroke, the pressure in the delivery chamber 38, 40 corresponds approximately to the pressure in the suction region. During a pressure stroke, however, the pressure in the delivery chamber 38, 40 substantially corresponds to the pressure in the high-pressure region of the pump.

The discharge lines 58, 60 of all three hollow cylinders 26, 28 open on a common circumferential line on the cylinder jacket-shaped outer surface of the cylinder block 10. They are connected via a high-pressure connecting line 62 with each other and with a arranged in the first pump housing part 14 pressure port 64 in the high pressure region of the pump, wherein this high-pressure connecting line 62 is formed as the aforementioned circumferential line along circumferential groove 62 in the cylinder jacket-shaped outer surface of the cylinder block 10 comprehensive surface of the first pump housing part 14. Similarly, the inflow lines 54, 56 are connected to the hollow cylinders 26, 28 via low-pressure connecting lines (not shown) with each other and with a suction port 66 arranged in the first pump housing part 14 in the low-pressure region of the pump.

The discharge line 58, 60 of each hollow cylinder 26, 28 is a channel in the cylinder block 10 formed on one side of the outer surface of the cylinder block 10 to this hollow cylinder 26, 28. This channel leads from the delivery chamber 38, 40 arranged in the hollow cylinder 26, 28 from a point in the immediate vicinity of the front base of the hollow cylinder 26, 28, straight on the direct and shortest way through the lateral surface of the hollow cylinder 26, 28 therethrough to the outer surface of the cylinder block 10. That is, the channel of the discharge line 58, 60 in the radial Direction both in relation to the axis 30, 32 of the hollow cylinder 26, 28 and with respect to the cylinder block axis 12 from the delivery chamber 38, 40 to the outer surface of the cylinder block 10 extends.

The delivery pistons 34, 36 have a circumferential reduction 68, 70 in their foremost region adjoining the front end side. As a result, in the foremost region of the delivery piston 34, 36, an annular channel between the Delivery piston 34, 36 and this comprehensive hollow cylinder 26, 28 created. As in Fig. 1 recognizable by the example of the upper delivery piston 34, its front end face in front of the mouth of the outflow line 58 is arranged in the delivery chamber 38 in its foremost position. However, in this piston position, the annular channel is arranged above the mouth of the outflow channel 58, so that even in this position fuel oil can still flow out of the delivery chamber 38 through the outflow channel 58.

Upstream of the delivery chamber 38, 40 is arranged in the axial direction immediately before each hollow cylinder 26, 28 depending serving as a suction valve check valve. At the in Fig. 1 The axial piston pump shown, the suction valves are each provided with a shut-off in the form of a ball 72, 74, which are arranged in the inflow line 54, 56 upstream of the hollow cylinder 26, 28 immediately before the first base.

In the Fig. 4 axial piston pump shown differs only in terms of the design of the suction valves of the in Fig. 1 shown axial piston pump and is otherwise identical to the latter formed. This in Fig. 4 illustrated suction valve in the form of a check valve is a conical seat valve. It has a shut-off, which is provided with a flat portion 174 and formed conically on its side facing the valve seat edge. The shut-off body is arranged in the axial direction upstream immediately before the hollow cylinder 28 such that the flat portion 174 forms a part of the boundary wall of the delivery chamber 40 in the closed state of the suction valve. As a result, a particularly small dead volume is achieved.

Both in the case of in Fig. 1 shown axial piston pump as well as in the case of Fig. 4 axial piston pump shown is in the inflow line 54, 56 upstream of the suction valves immediately before the same one each made of sintered bronze, disc-shaped diffusion element 76, 78 arranged in front of each suction valve. These diffusion elements 76, 78 cause a reduction in the size of any gas bubbles present in the heating oil.

Next is in all the in Fig. 1 - 4th Axial piston pumps shown in each case for each outflow line 58, 60 each serving as a pressure valve check valve in the vicinity of the mouth of the discharge line 58, 60 arranged in the cylinder jacket-shaped outer side of the cylinder block 10. This in Fig. 1 illustrated pressure valve is provided with a valve seat which is formed in a directly adjacent to the outer surface of the cylinder block 10 lot of the channel of the discharge line 58 as a bore in the channel. The cylinder block 10 is arranged in the first pump housing part 14 in such a way that the outer surface of the cylinder block 10 is enclosed by the first pump housing part 14 in the region of the outflow line 58 (ie in the region of the mouth of the discharge line 58 in the outer surface). The pressure valve is provided with a shut-off in the form of a ball 80 which rests on the valve seat and against the spring force of a closing spring 82 in the radial direction of the valve seat (and the cylinder block) is displaced away to open the pressure valve. In this case, the valve seat and the ball 80 are formed and arranged such that the ball 80 is arranged even in the closed state of the pressure valve to more than half outside the cylinder jacket-shaped outer surface of the cylinder block 10. The closing spring 82 of the pressure valve is arranged completely outside the cylinder block 10 in the first pump housing part 14. This makes it possible, in the course of a revision of the pump, to replace only the cylinder housing 10 together with the parts arranged therein, while the spherical shut-off body 80 and the closing spring 82 of the pressure valve can be left in the pump housing 14, 16.

The in the FIGS. 2 and 3 illustrated axial piston pumps, which relate to two embodiments of the invention, differ only in terms of the design of the pressure valves of the in Fig. 1 shown axial piston pump and are otherwise identical to the latter formed.

At the in Fig. 2 Axialkolbenpumpe shown in the cylinder jacket-shaped outer surface of the cylinder block 10, a circumferential groove 284 is formed, which extends along the circumferential line on which the outflow lines 58, 60 of the three hollow cylinders 26, 28 open. This in Fig. 2 Pressure valve shown by way of example is provided with a valve seat which, as a bore 286 leading from the outer surface of the cylinder block 10 through the groove 284, into the channel of the discharge line 58 is trained. The bore 286 is dimensioned such that it can accommodate a serving as a shut-off ball 280 completely such that it is disposed radially within the circumferential groove 284 in the cylinder block 10. In this groove 284, made of nitrile rubber O-ring 282 is arranged such that it presses on the balls 280 of all three along the groove 284, mutually identical pressure valves radially inwardly and thereby acts as a common closing spring for these pressure valves.

This in Fig. 3 illustrated pressure valve differs from that in Fig. 2 shown pressure valve only in that the circumferential groove 384 is formed slightly wider and neither balls as shut-off nor holes are provided as valve seats for such balls. Instead, the nitrile rubber O-ring 380 disposed in the circumferential groove 384 is configured and arranged to simultaneously act as both a shut-off and closing element for all three pressure valves.

In summary, it should be noted that the invention provides an axial piston pump which has a simple construction and a comparatively small dead volume between the suction valve and the pressure valve.

Claims (8)

1. Axial piston pump for conveying a fluid, having a cylinder block (10), at least one hollow cylinder (26, 28) which is formed in the cylinder block (10), which has an outer surface which is in the form of a cylinder at least in one portion, a conveying piston (34, 36) which is arranged so as to be able to be displaced in the hollow cylinder (26, 28), a conveying space (38, 40) being enclosed between the walls of the hollow cylinder (26, 28) and an end-face of the conveying piston (34, 36) for receiving the fluid to be conveyed, a discharge line (58, 60) which extends away from the conveying space (38, 40), and which is formed as a channel in the cylinder block (10) and extends from the conveying space (38, 40) to the at least one cylindrical portion of the outer face of the cylinder block (10) and at least one non-return valve which acts as a pressure valve and whose valve seat is arranged in a portion of the channel of the discharge line (58, 60) that directly adjoins the cylindrical portion of the outer face of the cylinder block (10), characterised in that an closure spring element (282, 380) which is annular or C-shaped and produced from a resilient material and the zylinder block (10) with the outer face which is in the form of an outer surface of a cylinder at least in one portion, and in that the closure spring element (282, 380) extends along a peripheral line of the cylindrical portion of the outer face of the cylinder block and being arranged in such a manner that it acts as a closure spring for the pressure valve.
2. Axial piston pump according to claim 1, characterised in that, along the peripheral line of the cylindrical portion of the outer face of the cylinder block (10), there is formed a continuous groove (284, 384) for receiving the closure spring element (282, 380), the discharge line (58, 60) opening in the groove (284, 384).
3. Axial piston pump according to claim 2, characterised in that the valve seat of the pressure valve is constructed in the channel of the discharge line (58) as a hole (286) that extends from the outer face of the cylinder block (10) through the groove (284), the hole (286) being sized in such a manner that it can completely receive a ball (280) which acts as a blocking member in such a manner that it is arranged radially within the peripheral groove (284) in the cylinder block and that it is pressed radially inwards by the closure spring element (282).
4. Axial piston pump according to claim 1 or 2, characterised by the closure spring element (380) being formed and arranged in such a manner that it also acts at the same time as a blocking member (380) of the pressure valve or the pressure valves for which it acts as a closure spring element (380).
5. Axial piston pump according to any one of claims 1 to 4, characterised in that it has at least two pressure valves which are constructed and arranged in such a manner that the closure spring element (282, 380) acts as a common closure spring for the at least two pressure valves.
6. Axial piston pump according to any one of claims 1 to 5, characterised by the channel of the discharge line (58, 60) being formed in such a manner that it extends over the shortest path from the hollow cylinder (26, 28) to the outer face of the cylinder block (10).
7. Axial piston pump according to any one of claims 1 to 6, characterised in that the cylinder block (10) is arranged so as to be able to be optionally replaced in a pump housing (14, 16) which at least partially surrounds the cylinder block in such a manner that the outer face of the cylinder block (10) is surrounded by the pump housing (14, 16) in the region of the discharge line (58, 60).
8. Axial piston pump according to any one of claims 1 to 7, characterised in that the cylinder block (10) is an integral moulded component.

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