Cylinder for an axial piston pump as well as axial piston pump with such a cylinder

Abstract

The invention relates to a cylinder for an axial piston pump, comprising: several piston recesses extending in the axial direction of the cylinder for the respective insertion of a piston element movable up and down in the axial direction, and an axially extending passage which is provided on its inner circumferential side with an internal toothing for interaction with a drive shaft, characterized in that the internal toothing of the passage is not continuous in the circumferential direction, but has at least one radially outwardly extending recessed area opposite the toothing, which serves for the passage of a pin element arranged in the axial direction.

Description

[0001] The present invention relates to a cylinder for an axial piston pump and to an axial piston pump with such a cylinder.

[0002] Electric motor pumps, e.g. embodied by an axial piston pump, are also used for aviation applications, especially for extending and retracting landing gear and for drives in flight control.

[0003] In the modern aviation industry, the efficiency and reliability of hydraulic systems are becoming increasingly important, especially when integrating high-pressure applications with nominal pressures up to 5000 psi. This necessitates increased component strength while simultaneously limiting installation space, particularly in the wing area of ​​an aircraft. Such pumps must therefore be not only powerful but also compact and lightweight to meet the stringent requirements of modern aircraft. Furthermore, aspects such as energy efficiency and ease of maintenance play a crucial role in improving operating costs and the environmental performance of aircraft.

[0004] Axial piston pumps have proven particularly effective in aerospace applications due to their compact dimensions and high power density. In current technology, the sliding shoes connected to the pistons move on the swashplate in axial piston pumps. Due to the forces acting here, especially at higher speeds, it is necessary to prevent the sliding shoes from tilting by means of a retainer, thus ensuring continuous good contact between the sliding shoes and the swashplate (also called the swashplate). The necessary force is provided by a central spring in the cylinder and transmitted to the retainer via at least one, and preferably three, pins and a ball bearing, the so-called return ball bearing, which prevents the sliding shoe from losing contact with the swashplate.In known prior art implementations, the space required for the pins is provided by bores in the cylinder of the axial piston pump in order to transmit the pressure force exerted on the pins by the central spring via the ball to the retainer. One such prior art implementation is described in... Fig. Figure 4 shows the holes through the cylinder required for the pins.

[0005] However, this leads to significant disadvantages: The cylinder neck, i.e., the area between the piston recesses and the bore for the drive shaft, is weakened by the pin bores, necessitating an increase in pump dimensions to compensate for this structural weakening. For the same nominal size, this results in increased installation space and additional weight. Furthermore, the pin size cannot be reduced further due to surface pressure and the availability of standard parts, which negatively impacts pump efficiency and weight.

[0006] The present invention therefore aims to reduce the space requirements and weight of axial piston pumps. Furthermore, the invention is intended to increase the strength of the components while simultaneously minimizing the required installation space. This enables more compact and lighter pump systems that meet the high demands of modern aircraft and at the same time improve the efficiency and reliability of the hydraulic systems.

[0007] In addition to reducing space and weight, the concept according to the invention contributes to improving the overall performance and sustainability of aircraft. The optimized design allows existing pumps to be more easily adapted to new requirements, making both manufacturing processes and system maintenance more efficient. Furthermore, the increased strength of the components enables more reliable performance under extreme operating conditions, further enhancing the safety and longevity of the aircraft.

[0008] The problems listed above are overcome or mitigated by means of a cylinder according to the invention for an axial piston pump having all the features of claim 1, or an axial piston pump according to claim 10. Further advantageous embodiments of the present invention are set forth in the dependent claims.

[0009] According to the invention, the cylinder for an axial piston pump comprises several piston recesses extending axially along the cylinder for the insertion of an axially movable piston element, and an axially extending passage which is provided on its inner circumferential side with internal teeth for interaction with a drive shaft. Furthermore, the cylinder is characterized in that the internal teeth of the passage are not continuous in the circumferential direction, but have at least one radially outwardly extending, recessed area opposite the teeth, which serves to guide an axially arranged pin element.

[0010] Unlike prior art implementations, it is no longer necessary to provide separate bores or feedthroughs for inserting the pin elements, which weaken the cylinder structure. According to the present invention, the feedthrough for inserting the drive shaft is enlarged at at least one point, so that when the drive shaft is inserted, space remains on the inner contour of the feedthrough in which the pin element can be arranged. The at least one pin element used for pressure transmission is therefore not arranged through a separate hole in the cylinder, but in the cylinder according to the invention can be arranged through the feedthrough for inserting the drive shaft, so that both the drive shaft and the at least one pin element are arranged within the feedthrough.

[0011] The radially outward extending, recessed recess can be the absence of a tooth element in a toothing and / or have an outward depth that exceeds the level of a regular tooth valley of the internal toothing (whereby the greater depth compared to a regular tooth valley is necessarily required for the invention). For example, such a recess can be formed by replacing a tooth in a sequence of teeth in a regular toothing with a free space, so that a tooth that would otherwise engage continuously in a meshed state has no contact partner for engaging in a tooth valley at least at one point in the recess area. This space is then used in the axial piston pump equipped with the cylinder according to the invention to arrange the pin element.

[0012] According to a further development of the present invention, it can be provided that several radially outwardly extending, recessed recess areas are equidistant from one another when viewed circumferentially. These radially outwardly extending, recessed recess areas can extend in the axial direction of the cylinder and are preferably parallel to the axial direction.

[0013] According to a further optional modification of the present invention, it can be provided that at least three radially outward extending recessed recess areas are provided.

[0014] It is particularly advantageous if these three radially outward extending, recessed expansion areas each form an angle of 120° with each other in a cross-sectional view. The uniform spacing in the circumferential direction ensures that a compressive force transmitted by means of pin elements placed in the recesses is evenly transferred to a retraction ball or a related hold-down device.

[0015] Furthermore, according to an optional modification of the present invention, it can be provided that the internal toothing on the inner circumferential side of the feedthrough is continuous except for the at least one radially outward extending recessed area.

[0016] This maximizes the contact area of ​​a correspondingly designed counterpart of the internal gearing, so that the force to be transmitted via the gearing is as large as possible.

[0017] According to a further advantageous embodiment of the present invention, it can be provided that the tooth pitch of the gearing is the same along the inner circumferential side and that the at least one radially outward extending recessed recess area has, viewed in the circumferential direction, at least the width of a tooth element of the gearing, so that the tooth elements adjacent to the recess area fit into the regular tooth pitch.

[0018] In this implementation, the internal toothing arranged on the inside is characterized by a constant tooth pitch, interrupted only by the radially outwardly extending, recessed area. The width of this recess, viewed in the circumferential direction, can be such that it corresponds to at least the width of a single tooth element or a multiple thereof. This allows tooth elements of the internal toothing to connect to both sides of the recess, spaced apart from each other in such a way that they still conform to the regular tooth pitch pattern. This simplifies the interaction with a drive shaft inserted into the feedthrough and thus leads to a preferred embodiment of the present invention.

[0019] According to a further advantageous modification of the present invention, it can be provided that the at least one radially outward extending recessed area in the transition to a tooth element adjacent to it in the circumferential direction is designed in such a way that an adjacent descending (or ascending) tooth flank is continued without steps and continuously, preferably wherein this applies to both tooth elements of the gearing adjacent to the recess area in the circumferential direction.

[0020] The stepless transitions, or the tangential transition to the adjacent teeth, result in improved strength, making it possible to use applications with very high pump output pressures, e.g. 5000 psi.

[0021] This achieves the most continuous shape possible at the transition of a tooth element of the internal gearing to the radially outwardly extending, recessed area, which is free of steps, shoulders, or the like and continues continuously or tangentially from the sloping tooth flank (when viewed from the direction of the recess). This results in a low-wear inner circumferential area of ​​the bushing, which is significantly more resistant.

[0022] Furthermore, it can be provided that the at least one radially outward extending recessed area, viewed in the circumferential direction, connects tangentially to the contour of the toothing.

[0023] According to a further optional embodiment of the present invention, it can be provided that the cylinder is rotationally symmetrical about an axis of rotation parallel to the axial direction.

[0024] It can also be provided that the axis of rotation is identical to the center of the process.

[0025] According to a further advantageous embodiment of the present invention, it can be provided that the feedthrough with the internal toothing provided on its inner circumferential side is arranged centrally to the several piston recesses, preferably wherein the several piston recesses have the same distance to the axis of the feedthrough and are in particular arranged equidistantly to each other.

[0026] The invention further relates to an axial piston pump comprising a cylinder, in particular one according to one of the aspects discussed above, and a drive shaft having external teeth extending along its circumferential side and being inserted into the passage, such that the external teeth engage with the internal teeth of the passage, preferably wherein the external teeth of the drive shaft are formed along the entire circumference.

[0027] Furthermore, it can be provided that the outer contour of the drive shaft and the inner contour of the feedthrough are aligned in a connected state in such a way that an axially extending clearance for the passage of a pin element is created at the at least one radially outwardly extending recessed recess area of ​​the feedthrough or a radially inwardly extending recessed recess area of ​​the drive shaft.

[0028] In other words, the axial piston pump according to the invention is designed such that the bore for inserting the drive shaft accommodates not only the drive shaft itself, but also at least one pin element, which serves to transmit a force exerted by a central spring outwards to fix a retainer. Unlike the prior art, the bore is therefore used not only to transmit the rotational force from the drive shaft, but also to accommodate the at least one pin element. Consequently, a further bore provided next to the bore for accommodating a respective pin element is not required according to the axial piston pump according to the invention.

[0029] Thus, if the drive shaft is inserted into the cylinder's passage, the inner contour of the passage together with the outer contour of the drive shaft forms at least one axially extending free space for arranging a pin element.

[0030] The radially inwardly extending recessed recess area of ​​the drive shaft can be designed analogously to the radially outwardly extending recessed recess area of ​​the feedthrough, as has already been explained in the aspects discussed above.

[0031] According to a further optional modification of the present invention, it can be provided that the external teeth of the drive shaft and the internal teeth of the bushing form a tooth pairing.

[0032] When the drive shaft is inserted into the cylinder bore, the external teeth of the drive shaft engage with the internal teeth of the cylinder, thus locking these two components together. The drive shaft then enables the cylinder to rotate around its axis.

[0033] According to a further optional modification of the present invention, the axial piston pump may further comprise at least one pin element for transmitting a pressure force to hold a sliding shoe down on a swashplate, wherein the at least one pin element is guided through the free space between the internal toothing of the feedthrough and the external toothing of the drive shaft, formed by the at least one radially outward extending recessed recess area of ​​the cylinder and / or a radially inward extending recessed recess area of ​​the drive shaft.

[0034] Preferably, the axial piston pump may further comprise: a central spring, the outer circumference of which is surrounded by the interior of the cylinder and exerts an axially acting force on the at least one pin element; a return ball, which is arranged axially offset on the outside of the cylinder on the side of the at least one pin element spaced away from the spring and preferably also has a passage for receiving the drive shaft; a pivot plate, which can vary an angle to the axial direction of the axial piston pump in order to influence the pumping performance; at least one sliding shoe, which slides on the pivot plate and is rigidly connected to a piston element arranged in a piston recess; and a retainer, which serves to press the sliding shoe against the pivot plate, wherein the at least one pin element serves toto transmit a spring force from the central spring via the return ball to the hold-down device in order to prevent loss of contact between the sliding shoe and the swivel plate.

[0035] According to a further advantageous embodiment of the present invention, it can be provided that the at least one pin element and the retraction ball are formed in one piece or that the at least one pin element is pressed into the retraction ball, and / or that the cylinder is formed continuously in the area between the passage and the piston recesses and in particular has no bore for passing through a pin element.

[0036] The complexity of the axial piston pump can be reduced by forming the retraction ball and the at least one pin element in one piece, or by pressing the at least one pin element into the retraction ball.

[0037] Furthermore, for stability, it is advantageous if there are no bores for inserting pin elements in the area between the passage and the piston recesses of the cylinder, as these weaken the basic structure and lead to an increase in dimensions as well as to increased material usage when forming the cylinder.

[0038] Further features, details, and advantages of the invention will become apparent from the following description of the figures. These show: Fig. 1: a sectional view along the axial direction of an axial piston pump according to the invention, Fig. 2: a cross-sectional view showing a top view of the cylinder and the inserted drive shaft, Fig. 3: a sectional view along the axial direction of an axial piston pump according to the invention, in which the force flow from the central spring to the retainer is shown by arrows, and Fig. 4 A cross-sectional view showing a top view of the cylinder and the inserted drive shaft of a state-of-the-art axial piston pump.

[0039] Fig. Figure 1 shows an axial piston pump 100 in a sectional view along the axial direction X according to an embodiment encompassed by the invention.

[0040] The cylinder 1 is visible, which has several piston recesses 2 in which the pistons 3 are mounted so as to be movable back and forth in the axial direction X. The stroke of the pistons 3 depends on the inclination of the pivot plate 12, since the head region of the pistons 3 is rigidly connected to a sliding shoe 13. This sliding shoe 13 is held on the surface of the pivot plate 12 facing the cylinder 1 by means of a retainer 14, so that an inclination of the pivot plate 12 when the cylinder 1 is rotated about an axis of rotation parallel to the axial direction X completes a full stroke cycle.

[0041] To ensure that the hold-down device 14 has sufficient force to press the sliding shoe 13 onto the surface of the swivel plate 12 facing the cylinder 1, a central spring 10 is provided inside the cylinder 1, which may be designed as a coil spring. This spring is fixed relative to the cylinder 1 at one point (e.g., at its end spaced apart from the at least one pin element) and pushes a pin element 9 out of the cylinder 1 in a direction parallel to the axial direction X, so that the hold-down device 14 is forced by means of a contact via the retraction ball 11 towards the surface of the swivel plate 12 facing the cylinder 1, thus securing the sliding shoe 13.

[0042] The cylinder 1 also has a through-hole 4 into which the drive shaft 7 is inserted, thus enabling a rotary connection via an interlocking toothed joint between the cylinder 1 and the drive shaft 7. The drive shaft 7 causes the cylinder 1 to rotate about the axis of rotation parallel to the axial direction X, resulting in the rotation of the cylinder 1 typical for the axial piston pump 100.

[0043] To vary the stroke height of the pistons 3 in their respective piston recesses 2, a mechanism for pivoting the swivel plate 12 is provided. The axial piston pump 100 idles when the swivel plate 12 forms a 90° angle to the axial direction X, since then no stroke of the piston element 3 is executed during one revolution of the cylinder 1 about its axis of rotation.

[0044] Fig. Figure 2 shows a cross-sectional view illustrating a top view of the cylinder 1 and the inserted drive shaft 7, in which it can be seen that the external teeth 71 of the drive shaft 7 engage with the internal teeth 6 of the bushing 4 of the cylinder 1, thereby forming a rotationally fixed connection between the drive shaft 7 and the cylinder 1. Furthermore, it can be seen that in the circumferential direction of the tooth connection of the two contact partners (drive shaft 7 and cylinder 1), the meshing tooth pair is not fully formed, but rather partially formed in the Fig. The illustrated embodiment is interrupted at three points. In this case, recessed recess areas 8 extending outwards are provided in the inner circumferential side of the passage 4 of the cylinder 1, which, in conjunction with the fully circumferential regular tooth contour of the outer shaft 7, create a free space in which a respective pin element 9 is arranged for transmitting the pressure from the central spring 10.

[0045] It can be provided that the recess area 8 thus formed has a width in the circumferential direction that exactly corresponds to the width of at least one tooth element of the toothing 6 arranged on the inner circumferential side of the passage 4. This also makes it possible to connect to an external shaft 7 which has regular teeth on its outer surface, since then no corresponding tooth of the internal toothing of the cylinder 1 engages in a tooth valley of the external toothing 71, but rather the space thus formed is used to allow the pin element 9 to pass through in the axial direction.

[0046] Also shown is a preferred embodiment in which several such radially outward extending recessed recess areas 8 are provided on the inner circumferential side of the passage 4 in order to ensure that the retraction ball 11 or the hold-down device 14 is subjected to the force of the central spring 10 as evenly as possible in the circumferential direction.

[0047] The basic idea of ​​the invention naturally also includes the fact that the tooth pitch of the internal toothing of the passage 4 is irregular and that the recess areas provided there are not evenly distributed around the circumference, but can also be unevenly distributed in the circumferential direction.

[0048] In Fig. 2 can also be seen that the radially outward extending recessed recess area 8 continuously transitions into the two adjacent tooth flanks of the adjacent tooth elements of the internal gearing, so that no steps or the like result in the transition from the recess area 8 to the adjacent tooth elements 61.

[0049] Furthermore, the expert understands that the in Fig. The basic idea shown in Figure 2 for forming the recess area 8 can also be implemented by omitting a tooth element and forming a radially inwardly extending, withdrawn recess area in the drive shaft 7.

[0050] Fig. Figure 3 shows a representation of the Fig. 1, in which the force flow for pushing the hold-down device 14 in the direction of the surface of the swivel plate 12 facing the cylinder 1 is shown with arrows.

[0051] It can be seen that the central spring 10 is fixed to the cylinder 1 in the axial direction X and the pin element 9 is axially (in the illustration of the Fig. 3 to the right). The spring force is then transmitted via the return ball 11 to the hold-down device 14, which presses the sliding shoe 13 onto the surface of the swivel plate 12 facing the cylinder 1. This is necessary, especially at higher speeds, to prevent the sliding shoe 13 from tilting and losing contact with the swivel plate 12.

[0052] Fig.Figure 4 shows a prior art implementation in which the pin elements 9 are guided through a respective bore in the neck region of the cylinder 1. However, this leads to a structural weakening of the cylinder 1, which can only be compensated for by making the cylinder 1 correspondingly larger. The required larger dimensions of the cylinder 1 consequently required more installation space and also resulted in a higher weight. Reference symbol list: 1 cylinder 2 piston recesses 3 piston element 4 Implementation 5 Inner circumference side of the feedthrough 6 Internal teeth on the inner circumferential side 61 Tooth element 62 Tooth flank 7 Drive shaft 71 External gearing 8 Exclusion area 9 pen element 10 Central spring 11 Retraction ball 12 Swivel plate 13. Sliding shoe 14 hold-down devices 100 axial piston pump X Axial direction

Claims

Cylinder (1) for an axial piston pump (100), comprising: several piston recesses (2) extending in the axial direction (X) of the cylinder (1) for the respective insertion of a piston element (3) movable up and down in the axial direction (X), and a passage (4) extending in the axial direction (X), which is provided on its inner circumferential side (5) with an internal toothing (6) for interaction with a drive shaft (7), characterized in that the internal toothing (6) of the passage (4) is not continuous in the circumferential direction, but has at least one radially outwardly extending recessed area (8) opposite the toothing, which serves to guide a pin element (9) arranged in the axial direction (X). Cylinder (1) according to the preceding claim 1, wherein several radially outward extending recessed recessed areas (8) are equidistantly spaced apart from each other in the circumferential direction. Cylinder (1) according to one of the preceding claims, wherein at least three radially outward extending recessed recessed areas (8) are provided. Cylinder (1) according to one of the preceding claims, wherein the internal toothing (6) on the inner circumferential side (5) of the passage (4) is continuous except for the at least one radially outward extending withdrawn recess area (8). Cylinder (1) according to one of the preceding claims, wherein the tooth pitch of the toothing (6) is the same along the inner circumferential side (5) and the at least one radially outward extending recessed recess area (8) has, in circumferential direction, the width of a tooth element (61) of the toothing (6) so that it fits into the regular tooth pitch. Cylinder (1) according to one of the preceding claims, wherein the at least one radially outward extending recessed recess area (8) is designed in transition to a tooth element (61) adjoining it in the circumferential direction such that an adjacent sloping tooth flank (62) is continued without steps and continuously, preferably wherein this applies to both tooth elements (61) of the toothing (6) adjoining the recess area (8) in the circumferential direction. Cylinder (1) according to the preceding claim 6, wherein the at least one radially outward extending recessed recess area (8) is tangentially connected to the contour of the toothing (6) when viewed in the circumferential direction. Cylinder (1) according to one of the preceding claims, wherein the cylinder (1) is rotationally symmetric about an axis of rotation parallel to the axial direction (X). Cylinder (1) according to one of the preceding claims, wherein the passage (4) with the internal toothing (6) provided on its inner circumferential side (5) is arranged centrally to the multiple piston recesses (2), preferably wherein the multiple piston recesses (2) are each equidistant from the axis of the passage (4) and are in particular arranged equidistantly to each other. Axial piston pump (100), comprising: a cylinder (1), in particular one according to any of the preceding claims 1 to 9, and a drive shaft (7) which has an external toothing (71) extending along its circumference and is inserted into the passage (4) so ​​that the external toothing (71) engages in the internal toothing (6) of the passage (4), preferably wherein the external toothing (71) of the drive shaft (7) is formed along the entire circumference. Axial piston pump (100) according to the preceding claim 10, wherein the outer contour of the drive shaft (7) and the inner contour of the feedthrough (4) are aligned in a connected state such that an axially extending (X) clearance for the passage of a pin element (9) is created on the at least one radially outward extending recessed area (8) of the feedthrough (4) or a radially inward extending recessed area (8) of the drive shaft (7). Axial piston pump (100) according to one of the preceding claims 10 or 11, wherein the external toothing (71) of the drive shaft (7) and the internal toothing (6) of the bushing (4) form a tooth pairing. Axial piston pump (100), in particular according to one of the preceding claims 10 to 12, comprising: at least one pin element (9) for transmitting a pressure force to hold a sliding shoe down on a swashplate, wherein the at least one pin element (9) is guided through the free space between the internal toothing (6) of the passage (4) and the external toothing (71) of the drive shaft (7), formed by the at least one radially outward extending recessed recessed area (8) of the cylinder (1) or a radially inward extending recessed recessed area (8) of the drive shaft (7). An axial piston pump (100) according to the preceding claim 13, further comprising: a central spring (10) which is surrounded on its outer circumference by an interior of the cylinder (1) and exerts a force acting in the axial direction (X) on the at least one pin element (9); a return ball (11) which is arranged on the cylinder (1) on the side of the at least one pin element (9) spaced apart from the spring (10) and is offset in the axial direction (X), and preferably also has a passage (4) for receiving the drive shaft (7); a pivot plate (12) which can vary an angle to the axial direction (X) of the axial piston pump (100) in order to influence the pumping performance; at least one sliding shoe (13) which slides on the pivot plate (12) and is fixedly connected to a piston element (3) arranged in a piston recess (2); and a retainer (14) which serves to hold the sliding shoe (13) against the pivot plate. (12) to press,wherein at least one pin element (9) serves to transmit a spring force of the central spring (10) via the return ball (10) to the retainer (14) in order to prevent loss of contact between the sliding shoe (13) and the pivot plate (12). Axial piston pump (100) according to one of the preceding claims, wherein the at least one pin element (9) and the retraction ball (10) are formed in one piece or the at least one pin element (9) is pressed into the retraction ball (10), and / or the cylinder (1) is formed continuously in the area between the passage (4) and the piston recesses (2) and in particular does not have a bore for passing a pin element (9).

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