EP2179175B1 - Swash-plate type axial piston machine with an actuating device - Google Patents

Description

The invention relates to an axial piston machine in swash plate design with an adjusting device.

Axial piston machines have a plurality of pistons, which are arranged longitudinally displaceably in a rotatably mounted cylinder drum. The pistons are supported on a swashplate or pivoting cradle whose angle of inclination is adjustable relative to the axis of rotation of the cylindrical drum. Depending on the angle of inclination, the displacement changes. To adjust the inclination angle of the swash plate an adjusting device is provided. This adjusting device may for example consist of a control piston for changing the inclination angle in a first direction and an opposed piston for changing the inclination angle of the swash plate in the opposite direction. In order to achieve a defined end position of the swash plate in a pressureless system and without the actuation of actuating means, the adjusting piston and / or the counter-piston are usually (in each case) acted upon by the force of a spring. At a balance of forces thus generated, the swash plate is in the end position of the axial piston machine. This rest position, for example, in a two-way adjustable axial piston machine be a neutral position, in which thus a zero stroke of the piston occurs during rotation of the cylinder drum.

The return springs are usually arranged in a one-sided limited by the control piston or piston, pressurizable volume and thus act on the front side of the control piston or opposed piston. However, if the adjusting piston and the counter-piston are integrated into the axial piston machine, this results in an increase in the overall length of the entire machine. Such axial piston machine with the features of the preamble of claim 1 is eg de EP 1462647 A2 known.

It is therefore the object of the invention to provide an axial piston machine in swash plate design with an adjusting device, in which the available space is advantageously used and which also can be easily assembled.

The object is achieved by the axial piston machine according to the invention with the characterizing features of claim 1.

The axial piston according to the invention is formed in a swash plate design with an adjusting device. The adjusting device comprises an actuating piston and an opposing piston, wherein the effective direction of the actuating piston and that of the counter-piston with respect to a movement of the swash plate are opposite to each other. Both the actuating piston and the counter-piston cooperate at their first end with the swash plate and can transmit a thrust force to them. At their respective second end both the actuating piston and the counter-piston can be acted upon individually with a control force. For resetting the swash plate in the direction of a rest position, which may coincide with a neutral position but need not, is both on the actuating piston and on the opposite piston in each case one provided elastic element. This, preferably designed as a spiral spring elastic element, is supported on a first spring bearing, which is arranged on the side facing the swash plate of the adjusting piston and the counter-piston. At the end facing away from the elastic element is supported in each case on a second spring bearing. In a deflection of the swash plate from the rest position, either the second spring bearing of the actuating piston or the second spring bearing of the counter-piston depends on the abutment direction of the swash plate on a fixed abutment on the housing side. The respective other second spring bearing of the counter-piston or actuating piston, on the other hand, is supported on an abutment which is fixed on the piston side.

By arranging the return springs in a formed between the first end and the second end portion of the actuating piston or the counter-piston, an increase in the length of the axial piston machine in the axial direction is not required. The use of two return springs, so that only one of the return springs is compressed by the housing-side system when the swash plate is deflected out of its rest position, has the advantage that provided for the control piston and the counter-piston only one direction of movement a housing-side abutment must become. In a direction of movement of this actuating piston or counter-piston in the opposite direction, however, the respective return spring is clamped between the first spring bearing and the second spring bearing, which is then supported on an abutment provided on the respective piston. This arrangement also allows a pre-assembly of the entire Perform adjusting device including the return springs before the engine of the axial piston machine is introduced into the housing.

Advantageous embodiments of the axial piston machine according to the invention are embodied in the subclaims.

To form the housing side fixed abutment for the return spring, a support ring is preferably provided, which is penetrated by the adjusting piston or the counter-piston. The inner diameter of the support ring is smaller than the radial extent of the respective second spring bearing. This support ring can either be firmly mounted in the housing, provided that the diameter of the actuating piston or counter-piston penetrating it is small enough that such an assembly is possible. According to an alternative embodiment, which is used in particular for large piston diameters of the second end of the actuating piston or counter-piston, however, a hold-down spring is arranged between the support ring, which is penetrated by the actuating piston or counter-piston, and the second spring bearing. This hold-down spring keeps the support ring in each position of the swash plate and thus of the control piston and the opposing piston that occurs during operation of the axial piston machine against a contact surface formed in the housing of the axial piston machine. Such an approach has the advantage that a pre-assembly of the support ring in the housing of the axial piston machine is not required, and in particular a subsequent fixation after assembly of the actuating piston or counter-piston is also not required.

The support ring in this case preferably has a radial extent which is greater than the setting pressure chamber diameter of the adjusting piston or counter-piston and whose passage opening, which is penetrated by the actuating piston or counter-piston, is smaller than the second end of the associated actuating or counter-piston.

In order to simplify the assembly, a centering device is formed on the second end of the actuating piston on a side facing the first end of the second actuating piston. On the support ring, a corresponding geometry is provided, is held at the pre-assembly of the support ring by the hold-down spring in abutment. In this defined position, a simple mounting of the support ring by inserting the actuating piston or counter-piston in the designated bore of the housing is possible. The centering device is provided at a position of the actuating piston, which at no time comes back in contact with the corresponding geometry of the support ring during operation of the machine, so that a secure fixation of the support ring is secured to the contact surface by the hold-down.

The support ring preferably partially closes a bore in which the second end of the control piston or the opposing piston is received, to form therein a control pressure chamber or a working pressure chamber. By this partial closure of the bore, it is possible to use a spring plate as a second spring bearing whose diameter is smaller than the diameter of the bore. By using such a smaller spring plate is required Movement created so that regardless of the position of the swash plate collision between the spring plate and the cylinder drum is safely excluded. In this case, openings are preferably provided in the support ring, which connects a relative to the second end of the actuating piston or counter-piston rear volume in the bore with the remaining housing volume. Such a diameter-reducing support ring is used in particular on the side of the adjusting piston, the diameter of which is generally larger than that of the counter-piston.

The following description refers to an embodiment of an axial piston according to the invention with an actuating piston large piston diameter and an opposed piston with the other hand, a significantly smaller diameter each at its second end. It is therefore shown below only for the actuator piston, that a support ring is used for piston diameter reduction to use a spring plate as a second spring bearing with a relatively small diameter can. However, it is also conceivable on the side of the counter-piston, that due to the diameter of the counter-piston, the diameter of the bore which receives it, is so large that even there a comparatively arranged and held by a hold-down spring support ring is used.

Fig. 1

einen gestuften Teilschnitt durch eine erfindungsgemäße Axialkolbenmaschine;

Fig. 2

eine vergrößerte Darstellung des Bereichs des Stellkolbens in einer Ruheposition der Axialkolbenmaschine;

Fig. 3

eine vergrößerte Darstellung des Bereichs des Stellkolbens in einer ersten Endposition der Schrägscheibe;

Fig. 4

eine erste Ansicht eines erfindungsgemäß ausgeführten Stützrings; und

Fig. 5

eine Schnittdarstellung durch einen Stützring der erfindungsgemäßen Axialkolbenmaschine.

An embodiment of an axial piston machine according to the invention in swash plate design is shown in the drawing and will be explained in more detail in the following description. Show it:

Fig. 1

a stepped partial section through an axial piston machine according to the invention;

Fig. 2

an enlarged view of the area of the actuating piston in a rest position of the axial piston machine;

Fig. 3

an enlarged view of the area of the actuating piston in a first end position of the swash plate;

Fig. 4

a first view of a support ring designed according to the invention; and

Fig. 5

a sectional view through a support ring of the axial piston machine according to the invention.

The Fig. 1 shows a stepped section through an axial piston machine according to the invention 1. The upper half of Fig. 1 runs along a first cutting plane, which is parallel to the sectional plane of the lower half of the axial piston machine. Both sectional planes are perpendicular to a rotational axis of the swash plate, which is designed as a pivoting cradle 2 in the illustrated embodiment. However, it is equally conceivable that the adjusting device is arranged with a control piston 3 and an opposed piston 4 in a plane. However, from a space-economical point of view, the staggered arrangement is preferred. The adjusting piston 3 and the counter-piston 4 each have a first end, which is connected via a respective ball joint connection, each with a hold-down segment. The hold-down segments are in turn firmly connected to the pivoting cradle 2, z. B. screwed. By the Control piston 3 is a thrust force on the pivoting cradle transferable, which leads to a rotation of the pivoting cradle 2 in the illustrated embodiment in the clockwise direction.

By the transmittable by the counter-piston 4 thrust force acting in the opposite direction force on the pivoting cradle 2 is transferable. Thus, counter to the movement described above, the pivoting cradle 2 is pivoted counterclockwise.

To generate the required for moving the pivoting cradle 2 actuating forces 1 two blind holes 50 and 60 are provided in the housing of the axial piston machine. In the blind bores 50 and 60, a respective second end of the actuating piston 3 and the counter-piston 4 is arranged. In the case of the actuating piston 3, a control pressure chamber 5 is thus formed in the housing of the axial piston machine 1. In contrast, the opposing piston 4 limits a working pressure chamber 6. The diameter of the second end of the opposing piston 4 is smaller than the diameter of the actuating piston 3. While the working pressure chamber 6 is permanently connected, for example, to a delivery pressure of an axial piston machine 1 designed as a pump, it is in the control pressure chamber 5 prevailing pressure by means of a control valve 7 adjustable. He can z. B. between a reduced from the working line pressure and the tank pressure can be adjusted.

While the working line pressure in the working pressure chamber 6 always acts on the opposing piston 4, the hydraulic force acting on the actuating piston 3 can be adjusted at the second end of the actuating piston 3. If the hydraulic force acting there exceeds the hydraulic force on the counter-piston 4 in the Working pressure chamber 6, so an adjusting movement of the pivoting cradle 2 is generated in a clockwise direction.

herrscht. Die Zentrierfedern haben nur eine Funktion im drucklosen Zustand. Im drucklosen Zustand wird die Schwenkwiege 2 in eine Ruheposition aufgrund der rückstellenden Kraft einer ersten Rückstellfeder 10 oder einer zweiten Rückstellfeder 11 gebracht. Die erste Rückstellfeder 10 ist als Spiralfeder ausgeführt und umgibt einen Teil des Gegenkolbens 4. An dem Gegenkolben 4 ist hierzu ein erstes Federlager 12 ausgebildet. Dieses erste Federlager 12 ist in der Nähe der Kugelgelenkverbindung, also dem ersten Ende des Gegenkolbens 4 angeordnet. Im dargestellten Ausführungsbeispiel ist das erste Federlager 12 beispielsweise durch spanende Bearbeitung eines Gegenkolbenrohlings hergestellt. In Richtung des zweiten Endes des Gegenkolbens 4 stützt sich die erste Rückstellfeder 10 an einem zweiten Federlager 13 ab. An dem Gegenkolben 4 ist ein radial verjüngter Bereich 14 ausgebildet, über den der geschlitzt ausgeführte zweite Federteller 13 aufgeschoben werden kann. In Richtung zu dem zweiten Ende des Gegenkolbens 4 hin erweitert sich der Gegenkolben 4 wiederum radial, sodass ein kolbenseitiges Widerlager 15 für das zweite Federlager 13 an dem Gegenkolben 4 ausgebildet ist. Ausgehend von diesem Widerlager 15 ist das zweite Federlager 13 über den radial verjüngten Bereich 14 des Gegenkolbens 4 in axialer Richtung verschiebbar. Der Abstand zwischen erstem Federlager 12 und dem kolbenseitigen Widerlager 15 ist so bemessen, dass die erste Rückstellfeder 10 in jeder Position des Gegenkolbens 4 vorgespannt ist.In the Fig. 1 an electro-proportional adjustment is shown, in which the position of the pivoting cradle 2 is fed back via a return lever 8 and a feedback spring 9 to the control valve 7. Such adjustment mechanisms are known per se, which is why further explanations are unnecessary. With vanishing control signals, the control valve 7 is in a neutral position, in which in the control pressure chamber 5 a from the tank pressure and the reduced working pressure averaged pressure $$P_{}$$$${}_5=\frac{A_6}{{\mathrm{<figure-callout\; id="5"\; label="A"\; filenames="imgf0003.png"\; state="\{\{state\}\}">A</figure-callout>}}_5}\cdot P_6$$

prevails. The centering springs have only one function in the pressureless state. In the pressureless state, the pivoting cradle 2 is brought into a rest position due to the restoring force of a first return spring 10 or a second return spring 11. The first return spring 10 is designed as a spiral spring and surrounds a part of the counter-piston 4. At the counter-piston 4, a first spring bearing 12 is formed for this purpose. This first spring bearing 12 is arranged in the vicinity of the ball joint connection, ie the first end of the counter-piston 4. In the illustrated embodiment, the first spring bearing 12 is made for example by machining an opposed piston blank. In the direction of the second end of the counter-piston 4, the first return spring 10 is supported on a second spring bearing 13. On the opposing piston 4 is a radially tapered portion 14th formed over which the slotted executed second spring plate 13 can be pushed. Towards the second end of the counter-piston 4, the opposing piston 4 in turn expands radially, so that a piston-side abutment 15 for the second spring bearing 13 is formed on the counter-piston 4. Starting from this abutment 15, the second spring bearing 13 is displaceable over the radially tapered region 14 of the counter-piston 4 in the axial direction. The distance between the first spring bearing 12 and the piston-side abutment 15 is dimensioned so that the first return spring 10 is biased in any position of the counter-piston 4.

In order to compress the first return spring 10 in an adjusting movement of the pivoting cradle 2 in a clockwise direction, a housing-side abutment is also provided. This housing-side abutment is designed in the form of a support ring 16 which is fixed in the housing of the axial piston machine 1 (for example screwed). An inner diameter of the support ring 16 is dimensioned such that the second end of the counter-piston 4 can be inserted through the support ring 16 into the blind bore 60 to form the working pressure chamber 6. Such a design is always possible if the diameter of the working pressure chamber 6 is so small that the second end of the counter-piston 4 can be inserted through the support ring 16 therethrough. Before the assembly of the engine and the counter-piston 4 can be fixed in the case of the axial piston machine 1 in the case of the support ring 16.

Moves, however, during operation of the axial piston machine 1 due to a relaxation of the control pressure chamber 5 from his in the Fig. 1 shown rest position against the Clockwise, so is the second spring plate 13 on the piston-side abutment 15. In such a movement, the hydraulic force on the second end of the opposed piston 4 due to the relaxation of the control pressure chamber 5 is greater than the sum of the hydraulic force to the second end of the actuating piston 3 and the force of the second return spring 11. As a result, moves in the Fig. 1 the opposing piston 4 to the left and the first return spring 10 clamped between the first spring bearing 12 and the second spring bearing 13 is moved with the opposed piston 4 without compression.

Also for the second return spring 11, which is also designed as a spiral spring and surrounds the actuating piston 3, a first spring bearing 17 and a second spring bearing 18 are provided. Due to the diameter of the bore 50, in which is formed by the second end of the actuating piston 3 of the control pressure chamber 5, and the associated diameter of the second end of the actuating piston 3, however, the support ring 19 can not be designed here so that the second end of the Adjusting piston 3 can be inserted through the support ring 19 into the bore 50 in the housing of the axial piston machine 1. Such a large inner diameter of the support ring 19 would have the consequence that a very large second spring bearing 18 must be used. However, the size of the spring bearing 18 would then lead to its collision with the engine of the axial piston machine 1. In order to prevent a dip of the second spring bearing 18 in the bore 50 for forming the control pressure chamber 5 with a reduction in the outer diameter of the second spring bearing 18 of the actuating piston 3, therefore, the bore 50 is partially covered by the support ring 19. However, since the second end of the actuating piston 3 now no longer through the support ring 19 can be inserted into the bore 50, a pre-assembly of the support ring 19 in the housing of the axial piston machine 1 before insertion of the actuating piston 3 is not possible. The support ring 19 is therefore first pushed onto the control piston 3 from the first end of the control piston 3 ago. Between the support ring 19 and the second spring bearing 18, a hold-down spring 20 is arranged, which holds the support ring 19 permanently in abutment against a contact surface, which is formed on the housing side of the axial piston machine 1 during operation of the axial piston machine 1. This will be explained below with reference to Fig. 2 still explained in detail.

The second end of the actuating piston 3 has a diameter which corresponds to the diameter of the bore 50 or an inner diameter of a bushing arranged therein. The second end of the control piston 3 thus limits a control pressure chamber 5 in the bore 50. Starting from the second end of the control piston 3, the diameter of the control piston 3 tapers.

When mounting the axial piston machine 1, the support ring 19 is first pushed from the first end of the actuating piston 3 forth on the actuating piston 3. Subsequently, the hold-down spring 20 is pushed over the control piston 3, followed by the second spring bearing 18. The support ring 19 and the second spring bearing 18 each have an inner diameter which is larger than the first end of the control piston 3. The inner diameter of the second spring bearing 18th is smaller than the inner diameter of the support ring 19. A formed on the control piston 3 near the second end paragraph 28 thus forms a piston-side abutment for the second spring bearing 18. After placing the second spring bearing 18 is the second return spring 11 is placed. Finally, the first spring bearing 17 is mounted. To fix the first spring bearing 17 on the actuating piston 3, a shoulder is formed as an abutment for the first spring bearing 17 and at the first end of the actuating piston 3. The first spring bearing 17 is designed radially slotted in a conventional manner, so that it can be pushed into a central, radially tapered portion 29 of the actuating piston 3. By the spring force of the second return spring 11, it is brought in the assembled state of the axial piston machine 1 in contact with the shoulder of the actuating piston 3, as shown in the Fig. 2 is shown. The diameter of the actuating piston 3 in this position is greater than the width of the slots, so that a radial offset during operation is excluded. Depending on the position of the pivoting cradle 2 and thus the position of the actuating piston 3 is supported, as was previously explained with respect to the opposed piston 4, the second spring bearing 18 either on the piston-side abutment 28 or on the in the form of the support ring 19th housing-side abutment from. Regardless of the position of the actuating piston 3 relative to the support ring 19 while the hold-down spring 20 ensures that the support ring 19 is always in contact with a contact surface 21 which is formed on the housing side. The hold-down spring 20 has a much smaller spring constant than the return springs 10, 11.

In order to ensure a secure mounting of the support ring 19, in which the positioning must be carried out solely by the insertion of the second end of the actuating piston 3 in the bore 50, is at the second end of the actuating piston 3 on a side oriented toward the first side a centering device 26 formed. These Centering device 26 is a frusto-conical portion which cooperates with a corresponding geometry 27 on the part of the support ring 19. The corresponding geometry 27 is formed by a chamfer in the region of the passage opening 25 of the support ring 19. After assembly of the first spring bearing 17, the hold-down spring 20 holds the support ring 19 with the corresponding geometry 27 in contact with the lateral surface of the frustoconical portion of the actuating piston 3. The support ring 19 thus has a defined position and applies itself to the contact surface 21, if the second end of the actuating piston 3 is inserted into the bore 50 during assembly of the axial piston machine 1.

In the Fig. 3 is once again the enlarged area of Fig. 2 shown when the swash plate 2 has been pivoted from its rest position clockwise. Accordingly, the actuator piston 3 is in the Fig. 3 further left than in the Fig. 2 , Due to the force of the hold-down spring 20 of the support ring 19 remains in contact with the contact surface 21. With maximum adjustment of the pivoting cradle 2 in the clockwise direction still remains a distance between the centering device 26 of the actuating piston 3 and the corresponding geometry 27 of the support ring 19. In this way It is ensured that an adjusting movement does not lead to an accidental movement of the support ring 19 through the second end of the actuating piston 3. Both in the support ring 19 and in the second spring bearing 18 recesses for receiving the hold-down spring 20 are preferably provided. These are provided in the form of grooves or steps, which are arranged in the mutually facing end faces of the second spring bearing 18 and the support ring 19. In the illustrated embodiment, the second spring bearing 18 a Groove 30, while on the support ring 19, a step 23 is formed.

In Fig. 4 is a view of the first end of the actuating piston 3 facing side of the support ring 19 is shown. It can be seen that a plurality of compensation openings 24 are provided distributed over the circumference. These compensation openings 24 serve to connect the volume formed in the bore 50 on the side of the second end 2 facing the first end of the actuating piston 3 to the remaining housing volume. This can be done with a movement of the actuating piston 3 in the bore 50, a pressure equalization.

It should be noted that the second end of the actuating piston 3 is sealed, for example by means of a piston ring with respect to the bore 50. In the illustrated embodiment, a bushing is inserted into the bore 50, in which the adjusting piston 3 can slide with reduced friction.

In order to determine the position of the housing-side abutment for the second spring bearing 18, a further shoulder 33 is formed in the support ring 19 in the illustrated embodiment. However, it is easy to understand that such a paragraph does not necessarily have to be present, since the second spring bearing 18 can also be supported on a non-stepped end face of the support ring 19. In the case of the further paragraph 33, however, an additional centering of the spring bearing 18th

As is apparent directly from the drawings, all the spring bearings in the illustrated embodiment are designed so that they have an extension, with they engage in the return springs 10 and 11 designed as a spiral spring. In this way, an alignment of the return springs 11 and 12 with respect to the actuating piston 3 and the counter-piston 4 is achieved.

The Fig. 5 shows finally a section through the support ring 19, which again shows the different diameters of the other paragraph 33, the through hole 25 and the step 23 for receiving the hold-down spring 20. In addition, it can be clearly seen that on the side facing the second end of the actuating piston 3 a chamfer is formed as a corresponding geometry 27 to the conical centering device 26.

All explained only in relation to the opposed piston 4 or the actuator piston 3 features can also be used for each other piston.

The invention is not limited to the illustrated axial piston machine. Rather, the features shown in particular in connection with the first control piston and the second control piston or the arrangement of the return spring can also advantageously combine with each other.

Claims (6)

1. Axial piston machine in a swash-plate construction having an adjusting device which includes an adjusting piston (3) and a counter-piston (4) which cooperate with the swash-plate (2) at their respective first ends and can be influenced at their respective second ends with a force acting in the direction of the first end, wherein in order to return the swash-plate (2) in the direction of a rest position a resilient element (10, 11) is provided in each case on the adjusting piston (3) and on the counter-piston (4)
   characterized in that the resilient element (10, 11) is supported in each case on a first spring bearing (12, 17) disposed on the end of the adjusting piston (3) or counter-piston (4) facing the swash-plate (2), and in each case on a second spring bearing (13, 18) disposed on the adjusting piston (3) or on the counter-piston (4) at a point further away from the swash-plate (2),
   wherein upon deflection of the swash-plate (2) from the rest position, the second spring bearing (13, 18) of the adjusting piston (3) or of the counter-piston (4) is supported on a counter-bearing fixed on the housing-side, whilst the second spring bearing of the respective other counter-piston (4) or adjusting piston (3) is supported on a counter-bearing (15, 28) fixed on the piston-side.
2. Axial piston machine as claimed in Claim 1, characterised in that a support ring (16, 19) is provided in each case to form the counter-bearing fixed on the housing-side and is penetrated by the adjusting piston (3) or the counter-piston (4).
3. Axial piston machine as claimed in Claim 2, characterised in that a holddown spring (20) is disposed at least between a support ring (16, 19) and the second spring bearing (13, 18) allocated to the same adjusting piston or counter-piston (3, 4) and in any position of this adjusting piston or counter-piston (3, 4) holds the support ring (16, 19) in abutment with a bearing surface (21) formed on the housing-side.
4. Axial piston machine as claimed in Claim 3, characterised in that the support ring (16, 19) has an outer, radial extension which is greater than an adjusting pressure chamber diameter and has a through-going aperture (25) which is smaller than the adjusting pressure chamber diameter in which the second end of the associated adjusting piston or counter-piston (3, 4) is disposed.
5. Axial piston machine as claimed in Claim 3 or 4, characterised in that a centring device (26) is formed on the second end of the adjusting piston (3) on the side facing the first end and co-operates in a centring manner with a corresponding geometry (27) on the support ring (19) for the purpose of simple assembly, wherein the centring device (26) is formed in the axial direction on the adjusting piston (3) such that during operation of the axial piston machine (1) a spaced disposition always remains between the centring device (26) and the support ring (19).
6. Axial piston machine as claimed in any one of Claims 2 to 5, characterised in that the support ring (16, 19) partly closes a bore (50) for receiving the second end of the adjusting piston (3) or the counter-piston (4), wherein at least one equalisation aperture (24) is provided in the support ring (16, 19) and connects the bore (50) to the remaining internal space of the housing.

Images