EP0360756B1 - Wobbling drive for an orbitally moving member - Google Patents

Description

Technical field

• welcher mittels Kurbeltrieb bewegt ist und hierzu an seinem kurbelseitigen Ende mit einem ersten Kugelabschnitt in einer Lagerbuchse der Kurbel einsitzt,
• welcher an seinem andern Ende mit einem zweiten Kugelabschnitt in einer Lagerbuchse des feststehenden Bauteils gelagert ist, und zwar koaxial zum Kurbeltrieb,
• und welcher zwischen seinen beiden Enden einen dritten Kugelabschnitt aufweist, welcher drehbar und taumelfähig in einer Lagerbuchse in der Nabe des translatorisch bewegten Bauteils gelagert ist.

The invention relates to a wobble drive for a component which is moved in translation and which is held in a predetermined angular relationship with a fixed component, essentially consisting of a wobble rod,

• which is moved by means of a crank mechanism and is seated at its crank-side end with a first ball section in a bearing bush of the crank,
• which is mounted at its other end with a second ball section in a bearing bush of the fixed component, namely coaxially to the crank mechanism,
• and which has a third spherical section between its two ends, which is rotatably and tumble-mounted in a bearing bush in the hub of the translationally moved component.

Such wobble drives are particularly suitable for devices such as rotary piston displacement machines.

State of the art

Swash drives of the type mentioned are known, for example from DE-C-2 603 462 and US-A-3 560 119. These devices are so-called displacement machines for compressible media. They consist, on the one hand, of a conveying space which is delimited by spiral-like circumferential walls which extend perpendicularly from a side wall and which leads from an inlet lying outside the spiral to an outlet lying inside the spiral. On the other hand, they have a likewise spiral-shaped displacement body protruding into this conveying space. This is mounted in relation to the conveying space in order to execute a circular, rotation-free movement. Its center is offset eccentrically from the center of the peripheral walls so that the displacer always touches both the outer and the inner peripheral wall of the delivery chamber on at least one progressive sealing line. During operation of the machine, therefore, several crescent-shaped work spaces are trapped along the delivery space between the displacer and the two peripheral walls of the delivery space, which move from the inlet through the delivery space to the outlet. Depending on the wrap angle of the spiral, the volume of the conveyed working medium can decrease increasingly with a corresponding increase in the working medium pressure.

In all these known machines, the wobble drive is in each case the means for converting the rotating movement of the drive machine into the translatory movement of the displacer. Its radial displacement is limited by the contact of the spiral ribs with the walls of the delivery chambers. The limit theoretically corresponds to a circle, in this case the translation circle.

The drive solution in DE-C-2 603 462 provides an eccentric body which is seated in a rotationally fixed manner with a counterweight and on which a drive disk is mounted by means of a ball bearing. This is equipped with four evenly distributed ball joint pans, in each of which the ball end of a wobble rod sits. The balls only have line contact in their associated pan. When the drive shaft rotates, the rotor body is excited by the wobble rods to perform a circular but not rotating movement. In addition to the drive function, the wobble rods also have to ensure the anti-rotation device in this solution.

In the embodiment according to US-A-3 560 119, the drive-side pin of the wobble rod is rotatably and pivotably mounted in an eccentric position by means of a self-aligning ball bearing. To prevent the displacement of the displacer, the second and third spherical sections are each provided with profile rings, e.g. Provide teeth, which in correspondingly profiled counterparts in the displacer or. intervene in the fixed housing part and are pivotally mounted therein. The wobble shaft is axially secured via a lock washer located in the fixed housing part.

For the transmission of the relative rotary movement, a highly loaded and therefore expensive ball bearing is used in the known machines. In addition, no measures are provided which guarantee play-free operation of the machine in the event of material abrasion on the wobble bar (s).

Presentation of the invention

The invention is therefore based on the object of designing a wobble drive of the type mentioned in such a way that play-free cooperation of the two components is made possible even with increasing material removal as a result of wear.

According to the invention, the object is achieved in that the bearing bushes for the second and third spherical sections are hemispherical joint sockets which are arranged in mirror image in the two components, spring means ensuring that the spherical sections abut in the joint sockets.

The advantage of the invention can be seen in the fact that the new configuration creates a self-adjusting and almost maintenance-free drive for the orbiting component during operation.

Brief description of the drawing

In the drawing, two exemplary embodiments and an application example of the invention are shown schematically.

• Fig.1 einen Längsschnitt durch eine Pumpe mit umlaufenden Ringkolben
• Fig.2 einen Querschnitt durch die Pumpe gemäss Linie A-A in Fig 1
• Fig.3 eine erste Einbauvariante des Taumelstabes im Längsschnitt
• Fig.4 eine zweite Einbauvariante des Taumelstabes im Längsschnitt

Show it:

• 1 shows a longitudinal section through a pump with rotating ring pistons
• 2 shows a cross section through the pump according to line AA in FIG. 1
• 3 shows a first installation variant of the wobble rod in longitudinal section
• 4 shows a second installation variant of the wobble rod in longitudinal section

In the greatly simplified pump illustration according to FIGS. 1 and 2, only the parts essential for understanding the invention are shown. In the different figures, the same parts are provided with the same reference numerals.

Way of carrying out the invention

At the outset it should be mentioned that in the sense of the invention the fixed component is designated with left housing half 1 and the rotating component with displacer 3.

The pump according to FIGS. 1 and 2 essentially consists of two housing halves 1, 2, which are connected to one another in a suitable manner, and the displacer 3 located therein. An annular delivery chamber 4 is incorporated into the left housing half 1. It is divided by means of a web 5 which extends over the entire depth of the chamber. Both sides of the web are in the rear wall of the housing half 1, the inlet 6 and the outlet 7 for the working medium to be conveyed. The likewise annular rib 8 of the displacer 3 engages in this delivery chamber. The ring is slotted at the point opposite the web 5. The displacer performs an orbital movement during operation.

On the occasion of this circular movement, the ring piston constantly touches both the inner and the outer peripheral wall of the delivery chamber. Due to its change in position, on the one hand, working fluid is sucked into the chamber 4 via the inlet 6 and, on the other hand, it is conveyed out of the machine via the outlet 7.

A cross-disk coupling is provided for the rotation-free guidance of the displacer 3. It consists essentially of an intermediate ring 9, which is provided with strips 10 on its two plan sides. The strips 10 facing the displacer 3 engage in appropriately configured, vertically running grooves 11 in the displacer 3. Those strips which face the fixed right housing half 2 must be arranged perpendicular to the former strips, in the present case thus horizontally and therefore not visible in the longitudinal section according to FIG. 1. They also slide in appropriately configured grooves that are machined horizontally in the front of the housing half 2

A drive by means of a wobble rod 12 is provided for the orbital rotation of the displacer 3. A crank mechanism 13, not shown, is equipped on the crank side with an articulated socket 14, in which the wobble rod 12 is rotatably and pivotably seated with a first ball section 15. It is understood that the invention is not limited to this drive variant. The only decisive factor is a construction in which the wobble rod does not perform a rotary movement but a wobble movement, the axis of movement being located on a cone jacket.

At the opposite end, the wobble rod 12 has a second ball section 16. Coaxial with the main axis of the crank mechanism 13, this second spherical section is rotatably supported in the left fixed housing part 1 and is capable of tumbling.

In the plane of the displacer 3, the wobble rod 12 is provided with a third ball section, the ball radius of which advantageously corresponds to that of the second ball section. This third spherical section is rotatably supported in the hub of the displacer 3 and is capable of tumbling.

If the bearing points for the two spherical sections 16 and 17 were now cylindrical bearing bushes, the purely radial forces caused, for example, by centrifugal force would only be supported on a semicircular line. Axial forces could not be transmitted at all.

These bearing points are therefore designed as hemispherical joint sockets 18, 19. Hemispherical because, on the one hand, this reduces the required individual parts to a minimum, and on the other hand, assembly is very easy.

However, this only applies if the load-bearing surface in the ball socket lies within one and the same spherical hemisphere. This condition means that the joint sockets 18, 19 for the receptacles of the second and third spherical sections are arranged in mirror image to one another, i.e. the supporting spherical surfaces are turned away from each other.

The axial force that is necessary for the spherical sections to fit snugly in their respective pans under all operating conditions is applied by spring means.

A first solution to this is shown in FIG. 3. The second ball section 16 'is provided with a central bore and loosely attached to the wobble rod 12', so that it is displaceable on the wobble rod. The opposing surfaces of the ball sections 16 'and 17' are flattened and each form a stop for a compression spring 20 '. In the assembled state, this spring 20 'pushes the ball sections apart. To accommodate the wobble rod 12 'on the occasion of a shift of the Ball section 16 'is the socket 18' in the fixed component 1 with a recess 21.

The solution shown in Figure 4 is based on a sliding block 22, which is axially displaceable in the left housing part 1. In the end face facing the displacer 3, the joint socket 18 is incorporated in the sliding block. The ball section 16 lies in this. So that the spherical section has a spherical support defined at all times, the base of the pan is also provided with a recess 21 here, so that the head end of the spherical section in no case has ground contact. The axial force is applied via the coil spring 20, which acts on the sliding block 22 from the housing part 1.

With reference to the arrangement according to FIG. 1, it is noted that the spring force must not be so great that the ribs 8 of the displacer 3 could lift off their sealing surface on the side wall of the housing 1. The counterforce that maintains this sealing effect is transmitted to the displacer 3 via the cross-plate coupling 9, 10.

After all, the spring force must be so great that the additional axial force in cooperation with the radial force mentioned causes the spherical sections to be supported in a spherical surface. This spherical contact zone must be preserved in any case, regardless of any material being removed from one of the machine parts involved.

• Anlässlich der Taumelbewegung kann Material an der Kugel abgetragen werden. Dadurch kann sich die Kugel in die Pfanne "hineinfressen". Die Durchmesser von Kugel und Pfanne werden hierbei kleiner. Durch die konstante sphärische Kugelauflage bleibt die Verbindung achsgleich und spielfrei, obschon sich neben der Verkleinerung der Durchmesser auch der Abstand zwischen den Kugelzentren der Kugelabschnitte 16 und 17 vergrössert hat.

The following examples show which possible errors can be compensated for using the invention:

• On the occasion of the tumbling movement, material can be removed from the ball. This allows the ball to "eat" into the pan. The diameter of the ball and pan will become smaller. Due to the constant spherical ball support, the connection remains coaxial and free of play, although in addition to the reduction in diameter, the distance between the ball centers of the ball sections 16 and 17 has increased.

• Anlässlich der orbitalen Bewegung können sich auch die Stirnseiten der Rippen 8 am feststehenden Gehäuse 1 abreiben. Nach Fig.1 würde demnach der Abstand zwischen den Kugelabschnitten 16 und 17 geringer. Auch dieses Verhalten verkraften die Lösungsprinzipien nach den Fig.3 und 4 mühelos.

This consideration also applies if only the balls or only the pans rub off.

• On the occasion of the orbital movement, the end faces of the ribs 8 can also rub against the fixed housing 1. According to Figure 1, the distance between the spherical sections 16 and 17 would be smaller. The solution principles according to FIGS. 3 and 4 can also easily cope with this behavior.

It goes without saying that when the distance between the second and third spherical sections changes, the angle of the movement axis located on a conical surface also changes. This also applies to the distance between the ball sections 16 and. 17 and 15. Eccentricity e (Fig. 4) must always be maintained. On the other hand, the plane of the second spherical section is decisive for the translation circle and is therefore the reference plane. Therefore, the first ball section 15 must also be designed to be displaceable. Namely, it must be displaceable on the one hand in the longitudinal direction of the wobble rod, as is indicated in FIG. 4; secondly, it must also be displaceable in the direction perpendicular to the plane of the drawing because of the possible change in angle mentioned. This first spherical section 15 is therefore preferably also embedded in a bearing bush designed as a joint socket 14. This joint socket 14, which is shown only schematically in the drawing, is in turn provided with a sliding surface 23 which can be displaced on all sides on a corresponding counter surface of the crank mechanism 13. The sliding surface 23 and counter surface are in one plane parallel to the axis of the crank mechanism.

The advantage of a wobble drive designed in this way can be determined on the basis of the following consideration: The greatest radial force prevailing in operation acts on the bearing combination 17/19. This force is absorbed by the two bearing combinations 15/14 and 16/18. By choosing the lever arms between the respective spherical sections you now have a means to keep the bearing load as low as possible in the combination 15/14. As a result, this bearing can be dimensioned small in its dimensions, ie in particular in its ball diameter with the result that it has a low friction. On the other hand, the joint sockets for the second and third spherical sections are not separate parts, but are integrated in existing components, on the one hand in the displacer, on the other hand in the fixed housing part or in the sliding block. For this reason alone, the solution is very inexpensive. Since these joint pans are also only half shells without an undercut, the injection or pressing tools required for the production are also not complex.

Reference symbol list

• 1.2 housing half
• 3 displacers
• 4 delivery chamber
• 5 bridge
• 6 admission
• 7 outlet
• 8 rib
• 9 intermediate ring
• 10 bars
• 11 groove
• 12.12 ′ wobble
• 13 crank mechanism
• 14 joint socket
• 15 first ball section
• 16.16 ′ second spherical section
• 17.17 'third spherical section
• 18.18 ′ socket in 1
• 19 socket in 3
• 20 spring means
• 21 recess
• 22 sliding block
• 23 sliding surface

Claims (4)

1. Wobbling drive for a translationally moving member (3) which is held relative to a fixed member (1) in a predetermined, angular relationship, essentially consisting of a wobbling bar (12, 12′)

- which is moved by means of a crank drive (13) and for this purpose sits at its crank-side end with a first ball section (15) in a bearing bush of the crank,

- is mounted at its other end with a second ball section (16, 16′) in a bearing bush of the fixed member (1), and in fact coaxially to the crank drive (13),

- and has between its two ends a third ball section (17, 17′) which is mounted in a bearing bush in the hub of the translationally moving member (3) in such a way as to be rotatable and capable of wobbling,
characterised in that
the bearing bushes for the second and third ball sections (16, 16′ and 17, 17′ resp.) are hemispherical joint sockets (18, 18′ and 19 resp.) which are arranged in mirror image in the two members (1, 3), spring means (20, 20′) ensuring a close fit of the ball sections in the joint sockets.

2. Wobbling drive according to Claim 1, characterised in that the second ball section (16′) is drawn loosely onto the wobbling rod (12′), and in that a helical spring (20′) is arranged between the second and the third ball section (16′ and 17′ resp.).

3. Wobbling drive according to Claim 1, characterised in that the joint socket (19) for accommodating the third ball section (17) is provided in a sliding block (22) which is displaceable in a spring-loaded manner (20) in the fixed housing part (1).

4. Wobbling drive according to Claim 1, characterised in that the bearing bush for accommodating the first ball section (15) is designed as a joint socket (14) which is displaceable in a plane parallel to the axis of the crank drive.

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