EP0491398A1 - Radial piston engine - Google Patents

Abstract

In the case of a radial piston engine with pistons bearing on the circumference of an eccentric, which pistons perform a swivel movement when the eccentric moves in rotation and engage with a guide element, which, on the radially outward side, bears swivellably, by means of a radially outwardly convex ball race-shaped bearing surface on a concave ball race-shaped bearing surface in the housing or cylinder cover, the bearing, in order to obtain complete piston relief, is designed in such a way that the guide element (2) is provided with an upper end face (8) acted upon by the pressure medium, the hydraulically active plane (de) end face (8) running perpendicular to the longitudinal axis of the guide element (2) of which, lies in the area of the bearing surface (5) on the housing (6), or intersects this, in any swivel position of the piston (3). <IMAGE>

Description

The invention relates to a radial piston motor according to the preamble of claim 1.

In the case of a radial piston motor of this type, as is known, for example, from FR-OS 2 296 778, only a partial compensation of the hydraulic forces acting on the guide body of the piston is possible in that the pressure medium applied to the guide body from the outside inwards always in the same direction acts on the guide body, while the pressurization in the opposite direction from the inside to the outside, by means of which the guide body is held in the bearing shell, follows the pivoting movement of the guide body in its orientation, i.e. constantly changes the orientation, so that the opposing compressive forces over the swivel range cannot be compensated.

This is explained in more detail with reference to FIG. 1, which schematically shows the known construction according to the FR-OS mentioned above. The pressure p _{B present} in the pressure chamber 1 above the guide body 2 at the diameter de of this pressure chamber of the pressure medium supplied, for example, through passages in the cylinder cover exerts a force F _H which occurs during the pivoting movement of the guide body 2, which engages in a hollow piston 3, remains stationary. In the pivot position of the piston and guide body shown in FIG. 1, the same pressure p _B acts on the underside of the guide body 2, which is provided with openings for the pressure medium passage, with the resulting force F _K , which the guide body 2 with its spherical bearing surface 4 holds against a spherical ring-shaped bearing surface 5 of the housing or cylinder cover. When this resultant is broken down, a force F _KY counteracts the bearing relief force F _H acting on the upper side. The component F _KX of the force pressing the guide body against the bearing extends transversely to the longitudinal axis of the guide body 2 and thus acts transversely on the piston 3.

Z.B. bei einem Schwenkwinkel α von 10° und φ = 35° ergibt sich ein zulässiger Entlastungsgrad von m_zul = 0,863, ohne daß Reibungskräfte berücksichtigt sind.The balance of the forces in this swivel position results in a dependency between the permissible bearing relief degree m and the geometry of the motor

${\text{m}}_{\text{perm}}{\text{= F}}_{\text{H}}{\text{/ F}}_{\text{K}}\text{= cos α - sin α tg φ.}$

For example, with a swivel angle α of 10 ° and φ = 35 °, there is a permissible degree of relief of m _perm = 0.863 without considering frictional forces.

If the working piston is not pivoted at α = 0, the guide body could theoretically be relieved completely with a hydraulic counterforce F _H which is the same size as F _K. In this case, the excess of the forces is 1 - 0.863 = 0.137, i.e. almost 14%, which has a negative influence on the surface pressure on the spherical ring surface between the guide body and the housing, combined with a corresponding frictional torque. An increased frictional torque on the spherical bearing of the guide body causes that in FIG. 1 Shoe of the piston, not shown, stands out from the eccentric circumference on one side, which results in increased friction and leakage losses in this area, because pressure medium is directed via throttle bores to the underside of the piston shoe to relieve the hollow piston.

Taking into account the friction forces N that occur. µ, the permissible degree of relief is reduced by a few percent. In order to be able to hold the oscillating guide body securely against the ball seat, a few percent must therefore be added, taking into account the dimensional and shape errors of the ball, so that the motor data (α, φ) given above have an effective degree of relief of approx. 70 to Results in 75%.

The invention has for its object to design a radial piston engine of the type mentioned so that the effective degree of relief can be designed to a maximum.

This object is achieved by the features in the characterizing part of claim 1. Characterized in that the spherical ring-shaped bearing surface on the housing is dimensioned in relation to the spherical ring-shaped bearing surface on the guide body so that when the guide body is pivoted, the bearing surface on the housing is partially released with respect to the pressure medium and not the bearing surface on the guide body, as is the case with the above prior art Case is, the relief diameter de on the guide body, on which the relief force F _H acts, the pendulum movement of the guide body, so that a constant high relief can be achieved in any pivot position, which can also be interpreted precisely due to the constant alignment of the forces acting against each other.

Fig. 1

in schematischer Darstellung die am Führungskörper eines Kolbens auftretenden Kräfte bei der bekannten Bauweise, wobei

Fig. 1a

eine schematisch vereinfachte Darstellung dieser bekannten Bauweise wiedergibt,

Fig. 2

in gleicher Darstellung wie Fig. 1 die Kräfteverteilung bei der Bauweise nach der Erfindung, wobei

Fig. 2a

die erfindungsgemäße Bauweise in der Darstellung nach Fig. 1a wiedergibt, und

Fig. 3

eine weitere Ausführungsform der erfindungsgemäßen Bauweise.

The invention is explained in more detail for example with reference to the drawing. Show it

Fig. 1

in a schematic representation of the forces occurring on the guide body of a piston in the known construction, wherein

Fig. 1a

shows a schematically simplified representation of this known construction,

Fig. 2

in the same representation as Fig. 1, the distribution of forces in the construction according to the invention, wherein

Fig. 2a

shows the construction according to the invention in the illustration of Fig. 1a, and

Fig. 3

a further embodiment of the construction according to the invention.

In the embodiment according to FIG. 2, the spherical ring bearing surface 4 on the guide body 2 is approximately the same width as the corresponding spherical ring bearing surface 5 on the housing or cylinder cover 6, so that in the illustrated maximum pivoting position of the guide body 2, the bearing surface 4 thereof has the bearing surface 5 on one side Housing 6 covers, while on the opposite side, the bearing surface 5 on the housing 6 is partially released. The width of the ball ring bearing surface 4 can be designed as desired. In theory, it can reach the extreme value zero, as shown in Fig. 2a. There is therefore no relationship between the width of the ball ring bearing surface 4 and the ball bearing surface 5 on the cylinder cover. The ball bearing surface in the cylinder cover must have a certain minimum width, because the ball ring bearing surface 4, if the degree of relief is not 100%, only has to transmit the resulting residual force.

As a result, the end face 8 of the guide body 2 which forms the relief diameter de is continuously acted upon by the pressure medium introduced through the pressure chamber 1, so that the relief force F _H as a resultant of the pressure force P _B follows the pivoting movement and always acts on the axis of the guide body 2.

In the middle position at α = 0, an outer part of the bearing surface 5 on the housing 6 is exposed over the entire circumference, so that the relief surface on the upper end face 8 of the guide body 2 is subjected to pressure in the same way as in the maximum pivoting position according to FIG . 2.

In contrast to the known construction according to FIG. 1, in the embodiment according to the invention according to FIG. 2, the relief surface on the end face of the guide body 2 is not partially formed by the bearing surface 4 on the guide body, but only by the straight end face 8, the edges of which during the pivoting movement Swipe over the bearing surface 5 on the housing 6. In the known design, a portion of the bearing surface 4 on the guide body 2 is always acted upon by the pressure of the pressure medium, so that the relief force F _H cannot follow the pivoting movement of the guide body 2.

In the known construction, the relief surface de is defined by the approximately cylindrical pressure chamber 1 in the housing 6, while in the construction according to the invention the relief surface de is fixed on the guide body 2. This is illustrated by the schematic representations in FIGS. 1a and 2a. In the known construction according to FIG. 1 a, the bearing surface on the housing is reduced to a circular sealing edge 5 ′ on which the ball ring bearing surface 4 of the guide body 2 bears. The pressure chamber 1 above the guide body is essentially fixed by a cylindrical recess Diameter de formed. The sealing edge 5 'determines the size of the pressure field p _B and thus also its stationary position, because the sealing edge 5' does not change during the pivoting movement of the guide body 2.

In contrast, in the construction according to the invention according to FIG. 2a, the pressure chamber 1 is formed above the guide body 2 by an approximately spherical-spherical recess, the bearing surface 4 of the guide body 2 reduced to a peripheral edge 4 ′ being present as a sealing edge in this spherical-spherical recess. The diameter de of this circular sealing edge 4 'determines the pressure field p _B acting on the guide body 2 according to size and position, so that the orientation of the pressure field inevitably follows the orientation of the sealing edge 4', which in this illustration forms the upper end face 8 of the guide body 2. The fact that according to the invention the cylindrical element 2 in Fig. 2a is movable relative to the fixed element 5 with a concave ball bearing surface, the sealing line 4 'between these two elements and the pressure field associated therewith is also movable.

In other words, in the construction according to the invention, the plane of the relief surface de or its projection in the axial direction intersects the spherical ring bearing surface 5 on the housing 6. The width of the bearing shell 5 on the housing 6 is essentially determined by the pivoting range of the relief surface de running perpendicular to the longitudinal axis of the guide body 2 certainly. This applies to the definition of the minimum height of the upper edge of the bearing shell 5. The lower edge of the bearing shell 5 is designed such that even in the maximum pivoting position according to FIG. 2, there is sufficient bearing surface for the guide body 2 at the bottom right.

Fig. 2 shows the maximum swivel position of the guide body 2 the minimum height of the upper edge of the bearing surface 5 on the housing. As FIG. 2a shows, this upper edge can also be higher. In the embodiment of FIG. 2, the width of the bearing surface 4 on the guide body corresponds to the width of the bearing surface 5 on the housing, so that the two bearing surfaces fully overlap on one side in the maximum pivoting position. However, this width of the bearing surface 4 is not necessary, as stated above.

This design of the bearing area between the guide body and the housing or cylinder cover ensures that the hydraulic relief field and the resulting relief force F _{H is} connected to the pivoting guide body. The hydraulic relief force acts in the same plane or orientation against the reaction force on the radially inner side of the guide body, so that there is no critical position in which lifting of the piston is to be feared because the same friction torque is present in every pivot position. F _H must not be greater than F _K , so that the degree of relief is no longer limited by the geometry of the radial piston motor, but only by the size of the pressure field. Theoretically, F _H = F _K , so that the degree of relief would theoretically be 100%.

With a high degree of relief, the frictional forces are minimized. This has a very positive effect on the friction torque of the guide body.

Fig. 3 shows a construction according to the invention, in which the guide body 2 'overlaps the piston 3'. The same condition applies to this construction, according to which the plane of the relief surface de can only be pivoted in the area of the bearing shell 5 on the housing 6 and not beyond. The frictional torque on the guide body 2 'can thereby be reduced to a minimum value, that due to a high degree of relief only low friction forces N. µ occur. Although for structural reasons a relatively large ball radius R _{K is} provided in this construction, which is larger than the piston diameter because the piston is immersed in the guide body, the frictional torque can nevertheless be kept very small.

3, the upper part of the guide body 2 'is spherical, a support ring 10 supported by springs 9 being provided in the lower region of the ball, which is supported in the housing or in the cylinder cover. At 11 in Fig. 3 the eccentric is indicated, on the circumference of which the pistons 3 'and 3 abut.

In Fig. 3, 12 designates an annular groove formed on the bearing surface 4, which is formed on the periphery of the guide body 2 'near the end face and is continuously connected to the leak oil chamber of the radial piston motor via an oblique bore 13. As in the embodiment according to FIG. 2, only a relatively narrow sealing surface between the bearing surfaces 4 and 5 is required in the construction according to FIG. 3 in order to obtain a high degree of relief and to transmit the remaining forces from F _K - F _H , such as this can also be derived from FIG. 2a. The annular groove 12 is therefore formed near the end face of the guide body 2 'in its spherical ring bearing surface 4. As a result, the pressure surface on the end face 8 of the guide body 2 ′ is precisely defined, since the annular groove 12 reduces the oil pressure in the remaining area of the ball ring bearing surface 4 via the oblique bore 13. Without this annular groove 12 with relief bore 13, the pressure reduction in the bearing area and thus the pressure relief field would not be precisely defined. The convex spherical ring bearing surface 4 lying below the annular groove 12 in FIG. 3 serves only for reducing the surface pressure and for better ball guidance in the cylinder cover.

Due to the construction according to the invention, the effective degree of relief can on the one hand be designed to a maximum and on the other hand the degree of relief can be clearly and precisely predetermined, because in each pivot position the pressure force acts on the guide body in the direction of the axis of the guide body.

2, the piston 3 is designed as a hollow piston and the guide body 2 is designed in accordance with a fully cylindrical component that is immersed in the hollow piston, in the construction according to FIG. 3 the guide body 2 'is provided with a cylindrical recess in which the fully cylindrical piston 3 'is guided so that the guide body 2' overlaps the piston 3 'in this construction.

Elevations or the like can also be formed in the central region on the end face 8 of the guide body 2 or 2 '. It is essential that the hydraulically effective relief surface determined by the diameter de is present, which cuts the bearing surface 5 on the housing during the pivoting movement of the piston.

Claims (3)

Radial piston motor with pistons resting on the circumference of an eccentric, which perform a pivoting movement when the eccentric rotates and are in engagement with a guide body which on the radially outer side by a radially outwardly convex spherical bearing surface on a concave spherical bearing surface in the housing or . The cylinder cover swivels,
characterized,
that the guide body (2) is provided with an upper end face (8) acted upon by the pressure medium, the hydraulically effective plane (de) of which runs perpendicular to the longitudinal axis of the guide body (2) in each pivoting position of the piston (3) in the region of the bearing surface ( 5) lies on the housing (6) or cuts it. Radial piston engine according to claim 1,
characterized,
that the ball ring bearing surface (4) on the guide body (2, 2 ') is narrow in relation to the width of the ball bearing surface (5) on the housing or cover (6). Radial piston engine according to claims 1 and 2,
characterized,
that an annular groove (12) is formed on the ball ring bearing surface (4) of the guide body (2, 2 ') near the end face of the guide body, which is connected via a bore (13) with the leakage oil chamber of the radial piston motor.

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