EP1272735A1

EP1272735A1 - Radial piston engine

Info

Publication number: EP1272735A1
Application number: EP01927816A
Authority: EP
Inventors: Chris Shrive; Sinclair SUC Design Ltd. Cunningham
Original assignee: Bosch Rexroth AG
Current assignee: Bosch Rexroth AG
Priority date: 2000-04-11
Filing date: 2001-03-27
Publication date: 2003-01-08
Anticipated expiration: 2021-03-27
Also published as: US6843162B2; EP1272735B1; WO2001077495A1; US20030159578A1

Abstract

The invention relates to a radial piston engine comprising a number of radial pistons that are guided in separate cylinder chambers, whereby the cylinder chambers can be joined via control passages with admission and discharge canals for pressure medium. The opening cross-sections of the control passages and of the admission and discharge channels are provided with curved face sections.

Description

description

Radial piston engine

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

A radial piston machine is known from DE 40 049 32 C2, in which a cylinder block with a plurality of cylinder spaces arranged in the radial direction is rotatably mounted in a housing. A piston is guided in each cylinder chamber, the end section protruding from the cylinder block is supported on a cam ring. This cam ring has a large number of control cams via which the pistons are radially displaced when the cylinder block rotates. In the housing of the radial piston machine, inlet and return channels for pressure medium are formed, which can alternately be overlapped with control openings in the cylinder block, via which the pressure medium supply and discharge to and from the cylinder chambers can be controlled.

In the exemplary embodiment disclosed in DE 40 049 32 C2, the control openings in the cylinder and the orifice cross sections in the housing are designed with a circular cross section. A disadvantage of such a solution is that the connection to the cylinder chambers is opened or closed comparatively slowly due to the circular control cross sections, so that flow losses can occur.

This disadvantage is compounded by one in the

EP 0 263 218 B1 overcome solution in which the control cross sections are not circular but approximately trapezoidal. The side faces of this Trapezoidal cross sections can be arched inwards or flat.

With such a solution, flow losses when opening and closing the connection to the cylinder chambers can be minimized, but it requires a considerable manufacturing outlay in order to form the trapezoidal control breakthroughs.

In contrast, the object of the invention is to create a radial piston machine which is subject to minimal flow losses and can be produced with minimal manufacturing outlay.

This object is achieved by a radial piston machine with the features of patent claim 1.

According to the invention, the openings for controlling the pressure medium supply and discharge are designed with curved end faces, with end faces being understood to mean the peripheral surface sections lying inside or outside in the radial direction. Such curved end faces can be produced much more easily than the straight-line end face sections known from EP 0 263 218 A1, so that the manufacturing outlay is minimized. Such a control cross section can be adjusted by extending the control opening in the radial direction without requiring an increase in the width (transverse to the radial direction).

The radius of curvature of the radially inner end face section is preferably made smaller than that of the radially outer end face section. In the solution known from DE 40 049 32 C2, the control cross section could only be enlarged by increasing the diameter. However, since the control breakthroughs and the mouth cross sections are preferably designed with zero overlap, the maximum width of the control breakthroughs and mouth cross sections is limited, so that the bore diameter cannot be increased arbitrarily in the known solution.

According to the invention, it is preferred if the end face sections each have a constant radius of curvature so that they can be formed by bores. This enables the end face sections to be formed by two through holes.

The manufacture of the openings is particularly simple if the two bores overlap one another, so that the openings can be made solely by forming the two bores and then have an approximately eight-shaped cross section.

Alternatively, the curved end faces can be connected to one another via tangential surfaces. In the case of different radii of curvature, the point of intersection of the two tangential surfaces lies in the axis of symmetry of the control cross section which tapers inwards in the radial direction.

The manufacture is particularly simple if the geometry of the control openings on the cylinder block side and the mouth cross sections on the housing side are selected identically. As already mentioned above, it is preferred that the mouth cross-sections and the control breakthroughs are designed with zero overlap with one another, so that the connection to the cylinder spaces is opened and closed as quickly as possible. The manufacture of the control breakthroughs and the mouth cross-sections can be further simplified if they are each formed in a control disk which is attached to the cylinder block or to the housing.

Other advantageous developments of the invention are the subject of the further subclaims.

Preferred exemplary embodiments are explained in more detail below with the aid of schematic drawings. Show it:

FIG. 1 shows a cross section through a radial piston engine;

FIG. 2 shows a detailed illustration of a control disk for controlling the pressure medium supply and discharge to cylinder spaces of the radial piston machine;

FIG. 3 geometrical details of a control breakthrough of the control disk from FIG. 2;

4 shows a simplified version of a control breakthrough for a control disk according to FIG. 2 and FIG

Figures 5 and 6 further simplified versions of a tax breakthrough.

Figure 1 shows a greatly simplified sectional view of a radial piston engine 1, which is constructed according to the multi-stroke principle. This radial piston motor 1 has a housing 2 to which a cam ring 4 is screwed. An output shaft 6 is mounted within the housing 2 and is connected via an external toothing to a cylinder block 8 designed as a rotor. In the illustrated embodiment, eight cylinder bores 10 are formed in the cylinder block 8, in each of which a piston 12 is guided radially displaceably. Between the radially inner piston crown 14 and the At the bottom of the cylinder bore 10, a cylinder space 16 is delimited, into which pressure medium can be fed. A roller 18 is mounted on the end section of each piston 12 that is distant from the cylinder space 16, and these rollers roll on a cam 20 of the cam ring 4 during the rotational movement of the cylinder block 8.

As can be seen from the illustration in FIG. 1, the control cam 20 is designed with 6 radially projecting control cams 22. When the control cams 22 run up, the pistons 12 are moved radially inward in the direction of their inner dead center. A valley 24 is formed between two adjacent control cams 22, so that the pistons 12 are at the apex of the valleys 24 at their outer dead center, in which the cylinder space has its maximum volume.

Each of the cylinder spaces 16 is assigned a control opening 26 formed in the cylinder block 8, through which the pressure medium is supplied or removed depending on the piston position. In the illustrated embodiment, eight control breakthroughs 26 are distributed on a pitch circle on the circumference in accordance with the number of pistons.

In the illustration according to FIG. 1, a control housing 30 lying behind the plane of the drawing and inserted into the housing 2, which is covered by the cylinder block 8, is only shown with dashed lines with its inner and outer circumference. Inlet and outlet channels 32, 34 are formed in this control housing 30, which are also only indicated by dashed lines in the illustration according to FIG. According to the number of control cams 22, six inlet channels 32 and six outlet channels 34 each open at the end, which are alternately evenly distributed over a pitch circle, the diameter of which corresponds to that of the pitch circle of the control cross sections 26. speaks. In the illustration according to FIG. 1, it should be noted that the mouth cross sections of the inlet and outlet channels 32, 34, which are set at 45 ° to the horizontal or vertical, are covered by the control openings 26 shown with a solid line.

The inlet channels are open to a first ring channel which is located radially between the control housing 30 and the housing 2 and is connected to an inlet connection on the housing 2, and the outlet channels 34 are open to a second ring channel which is axially spaced from the first ring channel , is also located radially between the control housing 30 and the housing 2 and is connected to a drain connection on the housing 2.

Depending on the design, the control openings 26 and / or the mouth cross-sections of the inlet and outlet channels 32, 34 can be axial bores in the cylinder block 8 or in the control housing 30, which is only indicated, or - similarly to those in EP 0 263 218 AI mentioned in the introduction The exemplary embodiments described - are located in control disks which are placed on the cylinder block 8 or the control housing and through which in each case only the front mouth areas of the assigned channels are formed. Such control disks forming the mouth cross-sections are easier to produce than bores or cutouts in the housing 2 or in the cylinder block 8.

FIGS. 2 and 3 show the geometrical relationships of a control breakthrough 26 and the associated opening cross section of an inlet and an outlet channel 32, 34. As already mentioned, the mouth cross sections 36, 38 of the channels 32 and 34 as well as the control openings 26 are designed with an identical geometry, which is described with reference to FIG. 3. at In this exemplary embodiment shown, the end face sections 40, 42 arranged diametrically to one another in the radial direction are each designed with a radius of curvature r2 or ri, the radius of curvature r2 of the radially outer end face section 40 being greater than the radius of curvature r ^ of the radially inner end face section. In the limit case, both end faces 40, 42 can be designed with identical radii r.

The side faces 44 connecting the two end face sections 40, 42 are in the case of FIGS

3 shown embodiment formed as tangential surfaces to the end face portions 40, 42, these tangential planes meet each other in the radial plane of symmetry 48. This intersection of the two tangential planes can lie, for example, in the axis of the output shaft 6.

Such an opening 26 (32, 34) is extremely simple to produce, since, for example, the two end face sections 42, 40 can be formed by bores, and then the tangential surfaces 44,

46 can be manufactured by milling or the like.

As can be seen in particular from FIG. 2, the geometries and the distance between two adjacent mouth cross-sections 36, 38 are selected such that a control opening 26 with zero overlap can be arranged in between in the relative position shown. In this relative position, the side faces 44, 46 of the control opening 26 are arranged in the axial direction in alignment with the adjacent side faces of the adjacent mouth cross sections 36, 38. That means that in this relative position there is neither a pressure medium supply nor a pressure medium discharge to or from the assigned cylinder space 16.

With a further rotation of the control opening 26 relative to the mouth cross-sections 36, 38, a large cross-section of the inlet or outlet channel 32, 34 is opened very quickly by the comparatively long side surface 44 or 46 of the control opening 26, so that the flow losses when reversing are minimal ,

FIG. 4 shows a simplified exemplary embodiment, in which the production outlay for the control breakthroughs 26 or the mouth cross sections 36, 38 is further minimized compared to the previously described exemplary embodiment. In the control breakthrough 26 shown by way of example in FIG. 4, the end face sections 40, 42 are formed by two bores with the radius r ^ and T2, similarly to the previously described exemplary embodiment. The axial distance d between the two bores is less than the sum r ^ + r2, so that the two bores overlap. The result is an approximately eight-shaped mouth cross section, the inwardly projecting side surfaces not being reworked as in the exemplary embodiment described above. In this simplified embodiment, the simplified manufacture is purchased with a slower opening and closing of the inlet and outlet channels 32, 34.

In the exemplary embodiments described above, the control openings 26 narrow in the radial direction toward the axis of the radial piston motor. FIGS. 5 and 6 show two further variants of a tax breakthrough 26, which is even easier to produce than the previously described solutions. In the exemplary embodiment shown in FIG. 5, the control breakthrough 26 is carried out, similarly to the exemplary embodiment described with reference to FIG. 4, by two overlapping bores with the diameter r ₂ ₌ r ₂ . The overlap of the two holes requires that the distance d is smaller than the dimension 2 r ^ (2 r ₂ ). This variant can be produced in a simple manner, for example, by drilling, with no reclamping of the drill as in the exemplary embodiment shown in FIG. 4 being necessary.

FIG. 6 finally shows an exemplary embodiment in which the end face sections 40, 42 are likewise made through two bores with the diameter r2 = r ^. In this variant, the distance d between the two bore centers is greater than the sum of the two radii 2 r ^ (2 r ₂ ), so that there is no overlap area. The two bore sections are then connected, as in the embodiment shown in FIG. 3, by tangentially extending side surfaces 44, 46, so that there is practically an elongated hole whose width is equal to the diameter rη_. That is, In the variants shown in FIGS. 5 and 6, the control breakthroughs 26 are therefore not youthful in the radial direction.

Of course, the cross sections described above can also be produced by machining processes other than drilling, such as milling, wire or die sinking EDM.

The area of the opening cross sections can be adapted to different requirements by a suitable choice of the distance d between the end face sections, the bore diameter or diameters being practical remain unchanged so that zero coverage is guaranteed.

What is disclosed is a radial piston machine with a plurality of radial pistons, each guided in a cylinder space, the cylinder spaces being connectable to supply and discharge channels for pressure medium via control breakthroughs. The mouth cross sections of the control breakthroughs and the inlet and outlet channels are provided with curved end face sections.

Claims

claims

1. Radial piston machine with a cylinder block (8) mounted in a housing (2), in which a plurality of pistons (12) guided in cylinder spaces (16) and supported on a cam ring (4) are mounted, and with a plurality of control openings on the cylinder block side (26), which can be brought to the inlet and outlet control overlapping with outlet cross sections (36, 38) on the housing side inlet and outlet channels (32, 34), characterized in that the control openings (26) and / or the outlet cross sections (36 , 38) curved end face sections (40, 42) and in the radial direction have a greater longitudinal extent than transverse to it.

2. Radial piston machine according to claim 1, wherein the mean radius of curvature (r2) of the radially outer end face section (40) is larger than that of the inner end face section (42).

3. Radial piston machine according to claim 1 or 2, wherein the end face portions (40, 42) each have a constant radius of curvature (ri, r2).

4. Radial piston machine according to one of claims 1 to 3, wherein the centers of curvature are less than the sum of the radii of curvature (r ^ + r2) apart.

5. Radial piston machine according to one of the preceding claims, wherein the end face portions

(40, 42) are connected to one another by approximately tangentially extending side surfaces (44, 46).

6. Radial piston machine according to one of claims 1 to 4, wherein the end face portions (40, 42) are formed by two overlapping bores.

7. Radial piston machine according to one of the preceding claims, wherein the geometry of the control openings (26) and the orifice cross sections (36, 38) is identical.

8. Radial piston machine according to one of the preceding claims, wherein the control openings (26) and / or the mouth cross-sections (36, 38) are each formed on a control disc which is fixed on the end face of the cylinder block (8) or on the housing (2).

9. Radial piston machine according to one of the preceding claims, wherein the control openings (26) and the mouth cross sections (36, 38) are formed with zero overlap.