WO1997009532A1

WO1997009532A1 - Hydraulic radial piston machine

Info

Publication number: WO1997009532A1
Application number: PCT/DK1996/000367
Authority: WO
Inventors: Jens Jørgen NIELSEN; René Andersen; Anders Valbjørn; Helge B. Nielsen
Original assignee: Danfoss A/S
Priority date: 1995-09-05
Filing date: 1996-09-04
Publication date: 1997-03-13
Also published as: DE19532713C1

Abstract

A hydraulic radial piston machine is disclosed, having at least one radially oriented cylinder (7) which is connected to a cylinder carrier. To manufacture a light-weight machine that is inexpensive to complete, the cylinder carrier (14) is formed from a sheet material (15) which is shaped circumferentially to form a closed ring.

Description

H^ydraulic radial piston mac_hinp..

The invention relates to a hydraulic ra_dial piston machine having at least one radially oriente_d cylinder which is connected to a cylinder carrier.

Such radial piston machines generally have several cylinders, in which pistons are movable back and forth radially. The pistons are in connection with an eccentrically mounted shaft by way of sli_de shoes. When the shaft rotates and by virtue of its eccentricity drives the pistons, the machine operates as a pump. When the pistons are driven by changing pressures in the work chambers of the cylin_ders, a torque acting on the shaft can be generated. In that case the machine operates as a motor.

Hydraulic machines of that kind have a comparatively high output for their overall size. T_heir use is becoming increasingly wide-spread. Manufacture of suc_h a machine is still relatively expensive, however, so that its use is often excluded on the groun_ds o_f cost.

The invention is based on the problem of providing a light-weight machine that is inexpensive to manufacture.

That problem is solved in a hydraulic radial piston machine of the kind mentioned in the introduction in that the cylinder carrier is formed from a sheet material which is shaped circumferentially to form a closed ring. Only relatively little material is therefore used for the cylinder carrier. The sheet material as such is relatively inexpensive. It can be easily worked. The closed ring on the other hand provides a certain strength, which is sufficient for operation of the machine. Complicated measures, such as those previously caused, for example, in the manufacture of the cylinder on account of the fact that the cylinders were in the form of bores in an otherwise solid housing, can be omitted. On the contrary, the cylinders are inserted as independent components in the cylinder carrier or are secured thereto. The cylinder carrier then serves for the mutual fixing of the cylinders with respect to one another and to the axis or drive shaft. The cylinder carrier can now be constructed exclusively from the point of view of mechanical considerations, such as stability combined with low weight, and the cylinders can be constructed from the point of view of hydraulic considerations, for example, with regard to the fluid to be used. Thus, water too can be used as hydraulic fluid.

The ring is preferably in the form of a bent part. Sheet material can generally be brought with relatively little effort into a desired form by bending.

In an especially preferred construction, provision is made for the ring to be in the form of a regular polygon. In principle it is, to be sure, sufficient for the ring to be round, that is, in the form of a hollow cylinder. But in the case of a polygon, flat surfaces in which the cylinders can be arranged are available. This allows an exact orientation of the cylinders with their axes on the axis of the machine. Fixing to a flat surface is easy. It is preferred here for each cylinder to be arranged substantially in the middle of one side of the polygon. Externally around the cylinder there is therefore sufficient space available for securing the cylinder or for mounting other parts.

The sheet material is preferably in the form of a strip which has tabs running transverse to the circumferential direction, the tabs being bent radially inwards and circumferentially adjacent tabs being joined to one another. On forming of the ring, this construction provides great stability of the cylinder carrier, combined with low weight. The inwardly angled tabs reinforce the sides of the polygon, especially when they are bent at an angle of 45° or more. Joining of the tabs to one another produces a reinforcement, and thus a stabilization, of the entire cylinder body. Both the strip and the tabs are initially in the form of sheet material, however, and are therefore located in one plane. Only by bending or angling the tabs and by bending the strip to form a ring is the desired stability produced.

The tabs are preferably arranged axially on each side of the strip. This produces even better stability of the cylinder carrier.

It is also an advantage that tabs that are circumferentially adjacent bear against one another with abutment edges and are joined to one another along these abutment edges. The tabs do not therefore overlap, and are therefore not thicker than the thickness of the sheet material. Consequently, no more material that is absolutely necessary is used. This measure contributes to a reduction in weight. Joining of the tabs along their abutment edges allows rapid and easily controllable fixing of the tabs to one another.

It is also preferred for each tab to have a recess in the shape of a segment of a circle and in the radially inwardly folded state to enclose an at least approximately circular opening. Also in the folded-in state the tabs therefore leave free a circular opening, through which, for example, it is possible to assemble the shaft with its eccentric. The tabs, together with the strip, partially enclose a cavity, however, which need not be filled. The slide shoes and, optionally, the pivotal joints of the piston, are able to move freely here.

In an especially preferred construction, provision is made for the tabs to be bent radially inwards substantially at right angles. Parallel surfaces which further facilitate the subsequent assembly of the machine are therefore produced at the axial front and axial rear sides of the cylinder carrier.

The cylinder carrier is preferably in the form of a stamped part. Such parts are inexpensive to manufacture, particularly when they are required in large piece numbers.

It is also advantageous for the cylinder carrier to be made from sheet metal or plastics material, sections that are joined to one another being welded to one another. Sheet material or plastics material of appropriate quality have the necessary stability and strength. Welding of the tabs along their abutment edge ensures reliable joining of parts touching one another. Welding can be carried out automatically with ease. In an especially preferred construction, each cylinder is in the form of a deep-drawn part. This also allows an inexpensive manufacture of the cylinder combined with low weight. Substantial parts of the machine are then produced with only relatively thin wall thicknesses, these parts having been formed by a deformation technique. Further machining, in particular material-removing machining, such as drilling, turning or milling, is largely unnecessary.

Each cylinder advantageously has at its radially inner end a widening which is arranged radially within the cylinder carrier. The cylinder is consequently mechanically supported in the cylinder carrier, to be precise, against a pressure towards the outside such as occurs during each piston movement. The widening towards the outside can also be achieved by a deformation technique, so that neither additional material needs to be used nor are additional machining steps necessary. This widening can generally be produced during the deep-drawing operation.

Fixing points, to which a retaining band passing radially outside over the cylinders is secured, are advantageously provided on the cylinder carrier between the cylinders. This further stabilizes the cylinders with respect to the cylinder carrier. Since the retaining band passes radially outside over the cylinders, the cylinders are primarily secured against radial outward movement. Furthermore, this retaining band also prevents skewing of the cylinders circumferentially with respect to the cylinder carrier, or at least renders this difficult. Together with the radially running cylinder wall and the cylinder carrier, the retaining band in fact forms a triangle, which in itself is very stable. In an advantageous configuration, the fixing points can be in the form of axially running tubes, which serve at the same time to receive fixing means with which the machine can be secured to the site where it will be used.

The cylinder carrier and the cylinders are advantageously surrounded by plastics material. The plastics material can be cast, for example. In this manner a compact exterior having a smooth outer surface is obtained, so that the risk that the assembly will become dirty is slight. The ease with which the cast- round cylinder carrier can be handled is improved. Moreover, the plastics material also provides yet further improved stabilization, both of the cylinder carrier and of the cylinders with respect to the cylinder carrier. The plastics material holds them in the defined position and imparts, in particular to the cylinders, an even greater resistance to pressure.

In that case it is especially preferred for the plastics material to project axially beyond the cylinder carrier and to support bearing carriers for a shaft. The plastics material is therefore also taken beyond the radially inwardly bent-over tabs. It therefore yet further stabilizes the cylinder carrier in this region axially. Since it supports the bearing carrierε, this load is not completely removed from the cylinder carrier. But the cylinder carrier is relieved of load to such an extent that despite its small material thickness it is able to effect the required fixing of the bearings to the cylinders. The plastics material selected is in most cases lighter in weight than a metal from which one would normally make the cylinder body. The cast plastics material, however, does not require further machining. The invention also relates to a method for manufacturing such a machine, the cylinders being inserted in the cylinder carrier prior to the bending operation. Prior to the bending operation, the cylinder carrier is in the form of a flat structure which is easy to handle. For example, the cylinders can be inserted and joined to the cylinder carrier. The widening here allows the cylinders simply to be inserted from the correct side into the cylinder carrier and pushed in as far as they will go. They can then be secured. As a further step, the cylinder carrier is bent and the cylinder body of the machine is virtually complete.

The invention is described in the following with reference to a preferred embodiment in conjunction with the drawings, in which:

Fig. 1 is a cross-section through a radial piston machine along the line I-I according to Fig.

2,

Fig . 2 is a longitudinal section through the machine along the line II-II according to Fig. 1,

Fig . 3 is a front view of a cylinder carrier with cylinders,

Fig . 4 is a section IV-IV according to Fig. 3, and

Fig . 5 is a plan view of sheet material used for the cylinder carrier.

A radial piston machine 1 has a shaft 2 on which an eccentric 3 is non-rotatably secured. Slide shoes 4 which are connected by way of respective ball-and- socket joints 5 to a piston 6, bear on the eccentric 3. The pistons 6 are movable back and forth in a cylinder 7. When the shaft 2 rotates, the pistons 6 are moved radially inwards and outwards in their cylinders 7. Conversely, a corresponding admission of pressure to the pressure chambers 8 formed between piston 6 and cylinder 7 also causes a torque to be applied to the eccentric 3 and thus to the shaft 2. In the first case, when the shaft is being driven, the radial piston machine 1 acts as a pump. In the latter case it functions as a motor.

The construction and the function of such a radial piston machine is known per se. Further explanation is therefore needless.

For the controlled supply to the pressure chambers 8 of the individual cylinders 7, a valve arrangement 9 is provided, which is joined to two lines 10, 11 through which hydraulic fluid is admitted in a controlled manner to the individual pressure chambers 8. Between the valve arrangement 9 and each pressure chamber 8 there is a feed line 12, which opens through an opening 13 into the pressure chamber 8.

The manner in which the cylinders 7 are secured in the machine will be explained with reference to Figs 3 to 5. The cylinders 7 are fastened to a cylinder carrier 14. The cylinder carrier is stamped from a sheet material, for example, sheet metal. A fragment of the stamped shape 15 is illustrated in Fig. 5. The stamped part consists of a strip 16 which, in the embodiment illustrated, is bent to form a regular pentagon, as shown in Fig. 3. Axially in front of and behind the strip 16, tabs 17 are joined to the strip 15. These tabs have a recess 18 in the shape of a segment of a circle. In addition, the tabs 17 are bounded, viewed peripherally, by edges 19, 20 which are to abut. The fourth boundary of the tabs 17 is formed by a bending line 21. Further bending lines 22 in the strip 16 form corners 23 of the polygon illustrated in Fig. 3.

If the strip 16 is bent along the bending lines 22 and at the same time the tabs 17 are bent inwards through 90° (Fig. 4), the abutment edges 19, 20 of adjacent tabs 17 butt against one another. They can then be butt-welded to one another. The ends of the strip 16 are also welded to one another. In the embodiment illustrated, a five-cornered housing with parallel front and rear sides is produced, which has a great stability.

On the rear side, illustrated in Fig. 3, the tabs 17 joined to one another have openings 24 which can be formed beforehand during stamping by means of corresponding semicircles 25, 26 in the tabs 17. The valve arrangement 9 can later be joined to the cylinder carrier 14 by means of these openings 24. The form illustrated in Fig. 5 can be produced very easily from sheet metal, by stamping. During stamping, both the tabs 17 and the abutment edges 19, 20 and also the semicircles 25, 26 can be stamped out. Furthermore, during stamping a cylinder-receiving opening 27 can be produced, through which the cylinders 7 can be passed. For that purpose the cylinders 7 are preferably introduced from the radially inner side of the cylinder carrier 14. They have at their radially inner end a widening 28 which forms a kind of stop. The cylinders 7 can be introduced into the cylinder carrier 14 as far as this widening 28 without fear that they will slip out again. When they are in position with their widening 28 against the cylinder carrier 14, they can be welded to the cylinder carrier 14. Insertion of the cylinders 7 into the cylinder carrier 14 is most suitably carried out before the polygon or polygonal ring is produced. The tabs 17 may already have been bent. When the cylinders 7 are inserted before the ring is made, there is free access to the openings 27 for receiving the cylinders.

As is especially clear from Fig. l, at the corners 23 there are fixing points which are formed by axially running tubes 29. These tubes 29 form a continuous opening through which, for example, screw bolts can be passed in order to secure the radial piston machine 1 to the site where it will be used.

The tubes 29 serve as fixing points for a band 30, which is passed radially outside over the cylinders 7 and holds the cylinders 7 fixedly with respect to the cylinder carrier. It is clearly seen that the cylinder carrier, the cylinders and the retaining band 30 form several triangles, that is, form a combination that is very stable against the effects of tension. The cylinders 7 are secured againεt skewing by means of the band 30.

As is apparent from Figs 1 and 2, the radial piston machine 1 is cast in a plastics material 31. The plastics material forms a smooth surface 32, 33 externally. Moreover, it stabilizes the cylinders 7 with respect to the cylinder carrier 14. The cylinder carrier 14 too is outwardly stabilized. The plasticε material 31 projects axially at the front and at the back beyond the cylinder carrier 14. It is thus able to support bearing carriers 34 for the shaft 2. The bearing carriers 34 are moreover also supported by the cylinder carrier 14 and held in a defined position. The cylinder carrier 14 is reinforced by the plastics material 31 in order to be able to take even relatively great bearing forces on the bearing carriers 34. Moreover, the plastics material 31 holds the bearing carriers 34 in a fixed and clearly defined connection with the cylinder carrier 14. Such a machine can be operated also with water aε the hydraulic fluid.

Claims

Patent Claimε

1. Hydraulic radial piston machine having at least one radially oriented cylinder, which is connected to a cylinder carrier, characterized in that the cylinder carrier (14) is formed from a sheet material (15) which is shaped circumferentially to form a closed ring.

2. Machine according to claim 1, characterized in that the ring is in the form of a bent part.

3. Machine according to claim 1 or 2, characterized in that the ring is in the form of a regular polygon.

4. Machine according to claim 3, characterized in that each cylinder (7) is arranged substantially in the middle of one side of the polygon.

5. Machine according to one of claims 1 to 4, characterized in that the sheet material (15) is in the form of a strip (16) which has tabs (17) running transverεe to the circumferential direction, the tabε being bent radially inwards and circumferentially adjacent tabs (17) being joined to one another.

6. Machine according to claim 5, characterized in that the tabs (17) are arranged axially on both sideε of the εtrip (16) .

7. Machine according to claim 5 or 6, characterized in that tabs (17) that are circumferentially adjacent bear against one another with abutment edges (19, 20) and are joined to one another along theεe abutment edges (19, 20) .

8. Machine according to one of claims 5 to 7, characterized in that each tab (17) has a recess (18) in the shape of a segment of a circle and in the radially inwardly folded εtate encloεe an at least approximately circular opening.

9. Machine according to one of claims 5 to 8, characterized in that the tabs (17) are bent radially inwards εubstantially at right angles.

10. Machine according to one of claims 1 to 9, characterized in that the cylinder carrier (14) is in the form of a stamped part.

11. Machine according to one of claims 1 to 10, characterized in that the cylinder carrier (14) is made from sheet metal or plasticε material, εectionε that are joined to one another being welded to one another.

12. Machine according to one of claims 1 to 11, characterized in that each cylinder (7) is in the form of a deep-drawn part.

13. Machine according to one of claims 1 to 12, characterized in that each cylinder (7) has at itε radially inner end a widening (28) which iε arranged radially within the cylinder carrier (14) .

14. Machine according to one of claims 1 to 13, characterized in that fixing points (29) , to which a retaining band (30) passing radially outside over the cylinders (7) is secured, are provided on the cylinder carrier (14) between the cylinders (7) .

15. Machine according to claim 14, characterized in that the fixing points (29) are in the form of axially running tubeε.

16. Machine according to one of claims 1 to 15, characterized in that the cylinder carrier (14) and the cylinders (7) are surrounded by plastics material (31) .

17. Machine according to claim 16, characterized in that the plastics material (31) projects axially beyond the cylinder carrier (14) and supportε bearing carriers (34) for a shaft (2) .

18. Method for manufacturing a machine according to one of claimε 1 to 17, characterized in that the cylinderε (7) are inserted in the cylinder carrier (14) prior to the bending operation.