DE2132252A1 - Device for holding a ball head in the pistons of hydraulic pumps and motors - Google Patents

Description

Device for holding a ball head in the piston of hydraulic pumps and motors

The invention relates to hydraulic pumps and motors. The invention is preferred with pumps and piston drum motors of the type of axial piston machines, in which the pistons have a back and forth perform her genende movement in a direction parallel to the axis of the motor or the pump and move on an inclinable disc with the help of hydrostatically balanced sliding blocks.

The object of the invention is primarily to develop a device that prevents the unwanted separation between the balanced sliding shoes and the pistons

109886/1191

prevents the effects of inertia and friction between sliding shoes at the same time and the piston can enter.

Another object of the invention is to develop a device for holding a ball head, the changing Is subjected to forces; the device can be used in pumps and engines with piston drums on the type of Use angle pumps to connect the piston connecting rods to the piston on one side and to the drive pulley on the other safe to connect.

For the sake of simplicity, only pumps will be spoken of in the description below, but of course the features described in connection with pumps can also be found in hydraulic motors.

In the main area of application of the device, it is common to use the piston-slide shoe component group the swash plate by a spring or with the help of hydraulic forces that put a constant pressure on it exert the plunger to keep it in contact.

It is recommended that this means producing an indirect force-fit connection by means of a holding device to replace, which connects the sliding shoe mechanically with the ball head of the piston and which is therefore safer works.

A known possibility for a fixed connection consists in placing a sliding shoe, which has a recess with a spherical surface, on a piston, the connecting piece of which is likewise spherical. When the piston is made of steel and the sliding shoe is made of

109886/1191

Bronze, there are favorable friction conditions between the slide shoe and piston head on the one hand and the slide shoe and drive pulley on the other.

The disadvantages of this design are evident in the insertion process. Namely, it becomes an exact bracket provided, the parts can no longer be manufactured with a rough fit and the sliding shoe can no longer be removed. It can also be seen that the excess of the radial force at the head of the piston pushed furthest into the cable drum and the excess of the radial force at the head of the furthest piston protruding from the piston drum is considerable, which creates high stresses at the points of contact between the piston and the cylinders of the piston drum result.

In a further known holder, a piston, the head of which has a hollow spherical recess, is opened a sliding shoe set in the form of a complementary spherical shape. This arrangement enables a reduction the excess of the radial force on the piston head and allows sliding shoe and piston in dimensions perform, through which a sufficient strength even for fairly large angles of the drive pulley is guaranteed. The disadvantage of this arrangement is the difficulty in making such a piston. The radial forces exerted on the pistons and the comparatively high relative speeds the cylinders of the piston drum require that the pistons are made of a metal, the senr has good mechanical properties so that premature piston wear is avoided. For this Basically, the piston head can only be used after a local heat treatment, which reduces the elasticity -

109886/1191

-If-

the limit of the material. Another disadvantage of this arrangement is that it cannot be disassembled and that the control and adjustment of the play between the sliding block and the piston is not easy is possible,

Furthermore, a holding device is known in which a ring inserted into a hemispherical groove of Circular cross-section prevents the ball head from stepping out of its seat. With this arrangement there is the disadvantage connected that between the ring and the ball head there remains an assembly play that affects the operation of the pump , if in this way the sliding shoe is to be positively connected to the pump piston. Of the Circular cross-section with the small diameter of the ring «makes the arrangement only relative low holding forces can be used.

The inventive device that these disadvantages allowed to avoid, in particular allows:

- Easier manufacture of the piston and the sliding block from materials that suit the working conditions

. the piston pump is adapted;

- a substantial reduction in the excess radial force on the piston head, even for large ones Drive pulley angle;

- easy assembly and disassembly;

- an automatic compensation of the play between piston and sliding shoe »

The device according to the invention described below

109886/1181

device has in particular a sliding shoe, the rear spherical section with a complementary thereto spherical surface on the piston and which is held in place with the help of an organ that is arranged in a groove made in the piston.

The invention relates in particular to a device in which the groove of the piston and the xialteorgan on the ball head have a special shape that requires a backlash-free assembly of the ball head and any allow automatic compensation of the game based on manufacturing tolerances, wherein the sliding shoe is held by a clamping process.

The inventive device for holding a Spherical head in a seat with a rotating surface, which has a hemispherical base that coincides with the surface of the Spherical head cooperates, and which device has a holding member for the ball head in the form of a cut open has elastic ring, is therefore characterized in that the seat has a surface in the form of a l ^ gel stump, whose large base area into the nalo-spherical base passes over, and that the holding Organ adapts itself in its contact area of the spherical head surface in such a way that at least one imaginary conical tangent surface rests simultaneously on the holding organ and on the spherical head in their contact area, the cross section of the holding organ runs in such a way that the difference of half the apex angle of the imaginary conical surface is the largest possible half the apex angle, and the l% obtuse surface of the Seat less than or equal to the sum of the angles of friction at the points of contact of the holding organ with the called conical surfaces.

109886/1191

Further details can be found in the following description of an exemplary embodiment of the invention referring to drawings showing:

1 shows a sectional view of a holding device; Fig. 2 is a plan view of the holding member;

Figures 3 to 6 are schematic drawings of sections through the holding member and its seat;

7 shows a view of a modified embodiment, the holding device.

The holding device has a seat 3 on the piston 1, the rotating surface of which is hemispherical Has reason 2 (radius R ^) for a ball head 10. The rotating surface of the seat 3 consists of a truncated conical surface 3, with the large base of the truncated cone a

over a toroidal surface part 3, in the hemispherical one Reason 2 skips.

Half the apex angle of the conical surface 3 is to be referred to as oil.

A holding member, which is inserted into the groove 3, is formed by a cut-open ring 4.

This generally toric ring is arranged so that its axis of rotation coincides with the axis XX ¹ of the recess guiding the piston.

The ring is used to hold the final ball

109886/1191

head 10 of a sliding shoe 5, the total of which is cylindrical trained foot 6 is slidable on a disc 7.

The spherical surface of the spherical head 10 merges into a neck part with the diameter D ^ and from there into the foot 6.

The holding organ 4 consists of part of a ring, which is cut open on a length L (Fig. 2) and has an inner surface piece, which the ball head

As shown in FIGS. 1, 3, 4, 5, 6, a peripheral piece of the holding member touches an imaginary conical surface C ₁ , and another peripheral piece touches the conical surface 3 of the piston seat.

egg

In this embodiment, the holding member U has a substantially circular cross-section, which is interrupted by a conical inner part 11, the half of the apex angle is denoted by ψ.

At its end 8, the piston 1 has a bore 9, which is connected to the base 2 via a passage 13 of small diameter; the passage 13 can between the Ball head of the slide shoe 5 and the piston 1 create an oil film which is under the same pressure like the cylinder of the piston.

^{A bore I 1} + of small diameter leads through the sliding shoe 5, so that the same pressure is established between the sliding shoe 5 and the disc 7 on which it slides.

The device is used as follows:

109886/1191

- First of all, the ring U is attached to the sliding block 5 in the In the area of the neck part by spreading the ring so far that d £> its opening L becomes equal to the diameter D. of the neck part. Then the ball head of the sliding shoe is inserted into its seat 2, the ring 4 still in the region of the neck part of the Sliding shoe is located;

- Then the ring is compressed so far that its outer radius is smaller than the radius R "of the input circle base of the conical surface is 3, and finally becomes the

Ring 4 pushed against the ball head of the slide shoe 5.

The ring 4 advances, expanding by itself, depending on / flem between the groove 3 and the spherical surface of the ball head 10 of the sliding block remaining space. The sliding shoe can work accordingly, i.e. that its axis with respect to the piston axis can assume all positions that are in a cone with half the apex angle of the order of 20. One can also exercise a pull on the sliding shoe in order to - without success try to separate the sliding shoe from the piston, because by a clever choice of the angles Qn and β (where ρ is greater than (Jn) a clamping effect is achieved, which allows a backlash-free assembly of the system, regardless of the manufacturing tolerances conditional "actual dimensions of the parts, with 7 is

Here a holding member is referred to, which is used to hold the sliding blocks on the disc 7 with the necessary clearance is determined.

The device works as follows:

- in order to simplify the description, let us first

109886/1181

taken that the mean diameter of the assembled ring 4 is the same as its mean diameter in a free position, and that the wire from which it is made cannot be twisted.

The respective contact forces run independently of the direction of the tensile forces acting on the slide shoe 5 between the ball head 10 and the ring 4 or between the ring 4 and the groove 3 of the piston 1 inside the friction cones at contact points B and A.

In Fig. 3, the force F _{1 of} the ball head of the slide shoe 5 on the ring 4 is shown in a ring section S (Fig. 2), and the reaction force F _{2 of} the riut 3 on the ring 4 in the same ring section.

If f * dzw. f _{2 represent} the coefficient of friction between the ring H and the ball head 10 or the ring 4 and the piston 1, then the half point angles of the friction cones are m, and nu, namely:

- f ₁ = tg In ₁

- f ₂ = tg üij,

We-d an inertia and frictional effect on the sliding shoe 5 based tensile force is exerted, it seeks to separate itself from the piston 1. This separation would occur a, the ring 4 would move away with the sliding shoe 5 in the direction of arrow 15 and the ring would go ahead of the sliding shoe in its movement, because the ring changes its diameter due to the shape of the surface 3

would have to wrestle, which is only possible if he gets closer to the Ilalteil of the sliding shoe.

109886/1191

The ring 4 therefore seeks to move in the direction of the rials of the sliding block. The force F _{1 of} the sliding shoe on the ring 4- therefore remains - based on the direction of arrow 15 - behind the common normal N ₁ at the point of contact B.

Correspondingly, the force F _{2 of} the groove 3 on the ring 4- - based on the direction of the arrow 15 - lies behind the normal N "at the point of contact A, because the groove 3 does not change.

In order for a clamping effect to occur, only the resultant of the forces F. and F “must be zero. However, since the ring 4 is provided as a non-twistable, "is the torque of the forces F ₁ and F" is not necessarily zero. In other 'words, it is sufficient to <4SS the forces F ₁ and F y are effective parallel to a To achieve clamping effect as long as they remain inside the friction cone, which are defined by the angles m. And m ₂ .

The limit of the clamping effect and the displacement of the ring occurs when the forces F ^ and F ₂ coincide with a generatrix of their respective friction cone, as indicated in FIG.

The forces F ₁ and F "in this case with their assigned normals DB and AO form the legs of the angles IH ₁ and m ₂ , where F ₁ and F" are parallel to one another and F _? encloses an angle m with the normal DB. From the triangle ACD it follows immediately that the angle between the two normals AO and DB is equal to Jj - CN and also equal to m ₁ + ■ nu.

This results in the condition for the clamping effect:

109886/1191

- ck,

Of course, the twisting of the ring actually acts as a slight deformation under the action of the torque of the forces F. and F2, which causes a displacement of the ball head with respect to the piston. However, this effect is negligible. The resistance to the bending of the ring, however, leads to the fact that the ring is pressed against the groove 3 by a return force which is placed in the direction of its equilibrium position in the free state when the ring in this equilibrium position has a mean diameter which is greater than its mean diameter in the working position. From Fig. 5 it can be seen that this return force T in the _{angular range defined above for F ^ and F 2 has} an effect which promotes the clamping effect. T is namely perpendicular to the piston axis and causes a pivoting of F. and F ", which approach the normals at the points of contact. This increases the clamping effect. It can be seen that this increase in the clamping effect is greater, the greater T is compared to F ^ and F ₂ . This gives the system additional security, because the more the sliding block moves away from the piston, the greater the return force T, and the more the clamping effect increases.

This property can obviously be used to increase the angle difference ρ - (A of the tangents at the point of contact and to facilitate the adjustment of the ring and the compensation of the play.

In this case, the clamping effect only occurs to the extent that the force separating the sliding shoe from the piston is below it

109886/1191

a predetermined value dependent on the return force T remains.

A significant advance of the device is to be seen in the fact that they are those left over from manufacture Compensates for dimension tolerances, in particular the play in the axial alignment of the groove 3 of the piston 1 opposite the center of the ball 10. FIG. 6 clearly shows how the play compensation takes place.

First, the equations of the triangle EFG are written, which are defined by two successive positions of the ring 4 with respect to the groove 3 and the ball 10 are defined.

If the machining error is denoted by ^ and is Δ the radial distance of the ring is:

= EG cosoC - EF cos β = EF sin β
= EG sin (K

and a simple conversion gives:

J- - 1 1

Δ "tg ~~ ÖC ~" tgß

When inserting numerical values, P = 30 °

and Ok = 20 °

This proves that the groove does not need to be machined with great accuracy in the device; the The radius of the circular surface forming the ring can vary by 0.1 mm without damage.

109886/1191

It follows that the production of the device does not involve great costs. The piston with his hemispherical bottom can be cold hammered. The groove 3 can be machined on a multi-spindle lathe, Cut the piston 1 to length and drill the connecting passage 13 between the two recesses. To a heat treatment that is supposed to increase the surface hardness and improve the friction conditions machining completed by grinding; the groove can also be produced by rolling or any other cold forming process as long as the required tolerances are observed.

The sliding shoe can also be manufactured at low cost. One can be made from a sintered or forged steel or bronze blank, the sliding part and the rear part Has hemisphere.

But you can also forge the ring if you give it a shape adapted to this technique.

For the preferred application to axial pumps, it can be seen from Fig. 1 that the radial force in this device at the head of the piston that is furthest back into the piston barrel is inside the barrel finds, whereby the excess of this radial force reaches its smallest value when the piston is furthest is extended, even with a large pane angle of the order of 20.

In the embodiment described so far, the Ring of partially circular disc-shaped cross-section cut inside by a cone. The same device

109886/1191

device can be carried out in the manner shown in Fig. 7 with a ring 4- any Hasisquer-

Section, cut from one of the ball 10 of the sliding shoe corresponding spherical surface and one of the

Seat 3 of the piston corresponding conical surface, or, a

In general terms, from two surfaces of rotation 11_, 13, approximately the tangents C .., C. «to the points of contact A1, B1, which between them enclose an angle (ρ. - (js.) which is at most equal to the half-angle sum at the tip is the cone of friction at these points of contact.

The advantage of a ring with a circular base cross-section, cut by one of the balls 10 of the sliding block corresponding spherical surface lies in the fact that the contact between the ring and the sliding shoe, which sicn Slidably into each other, there is a contact between two surfaces, through which considerable forces at lower Stress can be transferred and which is less sensitive to irregular surfaces.

One will therefore choose a shape for the ring that depends on the holding forces and the amounts of play required and the machining tolerances.

The holding device described can be used with essentially play-free mountings of two components that are connected to each other by a ball head and act on the forces that they seek to separate from each other.

The device is preferably used for holding connections used between sliding shoes and the pistons of hydraulic axial pumps and motors, but it can

109886/1191

also as a holder for the connecting rods of the pistons
Use in angle pumps or as a holder for connecting rods on the drive pulley of such pumps.

Patent claims :

109886/1191

Claims (3)

Claims Device for holding a ball head in a seat with a rotating surface, which has a hemispherical base cooperating with the surface of the ball head, with a holding member for the ball head in the form of a cut-open elastic ring, characterized in that the seat (3) has a surface (3a) in the form of a truncated cone, the large base surface of which merges into the hemispherical base surface (2), and that the holding member (H) adapts itself in its contact area to the spherical head surface in such a way that at least one imaginary conical tangent surface (C.) simultaneously on the holding organ (H) and on the ball head (10) in their contact area, the cross-section of the holding organ is such that the difference ( β - £ J the half apex angle of the imaginary conical surface (C ^), which is the largest possible half apex angle (ß) offers, and the truncated cone surface (3) of the seat is less than or equal to the sum (m. + m ") of the angles of friction at the points of contact (B, A) of the holding organ with said conical surfaces. 2. Apparatus according to claim 1, characterized in that the holding member (H) with at least one part Cl its surface is in contact with the surfaces of its seat and the ball head. 109886 / Π91 3. Device for holding a ball head, according to the
Claims 1 and 2, characterized in that it connects several components of a fluid pump or a fluid motor with one another, such as pistons, hydrostatic sliding blocks or connecting rods. The patent attorney 109886/1191