EP1328730A1

EP1328730A1 - Internal geared wheel pump without a filler piece

Info

Publication number: EP1328730A1
Application number: EP01978115A
Authority: EP
Inventors: Reinhard Pippes
Original assignee: Eckerle Industrie Elektronik GmbH
Current assignee: Eckerle Industrie Elektronik GmbH
Priority date: 2000-10-25
Filing date: 2001-09-07
Publication date: 2003-07-23
Anticipated expiration: 2021-09-07
Also published as: US20040091379A1; DE10052779A1; US6893239B2; WO2002035097A1; EP1328730B1; DE50104246D1

Abstract

The invention relates to an internal geared wheel pump without a filler piece, comprising a housing, an internal geared wheel (3) which rotates in said housing and an external geared pinion (2) which is rotationally mounted in the housing and which meshes with the geared wheel. The teeth of said pinion define a suction area and a pressure area in the gearing, by complete engagement with the tooth spaces of the geared wheel and by sealing contact with tooth crowns of said geared wheel in an engagement-free geared wheel area which lies approximately diametrically opposite the tooth space engagement. The toothing of the geared wheel and the pinion is an involute or cycloid toothing, the tooth crowns having a rounded peripheral surface (23, 34). The tooth crowns of the geared wheel (3) and/or the pinion (2) are asymmetrically rounded in relation to a centre line (40) of each tooth (22, 33), in such a way that a transition line (42) between the tooth face (24, 35) and the peripheral surface (41) is located on the rear tooth face (35) (in the direction of rotation) for the geared wheel and on the front tooth face (24) (in the direction of rotation) for the pinion, closer to the tooth base than on the opposite tooth face, respectively.

Description

Internal gear pump without filler

description

The invention relates to a filler-less internal gear pump with the features according to the preamble of claim 1.

Filling-free internal gear pumps or motors have a toothing of pinion and ring gear, the teeth of which are in sealing contact with one another both at the mutual engagement in tooth gaps and, approximately diametrically opposite, on the opposing tooth heads, in order to thereby delimit a suction area from a pressure area , Since it is not possible in practice due to unavoidable manufacturing tolerances and due to the elastic deformations that occur in particular at higher pressures to achieve the mentioned sealing contact, in particular in the area of the toothing in which the tooth heads are to be in contact with one another, measures must be taken to ensure this Ensure tight contact in all operating conditions.

For this purpose, it is provided in a known internal gear pump of the type mentioned at the outset that the ring gear is received with radial play in a race and rotates together with it. The circumferential surface of the ring gear has axial grooves in which sealing elements are accommodated in a radially movable manner. As a result, the annular gap between the race and the circumferential surface of the ring gear is divided into circumferential sections which can be sealed off from one another and which, in the pressure region, are connected to a groove acted upon by hydraulic fluid comes. As a result, a pressure build-up is provided in the annular gap in one or more circumferential sections, which presses the ring gear into engagement with the toothing of the pinion and thus holds the tooth heads against one another for sealing engagement (DE 44 21 255 C1).

In a further known internal gear machine, which also belongs to the type mentioned at the outset, the sealing contact of the tooth heads of the pinion and ring gear with respect to the engagement area is ensured in that the ring gear rotates in a bearing ring which is movable transversely to its axis but is non-rotatably accommodated in the housing is arranged. The bearing ring is pivotable relative to the housing about a pivot axis parallel to its axis. The swivel axis is such that the ring section of the bearing ring assigned to the non-meshing ring gear area is moved at least approximately radially towards the pinion axis by the pressure forces acting on the ring gear in the pressure chamber, as a result of which the tooth heads are held in mutual sealing contact in the non-meshing ring gear area (DE 196 51 683 A1 ).

Practical versions of these known internal gear pumps each have an involute toothing for the ring gear and pinion, in which the tooth flanks are designed as involute curves and the tooth heads have a circumferential surface that deviates from the involute shape, usually a circular cylinder surface. With this type of toothing, the teeth of the pinion and ring gear come out of contact in areas in the suction chamber, ie between full tooth engagement and the non-meshing ring gear area and only approach each other again shortly before the non-meshing area in which the tooth heads are to lie tightly against one another. Here, abrupt contact of the tooth edges in the transition area between the tooth flank and the peripheral surface of the teeth can occur, by which the sealing effect of the abutting peripheral surfaces of the tooth heads is impaired and considerable running noises can occur. In order to overcome these disadvantages, the tooth heads of these known internal gear pumps are rounded, ie the tooth edges are withdrawn at the transition between the tooth flank and the peripheral surface. On sweeping success to improve the sealing effect, especially at high pressures, has not yet been achieved.

The object of the invention is to provide an internal gear pump of the type mentioned, in which the sealing effect between the tooth heads is improved and the noise level is reduced.

According to the invention, this object is achieved by designing the generic internal gear pump in accordance with the characterizing part of patent claim 1.

Due to the fact that the tooth heads of either the pinion or the ring gear or both gear wheels have an asymmetrically reduced circumferential surface, the tooth heads can initially meet one another in the non-contacting ring gear region without any bumps. In the further course of the mutual contact, the tooth tip circumferential surfaces come into contact via the part thereof less drawn back due to the asymmetry. This ensures that the tooth tips are properly sealed to one another. The take-back surface attaches to the tooth flanks of the ring gear and pinion lying opposite each other when approaching and immediately before the meeting, and thus results in a smooth run-up of the tooth heads on one another. According to an advantageous development, the part of the asymmetrical circumferential surface that is closer to the tooth base extends from the transition to the tooth flank to the tooth center line or even into the region of the circumferential surface of the tooth head that lies beyond the tooth center line with respect to the transition mentioned. This means that approximately half of the original circumferential or rounded surface, not corrected according to the invention, is retained for the purpose of sealing.

Naturally, the extent of tooth tooth relief depends on the model size. It is therefore expedient, measured from the transition between the uncorrected circumferential or rounded surface and the tooth flank, to be 0.02-0.1 times the gear module m. Further advantages and features of the invention result from the following description of exemplary embodiments with reference to the accompanying drawings. The drawings show:

1 shows a cross section along the line l-l in Fig. 2.

Figure 2 is an axial section along the line II-II in Fig. 1.

3 shows a section analogous to FIG. 1 of a modified embodiment, and

FIG. 4 shows a representation of the ring gear region without engagement in both of the above embodiments on a greatly enlarged scale to illustrate the tooth tip withdrawal according to the invention.

The internal gear pump shown in FIGS. 1 and 2 comprises a housing, designated as a whole by 1, which is constructed from a pot-shaped housing part 11 and a housing cover 12 fastened to its end face. In the cup-shaped housing part 11, a pinion shaft 14 is rotatably mounted, on which a pinion 2 is fixed in a rotationally fixed manner. The pinion 2 meshes with a ring gear 3 which is received in a bearing ring 4 and is rotatably supported therein. The pinion 2 and the ring gear 3 are, as shown in FIG. 1, mounted relative to each other with an eccentricity e. The eccentricity e, ie the distance between the pinion axis and the ring gear axis, corresponds to the theoretical tooth geometry of the pinion and ring gear and presupposes that the toothings roll and slide against one another without play. The teeth of the pinion 2 and the ring gear 3 mesh with one another in such a way that on the left side in FIG. 1 in the region of the dividing line A, the teeth of the pinion 2 fully engage in the tooth gaps of the ring gear 3 and rest against the tooth flanks while they are on the opposite, in Fig. 1 right side have completely emerged from the tooth gaps of the ring gear 3. In this engagement-free ring gear region E, several of the tooth heads of the pinion 2 and the ring gear 3 (in the shown one) are supported Embodiment 3 tooth heads each) one after the other in the course of the rotation. The number of teeth and the geometry of the intermeshing teeth are chosen so that this type of meshing can be effected. In the exemplary embodiment shown, the ring gear 3 and pinion 2 each have involute teeth, ie the tooth flanks have an involute contour. The number of teeth of the ring gear 3 differs from that of the pinion 2 by 1.

When the pinion 2 rotates in the direction indicated by the arrow, the tooth space which becomes free increases, starting from the full engagement of the pinion toothing in the ring gear toothing above the dividing line A, until the state shown in FIG. 1 is reached when the dividing line is exceeded again A (on the right in Fig. 1). As a result, the suction space S of the internal gear pump is formed over the dividing line. Under the dividing line, the free space between the teeth gradually decreases again, so that the pressure space D is thereby formed. In Fig. 1 the suction space S and the pressure space D are indicated in their projection; however, it goes without saying that the suction space S and the pressure space D each extend in the circumferential direction within the toothing.

The bearing ring 4 is received in a housing bore 15 of the cup-shaped housing part 11 with a radial play of approximately 0.2 mm. The wall of the housing bore 15 is partially penetrated by a bearing pin 16 which is pressed firmly into the bottom of the housing bore 15. With the largely semi-cylindrical part of the bearing pin 16 protruding beyond the wall of the housing bore 15, it is received in an axially directed groove 17 of the bearing ring 4. The axial groove 17 is adapted to the shape of the bearing pin 16 and is also partially cylindrical.

The bearing pin 16 engaging in the axial groove 17 forms for the bearing ring 4 a pivot axis running parallel to the axes of the pinion 2 and the ring gear 3, about which the bearing ring 4 can be pivoted in the housing bore 15 within the scope of the radial play available. As is apparent from Fig. 1, this is Pivot axis in a quadrant of the bearing ring 4, which extends between the non-meshing ring gear region E and the center of the pressure chamber D. In the exemplary embodiment shown, the pivot axis is at an angular distance of approximately 80 ° from the apex of the non-meshing ring gear region E. At this apex, two teeth of pinion and ring gear are largely aligned with one another with their tooth heads.

The operation of the internal gear pump according to FIGS. 1 and 2 is as follows:

When the pinion 2 rotates in the direction of rotation shown, the conveyed medium is conveyed through a suction channel (not shown) into the suction space S between the teeth of the pinion 2 and the ring gear 3. The pumped medium is pressed out of the pressure chamber D with increased pressure through a pressure channel, not shown. The relevant structure of an internal gear pump is well known and therefore does not require a separate explanation here.

The pressure forces prevailing in the pressure space D between the intermeshing toothings act along a resultant R such that the ring gear 3 tries to move away from the pinion 2, i.e. there is a tendency that the contact between the teeth of pinion 2 due to the tooth geometry is present and ring gear 3, in particular the sealing contact between the tooth heads in the non-engaging ring gear region E, is lost. However, the pivot axis of the bearing ring 4 formed by the bearing pin 16 or its engagement in the axial groove 17 is closer to the engagement-free ring gear region E than the line of the resultant R. Since the resultant R acts on the bearing ring 4 via the ring gear 3, a torque is thus generated about the pivot axis 16, 17 in Fig. 1 counterclockwise. As a result of this torque, the bearing ring 4 is pivoted about the pivot axis 16, 17, as a result of which the ring section corresponding to the non-meshing ring gear region E is moved approximately radially with respect to the pinion axis and towards it. Consequently, the tooth heads of pinion 2 and ring gear 3 are moved against one another in the non-meshing ring gear region E with a force proportional to the size of the resultant R. As a result, the sealing contact in this tooth area is maintained in proportion to the pressure. The bearing ring 4 has a further axial groove 18 with a rectangular cross section on its outer circumference at a point which is assigned to the apex of the non-meshing ring gear region E. This axial groove 18 is assigned a receiving bore 19 in the bottom of the housing bore 15, in which a hairpin spring 20 is held. The hairpin spring 20 protrudes into the axial groove 18 and loads the bearing ring 4 radially such that the teeth of the ring gear 3 are pressed against one another with their tooth tips in the non-meshing ring gear region E. This direction of loading largely corresponds to the direction of movement which the bearing ring 4 executes as a result of the pivoting movement about the pivot axis 16, 17. The force of the hairpin spring 20 can be kept relatively low, since it only serves to ensure the necessary sealing contact between the tooth heads in the non-engaging ring gear region E during the starting process of the internal gear pump, ie at a time when no operating pressure has yet been built up in the pressure chamber D. and therefore no compressive forces act.

The position and direction of the resultant R can largely be predetermined and essentially corresponds to that shown in FIG. 1. The pressure build-up in the pressure chamber D can be influenced in a known manner by prefilling slots on the teeth of pinion 2 and / or ring gear 3, so that, for. B. across the tooth gaps of the pressure chamber D there is a largely equal pressure. In this case, the resultant R is perpendicular to the line shown in solid lines in FIG. 1, which connects the apex of the non-meshing ring gear region E with the pinion tooth with full engagement in a tooth gap of the ring gear.

The embodiment according to FIG. 3 differs from that according to FIGS. 1, 2 essentially in that the ring gear 3 'is widened in a known manner on its outer circumference in the axial direction to form a race 3 "by the specific bearing pressure in the bearing ring 4 '. In addition, there is no pressure spring 20. With regard to the axially widened running surface of the ring gear 3', which protrudes on both sides over the side surfaces of the ring gear and pinion and whose cross section is shown in FIG. 3, but for the present invention has no meaning, reference is made to DE 198 15 421 A1. The mode of operation of this embodiment corresponds to that of the embodiment according to FIGS. 1, 2.

In FIG. 4, the engagement-free ring gear region E of the two above embodiments is shown enlarged as a detail. The toothings are shown with the uncorrected tooth shape and - for the ring gear - with the tooth shape corrected according to the invention. The teeth 22 and 33 of pinion 2 or ring gear 3 are in a relative position in which they have moved so far towards one another in the direction of rotation indicated by the arrow that their outer circumferential surfaces 23 and 34 are at least partially opposite one another and against one another issue. The circumferential surfaces 23, 34 can be uncorrected partial cylinder surfaces with the tip circle diameter of the respective toothing or with a smaller diameter (see THE TOOTH FORMS OF THE GEARS H. Trier, Springer-Verlag 1954) and form a transition line 25 or 35 with the respective involute flank 24 or 35. 36, which in practice is always rounded to a transition area. This applies to uncorrected

Tooth tip for the front and rear tooth flanks of teeth 22 and 33.

4, the teeth 33 of the ring gear 3 are corrected according to the invention. That is, with respect to a tooth center line 40, which here also represents a tooth axis of symmetry or plane of symmetry, the teeth 33 are asymmetrically withdrawn in the head region. Thus, a withdrawal surface 41 ^'starting from the uncorrected circumferential surface 34 created, the transition line 42 to the involute wrap 35 on the tooth root 44 is closer than the transition 36 of the same tooth on the opposite side. To clarify the withdrawal, the extent of the removed amount of material, starting from the uncorrected contour of the toothing, is shown exaggerated and hatched in FIG. 4. In general, a withdrawal amount a between 0.02 m and 0.1 m (m = gear module measured in mm) can be used. It can be seen from the illustration that the take-back surface 41 can extend as far as a transition line 45 into the region of the original circumferential surface 34, which Tooth flank 35 is already beyond the center line 40. The withdrawal surface can also extend all the way to the opposite tooth flank, whereby the transition line 45 can coincide with the transition line 36 or even lie in the subsequent tooth flank, or can also be shorter than shown, for example in such a way that approximately half of the before the correction circumferential surface 34 available for the seal is retained. In the former case, care must be taken to ensure that the deviation of the withdrawal surface 41 from the uncorrected circumferential surface 34 in the section located beyond the center line 40 is small in order not to impair the sealing contact.

The take-back surface 41 has a smooth, continuous course in the exemplary embodiment shown and can be a cylindrical, in particular circular-cylindrical surface in all cases. The radius of this surface can in principle be selected within wide limits, which are determined only by the size of the toothing and thereby which extension of the withdrawal surface 41 to the opposite tooth flank is desired. It goes without saying that intersections occurring (transition lines 42, 45) are rounded or smoothed in order to avoid any edges.

In a corresponding manner, the teeth 22 of the pinion 2 can alternatively or additionally be corrected. In this case, however, the transition line corresponding to the transition line 42 from the withdrawal surface to the involute flank 24 lies on the involute flanks shown on the right in FIG. 4.

Due to the described correction of the teeth 33, when the teeth 22 and 33 converge, the circumferential surfaces 23, more precisely their transition edges 25, run smoothly and smoothly onto the withdrawal surfaces 41 and ultimately on the remaining part of the circumferential surface 34 which ensures the sealing of the tooth heads can be pressed as described above. In general, however, the retraction of the tooth tips and their function according to the invention is independent of the type of pressing of the tooth tips against one another. The tooth heads can be withdrawn during production by subsequent grinding after the generation of the uncorrected toothing or a DIN toothing, or during the generation of the toothing by means of a corresponding tool profile.

Within the scope of the invention, it is possible to deviate from the above exemplary embodiments. Thus, instead of the involute toothing, a cycloid toothing can be provided on the gear wheels. Furthermore, the internal gear pump, in particular at higher operating pressures, can be equipped in a known manner with axial pressure plates.

Claims

claims

1. Filling-free internal gear pump with a housing (1), an internal toothed ring gear (3) rotating in the housing and one in the

Housing rotatably mounted, with the ring gear meshing external toothed pinion (2), the teeth of which by a full engagement in tooth gaps of the ring gear, on the one hand, and a sealing contact with the tooth tips of the ring gear in an engagement-free ring gear region (E) approximately diametrically opposite the tooth gap engagement, on the other hand, Define a suction space (S) and a pressure space (D) of the toothing, the toothing of the ring gear and pinion being an involute or cycloid toothing and the tooth heads having a rounded circumferential surface, so that the rounded circumferential surface ( 41, 34) of the tooth heads of the ring gear (3, 3 ') and / or pinion (2) is asymmetrical with respect to a center line (40) of each tooth (22, 33) such that the transition (42) between the tooth flank (24, 35) and the peripheral surface (41, 34) in the ring gear on the rear tooth flank (35) in the direction of rotation and in the pinion on the in

Direction of rotation of the front tooth flank (24) is closer to the tooth base than on the opposite tooth flank.

2. Internal gear pump according to claim 1, d ad u rch ge ken nzeich net that the peripheral surface is composed of a return surface (41) and an uncorrected peripheral surface (34).

3. Internal gear pump according to claim 2, characterized in that the transition (42) between the withdrawal surface (41) and the uncorrected peripheral surface (34) is in the vicinity of the tooth center line (40).

4. Internal gear pump according to one of claims 1 to 3, characterized in that the withdrawal surface (41) and the uncorrected peripheral surface (34) are each circular cylinder surfaces.

5. Internal gear pump according to claim 1, characterized in that the asymmetrically rounded peripheral surface (41) extends continuously between the tooth flanks of each tooth.

6. Internal gear pump according to claim 5, characterized in that the peripheral surface (41) is a circular cylinder surface

7. Internal gear pump according to one of claims 1 to 6, characterized in that the extent (a) of the withdrawal of the tooth tip (in mm), measured from the transition (36) between the uncorrected peripheral surface (34) and the tooth flank (35) , 0.02m-0, m is (m = gear module).