阅读说明：本技术 调节活塞和调移装置 (Adjusting piston and adjusting and moving device ) 是由 B·许恩 于 2020-09-29 设计创作，主要内容包括：公开了一种用于静液压的调移装置的调节活塞,所述调节活塞具有至少一个密封和引导单元,所述密封和引导单元能够装入到调节活塞的由两个区域构成的圆周凹部中并且引起调节活塞的引导和密封的改进。同样公开了一种调移装置,该调移装置构造有这样的调节活塞。(An adjusting piston for a hydrostatic displacement device is disclosed, which has at least one sealing and guiding unit that can be inserted into a circumferential recess of the adjusting piston, which is formed by two regions, and which results in an improvement in the guiding and sealing of the adjusting piston. An adjusting and displacing device is likewise disclosed, which is designed with such an adjusting piston.)

1. An adjusting piston for a hydrostatic displacement device (2), in particular for displacing the plunger volume of a hydrostatic plunger machine having a variable displacement volume, having an outer circumferential surface (4) which is surrounded by a sealing and guiding unit (6) in the region of a circumferential recess (8) which is designed, on the one hand, to guide the adjusting piston (1) in an axially displaceable manner in an adjusting cylinder (1 a) of the hydrostatic displacement device (2) in a tilt-stable manner and, on the other hand, to seal a gap (12) between the outer circumferential surface (4) of the adjusting piston (1) and an inner circumferential surface (24) of the adjusting cylinder (1 a), characterized in that the circumferential recess (8) has a first region (14) and a second region (16), wherein the second region (16) has a projection (18 a, a, 18b, 18 c) and the first region (14) has a guide region (20) for the sealing and guide unit (6) for taking up transverse forces, the guide region having a greater axial extent than the second region (16) provided with the projections (18 a, 18b, 18 c).

2. The adjusting piston as claimed in claim 1, characterized in that the guide region (20) has an axial extent which is a multiple of the axial extent of the projection (18 a, 18b, 18 c) in the second region (16) of the circumferential recess (8).

3. An adjusting piston according to any one of the preceding claims, characterised in that the sealing and guiding unit (6) is formed in one piece.

4. An adjusting piston according to any one of the preceding claims, characterised in that the projection (18 a, 18b, 18 c) has a decreasing diameter in the second region (16) as seen in the direction of the axial force caused by the adjusting pressure.

5. Adjusting piston according to one of the preceding claims, characterized in that the projections (18 a, 18b, 18 c) are pressed into the circumference of the sealing and guiding unit (6) and/or are sunk into a recess of the sealing and guiding unit in a back-fitting manner at least partially.

6. The adjusting piston according to one of the preceding claims, characterized in that the projections (18 a, 18b, 18 c) receive axial forces acting on the sealing and guiding unit (6) with end face sections (22) and are designed to seal a gap between the outer circumferential surface (4) of the adjusting piston (1) and the inner circumferential surface (24) of the adjusting cylinder (1 a).

7. Adjusting piston according to claim 5, characterized in that the force (F) in the transverse direction_Q) During the deformation of the sealing and guiding unit (6) and/or after wear, the pressing-in of the projections (18 a, 18b, 18 c) into the sealing and guiding unit (6) takes place in the region of the largest projection (18 c) with at least 40%, preferably at most 42%, but preferably at most 50%, preferably at most 55% of the initial thickness of the sealing and guiding unit (6).

8. An adjusting piston according to any one of the preceding claims, characterised in that the sealing and guiding unit (6) after mounting on the adjusting piston (1) has a sealing diameter which is at most 0.5% larger than the inner diameter of the adjusting cylinder (1 a).

9. An adjusting piston according to any one of the preceding claims, characterized in that in the end sections (26, 28) of the circumferential recess (8) the diameter is smaller than the diameter of the seat of the guide region (20).

10. The adjusting piston according to claim 9, characterized in that the sealing and guiding unit (6) forms a gap with the end sections (26, 28) of the circumferential recess (8) which is reduced due to the inherent stress of the sealing and guiding unit (6) at least partially sinking into the gap and thus forms a chamfer (30, 32).

11. Adjustment and displacement device with an adjustment piston (1) according to one of the preceding claims.

Technical Field

The invention relates to an adjusting piston for a hydrostatic adjusting and displacing device (Verstellerinrichtung) according to the preamble of claim 1 and to an adjusting and displacing device according to claim 11.

Background

From the prior art, adjusting pistons are known which are accommodated in a longitudinally displaceable manner in an adjusting cylinder and thus form a hydrostatic displacement device which is capable of generating a large adjusting force even with small dimensions of the displacement device. If the adjusting element, which can be pivoted by the adjusting piston, is eccentrically articulated, the adjusting piston is subjected to both axial forces and radial or transverse forces acting transversely thereto in its guidance in the adjusting cylinder. Accordingly, the adjusting piston must be guided in its cylinder in a reliable, stable manner in terms of inclination. At the same time, the task is to reliably seal the regulating pressure chamber defined by the regulating piston in the regulating cylinder.

For piston machines with displaceable piston volumes, multi-part solutions for sealing and guiding devices are known from the prior art, which meet the above-mentioned requirements. Thus, for example, the Bosch-Rexroth data page RDE 92003-84-P/03.2016 describes an axial piston pump in the form of a swash plate construction with a displaceable piston volume and displacement device, in which a double-acting actuating piston is arranged in an actuating cylinder. The sealing of the adjusting piston and its guiding in the adjusting cylinder are functionally separated by a single element which is accommodated in the inner circumferential surface of the cylinder and is in sealing guiding contact with the outer circumferential surface of the piston. The sealing element is "pressure-effective" in this case, i.e. a lip which can be deformed radially inward is pressed against the outer circumferential surface of the control piston by the control pressure prevailing in the control pressure chamber. The guide element has a relatively large axial extension, so that the piston is given a tilting stability. Alternatively, the sealing and guiding device can also be arranged on the piston side or on the rod side. The individual elements are arranged here by fitting in suitable grooves which axially hold the elements. A disadvantage of this solution is that up to three components are to be assembled for each sealing and guiding device, which means high material and assembly expenditure. Furthermore, there may be assembly errors due to the number of parts. In the case of sintered elements, in particular those with polytetrafluoroethylene parts, calibration is also required after assembly.

DE 102017211750 a1 discloses a control piston for a hydrostatic displacement device of the type mentioned. The adjusting piston has an outer circumferential surface which is surrounded by a sealing and guiding device designed as a sealing collar, by means of which the adjusting piston is guided in an adjusting cylinder in a tilt-stable and axially displaceable manner and can seal a gap between the adjusting piston and the adjusting cylinder. The sealing and guiding unit is held on the adjusting piston and is of one-piece construction and therefore has a dual function, i.e. it guides the adjusting piston in the adjusting cylinder and seals it against the adjusting cylinder.

The production of the above-described sealing collar is described in DE 102017219361 a 1. Accordingly, the sealing collar forming the sealing and guiding unit is first present as an annular disk and then widened by means of a widening device, the annular disk being folded into a conical shape. Subsequently, the inner diameter of the sealing collar is widened in a further widening stage until the desired inner diameter is reached and the annular disk is reshaped into a conical or sleeve shape. The sealing collar is then mounted on the adjusting piston by means of a compression device, wherein the sealing collar is placed at its nominal diameter.

A disadvantage of the adjusting piston described above is that the lateral forces on the adjusting piston are limited and the friction between the adjusting piston and the adjusting cylinder increases.

Disclosure of Invention

In contrast, the object of the present invention is to provide an adjusting piston (in which the introduction of transverse forces is improved) and an adjusting device having such an adjusting piston.

This object is achieved by an adjusting piston having the features of claim 1 or by an adjusting and displacing device having the features of claim 11.

Advantageous developments of the invention are described in the respective dependent claims.

The adjusting piston according to the invention for a hydrostatic displacement device, in particular for displacing the plunger volume of a hydrostatic piston machine with a variable displacement volume, has an outer circumferential surface which is surrounded by a sealing and guiding unit. The sealing and guiding unit is arranged in the region of a circumferential recess of the outer circumferential surface of the adjusting piston. By means of the sealing and guiding unit, the adjusting piston can be guided in a tilt-stable manner and in an axially displaceable manner in the adjusting cylinder of the hydrostatic displacement device. The sealing and guiding unit is designed to seal a gap between an outer circumferential surface of the adjusting piston and an inner circumferential surface of the adjusting cylinder. According to the invention, the circumferential recess of the adjusting piston is divided into two regions, wherein a first region for receiving transverse forces and a second region for receiving axial forces are formed.

In contrast to the cited prior art, the base of the circumferential recess is designed in such a way that a projection is formed in the second region, while the first region is designed in such a way that it is optimized with regard to the transverse forces. Furthermore, by dividing into two regions, a particularly low-friction sealing and guiding is achieved. It is particularly advantageous that the hysteresis is significantly improved compared to the prior art.

The maximum diameter of the adjusting piston with the sealing/guiding portion is reduced compared to the prior art. The diameter of the high circumferential recess of the second region is smaller and therefore the compression tool can be smaller. After the sealing and guiding elements and the relaxation of the sealing and guiding material have been calibrated, a smaller sealing diameter results compared to the prior art, which results in significantly less friction and therefore less hysteresis.

The first region of the circumferential recess is preferably arranged on the side of the base of the circumferential recess facing away from the pressure chamber and is formed by a relatively wide guide region for receiving transverse forces, which is radially raised with respect to the base of the circumferential recess. The guide region can be used to introduce transverse forces from the adjusting piston into the housing bore via a large surface. As a result, the surface load in the guide region is significantly reduced compared to the solutions known from the prior art.

By means of the relatively wide guide region in the first region, the radial deformation of the sealing and guiding unit under load and the wear during operation are significantly reduced compared to the solutions known from the prior art.

Preferably, the radial dimension in the first region is such that a central gap of 0.01% to 0.25% of the diameter of the adjusting piston is formed after the sealing and guiding means have been installed.

The second region is preferably arranged on a side of the circumferential recess facing the pressure chamber.

In a further development of the invention, the axial extent of the guide region in the first region is a multiple of the axial extent of the projection in the second region.

It has proven to be particularly advantageous if the sealing and guide unit is formed in one piece.

Advantageously, the projection is stepped in the second region. In other words, the first projection closest to the first region, viewed in the radial direction of the control piston, is configured to be significantly smaller than the last projection closest to the end of the circumferential recess on the pressure chamber side.

Starting from the separating region between the first region and the second region, the diameter of the projection preferably increases towards the end of the circumferential recess on the pressure chamber side.

Preferably, the sealing and guiding unit is at least partially in direct engagement with the area of the circumferential recess. The sealing and guiding unit positively engages with at least one of the projections of the second region, in particular with all projections, and particularly preferably not with the guiding region in the first region. The projection thus partially engages behind a circumferential surface of the sealing and guiding unit, which faces the outer circumferential surface of the adjusting piston, in such a way that it is pressed into the sealing and guiding unit and/or engages into a recess of the sealing and guiding unit, which is arranged opposite the projection.

In one refinement, the projection is designed in such a way that it receives axial forces acting on the sealing and guiding unit and ensures a seal between the control piston and the control cylinder. The raised end surface section engages with the sealing and guiding unit and thus takes up forces, in particular axial forces, acting on the sealing and guiding unit and guides them out into the control piston.

In this case, it is particularly preferred that the projection penetrates into the sealing and guiding unit in the reassembled state at least over 40%, preferably up to 42%, of the initial thickness of the sealing and guiding unit, with the greatest radial extent (also referred to below as maximum projection) as seen from the adjusting piston.

By means of this shaping of the second region, which is subjected primarily to axial forces, in combination with the aforementioned design of the first region, which is subjected primarily to transverse forces, a gap in the sealing region between the adjusting piston and the adjusting cylinder, which gap may lead to leakages, is avoided in cooperation with the sealing and guiding unit. By reducing the deformation under load, for example due to acting transverse forces, and by reducing wear, the maximum projection on the side facing the pressure is also prevented from penetrating into the sealing and guiding unit beyond 55% of its material thickness and thus being structurally damaged.

In one refinement, the spring back of the sealing and guiding unit is designed, depending on the material, such that a low-friction sealing diameter is formed after the sealing and guiding unit has been installed (this is also referred to as calibration). It is decisive for the low friction between the adjusting piston and the adjusting cylinder that the maximum diameter of the adjusting piston, in combination with the sealing and guiding unit, is only minimally larger than the bore diameter of the adjusting cylinder. Therefore, sufficient sealability is obtained with reduced friction. The sealing diameter is, for example, at most 0.5% larger than the bore diameter of the adjusting cylinder. The sealing and guiding means are designed such that the sealing and guiding diameters are produced by calibration at room temperature.

A calibration sleeve may be used to mount the sealing and guiding unit to the adjustment piston. The diameter is at least 0.3% smaller than the bore diameter of the adjustment cylinder. In order to be able to calibrate the sealing and guiding unit at room temperature in a material-protecting manner, the guide diameter is formed primarily by the size of the diameter of the outer circumferential recess in the first region and the material thickness or wall thickness of the sealing and guiding unit, and not by the seal at the time of calibration. That is, the pilot diameter is located in the first region and is smaller than the sealing diameter in the second region.

It is particularly preferred if the diameter of the adjusting piston in the end sections of the first and second region of the circumferential recess, respectively, is smaller than in the guide region of the first region. Between the sealing and guiding unit and the bottom of the circumferential recess, a chamber is thus formed, which extends between the sealing and guiding unit and the adjusting piston. The inherent stresses in the material of the sealing and guiding unit draw it into the chamber formed in this way and form a chamfer on the end of the sealing and guiding unit, i.e. on the end section facing and facing away from the pressure chamber, respectively, which leads to the formation of a lubricating wedge during the movement of the adjusting piston, which further reduces the friction between the adjusting piston and the adjusting cylinder.

Drawings

The invention is explained in more detail below with the aid of an exemplary embodiment of an adjusting device with an adjusting piston. In which is shown:

FIG. 1 shows a cross-sectional view of an adjustment device;

FIG. 2 shows a detailed view of the displacement device, an

Figure 3 shows a detail of the projection.

Detailed Description

Fig. 1 shows an adjusting cylinder 1a of an adjusting piston 1 with a partially illustrated hydrostatic adjusting device 2. The control piston 1 has two circumferential outer circumferential surfaces 4, each of which has a sealing and guiding unit 6 in the shoulder region of the control piston 1, which sealing and guiding units are arranged on or in a corresponding circumferential recess 8 of the control piston 1. The sealing and guiding unit 6 is designed as a sealing collar and is preferably produced from an annular disk according to the method disclosed in the initially mentioned DE 102017219361 a 1. The sealing and guiding unit is preferably made of a fluoroplastic, in particular PTFE. This material has good sliding and sealing properties. For further details regarding the manufacturing process reference is made to the above mentioned documents.

The adjusting piston 1 is guided so as to be displaceable along a longitudinal axis 19 in the main section 3 of a double-acting adjusting cylinder 1a, which is formed integrally with or can be attached to the housing of the plunger machine to be moved. The end-side closing of the adjusting cylinder 1a is formed by a cover 10.

On the side of the adjusting piston 1 (shown on the right in fig. 1), a spring pack 5 is arranged in a spring chamber of the adjusting piston 1 which is in pressure medium connection with a first pressure chamber 11 of the adjusting cylinder 1 a. For adjusting the pivot angle, the pressure chamber 11 can be acted upon with an adjusting pressure. The pin 7 fixed to the housing is guided along the longitudinal axis 19 through the bottom of the cover 10 of the adjusting cylinder 1a and is fixed thereto. The sleeve-like section of the cover 10 extends in the axial direction into the main section 3, so that the adjusting piston 1 is partially immersed in the cover 10 and one of the two sealing and guiding units 6 guides the adjusting piston 1 along the inner circumferential surface of the sleeve-like section of the cover 10.

The pressure chamber 11, through which the pin 7 passes, is partially delimited by the cover 10 and, as described above, is in pressure medium connection with the spring chamber of the control piston 1, in which the spring pack 5 is accommodated, and is sealed off from the pressure-relieved region. The sealing and guiding unit 6 (on the right in fig. 1) is arranged in the gap between the adjusting piston 1 and the cover 10. As already mentioned, a sealing and guiding unit 6 assigned to the second pressure chamber 21 is provided on the side of the adjusting piston 1 (on the left in fig. 1) remote from the pressure chamber 11, which sealing and guiding unit has the same construction as the above-mentioned sealing collar.

In the case of the defined spring package 5, a support disk 13 and a support disk 15 are movably arranged on the pin 7 in the pressure chamber 11. When the pressure chamber 11 is loaded with a control pressure, the control piston 1 is acted upon by an axial force F_A(to the left according to the illustration in fig. 1). During this movement, the support disk 13 remains fixed in position, while the support disk 15 is moved by the adjusting piston 1 against the spring force of the spring pack 5.

When the second pressure chamber 21 is charged with a pressure for setting, the setting piston 1 overcomes F shown in fig. 1 by an axial force_AMoving to the right. The support disk 13 is thereby moved by the adjusting piston 1 against the spring force of the spring pack 5 and the support disk 15 is held stationary on the pin 7, which is also referred to as an adjusting lever. Thus, the plunger unit can be adjusted equally in both directions.

As mentioned at the outset in the state of the art according to DE 102017211750 a1, the adjusting pin 9 of the plunger machine to be adjusted engages with a slide which engages on one side in a circumferential groove of the adjusting piston 1. By means of the setting pressure application, the displacement pin 9 is displaced by the setting piston 1, which causes a displacement of the piston volume of the connected hydrostatic piston machine, not shown here.

The spring force of the spring pack 5 is opposite to the axial force acting during displacement, such as the axial forceForce F_AActs and, when no actuating pressure is applied, returns the actuating piston 1 into its intermediate position (shown in fig. 1).

By shifting the position of the pin 9 eccentrically on one side, a transverse force F occurs on the control piston 1_Q. The two sealing and guiding units 6 contribute to the stable guidance of the adjusting piston 1 in the region of the main section 3 and in the region of the cover 10.

The two sealing and guiding units 6, each designed as a sealing collar, have a small wall thickness and are accommodated in a collar-like or sleeve-like manner in a circumferential recess 8 of the outer circumferential surface 4 of the adjusting piston 1, which circumferential recess is adapted thereto. The sealing and guiding unit 6, its position, function and positioning are described in detail with the aid of fig. 2.

Fig. 2 shows a detail a defined according to fig. 1, wherein a part of the surrounding (on the right in fig. 1) sealing and guiding unit 6 can be seen. The cover 10 and the main section 3 of the control cylinder 1a form an inner circumferential surface 24 which surrounds the outer circumferential surface 4 of the control piston 1. A gap 12 is formed between the two circumferential surfaces 4, 24. According to fig. 2, the gap is shown too large for the sake of clarity. In this position, not only the outer side of the control piston 1, which delimits the gap 12, is referred to as the outer circumferential surface 4, but it also comprises a circumferential recess 8 in which the sealing and guiding unit 6 is arranged.

As already mentioned, the two sealing and guiding units 6 are each formed by widening and compressing an annular disk in the shape of a collar with a small wall thickness and are each arranged around/in a circumferential recess 8 of the control piston 1 (in fig. 1 only the circumferential recess adjacent to the pressure chamber 11 is provided with the reference numeral 8). Which are each designed in accordance with the associated sealing and guiding unit 6 in such a way that they have a first region 14 and a second region 16 spaced apart from one another in the axial direction. The second region 16 has circumferential projections 18a, 18b, 18c spaced apart from one another in the axial direction, which are referred to below as projections 18a, 18b, 18c and extend in the radial direction starting from the base 34 of the circumferential recess 8. The number of projections 18a, 18b, 18c is not limited to the three projections 18a, 18b, 18c shown here. Not only fewer, but also a greater number of projections can be considered.

The sealing and guiding unit 6 can have circumferential recesses corresponding to the projections 18a, 18b, 18c, which can locally accommodate the projections 18a, 18b, 18 c. Preferably, the circumferential surfaces of the two sealing and guiding units 6 (sealing collars) are designed in a planar manner (smoothly) without recesses, wherein the projections 18a, 18b, 18c are pressed into the circumferential wall, so that the projections 18a, 18b, 18c are radially recessed into the sealing and guiding units 6. A mixed form with circumferential recesses in the sealing and guiding unit 6 which are smaller in their radial extent than the projections 18a, 18b, 18c is likewise conceivable, so that the described sinking and pressing-in operations are combined. Irrespective of the type of embodiment described above, the projections 18a, 18b, 18c engage the sealing and guiding unit 6 in an axially rear-fitting manner.

The projections 18a, 18b, 18c are under an axial force F caused by the regulating pressure in the pressure chamber 11_AIs of different size, wherein the first projection 18c, which is arranged furthest from the first region 14, is larger than the second projection 18b, which is larger than the smallest projection 18a, which is arranged closest to the first region 14. Thus, the projections 18a, 18b, 18c are arranged in a step-like manner, or in the axial direction, under a force F_A(see fig. 2) are arranged in a direction of decreasing. The sealing and guiding unit 6 is thus secured against displacement in the axial direction relative to the outer circumferential surface 4 of the adjusting piston 1 by the end surface sections 22 of the projections 18a, 18b, 18c (in the illustration only one end surface section of the largest projection 18c is provided with a reference numeral).

A detailed view of the circumferential recess 8 is shown in fig. 3. The first region 14 of each circumferential recess 8 of the adjusting piston 1 has a guide region 20 on which the sealing and guiding unit 6 rests. Unlike the projections 18a, 18b, 18c in the second region 16, there is no engagement or rear engagement between the guide region 20 and the sealing and guide unit 6. The transverse force F acting on the adjusting piston 1 via the sealing and guiding unit 6 is transmitted via the large-area guide region 20_QCan be compared with the prior artThe case of the solution of (a) is clearly better tolerated and distributed.

The guide region 20 has a radial extent d, also referred to below as height d, which is significantly smaller than the axial extent a, also referred to below as length a. In the region of the end section 26, a chamber 40 is formed which is delimited on the one hand by the end face 36 of the circumferential recess 8 and on the other hand by the guide region 20 and on the circumferential side by the base 34. In the other end section 28, a corresponding chamber 41 is formed, which is delimited on the one hand by the end face 38, on the other hand by the projection 18c, and on the circumferential side by the base 34. Both the projections 18a, 18b, 18c and the guide regions 20 extend in the radial direction from the base 34.

Radial extension D of the smallest projection 18a_aGreater than the radial extension d of the seat formed by the guide region 20 and greater than the axial extension b of the projections 18a, 18b, 18 c. Radial extension D_cSpecific radial extension D_bLarge and its specific radial extension D_aIs large. The end surface sections 22 formed on the projections 18a, 18b, 18c engage behind sections of the sealing and guiding unit 6, not shown here, in the axial direction. The end surface section 22 is subjected to an axial force F acting on the sealing and guiding unit 6_AAnd this axial force is introduced via the projections 18a, 18b, 18c into the circumferential recess 8 and thus into the regulating piston 1.

The chambers 40, 41 form radial gaps in conjunction with the associated sealing and guide unit 6. Chambers are also formed between the guide region 20 and the projections 18a, 18b, 18c and between the projections 18a, 18b, 18 c. The sealing and guiding unit 6 accordingly does not rest against the bottom 34 of the circumferential recess 8 according to fig. 2. The inherent stresses in the material of the sealing and guiding unit 6 pull the sealing and guiding unit 6 into the chambers 40, 41 formed in the region of the end sections 24, 26. The sealing and guiding unit 6 then forms in the region of the end sections 24, 26 a chamfer 30, 32, respectively, which supports the formation of the lubricating wedge during the movement of the control piston 1. Furthermore, by applying an axial force F caused by the adjusting pressure_ALoading the sealing and guiding unit 6, causing the sealing and guiding unit to be sealed and guidedRadial deformation of the element 6, which has the effect of improving the seal.

An adjusting piston for a hydrostatic displacement device is disclosed, which has at least one sealing and guiding unit that is inserted into a circumferential recess of the adjusting piston, which recess is formed by two regions, and which results in an improvement in the guiding and sealing of the adjusting piston. Furthermore, an adjusting and displacing device is disclosed, which is designed with such an adjusting piston.

List of reference numerals

1a adjusting cylinder

1 regulating piston

Hydrostatic displacement device

3 main section of adjusting cylinder

4 peripheral surface

5 spring group

6 sealing and guiding unit

7 pin

8 circumferential recess

9 adjusting pin

10 cover of adjusting cylinder

11 pressure chamber

12 gap

13 supporting disk

14 first region

15 supporting disk

16 second region

17 air vent

18 projection

19 longitudinal axis

20 guide area

21 another pressure chamber

22 end face section

24 inner peripheral surface

26 end section

28 end section

30 chamfer

32 chamfer

34 bottom part

36 end face

38 end face

40 chamber

41 chamber

F_A Axial force

F_Q Transverse force

a length/axial extension of the guide area 20

b length/axial extension of the projection

d height/radial extension of the guide area 20

D height/radial extension of the protrusions.