Patent Application
20250010423
The invention concerns a honing tool for machining a bore in a workpiece according to the preamble of claim 1. The invention furthermore concerns a method for producing a honing tool.
The final quality-decisive machining of tribologically loadable faces of bores, such as e.g. cylinder run faces cylinder in blocks (cylinder crankcases) or cylinder liners, is usually performed by means of a fine machining process known as honing. Honing is a material-removal process with geometrically indeterminate cuts, which is carried out by a widenable honing tool. The honing process works with bonded cutting grains under constant superficial contact between the abrasive working face of the honing tool and the bore surface. The cutting grains are bonded in a binding system (also known as a binder) and, together with the binder, form an abrasive cutting coating. The purpose of the binder is to hold the bonded cutting grains until they are blunted by the cutting process. They are then released so that new, still sharp-edged cutting grains can come into engagement with the workpiece (self-sharpening effect).
In a typical honing operation, the honing tool is moved to and fro in the axial direction of the bore within the bore to be machined, and at the same time rotated with a suitable rotation speed in order to generate a rotational movement superposed over the reciprocating movement. The cutting means arranged on the honing tool are pressed via the feed system against the inner surface to be machined with a contact force acting radially to the tool axis. During the resulting material removal, the effective outer diameter of the honing tool is gradually enlarged by the feed system. The advance is therefore often called “widening”, and the feed system is also known as the “widening system”. In honing, usually a cutting grain pattern with intersecting machining tracks known as “cross-hatching”, typical of honing work, is produced on the inner surface.
A honing tool of the type concerned by this application is a honing tool with double feed or double widening, i.e. a honing tool having two cutter groups which can be advanced independently of one another. In this way multistage machining processes can be carried out, sometimes without tool change.
DE 10 2019 201 465 A1 discloses honing tools with double feed, having two cutter groups on the tool body which can be advanced independently of one another. A first cutter group has multiple, radially advanceable, first cutting material carriers which on a radial outside cover a circumferential angular region of at least 20° and on the outside carry a single first cutting means which is wide in the circumferential direction, or multiple narrow first cutting means which are arranged spaced apart from one another. A second cutter group has multiple, radially advanceable, second cutting means carriers which on their radial outside each have a single narrow second cutting means in the form of a cutting strip. All cutting means of the first and second cutter groups are arranged in an axially short cutting region having a length measured in the axial direction which is substantially smaller than an effective outer diameter of the cutter groups with the cutting means fully retracted.
WO 2018/149696 A1 (cf. DE 10 2017 202 573 A1) discloses amongst others honing tools with double widening. In a first group, the cutting means are attached directly to the assigned cutting means carrier without interposition of an elastic intermediate layer, and rigidly connected to the cutting means carrier. In the second group, the cutting means are individually attached on the assigned cutting means carrier in a flexible fashion via an elastic intermediate layer.
It is an object of the invention to provide a honing tool which is suitable for different honing tasks or can be configured for different tasks with only little complexity. In particular, surfaces of the highest quality can be produced thereby.
To achieve this object, the invention provides a honing tool with the features of claim 1. A method for producing a honing tool is also provided with the features of claim 13. Advantageous refinements are given in the dependent claims. The wording of all claims is made part of the description by reference.
The honing tool is a honing tool with double feed or double widening, which means that two cutter groups which can be advanced independently of one another are arranged on the tool body. Each of the cutter groups comprises multiple cutting means carriers which together can be advanced radially by axial displacement of the assigned feed element or widening element. A feature is that the tool body has fourteen or more guide openings. The guide openings have an irregular angular division, such that one or more of the guide openings have different angular spacings from the two directly adjacent guide openings in the circumferential direction.
“Directly adjacent” means in particular that no guide strip is arranged between directly adjacent guide openings. Differences in angular spacings may e.g. be of the order of approximately 1° or more, e.g. in the range from 0.8° to 3°.
The claimed invention according to this wording has proved very advantageous in practice in multiple aspects in comparison with conventional honing tools with double widening.
Honing tools according to this wording of the invention differ from conventional honing tools with double feed partly by the large number of fourteen or more guide openings, in each of which a single cutting means carrier may be inserted, the relatively wide outside of which in its circumferential direction may be fitted with cutting means. Thus in comparison with the prior art, larger cutting strip areas are possible in the sense that larger parts of the circumference can be fitted with cutting means. Then there is the irregular angular division, which differs from conventional angular divisions. A classic angular division here is an angular division in which the guide openings are evenly distributed over the circumference of the tool body, so that for example twelve guide openings are provided each with an angular spacing of 30°, or eight guide openings each with an angular spacing of 45°, or six guide openings each with an angular spacing of 60°.
It has been found that because of the degree of asymmetry in conjunction with the large number of guide openings, honing tools of this type can be used extremely flexibly and advantageously for various applications, and can achieve very good results with respect to shape and surface quality. These include improved shape and roundness values which are attributable to the better support of the cutting strips in the workpiece. Also, more even surface characteristics can be achieved; this is partly attributable to the possibility of relatively large area proportions of cutting means and hence lower necessary specific contact pressures. Also, larger areas of cutting means over the circumference lead to comparatively long service times. Furthermore, the large number of guide openings in conjunction with the irregular angular division between the guide openings creates the possibility of configuring such honing tools extremely flexibly for different applications, in that the tool body can be fitted with correspondingly distributed and designed cutting means carriers. Thus different first and second cutter groups can be formed, the group members of which can be distributed suitably over the circumference with different degrees of symmetry or asymmetry. Finally, the asymmetry of angular division appears to reduce the tendency to generate vibrations during honing, which may have a positive effect on the achievable quality of shape and surface.
Preferably, the number of guide openings is an even number, i.e. a number divisible by two, wherein the guide openings lie in pairs diametrically opposite one another relative to the tool axis. If identical cutting means carriers having identically arranged cutting means, which belong to the same cutter group and hence are advanced together, are provided on the tool body at the pairs of diametrically opposed points, this achieves a stabilization of the tool position in the bore, which has an advantageous effect on the bore quality.
It has proved particularly advantageous if the number of guide openings is not divisible by four. For example, the tool body may have preferably precisely 14 (fourteen) guide openings or precisely 18 (eighteen) guide openings or precisely 22 (twenty-two) guide openings. These may be distributed over the circumference of the tool body such that there is a two-fold rotational symmetry around the tool axis, but no mirror symmetry relative to a plane containing the tool axis. Thus a certain degree of asymmetry is possible.
In the context of the claimed invention, honing tools are possible with different distributions of cutting means carriers between the first and second cutter groups. For the purpose of this application, the term “division” refers to the number of guide openings, such that “14-division” corresponds to a honing tool with 14 guide openings distributed over the circumference. However, the term “angular division” refers to the angular spacings between the guide openings measured in the circumferential direction. The angular spacings are each measured between the centers of adjacent guide openings in the circumferential direction. An irregular angular division then means that the different angular spacings between directly adjacent guide openings differ to an extent which clearly lies outside production tolerances, so that irregular angular spacings may for example mean an angular difference of at least 1°.
In preferred embodiments, the division of cutting means carriers between the first and second cutter groups is such that for a total number T of cutting means carriers, one cutter group carries a number T/2−1 of cutting means carriers and the other cutter group a number T/2+1 of cutting means carriers. In an exemplary embodiment with precisely fourteen guide openings, accordingly one cutter group has precisely six and the other cutter group precisely eight cutting means carriers. These may be distributed differently over the circumference of the tool body, wherein as a peripheral condition, it is ensured that identical cutting means carriers fitted with cutting means of the same cutter group are arranged at diametrically opposite guide openings.
In some embodiments, the honing tool has a guide group with multiple non-cutting guide strips which are distributed on the tool body with an irregular angular division over the circumference of the tool body.
Preferably, four non-cutting guide strips are arranged on the tool body in pairs diametrically opposite one another, such that tool body segments lying between directly adjacent guide strips in the circumferential direction have per pair different circumferential widths. Preferably, the division is such that in the tool body segments with the greater circumferential width, there is a number N, and in the tool body segments with smaller circumferential width, a number N-1 of guide openings arranged directly next to one another.
A particularly high degree of flexibility for different applications can be achieved according to a refinement if the guide openings and/or the cutting means carriers have an axial length which amounts to more than 50% of the maximum effective outer diameter of the honing tool. The axial length may amount to more than 80% of this outer diameter, and in some cases may be larger than this outer diameter. Thus a correspondingly axially longer cutting region can be created.
It is however nonetheless possible to configure the honing tool such that cutting means are active only in an axially significantly shorter region. This is partly achieved in that the carrier portions can be fitted with cutting strips of different lengths. In order to achieve a great flexibility with respect to the distribution of cutting means over the circumference of the honing tool, in preferred embodiments it is provided that the carrier portions on the outsides have multiple, preferably two, three or four mutually parallel receiving grooves, each for receiving at least one strip-like cutting means unit (cutting strip). Such a cutting means unit may for example comprise a narrow, plate-like metal substrate on which, directly or with the interposition of an adhesive layer or similar, the actual cutting means layer is applied (cutting grains in corresponding binding). Depending on the design of cutting means carrier, cutting means of different widths may be fitted. It is also possible to provide a single, relatively long, individual strip. The receiving grooves need not be fitted with cutting means units which substantially fill the entire length of the receiving groove. It is also possible to provide, in a long receiving groove, a significantly shorter strip-like cutting means unit, for example with a length which corresponds to less than 50% of the axial length of the carrier portion. Such honing tools may thus also be configured such that all cutting means are arranged in an axially relatively short cutting region, the axial length of which may be smaller than the effective outer diameter of the honing tool.
Such honing tools may e.g. be advantageous when it is necessary to machine and/or generate bottle-shaped, conical or barrel-shaped bores.
The invention furthermore concerns a method for producing a honing tool for machining an inner face of a bore in a workpiece. In the method, a tool body which is designed according to the claimed invention is fitted with a plurality of cutting means carriers of the described type and assigned feed elements. By fitting the tool body with cutting means carriers and feed elements, different configurations of the honing tool can be produced which can be well adapted to the respective machining task.
Further advantages and aspects of the invention arise from the claims and the description of exemplary embodiments of the invention which are presented below with reference to the figures.
The honing tool is suitable and intended for machining an inner face of a bore in a workpiece by means of honing, and in the example is configured for honing cylinder run faces in the production of cylinder blocks or cylinder liners for reciprocating piston engines.
The honing tool is versatile in use and can be prepared or configured for widely varying machining tasks with few manual interventions. The honing tool may e.g. be used in different configurations for machining circular cylindrical bores, i.e. rotationally symmetrical bores without axial contour development. In other configurations, it may be used for machining rotationally symmetrical bores which have bore portions of different diameter and/or different shape, for example bottle-shaped or barrel-shaped bores, and/or bores which have at least one conical bore portion with axially continuously changing diameter.
The honing tool has a material body 110 made of a steel material and defining a tool axis 112, which simultaneously is the rotational axis of the honing tool during machining. On the spindle-side end of the honing tool is a coupling structure 120 for connecting the honing tool to a drive rod or working spindle of a honing machine, or another machining tool with a working spindle which can both rotate about the spindle axis and also oscillate to and fro parallel to the spindle axis. In
In the end portion of the tool body facing away from the coupling structure 120 or working spindle (not shown) is the cutting region 130 of the honing tool, in which all abrasive cutting means are arranged (in the form of cutting strips, general reference sign 170). The cutting region 130 is more or less flush with the end of the tool body remote from the spindle and arranged in the end portion of the tool body facing away from the spindle, so that if necessary blind bores can also be machined down to the bore base. Within the cutting region 130, many strip-like cutting means 170 (also referred to below as cutting strips) are distributed around the circumference of the tool body. The length LSB of the cutting region is here between 80% and 95% of the outer diameter AD of the honing tool. In this example, the outer diameter lies in the order of 80 mm; it may e.g. lie in the range from 60 mm to 90 mm but in some cases also above or below this.
The honing tool 100 has an integrated swivel joint 190 via which the tool body 110 is coupled with limited movability to the connection piece which serves for connection to the working spindle of the machining tool. The joint 180 in this example is configured as a ball joint, wherein the ball 192 is formed at the lower end of the connection piece while the corresponding bearing element with concave spherical bearing surfaces is arranged within the tool body 110. This allows a limited movability of the tool body relative to connection piece in an infinite multiplicity of directions running transversely to the tool axis, whereby the honing tool can particularly closely follow the casing surfaces for machining bore inner faces in order to improve the quality of shape and surface.
The honing tool 100 in
The tool body has multiple, axially elongate guide openings (general reference sign 160) which lead radially relative to the tool axis from the guide bore 115 to the outside of the tool body. In the tool body of the exemplary embodiment, fourteen guide openings 160 are formed which are distributed over the circumference with an irregular angular division. An irregular angular division here means that one or more of the guide openings have different angular spacings from the guide openings which lie directly adjacent thereto in the circumferential direction without interposed guide strip.
On the outside of the tool body, four non-advanceable, non-cutting guide strips 190-1 to 190-4 of a guide group are arranged diametrically opposite one another in pairs. The guide strips are distributed with an irregular angular division, so that tool body segments lying between directly adjacent guide strips in the circumferential direction have different circumferential widths in pairs. These are around 78° for the narrower tool body segments WS-S and around 102° for the wider tool body segments WS-B. The wider tool body segments each hold four, the narrower segments only three guide openings arranged directly adjacent to one another without interposed guide strips. The guide group has a two-fold rotational symmetry relative to the tool axis.
Two diametrically opposed guide strips 190-1 and 190-3 are designed as measuring strips. In the part of the cutting region furthest away from the coupling, they have a measurement region with three axially mutually offset radial bores 195, which may be used as measuring nozzles of a pneumatic diameter measuring system. To measure in a specific measurement plane, the radial bores lying in this plane are opened and the unused radial bores are closed.
Thus for each of the two middle guide openings 160-13 and 160-14, the angular spacing from the respective two guide openings directly adjacent in the circumferential direction is different. The differences in angular spacing (approximately 1°) clearly lie outside production tolerances and are of the order of a few percent (e.g. from 2% to 5%) of the absolute value of the angular spacing. For reasons of symmetry, this irregular angular distribution is also present on the opposite side, i.e. in the other wider tool body segment.
The guide openings which lie only indirectly next to one another with an interposed guide strip have a respective angular spacing of around 34°. Thus the angular distribution of the guide openings over the circumference is characterized by three different values for angular spacing, namely four times around 22°, two times around 23° and four times around 34°. Thus in this respect, there is an irregular or asymmetric angular division.
With the honing tool configured ready for use, the tool body 110 carries a plurality of cutting means carriers (general reference sign 150). The cutting means carriers are each one-piece components made of steel material which are substantially rigid. Each cutting means carrier has a carrier portion 152 which is relatively wide in the circumferential direction and on the outside has multiple, preferably two, three or four mutually parallel receiving grooves 156 lying in a common plane for each receiving a strip-like cutting means unit. The circumferential width of the carrier portions here lies in the range from around 15° to around 20°.
On the substantially flat inside of the carrier portion, an initially plate-like then slightly tapering feed portion 158 protrudes towards the inside. On the inside of the feed portion facing away from the outside 154 are sloping faces which cooperate with a corresponding sloping face of an axially displaceable feed cone in the manner of a wedge drive, so that an axial movement of the feed cone inside the tool body leads to a radial movement of the cutting means carrier. The plate-like part of the feed portion 158 thus sits radially movably in the substantially rectangular guide opening 160 of the tool body, so that a radial movement (relative to the tool axis 112) is possible while tilt movements in the transverse direction thereto are largely prevented. The cutting means carriers are preloaded into the inwardly retracted position by means of two peripheral coil springs, so that the radial feed takes place towards the outside against the force of these return springs.
In the exemplary embodiment, all cutting means are formed as cutting strips narrow in the circumferential direction, the width BS of which measured in the circumferential direction is small relative to the axial length LS. An aspect ratio between length LS and width BS may for example lie in the range from 4:1 to 55:1. The axial length LS is almost as large as the maximum effective outer diameter AD of the honing tool.
The honing tool 100 may be configured for different machining tasks without great complexity. For a specific configuration, usually two steps are required. A first step comprises fitting the tool body 110 with cutting means carriers equipped with suitable cutting means. The cutting means carriers are introduced from the outside into the respective guide openings 160 provided for these, with the desired distribution for the two cutter groups.
To ensure that the cutting means carriers belonging to a cutter group are advanced together during the advance of a feed element while the cutting means carriers of the other group are not advanced, the configuration comprises as a second step the installation of corresponding first and second feed elements. This is relatively easy with the honing tool since, in fitted state, the feed elements are secured against falling out and held in position only by two radially inwardly engaging screws. To exchange the feed elements, the retaining screws are unscrewed and the feed elements withdrawn from the free end face of the tool body. Then feed elements suitable for the desired configuration are inserted in the guide bore 115 and secured against falling out by tightening the retaining screws. There is a first and second feed element for each specific circumferential distribution of cutting means carriers between first and second cutter groups.
With reference to
Also, the number of receiving grooves 156 of rectangular cross-section on the carrier portions of the cutting means carriers should be noted. In the examples, cutting means carriers with either three or four equidistant receiving grooves of the same dimensions are shown. In all exemplary embodiments illustrated, the cutting means carriers 150 of the first cutter group each have three comparatively wide receiving grooves, while the cutting means carriers of the second cutter group each have four slightly narrower receiving grooves. Other divisions are possible. For example, the same number of receiving grooves (e.g. two, three or four) may be provided everywhere.
The respective first cutter group comprises six cutting means carriers, while the second cutter group comprises eight cutting means carriers. The number of receiving grooves on the respective cutting means carriers therefore corresponds to half the number of cutting means carriers of a cutter group. In these examples, this division means that for cutting means carriers of the first cutter group, for each carrier unit a larger part of the circumferential width is filled with cutting means than for the cutting means carriers of the second cutter group, where correspondingly a smaller proportion of the circumferential face of the cutting means carriers is filled with cutting means. Thus in all examples, the condition is fulfilled that for the cutting means carriers of the cutter group having fewer cutting outer means carriers, the faces viewed in the circumferential direction are more densely filled with cutting means than for the cutting means carriers of the group with the larger number. The allocation may however also be changed.
If all receiving grooves of the cutting means carriers are filled with cutting means, the first cutter group has 18 cutting strips and the second cutter group 32 cutting strips. However, not all receiving grooves need be filled with cutting means.
In this example, as in the other examples, the irregular angular division between adjacent cutting means carriers may lead to a reduction in chatter tendency during machining, also to solving overlap problems in so-called spiral honing which uses relatively large honing angles (for example up to the order of) 140°.
As already mentioned, the cutting means carriers may be variably equipped with cutting means of different widths and/or different lengths, and/or with different numbers of cutting means.
The following explanations may be useful for the selection of most suitable configuration, i.e. an arrangement or distribution of the cutting strips well adapted to the machining task.
Very stable bores (bores without local “weaknesses” such as e.g. absent stiffening ribs) or cylinder liners can be honed with a “shell arrangement” (see e.g.
With an almost fully symmetrical arrangement (see e.g.
The divisions between the limit cases of “shell arrangement” (see
The axial position of the measuring nozzles or measurement plane defined thereby can be adapted to the corresponding requirements. The axial position may be selected so that it lies approximately centrally in the region fitted with cutting means. The honing tool as a production tool can be easily adapted to different machining tasks. It is also very suitable as an experimental tool because of the flexibility of usage types.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 213 090.9 | Nov 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/082268 | 11/17/2022 | WO |
