EP2976184B1 - Honing method and honing tool - Google Patents

Description

BACKGROUND

The invention relates to a honing process for machining the inner surface of a bore in a workpiece by means of at least one honing operation according to the preamble of claim 1, as well as a honing tool usable in carrying out the honing process according to the preamble of claim 6. A preferred field of application is the honing of cylinder surfaces the production of cylinder blocks or cylinder liners for reciprocating engines.

The cylinder surfaces in cylinder blocks (cylinder crankcases) or cylinder liners of internal combustion engines or other reciprocating engines are exposed during operation of a strong tribological stress. Therefore, it is important in the production of cylinder blocks or cylinder liners to edit these cylinder surfaces so that later in all operating conditions sufficient lubrication is ensured by a lubricant film and the frictional resistance between relatively moving parts is minimized.

The quality-determining finishing of such tribologically stressable inner surfaces is usually carried out with suitable honing methods, which typically comprise several successive honing operations. Honing is a machining process with geometrically indeterminate cutting edges. In a honing operation an expandable honing tool is moved within the bore to be machined to generate a stroke in the axial direction of the bore with a stroke frequency up and down or back and forth and simultaneously rotated to produce a lifting movement superimposed rotary motion at a rotational frequency. The cutting material bodies attached to the honing tool are pressed against the inner surface to be machined via a feed system with a feed force acting radially to the tool axis. During honing, a cross-cut pattern typical of honing is produced on the inner surface with intersecting machining marks, which are also referred to as "honing marks".

With increasing demands on the thriftiness and environmental friendliness of Mobren, the optimization of the tribological system piston / piston rings / cylinder surface is of particular importance in order to reduce friction, to achieve low wear and low oil consumption. The friction ratio of the piston group can be up to 35%, so that the friction reduction in this area is desirable.

Different approaches are used to reduce the mechanical losses of a motor. These include u.a. the use of thermally sprayed cylinder surfaces, the use of coated piston rings, the development of particularly optimized honing surfaces etc.

A technology that is becoming increasingly important for the reduction of friction and wear is the avoidance or reduction of cylinder distortions or deformations of the engine block (cylinder crankcase) during assembly and / or operation. After conventional honing, a cylinder bore should typically have a bore shape that is as small as possible, e.g. a few micrometers, deviates from an ideal circular cylinder shape. During assembly or operation of the engine, however, it can lead to significant form errors, which can be up to several hundredths of a millimeter and reduce the performance of the engine. The causes of distortions or deformations are different. It may be static or quasi-static thermal and / or mechanical loads or dynamic loads. The construction and design of cylinder blocks also influence the tendency to deform. The sealing function of the piston ring package is typically degraded by such hard-to-control deformations, which can increase blow-by, oil consumption and friction.

To reduce problems due to distortion during assembly or in certain operating conditions, has been in the DE 28 10 322 C2 proposed to deform the engine block for the honing by means of a clamping device such that the subsequent deformation is simulated by the cylinder head. In the clamped state, which corresponds to the state present after assembly later, the honing takes place to produce a circular cylindrical bore shape, which should then be set again after assembly.

Another technology that is intended to ensure or approximate the formation of an ideal shape after assembly or in the operating state of the engine by an inversion of the cylinder distortions (generation of a negative shape of the error) is the so-called Formhonen. This is the unstrained workpiece By means of honing, a bore shape deviating from the circular cylindrical shape is produced, for example a cloverleaf shape. Such bore shapes are usually asymmetrical, because the deformations of the cylinder block are usually not symmetrical. In the operating state, the most ideal circular cylindrical shape should result, so that the piston ring package can seal well over the entire circumference of the bore. Different variants of the Formhonens become for example in the EP 1 790 435 B1 and in the prior art cited therein.

The EP 1 321 229 A1 , which forms the basis for the preambles of claims 1 and 6, describes a method for producing a bore which has an initial shape in the unloaded state and in the operating state a deviating from the initial shape desired shape. In the method, the deformation of a bore to the desired shape is determined in the operating state, by means of the desired shape and the deformation of the initial shape is determined and the bore is brought with a machining process in the initial form. In the exemplary embodiment, the initial shape of the bore is largely cylindrical in an upper region and elliptical in a lower region. The two areas merge into a middle transition area. For processing a honing machine is used which has one to four honing stones. Since the bore geometry changes continuously in the middle region between the cylindrical and the elliptical area, honing stones with very little axial extension are used.

The international patent application with publication number WO 01/76817 A1 discloses a hydraulically expandable honing tool with an annular cutting group at the spindle end of the honing tool. The cutting pads are attached to the end of outwardly expandable tongues formed integrally with the tool body. The tongues are spread outwardly upon delivery to increase the effective outer diameter.

The German patent application DE 16 52 074 A1 discloses a honing tool having a cutting assembly consisting of two diametrically opposed honing segments with outboard ribs on which the cutting pad sits.

TASK AND SOLUTION

It is an object of the present invention to provide a generic honing method and a honing tool which can be used in carrying it allow to produce reciprocating engines which have improved friction loss, oil consumption and blow-by characteristics.

To solve this problem, the invention provides a honing method having the features of claim 1. Furthermore, a honing tool with the features of claim 6 is provided, which can be used in the context of the honing process.

Advantageous developments are specified in the dependent claims. The wording of all claims is incorporated herein by reference.

In the honing process, a bottle-shaped bore, i. a hole with a bottle shape generated. A "bottle-shaped bore" immediately following a bore entry has a first bore portion having a first diameter remote from the bore entry, a second bore portion having a second diameter greater than the first diameter, and a transition portion between the first and second bore portions a continuous transition from the first diameter to the second diameter. The first bore portion and the second bore portion are generally circular cylindrical basic shape and are coaxial with each other. The transition portion may be partially conical and at its ends facing the outer bore sections each pass with suitable radii in the adjacent bore sections.

With a suitable design of the bottle-shaped macro-shape significant advantages in terms of friction reduction, reduced blow-by and reduced oil consumption can be achieved. Furthermore, improvements in the wear resistance of the piston ring package and positive influences on the noise during operation may result. In the relatively narrower first bore section near the bore entry, ie in the "bottleneck", an essential part of the combustion takes place in an internal combustion engine. Any high oil supply in this section could lead to emissions and oil consumption issues. In this narrower first bore portion, the ring pack of the piston rings can well fulfill its conventional functions (in particular the sealing against combustion gases and the stripping of the oil film in the backward movement) due to the relatively high hoop stress. Due to the pressure waves of combustion, the piston accelerates in first bore portion and reaches the transition portion with gradually increasing diameter. In the transition section, the piston ring tension is reduced by increasing the diameter. However, since a considerable piston speed is already present here and the internal pressure in the cylinder chamber decreases, the blow-by, oil consumption value and engine noise emission are not adversely affected. By suitable radii between the transition section and the adjacent first and second bore sections, a smooth inlet and outlet of the piston rings can be achieved at the transition section, so that ring wear or engine erosion can be avoided. In the downward movement of the ring package reaches its lowest voltage after passing through the transition section on entering the second bore section, so that where the piston reaches its maximum speed, the friction loss is automatically reduced.

As part of the honing process, which leads to a bottle-shaped bore with optimal surface texture, a honing tool particularly suitable for this purpose is used in at least one honing operation, which is also referred to here as "ring tool" due to its construction. An "annular tool" in the sense of this application has at least one annular cutting group with three or more distributed around the circumference of the tool body of the honing tool radially deliverable cutting bodies, which are designed as relatively wide in the circumferential direction of the honing tool and in the axial direction of the honing tool relatively narrow Honsegmente. The axial length of the honing segments measured in the axial direction of the honing tool is smaller than the width measured in the circumferential direction and the axial length of the cutting area equipped with cutting material bodies is smaller than the effective outside diameter of the honing tool.

If at least three Honsegmente are provided, the machining forces can be distributed well and relatively evenly over the circumference over the entire available through radial feed effective outside diameter range of the honing tool. It can e.g. be provided in a cutting group exactly three, exactly four, exactly five or exactly six Honsegmente same or different circumferential width. Although more than six honing segments within a cutting group are possible, they make the design more complicated and are generally not required.

Due to the radial deliverability (displacement of the Honsegmente in the radial direction at the delivery) can be achieved that the engagement conditions between Cutting material body and bore inner surface remain virtually constant regardless of the set diameter. By avoiding Schneidstoffkörper tilt during radial delivery uneven wear can be avoided.

These measures can individually and in combination have a positive effect on the achievable surface quality, in particular with regard to the uniformity of the surface quality over different bore sections.

The axial length of the segments may be e.g. less than 30% of the effective outer diameter of the honing tool, in particular between 10% and 20% of this outer diameter. For ring tools for machining typical cylinder bores in engine blocks for cars or trucks, the axial length may e.g. in the range of 5 mm to 20 mm. Relative to the bore length of a bore to be machined, the axial length is typically less than 10% of this bore length. If the upper limits are clearly exceeded, the possibility of axial contour tracing or contour generation usually suffers. In addition, small axial lengths are advantageous to produce sufficient surface pressure for machining. On the other hand, a minimum length in the axial direction is advantageous in order to allow a honing overflow for machining the bore ends and to limit a tilting tendency of the honing tool.

Such a ring tool represents a departure from conventional concepts of honing tool design, which assume that to achieve less Form errors a honed bore honing tools should be used in the axial direction relatively long, in the circumferential direction, however, relatively narrow honing stones. An annular tool is particularly well adapted to the machining of bottle-shaped bore shapes or generally of bore shapes with significantly varying bore diameter in the axial direction. In an annular cutting group, the cutting material (bonded cutting grains of appropriate granularity, density and hardness) is concentrated in an axially relatively narrow ring, typically more than half of the circumference of an annular cutting group is occupied by cutting means and, accordingly, effectively contributes to material removal.

The cutting area in which one or more annular cutting groups are located is short in the axial direction compared to the effective outer diameter of the honing tool, whereby the generation and / or tracking of an axially extending contour is possible.

An annular cutting group distinguishes itself in comparison with conventional honing stones in that in the axial section covered by the annular cutting group substantially more contact surface exists between the cutting bodies and the bore inner surface than in a comparatively narrow axial section of a conventional honing tool. In some embodiments, more than 60% of the circumference of an annular cutting group is occupied by cutting means, possibly even more than 70% or more than 80% of the circumference of the honing tool.

Preferably, a cutting group is arranged in the vicinity of a spindle end facing away from the tool body, that the cutting group is located exclusively in the spindle facing away from the tool body. If several annular cutting groups are provided, this condition can apply to all cutting groups. An arrangement near the end remote from the spindle allows i.a. Bearings with very little honing overflow.

When honing the stroke position of the honing tool can be used within the bore as a guide to specify the contact pressure or the delivery force as a function of the stroke position of the annular cutting group with high local resolution. This makes it possible to use a deliverable annular cutting group to produce a bore with an axially variable contour or to follow an already previously generated axially varying contour without unwanted Andruckkraftspitzen. When using a ring tool can be used in all axial areas the bore can be worked with substantially the same coverage, so that if necessary very uniform roughness images or surface structures can be produced. If an annular tool is used, it may be possible to work with very little honing overflow at the axial ends of a bore without problems of uneven cutting body wear.

Preferably, working with an electromechanical cutting group delivery system. In contrast to a hydraulic widening thereby a precise specification of the feed path (path control) is possible, whereby an axial contour generated selectively and / or a predetermined axial contour can be precisely tracked.

One or more sensors of a diameter measuring system can be arranged on the honing tool, so that an in-process diameter measurement is possible. For example, measuring nozzles of a pneumatic diameter measuring system can be mounted between adjacent honing segments on the tool body. As a result, the precision of the achievable bore contours can be improved.

By using a ring tool uniform wear of the cutting material body and very good form values and uniform surface roughness of the bore over the entire service life of the annular cutting group are ensured.

There are different embodiments of ring tools possible, between which a user can select depending on the processing task to be handled.

In some embodiments, the ring tool has a single annular cutting group, whose honing segments can be radially delivered or retracted via a single common delivery system. Typically, the annular cutting group has three or more uniform or uneven honeycomb segments distributed over the circumference of the honing tool, typically not more than six. Preferably, the single annular cutting group is arranged in the vicinity of the spindle-facing free end of the tool body, for example, flush with the end face remote from the spindle. Such constructions are particularly well suited for machining cylinder bores with reduced honing overflow. Such limitations in processing arise, for example, blind holes or cylinder bores in engine blocks for monobloc or V-engines.

It is also possible that an annular cutting group has two independently deliverable groups of honing segments, wherein the honing segments of the groups are arranged alternately in the circumferential direction. This makes it possible to combine the advantages of a single annular cutting group (for example, with respect to the machining of bores with short Honüberlauf) with the advantages of a double delivery of two independent groups of honing segments. With such a tool, two consecutive honing operations with different cutting materials without intermediate tool change can be performed. The honing segments of a group of honing segments usually have the same cutting deposit, while the groups have different cutting plaques, for example diamond plaques of different grain size.

It is also possible that a ring tool has a first annular Schnedgruppe and at least one second annular cutting group, which is axially offset from the first annular cutting group and can be delivered independently of the first annular cutting group. This also makes two consecutive honing operations with different cutting materials without intermediate tool change possible. Since the different cutting materials are distributed over the at least two axially offset annular cutting groups, each of which can cover a large part of the circumference of the honing tool, particularly high removal rates or relatively short honing times are possible in both honing operations. Such ring tools can be used for all holes that allow enough Honüberlauf. With two or more annular cutting groups bridging Pulsationsfenstern or cross holes or hole interruptions of any kind is particularly easy. Such a ring tool preferably has exactly two annular cutting groups, whereby a flexible use is possible despite a simple structure.

In preferred embodiments, an integrated, multi-axially movable joint, for example a ball joint or a cardan joint, is provided on the tool body. Thus, positional errors of the machine and / or a core offset of the bore can be compensated without changing the bore position. Embodiments without joint are also possible. Such ring tools can be rigidly coupled to a honing spindle or rigidly coupled to the honing spindle drive rod.

The bottle shape of the bore can be produced by any suitable machining process, for example by fine turning (fine spindles), ie by means of a machining process with a geometrically defined cutting edge, or by honing. This can be followed by one or more honing operations to arrive at the final desired hole geometry with a suitable surface structure.

Preferably, a hole with a circular cylindrical bore shape is first produced by fine turning or honing and then in a Flaschenhonoperation by honing with axially varying Honabtrag a bottle-shaped bore shape is generated. In comparison to fine turning, honing makes it possible to produce surfaces with particularly uniform surface quality without circumferential tracks. The self-sharpening effect of the cutting material body also contributes to the uniformity of the surface quality. When honing a continuous process monitoring is possible.

In a variant of the method an expandable honing tool with at least one annular cutting group is used in the bottle honing operation, ie an annular tool. Honsegmente the cutting group in a downstroke according to the bottle shape depending on stroke position, away and / or force controlled delivered radially outward and retracted radially in an upstroke according to the bottle shape in response to the stroke position. As a result of this processing variant, the transition section which is particularly difficult to machine results from the beginning in a relatively smooth contour course.

Alternatively, it is also possible for the bottle honing operation to use an expandable honing tool with honing stones whose length is more than 50% of the length of the bore. The length of the honing stones can for example be between 50% and 80% of the length of the bore. In the bottle honing operation, the honing tool is then moved in a first stroke position between an upper and a lower Umsteuerpunkt up and down or back and forth in order to bring the first hole along its entire length in a circular cylindrical shape. Thereafter, in a second phase, the upper Umsteuerpunkt incrementally, ie across several strokes, changed in the direction of the lower Umsteuerpunkts, so that the stroke length is gradually reduced. This results in a displacement of the stroke position in the direction of a second stroke position, which in the region of the second bore portion lies. Thereafter, in a third phase, the honing tool is moved back and forth in the second stroke position. In this variant of the method, the basic shape of the transitional section essentially arises during the second phase of the gradual stroke position displacement and lifting height reduction, whereby the diameter increase in the second bore section is generated simultaneously and also in the third phase.

When the bottle honing operation is performed by means of a honing tool with relatively long honing stones, a relatively rough surface structure with a profile similar to a saw profile can be produced in the transition section. In order to obtain the desired uniform surface structure in the transition section as well, a smooth honing operation is preferably carried out after the bottle honing operation for smoothing the bore profile in the transition region, wherein an annular tool is used in the smoothing honing operation, ie an expandable honing tool with at least one annular cutting group. With the help of the ring tool grooves or ridges in the transition section can be eliminated and the radii of the transition section rounded.

It has proven to be advantageous if, during the smoothing honing operation, the cutting material bodies of the annular cutting group are pressed against the inner surface of the bore with a constant feed force. This is achieved in some process variants in that a honing machine is used with a hydraulic feed system for the ring tool. The tracking of the contour of the bottle-shaped bore through the honing segments of the ring tool can already result from the design-related flexibility of the hydraulic expansion.

The invention also relates to a honing tool, which is particularly suitable for carrying out the honing process, but can also be used in other non-inventive honing process.

The invention also relates to a workpiece having at least one bore having a honed inner surface, wherein the bore is a bottle-shaped bore, which subsequent to a bore entry a first bore portion having a first diameter, remote from the bore entry, a second bore portion having a second diameter, is larger than the first diameter, and between the first and the second bore portion has a transition portion with a continuous transition from the first to the second diameter, wherein the workpiece has been machined using a honing tool according to the invention.

In particular, the workpiece may be a cylinder block or a cylinder liner for a reciprocating engine. The reciprocating engine may be e.g. to an internal combustion engine (internal combustion engine) or to act as a compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

• Fig. 1 shows a schematic longitudinal section through a bottle-shaped cylinder bore in an engine block;
• Fig. 2 FIG. 2A shows a longitudinal section through an embodiment of an annular tool with simple widening of a single annular cutting group and in FIG. 2B a cross section through the cutting group; FIG.
• Fig. 3 3A shows a longitudinal section through an embodiment of an annular tool with double widening of a single annular cutting group and in FIG. 3B a cross section through the cutting group;
• Fig. 4 4A shows a longitudinal section through an embodiment of a double widening ring tool in the case of two annular cutting groups arranged one above the other, and in FIG. 4B a cross section through one of the cutting groups;
• Fig. 5 shows schematically a longitudinal section through a bore which is machined by means of a honing tool with relatively long honing stones;
• Fig. 6 shows schematically the stroke position of a honing tool with long honing stones as a function of honing time t in the bottle honing operation.
• Fig. 7 shows a measurement diagram of a rounded profile of a bottle-shaped cylinder after the use of an annular tool.
• Fig. 8 FIG. 12 is a schematic diagram showing the dependence of the stroke position HP (solid line) and the expanding position AP (broken line) as a function of the honing time t in a second embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following, embodiments of honing methods and honing tools are described, which can be used in the context of embodiments of the invention both material-removing machining of workpieces having one or more holes, which should have the macro-shape of a bottle in the finished state.

Fig. 1 shows a schematic longitudinal section through such a bottle-shaped bore 110 in a workpiece 100 in the form of an engine block (cylinder crankcase) for an internal combustion engine. The bore is rotationally symmetric with respect to its bore axis 112 and extends over a bore length L from a bore inlet 114 facing the cylinder head to the bore exit 116 at the opposite end. The bore can be subdivided into three contiguous sections of different function, which merge into one another, ie without the formation of steps or edges.

A first bore portion 120 at the entrance end has a first diameter D1 and a first length L1. At the opposite exit-side end extends over a second length L2, a second bore portion 130 whose inner diameter (second diameter) D2 is greater than the first diameter D1. Between the first bore section 120 and the second bore section 130 there is a partially conical transition section 140 in which there is a continuous transition from the first diameter to the second diameter. Between the central, substantially conical part of the transition section and the first bore section, a first radius R1 is formed, while a second radius R2 is formed between the transition section and the second bore section. The radii R1 and R2 may be substantially equal, but it is also possible that the first radius is smaller or larger than the second radius.

For example, in typical bore geometries, the first length L1 may be between 15% and 40% of the bore length L. The second length L2 is typically greater than the first length and is often between 40% and 60% of the bore length L. The transition section is normally relatively short to the adjacent bore sections. Typical third lengths L3 can be in the range of 5% to 20% of the bore length L are. Even deviations from these geometrical conditions are possible.

The difference in diameter between the first diameter D1 and the second diameter D2 is well outside the tolerances typical for honing, which are for a cylindrical shape in the order of a maximum of 10 microns (based on the diameter). With an absolute value of the inner diameter in the order of between 70 mm and 150 mm, the difference in diameter may for example be between 20 μm and 90 μm.

The radii R1, R2, the lengths of the outer bore portions and the transition portion, and the tangent angle T between the bore axis and a tangent to the transition portion may be optimized to provide low blow-by, low oil consumption, and low wear in typical engine operating conditions Give piston rings.

The bottle shape of the bore means that the bore in the region near the inlet is comparatively narrow, so that the piston rings of the piston running in the bore are pressed against the bore inner surface 118 under high hoop stress. As a result, where the combustion takes place mainly and high pressures occur, a reliable seal is achieved and the oil film is stripped in the downstroke. The piston accelerated by the combustion then moves in the direction of the bore exit, whereby the piston rings first pass (partially) through the transition section with the continuously enlarged inner diameter and then the second bore section. In the transition section, the piston rings can gradually relax, with the seal remaining sufficient because the pressure difference across the piston rings decreases. At the beginning of the second bore section, the ring package reaches its lowest tension, so that friction losses are reduced by reduced ring tension, especially in the range of maximum piston speed. During the upward stroke, the hoop tension then increases again as soon as the piston rings reach the exit-side radius of the transition section and pass through it in the direction of the first bore section.

A finishing process that can economically produce such a well in terms of both the macro-shape (bottle shape) and in terms of the surface structure of the tribologically stressed bore inner surface in high quality, comprises in embodiments of the invention at least one honing operation, in which a honing tool of special construction is used, which is also referred to in this application as "ring tool". An annular tool has at least one annular group attached to the tool body cutting group with distributed around the circumference of the tool body Schneidstoffkörpern that can be delivered by an associated delivery system in the radial direction or withdrawn. The cutting material bodies are designed as Honsegmente whose width in the circumferential direction is significantly greater than their length in the axial direction. The cutting material bodies responsible for material removal on the workpiece are concentrated in an axially relatively narrow zone (a ring of the cutting group) and occupy a relatively large portion of the circumference of the honing tool. As a result, bore shapes can be produced with a relatively high material removal rate, in which bore sections of different diameters adjoin one another in the axial direction.

Fig. 2 2A shows a longitudinal section through an embodiment of an annular tool 200 with a single annular cutting group 220 and simple expansion. Fig. 2B shows a cross section through the cutting group The ring tool 200 has a tool body 210, which defines a tool axis 212, which is also the axis of rotation of the ring tool during honing. At the spindle end of the ring tool (in Fig. 2A Above) is a coupling structure not shown for coupling the ring tool to a drive rod of a honing machine or other machine tool, which has a work spindle which is both to the spindle axis rotatable and parallel to the spindle axis oscillating back and forth movable.

At the spindle end facing away from the tool body (in Fig. 2A below) is the annular cutting group 220, which has several (in the example, three) evenly distributed over the circumference of the tool body Schneidstoffkörper 220-1, 220-2, 220-3, which delivered by means of a Schneidstoffkörper-delivery system radially to the tool axis 212 to the outside can be used to press the abrasive outer sides of the Schneidstoffköpers with a defined pressure force or contact force against the inner surface of a bore to be machined. Each of the three curved cutting material body is designed as a very wide in the circumferential direction, in contrast, in the axial direction against narrow Honsegment which covers a circumferential angle range between 115 ° and 120 °. The honing segments are decoupled from the tool body and displaceable radially relative to the tool axis 212. The ring formed by the honing segments terminates flush with the tool body on the side facing away from the spindle, so that the ring is completely inside the spindle Half of the tool body sitting at the spindle end facing away from the ring tool.

The axial length LHS of the Honsegmente is less than 15%, in particular less than 10% of the bore length L. The Honsegmente are about 4 mm to 35 mm, in particular about 10 mm high (in the axial direction), which in the example between 5% and 30%, in particular between 10% and 20% of the effective outside diameter of the cutting group. The axial length LHS corresponds here simultaneously to the axial length of the entire cutting region of the honing tool.

Each cutting material body is fixed to an outside of an associated support bar 224-1, 224-2 made of steel by soldering. Alternatively, the cutting material body can also be attached by gluing or by screws, whereby an easier replacement is possible. Each support bar has on its inner side an inclined surface which cooperates with a conical outer surface of an axially displaceable Zustellkonus 232 in such a way that the support bars are delivered with the cutting material carried therefrom radially outward when the Zustellkonus means of a machine-side feed device against the force of return springs 234, 226, 228 is pressed in the direction of the spindle facing away from the end of the ring tool. In the case of an opposing feed movement, the carrying strips with the honing segments are retrieved radially inward with the aid of circulating return springs 226, 228. The radial position of the cutting material body is thereby controlled without play on the axial position of the Zustellkonus 232.

This tool concept is particularly suitable for machining cylinder bores with reduced honing overflow, for example with a maximum of 5 mm honing overflow. Such geometries typically occur in blind holes or in monoblock or V motors.

In Fig. 3 an embodiment of a ring tool 300 is shown, which also has a single annular cutting group 320, which is arranged at the end face facing away from the spindle 310 of the tool body. Fig. 3A shows a longitudinal section through the ring tool, Fig. 3B a cross section through the cutting group. In contrast to the embodiment of Fig. 2 but it is honing tool with double widening. The annular cutting group 320 has two independently deliverable groups of honing segments, wherein the honing segments of the groups are each arranged alternately in the circumferential direction are. A first group of honing segments has three first honing segments 320-1, which are arranged offset from each other by 120.degree. In each case there are arranged three second hearing segments 320-2 of a second group of hearing segments. The first group has cutting material body with a relatively coarse cutting surface, while the second group has cutting material body with a relatively finer cutting surface. Between immediately adjacent Honsegmenten axial guide rails 326 are arranged. A ball joint 350 is provided between the tool body 310 and the coupling structure 340 provided for coupling the honing tool to a work spindle or the like, so that the honing tool is limitedly movable in several axes with respect to the honing spindle.

The first honing segments can be delivered radially by means of a first delivery system. To this belongs a centric to the tool body extending first feed rod 332-I, which has a conical portion at the end remote from the spindle, which cooperates with the inclined surfaces of support strips of the first group of Honsegmenten. A second delivery system serves to deliver the second group of honing segments and has a tubular delivery element 332-A, which encloses the delivery rod 332-I and has at its end remote from the spindle a conical outer surface which cooperates with inclined surfaces on the support strips of the second honing segments.

With the aid of the first delivery system, the three honing segments of the first group of honing segments can be expanded to perform a specific honing operation, for example a smooth honing operation or a structure honing operation. Instead, if the other group of honing segments having a different cutting pad location is delivered, another honing operation such as a de-grating operation or a plateau honing operation may be performed. With the help of the ring tool with double widening, two different honing operations can be carried out one after the other, without having to change tools or use another honing spindle for machining.

Fig. 4 FIG. 4A shows a schematic longitudinal section through an embodiment of a double expansion ring tool 400, which, in contrast to the exemplary embodiment of FIG Fig. 3 has two annular cutting groups 420-1 and 420-2, which are axially offset from each other in the spindle facing away from the tool body 410 are mounted. Each of the annular cutting group (cross section in Fig. 4B ) has three common deliverable segments, each between about 110 ° and 115 ° of Cover the circumference. In contrast, the axial length of the honing segments is small and is typically less than 10% of the bore length and / or between 10% and 20% of the effective outside diameter of the honing tool in the area of the cutting material body. Between adjacent honing segments, measuring nozzles 440 of a pneumatic diameter measuring system are respectively attached to the tool body. The cutting groups are axially close to each other, so that the cutting region of the honing tool, in which the two annular cutting groups lie, in the axial direction is substantially shorter than the effective outer diameter of the honing tool.

In some embodiments, the cutting material bodies are elastically yielded with respect to the tool body. This can possibly improve the ability to trace the contour during axial movement. For example, spring elements (e.g., leaf springs, spiral compression springs of the like) may be interposed between the support members and the cutting material bodies. It is also possible to make the support elements elastically yielding, e.g. in that weakenings of the carrier material cross-section in the form of slots or the like are constructively provided at suitable locations.

There are various ways to make bottle-shaped holes with a desired surface structure of the bore inner surface using one or more ring tools of the type described in this application. A first embodiment will be described in connection with FIGS FIGS. 5 and 6 beschreben.

In this process variant, a conventional honing tool with axially relatively long, narrow honing stones was initially used in order to produce a honed bore with a circular cylindrical shape starting from, for example, a pre-machined hole by fine boring. The axial ledge length I was about 1/2 to 2/3 of the total hole length L. In a first honing operation (pre-honing) was worked with diamond strips type D107, a subsequent Zwischenhonoperation was carried out with fine grain size (grain size D54). As a result, a substantially circular-cylindrical bore shape with little deviation from the ideal shape and with a relatively smooth surface (R _Z <8 μm) was produced. The inlet-side and outlet-side honing overflow S was approximately 1/3 of the strip length, similar to conventional methods. The honing overflow can be shortened when machining V or monoblock motors.

A subsequent third honing operation was designed as a bottle honing operation. By means of a bottle honing operation, a bottle-shaped bore shape is produced by axially varying material removal with geometrically indefinite cutting. In the third honing operation (Flaschenhonoperation) also worked with relatively long honing stones with strip length I = 2/3 L and a special stroke control, based on Fig. 6 is explained. Fig. 6 shows schematically the stroke position HP of the honing tool as a function of honing time t in the bottle honing operation. After retraction of the honing tool, the machining of the cylinder running surface initially proceeds from a first time t ₁ to a second time t ₂ with the same stroke length in a first stroke position as in the machining of a circular cylindrical bore. The term "stroke position" here refers to the area between the upper Umsteuerpunkt UO and the lower Umsteuerpunkt UU a lifting movement. Each shift of a Umsteuerpunktes thus also changes the Hublage.

From a defined second time t ₂ , the honing machine switches automatically to an incremental change of the stroke position and after each stroke the upper Umsteuerpunkt UO is incrementally changed in the direction of the lower Umsteuerpunkts UU. The temporal position of the second time t ₂ can be defined for example over a certain number of strokes or over a predetermined honing time or over a predetermined material removal or other triggering parameters. The amount of increment IN by which the upper reversal point changes between two consecutive strokes can also be adjusted as needed. After completion of Hubverlagerungsphase at a third time t ₃ , the bore is honed with the reached, new third stroke position until the second bore section reaches the desired diameter and the bottle shape (see. Fig. 1 ) is generated.

Depending on how the incremental variation of the Hubverlagerung and the timing of Hubverlagerung be specified, different radii and tangent angles result in the transition section. These parameters can therefore be specified via the parameters of the stroke displacement. The bottle honing operation is expediently carried out with honing stones whose cutting material grains are finer than those during pre-honing or intermediate honing. For example, it is possible to work with diamond grains in the region D35 in order to obtain a bottle shape with already a relatively fine surface structure.

When producing the bottle shape with the aid of relatively long honing stones and incremental stroke displacement, a relatively rough surface structure with small steps similar to a saw profile can result in the transition region. Such structures are generally undesirable. In order to obtain the desired surface structure uniformly over the entire inner surface of the bore including the transition section and the radii thereafter, a rounding of the radii and a smoothing of the surface with the aid of a ring-work nose are therefore carried out in the method described here after the bottle honing operation. Here you can work with even finer cutting agents, for example in the range D10 to D15, in particular D12. The selection of a suitable ring tool (eg single widening, double widening with two cutting groups arranged in a common ring, or double widening with two cutting groups arranged in two axially offset annular cutting groups) depends inter alia on the design of the cylinder block. The tool selection can be oriented, for example, to the extent of the possible honing overflows and / or the position and size of transverse bores. If, for example, a cylinder crankcase has a large transverse bore, it usually makes sense to use a ring wrench with single widening (cf. Fig. 2 ) to work. In one exemplary process, such an annular tool has been employed with an annular cutting assembly to smooth grooves or burrs created during processing of the bottle honing operation in the transition section. With the aid of the ring tool, the radii of the transition region can also be rounded and the surface values changed to be substantially identical to the surface values in the adjacent first and third bore sections.

Fig. 7 shows a measurement diagram of a rounded profile of a bottle-shaped cylinder after the use of a ring tool with single expansion in the process shown here. The scale in the x-axis of the diagram (parallel to the bore axis) is 5 mm per unit of measurement shown, in the y-axis (in the radial direction of the bore) a unit of measure is 10 μm.

1. 1. Weil ein großer Anteil des Umfangs des Honwerkzeuges im Bereich einer ringförmigen Schneidgruppe mit Schneidstoffkörpern besetzt ist, kann eine Bohrungsinnenfläche mit Hilfe eines Ringwerkzeuges viel schneller strukturiert werden als mit Hilfe eines Leistenwerkzeuges. Dadurch können ggf. Taktzeiten verkürzt werden.
2. 2. Wird die Hublänge verstellt, um beispielsweise die Form zu korrigieren, ergeben sich bei Verwendung von Ringwerkzeugen keine störenden Ungleichmäßigkeiten der Rauheitsverteilung, da die Überdeckung auch bei veränderter Hublänge beibehalten wird.
3. 3. Ringförmige Schneidgruppen verschleißen im Wesentlichen gleichmäßig, so dass unerwünschte Konizitäten vor allem im Bereich des unteren Umsteuerpunkts bei Verwendung von Ringwerkzeugen vermieden werden können.
4. 4. Die Einrichtung einer Honmaschine für einen neuen Honprozess kann bei Verwendung von Ringwerkzeugen viel einfacher und schneller als bei Verwendung konventioneller Leistenhonwerkzeuge verlaufen. Die Überdeckung wird, bedingt durch die Werkzeugkonstruktion, im Rahmen der Anforderungen ausreichend gleichmäßig sein.

The use of an annular tool brings here not only advantages in terms of smooth, edge-free course of the bore contour in the axial direction. Since in ring tools of the type described here, the cutting material body of an annular cutting group occupy a large part of the circumference of the honing tool (for example, between 70% and 80%), also results in honing a very uniform coverage of the machined bore inner surface in all axial Positions. The term "overlap" qualitatively refers to the uniformity of the distribution of honing marks over the entire bore length and circumference. If conventional honing tools with axially relatively long honing stones are used, uneven roughness or waviness in the hole may possibly be generated. Depending on the block design, this problem can be even more acute if, for example, engine blocks with shorter honing discharges have to be machined. With a honing discharge of only a few millimeters in length, uneven wear of the long honing stones can occur, so that the hole in the lower Umsteuerpunkt can get a smaller diameter than in the upper Umsteuerpunkt. While using conventional honing tools (with long honing stones) such problems can be largely avoided by choosing suitable honing parameters, the design of the corresponding honing processes is relatively time-consuming and expensive. Often, multiple trials must be performed until a honing process design is optimized to avoid uneven machining with long ledges. When using a ring tool, many of the conventionally occurring problems can be avoided. The advantages of ring tools include:

1. 1. Because a large proportion of the circumference of the honing tool is occupied in the region of an annular cutting group with cutting material bodies, a bore inner surface can be structured using a ring tool much faster than with the aid of a strip tool. As a result, if necessary, cycle times can be shortened.
2. 2. If the stroke length is adjusted, for example, to correct the shape, resulting in the use of ring tools no disturbing irregularities of the roughness distribution, since the coverage is maintained even with changed stroke length.
3. 3. Ring-shaped cutting groups wear substantially uniformly, so that undesirable conicities can be avoided, especially in the region of the lower Umsteuerpunkts when using ring tools.
4. 4. The installation of a honing machine for a new honing process can be much easier and faster when using ring tools than with the use of conventional grooving tools. Due to the tool design, the overlap will be sufficiently even within the requirements.

If, instead of an annular tool with simple widening, an annular tool with a single cutting group ring and double widening (cf. Fig. 3 ) is used for patterning, it will usually be necessary to increase the number of strokes over the use of a simple expanding ring tool to ensure a uniform coverage. However, the benefits of ring tools are retained and the number of strokes required to uniformly contour the bore internal surface will still be less than the corresponding stroke rate when using a conventional honing tool with long honing stones.

When using an annular tool, the feed force can be expediently exerted by means of a hydraulic expansion, so that the surface can be processed with a constant force substantially. The tracking of the varying contour in the axial direction can then be adjusted by the type alone by the flexibility of the hydraulic expansion.

After the smoothing of the bore inner surface and rounding of the radii with the aid of an annular tool, one or more further honing operations can be followed in order to produce the final desired surface structure on the bottle-shaped bore.

The process described here by way of example initially follows a fifth honing operation, which is referred to here as "spiral structure honing with ring tool". In this honing operation, the axial speeds and the speed of the honing tool are coordinated so that relatively large honing angles, for example of the order of 140 °, are generated. Of course, other honing angles and / or roughness profiles can be generated in other variants of the method. The Spiralstrukturhonen is designed in the example so that virtually no global material removal is achieved, but only in the after-rounding very smooth surface using a relatively coarse cutting material body with low cutting grain density grooves of suitable depth and distribution are generated. It can, for example, cutting material body with Schneidmittelkorndichte 1.25 to 15 vol.% And / or grain size 35 to 200 microns are used (see, eg DE 10 2005 018 277 A1 ).

Then, in a sixth and final honing operation, the previously structured surface is deburred (deburring). For this purpose, an annular tool with fine cutting means is preferably also used, for example the same ring tool, which was also used for the fourth honing operation (rounding of radii and glatthones). Here you can work with different expansion types. The expansion can be designed hydraulic / hydraulic, hydraulic / mechanical or mechanical / mechanical. In the case of a mechanical widening, it is possible, for example, to use force-controlled power via a servo-mechanical expansion (hydraulic-like) or position and force-controlled.

In an alternative variant of the method, an expandable ring tool is used in the bottle honing operation, that is to say in the production of a bottle-shaped bore form from a previously circular-cylindrical bore shape. For this purpose, it is provided that the control of the expansion system for the radial delivery of the honing segments is coupled to the control for the stroke position, so that the ring tool can accurately generate the transition section with the changing diameter and also operates in the cylindrical first and second bore section with a suitable pressing force ( see. Fig. 8 ). The bottle honing operation may be provided as a second honing operation immediately after prehone, and so far may substitute the second to fourth honing operations of the first embodiment. The stroke-dependent control of the expansion is then carried out so that the honing segments of the cutting group in a downward stroke corresponding to the bottle shape as a function of the stroke position and force controlled delivered radially outwards and in an upstroke according to the bottle shape as a function of the stroke position in the transition section again be withdrawn radially. Thus, from the beginning, a smooth contour in the transition section can be achieved.

At the honing machine, this can be achieved by inputting certain stroke ranges corresponding to the first to third bore sections in the control program, so that the cutting group expands by way and away widening during the downward stroke from the end of the first bore section. On the upstroke, the widening of the cutting group then travels back from the end of the third bore section to generate the desired programmed bottle-shaped cylinder. Fig. 8 2 shows by way of example a schematic diagram which shows the dependence of the axial stroke position HP (solid line) and the radial widening position AP (dashed line) as a function of the honing time t during bottle honing with ring tool.

Ring tools of the type described here can not only be used for the production or processing of bottle-shaped holes, but can also bring significant benefits without modification when machining holes with different geometry. For example, it is possible to use a double expansion ring tool with a single cutting group ring identical or similar to the embodiment of FIG Fig. 3 to use to create a freeform on a bore with a non-circular bore cross-section. This is commonly referred to as form honing. For example, with the aid of the ring tool, a bore section with shamrock shape or elliptical shape of the cross section can be produced. For this purpose, the honing machine must have the ability to simultaneously control the first delivery system and the second delivery system, depending on the stroke position and angular position of the cutting group to the bore expansions must be controlled with different force / position, so that the freeform can arise.

It is also possible to use an annular tool to create and / or machine a bore shape that has a frusto-conical bore portion (cone portion) that transitions relatively abruptly or with transition radius into an adjacent cylindrical bore portion without joining another bore portion. Thereby, e.g. a bore of funnel shape having an input cylindrical first bore portion having a first diameter which increases conically in an adjacent second bore portion toward the bore bottom to a maximum diameter. The difference in diameter between the cylindrical first bore portion and the maximum diameter in the conical second bore portion may be e.g. between about 20 microns and about 90 microns. The axial length of the cylindrical first bore portion may be e.g. between 20% and 80% of the total bore length.

Furthermore, it is possible to use a ring tool in a bore to form a barrel-shaped bore section, i. to create a bulge in an otherwise largely cylindrical bore. The bulge may be approximately in the middle or close to one of the bore ends.

When using an annular tool, it is relatively inexpensive possible to edit a cylinder surface so that in the region of the top dead center and / or in the region of the bottom dead center narrow strip with different surface structures than in the middle region highest piston speed. This variant is referred to here as "strip honing". A conventional Verfanren suitable for this purpose and a correspondingly adapted honing tool are eg in the DE 195 42 892 C2 described. There, in addition to a honing process, the entire axial Length of the honing tool processed with long honing stones, a short-stroke honing performed using short honing stones, this honing covers only the top dead center and the bottom dead center.

When using a ring tool with double widening and two axially offset cutting groups (cf. Fig. 4 ) are appropriate surface treatments also possible. For example, a long-stroke machining of the entire bore length can be carried out with the first annular cutting group, before then, for example, with the second cutting group in the region of top dead center, a short-stroke machining to produce a special structure in the region of top dead center is performed.

With appropriate variable control of the ratio between the stroke frequency and rotational frequency of the work spindle can be achieved in a simple manner, such a honing honing with different honing angles in different axial bore sections perform (see, eg Fig. 4 out DE 10 2007 032 370 A1 ).

Claims (15)

1. Honing method for machining the internal surface of a bore in a workpiece with the aid of at least one honing operation, in particular for honing cylinder faces during the production of cylinder blocks or cylinder liners for reciprocating piston engines,
   wherein, during a honing operation, an expandable honing tool is moved up and down within the bore in order to produce a reciprocating movement in the axial direction of the bore and at the same time is rotated in order to produce a rotational movement combined with the reciprocating movement,
   wherein a bore shape deviating from the circular cylinder shape is produced,
   characterized in that
   a bottle-shaped bore is produced, said bore having, following a bore inlet, a first bore section with a first diameter, a second bore section with a second diameter, which is larger than the first diameter, away from the bore inlet, and a transition section with a continuous transition from the first to the second diameter between the first and the second bore section,
   wherein, during at least one honing operation, use is made of an annular tool (200, 300, 400) which has at least one annular cutting group (220, 320, 420) having three or more cutting material bodies which are distributed about the circumference of a tool body and radially infeedable by shifting in the radial direction during the infeeding, and are designed as honing segments which are wide in the circumferential direction and are narrow in the axial direction, wherein an axial length of the honing segments, as measured in the axial direction, is smaller than the width measured in the circumferential direction, and the axial length of the cutting region equipped with cutting material bodies is smaller than the effective outside diameter of the honing tool.
2. Honing method according to claim 1, characterized in that first of all a bore having a circular-cylindrical bore shape is produced and then, in a bottle honing operation, a bottle-shaped bore shape is produced by honing with axially varying honing removal.
3. Honing method according to claim 2, characterized in that, during the bottle honing operation, use is made of an expandable honing tool having at least one annular cutting group, wherein honing segments of the cutting group are infed radially during a downward stroke in accordance with the bottle shape depending on the stroke position and are radially retracted during an upward stroke in accordance with the bottle shape depending on the stroke position.
4. Honing method according to claim 2, characterized in that, during the bottle honing operation, use is made of an expandable honing tool with honing sticks, the length of which is more than 50% of the length of the bore, wherein, in a first phase, the honing tool is moved up and down between an upper and a lower reversing point in a first stroke position, then, in a second phase, the upper reversing point is changed incrementally in the direction of the lower reversing point, and therefore the stroke position is shifted in the direction of a second stroke position in the region of the second bore section, and then, in a third phase, the honing tool is moved up and down in the second stroke position.
5. Honing method according to claim 4, characterized in that, after the bottle honing operation, a smoothing honing operation for smoothing the bore profile in the transition region is carried out, wherein, during the smoothing honing operation, use is made of an expandable honing tool having at least one annular cutting group,
   wherein preferably, during the smoothing honing operation, the cutting material bodies are pressed at a constant infeed force on to the internal surface of the bore.
6. Honing tool, in particular for carrying out the honing method as claimed in one of the preceding claims, with a tool body (210, 310, 410) which defines a tool axis, at least one cutting group (220, 320, 420) which is attached to the tool body and has cutting material bodies for the material-removing machining of the internal surface of a bore, and a cutting-group infeed system, assigned to the cutting group, for exerting an infeed force, acting radially with respect to the tool axis, on the cutting material bodies of the cutting group,
   characterized in that
   the honing tool (200, 300, 400) is designed as an annular tool and has at least one annular cutting group (220, 320, 420) having three or more cutting material bodies (220-1, 220-2, 220-3) which are distributed about the circumference of the tool body and radially infeedable by shifting in the radial direction during the infeeding, and are designed as honing segments which are wide in the circumferential direction and are narrow in the axial direction, wherein an axial length (LHS) of the honing segments, as measured in the axial direction, is smaller than the width measured in the circumferential direction, and the axial length of the cutting region equipped with cutting material bodies is smaller than the effective outside diameter of the honing tool.
7. Honing tool according to claim 6, characterized in that the axial length of the honing segments is less than 30% of the effective outside diameter of the honing tool, in particular between 10% and 20% of said outside diameter, and/or in that the axial length of the honing segments lies within the range of 5 mm to 20 mm, and/or in that the axial length of the honing segments is less than 10% of the bore length of the bore to be honed.
8. Honing tool according to claim 6 or 7, characterized in that more than half of the circumference of an annular cutting group (220, 320, 420), in particular more than 70% of said circumference, is occupied with cutting material bodies.
9. Honing tool according to any of claims 6 to 8, characterized in that a cutting group is composed of three, four, five or six honing segments.
10. Honing tool according to any of claims 6 to 9, characterized in that the cutting group (220, 320, 420) is arranged in the vicinity of a spindle-remote end of the tool body in such a manner that the cutting group is located exclusively in the spindle-remote half of the tool body.
11. Honing tool according to any of claims 6 to 10, characterized in that the annular tool (200, 300) has a single annular cutting group (220, 320) which is preferably arranged at a free end of the tool body (210, 310).
12. Honing tool according to any of claims 6 to 11, characterized in that an annular cutting group (320) has two groups of honing segments (320-1, 320-2) which are infeedable independently of each other, wherein honing segments of the groups are arranged in an alternating manner in the circumferential direction.
13. Honing tool according to any of claims 6 to 10, characterized in that the annular tool (400) has a first annular cutting group (420-1) and at least one second annular cutting group (420-2) which is arranged axially offset with respect to the first annular cutting group and is infeedable independently of the first annular cutting group, wherein the annular tool preferably has precisely two annular cutting groups.
14. Honing tool according to any of claims 6 to 13, characterized in that one or more sensors of a diameter measuring system are arranged on the honing tool, wherein measuring nozzles (440) of a pneumatic diameter measuring system are in each case attached to the tool body, preferably between adjacent honing segments.
15. Honing tool according to any of claims 6 to 14, characterized in that an integrated, multi-axially movable joint, in particular a ball and socket joint (350), is provided on the tool body.

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