EP3259099B1 - Honing method for form honing and machining equipment - Google Patents

Description

The invention relates to a honing method for machining the inner surface of a bore in a workpiece using at least one honing operation according to the preamble of claim 1 and a machining system configured to carry out the honing method according to claim 9. A preferred area of application is the honing of cylinder running surfaces in the manufacture of cylinder blocks or Cylinder liners for reciprocating engines.

The cylinder running surfaces in cylinder blocks (cylinder crankcases) or cylinder liners of internal combustion engines or other reciprocating machines are exposed to strong tribological stress during operation. Therefore, when manufacturing cylinder blocks or cylinder liners, it is important to machine these cylinder running surfaces in such a way that later, under all operating conditions, adequate lubrication is ensured by a film of lubricant and the frictional resistance between parts that move relative to one another is kept as low as possible.

The quality-determining finishing of such tribologically stressable inner surfaces is usually carried out with suitable honing processes, which typically include several consecutive honing operations. Honing is a machining process with geometrically undefined cutting edges. In a honing operation, an expandable honing tool is moved back and forth within the bore to be machined to generate a stroke movement in the axial direction of the bore at a stroke frequency and at the same time rotated at a predeterminable speed to generate a rotary movement superimposed on the stroke movement. To widen the honing tool, the cutting material bodies attached to the honing tool are fed via a feed system with a feed force and/or feed speed acting radially to the tool axis and pressed against the inner surface to be machined. During honing, a cross-hatch pattern typical of honing occurs on the inner surface with crossing traces of processing, which are also referred to as "honing marks". With increasing demands on the economy and environmental friendliness of engines, the optimization of the tribological system of pistons/piston rings/cylinder running surface is of particular importance in order to achieve low friction, low wear and low oil consumption. The friction component of the piston group can be as high as 35%, so a reduction in friction in this area is desirable.

A technology that is becoming increasingly important for reducing friction and wear is the avoidance or reduction of cylinder distortions or deformations of the engine block (cylinder crankcase) during assembly and/or during operation. After conventional honing, a cylinder bore should typically have a bore shape that deviates as little as possible, e.g. a maximum of a few micrometers, from an ideal circular cylinder shape. However, during the assembly and/or operation of the motor, significant form defects (distortions) can occur, which can amount to several hundredths of a millimeter and reduce the performance of the motor. The causes of delays or deformations are different. These can be static or quasi-static thermal and/or mechanical loads or dynamic loads. The construction and design of cylinder blocks also have an impact on the tendency to deform. The sealing function of the piston ring pack is typically impaired by such hard-to-control deformations, which can increase blow-by, oil consumption and friction.

The so-called form honing is a technology which is intended to ensure or approximate the creation of an ideal form after assembly or in the operating state of the engine by inverting the cylinder distortions (creating a negative form of the error) during processing. Honing is used to create a bore shape that deviates from the circular-cylindrical shape on the unclamped workpiece. Borehole shapes of this type are generally asymmetrical in the axial direction and/or in the circumferential direction, because the deformations of the cylinder block are also generally not symmetrical. In the operating state, the ideal circular cylinder shape should result so that the piston ring pack can seal well over the entire circumference of the bore.

Various variants of form honing, which make it possible to produce non-rotationally symmetrical bore shapes with a systematic deviation from a 2-fold rotational symmetry, are described in the EP 1 790 435 B1 described. In one variant, the bore shape is measured during and/or after a shape-generating honing operation to determine actual shape values. A difference between the actual shape and the target shape is processed to correct the infeed control.

In the WO 2014/146919 A1 , which discloses the preamble of claim 1, describes a honing method for form honing in which a bore that is rotationally symmetrical with respect to the bore axis is produced, which has a narrower cylindrical bore section near the bore entry and then, i.e. further away from the bore entry, a has widening bore section with axially variable diameter. The application also describes honing tools, which have at least one ring-shaped cutting group with cutting material bodies which are designed as honing segments which are wide in the circumferential direction and narrow in the axial direction. When using such honing tools, bore shapes with axial contours can be machined particularly precisely and economically.

TASK AND SOLUTION

It is an object of the invention to provide a honing method of the type mentioned at the outset that allows bores that are to have an axial contour in the finished state to produce the desired contour over the entire relevant bore length with sufficient precision. Furthermore, a processing system suitable for carrying out the honing process is to be provided.

This object is achieved by a honing method having the features of claim 1 and by a machining system having the features of claim 9. Advantageous developments are specified in the dependent claims. The wording of all claims is incorporated into the description by reference.

In the honing process, a bore that is rotationally symmetrical with respect to a bore axis is produced by means of honing, the shape of which deviates from a circular cylinder. The bore has a circular-cylindrical first bore section and, adjoining it, a non-circular-cylindrical second bore section, the diameter of which changes in the axial direction. The circular-cylindrical first bore section is usually located directly on the entry side of the bore, while the second bore section is further away from the bore entry and has a larger diameter than the first bore section, so that the bore extends at least over a section in the direction of the end of the bore that is remote from the entry expanded. Additional bore sections may be present.

Investigations by the inventors have shown that the target shape of the bore desired after completion of the honing process can be achieved with particularly high precision if a special re-measuring strategy is used and the measurement results are taken into account when processing other workpieces. The diameter of the (circular-cylindrical) first bore section is measured in at least one first measurement plane in the region of the first bore section in order to determine a first diameter value. Furthermore, the diameter of the second bore section is measured in at least one second measurement plane in the area of the second bore section in order to determine a second diameter value. The order of these measurement steps is basically any, but it is often useful to measure first in the first bore section and then in the second bore section. The second diameter value is then evaluated using the first diameter value to determine actual shape values representing an actual shape of the bore. In this evaluation step, the second diameter value is evaluated in relation to the first diameter value determined in the circular-cylindrical first bore section. According to the invention, the first diameter value is used in the evaluation step as a workpiece-internal reference value for determining the dimensions. The actual shape values determined in this way are then compared with target shape values in order to determine shape deviation values. A subsequent honing operation is then controlled depending on the shape deviation values.

A special feature of this procedure is that this re-measuring strategy uses the first diameter value determined in the circular-cylindrical first bore section as a reference value for the evaluation of those diameter values which are determined by measurement in the (usually more difficult to assess) non-circular-cylindrical second bore section. The first bore section or the first diameter value determined therein thus serves as a workpiece-internal reference for the entire measurement.

It can be sufficient to measure the diameter of the first bore section only in a single measurement plane, for example in the middle area of the first bore section. A significant improvement in precision is achieved in embodiments in which, when measuring the diameter of the first bore section, a first diameter is measured in two or more first measuring planes axially offset from one another and a mean value of the first diameters is formed to determine the first diameter value. The referencing to the diameter values of the first bore section is thus less susceptible to accidental incorrect measurements or accidental local shape deviations within the first bore section. The arithmetic mean of several measurements is usually determined. Although measurements in two first measurement planes that are axially offset from one another can be sufficient, measurements are preferably made in three or more first measurement planes. In particular, measurements can be taken at exactly three first measurement planes. In this way, a good compromise can be achieved between the measurement accuracy that can be achieved and the total measurement time required for the measurement.

Even when measuring the second diameter, it can be sufficient to measure only in a single second measurement plane at a previously defined axial position. To reduce the measurement uncertainty or to improve the precision, however, it is preferably provided that when measuring the diameter of the second bore section in two or more a second diameter is measured at each of the second measuring planes, which are axially offset from one another, and an axial contour profile of the second bore section is determined using this plurality of second diameters. Here, too, measurements on two measurement planes that are axially offset from one another can be sufficient, although three or more measurements on three or more second measurement planes that are axially offset can deliver more precise measurement results. In this way, for example, precise statements can be made about the uniformity of a cone shape, a trumpet shape or a bell shape of the second bore section.

In a variant of the method, when measuring the diameter of the second bore section, a second diameter is measured in an end section of the second bore section remote from the first bore section and a prewidth value is determined from the second diameter in the end section and the first diameter value. The "oversize" is defined in this application as the difference between the bore diameter at the bore end remote from the inlet and the bore diameter in the cylindrical bore section. The prewidth value can be determined, for example, from the difference between the second diameter determined in the end area and the first diameter value. The end section provided for the measurement is preferably located in the third or in the fourth of the axial length of the second bore section, far from the entry, ie at a relatively large axial distance from the first bore section.

In a variant of the method, in which measurements are carried out in several measurement planes of the first and second bore section, an axial measurement interval between adjacent second measurement planes is preferably selected such that this axial measurement interval is smaller than an axial measurement interval between adjacent first measurement planes. It is therefore measured in the non-circular-cylindrical bore section with a higher axial resolution (or with a smaller distance between adjacent measurement planes), while a coarser grid of measurement planes can be provided in the circular-cylindrical first bore section. As a result, the total measurement time required for the measurement can be optimized without any substantial loss of measurement accuracy. An axial measurement interval between immediately adjacent measurement planes can be, for example, 50% or less and/or 40% or less and/or 30% or less than an axial measurement interval in the first bore section in the second bore section. It is also possible to select an inverse ratio of the axial measuring intervals (coarser raster in the second hole section) or to work with the same axial measuring interval over the entire length of the hole.

First diameter values and second diameter values of a bore are preferably stored in a memory of a control device in the form of a data record representing the actual shape of the bore. This makes the values available for later processing.

In preferred variants, the associated diameter values are measured in two measuring directions running perpendicular to one another in one measuring plane. The measured values obtained in this way can be averaged. This type of measurement also allows indications of possible critical shape deviations, i.e. deviations from the desired rotationally symmetrical bore shape. It can also be sufficient to measure only in a single diametrical measuring direction.

Different measuring techniques can be used for the measurements. For example, tactile measurements, capacitive or inductive measurements or other electromagnetic measurements would be possible. However, the measurements are preferably carried out with a pneumatic measuring system. Non-contact pneumatic measuring systems with sufficient measuring accuracy are available and sufficiently robust to be used permanently in production-related areas.

The honing process can be carried out with differently designed honing tools. An expandable honing tool is preferably used during machining, which has an expandable, ring-shaped cutting group with a plurality of cutting material bodies distributed around the circumference of the tool body in an end region of a tool body remote from the spindle, with an axial length of the cutting material body being smaller than the effective outer diameter of the ring-shaped cutting group when completely withdrawn cutting material bodies. Examples of suitable honing tools with one or two ring-shaped cutting groups and with a single widening or double widening are in WO 2014/146919 A1 specified. The revelation of the WO 2014/146919 A1 is made to this extent by reference to the content of this description. Alternatively, for example, piezoelectrically controlled honing tools can also be used.

The invention also relates to a machining installation configured to carry out the honing process. This can be a honing system with a specialized honing machine or a machining system with another machine tool that offers the functionalities required here.

The processing system preferably has a re-measuring station separate from a honing unit, to which the workpiece is transferred for the measurement after the end of processing. At the re-measuring station, measurements can possibly overlap with a honing process. With other variants, the diameter measurements can also be carried out using a measuring system integrated into a honing tool.

BRIEF DESCRIPTION OF THE DRAWINGS

• Fig. 1 zeigt einen schematischen Längsschnitt durch ein Ausführungsbeispiel einer zylindrisch-konischen Bohrung mit einen eintrittsseitigen kreiszylindrischen ersten Bohrungsabschnitt und einen eintrittsfernen konischen zweiten Bohrungsabschnitt;
• Fig. 2 zeigt ein Ausführungsbeispiel eines Honwerkzeugs bei der Bearbeitung einer zylindrisch-konischen Bohrung;
• Fig. 3 zeigt schematisch ein Beispiel für eine Nachmessstrategie; und
• Fig. 4 zeigt einen pneumatischen Messdorn bei der Durchführung einer Messung in der Bohrung.

Further advantages and aspects of the invention result from the claims and from the following description of preferred exemplary embodiments of the invention, which are explained below with reference to the figures.

• 1 shows a schematic longitudinal section through an embodiment of a cylindrical-conical bore with a circular-cylindrical first bore section on the inlet side and a conical second bore section remote from the inlet;
• 2 shows an embodiment of a honing tool when machining a cylindrical-conical bore;
• 3 schematically shows an example of a post-measurement strategy; and
• 4 shows a pneumatic plug gauge performing a measurement in the bore.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of honing methods are described below, which can be used within the scope of embodiments of the invention in order to produce rotationally symmetrical bores with an axial contour profile with high precision.

1 shows a schematic longitudinal section through an embodiment of such a bore 110 in a workpiece 100 in the form of an engine block (cylinder crankcase) for an internal combustion engine. The target shape of the bore is rotationally symmetrical with respect to its bore axis 112 and extends over a bore length L from a bore inlet 114 facing the cylinder head in the installed state to the bore outlet 116 at the opposite end. The bore can be divided into several adjacent sections different functions, which merge smoothly, ie without the formation of steps or edges.

A first bore section 120 at the inlet end has a first target diameter DS1 and a first length L1. The first target diameter is present over the entire first length L1, so that the first bore section has a circular-cylindrical shape. The first bore section transitions steplessly into an axially narrow transition section with a transition radius R1 into a second bore section 130, which extends from the transition section to the outlet-side end of the bore. The second bore portion 130 is generally conical or frusto-conical in shape and extends a second length L2. The second bore section consistently has an inside diameter (second target diameter) DS2 that is larger than the first target diameter DS1, with the second target diameter increasing continuously linearly in the axial direction, starting from the transition section toward the end of the bore. The cone angle α (angle between the axis of the bore and a surface line of the second bore section running in an axial plane) can be, for example, in the range of less than 1°, possibly also less than 0.2°. The difference between the target diameter DS1 in the cylindrical bore section and the target diameter at the bore exit 116 is referred to here as the target value for the "pre-width".

The first length L1 can be between 10% and 60% of the bore length L, for example. The second length L2 is typically greater than the first length and is often between 30% and 80% of the bore length L. The transition section is very short compared to the adjacent bore sections. Deviations from these geometric conditions are also possible.

The difference in diameter between the first target diameter DS1 and the second target diameter DS2 in parts further away from the inlet is well outside the tolerances typical for honing, which for a cylindrical shape are in the order of magnitude of a maximum of 10 μm (based on the diameter). With an absolute value of the inner diameter in the order of magnitude between 50 mm and 500 mm (the latter e.g. in ship engines), the maximum diameter difference (i.e. the front width) can be between 20 µm and 500 µm, for example.

The lengths of the outer bore sections and the radius of the transition section can be optimized in such a way that low blow-by, low oil consumption and low wear of the piston rings result in typical engine operating conditions.

The shape of the bore means that the bore is comparatively narrow in the area near the inlet, so that the piston rings of the piston running in the bore are pressed against the inner surface 118 of the bore under high ring stress. As a result, a reliable seal is achieved where combustion mainly occurs and high pressures occur, and the oil film is scraped off on the downstroke. The piston, which is accelerated by the combustion, then moves in the direction of the bore outlet, with the piston rings first passing through the transition section and then through the conical second bore section with the continuously expanding inner diameter. From the transition section, the piston rings can gradually relax, with the seal remaining adequate because the pressure difference across the piston rings decreases. At the end of the second bore section remote from the entry, the ring pack reaches its lowest stress. Then, on the upstroke, the ring tension gradually increases again until the piston rings reach the transition section and traverse it towards the first bore section. Furthermore, it is taken into account that an expansion of the cylinder liner caused by thermal influences is greater in the upper, cylindrical part of the bore than in the conical area. In the fired state, this results in a largely cylindrical or significantly less conical bore shape than in the cold state.

In a honing process for producing these cylindrical-conical bore shapes, in one exemplary embodiment, a continuous (over the entire bore length L) circular-cylindrical bore with a slight undersize relative to the target diameter SD1 is produced in the first bore section. A long-stroke honing tool with relatively long honing stones can be used for this purpose, for example. This honing operation can be performed as an intermediate honing operation after a previous pre-honing operation.

In a subsequent honing operation, with which, among other things, the conical shape that widens towards the end of the bore is produced in the second bore section, a honing tool of the type shown in 2 shown. The honing tool 200 has a single ring-shaped cutting group 220 with cutting material bodies distributed around the circumference of the tool body, which can be advanced or retracted in the radial direction to the tool axis 212 by means of a cutting material body infeed system (not shown in detail) (see double arrows). The cutting material bodies are designed as honing segments, the width of which in the circumferential direction is significantly greater than their length in the axial direction. As a result, the bodies of cutting material responsible for removing material from the workpiece are concentrated in an axially relatively narrow zone, ie a ring of the cutting group, and take up a relatively large proportion 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 in the axial direction border each other. In the example, the honing tool is coupled in an articulated manner to the honing spindle of a honing machine in order to permit limited mobility of the honing tool in relation to the honing spindle. For this purpose, a multi-axis joint 210 is formed on the spindle-side end of the honing tool, for example a cardan joint or a ball joint.

Other variants provide a rigid (non-joint) tool design in conjunction with a rigid drive rod, flex rod, or floating head rod.

In principle, all types of honing tools suitable for this process can be used, in particular honing tools such as those in WO 2014/146919 A1 are disclosed to the applicant. The relevant disclosure content of this application is incorporated into the content of the present description by reference.

In order to achieve the desired cylindrical-conical bore shape based on a continuously circular-cylindrical bore shape, the expansion of the honing tool can be controlled, for example, depending on the stroke, in such a way that the control of the infeed system for the radial infeed of the cutting material body can be combined with the control for the stroke position (in Axial direction) is coupled. This can be done, for example, in such a way that the infeed force and/or the infeed speed of cutting material bodies of the honing tool are controlled as a function of the stroke position of the honing tool. In the conical part (second bore section), the infeed force would then increase when the honing tool moves downwards (in the direction of bore outlet 116) and decrease when it moves upwards (in the direction of the first bore section). Other procedures are also possible, in particular those as in the WO 2014/146919 A1 are described.

After completion of the honing operation, through which the desired bore shape is produced, in preferred variants, a re-measuring operation is carried out on the finished workpiece at a separate measuring station from the honing unit. If the measurement shows that the values utilize the permitted tolerance range of the measured actual shape of the bore by more than 30%, 40%, 50% or 60% (e.g. with 40% utilization, there is a tolerance reserve of 30% for the upper and lower tolerance limit), corresponding compensation signals can be generated in order to work with changed honing parameters during the subsequent honing of a next bore and thereby achieve the desired target shape with better precision.

At one related to the Figures 3 and 4 In the honing process explained in more detail, measures are taken to ensure that the same ratio between the diameter dimensions of the circular-cylindrical first bore section 120 and the dimensions of the conical second bore section 130 always prevails within the scope of the tolerances. Furthermore, it should be ensured that the absolute values of the diameters in the circular-cylindrical bore section and in the conical bore section can be reliably recorded. In the event of deviations between the measured actual shape and the desired target shape that are outside the permitted range (compensation criterion), an automatic correction of the honing process is provided for the machining of subsequent bores.

In the example off 3 the diameter of the nominally circular-cylindrical first bore section 120 is measured in three measuring planes M1-1, M1-2 and M1-3 that are axially offset relative to one another. These are at equal axial distances, each offset axially from one another by a first measurement interval MI-1. The corresponding diameter values are denoted as D1, D2 and D3. The average of these three measurements gives the effective first diameter D _eff according to the rule D _eff = (D1+D2+D3)/3. The effective diameter is saved as the first diameter value to describe the actual shape. The individual measured values D1, D2 and D3 are also saved together with the associated axial positions of the measuring planes. The first diameter value D _eff determined in this way serves as a reference for the diameter values in the conical second bore section.

To measure the conical second bore section 130, diameter measurements are carried out in three second measuring planes M2-1, M2-2 and M2-3, which are axially offset from one another, in order to determine the associated second diameter values D4, D5 and D6. The second measurement planes are at equal axial distances from each other, offset axially by a second measurement interval MI-2. The second diameter values (D4, D5 and D6) obtained in this way are then automatically evaluated in a comparison operation using the first diameter value (D _eff ) in order to determine actual shape values which represent the present cylindrical-conical actual shape of the bore. Shape deviation values are determined from a comparison of the actual shape values with the target shape values specified by the specification. Subsequent honing operations are then controlled depending on the form error values. This makes it possible, among other things, to carry out diameter compensation in the event of diameter deviations of the conical bore section in relation to the cylindrical part of the cylinder bore (first bore section).

Alternatively or additionally, the effective diameter D _eff , which was determined for the cylindrical first bore section 120, can be compared with that diameter value D6 which was determined in the second measurement plane M2-3 furthest away from the entrance to the borehole in an end section EA of the second borehole section remote from the borehole. If the axial position of the measuring plane M2-3 is known, the difference between the effective diameter D _eff in the first bore section and the diameter D6 in the lowest measuring plane M2-3 can be used to calculate the actual pre-width of the bore shape, i.e. the actual pre-width. If necessary, the difference between the actual pre-width and the target pre-width is compensated for in the next processing cycle. The same applies to diameter deviations in the cylindrical area.

A possible correction scenario or compensation scenario is explained below using Table 1. The starting point here is a honing process in which a circular-cylindrical bore shape is first produced in an intermediate honing operation ZH by means of honing and then the desired bore shape with a cylindrical first bore section and conical second bore section is produced in a form honing operation FH by axially different amounts of material removal in the second bore section is produced. Table 1 Eg KB COMP ZH COMP FH Ø OK Volkswagen too big 0 - Ø OK Volkswagen too small 0 + Ø too big Volkswagen too big - - / - Ø too big Volkswagen too small - + Ø too small Volkswagen too big + - Ø too small Volkswagen too small + + / + Ø too big VW ok - - Ø too small VW ok + +

In the column headings in the table, the circular-cylindrical first bore section or the cylindrical area is abbreviated to "ZB" and the conical second bore section or the conical area to "KB". The abbreviation KOMP-ZH stands for a compensation in the Intermediate honing stage, while the abbreviation KOMP-FH stands for compensation in the form honing stage. The term compensation here means that the honing parameters are changed in relation to the honing parameters of the previous machining in order to avoid or reduce a determined deviation from the desired shape as far as possible during the next honing machining. The abbreviation VW stands for the determined actual value of the front width. In the columns on the right, "0" means that there is no adjustment or compensation, while "+" means that the compensation is advanced and "-" means that the compensation is deferred. Where there are two "+" signs or two "-" signs in the right column, a double correction step is performed to compensate for the shift in the intermediate honing stage ZH when compensating both in the cylindrical area and in the conical area must become.

The second line shows, for example, which measures are initiated by the control if the measurement shows that the diameter (symbol "Ø") in the cylindrical area ZB is in order ("OK") or within the tolerances, however, the front width VW is too small. In this case, the intermediate honing operation ZH remains unchanged when machining the subsequent workpiece (compensation = "0"), while the honing parameters for form honing FH are changed in the sense of an idea of the compensation so that there is a greater widening in the direction of the far entry Bore end results. The other rows of the table are to be interpreted accordingly.

For permanent recording of the bore geometry during form honing during series operation, a machining system is provided with a measuring station downstream of the honing machine, in which the finished honed components can be measured using a pneumatic measuring mandrel (i.e. by air measurement). The measurement results are fed back into the control of the honing machine in order to be able to react immediately to any deviations in shape when machining the next workpiece. The measuring station is configured in such a way that the axial contour can also be recorded and selected.

If a measuring system, for example, with a pneumatic measuring mandrel 400 according to 4 is available, the system can also be used to record the axial contour in the cylinder bore by changing the control software, ie by changing the test plan. In the embodiment of 4 two measuring channels are available, each with two measuring nozzles 410-A1, 410-A2 (measuring direction A) and 410-B1 arranged diametrically opposite one another in order to be able to measure the diameter in two measuring directions A and B perpendicular to one another.

Pneumatic plug gauges work according to the nozzle flapper principle. For the measurement, compressed air is blown out of the measuring nozzles in the direction of the bore wall. The resulting dynamic pressure in the area of the measuring nozzles can serve as a measure for the distance between the measuring nozzle and the wall of the bore. A transducer connected to the measuring nozzle via a pressure line converts the (pneumatic) pressure signal into a voltage signal that can be further processed electrically. Instead of the pressure, the volume flow of the compressed air can also be used for evaluation. By means of two diametrically opposed measuring nozzles, the bore diameter in the measuring plane can be determined at a given diametrical distance between the measuring nozzles. Pneumatic plug gauges enable non-contact measurement regardless of the material of the measurement object and, within the scope of their measurement range, high measurement accuracies, which in the case of final measurement units are usually well below a micrometer, for example in the range of 0.2 µm to 0.3 µm with repeated measurements .

Deviating from the schematic representation in 3 In a preferred method, the measurement is controlled in such a way that the axial measurement intervals MI-2 between immediately consecutive measurement planes in the second bore section 130, in which the diameter changes continuously, for example, are smaller than the measurement intervals MI-1 in the circular-cylindrical first bore section 120, in which the diameter is nominally the same in all axial positions. For example, the conical shape of the bore, which deviates from the circular-cylindrical shape, can be recorded very precisely by a measuring interval of, for example, 3 mm in the second bore section 130 . In combination with a larger measurement interval (eg 10 mm) in the circular-cylindrical first bore section 120, detection and evaluation over the entire bore length L is also possible. Permissible minimum and maximum values are specified for each measuring point or each measuring plane. In the event of deviations, compensation takes place on the respective honing spindle, for example in the manner explained in connection with Table 1. In addition, the values of a hole can be further processed, displayed in a diagram and permanently stored in a database.

With currently available air measurement systems, a dwell time in the respective measurement level of the order of 0.5 s can be sufficient to obtain sufficiently accurate measurement values. This makes it possible to reliably measure the diameter in a standard cycle time of 25 to 30 s, for example. The direction of measurement can also be freely selected, so that measurements can be taken both from the entry-side end to the end far from the entry and from the (wider) end far from the entry to the (narrower) bore entry.

In the embodiment illustrated by way of example, the desired axial contour in the second bore section is the contour of a simple cone with a continuous (linear) increase in diameter from the end of the first bore section in the direction of the end of the bore. Other bore shapes are also possible, e.g. a trumpet shape or a bell shape or bottle shape of a bore. In the case of a bottle shape, for example, a conical second bore section could be adjoined in the direction of the bore end remote from the inlet, which third bore section is circular-cylindrical or can have a different cone angle than the second bore section.

Claims (10)

1. Honing method for machining the inner surface of a bore (110) in a workpiece (100) with the aid of at least one honing operation, in particular for honing cylinder walls in the production of cylinder blocks or cylinder sleeves for reciprocating piston engines, wherein

   during a honing operation an expandable honing tool (200) which is coupled to a spindle is moved in a reciprocating manner within the bore so as to generate a stroke movement in the axial direction of the bore and, so as to generate a rotating movement that superimposes the stroke movement, is simultaneously rotated about a tool axis, and

   a bore which is rotationally symmetrical in relation to a bore axis (112) and deviates from the circular-cylindrical shape, has a circular-cylindrical first bore portion (120) and adjoining thereto a second bore portion (130) which is not circular-cylindrical and has an axially variable diameter is generated, characterized by the following steps:

   measuring the diameter of the first bore portion (120) in at least one first measuring plane (M1-1, M1-2, M1-3) so as to determine a first diameter value;

   measuring the diameter of the second bore portion (130) in at least one second measuring plane (M2-1, M2-2, M2-3) so as to determine a second diameter value;

   evaluating the second diameter value while using the first diameter value in order to determine actual shape values which represent an actual shape of the bore,

   wherein the first diameter value determined in the circular-cylindrical first bore portion is utilized as the reference value for evaluating those diameter values that by measuring are determined in the second bore portion which is not circular-cylindrical in such a manner that the first diameter value serves as the workpiece-internal reference for the entire measurement;

   comparing the actual shape values with nominal shape values in order to determine shape deviation values;

   controlling a subsequent honing operation as a function of the shape deviation values.
2. Honing method according to Claim 1, wherein when measuring the diameter of the first bore portion in two or more first measuring planes (M1-1 to M1-3) that are axially mutually offset, a first diameter is in each case measured, and a mean value of the first diameters is formed for determining the first diameter value, wherein the first diameter is preferably measured in exactly three measuring planes that are axially mutually offset.
3. Honing method according to Claim 1 or 2, wherein when measuring the diameter of the second bore portion (130) in two or more second measuring planes (M2-1, M2-2, M2-3) that are axially mutually offset, a second diameter is in each case measured, and an axial contour profile of the second bore portion is determined while using the second diameter.
4. Honing method according to one of the preceding claims, wherein when measuring the diameter of the second bore portion (130), a second diameter (D6) is measured in an end portion (EA) of the second bore portion that is distal from the first bore portion (120), and a preliminary width value is determined from the second diameter in the end portion and the first diameter value, wherein the preliminary width value is defined as the difference between the bore diameter at the entry-distal bore end and the bore diameter in the cylindrical bore portion.
5. Honing method according to one of the preceding claims, wherein first diameter values and second diameter values of a bore in the form of a dataset representing the actual shape of the bore are stored in a memory of a control installation.
6. Honing method according to one of the preceding claims, wherein associated diameter values in one measuring plane are measured in two measuring directions running so as to be mutually perpendicular.
7. Honing method according to one of the preceding claims, wherein in measurements in a plurality of measuring planes of the first bore portion (120) and of the second bore portion (130), an axial measuring interval (MI-2) between adjacent second measuring planes is smaller, in particular smaller by half, than an axial measuring interval (MI-1) between adjacent first measuring planes.
8. Honing method according to one of the preceding claims, wherein the measurements are carried out using a pneumatic measuring system.
9. Machining system for precision machining of an inner surface of a bore (110) in a workpiece (100) with the aid of at least one honing operation, in particular for honing cylinder walls in the production of cylinder blocks or cylinder sleeves for reciprocating piston engines, having at least one spindle for moving within the bore an expandable honing tool (200) coupled to the spindle in such a manner that machining of the inner surface takes place by at least one cutting stone attached to the honing tool, characterized in that the machining system has a controller and a measuring system for measuring the diameter of the bore and is configured for carrying out on the workpiece a honing method according to one of Claims 1 to 8.
10. Machining system according to Claim 9, characterized by a post-measurement station which is separate from a honing unit and to which the workpiece is able to be transferred upon completion of the machining for the measurement.

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