U.S. patent application number 14/777996 was filed with the patent office on 2016-10-20 for honing method and honing tool.
This patent application is currently assigned to ELGAN-Diamantwerkzeuge GmbH & Co. KG. The applicant listed for this patent is ELGAN-DIAMANTWERKZEUGE GMBH & CO. KG. Invention is credited to Oliver BACHMANN, Florian KRANICHSFELD, Herbert RAUSCHER, Fabio Antonio Xavier.
Application Number | 20160303702 14/777996 |
Document ID | / |
Family ID | 50238395 |
Filed Date | 2016-10-20 |
United States Patent
Application |
20160303702 |
Kind Code |
A1 |
Xavier; Fabio Antonio ; et
al. |
October 20, 2016 |
Honing Method and Honing Tool
Abstract
In a honing method for machining the internal surface of a bore
in a workpiece with the aid of at least one honing operation,
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. In the process, 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. During at least one honing operation, use is
made here of an annular tool (200) which has at least one annular
cutting group (220) having a plurality of radially infeedable
cutting material bodies which are distributed around the
circumference of a tool body 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.
The method is particularly suitable for honing cylinder faces
during the production of cylinder blocks or cylinder liners for
reciprocating piston engines.
Inventors: |
Xavier; Fabio Antonio;
(Nurtingen, DE) ; BACHMANN; Oliver;
(Frickenhausen, DE) ; KRANICHSFELD; Florian;
(Oberboihingen, DE) ; RAUSCHER; Herbert;
(Metzingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ELGAN-DIAMANTWERKZEUGE GMBH & CO. KG |
Nurtingen |
|
DE |
|
|
Assignee: |
ELGAN-Diamantwerkzeuge GmbH &
Co. KG
Nurtingen
DE
|
Family ID: |
50238395 |
Appl. No.: |
14/777996 |
Filed: |
March 10, 2014 |
PCT Filed: |
March 10, 2014 |
PCT NO: |
PCT/EP2014/054542 |
371 Date: |
July 6, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24B 33/088 20130101;
B24B 33/02 20130101 |
International
Class: |
B24B 33/02 20060101
B24B033/02; B24B 33/08 20060101 B24B033/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2013 |
DE |
10 2013 204 714.2 |
Claims
1. A 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 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 which has at least one
annular cutting group having a plurality of radially infeedable
cutting material bodies which are distributed about the
circumference of a tool body 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. The honing method as claimed in claim 1, wherein 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. The honing method as claimed in claim 2, wherein, 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. The honing method as claimed in claim 2, wherein, 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. The honing method as claimed in claim 4, wherein, 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.
6. A honing tool, in particular for carrying out the honing method
as claimed in claim 1, with a tool body which defines a tool axis,
at least one cutting group 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, wherein the honing tool is designed as
an annular tool and has at least one annular cutting group having
three or more radially infeedable cutting material bodies which are
distributed around the circumference of the tool body 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. The honing tool as claimed in claim 6, wherein the axial length
of the honing segments is less than 30% of the effective outside
diameter of the honing tool, and/or the axial length of the honing
segments lies within the range of 5 mm to 20 mm, and/or the axial
length of the honing segments is less than 10% of the bore length
of the bore to be honed.
8. The honing tool as claimed in claim 6, wherein more than half of
the circumference of an annular cutting group is occupied with
cutting material bodies.
9. The honing tool as claimed in claim 6, wherein a cutting group
is composed of three, four, five or six honing segments.
10. The honing tool as claimed in claim 6, wherein the cutting
group 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. The honing tool as claimed in claim 6, wherein the annular tool
has a single annular cutting group which is arranged at a free end
of the tool body.
12. The honing tool as claimed in claim 6, wherein an annular
cutting group has two groups of honing segments which are
infeedable independently of each other, wherein honing segments of
the groups are arranged in an alternating manner in the
circumferential direction.
13. The honing tool as claimed in claim 6, wherein the annular tool
has a first annular cutting group and at least one second annular
cutting group which is arranged axially offset with respect to the
first annular cutting group and is infeedable independently of the
first annular cutting group.
14. The honing tool as claimed in claim 6, wherein one or more
sensors of a diameter measuring system are arranged on the honing
tool, wherein measuring nozzles of a pneumatic diameter measuring
system are in each case attached to the tool body.
15. The honing tool as claimed in claim 6, wherein an integrated,
multiaxially movable joint is provided on the tool body.
16. The honing method as claimed in claim 5, wherein, during the
smoothing honing operation, the cutting material bodies are pressed
at a constant infeed force on to the internal surface of the
bore.
17. The honing tool as claimed in claim 7, wherein the axial length
of the honing segments is between 10% and 20% of said outside
diameter.
18. The honing tool as claimed in claim 8, wherein more than 70% of
the circumference of an annular cutting group is occupied with
cutting material bodies.
19. The honing tool as claimed in claim 13, wherein the annular
tool has precisely two annular cutting groups.
20. The honing tool as claimed in claim 14, wherein the measuring
nozzles of a pneumatic diameter measuring system are in each case
attached to the tool body between adjacent honing segments.
21. The honing tool as claimed in claim 15, wherein the integrated,
multiaxially moveable joint is a ball and socket joint.
Description
BACKGROUND
[0001] The invention relates to a honing method for machining the
internal surface of a bore in a workpiece with the aid of at least
one honing operation according to the preamble of claim 1, and to a
honing tool, which is usable for carrying out the honing method,
according to the preamble of claim 6. A preferred field of use is
the honing of cylinder faces during the production of cylinder
blocks or cylinder liners for reciprocating piston engines.
[0002] The cylinder faces in cylinder blocks (cylinder crank cases)
or cylinder liners of internal combustion engines or other
reciprocating piston engines are exposed to a severe tribological
stress during operation. During the production of cylinder blocks
or cylinder liners, said cylinder faces therefore have to be
machined in such a manner that sufficient lubrication by means of a
lubricant film is subsequently ensured under all operating
conditions and the frictional resistance between parts moving
relative to one another is kept as low as possible.
[0003] The quality-determining finish-machining of such
tribologically stressable internal surfaces generally takes place
with suitable honing methods which typically comprise a plurality
of successive honing operations. Honing is a cutting process using
geometrically undefined cutting edges. During a honing operation,
an expandable honing tool is moved up and down or to and fro within
the bore to be machined in order to produce a reciprocating
movement in the axial direction of the bore at a reciprocating
frequency and at the same time is rotated in order to produce a
rotational movement, which is combined with the reciprocating
movement, with a rotational frequency. The cutting material bodies
attached to the honing tool are pressed against the internal
surface to be machined by an infeed system having an infeed force
acting radially with respect to the tool axis. During the honing, a
cross-grinding pattern which is typical of the honing machining and
has intersecting finishing marks, which are also referred to as
"honing grooves" is produced on the internal surface.
[0004] With increasing requirements for economy and environmental
friendliness of engines, the optimization of the tribological
system of piston/piston rings, cylinder face is of particular
importance in order to achieve a low level of friction, low level
of wear and low oil consumption. The friction portion of the piston
group can be up to 35%, and therefore reduction of friction in this
region is desirable.
[0005] Different approaches for reducing the mechanical losses of
an engine are pursued. These include, inter alia, the use of
thermally sprayed cylinder faces, the use of coated piston rings,
the development of particularly optimized honing surfaces, etc.
[0006] A technology which is gaining increasing importance for
reducing the friction and the wear is the avoidance or reduction of
cylinder distortions or deformations of the engine block (cylinder
crank case) during assembly and/or during operation. After
conventional honing machining, a cylinder bore is intended
typically to have a bore shape which deviates as little as
possible, for example at maximum a few micrometers, from an ideal
circular-cylinder shape. However, during the assembly or the
operation of the engine, it is possible for significant shape
errors to occur which amount to up to several hundredth of a
millimeter and may reduce the performance of the engine. The causes
of distortions or deformations differ. They may involve static or
virtually static thermal and/or mechanical loads or dynamic loads.
The construction and the design of cylinder blocks also have an
effect on the deformation tendency. The sealing function of the
piston ring package is typically made worse by such deformations
which can be difficult to control, as a result of which the
blow-by, the oil consumption and also the friction may
increase.
[0007] In order to reduce problems due to distortions during
assembly or in certain operating states, it has been proposed, for
example, in DE 28 10 322 C2 to use a tensioning device to deform
the engine block for the honing machining in such a manner that the
subsequent deformation is simulated by the cylinder head. In the
braced state which corresponds to the state subsequently present
after assembly, honing machining takes place in order to produce a
circular-cylindrical bore shape which is then also intended to be
set again after the assembly.
[0008] Another technology which, by inverting the cylinder
distortions (production of a negative shape of the error) during
the machining, is intended to ensure or approximate the production
of an ideal shape after the assembly or in the operating state of
the engine is what is referred to as shape honing. A bore shape
deviating in a defined manner from the circular-cylinder shape, for
example a clover leaf shape, is produced here on the unbraced
workpiece by means of honing. Such bore shapes are generally
asymmetrical because the deformations of the cylinder block are
generally also not symmetrical. In the operating state, an ideal a
circular-cylinder shape as possible is intended to be produced such
that the piston ring package can provide a good seal over the
entire circumference of the bore. Various variants of shape honing
are described, for example, in EP 1 790 435 B1 and in the prior art
mentioned therein.
Problem and Solution
[0009] It is a problem of the present invention to provide a honing
method of the type in question and a honing tool usable for
carrying out said honing method, said honing method and honing tool
making it possible to produce reciprocating piston engines which
have improved properties in respect of friction losses, oil
consumption and blow-by.
[0010] In order to solve this problem, the invention provides a
honing method with the features of claim 1. Furthermore, a honing
tool with the features of claim 6, which can be used within the
scope of the honing method, is provided.
[0011] Advantageous developments are specified in the dependent
claims. The wording of all of the claims is provided by reference
to the contents of the description.
[0012] In the honing method, a bottle-shaped bore, i.e. a bore
having a bottle shape, is produced. A "bottle-shaped bore" has,
directly 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
diameter to the second diameter between the first and the second
bore section. The first bore section and the second bore section
generally have a circular-cylindrical basic shape and lie coaxially
with respect to each other. The transition section can be partially
conically formed and can merge at the ends thereof which face the
outer bore sections into the adjacent bore sections, in each case
with suitable radii.
[0013] Given a suitable configuration of the bottle-shaped macro
shape, substantial advantages can be obtained with respect to
reduction of friction, reduced blow-by and reduced oil consumption.
Furthermore, improvements in the wear resistance of the piston ring
package and positive influences on the production of noise during
the operation can be produced. A substantial part of the combustion
in an internal combustion engine takes place in the relatively
narrow first bore section in the vicinity of the bore inlet, i.e.
in the "bottle neck". A possible high provision of oil in this
section could lead to emission and oil consumption problems. In
this narrower first bore section, the annular package of the piston
rings can readily carry out the conventional functions thereof (in
particular the sealing against combustion gases and the scraping
off of the oil film in the return movement) because of a relatively
high edge stress. By means of the pressure waves of the combustion,
the piston is accelerated in the first bore section and reaches the
transition section with a gradually increasing diameter. In the
transition section, the piston ring tension is reduced by
increasing the diameter. Since, however, a considerable piston
speed is already present here and the internal pressure in the
cylinder space is diminished, blow-by, oil consumption value and
engine noise emission are not adversely affected. By means of
suitable radii between the transition section and the adjacent
first and second bore sections, a gentle entry and exit of the
piston rings can be achieved at the transition section, and
therefore ring wear or engine seizures can be avoided. In the
downward movement, the annular package, after passing through the
transition section, reaches its lowest tension on entry into the
second bore section, and therefore the friction loss is
automatically reduced at the point at which the piston reaches its
maximum speed.
[0014] Within the context of the honing method, which leads to a
bottle-shaped bore with a surface structure optimum for use, during
at least one honing operation use is made of a honing tool which is
particularly suitable for this purpose and which is also referred
to here because of the construction thereof as an "annular tool".
An "annular tool" within the context of this application has at
least one annular cutting group having three or more radially
infeedable cutting material bodies which are distributed around the
circumference of the tool body of the honing tool and are
configured as honing segments which are relatively wide in the
circumferential direction of the honing tool and are relatively
narrow in the axial direction of the honing tool. The axial length
of the honing segments, as measured in the axial direction of the
honing tool, is smaller here 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.
[0015] If at least three honing segments are provided, the
machining forces can be distributed readily over the entire
effective outside diameter region, which is available because of
radial infeeding, of the honing tool and relatively uniformly over
the circumference. For example, precisely three, precisely four,
precisely five or precisely six honing segments of identical or
different circumferential width can be provided in a cutting group.
Although more than six honing segments within a cutting group are
possible, these make the construction more complicated and are
generally not required. In some cases, it may optionally suffice if
the honing tool has only two honing segments.
[0016] The effect which can be achieved by the radial infeedability
(displacement of the honing segments in the radial direction during
the infeeding) is that the engagement conditions between cutting
material body and bore internal surface remain virtually constant
irrespective of the diameter set. Nonuniform wear can be avoided by
avoiding tilting of the cutting material bodies during the radial
infeeding.
[0017] The measures can have a positive effect individually and in
combination on the surface quality which can be achieved, in
particular with regard to the uniformity of the surface quality
over different bore sections.
[0018] The axial length of the honing segments can be, for example,
less than 30% of the effective outside diameter of the honing tool,
in particular can be between 10% and 20% of said outside diameter.
In the case of annular tools for machining typical cylinder bores
in engine blocks for passenger vehicles or trucks, the axial length
can be, for example, within the range of 5 mm to 20 mm. Based on
the bore length of a bore to be machined, the axial length is
typically less than 10% of said bore length. If the upper limits
are significantly exceeded, the possibility for axial following of
the contours or production of the contours generally suffers. In
addition, small axial lengths are advantageous in order to produce
a sufficient surface pressure for the machining. On the other hand,
a minimum length in the axial direction is advantageous in order to
permit a honing overrun for machining the bore ends and in order to
limit a tendency of the honing tool to tilt.
[0019] An annular tool of this type constitutes a reversal of
conventional concepts of the configuration of a honing tool that
are based on the fact that, in order to obtain small shape errors
in a honed bore, honing tools having honing sticks which are
relatively long in the axial direction, but are relatively narrow
in the circumferential direction should be used. An annular tool is
particularly readily adapted to the machining of bottle-shaped bore
shapes or in general of bore shapes having a bore diameter which
significantly varies in the axial direction. In an annular cutting
group, the cutting material (bonded cutting grains of suitable
grain size, density and hardness) is concentrated in an axially
relatively narrow ring, wherein typically more than half of the
circumference of an annular cutting group is occupied with cutting
means and accordingly effectively contributes to the removal of
material.
[0020] In comparison to the effective outside diameter of the
honing tool, the cutting region in which one or more annular
cutting groups lie is short or narrow in the axial direction, as a
result of which the production and/or following of a contour
running in the axial direction is possible.
[0021] In comparison to conventional honing sticks, an annular
cutting group is distinguished in that there is substantially more
contact surface between cutting material bodies and bore internal
surface in the axial section covered by the annular cutting group
than in a comparatively narrow axial section of a conventional
honing tool. In some embodiments, with an annular cutting group,
more than 60% of the circumference, possibly even more than 70% or
more than 80% of the circumference of the honing tool is occupied
with cutting means.
[0022] A cutting group is preferably arranged in the vicinity of a
spindle-remote end of the tool body in such a manner that the
cutting group is exclusively located in the spindle-remote half of
the tool body. If a plurality of annular cutting groups are
provided, this condition can apply to all cutting groups. An
arrangement in the vicinity of the spindle-remote end permits,
inter alia, machining operations with a very small honing
overrun.
[0023] During honing machining, the stroke position of the honing
tool within the bore can be used as a command variable in order,
with high local resolution, to predetermine the press-on pressure
or the infeed force as a function of the stroke position of the
annular cutting group. As a result, it is possible, with the aid of
an infeedable annular cutting group, to produce a bore with an
axially variable contour or else to follow an already previously
produced, axially varying contour without undesired contact
pressure force peaks. When an annular tool is used, the operation
can be carried out in all axial regions of the bore with
substantially identical overlap such that, when the need arises,
highly uniform roughness images or surface structures can be
produced. When an annular tool is used, the operation can
optionally also be carried out with a very small honing overrun at
the axial ends of a bore without problems with nonuniform wear of
the cutting bodies occurring.
[0024] The operation is preferably carried out with an
electromechanical cutting-group infeed system. In contrast to a
hydraulic expansion, a precise predetermination of the infeed
travel (travel control) is thereby possible, as a result of which
an axial contour can be produced in a specific manner and/or a
predetermined axial contour can be precisely followed.
[0025] One or more sensors of a diameter measuring system can be
arranged on the honing tool, and therefore an in-process diameter
measurement is possible. For example, measuring nozzles of a
pneumatic diameter measuring system can be attached in each case to
the tool body between adjacent honing segments. By this means, the
precision of the bore contours which can be achieved can be
improved.
[0026] By means of the use of an annular tool, uniform wear of the
cutting material bodies and very good shape values and uniform
surface roughnesses of the bore are ensured over the entire surface
life of the annular cutting group.
[0027] Different configurations of annular tools are possible,
between which a user can choose depending on the machining task to
be carried out.
[0028] In some embodiments, the annular tool has a single annular
cutting group, the honing segments of which can be fed in radially
or pulled back via a single common infeed system. The annular
cutting group typically has three or more, generally no more than
six, honing segments distributed uniformly or nonuniformly over the
circumference of the honing tool. The single annular cutting group
is preferably arranged in the vicinity of the spindle-remote free
end of the tool body, for example flush with the spindle-remote end
side. Constructions of this type are particularly readily suitable
for machining cylinder bores with a reduced honing overrun.
Restrictions of this type in the machining arise, for example, in
the case of blind hole bores or in the case of cylinder bores in
engine blocks for monoblock engines or V engines.
[0029] It is also possible for an annular cutting group to have two
groups of honing segments which are infeedable independently of
each other, wherein the honing segments of the groups are arranged
in an alternating manner in the circumferential direction. By this
means, it is possible to combine the advantages of a single annular
cutting group (for example with respect to the machining of bores
with a short honing overrun) with the advantages of a double
infeeding of two groups of honing segments which are independent of
each other. With a tool of this type, two consecutive honing
operations can be carried out with different cutting materials
without an intermediate changing of the tool. The honing segments
of one group of honing segments normally have the same cutting
layer while the groups have cutting layers which differ from one
another, for example diamond layers of different grain size.
[0030] It is also possible for an annular tool to have a first
annular cutting group and at least one second annular cutting group
which is arranged in a manner offset axially with respect to the
first annular cutting group and can be infed independently of the
first annular cutting group. By this means, two consecutive honing
operations are also possible with different cutting materials
without an intermediate changing of the tool. Since the different
cutting materials are distributed to the at least two annular
cutting groups which are offset axially in relation to each other
and can each cover a large part of the circumference of the honing
tool, particularly high removal capacities or relatively short
honing times are possible here in both honing operations. Annular
tools of this type can be used for all bores which permit a
sufficient honing overrun. With two or more annular cutting groups,
bridging of pulsation windows or transverse bores or bore
interruptions of any type is also possible in a particularly simple
manner. Such an annular tool preferably has precisely two annular
cutting groups, as a result of which flexible use is possible
despite a simple construction.
[0031] In preferred embodiments, an integrated, multiaxially
movable joint, for example a ball and socket joint or a cardanic
joint, is provided on the tool body. Position errors of the machine
and/or a core offset of the bore can thereby be compensated for
without changing the bore position. Exemplary embodiments without a
joint are also possible. Annular tools of this type can be coupled
rigidly to a honing spindle or to a drive rod coupled rigidly to
the honing spindle.
[0032] The bottle shape of the bore can be produced by any suitable
chip-removing machining method, for example by precision turning
(precision spindles), i.e. with the aid of a machining method with
a geometrically determined cutting edge, or by means of honing.
This can be followed by one or more honing operations in order to
arrive at the finally desired bore geometry with a suitable surface
structure.
[0033] A bore with a circular-cylindrical bore shape is preferably
initially produced by precision turning or honing and then, in a
bottle honing operation, a bottle-shaped bore shape is produced by
honing with axially varying honing removal. In comparison to
precision turning, surfaces can be produced with a particularly
uniform surface quality without peripheral marks by means of
honing. The self-sharpening effect of the cutting material bodies
also contributes to the uniformity of the surface quality. In the
case of honing, continuous process monitoring is possible.
[0034] In a method variant, during the bottle honing operation, use
is made of an expandable honing tool having at least one annular
cutting group, i.e. an annular tool. Honing segments of the cutting
group are infed radially outward here in a travel- and/or
force-controlled manner in a downward stroke in accordance with the
bottle shape depending on the stroke position and, during an upward
stroke, are retracted radially in accordance with the bottle shape
depending on the stroke position. By means of this machining
variant, a relatively smooth contour profile is produced from the
outset in the transition section which is particularly difficult to
machine.
[0035] Alternatively, it is also possible 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. The length of the honing sticks can be, for example,
between 50% and 80% of the length of the bore. During the bottle
honing operation, in a first phase, the honing tool is then moved
up and down or to and fro between an upper and a lower reversing
point in a first stroke position, in order to bring the bore
initially over the entire length thereof into a
circular-cylindrical shape. Then, in a second phase, the upper
reversing point is changed incrementally, i.e. by a plurality of
strokes, in the direction of the lower reversing point, and
therefore the stroke length is gradually reduced. As a result, the
stroke position is shifted in the direction of a second stroke
position which lies in the region of the second bore section. In a
third phase, the honing tool is then moved to and fro in the second
stroke position. In this method variant, the basic shape of the
transition section is substantially produced during the second
phase of the gradual shifting of the stroke position and reduction
in the stroke height, wherein the increase in diameter in the
second bore section is also produced both at the same time and in
the third phase.
[0036] If the bottle honing operation is carried out by means of a
honing tool having relatively long honing sticks, a relatively
rough surface structure with a profile similar to a saw profile can
be produced in the transition section. In order also to obtain the
desired uniform surface structure in the transition section, a
smoothing honing operation for smoothing the bore profile in the
transition region is therefore carried out preferably after the
bottle honing operation, wherein an annular tool is used in the
smoothing honing operation, i.e. an expandable honing tool with at
least one annular cutting group. With the aid of the annular tool,
grooves or burrs in the transition section can be eliminated and
the radii of the transition section can be rounded.
[0037] It has proven advantageous if, during the smoothing honing
operation, the cutting material bodies of the annular cutting group
are pressed with a constant infeed force onto the internal surface
of the bore. This is achieved in some method variants in that use
is made of a honing machine having a hydraulic infeed system for
the annular tool. The following of the contour of the bottle-shaped
bore by the honing segments of the annular tool can already be
produced here from the design-induced flexibility of the hydraulic
expansion.
[0038] The invention also relates to a honing tool which is
suitable particularly for carrying out the honing method, but can
also be used in other honing methods which are not according to the
invention.
[0039] The invention also relates to a workpiece with at least one
bore which has a honed internal surface, wherein the bore is a
bottle-shaped bore which, following a bore inlet, has 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 the workpiece has been machined using
a honing tool according to the invention.
[0040] In particular, the workpiece can be a cylinder block or a
cylinder liner for a reciprocating piston machine. The
reciprocating piston machine can be, for example, an internal
combustion engine (combustion engine) or a compressor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 shows a schematic longitudinal section through a
bottle-shaped cylinder bore in an engine block;
[0042] FIG. 2 shows, in 2A, a longitudinal section through an
embodiment of an annular tool with single expansion of a single
annular cutting group and, in 2B, a cross section through the
cutting group;
[0043] FIG. 3 shows, in 3A, a longitudinal section through an
embodiment of an annular tool with double expansion of a single
annular cutting group and, in 3B, a cross section through the
cutting group;
[0044] FIG. 4 shows, in 4A, a longitudinal section through an
embodiment of an annular tool with double expansion with two
annular cutting groups arranged one above the other and, in 4B, a
cross section through one of the cutting groups;
[0045] FIG. 5 shows schematically a longitudinal section through a
bore which is machined by means of a honing tool having relatively
long honing sticks;
[0046] FIG. 6 shows schematically the stroke position of a honing
tool having long honing sticks as a function of the honing time t
during the bottle honing operation;
[0047] FIG. 7 shows a measuring diagram of a rounded profile of a
bottle-shaped cylinder after the use of an annular tool;
[0048] FIG. 8 shows a schematic diagram which shows the dependency
of the stroke position HP (solid line) and the expansion position
AP (dashed line) as a function of the honing time t in a second
exemplary embodiment.
DETAILED DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS
[0049] The following is a description of exemplary embodiments of
honing methods and honing tools which can be used within the
context of embodiments of the invention during the
material-removing machining of workpieces which have one or more
bores which, in the end-machined state, are intended to have the
macroshape of a bottle.
[0050] FIG. 1 shows a schematic longitudinal section through one
such bottle-shaped bore 110 in a workpiece 100 in the form of an
engine block (cylinder crank case) for an internal combustion
engine. The bore is rotationally symmetrical with respect to the
bore axis 112 thereof and extends over a bore length L from a bore
inlet 114, which faces the cylinder head in the installed state, as
far as the bore outlet 116 at the opposite end. The bore can be
divided into three mutually adjacent sections of differing function
which merge in a sliding manner in one another, i.e. without the
formation of steps or edges.
[0051] A first bore section 120 at the inlet-side end has a first
diameter D1 and a first length L1. At the opposite, outlet-side
end, a second bore section 130, the inside diameter (second
diameter) D2 of which is larger than the first diameter D1, extends
over a second length L2. A partially conical transition section
140, in which a continuous transition from the first diameter to
the second diameter takes place, is located between the first bore
section 120 and the second bore section 130. A first radius R1 is
formed between the central, substantially conical part of the
transition section and the first bore section, while a second
radius R2 is formed between the transition section and the second
bore section. The radii R1 and R2 can be substantially identical,
but it is also possible for the first radius to be smaller or
larger than the second radius.
[0052] In the case of typical bore geometries, the first length L1
can be, for example, between 15% and 40% of the bore length L. The
second length L2 is typically larger than the first length and
frequently is between 40% and 60% of the bore length L. The
transition section is normally relatively short in relation to the
adjoining bore sections. Typical third lengths L3 can be within the
range of 5% to 20% of the bore length L. Deviations from said
geometrical ratios are also possible.
[0053] The diameter difference between the first diameter D1 and
the second diameter D2 lies significantly outside the tolerances
which are typical for the honing machining and, for a cylinder
shape, lie within the order of magnitude of at maximum 10 .mu.m
(based on the diameter). In the case of an absolute value of the
inside diameter in the order of magnitude of between 70 mm and 150
mm, the diameter difference can lie, for example, between 20 .mu.m
and 90 .mu.m.
[0054] The radii R1, R2, the lengths of the outer bore sections and
of the transition section and the tangent angle T between the bore
axis and a tangent to the transition section can be optimized in
such a manner that low blow-by, low oil consumption and low wear of
the piston rings are produced in typical operating states of the
engine.
[0055] The bottle shape of the bore results in the bore being
comparatively narrow in the region in the vicinity of the inlet,
and therefore the piston rings of the piston moving in the bore are
pressed against the bore internal surface 118 under high edge
stress. As a result, reliable sealing is achieved at the location
where the combustion primarily takes place and high pressures
occur, and the oil film is scraped off in the downward stroke. The
piston which is accelerated by the combustion then moves in the
direction of the bore outlet, with the piston rings first of all
running (partially) through the transition section with the
continuously widened inside diameter and subsequently through the
second bore section. The piston rings can gradually relax in the
transition section, with the sealing remaining to a sufficient
extent because the pressure difference drops at the piston rings.
At the beginning of the second bore section, the ring package
reaches the lowest stress thereof, and therefore friction losses
are reduced precisely in the region of maximum piston speed because
of reduced edge stress. During the upward stroke, the edge stress
then increases again as soon as the piston rings reach the
outlet-side radius of the transition section and run through the
latter in the direction of the first bore section.
[0056] A precision machining process which can economically produce
such a bore both with respect to the macroshape (bottle shape) and
with respect to the surface structure of the tribologically
stressed bore internal surface in high quality comprises, in the
embodiments of the invention, at least one honing operation, in
which use is made of a honing tool of particular construction which
is also referred to in this application as an "annular tool". An
annular tool has at least one cutting group which is attached
annularly to the tool body and has cutting material bodies which
are distributed around the circumference of the tool body and can
be infed in the radial direction by means of an associated infeed
system or retracted. The cutting material bodies are designed as
honing segments, the width of which is significantly larger in the
circumferential direction than the length thereof in the axial
direction. The cutting material bodies responsible for removing
material from the workpiece are concentrated in an axially
relatively narrow zone (a ring of the cutting group) and take up a
relatively large portion of the circumference of the honing tool.
As a result, bore shapes in which bore sections of differing
diameter are adjacent to one another in the axial direction can be
produced with a relatively high material removal capacity.
[0057] FIG. 2 shows, in 2A, a longitudinal section through an
embodiment of an annular tool 200 with a single annular cutting
group 220 and single expansion. FIG. 2B shows a cross section
through the cutting group. The annular tool 200 has a tool body 210
which defines a tool axis 212 which is at the same time the axis of
rotation of the ring tool during the honing machining. A coupling
structure (not illustrated specifically) for coupling the annular
tool to a drive rod of a honing machine or of another machining
machine which has a working spindle, which is both rotatable about
the spindle axis and also movable in an oscillating manner to and
fro parallel to the spindle axis, is located at the spindle-side
end of the annular tool (at the top in FIG. 2A).
[0058] The annular cutting group 220 which has a plurality (three
in the case of the example) of cutting material bodies 220-1,
220-2, 220-3, which are distributed uniformly over the
circumference of the tool body and can be infed outward radially
with respect to the tool axis 212 with the aid of a cutting
material body infeed system, in order to press the abrasively
acting outer sides of the cutting material body with a defined
contact pressure or press-on force against the internal surface of
a bore to be machined, is located at the spindle-remote end of the
tool body (at the bottom in FIG. 2A). Each of the three cutting
material bodies, which are curved arcuately, is designed as a
honing segment which is very wide in the circumferential direction
but is narrow in the axial direction and which covers a
circumferential angle region of between 115.degree. and
120.degree.. The honing segments are decoupled from the tool body
and are displaceable relative to the latter radially with respect
to the tool axis 212. The ring formed by the honing segments ends
at the spindle-remote side flush with the tool body such that the
ring sits completely within the spindle-remote half of the tool
body at the spindle-remote end of the annular tool.
[0059] The axial length LHS of the honing segments is less than
15%, in particular less than 10% of the bore length L. The height
of the honing segments is approx. 4 mm to 35 mm, in particular
approx. 10 mm (in the axial direction), which, in the case of the
example, corresponds to 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 at the same time to
the axial length of the entire cutting region of the honing
tool.
[0060] Each cutting material body is fastened by soldering to an
outer side of an associated steel support strip 224-1, 224-2.
Alternatively, the cutting material body can also be fastened by
adhesive bonding or by means of screws, as a result of which easier
replacement is possible. The inner side of each support strip has
an oblique surface which interacts with a conical outer surface of
an axially displaceable infeed cone 232 in such a manner that the
support strips with the cutting material bodies carried by them are
infed radially outward when the infeed cone is pressed in the
direction of the spindle-remote end of the annular tool counter to
the force of restoring springs 234, 226, 228 by means of a
machine-side infeed device. In the case of an opposed infeed
movement, the support strips are retrieved radially inwardly with
the honing segments with the aid of peripheral retrieving springs
226, 228. As a result, the radial position of the cutting material
bodies is controlled in a manner free from play via the axial
position of the infeed cone 232.
[0061] This tool concept is particularly suitable for machining
cylinder bores with a reduced honing overrun, for example with a
honing overrun of at maximum 5 mm. Geometries of this type
typically occur in the case of blind hole bores or in monoblock
engines or V engines.
[0062] FIG. 3 shows an exemplary embodiment of an annular tool 300
which likewise has a single annular cutting group 320 which is
arranged at the spindle-remote, end-side end of the tool body 310.
FIG. 3A shows a longitudinal section through the annular tool, FIG.
3B shows a cross section through the cutting group. However, in
contrast to the exemplary embodiment of FIG. 2, a honing tool with
double expansion is involved. The annular cutting group 320 has two
groups of honing segments which are infeedable independently of
each other, wherein the honing segments of the groups are each
arranged in an alternating manner with respect to one another in
the circumferential direction. A first group of honing segments has
three first honing segments 320-1 arranged offset circumferentially
with respect to one another by 120.degree. in each case. Three
second honing segments 320-2 of a second group of honing segments
are in each case arranged therebetween. The first group has cutting
material bodies with a relatively coarse cutting layer while the
second group has cutting material bodies with a cutting layer which
is relatively finer with respect thereto. Axial guide strips 326
are in each case arranged between directly adjacent honing
segments. A ball and socket joint 350 is provided between the tool
body 310 and the coupling structure 340, which is provided for
coupling the honing tool to a working spindle or the like, and
therefore the honing tool is movable to a limited extent in a
plurality of axes in relation to the honing spindle.
[0063] The first honing segments can be infed radially with the aid
of a first infeed system. The latter includes a first infeed rod
332-I which runs centrally on the tool body and, at the
spindle-remote end, has a conical section which interacts with the
oblique surfaces of support strips of the first group of honing
segments. A second infeed system serves for infeeding the second
group of honing segments and has a tubular infeed element 332-A,
which encloses the infeed rod 332-I and, at the spindle-remote end
thereof, has a conical outer surface which interacts with oblique
surfaces on the support strips of the second honing segments.
[0064] The three honing segments of the first group of honing
segments can be expanded with the aid of the first infeed system in
order to carry out a certain honing operation, for example a
smoothing honing operation or a structure honing operation. If,
instead, the other group of honing segments which have a different
type of cutting layer is infed, a different honing operation, for
example a deburring honing operation or a plateau honing operation,
can be carried out. With the aid of the annular tool with double
expansion, two different honing operations can be carried out
successively without in the meantime undertaking a change of tool
or using a different honing spindle for the machining.
[0065] FIG. 4 shows, in 4A, a schematic longitudinal section
through an embodiment of an annular tool 400 with double expansion,
which, in contrast to the exemplary embodiment of FIG. 3, has two
annular cutting groups 420-1 and 420-2 which are attached in a
manner offset axially with respect to each other in the
spindle-remote part of the tool body 410. Each of the annular
cutting groups (cross section in FIG. 4B) has three common
infeedable honing segments which each cover between approx.
110.degree. and 115.degree. of the circumference. By 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 region of the
cutting material bodies. Measuring nozzles 440 of a pneumatic
diameter measuring system are in each case attached to the tool
body between adjacent honing segments. The cutting groups are
located axially close to one another such that the cutting region
of the honing tool, in which the two annular cutting groups are
located, is substantially shorter in the axial direction than the
effective outside diameter of the honing tool.
[0066] In some embodiments, the cutting material bodies are mounted
in an elastically flexible manner with respect to the tool body. As
a result, the capability of following the contours during the axial
movement can optionally be improved. For example, spring elements
(for example, leaf springs, spiral compression springs or the like)
can be connected between the carrier elements and the cutting
material bodies. It is also possible to design the carrier elements
to be elastically flexible per se, for example by weakenings of the
carrier material cross section in the form of slots or the like
being structurally provided at suitable points.
[0067] There are various possibilities for producing bottle-shaped
bores with a desired surface structure of the bore internal surface
with the use of one or more annular tools of the type described in
this application. A first exemplary embodiment is described in
conjunction with FIGS. 5 and 6.
[0068] In the case of this method variant, first of all use has
been made of a conventional honing tool having axially relatively
long, narrow honing sticks in order, starting from a bore
premachined, for example, by precision drilling, to produce a honed
bore with a circular-cylinder shape. The axial stick length I was
approx. 1/2 to 2/3 of the entire bore length L here. In a first
honing operation (preliminary honing), the operation was carried
out using diamond sticks of type D107, and a subsequent
intermediate honing operation was carried out with a 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.sub.z<8
.mu.m) was produced. The inlet-side and outlet-side honing overrun
S here was approx. 1/3 of the stick length, similarly as in
conventional methods. The honing overrun can be reduced during the
machining of V- or monoblock engines.
[0069] A subsequent third honing operation was designed as a bottle
honing operation. With the aid of a bottle honing operation, a
bottle-shaped bore shape is produced by axially varying removal of
material using geometrically undefined cutting edges. In the third
honing operation (bottle honing operation), the operation was
likewise carried out with relatively long honing sticks with a
stick length I=2/3 L and a special stroke control which is
explained with reference to FIG. 6. FIG. 6 schematically shows the
stroke position HP of the honing tool as a function of the honing
time t during the bottle honing operation. After insertion of the
honing tool, the machining of the cylinder face initially proceeds
from a first time t.sub.1 to a second time t.sub.2 with the same
stroke length in a first stroke position precisely as in the case
of the machining of a circular-cylindrical bore. The term "stroke
position" refers here to the region between the upper reversing
point UO and the lower reversing point UU of a reciprocating
movement. Each shifting of a reversing point therefore also changes
the stroke position.
[0070] From a defined second time t.sub.2, the honing machine
automatically switches over to an incremental change in the stroke
position and, after each stroke, the upper reversing point UO is
changed incrementally in the direction of the lower reversing point
UU. The temporal position of the second time t.sub.2 can be
defined, for example, via a certain number of strokes or via a
predetermined honing time or via a predetermined removal of
material or another triggering parameter. The extent of the
increment IN about which the upper reversing point changes between
two consecutive strokes can likewise be adjusted as required. After
the stroke shifting phase has ended at a third time t.sub.3, the
bore is honed with the new third stroke position reached until the
second bore section reaches the desired diameter and the bottle
shape (cf. FIG. 1) is produced.
[0071] Depending on how the incremental variation in the stroke
shifting and the temporal sequence of the stroke shifting are
predetermined, different radii and tangent angles are produced in
the transition section. These parameters can therefore be
predetermined via the parameters of the stroke shifting. The bottle
honing operation is expediently carried out with honing sticks, the
cutting material grains of which are finer than those for the
preliminary honing or intermediate honing. For example, the
operation can be carried out with diamond grains within the range
of D35 in order to obtain a bottle shape having a surface structure
which is already relatively fine.
[0072] During the production of the bottle shape with the aid of
relatively long honing strips and incremental stroke shifting, a
relatively rough surface structure having small steps similar to a
saw profile may be produced in the transition region. Structures of
this type are generally undesired. In order to obtain the desired
surface structure uniformly over the entire internal surface of the
bore including the transition section and the adjoining radii, in
the method described here, after the bottle honing operation a
rounding of the radii and smoothing of the surface are therefore
carried out with the aid of an annular tool. The operation here can
be carried out with even finer cutting means, for example within
the range of D10 to D15, in particular D12. The selection of a
suitable annular tool (for example single expansion, double
expansion with two cutting groups, arranged in a common ring, or
double expansion 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 overruns and/or to
the position and size of transverse bores. If, for example, a
cylinder crank case has a large transverse bore, it is generally
expedient to carry out the operation using an annular tool with
single expansion (cf., for example, FIG. 2). In an exemplary
process, use has been made of such an annular tool with an annular
cutting group in order to smooth grooves or burrs which have arisen
in the transition section during the machining of the bottle honing
operation. With the aid of the annular tool, the radii of the
transition region can also be rounded and the surface values
changed in such a manner that they are substantially identical to
the surface values in the adjacent first and third bore
sections.
[0073] To this end, FIG. 7 shows a measuring diagram of a rounded
profile of a bottle-shaped cylinder after use of an annular tool
with single expansion in the process illustrated here. The scale on
the x axis of the diagram (parallel to the bore axis) is 5 mm per
unit of measurement shown, and on the y axis (in the radial
direction of the bore) is a unit of measurement of 10 .mu.m.
[0074] The use of an annular tool not only affords advantages here
in respect of the smooth, edge-free profile of the bore contour in
the axial direction. Since, in the case of annular tools of the
type described here, the cutting material bodies of an annular
cutting group occupy a large part of the circumference of the
honing tool (for example between 70% and 80%), a very uniform
overlapping of the machined bore internal surface is also produced
in all axial positions during the honing. The term "overlapping"
refers here qualitatively to the uniformity of the distribution of
honing grooves over the entire bore length and the circumference.
If use is made of conventional honing tools having axially
relatively long honing sticks, under some circumstances a
nonuniform roughness or waviness can be generated in the bore.
Depending on the design of the block, this problem may occur even
more acutely if, for example, engine blocks have to be machined
with shorter honing tool outlets. In the case of a honing tool
outlet of just a few millimeters in length, a nonuniform wear of
the long honing sticks may occur, and therefore the bore may obtain
a smaller diameter in the lower reversing point than in the upper
reversing point. Although such problems should be substantially
avoided by selection of suitable honing parameters when
conventional honing tools (with long honing sticks) are used, the
configuration of the corresponding honing processes is relatively
time- and cost-intensive. A plurality of tests frequently have to
be carried out until a honing process configuration is optimized
such that nonuniform machining with long sticks is avoided. When an
annular tool is used, a multiplicity of the conventionally
occurring problems can be avoided. The advantages of annular tools
include, inter alia: [0075] 1. Because a large portion of the
circumference of the honing tool in the region of an annular
cutting group is occupied with cutting material bodies, a bore
internal surface can be structured much more rapidly with the aid
of an annular tool than with the aid of a stick tool. As a result,
cycle times can optionally be reduced. [0076] 2. If the stroke
length is adjusted in order, for example, to correct the shape, no
annoying nonuniformities in the distribution of roughness arise
when annular tools are used since the overlapping is retained even
when the stroke length is changed. [0077] 3. Annular cutting groups
wear substantially uniformly, and therefore undesired conicities
can be avoided particularly in the region of the lower reversing
point when annular tools are used. [0078] 4. The installation of a
honing machine for a new honing process can proceed much more
simply and rapidly when annular tools are used than when
conventional stick honing tools are used. The overlapping will be
sufficiently uniform within the scope of the requirements because
of the tool construction.
[0079] If, instead of an annular tool having single expansion, use
is made of an annular tool having a single cutting group ring and
double expansion (cf., for example, FIG. 3) for the structuring, it
will generally be required to increase the stroke number in
comparison to the use of an annular tool with single expansion, in
order to ensure a uniform overlapping. However, the advantages of
annular tools are maintained and the required number of strokes for
a uniform structuring of the bore internal surface is still always
lower than the corresponding number of strokes during use of a
conventional honing tool with long honing sticks.
[0080] When an annular tool is used, the infeed force can
expediently be exerted by means of a hydraulic expansion, and
therefore the surface can be substantially machined with a constant
force. The following of the contour which varies in the axial
direction can then be brought about solely by means of the design
because of the flexibility of the hydraulic expansion.
[0081] After the smoothing of the bore internal surface and
rounding of the radii with the aid of an annular tool, one or more
further honing operations can subsequently be carried out in order
to produce the finally desired surface structure on the
bottle-shaped bore.
[0082] The process described here by way of example is first of all
adjoined by a fifth honing operation which is referred to here as
"spiral structure honing with an annular tool". In this honing
operation, the axial speeds and the speed of rotation of the honing
tool are coordinated with each other in such a manner that
relatively large honing angles, for example of the order of
magnitude of 140.degree., are produced. Of course, in other method
variants, other honing angles and/or roughness profiles can also be
produced. In the case of the example, the spiral structure honing
is configured in such a manner that virtually no more global
removal of material is obtained, but rather grooves of suitable
depth and distribution are produced merely in the surface, which is
very smooth after the rounding operation, with the aid of a
relatively rough-grained cutting material body having a low cutting
grain density. For example, cutting material bodies having a
cutting agent grain density of 1.25 to 15% by vol. and/or a grain
size of 35 to 200 .mu.m can be used (cf., for example, DE 10 2005
018 277 A1).
[0083] Subsequently, in a sixth and final honing operation, the
previously structured surface is also deburred (deburring honing).
For this purpose, use is preferably likewise made of an annular
tool with fine cutting agents, for example the same annular tool
which was also used for the fourth honing operation (rounding of
the radii and smooth honing). The operation here can be carried out
with different expansion types. The expansion type can be
configured hydraulically/hydraulically, hydraulically/mechanically
or mechanically/mechanically. In the case of a mechanical
expansion, the movement can be carried out, for example, in a
force-controlled manner via a servomechanical expansion
(hydraulic-like) or in a position- and force-controlled manner.
[0084] In an alternative method variant, use is made of an
expandable annular tool in the bottle honing operation, i.e. when
producing a bottle-shaped bore shape from a previously still
circular-cylindrical bore shape. For this purpose, it is provided
that the control of the expansion system for the radial infeeding
of the honing segments is coupled to the control for the stroke
position so that the annular tool can precisely generate the
transition section with the changing diameter and also operates
with a suitable contact pressure force in the cylindrical first and
second bore section (cf. FIG. 8). The bottle honing operation can
be provided as a second honing operation immediately after the
preliminary honing and in this respect can replace the second to
fourth honing operations of the first exemplary embodiment. The
stroke-dependent control of the expansion then takes place in such
a manner that the honing segments of the cutting group are infed
radially outward in a travel- and force-controlled manner during a
downward stroke in accordance with the bottle shape depending on
the stroke position and are retracted radially again in the region
of the transition section during an upward stroke in accordance
with the bottle shape depending on the stroke position. A smooth
contour profile can thus be achieved in the transition section from
the outset.
[0085] This can be achieved at the honing machine by the fact that
certain stroke ranges corresponding to the first to third bore
sections are input in the control program, and therefore the
cutting group expands from the end of the first bore section during
the downward stroke by means of travel- and force-controlled
expansion. During the upward stroke, the expansion of the cutting
group then retracts from the end of the third bore section such
that the desired, programmed, bottle-shaped cylinder is generated.
For this purpose, FIG. 8 shows, by way of example, a schematic
diagram which shows the dependency of the axial stroke position HP
(solid line) and of the radial expansion position AP (dashed line)
as a function of the honing time t during the bottle honing using
an annular tool.
[0086] Annular tools of the type described here can not only be
used for producing or machining bottle-shaped bores, but can afford
considerable advantages, even without modification, during the
machining of bores having a different geometry. For example, it is
possible to use an annular tool with double expansion and a single
cutting group ring in an identical or similar manner to the
exemplary embodiment of FIG. 3 for producing a free shape with a
noncircular bore cross section on a bore. This is customarily
referred to as shape honing. For example, a bore section with a
clover leaf shape or elliptical shape of the cross section can be
produced with the aid of the annular tool. For this purpose, the
honing machine has to have the possibility of simultaneously
controlling the first infeed system and the second infeed system,
wherein, depending in each case on the stroke position and angular
position of the cutting group with respect to the bore, the
expansions have to be controlled with a differing force/position
such that the free shape can arise.
[0087] It is also possible to use an annular tool to produce and/or
to machine a bore shape which has a frustoconical bore section
(conical section) which merges relatively abruptly or with a
transition radius into an adjacent cylindrical bore section without
the connection of a further bore section. As a result, for example,
a bore can be produced with a funnel shape which has an input-side,
cylindrical first bore section with a first diameter, which
increases conically in an adjacent, second bore section toward the
bore base as far as a maximum diameter. The diameter difference
between the cylindrical first bore section and the maximum diameter
in the conical second bore section can be, for example, between
approx. 20 .mu.m and approx. 90 .mu.m. The axial length of the
cylindrical first bore section can be, for example, between 20% and
80% of the entire bore length.
[0088] Furthermore, it is possible to produce a barrel-shaped bore
section in a bore, i.e. a bulge in an otherwise substantially
cylindrical bore, with the aid of an annular tool. The bulge can
lie approximately centrally or else in the vicinity of one of the
bore ends.
[0089] When an annular tool is used, it is also possible relatively
cost-effectively to machine a cylinder face in such a manner that
in the region of the upper dead center and/or in the region of the
lower dead center there are narrow strips having different surface
structures than in the central region of highest piston speed. This
variant is referred to here as "strip honing". A conventional
method suitable for this purpose and a correspondingly adapted
honing tool are described, for example, in DE 195 42 892 C2. In
addition to honing machining, which machines the entire axial
length of the honing tool with long honing sticks, short-stroke
honing machining is carried out here with the aid of short honing
sticks, wherein this honing machining covers only the region of the
upper dead center and/or of the lower dead center.
[0090] When an annular tool with double expansion and two axially
offset cutting groups is used (cf., for example, FIG. 4),
corresponding surface machinings are likewise possible. For
example, with the first annular cutting group, long-stroke
machining of the entire bore length can be carried out before then,
for example, with the second cutting group, short-stroke machining
is carried out in the region of the upper dead center in order to
produce a specific structure in the region of the upper dead
center.
[0091] In the event of corresponding variable control of the ratio
between stroke frequency and rotational frequency of the working
spindle, it is also possible in a simple manner to achieve the
effect that such strip honing can be carried out with different
honing angles in different axial bore sections (cf., for example,
FIG. 4 from DE 10 2007 032 370 A1).
* * * * *