Abstract
A grinding machine and a method for measuring and producing a target outer contour is disclosed, particularly for a pin-bearing journal of a crankshaft. First, a measurement device acquires measurement values for the dimensions and shape of a workpiece in at least two measurement planes that are spaced apart and extend transversely to a longitudinal extension of a workpiece region. The measurement planes are produced by a relative movement of the workpiece region and the measurement device in a Z axis direction, relative to the movement of a grinding disc in the direction of the Z-axis thereof. These measurement values are transmitted to a CNC system for advancing a grinding disc, such that any deviations from the target contour that may be present are corrected, and the target contour of the workpiece region in question is ground adaptively on the basis of the measurement values.
Claims
1. A method for measuring and producing a target outer contour of at least one region of a workpiece with regard to dimensions and shape, through continuous and adaptive longitudinal grinding or plunge grinding by means of a grinding disc having an axis of rotation, on a grinding center, with a CNC system for the X-axis thereof, wherein: a) an actual contour on the workpiece in the region being ground is measured during grinding of the at least one region of the workpiece; b) measurement values of the dimensions and the shape in at least two measurement planes in the region being ground of the workpiece that are spaced apart from one another, extend transversely to the longitudinal extension of the respective workpiece region, and are located in a grinding disc engagement region are acquired during the adaptive grinding of the at least one region of the workpiece by means of a measurement device; c) the measurement planes are produced during the continuous and adaptive grinding of the at least one region of the workpiece by a relative movement between the workpiece region and the measurement device in the Z-axis direction—which is configured along the axis of rotation in the longitudinal direction of a workpiece region to be ground—relative to the movement of the grinding disc in the direction of the Z-axis; d) the measurement values are transferred to the CNC system; and e) the CNC system is controlled in such a manner that any deviations from the target contour that may be present in the at least one region of the workpiece are in-process corrected, and the target contour of the workpiece region in question is ground adaptively on the basis of the measurement values that were acquired for the particular measurement planes of a workpiece region during the adaptive grinding of that region.
2. The method according to claim 1, wherein the workpiece regions are measured with regard to circularity, cylindricity, conicity, crowning, and/or concavity along the distance of at least two measurement planes spaced apart on the workpiece region, the measurement planes being adjusted.
3. The method according to claim 1, wherein the workpiece is clamped so as to be stationary with respect to the longitudinal axis thereof, and the measurement device is moved in the direction of the longitudinal axis into the respective measurement plane.
4. The method according to claim 1, wherein the measurement device is arranged on a grinding spindle head, and is moved relative thereto in the direction of the Z-axis in order to take measurements in different measurement planes.
5. The method according to claim 1, wherein the measurement device is moved by means of a programmable electric drive.
6. The method according to claim 1, wherein the measurement device is moved hydraulically or pneumatically in the Z-direction.
7. The method according to claim 1, wherein measurements are taken during the grinding.
8. The method according to claim 1, wherein measurements are taken in an interrupted grinding disc advancement, and the grinding disc remains in a holding position during the measurement until the measurement has been made.
9. The method according to claim 8, wherein the measurement values are acquired after the grinding, the measured contour of the workpiece is assessed, and any required correction to the contour is performed by means of the CNC system of the grinding disc when the next workpiece is ground.
10. The method according to claim 8, wherein the target shape of the workpiece region to be ground is produced by means of a grinding disc that has been previously dressed so as to correspond to the desired target shape, the workpiece region being ground in a corrected manner by again dressing the grinding disc.
11. The method according to claim 1, wherein the target shape of the workpiece region to be ground is produced by pivoting the grinding disc in the horizontal plane about a CNC-controlled axis, the plane lying horizontal to the central axis of the workpiece.
12. The method according to claim 1, wherein the target shape of the workpiece region is ground through a grinding program that is input to the CNC system.
13. A grinding machine for measuring and producing a target outer contour of at least one region of a workpiece with regard to dimensions and shape, through continuous and adaptive longitudinal grinding or plunge grinding, comprising a measurement device for measuring the dimensions and shape of a workpiece region being ground of a workpiece rotating about a center, comprising: a) a grinding disc that is mounted in a grinding spindle head and grinds with simultaneous advance in the direction of the X-axis thereof; b) wherein the measurement device is arranged on the grinding spindle head and is configured such that a sensor can be moved pivotably on a contact region on the workpiece lying in a grinding disc engagement region, in order to be contacted therewith in at least two programmable measurement planes that are spaced apart from one another and arranged transversely to the workpiece central longitudinal axis of the region being ground of the workpiece.
14. The grinding machine according to claim 13, wherein the sensor has two measurement surfaces arranged in the manner of a prism, which contact the workpiece region against the contact region during measurement.
15. The grinding machine according to claim 13, wherein the measurement device can be displaced hydraulically, pneumatically, or electrically.
16. The grinding machine according to claim 13, wherein the measurement device is displaceable on the grinding spindle head under the control of a CNC system.
17. The grinding machine according to claim 13, wherein the grinding disc has a width corresponding to the length of the workpiece region.
18. The grinding machine according to claim 13, wherein the grinding disc has a width (B) that is less than the axial length (L) of the workpiece region, and performs longitudinal grinding along the axis of rotation thereof over the axial longitudinal direction of the workpiece longitudinal direction.
19. The grinding machine according to claim 13, wherein the measurement device measures the dimensions of the respective workpiece region and a conical, crowned, or concave shape can be acquired and produced on the basis of the measured dimensions measurement values.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) More advantages, possible uses, and specific embodiments shall now be explained in greater detail, with reference to the accompanying drawings.
(2) FIG. 1 illustrates a principal side view of an assembly for grinding a pin bearing in pin-chasing grinding with a measurement device for measuring the diameter of a pin bearing journal according to the prior art;
(3) FIG. 2 illustrates an enlarged partial view of an assembly according to FIG. 1, at the measurement point of the pin bearing journal, during grinding and measurement at a bearing journal according to the prior art;
(4) FIG. 3 illustrates a partial front view of the grinding spindle head during grinding of a pin bearing of a crankshaft with a measurement device according to the invention;
(5) FIG. 4 illustrates a partial view with a guide rail for adjusting the measurement device in the direction of a ZM-axis according to the invention;
(6) FIG. 5 illustrates a schematic depiction of the measurement device according to the invention, along a cutting plane A according to FIG. 4;
(7) FIG. 6 illustrates a partial view of a grinding disc in engagement with a bearing point of a crankshaft with principal indication of two measurement planes according to the invention, spaced apart in the longitudinal direction of the bearing point;
(8) FIG. 7 illustrates a partial view of a bearing journal of a crankshaft during the grinding with a grinding disc of a lesser width than the length of the journal region, and different given measurement planes, spaced apart axially from one another;
(9) FIG. 8 illustrates a pin bearing journal of a crankshaft with an indicated conical target contour; and
(10) FIG. 9 illustrates a pin bearing journal with a crowned, convex, and indicated concave target outer contour.
DETAILED DESCRIPTION OF THE DRAWINGS
(11) FIG. 1 illustrates a principal depiction of an assembly, which illustrates the pin-chasing grinding of a pin bearing journal 2 by means of a grinding disc 5 performing a pin-chasing movement. A grinding spindle head 4 bears, on an upper region thereof relative to the grinding disc 5, a measurement device 1 that can be moved in dotted lines from a measurement arm—which is applied against the pin bearing journal 2 of the crankshaft 3 that is to be measured—in a manner corresponding to the solid lines into a withdrawn position in which measurements are not taken. The grinding disc 5 with the axis of rotation 13 thereof can be advanced onto the pin bearing journal to be ground in a controlled manner over a CNC-controlled X-axis. The axis of rotation 13 of the grinding disc is also called the C-axis, and is also CNC-controlled. The elements required to realize movement in the X-axis direction are built in a known manner on a machine bed (not shown), as is the workpiece spindle head with the C-axis thereof (also not shown separately). The grinding is performed by an interpolating grinding method via corresponding adjustments to the CNC-controlled X- and C-axes.
(12) The pivotable measurement system 1 illustrated in FIG. 1 is arranged with the drive thereof on the grinding spindle head 4, and comprises an articulated arm, a measuring head 7 being arranged on the front end thereof. With the articulated arm of the measurement device 1, the measuring head 7 can be placed against the outer contour of the depicted pin bearing journal 2 in order to measure the dimensions thereof. During the grinding against the grinding disc engagement region 8, the crankshaft 3 also rotates about the center 6 thereof, and the grinding disc 5—performing pin-chasing grinding—follows the eccentric movement of the pin bearing journal 2 and remains in constant grinding engagement therewith during the entire grinding process. The illustrated measurement device 1 abuts with the sensor 7 against the contact region 9, and is thus able to measure the current diameter of the pin bearing journal 2, by means of the sensing element 15. If measurements are not to be taken—which is the case, for example, when a new crankshaft is loaded into the grinding machine or unloaded therefrom—then the measurement device has the articulated arm and sensor in a withdrawn position, which is depicted in the drawings by dotted lines.
(13) The measurement device 1 is arranged fixedly on the grinding spindle head with regard to the X-axis thereof, so that when the grinding disc 5 is moved with the grinding spindle head 4 along the X-direction of the measurement device 1, the measurement device is also moved along.
(14) FIG. 2 depicts an enlarged partial view of the engagement of the grinding disc 5 with the grinding disc engagement region 8 on the pin bearing journal 2 to be ground, the longitudinal axis being denoted by “14”. The target outer contour 10 of the pin bearing journal 2 is produced by means of the grinding disc 5. During the grinding, the measurement device 1 is placed with the measuring head 7 thereof—and the measurement surfaces 11 arranged thereon—against the contact region 9 of the pin bearing journal 2. The measurement surfaces 11 form a prism, which comes up against different diameters to be ground. The actual measurement device, which is arranged between the measurement surfaces 11, constitutes a linear measurement device and can be moved in the direction of the depicted double-headed arrow in accordance with the diameter to be measured or the contour to be measured of the pin bearing journal 2 to be ground. The advance of the grinding disc 5 against the pin bearing journal 2 is illustrated with the indicated X-axis. The prism-shaped measurement fork abuts with the two measurement surfaces 11—defined by bearing pins—on the workpiece against the component to be measured, i.e., against the surface thereof, in a prism-shaped bearing through a predetermined bearing force. The bearing pins are made of cemented carbide or diamond-coated material. The actual measurement device, which is arranged between the two bearing pins approximately in the middle of the V-shaped prism, is a measuring sensor by means of which the bearing point is measured.
(15) FIG. 3 depicts a partial front view of the grinding spindle head 4, when a pin bearing journal 2 of a crankshaft 3 is being ground. The crankshaft 3 is indicated by two main bearings, two crank webs, and a pin bearing 2 arranged between the two crank webs. The rotational movement of the crankshaft 3 is realized through the CNC-controlled C-axis. The grinding disc 5, having a width B, is engaged with the pin bearing journal 2 and is depicted during grinding thereof. The measurement device 1—which is placed with the measurement surfaces 11 thereof against the pin bearing journal 2 for the purpose of measurement—is depicted on the side of the pin bearing journal 2 that is displaced circumferentially to the engagement region 8 of the grinding disc 5. The measurement device 1 is mounted onto the grinding spindle head 4 by means of an adjusting carriage, and takes the same advancing movements of the X-axis of the grinding disc 5, which is mounted onto a grinding spindle. According to one embodiment of the invention, the measurement device 1 can be moved in the Z-direction by means of a CNC-controlled separate ZM-axis in a plurality of measurement planes on the pin bearing journal 2 to be measured (this being indicated by the double arrow over the measurement device 1). On the lower right in the drawing is the indication of the Z-axis for the grinding disc 5 or the grinding spindle head 4. The movement of the measurement device 1 in the Z-axis direction is realized by the depicted, autonomous, CNC-controlled ZM-axis.
(16) In a conventional manner, the grinding disc 5 is advanced over the X-axis thereof, which is also CNC-controlled, against the pin bearing journal 2 to be ground. The Z-axis of the grinding spindle head 4 may either be arranged under the X-axis—in which case a cross slide construction (not shown) is preferably provided—or under the grinding table, in which case the grinding table is moved with the corresponding grinding table structures, such as a workpiece spindle head and tailstock (both not shown). These two embodiments are quite common in the construction of grinding machines.
(17) According to the invention, it is important that a relative movement in the direction of the Z-axis or ZM-axis is provided between the workpiece—i.e., the crankshaft 3—and the grinding disc 5. This causes the measurement device 1 to take measurements in different measurement planes, so that the component to be measured can be precisely measured in a plurality of planes along the axis thereof, and also the complete target outer contour 10 can be measured, which has not been the case thus far with measurement devices and systems according to the prior art.
(18) It is thus evident in FIG. 3 that the measurement device 1 can be automatically displaced axially parallel to the axis of rotation 13 of the grinding disc 5 during the grinding, i.e., during the grinding cycle, in any number of measurement planes that are spaced apart from one another and run perpendicular to the longitudinal axis 14 of the pin bearing journal 2. The direction for this movement is indicated by the designation “ZM”.
(19) The CNC-controlled ZM-axis is independent of the CNC-controlled Z-axis, and therefore, during the grinding, the measurement device 1 can automatically adjust, in the ZM-axis, the measurement plane on the pin bearing journal 2 being ground in parallel to the axis direction of the grinding disc 5 on the pin bearing journal 2. The measurement device 1 according to the invention thus makes it possible, even during the grinding, to conduct the measurements on the bearing point being ground—i.e., during the continuous grinding process, i.e., an in-process measurement method—with regard to the cylindrical shape, conicity, crown, or concavity, and to correct the advances of the grinding disc 5 through the grinding program during the grinding.
(20) Thus, high-precision bearing points are produced with the method according to the invention, because the results of the in-process measurement with regard to dimensions and shape of the bearing point to be measured are inputted to the control device, and a corrected target outer contour 10 is produced on the basis of these measurement values. This results in a significantly higher quality of the ground workpiece regions, i.e., the bearing points of the crankshaft.
(21) FIG. 4 depicts a partial section view of a rail guide of the measurement device 1, along the ZM-axis thereof. The ZM-axis is arranged perpendicular to the plane of the drawing. The double arrow and the “X” indicate that the X-axis takes place via the movement of the grinding spindle head 4, because the measurement device 1 is arranged fixedly on this grinding spindle head 4, and thus tracks the movements of the grinding spindle head 4 along the X-axis. FIG. 4 shows that the base plate of the measurement device 1 is mounted onto a guide by means of guide rails 12 on the grinding spindle head 4. The present case depicts a guide that is composed of two guide rails 12, each constructed of roller circulating shoes pre-tensioned without backlash. An axis drive is shown with a simplified depiction in the middle between the guide rails 12, by means of a ball roll spindle.
(22) FIG. 5 depicts a sectional view through the measurement device 1 along the cutting plane A-A drawn in FIG. 4. The cutting plane is located below an adjusting plate (not shown), which receives the first pivot bearing of the pivot arm of the measurement device 1.
(23) FIG. 5 illustrates a plan view of the two guide rails 12, with the associated roller circulating shoe. The roller circulating shoes are fixedly connected to the adjusting plate by a threaded connection. Depicted in the middle between the guide rails 12 is the adjusting drive, which in this case is a drive via a ball roll spindle (not shown in greater detail) that is separately mounted and is driven via a coupling to a CNC-controlled servomotor. Such a design of the displacement or movement of the measurement device 1 in the ZM-axis direction thereof is sufficiently stable and rigid to be able to automatically ensure a high-precision positioning of the measurement device 1 in connection with the CNC system in any defined number of measurement planes, arranged in accordance with the surface shape of the bearing journal to be ground, during the grinding process.
(24) FIG. 6 illustrates a pin bearing journal 2 of a crankshaft 3—indicated with two crank webs 3—that is being ground by means of a grinding disc 5 having a width B. The width B of the grinding disc 5 is so large that the length L of the pin bearing journal 2 to be ground can be ground by plunge grinding. In addition, the longitudinal axes 14—arranged parallel to one another—of the pin bearing journal and the axis of rotation 13 of the grinding disc 5 are drawn. In the grinding disc engagement region 8, the arrangement of three measurement planes of the measurement device (not shown) are depicted schematically, wherein the middle measurement plane is arranged between the two outer measurement planes, which are indicated by the double arrow ZM and delimit the measurement region. The adjustability of the measurement device 1 along the CNC-controlled ZM-axis thus makes it possible to steplessly shift the measurement plane in the entire region, which can be set depending on the design and dimensions through the configuration of the ZM-axis. The depicted pin bearing has undercuts on both sides of the actual pin bearing journal 2. However, plunge grinding in order to produce the target outer contour 10 of the pin bearing journal 2 may also been performed by way of plunge grinding in such a case, if transition radii are provided to both plan sides instead of the undercuts.
(25) FIG. 7 also illustrates a pin bearing (partially shown) with a pin bearing journal 2 between two crank webs (partially shown) of a crankshaft 3. The pin bearing journal 2, which has a pin bearing journal length L, is ground by means of a grinding disc 5 against the grinding disc engagement region 8. The width B of the grinding disc 5 is less than the pin bearing journal length L, so that the grinding disc 5 produces the target outer contour 10 of the pin bearing journal 2 by way of longitudinal grinding along the axis of rotation 13 thereof, which runs parallel to the longitudinal axis 14 of the pin bearing journal 2. By way of example, there are six different measurement planes depicted, which walk in the axial direction of the longitudinal axis 14 of the pin bearing journal 2 and two of which (by way of example) are indicated by means of the double arrow designated “ZM”. The grinding disc 5 is then moved by way of longitudinal grinding from the left position—depicted in FIG. 7—to the rightmost position thereof, in which the grinding disc 5 is depicted with dashed lines. In principle, it is also possible to produce the target outer contour 10 of the pin bearing journal 2 by two plunge grinding processes where the grinding disc 5 has a width B as shown, instead of the aforementioned longitudinal grinding. If grinding is to be down with at least two plunge grinding processes, then the bearing point must be ground by two or more consecutive, side-by-side plunge grinding processes. The different measurement planes may be arranged over the entire width of the pin bearing and approached steplessly. The number of measurement planes in which a measurement process is performed during the grinding depends then on the precision of the target outer shape 10 to be achieved, as well as the shape thereof.
(26) FIG. 8 shows a pin bearing having a pin bearing journal 2 between two crank webs (partially shown) of a crankshaft 3, which has a pin journal length L. The dashed lines are intended to illustrate what is meant by the conicity of a bearing journal in the context of the present application. First, a specially profiled or obliquely placed grinding disc grinds the conicity on the pin bearing journal 2, wherein the outer contour of the bearing journal can be produced in accordance with the width of the grinding disc or length of the pin bearing journal by way of plunge grinding, longitudinal grinding, or double disc grinding. A corresponding number of measurement planes and implementations of ongoing measurements during the grinding—i.e., implementation of so-called in-process measurement—makes it possible grind a highly precise conical shape of a bearing journal, without the need to wait until the end of the grinding—as was the case with the circumstances in the prior art—with measurement after the grinding to decide that the conical outer contour is too small relative to the target contour to be achieved, and thus that the entire crankshaft is not fit for purpose.
(27) The shape of a pin bearing journal 2 may also be crowned or concave, for load-related reasons or, for example, for lubrication-related reasons. This is depicted in FIG. 9, where the solid lines represent the crowned shape of the pin bearing journal 2 and the dashed shape represents a concave shape. The pin bearing journal 2 has undercuts in the transitions thereof to the crank webs of the crankshaft 3. The measurement method according to the invention, in connection with the grinding method by means of which measurement values obtained in-process are continuously inputted to the control unit in order to adjust the grinding disc, makes it possible to grind virtually any target outer contour 10 of a bearing journal, i.e., even a pin bearing journal 2, wherein a very high precision of the respective ground bearing journal can be achieved.
