Method for determining the undercut of a profile

Abstract

Method for determining an undercut (12) of a profile (1) formed in a cylinder wall (2) of an internal combustion engine, in which in one step (a) at least a first characteristic parameter (H0, L0) of a web (3) or a groove (4) of the profile (1) before formation of the undercut (12) and at least a second characteristic parameter (H1, L1) of the web (3) or the groove (4) of the profile (1) after formation of the undercut (12) are measured, and In step (b) a measure for the undercut (12) of the profile (1) is then determined from the parameters (H0, L0; H1, L1) measured in step (a) based on a characteristic map previously determined in a series of measurements, which assigns a corresponding measure for the undercut (12) to each of the given first and second parameters (H0, L0, H1, L1) of the profile (1).

Description

[0001] The invention relates to a method for determining an undercut of a profile formed in a cylinder wall of an internal combustion engine.

[0002] German patent application DE 10 2013 011 726 A1 discloses a technology for the cost-effective coating of workpieces, particularly those made of aluminum, which describes the so-called "mechanical activation" or "grooving" process. In this process, a profile with a dovetail contour is introduced into the matrix material of the cylinder wall to be coated. This undercut of the so-called dovetail profile is produced in one to seven individual process steps and results in a profile into which coatings, particularly sprayed coatings (e.g., by arc wire spraying), but also lacquers, can permanently adhere.

[0003] Such a dovetail profile has numerous webs with a dovetail-shaped cross-section, with adjacent webs separated by appropriately shaped grooves. The mechanically created undercut has an angle enclosed by a web flank and the groove base, which is between 89° and 45°, usually between 75° and 85°. The exact size of the undercut is difficult or very difficult to measure optically or by probing, since the dimensions, for example, of the web or groove height and web width, are usually between approximately 0.15 mm and 0.3 mm, and, moreover, the undercut would essentially require measuring around the lateral edges of the web. Therefore, such workpieces are often examined destructively by microsectioning. However, such examinations are complex and expensive.Furthermore, even if the examination yields a positive result, the workpiece cannot be reused due to the damage. Currently, no measuring system is available that would be capable of reliably determining undercuts of such small dimensions.

[0004] From DE 10 2008 024 313 A1 a method for preconditioning a surface to be coated is known, in which undercuts and / or preforms of the undercuts are introduced into the surface by machining and / or embossing, wherein at least one further, non-machining process step is carried out for the preforms to produce the undercuts.

[0005] From DE 10 2013 014 844 A1, a method for machining the wall of a cylinder of an internal combustion engine is known, in which depressions are introduced into the wall by means of mechanical machining. In this process, the wall is irradiated with a medium under high pressure after the mechanical machining to create micro-depressions.

[0006] From US Patent 8,726,874 B2, a cylinder with selective surface treatment is known, wherein the cylinder has a longitudinal axis and a cylindrical wall extending along the longitudinal axis. The cylindrical wall has a first and a second end section and a middle section arranged between the first and the second end section, the middle section having a greater surface roughness than the first and / or the second end section. The surface roughness has teeth, each with a width, a height, and gaps between the teeth. These parameters are determined using a coordinate measuring machine (CMM).

[0007] US Patent 2005 / 0064146 A1 describes an article with a surface having the following features: undercut grooves extending below the surface to a lower section, wherein the grooves have an upper width at the surface and a lower width at the lower section, connected by side walls, and wherein at least one of the side walls connects the upper width to the lower width to form an undercut angle with the surface of less than 90°. The article is covered with a coating that includes weakened sections for stress relief.

[0008] The coating fills the undercut grooves and extends beyond the surface with a thickness of approximately 0.1 to 50 mm.

[0009] DE 10 2013 011 726 A1 describes a method for machining the wall of a cylinder of an internal combustion engine, in which circumferential grooves are machined into the wall. At least one ring-shaped saw blade is used to machine the grooves. This blade is provided with a plurality of cutting teeth around its circumference and rotates about its longitudinal axis while moving along a ring track. Subsequent forming of the webs created between adjacent grooves produces undercuts that improve the bond between the cylinder wall and a subsequently applied coating layer.

[0010] The invention is based on the objective of providing a method of the type mentioned at the outset with which such undercuts, for example of dovetail profiles, can be determined.

[0011] This problem is solved according to the invention by a method having the features of claim 1. Advantageous further developments are the subject of the dependent claims.

[0012] In the method according to the invention, in step (a) at least one first characteristic parameter of a web or groove of the profile is measured before the undercut is formed, and at least one second characteristic parameter of the web or groove of the profile is measured after the undercut is formed. Then, in step (b), a dimension for the undercut of the profile is determined from the characteristic parameters measured in step (a) based on a characteristic map previously determined in a series of measurements. This map assigns a corresponding dimension for the undercut to each of the predetermined first and second characteristic parameters of the profile. Thus, the invention is based on the concept of determining the undercut produced in a workpiece using, on the one hand, measured characteristic parameters of the web or groove, and on the other hand, a characteristic map based on predetermined characteristic parameters from previously conducted series of measurements.The undercut to be determined is thus calculated based on two factors: firstly, on parameters measured on the workpiece under investigation, and secondly, on preliminary tests stored in the characteristic curve. The desired undercut can be reliably determined from this data.

[0013] Advantageously, the profile includes a dovetail profile for receiving a coating applied to the cylinder wall, which serves as the cylinder's running surface. As mentioned previously, the coating can permanently bond to such profiles, resulting in highly durable running surfaces. After the coating has cured, the dovetail profile creates a positive-locking connection between the coating material and the cylinder wall.

[0014] According to a further development of the invention, the first parameter comprises a web or groove height and / or a web width, and the second parameter comprises a web or groove height and / or a web width. Thus, the inventive method for determining the undercut incorporates values ​​measured on the actual workpiece for the profile design before the undercut is formed, as well as values ​​measured on the actual workpiece after the undercut is formed. In particular, the ratios of the parameters before and after the undercut is formed can therefore provide an important basis for determining the undercut dimension. It is advantageous that such parameters can be measured easily and cost-effectively using existing devices.

[0015] According to another embodiment of the invention, the dimension for the profile undercut is determined by interpolation using the characteristic map. This makes it possible to determine undercuts on workpieces that do not exactly correspond to the predetermined values, even with a limited number of previously performed measurements. Thus, the expected behavior of the formed profile can ultimately be predicted based on preliminary tests.

[0016] According to another embodiment of the invention, the characteristic curve includes further parameters that depict the forming process for creating the undercut, the material behavior, and the results of tensile and compression tests. Thus, the material used in the current workpiece and the preliminary tests carried out for this material can also be taken into account in the inventive method. This approach contributes to increasing the accuracy of the inventive method.

[0017] Advantageously, the web root width and preferably also a correction factor for the forming process are determined using the characteristic curve as the corresponding measure for the undercut. The web root width enables a mathematically simple determination of the undercut dimension. Additionally, the correction factor for the forming process allows for the consideration of changes in the workpiece under investigation, which, for example, arise because the web flank is often not a straight line in practice, unlike in a theoretical analysis, but rather a curved line. Such a correction factor thus makes it possible to determine the undercut more precisely. This factor also takes into account differences resulting from theoretically calculated and practically determined, measured values.

[0018] According to a preferred embodiment of the invention, the dimension for the undercut comprises the undercut area and / or the angle enclosed by the web flank and the groove base. The undercut area, particularly in conjunction with the aforementioned angle, provides a reliable dimension for the undercut and thus for the potential adhesion of a coating to the cylinder wall of the internal combustion engine. If certain predetermined limit values ​​for the undercut area and the aforementioned angle are exceeded or not met when applying the method according to the invention, the workpiece in question can be rejected or subjected to further processing. Furthermore, if the method according to the invention yields a value approaching a limit value, a readjustment of a device for creating the grooves or forming the relevant profile can also be initiated.

[0019] According to another embodiment of the invention, the undercut surface is determined by means of the equation AHinterschnitt=(0.5×L1−B2×H1)×K(H0H1;L0L1) The undercut area is determined using the following equation, where H0 and H1 represent the web or groove height before and after the undercut formation, L0 and L1 the web width before and after the undercut formation, B the web root width, and K the correction factor for the forming process. This equation is mathematically easy to use and allows for the consideration of measurements taken on the workpiece under investigation, as well as data and measurements obtained from previously defined tests. This enables the reliable and relatively precise determination of the undercut area as a measure of the undercut.

[0020] According to another further development, the angle enclosed by the web flank and the groove base is determined using the equation W=arcsin(L1−B2(H1)2+(L1−B2)2) The undercut is determined using the following equation, where H1 represents the web or groove height after the undercut is formed, L1 the web width after the undercut is formed, and B the web root width. This equation also incorporates parameters currently measured on the material under investigation, as well as the web root width, a further parameter derived from the characteristic curve obtained through previously conducted investigations, such as measurement series. This equation also contributes to determining the undercut of profiles in a relatively simple and therefore cost-effective manner.

[0021] Exemplary embodiments of the invention are explained in more detail below with reference to the drawing. The drawing shows: Fig. 1 A schematic, cutaway, partial representation of a profile cut into a cylindrical bore before the formation of an undercut; Fig. 2 a schematic, sectioned, partial representation of the profile according to Fig. 1 after forming an undercut; Fig. 3 a schematic, sectioned, partial representation of the profile according to Fig. 2 with parameters to be measured; and Fig. 4 A schematic, cutaway view of a web of the profile according to the Fig. 2 and Fig. 3 with undercut dimension determined according to the invention.

[0022] In Fig. Figure 1 is a schematic, partially cross-sectional section of a profile 1 as it is formed circumferentially in a cylinder wall 2 of an internal combustion engine (not shown in detail). The following are shown in Fig. 1. Webs 3 and grooves 4 each have a rectangular profile. It follows that in Fig. 1 the angles 7 enclosed by a web flank 5 and the groove base 6 are approximately 90°.

[0023] The representation according to Fig. Figure 1 shows the profile before the formation of an undercut.

[0024] After all grooves 4 have been cut into the cylinder wall 2, the webs 3 formed between adjacent grooves 4 are plastically deformed to create undercuts or constrictions in the groove cross-sections. These ensure the aforementioned positive-locking fixation of the coating, which is not shown in detail in the figures and is subsequently applied, to the cylinder wall 2. This coating completely fills the cross-section of the grooves and slightly reduces the cross-section of the cylinder wall.

[0025] For the forming process, a rolling tool (not shown in detail) is used, which typically comprises a plurality of rolling elements (also not shown). The rotating rolling tool is moved along the longitudinal axis of the cylinder, whereby the forming of the webs 3 is achieved by ensuring that the largest circumference formed by the rolling elements has a diameter larger than that of the webs 3 according to Fig. 1 is the formed inner diameter of the cylinder.

[0026] The rolling tool therefore exerts a force 11 on the upper surface 10 of each web 3 (see Fig. 1), which ultimately enables the profile after the undercut has formed, as shown schematically in the section in Fig. 2 is shown. In the Fig. For the sake of clarity, the diagonal hatching symbolizing a cut in sections 2 to 4 has been omitted.

[0027] For the formation of sufficiently large undercuts during forming, a ratio of web width to groove depth of approximately 1:1 can be advantageous. Before forming, i.e., before the undercut is formed, the web width L0 can be, for example, 0.15 mm to 0.3 mm and the groove depth or web height 0.1 mm to 0.4 mm. After forming, i.e., after the undercut is formed, the following results: Fig. 3. The dimension L1 is used for the web width and the dimension H1 for the groove depth or web height, whereby a comparison of the Fig. 1 and Fig. 3 without further ado, it follows that the web width L0 before the formation of the undercut is smaller than the web width L1 after the formation of the undercut, and the groove depth or web height H1 after the formation of the undercut is smaller than the groove depth or web height H0 before the formation of the undercut.

[0028] The method according to the invention serves to determine an undercut 12 of a profile 1 formed in a cylinder wall 2 of an internal combustion engine (not shown in detail). According to the method, in a step (a) at least a first characteristic value H0, L0 of a web 3 or a groove 4 of the profile 1 are determined before the undercut 12 is formed (see Fig. 1) and at least a second characteristic parameter H1, L1 of the web 3 or the groove 4 of the profile 1 after formation of the undercut 12 (see Fig. 2) measured. Such a measurement can be performed, for example, using a camera system (not shown) that enters the cylinder bore and uses a 360° lens to create a high-resolution unfolded image of the bore's surface. The web widths L1 and groove depths or web heights H1 can then be determined using software by comparing pixels and grayscale values.

[0029] According to an alternative embodiment, the aforementioned values ​​can also be measured using a displacement sensor. This sensor scans the profile contour along a line in the cylinder axis direction. By determining the distance between the input and output signals, profile parameters, such as the aforementioned web width L1 and the groove depth or web height H1, can be unambiguously determined. Lasers, confocal systems, systems based on focus variation, or white light or scattered light sensors can be used as sensors.

[0030] The survey lines of such so-called straight systems are in Fig. 2 shown using arrows A.

[0031] According to the invention, in step (b) a dimension for the undercut 12 of the profile 1 is then determined from the characteristic parameters H0, L0; H1, L1 measured in step (a) based on or taking into account a characteristic map previously determined in a series of measurements, which assigns a corresponding dimension for the undercut 12 to each of the given first and second characteristic parameters of the profile.

[0032] According to the in the Fig. In the embodiment shown in Figures 2 to 4, the profile 1 is a dovetail profile 13 for receiving a coating (not shown) applied to the cylinder wall 2 and serving as the running surface of the cylinder, as previously explained.

[0033] According to a preferred embodiment of the invention, the first parameter comprises the web or groove height H0 and / or the web width L0, i.e., dimensions of the profile before the undercut is formed. The second parameter comprises the web or groove height H1 and / or the web width L1, i.e., dimensions of the profile after the undercut is formed.

[0034] As previously indicated, the undercut 12 cannot be measured by scanning or with one of the aforementioned straight measuring systems. With such straight measuring systems, the web width L0 and the groove depth or web height H0 can be determined before the undercut is formed and according to the Fig. 2 and Fig. 3. Measure the web width L1 and the groove depth or web height H1 after forming the undercut, i.e., after forming the dovetail profile 13. It is not possible to measure the angles W1 and W2 and the groove base width G with such straight measuring systems. The angles W1 and W2 and the groove base width G are in Fig. 3 shown.

[0035] The dimension for the undercut 12 of profile 1 is determined by interpolation using the characteristic map. This map includes further parameters that, for example, depict the forming process for creating the undercut 12, the material behavior, and the results of tensile and compression tests of the material used. The characteristic map is, for example, a database for the forming behavior or stored in such a database. Input parameters for this database are the previously mentioned parameters H0, L0, H1, and L1, i.e., groove depth or web height and web width before the undercut is formed, and groove depth or web height and web width after the undercut is formed. Furthermore, the database contains empirically determined values ​​for the groove depth and web width, i.e., values ​​obtained from measurement series or preliminary tests, both before and after the undercut is formed.Typically, the parameters H0, L0, H1, and L1 measured on the actual workpiece deviate from the stored values. Therefore, the characteristic map or database can determine relevant output parameters, also known as the corresponding measure for the undercut, based on interpolation. Furthermore, the kinematics of the forming process can be represented in the characteristic map or database using a simulation. Since the output parameters for determining the undercut also depend on the material used, the characteristic map or database also contains characteristic parameters and / or a material data sheet describing the material's behavior and tensile and compression tests on the material in question.

[0036] Using the characteristic curve or the database, the web root width B and preferably also a correction factor K for the forming process are then determined as the corresponding dimension for the undercut 12. The web root width B is shown in the schematic representation according to Fig. Figure 4 shows that, using these output parameters determined with the aid of the characteristic map or the database, it is now possible to determine the dimension for the undercut 12, which, according to a particularly preferred embodiment, is the undercut area A. Hinterschnitt and / or the angle W enclosed by the web flank 5 and the groove base 6, to be determined in a relatively simple way yet with high accuracy.

[0037] The undercut surface A Hinterschnitt can be done using the equation AHinterschnitt=(0.5×L1−B2×H1)×K(H0H1;L0L1) determine where H0 or H1 represent the web or groove height before or after the formation of the undercut 12, L0 or L1 represent the web width before or after the formation of the undercut 12, B represent the web foot width and K represent the correction factor for the forming process.

[0038] Furthermore, the angle W enclosed by the web flank 5 and the groove base 6 can be determined as shown in Fig. 4 is shown using the equation W=arcsin(L1−B2(H1)2+(L1−B2)2) determine where H1 represents the web or groove height after the undercut has been formed, L1 represents the web width after the undercut has been formed, and B represents the web foot width.

[0039] Undercut surface A HinterschnittThe angle W represents relevant criteria for the quality of the dovetail profile 13 and thus a relevant measure for the undercut 12. In this way, it is possible to efficiently determine the undercut of a profile, especially a dovetail profile, and to establish easily verifiable criteria based on previously defined limit values ​​for the undercut area and the aforementioned angle W. These criteria determine whether workpieces within the limit values ​​are accepted or whether workpieces outside the limit values ​​are rejected. Furthermore, it is possible to make changes to the forming process if the undercut area and / or the aforementioned angle W are close to the previously established limit values.

[0040] Using the aforementioned optical system, for example, a camera system with a 360° lens or a displacement sensor, it is possible to photograph and analyze the grooves and their diameters formed by webs and slots from either the outside or the inside. By comparing the input parameters H0, L0, H1, and L1 before and after the undercut is formed, the degree of deformation can be determined. Based on the material behavior, such as a material properties sheet for the matrix material used, the simulated compression behavior can be deduced, thus determining the undercut area and the angle W enclosed between the web flank and the groove base (before). The degree of deformation, which characterizes the undercut, can be determined relatively precisely using the measured ratios H0 / L0 and H1 / L1, as previously explained.

[0041] This makes it possible to determine the undercut of a profile, in particular a dovetail profile formed in a cylinder wall of an internal combustion engine, in a relatively simple way.

Claims

[1] Method for determining an undercut (12) of a profile (1) formed in a cylinder wall (2) of an internal combustion engine, in which in a step (a) at least one first characteristic (H0, L0) of a web (3) or a groove (4) of the profile (1) before formation of the undercut (12) and at least one second characteristic (H1, L1) of the web (3) or the groove (4) of the profile (1) after formation of the undercut (12) are measured, and in a step (b) a dimension for the undercut (12) of the profile (1) is then determined from the parameters (H0, L0; H1, L1) measured in step (a) on the basis of a characteristic map previously determined in a series of measurements, which map assigns a respective dimension for the undercut (12) to predetermined first and second parameters (H0, L0, H1, L1) of the profile (1). [2] Method according to claim 1, characterized bythat the profile (1) comprises a dovetail profile (13) for receiving a coating applied to the cylinder wall (2) and serving as a running surface of a cylinder. [3] Method according to claim 1 or 2, characterized by that the first characteristic comprises a web or groove height (H0) and / or a web width (L0) and the second characteristic comprises a web or groove height (H1) and / or a web width (L1). [4] Method according to one of claims 1 to 3, characterized by that the dimension for the undercut (12) of the profile (1) is determined by interpolation using the characteristic map. [5] Method according to one of the preceding claims, characterized by that the characteristic map includes further parameters which represent a forming process for forming the undercut (12), a material behavior as well as results of tensile and compression tests. [6] Method according to one of the preceding claims, characterized bythat with the aid of the characteristic map a web foot width (B) is determined as the corresponding dimension for the undercut (12). [7] Method according to one of the preceding claims, characterized by that a correction factor (K) for the forming process is determined with the aid of the characteristic map as the corresponding dimension for the undercut (12). [8] Method according to one of the preceding claims, characterized by that the dimension for the undercut (12) is an undercut area (A Hinterschnitt ) and / or an angle (W) enclosed by a web flank (5) and a groove base (6). [9] Method according to claim 6, claim 7 and claim 8, characterized by that the undercut surface (A Hinterschnitt ) using the equation AHundercut=(0.5×L1−B2×H1)×K(H0H1;L0L1) is determined, where H0 stands for the web or groove height before the formation of the undercut (12), H1 for the web or groove height after the formation of the undercut (12), L0 for the web width before the formation of the undercut (12), L1 for the web width after the formation of the undercut (12), B for the web foot width and K for the correction factor for the forming process. [10] Method according to claim 6 and claim 8, characterized by that the angle (W) enclosed by the web flank (5) and the groove base (6) is determined by the equation W=arcsin(L1−B2(H1)2+(L1−B2)2) is determined, where H1 stands for the web or groove height after the formation of the undercut (12), L1 for the web width after the formation of the undercut (12) and B for the web foot width.

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