Method for mechanized gear tooth grinding
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- REISHAUER AG
- Filing Date
- 2024-08-14
- Publication Date
- 2026-07-08
Smart Images
Figure EP2024072898_06032025_PF_FP_ABST
Abstract
Description
[0001] Process for mechanical gear grinding
[0002] Technical area
[0003] The invention relates to a method for mechanical gear grinding, in particular for pitch profile grinding, of a workpiece with a run-out-limited gear structure.
[0004] State of the art
[0005] Mechanical gear grinding refers to process techniques that are used on workpieces with gear structures, especially gear blanks, to grind the gear structure(s) of the workpiece.
[0006] A workpiece refers to a blank that already has a gear structure, especially a milled one, which is subsequently further processed by gear grinding to produce usable gear teeth. Apart from the gear structure, such a workpiece is generally cylindrically symmetrical.
[0007] In the following, a gear structure refers in particular to at least one structure of the workpiece surface that corresponds to a single gear gap, where the gear gap contains a single pitch or pitch profile. It thus generally includes two opposing tooth flanks (each including half the tip area) and the root area located between the teeth. The gear structure runs along the workpiece's axis of symmetry (the gear axis) on the outer surface of the workpiece. In turn, its course can form an angle to the axis of symmetry, the helix angle.
[0008] There are various grinding techniques, including pitch profile grinding and continuous generating grinding. In pitch profile grinding, a grinding wheel grinds individual pitch profiles. Typically, a grinding wheel is advanced to a workpiece, i.e., it is moved towards the workpiece from the outside, and then travels along the workpiece in a reciprocating motion with a certain feed rate. To completely grind all of the workpiece's gear structures, this process must be performed individually for each gear structure. In contrast, generating grinding uses a grinding worm, which rotates the workpiece, similar to a worm gear. The grinding worm can also perform an axial reciprocating motion.
[0009] For workpieces with a gear structure with limited runout, i.e., a gear structure with a gear runout structure where the depth of the gear structure (also called tooth height) tapers continuously along the workpiece or along the gear structure, special aspects must be considered. The varying depth along the gear structure also changes the interaction of the grinding wheel or worm with the workpiece. In particular, a common curvature of the depth profile of the gear runout structure and the grinding tool increases the grinding surface, which also increases heat input. This can lead to grinding burns on the workpiece, particularly in the area of the gear runout structure.
[0010] This is typically prevented by moving the grinding tool, especially a grinding wheel or worm, toward the tooth runout structure of the workpiece at a relatively slow infeed speed. The reciprocating movement then occurs away from the tooth runout structure. This ensures that the grinding tool does not introduce heat into the area of the tooth runout structure, which would lead to grinding burn.
[0011] The disadvantage of this approach is that the feed rate cannot be increased, as this would lead to greater heat input into the workpiece and thus to grinding burns. This makes gear grinding of workpieces with runout-limited gear structures a very time-consuming process. A further disadvantage is that the stroke movement must be directed away from the gear runout structure. This complicates the grinding of gear structures with double runout limits. This makes existing processes less flexible. Description of the invention
[0012] The object of the invention is to create a method belonging to the technical field mentioned at the outset, which enables more flexible mechanical gear grinding of a workpiece with a run-out-limited gear structure.
[0013] The solution to the problem is defined by the features of claim 1. According to the invention, the method for mechanical gear grinding comprises the following steps: a) providing and positioning a workpiece, wherein the workpiece comprises a run-out-limited gear structure with at least one first gear run-out structure; b) advancing a grinding tool, in particular a grinding wheel, to a feed position; c) reciprocating movement of the grinding tool from the feed position along the gear structure in the direction of the first gear run-out structure with a feed that corresponds to an initial feed; d) beginning a reduction in the feed compared to the initial feed as soon as the grinding tool reaches a predetermined first reduction position along the reciprocating movement; e) completing the reciprocating movement at a reduced feed; f) releasing the grinding tool.
[0014] The following terms are used to describe the invention: Axial refers to a position, direction, or distance parallel to the axis of symmetry of the basic shape of the workpiece (without taking into account the gear structure(s)). Radial refers to a position, direction, or distance perpendicular to this axis of symmetry.
[0015] The workpiece mentioned in step a) corresponds to a workpiece as described in the introduction, i.e., it is preferably essentially cylindrically symmetrical, apart from the toothing structure(s), and can serve, for example, as a gear after completion. The runout-limited toothing structure corresponds to the toothing structure described above with a first toothing runout structure.
[0016] Positioning involves securing the workpiece so that it remains in position for the remaining process steps. Rotation around the axis of symmetry may be permitted, particularly in a generating grinding process. In pitch profile grinding, the workpiece is generally rotated only to a limited extent during grinding (e.g., if a helix angle is present, see below).
[0017] A grinding tool used in this process is a grinding wheel, particularly for pitch profile grinding, or a grinding worm, particularly for continuous grinding. The use of such a grinding tool is known per se.
[0018] The infeed position is the position to which the grinding tool must be moved before the stroke movement can begin. During infeed, the grinding tool is moved, at least partially in a radial movement, from a position further outside the workpiece, such as a maintenance position, to an operating position. The infeed speed typically ranges from 1 mm / min (very slow) to 100 mm / min (e.g., for infeed positions without the risk of grinding burns).
[0019] The reciprocating motion is a movement of the grinding tool along the gear structure and thus essentially an axial movement relative to the workpiece, so that the grinding tool and the workpiece interact, and the workpiece is ground during the reciprocating motion. If a grinding wheel is involved, it will rotate, particularly during the reciprocating motion. If the gear structure has a helix angle, the grinding wheel can be aligned according to the helix angle and perform an axial reciprocating motion while the workpiece is rotated so that the grinding wheel remains within the gear structure. Alternatively, the grinding wheel can perform a not entirely axial reciprocating motion along the gear without rotating the workpiece.
[0020] In a continuous grinding process using a grinding worm, not a single gear structure (as defined above) is ground individually. Here, the workpiece rotates, allowing the grinding worm to engage with different gear structures at different times during the process. The reciprocating movement occurs axially relative to the workpiece. According to the invention, the reciprocating movement occurs in the direction of the first gear runout structure at a feed rate, i.e., a reciprocating speed corresponding to the initial feed rate. This feed rate can, for example, be up to 1200 mm / min, but can also be higher or lower.
[0021] The start of a reduction in the feed compared to the initial feed occurs as soon as the workpiece has reached a predetermined first reduction position along the stroke movement. A reduction is a reduction in the feed, in particular a reduction over a certain distance of the stroke movement. The first reduction position of the grinding tool is predetermined, i.e. it was already set before the reduction position was reached, in particular before the stroke movement, particularly preferably before the workpiece was positioned. In particular, in a further step of the method, the first reduction position is selected taking into account the geometry of the gear structure of the workpiece. This ensures a timely reduction in the feed (even without simultaneous measurements). The reduction in the feed can take place in various ways and with different profiles, as explained below.
[0022] The reciprocating movement, and thus the grinding process, is then completed at a reduced feed rate. In particular, the reciprocating movement ends when the grinding tool has also ground the outermost parts of the first tooth runout structure.
[0023] After the lifting movement, a return movement, particularly a radial one, takes place to release the grinding tool. The return movement is particularly a radial movement that moves the grinding tool out of engagement with the tooth structure.
[0024] The grinding tool is released, particularly after the stroke movement has been completed. The grinding tool is returned, particularly in a radial movement, to the radial position it occupied before the start of the process. The return movement occurs primarily in rapid traverse, i.e., it occurs at the maximum possible speed, typically at a speed of approximately 15,000 mm / min.
[0025] A reduced feed rate reduces the introduction of heat into the workpiece during the grinding process, even when the grinding tool is fully engaged with the gear teeth. This, in turn, reduces any grinding burn to an acceptable level or prevents it from occurring completely. Thus, the reduction in feed rate in the method according to the invention allows a reciprocating movement towards the gear run-out structure. This, in turn, has various advantages: If the feed position is selected accordingly, the feed can be carried out at a high speed. This increases the process speed. A further advantage is the particularly simple possibility of grinding workpieces that have a double gear run-out structure (further details below). The fact that the reduction in feed rate takes place at a predetermined reduction position and not, for example,The fact that the feed rate is initiated by a simultaneous measurement makes the process less complex and therefore particularly easy to implement. Thus, the feed rate reduction increases the overall flexibility of the process.
[0026] In a preferred embodiment of the invention, a workpiece is provided in which the toothing structure continues axially to a first free end of the workpiece without run-out, and the feed position is located axially outside the first free end of the workpiece and radially at the level of a depth of the toothing structure at the first free end of the workpiece.
[0027] The first free end of the workpiece refers to a part of the workpiece at which the gear structure ends (axially) and at which no other part of the workpiece, e.g. a shaft, extends radially at the level of the gear structure (or its deepest depth) axially beyond the gear structure. The deepest depth of the gear structure refers here to the areas of the gear structure that have the lowest radial height within the gear structure, in particular a root area or a root line of the gear structure. The radial height of a deepest depth of the gear structure is accordingly in particular a tooth root height of the gear structure. Axially outside the first free end refers here to a position that is selected in the axial direction so that the grinding tool does not touch the workpiece.
[0028] The advantage of this process variant is that the grinding tool can be advanced to the feed position very quickly, since the grinding tool does not interact with the workpiece in the feed position and therefore does not introduce any significant heat into the workpiece. In particular, the feed speed for this variant of the process is 40 mm / min to 100 mm / min. From this feed position, the lifting movement toward the first gear run-out structure can then begin directly. This eliminates the need for slow advance of the grinding tool to the workpiece, allowing gear grinding to be completed more quickly without grinding burn reducing the quality of the product.
[0029] Alternatively, the infeed position can be set radially at a different height. The grinding tool can then, for example, be advanced to a position that engages the gear structure of the workpiece. However, grinding burns could occur at the infeed location if the infeed speed is not adjusted accordingly. A corresponding variant is discussed further down in this document.
[0030] In a preferred variant of the above embodiment of the inventive method, the workpiece is positioned vertically in an axial orientation, with the first free end pointing downwards and the feed position being axially below the workpiece.
[0031] Typically, oil for cooling the workpiece during the grinding process is supplied from above. When the workpiece is oriented with the free end facing downward, the oil is supplied in the opposite direction to the reciprocating motion of the grinding tool. This allows for effective cooling during the inventive method.
[0032] Alternatively, the workpiece can be positioned differently.
[0033] In a preferred alternative to the above-mentioned methods, the provided workpiece comprises a second tooth run-out structure axially opposite the first tooth run-out structure, wherein the feed position is located axially at the level of the second tooth run-out structure and radially at a level of a depth of the tooth structure at an engagement point of the grinding tool.
[0034] In this method, a workpiece is ground whose gear structure includes a second gear run-out structure. The grinding tool is first advanced at the infeed speed to the infeed position on the second gear run-out structure. In particular, the infeed speed has a value of 1% to 3% compared to a typical fastest infeed speed. Preferably, the infeed speed has a value of 1 mm / min to 4 mm / min. The infeed position is located axially in the region of the second gear run-out structure and radially at a position that corresponds to the depth of the gear structure at an engagement point of the grinding tool. The depth of the gear structure at an engagement point of the grinding tool refers to the depth that the gear structure has at the axial position of the infeed position.The grinding tool is positioned so that it can interact with the root area of the gear structure, as well as with the rest of the gear structure. In particular, it is positioned so that it touches the outermost areas of the second gear runout structure.
[0035] The feed rate during the stroke movement can be slower, in particular, than during stroke movements on workpieces without a second gear runout structure. In particular, it has an initial value that is approximately 80% of the maximum feed rate within the grinding process or less, in particular 80% to 20%, preferably 60% to 30%, of the maximum feed rate within the grinding process. In particular, the feed rate is accelerated up to an initial feed rate. The acceleration can be step-like, linear, exponential, or follow a depth profile of the second gear runout structure. In particular, the acceleration can also have a profile that deviates from the (later) reduction in the feed rate (also mirrored in time).
[0036] Alternatively, the feed rate can already correspond to the initial feed rate at the beginning of the stroke movement. In particular, the feed rate can also already correspond to the maximum feed rate within the grinding process.
[0037] Then, the feed is reduced upon reaching a predetermined first reduction position, in particular before reaching the first gear run-out structure.
[0038] This embodiment allows the gear structure of a workpiece having two opposing gear runout structures to be ground in a time-efficient manner.
[0039] In a preferred variant of the invention according to all the above-mentioned alternatives, the feed is reduced to a final feed, wherein the final feed is 80% of the initial feed or less, in particular 80% to 20%, preferably 60% to 30%, of the initial feed.
[0040] The final feed rate refers to the feed rate at which the stroke movement ends when the feed rate is reduced. The feed rate can be reduced to the final feed rate within a short distance of the stroke movement, or it may not reach this value until the end of the stroke movement, for example (see below for further details). A feed rate reduction to a value of 80% of the initial feed rate or less, in particular 80% to 20% of the initial feed rate, preferably 60% to 30% of the initial feed rate, has been shown in tests to effectively prevent grinding burn in the area of the gear run-out structure.
[0041] Alternatively, the feed rate can be reduced to a higher or lower value. However, this could result in less effective burn prevention or a slower process.
[0042] In a preferred embodiment of the invention, the feed is reduced in steps from the initial feed to the final feed. "Stepwise" refers to one or more relatively instantaneous reductions in the feed. The speed progression of the feed along a path of the stroke movement thus follows a descending step function. Preferably, the feed is reduced in a single step from the initial feed to the final feed.
[0043] During the individual reduction stages, the feed is reduced to a different feed value in relation to the distance of the stroke movement or to the length of the gear structure in a comparatively very short distance interval, in particular in a distance interval of 0% to 1% of the length of the gear structure.
[0044] This variant is relatively uncomplicated and therefore easy to monitor and define. Input parameters could, for example, be one (first) or several reduction positions with a corresponding final value for the feed, with the last final value corresponding to the final feed. This is also an attractive variant for studies and measurement series, as the individual measurements would only differ from one another in a few parameters. If the feed is reduced directly from the initial feed to the final feed, this has the advantage that the reduction takes full effect immediately. This also allows the first reduction position to be selected at a comparatively short distance from areas of the gear structure that are critical for grinding burn. This, in turn, ensures an efficient process.In a likewise preferred alternative to the method described above, the reduction of the feed compared to the initial feed is carried out linearly, wherein the feed is continuously reduced linearly to the final feed over a first reduction distance of the stroke movement, starting from the first reduction position and up to a reduction end position.
[0045] A linear reduction means that the feed along a reduction path, between the first reduction position and the end reduction position, essentially follows a linear function, whereby the feed is reduced compared to the initial feed. In particular, the linear reduction also includes feed curves in which the feed is non-linear over relatively short sections at the edges of the reduction path. These short, non-linear curves, in the sense of a smooth reduction of the feed, can ensure that the acceleration (i.e., the first derivative of the feed curve) does not exhibit any jumps. This results in a comparatively smooth reduction of the feed.
[0046] The advantage of this variant is the comparatively simple process, which can be defined with just a few parameters, such as an initial reduction position, an end reduction position, and a final feed rate. At the same time, the feed rate reduction in this variant is minimal or non-steppy, making it suitable, for example, for avoiding unwanted vibrations of the grinding tool during reduction, especially with comparatively high initial feed rates.
[0047] In a further preferred alternative to the above-mentioned method, the feed is reduced exponentially compared to the initial feed, wherein the feed is reduced over a first reduction distance of the stroke movement, starting from the first reduction position and up to a reduction end position to the final feed according to a predetermined exponential function, with the degree of reduction decreasing. This means a profile of the feed along a reduction distance between the first reduction position and the reduction end position essentially according to an exponential function. Exponential functions, in turn, refer to functions that have the profile of an exponential function that consistently corresponds to a reduction in the feed, with the degree of reduction (i.e., the negative slope of the curve) decreasing.
[0048] A possible example is an exponential function of the form f(x) = a exp(-bx) + c, where f(.r) specifies the feedrate at waypoint x, the reduction starts at x = 0 and ends at a positive value of x. The values a and c are positive feedrate values, where (a + c) corresponds to the initial feedrate and c corresponds to a feedrate value that is lower than the final feedrate. The also positive value b is a calibration value that influences how steeply the feedrate converges to the feedrate value c. In particular, the reduction in feedrate can deviate from the exponential form in a comparatively small part of the reduction distance (in particular less than 10% of the reduction distance) at the beginning of the reduction, for example to avoid a sudden change in feedrate.
[0049] The advantage of this type of process is that during the comparatively strongly changing reduction within the reduction section, no acceleration jumps in the feed rate occur, which reduces vibrations.
[0050] In a further preferred variant of the method, the reduction of the feed compared to the initial feed corresponds linearly scaled to a profile of a toothing structure depth of the first toothing run-out structure, wherein the feed of the lifting movement, starting from the first reduction position, is reduced to the final feed according to the profile of the toothing structure depth.
[0051] In this variant, the feed is reduced according to a curve that corresponds to the curve of the gear depth within the gear run-out structure. The reduction distance is again the distance between the first reduction position and the end reduction position. Linearly scaled means that the shape of the reduction corresponds to the shape of the gear structure depth, but can be scaled by a fixed value in relation to this. This scaling thus allows a freely adjustable end feed to be achieved. With this type of process, the total reduction can also be defined in advance. The curve of the gear structure depth must be known at the latest before the reduction begins. The first reduction position can be selected in such a way that the reduction distance corresponds to the length of the gear run-out structure. However, the reduction can also be carried out shortly before this length (e.g.over a distance of less than 10% of the reduction distance) and then follow the course of the gear structure depth as soon as the remaining distance corresponds to the length of the gear run-out structure.
[0052] The advantage of this process is that the feed rate reduction is adapted to the actual shape of the gear structure. The feed rate reduction also starts less abruptly, thus avoiding initial vibrations of the grinding tool during the feed rate reduction.
[0053] In a preferred variant of all the above-mentioned embodiments of the inventive method, the first reduction position is selected such that the reduction of the feed begins before reaching the tooth run-out structure of the workpiece.
[0054] In this case, "before reaching the tooth runout structure" means that the first reduction position is located in an area that lies within the stroke of the stroke movement before the tooth runout structure, i.e., an area in which no point on the grinding tool is at the same axial height as the first tooth runout structure. In particular, the first reduction position is selected such that it triggers a reduction before reaching the tooth runout for a specific workpiece type, preferably for different workpiece types.
[0055] The advantage of this variant of the process is that the reduction ensures that the grinding tool has started the reduction in the area of the first gear run-out structure.
[0056] In a preferred variant of all the above-mentioned embodiments of the inventive method, the workpiece is cooled by an oil cooling system, characterized in that in addition to reducing the feed, an increase in the oil pressure of the oil cooling system of the workpiece takes place.
[0057] Oil cooling here refers to process cooling using a cooling oil, in particular a cooling emulsion. Process heat is dissipated by introducing, in particular spraying, the cooling oil into the grinding area using a feed medium, e.g. a nozzle. This heat dissipation can also influence the formation of grinding burn. The oil pressure refers to the pressure that the cooling oil has at the outlet of the feed medium. In this variant of the process, the workpiece and the grinding tool are cooled by supplying cooling oil to the grinding area. To prevent the formation of grinding burn in the area of the gear run-out structure even more effectively, the oil pressure is increased in addition to reducing the feed rate. The oil pressure influences the amount of cooling oil that is introduced into the grinding area, with higher pressure meaning more cooling oil. This specifically increases the cooling performance of the oil cooling system.
[0058] The advantage of this design is that a targeted increase in the cooling capacity of the oil cooling system, especially in the area of the gear runout structure, contributes to the prevention of grinding burns. This allows for a smaller reduction in feed rate, making the process more time-efficient.
[0059] In a preferred embodiment of the invention, the feed rate has a value in the range from 40 mm / min to 80 mm / min. In particular, this is a preferred embodiment of one of the alternatives in which the feed position is located axially outside a first free end of the workpiece and radially at the level of a depth of the gear structure at the first free end of the workpiece. Thus, the feed rate is significantly faster, in particular by a factor of 10, than a typical feed rate into a position with engagement in the gear structure. The reduction in feed rate in the inventive method can, in particular, be relatively lower (compared to the initial feed rate) than a possible (if at all feasible) reduction in feed rate from such a fast feed rate to a feed rate at which no grinding burn occurs even during engagement.
[0060] The comparatively fast feed rate increases the time efficiency of the process without the risk of grinding burn.
[0061] Such a fast infeed speed can also increase the efficiency of the process for the alternative method in which the workpiece comprises a second gear runout structure axially opposite the first gear runout structure. However, in this variant, the infeed speed should be reduced before the intervention and, in particular, significantly slower after the reduction in the infeed speed to avoid grinding burns. It may also be necessary with this variant to ensure that the reduction occurs far enough away from the workpiece to prevent vibrations from causing damage to the workpiece when reducing the infeed speed.
[0062] Alternatively, the delivery speed can also take on a different, particularly slower, value.
[0063] In a preferred variant of the invention according to all the alternatives already mentioned, the initial feed rate has a value in the range of 500 mm / min to 1300 mm / min. The initial feed rate thus selected is comparatively fast, making the process very efficient.
[0064] Alternatively, the initial feed rate can be set to a different value, particularly slower. However, this makes the process less efficient.
[0065] In a preferred embodiment of the invention, the method comprises the additional step of determining the first reduction position taking into account a grinding tool diameter, in particular a grinding wheel diameter.
[0066] A grinding tool diameter is, for example, the maximum diameter of the grinding tool perpendicular to the axis around which the grinding tool can rotate. In particular, this is the grinding wheel diameter if the grinding tool is a grinding wheel.
[0067] Because the first reduction position is predetermined, the efficiency of the process and the quality of the result depend on the choice of the first reduction position. The effect of the grinding tool on the workpiece, in turn, also depends on the grinding tool diameter. For example, with a comparatively large diameter, the curvature of the grinding tool on its grinding surface becomes less pronounced. This, in turn, makes its grinding effect on the workpiece more extensive, i.e., less localized. Conversely, a grinding tool with a comparatively small diameter has a more localized or pinpoint grinding effect.
[0068] If this factor is taken into account when selecting the first reduction position, the occurrence of grinding burns can be effectively prevented and the process can be made even more efficient. For example, the first reduction position can be positioned particularly close to the tooth run-out structure without the flat effect of the grinding tool causing grinding burns.
[0069] In particular, the first reduction position can be selected so that the reduction distance corresponds to the length of the grinding wheel radius and thus half the grinding tool diameter.
[0070] Alternatively, the first reduction position can be determined without considering the grinding tool diameter, for example. However, this would require larger safety tolerances, making the process less efficient.
[0071] Further advantageous embodiments and combinations of features of the invention emerge from the following detailed description and the entirety of the patent claims.
[0072] Short description of the drawings
[0073] The drawings used to explain the embodiment show:
[0074] Fig. 1 is a schematic representation of a first method according to the invention based on an isometric plan view of a first gear blank,
[0075] Fig. 2 is a schematic representation of the first method using a
[0076] Cross-sectional view of the gear blank, wherein the gear blank is cut at a plane located centrally in a gear structure and running parallel to its depth,
[0077] Fig. 3A shows a first feed curve according to the invention based on an XY-
[0078] diagram, where the feed is reduced step by step,
[0079] Fig. 3B shows a second feed curve according to the invention based on an XY-
[0080] diagram, where the feed is reduced linearly,
[0081] Fig. 3C shows a third feed curve according to the invention based on an XY-
[0082] diagram, where the feed is reduced exponentially,
[0083] Fig. 3D shows a fourth feed curve according to the invention based on an XY-
[0084] diagram, where the feed is reduced linearly scaled following a depth profile of a gear run-out structure, together with a cross-sectional view of a gear blank,
[0085] Fig. 4 shows a second method according to the invention using an isometric
[0086] Top view of a second gear blank with a toothing structure with two toothing run-out structures and
[0087] Fig. 5 is a schematic representation of the second method using a
[0088] Cross-sectional view of the second gear blank, wherein the second gear blank is cut at a plane located centrally in a gear structure and parallel to its depth.
[0089] In principle, identical parts in the figures are provided with identical reference symbols.
[0090] Ways to implement the invention
[0091] Fig. 1 and Fig. 2 show schematic representations of a method 1 according to the invention for pitch profile grinding a gear blank 2. Fig. 1 shows the method 1 using a schematic isometric plan view of the gear blank 2. Fig. 2 shows the method 1 using a partial cross-section of the gear blank 2. The gear blank 2 is essentially cylindrically symmetrical and comprises a likewise cylindrically symmetrical shaft 2.1. Adjacent to the shaft 2.1, the gear blank 2 comprises toothing structures evenly distributed over the circumference, of which the toothing structures 3.1, ..., 3.5 can be seen in Fig. 1. A toothing structure 3.1, ... , 3.5 comprises a groove-shaped depression in the surface of the gear blank 2, running parallel to the cylindrical axis of the gear blank 2. The toothing structures 3.1, ... , 3.5 therefore have no helix angle. The areas between these depressions form the teeth of the gear blank 2.The toothing structures 3.1, ..., 3.5 each have a length (vertical in Fig. 1 and Fig. 2) which corresponds approximately to half the length of the gear blank 2.
[0092] The depth profile of the toothing structure 3.3 can be seen in Fig. 2, which shows a partial cross-section of the gear blank 2 in a plane that runs centrally within the toothing structure 3.3 and parallel to the depth of the toothing structure 3.3. The depth of the toothing structures 3.1, ..., 3.5 remains constant from the free end over approximately 60% of the length of the respective toothing structure 3.1, ..., 3.5. Within the remaining 40% of the length, the toothing structures 3.1, 3.5 comprise tooth runout structures 3.1a,
[0093] ... , 3.5a. In these areas, the depth of the respective toothing structure 3.1, ... , 3.5 decreases along its length with a constant radius of curvature until the depth is completely exhausted.
[0094] In method 1, the gear blank 2 is positioned so that it is fixed for the grinding process. The gear blank 2 is aligned vertically along its axis of symmetry (vertically in the image plane of Fig. 1 and Fig. 2), with the free end pointing downwards. In method 1, a grinding wheel 4 is used for grinding, the radius of which corresponds to the radius of curvature of the tooth run-out structures 3.1a, ... , 3.5a. In a feed movement of 60 mm / min, the grinding wheel 4 is fed to a first feed position 6. The feed position 6 is located axially below the gear blank 2. Radially, the feed position 6 is at a height that corresponds to the root area of the tooth structure 3.3 at the end of the gear blank, i.e. the height of the deepest depth of the tooth structure 3.3 (see Fig. 2).
[0095] After the infeed movement 5 into the infeed position 6, the grinding wheel rotates into the gear structure 3.3 in an initial stroke movement 7, thereby grinding the gear structure 3.3. The grinding wheel rotates in the opposite direction to the stroke movement. The initial stroke movement 7 occurs at an initial feed rate of 600 mm / min and runs parallel to the length of the gear structure 3.3.
[0096] From a predetermined reduction position 8 along the total stroke movement, a reduction in the feed begins, and thus the reduction stroke movement 9. The reduction position 8 was predetermined based on the grinding wheel diameter and the profile of the gear run-out structure 3.3a such that the reduction in the feed occurs before reaching the gear run-out structure 3.3a and without the grinding wheel touching an area of reduced depth (i.e., the gear run-out structure 3.3a) in the reduction position 8. Within the reduction stroke movement 9, the feed is reduced to a final feed that is 50% of the initial feed.
[0097] In this embodiment of the invention, the feed is reduced linearly (see below, Fig. 3B). Further variants of the reduction are illustrated in Fig. 3A, Fig. 3C and Fig. 3D (see further below). The lifting movement 9 ends when the grinding wheel 4 touches the outermost part of the gear run-out structure 3.3a. At the end of the total lifting movement, the grinding wheel 4 is released 10 at a release speed of 15,000 mm / min. After the release 10 is completed, a return stroke movement 11 to the starting position of the grinding wheel takes place with a return feed that is approximately 700% of the initial feed. During the grinding process, cooling oil 12 is supplied. In order to grind further or all of the gear structures 3.1, ..., 3.5, the process 1 must be repeated several times, whereby the gear blank 2 is rotated about its axis of symmetry at a time when the grinding wheel 4 is not in engagement so that a further gear structure 3.1, ..., 3.5 can be ground.
[0098] 3A to 3D schematically show various feed profiles that are possible according to a method according to the invention (e.g. method 1 from Fig. 1 and Fig. 2 or method 401 from Fig. 4 and Fig. 5). Fig. 3A shows a step-like feed reduction. The XY diagram 50 has a Y-axis 50Y, which describes a feed value. The X-axis 50X shows the axial distance of the respective location of the grinding wheel from the infeed position (e.g. infeed position 6 in Fig. 1 and Fig. 2) at the coordinate origin and thus the respective location along the stroke movement. The feed phases 51, 52, 53, 54 and 55 describe the feed along the stroke movement. In a relatively short acceleration phase, via the feed phase 51, the feed is increased to the initial feed. Once the initial feed rate is reached, the feed rate remains constant over a feed phase 52.
[0099] Once the predetermined reduction position 56 is reached (e.g., reduction position 8 in Fig. 1 and Fig. 2), the feed is reduced to a final feed via the feed phase 53. The reduction position 56 is selected such that the feed is reduced from approximately 60% of the total stroke. The feed phase 53 runs over a short distance within the stroke and is therefore step-like. The final feed is 50% of the initial feed. The final feed is maintained constant during the feed phase 54 until the grinding process is completed. After the grinding process has been completed at the feed end position 57, the feed is reduced to zero according to the feed phase 55.
[0100] Fig. 3B shows a linear feed reduction. The X-axis 150X and the Y-axis 150Y of the XY diagram 150 correspond to those in Fig. 3A. In this XY diagram 150, feed phases 151, 152, 153, 154, and 155 describe the feed along the stroke movement. Again, in a brief acceleration via feed phase 151, the feed is increased to the initial feed. Feed phase 152 also corresponds to feed phase 52 from Fig. 3A.
[0101] Upon reaching the predetermined reduction position 156, a linear reduction of the feed begins according to the feed phase 153 over a reduction distance to a final feed at the reduction end position 158, where the final feed is 50% of the initial feed. The reduction position 56 is selected so that the feed is reduced from approximately 60% of the total stroke. The final feed is then maintained through a feed phase 154, which accounts for approximately 11% of the total stroke, until the feed end position 157. It is then reduced to zero over a short distance during the feed phase 155.
[0102] Fig. 3C shows an exponential feed reduction. The X-axis 250X and the Y-axis 250Y of the XY diagram 250 correspond to those of Fig. 3A and Fig. 3B. The feed phases 251 and 252 correspond to those of the embodiments of Fig. 3A and Fig. 3B up to the predetermined reduction position 256. From the reduction position 256 to the end reduction position 258, the feed phase 253 follows an exponential function of the form: jx) = 0.55A exp(-bx) + 0.45A. Here, / (x) is the feed at location x, with x having the value zero at the reduction position 256. A describes the initial feedrate value, and b is a positive calibration value chosen so that f(x) at the reduction end position has the value f(x) = 0.5A, i.e., the final feedrate, which is 50% of the initial feedrate. Starting at the reduction end position 258, the feedrate is kept constant at the final feedrate throughout the feed phase 254.From the feed end position 257, the feed is then reduced relatively quickly to zero.
[0103] Fig. 3D shows a linearly scaled feed reduction following a depth profile. The X-Y diagram 350 as well as the X-axis 350X and the Y-axis 350Y correspond to the XY diagrams 50, 150, and 250 in Figs. 3A to 3C. The initial feed phases 351 and 352 are also analogous to the other exemplary embodiments (Figs. 3A to 3C). For illustration, this time a cross-section of a workpiece 302 with a toothing structure 303.3 and a toothing run-out structure 303.3a is shown, analogous to the cross-section in Fig. 2. In addition, the diagram 350S shows the position of a grinding tool at the reduction position 356 and the end feed position 357. From the reduction position 356, the feed is reduced. The shape of the feed phase 353 corresponds to the depth profile of the gear run-out structure 303.3a with a corresponding linear scaling factor.The feed is thus reduced from an initial feed to a final feed, with the initial feed prevailing at the reduction position 356. The reduction position 356 is selected such that the grinding tool travels a distance to the end feed position 357 that corresponds to the extent of the tooth run-out structure 303.3a (see diagram 350S). The end feed position 357, in turn, is reached when the grinding tool touches the outermost area of the tooth run-out structure 303.3a.
[0104] The progression of the feed in the feed phase 353 then has the same progression as the toothing depth of the toothing run-out structure 303.3a: For example, after the same distance within which the toothing depth drops to half, the feed behind the reduction position 356 is reduced to the feed value that lies midway between the initial and final feed.
[0105] When the grinding tool reaches the feed end position 357, the feed rate is set to the final feed rate, in this case 50% of the initial feed rate. Once the feed end position 357 is reached, the feed rate is then reduced relatively quickly to zero in the feed phase 354.
[0106] Fig. 4 and Fig. 5 show a method 401 as a further embodiment of the invention. Fig. 4 shows the method 401 as a schematic isometric plan view of a provided gear blank 402 with a shaft 402.1. The gear blank 402 comprises evenly distributed and uniform toothing structures on its circumference, of which the toothing structures 403.1, ... 403.5 can be seen in Fig. 4. The toothing structures 403.1, ... , 403.5 are aligned parallel to the axis of symmetry of the gear blank 402 and have a length that corresponds to approximately 80% of the length of the body of the gear blank 402 without the shaft 402.1 along the axis of symmetry of the gear blank 402. Each toothing structure 403.1, ... , 403.5 comprises two opposite
[0107] Gear runout structures, a first gear runout structure 403.1al, ..., 403.5al and a second gear runout structure 403.1a2, ..., 403.5a2.
[0108] The resulting depth profile can be seen in Fig. 5: Fig. 5 shows the method 401 using a schematic cross-section of the provided gear blank 402, wherein the gear blank 402 is cut to a plane that lies centrally within the toothing structure 403.3 and runs parallel to its depth. The depth of the toothing structure 403.3 is constant and maximum centrally over approximately 60% of its length. The toothing runout structures 403.3a1 and 403.3a2 are located at the two longitudinal ends of the toothing structure 403.3. Within each
[0109] In the toothing run-out structure 403.3al and 403.3a2, the depth runs continuously (and following a continuously differentiable curve) to the end of the toothing structure 403.3.
[0110] According to the process, the gear blank 402 is positioned vertically with its shank facing upward and its free end facing downward. The grinding wheel 404 is then advanced to the feed position 406 in an infeed movement 405 at a feed rate of 1.5 mm / min. During the infeed movement 405, the grinding wheel 404 is already rotating.
[0111] The feed position 406 is located axially on the gear blank 402, at the toothing run-out structure 403.3a2 and radially at a height of a depth of the toothing structure 403.3 at an engagement point of the grinding wheel 404. It is located such that the grinding wheel in the feed position 406 touches the outermost area of the toothing run-out structure 403.3a2.
[0112] After completion of the infeed, a lifting movement 407 takes place with a feed rate of 600 mm / min. The lifting movement 407 takes place along the tooth structure 403.3, which is ground by the grinding wheel 404.
[0113] A reduction position 408 is located along the stroke movement before the first tooth run-out structure 403.3al. After reaching the reduction position 408, a reduction stroke movement 409 occurs, during which the feed is reduced to a final feed amounting to 50% of the previous feed. The reduction curve in this case is step-like. However, it can also be analogous to one of the feed curves shown in Fig. 3B to Fig. 3D. The stroke movement 409 ends when the grinding wheel 404 touches the outermost part of the tooth run-out structure 403.3al. At the end of the total stroke movement, a release 410 of the grinding wheel 404 takes place, with a release speed of 15000 mm / min. After completion of the release 410, a return stroke movement 411 to the starting position of the grinding wheel 402 takes place, with a return feed that is approximately 700% of the maximum feed.During the grinding process, cooling oil is supplied 412, with cooling oil being sprayed into the grinding area via a nozzle. To grind additional or all gear structures 403.1, 403.5, process 401 must be repeated several times.
[0114] The invention is not limited to the embodiments described above. For example, a workpiece can be provided that has more or fewer toothed structures. The workpiece need not include a shaft, or can include a shaft with a different shape. The shape of the workpiece can be different from the shapes shown. For example, the workpiece can have different diameters at different positions along the workpiece axis. It is also possible, for example, to provide a workpiece that is longer along the workpiece axis than its diameter.
[0115] The toothing structures can be deeper and longer, or even shallower and shorter, than the toothing structures shown. The toothing depths shown can have a different profile, for example, tapering off at the toothing runout structures with a lesser curvature.
[0116] The grinding tool can also be a grinding worm used in a continuous grinding process. The grinding tool used may have a different dimension than the one shown (schematically) compared to the workpiece and, for example, may have a larger or smaller diameter.
[0117] The workpiece can be positioned differently, e.g., vertically with a shaft pointing downwards, or not vertically but at an angle to a vertical axis. The speed values for the feed, return, stroke, and return stroke movements are purely examples and can be selected differently. The first reduction position can also be different, e.g., positioned so that it initiates a reduction starting halfway through the total stroke. The position outside the workpiece is shown purely schematically and can be further outside the workpiece or closer to it. The oil cooling system can also differ from the schematic representation shown.
[0118] The gradients of the feed curves shown and the relative values of the initial and final feeds may vary. For example, the linear reduction may be steeper, with the final feed being only 40% of the initial feed. It is not necessary for the stroke movement to continue during the final feed with a linear reduction. With a step-like reduction, more than one step-like reduction can occur. The exponential reduction can be steeper or less steep. Here, too, it is optional for a constant feed phase to follow the exponential reduction.
[0119] The toothing structures shown, each with two tooth runout structures, can also have a different shape and, for example, differing depth profiles. In addition to the radial infeed movement, other motion components can exist, bringing the grinding tool to the first infeed position along a more complex path.
[0120] Also, in the case of linear, exponential and linearly scaled reduction following a depth profile, the feed curves can deviate at the transitions (shortly after the reduction position or shortly before the end of the reduction) so that the feed follows a continuously differentiable curve (without abrupt acceleration changes).
[0121] In summary, reducing the feed rate creates a grinding process that enables more flexible machine gear grinding of a workpiece with a runout-limited gear structure.
Claims
Patent claims 1. A method for mechanical gear grinding, in particular for pitch profile grinding, of a workpiece with a run-out-limited gear structure, comprising the following steps: a) providing and positioning a workpiece, wherein the workpiece comprises a run-out-limited gear structure with at least one first gear run-out structure; b) advancing a grinding tool, in particular a grinding wheel, to a feed position; c) reciprocating movement of the grinding tool from the feed position along the gear structure in the direction of the first gear run-out structure with a feed that corresponds to an initial feed; d) beginning a reduction in the feed compared to the initial feed as soon as the grinding tool reaches a predetermined first reduction position along the reciprocating movement; e) completing the reciprocating movement at a reduced feed; f) releasing the grinding tool.
2. The method according to claim 1, wherein a workpiece is provided in which the toothing structure continues axially to a first free end of the workpiece without run-out, and wherein the feed position is located axially outside the first free end of the workpiece and radially at the level of a depth of the toothing structure at the first free end of the workpiece.
3. Method according to claim 2, characterized in that the workpiece is positioned vertically in an axial orientation, with the first free end pointing downwards and the feed position being axially below the workpiece.
4. Method according to claim 1, characterized in that the provided workpiece comprises a second toothing run-out structure axially opposite the first toothing run-out structure, wherein the feed position is located axially at the level of the second toothing run-out structure and radially at a level of a depth of the toothing structure at an engagement point of the grinding tool.
5. Method according to one of claims 1 to 4, characterized in that the feed is reduced to a final feed, wherein the final feed is 80% of the initial feed or less, in particular 80% to 20%, preferably 60% to 30%, of the initial feed.
6. Method according to claim 5, characterized in that the feed is reduced stepwise from the initial feed to the final feed.
7. Method according to claim 5, characterized in that the reduction of the feed compared to the initial feed is linear, wherein the feed is continuously reduced linearly to the final feed over a first reduction distance of the stroke movement, starting from the first reduction position and up to a reduction end position.
8. Method according to claim 5, characterized in that the reduction of the feed compared to the initial feed takes place exponentially, wherein the feed is reduced over a first reduction distance of the stroke movement, starting from the first reduction position and up to a reduction end position to the final feed according to a predetermined exponential function, wherein the degree of reduction decreases.
9. Method according to claim 5, characterized in that the reduction of the feed compared to the initial feed corresponds linearly scaled to a profile of a toothing structure depth of the first toothing run-out structure, wherein the feed of the lifting movement, starting from the first reduction position, is reduced to the final feed according to the profile of the toothing structure depth.
10. Method according to one of claims 1 to 9, characterized in that the first reduction position is selected so that the reduction of the feed begins before reaching the tooth run-out structure of the workpiece.
11. Method according to one of claims 1 to 10, wherein the workpiece is cooled by an oil cooling system, characterized in that in addition to reducing the feed, an increase in the oil pressure of the oil cooling system of the workpiece takes place.
12. The method according to any one of claims 1 to 11, wherein a feed rate has a value in the range of 40 mm / min to 80 mm / min.
13. The method according to any one of claims 1 to 12, wherein the initial feed rate has a value in the range of 500 mm / min to 1300 mm / min.
14. Method according to one of claims 1 to 13, comprising the additional step of determining the first reduction position taking into account the grinding tool diameter, in particular a grinding wheel diameter.