Method for manufacturing gears, and apparatus for manufacturing gears

Abstract

To provide a gear manufacturing method that allows control of the gear pressure angle bias even when using a conventional gear grinding device. [Solution] The method for manufacturing a gear involves using a screw grinding wheel having a screw-shaped grinding section that is formed with a narrow pitch at one end and gradually widens towards the other end, and is formed with the same pressure angle from one end to the other end, and rotating the gear around the axis of the gear's central axis and the screw grinding wheel in the axial direction, while controlling the combined feed in the X-axis direction and the Z-axis direction to perform lead crowning on each tooth of the gear with the screw grinding wheel, and also controlling the feed direction and feed speed of the combined feed in the Y-axis direction and the Z-axis direction to perform grinding on each tooth of the gear with the screw grinding wheel in a way that changes the reference pitch circle diameter of the gear between one end and the other end along the tooth width direction of each tooth of the gear.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a gear and a gear manufacturing apparatus.

Background Art

[0002] The grinding process of the teeth of a gear as a workpiece to be machined is generally performed by three-dimensionally moving a thread grinding wheel disposed in a numerically controlled continuous generating gear grinding apparatus (hereinafter, mainly referred to as a gear grinding apparatus). Currently, there are a conventional gear grinding apparatus without a pressure angle bias adjustment mechanism and a latest gear grinding apparatus equipped with a pressure angle bias adjustment mechanism (adjustment grinding mechanism).

[0003] The latest gear grinding apparatus is very expensive and difficult to introduce easily. Therefore, the conventional gear grinding apparatus occupies most of the existing machines in the world. Usually, since the purchased machining equipment is generally used continuously for about 20 to 40 years, it is expected that the conventional gear grinding apparatus will continue to be used for some time.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] To ensure that even with variations in precision, gear teeth have a lead crowning shape to avoid problems with strength and noise. When a lead crowning shape is created on gear teeth using a conventional or state-of-the-art gear grinding machine with an appropriate screw grinding wheel, a pressure angle bias is applied to the gear teeth. There is an optimal amount of pressure angle bias; if the bias is too large or too small, problems with noise and strength performance are likely to occur when the gear teeth are in contact with the mating gear. Therefore, when manufacturing (grinding) gears, it is necessary to control the pressure angle bias (i.e., control the tooth contact with the mating gear).

[0006] When grinding a workpiece (machined workpiece) such as a helical gear using a conventional gear grinding machine with a standard constant-pitch screw grinding wheel, if a lead crowning shape is created on the gear teeth, an uncontrolled, spontaneous pressure angle is formed on the gear teeth.

[0007] The present invention aims to provide a gear manufacturing method and a gear manufacturing apparatus that can control the pressure angle bias by changing the pressure angle of the teeth of the gear workpiece in the tooth trace direction (tooth width direction), even when using a conventional gear grinding apparatus that does not have a pressure angle bias adjustment mechanism. [Means for solving the problem]

[0008] To solve the above problems, a gear manufacturing method according to one aspect of the present invention involves a screw grinding wheel having a screw-shaped grinding portion which is formed to gradually widen or gradually narrow as it moves from one end to the other end, and which is formed to have the same pressure angle from one end to the other end, and the movement of the screw grinding wheel in the Y-axis direction (Y) along the central axis of the screw grinding wheel, the movement of the screw grinding wheel in the X-axis direction (X) perpendicular to the central axis of the gear which is the workpiece to be machined using the screw grinding wheel, and moving closer to and further away from the gear, the movement of the screw grinding wheel in the Z-axis direction (Z) parallel to the central axis of the gear and perpendicular to the X-axis direction and the Y-axis direction, and the movement of the screw grinding wheel The method involves rotating the central axis in the direction of rotation (B) and making the central axis of the screw grinding wheel rotatable in a predetermined YZ plane in the direction of rotation (A), rotating the gear around the axis of the central axis of the gear, and rotating the screw grinding wheel in the direction of rotation (B), while controlling the combined feed in the X-axis direction and the Z-axis direction to perform lead crowning on each tooth of the gear with the screw grinding wheel, and controlling the feed direction and feed rate of the combined feed in the Y-axis direction and the Z-axis direction to perform grinding on each tooth of the gear with the screw grinding wheel in a way that changes the reference pitch circle diameter of the gear between one end and the other end along the tooth width direction of each tooth of the gear. [Effects of the Invention]

[0009] According to the present invention, even when using a conventional gear grinding apparatus that does not have a pressure angle bias adjustment mechanism, it is possible to change the pressure angle of the teeth of the gear workpiece and control the pressure angle bias, thereby providing a gear manufacturing method and a gear manufacturing apparatus. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic block diagram of a gear grinding apparatus (screw grinding wheel, gear manufacturing apparatus) according to one embodiment. [Figure 2] A schematic diagram showing the positional relationship between the threaded grinding portion of the screw grinding wheel and the dresser, as well as the feed direction of the dresser. [Figure 3]Figure 2 shows a schematic diagram of one end, the other end, and the region between them of a screw grinding wheel sharpened using the dresser shown, as well as a magnified view of one end and the other end. [Figure 4] A schematic diagram showing the positional relationship between the grinding part of the screw grinding wheel and the gear, which is the workpiece (processed workpiece), before and after grinding. [Figure 5] A schematic diagram showing the relationship between the grinding part of the screw grinding wheel and the gear, viewed from the direction indicated by arrow V in Figure 4. [Figure 6] Figures 4 and 5 show schematic diagrams of an example where the grinding portion of the screw grinding wheel is applied to the teeth of a gear, and a schematic enlarged view of the position indicated by reference numeral 6A. [Figure 7] A schematic flowchart illustrating the series of gear manufacturing processes (manufacturing methods) using screw grinding wheels. [Figure 8] A schematic diagram showing the movement of one end of the grinding portion of a screw grinding wheel when grinding the teeth of a gear, as viewed from the gear side (the workpiece) during the creation of a gear. [Figure 9] A schematic diagram showing the movement of the other end of the grinding portion of a screw grinding wheel when grinding the teeth of a gear, as viewed from the gear side (the workpiece) during the creation of a gear. [Figure 10] Figure 8 shows a gear tooth ground with one end of the grinding section of the screw grinding wheel, and Figure 9 shows a gear tooth ground with the other end of the grinding section of the screw grinding wheel, superimposed on each other. [Figure 11] (A) is a schematic perspective view of a helical gear, and (B) is a schematic view of one tooth of the helical gear shown in (A) from the direction indicated by arrow 11B in (A). [Figure 12] (A) is a schematic cross-sectional view along the ZX plane of one tooth shown in Figure 11(B), and (B) is a diagram showing the tooth profile on the side indicated by the symbol R (R tooth profile) and the tooth profile on the side indicated by the symbol L (L tooth profile) at the positions indicated by the symbols I, II, and III in (A). [Figure 13] A schematic diagram showing the direction and region of meshing (contact line) between the tooth surface of one tooth of a helical gear acting as the driving gear and the tooth surface of one tooth of a helical gear acting as the driven gear. [Figure 14] Schematic diagram showing the positions of the contact lines at the initial stage of engagement, the mid-stage of engagement, and the final stage of engagement between the tooth surface of one tooth of the hypoid gear as the driving-side gear shown in FIG. 13 and the tooth surface of one tooth of the hypoid gear as the driven-side gear. [Figure 15] Schematic diagram showing a state in which the tooth contact surface on the tooth surface of the hypoid gear as the driving-side gear is controlled to an appropriate bias amount during the period from the initial stage of engagement to the final stage of engagement between the hypoid gears shown in FIG. 14. [Figure 16] (A) is a schematic diagram showing a state in which the tooth contact surface on the tooth surface of the hypoid gear as the driving-side gear is formed with an insufficient bias amount during the period from the initial stage of engagement to the final stage of engagement between the hypoid gears shown in FIG. 14. (B) is a schematic diagram showing an example of the actual tooth contact surface due to variations in the component accuracy of the gears when using the gear in the state of being formed with the insufficient bias amount shown in (A). (C) is a schematic diagram showing another example different from (B) of the actual tooth contact surface due to variations in the component accuracy of the gears when using the gear in the state of being formed with the insufficient bias amount shown in (A). [Figure 17] Schematic diagram showing a state in which the tooth contact surface on the tooth surface of the hypoid gear as the driving-side gear is formed with an excessive bias amount during the period from the initial stage of engagement to the final stage of engagement between the hypoid gears shown in FIG. 14.

Embodiments for Carrying out the Invention

[0011] Hereinafter, an NC continuous generating gear grinding apparatus (hereinafter, mainly referred to as a gear grinding apparatus) 1 according to an embodiment of the present invention, and a method for manufacturing a thread grinding wheel 10 and a gear 50 using the same will be described with reference to FIGS. 1 to 17.

[0012] FIG. 1 shows a schematic block diagram of the gear grinding apparatus 1.

[0013] FIG. 2 shows a schematic view showing the positional relationship between the threaded grinding portion 10a of the screw grinding wheel 10 and the dresser 30, and the feed direction of the dresser 30. FIG. 3 shows a schematic view of one end portion 20a, the other end portion 20b of the grinding portion 10a of the screw grinding wheel 10, and the region therebetween, which are highlighted using the dresser 30 shown in FIG. 2. In FIG. 3, one end portion 20a and the other end portion 20b of the grinding portion 10a of the screw grinding wheel 10 are shown enlarged, while the illustration of the grinding portion 10a in the region between the one end portion 20a and the other end portion 20b is omitted. The two-dot chain line of the one end portion 20a in FIG. 3 indicates the depth-side surface of the threaded grinding portion 10a. In the present embodiment, the grinding portion 10a of the screw grinding wheel 10 will be described as a single-thread screw, but it may be a double-thread screw, a triple-thread screw, or the like.

[0014] FIG. 4 shows a schematic view showing the positional relationship before or after grinding between the grinding portion 10a of the screw grinding wheel 10 and a gear 50 as a workpiece to be machined (workpiece). FIG. 5 shows a schematic view showing the relationship between the grinding portion 10a of the screw grinding wheel 10 and the gear 50. Note that FIG. 4 is a schematic view seen from the direction indicated by arrow IV in FIG. 5. FIG. 5 is a schematic view seen from the direction indicated by arrow V in FIG. 4.

[0015] In FIGS. 4 and 5, the symbol I refers to a cross-section at the same position of the gear 50. The symbol II in FIGS. 4 and 5 refers to a cross-section at the same position of the gear 50, and the symbol III in FIGS. 4 and 5 refers to a cross-section at the same position of the gear 50.

[0016] FIG. 6 is a schematic view showing an example of a state where the grinding portion 10a of the screw grinding wheel 10 shown in FIGS. 4 and 5 is applied to the tooth 62 of the gear 50.

[0017] The gear grinding apparatus 1 shown in Figure 1 comprises a screw grinding wheel holder 12 for holding a screw grinding wheel 10 (see Figures 2-6), a screw grinding wheel operating mechanism 14 for operating the screw grinding wheel 10 by operating the screw grinding wheel holder 12, a dresser holder 32 for holding a dresser 30 (see Figure 2), a dresser operating mechanism 34 for moving the dresser 30 in a predetermined direction by moving the dresser holder 32 in a predetermined direction, a workpiece holder 52 for holding a workpiece 50 (see Figures 4-6), a workpiece rotation mechanism 54 for rotating the workpiece 50 in an appropriate direction by operating the workpiece holder 52, and a control unit 3 for controlling the screw grinding wheel operating mechanism 14, the dresser feeding mechanism 34, and the workpiece rotation mechanism 54.

[0018] Generally, the gear grinding apparatus 1 is capable of dressing the screw grinding wheel 10 and grinding, i.e., manufacturing, the gear 50 using the screw grinding wheel 10. For this reason, the gear grinding apparatus 1 can be used as a manufacturing apparatus for the screw grinding wheel 10 and also as a manufacturing apparatus for the gear 50.

[0019] The screw grinding wheel holder 12 holds a screw grinding wheel 10, which can be selected from, for example, several types. The screw grinding wheel operating mechanism 14 moves the screw grinding wheel holder 12 in three dimensions. Therefore, the screw grinding wheel 10 fixed to the screw grinding wheel holder 12 is moved in three dimensions by the screw grinding wheel operating mechanism 14.

[0020] In this embodiment, the operating mechanism 14 of the screw grinding wheel 10 is (1) Movement of the screw grinding wheel 10 in the Y-axis direction (Y) along the central axis (Y) of the screw grinding wheel 10, (2) Movement of the screw grinding wheel 10 in the X-axis direction (X) perpendicular to the central axis (C) of the gear 50, and approaching and moving away from the gear 50, (3) Movement of the screw grinding wheel 10 in the Z-axis direction (Z) parallel to the central axis C of the gear 50 and perpendicular to the X-axis and Y-axis, (4) Rotation of the screw grinding wheel 10 in the direction (B) around its central axis (Y), and (5) Rotation of the central axis (Y) of the screw grinding wheel 10 in the direction (A) This is possible. The rotation of the central axis (Y) of the screw grinding wheel 10 in the rotation direction (A) described in (5) above is rotation in the YZ plane. In Figure 4, the X-axis direction and the Z-axis direction are orthogonal for the screw grinding wheel 10. On the other hand, in Figure 5, the Y-axis direction and the Z-axis direction are not orthogonal for the screw grinding wheel 10, but they may be orthogonal.

[0021] The dresser holder 32 holds, for example, a dresser 30 selected from multiple options. The dresser operating mechanism 34 operates the dresser holder 32. Therefore, the dresser 30 fixed to the dresser holder 32 is operated by the dresser operating mechanism 34.

[0022] In this embodiment, the dresser operating mechanism 34 has a feed mechanism that moves the dresser 30 in a predetermined direction. The dresser operating mechanism (feed mechanism) 34 moves the dresser holder 32 while adjusting it to an appropriate speed. As a result, the dresser 30 is moved in a predetermined direction while being adjusted to an appropriate speed. The control unit 3 controls the dresser operating mechanism 34 and can vary the speed of the dresser holder 32 and the dresser 30. As a result, the control unit 3 can control the dresser operating mechanism 34 and gradually increase or decrease the feed speed of the dresser holder 32 and the dresser 30.

[0023] The dresser 30 can be selected from single-point dressers, multi-point dressers, embedded dressers, block dressers, rotary dressers, etc. When a rotary dresser is used as the dresser 30, the dresser operating mechanism 34 has a rotary dresser rotation mechanism. The rotation axis of the rotary dresser rotation mechanism is parallel to the central axis of the screw grinding wheel 10.

[0024] The dresser operating mechanism 34 according to this embodiment preferably does not have a mechanism for oscillating the dresser 34 within the plane of the paper shown in Figure 2, for example, and does not have an adjustment mechanism for adjusting the pressure angle of the grinding portion 10a of the screw grinding wheel 10, but even if it has such a mechanism, it does not need to be used. Furthermore, the screw grinding wheel 10 according to this embodiment can be used in conventional gear grinding devices 1 that do not have a pressure angle bias adjustment mechanism, as well as in the latest gear grinding devices 1 that do have a pressure angle bias adjustment mechanism.

[0025] The workpiece holder 52 holds, for example, a gear 50, which is a workpiece selected from multiple options. The workpiece rotation mechanism 54 rotates the workpiece holder 52 around the axis of its central axis C. Therefore, the gear 50 fixed to the workpiece holder 52 is rotatable around the axis of its central axis C by the workpiece rotation mechanism 54.

[0026] The control unit 3 is a computer, and physically comprises memory such as RAM and ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, and an information storage unit such as a hard disk. Examples of the control unit 3 include a personal computer, a cloud server, and a tablet terminal. The control unit 3 functions by executing programs stored in memory using the processor.

[0027] The control unit 3 can, for example, synchronously control the rotational speed of the central axis Y of the screw grinding wheel 10 and the dressing feed speed, which moves the dresser 30 in the direction along the central axis Y of the screw grinding wheel 10 while fixing the angle of the screw grinding wheel shaping dresser 30 with respect to the thread-shaped grinding portion 10a of the screw grinding wheel 10. If the dresser 30 is a rotary dresser, rotation around the central axis of the dresser 30 is permitted. Furthermore, the control unit 3 can, for example, perform lead crowning (for example, the feed indicated by the symbol CF1 in Figure 4) on each tooth 62 of the gear 50 by controlling the combined feed in the X-axis direction and the Z-axis direction while rotating the gear 50 around the central axis C of the gear 50 and the screw grinding wheel 10 in the axial direction (B), and can also perform shift grinding (for example, the feed indicated by the symbol CF2 in Figure 5) by controlling the feed direction and feed speed of the combined feed in the Y-axis direction and the Z-axis direction.

[0028] The manufacturing process (manufacturing method) for a gear 50 using a screw grinding wheel 10 with a gear grinding machine (screw grinding wheel, gear manufacturing machine) 1 will be explained using the flowchart shown in Figure 7. Here, an example using a conventional gear grinding machine 1 that does not have a pressure angle bias adjustment mechanism will be explained, but the same screw grinding wheel 10 may also be used with a state-of-the-art gear grinding machine 1 that has a pressure angle bias adjustment mechanism, and the gear grinding machine 1 may be operated according to the operation described later.

[0029] In this embodiment, an example of manufacturing a helical gear as the gear 50 is described, but it can be similarly used to manufacture other types of gears, such as spur gears, bevel gears, and worm gears.

[0030] [Dressing of screw grinding wheel 10 (Step ST1)] This section describes a method for dressing the grinding portion 10a of the screw grinding wheel 10, that is, a method for manufacturing the grinding portion 10a of the screw grinding wheel 10.

[0031] The screw grinding wheel 10 shown in Figure 2 is rotatable in the direction (B) around its central axis Y by the operating mechanism 14 of the screw grinding wheel 10. Furthermore, the dresser 30 shown in Figure 2 is movable parallel to the axial direction of the central axis Y of the screw grinding wheel 10 by the operating mechanism (feed mechanism) 34 of the dresser 30.

[0032] The control unit 3 then synchronously controls the rotational speed of the central axis Y of the screw grinding wheel 10 and the dressing feed speed, which moves the dresser 30 in a direction along the central axis Y of the screw grinding wheel 10 while fixing the angle of the screw grinding wheel shaping dresser 30 with respect to the screw-shaped grinding portion 10a of the screw grinding wheel 10.

[0033] In this process, the dresser 30 fixes the angle of the screw grinding wheel shaping dresser 30 relative to the screw-shaped grinding portion 10a of the screw grinding wheel 10, thereby manufacturing the screw-shaped grinding portion 10a of the screw grinding wheel 10 to have the same pressure angle from one end 20a on one end of the screw grinding wheel 10 to the other end 20b on the other end. Therefore, the pressure angle of the screw-shaped grinding portion 10a of the screw grinding wheel 10 does not change along the tooth trace direction of the grinding portion 10a.

[0034] Furthermore, the control unit 3 maintains, for example, the rotational speed (B) around the central axis Y of the screw grinding wheel 10 at a predetermined state, and controls the feed rate of the dresser 30 parallel to the central axis Y of the screw grinding wheel 10 to shape the screw grinding wheel 10 so that one end has a narrow pitch and the pitch gradually widens towards the other end, or so that one end has a wide pitch and the pitch gradually narrows towards the other end. The control unit 3 gradually increases the feed rate (dressing feed rate) of the dresser 30 when shaping the screw grinding wheel 10 from one end to the other, so that one end has a narrow pitch and the pitch gradually widens towards the other end. Also, the control unit 3 gradually decreases the feed rate (dressing feed rate) of the dresser 30 when shaping the screw grinding wheel 10 so that one end has a wide pitch and the pitch gradually narrows towards the other end. For example, one end of the screw grinding wheel 10 is designated as an expanded pitch section 20a, and the other end is designated as a narrow pitch section 20b. The pitch of the expanded pitch section 20a is Pa, and the pitch of the narrow pitch section 20b is Pb( <Pa)である。

[0035] In this way, the gear grinding apparatus 1 manufactures a screw grinding wheel 10 which has a screw-shaped grinding section 10a with gradually different pitches from one end to the other, but with the same pressure angle.

[0036] The same pressure angle means that the pressure angle α on the left side of the grinding section 10a, as shown in Figure 3, is the same in all sections between the widened pitch section 20a and the narrowed pitch section 20b, and the pressure angle β on the right side, as shown in Figure 3, is the same in all sections between the widened pitch section 20a and the narrowed pitch section 20b. Therefore, the pressure angles α and β are the same on both the left and right sides of the section between the widened pitch section 20a and the narrowed pitch section 20b (the section where the pitch is narrower than the widened pitch section 20a and wider than the narrowed pitch section 20b). A reasonable error between angles α and angles β is permitted. Angles α and β are angles with respect to a virtual line extending radially from the central axis Y of the screw grinding wheel 10. The absolute values ​​of angles α and β may be the same or different.

[0037] [Method for grinding a workpiece (gear 50) (manufacturing method) (Steps ST2-ST3)] This document describes a method for grinding the teeth 62 of a gear 50 using the grinding portion 10a of a screw grinding wheel 10, that is, a method for manufacturing a gear 50 using the grinding portion 10a of a screw grinding wheel 10.

[0038] In the gear grinding apparatus 1, it is preferable to use the screw grinding wheel 10, as described in [Dressing Method (Manufacturing Method) for Screw Grinding Wheel 10], without removing it from the screw grinding wheel holder 12. Of course, it is also preferable to remove the screw grinding wheel 10 from the screw grinding wheel holder 12 in order to grind the target gear 50, and then appropriately attach a screw grinding wheel 10, for example, one stocked in the same factory where the gear grinding apparatus 1 is installed, to the screw grinding wheel holder 12 for use. Here, we will assume that the screw grinding wheel 10, as described in [Dressing Method (Manufacturing Method) for Screw Grinding Wheel 10], is used without removing it from the screw grinding wheel holder 12.

[0039] When grinding the teeth 62 of the gear 50, the operating mechanism 14 of the screw grinding wheel 10 of the gear grinding device 1 is controlled by the control unit 3 to operate the screw grinding wheel holder 12 and the screw grinding wheel 10 as described in (1)-(5) above.

[0040] The control unit 3 determines whether the gear 50 is properly attached to the work holder 52 (step ST2). The gear 50 is fixed to the work holder 52 and rotatable by the work rotation mechanism 54. Therefore, the gear 50 is rotatable around a predetermined central axis C.

[0041] If the gear 50 is not properly mounted to the work holder 52 (Step ST2-No), the process is repeated until the gear 50 is properly mounted to the work holder 52. If the gear 50 is properly mounted to the work holder 52 (Step ST2-Yes), the screw grinding wheel 10 is moved and the gear 50 is rotated around its central axis C to perform gear grinding (Step ST3).

[0042] When grinding the gear 50 using the screw grinding wheel 10, the control unit 3 rotates the gear 50 around a predetermined central axis C, for example, at a predetermined number of rotations per unit time, more specifically, at a constant rotational speed. In this state, the control unit 3 rotates the gear 50 around the central axis C of the gear 50 and the screw grinding wheel 10 in the axial direction B, and controls the combined feed of the screw grinding wheel 10 in the X-axis and Z-axis directions as shown in Figure 4, thereby performing lead crowning (for example, the feed indicated by the symbol CF1 in Figure 4) on each tooth 62 of the gear 50 with the screw grinding wheel 10. Furthermore, the control unit 3 rotates the gear 50 around the axis C of the gear 50 and the screw grinding wheel 10 in the axial direction B, and controls the feed direction and feed speed of the combined feed in the Y-axis direction and Z-axis direction as shown in Figure 5, thereby performing shift grinding (for example, the feed indicated by the symbol CF2 in Figure 5) along the tooth width direction (tooth trace direction) of each tooth 62 of the gear 50 between one end 621 (see Figure 11(B)) and the other end 622 (see Figure 11(B)). The control unit 3 simultaneously performs these three-dimensional operations of lead crowning and shift grinding of the screw grinding wheel 10, and performs generative grinding on the teeth 62 of the gear 50 as shown in Figures 8 and 9.

[0043] If the thread grinding wheel 10 is, for example, a single-start thread grinding wheel, the thread advances by one pitch for each rotation of the grinding wheel axis Y. Simultaneously, the rotation axis C of the gear 50, which is the workpiece, is rotated by one tooth pitch, resulting in a generation process that forms an involute tooth surface.

[0044] Figure 8 shows one end 20a of the grinding portion 10a of the screw grinding wheel 10, and also shows the movement of the end 20a of the grinding portion 10a of the screw grinding wheel 10 when grinding the teeth 62 of the gear 50 with the end 20a of the grinding portion 10a of the screw grinding wheel 10, as viewed from the gear 50 side, which is the workpiece during the generation process. Therefore, Figure 8 shows a part of the trajectory Ea of the end 20a of the grinding portion 10a of the screw grinding wheel 10 relative to the gear 50 during the generation process. Figure 9 shows the other end 20b of the grinding portion 10a of the screw grinding wheel 10, and also shows the movement of the other end 20b of the grinding portion 10a of the screw grinding wheel 10 when grinding the teeth 62 of the gear 50 with the end 20b of the grinding portion 10a of the screw grinding wheel 10, as viewed from the gear 50 side, which is the workpiece during the generation process. Therefore, Figure 9 shows a portion of the trajectory Eb of the other end 20b of the grinding portion 10a of the screw grinding wheel 10 relative to the gear 50 during the generation process.

[0045] Figure 10 shows, superimposed, the teeth 62 of a gear 50 ground with one end 20a of the grinding portion 10a of the screw grinding wheel 10 shown in Figure 8, and the teeth 62 of a gear 50 ground with the other end 20b of the grinding portion 10a of the screw grinding wheel 10 shown in Figure 9. The solid lines in Figure 10 represent the teeth 62 of the gear 50 shown in Figure 8, and the dashed lines represent the teeth 62 of the gear 50 shown in Figure 9.

[0046] As shown in Figures 8 to 10, the tooth surfaces 62a and 62b of the teeth 62 of the gear 50 were shift-ground using the screw grinding wheel 10, which has a grinding section 10a where the pitch gradually changes between one end 20a and the other end 20b, as described in this embodiment, by moving the screw grinding wheel 10 in the Y-axis direction. Therefore, grinding of the tooth surfaces 62a of the teeth 62 of the gear 50 was performed using the screw grinding wheel 10, while shifting the axis of the screw grinding wheel 10 in synchronization with the axial grinding feed of the gear 50. At this time, the pitch circle diameter of the gear 50 changes continuously for each cross section perpendicular to the central axis C of the gear 50, corresponding to the screw pitch of the grinding section 10a of the screw grinding wheel 10, as the gear 50 is formed. Therefore, the tooth surfaces 62a and 62b of the teeth 62 of the gear 50 are machined along the tooth width direction of the teeth 62 of the gear 50, where the reference pitch circle diameter of the gear 50 gradually changes between one end and the other end. As shown in Figure 8, the reference pitch circle diameter dwa of the portion of the gear teeth 62 machined at one end 20a of the screw grinding wheel 10 with a wider pitch is larger than the reference pitch circle diameter dwb of the portion of the gear teeth 62 machined at the other end 20b of the gear 50 with a narrower pitch. Therefore, the pressure angle of the tooth surfaces 62a and 62b of each tooth 62 machined using the screw grinding wheel 10 according to this embodiment changes along the tooth trace direction of the tooth 62.

[0047] Since the pressure angle of the grinding portion (teeth) 10a of the screw grinding wheel 10 is constant, the machining process imposes a pressure angle bias on the tooth surface 62a of the teeth 62 of the gear 50, which is the workpiece. However, the pressure angle bias can be adjusted by changing the shift feed direction and shift feed speed of the screw grinding wheel 10's axis relative to the axial feed of the screw grinding wheel 10 along the central axis C of the gear 50 during machining. For example, when grinding the gear 50 with the screw grinding wheel 10, it is preferable to keep the movement of the screw grinding wheel 10 in the Y-axis direction (Y) at a constant speed.

[0048] Therefore, when shift grinding is performed on each tooth 62 of a gear 50 using a screw grinding wheel 10 having a grinding portion 10a with the same pressure angle from one end to the other, the tooth profile of each tooth 62 of the gear 50 gradually changes between the one end 621 and the other end 622 along the tooth width direction, resulting in gears 50 with different pressure angle tooth profiles. In other words, regardless of the pressure angle of the grinding portion 10a of the screw grinding wheel 10, the screw pitch of the grinding portion 10a is gradually changed from one end to the other, thereby gradually changing the pressure angle of the teeth 62 of the gear 50, which is the workpiece, along the tooth trace direction. Such a pressure angle is controlled by controlling the feed direction and feed rate of the combined feed in the Y-axis and Z-axis directions during shift grinding.

[0049] After grinding the gear 50 using the screw grinding wheel 10 in this manner, the control unit 3 determines whether the processed gear 50 has been removed from the screw grinding wheel holder 12 and whether there is another gear 50 to be processed (step ST4).

[0050] If there is no gear 50 to be machined next (step ST4-No), the grinding process of the workpiece (gear 50) is terminated.

[0051] If there are gears 50 to be machined next (step ST4-Yes), the control unit 3 determines whether a predetermined number of gears 50 have been manufactured using the same screw grinding wheel 10 (step ST5).

[0052] If the predetermined number of gears 50 have not been manufactured (step ST5-No), the process of steps ST2-ST5 is performed.

[0053] If this process is repeated and a predetermined number of gears 50 are manufactured (step ST5-Yes), then the processes in steps ST1-ST5 are performed.

[0054] Here, Figure 11(A) shows a schematic perspective view of the helical gear 50, and Figure 11(B) shows a schematic view of one tooth of the helical gear 50 shown in Figure 11(A) from the direction indicated by arrow 11B in Figure 11(A). Note that the symbols I, II, and III in Figures 11(A) and 11(B) correspond to the positions indicated by symbols I, II, and III in Figures 4 and 5. Figure 12(A) shows a schematic cross-sectional view of one tooth 62 shown in Figure 11(B) along the ZX plane. Note that Figure 12(A) shows not only one tooth 62 but also adjacent teeth 62. Figure 12(B) shows the tooth profile on the side indicated by symbol R (R tooth profile) and the tooth profile on the side indicated by symbol L (L tooth profile) at the positions indicated by symbols I, II, and III in Figure 12(A).

[0055] As shown in Figures 12(A) and 12(B), each tooth 62 of the gear 50, which is the workpiece, has a different pressure angle tooth profile at the positions indicated by symbols I, II, and III. Therefore, the pressure angles in the tooth trace direction of the tooth surfaces 62a and 62b of each tooth 62 of the gear 50 are different. A gear 50 in which the pressure angles along the tooth trace direction of the tooth surfaces 62a and 62b of each tooth 62 are adjusted (controlled) can be obtained by shift grinding using a screw grinding wheel 10 with a constant pressure angle and a screw-shaped grinding section 10a in which the screw pitch gradually changes from one end to the other, while controlling the feed direction and feed speed of the combined feed in the Y-axis and Z-axis directions of the screw grinding wheel 10.

[0056] Here, pressure angle bias refers to the error in the pressure angle (inclination of the tooth profile) of each tooth 62 of the gear 50, which is varied for each cross-section indicated by symbols I, II, and III. In reality, the pressure angle of each tooth 62 of the gear 50 is varied not only for the three cross-sections indicated by symbols I, II, and III, but for many more cross-sections.

[0057] In the generation process using the screw grinding wheel 10, if a lead crowning shape is created on each tooth 62 of the workpiece gear 50 by lead crowning, the helix angle of the gear 50 will be different for each cross section indicated by symbols I, II, and III, which unintentionally introduces a pressure angle bias.

[0058] Figure 13 shows the direction in which the contact line between the tooth surface 62a of one tooth 62 of the helical gear 50a (the driving gear) and the tooth surface 64a of one tooth 64 of the helical gear 50b (the driven gear) advances, and the meshing region is indicated by reference numerals 63 and 65. Figure 14 shows the positions of the contact lines 63a and 65a at the initial stage of meshing, the contact lines 63b and 65b at the middle stage of meshing, and the contact lines 63c and 65c at the final stage of meshing of the tooth surfaces 62a and 64 of one tooth 62 and 64 of the gears 50a and 50b.

[0059] As shown in Figures 13 and 14, the teeth 62 of the helical gear 50a, which is the driving gear, have contact lines 63a-63c moving from the tooth root side to the tooth tip side, and the teeth 64 of the helical gear 50b, which is the driven gear, have contact lines 65a-65c moving from the tooth tip side to the tooth root side.

[0060] Figures 15 to 17 will be used to explain the magnitude of the bias amount in the pressure angle bias of gears 50a and 50b.

[0061] Figure 15 is a schematic diagram showing the state in which the tooth contact surface S0 of the tooth surface 62a of tooth 62 of helical gear 50a, which acts as the driving gear, is controlled to an appropriate bias amount from the initial stage to the final stage of meshing between the helical gears 50a and 50b shown in Figure 14. In the example shown in Figure 15, the tooth contact surface S0 of the tooth surface 62a of tooth 62 of helical gear 50a follows the region that is the trajectory of the meshing contact line, indicated by reference numeral 63 in Figure 13, between it and the tooth surface 64a of tooth 64 of helical gear 50b. This state is described as the state in which the tooth surface 62a of tooth 62 of helical gear 50a is controlled to an appropriate bias amount. In this way, when the shape of the tooth surface 62a is controlled so that the tooth contact is along the direction of progression 63 of the meshing contact, even if there is some variation in the precision of the helical gears 50a and 50b, the tooth contact between the helical gears 50a and 50b is stable, and the gear noise is stabilized.

[0062] Figure 16(A) is a schematic diagram showing the state in which the tooth contact surface S1 on the tooth surface 62a of the tooth 62 of the helical gear 50a, which acts as the drive gear, is formed with an insufficient bias amount from the initial stage to the final stage of meshing of the helical gears shown in Figure 14. When the tooth contact surface S1 is larger than the tooth contact surface S0 shown in Figure 15, which is along the direction of progression 63 of the meshing contact, the bias amount of the tooth contact surface S1 is said to be small. In the case of an insufficient bias amount, for example, if there is no bias amount, the tooth contact surface S1 of the teeth 62 and 64 of the helical gears 50a and 50b is theoretically wide, as shown in Figure 16(A), and the tooth surfaces 62a and 64a of the teeth 62 and 64 of the helical gears 50a and 50b make contact over a large surface area, which should result in high performance. However, variations within the precision tolerance of gears 50a and 50b are naturally acceptable. In reality, due to variations in the precision of the gears 50a and 50b, the tooth surfaces 62a and 64a of teeth 62 and 64 of the helical gears 50a and 50b tend to make uneven contact, as shown by the tooth contact surface indicated by the symbol S1a in Figure 16(B) or the tooth contact surface indicated by the symbol S1b in Figure 16(C). Therefore, if the tooth surfaces 62a and 64a of teeth 62 and 64 of gears 50a and 50b are controlled to an insufficient bias amount, the gear noise performance tends to vary.

[0063] Figure 17 is a schematic diagram showing the state in which the tooth contact surface S2 on the tooth surface 62a of the tooth 62 of the helical gear 50a, which is the driving gear, is formed with an excessive bias amount from the initial stage to the final stage of meshing of the helical gears 50a and 50b shown in Figure 14. When the tooth contact surface S2 is small compared to the tooth contact surface S0 shown in Figure 15, which is along the direction of progression 63 of the meshing contact, the bias amount of the tooth contact surface S2 is considered to be large. In the case of an excessive bias amount, the tooth contact surface S2 tends to be narrower compared to the example shown in Figure 15 or Figure 16(A). Even if the precision of the individual gears 50a and 50b varies, the tooth contact is less affected, but the area of ​​the tooth contact surface S2 is small. For this reason, if the tooth surfaces 62a and 64a of the teeth 62 and 64 of gears 50a and 50b are controlled with an excessive bias amount, it is difficult to improve the gear noise performance.

[0064] Therefore, when manufacturing a gear 50 by grinding it using a screw grinding wheel 10, as described above, it is required that the pressure angle bias of each tooth 62 of the gear 50 be controlled so that it has an appropriate bias amount (see Figure 15).

[0065] For example, suppose the grinding surface of a screw grinding wheel has the same pressure angle and the same pitch from one end to the other. In this case, if lead crowning is performed on each tooth of a gear to create a lead crowning shape, the amount of bias in the pressure angle bias cannot be controlled and will be determined as it is.

[0066] On the other hand, in this embodiment, when lead crowning is performed on a screw grinding wheel 10 having a grinding section 10a where the pitch gradually changes from one end to the other while maintaining the same pressure angle from one end to the other, shift grinding is combined to machine each tooth 62 of the gear 50. When performing shift grinding, the reference pitch circle diameter is adjusted between one end and the other end along the tooth trace direction (tooth width direction) of the teeth 62 of the gear 50 by controlling, for example, the feed direction and feed speed of the screw grinding wheel 10, and the tooth surfaces 62a and 62b of each tooth 62 are machined while the pressure angle is adjusted. For this reason, in this embodiment, the tooth surfaces 62a and 62b of each tooth 62 of the gear 50 are formed by controlling the reference pitch circle diameter along the tooth width direction.

[0067] Furthermore, when performing shift grinding, by appropriately controlling not only the feed direction and feed speed of the screw grinding wheel 10, but also the way (amount of change) the pitch changes from one end to the other of the grinding section 10a, the adjustment range of the reference pitch circle diameter that changes from one end to the other along the tooth trace direction (tooth width direction) of the teeth 62 of the gear 50 can be increased.

[0068] Therefore, when a gear 50 is manufactured by grinding the screw grinding wheel 10 according to this embodiment using the gear grinding device 1, the pressure angle bias of each tooth 62 of the gear 50 can be controlled to achieve an appropriate bias amount (see Figure 15).

[0069] In the case of manufacturing a gear 50 by grinding a screw grinding wheel 10 using a gear grinding apparatus 1 according to this embodiment, the gear grinding apparatus 1 appropriately modifies the programs for dressing the screw grinding wheel 10 and grinding the gear 50, stores them in a control unit 3 (which is a computer), and controls the screw grinding wheel 10 and the dresser 30, as well as the gear 50 and the screw grinding wheel 10, according to these programs. Therefore, the gear grinding apparatus 1 does not require any hardware modifications or improvements, such as adding a new movable axis to the dresser 30.

[0070] When grinding a gear 50 using a screw grinding wheel 10, the control unit 3 appropriately synchronizes the workpiece rotation mechanism 54 and the screw grinding wheel operating mechanism 14 of the screw grinding wheel 10, operates the screw grinding wheel operating mechanism 14, and performs shift grinding, which controls the feed direction and feed speed of the combined feed of the screw grinding wheel 10 in the Y-axis and Z-axis directions, thereby controlling the pressure angle bias of the teeth 62 of the gear 50 being ground.

[0071] Furthermore, by controlling the tooth contact in the meshing of the tooth surfaces 62a of the teeth 62 of the gear 50 manufactured using the gear grinding apparatus 1 according to this embodiment, and adjusting (controlling) the tooth contact with a pressure angle bias, the meshing noise and vibration level of the tooth surfaces 62a of the teeth 62 of the gear 50 can be reduced.

[0072] In this embodiment, by applying a screw grinding wheel 10, which has a screw-shaped grinding portion 10a formed with a pitch that gradually expands or contracts from one end to the other and is formed with the same pressure angle from one end to the other, to a conventional gear grinding device 1 that does not have a pressure angle bias adjustment mechanism, the pressure angle bias of the tooth surfaces 62a and 62b of each tooth 62 of the gear 50 can be adjusted. Therefore, even when using a conventional gear grinding device 1, the pressure angle bias of the tooth surfaces 62a and 62b of each tooth 62 of the gear 50 can be controlled in the same way as with the latest gear grinding devices. At this time, the teeth 62 of the gear 50 can be formed with the intended pressure angle bias, and the pressure angle bias of the workpiece gear 50 can be adjusted at a very low cost.

[0073] Furthermore, the screw grinding wheel 10 having the grinding section 10a can also be used in a state-of-the-art gear grinding device 1 that has a pressure angle bias adjustment mechanism.

[0074] Therefore, according to this embodiment, even when using a conventional gear grinding device that does not have a pressure angle bias adjustment mechanism, it is possible to provide a method for manufacturing a screw grinding wheel 10, a screw grinding wheel 10, a method for manufacturing a gear 50 using the screw grinding wheel 10, and a gear manufacturing device 1 for the gear 50, which can change the pressure angle of the teeth 62 of the gear 50 and control the pressure angle bias.

[0075] With respect to the screw grinding wheel 10 described in this embodiment, the following matters can be obtained as described in the appendix below.

[0076] [Note 1] The screw grinding wheel rotates around a predetermined central axis. The rotational speed of the central axis of the screw grinding wheel and the dressing feed speed, which moves the dresser in a direction along the central axis of the screw grinding wheel while fixing the angle of the dresser relative to the screw grinding wheel, are controlled synchronously to shape the screw grinding wheel with the same pressure angle from one end to the other, and with the pitch gradually widening or narrowing as the screw grinding wheel moves from one end to the other. A method for manufacturing a screw grinding wheel.

[0077] [Note 2] A screw grinding wheel having a thread-shaped grinding section that is formed with a gradually widening pitch or gradually narrowing pitch from one end to the other, and with the same pressure angle from one end to the other.

[0078] It should be noted that the present invention is not limited to the embodiments described above, and can be modified in various ways during implementation without departing from its essence. Furthermore, each embodiment may be combined as appropriate, and in that case, the combined effects can be obtained. Moreover, the above embodiments include various inventions, and various inventions can be extracted by selecting combinations from the multiple constituent elements disclosed. For example, if the problem can be solved and effects obtained even if some constituent elements are deleted from all the constituent elements shown in the embodiment, then the configuration with these deleted constituent elements can be extracted as an invention. [Explanation of Symbols]

[0079] 1...Gear grinding machine (screw grinding wheel, gear manufacturing machine), 3...Control unit, 10...Screw grinding wheel, 10a...Grinding section, 12...Screw grinding wheel holder, 14...Screw grinding wheel operating mechanism, 20a...One end (wide pitch section), 20b...Other end (narrow pitch section), 30...Screw grinding wheel shaping dresser, 32...Dresser holder, 34...Dresser operating mechanism, 50...Workpiece (gear), 50a, 50b...Gear, 52...Workpiece holder, 54...Workpiece rotation mechanism, 62...Tooth, 62a...Tooth surface, 63a-63c...Contact line, 64...Tooth, 64a...Tooth surface, 65a-65c...Contact line, 621...One end, 622...Other end, S0, S1, S1a, S1b, S2...Tooth contact surface.

Claims

1. A screw grinding wheel having a threaded grinding section, which is formed with a gradually widening pitch or gradually narrowing pitch from one end to the other, and with the same pressure angle from one end to the other, Movement of the screw grinding wheel in the Y-axis direction (Y) along the central axis of the screw grinding wheel, The movement of the screw grinding wheel in the X-axis direction (X) is perpendicular to the central axis of the gear, which is the workpiece to be machined using the screw grinding wheel, and moves closer to and further away from the gear. Movement of the screw grinding wheel in the Z-axis direction (Z) parallel to the central axis of the gear and perpendicular to the X-axis direction and the Y-axis direction, The rotation of the screw grinding wheel in the direction (B) around the central axis, The central axis of the screw grinding wheel rotates in a predetermined YZ plane in a rotational direction (A) This enables the following: the gear is rotated around the axis of the gear's central axis, and the screw grinding wheel is rotated in the direction of the axis (B). By controlling the combined feed in the X-axis direction and the Z-axis direction, lead crowning is performed on each tooth of the gear with the screw grinding wheel. Furthermore, by controlling the feed direction and feed speed of the combined feed in the Y-axis direction and the Z-axis direction, the screw grinding wheel is used to perform grinding along the tooth width direction of each tooth of the gear, changing the reference pitch circle diameter of the gear between one end and the other end. A method for manufacturing gears, comprising:

2. The grinding portion of the screw grinding wheel is formed by synchronously controlling the rotational speed of the central axis of the screw grinding wheel, which rotates the screw grinding wheel around a predetermined central axis, and the dressing feed speed, which moves the dresser in a direction along the central axis of the screw grinding wheel while fixing the angle of the dresser for forming the screw grinding wheel with respect to the grinding portion, thereby forming the screw grinding wheel with a gradually widening pitch or a gradually narrowing pitch from one end to the other, and maintaining the same pressure angle from one end to the other. A manufacturing method according to claim 1, comprising:

3. The dressing feed rate is set from one end of the screw grinding wheel toward the other end. When forming the screw grinding wheel with a narrow pitch at one end and gradually increasing the pitch towards the other end, the speed is gradually increased. When shaping the screw grinding wheel by widening the pitch at one end and gradually narrowing the pitch towards the other end, the process is to gradually slow down. The manufacturing method according to claim 2.

4. Grinding the gear with the screw grinding wheel includes maintaining a constant speed for the movement of the screw grinding wheel in the Y-axis direction (Y). The manufacturing method according to any one of claims 1 to 3.

5. A rotation mechanism that rotates a gear, which is the workpiece, around a predetermined central axis, A screw grinding wheel having a threaded grinding section that is formed with a gradually widening pitch or gradually narrowing pitch from one end to the other, and with the same pressure angle from one end to the other, Movement of the screw grinding wheel in the Y-axis direction (Y) along the central axis of the screw grinding wheel, Movement of the screw grinding wheel in the X-axis direction (X) perpendicular to the central axis of the gear, and approaching and moving away from the gear, Movement of the screw grinding wheel in the Z-axis direction (Z) parallel to the central axis of the gear and perpendicular to the X-axis direction and the Y-axis direction, The rotation of the screw grinding wheel in the direction (B) around the central axis, The central axis of the screw grinding wheel rotates in a predetermined YZ plane in a rotational direction (A) The operating mechanism of the screw grinding wheel, Control unit controls the rotation mechanism to rotate the gear around the axis of the gear's central axis, and controls the operating mechanism to rotate the screw grinding wheel in the axial direction (B), while performing lead crowning on each tooth of the gear with the screw grinding wheel, which has a different pitch on one end and the other end, by a combined feed in the X-axis direction and the Z-axis direction, and by controlling the feed direction and feed speed of the combined feed in the Y-axis direction and the Z-axis direction, the screw grinding wheel performs grinding that changes the reference pitch circle diameter of the gear between one end and the other end along the tooth width direction of each tooth of the gear. A gear manufacturing apparatus having the following features.

6. A dresser for shaping screw grinding wheels, which is applied to the grinding portion of the screw grinding wheel and sharpens the grinding portion while keeping its angle fixed, A dresser feed mechanism moves the dresser while changing the feed speed in a direction along the central axis of the screw grinding wheel. It has, The control unit is capable of synchronously controlling the feed speed of the dresser by the dresser feed mechanism with the rotational speed of the screw grinding wheel. The manufacturing apparatus according to claim 5.

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