Carbide hob, hobbing machine, and gear finishing method
The cemented carbide hob with specific flute and groove ratios addresses inefficiencies in gear finishing post-quenching by shortening processing time and reducing man-hours through optimized cutting edge distribution.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- KASHIFUJI
- Filing Date
- 2026-05-27
- Publication Date
- 2026-07-24
Smart Images
Figure 2026121604000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a cemented carbide hob, a hob arbor, and a gear finishing method.
Background Art
[0002] As a processing method for finishing a gear after quenching, a method of finishing the quenched gear with a hob is known. For example, Patent Document 1 describes a gear finishing method for finishing a hardened work gear with a hob.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] In the finishing of a gear after quenching, it is required to shorten the processing time while using a cemented carbide hob suitable for finishing. An object of the present invention is to provide a cemented carbide hob, a hob arbor, and a gear finishing method that are easy to shorten the processing time in the finishing of a gear after quenching.
Means for Solving the Problems
[0005] A cemented carbide hob as one aspect of the present means is a cemented carbide hob for finishing a gear after quenching, comprising a plurality of flutes and a plurality of cutting edge grooves, the number of flutes which is the total number of the plurality of flutes is 6 or more, and the groove number to flute number ratio which is a value obtained by dividing the total number of the plurality of cutting edge grooves by the number of flutes is 5 or less.
[0006] A hob arbor as one aspect of the present means comprises the above cemented carbide hob.
[0007] One embodiment of the present invention is a gear finishing method in which a hardened gear is finished with a carbide hob, wherein the carbide hob has a plurality of grooves and a plurality of cutting edge grooves, and the method includes the steps of selecting a carbide hob that satisfies all of conditions A, B, C, and D according to the number of teeth of the gear, and finishing the gear with the selected carbide hob, wherein condition A is that the total number of grooves is 6 or more, condition B is that the groove-to-groove ratio obtained by dividing the total number of cutting edge grooves by the number of grooves is 5 or less, condition C is that the number of grooves is a non-integer multiple of the number of grooves, and condition D is that the number of teeth of the gear is a non-integer multiple of the number of grooves.
[0008] The above-described carbide hob, hobbing machine, or gear finishing method can provide the following effects, for example: Since the number of grooves in the carbide hob is 6 or more, the amount of machining progress per revolution of the carbide hob is greater compared to when a hob with fewer grooves is used for finishing. This makes it easier to shorten the machining time per gear in the finishing of gears after hardening. In addition, since the groove-to-groove ratio of the carbide hob is 5 or less, it is easier to prevent the number of grooves from becoming excessively large relative to the number of grooves. This makes it easier to suppress the increase in manufacturing man-hours for carbide hobs that occurs with an increase in the number of grooves. [Effects of the Invention]
[0009] According to the carbide hob, hobbing machine, and gear finishing method of the present invention, the processing time can be easily shortened when finishing gears after hardening. [Brief explanation of the drawing]
[0010] [Figure 1] A diagram showing an example of a hobbing machine according to an embodiment. [Figure 2] A diagram showing an example of a carbide hob and gear according to an embodiment. [Figure 3] A diagram showing tooth profile errors corresponding to carbide hobs with 15 grooves and 24 grooves, and 15 grooves and 25 grooves. [Figure 4] A diagram showing tooth profile errors corresponding to carbide hobs with 15 grooves and 26 grooves, and 15 grooves and 27 grooves. [Figure 5] A diagram showing tooth profile errors corresponding to carbide hobs with 15 grooves and 28 grooves, and 15 grooves and 29 grooves. [Figure 6] A diagram showing tooth profile errors corresponding to carbide hobs with 15 grooves and 30 grooves, and 15 grooves and 31 grooves. [Figure 7] A diagram showing tooth profile errors corresponding to a carbide hob with 15 grooves and 32 grooves. [Modes for carrying out the invention]
[0011] (Hob record) Refer to Figure 1. The hobbing machine 10 is a device for machining the gear 100 using a hob. Examples of machining the gear 100 using the hobbing machine 10 include rough machining, semi-finishing, and finishing.
[0012] Hobs are classified according to their application or material. Examples of hob classification by application include roughing hobs, semi-finishing hobs, and finishing hobs. Examples of hob classification by material include high-speed tool steel hobs and carbide hobs. Carbide hobs are an example of hobs used in gear finishing after heat treatment.
[0013] The hobbing machine 10 of this embodiment is used to finish a hardened gear 100 with a carbide hob 20. The hobbing machine 10 comprises a bed 11, a hob support section 12, a workpiece support section 13, a hob-side feed mechanism 14, and a workpiece-side feed mechanism 15.
[0014] The bed 11 supports the components of the hobbing machine 10. The bed 11 is located at the bottom of the hobbing machine 10. The bed 11 is directly or indirectly provided with a hob support section 12, a workpiece support section 13, a hob-side feeding mechanism 14, and a workpiece-side feeding mechanism 15.
[0015] The hob support 12 supports the carbide hob 20. The hob support 12 supports the carbide hob 20 so that it can rotate around its axis. The hob support 12 rotates the carbide hob 20. The carbide hob 20 rotates while being supported by the hob support 12.
[0016] The workpiece support portion 13 supports the gear 100. The workpiece support portion 13 rotatably supports the gear 100. The gear 100 rotates while being supported by the workpiece support portion 13. The gear 100 rotates in synchronization with the carbide hob 20.
[0017] The hob side feed mechanism 14 moves the hob support portion 12. The hob side feed mechanism 14 moves the carbide hob 20 supported by the hob support portion 12 relative to the gear 100. In one example, the hob side feed mechanism 14 moves the carbide hob 20 in a direction approaching or separating from the gear 100. In another example, the hob side feed mechanism 14 moves the carbide hob 20 in a direction along the axial direction of the gear 100.
[0018] The workpiece side feed mechanism 15 moves the workpiece support portion 13. The workpiece side feed mechanism 15 moves the gear 100 supported by the workpiece support portion 13 relative to the carbide hob 20. In one example, the workpiece side feed mechanism 15 moves the gear 100 in a direction approaching or separating from the carbide hob 20. In another example, the workpiece side feed mechanism 15 moves the gear 100 in a direction along the axial direction of the gear 100.
[0019] At least one of the hob side feed mechanism 14 and the workpiece side feed mechanism 15 relatively moves the carbide hob 20 and the gear 100. Thereby, the machining position between the carbide hob 20 and the gear 100 changes. The hob disk 10 synchronizes the rotation of the carbide hob 20 supported by the hob support portion 12 and the rotation of the gear 100 supported by the workpiece support portion 13.
[0020] (Carbide hob) Referring to FIG. 2, the carbide hob 20 is a finishing hob for finishing the heat-treated gear 100. The carbide hob 20 includes a plurality of strips 21, a plurality of cutting edge grooves 22, and a plurality of cutting edges 23.
[0021] The groove 21 is a threaded cutting portion formed on the carbide hob 20. The cutting edge groove 22 is a groove provided in the groove 21 to form the cutting edge 23. Multiple cutting edge grooves 22 are provided on the carbide hob 20 at intervals from each other in the circumferential direction.
[0022] The cutting edge 23 is a cutting edge that cuts the gear 100. The cutting edge 23 is formed in the groove 21 in a portion adjacent to the cutting groove 22. As the carbide hob 20 rotates, the cutting edge 23 cuts the tooth surface 102 of the gear 100.
[0023] In the carbide hob 20, at least the portion constituting the cutting edge 23 is formed of carbide material. The entire carbide hob 20 may be formed of carbide material. The carbide hob 20 may have a wear-resistant coating on the surface of the cutting edge 23.
[0024] Carbide materials are sintered materials containing hard particles and a binder phase that binds the hard particles together. The hard particles include, for example, tungsten carbide. The binder phase includes, for example, cobalt. Carbide materials have high hardness and wear resistance. Therefore, even when a carbide hob 20 is used for finishing the gear 100 after quenching, wear on the cutting edge 23 is not easily advanced.
[0025] (Specifications of a carbide hob) The total number of grooves 21 formed on the carbide hob 20 is denoted as "Number of grooves N". The total number of cutting edge grooves 22 formed on the carbide hob 20 is denoted as "Number of grooves G". The groove-to-groove ratio, which is the value obtained by dividing the groove-to-groove ratio G by the number of grooves N, is denoted as "Groove-to-groove ratio K".
[0026] The groove-to-thread ratio K of the carbide hob 20 is 5 or less. Assuming that the carbide hob 20 is used for finishing the gear 100 after hardening, any groove-to-thread ratio K of 5 or less can be adopted. Examples of the range of groove-to-thread ratio K that can be adopted in the carbide hob 20 are given below. In the first example, the ratio of grooves to rows K is between 1.2 and 5. In the second example, the ratio of grooves to rows K is between 1.5 and 5. In the third example, the ratio of grooves to rows K is between 1.5 and 3. In the fourth example, the ratio of grooves to rows K is between 2 and 3.
[0027] The number of threads N for the carbide hob 20 is 6 or more. Assuming that the carbide hob 20 is used for finishing the gear 100 after hardening, any number of threads N greater than or equal to 6 can be adopted. Examples of the range of threads N that can be adopted for the carbide hob 20 are given below. In the first example, the number of rows N is 6 or greater. In the second example, the number of rows N is 8 or greater. In the third example, the number of rows N is 9 or greater. In the fourth example, the number of rows N is 10 or greater. In the fifth example, the number of rows N is 16 or greater.
[0028] (gear) Gear 100 is to be finished with a carbide hob 20. Gear 100 is, for example, a spur gear or a helical gear. Gear 100 is, for example, an external gear or an internal gear. Gear 100 is a hardened gear. Hardened gears include gears that have undergone heat treatment including hardening. Examples of heat treatments including hardening include carburizing, hardening and tempering, and induction hardening.
[0029] Gear 100 has multiple teeth 101. The total number of teeth 101 formed on gear 100 is denoted as "tooth count Z". Each tooth 101 has a pair of tooth surfaces 102. The tooth surfaces 102 are surfaces that are finished by a carbide hob 20. Before finishing, gear 100 has machining allowance on the tooth surfaces 102. Tooth grooves 103 are formed between adjacent teeth 101. The tooth grooves 103 are defined by the tooth surface 102 of one tooth 101 and the tooth surface 102 of the other tooth 101.
[0030] (Finishing process) The carbide hob 20 removes the remaining machining allowance from the tooth surface 102. The carbide hob 20 finishes machining the tooth surface 102 along the tooth groove 103. In the finishing of gear 100, after gear 100 has completed one rotation, the same tooth 101 reaches the machining position again. For the finishing of the same tooth 101 by the carbide hob 20, the machining performed earlier in a series of machining operations will be referred to as the "previous machining operation," and the machining performed later will be referred to as the "next machining operation."
[0031] When the cutting edge 23 acts on the tooth surface 102, machining marks are formed on the tooth surface 102. These machining marks are formed in accordance with the position where the cutting edge 23 cuts the tooth surface 102. When the same tooth 101 is machined again, the position of the machining marks formed on the tooth surface 102 changes according to the change in the position where the cutting edge 23 acts on the tooth surface 102.
[0032] (Selection of carbide hobs according to the number of teeth) This section explains the selection of a carbide hob 20 according to the number of teeth Z. In one example, the number of threads N and the number of grooves G of the carbide hob 20 used for finishing gear 100 are set according to the number of teeth Z of gear 100. The number of teeth divided by the number of threads N is called the "number of teeth ratio L".
[0033] When the number of grooves G is an integer multiple of the number of threads N, the arrangement of the cutting edge grooves 22 corresponding to each thread 21 is aligned. Therefore, when machining the gear 100 with the carbide hob 20, the positional relationship in which the cutting edges 23 act on the tooth surface 102 is aligned at a constant period. As a result, when the same tooth 101 is machined again, the position of the machined mark aligns with the position in the tooth profile direction from the previous machining.
[0034] In one example, the number of grooves G in the carbide hob 20 is a non-integer multiple of the number of threads N. That is, the groove-to-thread ratio K is not an integer. When the number of grooves G is a non-integer multiple of the number of threads N, the relationship between the number of grooves G and the number of threads N is not divisible. Therefore, the positional relationship between each thread 21 and the cutting edge groove 22 differs for each thread 21. As a result, when the same tooth 101 is machined again, the position in which the cutting edge 23 acts on the tooth surface 102 is unlikely to be the same as in the previous machining.
[0035] When the number of teeth Z is an integer multiple of the number of threads N, the threads 21 that machine the same tooth are common to both the previous and next machining operations. Therefore, when the same tooth 101 reaches the machining position again after one rotation of the gear 100, the positional relationship in which the cutting edge 23 acts on the tooth surface 102 is the same as in the previous machining operation. As a result, when the same tooth 101 is machined again, the position of the machining marks aligns with the position in the tooth profile direction to that of the previous machining operation.
[0036] In one example, the number of teeth Z of gear 100 is a non-integer multiple of the number of threads N. That is, the tooth-to-thread ratio L is not an integer. When the number of teeth Z is a non-integer multiple of the number of threads N, the number of teeth Z and the number of threads N have an indivisible relationship. Therefore, even if the same tooth 101 reaches the machining position again after gear 100 has completed one rotation, the positional relationship between gear 100 and the carbide hob 20 will not be repeated in the same state. As a result, when the same tooth 101 is machined again, the position in which the cutting edge 23 acts on the tooth surface 102 will not be the same as the position in the previous machining operation.
[0037] If the number of grooves G is a non-integer multiple of the number of threads N, and the number of teeth Z is a non-integer multiple of the number of threads N, then when the same tooth 101 is machined again, the position where the cutting edge 23 acts on the tooth surface 102 will be shifted from the position where the cutting edge 23 acted during the previous machining.
[0038] If the position in which the cutting edge 23 acts on the tooth surface 102 shifts, the position of the next machining mark will also shift relative to the position of the previous machining mark. As a result, the previous machining mark, which was formed during the previous machining, and the next machining mark, which will be formed during the next machining, will be shifted in the tooth profile direction on the tooth surface 102.
[0039] When machining marks are repeatedly formed at the same position on the tooth surface 102, periodic fluctuations in the amount of error on the tooth surface 102 or tooth profile are likely to occur. In contrast, when there is a difference between the previous machining mark and the next machining mark, the phase of the periodic fluctuations in the amount of error appearing on the tooth surface 102 or tooth profile changes. This makes it easier to suppress the increase in polygonal error, which will be discussed later.
[0040] (polygon error) This section explains polygonal error. Polygonal error is an error that periodically appears on the tooth surface 102 or tooth profile of gear 100. At each evaluation position on the tooth surface 102 or tooth profile, the difference between the shape obtained by measurement or calculation and the reference shape is determined as the amount of error. Polygonal error appears as a periodic fluctuation in the distribution of the amount of error at multiple evaluation positions. Polygonal error can be represented, for example, as a waveform that shows the periodic fluctuation of the amount of error. Reduction of polygonal error is evaluated, for example, by reducing the amplitude of the waveform, the difference between the maximum and minimum values, or the peak-to-peak value.
[0041] A waveform is composed of multiple peaks and troughs. The phase of polygonal error is represented by the positional relationship between the peaks and troughs in the waveform. A change in the phase of polygonal error means that the positions of the peaks and troughs in the waveform during the next machining process are different from the positions of the peaks and troughs in the waveform during the previous machining process.
[0042] When the number of grooves G is a non-integer multiple of the number of threads N, and the number of teeth Z is a non-integer multiple of the number of threads N, when the same tooth 101 is machined again after one rotation of the gear 100, the machined marks on the tooth surface 102 are likely to be shifted relative to the machined marks on the previous machined marks. As a result, the phase of the waveform representing the polygonal error during the next machining is likely to change relative to the phase of the waveform representing the polygonal error during the previous machining.
[0043] An example of waveform phase change is given. The waveform representing the polygonal error formed during the previous machining process is referred to as the "previous waveform," and the waveform representing the polygonal error formed during the next machining process is referred to as the "next waveform." The previous waveform has a first peak and a first trough. The next waveform has a second peak and a second trough.
[0044] If the phase of the next waveform is shifted relative to the phase of the previous waveform, the first peak of the previous waveform and the second peak of the next waveform will not easily correspond to the same position on the tooth surface 102. In this case, the machining marks of the next work will not easily overlap with the position corresponding to the first peak of the previous waveform. As a result, the error component corresponding to the first peak of the previous waveform will be reduced by being machined away during the next machining process. Consequently, polygonal errors are more easily reduced during the finishing process of the gear 100 after hardening with the carbide hob 20.
[0045] (Regarding wear resistance) Since gear 100 is a hardened gear, the tooth surface 102 is highly hard at the time of finishing. Therefore, the hob used for finishing requires high wear resistance. In the hobbing machine 10 of this embodiment, a carbide hob 20 is used as the hob for finishing gear 100.
[0046] The carbide hob 20 is formed from carbide material, at least in the portion constituting the cutting edge 23. Carbide material is superior in hardness and wear resistance compared to high-speed tool steel. For this reason, the carbide hob 20 is suitable for finishing the gear 100 after quenching.
[0047] In the finishing process of the gear 100 after hardening, the amount of material removed from the tooth surface 102 is smaller compared to the rough machining. As a result, the cutting edge 23 may not cut sufficiently into the tooth surface 102, and contact between the cutting edge 23 and the tooth surface 102 may continue. In this case, wear of the cutting edge 23 may progress more easily.
[0048] In the carbide hob 20, the number of threads N is 6 or more. Therefore, compared to using a hob with fewer than 6 threads N, the number of threads 21 on the carbide hob 20 is greater. For example, having 6 or more threads N makes it easier to shorten the distance that a single cutting edge 23 travels while acting on the tooth surface 102. This makes it easier to suppress prolonged contact between a single cutting edge 23 and the tooth surface 102. In addition, it is easier to increase the number of threads 21 involved in machining the gear 100, and the cutting action on the tooth surface 102 is more easily distributed among multiple threads 21. As a result, when finishing the gear 100 after hardening, the load acting on a single cutting edge 23 is more easily reduced. With the reduction in load, wear of the carbide hob 20 is more easily suppressed. In addition, the finishing of the gear 100 becomes more stable.
[0049] (Examples) Examples of the carbide hob 20 will be described. The number of grooves N and the number of teeth G of the carbide hob 20 in each example are set according to the gear 100 having 8 teeth Z.
[0050] The carbide hob 20 of Example Q1 has the following specifications: The number of threads N is 15. The number of grooves G is 24. The groove-to-thread ratio K is 24 / 15, which is approximately 1.60. The tooth-to-thread ratio L is 8 / 15, which is approximately 0.53. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0051] The carbide hob 20 of Example Q2 has the following specifications: The number of threads N is 15. The number of grooves G is 25. The groove-to-thread ratio K is 25 / 15, which is approximately 1.67. The tooth-to-thread ratio L is 8 / 15, which is approximately 0.53. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0052] The carbide hob 20 of Example Q3 has the following specifications: The number of threads N is 15. The number of grooves G is 26. The groove-to-thread ratio K is 26 / 15, which is approximately 1.73. The tooth-to-thread ratio L is 8 / 15, which is approximately 0.53. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0053] The carbide hob 20 of Example Q4 has the following specifications: The number of threads N is 15. The number of grooves G is 27. The groove-to-thread ratio K is 27 / 15, which is approximately 1.80. The tooth-to-thread ratio L is 8 / 15, which is approximately 0.53. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0054] The carbide hob 20 of Example Q5 has the following specifications: The number of threads N is 15. The number of grooves G is 28. The groove-to-thread ratio K is 28 / 15, which is approximately 1.87. The tooth-to-thread ratio L is 8 / 15, which is approximately 0.53. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0055] The carbide hob 20 of Example Q6 has the following specifications: The number of threads N is 15. The number of grooves G is 29. The groove-to-thread ratio K is 29 / 15, which is approximately 1.93. The tooth-to-thread ratio L is 8 / 15, which is approximately 0.53. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0056] The carbide hob 20 of Example Q7 has the following specifications: The number of threads N is 15. The number of grooves G is 30. The groove-to-thread ratio K is 30 / 15, which is 2.00. The tooth-to-thread ratio L is 8 / 15, which is approximately 0.53. The groove-to-thread ratio K is an integer. The tooth-to-thread ratio L is not an integer.
[0057] The carbide hob 20 of Example Q8 has the following specifications: The number of threads N is 15. The number of grooves G is 31. The groove-to-thread ratio K is 31 / 15, which is approximately 2.07. The tooth-to-thread ratio L is 8 / 15, which is approximately 0.53. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0058] The carbide hob 20 of Example Q9 has the following specifications: The number of threads N is 15. The number of grooves G is 32. The groove-to-thread ratio K is 32 / 15, which is approximately 2.13. The tooth-to-thread ratio L is 8 / 15, which is approximately 0.53. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0059] Figures 3 to 7 show the tooth profile errors for hardened gears 100 finished with carbide hobs 20 in each embodiment. Figure 3 shows the tooth profile errors for gears 100 finished with carbide hobs 20 with 15 grooves and 15 grooves and 25 grooves. Figure 4 shows the tooth profile errors for gears 100 finished with carbide hobs 20 with 15 grooves and 26 grooves and 15 grooves and 27 grooves. Figure 5 shows the tooth profile errors for gears 100 finished with carbide hobs 20 with 15 grooves and 28 grooves and 15 grooves and 29 grooves. Figure 6 shows the tooth profile errors for gears 100 finished with carbide hobs 20 with 15 grooves and 30 grooves and 15 grooves and 31 grooves. Figure 7 shows the tooth profile errors for gears 100 finished with carbide hobs 20 with 15 grooves and 32 grooves. Furthermore, the carbide hob 20 with 15 grooves and 30 grooves corresponding to Example Q7 is similar to Examples Q1-Q6, Q8, and Q9 in that the number of grooves N is 6 or more, and the groove-to-groove ratio K is 5 or less. On the other hand, Example Q7 differs from Examples Q1-Q6, Q8, and Q9 in that the number of grooves G is an integer multiple of the number of grooves N.
[0060] The horizontal axis in Figures 3 to 7 indicates the measurement position in the tooth profile. The measurement position is the position on the tooth surface 102, indicated by a value corresponding to the radial direction of gear 100. The vertical axis in Figures 3 to 7 indicates the tooth profile error. Note that the tooth profile error of the 15-row, 30-groove gear shown in Figure 6 is larger than that of the other embodiments. Therefore, in the graph of the 15-row, 30-groove gear in Figure 6, the display range of the vertical axis differs from that of the other graphs in order to show the entire tooth profile error. When comparing each graph, the difference in the display range of the vertical axis can be taken into consideration.
[0061] The tooth profile is a shape curve or shape data that shows the shape of the tooth surface 102 along the tooth profile direction. The tooth profile error is the amount of error on the tooth profile. The tooth profile error is the difference between the tooth profile obtained by measurement or calculation and the reference tooth profile. The reference tooth profile is the tooth profile determined based on the design values of the gear 100. In Figures 3 to 7, the position where the vertical value is 0 corresponds to the reference line that indicates that the tooth profile error relative to the reference tooth profile is 0.
[0062] The tooth profile is obtained, for example, by contacting a measuring probe with the tooth surface 102 of the gear 100 and scanning the probe along the tooth profile direction. The obtained tooth profile is compared with a reference tooth profile. This allows for the determination of the tooth profile error at each measurement position on the tooth profile. The tooth profile may be obtained by actual measurement, or by calculation based on the number of teeth Z of the gear 100, the number of grooves N of the carbide hob 20, and the number of grooves G.
[0063] When calculating tooth profile error, for example, the position where the cutting edge 23 of the carbide hob 20 acts on the tooth surface 102 is calculated for each measurement position based on the number of teeth Z of the gear 100, the number of threads N of the carbide hob 20, and the number of grooves G. At each measurement position, the difference between the calculated tooth profile profile and the reference tooth profile is obtained as the tooth profile error. This allows the change in tooth profile error according to the measurement position to be obtained as a waveform. If periodic fluctuations appear in the tooth profile error, these periodic fluctuations can be evaluated as polygonal errors.
[0064] In comparing each embodiment, we can focus on the amplitude of the waveform, the difference between the maximum and minimum values, or the peak-to-peak value. When the periodic fluctuation of the tooth profile error becomes smaller, the range of error fluctuation in the tooth profile direction tends to decrease. This makes it easier to improve the tooth profile accuracy in the finishing process of the gear 100 after hardening.
[0065] (Examples based on error reduction) The following are some examples of embodiments in which the amount of error on the tooth profile is easily reduced by combining the number of teeth Z, the number of threads N, and the number of grooves G. There are many combinations of the number of teeth Z, the number of threads N, and the number of grooves G. In particular, the number of teeth Z can be selected from a wide range depending on the specifications of the gear 100 to be machined.
[0066] Instead of comprehensively showing all embodiments that are likely to reduce errors in the tooth profile, the following embodiments are presented as a selection. Embodiments that are likely to reduce errors in the tooth profile are not limited to the following embodiments. The carbide hob 20 may be selected based on a different combination of tooth count Z, tooth count N, and groove count G than those in the following embodiments, within the range that satisfies the conditions that the number of threads N is 6 or more and the groove-to-thread ratio K is 5 or less.
[0067] In Example R1, the gear 100 and the carbide hob 20 have the following specifications: The number of teeth Z is 41. The number of threads N is 9. The number of grooves G is 19. The groove-to-thread ratio K is 19 / 9, which is approximately 2.11. The tooth-to-thread ratio L is 41 / 9, which is approximately 4.56. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0068] In Example R2, the gear 100 and the carbide hob 20 have the following specifications: The number of teeth Z is 41. The number of threads N is 9. The number of grooves G is 26. The groove-to-thread ratio K is 26 / 9, which is approximately 2.89. The tooth-to-thread ratio L is 41 / 9, which is approximately 4.56. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0069] In Example R3, the gear 100 and the carbide hob 20 have the following specifications: The number of teeth Z is 41. The number of threads N is 9. The number of grooves G is 33. The groove-to-thread ratio K is 33 / 9, which is approximately 3.67. The tooth-to-thread ratio L is 41 / 9, which is approximately 4.56. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0070] In Example R4, the gear 100 and the carbide hob 20 have the following specifications: The number of teeth Z is 8. The number of threads N is 15. The number of grooves G is 26. The groove-to-thread ratio K is 26 / 15, which is approximately 1.73. The tooth-to-thread ratio L is 8 / 15, which is approximately 0.53. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0071] In Example R5, the gear 100 and the carbide hob 20 have the following specifications: The number of teeth Z is 82. The number of threads N is 11. The number of grooves G is 25. The groove-to-thread ratio K is 25 / 11, which is approximately 2.27. The tooth-to-thread ratio L is 82 / 11, which is approximately 7.45. The groove-to-thread ratio K is not an integer. The tooth-to-thread ratio L is not an integer.
[0072] (Gear finishing process) The gear finishing method of this embodiment is a method of finishing a hardened gear 100 with a carbide hob 20. In the gear finishing method, a carbide hob 20 is selected according to the number of teeth Z of the gear 100. The tooth surface 102 of the gear 100 is finished using the selected carbide hob 20. The gear finishing method includes, for example, the first to fourth steps.
[0073] In the first step, the number of teeth Z of the gear 100 is obtained. The number of teeth Z is obtained, for example, based on design information, machining instruction information, or measurement information of the gear 100 to be machined. The number of teeth Z may be input by the operator to the control device of the hobbing machine 10, or it may be obtained by the control device of the hobbing machine 10.
[0074] In the second step, the candidate range for the groove-to-thread ratio K, the number of threads N, and the number of grooves G are set based on the number of teeth Z. For example, the candidate range for the groove-to-thread ratio K is set based on the number of teeth Z, machining conditions, required finish accuracy, machining time, and at least one of the manufacturing conditions for the carbide hob 20. The candidate range for the groove-to-thread ratio K is set within a range of, for example, 5 or less.
[0075] Next, candidate groove counts N and groove counts G are set based on the set groove count-to-groove ratio K. In one example, groove count N is set as an integer of 6 or more, and groove count G is set such that the value obtained by dividing groove count G by groove count N falls within the candidate range of groove count-to-groove ratio K. Groove counts N and groove counts G may be set by the operator, by the control device of the hobbing machine 10, or by an external device separate from the hobbing machine 10. The external device may be, for example, a computer for managing machining conditions or a device for tool selection.
[0076] In the third step, a carbide hob 20 is selected according to the number of teeth Z. In one example, a carbide hob 20 that satisfies all of the following conditions A, B, C, and D is selected from the candidates set in the second step. (Condition A) The number of rows N is 6 or greater. (Condition B) The groove-to-row ratio K, obtained by dividing the number of grooves G by the number of rows N, is 5 or less. (Condition C) The number of grooves G is a non-integer multiple of the number of rows N. (Condition D) The number of teeth Z is a non-integer multiple of the number of threads N.
[0077] In the fourth step, the hardened gear 100 is finished using the selected carbide hob 20. Specifically, the gear 100 is finished in the following order: The selected carbide hob 20 is mounted on the hobbing machine 10. The gear 100 is supported by the workpiece support section 13. The hobbing machine 10 rotates the carbide hob 20 and the gear 100 synchronously. The carbide hob 20 and the gear 100 move relative to each other due to the movement of the carbide hob 20 by the hob-side feed mechanism 14 and the movement of the gear 100 by the workpiece-side feed mechanism 15.
[0078] The carbide hob 20 cuts the tooth surface 102 along the tooth groove 103 of the gear 100. The carbide hob 20 removes the remaining machining allowance on the tooth surface 102. This finishes the tooth surface 102 of the hardened gear 100.
[0079] In each of the exemplary embodiments, namely Examples Q1-Q9 and Examples R1-R5, in Examples Q1-Q6, Q8, Q9, and R1-R5, the number of grooves N is 6 or more, the groove-to-groove ratio K is 5 or less, the number of grooves G is a non-integer multiple of the number of grooves N, and the number of teeth Z is a non-integer multiple of the number of grooves N. In other words, Examples Q1-Q6, Q8, Q9, and R1-R5 are embodiments that satisfy all of conditions A to D.
[0080] On the other hand, in Example Q7, the number of threads N is 6 or more, the groove-to-thread ratio K is 5 or less, the number of teeth Z is a non-integer multiple of the number of threads N, and the number of grooves G is an integer multiple of the number of threads N. That is, Example Q7 satisfies conditions A, B, and D, but does not satisfy condition C. Example Q7 is an example of a carbide hob 20 in that the number of threads N is 6 or more and the groove-to-thread ratio K is 5 or less. Example Q7 is used as a control example to confirm the effect of the number of grooves G being a non-integer multiple of the number of threads N.
[0081] In the gear finishing method, for example, a carbide hob 20 from any of Examples Q1 to Q6, Example Q8, Example Q9, and Example R1 to R5 may be selected, and the gear 100 may be finished using the selected carbide hob 20. The carbide hob 20 selected in the gear finishing method is not limited to the exemplified carbide hobs 20, as long as it satisfies all of conditions A to D.
[0082] (Effects of the embodiment) (1) The number of threads N of the carbide hob 20 is 6 or more. The above configuration provides, for example, the following effects: Compared to using a hob with fewer than 6 threads for finishing the gear 100 after hardening, it is easier to increase the amount of machining progress per revolution of the carbide hob 20. This makes it easier to shorten the machining time per gear 100 during the finishing of the gear 100 after hardening using the carbide hob 20.
[0083] (2) The groove-to-thread ratio K, which is the value obtained by dividing the number of grooves G of the carbide hob 20 by the number of threads N, is 5 or less. The above configuration provides, for example, the following effects: Compared to using a hob with a groove-to-thread ratio K greater than 5 for finishing the gear 100 after hardening, it is easier to suppress the excessively large ratio of grooves G to threads N. This makes it easier to suppress the increase in manufacturing man-hours for the carbide hob 20 that accompanies an increase in the number of grooves G.
[0084] (3) The groove-to-groove ratio K of the carbide hob 20 is between 1.2 and 5. The above configuration provides, for example, the following effects: Because the groove-to-thread ratio K is 1.2 or higher, it is less likely to result in a configuration where the number of grooves G is less than the number of threads N, compared to the case where the groove-to-thread ratio K is less than 1.2. This makes it easier to secure a number of cutting edge grooves 22 suitable for finishing the gear 100 after hardening.
[0085] (4) The groove-to-groove ratio K of the carbide hob 20 is between 1.5 and 5. The above configuration provides, for example, the following effects: Because the groove-to-thread ratio K is 1.5 or higher, it is less likely to result in a configuration where the number of grooves G is less than the number of threads N, compared to the case where the groove-to-thread ratio K is less than 1.5. This makes it easier to secure a number of cutting edge grooves 22 suitable for finishing the gear 100 after hardening.
[0086] (5) The groove-to-groove ratio K of the carbide hob 20 is between 1.5 and 3. The above configuration provides the following effects, for example: A groove-to-thread ratio K of 1.5 or higher makes it less likely to have a configuration where the number of grooves G is less than the number of threads N, compared to the case where the groove-to-thread ratio K is less than 1.5. This makes it easier to secure a number of cutting edge grooves 22 suitable for finishing the gear 100 after hardening. A groove-to-thread ratio K of 3 or lower makes it easier to suppress the increase in manufacturing man-hours for the carbide hob 20 that occurs with an increase in the number of grooves G, compared to the case where the groove-to-thread ratio K is greater than 3.
[0087] (6) The ratio K of the number of grooves in the carbide hob 20 is between 2 and 3. The above configuration provides the following effects, for example: A groove-to-thread ratio K of 2 or more makes it less likely to have a configuration where the number of grooves G is less than the number of threads N, compared to the case where the groove-to-thread ratio K is less than 2. This makes it easier to secure a number of cutting edge grooves 22 suitable for finishing the gear 100 after hardening. A groove-to-thread ratio K of 3 or less makes it easier to suppress the increase in manufacturing man-hours for the carbide hob 20 that occurs with an increase in the number of grooves G, compared to the case where the groove-to-thread ratio K is greater than 3.
[0088] (7) The number of grooves G in the carbide hob 20 is a non-integer multiple of the number of grooves N. According to the above configuration, for example, the following effects can be obtained: Even when the carbide hob 20 rotates, the positional relationship between each groove 21 and the cutting edge groove 22 is unlikely to be repeated in the same state. As a result, when the same tooth 101 is machined again, the position in which the cutting edge 23 acts on the tooth surface 102 is unlikely to be the same as in the previous machining.
[0089] (8) The carbide hob 20 is used for finishing the gear 100 in which the number of teeth Z is a non-integer multiple of the number of threads N. According to the above configuration, for example, the following effects can be obtained: Even if the same tooth 101 reaches the machining position again after the gear 100 has completed one rotation, the positional relationship between the gear 100 and the carbide hob 20 is unlikely to be repeated in the same state. As a result, when the same tooth 101 is machined again, the position in which the cutting edge 23 acts on the tooth surface 102 is unlikely to be the same as the position in the previous machining operation.
[0090] (9) The number of grooves G of the carbide hob 20 is a non-integer multiple of the number of threads N. The carbide hob 20 is used for finishing the gear 100, in which the number of teeth Z is a non-integer multiple of the number of threads N. The above configuration provides, for example, the following effects: The next machining mark is more likely to be shifted on the tooth surface 102 relative to the previous machining mark. This makes it easier to suppress the repeated formation of machining marks at the same position on the tooth surface 102. This makes it easier to suppress periodic fluctuations in the amount of error on the tooth profile. As a result, polygonal errors are more easily reduced during the finishing process of the gear 100 after hardening.
[0091] (10) The number of threads N of the carbide hob 20 is 6 or more. The groove-to-thread ratio K of the carbide hob 20 is 5 or less. The number of grooves G of the carbide hob 20 is a non-integer multiple of the number of threads N. The carbide hob 20 is used for finishing gear 100, where the number of teeth Z is a non-integer multiple of the number of threads N. The above configuration provides the following effects, for example: Having a thread count N of 6 or more makes it easier to shorten the machining time during the finishing process of the gear 100 after quenching. Also, having a groove-to-thread ratio K of 5 or less makes it easier to prevent the number of grooves G from becoming excessively large relative to the thread count N. Furthermore, having a groove count G that is not an integer multiple of the thread count N, and a tooth count Z that is not an integer multiple of the thread count N, makes it easier for the next machining mark to shift on the tooth surface 102 relative to the previous machining mark. This makes it easier to achieve both a reduction in machining time and a reduction in the increase of polygonal errors during the finishing process of the gear 100 after quenching, while suppressing an excessive increase in the number of grooves G.
[0092] (11) The hobbing machine 10 is equipped with a carbide hob 20. According to the above configuration, for example, the following effects can be obtained. In the hobbing machine 10, the above effects can be obtained depending on the configuration of the carbide hob 20.
[0093] (12) The gear finishing method includes the steps of selecting a carbide hob 20 that satisfies all of conditions A, B, C, and D according to the number of teeth Z of the gear 100, and finishing the gear 100 with the selected carbide hob 20. According to the above configuration, for example, the following effects can be obtained. In the gear finishing process, the above effects can be obtained depending on the configuration of the selected carbide hob 20.
[0094] (modified version) The above description of embodiments is illustrative of possible forms of the carbide hob and gear finishing method according to the present invention and is not intended to limit its form. The carbide hob and gear finishing method according to the present invention may take the form of, for example, modifications of the embodiments shown below, and combinations of at least two non-inconsistent modifications. In the following modifications, parts common to the embodiments are denoted by the same reference numerals as in the embodiments and their descriptions are omitted.
[0095] (1) The number of threads N of the carbide hob 20 may be arbitrarily changed within the range of 6 or more. For example, the number of threads N may be 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or an integer greater than these. The number of threads N may be set according to the number of teeth Z of the gear 100, machining conditions, required finish accuracy, machining time, and at least one of the manufacturing conditions of the carbide hob 20.
[0096] (2) The number of grooves G of the carbide hob 20 may be arbitrarily changed within the range in which the groove-to-thread ratio K is 5 or less. In one example, the number of grooves G is set based on the number of threads N and the groove-to-thread ratio K. The number of grooves G may be set according to the number of teeth Z of the gear 100, machining conditions, required finish accuracy, machining time, and at least one of the manufacturing conditions of the carbide hob 20.
[0097] (3) The number of grooves G of the carbide hob 20 may be a non-integer multiple of the number of threads N. In this case, the groove-to-thread ratio K is not an integer. In one example, the number of grooves G is set to avoid values that are integer multiples of the number of threads N. This makes it less likely for the positional relationship between each thread 21 and the cutting edge groove 22 to be the same and repeat.
[0098] (4) The number of teeth Z of gear 100 may be a non-integer multiple of the number of threads N. In this case, the number of teeth-to-thread ratio L is not an integer. In one example, the number of threads N is set to avoid values that are divisors of the number of teeth Z. This makes it less likely that the positional relationship between gear 100 and the carbide hob 20 will be the same even if the same tooth 101 reaches the machining position again after gear 100 has completed one rotation.
[0099] (5) The second step of the gear finishing process may be modified as follows. In the modified second step, after setting the number of threads N and the number of grooves G, the groove-to-thread ratio K may be calculated by dividing the number of grooves G by the number of threads N. In this case, it may be determined whether or not the calculated groove-to-thread ratio K falls within a predetermined candidate range.
[0100] (6) In the second step of the gear finishing process, candidates for the number of grooves N and the number of grooves G may be set without setting a candidate range for the groove-to-thread ratio K. In this case, in the third step, candidates may be selected in which the groove-to-thread ratio K obtained by dividing the number of grooves G by the number of grooves N is 5 or less.
[0101] (7) In the second step of the gear finishing process, the number of teeth N and the number of grooves G may be set based on pre-prepared correspondence information. The correspondence information may include the correspondence between the number of teeth Z, the number of teeth N, the number of grooves G, and the groove-to-teeth ratio K. The correspondence information may be data stored in a table, database, or control device.
[0102] (8) In the second step of the gear finishing process, several carbide hobs 20 that are candidates for use in the finishing process may be selected. In the third step, one carbide hob 20 may be selected from the candidates based on at least one of the processing time, the required finishing accuracy, the manufacturing conditions of the carbide hob 20, and the inventory status of the carbide hob 20.
[0103] (9) The third step of the gear finishing method may be modified as follows: In the modified third step, a carbide hob 20 that satisfies at least conditions A and B is selected. In one example, a carbide hob 20 from any of the illustrated embodiments, i.e., embodiments Q1 to Q9 and embodiments R1 to R5, is selected.
[0104] (10) The second and third steps of the gear finishing process may be performed by an operator, by the control device of the hobbing machine 10, or by an external device separate from the hobbing machine 10. [Explanation of Symbols]
[0105] 10: Hob disc 11: Bed 12: Hob support 13: Work support section 14: Hob-side feed mechanism 15: Workpiece-side feeding mechanism 20: Carbide hob Article 21:Article 21 22: Cutting edge groove 23: Cutting edge 100: Gear 101: Teeth 102: Tooth surface 103: Tooth groove Z: Number of teeth N:Number of threads G: Number of grooves K: Groove number ratio L: Ratio of tooth count to tooth count
Claims
1. A carbide hob for finishing gears after hardening, Equipped with multiple grooves and multiple cutting edge grooves, The total number of articles, which is the sum of the aforementioned articles, is six or more. The groove-to-number-number ratio, which is the value obtained by dividing the total number of cutting grooves by the number of threads, is 5 or less. Superhard hob.
2. The ratio of grooves to threads is between 1.2 and 5. The carbide hob according to claim 1.
3. The ratio of grooves to threads is 1.5 or more and 5 or less. The carbide hob according to claim 2.
4. The ratio of grooves to threads is 1.5 or more and 3 or less. The carbide hob according to claim 3.
5. The ratio of grooves to threads is between 2 and 3. The carbide hob according to claim 4.
6. The number of grooves is a non-integer multiple of the number of rows. A carbide hob according to any one of claims 1 to 5.
7. Used for finishing the gear whose number of teeth is a non-integer multiple of the number of teeth, A carbide hob according to any one of claims 1 to 5.
8. The number of grooves is a non-integer multiple of the number of rows, Used for finishing the gear whose number of teeth is a non-integer multiple of the number of teeth, A carbide hob according to any one of claims 1 to 5.
9. A carbide hob according to any one of claims 1 to 5, Hob disc.
10. A gear finishing method in which a gear after hardening is finished using a carbide hob, The carbide hob is provided with multiple grooves and multiple cutting edge grooves, A step of selecting a carbide hob that satisfies all of conditions A, B, C, and D according to the number of teeth of the gear, The process includes finishing the gear using the selected carbide hob, As for condition A, the total number of articles is 6 or more. As condition B, the ratio of grooves to threads, obtained by dividing the total number of cutting edge grooves by the number of threads, is 5 or less. As for condition C, the number of grooves is a non-integer multiple of the number of rows. As for condition D, the number of teeth on the gear is a non-integer multiple of the number of threads. Gear finishing process.