Helical gear and processing method of helical gear

Abstract

A helical gear and a method of machining a helical gear, each tooth of the helical gear having a tooth surface profile having a series of crests and a series of troughs, the series of crests or troughs forming a corrugation direction, the helical gear forming a meshing line during meshing, the helical gear having a predetermined noise pressure level threshold, the angle between the corrugation direction and the meshing line is selected to enable the actual noise pressure level of the bevel gear to be smaller than the preset noise pressure level threshold value, and the difference between the actual noise pressure level and the preset noise pressure level threshold value is increased along with increasing of the angle.

Description

Technical Field

[0001] The present application relates to a helical gear and a method for processing the helical gear, and more specifically to a method for processing the helical gear by changing the tooth surface profile of the helical gear to change the corrugation direction. The helical gear can be used for a transmission of a motor vehicle, especially an electric vehicle. Background Art

[0002] Electric vehicles are hybrid or fully electric powered vehicles. Since there is no background noise from the engine to cover it, higher requirements are placed on NVH (Noise, Vibration, Harshness) in terms of vehicle manufacturing quality.

[0003] As we all know, helical gears are a key component of the transmission. The noise generated when the helical gears mesh is the main source of noise in the transmission and even electric vehicles.

[0004] In order to improve the NVH performance of the transmission, the ripple amplitude of different orders of the helical gear is generally controlled. However, this solution has the following disadvantages: 1. It is difficult to always control the amplitude, especially when the processing tools of the helical gear are worn; 2. The number of orders is too large and is affected by factors such as processing tools, environment, and processing parameters; 3. The cost of controlling the amplitude is high.

[0005] Therefore, there is a need for a new type of helical gear that can improve NVH performance in a simple and cost-effective manner. Summary of the invention

[0006] The present invention provides a helical gear, each tooth of the helical gear has a tooth surface profile, the tooth surface profile has a series of peaks and a series of troughs, the series of peaks or the series of troughs form a corrugation direction, the helical gear will form a meshing line during the meshing process, the helical gear has a predetermined noise sound pressure level threshold, the angle between the corrugation direction and the meshing line is selected so that the actual noise sound pressure level of the helical gear is less than the predetermined noise sound pressure level threshold, and the difference between the actual noise sound pressure level and the predetermined noise sound pressure level threshold increases with the increase of the angle.

[0007] Advantageously, the angle between the corrugation direction and the meshing line is greater than 20 degrees.

[0008] Advantageously, the angle between the corrugation direction and the meshing line is greater than 25 degrees.

[0009] Advantageously, the helical gears are of the honed or ground type.

[0010] In another aspect, the present application also provides a method for processing a helical gear, comprising: providing a processing tool; providing a helical gear blank; using the processing tool to process the helical gear blank to form a helical gear, wherein each tooth of the helical gear has a tooth surface profile, the tooth surface profile has a series of peaks and a series of troughs, the series of peaks or the series of troughs forming a corrugation direction, the helical gear will form a meshing line during the meshing process, the helical gear has a predetermined noise sound pressure level threshold, wherein the angle between the corrugation direction and the meshing line is selected so that the actual noise sound pressure level of the helical gear is less than the predetermined noise sound pressure level threshold, and the difference between the actual noise sound pressure level and the predetermined noise sound pressure level threshold increases with the increase of the angle.

[0011] Advantageously, the machining tool has a body and a series of inclined teeth arranged on a circumferential surface of the body, the series of inclined teeth being at a first predetermined angle relative to a first central axis of the body,

[0012] The helical gear blank has a second central axis,

[0013] The machining method includes tilting the machining tool so that a first center axis of the machining tool and a second center axis of the helical gear blank form a second predetermined angle.

[0014] Advantageously, the first predetermined angle and the second predetermined angle are selected such that the sum of the first predetermined angle and the second predetermined angle is equal to the helix angle of the helical gear and the actual noise pressure level of the helical gear is less than the predetermined noise pressure level threshold.

[0015] Advantageously, the angle between the corrugation direction of the helical gear and the meshing line is greater than 20 degrees.

[0016] Advantageously, the angle between the corrugation direction of the helical gear and the meshing line is greater than 25 degrees.

[0017] Advantageously, the machining tool is a gear honing tool or a gear grinding tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other features and advantages of exemplary embodiments of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, which are for illustrative purposes only and are not intended to limit the scope of the present invention in any way, wherein:

[0019] Figure 1 The tooth profile of one tooth of a helical gear is shown to illustrate the wave direction and meshing line.

[0020] Figure 2 A comparison of the NVH performance of the helical gear according to the present application and the NVH performance of the existing helical gear is shown.

[0021] Figure 3A flow chart showing a method for machining a helical gear according to the present application.

[0022] Figure 4(a) shows the Figure 3 The flowchart of steps 100 and 200 corresponds to a schematic diagram.

[0023] Figure 4(b) shows that Figure 3 A schematic diagram corresponding to step 300 of the flowchart. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the technical solution of the present disclosure clearer, the technical solution of the embodiment of the present disclosure will be clearly and completely described in conjunction with the drawings of the specific embodiments of the present disclosure. The same figure marks in the drawings represent the same parts. It should be noted that the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0025] Compared to the embodiments shown in the drawings, feasible implementations within the scope of the present disclosure may have fewer components, other components not shown in the drawings, different components, differently arranged components, or differently connected components, etc. In addition, two or more components in the drawings may be implemented in a single component, or a single component shown in the drawings may be implemented as multiple separate components.

[0026] Unless otherwise defined, the technical or scientific terms used herein shall have the usual meanings understood by persons of ordinary skill in the field to which the present disclosure belongs. The words "first", "second" and similar words used in the patent specification and claims of the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. When the number of components is not specified, the number of components may be one or more; similarly, words such as "one", "the", "said" and the like do not necessarily indicate a quantity limitation. Words such as "include" or "comprise" and the like mean that the element or object appearing before the word includes the element or object listed after the word and its equivalent, without excluding other elements or objects. Words such as "install", "set", "connect" or "connected" and the like are not limited to physical or mechanical installation, setting, connection, but may include electrical installation, setting, connection, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate the relative position relationship when the device is in use or the position relationship shown in the drawings. When the absolute position of the described object changes, the relative position relationship may also change accordingly.

[0027] Figure 1The tooth surface profile 1 of a tooth of a helical gear is shown to illustrate the corrugation direction S and the meshing line L. Due to processing reasons, the tooth surface profile 1 is not completely smooth, but has a series of crests 11 and a series of troughs 12. Under normal circumstances, a series of crests form the corrugation direction, and a series of troughs also form the corrugation direction in the same direction, such as Figure 1 As shown, the direction of the virtual straight line connecting a series of wave crests is the wave direction. In this application, the wave direction formed by the wave crests is taken as an example for explanation.

[0028] The inventors of the present application have found that the direction of the corrugation has a significant effect on the NVH performance of the helical gear. By controlling the angle between the corrugation direction and the meshing line, the NVH performance can be significantly improved. In the present application, the NVH performance can be expressed in terms of noise sound pressure level (in decibels). For a designed helical gear, there is a predetermined noise sound pressure level threshold. In the prior art, the corrugation amplitude is generally changed to make the actual noise sound pressure level of the helical gear less than the predetermined noise sound pressure level threshold. The present application selects the angle between the corrugation direction S and the meshing line L of the helical gear so that the actual noise sound pressure level of the helical gear is less than the predetermined noise sound pressure level threshold, and the difference between the actual noise sound pressure level and the predetermined noise sound pressure level threshold increases with the increase of the angle.

[0029] As an example, the angle between the corrugation direction S of the helical gear of the present application and the meshing line L is greater than 20 degrees, preferably greater than 25 degrees, so that the NVH performance is significantly improved. Figure 2 As shown in the figure, a sample batch of helical gears is used as an example to illustrate that changing the angle between the corrugation direction and the meshing line will affect the NVH performance. Figure 2 In the batch of helical gears shown, the angle between the corrugation direction and the meshing line is set to 45 degrees. The noise sound pressure level of the helical gears is as follows: Figure 2 As shown in a in FIG. 1 , it is significantly lower than the predetermined noise sound pressure level threshold (indicated by the straight line T). In comparison, the noise sound pressure level of the existing helical gears where the angle between the corrugation direction and the meshing line is very small or almost coincident is as follows: Figure 2 As shown in b in FIG. 1 , it can be seen that the noise sound pressure level of the existing helical gear is very close to the predetermined noise sound pressure level threshold, and even some of them exceed the predetermined noise sound pressure level threshold. In this way, when processing helical gears, the control accuracy of the ripple amplitude can be relaxed, the measurement frequency can be reduced, and the cost can be reduced, while still meeting the required NVH performance, that is, below the NVH threshold. Figure 2 The horizontal axis in FIG. 1 shows the number of helical gears, which is only exemplary, and the vertical axis shows the NVH performance, which is expressed as the noise sound pressure level in decibels.

[0030] Although Figure 2Taking 45 degrees as an example, the inventors found that for the same helical gear, as the angle between the corrugation direction and the meshing line increases, the noise sound pressure level obtained is farther from the predetermined noise sound pressure level threshold, that is, the difference between the two is greater. For example, for 45 degrees, the noise sound pressure level is about 11.3dB away from the predetermined noise sound pressure level threshold, for 60 degrees, the noise sound pressure level is greater than 11.3dB away from the predetermined noise sound pressure level threshold, and for 20 degrees, the noise sound pressure level is less than 11.3dB away from the predetermined noise sound pressure level threshold. It should also be noted that the difference between the noise sound pressure level and the predetermined noise sound pressure level threshold does not necessarily increase proportionally with the increase of the angle, as long as the difference between the noise sound pressure level and the predetermined noise sound pressure level threshold increases with the increase of the angle.

[0031] Figure 3 Combination Figure 4(a)-4(b) Together, the processing method of processing helical gears according to the present application is shown. Figure 3 In the process, first, in step 100, a processing tool 2 is provided, which has a body 21 and a series of inclined teeth 22 arranged on the circumferential surface of the body, and the series of inclined teeth are at a first predetermined angle α relative to the first center axis 23 of the body 21. In step 200, a helical gear blank 3 is provided, and the helical gear blank 3 is clamped by a clamping tool (description omitted). The helical gear blank has a second center axis 31. At this time, the first center axis of the processing tool is parallel to the second center axis of the helical gear blank, and the rotation axis of the processing tool coincides with the first center axis. Although FIG. 4(a) shows that the first center axis 23 and the second center axis 31 coincide, this is only for the purpose of description. In fact, the second center axis 31 will be spaced apart from the first center axis 23 and will not coincide.

[0032] Next, in step 300, the helical gear blank is processed by the tilting processing tool to form the helical gear so that the angle between the corrugation direction of the helical gear and the meshing line is greater than 20 degrees. During this step, in particular, the tilting processing tool forms a second predetermined angle β between the first center axis 23 and the second center axis 31 of the processing tool, as shown in FIG4(b).

[0033] The first predetermined angle α and the second predetermined angle β are selected so that the sum of the first predetermined angle and the second predetermined angle is equal to the helical angle γ of the helical gear, while ensuring that the actual noise sound pressure level of the helical gear is less than the predetermined noise sound pressure level threshold. For example, the angle between the corrugation direction of the formed helical gear and the meshing line is greater than 20 degrees, preferably greater than 25 degrees.

[0034] It should be noted that the second predetermined angle β can be defined as a positive value or a negative value, for example, when the machining tool rotates counterclockwise in the figure, it is defined as a positive value, and when it rotates clockwise in the figure, it is defined as a negative value. Regardless of whether the second predetermined angle is a positive value or a negative value, it is sufficient to ensure that the sum of the first predetermined angle and the second predetermined angle is equal to the helical angle of the helical gear.

[0035] The above-mentioned machining tool is a gear honing tool or a gear grinding tool, that is, the helical gear is of a gear honing type or a gear grinding type.

[0036] For example, the helical angle γ of the helical gear is 30°, the first predetermined angle α of the cutting tool can be selected as 17°, and the second predetermined angle β can be selected as +13°, so that the sum of the first predetermined angle and the second predetermined angle is 30°, and the actual noise sound pressure level of the helical gear is less than the predetermined noise sound pressure level threshold. Those skilled in the art should understand that the above values ​​are only exemplary.

[0037] In the present application, by selecting the angle between the corrugation direction of the helical gear and the meshing line, the actual noise sound pressure level of the helical gear is achieved to be less than the predetermined noise sound pressure level threshold, and the difference between the actual noise sound pressure level of the helical gear and the predetermined noise sound pressure level threshold increases with the increase of the angle, thereby significantly improving the NVH performance, making it possible to relax the control accuracy of the corrugation amplitude, reduce the measurement frequency, and thus reduce costs, while still ensuring that the helical gear meets the requirements. In addition, the corrugation direction is insensitive to the wear of the processing tool, that is, when other factors remain unchanged, even if the processing tool is worn, the corrugation direction will not change significantly, while in the prior art, the corrugation amplitude is very sensitive to the wear of the processing tool.

[0038] Although the present invention has been described in the specification and illustrated in the drawings with reference to various embodiments, those skilled in the art will appreciate that the above embodiments are merely preferred implementations, and certain technical features in the embodiments may not be necessary for solving specific technical problems, and thus these technical features may be absent or omitted without affecting the solution of the technical problems or the formation of technical solutions; moreover, the features, elements and / or functions of one embodiment may be appropriately combined, coupled or coordinated with the features, elements and / or functions of one or more other embodiments, unless the combination, coupling or coordination is obviously not feasible.

Claims

1. A helical gear, each tooth of the helical gear having a tooth surface profile, the tooth surface profile having a series of crests and a series of troughs, the series of crests or the series of troughs forming a corrugation direction, the helical gear forming a meshing line during meshing, the helical gear having a predetermined noise sound pressure level threshold, characterized in that: The angle between the corrugation direction and the meshing line is selected so that the actual noise sound pressure level of the helical gear is less than the predetermined noise sound pressure level threshold.

2. The helical gear according to claim 1, characterized in that: The difference between the actual noise sound pressure level and the predetermined noise sound pressure level threshold increases as the angle increases.

3. The helical gear according to claim 1, characterized in that: The angle between the corrugation direction and the meshing line is greater than 20 degrees.

4. The helical gear according to claim 3, characterized in that: The angle between the corrugation direction and the meshing line is greater than 25 degrees.

5. The helical gear according to any one of claims 1 to 4, characterized in that The helical gears are of the honed type or the ground type.

6. A method for processing a helical gear, comprising: Provide processing tools; Providing a helical gear blank; A helical gear blank is processed by a processing tool to form a helical gear, each tooth of the helical gear has a tooth surface profile, the tooth surface profile has a series of crests and a series of troughs, the series of crests or the series of troughs form a corrugation direction, the helical gear forms a meshing line during meshing, and the helical gear has a predetermined noise sound pressure level threshold, The invention is characterized in that the angle between the corrugation direction and the meshing line is selected so that the actual noise sound pressure level of the helical gear is less than the predetermined noise sound pressure level threshold.

7. The processing method according to claim 6, characterized in that: The difference between the actual noise sound pressure level and the predetermined noise sound pressure level threshold increases as the angle increases.

8. The processing method according to claim 6, characterized in that: The machining tool has a body and a series of inclined teeth arranged on a circumferential surface of the body, the series of inclined teeth being at a first predetermined angle relative to a first central axis of the body, The helical gear blank has a second central axis, The machining method includes tilting the machining tool so that a first center axis of the machining tool and a second center axis of the helical gear blank form a second predetermined angle.

9. The processing method according to claim 8, characterized in that: The first predetermined angle and the second predetermined angle are selected such that the sum of the first predetermined angle and the second predetermined angle is equal to the helix angle of the helical gear and the actual noise sound pressure level of the helical gear is less than the predetermined noise sound pressure level threshold.

10. The processing method according to claim 6, characterized in that: The angle between the corrugation direction of the helical gear and the meshing line is greater than 20 degrees.

11. The processing method according to claim 10, characterized in that: The angle between the corrugation direction of the helical gear and the meshing line is greater than 25 degrees.

12. The processing method according to any one of claims 6 to 11, characterized in that: The processing tool is a gear honing tool or a gear grinding tool.

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