Tensioner guide or arm surfaces with patterns that affect the NVH performance of the chain system

Abstract

To provide a method of decreasing noise, vibration, and harshness within a chain system.SOLUTION: A pattern applied to a face of a tensioner arm, guide or snubber in contact with a chain intentionally breaks up the chain contact force between a back of chain links and the tensioner arm, guide or snubber face. This is done to prevent alignment with the chain-related orders which cause NVH within the chain system or to increase overall NVH to obscure chain-related orders.SELECTED DRAWING: Figure 3

Description

[Background technology]

[0001] The present invention relates to a tensioner arm, guide or snubber surface, and more particularly to a unique pattern applied to the surface of a tensioner arm, guide or snubber to affect the Noise, Vibration and Harshness (NVH) of a chain system.

[0002] The chain or toothed belt drive is vibratory excited. For example, a chain or toothed belt drive may be used between the crankshaft and camshaft of an engine. The vibratory excitation may be torsional vibrations of the crankshaft and / or fluctuating torque loads from the valve train and / or fuel pump.

[0003] In chain applications, whether timing or drive systems, the backside of the chain may need to contact a surface on a tensioner guide, arm, or buffer to control the chain movement. Contact between the chain and the surface can result in engagement noise that increases NVH and reduces the perceived performance of the chain system. In particular, chain-surface contact forces can coincide with chain related orders such as pitch frequency, resulting in additional excitation and unacceptable performance. Orders related to events per revolution of the shaft are events per unit time.

[0004] NVH in chain systems is typically caused by pitch orders, which are noises associated with the engagement of each link of the chain with the sprocket and tensioner, and differences in engagement that occur at half-pitch and double-pitch orders as a result of the difference in engagement from links in the guide row to links in the non-guide row, or transitions along the sides of the chain link teeth. The pitch order is equal to the number of teeth on the driving sprocket. Thus, if the driving sprocket has 40 teeth, the number of revolutions of the sprocket will be equal to the 40th order, called the pitch order. The frequency (Hz) can be expressed as (order number x rpm) / 60.

[0005] FIG. 1 shows a conventional chain system 1. The chain system 1 includes a driven sprocket 6 connected to a driving sprocket 2 via a toothed chain 8. The toothed chain 8 includes a number of chain links 5 connected to each other by a coupling element 7. The teeth 3 of the chain links 5 engage with the toothed driven sprocket 6 and the driving sprocket 2. A first tensioner 10 is adjacent to a first strand 8a of the chain 8 to maintain tension in the first strand 8a, and a second tensioner 12 is adjacent to a second strand 8b of the chain 8 to maintain tension in the second strand 8b. The first and second tensioners 10, 12 are in biasing contact with the back of the chain link 5 at specific regions of the chain strands 8a, 8b, biasing the chain strands 8a, 8b against each other to maintain tension.

[0006] FIG. 2 shows an example of a conventional first tensioner 10 or second tensioner 12. The tensioner 10, 12 has a mounting bracket 62 with a pivot shaft 64 extending perpendicularly therefrom. A shaft 65 with a stopper 69 is provided parallel to the pivot shaft 64. The pivot shaft 64 receives an arm 68. The arm 68 preferably has a one-piece body 78 having a first end 68a, a second end 68b, and a smooth chain sliding face 74 extending over a majority of the body between the first end 68a and the second end 68b, the sliding face interacting with the chain strand 8a or 8b. More specifically, the chain sliding face 74 interacts with the back surface 9 of the chain link 5 opposite the tooth 3. The first end 68a of the body 78 has a hole (not shown) for receiving the pivot shaft 64.

[0007] The torsion spring 66 is present between the mounting brackets 62 and is for biasing the arm 68 in one direction. A first end 68a of the spring 66 is grounded to the mounting brackets 62, and a second end 66b of the spring 66 contacts the arm 68 to provide a biasing force.

[0008] Other prior art designs include applying oil to the chain sliding surface to reduce friction between the chain and the surface of the tensioner, or dimples or slits to guide the chain as it slides along the chain sliding surface. The prior art designs do not actively control the alignment of the chain with the back surface to either reduce engagement at certain chain related orders to reduce NVH, or configure a pattern that increases overall noise to obscure chain related orders that increase NVH. Summary of the Invention

[0009] According to one embodiment of the present invention, a special pattern is applied to the surface of the tensioner arm, guide, or snubber to intentionally disrupt the chain contact force between the backside of the chain and the surface of the tensioner arm, guide, or snubber, preventing alignment of chain related orders that contribute to NVH in the chain system.

[0010] According to another embodiment of the invention, a pattern on the surface of the tensioner arm, guide, or snubber is designed to intentionally excite non-chain related orders of noise with low amplitude, thereby increasing the overall noise level and masking or obscuring orders that cause significant NVH. [Brief description of the drawings]

[0011] [Figure 1] 1 shows a schematic diagram of a chain drive system that superficially interacts with the tension surface of a tensioner arm, guide or snubber. [Diagram 2] 1 shows a diagram of a conventional tensioner arm for a chain drive system. [Diagram 3] FIG. 1 illustrates an isometric view of a tensioner arm having a tension surface with a pattern that includes straight grooves. [Figure 4] FIG. 2 illustrates a top view of a tensioner arm having a tension surface with a pattern that includes straight grooves. [Diagram 5] FIG. 1 illustrates an isometric view of a tensioner arm having a tension surface with a pattern that includes diagonal grooves. [Figure 6] FIG. 2 shows a top view of a tensioner arm having a tension surface with a pattern including diagonal grooves. [Figure 7] 1 shows a perspective view of a tensioner arm having different axial chain paths. [Figure 8] 1 shows a graph of half-pitch frequency NVH metrics of tensioner surface geometry versus tensioner torque amount. [Figure 9] 1 shows a graph of pitch frequency NVH metrics for tensioner surface geometry versus tensioner torque amount. [Figure 10] 1 shows a graph of double pitch frequency NVH metrics of tensioner surface geometry versus amount of torque in the tensioner. [Figure 11] FIG. 2 illustrates a perspective view of a tensioner arm having a pattern including variable spacing. [Figure 12] FIG. 1 illustrates a top view of a tensioner arm having a pattern including variable spacing. [Figure 13] FIG. 2 illustrates a top view of a tensioner arm having a pattern including variable spacing and diagonal grooves. [Figure 14] 1 shows a flow diagram of a method for applying a unique pattern to a surface of a tensioner arm, guide, or shock absorber to modify NVH. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 3-4 show tensioner arms 120 having a pattern including linear grooves 180. The tensioner arms 120 are adjacent to one or both of the chain strands 8a, 8b. Each tensioner arm 120 has a bracket 162 which is connected to a drivetrain case (not shown) via bolt holes 163. Axle 165 and pivot shaft 164 extend perpendicularly from the mounting bracket 162. Axle 165 is parallel to pivot shaft 164. Pivot shaft 164 receives arm 168 formed of a body 178 having a first end 178a, a second end 178b, a first surface 188 and a second surface 183 opposite first surface 181. The second surface 183 is defined by a first end 183a, a second end 183b, a first side 183c, a second side 183d, and an arcuate boss 185. The second surface 183 includes a chain sliding surface 174, a non-engaging surface 174, and a boss 185 from the first end 178a to the second end 178b. The chain sliding surface 174 has a unique pattern of grooves 180 and spacers 181 that engage or interact with the back surface 5 of the chain link 7 of each of the chain strands 8a, 8b. The pattern includes a plurality of radial grooves 180 separated by spacers 181 of width w. In this embodiment, the width w of the spacers 180 is constant throughout the pattern. The grooves 181 extend between the first and second sides 183c, 183d and are linear such that the grooves 181 are perpendicular to the first side 183c or the second side 183d. The number of grooves 180, spacers 181, and width w of spacers 181 may vary. The width w of spacers 181 that separates grooves 180 and the number of grooves 180 intentionally disrupts the chain contact forces between the back faces 5 of chain links 7 of chain strands 8a, 8b and the chain sliding face 174 of tensioner arm 168, preventing alignment with chain related orders that contribute to NVH in the chain system.

[0013] The non-engaging portion 175 of the second surface 183 does not engage the chain strands 8 a , 8 b and extends into a boss portion 185 that defines a bore 186 for rotatably receiving the pivot axle 164 . In another embodiment, the body 178 of the arm 168 may be manufactured from multiple pieces. The spacing of the unique pattern and associated groove pattern is preferably calculated using equations 1.1 and 1.2 below: The pattern engagement dimension is the width of the spacer between the grooves.

number

number

[0014] 8-10 show examples of prior art tensioner surface geometries including smooth or continuous surfaces 74, the integers used with equations 1.1 and 1.2 to determine groove pattern spacing, and non-integer numbers used to determine groove pattern spacing. For example, if the integer is 2, then:

number

number

[0015] A stop 169 is present on the shaft 165 and can interact with a boss 185 on the arm 168 if the arm 168 pivots too far.

[0016] 5-6 show a tensioner arm 220 having a tension surface with a pattern that includes angled or diagonal grooves.

[0017] The pivot shaft 164 receives an arm 168 formed of a body 178 having a first end 178a, a second end 178b, a first surface 188, and a second surface 183 opposite the first surface 188. The second surface 183 is defined by a first end 183a, a second end 183b, a first side 183c, a second side 183d, and an arcuate boss 185. From the first end 178a to the second end 178b, the second surface 183 includes a chain sliding surface 274, a non-engaging surface 175, and the boss 185. The chain sliding surface 274 has a unique pattern of grooves 280 and spacers 281 that engage or interact with the back surface 5 of the chain links 7 of each chain strand 8a, 8b. The pattern preferably includes a number of radial grooves 280 separated by spacers 281 of width w, using Equation 1.1 and Equation 1.2 to calculate the spacing of the unique pattern and associated groove pattern. In this embodiment, the width w of the spacers 281 is constant throughout the pattern. The grooves 280 extend between the first side 183c and the second side 183d, and are angled such that the grooves 280 are not at 90 degrees to either the first side 183c or the second side 183d. The minimum angle allows the entire width of the chain to pass through a given groove during contact with the tensioner. This angle θ can be calculated as tan-1(y / x) from the tensioner contact length (x) and the width of the chain (y). The number of grooves 280 and spacers 281 may vary. The width (w) of the spacer 281 that spaces the grooves 280 and the number of grooves 280 intentionally disrupts the chain contact forces between the back faces 5 of the chain links 7 of the chain strands 8 a, 8 b and the chain sliding face 174 of the tensioner arm 168, preventing alignment with chain related orders that contribute to NVH in the chain system.

[0018] The non-engaging portion 175 of the second surface 181 does not engage the chain strands 8 a , 8 b and extends into a boss portion 185 that defines a bore 186 for rotatably receiving the pivot axle 164 .

[0019] A stop 169 is present on the shaft 165 and can interact with a boss 185 on the arm 168 if the arm 168 pivots too far.

[0020] 11-12 show an alternative tensioner arm 420 having a tensioning surface with a pattern including linear grooves. In this embodiment, the widths of the spacers 481a, 481b between the grooves 480 in the chain sliding face 474 vary within the pattern. For example, in the illustrated pattern, at least one spacer 481b has a width w1 that is greater than the width w of the other spacers 481a in the pattern. The grooves 480 are linear, extending between the first and second sides 183c, 183d such that they are perpendicular to the first or second sides 183c, 183d of the second surface 183 of the tensioner arm 420.

[0021] 13 illustrates an alternative tensioner arm 620 having a tensioning surface 674 with a pattern including diagonal or angled grooves. In this embodiment, the width of the spacers between the grooves of the chain sliding surface vary within the pattern. For example, in the illustrated pattern, at least one spacer 681b has a width w1 that is greater than the width w of other spacers 681a in the pattern. The groove 680 extends between the first side 183c and the second side 183d and is angled such that the groove 680 is at an angle of less than 90 degrees with respect to either the first side 183c or the second side 183d.

[0022] FIG. 14 is a flow diagram of a method for uniquely patterning a surface of a tensioner arm, guide, or shock absorber to modify NVH.

[0023] The first step is to determine the chain related orders that cause NVH in the chain system, step 502. The chain related orders can be determined by computer simulation or by testing the chain system itself.

[0024] Based on the determined chain-related orders causing the NVH problem, a pattern including a plurality of grooves and spacers is created for application to the surface of the tensioner arm, guide, or shock absorber (step 506). The specific geometry of the grooves may be determined by simulation, testing, or a combination thereof. This process is iteratively performed by experimentation. The geometry of the grooves should be selected such that the sequence of the known chain-related orders determined by Equations 1.1 and 1.2 is not reduced.

[0025] The pattern is then applied to the chain sliding surface of the tensioner arm, guide or snubber (step 508) and the method ends.

[0026] It is noted in Figures 8-10 that the chain system has known NVH issues at half pitch and double pitch frequencies. An analysis of the two tensioner surface geometries shows that the groove shape at 0.5x pitch performs poorly, but at 0.4x pitch it performs well.

[0027] FIG. 7 shows a perspective view of another embodiment of a tensioner arm 320 having different axial chain paths 321, 322, 323, each formed of a protrusion 380 similar to the spacer in the other embodiments and a recess 381 similar to the groove in the other embodiments that contacts the back of the links of the chain strands 8a, 8b. In this embodiment, the arm 320 replaces the arm of the other embodiment and is connected to the pivot axle 164 of the bracket 162 through a hole 386. The arm 320 is formed of a body 378 having a first end 378a, a second end 378b, a first surface 388, and a second surface 383 opposite the first surface 388. The second surface 383 is defined by a first end 383a, a second end 383b, a first side 383c, a second side 383d, and an arcuate boss 385. The second surface 383, from the first end 378a to the second end 378b, includes a chain sliding face 374, a non-engagement face 375, and a boss portion 385. The chain sliding face 374 has a unique pattern of protrusions 380 and recesses 381, with the raised protrusions 380 being in different areas of the axial chain paths 321, 322, 323, varying the location where the back surface 5 of the chain link 7 interacts with the tensioner arm 320.

[0028] Three different axial paths extending from the first side 383c to the second side 383d of the second surface 383 of the arm 320 are provided instead of having grooves and spacers extending between the sides of the chain sliding face. Each axial path has a series of protrusions and recesses located at different points so that when the tensioner tensions the chain strand, the chain contacts a different protrusion and recess of each axial path. The protrusions and recesses are located such that the chain related orders are broken, similar to the above embodiment with grooves. Similarly, the dimensions of these protrusions are controlled by equations 1.1 and 1.2.

[0029] Although the example chain sliding surface pattern is shown as being on a tensioner arm, it is understood that the chain sliding surface pattern may be on a guide or buffer without departing from the scope of the present invention.

[0030] Accordingly, it is to be understood that the embodiments of the invention described herein are merely illustrative of the application of the principles of the invention. References to details of the embodiments shown herein are not intended to limit the scope of the claims, but rather to recite those features which are themselves regarded as essential to the invention.

Claims

1. 1. A method for reducing noise, vibration, and harshness in a chain system, comprising: determining chain-related orders of noise, vibration, and harshness occurring within the chain system; determining a chain-related order so as not to increase the noise, vibration, and harshness determined to be generated; creating a pattern on a surface of a tensioner, guide or snubber including a plurality of grooves separated by spacers having a width, the plurality of grooves and the spacers being angled relative to first and second edges of the surface, the pattern including a pattern engagement dimension that is not equal to an integer multiple of pitch or a product of pitch and one divided by an integer, such that the surface of the tensioner, guide or snubber engages a chain of the chain system of at least one chain order rather than a chain related order determined to generate increased noise, vibration and harshness; applying the pattern to a surface of the tensioner, the guide, or the shock absorber.

2. The method of claim 1 , wherein the angle is less than or equal to 90 degrees.

3. The method of claim 1 , wherein the spacer width is constant within the pattern.

4. The method of claim 1 , wherein the spacers have widths that vary within the pattern.

5. The method of claim 1 , wherein the groove extends radially around the surface of the tensioner, the guide, or the shock absorber.

6. The method of claim 1 , wherein the groove extends axially through the surface of the tensioner, the guide, or the bumper.

7. The method of claim 6 , wherein each of said grooves defines an axial chain path.

8. 1. A tensioner arm for tensioning a chain in a chain system, comprising: a mounting bracket attached to a drivetrain transfer case housing the chain system and having a pivot axis extending perpendicularly from the mounting bracket; an arm including a body having a first end, a second end, a first surface, and a second surface opposite the first surface, the second surface including, from the first end to the second end, a chain sliding surface, a non-engagement surface, and a boss defining a hole for rotatably receiving the pivot axle, the second surface being further defined by a first edge and a second edge; a pattern including a plurality of grooves and spacers applied to the chain sliding surface of the second surface and angled relative to the first edge and the second edge of the second surface of the body, the pattern including a pattern engagement dimension that is not equal to an integer multiple of pitch or a product of pitch and one divided by an integer, such that a surface of a tensioner, guide, or snubber engages a chain of the chain system of at least one chain order rather than a chain related order determined to cause increased noise, vibration, and harshness; a torsion spring mounted between the mounting bracket and the boss adjacent the non-engagement surface and biasing an arm at the pivot axis toward the strand of chain.

9. 9. The tensioner arm of claim 8, wherein said groove extends radially from said first end to said chain sliding surface defined at said second end.

10. The tensioner arm of claim 9 , wherein each of said grooves defines an axial chain path.

11. 9. The tensioner arm of claim 8, wherein the angle is less than or equal to 90 degrees.

12. The tensioner arm of claim 8 , wherein the spacer width is constant within the pattern.

13. The tensioner arm of claim 8 , wherein the spacer width varies within the pattern.

14. 9. The tensioner arm of claim 8, further comprising an axis extending perpendicularly from said mounting bracket, said axis being parallel to said pivot axis.

15. 15. The tensioner arm of claim 14, wherein the first end of the torsion spring is attached to the mounting bracket and the second end of the torsion spring is attached to the shaft such that the torsion spring acts on the arm to bias the arm toward the chain.

Images