TWI865365B - Optimization design method for non-circular sprocket - Google Patents

Abstract

The present invention sequentially comprises a step of obtaining a non-circular sprocket image, a step of positioning a contour image, a step of obtaining a plurality of original reference points, a step of obtaining a crankshaft torque curve, a step of obtaining a characteristic of the torque curve, a step of defining an optimized region, a step of adjusting a point position, a step of generating a second contour, and a step of forming a sprocket. The plurality of tooth valley images of the contour image are connected to form a first contour having an origin, and the coordinate values of the plurality of original reference points of the first contour are obtained. A right and a left leg crankshaft torque curve are matched on the first contour to define a right and a left leg optimized region respectively. In accordance with the optimized areas of the right and left feet, the corresponding original reference points are moved outward and inward to form a second profile, and a non-circular chain wheel shape is generated based on the second profile. This achieves the advantage of being able to further improve the commercially available products according to specific users, which can significantly increase the crank torque, crank power and rear wheel speed.

Description

Optimization design method for non-circular sprockets

The present invention relates to a design method for optimizing a non-circular sprocket, and in particular, to a design method for optimizing a non-circular sprocket that can improve a commercially available product according to a specific user and can significantly increase crank torque, crank power, and rear wheel rotation speed.

Traditional bicycle sprockets have gradually changed from circular to non-circular, and there are many manufacturers or research institutions on the market that produce or design various types of non-circular sprockets. For example: Republic of China Patent No. I712544 (Compound sprocket and bicycle with compound sprocket), I722688 (Bicycle with compound sprocket composed of four elliptical arcs), I805512 (Bicycle sprocket structure with four elliptical arcs and design method thereof) and I828465 (Method of generating asymmetric sprocket by pedal torque), etc.

However, the body structure and pedaling force of each bicycle user (or player) are unique. Therefore, even if there is a well-reviewed commercially available known non-circular sprocket product, it may be suitable for some people, but not necessarily for others.

Currently, there is no product design method on the market that utilizes existing known non-circular sprockets and optimizes the product for a specific user.

In view of this, it is necessary to develop technologies that can solve the above problems.

The purpose of this invention is to provide a non-circular sprocket optimization design method, which has the advantages of being able to improve commercially available products according to specific users, and can significantly increase crank torque, crank power and rear wheel speed. In particular, the problem that this invention aims to solve is that there is currently no product on the market that utilizes the existing known non-circular sprockets and optimizes the product design method for a specific user.

The technical means to solve the above problem is to provide a non-circular sprocket optimization design method, which includes the following steps in sequence: a step of obtaining a non-circular sprocket image; a step of positioning a contour image; a step of obtaining a plurality of original reference points; a step of obtaining a crankshaft torque curve; a step of obtaining the characteristics of the torque curve; a step of defining an optimization region; a step of adjusting a point position; a step of generating a second contour; and a step of forming a sprocket.

The above-mentioned purposes and advantages of the present invention can be easily understood from the detailed description and accompanying drawings of the following selected embodiments.

The present invention is described in detail with the following embodiments and accompanying drawings:

10: Outline image

11: Tooth peak image

12: Tooth Valley Image

S1: Step of obtaining non-circular sprocket image

S2: Contour image positioning step

S3: Step of obtaining multiple original reference points

S4: Step of obtaining crankshaft torque curve

S5: Characteristic step of obtaining torque curve

S6: Optimization region definition step

S7: Point adjustment steps

S8: Second contour generation step

S9: Sprocket forming step

L1: First outline

L2: Second outline

LA: Right foot crankshaft torque curve

LB: Left foot crankshaft torque curve

W: Origin

W1: First outward shift point

W2: First retraction point

W3: Second outward shift point

W4: Second retraction point

Q:Original reference point

Q1: The first basic point

Q2: The second basic point

Q3: The third basic point

Q4: The fourth basic point

QA: Right foot optimization area

QB: Left foot optimization area

QC: Right constant zone

QD: Left invariant zone

P: Pitch

N1: Maximum right value

N2: maximum left value

θ1: first angle

θ2: Second angle

MA1, MB1: first long bar chart

MA2, MB2: Second long bar chart

MA3, MB3: The third long bar chart

MA4, MB4: the fourth long bar chart

MA4, MB4: The fifth bar chart

MA6, MB6: The sixth long bar chart

Figure 1 is a flow chart of the method of the present invention.

Figure 2 is a schematic diagram of the present invention for obtaining the contour image of a non-circular sprocket.

Figure 3 is a schematic diagram of the first contour positioning of Figure 2.

Figure 4 is a schematic diagram showing that the first contour of the present invention is composed of multiple points.

Figure 5 is a schematic diagram of the complete pitch (coordinates) of the first contour of the present invention.

Figure 6 is a curve diagram of the right and left leg crankshaft torque of the present invention.

Figure 7 is a schematic diagram showing the correspondence between Figure 6 and the optimized area of Figure 5.

Figure 8 is a schematic diagram of the corresponding relationship between the first contour and the second contour of the present invention.

Figure 9 is a bar graph showing the crank torque output results of the present invention and the known product at different pedaling speeds.

Figure 10 is a bar graph showing the crank power output results of the present invention and the known product at different pedaling speeds.

"Appendix 1"

Figure A is a solid photograph of the optimized non-circular sprocket of the present invention.

Referring to the first, second, third, fourth, fifth, sixth, seventh and eighth figures, the present invention is a method for optimizing the design of a non-circular sprocket, which includes the following steps in sequence: a step S1 of obtaining a non-circular sprocket image. Referring to Figure 2, a contour image 10 of a non-circular sprocket (e.g., a commercially available product) is obtained, and the contour image 10 has a plurality of tooth peak images 11 and a plurality of tooth valley images 12; and the number of teeth of the contour image 10 is defined as N.

A contour image positioning step S2. Referring to FIG. 3, the plurality of valley images 12 are connected to form a first contour L1, the first contour L1 is approximately an ellipse; the center point of the first contour L1 is placed at an origin W, a minor axis of the first contour L1 is placed at the X axis; and a major axis of the first contour L1 is placed at the Y axis. In fact, the first contour L1 can be composed of a plurality of points (as shown by the black dots in Figure 4, which are not numbered, as previously explained). The two-dimensional coordinates of each of the plurality of points can be obtained through an existing computer software (for example, using WebPlotDigitizer or existing computer software with similar functions). If the first contour L1 in other figures is a continuous line, it is only for illustration, and in fact it is composed of the plurality of points.

1. Obtain multiple original reference points step S3. Referring to Figure 5, the first contour L1 (the first contour L1 has a pitch P, for example, the pitch P can be 12.7 mm) is divided into M segments, and multiple original reference points Q are obtained, and the coordinate values of the multiple original reference points Q are obtained (for example, this can be achieved through existing computer software).

A crankshaft torque curve acquisition step S4. Referring to Figure 6, a right-foot crankshaft torque curve LA and a left-foot crankshaft torque curve LB are obtained by actual measurement after a user actually steps on the non-circular sprocket.

A characteristic step S5 of obtaining a torque curve. A first angle θ1 (see FIG. 7) is obtained by a right maximum value N1 of the right leg crankshaft torque curve LA (as shown in FIG. 6); and a second angle θ2 is obtained by a left maximum value N2 of the left leg crankshaft torque curve LB.

An optimization region definition step S6. Referring to FIG. 7, it is in conjunction with the right maximum value N1, the first angle θ1, the left maximum value N2 and the second angle θ2. A first basic point Q1, a second basic point Q2, a third basic point Q3 and a fourth basic point Q4 are selected from the plurality of original reference points Q; wherein the selection rule of the first basic point Q1, the second basic point Q2, the third basic point Q3 and the fourth basic point Q4 is: the first basic point Q1, the second basic point Q2, the third basic point Q3 and the fourth basic point Q4 are adjacent to 30 degrees, 150 degrees, 210 degrees and 330 degrees respectively; wherein the region between the first basic point Q1 and the second basic point Q2 is defined as a right foot optimization region QA; and the first angle θ1 falls within the range of the right foot optimization region QA.

The area between the third basic point Q3 and the fourth basic point Q4 is defined as a left foot optimization area QB; and the second angle θ2 falls within the range of the left foot optimization area QB.

The area between the first basic point Q1 and the fourth basic point Q4 is defined as a right invariant area QC.

The area between the second base point Q2 and the third base point Q3 is defined as a left invariant area QD.

A point adjustment step S7. Referring to FIG. 7, the origin W extends toward the first contour L1 according to the first angle θ1 and intersects with the first contour L1 to form a first outward displacement point W1; and one of the plurality of original reference points Q, which falls within the right foot optimization area QA and is farthest from the origin W, is defined as a first inward retraction point W2. Furthermore, the origin W can be further extended toward the first contour L1 according to the second angle θ2 and intersects with the first contour L1 to form a second outward displacement point W3; and one of the plurality of original reference points Q, which falls within the left foot optimization area QB and is farthest from the origin W, is defined as a second inward retraction point W4.

A second contour generation step S8. Referring to FIG. 8, the first outward displacement point W1 is outwardly displaced in a direction away from the origin W, and the first inward retraction point W2 is inwardly displaced in a direction close to the origin W, and the remaining original reference points Q within the right foot optimization area QA are adjusted in conjunction. Furthermore, the second outward displacement point W3 is outwardly displaced in a direction away from the origin W, and the second inward retraction point W4 is inwardly displaced in a direction close to the origin W, and the remaining original reference points Q within the left foot optimization area QB are adjusted in conjunction. At this time, the sum of the neighboring distances between all the original reference points Q after adjustment is defined as a second contour L2, and its length is equal to that of the first contour L1.

A sprocket forming step S9. Based on the second contour L2 and all the adjusted original reference points Q, an optimized non-circular sprocket shape is formed (as shown in Figure A of Appendix 1).

In practice, the number of teeth of the contour image 10 is defined as N; when N=34 (refer to FIG. 7 ): the range of the right foot optimization area QA can be about 1/3 of the first contour L1 (approximately 110 to 130 degrees, and preferably 120 degrees), taking 34 teeth as an example, 34/3=11.33 teeth (e.g. 11 teeth or 11 pitches P). Therefore, it can be between 10 and 13 teeth. Similarly, the left foot optimization area QB can be around 1/3 of a circle (approximately 110 to 130 degrees, and 120 degrees is preferred). Taking 34 teeth as an example, 34/3=11.33 teeth (e.g. 11 teeth or 11 pitches P), so it can be between 10 and 13 teeth, and the rest is the right invariant area QC and the left invariant area QD.

Furthermore, the distance that the first outward displacement point W1 moves away from the origin W is the distance from the origin W to the first outward displacement point W1 increased by 5%±3%; the effect can be produced.

The distance that the first inward contraction point W2 moves inward in the direction approaching the origin W is the distance from the origin W to the first inward contraction point W2 reduced by 5%±3%; the effect can be produced.

The distance that the second outward displacement point W3 moves away from the origin W is the distance from the origin W to the second outward displacement point W3 increased by 5%±3%; the effect can be produced.

The distance that the second retracted point W4 moves inwards towards the origin W is the distance from the origin W to the second retracted point W4 reduced by 5%±3%; the effect can be produced.

Of course, the aforementioned 5% increase in distance and 5% decrease in distance have the best effect.

Furthermore, there may be the following example: the first basic point Q1 is located at the 3rd original reference point Q; the second basic point Q2 is located at the 14th original reference point Q; the third basic point Q3 is located at the 20th original reference point Q; the fourth basic point Q4 is located at the 31st original reference point Q; the first outward displacement point W1 is located between the 8th original reference point Q and the 9th original reference point Q; the first inward contraction point W2 is located at the 12th original reference point Q; the second outward displacement point W3 is located between the 23rd original reference point Q and the 24th original reference point Q; and the second inward contraction point W4 is located at the 29th original reference point Q.

The first angle θ1 may be between 90 degrees and 96 degrees, for example, 93.164 degrees.

The second angle θ2 may be between 251 degrees and 258 degrees, for example, 254.311 degrees.

The focus of this case is on the following two points:

[a] It is quite convenient to perform local optimization with an existing finished product. The present invention directly performs local optimization with an existing non-circular sprocket that is closest to the pedaling habit of a certain user, which means that the shape modification is only applied to a specific part of the existing non-circular sprocket, so only a small part of the shape of the existing non-circular sprocket is changed. The modification is performed by adjusting the position of the maximum radius of the sprocket to the position where the subject's leg generates the maximum torque.

[b] It can improve pedaling efficiency. To illustrate this, let's assume that a non-circular chainring (or chainring, or toothed disc) of one of the popular commercial brands is modified. It is manufactured by a company in Europe, has been used by many professional cyclists, and has won excellent results in some famous international competitions.

Regarding the actual measurement method of this case, a known product with 34 teeth (N=34) was optimized to obtain this product, and then the two were compared in actual measurement.

The pedaling speed was high: 90 (rpm), 100 (rpm) or 110 (rpm). Each test lasted 30 seconds and included 45 pedaling cycles, which were performed three times and then the average value was taken.

The data obtained can be analyzed using existing analysis software, for example: using IBM SPSS Statistics version 26 software, employing the Paired Sample T-Test method.

Please refer to Figure 9, which shows the crank torque output results of the present invention and the known product at different pedaling speeds, which shows that the crank torque of the present invention (including a first bar graph MA1, a second bar graph MA2 and a third bar graph MA3) is better than the crank torque of the known product (correspondingly having a first bar graph MB1, a second bar graph MB2 and a third bar graph MB3). In addition, the "*" in Figure 9 represents: the probability value (p value) of the statistical analysis of the significant difference (Significant difference) compared with the known product, where p<0.01.

For example, the maximum crank torque of this case is 48.74Nm (i.e. the second bar graph MA2), and the corresponding crank torque of the known product is 33.39Nm (i.e. the second bar graph MB2), then: (48.74-33.39)/48.74; = 15.35/48.74; = 31.5%.

That is to say, the product in this case has a crank torque improvement efficiency of 31.5%.

Please refer to Figure 10, which shows the crank power output results of the present invention and the known product at different pedaling speeds. It shows that the crank power of the present invention (including a fourth bar graph MA4, a fifth bar graph MA5 and a sixth bar graph MA6) is better than the crank power of the known product (correspondingly having a fourth bar graph MB4, a fifth bar graph MB5 and a sixth bar graph MB6). In addition, the "*" in Figure 10 represents: the probability value (p value) of the statistical analysis of the significant difference (Significant difference) compared with the known product, where p<0.01.

For example, at a speed of 100 rpm, the crank power increases from 328.66 watts (i.e., the fifth bar graph MB5 representing the known product) to 479.24 watts (i.e., the fifth bar graph MA5 representing the present case), then: (479.24-328.66)/479.24; = 150.58/479.24; = 31.4%.

That is to say, the product in this case has a crank power improvement efficiency of 31.4%.

*統計分析之對比公知產品之顯著性差異(Significant difference)之機率值(p值)，其中p<0.05。 In addition, for a comparison of rear wheel speed at different pedaling speeds, please refer to Table 1 below:

*The probability value (p value) of the statistical analysis showing a significant difference compared with the known products, where p<0.05.

Table 1 above is a comparison table of the rear wheel speed of the known product and the product of this case at the same pedaling speed. Among them, whether the pedaling speed is 90 (rpm), 100 (rpm) or 110 (rpm), the rear wheel speed generated by the product of this case is better than that of the known product, and the difference is 1.55 (%), 1.70 (%) and 1.75 (%) respectively. In other words, the average improvement is 1.67 (%).

In particular, when the user is a professional cyclist, if the rear wheel speed can be increased by at least 1.55% at the same pedaling speed, the chances of improving rankings in various bicycle competitions can be greatly increased.

The advantages and effects of this case can be summarized as follows:

[1] Commercially available products can be further improved according to specific users. The original commercially available products already have quite good advantages. The design method of this case can improve these commercially available products and make them optimized products that are more suitable for specific users. Therefore, commercially available products can be further improved according to specific users.

[2] It is very beneficial to improve crank torque, crank power and rear wheel speed. In a bicycle race where every second counts, being a few seconds faster can improve your ranking. This case only customizes the shape of the existing non-circular sprocket to improve crank torque, crank power and rear wheel speed, which is very helpful for professional cyclists to improve their ranking in the competition. Therefore, it is very beneficial to improve crank torque, crank power and rear wheel speed.

The above is only a detailed description of the present invention through a preferred embodiment. Any simple modification and changes made to the embodiment do not deviate from the spirit and scope of the present invention.

S1: Step of obtaining non-circular sprocket image

S2: Contour image positioning step

S3: Step of obtaining multiple original reference points

S4: Step of obtaining crankshaft torque curve

S5: Characteristic step of obtaining torque curve

S6: Optimization region definition step

S7: Point adjustment steps

S8: Second contour generation step

S9: Sprocket forming step

Claims (9)

A method for optimizing the design of a non-circular sprocket includes: a step of obtaining a non-circular sprocket image, which is to obtain a contour image of a non-circular sprocket, wherein the contour image has a plurality of tooth peak images and a plurality of tooth valley images; and the number of teeth in the contour image is defined as N; a contour image positioning step, which is to connect the plurality of tooth valley images to form a first contour, wherein the first contour is approximately an ellipse; and the center point of the first contour is placed at an origin. , and a short axis of the first profile is placed on the X axis, and a long axis of the first profile is placed on the Y axis; a step of obtaining a plurality of original reference points is to divide the first profile into M segments, and obtain a plurality of original reference points, and obtain the coordinate values of the plurality of original reference points; a step of obtaining a crankshaft torque curve is to obtain a right-foot crankshaft torque curve and a left-foot crankshaft torque curve actually measured by a user after actually stepping on the non-circular sprocket. a characteristic step of obtaining a torque curve, in which a right maximum value of the right leg crankshaft torque curve corresponds to a first angle; and a left maximum value of the left leg crankshaft torque curve corresponds to a second angle; an optimization region definition step, in which a first basic point, a second basic point, a third basic point and a left maximum value of the left leg crankshaft torque curve are selected from the plurality of original reference points in accordance with the right maximum value, the first angle, the left maximum value and the second angle. a fourth basic point; wherein the selection rule of the first basic point, the second basic point, the third basic point and the fourth basic point is: the first basic point, the second basic point, the third basic point and the fourth basic point are adjacent to 30 degrees, 150 degrees, 210 degrees and 330 degrees respectively; wherein the area between the first basic point and the second basic point is defined as a right foot optimization area, and the first angle falls on the right foot The area between the third basic point and the fourth basic point is defined as a left foot optimization area, and the second angle falls within the range of the left foot optimization area; the area between the first basic point and the fourth basic point is defined as a right invariant area; the area between the second basic point and the third basic point is defined as a left invariant area; a point position adjustment step, the origin is based on the first angle The first contour is extended in the direction of the first contour and intersects with the first contour to form a first outward displacement point; and one of the plurality of original reference points, which is within the right foot optimization area and is farthest from the origin, is defined as a first inward retraction point; and the origin can be further extended in the direction of the first contour according to the second angle and intersects with the first contour to form a second outward displacement point; and one of the plurality of original reference points, which is within the right foot optimization area and is farthest from the origin, is defined as a first inward retraction point. The point that is within the left foot optimization region and is farthest from the origin is defined as a second retracted point; a second contour generation step is to move the first outward point outward away from the origin, and at the same time move the first inward point inward toward the origin, and adjust the remaining original reference points within the right foot optimization region in a linked manner; and, move the second outward point outward away from the origin, and at the same time move the second inward point inward toward the origin. The contraction point is moved inwards toward the origin, and the remaining original reference points within the left foot optimization area are adjusted in conjunction; at this time, the sum of the adjacent distances between all the adjusted original reference points is defined as a second contour, the length of which is equal to the first contour; and a sprocket forming step is performed, based on the second contour and all the adjusted original reference points, to form an optimized non-circular sprocket shape. The optimized design method of the non-circular sprocket as described in claim 1, wherein N=34. The method for optimizing the design of a non-circular sprocket as described in claim 1, wherein: the right foot optimization area is located within the range of the first contour, which is between 110 degrees and 130 degrees; the left foot optimization area is located within the range of the first contour, which is between 110 degrees and 130 degrees; and the remaining part of the first contour is the right invariant area and the left invariant area. The optimization design method of the non-circular sprocket as described in claim 3, wherein: the distance that the first outward displacement point moves outward in the direction away from the origin is an increase of 5%±3% in the distance from the origin to the first outward displacement point; the distance that the first inward displacement point moves in the direction close to the origin is a decrease of 5%±3% in the distance from the origin W to the first inward displacement point W2; the distance that the second outward displacement point moves outward in the direction away from the origin is an increase of 5%±3% in the distance from the origin to the second outward displacement point; and the distance that the second inward displacement point moves in the direction close to the origin is a decrease of 5%±3% in the distance from the origin to the second inward displacement point. The optimization design method of the non-circular sprocket as described in claim 4, wherein: the first base point is located at the 3rd original reference point; the second base point is located at the 14th original reference point; the third base point is located at the 20th original reference point; the fourth base point is located at the 31st original reference point; the first outward displacement point is located between the 8th original reference point and the 9th original reference point; the first inward retraction point is located at the 12th original reference point; the second outward displacement point is located between the 23rd original reference point and the 24th original reference point; and the second inward retraction point is located at the 29th original reference point. The method for optimizing the design of a non-circular sprocket as described in claim 3, wherein the first angle is between 90 degrees and 96 degrees. The optimized design method of a non-circular sprocket as described in claim 6, wherein the first angle is 93.164 degrees. The optimized design method of a non-circular sprocket as described in claim 3, wherein the second angle is between 251 degrees and 258 degrees. The optimized design method of a non-circular sprocket as described in claim 8, wherein the second angle is 254.311 degrees.

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