A method for imitating a valve cam

Abstract

A method for replicating a valve cam comprises the following steps: segmenting an original cam to obtain the characteristic lift, characteristic angle, and lift function of each segment; determining the target characteristic lift and target characteristic angle for each segment of the new cam; calculating the lift function for each segment of the new cam, and finally obtaining the overall lift data for the new cam. The valve cam replicating method of the present invention segments the original cam according to its characteristics and performs replica processing based on the segmented characteristics. It can consider symmetry and the presence of a maximum lift holding segment, thus addressing the shortcomings of existing cam replicating methods. This solution can process both the buffer and working segments of the original cam, resulting in a replica cam with curve shapes similar to those of the original cam in terms of lift, velocity, acceleration, and other characteristics across the entire range, thus expanding the application scope of the valve cam replicating method.

Description

Technical Field

[0001] The invention belongs to the field of internal combustion engines and relates to a method for imitating a valve cam. Background Art

[0002] When designing an engine valve cam, a cam imitation is often used: that is, a new cam is designed so that its lift, speed, acceleration and other curve shapes are similar to the original cam while the follower lift and working section wrap angle are different from the original cam.

[0003] In the existing data, the solution to this imitation cam situation is: assuming that the original cam is a symmetrical cam, the original cam follower lift function is h(a), the original cam working section half angle is A1, and the total lift is H1; assuming that the new design cam working section half angle is A2, and the total lift is H2; then the follower function of the new design cam is The lift, speed and acceleration curves of the new cam can be made similar to those of the original cam.

[0004] As can be seen, this method has obvious shortcomings. It only processes the working section of the cam and does not address how to handle the buffer section. However, most valve cams have a buffer section. Processing only the working section does not yield a complete cam lift function, and does not fully address the cam's imitation problem. Furthermore, in many cases, the requirements for the working and buffer sections vary. Directly applying the working section processing method to the buffer section will result in the buffer section end lift not meeting the requirements. Furthermore, this method only applies to symmetrical cams and does not address how to handle asymmetrical cams, making it incapable of fully meeting the requirements for valve cam imitation. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a method for imitating a valve cam. Regardless of whether the original cam is symmetrical, the method can process the buffer section and working section of the original cam to obtain an imitation cam with similar curve shapes such as lift, speed, acceleration, etc. to the original cam buffer section and working section.

[0006] The technical solution adopted by the present invention is: a method for imitating a valve cam, comprising the following steps:

[0007] Step 1: Divide the original cam into segments to obtain the characteristic lift, characteristic angle and lift function of each segment;

[0008] Step 2: Determine the target characteristic lift and target characteristic angle of each section of the new cam;

[0009] Step 3: Calculate the lift function of each section of the new cam, and then obtain the overall lift data of the new cam.

[0010] As a preferred solution, in the step one, when segmenting the original cam, first determine whether the original cam has a maximum lift holding section. If so, divide the cam into five sections, namely, the rising buffer section, the rising working section, the maximum lift holding section, the descending working section and the descending buffer section; if not, divide the cam into four sections, namely, the rising buffer section, the rising working section, the descending working section and the descending buffer section; the characteristic lift of each section is equal to the end lift of each section minus the starting lift, and the characteristic angle is equal to the end angle minus the starting angle. The lift function of each section is obtained based on the original lift data of the original cam and the number of segmented sections. The processing method is that starting from the second section, the lift of any point in each section must be subtracted from the lift of the end point of the previous section, and the angle is also subtracted from the angle of the end point of the previous section.

[0011] As a preferred solution, in the step 2, the number of segments of the new cam is consistent with the number of segments of the original cam, and the target characteristic lift and target characteristic angle of each segment of the new cam are determined based on the design requirements, relevant constraints and some assumptions of the new cam. The target characteristic lift of each segment of the new cam is the characteristic lift required by the new cam, which is equal to the end lift of each segment of the new cam minus the starting lift. The target characteristic angle of each segment of the new cam is the characteristic angle required by the new cam, which is equal to the end angle of each segment of the new cam minus the starting angle.

[0012] As a preferred solution, the constraint condition is: for a cam divided into four sections, the characteristic lift and characteristic angle of the four sections of the original cam are H o1 、H o2 、H o3 、H o4 and A o1 、A o2 、A o3 、A o4 The target characteristic lift and target characteristic angle of the new cam for the four sections are H n1 、H n2 、H n3 、H n4 and A n1 、A n2 、A n3 、A n4 , these parameters need to meet the following conditions:

[0013] H n1 *A 01 / H 01 / A n1 =H n2 *A o2 / H 02 / A n2 ,

[0014] H n2 *A 02 *A 02 / H02 / A n2 / A n2 =H n3 *A o3 *A o3 / H 03 / A n3 / A n3 ,

[0015] H n3 *A o3 / H 03 / A n3 =H n4 *A o4 / H 04 / A n4 .

[0016] As a preferred solution, the constraint condition is: for a cam divided into five sections, the characteristic lift and characteristic angle of the original cam are H o1 、H o2 、H o3 、H o4 、H o5 and A o1 、A o2 、A o3 、A o4 、A o5 The target characteristic lift and target characteristic angle of the new cam corresponding to the five sections are H n1 、H n2 、H n3 、H n4 、H n5 and A n1 、A n2 、A n3 、A n4 、A n5 , these parameters need to meet the following conditions:

[0017] H n1 *A 01 / H 01 / A n1 =H n2 *A o2 / H 02 / A n2 ,

[0018] H n4 *A o4 / H 04 / A n4 =H n5 *A o5 / H 05 / A n5 .

[0019] As a preferred solution, the design requirements of the new cam are: specifying the maximum lift of the new cam, the lift at the end of the buffer segment and the total continuous angle of the working segment, the lift at the end of the buffer segment includes the lift at the end of the rising buffer segment and the lift at the end of the falling buffer segment, and the total continuous angle of the working segment refers to the sum of the continuous angle of the rising working segment, the continuous angle of the maximum lift holding segment and the continuous angle of the falling working segment.

[0020] As a preferred solution, the partial assumptions refer to: for a new cam with a maximum lift holding section, according to the two formulas determined by the known total continuous angle of the new cam working section and the constraints, it is impossible to solve the five target characteristic angles of the rising buffer section, the rising working section, the maximum lift holding section, the descending working section and the descending buffer section. It is necessary to assume two parameters to completely solve these parameters. Since there are constraints on the target characteristic angles of the rising buffer section and the rising working section, and the descending working section and the descending buffer section, these two sets of parameters cannot be assumed at the same time. In other cases, two parameters can be arbitrarily assumed to obtain all the target characteristic angles of the new cam.

[0021] As a preferred solution, in the step three, the lift function of each segment of the new cam is calculated using a formula based on the segmentation of the original cam, the characteristic lift, characteristic angle and lift function of each segment, and the target characteristic lift and target characteristic angle of each segment of the new cam; the lift data of each segment of the new cam is processed to obtain the overall lift data, and the obtained lift is continuous and the angle increases sequentially. The processing method is to start from the second segment, and the lift of any point in each segment must be added to the lift of the end point of the previous segment, and the angle is also added to the angle of the end point of the previous segment. After each segment is processed, the lift data of the entire angle range of the new cam is obtained.

[0022] As a preferred solution, in step three, the corresponding angles of the new cam and the original cam have the following two situations: first, for a cam without a maximum lift holding section, ensure that the crankshaft angle at which the new cam has the maximum lift is consistent with that of the original cam; for a cam with a maximum lift holding section, ensure that the crankshaft angle at which the midpoint of the maximum lift holding section is consistent with that of the original cam; second, ensure that the crankshaft angle at which the starting point of the rising working section or the end point of the descending working section of the new cam is consistent with that of the original cam.

[0023] As a preferred solution, in step 3, the lift function of each section of the new cam is calculated using the formula, where the formula used is: Assume that the characteristic lift and characteristic angle of each section of the original cam are: H ok and A ok , the general expression of each lift function is: f k (a) = f k (H ok , A ok ), k is a natural number, the target characteristic lift and target characteristic angle of each section of the new cam are: Hnk and A nk , then the general expression of each lift function of the new cam is:

[0024] By adopting the above-mentioned technical solution, the present invention can achieve the following beneficial effects:

[0025] 1. The method for imitating a valve timing cam described in the present invention can process both the buffer section and the working section of the original cam to obtain an imitation cam with curve shapes similar to those of the original cam in terms of lift, velocity, acceleration, etc. within the entire range, thereby expanding the application scope of the valve timing cam imitation method.

[0026] 2. The method for imitating the valve cam of the present invention divides the original cam into sections according to the situation of the original cam, and performs imitation processing according to the section situation. It can consider whether it is symmetrical and whether it has a maximum lift holding section, thereby improving the shortcomings of the existing cam imitation method.

[0027] 3. The method for replicating the valve cam of the present invention is easy to implement, has good engineering practical value, and can meet the needs of cam replication. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the description of each embodiment or the prior art. Obviously, the drawings described below are only some embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on the drawings of these embodiments without paying any creative work.

[0029] Figure 1 This is a flow chart of the valve cam imitation method of the present invention;

[0030] Figure 2 This is a diagram illustrating the cam segmentation method of the present invention;

[0031] Figure 3 Schematic diagram of characteristic lift and characteristic angle of the original cam of the present invention divided into four sections;

[0032] Figure 4 This is a schematic diagram of characteristic lift and characteristic angle of the original cam of the present invention divided into five sections;

[0033] Figure 5 A schematic diagram showing that the maximum lift angle of the new cam according to the present invention is consistent with that of the original cam;

[0034] Figure 6 This is a schematic diagram showing that the new cam of the present invention maintains the same midpoint angle as the original cam in the maximum lift maintaining section;

[0035] Figure 7 This is a schematic diagram showing that the new cam of the present invention maintains the same angle as the original cam at the starting point of the ascending working section;

[0036] Figure 8 This is a schematic diagram showing that the angles of the new cam and the original cam are consistent at the end point of the descending working section;

[0037] Figure 9 This is a schematic diagram of a speed curve when the original cam of the present invention is divided into four sections;

[0038] Figure 10 This is a schematic diagram of the acceleration curve when the original cam of the present invention is divided into four sections;

[0039] Figure 11 This is a schematic diagram of a speed curve when the original cam of the present invention is divided into five sections;

[0040] Figure 12 This is a schematic diagram of the acceleration curve when the original cam of the present invention is divided into five sections;

[0041] Figure 13 This is a partial data diagram used in the implementation of the imitation method in specific embodiment 1 of the present invention;

[0042] Figure 14 1 is a lift curve diagram of the original cam and the new cam in specific embodiment 1 of the present invention;

[0043] Figure 15 1 is a velocity curve diagram of the original cam and the new cam of the specific embodiment 1 of the present invention;

[0044] Figure 16 1 is an acceleration curve diagram of the original cam and the new cam in specific embodiment 1 of the present invention;

[0045] Figure 17 This is a partial data diagram used in the implementation of the imitation method in specific embodiment 2 of the present invention;

[0046] Figure 18 1 is a lift curve diagram of the original cam and the new cam in specific embodiment 2 of the present invention;

[0047] Figure 19 This is a partial data diagram used in the implementation of the imitation method in specific embodiment 3 of the present invention;

[0048] Figure 20 1 is a lift curve diagram of the original cam and the new cam in specific embodiment 3 of the present invention;

[0049] Figure 21 This is a partial data diagram used in the implementation of the imitation method in specific embodiment 4 of the present invention;

[0050] Figure 221 is a lift curve diagram of the original cam and the new cam in specific embodiment 4 of the present invention;

[0051] Figure 23 This is a partial data diagram used in the implementation of the imitation method in specific embodiment 5 of the present invention;

[0052] Figure 24 1 is a lift curve diagram of the original cam and the new cam in specific embodiment 5 of the present invention;

[0053] Figure 25 1 is a velocity curve diagram of the original cam and the new cam of the specific embodiment 5 of the present invention;

[0054] Figure 26 Graphs showing accelerations of the original cam and the new cam according to Embodiment 5 of the present invention;

[0055] In the figure, H m is the maximum lift of the cam, H1 is the lift at the end of the rising buffer section, H2 is the lift at the end of the falling buffer section, v1 is the speed at the end of the rising buffer section, v2 is the speed at the end of the falling buffer section, a m is the acceleration of the maximum lift point of the cam without the maximum lift holding section. A1, A2, A3, A4, and A5 are the continuous angles of the rising buffer section, rising working section, maximum lift holding section, descending working section, and descending buffer section respectively. H o1 、H o2 、H o3 、H o4 、H o5 is the characteristic lift of each segment after the original cam is segmented, A o1 、A o2 、A o3 、A o4 、A o5 It is the characteristic angle of each segment after the original cam is segmented. Curve 1 is the original cam lift curve, and curve 2 is the new cam lift curve. DETAILED DESCRIPTION

[0056] The present invention will be described in detail below with reference to the accompanying drawings and examples.

[0057] A method for imitating a valve cam. Figure 1 1 is a flow chart of the valve cam imitation method of the present invention, which comprises the following steps:

[0058] Step 1: Divide the original cam into segments to obtain the characteristic lift, characteristic angle and lift function of each segment;

[0059] Furthermore, the number of segments is determined based on the lift data of the original cam, refer to Figure 2The cam segmentation method shown in the figure is converted from the lift data of the original cam, indicating that the general valve cam is composed of five sections at most, which are the rising buffer section, the rising working section, the maximum lift holding section, the descending working section and the descending buffer section from front to back. The rising buffer section and the rising working section are separated at the lift H1, and the descending working section and the descending buffer section are separated at the lift H2. The maximum lift holding section is the section with the lift always at the maximum lift H1. m A section, H 1、 H 2、 H m They are the end lift of the rising buffer section, the end lift of the falling buffer section and the maximum lift of the cam. The continuous angles of each section are A1, A2, A3, A4 and A5 respectively. When the maximum lift holding section angle A3 is zero, the rising working section is directly connected to the falling working section, there is no maximum lift holding section, the cam section becomes four sections, and the continuous angles of each section become A1, A2, A4 and A5.

[0060] The original cam lift data can be obtained from the relevant cam lift expression, the relevant cam drawing, or the actual cam measurement processing; the cam with the cam lift expression can directly obtain the function type and segmentation of the lift curve, and can further deduce the function type of the derivatives such as velocity and acceleration, which can accurately distinguish the buffer section, working section and maximum lift holding section, so it is the simplest to segment this original cam; the lift data obtained from the cam drawing cannot directly obtain the function type of velocity and acceleration, and it is necessary to perform derivative calculations based on the lift data to obtain the function type of the derivatives such as velocity and acceleration, and then distinguish the buffer section, working section and maximum lift holding section. The original cam segmentation process is slightly complicated; the lift data obtained from the actual cam measurement processing has certain processing and measurement errors, and needs to be processed and converted into smooth lift data, and then derived to obtain the function type of the derivatives such as velocity and acceleration, and finally distinguish the buffer section, working section and maximum lift holding section. This original cam segmentation is the most complicated and has poor segmentation accuracy;

[0061] The characteristic lift of each section is equal to the end lift of each section minus the starting lift, and the characteristic angle is equal to the end angle minus the starting angle; for the cam without the maximum lift holding section, the cam is divided into four sections, namely the rising buffer section, the rising working section, the descending working section and the descending buffer section. In the rising buffer section, its characteristic lift is equal to the end lift of the rising buffer section, and its characteristic angle is equal to the continuous angle of the rising buffer section. In the rising working section, its characteristic lift is equal to the maximum lift of the cam minus the end lift of the rising buffer section, and its characteristic angle is equal to the continuous angle of the rising working section. In the descending working section, its characteristic lift is equal to the end lift of the descending buffer section minus the maximum lift of the cam, and its characteristic angle is equal to the continuous angle of the descending working section. In the descending buffer section, its characteristic lift is equal to the negative end lift of the descending buffer section, and its characteristic angle is equal to the continuous angle of the descending buffer section. Figure 3 The original cam has no maximum lift holding section. The original cam is divided into four sections, with characteristic lifts of H o1 、H o2 、H o3 、H o4 , H o1 Equal to H1, H o2 Equal to H m Subtract H1, H o3 Equal to H2 minus H m , H o4 Equal to -H2, the characteristic angles are A o1 、A o2 、A o3 、A o4 , A o1 Equal to A1, A o2 Equal to A2, A o3 Equal to A4, A o4 Equal to A5;

[0062] For the cam with maximum lift holding section, the cam is divided into five sections, namely rising buffer section, rising working section, maximum lift holding section, descending working section and descending buffer section. In the rising buffer section, its characteristic lift is equal to the lift at the end of the rising buffer section, and its characteristic angle is equal to the continuous angle of the rising buffer section. In the rising working section, its characteristic lift is equal to the maximum lift of the cam minus the lift at the end of the rising buffer section, and its characteristic angle is equal to the continuous angle of the rising working section. In the maximum lift holding section, its characteristic lift is equal to zero, and its characteristic angle is equal to the continuous angle of the maximum lift holding section. In the descending working section, its characteristic lift is equal to the lift at the end of the descending buffer section minus the maximum lift of the cam, and its characteristic angle is equal to the continuous angle of the descending working section. In the descending buffer section, its characteristic lift is equal to the negative lift at the end of the descending buffer section, and its characteristic angle is equal to the continuous angle of the descending buffer section. Figure 4 The original cam has a maximum lift holding section. The original cam is divided into five sections, and the characteristic lifts are H o1 、H o2 、H o3 、H o4 、H o5 , H o1 Equal to H1, H o2 Equal to H m Subtract H1, H o3 Equal to zero, H 04 Equal to H2 minus H m 、H o5 Equal to -H2, the characteristic angles are A o1 、A o2 、A o3 、A o4 、A o5 , A o1 Equal to A1, Ao2 Equal to A2, A o3 Equal to A3, A o4 Equal to A4, A o5 Equal to A5;

[0063] The lift function of each segment is obtained according to the original lift data of the original cam and the number of segments. The lift function of each segment only considers the lift and angle changes within each segment. The lift of the original cam is a function of the angle, and all lifts are continuous, and all angles increase sequentially. After segmentation, the first segment remains unchanged. Starting from the second segment, the lift of any point in each segment must be subtracted from the lift of the end point of the previous segment, and the angle is also subtracted from the angle of the end point of the previous segment. In this way, the lift function of all points in each segment starts from zero and ends with the characteristic lift, and the angle starts from zero and ends with the characteristic angle. This obtains the lift function of each segment of the original cam, which is convenient for later operations on the lift function of each segment.

[0064] Assume that the characteristic lift and characteristic angle of each section of the original cam are: H ok and A ok , then the general expression of each lift function is: f k (a) = f k (H ok , A ok ), k is a natural number;

[0065] Step 2: Determine the target characteristic lift and target characteristic angle of each section of the new cam;

[0066] The number of segments of the new cam is consistent with that of the original cam, and the target characteristic lift and target characteristic angle of each segment of the new cam are determined according to the design requirements, relevant constraints and some assumptions of the new cam; the target characteristic lift of each segment of the new cam is the characteristic lift required by the new cam, which is equal to the end lift of each segment of the new cam minus the starting lift, and the target characteristic angle of each segment of the new cam is the characteristic angle required by the new cam, which is equal to the end angle of each segment of the new cam minus the starting angle; the maximum lift, buffer segment lift and angle of each segment of the imitated new cam may be different from those of the original cam. In order to ensure that the new cam and the original cam are similar in curve shape such as lift, speed and acceleration, the number of segments of the new cam needs to be consistent with that of the original cam, and then certain restrictions are imposed on the target characteristic lift and target characteristic angle of each segment according to the segmentation situation to ensure that the new cam and the original cam have the same curve shape and maintain the continuity of the relevant curves;

[0067] Assume that the target characteristic lift and target characteristic angle of each section of the new cam are: H nk and A nk , k is a natural number; the relevant constraints are as follows:

[0068] For a cam divided into four sections, the characteristic lift and characteristic angle of the four sections of the original cam are Ho1 、H o2 、H o3 、H o4 and A o1 、A o2 、A o3 、A o4 The target characteristic lift and target characteristic angle of the new cam for the four sections are H n1 、H n2 、H n3 、H n4 and A n1 、A n2 、A n3 、A n4 , then the following conditions must be met: H n1 *A 01 / H 01 / A n1 =H n2 *A o2 / H 02 / A n2 , H n2 *A 02 *A 02 / H 02 / A n2 / A n2 =H n3 *A o3 *A o3 / H 03 / A n3 / A n3 , H n3 *A o3 / H 03 / A n3 =H n4 *A o4 / H 04 / A n4 ;

[0069] For a cam divided into five sections, the characteristic lift and characteristic angle of the original cam are H o1 、H o2 、H o3 、H o4 、H o5 and A o1 、A o2 、A o3 、A o4 、A o5 The target characteristic lift and target characteristic angle of the new cam corresponding to the five sections are H n1 、H n2 、H n3 、H n4 、H n5 and An1 、A n2 、A n3 、A n4 、A n5 , then the conditions that need to be met are: H n1 *A 01 / H 01 / A n1 =H n2 *A o2 / H 02 / A n2 , H n4 *A o4 / H 04 / A n4 =H n5 *A o5 / H 05 / A n5 ;

[0070] The above constraints have a total of five sets of formulas. Each set of formulas has four original cam parameters and four new cam parameters. The original cam parameters are known. If three of the four new cam parameters are determined, the other one can be calculated.

[0071] The design requirements of a new cam are generally to specify the maximum lift of the cam, the lift at the end of the buffer segment and the total continuous angle of the working segment. The lift at the end of the buffer segment includes the lift at the end of the rising buffer segment and the lift at the end of the falling buffer segment. The total continuous angle of the working segment refers to the sum of the continuous angle of the rising working segment, the continuous angle of the maximum lift holding segment and the continuous angle of the falling working segment. For a cam without a maximum lift holding segment, the target characteristic lift of the rising working segment and the target characteristic lift of the rising buffer segment and the falling buffer segment can be calculated based on the maximum lift of the cam and the lift at the end of the buffer segment. Then, based on the target characteristic lift of the rising and falling working segments of the new cam, the total continuous angle of the rising and falling working segments of the new cam, and the characteristic lift and characteristic angle of the rising and falling working segments of the original cam, the target characteristic angle of the rising working segment and the falling working segment of the new cam can be calculated by the relevant constraints. Then, based on the target characteristic lift of the working segment of the new cam, the target characteristic lift of the buffer segment and the target characteristic angle of the working segment, the target characteristic angle of the buffer segment can be calculated by the constraints, and then Determine all target characteristic lifts and target characteristic angles of the new cam; for a cam with a maximum lift holding section, the target characteristic lifts of the rising working section and the falling working section, and the target characteristic lifts of the rising buffer section and the falling buffer section can be calculated based on the maximum lift of the cam and the lift at the end of the buffer section, while the target characteristic lift of the maximum lift holding section is zero, and the total continuous angle of the working section is known, that is, the sum of the target characteristic angles of the rising working section, the maximum lift holding section, and the falling working section is known. In addition, there are two formulas for the constraints, and it is necessary to solve the five target characteristic angles of the rising buffer section, the rising working section, the maximum lift holding section, the falling working section, and the falling buffer section. Two parameters need to be assumed to fully solve these parameters. Since there are constraints on the target characteristic angles of the rising buffer section and the rising working section, and the falling working section and the falling buffer section, these two sets of parameters cannot be assumed at the same time. In other cases, two parameters can be assumed arbitrarily, and then all target characteristic angles are obtained to complete the determination of all target characteristic lifts and target characteristic angles of the new cam;

[0072] Step 3: Calculate the lift function of each section of the new cam, and then obtain the overall lift data of the new cam;

[0073] According to the segmentation of the original cam, the characteristic lift, characteristic angle and lift function of each segment, and the target characteristic lift and target characteristic angle of each segment of the new cam, the lift function of each segment of the new cam is calculated using the formula;

[0074] Assume that the characteristic lift and characteristic angle of each section of the original cam are: H ok and A ok , the general expression of each lift function is: f k (a) = f k (H ok , A ok ), the target characteristic lift and target characteristic angle of each section of the new cam are: Hnk and A nk , then the general expression of each lift function of the new cam is: In the maximum lift holding section, the characteristic lift of the original cam and the new cam are both zero, and the new cam lift function needs to be changed to Since all the parameters in the formula are known, the lift data of each section of the new cam can be calculated;

[0075] The lift data of each section of the new cam is processed to obtain the overall lift data, that is, the lift is continuous and the angle is successively increased. The processing method is to keep the first section unchanged. Starting from the second section, the lift of any point in each section must be added to the lift of the end point of the previous section, and the angle is also added to the angle of the end point of the previous section. After each section is processed, the lift data of the entire angle range of the new cam is obtained;

[0076] In order to obtain better engine performance, the angle of the new cam needs to have a certain correspondence with the original cam; the preferred solution is to ensure that the maximum lift angle of the new cam is consistent with the original cam for the cam without the maximum lift holding section. Figure 5 , the new cam is consistent with the original cam's maximum lift angle; for the cam with the maximum lift holding section, ensure that the maximum lift holding section midpoint angle is consistent with the original cam, refer to Figure 6 , the new cam and the original cam keep the same angle at the midpoint of the maximum lift section; the optional solution is to ensure that the angle of the starting point of the rising working section or the end point of the descending working section of the new cam is consistent with that of the original cam, refer to Figure 7 and Figure 8 , Figure 7 The angle of the connection point between the rising buffer section and the rising working section of the new cam and the original cam is consistent. Figure 8 The angle of the connection point between the new cam and the original cam at the descending working section and the descending buffer section is consistent.

[0077] From then on, a replica cam can be obtained with the same number of segments as the original cam and similar lift, speed and acceleration curve shapes.

[0078] The following describes why the imitation cam can maintain the continuity of the speed and acceleration curves.

[0079] Figure 9 、 Figure 10 These are the speed and acceleration curve diagrams when the original cam is divided into four sections. Figure 11 、 Figure 12They are schematic diagrams of the velocity and acceleration curves when the original cam is divided into five sections. It can be seen that for the original cam, the acceleration of the connection point between the buffer section and the working section is zero, the speed of the starting point of the rising buffer section and the end point of the rising working section is zero, and the speed of the starting point of the descending working section and the end point of the descending buffer section is zero. For the cam divided into four sections, the acceleration of the connection point of the ascending working section and the descending working section is equal. For the cam divided into five sections, the acceleration of the end point of the ascending working section and the starting point of the descending working section is zero.

[0080] According to the continuity and related characteristics of the cam, for the original cam, it is necessary to ensure that the lift, speed, and acceleration at the connection points of each section are equal. In the rising buffer section and the rising working section, the starting speed of the rising buffer section is zero, the speed of the connection point between the rising buffer section and the rising working section is v1, and the end speed of the rising working section is zero. Therefore, after segmentation, the end speed of the rising buffer section is v1, and the end speed of the rising working section is -v1. Only in this way can the end speed of the original lifting rising working section be zero. When copying the cam, the new cam must also ensure that the speed at the end of the rising working section is zero, that is, the sum of the end speed of the rising buffer section and the end speed of the rising working section of the new cam is zero when segmenting;

[0081] The new cam segment function is obtained by changing the original cam segment function. The general expression of each segment lift function of the new cam is: According to the derivation formula, the new cam segment speed function is: The new cam segment acceleration function is:

[0082] That is to say, After substituting into the formula, we get After simplification, we get This is the constraint condition H in step 2 n1 *A 01 / H 01 / A n1 =H n2 *A o2 / H 02 / A n2 .

[0083] Similarly, for the descending working section and the descending buffer section, in order to ensure continuity, the original cam must ensure that the speed at the starting point of the descending working section is zero, the speed at the connection point of the descending working section and the descending buffer section is v2, and the speed at the end of the descending buffer section is zero. Therefore, after segmentation, the speed at the end of the descending working section is v2, and the speed at the end of the descending buffer section is -v2. The new cam must also ensure that the speed at the starting point of the descending working section and the end of the descending buffer section is zero, that is, when segmenting, the sum of the speed at the end of the descending working section and the speed at the end of the descending buffer section of the new cam is zero. In this way, according to the above derivation, the constraint condition H can be obtained. n3 *A o3 / H03 / A n3 =H n4 *A o4 / H 04 / A n4 (for cams with four sections) and H n4 *A o4 / H 04 / A n4 =H n5 *A o5 / H 05 / A n5 (For cams with five sections).

[0084] For a cam with four sections, the acceleration a at the end of the rising working section is required at the maximum lift point. m Equal to the acceleration a at the beginning of the descending working section m Therefore, after segmentation, the acceleration of the original cam and the new cam at the end of the rising working section is equal to the acceleration at the beginning of the descending working section.

[0085] It is known that After substituting into the formula, we get After simplification, we get This is the constraint condition H in step 2 n2 *A 02 *A 02 / H 02 / A n2 / A n2 =H n3 *A o3 *A o3 / H 03 / A n3 / A n3 .

[0086] For a cam divided into five sections, the acceleration at the connection between the rising working section and the maximum lift holding section of the original cam is zero, and the acceleration at the connection between the maximum lift holding section and the descending working section is also zero. Similarly, the acceleration at these connections of the new cam is also zero, and the acceleration continuity can be guaranteed without adding constraints.

[0087] By adopting the above-described technical solution, the valve timing cam replication method of the present invention can segment the original cam according to its characteristics, obtain the characteristic lift, characteristic angle, and lift function of each segment, then determine the target characteristic lift and target characteristic angle of each segment of the new cam based on the design requirements and relevant constraints of the new cam. The replication formula is then used to calculate each segment to obtain lift data for each segment. Finally, the overall lift data is obtained and the crankshaft angle of the new cam is determined, completing the cam replication process. After segmentation, since each segment is replicated separately, the lift, velocity, and acceleration curves of each segment are guaranteed to be consistent. Moreover, since the characteristic lift and characteristic angle of the original cam and the target characteristic lift and target characteristic angle of the new cam meet certain constraints, the new cam is guaranteed to have the same continuity as the original cam, meeting the requirements of the replicated cam.

[0088] It can be seen that the valve cam imitation method described in the present invention processes both the buffer section and the working section of the original cam, and can obtain an imitation cam with curve shapes such as lift, speed, acceleration, etc. that are similar to those of the original cam within the entire range, thereby expanding the application scope of the valve cam imitation method and making complete imitation of the valve cam a reality.

[0089] The method for imitating the valve timing cam described in the present invention divides the original cam into segments according to the situation, and performs imitation processing according to the segmentation situation. It can consider various cam types such as whether they are symmetrical and whether they have maximum lift holding segments, and can ensure the continuity between all cam segments, thereby improving the shortcomings of existing cam imitation methods.

[0090] The valve cam imitation method of the present invention is easy to implement, has good engineering practical value, and can meet the needs of cam imitation.

[0091] The following are some specific embodiments, in which some specific cam imitation processes are given to explain in detail the process of the valve cam imitation method of the present invention:

[0092] Example 1

[0093] The maximum lift of an original exhaust cam is 8mm, the lift at the end of the rising buffer section is 0.5mm, the lift at the end of the falling buffer section is 0.4mm, the cam rising buffer section continuous angle is 37 degrees, the rising working section continuous angle is 50 degrees, the falling working section continuous angle is 50 degrees, the falling buffer section continuous angle is 33 degrees, and the cam maximum lift angle is 252 crankshaft degrees. The imitation new cam design requires a maximum lift of 9mm, the lift at the end of the rising and falling buffer sections remains unchanged, the total continuous angle of the cam working section is 105 degrees, and the crankshaft angle at the maximum lift remains unchanged.

[0094] Step 1: Divide the original cam into segments and obtain the characteristic lift, characteristic angle and lift function of each segment. First, obtain the original cam lift data and refer to Figure 2 After analyzing the original cam, we found that the cam has no maximum lift holding section, so the original cam is divided into four sections, namely the rising buffer section, the rising working section, the descending working section and the descending buffer section, and the original cam is asymmetric. Figure 3 , its characteristic lift H o1 、H o2 、H o3 、H o4 They are 0.5, 7.5, -7.6, and -0.4 respectively, and the characteristic angle A o1 、A o2 、A o3 、A o4 They are 37, 50, 50, and 33 respectively. The original cam lift is then segmented to obtain the lift function of each segment. Starting from the second segment, the lift of any point in each segment must be subtracted from the lift of the end point of the previous segment, and the angle is also subtracted from the angle of the end point of the previous segment. In this way, each lift function starts from zero and ends with the characteristic lift, and the angle starts from zero and ends with the characteristic angle. This makes it easier to process each lift function. Suppose the four-segment lift functions of the original cam are: f1(a)=f1(0.5,37), f2(a)=f2(7.5,50), f3(a)=f3(-7.6,50), f4(a)=f4(-0.4,33);

[0095] Step 2: Determine the target characteristic lift and target characteristic angle of each section of the new cam. The new cam has four sections like the original cam. According to the design requirements of the new cam, the maximum lift of the new cam is 9mm, the end lift of the rising and falling buffer sections remains unchanged, and the total continuous angle of the cam working section is 105 degrees. Therefore, its target characteristic lift H n1 、H n2 、H n3 、H n4 They are 0.5, 8.5, -8.6, and -0.4 respectively, and the target feature angle A n2 With A n3 The sum is 105; In addition, according to the constraints that the four cams above should meet: H n2 *A 02 *A 02 / H 02 / A n2 / A n2 =H n3 *A o3 *A o3 / H 03 / A n3 / A n3 You can get an A n2 With A n3 The relationship, combined with A n2 With A n3 The sum is 105, so we can calculate An2 With A n3 They are approximately 52.520 and 52.480 respectively. According to the formula H n1 *A 01 / H 01 / A n1 =H n2 *A o2 / H 02 / A n2 and H n3 *A o3 / H 03 / A n3 =H n4 *A o4 / H 04 / A n4 A can be calculated n1 About 34.293, A n4 About 30.609;

[0096] Step 3: Calculate the lift function of each section of the new cam, and then get the lift data of the new cam as a whole. According to the segmentation of the original cam, substitute the characteristic lift, characteristic angle and lift function of each section of the original cam, the target characteristic lift and target characteristic angle of each section of the new cam into the general formula. The formulas for obtaining the lift functions of each section of the new cam are: After calculation, the lift of each section of the new cam is obtained, and then the lift of each section of the new cam is processed to obtain the overall lift data. That is, starting from the second section, the lift of any point in each section must be added to the lift of the end point of the previous section, and the angle is also added to the angle of the end point of the previous section. After each section is processed, the overall lift of the overall angle range of the new cam is obtained. Finally, according to the design requirements, the angle of the maximum lift of the new cam is fixed at 252 degrees, which is consistent with the design requirements of the original cam. The crankshaft angles of other points are calculated, such as Figure 5 shown.

[0097] Figure 13 It is part of the data used in the cam imitation method of Example 1 (the maximum interval is 5 degrees of cam angle), including the crankshaft angle, cam angle, cam lift of the original cam, the segmented angle and segmented lift of each segment after the original cam is segmented, the changed segmented angle and segmented lift of the new cam obtained according to the imitation requirements, and the overall angle and overall lift obtained after reprocessing, and finally the corresponding crankshaft angle.

[0098] from Figure 13It can be seen that the maximum lift of the original cam in Example 1 is 8mm at a cam angle of 87 degrees, corresponding to a crankshaft angle of 252 degrees. There is no maximum lift holding section. The original cam is divided into four sections, namely, an ascending buffer section, an ascending working section, a descending working section, and a descending buffer section. The corresponding cam angles are 0-37 degrees, 37-87 degrees, 87-137 degrees, and 137-170 degrees, respectively. The corresponding cam lifts are 0-0.5mm, 0.5-8mm, 8-0.4mm, and 0.4-0mm, respectively. The segmented angles corresponding to these four sections are 0-37 degrees, 0-50 degrees, 0-50 degrees, and 0-33 degrees, respectively. The segmented lifts are 0-0.5mm, 0-7.5mm, 0-(-7.6)mm, and 0-(-0.4)mm, respectively. The four sections of the new cam correspond to The segmented angles are 0-34.293 degrees, 0-52.520 degrees, 0-52.480 degrees, and 0-30.609 degrees, and the segmented lifts are 0-0.5mm, 0-8.5mm, 0-(-8.6)mm, and 0-(-0.4)mm, respectively. The cam angles corresponding to each segment of the new cam's overall lift are 0-34.293 degrees, 34.293-86.813 degrees, 86.813-139.293 degrees, and 139.293-169.902 degrees, respectively. The corresponding cam lifts are 0-0.5mm, 0.5-9mm, 9-0.4mm, and 0.4-0mm, respectively. The new cam has a maximum lift of 9mm at a cam angle of 86.813 degrees, corresponding to a crankshaft angle of 252 degrees, which is consistent with the angle of the original cam's maximum lift.

[0099] Through the above steps, the cam imitation work of Example 1 is completed. Figure 14 、 15 Figures 16 and 17 show the lift, velocity, and acceleration curves for the original and new cams of Example 1, obtained using this replication method. As can be seen, the new cam is similar to the original cam, both including an ascending buffer section, an ascending operating section, a descending operating section, and a descending buffer section. Both are asymmetrical, and their lift, velocity, and acceleration curves are similar. Furthermore, because the corresponding constraints are met, their velocity and acceleration curves are guaranteed to be continuous, meeting the requirements for cam replication.

[0100] Example 2

[0101] The maximum lift of an original exhaust cam is 8mm, the lift at the end of the rising buffer section is 0.5mm, the lift at the end of the falling buffer section is 0.4mm, the cam rising buffer section duration angle is 37 degrees, the rising working section duration angle is 50 degrees, the falling working section duration angle is 50 degrees, the falling buffer section duration angle is 33 degrees, and the starting point angle of the cam rising working section is 152 crankshaft degrees. The design requirement of the imitated new cam is a maximum lift of 8.1mm, the lift at the end of the rising buffer section is 0.6mm, the lift at the end of the falling buffer section is 0.5mm, the total duration angle of the cam working section is 105 degrees, and the crankshaft angle at the starting point of the rising working section remains unchanged.

[0102] Step 1: Divide the original cam into segments and obtain the characteristic lift, characteristic angle and lift function of each segment. First, obtain the original cam lift data and refer to Figure 2 After analyzing the original cam, we found that the cam has no maximum lift holding section, so the original cam is divided into four sections, namely the rising buffer section, the rising working section, the descending working section and the descending buffer section, and the original cam is asymmetric. Figure 3 , its characteristic lift H o1 、H o2 、H o3 、H o4 They are 0.5, 7.5, -7.6, and -0.4 respectively, and the characteristic angle A o1 、A o2 、A o3 、A o4 They are 37, 50, 50, and 33 respectively. The original cam lift is then segmented to obtain the lift function of each segment. Starting from the second segment, the lift of any point in each segment must be subtracted from the lift of the end point of the previous segment, and the angle is also subtracted from the angle of the end point of the previous segment. In this way, each lift function starts from zero and ends with the characteristic lift, and the angle starts from zero and ends with the characteristic angle. This makes it easier to process each lift function. Suppose the four-segment lift functions of the original cam are: f1(a)=f1(0.5,37), f2(a)=f2(7.5,50), f3(a)=f3(-7.6,50), f4(a)=f4(-0.4,33);

[0103] Step 2: Determine the target characteristic lift and target characteristic angle of each section of the new cam. The new cam has four sections like the original cam. According to the design requirements of the new cam, the maximum lift of the new cam is 8.1mm, the lift at the end of the rising buffer section is 0.6mm, the lift at the end of the falling buffer section is 0.5mm, and the total continuous angle of the cam working section is 105 degrees. Therefore, its target characteristic lift H n1 、H n2 、H n3 、H n4 They are 0.6, 7.5, -7.6, and -0.5 respectively, and the target feature angle A n2 With A n3 The sum is 105; In addition, according to the constraints that the four cams above should meet: H n2 *A 02 *A 02 / H 02 / A n2 / A n2 =H n3 *A o3 *A o3 / H 03 / A n3 / An3 You can get an A n2 With A n3 The relationship, combined with A n2 With A n3 The sum is 105, so we can calculate A n2 With A n3 Both are 52.5, and then according to the formula H n1 *A 01 / H 01 / A n1 =H n2 *A o2 / H 02 / A n2 and H n3 *A o3 / H 03 / A n3 =H n4 *A o4 / H 04 / A n4 A can be calculated n1 is 46.62, A n4 is 43.3125;

[0104] Step 3: Calculate the lift function of each section of the new cam, and then get the lift data of the new cam as a whole. According to the segmentation of the original cam, substitute the characteristic lift, characteristic angle and lift function of each section of the original cam, the target characteristic lift and target characteristic angle of each section of the new cam into the general formula. The formulas for each section of the new cam are: After calculation, the lift of each section of the new cam is obtained, and then the lift of each section of the new cam is processed to obtain the overall lift data. That is, starting from the second section, the lift of any point in each section must be added to the lift of the end point of the previous section, and the angle is also added to the angle of the end point of the previous section. After each section is processed, the overall lift of the overall angle range of the new cam is obtained. Finally, according to the design requirements, the starting point angle of the new cam rising working section is fixed at 152 degrees, which is consistent with the design requirement and the starting point angle of the original cam rising working section. The crankshaft angles of other points are calculated, such as Figure 7 shown.

[0105] Figure 17 These are some of the data used in the cam imitation method of Example 2 (with a maximum cam angle interval of 5 degrees), including data content that is consistent with that of Example 1.

[0106] from Figure 17It can be seen that the starting point of the rising working section of the original cam in Example 2 is at a cam angle of 37 degrees, corresponding to a crankshaft angle of 152 degrees, and there is no maximum lift holding section. The original cam is divided into four sections, namely, a rising buffer section, a rising working section, a descending working section, and a descending buffer section. The corresponding cam angles are 0-37 degrees, 37-87 degrees, 87-137 degrees, and 137-170 degrees, respectively, and the corresponding cam lifts are 0-0.5mm, 0.5-8mm, 8-0.4mm, and 0.4-0mm, respectively. The segmented angles corresponding to these four sections are 0-37 degrees, 0-50 degrees, 0-50 degrees, and 0-33 degrees, respectively, and the segmented lifts are 0-0.5mm, 0-7.5mm, 0-(-7.6)mm, and 0-(-0.4)mm, respectively; the four sections of the new cam correspond to The segmented angles are 0-46.62 degrees, 0-52.5 degrees, 0-52.5 degrees, and 0-43.3125 degrees, and the segmented lifts are 0-0.6mm, 0-7.5mm, 0-(-7.6)mm, and 0-(-0.5)mm. The cam angles corresponding to each segment of the new cam's overall lift are 0-46.62 degrees, 46.62-99.12 degrees, 99.12-151.62 degrees, and 151.62-194.9325 degrees, and the corresponding cam lifts are 0-0.6mm, 0.6-8.1mm, 8.1-0.5mm, and 0.5-0mm. The starting point of the new cam's rising working section is a cam angle of 46.62 degrees, corresponding to a crankshaft angle of 152 degrees, which is the same as the angle of the starting point of the original cam's rising working section.

[0107] Through the above steps, the cam imitation work of Example 2 is completed. Figure 18 These are the lift curves for the original cam and the new cam of Example 2, obtained using this replication method. As can be seen, the new cam, like the original, includes a rising buffer section, an rising operating section, a descending operating section, and a descending buffer section, and is asymmetrical. Similar to Example 1, because it meets the corresponding constraints, its velocity and acceleration curves are guaranteed to be continuous, meeting the requirements for cam replication.

[0108] Example 3

[0109] The maximum lift of an original intake cam is 8mm, the lift at the end of the rising buffer section is 0.5mm, the lift at the end of the falling buffer section is 0.5mm, the rising buffer section duration angle is 30 degrees, the rising working section duration angle is 55 degrees, the falling working section duration angle is 55 degrees, the falling buffer section duration angle is 30 degrees, and the maximum lift angle of the cam is 460 degrees of crankshaft angle. The imitation cam design requires a maximum lift of 7.5mm, a lift at the end of the buffer section of 0.4mm, and a total working section duration angle of 112 degrees.

[0110] Step 1: Divide the original cam into segments and obtain the characteristic lift, characteristic angle and lift function of each segment. First, obtain the original cam lift data and refer to Figure 2 After analyzing the original cam, we found that the cam has no maximum lift holding section, so the original cam is divided into four sections, namely the rising buffer section, the rising working section, the descending working section and the descending buffer section, and the original cam is symmetrical. Figure 3 , its characteristic lift H o1 、H o2 、H o3 、H o4 They are 0.5, 7.5, -7.5, and -0.5 respectively, and the characteristic angle A o1 、A o2 、A o3 、A o4 They are 30, 55, 55, and 30 respectively. Then the original cam lift is segmented to obtain the lift function of each segment. Starting from the second segment, the lift of any point in each segment must be subtracted from the lift of the end point of the previous segment, and the angle is also subtracted from the angle of the end point of the previous segment. In this way, each lift function starts from zero and ends with the characteristic lift, and the angle starts from zero and ends with the characteristic angle. This makes it easier to process each lift function. Suppose the four-segment lift functions of the original cam are: f1(a)=f1(0.5,30), f2(a)=f2(7.5,55), f3(a)=f3(-7.5,55), f4(a)=f4(-0.5,30);

[0111] Step 2: Determine the target characteristic lift and target characteristic angle of each section of the new cam. The new cam has four sections like the original cam. According to the design requirements of the new cam, the maximum lift of the new cam is 7.5mm, the lift at the end of the rising buffer section is 0.4mm, the lift at the end of the falling buffer section is 0.4mm, and the total continuous angle of the cam working section is 112 degrees. Therefore, its target characteristic lift H n1 、H n2 、H n3 、H n4 They are 0.4, 7.1, -7.1, and -0.4 respectively, and the target feature angle A n2 With A n3 The sum is 112; In addition, according to the constraints that the four cams above should meet: H n2 *A 02 *A 02 / H 02 / A n2 / A n2 =H n3 *A o3 *A o3 / H 03 / A n3 / A n3 You can get an A n2 With A n3 The relationship, combined with A n2 With A n3The sum is 112, so we can calculate A n2 With A n3 Both are 56, and then according to the formula H n1 *A 01 / H 01 / A n1 =H n2 *A o2 / H 02 / A n2 and H n3 *A o3 / H 03 / A n3 =H n4 *A o4 / H 04 / A n4 A can be calculated n1 With A n4 Both are approximately 25.813;

[0112] Step 3: Calculate the lift function of each section of the new cam, and then get the lift data of the new cam as a whole. According to the segmentation of the original cam, substitute the characteristic lift, characteristic angle and lift function of each section of the original cam, the target characteristic lift and target characteristic angle of each section of the new cam into the general formula. The formulas for each section of the new cam are: After calculation, the lift of each section of the new cam is obtained, and then the lift of each section of the new cam is processed to obtain the overall lift data. That is, starting from the second section, the lift of any point in each section must be added to the lift of the end point of the previous section, and the angle is also added to the angle of the end point of the previous section. After each section is processed, the overall lift of the overall angle range of the new cam is obtained. For the new cam, the design requirements do not mention the angle requirement, and the maximum lift angle of the new cam can be set to be consistent with the original cam, such as Figure 5 As shown; you can also set Figure 7 The angle of the connection point between the rising buffer section and the rising working section of the new cam and the original cam is consistent, such as Figure 8 The angles of the new cam and the original cam at the connection point between the descending buffer section and the descending working section are consistent. Here, it is preferred to keep the maximum lift angle of the new cam consistent with the original cam. This is the most commonly used and optimal choice for cam imitation. The angle of the new cam's maximum lift is fixed at 460 degrees, which is consistent with the original cam, and the crankshaft angles of other points are calculated.

[0113] Figure 19 These are some of the data used in the cam imitation method of Example 3 (with a maximum cam angle interval of 5 degrees), including data content that is consistent with that of Example 1.

[0114] from Figure 19It can be seen that the maximum lift of the original cam in Example 3 is 8mm at a cam angle of 85 degrees, corresponding to a crankshaft angle of 460 degrees. There is no maximum lift holding section. The original cam is divided into four sections, namely, an ascending buffer section, an ascending working section, a descending working section, and a descending buffer section. The corresponding cam angles are 0-30 degrees, 30-85 degrees, 85-140 degrees, and 140-170 degrees, respectively. The corresponding cam lifts are 0-0.5mm, 0.5-8mm, 8-0.5mm, and 0.5-0mm, respectively. The segmented angles corresponding to these four sections are 0-30 degrees, 0-55 degrees, 0-55 degrees, and 0-30 degrees, respectively. The segmented lifts are 0-0.5mm, 0-7.5mm, 0-(-7.5)mm, and 0-(-0.5)mm, respectively. The four sections of the new cam correspond to The segmented angles are 0-25.813 degrees, 0-56 degrees, 0-56 degrees, and 0-25.813 degrees, and the segmented lifts are 0-0.4mm, 0-7.1mm, 0-(-7.1)mm, and 0-(-0.4)mm. The cam angles corresponding to each segment of the new cam's overall lift are 0-25.813 degrees, 25.813-81.813 degrees, 81.813-137.813 degrees, and 137.813-163.626 degrees, and the corresponding cam lifts are 0-0.4mm, 0.4-7.5mm, 7.5-0.4mm, and 0.4-0mm. The maximum lift of the new cam is 7.5mm at a cam angle of 81.813 degrees, corresponding to a crankshaft angle of 460 degrees, which is consistent with the angle of the maximum lift of the original cam.

[0115] Through the above steps, the cam imitation work of Example 3 is completed. Figure 20 The following are lift curves for the original cam and the new cam of Example 3, obtained using this replication method. As can be seen, the new cam is similar to the original cam, including a rising buffer section, an rising operating section, a descending operating section, and a descending buffer section. Furthermore, both are symmetrical cams. Similar to Example 1, since the corresponding constraints are met, its velocity and acceleration curves are guaranteed to be continuous, meeting the requirements for cam replication.

[0116] Example 4

[0117] The maximum lift of an original exhaust cam is 8.5mm, the lift at the end of the rising buffer section is 0.5mm, the lift at the end of the falling buffer section is 0.5mm, the rising buffer section duration angle is 24 degrees, the rising working section duration angle is 60 degrees, the falling working section duration angle is 60 degrees, the falling buffer section duration angle is 30 degrees, and the end point angle of the cam's falling working section is 374 degrees of crankshaft angle. The imitation cam design requires a maximum lift of 8mm, a lift at the end of the buffer section of 0.4mm, a total working section duration angle of 116 degrees, and the crankshaft angle at the end point of the falling working section remains unchanged.

[0118] Step 1: Divide the original cam into segments and obtain the characteristic lift, characteristic angle and lift function of each segment. First, obtain the original cam lift data and refer to Figure 2 After analyzing the original cam, we found that the cam has no maximum lift holding section, so the original cam is divided into four sections, namely the rising buffer section, the rising working section, the descending working section and the descending buffer section, and the original cam is asymmetric. Figure 3 , its characteristic lift H o1 、H o2 、H o3 、H o4 They are 0.5, 8, -8, and -0.5 respectively, and the characteristic angle A o1 、A o2 、A o3 、A o4 They are 24, 60, 60, and 30 respectively. Then the original cam lift is segmented to obtain the lift function of each segment. Starting from the second segment, the lift of any point in each segment must be subtracted from the lift of the end point of the previous segment, and the angle is also subtracted from the angle of the end point of the previous segment. In this way, each lift function starts from zero and ends with the characteristic lift, and the angle starts from zero and ends with the characteristic angle. This makes it easier to process each lift function. Suppose the four-segment lift functions of the original cam are: f1(a)=f1(0.5, 24), f2(a)=f2(8, 60), f3(a)=f3(-8, 60), f4(a)=f4(-0.5, 30);

[0119] Step 2: Determine the target characteristic lift and target characteristic angle of each section of the new cam. The new cam has four sections like the original cam. According to the design requirements of the new cam, the maximum lift of the new cam is 8mm, the lift at the end of the rising buffer section is 0.4mm, the lift at the end of the falling buffer section is 0.4mm, and the total continuous angle of the cam working section is 116 degrees. Therefore, its target characteristic lift H n1 、H n2 、H n3 、H n4 They are 0.4, 7.6, -7.6, and -0.4 respectively, and the target feature angle A n2 With A n3 The sum is 116; In addition, according to the constraints that the four cams above should meet: H n2 *A 02 *A 02 / H 02 / A n2 / A n2 =H n3 *A o3 *A o3 / H 03 / A n3 / A n3 You can get an A n2 With An3 The relationship, combined with A n2 With A n3 The sum is 116, so we can calculate A n2 With A n3 All are 58, then according to the formula H n1 *A 01 / H 01 / A n1 =H n2 *A o2 / H 02 / A n2 and H n3 *A o3 / H 03 / A n3 =H n4 *A o4 / H 04 / A n4 A can be calculated n1 About 19.537; A n4 It is approximately 24.421;

[0120] Step 3: Calculate the lift function of each section of the new cam, and then get the lift data of the new cam as a whole. According to the segmentation of the original cam, substitute the characteristic lift, characteristic angle and lift function of each section of the original cam, the target characteristic lift and target characteristic angle of each section of the new cam into the general formula. The formulas for each section of the new cam are: After calculation, the lift of each section of the new cam is obtained, and then the lift of each section of the new cam is processed to obtain the overall lift data. That is, starting from the second section, the lift of any point in each section must be added to the lift of the end point of the previous section, and the angle is also added to the angle of the end point of the previous section. After each section is processed, the overall lift of the overall angle range of the new cam is obtained. Finally, according to the design requirements, the end point angle of the new cam's descending working section is fixed at 374 degrees, which is consistent with the design requirement and the end point angle of the original cam's descending working section. The crankshaft angles of other points are calculated, such as Figure 8 shown.

[0121] Figure 21 These are some of the data used in the cam imitation method of Example 4 (with a maximum cam angle interval of 5 degrees), including data content that is consistent with that of Example 1.

[0122] from Figure 21It can be seen that the end point of the descending working section of the original cam in Example 4 is at a cam angle of 144 degrees, corresponding to a crankshaft angle of 374 degrees. There is no maximum lift holding section. The original cam is divided into four sections, namely, an ascending buffer section, an ascending working section, a descending working section, and a descending buffer section. The corresponding cam angles are 0-24 degrees, 24-84 degrees, 84-144 degrees, and 144-174 degrees, respectively. The corresponding cam lifts are 0-0.5mm, 0.5-8.5mm, 8.5-0.5mm, and 0.5-0mm, respectively. The segmented angles corresponding to these four sections are 0-24 degrees, 0-60 degrees, 0-60 degrees, and 0-30 degrees, respectively. The segmented lifts are 0-0.5mm, 0-8.0mm, 0-(-8.0)mm, and 0-(-0.5)mm, respectively. The new cam has four sections. The corresponding segmented angles are 0-19.537 degrees, 0-58 degrees, 0-58 degrees, and 0-24.421 degrees, and the segmented lifts are 0-0.4mm, 0-7.6mm, 0-(-7.6)mm, and 0-(-0.4)mm, respectively. The cam angles corresponding to each segment of the new cam's overall lift are 0-19.537 degrees, 19.537-77.537 degrees, 77.537-135.537 degrees, and 135.537-159.958 degrees, and the corresponding cam lifts are 0-0.4mm, 0.4-8.0mm, 8.0-0.4mm, and 0.4-0mm, respectively. The end point of the new cam's descending working section is a cam angle of 135.537 degrees, corresponding to a crankshaft angle of 374 degrees, which is consistent with the angle at which the original cam's descending working section ends.

[0123] Through the above steps, the cam imitation work of Example 4 is completed. Figure 22 These are the lift curves for the original cam and the new cam of Example 4, obtained using this replication method. As can be seen, the new cam is similar to the original cam, including a rising buffer section, an rising operating section, a descending operating section, and a descending buffer section. Both are asymmetric. Similar to Example 1, because it meets the corresponding constraints, its velocity and acceleration curves are guaranteed to be continuous, meeting the requirements for cam replication.

[0124] Example 5

[0125] The maximum lift of an original intake cam is 6.4mm, the lift at the end of the rising buffer section is 0.4mm, the lift at the end of the falling buffer section is 0.4mm, the continuous angle of the rising buffer section is 27 degrees, the continuous angle of the rising working section is 54 degrees, the continuous angle of the maximum lift holding section is 12 degrees, the continuous angle of the descending working section is 54 degrees, the continuous angle of the descending buffer section is 27 degrees, and the midpoint angle of the cam's maximum lift holding section is 462 crankshaft angles. The imitation cam design requires a maximum lift of 6.9mm, a lift at the end of the rising buffer section is 0.4mm, and a lift at the end of the descending buffer section is 0.4mm. The continuous angles of the rising working section, the maximum lift holding section, and the descending working section are 118 degrees in total, and the midpoint angle of the maximum lift holding section remains unchanged.

[0126] Step 1: Divide the original cam into segments and obtain the characteristic lift, characteristic angle and lift function of each segment. First, obtain the original cam lift data and refer to Figure 2 After analyzing the original cam, we found that the cam has a maximum lift holding section. Therefore, the original cam is divided into five sections, namely the rising buffer section, the rising working section, the maximum lift holding section, the descending working section and the descending buffer section. Moreover, the original cam is symmetrical. Figure 4 , its characteristic lift H o1 、H o2 、H o3 、H o4 、H o5 They are 0.4, 6, 0, -6, and -0.4 respectively, and the characteristic angle A o1 、A o2 、A o3 、A o4 、A o5 They are 27, 54, 12, 54, and 27 respectively. The original cam lift is then segmented to obtain the lift function of each segment. Starting from the second segment, the lift of any point in each segment is subtracted from the lift of the end point of the previous segment, and the angle is also subtracted from the angle of the end point of the previous segment. In this way, each lift function starts from zero and ends with the characteristic lift, and the angle starts from zero and ends with the characteristic angle. This makes it easier to process each lift function. Suppose the five-segment lift functions of the original cam are: f1(a)=f1(0.4, 27), f2(a)=f2(6, 54), f3(a)=f3(0, 12), f4(a)=f4(-6, 54), f5(a)=f5(-0.4, 27);

[0127] Step 2: Determine the target characteristic lift and target characteristic angle of each section of the new cam. The new cam has five sections like the original cam. According to the design requirements of the new cam, the maximum lift of the new cam is 6.9mm, the lift at the end of the rising buffer section is 0.4mm, the lift at the end of the falling buffer section is 0.4mm, and the continuous angle of the rising working section, the maximum lift holding section, and the falling working section is 118 degrees. Therefore, its target characteristic lift H n1 、H n2 、H n3 、H n4 、H n5 They are 0.4, 6.5, 0, -6.5, and -0.4 respectively, while the target feature angle requires A n2 Add A n3 Add A n4 is 118; at the same time, the constraint condition that the five-segment cam should satisfy is H n1 *A o1 / H 01 / A n1 =H n2 *Ao2 / H 02 / A n2 and H n4 *A o4 / H 04 / A n4 =H n5 *A o5 / H 05 / A n5 ; Since the five target feature angles are unknown, there are only three equations, and two of them need to be assumed to fully determine these parameters. n1 With A n2 、A n4 With A n5 There are constraints, and these two sets of parameters cannot be assumed at the same time. In other cases, any two parameters can be assumed. For example: Assume 1 that the target characteristic angle of the rising working section and the target characteristic angle of the falling buffer section are the same as the original cam, that is, A n2 Equal to 54, A n5 Equal to 27, so according to the constraint formula, A can be calculated n1 Equal to 24.923, A n4 Equal to 58.5, and then according to the rising working section, maximum lift holding section, and descending working section continuous angle totaling 118 degrees, we can get A n3 =5.5; Assume that the target characteristic angles of the rising and falling working sections set in 2 are the same as those of the original cam, that is, A n2 、A n4 Equal to 54, so according to the constraint formula, A can be calculated n1 、A n5 Equal to 24.923, and then according to the rising working section, maximum lift holding section, and descending working section continuous angle totaling 118 degrees, we can get A n3 =10; Assume that the target characteristic angles of the rising and falling buffer sections set in 3 are the same as those of the original cam, that is, A n1 、A n5 Equal to 27, so according to the constraint formula, A can be calculated n2 、A n4 Equal to 58.5, and then according to the rising working section, maximum lift holding section, and descending working section continuous angle totaling 118 degrees, we can get A n3 =1; Assume that the target characteristic angle of the rising working section and the target characteristic angle of the maximum lift holding section set in 4 are the same as those of the original cam, that is, A n2 Equal to 54, A n3 Equal to 12, so according to the rising working section, maximum lift holding section, and descending working section continuous angle of 118 degrees, we can get A n4 Equal to 52, and then according to the constraint formula, we can calculate A n1 Equal to 24.923, A n5=24; Assume that 5 sets the target characteristic angle of the rising buffer section and the target characteristic angle of the maximum lift holding section to be the same as the original cam, that is, A n1 Equal to 27, A n3 Equal to 12, so according to the constraint formula, A can be calculated n2 Equal to 58.5, and then according to the rising working section, maximum lift holding section, and descending working section continuous angle totaling 118 degrees, we can get A n4 Equal to 47.5, and finally calculated according to the constraint formula to get A n5 =21.923; In addition, a variety of assumptions can be made to determine the target feature angle, which will not be listed here. The target feature angle obtained by assumption 1 will be used for the next step, that is, the target feature angle A n1 、A n2 、A n3 、A n4 、A n5 They are 24.923, 54, 5.5, 58.5, and 27 respectively;

[0128] Step 3: Calculate the lift function of each section of the new cam, and then get the lift data of the new cam as a whole. According to the segmentation of the original cam, substitute the characteristic lift, characteristic angle and lift function of each section of the original cam, the target characteristic lift and target characteristic angle of each section of the new cam into the general formula. The formulas for each section of the new cam are: After obtaining the lift function of each section of the new cam, the lift of each section of the new cam is processed to obtain the overall lift data. That is, starting from the second section, the lift of any point in each section is added to the lift of the end point of the previous section, and the angle is also added to the angle of the end point of the previous section. After each section is processed, the overall lift of the overall angle range of the new cam is obtained; finally, according to the design requirements, the midpoint angle of the new cam's maximum lift holding section is fixed at 462 degrees, which is consistent with the design requirement and the midpoint angle of the original cam's maximum lift holding section. The crankshaft angles of other points are calculated, such as Figure 6 shown.

[0129] Figure 23 These are some of the data used in the cam imitation method of Example 5 (with a maximum cam angle interval of 5 degrees), including data content that is consistent with that of Example 1.

[0130] from Figure 23It can be seen that the maximum lift of the original cam of Example 5 is 6.4mm, and the midpoint of the maximum lift holding section is at a cam angle of 87 degrees, corresponding to a crankshaft angle of 462 degrees. The original cam is divided into five sections, namely, the rising buffer section, the rising working section, the maximum lift holding section, the descending working section, and the descending buffer section. The corresponding cam angles are 0-27 degrees, 27-81 degrees, 81-93 degrees, 93-147 degrees, and 147-174 degrees, respectively. The corresponding cam lift is They are 0-0.4mm, 0.4-6.4mm, 6.4-6.4mm, 6.4-0.4mm, and 0.4-0mm. The corresponding segment angles of these five sections are 0-27 degrees, 0-54 degrees, 0-12 degrees, 0-54 degrees, and 0-27 degrees. The segment lifts are 0-0.4mm, 0-6.0mm, 0-0mm, 0-(-6.0)mm, and 0-(-0.4)mm. The five sections of the new cam are The corresponding segment angles are 0-24.923 degrees, 0-54 degrees, 0-5.5 degrees, 0-58.5 degrees, and 0-27 degrees, and the segment lifts are 0-0.4mm, 0-6.5mm, 0-0mm, 0-(-6.5)mm, and 0-(-0.4)mm. The cam angles corresponding to the overall lift of the new cam are 0-24.923 degrees, 24.923-78.923 degrees, and 78.923-84 .423 degrees, 84.423-142.923 degrees, 142.923-169.923 degrees, and the corresponding cam lifts are 0-0.4mm, 0.4-6.9mm, 6.9-6.9mm, 6.9-0.4mm, and 0.4-0mm respectively. The midpoint of the new cam's maximum lift holding section is at a cam angle of 81.673 degrees, corresponding to a crankshaft angle of 462 degrees, which is consistent with the angle of the midpoint of the original cam's maximum lift holding section.

[0131] Through the above steps, the cam imitation work of Example 5 is completed. Figure 24 、 25 Figures 26 and 27 show the lift, velocity, and acceleration curves of the original cam and the new cam of Example 5 obtained using this replication method. As can be seen, the original cam includes a rising buffer section, an rising operating section, a maximum lift holding section, a descending operating section, and a descending buffer section, and is symmetrical. The new cam has the same number of sections as the original cam, also including a rising buffer section, an rising operating section, a maximum lift holding section, a descending operating section, and a descending buffer section. However, due to different angle requirements for the rising and descending sections, the new cam is asymmetrical. However, its lift, velocity, and acceleration curves are similar in shape. Furthermore, since the corresponding constraints are met, its velocity and acceleration curves are guaranteed to be continuous, meeting the requirements for cam replication.

Claims

1. A method for imitating a valve cam, characterized in that: The following steps are involved: Step 1: Divide the original cam into segments to obtain the characteristic lift, characteristic angle and lift function of each segment; Step 2: Determine the target characteristic lift and target characteristic angle of each section of the new cam; Step 3: Calculate the lift function of each section of the new cam, and then obtain the overall lift data of the new cam; In step 2, the number of segments of the new cam is consistent with the number of segments of the original cam, and the target characteristic lift and target characteristic angle of each segment of the new cam are determined according to the design requirements of the new cam, relevant constraints and partial assumptions. The partial assumptions refer to: for a new cam with a maximum lift holding segment, according to the two formulas determined by the known total continuous angle of the new cam working segment and the constraints, it is impossible to solve the five target characteristic angles of the rising buffer segment, the rising working segment, the maximum lift holding segment, the descending working segment and the descending buffer segment. Two parameters need to be assumed to completely solve these parameters. Since there are constraints on the target characteristic angles of the rising buffer segment and the rising working segment, and the descending working segment and the descending buffer segment, these two sets of parameters cannot be assumed at the same time. In other cases, two parameters can be arbitrarily assumed to obtain all the target characteristic angles of the new cam; In step three, the corresponding angles of the new cam and the original cam have the following two situations: First, for the cam without the maximum lift holding section, ensure that the crankshaft angle of the new cam at the maximum lift is consistent with that of the original cam; for the cam with the maximum lift holding section, ensure that the crankshaft angle of the midpoint of the maximum lift holding section is consistent with that of the original cam; second, ensure that the crankshaft angle of the starting point of the rising working section or the end point of the descending working section of the new cam is consistent with that of the original cam.

2. The method for imitating a valve cam according to claim 1, characterized in that: In the step 1, when the original cam is segmented, it is first determined whether the original cam has a maximum lift holding section. If so, the cam is divided into five sections, namely, an ascending buffer section, an ascending working section, a maximum lift holding section, a descending working section and a descending buffer section; if not, the cam is divided into four sections, namely, an ascending buffer section, an ascending working section, a descending working section and a descending buffer section; the characteristic lift of each section is equal to the end lift of each section minus the starting lift, and the characteristic angle is equal to the end angle minus the starting angle. The lift function of each section is obtained based on the original lift data of the original cam and the number of segmented sections. The processing method is that starting from the second section, the lift of any point in each section must be subtracted from the lift of the end point of the previous section, and the angle is also subtracted from the angle of the end point of the previous section.

3. The method for imitating a valve cam according to claim 1, characterized in that: The target characteristic lift of each section of the new cam is the characteristic lift required by the new cam, which is equal to the end lift of each section of the new cam minus the starting lift. The target characteristic angle of each section of the new cam is the characteristic angle required by the new cam, which is equal to the end angle of each section of the new cam minus the starting angle.

4. The method for imitating a valve cam according to claim 3, characterized in that: The constraint condition is: for a cam divided into four sections, the characteristic lift and characteristic angle of the four sections of the original cam are H o1 、H o2 、H o3 、H o4 and A o1 、A o2 、A o3 、A o4 The target characteristic lift and target characteristic angle of the new cam for the four sections are H n1 、H n2 、H n3 、H n4 and A n1 、A n2 、A n3 、A n4 , these parameters need to meet the following conditions: H n1 *A o1 / H o1 / A n1 =H n2 *A o2 / H o2 / A n2 , H n2 *A o2 *A o2 / H o2 / A n2 / A n2 =H n3 *A o3 *A o3 / H o3 / A n3 / A n3 , H n3 *A o3 / H o3 / A n3 =H n4 *A o4 / H o4 / A n4 。 5. The method for imitating a valve cam according to claim 3, characterized in that: The constraint condition is: for a cam divided into five sections, the characteristic lift and characteristic angle of the original cam are H o11 、H o22 、H o33 、H o44 、H o55 and A o11 、A o22 、A o33 、A o44 、A o55 The target characteristic lift and target characteristic angle of the new cam corresponding to the five sections are H n11 、H n22 、H n33 、H n44 、H n55 and A n11 、A n22 、A n33 、A n44 、A n55 , these parameters need to meet the following conditions: H n11 *A o11 / H o11 / A n11 =H n22 *A o22 / H o22 / A n22 , H n44 *A o44 / H o44 / A n44 =H n55 *A o55 / H o55 / A n55 。 6. The method for imitating a valve cam according to claim 3, characterized in that: The design requirements of the new cam are: specifying the maximum lift of the new cam, the end lift of the buffer section and the total continuous angle of the working section, the end lift of the buffer section includes the end lift of the rising buffer section and the end lift of the falling buffer section, and the total continuous angle of the working section refers to the sum of the continuous angle of the rising working section, the continuous angle of the maximum lift holding section and the continuous angle of the falling working section.

7. The method for imitating a valve cam according to claim 1, characterized in that: In the step three, the lift function of each segment of the new cam is calculated using a formula based on the segmentation of the original cam, the characteristic lift, characteristic angle and lift function of each segment, and the target characteristic lift and target characteristic angle of each segment of the new cam; the lift data of each segment of the new cam is processed to obtain the overall lift data, and the obtained lift is continuous and the angle increases sequentially. The processing method is to start from the second segment, and the lift of any point in each segment must be added to the lift of the end point of the previous segment, and the angle is also added to the angle of the end point of the previous segment. After each segment is processed, the lift data of the entire angle range of the new cam is obtained.

8. The method for imitating a valve cam according to claim 7, characterized in that: In step 3, the lift function of each section of the new cam is calculated using the formula: Assume that the characteristic lift and characteristic angle of each section of the original cam are: H ok and A ok , the general expression of each lift function is: f k (a) = f k (H ok , A ok ), k is a natural number, the target characteristic lift and target characteristic angle of each section of the new cam are: H nk and A nk , then the general expression of each lift function of the new cam is:

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