Cam profile, cam and design method of integral cam profile

Abstract

The invention discloses a cam profile, a cam and a design method of an integral cam profile, and relates to the technical field of cam mechanism manufacturing. Linear ascending, keeping unchanged, linear descending, keeping zero, linear descending, keeping unchanged, linear ascending, keeping zero, linear descending, keeping unchanged, linear ascending, keeping zero, linear ascending, keeping unchanged, linear ascending, keeping zero, linear ascending, keeping unchanged and linear descending are sequentially performed from front to back, and the joints of all the sections of straight lines are kept continuous; the cam profile further comprises a cam designed based on the cam profile and an overall cam profile. According to the cam profile and the cam, it can be guaranteed that all jump curves of the basic section are continuous, jump of the jump curves is a limited value, the buffer section with the continuous jump is matched, it can be guaranteed that the jump curves of the whole cam are continuous, and compared with most of the prior art, the smoothness of the cam profile is good, impact of movement of a cam mechanism can be reduced, and the service life of the cam mechanism is prolonged. And excessive abrasion of the cam is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cam mechanism, and particularly relates to a cam profile, a cam and a design method of the overall cam profile. BACKGROUND

[0002] The cam mechanism is a typical commonly used mechanism, has the advantages of easy design and accurate prediction of the motion characteristics of a driven member, and can realize complex motion rules. Therefore, the cam mechanism is widely applied in engineering to automatic machines, automatic control devices and production lines, such as internal combustion engines, packaging machines, forming machines, assembly machines, automatic machine tools, textile machines, printing machines and automatic equipment.

[0003] Most of the existing cam profiles can only ensure continuous acceleration and have poor smoothness, and are prone to cause vibration and impact problems in high-speed mechanisms, and are prone to cause excessive wear of the cam after a long time. SUMMARY

[0004] To solve the above technical problems, the present application provides a cam profile, a cam and a design method of the overall cam profile. The cam profile, the cam and the design method of the overall cam profile can ensure continuous cam lift, have good smoothness, reduce impact and reduce excessive wear of the cam.

[0005] The technical scheme adopted by the present application is as follows:

[0006] A cam profile, in a basic section of the cam profile, the lift curve is composed of 15 straight lines, from front to back, linearly rising, keeping unchanged, linearly falling, keeping zero, linearly falling, keeping unchanged, linearly rising, keeping zero, linearly falling, keeping unchanged, linearly rising, keeping zero, linearly rising, keeping unchanged, linearly falling, and each straight line connection is kept continuous.

[0007] As a preferred scheme, the related parameters of the cam profile include: maximum lift H m , initial lift H h , maximum speed V m , initial speed V h , maximum positive acceleration A max , maximum negative acceleration -A min , terminal negative acceleration -A end , maximum lift J and maximum jump K; the speed curve of the cam profile keeps the maximum speed V m at the 8th section.

[0008] As a preferred scheme, at the beginning point of the basic section: the lift is the initial lift H h , the speed is the initial speed V h , the acceleration and the lift are zero; at the end point of the basic section: the lift is the maximum lift H m, the speed is zero, the acceleration is the end negative acceleration -A end , the jerk is zero.

[0009] As a preferred solution, the cam profile acceleration curve keeps the maximum positive acceleration A max at the 4th segment, keeps the maximum negative acceleration -A min at the 12th segment; the cam profile jerk curve keeps the maximum jerk J at the 2nd, 14th segment, keeps the maximum negative jerk -J at the 6th, 10th segment; the cam profile jump curve keeps the maximum jump K at the 1st, 7th, 11th, 13th segment, keeps the maximum negative jump -K at the 3rd, 5th, 9th, 15th segment.

[0010] As a preferred solution, the cam profile, its related parameters H m , V m , A max , A min , J and K are all greater than zero; H h , V h , A end are all greater than or equal to zero.

[0011] As a preferred solution, the cam profile, its related parameters need to meet the following conditions:

[0012]

[0013] The scheme also contains a cam, which applies the cam profile described above, and the cam has the characteristics that the basic segment jerk curve is all kept continuous.

[0014] The scheme also contains a design method of the overall cam profile, and the design steps are as follows:

[0015] Step one: determine the characteristics of the overall cam profile according to the requirements;

[0016] Further, the characteristics of the overall cam profile include whether to have the maximum lift keeping segment, whether the ascending segment and the descending segment are symmetrical, and whether the ascending segment and the descending segment have the buffer segment;

[0017] Step two: determine the related parameters of the ascending segment of the overall cam profile;

[0018] The related parameters of the ascending segment include the maximum lift H m , the initial lift H h , the maximum speed V m , the initial speed V h , the maximum positive acceleration A max , the maximum negative acceleration -A min , the end negative acceleration -A end, the maximum jump J and the maximum jump K; for the cam with the buffer section in the ascending section, the initial lift H h is equal to the lift at the end of the buffer section, the initial velocity V h is equal to the velocity at the end of the buffer section; for the cam without the buffer section in the ascending section, the initial lift H h , the initial velocity V h are all equal to zero.

[0019] Step three: determining the mathematical expression of the overall cam profile in the ascending section;

[0020] For the cam with the buffer section, the buffer section cam profile that can keep the jump continuous is determined according to the initial lift H h and the initial velocity V h ; in the basic section of the cam, the expressions of the jump, acceleration, velocity and lift of each section are obtained from the characteristics of the cam profile, and the angles of each section are calculated according to the characteristics of the motion law, the integral characteristics of the function and the related parameters, the mathematical expression of each section of the basic section of the cam is calculated, and the mathematical expression of the overall cam profile in the ascending section is determined;

[0021] Step four: determining the mathematical expression of the overall cam profile in the descending section;

[0022] For the cam with symmetrical ascending section and descending section, the mathematical expression of the descending section is directly obtained by symmetrical processing of the mathematical expression of the ascending section according to the symmetrical relationship of the cam function;

[0023] For the cam with asymmetric ascending section and descending section, the mathematical expression of the ascending section that meets the design requirements of the descending section is obtained according to the methods of steps two to three according to the design requirements of the descending section, and the mathematical expression of the descending section is obtained by symmetrical processing of the mathematical expression of the ascending section that meets the design requirements of the descending section according to the symmetrical relationship of the cam function.

[0024] Step five: for the cam profile with the maximum lift maintaining section, the maximum maintaining section lift is added to complete the design of the overall cam profile.

[0025] By adopting the above technical scheme, the present application can achieve the following beneficial effects:

[0026] 1. The cam profile and cam provided by the present application can ensure that the jump curve of the basic section is completely continuous, and the mutation of the jump curve is also a limited value, and the buffer section with continuous jump can ensure that the overall jump curve of the cam is continuous, compared with most of the existing technologies, the smoothness of the cam profile is better, the impact of the cam mechanism movement can be reduced, and the excessive wear of the cam can be reduced.

[0027] 2. The whole cam profile design method provided by the application can directly determine all cam segment angles after determining relevant parameters, does not need to establish an equation group, does not need to perform iterative calculation and optimization, and obtains a unique cam profile, so that the cam profile design process is obviously simplified, the process of performing multiple calculation and optimization by using iteration for cam profile design in the prior art is avoided, and special software is not needed, thereby improving design efficiency.

[0028] 3. The whole cam profile design method provided by the application, relevant parameters include maximum lift, maximum speed, maximum acceleration, maximum jump and maximum skip, after determining the parameters, the motion characteristics of the cam can be reflected, and the cam profile meeting the requirements is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0030] Figure 1 It is a skip curve schematic diagram of a basic segment of the cam profile of the application;

[0031] Figure 2 It is an acceleration curve schematic diagram of a basic segment of the cam profile of the application;

[0032] Figure 3 It is a speed curve schematic diagram of a basic segment of the cam profile of the application;

[0033] Figure 4 It is a lift curve schematic diagram of a basic segment of the cam profile of the application;

[0034] Figure 5 It is a skip curve schematic diagram of a basic segment of the cam profile of the application;

[0035] Figure 6 It is a cam skip and acceleration curve diagram of embodiment 1 of the application using specific numerical values;

[0036] Figure 7 It is a cam speed and lift curve diagram of embodiment 1 of the application using specific numerical values;

[0037] Figure 8 It is a cam skip and acceleration curve diagram of embodiment 2 of the application using specific numerical values;

[0038] Figure 9 It is a cam speed and lift curve diagram of embodiment 2 of the application using specific numerical values;

[0039] Figure 10 Cam lift, acceleration graph for Example 3 using specific values for the present invention;

[0040] Figure 11 Cam speed, lift graph for Example 3 using specific values for the present invention;

[0041] Figure 12 Cam lift, acceleration graph for Example 4 using specific values for the present invention;

[0042] Figure 13 Cam speed, lift graph for Example 4 using specific values for the present invention;

[0043] In the figure, J is the maximum lift, -J is the maximum negative lift, A max is the maximum positive acceleration, -A min is the maximum negative acceleration, -A end is the end negative acceleration, V h is the initial velocity, V m is the maximum velocity, H h is the initial lift, H m is the maximum lift, K is the maximum lift, -K is the maximum negative lift, θ1 to θ 15 are the angles of the respective segments. DETAILED DESCRIPTION

[0044] The present invention will be described in detail below with reference to the accompanying drawings and examples.

[0045] The present invention provides a cam profile, in which the lift curve of the cam basic segment is composed of 15 straight lines, and the connection of each straight line is kept continuous. The 15 straight lines are linearly ascending, keeping constant, linearly descending, keeping zero, linearly descending, keeping constant, linearly ascending, keeping zero, linearly descending, keeping constant, linearly ascending, keeping zero, linearly ascending, keeping constant, linearly descending, in order from the front to the back. The lift curve is shown in Figure 1 ;

[0046] Further, the parameters of the cam basic segment include the maximum lift H m , the initial lift H h , the maximum velocity V m , the initial velocity V h , the maximum positive acceleration A max , the maximum negative acceleration -A min , the end negative acceleration -A end , the maximum lift J, and the maximum lift K.

[0047] At the starting point of the basic segment, the lift is the initial lift H h, the speed is initial speed V h , the acceleration, the jump is zero, at the end point of the basic section, the lift is maximum lift H m , the speed is zero, the acceleration is terminal negative acceleration -A end , the jump is zero

[0048] Further, in paragraph 8, the speed remains the maximum speed V m , in paragraph 4, the acceleration remains the maximum positive acceleration A max , in paragraph 12, the acceleration remains the maximum negative acceleration -A min , in paragraphs 2, 14, the jump remains the maximum jump J, in paragraphs 6, 10, the jump remains the negative maximum jump -J, in paragraphs 1, 7, 11, 13, the jump remains the maximum jump K, in paragraphs 3, 5, 9, 15, the jump remains the negative maximum jump -K; the acceleration, speed, lift, and jump curve schematic diagram is shown in Figure 2 , 3 , 4, 5;

[0049] A cam, which applies the cam profile of the first aspect, has the characteristics that the basic section jump curve is all continuous.

[0050] From the drawings and the above-described cam profile features, the cam profile and the cam applying the cam profile of the present application can ensure that the jump curve is all continuous, and the mutation of the jump curve is also limited, and the continuous buffer section of the jump can ensure that the overall jump curve of the cam is continuous. Compared with most existing technologies, the smoothness of the cam profile is better, which can reduce the impact of the cam mechanism movement and reduce the excessive wear of the cam.

[0051] In addition, the cam profile and the cam applying the cam profile provided by the present application can specify related parameters to meet these requirements at specific positions, including maximum lift, maximum speed, maximum acceleration, maximum jump, and maximum jump, etc. This can limit the design of the cam profile and the cam, and reflect the motion and dynamic characteristics of the cam, so as to obtain the cam profile and the cam that meet the requirements.

[0052] A design method of an overall cam profile, which can obtain the cam profile of the first aspect, and the design steps are as follows:

[0053] Step 1: Determine the characteristics of the overall cam profile according to the requirements

[0054] Cam mechanisms have different characteristics according to different application occasions, and the main characteristics include whether to have maximum lift holding section, whether the ascending section and descending section are symmetrical, and whether the ascending section and descending section have buffer section. In most cam application occasions, the cam is asymmetrical, does not have buffer section, and has maximum lift holding section. In the valve train of internal combustion engine, symmetrical cam is widely used, and generally has buffer section and can have maximum lift holding section.

[0055] Step two: determine the related parameters of the ascending section of the overall cam profile;

[0056] The related parameters of the ascending section include maximum lift H m , initial lift H h , maximum speed V m , initial speed V h , maximum positive acceleration A max , maximum negative acceleration -A min , terminal negative acceleration -A end , maximum jump J and maximum jump K. For the cam with buffer section in the ascending section, the initial lift H h is equal to the end lift of the buffer section, and the initial speed V h is equal to the end speed of the buffer section. For the cam without buffer section in the ascending section, the initial lift H h and the initial speed V h are both equal to zero.

[0057] Step three: determine the mathematical expression of the overall cam profile in the ascending section;

[0058] For the cam with buffer section, the buffer section cam profile that can keep the jump continuous is determined according to the initial lift H h and the initial speed V h .

[0059] In the basic section of the cam, the expressions of the jump, acceleration, speed and lift of each section are obtained from the characteristics of the cam profile.

[0060] The characteristics of the basic section of the cam profile are as follows: the jump curve is composed of 15 straight lines, and the connection points of each straight line are kept continuous. The 15 straight lines of jump from front to back are linearly ascending, keeping unchanged, linearly descending, keeping zero, linearly descending, keeping unchanged, linearly ascending, keeping zero, linearly descending, keeping unchanged, linearly ascending, keeping zero, linearly ascending, keeping unchanged, linearly descending. At the starting point of the basic section, the lift is the initial lift H h , the speed is the initial speed V h , and the acceleration and jump are zero. At the end point of the basic section, the lift is the maximum lift H m , the speed is zero, and the acceleration is the terminal negative acceleration -A endThe jump is zero; in segment 8, the speed remains at the maximum speed V. m In segment 4, the acceleration remains at the maximum positive acceleration A. max In the 12th segment, the acceleration remains at the maximum negative acceleration -A. min In segments 2 and 14, the jump remains at the maximum jump J; in segments 6 and 10, the jump remains at the negative maximum jump -J; in segments 1, 7, 11, and 13, the jump remains at the maximum jump K; and in segments 3, 5, 9, and 15, the jump remains at the negative maximum jump -K.

[0061] refer to Figures 1-5 The schematic diagram of the cam-type linear jump, acceleration, velocity, lift, and jump curves shown below yields the following expressions for each segment, where a is the cam angle, and θ1 to θ... 15 The angles of each curve segment:

[0062] Its jump expression is:

[0063] J1=Ka a∈[0,θ1]

[0064] J2=J a∈[0,θ2]

[0065] J3=J-Ka a∈[0,θ3]

[0066] J4=0 a∈[0,θ4]

[0067] J5=-Ka a∈[0,θ5]

[0068] J6=-J a∈[0,θ6]

[0069] J7=Ka-J a∈[0,θ7]

[0070] J8=0 a∈[0,θ8]

[0071] J9=-Ka a∈[0,θ9]

[0072] J 10 =-J a∈[0,θ 10 ]

[0073] J 11 =Ka-J a∈[0,θ 11 ]

[0074] J 12 =0 a∈[0,θ 12 ]

[0075] J 13 =Ka a∈[0,θ 13 ]

[0076] J 14= J a e [0, θ 14 ]

[0077] J 15 = J - Ka a e [0, θ 15 ]

[0078] Its acceleration expression is:

[0079]

[0080] a e [0, θ2]

[0081]

[0082] A4= A max a e [0, θ4]

[0083]

[0084] A8= 0 a e [0, θ8]

[0085]

[0086] A 12 = -A min a e [0, θ 12 ]

[0087]

[0088] Its velocity expression is:

[0089]

[0090] V4= A max a + V3(θ3) a e [0, θ4]

[0091]

[0092]

[0093] V8= V m a e [0, θ8]

[0094]

[0095] V 12 = -A min a + V 11 (θ 11 ) a e [0, θ 12 ]

[0096]

[0097] The lift expression is:

[0098]

[0099] a∈[0,θ3]

[0100]

[0101] H8=V m a+H7(θ7)a∈[0,θ8]

[0102]

[0103]

[0104]

[0105] In the formula, V1(θ1), V2(θ2), …V 14 (θ 14 ) are the speed values at the end of the first, second, …fourteenth section of the speed curve, which are calculated by substituting θ1, θ2, …θ 14 into the speed expression of V1, V2, …V 14 ; H1(θ1), H2(θ2), …H 14 (θ 14 ) are the lift values at the end of the first, second, …fourteenth section of the lift curve, which are calculated by substituting θ1, θ2, …θ 14 into the lift expression of H1, H2, …H 14 .

[0106] From the above expressions, it can be seen that, in all the expressions, in addition to the related parameters, only the angle of each section and the expression value at the specific position are known, and no other unknown quantity exists.

[0107] According to the motion law characteristics of the cam profile, the integral characteristics of the function and the related parameters, the angle of each section can be obtained, and the numerical expression of each section of the cam basic section is calculated to be known.

[0108] According to the motion law characteristics of the cam profile, the integral characteristics of the function and the related parameters, the angle of each section can be obtained.

[0109]

[0110]

[0111] From the above, it can be seen that the angle in the related expression of the ascending section can be directly obtained, and the expression value at the specific position can also be calculated. In the maximum lift H m , the initial lift H h , the maximum speed V m, initial velocity V h , maximum positive acceleration A max , maximum negative acceleration -A min , end negative acceleration -A end , maximum lift J and maximum jump K are given, the unique cam profile can be obtained.

[0112] Step four: determine the mathematical expression of the overall cam profile in the descending section;

[0113] For the cam profile symmetrical in the ascending section and the descending section, the mathematical expression of the descending section can be directly obtained by symmetrical processing of the mathematical expression of the ascending section according to the symmetry of the cam function;

[0114] For the cam profile asymmetrical in the ascending section and the descending section, the mathematical expression of the ascending section satisfying the design requirements of the descending section is obtained according to the method of steps two to three first, and then the mathematical expression of the descending section is obtained by symmetrical processing of the mathematical expression of the ascending section satisfying the design requirements of the descending section according to the symmetry of the cam function.

[0115] Step five: for the cam profile with the maximum lift holding section, the maximum holding section lift is increased to complete the design of the overall cam profile;

[0116] In order to ensure that there is a clear physical meaning, the related parameters H m , V m , A max , A min , J and K are greater than zero, H h , V h , A end are greater than or equal to zero, H h , V h are equal to zero when there is no buffer section, and A end is equal to zero when there is a maximum lift holding section;

[0117] Further limitation, in order to ensure that the length of each section angle is greater than zero, the related parameters need to meet the following conditions:

[0118]

[0119] As can be seen from the above design method process of the cam profile, after the related parameters are given, all the cam section angles can be directly obtained from the given related parameters, without the need to establish an equation group, and without the need for iterative calculation and optimization. The obtained cam profile is unique, which obviously simplifies the cam design process, avoids the process of multiple calculations and optimization by using iteration for cam profile design in the prior art, and also does not need to use special software, thereby improving the design efficiency.

[0120] In addition, the related parameters in the design method include the maximum lift Hm , maximum velocity V m , maximum positive acceleration A max , maximum negative acceleration -A min , maximum jerk J and maximum snap K, the cam profile can be obtained which can guarantee these parameters and the jerk is continuous. After these parameters are determined, the motion and dynamic characteristics of the cam can be directly reflected, and the cam profile which meets the requirements can be obtained.

[0121] The following shows a specific embodiment, in which the specific values of the relevant parameters are given, and the specific cam profile is designed according to the above steps:

[0122] Example 1.

[0123] A certain transmission cam mechanism, without buffer section, without maximum lift holding section, the ascending section and the descending section are asymmetric, the maximum lift H m of the ascending section is 16mm, the maximum velocity V m is 0.36mm / deg, the maximum positive acceleration A max is 0.016mm / deg 2 , the maximum negative acceleration -A min is -0.01mm / deg 2 , the terminal negative acceleration -A end is -0.004mm / deg 2 , the maximum jerk J is 0.002mm / deg 3 , the maximum snap K is 0.001mm / deg 4 ; the maximum positive acceleration A max of the descending section is 0.015mm / deg 2 , and the rest are consistent with the parameters of the ascending section.

[0124] Since there is no buffer section, the initial lift H h and the initial velocity V h are equal to zero, and the relevant angles of each section of the basic section can be calculated according to the formula of the above design method of the overall cam according to the relevant parameters.

[0125] In the ascending section:

[0126] θ1=θ3=θ5=θ7=θ9=θ 11 =θ 13 =θ 15 =J / K=0.002 / 0.001=2deg,

[0127] θ2=θ6=A max / J-J / K=0.016 / 0.002-0.002 / 0.001=6deg,

[0128] θ4=(Vm -V h ) / A max -A max / J-J / K=(0.36-0) / 0.016-0.016 / 0.002-0.002 / 0.001=12.5deg,

[0129] θ 10 =A min / J-J / K=0.01 / 0.002-0.002 / 0.001=3deg,

[0130] θ 12 =V m / A min -A min / J+A end / 2J-J / K-((A min -A end ) / 2J+J / 2K)*A end / A min =0.36 / 0.01-0.01 / 0.002+0.004 / 2 / 0.002-0.002 / 0.001-((0.01-0.004) / 2 / 0.002+0.002 / 2 / 0.001)*0.004 / 0.01=29deg,

[0131] θ 14 =(A min -A end ) / J-J / K=(0.01-0.004) / 0.002-0.002 / 0.001=1deg,

[0132] θ8=(H m -H h +A min / 2*(θ 12 +θ 13 +θ 14 +θ 15 ) 2 -A max / 2*(θ4+θ5+θ6+θ7) 2 -J 3 / K 2 (4θ2+θ4-25θ 10 / 6-θ 12 +θ 14 / 6)-J 2 / K(2.5θ2 2 +1.5θ2θ4-1.75θ 10 2 -1.5θ 10 θ 12 +0.75θ14 2 -1.5θ 10 θ 14 )-J / 2(θ2 3 +θ2 2 θ4-θ 10 3 / 3-θ 10 2 θ 12 +θ 14 3 / 3-θ 10 2 θ 14 )-V h (4θ1+2θ2+θ4)) / V m -(4θ1+θ 10 +θ 12 +θ 14 )=(16-0+0.01 / 2*(29+2+1+2) 2 -0.016 / 2*(12.5+2+6+2) 2 -0.002 3 / 0.001 2 *(4*6+12.5-25*3 / 6-29+1 / 6)-0.002 2 / 0.001*(2.5*6 2 +1.5*6*12.5-1.75*3 2 -1.5*3*29+0.75*1 2 -1.5*3*1)-0.002 / 2*(6 3 +6 2 *12.5-3 3 / 3-3 2 *29+1 3 / 3-3 2 *1)-0*(4*2+2*6+12.5)) / 0.36-(4*2+3+29+1)=6.69814815deg;

[0133] Similarly, the angle of the descending section is:

[0134] θ1=θ3=θ5=θ7=θ9=θ 11 =θ 13 =θ 15 =J / K=2deg,

[0135] θ2=θ6=A max / J-J / K=5.5deg,

[0136] θ4=(V m -V h ) / Amax -A max / J-J / K = 14.5 deg,

[0137] θ 10 = A min / J-J / K = 3 deg,

[0138] θ 12 = V m / A min -A min / J+A end / 2J-J / K-((A min -A end ) / 2J+J / 2K)*A end / A min = 29 deg,

[0139] θ 14 = (A min -A end ) / J-J / K = 1 deg,

[0140] θ8= (H m -H h +A min / 2*(θ 12 +θ 13 +θ 14 +θ 15 ) 2 -A max / 2*(θ4+θ5+θ6+θ7) 2 -J 3 / K 2 (4θ2+θ4-25θ 10 / 6-θ 12 +θ 14 / 6)-J 2 / K(2.5θ2 2 +1.5θ2θ4-1.75θ 10 2 -1.5θ 10 θ 12 +0.75θ 14 2 -1.5θ 10 θ 14 )-J / 2(θ2 3 +θ2 2 θ4-θ 10 3 / 3-θ 10 2 θ 12 +θ 14 3 / 3-θ 102 θ 14 )-V h (4θ1+2θ2+θ4)) / V m -(4θ1+θ 10 +θ 12 +θ 14 )=6.19814815deg;

[0141] Put the relevant angle into the formula of the cam profile basic segment, the function expression of each segment can be obtained, and the whole cam profile can be obtained by symmetrical processing of the descending segment, and the jerk, acceleration, speed and lift curve of the whole cam profile are shown in Figure 6 、 Figure 7 .

[0142] The whole cam profile can be obtained from the above, and the whole cam can be obtained by applying the cam profile.

[0143] As can be seen from example 1, in the cam basic segment, the jerk curve is composed of 15 straight lines, and the connection of each straight line is continuous. Therefore, the cam has the characteristics that the basic segment jerk curve is completely continuous, and the mutation of the jerk curve is limited. In the absence of a buffer segment, the whole cam jerk curve can be directly ensured to be continuous. Compared with most existing technologies, the smoothness of the cam profile is better, which can reduce the impact of the cam mechanism movement and reduce the excessive wear of the cam. At present, most of the cam profiles have poor smoothness, cannot ensure the continuity of the jerk curve, and are prone to a certain impact when running at high speed, which can cause excessive wear of the cam over time.

[0144] Example 2.

[0145] A certain internal combustion engine intake cam mechanism has a buffer segment, a maximum lift maintaining segment of 10 deg, and an ascending segment and a descending segment which are symmetrical. The parameters of the ascending segment are as follows: the initial lift H h is 0.25 mm, the initial speed V h is 0.016 mm / deg, the maximum lift H m is 6.25 mm, the maximum speed V m is 0.216 mm / deg, the maximum positive acceleration A max is 0.02 mm / deg 2 , the maximum negative acceleration -A min is -0.01 mm / deg 2 , the terminal negative acceleration -A end is 0.0 mm / deg 2 , the maximum jerk J is 0.004 mm / deg 3 , and the maximum jump K is 0.002 mm / deg 4 . The parameters of the descending segment are consistent with those of the ascending segment.

[0146] The initial lift H h is 0.25mm, the initial velocity V h is 0.016mm / deg, i.e. the lift at the end of the buffer section is 0.25mm and the velocity at the end of the buffer section is 0.016mm / deg, a buffer section which satisfies the above requirements and which has a continuous holding lap can be obtained according to the prior art.

[0147] The relevant angles of each section of the basic section are then obtained according to the formulae of the above-mentioned design method of the overall cam according to the relevant parameters.

[0148] In the ascending section:

[0149] θ1=θ3=θ5=θ7=θ9=θ 11 =θ 13 =θ 15 =J / K=2deg,

[0150] θ2=θ6=A max / J-J / K=3deg,

[0151] θ4=(V m -V h ) / A max -A max / J-J / K=3deg,

[0152] θ 10 =A min / J-J / K=0.5deg,

[0153] θ 12 =V m / A min -A min / J+A end / 2J-J / K-((A min -A end ) / 2J+J / 2K)*A end / A min =17.1deg,

[0154] θ 14 =(A min -A end ) / J-J / K=0.5deg,

[0155] θ8=(H m -H h +A min / 2*(θ 12 +θ 13 +θ 14 +θ 15 ) 2 -A max / 2*(θ4+θ5+θ6+θ7) 2 -J 3 / K 2 (4θ2+θ4-25θ 10 / 6-θ 12 +θ 14 / 6)-J 2 / K(2.5θ2 2 +1.5θ2θ4-1.75θ 10 2 -1.5θ 10 θ 12 +0.75θ 14 2 -1.5θ 10 θ 14 )-J / 2(θ2 3 +θ2 2 θ4-θ 10 3 / 3-θ 10 2 θ 12 +θ 14 3 / 3-θ 10 2 θ 14 )-V h (4θ1+2θ2+θ4)) / V m -(4θ1+θ 10 +θ 12 +θ 14 )=5.59814815deg;

[0156] Due to symmetry, the angles of each section of the descending section are the same as the angles of the ascending section.

[0157] Substitute the relevant angles into the formula of the basic section of the cam profile, and the function expression of each section of the ascending section can be obtained. After symmetrical processing of the descending section and adding the middle maximum lift holding section, the overall cam profile can be obtained. The jerk, acceleration, speed and lift curve of the cam profile are shown in Figure 8 、 Figure 9 .

[0158] The overall cam profile can be obtained from the above. By applying the cam profile, the overall cam can be obtained.

[0159] As shown in Example 2, in the basic section of the cam, the jump curve is composed of 15 straight lines, and the connection of each straight line is continuous. The cam has the characteristic that the jump curve of the basic section is completely continuous, and the abrupt change of the jump curve is also limited. When combined with the buffer section with continuous jump, the continuity of the overall jump curve of the cam can be directly guaranteed. Compared with most existing technologies, the cam profile has better smoothness, which can reduce the impact of the cam mechanism movement and reduce the excessive wear of the cam.

[0160] Example 3.

[0161] The exhaust camshaft mechanism of a certain internal combustion engine has a buffer section but no maximum lift holding section. The rising and falling sections are asymmetrical. The rising section parameters are: initial lift H. h The initial velocity V is 0.3 mm. h The maximum lift is 0.02 mm / deg. m It is 6.8mm, and the maximum speed is V. m The maximum positive acceleration A is 0.188 mm / deg. max 0.012mm / deg 2 Maximum negative acceleration -A min -0.006mm / deg 2 Terminal negative acceleration -A end -0.001mm / deg 2 Maximum jump J m 0.002mm / deg 3 The maximum jump K is 0.001 mm / deg 4 Maximum positive acceleration A during descent max 0.014mm / deg 2 The rest are the same as the parameters for the rising segment.

[0162] First, based on the initial lift H h and initial velocity V h According to existing technology, a buffer segment that can meet the requirements and maintain the continuity of the jump can be obtained.

[0163] Then, based on the formula of the above-mentioned overall cam design method, the relevant angles of each segment of the basic section are calculated according to the relevant parameters.

[0164] During the ascending phase:

[0165] θ1=θ3=θ5=θ7=θ9=θ 11 =θ 13 =θ 15 =2deg,

[0166] θ2=θ6=4deg,θ4=6deg,θ 10 =1deg,θ 12= 26.20833333 deg, θ 14 = 0.5 deg,

[0167] θ8 = 4.23229721 deg;

[0168] Downward segment:

[0169] θ1 = θ3 = θ5 = θ7 = θ9 = θ 11 = θ 13 = θ 15 = 2 deg,

[0170] θ2 = θ6 = 5 deg, θ4 = 3 deg, θ 10 = 1 deg, θ 12 = 26.20833333 deg, θ 14 = 0.5 deg,

[0171] θ8 = 4.78548869 deg;

[0172] Substitute the relevant angles into the formula of the cam profile basic segment, the function expression of each segment can be obtained, and the whole cam profile can be obtained by symmetrically processing the downward segment, and the jerk, acceleration, speed and lift curve of the whole cam profile are shown in Figure 10 , Figure 11 .

[0173] The whole cam profile can be obtained from the above, and the whole cam can be obtained by applying the cam profile.

[0174] As can be known from Example 3, in the cam basic segment, the jerk curve is composed of 15 straight lines, and the connection of each straight line is continuous. The cam has the characteristics that the basic segment jerk curve is continuous, and the mutation of the jerk curve is limited. When the jerk continuous buffer segment is matched, the whole cam jerk curve can be directly ensured to be continuous. Compared with most existing technologies, the smoothness of the cam profile is better, the impact of the cam mechanism movement can be reduced, and the excessive wear of the cam can be reduced.

[0175] Example 4.

[0176] A certain transmission cam mechanism has no buffer segment, has a maximum lift maintaining segment of 10 deg, the upward segment and the downward segment are symmetrical, and the related parameters are as follows: the maximum lift H m is 10 mm, the maximum speed V m is 0.34 mm / deg, the maximum positive acceleration A max is 0.02 mm / deg 2 , the maximum negative acceleration -A min is -0.016 mm / deg 2 , and the terminal negative acceleration -A end0 mm / deg 2 , the maximum jump J is 0.004 mm / deg 3 , the maximum jump K is 0.002 mm / deg 4 .

[0177] Since there is no buffer section, the initial lift H h and the initial speed V h are equal to zero, and the formula according to the design method of the overall cam can be used to calculate the relevant angles of each section of the basic section according to the relevant parameters.

[0178] Due to symmetry, the relevant angles of the ascending section and the descending section are the same, and the angles of each section are:

[0179] θ1 = θ3 = θ5 = θ7 = θ9 = θ 11 = θ 13 = θ 15 = 2 deg, θ2 = θ6 = 3 deg, θ4 = 10 deg,

[0180] θ 10 = 2 deg, θ 12 = 15.25 deg, θ 14 = 2 deg, θ8 = 3.78676471 deg;

[0181] Substitute the relevant angles into the formula of the cam profile basic section, and the function expression of each section can be obtained. After symmetrical processing of the descending section and adding the intermediate maximum lift maintaining section, the overall cam profile can be obtained, and the jump, acceleration, speed, and lift curves are shown in Figure 12 , Figure 13 .

[0182] From the above, the overall cam profile can be obtained, and the overall cam can be obtained by applying the cam profile.

[0183] As can be seen from Example 4, in the cam basic section, the jump curve is composed of 15 straight lines, each straight line connection is continuous, and the length of each straight line is greater than zero. The cam has the characteristics that the basic section jump curve is continuous, and the jump curve mutation is also limited, which can ensure the continuity of the overall cam jump curve. Compared with most existing technologies, the smoothness of the cam profile is better, which can reduce the impact of the cam mechanism movement and reduce the excessive wear of the cam.

[0184] From the cam profile design method of the above embodiment, it can be known that the obtained cam profile is unique after the related parameters are determined, and it is not necessary to input any cam angle information, all cam segment angles are directly determined by the given related parameters, and it is not necessary to establish equation groups to directly obtain all cam segment angles, which obviously simplifies the cam design process, avoids the process of using iteration for multiple calculations and optimization for cam profile design in the prior art, and does not need to use special software, and the design efficiency is improved. When the segment angle is zero, the related formula can still be used, and the continuous characteristics of the jump degree can still be guaranteed. In addition, the related parameters in the design method include the maximum lift, the maximum speed, the maximum positive acceleration, the maximum negative acceleration, the terminal negative acceleration, the maximum jump degree and the maximum jump degree, and the cam profile which can guarantee these parameters and the continuous jump degree can be obtained by using the method, and through these parameters, the motion and power characteristics of the cam can be directly reflected, and the cam profile which meets the motion law requirements is obtained.

[0185] In conclusion, the above is only some preferred embodiments of the present application, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A cam profile characterized in that: In the cam profile basic section, its lift curve is composed of 15 straight lines, from front to back, they are linear rise, keep constant, linear fall, keep zero, linear fall, keep constant, linear rise, keep zero, linear fall, keep constant, linear rise, keep zero, linear rise, keep constant, linear fall, and each connection of the straight lines keeps continuous.

2. A cam profile according to claim 1, wherein: The relevant parameters of the cam profile include: maximum lift H m , initial lift H h , maximum speed V m , initial speed V h , maximum positive acceleration A max , maximum negative acceleration -A min , end negative acceleration -A end , maximum jump J and maximum jump K; the cam profile speed curve keeps the maximum speed V m at the 8th segment.

3. A cam profile according to claim 2, wherein: At the beginning of the basic segment: lift is initial lift H h , velocity is initial velocity V h , acceleration and jump are zero; at the end of the basic segment: lift is maximum lift H m , velocity is zero, acceleration is terminal negative acceleration -A end , jump is zero.

4. A cam profile according to claim 2, wherein: The cam profile acceleration curve maintains a maximum positive acceleration A at the 4th segment max The cam profile acceleration curve maintains a maximum positive acceleration A at the 4th segment min The cam profile jerk curve maintains a maximum jerk J at the 2nd, 14th segments, and a negative maximum jerk -J at the 6th, 10th segments; the cam profile jump curve maintains a maximum jump K at the 1st, 7th, 11th, 13th segments, and a negative maximum jump -K at the 3rd, 5th, 9th, 15th segments.

5. A cam profile according to claim 2, wherein: The relevant parameters H m , V m , A max , A min , J and K are all greater than zero; H h , V h , A end are all greater than or equal to zero.

6. A cam profile according to claim 2, wherein: The related parameters need to meet the following conditions:

7. A cam, characterized by: The cam applies the cam profile of any one of claims 1-6.

8. A design method of an integral cam profile characterized in that: Step one: determine the characteristics of the integral cam profile according to requirements; The characteristics of the integral cam profile include whether to have a maximum lift keeping section, whether the rise section and the fall section are symmetrical, and whether to have a buffer section in each section; Step two: determine the related parameters of the rise section of the integral cam profile; The relevant parameters of the ascending section include maximum lift H m , initial lift H h , maximum speed V m , initial speed V h , maximum positive acceleration A max , maximum negative acceleration -A min , end negative acceleration -A end , maximum jump J and maximum kick K; for the cam with a buffer section for the ascending section, the initial lift H h is equal to the end lift of the buffer section, the initial speed V h is equal to the end speed of the buffer section; for the cam without a buffer section for the ascending section, the initial lift H h , the initial speed V h are all equal to zero; Step three: determine the mathematical expression of the rise section of the integral cam profile; For cam with buffer section, according to initial lift H h and initial speed V h determine the cam profile of buffer section which can keep the lift continuous; in the basic section of cam, the expressions of lift, acceleration, speed and lift of each section are obtained from the characteristics of cam profile, and then the angle of each section is calculated according to the characteristics of motion law, integral characteristics of function and related parameters; the mathematical expressions of each section of basic section of cam are calculated, and then the mathematical expressions of all the rising sections are determined; Step four: determine the mathematical expression of the fall section of the integral cam profile; For the cam with symmetrical rise section and fall section, the mathematical expression of the fall section is directly obtained by symmetrical processing of the mathematical expression of the rise section according to the symmetrical relationship of the cam function; for the cam with asymmetrical rise section and fall section, first, the mathematical expression of the rise section that meets the design requirements of the fall section is obtained according to the method of steps two to three according to the design requirements of the fall section, and then the mathematical expression of the fall section is obtained by symmetrical processing of the mathematical expression of the rise section that meets the design requirements of the fall section according to the symmetrical relationship of the cam function; Step five: for the cam profile with a maximum lift keeping section, increase the maximum keeping section lift to complete the design of the integral cam profile.

9. A method of designing a solid cam profile according to claim 8, characterized in that: In the step three, the angle of each section is:

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