A design method for dynamic balancing of camshafts of servo mechanical presses

Abstract

The present application discloses a design method for the dynamic balancing of a camshaft of a servo mechanical press. The method comprises: obtaining the contour curve of the cam in the cam coordinate system; obtaining the first center of mass position of the cam in the cam coordinate system based on the contour curve; establishing a dynamic balancing coordinate system based on the first center of mass position; obtaining the second center of mass position of the cam in the dynamic balancing coordinate system after the cam hole is opened; setting an arc-shaped groove symmetrical about the horizontal axis X of the dynamic balancing coordinate system on one side of the second center of mass position, and obtaining the third center of mass position of the cam; setting a counterweight structure on the other side of the second center of mass position, and obtaining the center of mass position of the counterweight structure; obtaining the target parameters required for dynamic balancing from the third center of mass position of the cam and the center of mass position of the counterweight structure. In this solution, the center of mass of the cam mechanism can be located at the center of the camshaft through reasonable parameter design and formula calculation, thereby reducing the periodic vibration of the camshaft under high-speed rotation, thereby improving the dynamic balancing effect.

Description

Technical Field

[0001] The present application relates to the technical field of forging equipment, and in particular to a design method for dynamic balancing of a camshaft of a servo mechanical press. Background Art

[0002] The drive systems of servo presses are primarily hydraulic and mechanical. Mechanical transmissions primarily include four-bar linkages such as crankshafts, eccentric gears, and crankshafts, as well as various multi-link transmissions. The advantages of servo presses are flexibility, intelligence, energy conservation, and environmental protection. To further enhance and meet the advantages of servo presses, their drive systems have been gradually simplified, and cam-driven servo presses have gradually appeared on the market. The emergence of new energy electric vehicles, in particular, has led to a surge in demand for battery casings in sizes such as 18650, 21700, and 4680. This requires high-precision and efficient production equipment, particularly cam-driven servo presses. However, due to the asymmetric rotating cam, the servo press drive system is difficult to balance, resulting in vibration and noise, which reduces the accuracy, reliability, and lifespan of the servo press.

[0003] In related technologies, dynamic balancing designs are widely used in textile machinery and some areas of automobile engines. For example, patent CN201621436269.5 designs a dynamically balanced embroidery machine head, which is hinged to one end of the needle bar drive connecting rod assembly through an eccentric column to avoid the problem of loose counterweight blocks requiring frequent maintenance; patent CN201821228382.3 designs a camshaft dynamic balancing device for automobile engines, which achieves dynamic balancing adjustment by adding a counterweight ring to improve the working performance of the cam; patent CN202022019912.7 discloses a camshaft balancing assembly, in which a main gear is installed on the camshaft, and a balancing block is fixed to a slave gear. During rotation, the main gear drives the balancing block on the slave gear in the opposite direction of the cam, and the centrifugal forces offset each other, achieving the effect of reducing vibration of the cam part. Summary of the Invention

[0004] In view of this, the present application provides a design method for dynamic balancing of a camshaft of a servo mechanical press, which can improve the dynamic balancing effect and thus improve the accuracy of the battery shell of new energy vehicles.

[0005] The present application provides a design method for dynamic balancing of a camshaft of a servo mechanical press, comprising:

[0006] According to the cam motion characteristics, the contour curve of the cam in the cam coordinate system is obtained;

[0007] Obtaining a first centroid position of the cam in the cam coordinate system according to the profile curve;

[0008] Establishing a dynamic balance coordinate system according to the first center of mass position;

[0009] After the cam hole is opened in the cam, a second center of mass position of the cam in the dynamic balancing coordinate system is obtained;

[0010] In a dynamic balancing coordinate system, an arc-shaped groove symmetrical about the horizontal axis X of the dynamic balancing coordinate system is provided on one side of the second mass center position, and a third mass center position of the cam is obtained;

[0011] In a dynamic balancing coordinate system, disposing a counterweight structure on the other side of the second mass center position, and obtaining the mass center position of the counterweight structure;

[0012] The target parameters required for dynamic balancing are obtained from the third mass center position of the cam and the mass center position of the counterweight structure.

[0013] Optionally, the contour curve is obtained by formula (1),

[0014]

[0015] where r b is the cam base circle radius, h is the stroke, δ1 is the push motion angle, δ2 is the distal repose angle, δ3 is the return motion angle, δ4 is the proximal repose angle, S1 is the cam push motion curve, S2 is the cam distal repose angle motion curve, S3 is the cam return motion curve, S4 is the cam proximal repose angle motion curve, δ is the cam motion angle, x is the X-axis component in the cam coordinate system, y is the Y-axis component in the cam coordinate system, and R(δ) is the radial dimension on the cam profile point.

[0016] Optionally, the first centroid position is obtained by formulas (2) and (3):

[0017] (2)

[0018]

[0019] Among them A c is the projected area of ​​the cam in the cam coordinate system, and are the components of the center of mass on the X and Y axes, is the centroid coordinate matrix.

[0020] Optionally, the second centroid position is obtained by formulas (4), (5), (6), and (7):

[0021]

[0022]

[0023] where Rs is the cam hole radius, A s is the cam hole area, is the coordinate of the centroid of the cam hole, and They are respectively expressed as the X-axis component and Y-axis component of the cam hole mass center;

[0024]

[0025]

[0026] in is the cam area, is the second center of mass position.

[0027] Optionally, the third centroid position is obtained by formulas (8), (9), (10), and (11):

[0028]

[0029]

[0030] where r h R is the radius of the semicircular arc at both ends of the arc groove, h is the radius of the centerline of the arc groove, β1 is the angle between the left side of the annular sector and the positive direction of the X axis, and β2 is the angle A of the annular sector of the arc groove h is the area of ​​the arc groove part, is the centroid of the arc-shaped slot part, and Respectively expressed as the X-axis and Y-axis components of the cam center of mass;

[0031]

[0032]

[0033] in is the area of ​​the arc groove cam, is the center of mass of the arc groove cam, and The X-axis and Y-axis components of the arc groove cam's center of mass.

[0034] Optionally, the center of mass position of the counterweight structure is obtained by formulas (12) and (13):

[0035]

[0036] Where β3 is the angle between the outer line of the convex part and the positive direction of the X axis, A w is the area of ​​the raised portion of the counterweight, is the center of mass of the raised part of the counterweight, and are the X-axis and Y-axis components of the center of mass of the counterweight protrusion.

[0037] Optionally, the target parameters required for dynamic balancing are obtained through formula (14):

[0038]

[0039] where m c The part represents the center of mass position of the arc groove disc cam, m w represents the center of mass position of the counterweight cam block, ρ represents the cam density, T1 is the cam disc thickness, and T2 is the counterweight block thickness.

[0040] Optionally, the cam motion characteristic is simple harmonic motion.

[0041] Compared with the servo pressure dynamic balance of cam drive in related art, the design method of this application has the following significant advantages:

[0042] (1) The symmetrical distribution design process only requires considering the static balance condition of the cam. The integration of the cam and its counterweight effectively avoids the loosening of the external counterweight block, ensures the transmission performance of the camshaft, and optimizes the spatial structure of the servo mechanical press.

[0043] (2) Compared with a single cam drive, the use of a dual main cam to drive the slider is more conducive to uniform force on both ends of the slider, further improving the smoothness of the slider operation and improving the stamping accuracy of the new energy vehicle battery shell.

[0044] (3) Through reasonable parameter design and formula calculation, the center of mass of the cam mechanism can be located at the center of the camshaft, reducing the periodic vibration of the camshaft under high-speed rotation. The present invention designs different types of built-in balances according to actual design requirements to make force balance easier to achieve.

[0045] (4) When establishing the cam dynamic balance coordinate system, the horizontal coordinate direction coincides with the direction of the line connecting the center of the camshaft hole and the center of mass, which can reduce the determination of parameters and simplify the dynamic balance design process.

[0046] (5) When designing the counterweight protrusion of the cam, the inner arc has the same radius as the cam hole, which can expand the range of keyway selection, increase the ability of the keyway to transmit torque, and effectively prevent the "sand hole" defect caused by shaking during the production of new energy vehicle battery shells. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The following detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings will make the technical solutions and other beneficial effects of the present application apparent.

[0048] Figure 1 This is a diagram of the center of mass position of a traditional cam on a press for making battery shells for new energy vehicles before the calculation of this application;

[0049] Figure 2 This is the center of mass position diagram of the press cam for making new energy vehicle battery shells after calculation in this application;

[0050] Figure 3 It is a schematic diagram of the three-dimensional structure of the cam in four different stages of the present application;

[0051] Figure 4 This is a three-dimensional structural diagram of the cam direct-drive slider structure of the new energy vehicle battery shell press machine of this application;

[0052] Figure 5 This is a cross-sectional view of the camshaft components of the cam press used in the present application to manufacture battery housings for new energy vehicles;

[0053] Figure 6 This is the projection diagram and parameter marking of the cam in different planes;

[0054] Figure 7 This is a simplified diagram of the center of mass position of the different parts of the cam of this application;

[0055] The components in the figure are identified as follows:

[0056] 1- camshaft, 2- bevel gear, 3- end cover, 4- oil baffle, 5- camshaft copper sleeve, 6- camshaft sleeve, 7- main cam, 8- return cam, 9- main cam roller, 10- return cam roller, 11- upper roller slider pressure cover, 12- roller support fastener, 13- slider, 14- mold splint. DETAILED DESCRIPTION

[0057] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0058] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the described features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0059] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or mutual communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0060] The disclosure below provides many different embodiments or examples for realizing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numbers and / or reference letters in different examples, and such repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art will appreciate the application of other processes and / or the use of other materials.

[0061] Before introducing the technical solution of this application, it is necessary to explain the background of the invention of this application.

[0062] It is common in the field of servo forming equipment. Cam-driven servo presses used to produce battery casings for new energy vehicles are high-speed, high-precision machines whose primary transmission component is the camshaft. To prevent unbalanced loading, cam-driven servo presses typically utilize a two-point symmetrical transmission. Camshafts on textile machinery typically utilize a single cam. However, when a cam-driven press utilizes a single cam, the required transmission strength requires a thicker cam. The high inertia generated by the cam at high speeds can cause significant vibration in the equipment. Therefore, dynamic balancing is essential when the camshaft operates at excessive speeds. Furthermore, compared to cams used in textile machinery and automotive engine cams, the camshaft components used in cam-driven presses for producing battery housings for new energy vehicles are large and heavy, and require high precision in manufacturing. Punching to improve cam eccentricity is ineffective, and the aforementioned balancing methods are ineffective, still failing to achieve a fully dynamically balanced design and further improve the precision of battery housings for new energy vehicles. Because the transmission space of cam-driven presses is compact, adding external counterweights to the cams at high speeds requires larger counterweights, which not only causes the counterweights to loosen at high speeds but also results in excessive installation space, further increasing the overall size and tonnage of the cam-driven presses, which does not meet the development requirements of green equipment design, energy conservation, and environmental protection. Therefore, the cam dynamic balancing design methods used in fields such as textile machinery and automotive engines cannot be directly applied to the dynamic balancing design of camshafts in cam presses for producing battery housings for new energy vehicles.

[0063] Based on the inventor's awareness of the above-mentioned difficulties, the inventors proposed a camshaft dynamic balancing design method for the structure, dimensions, and processing and assembly of a cam-driven press for manufacturing battery cases for new energy vehicles. When considering the dynamic balancing of the camshaft of a cam-driven servo press, the inventors first adopted a structure with two main cams and one return cam to drive the slider. The return cam is located at the center of the camshaft, and the main cams are symmetrically distributed. For a single cam, a design combining a counterweight block with the cam and a traditional punching method is used. The symmetrical distribution design process only requires considering the static balance of the cam. The integration of the cam and its counterweight effectively prevents loosening of the external counterweight block, ensures camshaft transmission performance, optimizes the spatial structure of the servo mechanical press, and improves the manufacturing accuracy of new energy vehicle battery cases. When establishing the cam dynamic balancing coordinate system, the horizontal axis direction coincides with the direction of the line connecting the center of the camshaft hole and the center of mass, which can reduce parameter determination and simplify the dynamic balancing design process. When designing the cam counterweight block, the inner arc has the same radius as the cam hole, which can expand the range of key selection, enhance the key's fixation and torque transmission stability, and effectively prevent the "sand hole" defect caused by vibration during the manufacturing of new energy vehicle battery cases. Thus, the invention was created.

[0064] Before introducing the dynamic balancing design method of this application, we take the cam direct drive slider structure as an example. Figure 4 The cam direct-drive slider structure includes a camshaft 1, a bevel gear 2, an end cover 3, an oil baffle 4, a camshaft copper sleeve 5, a camshaft sleeve 6, a main cam 7, a return cam 8, a main cam roller 9, a return cam roller 10, an upper roller slider pressure cover 11, a roller support block 12, a slider 13, and a mold clamp 14.

[0065] Bevel gear 2, which receives external force, is coaxially fixed to the end of camshaft 1 and protected by end cap 3. Two main cams 7 are coaxially fixed to one side of end cap 3, along with a return cam 8 positioned directly between them. The two main cams 7 are symmetrically arranged around return cam 8. The main cams 7 are drivingly connected to main cam rollers 9, while the return cams 8 are drivingly connected to return cam rollers 10. Roller support blocks 12 support and mount the main and return cam rollers 9 and 10.

[0066] The slider 13 is located below the main cam roller 9 and is driven by the main cam roller 9. The upper roller slider gland 11 is located above the return cam roller 10 and is driven by the return cam roller 10. The mold clamping plate 14 is used to support the sliding of the slider 13.

[0067] refer to Figure 5 The main cam 7 is mounted on the camshaft 1 through the camshaft sleeve 6, the camshaft copper sleeve 5 is arranged at the end position of the camshaft sleeve 6, and the end cover 3 is mounted on the end of the camshaft sleeve 6 through the camshaft copper sleeve 5. An oil baffle 4 is provided at the end edge of the end cover 3.

[0068] The cam structure of the cam direct drive press is assembled on the camshaft Figure 4 Three-dimensional model diagram of the cam structure of a cam direct-drive press. Figure 5 From the partial cross-sectional view of the camshaft, it can be seen that the cam body is composed of two main cams and one return cam that jointly drive the slider, making the camshaft mass symmetrical on the left and right, and the center of mass is located at the center of the camshaft.

[0069] The design method of this application takes a main cam in a cam press for making battery shells of new energy vehicles as an example ( Figure 3-1 ), the base circle radius of the cam is 80mm, the stroke is 50mm, the push motion angle is 90°, the far rest angle is 90°, the return motion angle is 90°, and the near rest angle is 90° to establish the expression of the cam profile.

[0070] 1. Analytical expression of cam profile

[0071] The slider motion trajectory is determined based on the manufacturing process of the new energy vehicle battery shell, and the cam profile curve is designed based on the slider motion trajectory. The cam profile analytical formula of the present invention uses the following parameters for main calculation. The cam profile curve is designed using the law of simple harmonic motion for both the push and return strokes:

[0072]

[0073] where r b is the base circle radius of the cam, h is the stroke, δ1 is the push motion angle, δ2 is the distal repose angle, δ3 is the return motion angle, δ4 is the proximal repose angle, S1 is the cam push motion curve, S2 is the cam distal repose angle motion curve, S3 is the cam return motion curve, S4 is the cam proximal repose angle motion curve, δ is the cam motion angle, x is the X-axis component in the cam coordinate system, y is the Y-axis component in the cam coordinate system, and R(δ) is the radial dimension expression on the cam profile point.

[0074] 2. Cam dynamic balancing design process

[0075] The geometric characteristics of the disc cam must be derived, which is necessary for the overall forming design. This section introduces the cam projected area and center of mass at different stages.

[0076] (1) The cam is (as Figure 3-1 The projected area A in the XY coordinate system c for:

[0077]

[0078] The center of gravity of the disc cam is also its center of mass on the XY plane, where x = rcosδ and y = rsinδ represent the horizontal and vertical coordinate expressions of the radial radius at any position of the cam. The components of the center of mass on the X and Y axes are calculated as follows: and Denoted as:

[0079]

[0080] (2) The cam designed according to the size of the camshaft is as follows Figure 3-2 As shown, the cam hole area A s The formula is:

[0081]

[0082] where R s is the camshaft hole radius

[0083] The camshaft hole is a standard circle, and the centroid coordinate of this part is for:

[0084]

[0085] in and They are respectively expressed as the X-axis and Y-axis components of the center of mass of the cam hole part.

[0086] Figure 3-2 Area of ​​the cam shown for:

[0087]

[0088] Figure 3-2 Cam center of mass for:

[0089]

[0090] (3) Figure 3-2 Based on the cam, we design an arc groove symmetrical about the line connecting the center of mass and the origin to obtain the following Figure 3-3 The cam shown in the figure has an arc groove area A. h for:

[0091]

[0092] where r h R is the radius of the semicircular arc at both ends of the arc groove, h is the centerline radius of the arc groove, and β2 is the annular sector angle of the arc groove.

[0093] For the centroid of the arc groove part It can be calculated by the following formula:

[0094]

[0095] Where β1 is the angle between the left side of the annular sector and the positive direction of the X axis.

[0096] The centroid is defined as the combined centroid of the combined area of ​​two semicircles and a circular sector. Figure 3-3 Area of ​​arc groove disc cam and centroid coordinates for:

[0097]

[0098]

[0099] (4) Figure 3-3 Based on the cam, the counterweight protrusion is designed for the cam and the following is obtained: Figure 3-4 The cam shown in the figure has a raised area A w for:

[0100]

[0101] Wherein β3 is the angle between the outer line of the convex part and the positive direction of the X axis.

[0102] Center of mass of the raised portion of the counterweight for

[0103]

[0104] The centroid of the arc groove cam is obtained by the above formula and the center of mass of the counterweight protrusion According to the cam's centroid position, establish the relationship diagram of the centroid position of different parts of the cam ( Figure 7 ), where m c The part represents the center of mass position of the arc groove disc cam, m w It represents the center of mass position of the counterweight cam block, ρ represents the cam density, T1 is the cam disc thickness, and T2 is the counterweight protrusion thickness. According to the static balance condition of the cam, it can be obtained that:

[0105]

[0106] The undetermined parameters designed in this paper are β2, β3, r h ,T2, where β2,r h Affects the cam's arcuate groove's curvature and width; T2 and β3 affect the cam's counterweight protrusion's curvature and thickness. Formula (14) provides a unique cam counterweight method based on two of these parameters. Adjustments can be made based on actual needs. Providing the counterweight protrusions of equal size on both sides of the cam can avoid dynamic balancing issues at high speeds. By establishing a suitable coordinate system, calculation steps can be simplified and parameter settings can be reduced. Figure 1 and Figure 2 They represent the center of mass of the cam before and after dynamic balancing, and it can be seen that the latter has a more obvious effect.

[0107] Figure 1 and Figure 2 The figures show the center of mass of the cam before and after dynamic balancing. It can be seen that the latter has a significant effect. Both the main cam and the return cam are designed to be balanced.

[0108] The above is only a preferred specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in this application should be covered by the scope of protection of the present application.

Claims

1. A design method for dynamic balancing of a camshaft of a servo mechanical press, characterized in that: include: According to the cam motion characteristics, the contour curve of the cam in the cam coordinate system is obtained; Obtaining a first centroid position of the cam in the cam coordinate system according to the profile curve; Establishing a dynamic balance coordinate system according to the first center of mass position; After the cam hole is opened in the cam, a second center of mass position of the cam in the dynamic balancing coordinate system is obtained; In a dynamic balancing coordinate system, an arc-shaped groove symmetrical about the horizontal axis X of the dynamic balancing coordinate system is provided on one side of the second mass center position, and a third mass center position of the cam is obtained; In a dynamic balancing coordinate system, disposing a counterweight structure on the other side of the second mass center position, and obtaining the mass center position of the counterweight structure; The target parameters required for dynamic balancing are obtained from the third mass center position of the cam and the mass center position of the counterweight structure.

2. The design method according to claim 1, characterized in that: By formula (1), the contour curve is obtained. where r b is the cam base circle radius, h is the stroke, δ1 is the push motion angle, δ2 is the distal repose angle, δ3 is the return motion angle, δ4 is the proximal repose angle, S1 is the cam push motion curve, S2 is the cam distal repose angle motion curve, S3 is the cam return motion curve, S4 is the cam proximal repose angle motion curve, δ is the cam motion angle, x is the X-axis component in the cam coordinate system, y is the Y-axis component in the cam coordinate system, and R(δ) is the radial dimension on the cam profile point.

3. The design method according to claim 1, characterized in that: By using formulas (2) and (3), we can obtain the first centroid position. Among them A c is the projected area of ​​the cam in the cam coordinate system, and are the components of the center of mass on the X and Y axes, is the centroid coordinate matrix.

4. The design method according to claim 1, characterized in that: The second centroid position is obtained by formulas (4), (5), (6), and (7). where R s is the cam hole radius, A s is the cam hole area, is the coordinate of the centroid of the cam hole, and They are respectively expressed as the X-axis component and Y-axis component of the cam hole mass center; in is the cam area, is the second centroid position.

5. The design method according to claim 1, characterized in that: The third centroid position is obtained by formulas (8), (9), (10), and (11): where r h R is the radius of the semicircular arc at both ends of the arc groove, h is the radius of the centerline of the arc groove, β1 is the angle between the left side of the annular sector and the positive direction of the X axis, and β2 is the angle A of the annular sector of the arc groove h is the area of ​​the arc groove part, is the centroid of the arc-shaped slot part, and Respectively expressed as the X-axis and Y-axis components of the cam center of mass; in is the area of ​​the arc groove cam, is the center of mass of the arc groove cam, and The X-axis and Y-axis components of the arc groove cam's center of mass.

6. The design method according to claim 1, characterized in that: The center of mass position of the counterweight structure is obtained by formulas (12) and (13): Where β3 is the angle between the outer line of the convex part and the positive direction of the X axis, A w is the area of ​​the raised portion of the counterweight, is the center of mass of the raised part of the counterweight, and are the X-axis and Y-axis components of the center of mass of the counterweight protrusion.

7. The design method according to claim 1, characterized in that: By using formula (14), we can obtain the target parameters required for dynamic balancing: where m c The part represents the center of mass position of the arc groove disc cam, m w represents the center of mass position of the counterweight cam block, ρ represents the cam density, T1 is the cam disc thickness, and T2 is the counterweight block thickness.

8. The design method according to claim 1, characterized in that: The cam motion characteristic is simple harmonic motion.

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