Maintenance method for cam ring of radial plunger inner curve hydraulic motor

Abstract

The invention relates to a maintenance method of an inner curve hydraulic motor cam ring, which comprises the following steps of: scanning point coordinates of an original cam ring curve, and calculating a motion equation of the center of a roller according to the point scanning coordinates of the cam ring and the radius of the roller by using software; and then, according to the new small diameter of the cam ring and the roller center motion equation, calculating the curve point coordinates of the cam ring after maintenance. According to the cam ring maintained by the method, the original design movement rule of the original motor is not changed under the condition that the curve design principle of the original cam ring is not known, and the stable operation of the maintained motor is ensured. Meanwhile, the machining error of an original curve can be compensated by using the method to repair the cam ring, and the pulsatility of the repaired motor is even possibly lower than the pulsatility of the original curve.

Description

Technical Field

[0001] The invention relates to a method for repairing a cam ring of a radial plunger inner curve hydraulic motor in the field of hydraulic motors, and in particular to a method for repairing a cam ring of a radial plunger inner curve hydraulic motor. Background Art

[0002] The cam ring is one of the key parts of the radial piston hydraulic motor, and its shape determines the movement law of each component inside the motor. At present, most hydraulic component repair manufacturers do not understand the design theory of the cam ring. After the cam ring is worn, they only remove the damaged cam ring through simple and intuitive methods such as overall offset and proportional enlargement. The cam ring repaired in this way changes the design movement law of the roller and the plunger, causing pressure and speed pulsation during the operation of the motor, reducing the life and stability of the motor. The cam ring is designed together with the motor's distribution window, and the cam ring curves of different manufacturers are not universal. Therefore, it is very important to ensure that the cam ring after material removal follows the original movement law.

[0003] In view of the above-mentioned defects in the existing technology, the inventor has finally created the present invention which is of practical value after continuous research, design, repeated trials and improvements. Summary of the invention

[0004] The main purpose of the present invention is to overcome the defects of the existing technology and provide a new method for repairing the cam ring of a radial piston internal curve hydraulic motor. The technical problem to be solved is to make up for the original processing error without changing the original motion law of the motor without knowing the specific form of the original curve, thereby effectively improving the durability and stability of the motor after repair, which is very suitable for practical use.

[0005] The purpose of the present invention and the technical problem to be solved are achieved by adopting the following technical solutions. According to a radial piston inner curve hydraulic motor cam ring maintenance method proposed by the present invention, the method comprises the following steps:

[0006] Step 1: Scan the original motor cam loop curve and present it in the form of discrete data points;

[0007] Step 2: Calculate the motion path of the roller center according to the roller radius and the cam ring curve, and present it in the form of discrete data points;

[0008] Step 3: Calculate the speed of the roller according to the center path of the roller and present it in the form of discrete data points;

[0009] Step 4: Calculate the acceleration of the roller according to its center velocity and present it in the form of discrete data points;

[0010] HDP240219CNPage 2 / 8

[0011] Step 5: Adjust the roller center acceleration, including removing protruding points, setting the acceleration of the constant speed area and the equal radius area to zero, to make it more reasonable;

[0012] Step 6: Use the n-order Fourier function to fit the adjusted roller center motion acceleration;

[0013] Step 7: Adjust the value n until the fitted acceleration and the adjusted acceleration are highly consistent to avoid overfitting and underfitting;

[0014] Step 8: Take multiple points on the fitted acceleration curve and calculate the velocity using numerical integration

[0015] Step 9: Determine the grinding amount according to the wear of the cam ring. It should be ensured that the surface of the cam ring is smooth after grinding, without any damage marks, and the depth of the quenching layer can still meet the use requirements. The major and minor diameters of the cam ring after maintenance are determined by the measured values ​​before maintenance and the grinding amount;

[0016] Step 10: Use the fitted acceleration and minimum radius to recalculate the cam ring curve equation. If the calculated cam ring major diameter does not match the theoretical value, then the fitted acceleration data at all points will be uniformly multiplied by a coefficient obtained through repeated corrections.

[0017] Step 11: Repeat step 10 and correct the coefficient until the cam ring major diameter matches the theoretical value;

[0018] Step 12: Output the point data to the CNC machine tool for grinding the cam ring.

[0019] Furthermore, in the steps, for discrete data points, two points before and after the desired point are taken to calculate the offset angle of the roller center relative to the contact point between the roller and the stator.

[0020] Furthermore, in the steps, for discrete data points, two points before and after the desired point are taken to calculate the speed of the center of the roller.

[0021] Furthermore, in the steps, for discrete data points, two points before and after the desired point are taken to calculate the acceleration of the center of the roller.

[0022] Compared with the prior art, the present invention has obvious advantages and beneficial effects, and has at least the following advantages:

[0023] 1. The universal maintenance method of the present invention is applicable to curves of various theoretical designs. Maintenance can be performed after the original curve is scanned into discrete point data and recalculated according to the movement law of the roller.

[0024] 2. The present invention ensures smooth movement and small pulsation without changing the original movement law of the motor.

[0025] 3. The present invention can correct the original processing error of the cam ring.

[0026] 4. The calculation process of the present invention is simple and the solution accuracy is high.

[0027] 5. The method of using the present invention can directly obtain point data for CNC machine tool processing without additional conversion.

[0028] The specific method of the present invention is given in detail by the following examples and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the cam ring curve and the roller of the present invention.

[0030] Figure 2 : is a schematic diagram of the roller center speed of the present invention.

[0031] Figure 3 : is a schematic diagram of the roller center acceleration fitting of the present invention.

[0032] Figure 4 : It is the comparison of the curves before and after maintenance of the present invention.

[0033] HDP240219CNPage 3 / 8 DETAILED DESCRIPTION

[0034] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following is a detailed description of a radial piston internal curve hydraulic motor cam ring maintenance method proposed by the present invention, in combination with the accompanying drawings and preferred embodiments, its specific implementation method, steps, characteristics and effects are as follows.

[0035] A method for repairing a cam ring of a radial piston inner curve hydraulic motor comprises the following steps:

[0036] Step 1: Scan the original motor cam loop curve and present it in the form of discrete data points (see Figure 1 shown);

[0037] Step 2: Calculate the motion path of the roller center based on the roller radius and the cam ring curve, and present it in the form of discrete data points; for discrete data points, take the two points before and after the point to be calculated, and calculate the offset angle of the roller center relative to the contact point between the roller and the stator

[0038] Step 3: Calculate the speed of the roller according to the path of the roller center and present it in the form of discrete data points; for discrete data points, take the two points before and after the point to be calculated and calculate the speed of the roller center;

[0039] Step 4: Calculate the acceleration of the roller center according to its velocity. For discrete data points, take the two points before and after the point to be calculated and calculate the acceleration of the roller center.

[0040] Step 5: Adjust the roller center acceleration, including removing protruding points, setting the acceleration of the constant speed area and the equal radius area to zero, etc., to make it more reasonable;

[0041] Step 6: Use the n-order Fourier function to fit the adjusted roller center motion acceleration;

[0042] Step 7: Adjust the value n until the fitted acceleration and the adjusted acceleration are highly consistent to avoid overfitting and underfitting;

[0043] Step 8: Take multiple points on the fitted acceleration curve and calculate the velocity using numerical integration

[0044] Step 9: Determine the grinding amount according to the wear of the cam ring. It should be ensured that the surface of the cam ring is smooth after grinding, without any damage marks, and the depth of the quenching layer can still meet the use requirements. The major and minor diameters of the cam ring after maintenance can be determined by the actual measured values ​​before maintenance and the grinding amount;

[0045] Step 10: Use the fitted acceleration and minimum radius to recalculate the cam ring curve equation. If the calculated cam ring major diameter does not match the theoretical value, then the fitted acceleration data at all points will be uniformly multiplied by a coefficient obtained through repeated corrections.

[0046] Step 11: Repeat step (10) and correct the coefficient until the cam ring major diameter matches the theoretical value;

[0047] Step 12: Output the point data to the CNC machine tool for grinding the cam ring.

[0048] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0049] like Figure 1 As shown, the inner curve hydraulic motor cam ring curve, where Figure 1 r g is the roller radius; σ is the angle between the tangent of a point on the cam ring and the horizontal line; θ is the angle between the line connecting the roller center and the motor center and the positive direction of the x-axis; ρ(θ) is the polar radius of the roller center when the angle is θ; ρ′(θ) is the speed at the angle θ, that is, the derivative of the polar radius ρ(θ) with respect to θ

[0050] ρ″(θ) is the acceleration at angle θ, that is, the derivative of velocity ρ′(θ) with respect to θ ρ0 is the minimum distance from the center of the roller to the center of the motor; ρ1 is the maximum distance from the center of the roller to the center of the motor;

[0051] The specific steps are as follows:

[0052] Step 1: Scan the original motor cam loop curve and present it in the form of discrete data points;

[0053] The actual curve is directly obtained through three-coordinate measurement, converted into rectangular coordinate form, and the curve is presented in the form of discrete data points.

[0054] Step 2: Calculate the motion path of the roller center based on the roller radius and the cam ring curve:

[0055] For any point (x n ,y n ), the angle between the tangent line of the cam ring and the horizontal line at that point can be estimated by the slope of the line connecting the two points before and after:

[0056]

[0057] Where:

[0058] x n – The horizontal coordinate of the nth point on the cam ring

[0059] y n – The ordinate of the nth point on the cam ring

[0060] σ n – The angle between the tangent line at the nth point on the cam ring and the positive direction of the x-axis

[0061] The roller moves to point (x n ,y n ) contacts the cam ring, the roller center (xg n ,yg n ) and the angle σ′ between the line connecting this point and the horizontal line n That is:

[0062]

[0063] σ n –Same meaning as above

[0064] Roller center(xg n ,yg n ) can be calculated by the following formula:

[0065] xg n =x n +r g ·cosσ′ n (3)

[0066] yg n =y n +rg ·sinσ′ n (4)

[0067] Where:

[0068] xg n – Horizontal coordinate of the roller center

[0069] yg n – Vertical coordinate of the roller center

[0070] σ′ n 、x n ,y n 、r g –Same meaning as above

[0071] Step 3: Calculate the speed of the roller according to the roller center path:

[0072] The center of the roller (xg n ,yg n ) is converted into polar coordinates (ρ(θ n ),θ n ):

[0073]

[0074] Where:

[0075] ρ(θ n ) – Roller center (xg n ,yg n ) corresponds to the polar radius

[0076] θ n -Roller center(xg n ,yg n ) corresponds to the polar angle

[0077] xg n ,yg n –Same meaning as above

[0078] The center velocity of the roller at any point can be determined by numerically differentiating the polar coordinates of the two points in front and behind it. The graph is as follows: Figure 2 As shown, the calculation formula is as follows:

[0079]

[0080] Where:

[0081] ρ′(θ n )-The roller center polar angle is θ n The corresponding speed

[0082] ρ(θ n ), θ n –Same meaning as above

[0083] Step 4: Calculate the acceleration based on the center velocity of the roller:

[0084] Similar to step 3, the acceleration of the roller center at any point can be calculated from its velocity and the velocity of the two points before and after it. The calculation formula is as follows:

[0085]

[0086] Where:

[0087] ρ″(θ n )-The roller center polar angle is θ n The corresponding acceleration

[0088] ρ′(θ n ), θ n -Same meaning as above

[0089] Step 5: Adjust the roller center acceleration, including removing protruding points, setting the acceleration of the constant speed area and the constant radius area to zero, etc., to make it more reasonable; the acceleration curves before and after adjustment are shown in Figure 3 .

[0090] Step 6: Fit ρ″(θ) using the m-th order Fourier function f(θ) by the least squares method n ):

[0091]

[0092] Where:

[0093] a k –The kth undetermined coefficient is determined by fitting

[0094] l-half of the cam ring cycle, i.e. Where z is the cam ring action number

[0095] Step 7: Adjust the value m until the fitted acceleration and the adjusted acceleration are highly consistent to avoid overfitting and underfitting: The value of m depends on the fitting effect and needs to be adjusted according to the actual situation. Figure 3 shown.

[0096] Step 8: Take x points equally divided on the horizontal axis on the fitted acceleration curve f(θ) and calculate the velocity by numerical integration:

[0097]

[0098] Where:

[0099] n – the ordinal number of the calculated point (1, 2, 3…x)

[0100] θn –The roller center level angle corresponding to the nth point, the value is f(θ n ) – the value of the fitted acceleration f(θ) at point n

[0101] ρ′(θ n ) – calculated velocity at the nth point

[0102] Step 9: Determine the grinding amount according to the wear of the cam ring. It should ensure that the surface of the cam ring is smooth after grinding, without any damage marks, and the depth of the quenching layer can still meet the use requirements. The major and minor diameters of the cam ring after maintenance can be determined by the measured values ​​before maintenance and the grinding amount. It is necessary to ensure that the difference between the major and minor diameters before and after grinding, that is, the stroke of the roller is consistent.

[0103] Determine the grinding amount according to the wear of the cam ring, and the minor diameter R2 after grinding, and calculate the major diameter of the cam ring. The theoretical major diameter of the cam ring is calculated according to the motor displacement:

[0104] V=xzπr 2 (R3-R2) (11)

[0105] Where:

[0106] V – Motor displacement

[0107] x – number of plungers

[0108] z – Cam ring action number

[0109] r – plunger radius

[0110] R2 – Grind the rear cam ring minor diameter

[0111] R3 – Grinding the large diameter of the rear cam ring

[0112] Step 10 Recalculate the cam ring curve equation using the fitted acceleration and cam ring diameter

[0113] Where:

[0114] ρ(θ n ) – The calculated roller center polar radius at the nth point

[0115] n,θ n ,ρ′(θ n ) – Same meaning as above

[0116] Since the direction of the roller center movement is always parallel to the tangent line between the roller and the cam ring, the slope of the tangent line between the roller and the cam ring at point n can be derived from the coordinates of the n-1, n, and n+1 points.

[0117] xg n= ρ(θ n )×cos(θ n ) (13)

[0118] yg n = ρ(θ n )×sin(θ n ) (14)

[0119] Where:

[0120] xg n –The horizontal coordinate of the nth point on the roller center path

[0121] yg n – The vertical coordinate of the nth point on the roller center path

[0122]

[0123] Where:

[0124] σ n – The slope of the tangent line between the roller and the cam ring at the nth point

[0125] σ′ n -The angle between the line between the roller center and the cam ring tangent point at the nth point and the positive direction of the x-axis

[0126] x n =xg n +r g ×cos σ′ n (17)

[0127] y n =yg n +r g ×sin σ′ n (18) Where:

[0128] x n – The horizontal coordinate of the nth point on the cam ring

[0129] y n – The ordinate of the nth point on the cam ring

[0130] r g – Roller radius

[0131] xg n ,yg n ,σ′ n -Same meaning as above

[0132]

[0133] Where:

[0134] R n -The polar diameter of the nth point on the cam ring

[0135] α n - Polar angle of the nth point on the cam ring

[0136] x n ,y n -Same meaning as above

[0137] Step 11: If the cam ring major diameter calculated by equation (19) is significantly different from the theoretical value calculated by equation (11), the fitted acceleration f(θ n ) multiply the acceleration of all points on the cam ring by a coefficient to recalculate the major diameter; repeat the above steps until the major diameter of the cam ring is very close to the theoretical value;

[0138] Step 12: Export the calculated cam ring position data to the CNC machine tool for grinding the cam ring:

[0139] (R n ,α n ) is the new cam ring curve polar coordinate, which is input into the machine tool to repair the cam ring. Figure 4 Comparison of grinding front and rear cam rings.

[0140] The cam ring repaired by the method of the present invention can ensure the smooth operation of the motor after repair without understanding the design principle of the original cam ring curve and changing the original design movement law of the original motor. At the same time, the cam ring repaired by this method can also compensate for the processing error of the original curve, and the pulsation of the repaired motor may even be lower than the original curve.

[0141] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for repairing a cam ring of a radial piston inner curve hydraulic motor, characterized in that: The method comprises the following steps: Step 1: Scan the original motor cam loop curve and present it in the form of discrete data points; Step 2: Calculate the motion path of the roller center according to the roller radius and the cam ring curve, and present it in the form of discrete data points; Step 3: Calculate the speed of the roller according to the center path of the roller and present it in the form of discrete data points; Step 4: Calculate the acceleration of the roller according to its center velocity and present it in the form of discrete data points; Step 5: Adjust the roller center acceleration, including removing protruding points, setting the acceleration of the constant speed area and the equal radius area to zero, to make it more reasonable; Step 6: Use the n-order Fourier function to fit the adjusted roller center motion acceleration; Step 7: Adjust the value n until the fitted acceleration and the adjusted acceleration are highly consistent to avoid overfitting and underfitting; Step 8: Take multiple points on the fitted acceleration curve and calculate the velocity by numerical integration; Step 9: Determine the grinding amount according to the wear of the cam ring. It should be ensured that the surface of the cam ring is smooth after grinding, without any damage marks, and the depth of the quenching layer can still meet the use requirements. The major and minor diameters of the cam ring after maintenance are determined by the measured values ​​before maintenance and the grinding amount; Step 10: Use the fitted acceleration and minimum radius to recalculate the cam ring curve equation. If the calculated cam ring major diameter does not match the theoretical value, then the fitted acceleration data at all points will be uniformly multiplied by a coefficient obtained through repeated corrections. Step 11: Repeat step 10 and correct the coefficient until the cam ring major diameter matches the theoretical value; Step 12: Output the point data to the CNC machine tool for grinding the cam ring.

2. A method for repairing a cam ring of a radial piston inner curve hydraulic motor according to claim 1, characterized in that: In the step (2), for discrete data points, two points before and after the desired point are taken to calculate the offset angle of the roller center relative to the contact point between the roller and the stator. According to the method for repairing the cam ring of a radial piston internal curve hydraulic motor as described in claim 1, it is characterized in that in the step (3), for discrete data points, the two points before and after the required point are taken to calculate the speed of the roller center.

3. A method for repairing a cam ring of a radial piston inner curve hydraulic motor according to claim 1, characterized in that: In the step (4), for discrete data points, two points before and after the desired point are taken to calculate the acceleration of the center of the roller.

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