A pulley with an automatic deviation correction function and its selection method

Abstract

The present invention relates to a pulley with an automatic deviation rectification function and a selection method thereof. The outer surface of the pulley is designed as an arc surface structure. The design of this arc surface structure enables the belt to have a certain deviation rectification ability after deviation. Due to the existence of this deviation rectification ability, it can be directly installed without an adjustment device during assembly. In addition, the present invention calculates the deviation angle of the pulley that satisfies the inequality F max ≥F 偏 through the selection method, and also calculates the deviation angle of the pulley whose parameters satisfy the inequality #imgabs0#. By combining the deviation angles under the two conditions, the deviation angle selection range is obtained, thereby completing the selection of the pulley, so as to ensure that the pulley does not deviate and at the same time ensure that the service life of the belt cooperating with the pulley meets the requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of pulley design, and particularly relates to a pulley with an automatic deviation rectification function and a selection method thereof. Background Art

[0002] In a pulley system, due to the combined effects of machining errors of workpieces, assembly errors, and other factors, the forces on the pulley system are uneven during operation, resulting in belt deviation. The belt will show a phenomenon of lateral movement. When the movement range is large, the side of the belt will rub against the workpiece, causing wear. If frequent friction causes severe wear on the side of the belt, there will be a safety hazard of belt breakage. Therefore, during the design of the pulley system, it is necessary to design a pulley offset adjustment structure so that various offsets caused by errors can be easily adjusted during the assembly process of the pulley system, thereby reducing the lateral movement of the belt during operation. However, the existing adjustment structures are complex in adjustment operation and affect the assembly progress. This method can solve the problem of complex pulley adjustment. During assembly, the offset does not need to be adjusted, and the belt can still move laterally within the allowable offset range during operation.

[0003] The existing belt adjustment structures are complex in structure, have many assembly processes, and are cumbersome in adjustment operation. Therefore, when assembling a pulley set, assembly workers need to spend a lot of time on adjustment to ensure that the degree of belt deviation is within a reasonable range. In addition, since the degree of screw insertion needs to be adjusted to control the belt offset, it is easy to blindly pursue the offset amount during adjustment, thus ignoring the degree of belt tension. Both too loose and too tight belt tension will cause adverse effects. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a pulley with a simple structure and an automatic deviation rectification function and a selection method thereof, which can ensure that the pulley does not deviate and at the same time ensure that the service life of the belt cooperating with the pulley meets the requirements.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A pulley with an automatic deviation rectification function includes a bearing and a pulley sleeved outside the bearing, and the outer surface of the pulley is an arc surface structure.

[0007] A selection method for a pulley includes the following steps:

[0008] Step 1: Define the operating state and a single operating cycle, and set the operating distance S, operating time T, and acceleration time T 1 ;

[0009] Step 2: Obtain three external forces during the operating cycle: load force Fg , inertial force F f , initial tension force F t ;

[0010] Step 3: Based on the load force F g , inertial force F f , initial tension force F t calculate the tight-side tension force F N1 , slack-side tension force F N2 , resultant force on the tight side F 1 , resultant force on the slack side F 2 ;

[0011] Step 4: Based on the tight-side tension force F N1 , slack-side tension force F N2 , resultant force on the tight side F 1 , resultant force on the slack side F 2 and combined with the contact surface coefficient and the error resultant deflection angle β, calculate the maximum self-aligning force F max and the maximum offset force F 偏 ;

[0012] Step 6: Establish the inequality F max ≥F 偏 . If the inequality does not hold, reselect the contact surface coefficient. If the inequality holds, output the calculation result of the inequality α≥α 1 , where α is the offset angle;

[0013] Step 5: Based on the load force F g , running distance S, acceleration time T 1 , running time T, service factor KA, calculate the transmitted power P, and then select the belt type of the synchronous belt according to the transmitted power P in the database;

[0014] Step 7: Look up and calculate according to the transmitted power P, number of teeth meshing of the small pulley Kz, reference width bs0, reference rated power P0 in the database, and select the belt width db;

[0015] Determine the synchronous belt material, and find the wear ratio K of the belt pulley material for this material according to the stress condition and running speed in the database b ;

[0016] Determine the volume Vs of the selected synchronous belt with length s, and determine the number of usage cycles n;

[0017] Step 8: Calculate the wear volume V and the cumulative friction work ∑W of the synchronous belt according to the selection of the synchronous belt, belt width db, wear ratio K b , number of usage cycles n;

[0018] Step 9: Calculate the wear rate γ of the synchronous belt based on the wear volume V and the cumulative friction work ∑W;

[0019] Step 10: Establish an inequality If the inequality does not hold, it means that the expected service life cannot be achieved, and the number of usage cycle times n is reselected for calculation; if the inequality holds, the calculation result α ≤ α 2 is obtained, and the contact surface coefficient is reselected according to the wear volume V, and the maximum offset force F_offset and the maximum return force F max after wear are recalculated;

[0020] Step 11: Establish an inequality F max ≥ F 偏 If the inequality does not hold, the number of usage cycle times is reselected; if the inequality holds, the inequality calculation result α ≥ α 3 is obtained, and the two are combined to output the two inequality calculation results α 3 ≤ α ≤ α 2 ;

[0021] Step 12: Combine the calculation result α ≥ α 1 obtained in Step 6 with the calculation result α 3 ≤ α ≤ α 2 obtained in Step 11, and output the final calculation result α 4 ≤ α ≤ α 2 , where α 4 = max{α 1 , α 3};

[0022] Step 13: The pulley determines the offset angle α of the pulley according to the inequality α 4 ≤ α ≤ α 2 to determine the arc surface structure of the pulley and complete the pulley selection.

[0023] In the said Step 2,

[0024] The maximum inertial force F f during the operation cycle is:

[0025]

[0026] where S is the single-cycle operation length, and F g is the load force;

[0027] The initial tension F t of the belt is:

[0028]

[0029] where T dis the bending load, L is the shaft spacing, C is the compensation coefficient, d p is the diameter of the small pulley, D p is the diameter of the large pulley.

[0030] The calculation in step 3 is specifically as follows:

[0031] According to the inertial force F f , the load force F g , the initial tension force F t , the tight-side tension of the belt is derived as:

[0032]

[0033] The slack-side tension of the belt:

[0034]

[0035] When F N2 < 0, F N2 shall be taken as 0;

[0036] Calculate the tight-side supporting force:

[0037]

[0038] The slack-side supporting force:

[0039]

[0040] Calculate the tight-side frictional force:

[0041]

[0042] The slack-side frictional force:

[0043]

[0044] where μ is the dynamic friction coefficient of the pulley;

[0045] Finally, calculate the resultant force on the tight side:

[0046]

[0047] The resultant force on the slack side:

[0048]

[0049] In step 4,

[0050] The maximum self-aligning force is:

[0051] F max = |A 1 - B 1 |(F 1 + F2 )

[0052] The maximum offset force is:

[0053]

[0054] Wherein, A 1 and B 1 are both contact surface coefficients, and β is the error resultant deflection angle.

[0055] In the said step 8,

[0056] The wear volume is:

[0057]

[0058] The cumulative friction work is:

[0059]

[0060] In the said step 9,

[0061] The wear rate is:

[0062]

[0063] γ is the volume worn under certain load and speed conditions within a single cycle.

[0064] After adopting the above scheme, the outer surface of the pulley of the present invention is designed as an arc surface structure. The design of this arc surface structure enables the belt to have a certain self-aligning ability after offset. Due to the existence of this self-aligning ability, it can be directly installed without an adjustment device during assembly. In addition, the present invention calculates the offset angle of the pulley that satisfies the inequality F max ≥F 偏 , and also calculates the offset angle of the pulley that satisfies the inequality . By combining the offset angles under the two conditions, the offset angle selection range is obtained, thereby completing the selection of the pulley, so as to ensure that the pulley does not run off track and at the same time ensure that the service life of the belt cooperating with the pulley meets the requirements. Brief Description of the Drawings

[0065] Figure 1 is a schematic structural diagram of the pulley of the present invention;

[0066] Figure 2 is a schematic structural diagram when the forces on both sides of the belt are balanced;

[0067] Figure 3 is a schematic structural diagram when the forces on the belt are uneven;

[0068] Figure 4 is a schematic diagram of the offset angle;

[0069] Figure 5 is the flowchart of the selection method of the present invention;

[0070] Figure 6 is the schematic diagram of the belt wear stage;

[0071] Figure 7 is the schematic diagram of the injection molding robot arm used in the embodiment of the present invention.

[0072] Label description:

[0073] Bearing 10; pulley 20; belt 30. Specific implementation manner

[0074] As Figure 1 shown, the present invention discloses a pulley with an automatic deviation rectification function, which includes a bearing 10 and a pulley 20 sleeved outside the bearing 10, and the outer surface of the pulley 20 is an arc surface structure. The design of this arc surface structure enables the belt 30 to have a certain deviation rectification ability after deviation. Due to the existence of this deviation rectification ability, it can be directly installed without an adjustment device during assembly.

[0075] The basic principle of the automatic deviation rectification of the pulley of the present invention is:

[0076] As Figure 2 shown, when the belt 30 runs on the pulley 20, due to the balanced force on both sides, it runs normally without external force intervention. As Figure 3 shown, if the uneven force causes the belt to deviate, it will change the contact surface between the belt 30 and the pulley 20. At this time, due to the internal tension of the belt 30 and the toughness and plasticity of the material itself, the contact surface size in the deviation direction will decrease, while the contact surface size in the opposite direction of the deviation will increase. The direction of the resultant external force at this time is the opposite direction of the belt deviation, which will cause the belt to return to the correct position, which can be called the deviation rectification force. Due to the existence of this deviation rectification force, the belt will never deviate from the pulley track within a certain range.

[0077] The magnitude of the deviation rectification force of the arc surface pulley 20 is related to the arc surface. However, the arc surface is also related to the service life of the belt 30. The steeper the arc surface, the smaller the relative contact surface between the belt 30 and the pulley 20, the greater the pressure, the faster the wear, and the lower the service life of the belt 30. Therefore, in order to apply this pulley 20, a selection method needs to be found, which can ensure that the pulley does not deviate in different application environments, and the service life of the belt meets the annual requirements.

[0078] Therefore, as Figure 5 shown, the present invention also discloses a selection method for a pulley with an automatic deviation rectification function, which includes the following steps:

[0079] Step 1: Define the operating state and a single operating cycle, and set the operating distance S, operating time T, and acceleration time T 1 ;

[0080] Step 2: Obtain three external forces within the operating cycle: load force F g , inertial force F f , and initial tension force F t .

[0081] The maximum inertial force F f within the operating cycle is:

[0082]

[0083] where S is the single-cycle operating length, and F g is the load force.

[0084] The initial tension force F t of the belt is:

[0085]

[0086] where T d is the bending load, L is the shaft spacing, C is the compensation coefficient, d p is the diameter of the small pulley, D p is the diameter of the large pulley (the large and small pulleys refer to belt pulleys). These values need to be calculated and selected in advance. Except for the bending load, there are relatively complete calculation formulas for these other data, so they will not be elaborated here. The value of the bending load is related to the belt material, model, etc., and needs to be selected from the database.

[0087] Step 3: Calculate the tight-side tension F g , slack-side tension F f , resultant force of the tight side F t , and resultant force of the slack side F N1 , N2 , 1 , 2 .

[0088] Specifically,

[0089] Based on the inertial force F f , load force F g , and initial tension force F t , the tight-side tension of the belt is derived as:

[0090]

[0091] The slack-side tension of the belt is:

[0092] ​​​

[0093] When FN2 < 0, FN2 shall be taken as 0.

[0094] Then, calculate the tight-side supporting force:

[0095]

[0096] Slack-side supporting force:

[0097]

[0098] where α is the offset angle and also the tangent angle of the pulley radian, as shown in Figure 4 the figure.

[0099] According to Figure 4 the force analysis, the tight-side frictional force can be calculated:

[0100]

[0101] Slack-side frictional force:

[0102]

[0103] where μ is the dynamic friction coefficient of the pulley.

[0104] Finally, calculate the tight-side resultant force:

[0105]

[0106] Slack-side resultant force:

[0107]

[0108] Step 4. According to the tight-side tension F N1 , slack-side tension F N2 , tight-side resultant force F 1 , slack-side resultant force F 2 calculated in Step 3, and combined with the contact surface coefficients A 1 , B 1 and the error resultant deflection angle β, calculate the maximum restoring force F max and the maximum offset force F 偏 .

[0109] Maximum restoring force:

[0110] F max = |A 1 - B 1 |(F 1 + F 2 )

[0111] And the maximum offset force

[0112]

[0113] Among them, A 1 and B 1 are both contact surface coefficients, which are selected from the database or can be obtained by calculation. For the same working condition, the sum of A 1 and B 1 is a fixed value (which can be set to 1). β is the error resultant deflection angle, and its value is related to factors such as machining error, assembly error, load, and material deformation. Generally, it is an empirical value or can be obtained by calculation and simulation.

[0114] Step 6: Establish the inequality F max ≥F 偏 . If the inequality does not hold, reselect the contact surface coefficients A and B. If the inequality holds, output the calculation result of the inequality α≥α 1 .

[0115] Step 5: According to the load force F g , running distance S, acceleration time T 1 , running time T, and service condition factor KA, calculate the transmitted power P, and then select the belt type of the synchronous belt from the database according to the transmitted power P. There are also improvement methods for the calculation of this step, which will not be elaborated here.

[0116] Step 7: Look up the table and calculate according to the transmitted power P, number of teeth meshing of the small pulley Kz, reference width bs0, and reference rated power P0 in the database to select the belt width db.

[0117] Determine the synchronous belt material, and then find the wear ratio K b of this material to the pulley material in the database according to the force condition (the initial tension force, load force, and inertia force received by the synchronous pulley, and the synchronous belt is also the same. Based on these three forces, a rough surface pressure value can be obtained, and the wear ratio can be found in the database through the speed, surface pressure, and the materials of the two contact surfaces) and running speed (this value is a constant under the determined load and speed).

[0118] Determine the volume Vs of the selected synchronous belt with length s, and determine the service life n (i.e., the number of use cycles, and the life selection does not exceed the stable wear stage of the material. The running-in stage is not considered in the calculation, such as within the A-B section shown in Figure 6 ).

[0119] Step 8: Calculate the wear volume V and cumulative friction work ∑W of the synchronous belt according to the selection of the synchronous belt, belt width db, wear ratio kb, and number of use cycles n;

[0120] The wear volume is:

[0121]

[0122] Cumulative friction work:

[0123]

[0124] Step 9: Calculate the wear rate γ of the synchronous belt according to the wear volume V of the synchronous belt and the cumulative friction work ∑W.

[0125] The wear rate is:

[0126]

[0127] γ is the volume worn under certain load and speed conditions within a single cycle.

[0128] Step 10: Establish an inequality If the inequality does not hold, it means that the expected service life cannot be achieved, and the number of usage cycles n needs to be reselected for calculation; if the inequality holds, the calculation result α ≤ α 2 is obtained, and the contact surface coefficients A2 and B2 are reselected according to the wear volume V, and the maximum offset force F_offset and the maximum return force F_max after wear are recalculated.

[0129] Step 11: Establish an inequality F max ≥ F 偏 , if the inequality does not hold, the number of service life is reselected, if the inequality holds, the inequality calculation result α ≥ α 3 is obtained, and the two are combined to output the two inequality calculation results α 3 ≤ α ≤ α 2 .

[0130] Step 12: Combine the calculation result α ≥ α 1 obtained in Step 6 with the calculation result α 3 ≤ α ≤ α 2 obtained in Step 11, and output the final calculation result α 4 ≤ α ≤ α 2 , where α 4 = max{α 1 , α 3}.

[0131] Step 13: The pulley determines the offset angle α of the pulley according to the inequality α 4 ≤ α ≤ α 2 , thereby determining the arc surface structure of the pulley and completing the pulley selection.

[0132] To elaborate on the technical solution of the present invention, the following will take the pulley selection on the arm of an injection molding manipulator as an example for illustration.

[0133] As Figure 7Design a pulley that can run for at least five years without deviation according to its working status. Its parameters are shown in Table 1 below.

[0134]

[0135] Table 1

[0136] According to the parameters in Table 1, the initial belt tension F is calculated according to the formula t = 1404.8N; the maximum inertia force F f = 621.6N, and then the resultant force F on the tight side is calculated 1 = 2124.4N; the resultant force F on the slack side 2 = 0N.

[0137] Since the pulley width is 20mm and the belt width is 15mm, according to the working conditions, machining errors, and assembly errors, the contact surface coefficient A 1 = 0.825; B 1 = 0.175 can be obtained by querying in the database, and then the maximum restoring force F max = 1380.86(sinαcosα + 0.1cos 2 α) is calculated.

[0138] Since the upper and lower mounting plates are made of A3 and the middle mounting structural beam is made of T6-treated aluminum alloy, the deformation under force during operation can be simulated. Then, the error resultant angle β = 10° is selected in the database, and the maximum offset force F 偏 = 2124.4(sin(α - 10°)cos(α - 10°) + 0.1cos 2 (α - 10°)) is calculated.

[0139] By establishing the inequality F max ≥ F 偏 , taking integers, α ≥ 20° can be calculated.

[0140] Since the belt is made of polyurethane, the pulley material can be carbon steel, or POM, or aluminum alloy, etc. Considering the operating conditions, processing costs, etc., choosing POM material for mold opening is the most cost-effective way. The wear ratio K of the corresponding material is found in the database b = 0.1.

[0141] The wear volume V = 79.72cosα and the cumulative friction work ∑W = 1.08x10∧8 within the service life are calculated, and then the wear rate of the belt is calculated

[0142] Substituting into the inequality τ ≤ 0.02 and taking integers, α ≤ 46° can be obtained.

[0143] Find a new contact surface coefficient A again in the database through the wear volume V 2 = 0.788, B 2 = 0.212.

[0144] Rededuct the maximum self-aligning force F after wear according to the above steps max = 1223.65(sinαcosα + 0.1cos 2 α), the maximum offset force F 偏 = 2124.4(sin(α - 10°)cos(α - 10°) + 0.1cos 2 (α - 10°)).

[0145] By calculating the inequality F max ≥ F 偏 We get α ≥ 25°.

[0146] Summarizing all the results, we can get 25° ≤ α ≤ 46°

[0147] Select α = 30° for design, and the designed pulley size can be obtained as shown in the figure. Since the size is taken as an integer, the actual obtained angle α = 33° is also within the value range.

[0148] As mentioned above, it is only an embodiment of the present invention and does not impose any limitation on the technical scope of the present invention. Therefore, any minor modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for selecting a pulley with an automatic deviation rectification function, characterized in that: The pulley with an automatic deviation rectification function includes a bearing and a pulley sleeved outside the bearing, and the outer surface of the pulley is an arc surface structure; the method includes the following steps: Step 1, define the running state and a single running cycle, and set the running distance S, running time T, and acceleration time T 1 ; Step 2: Obtain three external forces during the operating cycle: load force F g , inertial force F f , and initial tension force F t ; Step 3: Calculate the tight-side tension force F g 、inertia force F f 、initial tension force F t to calculate the tight-side tension force F N1 、slack-side tension force F N2 、resultant force on the tight side F 1 、resultant force on the slack side F 2 ; Step 4: Based on the tight side tension F calculated in Step 3 N1 , slack side tension F N2 , resultant force of the tight side F 1 , resultant force of the slack side F 2 and combined with the contact surface coefficient and the error resultant deflection angle β, calculate the maximum self-aligning force F max and the maximum offset force F 偏 ; Step 6, establish the inequality F max ≥ F 偏 , if the inequality does not hold, reselect the contact surface coefficient, if the inequality holds, output the inequality calculation result α ≥ α 1 , where α is the offset angle; Step 5. According to the load force F g , running distance S, acceleration time T 1 , running time T, service factor KA, calculate the transmitted power P, and then select the belt type of the synchronous belt in the database according to the transmitted power P; Step 7: Look up and calculate in the database according to the transmission power P, the number of teeth meshing of the small pulley Kz, the reference width bs0, and the reference rated power P0 to select the belt width db; Determine the material of the synchronous belt, and find the wear amount ratio K of the pulley material for this material in the database according to the force condition and running speed b ; Determine the volume Vs of the timing belt for selection with a length of s, and determine the number of use cycles n; Step 8. Calculate the wear volume V and the cumulative friction work ∑W of the synchronous belt according to the selection of the synchronous belt, the bandwidth db, and the wear ratio K b and the number of use cycles n; Step 9: Calculate the wear rate γ of the timing belt according to the wear volume V of the timing belt and the cumulative friction work ΣW; Step 10: Establish an inequality If the inequality does not hold, it indicates that the expected service life cannot be achieved, and the number of usage cycles n is reselected for calculation; if the inequality holds, the calculation result α ≤ α 2 is obtained, and the contact surface coefficient is reselected according to the wear volume V, and the maximum offset force F_offset and the maximum return force F max after wear are recalculated; Step 11. Establish the inequality F max ≥F 偏 , if the inequality does not hold, reselect the usage cycle number; if the inequality holds, obtain the inequality calculation result α≥α 3 , combine the two and output the two inequality calculation results α 3 ≤α≤α 2 ; Step 12: Combine the calculation result α≥α obtained in Step 6 1 with the calculation result α 3 ≤α≤α 2 obtained in Step 11, and output the final calculation result α 4 ≤α≤α 2 , where α 4 = max{α 1 ,α 3}; Step 13. The pulley determines the offset angle α of the pulley according to the inequality α 4 ≤α≤α 2 to determine the arc surface structure of the pulley, thereby completing the selection of the pulley.

2. The selection method according to claim 1, characterized in that: In the said step 2, The maximum inertial force F during the operating cycle f is as follows: Among them, S is the single-cycle operation length, and F g is the load force; Initial belt tension F t is: Among them, T d is the bending load, L is the shaft spacing, C is the compensation coefficient, d p is the diameter of the pinion, D p is the diameter of the big wheel.

3. The selection method according to claim 2, characterized in that: The calculation in the said step 3 is specifically as follows: According to the inertial force F f , the load force F g , and the initial tension force F t , the belt tight-side tension is derived as follows: Tension of the loose side of the belt: When F N2 < 0, it is necessary to take F N2 = 0; Calculate the support force of the tight side: Support force of the loose side: Calculate the friction force of the tight side: Friction force of the loose side: where μ is the dynamic friction coefficient of the pulley; Finally calculate the resultant force of the tight side: Resultant force of the loose side:

4. The selection method according to claim 3, characterized in that: In the said step 4, The maximum rectification force is: F max = |A 1 - B 1 | (F 1 + F 2 ) The maximum deviation force is: where A 1 and B 1 are both contact surface coefficients, and β is the error resultant declination angle.

5. The selection method according to claim 4, characterized in that: In the said step 8, The wear volume is: The cumulative friction work is:

6. The selection method according to claim 5, characterized in that: In the said step 9, The wear rate is: γ is the volume worn under certain load and speed conditions within a single cycle.

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