A method for detecting a starting torque of a gear box

Abstract

A kind of gear box starting torque detection method, gear box starting torque includes intermediate shaft bearing starting torque and differential bearing starting torque, in the normal working state of gear box, by measuring the current value of gear box input end and the current value of output end, then according to the accompanying loss power of gear box and transmission ratio, to determine intermediate shaft bearing starting torque and differential bearing starting torque.The present application solves the technical problem that in the prior art, in the normal working state of gear box, only the starting torque of gear box assembly input end and the starting torque of gear box assembly output end can be determined, and the pre-tightening of specific intermediate shaft bearing and differential bearing cannot be accurately determined;And the detected torque value is more accurate, also does not need to invest complex tooling and instrument, can save cost.

Description

Technical Field

[0001] This invention relates to new energy vehicles, and more specifically to a method for detecting the starting torque of a gearbox in a new energy vehicle. Background Technology

[0002] Excessive preload in a tapered bearing leads to increased wear and shortens its service life. Conversely, insufficient preload can cause shaft misalignment and movement, affecting the normal operation of the gearbox. Therefore, strict requirements apply to the preload of each tapered bearing.

[0003] When a tapered bearing is subjected to an axial external force, it will generate an axial preload, thus balancing the axial force with the external force. Different axial preloads correspond to different axial forces, and at a certain input shaft speed, different axial forces correspond to different rotational friction torques. Furthermore, the relationship between axial force and rotational friction torque is different at different input shaft speeds. The preload of the tapered bearing in the gearbox of an electric drive assembly generally needs to be tested with a starting torque after assembly to ensure that the preload is within the required range for the tapered bearing.

[0004] The preload of the tapered bearings in the gearbox of an electric drive assembly is typically checked after assembly using a torque wrench to determine if the preload is within the required range. However, this method is cumbersome, requires specialized tooling, and necessitates recording the maximum value, which can lead to inaccurate readings. Currently, the gearbox's starting torque is measured using a torque wrench, rotating the planetary gear shaft on the differential at a constant speed, and recording the maximum torque reading on the wrench. Existing testing methods have the following drawbacks:

[0005] 1. The magnitude of torque is related to the rotational speed of the object being measured. The greater the acceleration, the greater the torque value, which cannot reflect the true torque when the bearing is preloaded.

[0006] 2. The tested speed of the tapered bearing can only be a low speed achievable by hand rotation and cannot be applied to the speeds of various tapered bearings under normal operating conditions.

[0007] 3. When both the intermediate shaft and the differential use tapered bearings, the measured starting torque is the sum of the tapered bearing torques of the two shafts. It can only determine the total starting torque and cannot accurately determine whether the preload of the specific intermediate shaft bearing and differential bearing meets the standard. Summary of the Invention

[0008] The technical problem to be solved by this invention is: how to detect the starting torque of the intermediate shaft bearing and the starting torque of the differential bearing under normal gearbox conditions, so as to accurately determine whether the preload of the specific intermediate shaft bearing and differential bearing meets the standard.

[0009] To address the above problems, the technical solution proposed by this invention is: a method for detecting the starting torque of a gearbox, wherein the starting torque of the gearbox includes the starting torque of the intermediate shaft bearing and the starting torque of the differential bearing. Under normal operating conditions of the gearbox, the starting torque of the intermediate shaft bearing and the starting torque of the differential bearing are determined by measuring the input current value and the output current value of the gearbox, and then based on the associated power loss and transmission ratio of the gearbox.

[0010] Preferably, the determination of the gearbox starting torque includes the following steps:

[0011] a) Keep the gearbox in normal working condition and keep the input shaft running at low speed;

[0012] b) First, determine the starting torque at the input end and the starting torque at the output end of the gearbox assembly by measuring the input current value, the output current value, and the power loss of the gearbox.

[0013] c) Then, determine the starting torque of the intermediate shaft bearing and the starting torque of the differential bearing based on the starting torque at the input end of the gearbox assembly, the starting torque at the output end of the gearbox assembly, the transmission ratio from the input shaft to the intermediate shaft, and the transmission ratio from the intermediate shaft to the differential shaft.

[0014] d) When the gearbox is operating normally and the input shaft is at high speed: repeat steps b and c.

[0015] Preferably, in step b, the input current value and the power loss of the gearbox are measured first, and then the starting torque of the gearbox assembly output is determined according to formula (1);

[0016] ;

[0017] In formula (1), I 出 U is the output current, U is the voltage of the drive motor, and P is the output current. 损 The power loss due to gearbox loss is denoted by n1, where n1 is the speed of the input shaft at low speeds under normal gearbox operation, i1 is the transmission ratio from the input shaft to the intermediate shaft, i2 is the transmission ratio from the intermediate shaft to the differential shaft, and M is the transmission ratio from the intermediate shaft to the differential shaft. 出 This refers to the starting torque at the output end of the gearbox assembly.

[0018] In formula (1), only the starting torque M at the output end of the gearbox assembly is considered. 出 Since it is an unknown quantity, the starting torque M at the output end of the gearbox assembly can be calculated according to formula (1). 出 .

[0019] Preferably, the gearbox-related power loss P in formula (1) is measured by running the gearbox without load.

[0020] Preferably, in step b, the starting torque at the input end of the gearbox assembly is determined according to formula (2);

[0021] ;

[0022] In formula (2), I 入 The input current is the starting torque M at the input of the gearbox assembly. 入 Since it is an unknown quantity, the starting torque M at the input end of the gearbox assembly can be calculated according to formula (2). 入 .

[0023] Preferably, in step c, the relationship between the starting torque at the output end of the gearbox assembly, the starting torque of the intermediate shaft bearing, and the starting torque of the differential bearing is shown in formula (3).

[0024] ;

[0025] In formula (3), M 中 M is the starting torque of the intermediate shaft bearing. 差 This refers to the starting torque of the differential bearing.

[0026] Preferably, in step c, the relationship between the starting torque at the input end of the gearbox assembly, the starting torque of the intermediate shaft bearing, and the starting torque of the differential bearing is shown in formula (4).

[0027] ;

[0028] In formula (4), i1 is the transmission ratio from the input shaft to the intermediate shaft; i2 is the transmission ratio from the intermediate shaft to the differential shaft.

[0029] Preferably, since the starting torque M at the output end of the gearbox assembly has already been obtained in formulas (1) and (2), 出 Starting torque M at the input end of the gearbox assembly 入 Therefore, the starting torque M of the intermediate shaft bearing in step c can be determined according to formulas (3) and (4). 中 and differential bearing starting torque M 差 .

[0030] Preferably, under normal gearbox operating conditions and when the input shaft is at high speed, the speed n2 of the input shaft at high speed is used to replace n1 in formulas (1) and (2) to calculate the starting torque at the input end of the gearbox assembly and the starting torque at the output end of the gearbox assembly; then, based on the starting torque at the input end of the gearbox assembly, the starting torque at the output end of the gearbox assembly, the transmission ratio from the input shaft to the intermediate shaft, and the transmission ratio from the intermediate shaft to the differential shaft, the starting torque of the intermediate shaft bearing and the starting torque of the differential bearing are determined.

[0031] The beneficial technical effects of this invention are:

[0032] 1. The starting torque at the input end and the starting torque at the output end of the gearbox assembly are determined by measuring the input current value, the output current value, and the power loss of the gearbox. Compared with the existing method of using a torque wrench and special tooling, the torque value detected by this invention is more accurate and does not require complex tooling and instruments, thus saving costs.

[0033] 2. The starting torque of the intermediate shaft bearing and the starting torque of the differential bearing are determined by formulas based on the starting torque at the input and output ends of the gearbox assembly, the transmission ratio from the input shaft to the intermediate shaft, and the transmission ratio from the intermediate shaft to the differential shaft. This solves the technical problem in the prior art where, under normal gearbox operating conditions, only the starting torque at the input and output ends of the gearbox assembly can be determined, but the preload of specific intermediate shaft bearings and differential bearings cannot be accurately determined.

[0034] 3. This invention only requires measuring the current and voltage values ​​of the drive motor and then applying the formula to quickly and accurately determine whether the preload of the intermediate shaft bearing and differential bearing meets the standard, thus improving the efficiency of the test. Attached Figure Description

[0035] Figure 1 This is a flowchart of the gearbox starting torque detection process in Example 1;

[0036] Figure 2 This is a diagram showing the relationship between the axial force and preload of a tapered bearing.

[0037] Figure 3 This diagram shows the relationship between the axial force and rotational friction torque of a tapered bearing at different speeds. Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments and accompanying drawings:

[0039] like Figure 2 and Figure 3 As shown, taking the tapered bearing 30208 as an example, after being subjected to axial external force, the tapered bearing will generate axial preload, thereby balancing the axial force and the external force. From Figure 2 It can be seen that different axial preload amounts correspond to different axial forces. From... Figure 3 As can be seen, at a certain input shaft speed, the tapered bearing corresponds to different rotational friction torques under different axial forces. Furthermore, the relationship between axial force and rotational friction torque varies at different input shaft speeds. Example 1

[0040] In this embodiment, both the intermediate shaft and the differential of the gearbox use tapered bearings. The starting torque measured with a conventional torque wrench is the sum of the tapered bearing torques of both shafts, which can only determine the total starting torque and cannot accurately determine whether the preload of the specific intermediate shaft bearing and differential bearing meets the standard. Therefore, it is necessary to determine the starting torque values ​​of the intermediate shaft bearing and the differential shaft under normal gearbox operating conditions and at different input shaft speeds. Then, based on the correspondence between starting torque, axial force, and preload, the precise preload of the specific intermediate shaft bearing and differential bearing can be determined to ensure normal gearbox operation and extend the service life of the intermediate shaft bearing and differential bearing.

[0041] like Figure 1 As shown, the gearbox starting torque includes the intermediate shaft bearing starting torque and the differential shaft starting torque. The specific steps for determining the gearbox starting torque are as follows:

[0042] First, we keep the gearbox in normal working condition and run the input shaft at a low speed;

[0043] Formula (1) is as follows:

[0044] ;

[0045] In formula (1), I 出 U is the output current, U is the voltage of the drive motor, and P is the output current. 损 The power loss due to gearbox loss is denoted by n1, where n1 is the speed of the input shaft at low speeds under normal gearbox operation, i1 is the transmission ratio from the input shaft to the intermediate shaft, i2 is the transmission ratio from the intermediate shaft to the differential shaft, and M is the transmission ratio from the intermediate shaft to the differential shaft. 出 This refers to the starting torque at the output end of the gearbox assembly.

[0046] Because the output current I 出 The voltage U of the drive motor and the speed n1 of the input shaft at low speed can be directly measured. The transmission ratio i1 from the input shaft to the intermediate shaft and the transmission ratio i2 from the intermediate shaft to the differential shaft are known quantities. The power loss P of the gearbox is also known. 损 This can be measured when the gearbox is running without load. Therefore, only M in formula (1) 出 An unknown quantity can be used to determine the starting torque M at the output end of the gearbox assembly according to formula (1). 出 It was calculated accurately.

[0047] Formula (2) is as follows:

[0048] ;

[0049] In formula (2), I 入 The input current can be directly measured. M 入For the starting torque at the input end of the gearbox assembly, refer to the known parameters in formula (1). Since only the starting torque M at the input end of the gearbox assembly is... 入 Since it is an unknown quantity, in step b, the starting torque M at the input end of the gearbox assembly can be calculated according to formula (2). 入 .

[0050] Formulas (3) and (4) are as follows:

[0051] ;

[0052] In formulas (3) and (4), M 中 M is the starting torque of the intermediate shaft bearing. 差 M is the starting torque of the differential bearing. 出 M 入 Please refer to the explanations in formulas (1) and (2) for i1 and i2.

[0053] Since the starting torque M at the output end of the gearbox assembly has already been obtained in formulas (1) and (2), 出 Starting torque M at the input end of the gearbox assembly 入 The value of M. Therefore, based on equations (3) and (4), the two variables M can be solved. 中 and M 差 The value, that is: can determine the starting torque M of the intermediate shaft bearing in step c. 中 and differential bearing starting torque M 差 .

[0054] like Figure 2 and Figure 3 As shown, we can determine the range of axial force of the intermediate shaft bearing based on the specific requirements of the intermediate shaft bearing preload. Then, based on this range of axial force, we can determine the required starting torque M of the intermediate shaft bearing. 中 Similarly, the range of values ​​for M can be used to determine the required starting torque M of the differential bearing. 差 The range of values ​​for .

[0055] If the actual measured starting torque M of the intermediate shaft bearing 中 and differential bearing starting torque M 差 If the requirements are not met, the preload, axial force, and starting torque of the intermediate shaft bearing and differential bearing are changed by replacing the preload shims of different thicknesses in these bearings. Then, the above measurement and calculation process is repeated to obtain the new intermediate shaft bearing starting torque M. 中 and differential bearing starting torque M 差 Until the starting torque M of the new intermediate shaft bearing 中 and differential bearing starting torque M差 Meets the requirements.

[0056] Thus, we have obtained M under normal gearbox operating conditions and with the input shaft meeting the requirements at low speeds. 中 and M 差 Then, we keep the gearbox in normal operating condition and run the input shaft at high speed, and repeat the above testing process to obtain the required M value when the input shaft is running at high speed. 中 and M 差 .

[0057] In summary, determining the starting torque of the gearbox involves the following steps:

[0058] a) Keep the gearbox in normal working condition and allow the input shaft to run at low speed;

[0059] b) First, determine the starting torque at the input end and the starting torque at the output end of the gearbox assembly by measuring the input current value, the output current value, and the power loss of the gearbox;

[0060] c) Then, determine the starting torque of the intermediate shaft bearing and the starting torque of the differential bearing based on the starting torque at the input end of the gearbox assembly, the starting torque at the output end of the gearbox assembly, the transmission ratio from the input shaft to the intermediate shaft, and the transmission ratio from the intermediate shaft to the differential shaft.

[0061] d) When the gearbox is operating normally and the input shaft is at high speed: repeat steps b and c.

[0062] By repeatedly testing under normal gearbox conditions and at both low and high input shaft speeds, and by replacing preload shims of different thicknesses, the starting torque M of the intermediate shaft bearing was determined. 中 and differential bearing starting torque M 差 Continue until the starting torque Mneutral of the intermediate shaft bearing and the starting torque Mdifference of the differential bearing both meet the requirements at both low and high input shaft speeds.

[0063] Obviously, any improvements or modifications made without departing from the principles described in this invention should be considered within the scope of protection of this invention.

Claims

1. A method for detecting the starting torque of a gearbox, wherein the starting torque of the gearbox includes the starting torque of the intermediate shaft bearing and the starting torque of the differential bearing, characterized in that, Determining the starting torque of the gearbox involves the following steps: a) Keep the gearbox in normal working condition and keep the input shaft running at low speed; b） ； In formula (1), I 出 U is the output current, U is the voltage of the drive motor, and P is the output current. 损 The gearbox has associated power loss, and the gearbox has associated power loss P. 损 The speed is measured by running the gearbox under no load. n1 is the speed of the input shaft at low speed under normal gearbox operating conditions; i1 is the transmission ratio from the input shaft to the intermediate shaft; i2 is the transmission ratio from the intermediate shaft to the differential shaft; M... 出 This refers to the starting torque at the output end of the gearbox assembly. First, measure the output current value and the power loss of the gearbox. In formula (1), only the starting torque M at the output of the gearbox assembly is considered. 出 Since it is an unknown quantity, the starting torque M at the output end of the gearbox assembly can be calculated according to formula (1). 出 ; c) Then, determine the starting torque of the intermediate shaft bearing and the starting torque of the differential bearing based on the starting torque at the input end of the gearbox assembly, the starting torque at the output end of the gearbox assembly, the transmission ratio from the input shaft to the intermediate shaft, and the transmission ratio from the intermediate shaft to the differential shaft. ； In formula (2), I 入 P is the input current, U is the voltage of the drive motor; 损 The power loss of the gearbox is n1, which is the speed of the input shaft when the gearbox is running at low speed under normal operating conditions. First, measure the input current value and the power loss of the gearbox. Since only the starting torque M at the input end of the gearbox assembly is in formula (2), 入 Since it is an unknown quantity, the starting torque M at the input end of the gearbox assembly can be calculated according to formula (2). 入 ; d) When the gearbox is operating normally and the input shaft is at high speed: repeat steps b and c; In step c, the relationship between the starting torque at the output end of the gearbox assembly, the starting torque of the intermediate shaft bearing, and the starting torque of the differential bearing is shown in formula (3). ； In formula (3), M 出 Starting torque at the output end of the gearbox assembly ， M 中 i1 is the starting torque of the intermediate shaft bearing, i2 is the transmission ratio from the intermediate shaft to the differential shaft, and M is the starting torque of the intermediate shaft bearing. 差 This refers to the starting torque of the differential bearing. The relationship between the starting torque at the input end of the gearbox assembly, the starting torque of the intermediate shaft bearing, and the starting torque of the differential bearing is shown in formula (4). ； In formula (4), M 入 Starting torque at the input end of the gearbox assembly ， i1 is the transmission ratio from the input shaft to the intermediate shaft; i2 is the transmission ratio from the intermediate shaft to the differential shaft, M 中 M is the starting torque of the intermediate shaft bearing. 差 This refers to the starting torque of the differential bearing.

2. The method for detecting the starting torque of a gearbox according to claim 1, characterized in that, Since the starting torque M at the output end of the gearbox assembly has already been obtained in formulas (1) and (2), 出 Starting torque M at the input end of the gearbox assembly 入 Therefore, the starting torque M of the intermediate shaft bearing in step c can be determined according to formulas (3) and (4). 中 and differential bearing starting torque M 差 .

3. The method for detecting the starting torque of a gearbox according to claim 2, characterized in that, Under normal operating conditions of the gearbox and when the input shaft is at high speed, replace n1 in formulas (1) and (2) with the speed n2 of the input shaft at high speed to calculate the starting torque at the input end of the gearbox assembly and the starting torque at the output end of the gearbox assembly; then determine the starting torque of the intermediate shaft bearing and the starting torque of the differential bearing based on the starting torque at the input end of the gearbox assembly, the starting torque at the output end of the gearbox assembly, the transmission ratio from the input shaft to the intermediate shaft, and the transmission ratio from the intermediate shaft to the differential shaft.

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