QC/T 291-2023Performance requirements and bench test methods for automotive mechanical transfer case assemblies (English PDF)

3.1 Static shift force

Shifting is performed without the transfer case running, and the axial force acting on the gear sleeve during the shifting process.

3.2 Dynamic shift force

Shifting is performed with the transfer case running, and the axial force acting on the gear sleeve during the shifting process.

3.3 Shifting time

The time that is taken to shift from transfer case neutral to the transfer case target gear.

3.4 Maximum test torque of transfer case assembly

The maximum test torque of the transfer case assembly is the smaller OF the product of the maximum torque of the engine and the first gear ratio of the transmission that matches the transfer case AND the maximum wheel adhesion torque converted to the input shaft of the transfer case. The force direction is the same as the forward direction of the actual vehicle.

When the transfer case has only one gear, the maximum test torque of the transfer case assembly is expressed by Mmax. When the transfer case has two gears, high and low, the maximum test torque of the high gear of the transfer case is expressed by MHmax, and the maximum test torque of the low gear of the transfer case is expressed by MLmax.

4.1 Static shift force and static shifting time

The test shall be conducted according to the method specified in 5.1. The static shift force and static shifting time indicators shall meet the product technical requirements.

4.2 Dynamic shift force and dynamic shifting time

The test shall be conducted according to the method specified in 5.2. The dynamic shift force and dynamic shifting time indicators of the transfer case shall meet the product technical requirements.

4.3 Fatigue life of the shift actuator bench

The test shall be conducted according to the method specified in 5.3.

4.4 Transmission efficiency of the transfer case

The test shall be conducted according to the method specified in 5.4. The transfer case transmission efficiency shall meet the product technical requirements.

4.5 Lubrication of the transfer case

The test shall be conducted according to the method specified in 5.5. The components involved in the transmission shall have obvious lubricating oil infiltration.

4.6 Sealing of the transfer case

The test shall be conducted according to the method specified in 5.6. During the test, there shall be no oil seepage or oil leakage in the transfer case.

4.7 Temperature rise of the transfer case

The test shall be carried out according to the method specified in 5.7. During the test, the maximum oil temperature of the lubricant shall meet the requirements of the product technical conditions; and the lubricant temperature-time curve shall be smooth without mutation.

4.8 Noise of the transfer case

The test shall be carried out according to the method specified in 5.8. The maximum allowable noise sound pressure level of the gear transfer case (a transfer case that mainly uses a gear pair as a power transmission device between the input shaft and the output shaft) is 91dB (A). The maximum allowable noise sound pressure level of the chain transfer case (a transfer case that mainly uses a sprocket chain pair as a power transmission device between the input shaft and the output shaft) is 93dB (A).

4.9 Static torsional strength of the transfer case

The test shall be completed according to the method specified in 5.9. The static torsional reserve coefficient of the transfer case shall meet the requirements of the product technical conditions, but the minimum value shall be no less than 1.8.

5.1 Test on static shift force and static shifting time

5.1.1 Test sample

5.1.1.1 The test sample is a transfer case with high and low gears.

5.1.1.2 The test sample shall meet the requirements of the design drawings and the number shall be no less than 2.

5.1.2 Test equipment and devices

5.1.2.1 The test equipment can perform the shift action of the transfer case and measure the shift force, shifting time, gear position and other information during the shift process. Thereof, the sampling frequency of the shift force, shifting time and gear position information shall be no less than 100 Hz.

5.1.2.2 The test device can simulate the moments of inertia on the input end and the output end of the transfer case.

5.1.2.3 The measuring device of the test equipment can measure the static shift force. The maximum allowable error of measuring the static shift force shall be within the range of ±5%.

NOTE: The shift force can be measured by attaching a strain gauge to the shift fork, or by other methods such as using a force sensor to measure the force acting on the shift rocker arm, and then converting the transmission lever ratio between the shift sleeve and the shift rocker arm force measuring point to the shift sleeve to calculate the shift force.

5.1.3 Test methods

5.1.3.1 Install the sample on the test bench, and the posture after installation shall be consistent with the design posture.

5.1.3.2 Adjust the moments of inertia on the input end and output end of the transfer case so that the moment of inertia on the input end of the transfer case is equivalent to the moment of inertia between the input shaft of the transfer case and the neutral gear of the transmission; and the moment of inertia on the output end of the transfer case is equivalent to the moment of inertia of the whole vehicle converted to the output end of the transfer case.

5.1.3.3 Put the transfer case in neutral and randomly rotate the input shaft or output shaft for several turns before shifting.

5.1.3.4 When the input and output ends of the transfer case are stationary, the target test gear shall be connected; and the relationship curve between the shift force and the shifting time during the shifting process shall be recorded.

5.1.3.5 The target test gear is connected to the neutral gear.

5.1.3.6 When the input and output ends of the transfer case are stationary, another target test gear shall be connected; and the static shift test is carried out in the order of 5.1.3.3 to 5.1.3.5. The shifting process can be tested by alternating shifting or unidirectional shifting.

5.1.3.7 Record the relationship curve between the shift force and the shifting time during the shifting process.

5.1.3.8 The static shift test of each gear shall be no less than 3 times.

5.1.4 Processing of test results

5.1.4.1 The maximum shift force in the relationship curve between the shift force and the shifting time is taken as the maximum static shift force of the gear.

5.1.4.2 The maximum shifting time in the relationship curve between shift force and shifting time is taken as the maximum static shifting time; and the minimum shifting time in the relationship curve between shift force and shifting time is taken as the minimum static shifting time.

5.2 Test on dynamic shift force and dynamic shifting time

5.2.1 Test sample

5.2.1.1 The test sample is a transfer case with high and low gears.

5.2.1.2 The test sample shall meet the requirements of the design drawings and the number shall be no less than 2.

5.2.2 Test equipment and devices

5.2.2.1 The test equipment can perform the shift action of the transfer case; and can measure the shift force, shifting time, gear information, input shaft and output shaft speed of the transfer case and other information during the shifting process. Thereof, the sampling frequency of the shift force, shifting time and gear information shall be no less than 100Hz.

5.2.2.2 The maximum allowable error of measuring dynamic shift force shall be within ±5%.

NOTE: The shift force can be measured by attaching a strain gauge to the shift fork; or by other methods such as using a force sensor to measure the force acting on the shift rocker arm; and then converting the transmission lever ratio between the shift sleeve and the shift rocker arm force measuring point to the shift sleeve to calculate the shift force.

5.2.2.3 The test equipment can determine whether the transfer case shift is successful.

5.2.2.4 The test equipment can simulate the moments of inertia on the input end and the output end of the transfer case.

5.2.2.5 The test equipment can drive the output end of the transfer case to operate; and the maximum control error of the speed of the driving device shall be within the range of ±5 r/min.

5.2.2.6 The maximum allowable error of the speed measuring device of the test equipment shall be within the range of ±1 r/min.

5.2.3 Test methods

5.2.3.1 Install the sample on the test bench. The posture after installation shall be consistent with the design posture.

5.2.3.2 Adjust the rotational moments of inertia on the input end and output end of the transfer case so that the moment of inertia on the input end of the transfer case is equivalent to the rotational moment of inertia between the input shaft of the transfer case and the neutral gear of the transmission; and the rotational moment of inertia on the output end of the transfer case is equivalent to the moment of inertia of the whole vehicle converted to the output end of the transfer case.

5.2.3.3 When the input end and output end of the transfer case are stationary, the target test gear shall be connected.

5.2.3.4 Adjust the output speed of the transfer case so that the output speed of the transfer case is equal to the minimum design speed corresponding to the target test gear and run for at least 3s.

5.2.3.5 Switch from the target test gear to the neutral gear.

5.2.3.6 Switch from the neutral gear to another target test gear after running for at least 1s.

5.2.3.7 Carry out the shift test in the order of 5.2.3.4 to 5.2.3.6. The shifting process can be tested by alternating shift or unidirectional shift.

5.2.3.8 Repeat 5.2.3.4 to 5.2.3.6 at least 3 times.

5.2.3.9 Record the relationship curve between the shift force and the shifting time during the shifting process.

5.2.4 Processing of test results

5.2.4.1 The maximum shift force in the relationship curve between the shift force and the shifting time is taken as the maximum dynamic shift force of the gear.

5.2.4.2 The maximum shifting time in the relationship curve between the shift force and the shifting time is taken as the maximum dynamic shifting time of the gear; and the minimum shifting time in the relationship curve between the shift force and the shifting time is taken as the minimum dynamic shifting time of the gear.

5.3 Test on fatigue life of the shift actuator bench

5.3.1 Test sample

5.3.1.1 The test sample is a transfer case with high and low gears.

5.3.1.2 The test sample shall meet the requirements of the design drawings, and the number of samples shall be no less than 2.

5.3.2 Test equipment and devices

5.3.2.1 The test equipment can complete the shifting action of the transfer case and determine whether the transfer case shifting is successful.

5.3.2.2 The test equipment can drive the transfer case output end to operate after the transfer case shifts; and the maximum speed control error of the driving device shall be within the range of ±5 r/min.

5.3.2.3 The oil temperature control device of the test equipment can ensure that the lubricant temperature is maintained in the range of 60 °C~90 °C during the shifting process of the transfer case. During a single test, the lubricant temperature fluctuation range is ±5 °C.

5.3.2.4 The maximum allowable error of the oil temperature measuring device shall be within the range of ±1 °C.

5.3.2.5 The test equipment can simulate the moments of inertia on the input end and the output end of the transfer case.

5.3.2.6 The maximum allowable error of the speed measuring device shall be within the range of ±1 r/min.

5.3.2.7 The lubrication system of the test equipment can ensure that the gears, shafts, bearings and other parts inside the transfer case are fully lubricated during the shifting process.

5.3.3 Test methods

5.3.3.1 Test methods for fatigue life of the shift actuator bench of the transfer case with synchronizer

5.3.3.1.1 Fill lubricant according to product technical requirements and install the temperature sensor on the drain plug.

5.3.3.1.2 Install the sample on the test bench. The posture after installation shall be consistent with the design posture.

5.3.3.2 Test method for fatigue life of the shift actuator bench of the electronically controlled and pneumatic mechanical transfer case

5.3.3.2.1 Add lubricant according to the technical requirements of electronically controlled and pneumatic mechanical transfer cases and install the temperature sensor on the drain plug.

NOTE: The electronically controlled mechanical transfer case is a transfer case that changes the gear meshing position in the transfer case through the electronically controlled actuator, thereby changing the transmission ratio or transmission mode to achieve the purpose of speed change. Pneumatic mechanical transfer case is a transfer case that changes the gear meshing position in the transfer case through a pneumatic actuator, thereby changing the transmission ratio or transmission mode to achieve the purpose of speed change.

5.3.3.2.2 Install the sample on the test bench; and the posture after installation shall be consistent with the design posture.

5.3.3.2.3 Adjust the rotational moment of inertia on the input end and output end of the transfer case so that the moment of inertia on the input end of the transfer case is equivalent to the rotational moment of inertia between the input shaft of the transfer case and the neutral gear of the transmission; and the rotational moment of inertia on the output end of the transfer case is equivalent to the moment of inertia of the whole vehicle converted to the moment of inertia on the output end of the transfer case.

5.3.4 Processing of test results

5.3.4.1 When the number of shifting cycles reaches the number of cycles specified in the technical requirements, the shift actuator of the transfer case shall not appear the damage that affects the shifting performance.

5.3.4.2 For the shift actuator of the transfer case with synchronizer, the synchronizer shall not fail in any form; and the synchronizer ring axial clearance shall be no less than the designed limit value.

5.4 Test on transmission efficiency of the transfer case

5.4.1 Test sample

The test sample shall meet the requirements of the design drawing and the number shall be no less than 1.

5.4.2 Test equipment and devices

5.4.2.1 The transfer case transmission efficiency test bench or similar device, the maximum allowable error of the equipment speed control shall be within the range of ±5 r/min; and the maximum allowable error of the torque control shall be within the range of ±2%.

5.4.2.2 There is a lubricant temperature controlling device.

5.4.3 Test methods

5.4.3.1 Fill the specified lubricant according to the product technical requirements and install the temperature sensor on the drain plug.

5.4.3.2 Install the sample on the test bench; and the posture after installation shall be consistent with the design posture.

5.4.3.3 When the transfer case has two gears, high and low, the transfer case is connected to high gear.