When designing a gearbox, we should pay attention to the following points?


Release time:

2022-12-26

The gearbox is an indispensable part of the transmission. It is mainly used to support the gear shaft to ensure that the gear can transmit speed and torque normally. When designing a gearbox, we should pay attention to the following points?

The gearbox is an indispensable part of the transmission. It is mainly used to support the gear shaft to ensure that the gear can transmit speed and torque normally. When designing a gearbox, we should pay attention to the following points?

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1. Total wall thickness of shell

Depending on the type of casting, the wall thickness is also different. If it is low pressure casting, the wall thickness should be 6-8mm. If it is high-pressure casting, the wall thickness can be thinner, only 3.5-5mm. In the design, the wall thickness should be as uniform as possible to better reduce the occurrence of die casting defects.

2. Draft direction and draft angle.

When designing the gearbox, we should also pay attention to the drawing direction of the shell. We should try to use up and down demoulding to reduce the use of sliders. The stretch angle is typically 1.5 degrees. However, if the cavity is too deep, we need to increase the stretching angle to facilitate demoulding.

3. Bearing hole design

Bearing hole wall thickness is generally 6-8mm. If the bearing hole is subjected to greater force and deformation, it can be appropriately thickened. Attention should also be paid to the lubrication of the bearing and the reasonable arrangement of the oil passage. When arranging the oil passage, the position of the oil inlet should be preliminarily arranged according to the oil stirring direction of the gear. The position of the oil inlet can then be adjusted according to the lubrication simulation results.

4. Gearbox closed surface design

The width of the closed surface is greater than 10mm, the thickness is greater than 10mm, and the positions of bolt holes and pin holes are greater than 6mm. The closed surface needs to be designed with a sol tank, usually 1.5 (wide) x 30 degrees.

5. Bolt hole design

The bolt is generally arranged in the middle of the closed surface of the box. Try to make sure that the center of two adjacent bolts are connected in the joint plane. The distance between two bolts shall not exceed 65mm. The actual arrangement can be adjusted according to the seal analysis.

6. Magnetic slot design

The magnet should be located under the gearbox, and the gap between the magnet and the housing should be as small as possible to prevent the magnet from shaking too much, which may cause damage to the magnet. In general, it is sufficient to ensure that the gap between the magnet and the case is 0.5mm.

7. Vlast plug

The vent plug should be placed on the top of the gearbox and, as far as possible, in a position where the oil is not easily accessible. The inside of the shell should also be designed with corresponding oil retaining structure to prevent lubricating oil from spraying out from the vent plug.

8. Ribbed plate design

Firstly, the wall thickness of the ribs should correspond as much as possible to the wall thickness of the housing. The diverging ribs shall be distributed as evenly as possible around the bearing bore. There are also some taller columns that need to be equipped with corresponding ribs to ensure that the casting is liquid aluminum flow and reduce casting defects at this location.

9. Other Precautions

(1) There should be no small deep cavity in the shell. If there is a small deep cavity in the shell, the mold is fragile here, which will affect the life of the mold. (2) The shell should not have a thicker part, because the thicker part of the wall will create a larger shrinkage cavity in the shell. (3) The chamfer of the bearing hole and the pin hole cannot be too small. If the chamfer is too small, it will be difficult to assemble.

The gearbox body mainly controls the clutch and shift fork through the hydraulic principle. The valve body is usually equipped with some solenoid valves and mechanical valves as control components, corresponding to the clutch actuator and shift fork actuator. The valve body is usually damaged in two ways:

1. The valve body structure itself is damaged, and there is a problem of sealing or structural damage, which causes excessive oil pressure leakage and cannot meet the control pressure requirements, resulting in difficulty in clutch engagement or shift fork action.

2. The solenoid valve or mechanical valve is damaged, the valve is stuck or the valve body is damaged. Due to long-term operation, there are many impurities in the oil, which may cause the valve to jam; or the valve structure is damaged due to durability. The possibility of valve body damage needs to exist. During the warranty period, the valve body should be maintained according to the maintenance rules. Generally, this problem should not occur.