Design of automatic anti-skid differential system based on electronic control technology and pressure sensor

Design of automatic anti-skid differential system based on electronic control technology and pressure sensor

When the wheeled construction machinery is driving or working, due to turning, uneven road surface or different road resistance, the wheels on the left and right sides turn unequal distances at the same time, and the rolling resistance is not equal; even when driving in a straight line, due to the tire diameter The difference in air pressure, unequal inflation pressure, uneven wear, and different loads also cause the wheels on both sides to rotate at different speeds.

1 Introduction

When the wheeled construction machinery is driving or working, due to turning, uneven road surface or different road resistance, the wheels on the left and right sides turn unequal distances at the same time, and the rolling resistance is not equal; even if driving in a straight line, due to the tire diameter The difference in air pressure, unequal inflation pressure, uneven wear, and different loads also cause the wheels on both sides to rotate at different speeds.

Under the above circumstances, if a whole axle is used to rigidly connect the wheels on both sides, there will inevitably be problems such as slippage, slippage, accelerated tire wear, increased power consumption and steering difficulties, which will affect the stability of wheeled construction machinery. , also increases power consumption and fuel consumption.

In order to eliminate the above-mentioned bad factors, an automatic anti-skid differential system is designed. The system is proven to achieve automatic anti-skid performance, improving operational stability.

2. Differential

Differentials can be divided into ordinary differentials and anti-skid differentials according to their working characteristics.

2.1 Ordinary differential

At present, construction vehicles basically use symmetrical bevel gear ordinary differentials. The symmetrical bevel gear differential consists of planetary gears, side gears, planetary gear shafts (cross shafts or a straight pin shaft) and differential housings. As shown in Figure 1. The left half differential case and the right half differential case are bolted together. The driven gear of the final reducer is bolted (or rivets) to the flange on the right half of the differential case. The cross-shaped planetary gear shaft is installed in the circular hole facing the joint surface of the differential case, and a straight-toothed conical planetary gear with a sliding bearing (bushing) is sleeved on each journal. Both sides are meshed with a straight-toothed conical side gear. The journal of the side gear is supported in the corresponding holes on the left and right of the differential case, and its internal splines are connected with the side shaft. The planetary gear that rotates (revolves) together with the differential case drives the side gears on both sides to rotate. When the resistance of the wheels on both sides is different, the planetary gear also rotates around its own axis to realize the rotation of the wheels on both sides. Differential drive.

  Design of automatic anti-skid differential system based on electronic control technology and pressure sensor

2.2 Slip differential

Ordinary differential not only makes the car poor in ability to pass through complex roads, but also when turning at high speed, the inner wheel will slip due to the reduced adhesion, which not only makes the car insufficient in power, but also affects the handling stability. To this end, some off-road vehicles, luxury cars and light vehicles are equipped with a slip differential. Commonly used anti-skid differentials can be divided into two categories: manual forced locking and self-locking.

The manual positive locking differential is a differential lock added to the ordinary differential. When needed, the driver operates the differential lock to make the two half shafts as a whole, and the differential does not work, destroying the characteristic of the differential splitting torque to achieve the required driving requirements.

There are many types of self-locking differentials, such as friction plate type, slider cam type and variable transmission type. Their common feature is that when the rotational speed of the two driving wheels (inter-wheel differential) or the two drive axles (inter-axle differential) is different, no manual operation is required, and more torque can be automatically allocated to the slow-speed wheels, thereby improving the The passability and handling stability of the car. Figure 2 shows a friction-plate self-locking differential, which is a variation of a common planetary gear differential.

Design of automatic anti-skid differential system based on electronic control technology and pressure sensor

The ends of the cross shafts are all cut with convex V-shaped inclined surfaces, and the matching holes on the differential case are larger, with concave V-shaped inclined surfaces, and the V-shaped inclined surfaces of the two planetary gear shafts are installed in reverse. The housing transmits torque to the planetary gear shaft through a V-shaped ramp. The back of each side gear has a pressure plate and a main and driven friction plate. The inner spline of the pressure plate is connected with the half shaft, the inner spline of the driven plate is connected with the pressure plate, and the outer spline of the active friction plate is connected with the differential case. There is a slight axial movement between the pressure plate and the main and driven friction plates.

3. A new type of automatic anti-skid differential system

The operation of construction machinery is generally in harsh environments, and the traditional differential system has a small locking range and poor traction operation. This paper proposes an electronically controlled automatic anti-skid differential system. It can control the difference between the slip rates of the left and right wheels within the allowable range. When the adhesion coefficients on both sides of the road surface are different, the driving wheel on the side with the low adhesion coefficient slips. At this time, the Electronic controller drives the locking valve to lock the differential to a certain extent, so that the driving wheel on the high adhesion coefficient side is driven. power is fully exerted. This improves vehicle speed and driving stability. Controlling the degree of differential locking also benefits cornering stability and handling.

3.1 System composition principle

As shown in Figure 3, a solenoid valve and an accumulator are installed on the multi-plate clutch plates at the output end of the traditional differential system, and the pressure sensor is used to achieve pressure increase and pressure control. This way, the degree of locking can be gradually changed and is an electronically controlled hydraulically operated variable locking differential system that controls the high pressure oil pressure from the accumulator. The electronic control unit controls the pressure value by adjusting the solenoid valve; the signals generated by the pressure sensor and the driving wheel speed sensor are fed back to the electronic control unit to implement feedback control. The electronically controlled differential system can control the slip ratio of the left and right drive wheels or the front and rear drive axles within the allowable range.

Design of automatic anti-skid differential system based on electronic control technology and pressure sensor

When the vehicle starts, adjusting the locking degree of the differential can make full use of the driving force and improve the speed and driving stability; when the left and right driving wheels are driving on roads with different separation adhesion coefficients and on curves. It can improve the stability and driving ability of the car.

3.2 System Hardware Design

The automatic anti-skid differential system is based on the AT89C4051 single-chip microcomputer, which processes the sensor signal and controls the on-off of the solenoid valve. The hardware circuit of the whole system includes: single chip microcomputer and its peripheral circuit, wheel speed sampling processing circuit, solenoid valve control circuit, system protection circuit, etc., as shown in Figure 4. The P3.4 and P3.5 pins of AT89C4051 process the sensor acquisition signal; the P1.7 pin controls the on-off of the solenoid valve to control the pressure; P1.O-P1.3 is connected to the X25045 watchdog circuit.

Design of automatic anti-skid differential system based on electronic control technology and pressure sensor

3.2.1 System Protection Circuit

X25045 is a programmable circuit integrating three functions of watchdog, voltage monitoring and serial EEP-ROM. This combined design reduces circuit board space requirements.

The watchdog of X25045 provides protection function for the system. When the system fails beyond the set time, the watchdog in the circuit will pass. The RESET signal reacts to the CPU. X25045 provides 3 times for users to choose and use. The voltage monitoring function it has also protects the system from low voltage, when the supply voltage drops below the allowable range, the system will reset until the supply voltage returns to a stable value. The memory and CPU of X25045 can be connected through serial communication interface, with a total of 4096 bits, which can store data in 512*8 bytes.

3.2.2 Wheel speed identification circuit

Automatic Anti-Slip Differential System Technology Sensing Wheel Speed ​​Sensing

Design of automatic anti-skid differential system based on electronic control technology and pressure sensor

Design of automatic anti-skid differential system based on electronic control technology and pressure sensor

The Links:   7MBR100VX120-51 G185BGE-L01 IGBT