The basic structure of a micro loader

The development and changes of micro-structured structures

Before 2002, there were already such micro-tractors modified from tractors, but due to their poor performance, they never developed. Based on this, a micro-installation of a dedicated chassis (frame) was still designed using this integrated box-axle tractor transmission device. However, its chassis (frame) remains an integral rigid type, still featuring front-wheel steering and rear-wheel drive. This type of micro-mounting has seen a significant improvement in performance compared to tractor modifications. However, it features single-axle drive and an integral frame, resulting in low traction, low operational efficiency, a large turning radius, and poor maneuverability. It has gradually been replaced by micro-mounting with articulated steering and four-wheel drive.

At first, to save money, only a simple driving canopy was made. However, due to the poor working conditions of the drivers, it was gradually phased out. The current fully enclosed cabs of micro-loaders have gradually evolved into true micro-loaders that are in line with ordinary loaders. At present, most micro-installations have a relatively beautiful appearance with only a small increase in price. Their performance has been greatly improved and their operation efficiency has also been significantly enhanced. Therefore, the user base has expanded rapidly and the development is very fast.

2. The main structural forms of current micro-installations

At present, the micro loaders produced in large quantities in our country are basically wheeled, and there are no traces of tractors anymore, thus becoming true loaders in the real sense. It possesses the basic structure of modern loaders, which mainly includes diesel engine-powered, four-wheel drive, hydraulic control, articulated full hydraulic power steering, hydraulic braking, an advanced single rocker arm "Z" -shaped connecting rod mechanism working device and articulated front and rear frames, etc. It is equipped with an electrical system, cab, cover parts and a mechanical gearbox with a mechanical clutch, etc. The working device is basically the same as that of a common loader. Some products have been optimized by computer design and have a relatively advanced structure. The interior of the cab is not sealed, nor is it equipped with air conditioning or interior decoration. However, the appearance of the cab and its cover parts is mostly as beautiful as that of a regular loader. The electrical system only has start-up and lighting functions, which is very simple. The braking system is a hydraulic pump without power. The driver directly steps on the brake pump to generate pressure oil for braking.

The following will focus on introducing the core components of micro-equipment in China at present - the transmission system and the hydraulic steering system.

(1) Micro-installed transmission system.

At present, the transmission systems of most micro-transmissions in our country mainly consist of mechanical gearboxes, pulleys with mechanical clutches, front and rear drive axles, front and rear transmission shafts, etc. The power is transmitted to the pulley, then to the transmission through the clutch. The transmission then transmits it to the front and rear drive axles through the front and rear drive shafts, thereby driving the wheels to move. The transmission is mechanical and the clutch must be depressed every time a gear is shifted. The drive axle is equipped with a first-stage main reducer with a differential, without wheel-end reducers. Its service brake is of the drum type. The structural type of the drive shaft is the same as that of the drive shaft of a common loader.

(2) Micro-installed hydraulic steering system.

The micro-mounted hydraulic steering system mainly consists of two parts: the working hydraulic system and the steering hydraulic system. The working hydraulic system mainly consists of distribution valves, bucket cylinders and boom cylinders. The steering hydraulic system mainly consists of a fully hydraulic steering gear and a steering cylinder. The hydraulic oil radiator, hydraulic oil tank, oil filter and gear oil pump, etc. are shared by two hydraulic systems. The hydraulic oil from the gear oil pump enters the steering gear through the distribution valve, and the steering gear returns the oil to the radiator for heat dissipation before returning to the oil tank. Its structure and working principle are basically similar to those of ordinary loaders. The distribution valve is basically the same as that of a common loader. The system pressure of the hydraulic system is controlled by the relief valve installed on this valve. The slight difference from the distribution valve of a common loader is that the sliding valve of the boom cylinder of the distribution valve of a common loader has four positions, while this distribution valve has only three positions, one less floating position. The fully hydraulic steering gear is equipped with a valve block for controlling the system pressure. Some micro-mounted hydraulic steering systems are equipped with an additional priority valve. Through this priority valve, oil is supplied to the steering gear first. When not steering, the entire flow of the pump is supplied to the working device, preventing a large amount of oil from passing through the steering gear entirely. This reduces heat generation and energy loss, and the system is relatively reasonable. However, with an additional priority valve, the structure becomes relatively complex and the cost increases. Therefore, the vast majority of micro-steering systems still adopt the hydraulic steering system shown in Figure 4 at present.