At present, the hydraulic transmission cooling system used in the forklift mostly incorporates the hydraulic transmission oil radiator into the water chamber of the engine tube belt radiator. This heat dissipation method has the following three problems: one is the low temperature of the hydraulic transmission oil at the initial start-up, the viscosity of the oil is large, and the transmission efficiency is low; the second is that the temperature of the hydraulic transmission oil is too high when the working conditions are bad; The oil and the coolant are easy to cross the cavity. In view of the above problems, it was decided to improve the hydraulic transmission cooling system of the forklift. The improved hydraulic transmission cooling system includes torque converter 1, thermostat 2 and external plate-fin radiator 3, as shown in Figure 1. The specific improvement plan is as follows:
1. Install thermostat
In order to solve the problem that the temperature of the hydraulic transmission oil is too low at the beginning of the forklift, a thermostat is added in the cooling oil circulation path of the hydraulic transmission cooling system. According to the hydraulic transmission oil temperature, the thermostat can automatically change the circulation range (large or small circulation) of the hydraulic transmission oil, adjust the cooling capacity of the cooling system, and ensure that the hydraulic transmission gearbox is within the appropriate oil temperature range jobs.
When the forklift started to work, the temperature of the hydraulic transmission oil was lower than 70 ℃, and the hydraulic transmission oil circulated for a small period. Under the action of the torque converter oil pump, the transmission oil enters the thermostat through the torque converter oil outlet, the thermostat oil outlet C is closed, and the oil returns directly to the torque converter without the oil radiator, forming a small cycle , So that the hydraulic transmission oil quickly rises to a suitable working temperature.
When the temperature of the hydraulic transmission oil rises to 70 ～ 80 ℃, the oil outlet A and the oil outlet C of the thermostat are at the same time half open. At this time, part of the hydraulic transmission oil passes through the thermostat oil outlet C to the radiator to cool Then it enters the torque converter, and the other part of the hydraulic transmission oil directly returns to the torque converter, and the large cycle and the small cycle are simultaneously performed.
When the temperature of the hydraulic transmission oil is higher than 80 ℃, the oil outlet C of the thermostat is fully opened, and the oil outlet B is closed. At this time, the hydraulic transmission oil passes through the oil outlet C of the thermostat and enters the radiator to cool and then enters the hydraulic power The torque converter forms a large cycle.
2. Improve the structure of radiator
In order to solve the problem of excessive oil temperature under severe working conditions and the mutual transmission of hydraulic transmission oil and engine coolant, it was decided to replace the built-in hydraulic transmission oil radiator with an external plate-fin radiator. The plate-fin radiator is mainly composed of a set of sandwich structures stacked and welded. Each sandwich structure is composed of 2 parallel partition plates 1, wave-shaped fins 2 and seals 3, as shown in FIG. 2. After each sandwich structure is welded into a whole, it is equipped with necessary heads and takeovers.
Plate-fin radiator not only has the characteristics of high heat transfer efficiency, compact structure, high strength, strong adaptability, etc., but also has an extended secondary surface, which makes its heat dissipation area much larger than that of tube-and-belt radiators. This type of radiator is not affected by the water chamber space and the heat dissipation medium, and its specifications can be selected according to the heat dissipation power of the torque converter. In addition, since the hydraulic transmission oil radiator and the engine water radiator are two independent radiators, it is impossible for the hydraulic transmission oil and the engine coolant to cross each other.
3. Improvement effect
The improved new hydraulic transmission cooling system was trial-installed on our company's 25t forklift. When the forklift is working, the hydraulic transmission oil temperature is always in the range of 70 ～ 90 ℃, and the cooling effect is good.
