System for the circulation of the coolant of the oil cooler for the automatic transmission of a motor vehicle

Circulation system for the coolant in an oil cooler (13) adapted to cool down the oil of the automatic transmission (2) of a motor vehicle in which the drain conduit (15) for the coolant from the oil cooler (13) of the transmission (2) is connected to said return conduit from the radiator, and that the exit mouth (16), of said drain conduit is inserted in the return conduit forming an angle A, said angle being more than 0° and less than 90°.

The present invention refers to a system for the circulation of the coolant in an oil cooler of the transmission of a motor vehicle, more in particular for motor vehicles with automatic transmission.

Commercial motor vehicles of limited capacity, can present automatic transmissions, which generally implement simple air cooled radiators which guarantee acceptable levels in the temperature of the oil of the transmission so that the transmission itself works properly and lasts in time.

Said radiators cannot be implemented on commercial vehicle due to the very low speed of the vehicle itself especially on steep slopes, and to the consequent poor air flow on said radiator.

In order to make the automatic transmission work at its best, it is therefore necessary to use oil coolers of the known type, which are already available on the market. However, said oil coolers need an auxiliary electric pump and its relative installation and control system in case it is not possible, for any reasons (water too hot, connection problems, etc) to place them into the cooling circuit of the motor, upstream and next to the main water pump.

The overall installation costs are therefore significantly increased, and there are more risks of failure and of high operation load for the battery.

It is an object of the present invention to provide a circulation system for the coolant of an oil cooler that overcomes the aforementioned drawbacks.

Said object is achieved by means of a circulation system for the coolant in an oil cooler as claimed in claim1.

With reference to the figures, reference number1indicates schematically an engine for a motor vehicle provided with automatic transmission2containing oil. The cooling system of the engine1, here schematically shown, includes a radiator4provided with an expansion tank for the coolant5, generally consisting of water mixed with antifreezing fluid, a thermostat6connected to the radiator by means of a delivery conduit7and a return conduit8. The return conduit further connects said thermostat6to the pump9for the coolant, which guarantees the circulation of the coolant itself in the engine. The system further consists of a heater11for the passenger compartment and of an oil cooler12, both being fed by the coolant pump under control of the thermostat6.

The automatic transmission2is provided with its own oil cooler13where the circulation of the water, according to the invention, is achieved as disclosed in the following, not by means of a pump but thanks to the flow of the coolant in the return conduit8from the thermostat6to the pump9of the main circuit. Said conduit is the one where the flow is constant and higher in intensity.

The oil cooler13of the transmission is therefore provided with a delivery conduit14for the coolant, which is obtained by connecting said conduit to the return conduit8from the radiator4, that is from the conduit where the coolant presents the most suitable temperature for the whole system. The drain conduit15of the oil cooler13is connected to the part of the return conduit8from the thermostatic device6to the pump9for the coolant.

In order to take maximum advantage from the flow of the fluid sucked by the w pump9, the connection of the drain15to the return conduit is to be realised as described in the following description referring toFIG. 2.

The end of the conduit15is to be sectioned in a direction which is basically perpendicular to its own axis, and the mouth16of the conduit is to be introduced into the conduit8until it reaches its central axis, where the flow of the coolant is higher, forming an angle A with the axis of said conduit8, said angle being more than 0° and less than 90°, preferably between 40° and 50°, when measured from the side of the oil cooler.

With this arrangement, the flow of the fluid in the conduit8creates a vortex at the mouth16of the conduit15, said vortex generating a depression which can suck the fluid inside the conduit15and consequently produce a cooling circulation in the oil cooler13associated to the automatic transmission2, with no need of an auxiliary pump.

The invention is obviously not limited to the embodiment here described and can be realised in equivalent ways without going beyond the scope of the present invention.