Browse Prior Art Database

An arrangement and a method for controlling the braking action of a retarder

IP.com Disclosure Number: IPCOM000032895D
Publication Date: 2004-Nov-18
Document File: 2 page(s) / 24K

Publishing Venue

The IP.com Prior Art Database

Abstract

The oil of a hydrodynamic retarder is usually cooled by means of the ordinary cooling system in a vehicle. Thereby, the available braking effect of the retarder is restricted by the capacity of the cooling system. The capacity of the cooling system depends on, for example, the specific heat CP of the used cooling liquid. In cold climates, a cooling liquid is used containing a mixture of water and glycol. In hot climates, a cooling liquid normally is used containing water and a smaller amount of an antioxidant. The difference in specific heat CP between such cooling liquid mixtures is relatively large. According to the invention, the activation of the retarder is controlled by means of information about the value of the specific heat CP of the cooling liquid mixture, which for the moment is used in the cooling system. Thereby, it is possible to control the activation of the retarder in a more optimally manner without the risk that the cooling system is overheated.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

An arrangement and a method for controlling the braking action of a retarder

Heavy motor vehicles are many times equipped with an auxiliary brake in the form of a hydrodynamic retarder having an oil as working fluid. During the activation of the hydrodynamic retarder, a braking effect is provided which substantially corresponds to the heating effect transmitted to the oil. Mostly, the oil is cooled in an oil cooler by means of the cooling liquid of the ordinary cooling system of the vehicle. Thereby, the available braking effect of the retarder is restricted by the cooling capacity of the cooling system.

The capacity of a cooling system depends on a plurality of parameters such as the specific heat CP of the cooling liquid used in the cooling system. In cold climates, a cooling liquid is used containing a mixture of water and an antifreeze, which normally is glycol. In hot climates, a cooling liquid normally is used containing water and a smaller amount of an antioxidant. A cooling liquid, which contains a mixture of 50 % glycol and 50 % water, has a specific heat CP of about 3,6 kJ/kg˚C.  A cooling liquid, which substantially contains pure water, has a specific heat CP of about 4,2 kJ/kg˚C. Consequently, the difference in specific heat CP is significant for the cooling liquid mixtures used in different climates.

According to the invention, the activation of the retarder is controlled by means of information about the value of the specific heat CP of the cooling liquid mixture, which for the moment is used in the cooling system. By such a method, it is possible to control the activatio...