The present application is based on, and claims priority from, German Application Number 10 2005 048 286.4, filed Oct. 8, 2005, the disclosure of which is hereby incorporated by reference herein in its entirety.
The present invention is related to a cooling system for a combustion engine.
In the context of regulations for exhaust gas and consumption, it is necessary to achieve rapid warming up of the combustion engine to its working temperature, in automobiles in particular, because a big part of the relevant emissions and of the consumption is created in the cold operation. The rapid warming is obtained when the amount of cooling fluid circulating through the engine in the cold start is reduced to a minimum degree. However, it has to be taken care with respect to the operational safety that the amount of cooling fluid is sufficient to securely prevent local overheating on critical points of the engine. In addition, legal rules for the defrosting of the glazing at cold outside temperatures must be fulfilled.
In cooling systems for combustion engines, it is distinguished between engine blocks which have only one cycle and such ones which have separate cooling of the head and the block. In the latter case, the water jacket of the engine has two cycles.
Conventionally, one thermostat is provided in single-cycle cooling systems, which is realised as a double valve. Below the working temperature, cooling fluid is conveyed through the cooling passage system of the engine via a heat exchanger for heating (for heating the passenger compartment), the second valve of the thermostat and a bypass. When the working temperature is reached, the thermostat opens and by doing so it throttles the flow across the heat exchanger for heating by the second valve, whereas the main part of the cooling fluid is led through a main cooler.
The present invention is based on the objective to provide a cooling system for a combustion engine by which a very rapid heating up of the engine can be achieved.
In the cooling system according to the present invention, a second thermostat valve is arranged in the bypass branch, which has an opening temperature which is significantly lower than the opening temperature of the first thermostat valve. The two thermostat valves are arranged such that upon closed second thermostat valve, a minimum amount of water flows through the cooling passage system of the engine below its opening temperature, which makes it possible that the engine is heated up in a very short time. In doing so, the circulating amount of cooling fluid flows through the heat exchanger for heating. After the opening temperature of the second thermostat valve is reached, cooling fluid flows through the system in a larger amount, by forming a bypass to the heat exchanger for heating, for instance. After the opening temperature of the first thermostat valve is reached, the cooling fluid flows through the main cooler, the first thermostat valve providing control of the cooling fluid temperature in doing so, as is per se known. With increasing temperature, the amount of cooling fluid flowing through the bypass is progressively throttled.
In the present invention, minimizing the cooling fluid which circulates through the engine at cold start is achieved by using a thermostat with low opening temperature, wherein this thermostat permits a continuous increase of the flow of cooling fluid through the engine and an additional connection of additional heat exchangers at option conforming to demand, like an engine oil cooler or a gear oil cooler.
The thermostat valves may be arranged in a common casing or separately.
Preferably, the thermostat valves are realised as double valves with a second valve each, such that the same is opened upon closed thermostat valve and reduces its effective area with increasing opening of the thermostat valve. Preferably, according to one embodiment of the invention, the second valve of the first thermostat valve is completely closed when the first thermostat valve is completely opened. With respect to the second thermostat valve, one embodiment provides that the second valve is in a throttling position when the second thermostat valve is completely opened.
Depending on which control is preferred, namely either an engine outlet control or a water pump inlet control, the connection of the first thermostat and in connection therewith also of the second thermostat takes place. In the first case, the advantage is obtained that tubes and the main cooler are relieved from the cooling system pressure at the cold start. The latter configuration permits good control behaviour.
Depending on the configuration, the system according to the present invention makes the additional connection of at least one additional heat exchanger possible, like an engine oil or gear oil cooler, for instance. This additional heat exchanger is connected with the cooling system according to the present invention such that cooling fluid flows through it either below the opening temperature of the second thermostat valve or from the opening temperature of the second thermostat valve on or from the opening temperature of the first thermostat valve on.
The cooling system according to the present invention can also be applied to separate cooling systems for the engine block and the cylinder head, wherein one thermostat is assigned to each cooling system, as is usual. In the solution according to the present invention, a third thermostat is assigned to the cooling system for the engine block, the two thermostats for the cooling system of the engine block working and being connected in that manner as has been described in connection with one single cooling circuit.
In the following, the present invention will be explained in more detail by means of drawings.
The cooling system for a combustion engine represented in
The thermostats TH1 and TH2 are realised as double valves with a thermostat valve A or B, respectively, and a second valve a or b, respectively, which are jointly shifted through an expansion wax element, but work in opposite senses, with which will be dealt again below.
The thermostat valve A opens at about 87° C., which is commonly the opening temperature for cooling water thermostats. On the other hand, the thermostat valve B opens at a significantly lower temperature, of 30-35° C., for instance.
In the embodiment according
In
In the case that the temperature of the water rises further, the thermostat valve A is completely opened according to
In the embodiments of the represented cooling system according to
In the embodiment according to
After reaching the opening temperature of the thermostat TH2, an additional bypass path is opened via the second valve a and the thermostat valve B. This increases the amount of water circulating in the engine and prevents local overheatings. The use of the additional amount of water takes place smoothly. The thermostat TH2 is dimensioned such that throttling of the water from the heat exchanger for heating HWT by the valve b takes place only when the temperature of the water is higher than 90° C., for instance. The valve b never closes completely.
After reaching the opening temperature of the thermostat TH1, the thermostat valve A begins to open slowly and the second valve b begins to close. In doing so, the water is led through the main water cooler HWK, and at the same time, the additional water path via the bypass is throttled. In the hot operation, the water path via the main water cooler is completely opened and the bypass path is completely closed. At the same time, the water circuit via the heat exchanger for heating HTW is strongly throttled. This prevents any overheating of the passenger compartment and makes it possible to lead an amount as big as possible via the main water cooler HWK.
The embodiment according to
In the embodiment according to
As emerges from the embodiment according to
The main water cooler HWK is connected via the first thermostat TH1. In this configuration, an additional stream of cooling fluid flows through the second valve a of the first thermostat TH1.
Number | Date | Country | Kind |
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10 2005 048 286.4 | Oct 2005 | DE | national |