A METHOD AND A DEVICE FOR DEGASSING A COOLING SYSTEM FOR AN INTERNAL COMBUSTION ENGINE

Abstract: The present invention relates to a method for degassing a cooling system for an internal combustion engine (1), in which a coolant is brought to circulate on the one hand in a cooling circuit between the engine and a radiator unit (2) and on the other between the engine and a bypass circuit, past the radiator unit. The coolant is hereby controlled, in dependence of the temperature, to flow through the cooling circuit and/or the bypass circuit, and the degassing is performed through draining off a limited coolant flow. The degassing is achieved by draining off of a limited portion of that coolant flow which is brought to flow through the bypass circuit, and is thus performed in dependence of the coolant temperature.

Description: A METHOD AND A DEVICE FOR DEGASSING A COOLING SYSTEM FOR AN INTERNAL COMBUSTION ENGINE TECHNICAL FIELD The present invention relates to a method and a device for degassing a cooling system for an internal combustion engine, in which a coolant is brought to circulate partly in a cooling circuit between the engine and a radiator unit and partly between the engine and a bypass circuit past the radiator unit, the coolant flow being controlled, in dependence of the temperature, to flow through the cooling circuit and/or the bypass circuit, and the degassing being performed through draining off a limited coolant flow. BACKGROUND ART In principle, cooling systems for internal combustion engines are closed systems, in which the coolant is circulated, under a certain pressure, by the coolant pump. When filling up, and also during operation, gas pockets may occur inside the system, which is degassed continuously by means of degassing passages, which also release a small amount of coolant to an expansion reservoir. Hereby, a so-called parasite flow will occur, i.e. a non-wanted flow of coolant, which is however recirculated, and will be pressurised again in the coolant pump. Nevertheless, due to this, the pump must be sized for a larger flow than the useful coolant flow, thus limiting the efficient capacity of the pump. DISCLOSURE OF INVENTION The object of the present invention is to provide a method and a device, whereby the non-useful coolant flow can be reduced. Said object is achieved by a method and a device according to the invention, whereby degassing is obtained through draining off of a limited portion of that coolant flow which is brought to flow through the bypass circuit. Hereby it is achieved, that when the cooling requirement is at a maximum, the entire coolant flow will be directed through the radiator unit. DESCRIPTION OF THE DRAWING The invention will be explained in more detail by way of an embodiment example, with reference to the accompanying drawing, in which the figure schematically illustrates a cooling system according to the invention. PREFERRED EMBODIMENT The figure shows, schematically, an internal combustion engine 1, of e.g. the diesel type, for propulsion of automotive vehicles, ships or other machinery, such as power plants, forest machinery, etc. The figure further schematically depicts a cooling sys- tern for cooling the combustion engine 1 by bringing a coolant flow to circulate through cooling ducts in the engine cylinder block and cylinder head, and between the engine and a radiator unit 2 comprised in the cooling system, intended for through flow of the coolant, which is subjected to cooling air. The cooling system further comprises a pump 3, being driven either by the combustion engine 1 or by a separate electric motor. The system includes a thermostatic valve 4, functioning to control the coolant flow, in dependence of the coolant temperature, between a cooling circuit, see arrow 5, through the radiator unit 2, or a shunt or bypass circuit, see arrow 6, conducting the coolant past the radiator unit 2. The thermostatic valve 4 exhibits an inlet passage, 7, and two outlet passages 8, 9. The inlet passage 7 is connected to the cooling ducts in the combustion engine 1 , whereas one outlet passage, 8, is connected through a cooling line 10 to an inlet 11 of the radiator unit 2, and thus leads to the cooling circuit, whereas the other outlet passage 9 is connected to a bypass or shunt line 12, thus defining the bypass or shunt circuit discussed above. The thermostatic valve 4 is functioning, at temperatures below a selected lower limit value, to direct the coolant flow through the outlet passage 9 to the bypass line 12 and, for a rising temperature, when the selected lower limit value has been exceeded, to successively close the outlet passage 9 and open the outlet passage 8, so as, when exceeding an upper limit value, to direct the flow to the cooling circuit, i. e. via the cooling line 10 and the radiator 2. For a dropping tem- perature, when the coolant has reached the upper limit value, the coolant flow is again successively directed from the cooling circuit via the outlet passage 8, to the bypass circuit 6 via the outlet passage 9, until, when the lower limit value has been passed, it is directed entirely through the outlet passage 9. Depending on the type of thermostat, the temperature regulation may be of the on/off type, with rapid changes between the two end positions of the valve, or of the slow, gradual type with the valve being partly open towards both outlet passages 8, 9. The cooling system further comprises a coolant reservoir 13, partly functioning as a replenishing reservoir for the coolant, partly as an expansion reservoir, which will be explained further below. The coolant reservoir 13 exhibits a removable pressure cap 14, closing off a coolant replenishing opening 15. The coolant reservoir 13 is provided with a bottom coolant outlet 16 for a replenishing line 17, connected to the inlet side 18 of the pump 3. From the radiator unit 2, more particularly from its top end, a degassing line 19 is connected to the coolant reservoir 13 for the release of entrapped air from the radiator unit 2. in this process, a certain amount of coolant waste flow is also released, in the order of about 1% of the pump flow. This flow is limited by means of a flow limiter 20, in the form of a preferably fixed restriction inserted into the degassing line 19. For degassing of the remaining parts of the cooling system, such as the cooling ducts inside the combustion engine 1 , and the pump 3, a further degassing line 21 is arranged, with one end, 22, thereof connected to the thermostatic valve 4 outlet 9 to the bypass circuit, i.e. the bypass line 12, and the other end, 23, running into the coolant reservoir 13. The mouth is advantageously located at the top end of the reservoir, but, in principle, it might also be located below the coolant level in the reservoir. The degassing line 21 from the outlet 9 of the thermostatic valve exhibits a flow limiter 24 in the form of a preferably fixed restriction, securing a limitation of the coolant flow to about 2% of the total flow. Through the arrangement described above, with degassing after the thermostatic valve, 4, i.e. at the outlet side thereof and, more particularly, on that side which is connected to the bypass circuit, i.e. the line 12, a limited portion of that coolant flow which is brought to flow through the bypass circuit 6 is drained off. Thereby, the degassing and the waste flow will vary in such a way, depending on temperature, that when the cooling requirement is at a maximum, the entire coolant flow is brought to flow through the radiator unit. In an actual case, with a thermostat having a lower temperature limit value of e.g. 86°C and an upper limit value of 96°C, the degassing is controlled by the thermostatic valve as follows: For coolant temperatures below 86°C, degassing takes place only through the degassing line 21. For coolant temperatures in the range of 86-96°C, degassing takes place through both degassing lines, 19 and 21. For coolant temperatures exceeding 96°C, degassing takes place only through the degassing line 19, i.e. the degassing of the flow through the thermostatic valve 4 is then interrupted. To summarise, the present invention can thus be regarded on the one hand as a method and on the other as a device for degassing a cooling system of an internal combustion engine. The method, in summary, consists of bringing coolant, for cooling of the engine, to circulate between the engine and the cooling circuit through the radiator unit 2 and/or through a bypass circuit, past the radiator unit, depending on the temperature, whereby the coolant flow is directed between the two circuits by means of the thermostat-controlled valve 4 and whereby degassing of the cooling system is performed in dependence of the coolant temperature. The invention is not limited to the embodiment example described above and shown in the drawing, but can be varied within the scope of the appended patent claims. By way of example, it is conceivable, in principle, to eliminate the degassing through the line 19 from the radiator unit 2.

Claims: CLAIMS 1. A method for degassing a cooling system for an internal combustion engine (1), in which a coolant is brought to circulate partly in a cooling circuit between the engine and a radiator unit (2) and partly between the engine and a bypass circuit past the radiator unit, the coolant flow being controlled, depending on the temperature, to flow through the cooling circuit and/or the bypass circuit, and the degassing being performed through draining off a limited coolant flow, characterised in that said degassing is achieved through draining off of a limited portion of that coolant flow which is brought to flow through the bypass circuit, thus being achieved in dependence of the coolant temperature. 2. The method according to claim 1, characterised in that said degassing is interrupted when the coolant temperature is equal to, or higher than, a predetermined upper limit value for the thermostatic valve (4). 3. A device for degassing a cooling system for an internal combustion engine (1), comprising a radiator unit (2) for cooling the through-flowing coolant, a pump (3) for circulation of the coolant, partly between the internal combustion engine and the radiator unit and partly through a bypass line past the radiator unit, a thermostatic valve (4) for controlling, in dependence of the coolant temperature, the coolant flow through the radiator unit and the bypass line, respectively, said thermostatic valve exhibiting an inlet passage (7) from the engine and two outlet passages (8, 9), whereby one of the outlet passages is functioning to direct coolant to the radiator unit, and the other is functioning to direct coolant through the bypass line; and further comprising a coolant reservoir (13), to which is connected at least one degassing line (21) and which is connected, via a replenishing line (17), to the inlet (18) of the pump, characterised in that said degassing line (21) is con- nected to that outlet passage (8) which is functioning to direct coolant through the bypass line. 4. The device according to claim 3, characterised in that the thermostatic valve (4) is functioning to close off said degassing line (21) when the coolant temperature is equal to, or higher than, a predetermined upper limit value for the thermostatic valve. 5. The device according to claim 4, characterised in that a further degassing line (19) is arranged for allowing a limited flow between the radiator unit (2) and the coolant reservoir (13), except when the coolant temperature is equal to, or lower than, a predetermined limit value for the thermostatic valve (4).

Inventors: HOLMSTROEM JAN CHRISTIAN, HOLMSTROEM, JAN, CHRISTIAN
Applicants: HOLMSTROEM JAN CHRISTIAN, VOLVO LASTVAGNAR AB, HOLMSTROEM, JAN, CHRISTIAN
Application year: 1999
Main classification: F01P11
IPC codes: F01P7, F01P11