EP1653062A1

EP1653062A1 - Oil temperature control system for vehicles with a liquid cooling circuit and method therefor

Info

Publication number: EP1653062A1
Application number: EP04744079A
Authority: EP
Inventors: Sergio Santo Domingo; Vicente Gambon; Bertrand Gessier; Patrick Perrin
Original assignee: Valeo Termico SA
Current assignee: Valeo Termico SA
Priority date: 2003-07-29
Filing date: 2004-07-27
Publication date: 2006-05-03
Also published as: ES2249094A1; WO2005010327A1; ES2249094B1

Abstract

It comprises an internal-combustion engine (1), a radiator (2), a coolant liquid for the engine (1), a heat exchanger (3), and a first heat-regulation device (4) for the engine (1). It is characterized in that it comprises a single coolant liquid inlet to the heat exchanger (3) coming from the radiator (2) or from the engine (1), and a second temperature-regulation device (6), controlled by means of the oil temperature at the entry to or at the exit from the exchanger (3), allowing the oil to be heated in a forced-heating step and a natural-heating step, and the oil temperature to be regulated in order to keep it at its ideal operating temperature. The oil-temperature-regulation system is greatly simplified.

Description

The present invention relates to an oil-temperature-regulation system for vehicles equipped with a liquid-cooling circuit. The invention also relates to the corresponding method therefor.
The oil-temperature-regulation system for vehicles equipped with a liquid-cooling circuit of the present invention is of the type that comprises an internal-combustion engine, a radiator connected to the outlet from the engine, a coolant liquid for the engine, a heat exchanger that comprises a first circuit for circulating the coolant liquid and a second circuit for circulating the oil to be heated or cooled by heat exchange with said coolant liquid and a first heat-regulation device for the engine, which regulates the passage of coolant liquid from the engine either via the radiator in order to cool it or via a bypass line, which directs it toward the heat exchanger, as a function of a first operating temperature of the coolant liquid.

BACKGROUND OF THE INVENTION

It is known that operation of a vehicle gives rise to heat dissipation in the oil for lubricating certain components, such as the engine, the gearbox, etc., and requires this oil to be cooled (engine oil or transmission oil, or another oil circuit) in order to prevent an excess of heat that may be detrimental to its functional characteristics.
The oil may be cooled naturally, i.e. by exchange of heat with the exterior or with the liquid-cooling circuit through the walls of the oil pan or of other parts of the oil circuit, or its cooling may be forced.
In the case of forced cooling, the oil circuit comprises an exchanger for dissipating the heat from the oil into the ambient air (oil/air cooler) or into the coolant liquid (oil/water cooler).
In certain systems for forced cooling of oil, regulation of oil cooling is obtained by incorporating a regulation device, such as, for example, a thermostat, into the oil circuit. In these systems, the regulation device is generally based on regulating the cooling intensity, for example by modifying the flow of oil or water in the exchanger as a function of temperature in order to keep it constant.
These systems for regulating oil cooling may switch continuously between two states: no oil cooling and maximum oil cooling. However, these systems do not allow the oil to be heated.
In practice, it has been found that, in certain circumstances, for example when starting up the vehicle, the coolant liquid from the engine may be at a higher temperature than the oil, while the oil has a temperature that is as yet too low for optimum functioning, it being, in this case, appropriate to heat the oil.
In order to improve this situation, other forced oil-cooling systems are used that involve an oil/water exchanger, and these comprise a function of heating the oil by means of the incorporation into the system of an inlet for hot water, for example coming directly from the engine. In this case, the regulation device is based on conveying hot water (which comes, from example, from the engine) or cold water (which comes, for example, from a low-temperature radiator) through the oil exchanger, as a function of its temperature. This system thus allows heating of the oil to be speeded up.
Patent US 6 196 168 relates to a device and method for preheating and cooling especially a transmission fluid of an internal-combustion engine.
Said device is characterized in that it comprises a thermostatic valve that makes it possible to switch between two states: a first state causing the coolant fluid to circulate from the engine to the heat exchanger, without passing via the radiator, in order to heat the oil; and a second state causing the coolant fluid to circulate from two different paths toward the heat exchanger, specifically from the radiator (for cooling) and from the engine (for heating), so that the oil reaches the desired temperature.
In these oil-temperature-regulation systems that comprise both a heating function and a cooling function, the oil exchanger is constantly in operation, either functioning in oil-heating mode (temperature of the oil below the temperature of the cooling water), or in oil-cooling mode (temperature of the oil higher than the temperature of the cooling water).
These systems may switch continuously between these two states (heating or cooling), passing via an intermediate specific-point state (temperature of the oil equal to the temperature of the cooling water), when exchanger efficiency is canceled out.
However, it may be that the oil temperature is higher than the temperature of the cooling water but below its ideal temperature. In this case, this second type of system will always function in cooling mode, and will therefore halt the desirable heating of the oil up to its ideal temperature, thereby giving rise to friction wear on the lubricated components.

DESCRIPTION OF THE INVENTION

The object of the oil-temperature-regulation system and method for vehicles equipped with a liquid-cooling circuit of the present invention is to resolve the drawbacks of systems known in the prior art by providing a major simplification of the system by means of a single coolant fluid inlet and allowing the function of heating or cooling the oil.
The oil-temperature-regulation system for vehicles equipped with a liquid-cooling circuit, which is the subject of the present invention, is characterized in that it comprises a single coolant liquid inlet to the heat exchanger coming from the radiator or from the engine, and a second temperature-regulation device, controlled by means of the oil temperature at the entry to or at the exit from the exchanger, which regulates the heat exchange between the coolant liquid and the oil, allowing the oil to be heated in a forced-heating step and a natural-heating step, and the oil temperature to be regulated in order to keep it at its ideal operating temperature.
This provides a more simplified oil-temperature-regulation system, since, by means of a single inlet of coolant fluid to the exchanger, as in the case of a conventional passive exchanger, the system is also able to carry out the function of heating the oil in two stages: forced heating of the oil by means of the coolant fluid ("water-forced heating-up") and then natural heating of the oil ("self-heating-up"), owing to circulation in the engine and the function of regulating the temperature of the oil.
Furthermore, it is unnecessary to make any modification to the oil circuit as compared to a conventional passive exchanger.
Preferably, the first temperature-regulation device may be a thermostat or a pneumatically or electrically controlled thermostatic valve.
Preferably, also, the second temperature-regulation device is a thermostat or a pneumatically or electrically controlled thermostatic valve.
Advantageously, the ideal temperature of the oil is between 90°C and 130°C.
According to a first aspect of the invention, the second temperature-regulation device is arranged in the cooling circuit and is controlled by the oil temperature at the entry to or at the exit from the exchanger, regulating the passage of coolant liquid either through the heat exchanger or through a bypass line of said exchanger.
In this case, when the coolant liquid coming from the engine circulates through the heat exchanger, the forced oil-heating stage takes place, whereas, when the coolant liquid circulates through the bypass line, natural heating of the oil is obtained.
According to a first embodiment of the invention, the supply of coolant liquid in the exchanger is caused by a pressure drop in its corresponding bypass line.
According to a second embodiment of the invention, the supply of coolant liquid in the exchanger is achieved by a bypass line directly from the engine.
In this way, direct supply to the exchanger avoids the creation of a pressure drop in the circuit, as happens in the case described in the first embodiment, and therefore the thermal performance is improved.
According to a second aspect of the invention, the second temperature-regulation device is arranged in the oil circuit and is controlled by means of the oil temperature at the entry to or at the exit from the exchanger, regulating the passage of oil either through the heat exchanger or through a bypass line of said exchanger.
In this other case, when the oil circulates through the heat exchanger, forced heating of the oil takes place by thermal exchange with the coolant liquid coming from the engine, whereas, when the oil circulates through the bypass line, natural heating of the oil is obtained.
According to a third embodiment of the invention, the heat exchanger is located at the exit from a discharge valve of the oil pump.
The oil-temperature-regulation method for vehicles equipped with a liquid-cooling circuit, applied to the system of the invention, is characterized in that, in a first stage, it consists in carrying out the following steps:

a) when the oil temperature is below its ideal temperature, allowing the coolant liquid to circulate from the engine through the heat exchanger in order to heat the oil until its temperature reaches a value slightly below the operating temperature of the coolant liquid, by forced heating;
b) while the oil temperature is higher than or equal to the operating temperature of the coolant liquid but below its ideal value, stopping the coolant liquid or oil from circulating in the exchanger, conveying it through its corresponding bypass line in order for the oil temperature to increase progressively until it reaches its ideal value, by natural heating;
and, in a second stage, the following step is carried out:
c) when the oil temperature has reached its ideal, progressively re-establishing circulation of coolant liquid or of oil through the exchanger so as to obtain oil-temperature regulation in order to keep it at its ideal value.

Advantageously, each one of the above steps a), b) and c) is controlled by the second temperature-regulation device as a function of the oil temperature at the entry to or at the exit from the heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to facilitate the description of that which has been set forth above, drawings are attached in which, diagrammatically and solely by way of nonlimiting example, three practical embodiments of the oil-temperature-regulation system for vehicles equipped with a liquid-cooling circuit of the invention are shown, in which:

Figure 1 is a diagrammatic circuit of the regulation system of the invention, according to a first embodiment;
Figure 2 is a diagrammatic circuit of the regulation system of the invention, according to a second embodiment; and
Figure 3 is a diagrammatic circuit of the regulation system of the invention, according to a third embodiment.

DESCRIPTION OF PREFERRED EMBODIMENTS

A first embodiment of the invention is shown in Figure 1, which shows the coolant liquid circuit.
As may be seen from Figure 1, the oil-temperature-regulation system comprises an internal-combustion engine 1, a radiator 2 connected to the outlet from the engine 1, a coolant liquid for the engine, a heat exchanger 3 located in the water circuit, which comprises a first circuit for circulating water and a second circuit for circulating the oil to be heated or to be cooled by heat exchange with the water, and a first thermostat 4 of the engine 1 that regulates the passage of water from the engine 1 either through the radiator 2 in order to cool it or through a bypass line 5a that directs it toward the heat exchanger 3 as a function of a first operating temperature of the water.
It also comprises a single inlet of water to the heat exchanger 3 coming from the radiator 2 or from the engine 1, a second thermostat 6 controlled by means of the oil temperature at the entry to or at the exit from the exchanger 3, and a pump 7 that recirculates the water toward the engine 1.
In the circuit of Figure 1, it is possible to see that the supply of coolant liquid in the exchanger 3 is achieved by means of a pressure drop in its corresponding bypass line.
A second embodiment of the invention is shown in Figure 2, which also shows the coolant liquid circuit.
In this case, the oil-temperature-regulation system comprises the same elements as those described in the first embodiment, the difference being that the supply of coolant liquid in the exchanger 3 is achieved by means of a bypass line 5b directly from the engine 1.
In this way, direct supply to the exchanger 3 avoids the creation of a pressure drop in the circuit, as happens in the case described in the first embodiment, and therefore the thermal performance is improved.
A third embodiment of the invention is shown in Figure 3, which shows the oil circuit.
In this case, the oil-temperature-regulation system comprises the same elements as those described in the first and second embodiments, the difference being that the heat exchanger 3 is located in the oil circuit.
In the same way, the second thermostat 6 is controlled by means of the oil temperature at the entry to or at the exit from the exchanger 3.
It also comprises a pump 8 that aspirates the oil toward the heat exchanger 3, and a discharge valve 9 located between said oil pump 8 and the heat exchanger 3.
For any of the embodiments described above, the second thermostat 6 regulates the heat exchange between the water and the oil, in accordance with the following mode of operation:
Firstly, the second thermostat 6 allows circulation of the water from the engine 1 (water temperature higher than the oil temperature) to the exchanger 3, until the oil reaches a temperature close to or below the temperature of the water, which is at 90°C. This stage corresponds to forced heating of the oil.
Next, the second thermostat 6 stops circulation of the water or oil to the exchanger 3 and conveys it toward its corresponding bypass line such that the oil temperature will increase from 90°C to 115°C. This stage corresponds to natural heating of the oil and allows the oil temperature to increase to its ideal temperature, which in this example is 115°C.
Lastly, the second thermostat 6 progressively re-establishes circulation of the water or oil in order to keep the oil at its ideal temperature of 115°C.
Therefore, major simplification of the water circuit is achieved with a single inlet of water to the exchanger 3, also allowing the function of heating to be achieved in two stages: forced heating of the oil by heat exchange with the water, and then natural heating, and the function of regulating the oil temperature.
In addition, it is unnecessary to make any modification to the oil circuit as compared to a conventional passive exchanger.
Furthermore, although these three preferred embodiments have been described, it should be pointed out that the proposed system could function solely in natural-heating mode owing to circulation in the engine. This natural heating could be forced by means of the incorporation of an element providing an artificial-heating stage, such as an electrical resistance element within the oil, or a three-fluid exchanger to allow, for example, heating of the oil using the gases from the EGR system (exhaust gas recirculation system of an engine).

Claims

Oil-temperature-regulation system for vehicles equipped with a liquid-cooling circuit, which comprises an internal-combustion engine (1), a radiator (2) connected to the outlet from the engine (1), a coolant liquid for the engine (1), a heat exchanger (3) that comprises a first circuit for circulating the coolant liquid and a second circuit for circulating the oil to be heated or cooled by heat exchange with said coolant liquid and a first heat-regulation device (4) for the engine (1), which regulates the passage of coolant liquid from the engine (1) either via the radiator (2) in order to cool it or via a bypass line (5a, 5b), which directs it toward the heat exchanger (3), as a function of a first operating temperature of the coolant liquid, characterized in that it comprises a single coolant liquid inlet to the heat exchanger (3) coming from the radiator (2) or from the engine (1), and a second temperature-regulation device (6), controlled by means of the oil temperature at the entry to or at the exit from the exchanger (3), which regulates the heat exchange between the coolant liquid and the oil, allowing the oil to be heated in a forced-heating step and a natural-heating step, and the oil temperature to be regulated in order to keep it at its ideal operating temperature.
System according to Claim 1, characterized in that the first temperature-regulation device (4) is a thermostat.
System according to Claim 1, characterized in that the first temperature-regulation device (4) is a pneumatically or electrically controlled thermostatic valve.
System according to Claim 1, characterized in that the second temperature-regulation device (6) is a thermostat.
System according to Claim 1, characterized in that the second temperature-regulation device (6) is a pneumatically or electrically controlled thermostatic valve.
System according to Claim 1, characterized in that the ideal temperature of the oil is between 90°C and 130°C.
System according to any of Claims 1 to 6, characterized in that the second temperature-regulation device (6) is arranged in the cooling circuit and is controlled by the oil temperature at the entry to or at the exit from the exchanger (3), regulating the passage of coolant liquid either through the heat exchanger (3) or through a bypass line of said exchanger (3).
System according to Claim 7, characterized in that the supply of coolant liquid in the exchanger (3) is caused by a pressure drop in its corresponding bypass line.
System according to Claim 7, characterized in that the supply of coolant liquid in the exchanger (3) is achieved by a bypass line (5b) directly from the engine (1) .
System according to any of Claims 1 to 6, characterized in that the second temperature-regulation device (6) is arranged in the oil circuit and is controlled by means of the oil temperature at the entry to or at the exit from the exchanger (3), regulating the passage of oil either through the heat exchanger (3) or through a bypass line of said exchanger (3).
System according to Claim 10, characterized in that the heat exchanger (3) is located at the exit from a discharge valve (9) of the oil pump (8).
Oil-temperature-regulation method for vehicles equipped with a liquid-cooling circuit, applied to the system of the invention, according to any of the preceding claims, characterized in that, in a first stage, it consists in carrying out the following steps:
a) when the oil temperature is below its ideal temperature, allowing the coolant liquid to circulate from the engine (1) through the heat exchanger (3) in order to heat the oil until its temperature reaches a value slightly below the operating temperature of the coolant liquid, by forced heating;

b) while the oil temperature is higher than or equal to the operating temperature of the coolant liquid but below its ideal value, stopping the coolant liquid or oil from circulating in the exchanger (3), conveying it through its corresponding bypass line in order for the oil temperature to increase progressively until it reaches its ideal value, by natural heating;
and, in a second stage, the following step is carried out:
c) when the oil temperature has reached its ideal, progressively re-establishing circulation of coolant liquid or of oil through the exchanger (3) so as to obtain oil-temperature regulation in order to keep it at its ideal value.
Method according to Claim 12, characterized in that each one of the steps a), b) and c) is controlled by the second temperature-regulation device (6) as a function of the oil temperature at the entry to or at the exit from the heat exchanger (3).