WO2008029058A2

WO2008029058A2 - Device for distributing cooling fluid in a motor vehicle engine

Info

Publication number: WO2008029058A2
Application number: PCT/FR2007/051873
Authority: WO
Inventors: Frédéric ABAD
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2006-09-06
Filing date: 2007-09-05
Publication date: 2008-03-13
Also published as: FR2905423B1; WO2008029058A3; FR2905423A1; EP2069620A2

Abstract

System for cooling a motor vehicle engine comprising a crankcase (10), a cylinder head (12) containing the passages and seats of the intake valves and exhaust valves, said system comprising a pump (24) and a heat-transfer fluid circuit which branches downstream of the pump (24) in order to separately supply a bottom chamber (14, 18) for cooling the crankcase (10) and that part of the cylinder head surrounding the intake valves, and a top chamber (16) for cooling that part of the cylinder head surrounding the exhaust valves, the two branches of the heat-transfer fluid circuit converging at the outlet of the top and bottom chambers. The invention also relates to a diesel engine comprising such a cooling system.

Description

DEVICE FOR DISPENSING COOLANT IN A MOTOR VEHICLE ENGINE

The present invention claims the priority of the French application 0653585 filed on 06/09/2006 whose content (description, claims and drawings) is incorporated herein by reference.

The present invention relates to a cooling system of a motor vehicle engine, the so-called double cooling type or "split-cooling", particularly suitable for cooling engines whose combustion is auto-ignited (Diesel).

[0003] An internal combustion engine usually comprises a housing closed by a cylinder head. For the proper functioning of the engine, these elements must be cooled. To do this, the engine is provided with a cooling circuit in which a heat transfer fluid is circulated by means of a pump and which, in turn, is cooled by passing through a radiator.

[0004] However, the operating temperature of an engine is normally much higher than the outside temperature, especially in cold weather. Any start is therefore accompanied by a preheating phase during which the performance is not optimal, in particular during which the pollutant emissions (unburned hydrocarbons) are in much greater quantity than in nominal regime.

To reduce this preheating time, it is known so-called double cooling systems, often known as Anglo-Saxon split-cooling, in which the coolant circulates independently in the cylinder head and in the housing, the circulation in the crankcase being established only after the preheating phase has been completed.

US Patent No. 6,823,823 discloses a cooling system of this type, comprising a cooling chamber disposed in the housing and a second chamber, isolated from the first, disposed in the housing. The supply of the coolant in the two cooling chambers is carried out using a single column consisting of two parts, arranged respectively in the housing and the cylinder head. This column comprises for this purpose two superimposed orifices, passing through a wall of the column and opening respectively in each of the two cooling chambers. The heat transfer fluid is separated into two streams for the respective cooling of the housing and the cylinder head by means internal to the column which comprise the orifice opening into the housing cooling chamber.

This arrangement results in non-homogeneous cooling of the rolls, particularly when the circulation is cut in the housing, the cylinder closest to the inlet orifice remaining partly cooled unlike the other cylinders. In addition, when the housing is effectively cooled, the coolant flow circulating in the cylinder head is reduced and it is not necessarily properly cooled. These disadvantages are especially sensitive for Diesel type engines.

Furthermore, a double cooling system assumes means to cut the circulation of the coolant in the casing cooling chamber.

GB Patent 2,245,703 discloses a cooling fluid distribution device for a double cooling system having downstream of the cylinder head cooling chamber a main thermostat and downstream of the cooling chamber of the casing a auxiliary thermostat. Below a first threshold temperature, the coolant circulates only in the cylinder head and the main thermostat cuts the flow in the branch of the circuit through the radiator, so that the coolant is not cooled. Beyond a second threshold temperature, greater than the first, the auxiliary thermostat further allows the circulation of the cooling fluid in the crankcase.

With such a device, as the flow rate is zero in the housing, the fluid temperature at the auxiliary thermostat may not be identical to that of the fluid in the housing cooling chamber which generates a risk of overheating of the engine. The present invention relates to a new cooling system obviant all or part of the problems mentioned and in particular, particularly suitable for cooling diesel engines.

The solution to the technical problem is that the "breech" branch is exclusively dedicated to the exhaust side of the cylinder head, and that the intake side of the cylinder head is integrated with the branch "housing" of the cooling circuit. In other words, the separate cylinder head and crank chamber are replaced by a lower chamber, comprising the crankcase chamber and the cooling chamber of the intake valves of the cylinder head and a high chamber for cooling the exhaust valves.

The invention starts from the consideration that the cooling requirements of the intake zone of the cylinder head, that is to say the area surrounding the intake valves fresh air, are substantially equivalent to those of the crankcase. engine, the exhaust zone, which surrounds the exhaust gas exhaust valves for its part a need for permanent cooling even when the engine is still "cold".

The outputs of the high and low chambers are connected to the inputs of a liquid distribution box in the cooling circuit. This housing is generally arranged on the cylinder head. As the circuit of the coolant essentially follows a U-shaped path, with a passage in the lower part and then in the opposite direction, in the upper part, the association of the intake zone of the cylinder head with the crankcase cooling zone allows an output of the lower chamber on the same side as the outlet of the upper chamber so that the design of the housing and fittings on it does not have to be fully recovered.

According to a more specifically preferred variant of the invention, the heat transfer fluid flow is separated between two separate flows directed towards the lower chamber and the upper chamber, by separating means located upstream of an inlet of the heat transfer fluid in the carter part of the lower chamber.

This allows a direct water flow to the upper chamber and avoids inhomogeneous cooling of the housing which generates deformations of the barrels of the cylinders that are associated with problems with scrubbing or galling and increased leaking of blow-by gas.

With a cooling system of an engine according to the invention, it is advantageously provided three modes of operation:

"A main mode, in which the coolant is cooled by a radiator and circulates in the high and low chambers;

• a "cold" mode, in which the heat transfer fluid circulates exclusively in the upper chamber, without even being cooled by the radiator and;

• an intermediate mode, in which the coolant is cooled by the radiator but the circulation is not established in the lower chamber.

For the implementation of these three modes of operation, the distribution of the heat transfer fluid in the various branches of the cooling system is advantageously obtained by means of a distribution system having on the one hand a junction having at least 4 inputs / outputs one of them being connected to the upper chamber and secondly a connector whose input connected to the lower chamber and whose output is one of the 4 inputs / outputs of the junction.

The other two inputs / outputs of the junction constitute a main output and an auxiliary output leading to a shunt passing through the radiator. This auxiliary output is controlled by a controlled valve Th1 to reach an open position when the coolant circulating in the junction reaches a first threshold temperature T _s i.

Another valve Th2 can block the incoming flow from the connection (and therefore the lower chamber). This valve Th2 is controlled to reach an open position when the heat transfer fluid present in the connection reaches a second threshold temperature T _S 2 different from the first threshold temperature T _s i.

Furthermore, the distribution circuit comprises means for establishing a heat transfer fluid leak between the junction and the fitting, but only when the valve Th2 is in the open position and the valve Th1 in the closed position, or in other in other words, when the temperature of the coolant is between the two threshold temperatures. Such an arrangement optimizes the rise in temperature of the heat transfer fluid while avoiding any risk of overheating due to late opening of the valve Th2 because as soon as the temperature of the heat transfer fluid exceeds the first threshold temperature, the flow rate leakage is sufficient to ensure that the coolant present in the fitting is not significantly cooler than that present in the crankcase.

The following description with reference to the accompanying drawings, given by way of non-limiting examples, will explain in what the invention is and how it can be achieved.

Figure 1 is an overall perspective view of an engine comprising a cooling system according to one embodiment of the invention.

FIG. 2 is a schematic view of the engine cooling chambers belonging to the cooling system according to the embodiment shown in FIG. 1.

Figure 3 is a detailed view of the separation means of the cooling system of Figure 1.

Figure 4 is a diagram of a cooling system of an engine according to a first particular embodiment of the invention. FIGS. 4A, 4B and 4C illustrate the circulation flows of the cooling fluid according to different engine temperatures;

FIG. 5 is a detailed diagram of the liquid distribution device of the cooling system of FIG. 4.

In Figures 1 and 2, there is shown a motor having a housing 10 and a cylinder head 12. This engine is for example diesel type. This cooling system comprises a cooling chamber 14, disposed in the casing 10 and intended to receive a cooling liquid, exchanging heat with the cylinders C1, C2, C3, C4 of the engine in which combustion of the fuel occurs. The cooling chamber 14 communicates with a chamber 18 which surrounds the intake valves SA of the cylinder head 12, the chambers 14 and 18 constituting within the meaning of the invention the low cooling chamber.

The system of Figures 1 and 2 also comprises a cooling chamber 16, isolated from the chamber 18 by a wall 19 inside the cylinder head and the chamber 14 by a cylinder head gasket 20 placed between the housing 10 and the cylinder head 12. The chamber 16 surrounds the exhaust valves SA and thus forms the upper chamber. This upper chamber is isolated from the lower chamber and allows separate cooling of the cylinder head 1 at the exhaust.

The gasket 20 comprises orifices 22, made only in the part of the gasket 20 for the circulation of the coolant between the chambers 14 and 18.

As shown in Figure 1, the cooling system described in this example also includes a pump 24 for supplying the chambers 14, 16, 18 with heat transfer fluid.

A baffle 26 is disposed downstream of the feed pump 24 and upstream of an inlet 34 of the liquid in the housing 10. This baffle ensures the separation of the liquid into two separate streams 28 and 28 '. As can be seen more clearly in FIG. 3, the baffle 26 may be constituted by a prism of generally triangular cross section, an apex 30 of which is disposed facing the liquid outlet of the feed pump 24.

The two sides connecting the vertex 30 to the side 38, opposite the vertex 30, are curved, their center of curvature being on the same side of the median from the top 30, to allow the progressive deflection of the streams 28, 28 ' to the inlets 34, 40 of the first 14 and second 16 cooling chambers, both located in the engine.

The baffle 26 is designed to direct the flow 28, 28 'to the inputs 34, 40 of the chambers 14, 16, 18 cooling and profiled to prevent the formation of turbulence in the coolant. A deflector 36 is also arranged in the first cooling chamber 14 and disposed in the vicinity of the inlet 34 of the liquid in said chamber 14. This deflector 36 is of generally elongate shape parallel to the axes of the casing cylinders and is of the same size as the cooling chamber 14 in this direction. It is intended to direct the liquid entering the first chamber 14 in a given direction. Indeed, it prevents the passage of the liquid in the direction opposite to the given direction by closing the space between the internal walls of the cooling chamber 14.

We will now describe the circulation of the heat transfer fluid in the system described in this example.

The heat transfer fluid, in this case the coolant, first comes out of the feed pump 24. It is then separated by the baffle 26 in two separate streams 28, 28 'intended for cooling, respectively of the housing 10 and the cylinder head 12. In a variant of the invention, the baffle 26 is perforated to allow the circulation of a residual flow.

The flow 28 then enters the first cooling chamber by an inlet 34. Then, it is directed by the deflector 36 in the given direction, shown in Figure 2. The liquid therefore flows in the first chamber 14 around the cylinders in a single direction, trombone, as shown in Figure 2. When the chamber 14 is filled with the liquid, the latter through the holes 22 of the cylinder head gasket 20 and enters the chamber 8.

In parallel, the flow 28 'engages in a rise 38 of water of the cylinder head 12 and enters the chamber 16 by an inlet 40. The two flows 28 and 28' flow substantially parallel in the chambers 16 and 18 and escape from the yoke 12 by respective outlets 42, 44, disposed at the same end of said yoke 12.

Once the liquid has passed through the outlets 42, 44, it circulates in a liquid distribution box in the cooling circuit (not shown in the figures), arranged on the cylinder head 12. This housing directs the liquid to a radiator of the engine, allowing the cooling thereof, where it is again sent to the pump 24 supply. The design of the distribution system is more particularly illustrated with reference to FIGS. 4 and 5. In these figures, there are the chambers 14, 16 and 18 supplied with cooling liquid by the pump 24. The circuit comprises by elsewhere a radiator 15 for cooling the fluid after the engine is passed through. Furthermore, in and possibly other means heat exchangers, such as a heater A - to heat air for the habitable and EE EGR exchanger (EGR is the acronym for Exhaust Gas Recirculation, meaning "exhaust gas recirculation"), for cooling a fraction of the exhaust gases re-injected into the combustion chambers.

Under certain conditions, for example following a cold start, an immediate start of the entire cooling system can lead to a delay in temperature rise of the engine, detrimental to its performance. The authors of the present invention thus propose 3 modes of operation, illustrated respectively in FIGS. 4A, 4B and 4C:

The mode illustrated in FIG. 1A corresponds to a "cold" cooling fluid, the temperature of which is lower than a first threshold temperature T _s1, for example of the order of 83 ° C. In these conditions, it is there is no need to cool the cooling fluid which can thus bypass the radiator 15, which furthermore makes it possible to promote the rise in temperature of the casing to reach as quickly as possible a steady state temperature, if only to place itself in the Optimum temperature range for lubrication. The cooling fluid therefore simply passes through the cylinder head, with a "direct" return 3 to the pump 24 - or possibly passes through the branch 4 carrying the heater and the EGR exchanger, the flow rates of cooling liquid passing through these elements or passing by the branch 4 being controlled for example by means of a valve here not shown.

When the temperature of the cooling fluid rises beyond this threshold temperature T _s- 1 _, a cooling of the liquid becomes necessary, hence as shown in FIG. 4B the circulation in the branch 5 passing through the radiator 15, with a bypass at the Th1 valve. As will be more particularly explained in connection with FIG. 5, at the same time the circulation in the bypass 3 is cut off. Finally, in the operating mode corresponding to Figure 4C, beyond a second threshold temperature, T _s2 , for example of the order of 105 ° C, the circulation is established in the housing 14 to means of the branch 6 whose flow is controlled at the valve Th2.

Figure 5 shows more particularly the heat transfer fluid distribution device at the motor output, with the combination of the two valves Th1 and Th2.

This device disposed on the cylinder head comprises a junction 70 disposed downstream of the chamber 16. The coolant is admitted into the junction 70 by a main inlet 21 connected to the cooling chamber on the exhaust side of the cylinder head. The junction 70 constitutes the main element of the distribution system of the coolant towards the different branches of the cooling circuit and to this end, communicates with the branches 3, 4, 5 and 6 respectively by the inlets / outlets 31, 41, 51 and 61. In the embodiment shown here, only the output 41 is not provided with flow control means therethrough.

The outputs 31 and 51 are controlled by the valve Th1 constituted by a system with two valves, with a valve 32 sized to close the outlet 31 and a valve 52 sized to close the outlet 51. The valve 52 is applied against the output 51 by a spring 53. In addition, the valves 32 and 52 are controlled by control means comprising a thermoactive member 54, for example constituted by wax, bathed by the liquid of the junction 70. This member 54 is suitable to control the valve Th1 between a first position in which the valve 52 obstructs the outlet 51, while the outlet 31 is open (hypothesis of Figures 1A and 2A, the temperature of the coolant is less than T _s i) and a second position, in which the valve 32 obstructs the outlet 31 while the circulation is established in the branch 5 (the temperature of the coolant is greater than T _s -ι).

The fourth output of the junction 70 is the output 61 for establishing a circulation in the cooling chamber of the housing 14. To do this, this output 61 (or more precisely this input if we consider the direction of flow of the cooling fluid) communicates with a connector 71 defining the pipe 6. The outlet 61 is controlled by the valve Th2. Any circulation between the coupling 71 (and therefore the crank chamber) and the junction 70 downstream of the cylinder head is thus blocked by a valve 62 displaced on the one hand by a return spring 63, means 64 - similar to the means 74 and electrical means 75.

The means 64 are designed to cause the valve 62 to open when the heat transfer fluid has reached a temperature greater than the second threshold temperature T _S 2 However, insofar as these means are located in the coupling 71 in which the heat transfer fluid does not circulate as the valve 62 is closed, the temperature rise of the fluid in the connection can be delayed, with the risk of overheating of the engine whose housing is not cooled.

This is why according to the invention a pipe 76 is provided opening on the one hand in the connector 71 and on the other hand at the valve 52 which in the closed position also closes the pipe 76. The pipe 76 has a narrow section, for example of the order of one-tenth of the section of the outlet 61.

Thus, when the temperature of the heat transfer fluid is lower than the first threshold temperature T _s i, no heat transfer fluid circulation is allowed in the casing chamber. Once the pipe opens, a low circulation is set up through this pipe 76. As the section of the pipe is small, this circulation is not sufficient to counteract the rise in temperature of the housing but it is sufficient to guarantee that the temperature of the coolant in the connector 71 is the same as that of the fluid in the housing, so that the opening of the valve 62 is performed as soon as the preheating phase of the engine is complete.

The electrical means 75 are auxiliary control means for opening the valve 62 during the preheating phase, especially when the engine operates at high speeds during this phase. These means are therefore controlled by the engine control, which for example according to a map based on the engine speed, the torque and a temperature taken by a sensor 77, and will for example act on an electrical resistance which, by Joule effect , will heat the wax to operate the flap.

Claims

A motor vehicle engine cooling system comprising a housing (10), a cylinder head (12) containing the intake valve ducts and seats, and exhaust valves, said system comprising a pump (24) and a coolant circuit bifurcating downstream of the pump (24) for separately supplying a lower chamber (14, 18) for cooling the housing (10) and the part of the cylinder head surrounding the intake valves and an upper chamber (16) for cooling the portion of the cylinder head surrounding the exhaust valves, the two branches of the coolant circuit converging at the output of the high and low chambers.

Cooling system according to claim 1, characterized in that it comprises a cylinder head gasket (20) arranged between the housing (10) and the cylinder head (12), and at least one orifice (22) intended for the circulation of the coolant in the lower chamber (14, 18), between the casing portion (14) and the inlet portion (18).

3. Cooling system according to claim 1, characterized in that the coolant flows in substantially parallel flows (28, 28 ') in the upper chamber (16) and the inlet portion (18) of the upper chamber ( 14) and escapes from the cylinder head (12) at the same end of said cylinder head (12).

4. Cooling system according to any one of the preceding claims, characterized in that the bifurcation is obtained with means (26) for separating the liquid located upstream of an inlet (34) of the liquid in the housing (10).

5. Cooling system according to claim 3, characterized in that the separating means comprise a baffle (26) disposed downstream of the pump (24) supply.

6. Cooling system according to claim 5, characterized in that the baffle (26) is perforated to allow the circulation of a residual flow.

Cooling system according to one of Claims 1 to 7, characterized in that a deflector (36) is arranged in the first cooling chamber (14) so as to direct the liquid entering the said first chamber into a chamber (14). direction given.

8. Cooling system according to claim 7, characterized in that the deflector (36) is of generally elongate shape parallel to the axes of the casing cylinders.

9. Cooling system according to any one of the preceding claims, characterized in that the flows having passed through the high and low chambers converge in a dispensing device comprising:

A junction (70) having a main input (21), an auxiliary input (61) whose opening is controlled by an inlet valve Th2, a main output (41) and an auxiliary output (51) leading to a radiator (15), the auxiliary output (51) being controlled by a controlled outlet valve Th1 to reach an open position when the coolant flowing in the junction (70) reaches a first threshold temperature T _s1 ;

A connection (71) leading to the auxiliary input (61) of the junction, the inlet valve Th2 being controlled to reach an open position when the heat transfer fluid present in the connection (71) reaches a second temperature of threshold

T _s2 greater than the first threshold temperature T _s1 ; and

Means (76) for creating a heat transfer fluid leakage flow between the junction (70) and the connector (71) when the outlet valve Th1 is in the open position and the inlet valve Th2 is in the closed position.

10. Cooling system according to claim 9, characterized in that the outlet valve Th 1 and the inlet valve Th 2 are of the type comprising a thermoactive element bathed by the coolant.

1 1. Cooling system according to claim 10, characterized in that said thermoactive element is wax.

12. Cooling system according to one of claims 10 or 11 characterized in that the control means of the inlet valve Th2 further comprise an electrical resistance, disposed on the thermoactive member and electrically powered by a generator member. current to control the inlet valve when the temperature of the coolant has not reached T _S 2-

13. Cooling system according to any one of claims 9 to 12 characterized in that the means for creating a leakage flow comprise a pipe whose section is smaller than the section of the auxiliary input, the pipe opening in the vicinity of the outlet valve so that the pipe is closed when this outlet valve is in the closed position.

14. Cooling system according to any one of claims 9 to 13, characterized in that a heater contributing to the thermal conditioning of the air of the passenger compartment of the vehicle is disposed in the portion of the circuit of the coolant between the main outlet (41) and the pump (24).

15. Cooling system according to any one of claims 9 to 14, characterized in that a heat exchanger contributing to the cooling of the recirculated fraction of the exhaust gas is disposed in the portion of the circuit of the coolant between the main outlet (41) and the pump (24).

16. Cooling system according to any one of claims 13 to 15, characterized in that the junction further comprises an outlet (31) opening on a bypass directly to the pump.

17. Cooling system according to claim 16, characterized in that the valve Th 1 further controls the closure of a valve (52) closing the bypass outlet (51) when the outlet (31) is in the open position.

18. Cooling system according to claim 16, characterized in that the outlet (41) is provided with flow control means for controlling the fraction of the coolant flow directed towards the bypass and the fraction directed towards the main loop. .

Diesel engine equipped with a cooling system according to any one of claims 1 to 18.