WO1982004095A1

WO1982004095A1 - Method and device for coolant temperature control

Info

Publication number: WO1982004095A1
Application number: PCT/NL1982/000015
Authority: WO
Inventors: Werkspoor Diesel Bv Stork; Albert Jan Beuzel
Original assignee: Werkspoor Diesel Bv Stork
Priority date: 1981-05-12
Filing date: 1982-05-12
Publication date: 1982-11-25
Also published as: NL8102340A; GB8300068D0; GB2112924B; GB2112924A

Abstract

A method and a device of controlling the temperature of the coolant in a heat source of variable thermal yield, for example, a water-cooled internal combustion engine (1), in which the cooling circuit comprises a heat exchanger (2) communicating with the heat source through a supply duct (3) and a return duct (4) and a by-pass duct (5) arranged parallel thereto between the supply duct (3) and the return duct (4), wherein depending on the temperature difference of the coolant in the supply duct (3) or by-pass duct (5) and the return duct (4) as well as on the absolute temperature values thereof such a volume of coolant is passed through the heat exchanger (2) that a new state of equilibrium is produced in which the temperature in the supply duct (3) has dropped at an increase in heat production, in order to obtain a temperature decreasing tendency, that is to say, at a low load the coolant temperature in the engine is at a level which is higher than the required at full load.

Description

METHOD AND DEVICE FOR COOLANT TEMPERATURE CONTROL

The invention relates to a method of controlling the temperature of the coolant in a heat source of variable thermal yield, for example, a water-cooled internal combustion engine, in which the cooling circuit comprises a heat ex changer communicating with the heat source through a supply duct and a return duct and a by-pass duct arranged parallel thereto between the supply duct and the return duct.

In the known control-systems a cooling circuit, for example, in Diesel engines temperature-sensitive expansion elements may be used for controlling valves in the ducts in a manner such that at an increase in engine load the higher heat production is conducted away by means of greater cooling through a heat exchanger. However, the control-systems hitherto known then have a rising temperature characteristic curve, that is to say, the temperature in the supply duct increases at an increase in engine lead. A disadvantage of such a system is that at a low load of, for example, a Diesel engine great wear may occur as a result of the formation of corrosive condensate precipitating on the excessively cold cylinder walls.

Object of the invention is to provide a mode of control in which a temperature decreasing tendency is obtained at an increasing load of the engine that is to say, at a low load the coolant temperature in the engine is at a level which is higher than the required at full load.

The method according to the invention is distinguished in that in dependence on the temperature difference of the coolant in the supply or by-pass duct and the return duct as well as on the absolute temperature values thereof such a volume of coolant is passed through the heat exchanger that a new state of equilibrium is produced in which the temperature in the supply duct has dropped at an increase in heat production.

The advantage of the method proposed is that control can be continuously carried out, that is to say, at any load of the engine the optimum coolant temperature can be attained. In pressure-filling Diesel engines, in which the combustion air downstream the pressure-filling group is coole in an air cooler having a coolant,, it is desired to withdraw heat at a high engine load and to supply heat to the combustion air at a low load. The invention provides a mode of control which also satisfies this demand. Herein the air cooler is included in the return duct of the coolant.

In order to attain the low temperature in the return duct desired at full load of the engine, only part of the total amount of coolant is passed, in accordance with the invention, across the heat exchanger for the control aimed at, the remaining part being circulated through an additional by-pass duct.

In the proposed control-mode the temperature in the return duct i.e. in front of the air cooler will strongly increase with a decreasing engine load. Since the temperature of the combustion air for the air cooler drops at a decrease in engine load, the temperature of the coolant will exceed, below a given load, the temperature of the combustion air so that heat is supplied to the combustion air. The advantage of the method proposed is that by heating the combustion air in the low load range formation of condensate and hence heavy wear are avoided, whilst at the same time ignition and combustion conditions are improved.

If at a load decreasing from full load a still faster temperature increase is desired, the control-mode proposed provides the possibility of controlling the increase or decrease in the passage of the additional by-pass duct in the same sense as the increase or decrease in the passage of coolant across the heat exchanger. Thus the point where the temperature of the coolant in the return duct exceeds the temperature of the combustion air is shifted to a higher engine load. In order to obtain a faster response of the control- system a restricted temperature range in the return duct lies between a maximum and a minimum value.

According to the invention, when a preset maximum or minimum temperature in the return duct is attained, the supply of coolant to the heat exchanger is controlled solely by the temperature in the forward duct.

The invention furthermore relates to a device for carrying out the above described control-mode, said device being employed in a water-cooled internal combustion engine, for example, a Diesel engine and being included in a cooling circuit comprising a heat exchanger connected through the forward and return ducts with the engine and a by-pass duct directly arranged between the forward and return ducts.

According to the invention the device is distinguishe in that the forward duct or by-pass duct and the return duct each include a temperature-sensitive element, whilst a converter controlled by the two temperature-sensitive elements actuates a valve set for closing or, respectively, opening the by-pass duct and in conjunction, for opening or, respectively closing the heat exchanger.

The converter may be constructed in various ways, for example, electronically, hydraulically, pneumatically or mechanically.

In the mechanically design a coupling lever is pivotally connected with two temperature-sensitive expansion members, said coupling lever being furthermore connected with the valve set. Thus the temperature change is directly converted into a place shift of the coupling lever, that is to say, into a translation or a rotation respectively, both movements being transferable to a displacement of a leverage or gear wheel set for the valves to be included in the ducts. If the cooling circuit is equipped with an additional by-pass duct between the forward and return ducts, the con verter embodying the invention can, in addition, actuate a valve for controlling the passage of said additional by-pass duct so that it changes in the same sense as the passage in the heat exchanger. The aforesaid and further features of the invention will be explained more fully in the following description of the drawing showing two embodiments of the cooling circuit in a Diesel engine.

In the drawing Figs. 1 to 4 relate to the first embodiment.

Fig. 1 is a diagram of the cooling circuit in a first embodiment.

Figs. 2 and 3 are two graphs in which the temperature and, respectively, the amount of flow of the coolant are plotted against the extent of load of the engine.

Fig. 4 is schematic representation of a control-valve with the associated control-device for use in a control-system as shown in Fig. 1.

Figs. 5 to 8 relate to a second embodiment. Fig. 5 is a schematic representation of a second embodiment of the cooling circuit in a Diesel engine.

Figs. 6 and 7 are two graphs in which the temperature and, respectively, the amount of flow of the coolant are plotted against the extent of load of the engine. Fig. 8 shows a valve set as used in the cooling circuit of Fig. 5.

Referring to Fig. 1, reference numeral 1 designates schematically an internal combustion engine, for example, a Diesel engine provided with a cooling circuit comprising a heat exchanger 2, a forward duct 3 leading to said exchanger and a return duct 4 leading from said exchanger to the engine. Between the forward and return ducts 3, 4 a by-pass duct 5 is provided via the heat exchanger 2. An additional by-pass duct 6 having a predetermined passage directly passes an amount of coolant from the duct 3 to the duct 4. Upstream the junction of ducts 4 and 6 the return duct 4 includes an air cooler 7 for cooling or heating compressed combustion air for the engine 1. At the junction of the return duct 4, the by-pass duct 5 and the outlet 12 of the heat exchanger 2 is arranged a valve set 8.

A circulation pump 9 ensures the circulation of the coolant through the circuits.

The by-pass duct 5 and the return duct 4 include each a temperature-sensitive expansion member 10 and 11 respectively, said members actuating the valve set 8 by means of a coupling lever pivoted to said two members. The position of the valve set 8 determined by the values of the temperatures of the coolant at the expansion members is determinative of the distribution of the flow of coolant among the by-pass duct 5 and the heat exchanger 2. This takes place in a manner such that at an increase in engine load the coolant tempera ture decreases both in the forward and return ducts until a new state of equilibrium is reached.

The foregoing is graphically represented in Figs. 2 and 3.

In Fig. 2 the coolant temperature is plotted for different places of the circuitry against the extent of load L of the engine 1. In the graph the indices a t the temperatures correspond to the reference numerals of the ducts concerned. From the graph it will be apparent that an increase in load L the temperature in duct 3 decreases. This is the result of an increasing rate of coolant flow through the heat exchanger 2.

Fig. 3 illustrates the relationship between the various coolant flows. A portion W6 of the overall water flow is directly circulated through the duct 6. The remaining portion W4 is divided in accordance with the position of the valve set 8 into the flows W5 and W12. At an increase in load L of the engine from point A to point C (full load) the stream of coolant W12 across the heat exchanger increases. Owing to the relatively low temperature T12 the temperature in duct T4 will drop. Downstream of the aircooler 7 T4 is raised to T4' and after having met the coolant from duct 6 it rises to T4".

In the engine 1 the coolant is heated to T3. At full load T3 is, however, lower than at no-load owing to the control-system embodying the invention: see the situations A, B and C.

Fig. 4 shows a mechanical embodiment of a valve set. With the valve housing 8 are connected three ducts 5, 4 and 12 corresponding with the ducts of Fig. 1. Inside the valve housing 8 a slide valve can open the ports of the ducts 5 and 12 respectively and close the same respectively. The ducts 5 and 4 include temperature-sensitive expansion members 10 and 11 respectively. These members are connected with a coupling lever 13, which is rotatably coupled at one end with a connecting rod 14, which, in turn, actuates the lever 15 of the rotatable slide valve in the housing 8. Out of the state of equilibrium at no-load at point A in Figs. 2 and 3 and, respectively, point A' in Fig. 4 the temperature T3 will initially rise with an increasing load. This temperature increase is converted into a turn of the coupling lever 13 about point A in anti-clockwise direction, so that the slide valve in the valve housing 8 is turned to an extent such that the passage of duct 5 is reduced and that of duct 12 is enlarged, as a result of which more coolant is passed across the heat exchanger 2 and hence the temperature in duct 4 drops. The coupling lever 13 will, as a result, turn in the same direction but in this case about the junction with the expansion member 10 so that the passage of duct 5 is further diminished. The drop of temperature T4 results in that the temperature T3 will decrease after an initial slight rise so that the coupling lever 13 will turn in the opposite sense with respect to the turn resulting from the decreasing temperature T14. Finally, at a heavier load B a state B' of the coupling lever 13 will establish, in which the temperature T3 and the temperature T4 are lower than at an engine load A, whilst the temperature difference T3 - T4 is greater (see Fig. 2). At an increase to full load C of the engine a position C' of the coupling lever is reached, the lever having turned to an extent such that the passage of duct 5 is completely shut and that of duct 12 is fully open. The temperature T4 then corresponds with temperature T12 and has then dropped to its minimum value. The temperature T3 then also has its lowest value (see Fig. 2).

The difference between T3 and T4 in a state of equilibrium is a function of the engine load and, therefore, increases at an increasing load.

The displacement of the coupling lever 13 connected with the temperature-sensitive expansion members 10 and 11 and the valve set 8 is a function of the same temperature T3 and T4. The desired relationship between T3 and T4 is obtained by concretising the cinematic relations between the displacements of the expansion members and the desired turn of the coupling lever in a structural manner in the control. It is thus ensured that at an increasing load, it is to say, at an increasing value of the difference between the temperatures T3 and T4 T3 drops due to a relatively great decrease of T4.

If at a given engine load B in the position B' of the coupling lever the heat transfer in the heat exchanger 2 deteriorates, for example, due to fouling or to a higher temperature of the outer coolant, the temperatures T3 and T4 will increase. Since the heat supply at constant engine load will not change, the temperature difference T3 - T4 will not change either so that the two temperatures T3 and T4 increase by equal values. As a result the coupling lever 13 is raised in translation so that the slide valve in valve housing 8 reduces the passage of duct 5 and enlarges that of duct 12 until a new state of equilibirum is reached.

It may be preferred to restrict the control-range of the temperature sensor 11 so that the final positions A' and C' are limited to a lower value A" and a higher value C" respectively (see Fig. 4). This has the result that near the final positions of the expansion member 11 the control is further performed by the expansion member 10. This provides a faster control-response.

Fig. 5 shows a variant of the cooling system. Corresponding parts are designated by the same reference numerals. The difference resides in that the duct 6 is not direct ly branched from the forward supply duct 3, rather passes via the valve set 18. This permits of controlling also the passage of the duct 6 in a manner such that it is changed in the same sense as the change of passage of duct 12 emanating from the heat exchanger 2. When the passage 12 is further closed, the passage 6 is also further closed as a result of which more and hotter coolant is passed across the air cooler 7, which brings about a faster increase in temperature in the system at a decreasing engine load than in the first embodiment.

This is illustrated in Fig. 6, from which it can be seen, in comparison with Fig. 2, that the temperature curves T3 and T4 respectively have a more convex shape.

From Fig. 7, as compared with Fig. 3, it will be apparent that the rate of flow of coolant through duct 6 can be controlled in accordance with the upper curve, the overall coolant flow being divided among ducts 4 and 6 respectively.

Fig. 8 shows a potential embodiment of a valve set 18 comprising three rotary valves included in a duct system having four ducts 4, 5 6 and 12. The valves 19 can be relatively turned and coupled with a central connecting rod 20 in a manner such that, when the middle valve in duct 5 is opened, the outer valves will shut the ducts 12 and 6 respectively and conversely. The valves and the connecting rod 20 respectively are actuated in the same manner as described above by means of temperature-sensitive expansion elements 10 and 11 in ducts 6 and 4 respectively. In duct 6 prevails the same temperature T3 as in ducts 3 and 5. The effect of the temperature-sensitive expansion members 10 and 11 and of the coupling lever 13 respectively corresponds to what is described with reference to Fig. 4.

This means that in position A' (no-load) substantially all coolant is conducted away through duct 4 and in position C' (full load) the coolant passes through ducts 4 and 6. In this position the maximum amount of coolant is passed across the heat exchanger 2.

The ratio between the lengths of the lever arms between the fulcrums of the coupling lever 13 can be adapted to the characteristics of the temperature-sensitive expansion members. They may have either the same or a different variation in length per degree of temperature change. The invention is not limited to the mechanical embodiments described above which directly respond to temperature. For example, the expansion members 10 and 11 may be replaced by temperature-dependent signal producers. These signals may be converted by mechanical, electrical, hydraulic or pneumatic agency or a combination thereof into a valve displacement.

Claims

WHAT IS CLAIMED IS:

1. A method of controlling the temperature of the coolant in a heat source of variable thermal yield, for example, a water-cooled internal combustion engine, in which the coolant circuit comprises a heat exchanger connected through a forward duct and a return duct with the heat source and a by-pass duct arranged parallel thereto between the forward and return ducts characterized in that in dependence on the temperature difference of the coolant in the forward duct and the return duct as well as on the absolute temperature value thereof such a volume of coolant is passed through the heat exchanger that, a new state of equilibrium is established,in which the temperature in the forward duct has dropped at an increase in thermal yield.

2. A method as claimed in Claim 1 wherein the return duct includes a second heat exchanger, for example, for the combustion air to be compressed for the heat source, characterized in that only a portion of the total amount of coolant is used for the control aimed at across the heat exchanger and the remaining portion is circulated through an additional by-pass duct.

3. A method as claimed in Claim 1 characterized in that the enlargment or reduction of the passage of the additional by-pass are controlled in the same sense as the enlargment or reduction of the passage across the heat exchanger.

4. A method as claimed in anyone of the preceding Claims characterized in that, when a preset maximum and minimum temperature respectively in the return duct is attained, the supply of the amount of coolant to the heat exchanger is solely controlled by the temperature in the forward duct.

5. A device for carrying out the method claimed in anyone of the preceding Claims used in a water-cooled internal combustion engine, for example, a Diesel engine, said device being included in a cooling circuit comprising a heat ex chanber connected with the engine through a forward and return duct and a by-pass duct arranged parallel thereto between the forward and return ducts, as well as control- valves for distributing the flow of coolant among the heat exchanger and the by-pass duct characterized in that the forward duct and the return duct each include a temperature- sensitive element and in that a converter controlled by said two temperature-sensitive elements actuates a valve set for closing and, respectively, opening the by-pass dues and, in conjunction, for opening and, respectively, closing the heat exchanger.

6. A device as claimed in Claim 5 used in a cooling circuit having an additional by-pass between the forward and return ducts characterized in that the converter actuates a valve for controlling the passage of the additional by-passin the same sense as that for the passage across the heat exchanger.

7. A device as claimed in Claim 4 characterized in that the temperature-sensitive elements are formed by temperature-sensitive expansion members and in that the converter in the form-of a coupling lever pivoted-to said expansion members actuates the valve set.

8. A device as claimed in Claim 7 characterized in that two expansion members are used for the same variation in length per degree of temperature change.

9. A device as claimed in Claim 7 characterized in that two expansion members are used for different variations in length per degree of temperature change.

10. A device as claimed in anyone of Claims 5 to 9 characterized in that the range of action of the temperature sensitive expansion members is adjustable to a maximum and minimum value respectively.

11. A device as claimed in Claim 5 characterized in that the temperature-sensitive elements provide a signal applied as a control-signal to, at will, an electrical, hydraulic or pneumatic control-member for actuating the valves of the valve set.