The present invention relates to a multi-channel or multi-way mixing device which allows proportional control of the temperature of a liquid by mixing flows having dif¬ ferent temperatures. More particularly, the present inven¬ tion relates to a multi-way mixing device of the type men¬ tioned by way of introduction, which does not cause any pressure drops in the flows to be mixed, i.e. the amount of flows is unchanged.

Reaching and maintaining a desired temperature in the passenger compartment of a motor vehicle is a problem that is difficult to solve and is caused by a number of diffe¬ rent factors. Examples of such factors are the speed of the vehicle, the outdoor temperature and exposure to sun¬ light. If the temperature of the air in the passenger com¬ partment is affected, this air or the air supplied from outside must therefore be heated or cooled.

Prior-art air-conditioning systems for motor vehicles generally consist of a heating circuit, a cooling circuit and a heat exchanger. Usually the cooling side is put out of service when the outdoor temperature falls below a cer¬ tain level, and the heat requirement is controlled by directly actuating a heat control valve or by feeding the desired temperature into a control system which is inte¬ grated with the air-conditioning system and whose details will not be entered upon. Depending on the position of the heat control valve, the flow of liquid through the heat exchanger is altered, and air heated when passing the heat exchanger is blown into the compartment by starting the ventilator in the compartment.

As temperature rises, the cooling side is used, if required, while the heat exchanger is disconnected by closing the heat control valve. A compressor compresses a gaseous coolant which by the increase in pressure is caus¬ ed to condensate in a condenser and thereby emits part of its heat content. The supercooled liquid is supplied via

conduits into an evaporator in which the liquid is vapor¬ ised at a lower pressure, while absorbing heat which is then released during condensing in the condenser. Part of the heat in the air which is caused by the ventilator to pass the evaporator, .e.g. from outside, thus is absorbed by the coolant and drawn off, while cool air is blown into the compartment.

Such air-conditioning systems for motor vehicles are disclosed in e.g. SE-B-357,329, EP-A2-095,704, GB-A- 1,548,561, GB-A-2,072,318, US-A-3,779,307 and US-A- 3,990,505.

SE-B-357,329 discloses a system for heating or cool¬ ing the air in the passenger compartment of a motor vehi¬ cle. The system comprises a heating circuit and a cooling circuit which are combined via a common heat exchanger, and two water pumps, one of which is the normal water pump of the vehicle, which thus is dependent on the number of revolutions of the power unit. The other water pump is connected only to cool the air which is blown into the compartment.

EP-A2-095,704 discloses an air-conditioning system for vehicles in which the coolant in the heat exchanger is connected thermally with the engine cooling water flowing through a per se known air/cooling water heat exchanger. The flows are mixed via a three-way valve.

GB-A-1,548,561 discloses a valve for alternately connecting a cooling circuit or a heating circuit to a heat exchanger.

GB-A-2,072,318 concerns a heating and cooling system for motor vehicles. According to this publication, an eva¬ porator is arranged to transfer heat from the liquid coolant to the refrigerant in a cooling circuit, and single valves are provided for directing liquid coolant either from the evaporator or from the engine cooling cir- cuit to a heat exchanger.

US-A-3,779,307 discloses a heating and cooling system for motor vehicles having a primary engine cooling circuit and a second circuit including a heat exchanger, cooling means and a plurality of pipes connecting the cooling means with the heat exchanger, and a multi-channel mixing means for connecting the first circuit with the second circuit.

US-A-3,990,505 discloses an air-conditioning system comprising a liquid/air heat exchanger, a two-way valve having two inlets and one outlet. Moreover, there are means for feeding hot liquid to a valve inlet, and further means for feeding cooled liquid to the other inlet of the valve. A coolant/liquid heat exchanger for cooling the liquid is also included. It can be noted that a great deal of development work has been performed to provide efficient a. conditioning systems in vehicles. In thee _/ , prior-art t. _/ stems function without any particular problems. What has in practice proved to function in a less satisfactory manner is, how- ever, the actual control of the temperature also when employing sophisticated, electronic control systems, and furthermore problems arise as liquid flows are throttled. In many cases, mechanical setting means have a working range which is far too narrow, turning through a few degrees or movement by some millimetres causing a con¬ siderable change in temperature. However, even when using sophisticated control systems the actual air temperature can in some cases deviate drastically from the preselected temperature, especially when measuring the temperature at different inlets or nozzles in the compartment.

A further drawback of prior-art systems is the total pressure drop across the evaporator and the heat exchanger, which leads to a poor capacity of the avail¬ able ventilator and to equilibration problems in connec- tion with an increasing number of inlets or nozzles.

Valve means used in air-conditioning systems accord¬ ing to the prior-art technique are in many cases of a most simple design, cf. GB-A-1,548,561 and GB-A-2,072,318, which permits but switching between different flows or is described in a desiderative fashion, cf. the valve means 21 in US-A-3,779,307.

One object of the present invention therefore is to provide a multi-channel or multi-way mixing device which permits accurate and continuous mixing of flows of liquid having different temperatures, thereby obtaining simple, efficient and more accurate adjustment of the temperature. A further object of the present invention is to pro¬ vide a multi-way mixing device which does not cause pres¬ sure drops when mixing different flows. Moreover, the multi-way mixing device according to the present invention should be cost-effective, useful in modern air-conditioning systems and allow combination with thermostatically controlled control systems.

These and other objects are achieved by means of a multi-way mixing device according to the characterising clause of claim 1.

The invention will now be described in more detail with reference to the accompanying drawings in which two embodiments of a multi-way mixing device for controlling the flow rates in a modern air-conditioning system for motor vehicles are illustrated and in which:

Fig. 1 is a schematic sectional view of a multi-way mixing device according to the present invention,

Fig. 2 is a partly sectional side view of a different embodiment of the multi-way mixing device according to the invention,

Fig. 3 is a top plan view of a valve disc which con¬ stitutes an important part of the multi-way mixing device, and Fig. 4 illustrates the position of a multi-way mixing device according to the present invention in a schemati¬ cally illustrated air-conditioning system for vehicles.

Fig. 1 illustrates the working principle of a multi- way mixing device 46' according to the present invention. The fundamental idea is to produce, based on at least two flows of liquid which are completely separated, a con- tinuous mixing of these flows from 0 to 100%, i.e. conti¬ nuous adjustment from complete separation to complete mix¬ ing of the flows.

The embodiment shown in Fig. 1 comprises an elongate duct 84 arranged in a housing 82 and having an inlet 86 and an outlet 88, the inlet 86 being connected to a coolant duct 70 from an internal combustion engine 62, and the outlet being connected to a coolant return duct 76 (see Fig. 4).

Further the housing 82 is formed with a pump duct 90 having an inlet 92 and an outlet 94, the inlet 92 being connected to a heat exchanger 44, and the outlet 94 being connected via a tank 50' to the heat exchanger 44 (see Fig. 4).

Moreover, the inlet 92 of the pump duct 90 is via a duct 96 connected to the outlet 88 of the elongate duct 84.

At the transition of the inlet limb to the curved portion of the pump duct 90, the inlet limb is via a duct 98 connected to the inlet 86 of the elongate duct 84. A circulation pump 100 is fitted with an impeller 102 arranged in the transition between the curved portion of the pump duct 90 and the outlet limb connected with the outlet 94.

A pressure regulator 104 permits closing of the pas- sage between the inlet 92 and the outlet 94 of the pump duct 90, without affecting the flow of liquid via the ducts 96 and 98 between the inlet 86 of the elongate duct 84 and the outlet 94 of the pump duct 90 and, respective¬ ly, between the inlet 92 of the pump duct 90 and the out- let 88 of the elongate duct 84.

For complete separation of the flows moving through the elongate duct 84 and the pump duct 90, respectively, a valve disc 106 is rotatably arranged in the ducts 96 and 98, which in a closed position prevents liquid from pass- ing between the elongate duct 84 and the pump duct 90, the pressure regulator opening and allowing liquid advanced by the circulation pump 100 to pass in said duct 90.

Depending on the position of the valve disc 106 and, consequently, the throttling of the ducts 96 and 98, con- tinuous mixing from 0 to 100% of the flows through the elongate duct 84 and the pump duct 90 thus is effected. For altering the position of the valve disc 106 this is connected via a shaft 105 to e.g. a stepping motor 107.

Fig. 2 illustrates a further embodiment of the multi- way mixing device according to the invention. This is a preferred embodiment in which the pressure regulator shown in Fig. 1 has been replaced by a more sophisticated valve disc 108 which is shown in a top plan view in Fig. 3 and which will be described in more detail below. The embodiment of the multi-way mixing device 46" shown in Fig. 2 also comprises a coolant duct 110 which is connected to the engine (not shown) and which is of U shape and has a coolant inlet (concealed) and a coolant outlet 112. An inlet 114 connected to the heat exchanger is connectible via a duct 116 and the valve disc 108 with the end of the duct 110 facing away from the inlet and outlet 112, while an outlet 118, which via the tank 50' (see Fig. 4) is connected to the heat exchanger, is con¬ nectible to the duct 110 via a duct 120 and the valve disc 108. Like in the embodiment shown in Fig. 1, an impeller 122 of a circulation pump 124 is arranged in the duct 120. In a certain position (shown in Fig. 2) of the rotatable valve disc 108 there is formed a cavity 126 via which the heat exchanger circuit is closed, i.e. the inlet 114 is connected to the outlet 118. The valve disk 108 is rotated manually or by means of a stepping motor (not shown) which is connected to a shaft 127 connected with the valve disc.

Reference is now made to Fig. 3 which in the form of a top plan view illustrates a preferred embodimei ; of the valve disc 108.

Through openings or holes designated 130 and 132 con- nect with quarter-circular grooves 134 and 136 which become shallower counter-clockwise. An elongate channel 138 extends along an imagined symmetry line. The ends of the channel facing the rim of the disc form wings 140, 142 tapering to the centre, while the central portion has laterally cut recesses 144, 146.

By rotating the valve disc 108 in relation to e.g. the openings of the duct 116 and 120 (see Fig. 2) facing the valve disc, the flows between the heat exchanger cir¬ cuit and the heating circuit are affected. In one position of the valve disc 108, the opening of the duct 116 is positioned opposite the wing 142 of the channel 138, and the opening of the duct 120 is positioned opposite the other wing 140 of the channel 138. Otherwise the disc 108 is sealingly covered. In this position of the valve disc 108, the inlet 114 is connected via the channel 138 to the outlet 118, and no mixing with the coolant flowing in the duct 110 under the valve disc 108 (see Fig. 2) is effected, i.e. 0 ⁹ mixing.

When rotating the valvt. disc 108 counter-clockwise from this position, first the quarter-circular grooves 134 and 136, and part of the recesses 144, 146 are caused to extend in front of the openings of the ducts 116, 120. In such an intermediate position, the connection via the channel 138 is throttled into minor passages at the recesses 144, 146, while the grooves 134, 136 which, as the disc 108 is rotated counter-clockwise, become deeper and deeper, via the through holes 130, 132 mix hot coolant from the duct 110 in the heat exchanger circuit, i.e. the mixing is higher than 0% and lower than 100%. In continued counter-clockwise rotation of the valve disc 108 to a stop position, the through »αles 130, 132 are finally moved to a position opposite .he openings of

the ducts 116, 120, whereby full communication between the heat exchanger circuit and the heating circuit is estab¬ lished, whereas the direct communication between the inlet 114 and the outlet 118 of the heat exchanger circuit is interrupted. Thus, the mixing is complete, i.e. 100%.

A modern air-conditioning system for vehicles which comprises a multi-valve mixing device according to the invention is shown in Fig. 4. Like the prior-art technique described by way of introduction, this system has a cool- ing side to the left in Fig. 4, and a heating side to the right in Fig. 4.

In a ventilator duct 40 leading to the compartment, a ventilator 42 is arranged in a known manner. This makes outdoor air and/or recirculated compartment air pass the heat exchanger 44 which, as described below, serves as a cooling or heating element, according to the relations between the desired compartment temperature and the out¬ door temperature, exposure to sunlight etc. The heat exchanger 44 is passed by a flow of liquid, in the case shown the vehicle coolant, and is connectible, via the schematically shown multi-way mixing device 46 according to one of the embodiments 46' or 46" described above, to the pipe and/or tube system for the vehicle coolant system. The tank 50' in the conduit 48 of the heat exchanger 44 accommodates an evaporator 50 surrounded by the coolant and passed by a cooling agent, e.g. freon.

In addition to the evaporator 50 arranged in the con¬ duit 48 of the heat exchanger 44, the cooling side com- prises in prior-art manner a compressor 52, a condenser 54, an expansion valve 56 and the necessary conduits 58, such as pipes and/or tubes. The condenser 54 is cooled by the relative wind, the cooling fan 60 of the vehicle and/ or a separate, electric cooling fan. The heat on the heating side is produced in the cool¬ ing of the engine 62 of the vehicle and is pumped by a coolant pump 64 via a thermostat valve 66 to the engine

radiator 6 of the vehicle, and via the above-mentioned multi-way mixing device 46 back to the engine 62.

Simplified, exemplifying operative situations will be described below, from which the function of the air-condi- tioning system and the demands placed on the multi-way mixing device 46 will be evident.

At a desired air temperature in the compartment exceeding the outdoor temperature, the cooling side is closed, and essentially the following occurs. The hot coolant is pumped by the coolant pump 64 via the duct 70 to the multi-way mixing device 46. Here the flow of coo¬ lant is divided into a first partial flow in a conduit 72 and a second partial flow in a conduit 74, the conduit 72 being connected to the coolant return duct 76 of the engine, and the conduit 74 being connected to the coolant inlet of the evaporator tank 50' . The amount of partial flows is determined from outside and is affected by a number of factors, such as coolant temperature, outdoor temperature and desired air temperature in the compart- ment. The lower the outdoor temperature relative to the compartment temperature, the larger amount of hot coolant supplied to the conduit 74. This partial flow is caused to pass the tank 50', the conduit 48, the heat exchanger 44 and is pumped via the multi-valve mixing device 46 and the conduit 72 to the coolant return duct 76. Thus, the liquid flow in the duct 70 is constant and as large as the liquid flow in the coolant return duct 76. The main object of the multi-way mixing device 46 thus is to mix, according to the desired temperature, hot coolant with cooler heat exchanger liquid in such a manner that the desired tempe¬ rature is achieved, without affecting, i.e. decreasing or increasing, the amount of liquid flows. By continuous influx of the amount of coolant necessary for the desired temperature, the heat is distributed evenly over the entire surface of the heat exchanger 44, and heat is also evenly distributed in the air flow produced by the ven¬ tilator 42 and entering the vehicle compartment.

When the outdoor conditions are constant, the tem¬ perature in the compartment can be increased or decreased by increasing or decreasing the flow of hot coolant through the multi-way mixing device 46 into the liquid circuit of the heat exchanger 44.

At high outdoor temperatures and/or in strong sun¬ light, the air in the compartment need be cooled so as to to obtain agreeable conditions.

In extreme cases, the communication between the coolant circuit of the engine 62 and the heat exchanger circuit must therefore be prevented by means of the multi- way mixing device 46 illustrated especially in Figs 1-3. Since the coolant circuit of the engine 62 is completely separated from the heat exchanger circuit and, consequent- ly, the coolant pump 64 has no effect on the liquid in the heat exchanger circuit, the significance of the pump of the multi-way mixing device 46 will be appreciated.

In the embodiment shown, the evaporator 50 of the cooling circuit is arranged in a cylindrical tank 50' having an inlet and an outlet which are connected to the conduit 74 and, respectively, the conduit 48 which is con¬ nected to the heat exchanger 44. The cylindrical tank 50' thus is filled with liquid which surrounds the evaporator 50. When operating the compressor 52, the liquid sur- rounding the evaporator 50 thus is cooled, i.e. the coolant in the evaporator 50 absorbs part of the heat in the surrounding liquid. The cold liquid is circulated to the heat exchanger 44 which in this position serves as a cooling element, the cold liquid in the heat exchanger 44 absorbing part of the heat of the passing air.

In this case, too, an even distribution of tempe¬ rature is obtained over the entire surface of the heat exchanger. The liquid volume of the heat exchanger is adjusted so that variations of the temperature are levelled out in discontinuous operation of the com¬ pressor.

In the extreme cases as described, the multi-way mix¬ ing device 46 is fully open or fully closed, i.e. permits and prevents, respectively, communication between the coolant circuit and the heat exchanger circuit. Such con- ditions can be satisfied relatively easily by means of known valves or valve combinations. By means of the multi- way mixing device according to the invention it is, how¬ ever, in a simple manner also possible to continuously control the supply air temperature of the compartment between about 0°C and 80°C.

Thus, a new multi-way mixing device has been describ¬ ed for use in modern air-conditioning systems for vehi¬ cles, which permits continuous and proportional control of the temperature of the liquid to the heat exchanger between about 0°C and 100°C. The same temperature is obtained over the entire heat exchanger surface, which yields substantially the same air temperature at all inlets or nozzles in the compartment. The liquid volume of the system for heating and cooling, respectively, can be reduced to a considerable extent, which involves, in addi¬ tion to smaller physical dimensions, quick responses to alterations of the position of the control valve. More¬ over, it is advantageous that in normal cases the tempera¬ ture in the heat exchanger is completely independent of the number of revolutions of the engine. Thus, an even flow of heat (cold) into the compartment is obtained inde¬ pendently of the speed of the vehicle.

It is understood that an expert may find modifica¬ tions or construction details which are comprised by the inventive idea. Thus, the valve disc described can be designed in alternative manners, or a simpler valve disc can be supplemented by other means, such as the above- mentioned pressure regulator, which can be a throttle or the like. Morever, it is not absolutely necessary to integrate the pump with the multi-way mixing device.

Thus, one or more pumps can be arranged in the conduits connected to the multi-way mixing device. It is therefore

understood that the accompanying claims should comprise all the changes and modifications that are within the scope of the inventive idea.