Controllable coolant pump

A controllable coolant pump driven by a belt pulley for internal combustion engines is equipped with a valve slide. A seal is disposed on the outer edge of the wall plate between the plate and the outer cylinder of the valve slide. At least one additional flow outlet opening is disposed on the pump housing, the outlet volume stream of which openings can be additionally controlled, aside from the controllable volume stream that exits from the flow exit opening. The flow outlet opening from which the controllable outlet volume stream exits is connected with an outflow opening disposed near the rear wall of the valve slide, in the pump chamber rear wall, via an outflow channel. The outflow opening is enclosed by a ring seal disposed in the pump chamber rear wall, which enters into operative engagement with the valve slide in its rear end position.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of PCT/DE2012/000846 filed on Aug. 17, 2012, which claims priority under 35 U.S.C. §119 of German Application No. 10 2011 113 040.7 filed on Sep. 9, 2011, the disclosure of which is incorporated by reference. The international application under PCT article 21(2) was not published in English.

The invention relates to a controllable coolant pump driven by way of a belt pulley, for internal combustion engines.

In the course of constant optimization of internal combustion engines with regard to the lowest emissions and low fuel consumption, warming up of the engine after a cold start, as quickly as possible, has great importance. The following interrelationships come to bear in this.

The viscosity of the oil decreases with an increasing oil temperature, and, at the same time, the friction at all oil-lubricated moving components also decreases.

At the same time, after what is called the “start-up temperature,” the catalysts also become active, so that it is aimed at to further shorten this time window, in order to thereby guarantee that the catalysts become effective quickly.

Experiments within the scope of engine development have shown that a very effective measure for faster engine warm-up is the “standing water” during the cold-start phase. For this reason, the coolant volume situated in the water jacket of the cylinder block should not be exchanged during the cold-start phase, in order to prevent any unnecessary heat transport.

Likewise, the cylinder head should also not have coolant flowing through it during the cold-start phase, in order to bring the exhaust gas temperature to the desired level as quickly as possible.

In order to bring about this fastest possible engine warm-up, switchable coolant pumps were introduced in past years, with great success, which make it possible to reduce the coolant volume stream that exits from the pump to “zero” during the cold-start phase. A design of this switchable pump that has proven itself in practice was also disclosed by the applicant in WO 2009/143832 A2.

During the further course of engine development, with the target direction of further lowering of fuel consumption, what are called split-cooling systems are increasingly being used at this time.

In these new systems, the cylinder head and the cylinder block are supplied with an individually controlled coolant stream, by way of separate connectors.

The background of these systems is the fact that the cylinder block should preferably experience higher coolant temperatures than the cylinder head. The oil-lubrication friction locations in the cylinder block (i.e. the piston module and the crankshaft bearings) cause greater friction losses, because of the reduced oil viscosity at higher working temperatures.

For the cylinder head, in contrast, the requirement exists, after the engine has warmed up (i.e. after the cold-start phase), to reliably protect the valve crosspieces, which are subject to thermal stress, by means of good cooling, and furthermore to bring about good filling of the combustion chamber.

In the state of the art, cooling systems or distributor devices for the cooling system of internal combustion engines, having split-cooling concepts, were already described in DE 44 07 984 A1 and in DE 44 32 292 A1, which allow individual flow through the cylinder head and the cylinder block.

The significant disadvantage of these systems described in DE 44 07 984 A1 and also in DE 44 32 292 A1 is not only the great equipment technology effort, which necessarily requires not only the coolant pump but also separate lines and valves in the cooling circuit, which can then be opened or closed as needed, but also the great construction volume connected with these systems.

A more recent solution of the split-cooling systems was described in MTZ [Motortechnische Zeitschrift=Technical Motor/Engine Journal] June 2011 on page 473. Here, the valves required to control the volume streams are brought together in the pump housing; two electrically driven rotary slide valves are required for this purpose.

In this solution, too, the equipment technology effort and the construction volume are enormous. This solution is also eliminated for many engine applications, if only due to the great required construction volume.

Furthermore, a cooling system for liquid-cooled internal combustion engines is known from EP 2 169 233 A2, having a multi-flow coolant pump, the pump flows of which are assigned to separate coolant circuits, in each instance, and in which at least one of the pump flows can be changed, with regard to the conveying output, by means of a valve slide.

Furthermore, a controllable coolant pump is known from DE 10 2009 036 602 A1, having an inlet channel, a pump wheel, and a displaceable valve slide disposed on the outer circumference of the pump wheel, which pump is characterized in that at least three outlet channels that proceed in spiral shape from the pump wheel are disposed in the pump housing, whereby the valve slide always controls, i.e. opens or closes all three outlet channels at the same time.

The invention is therefore based on the task of developing a controllable coolant pump that can be driven by way of a belt pulley, which eliminates the aforementioned disadvantages of the state of the art, and, in this connection, on the one hand guarantees optimal warm-up of the engine during the cold-start phase, by means of complete “zero leakage,” and, at the same time, on the other hand allows individually controllable flow of coolant through cylinder head and cylinder block, at a low drive power, with minimal equipment technology effort and the smallest possible construction space requirement, i.e. even with a very limited installation space for the coolant pump in the engine space, in order to guarantee optimal, demand-appropriate, individual cooling of cylinder block and cylinder head both during the cold-start phase and in ongoing operation, so that not only the cylinder block but also the cylinder head can be run at optimal working temperatures, in individually controllable manner, so that the friction losses, the fuel consumption and also the emission of pollutants are clearly reduced over the entire working range of the engine, whereby the solution to be developed, in special designs, is supposed to guarantee not only separate, individually controlled coolant supply to cylinder head and cylinder block, but also, at the same time, without great additional effort and construction space, continuous cooling of the exhaust gas recirculation.

According to the invention, this task is accomplished by means of a controllable coolant pump for internal combustion engines, driven by way of a belt pulley, in accordance with the characteristics of the independent claim of the invention.

Advantageous embodiments, details, and characteristics of the invention are evident from the dependent claims and from the following description of the solution according to the invention, in connection with the three representations of two different designs of the solution according to the invention.

FIG. 1shows the controllable coolant pump according to the invention, in a design for individually controlled coolant supply to cylinder head and cylinder block and simultaneous continuous coolant supply to the exhaust gas recirculation, for example, in a side view, in section, with the position of the valve slide in a center position.

A pump shaft5, driven by a belt pulley, for example, is disposed in a pump housing1having a flow entry region2and a flow exit opening3for exit of a controllable conveyed volume stream, in a pump bearing4.

An impeller wheel6is disposed at the free, flow-side end of this pump shaft5, so as to rotate with it. The pump chamber rear wall7is situated between the impeller wheel6and the pump bearing4.

A wall plate8is disposed between the impeller wheel6and the pump chamber rear wall7, fixed in place on the housing. A working cylinder9is disposed on the circumference of the pump shaft5, fixed in place on the housing, in the pump housing1, in which cylinder a working piston10is movably disposed, activated by control pressure.

The rear wall12of a valve slide13having an outer cylinder14is disposed on the working piston10. This outer cylinder14, which is variably movable using the working piston10, now covers the outflow region15of the impeller wheel6, as a function of the control pressure.

A reset spring11is disposed between the wall plate8fixed on the housing and the working piston(s)10that can be moved in the longitudinal pump shaft direction or the valve slide13that is connected with the working piston10, which spring guarantees precise, reproducible positioning of the outer cylinder14at the outflow region15of the impeller wheel6, as a function of the control pressure.

It is essential to the invention that a seal18is disposed on the outer edge17of the wall plate8, between the edge and the outer cylinder14of the valve slide13.

This seal18prevents flow around the valve slide13in the region of the outer edge17of the wall plate8and thereby allows separate pressure buildup in front of and behind the wall plate8.

According to the invention, two further flow outlet openings16are disposed on the pump housing1, whereby the outlet volume stream that exits from one of the flow outlet openings16cannot be controlled, and here serves for continuous coolant supply to the exhaust gas recirculation.

The outlet volume stream that exits from the other flow outlet opening16can be controlled, along with the controllable volume stream that exits from the flow exit opening3.

It is characteristic that the flow outlet opening16from which the non-controllable outlet volume stream exits is directly connected with an outlet connector20disposed in the wall plate8, by means of an outlet channel19, in the pump housing1.

It is also essential to the invention that the other flow outlet opening16, from which not only the controllable volume stream that exits from the flow exit opening3but also a controllable outlet volume stream exit, is connected with an outflow opening22disposed in the region of the rear wall12of the valve slide13, in the pump chamber rear wall7, by way of an outflow channel21, whereby this outflow opening22is enclosed by a ring seal23disposed in the pump chamber rear wall7, which enters into operative engagement with the valve slide13in the rear end position of the latter.

The solution according to the invention makes it possible that even when the outer cylinder14of the valve slide13lies against the housing in the front end position, i.e. when the outer cylinder14of the valve slide13covers the outflow region of the impeller wheel, an uncontrolled coolant volume stream along the inner wall of the outer cylinder14, by way of the outlet connector20, into the outlet channel19, for cooling of the exhaust gas recirculation, is guaranteed, as it is, of course, in every other position of the valve slide, as well.

The two aforementioned controllable volume streams of the coolant pump according to the invention are integrated, according to the invention, into an individual through-flow of cylinder head and cylinder block of an internal combustion engine, as follows.

The controllable volume stream that exits from the flow exit opening3serves for separate, controlled coolant supply to the cylinder head, and the controllable outlet volume stream that furthermore exits from the controllable coolant pump according to the invention by way of the outflow opening22and the outflow channel21disposed in the pump chamber rear wall7serve for separate, controlled coolant supply to the cylinder block.

In the design shown inFIGS. 1 and 2, the control pressure in the working cylinder(s)9is generated for defined displacement of the valve slide13by a working pump25disposed outside of the pump housing1, and controlled by way of a working valve26disposed outside of the pump housing1.

In the cold-start phase, the valve slide13is first moved into the front end position, so that the outer cylinder14of the valve slide13lies against the housing.

This position of the valve slide is not shown in any of the twoFIGS. 1 and 2.

In this front end position, the valve slide brings about the result that both of the controllable volume streams that exit from the coolant pump according to the invention,i.e. the controllable volume stream that exits from the flow exit opening3,and the controllable outlet volume stream that exits by way of the outflow opening22disposed in the pump chamber rear wall7and the outflow channel21
are completely regulated.

This front end position of the valve slide guarantees fast engine warm-up during the cold-start phase by means of the “standing water,” thereby avoiding any unnecessary heat transport, so that rapid warm-up of all modules of the engine is guaranteed during the cold-start phase.

After the operating temperature of the cylinder head has been reached in the cold-start phase, the valve slide moves into the rear end position under a partial load, by means of spring reset. Through-flow and cooling of the cylinder head are now released, while through-flow of the cylinder block continues to be prevented. In this manner, the oil temperature can be further increased at the relevant friction locations such as the piston module and crankshaft bearing, despite active cylinder head cooling, and thus the viscous oil friction can be further reduced. Only once the oil temperature reaches the predetermined limit value is the valve slide moved into a defined intermediate position, and thereby demand-appropriate cooling of the cylinder block and of the cylinder head is released.

As a result of the spring reset of the valve slide, through-flow of the cylinder block is prevented when the internal combustion engine is shut off, and as a result, the stored heat energy can be stored longer and is available again when the engine is started again.

This positive effect is particularly active if what is called an electrical over-run pump is used, which serves for cooling components subject to great thermal stress, such as the turbocharger. Even in the case of active over-run cooling, the stored heat of the engine block is maintained and contributes to a reduction in fuel consumption when the engine is started again.

One of these possible defined intermediate positions of the valve slide, which are moved to within the scope of demand-appropriate cooling of the cylinder block and of the cylinder head, is the center position shown inFIG. 1, for example, whereby the demand appropriate through-flow of cylinder head and cylinder block, as explained, is guaranteed as a function of the position of the valve slide, in each instance.

FIG. 2now shows the controllable coolant pump according to the invention fromFIG. 1, with continuous coolant supply to the exhaust gas recirculation by way of the outlet channel19, with a section that lies somewhat differently, in a side view.

The section line is selected, in thisFIG. 2, in such a manner that now a path measurement sensor24disposed in the pump housing becomes visible, which serves to precisely detect the position of the valve slide, in each instance, in order to control the valve slide by way of regulating the control pressure of the working pump25, in such a manner that demand-appropriate individual coolant supply to cylinder head and cylinder block is guaranteed.

InFIG. 2, the valve slide is now situated in its rear end position and lies against the ring seal23disposed in the pump chamber rear wall7there, in its transition region from the outer cylinder14into the rear wall12, from the press-down pressure of the reset spring11, and thereby closes the outflow opening22disposed in the pump chamber rear wall7, forming a seal.

This position of the valve slide, shown inFIG. 2, in its rear end position, brings about very good cooling of the cylinder head in accordance with the required current coolant demand, in each instance, in the case of a non-cooled cylinder block (cool head and warm feet).

InFIG. 3, another design of the controllable coolant pump according to the invention, for individually controlled coolant supply to cylinder head and cylinder block is now shown in section, in a side view. This solution shown inFIG. 3represents a further development of the design of a controllable coolant pump already disclosed by the applicant in WO 2009/143832 A2, which has proven itself in practice for many years, in which the control pressure in the working cylinder9is generated for defined displacement of the valve slide13, by a working pump25disposed in the pump housing1, and is controlled by way of a working valve26disposed in the pump housing1.

The solution shown inFIG. 3now allows, as was already explained in connection withFIGS. 1 and 2, demand-dependent individually controlled separate coolant supply to cylinder head and cylinder block.

In this representation, the valve slide13is again in a center position, analogous toFIG. 1.

The path measurement sensor24also shown inFIG. 3, in operative engagement with the working pump25disposed in the pump housing1and the working valve26also disposed in the pump housing1, guarantees, by means of precise detection of the working position of the valve slide13, in each instance, in connection with precise regulation of the control pressure of the working pump25, that the coolant supply to cylinder head and cylinder block can be individually controlled as a function of demand.

In the case of the design shown inFIG. 3, as well, the controllable volume stream that exits from the flow exit opening3serves for separate controlled coolant supply to the cylinder head, and the additional controllable outlet volume stream that also exits from the controllable coolant pump according to the invention, by way of the outflow opening22disposed in the pump chamber rear wall7and the outflow channel21, serves for separate controlled coolant supply to the cylinder block.

The explanations concerning the method of effect and the function of the controllable coolant pump according to the invention, in connection withFIGS. 1 and 2, apply in the figurative sense also for the design shown inFIG. 3.

It is possible that the cylinder block can be operated at a higher coolant temperature, as compared with the cylinder head, during ongoing operation, by means of the solution according to the invention, thereby clearly reducing not only the pollutant emissions but also the friction losses and the fuel consumption over the entire working range of the engine. By means of the solution presented here, separate coolant supply to cylinder head and cylinder block can be guaranteed with the least construction space requirement, i.e. even in the case of very greatly limited installation space for the coolant pump in the engine space.

At the same time, reliable activation of the valve slide is always guaranteed, at very low drive power.

In the case of the design shown inFIG. 3, as well, not only can separate, individually controlled coolant supply to cylinder head and cylinder block be guaranteed, by means of placing an outlet connector20in the wall plate8and connecting this outlet connector20with a flow outlet opening16, by way of an outlet channel19(analogous to the representations inFIGS. 1 and 2), but so can continuous cooling of the exhaust gas recirculation (as was already explained in connection withFIGS. 1 and 2).

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