Thermostatic valve for controlling the temperature of the coolant in an internal combustion engine

A thermostatic valve for controlling the temperature of the coolant in an internal combustion engine controls the flow of coolant between the internal combustion engine and a heat exchanger. The valve includes an actuation element which functions in a temperature-dependent manner for actuating lift of a main valve and of a bypass valve in a valve housing. The actuation element has a stationary piston supported on a valve housing part. A housing can be displaced relative to the piston and on which the valve members of the main valve and of the bypass valve are arranged. Further provided is a monitoring device for the position of the main valve, which works in a contactless manner and which has at least one sensor element contained in the valve housing part, and at least one associated permanent magnet for generating a magnetic field to which the sensor element is exposed.

FIELD OF THE INVENTION

The invention relates to a thermostatic valve for controlling the temperature of the coolant of an internal combustion engine, in particular in a motor vehicle engine, which controls the flow of coolant between the internal combustion engine and a heat exchanger, in particular cooler, and/or a bypass, comprising an actuation element functioning in a temperature-dependent manner for actuating a lift of a main valve and of a bypass valve in a valve housing, wherein the actuation element has a stationary piston supported on a valve housing part and a housing which is displaceable relative to the piston and on which the valve members of the main valve and of the bypass valve are arranged.

BACKGROUND OF THE INVENTION

The cooling system of modern internal combustion engines plays a crucial role with regard to the pollutant emission and the fuel consumption. The warm-up of an engine can for example be distinctly shortened by switching off the circulation of the coolant flow through the engine block. Thereby, the friction losses are reduced, the fuel consumption reduces, the exhaust gas catalysts reach their operating temperature earlier and therefore start their function earlier. A favorable solution, in order to prevent the flow through the engine in the cold state and to control the coolant temperature actively in an engine at operating state temperature consists in the construction of a thermostatic valve with electric heating and switch-off function. Such thermostatic valves operate today with great reliability. Nevertheless, the requirement arises for a monitoring of the functional capability of the thermostatic valve.

It may be one of many objects of the present invention to configure a thermostatic valve of the type named in the introduction so that its function is monitored in a simple manner, at least with respect to establishing whether the opened or closed valve position of the main valve is present.

SUMMARY OF THE INVENTION

A thermostatic valve of the type named in the introduction according to the invention comprises a monitoring device for the position of the main valve is provided, which works in a contactless manner and which has at least one sensor element contained in the valve housing part and at least one associated permanent magnet for generating a magnetic field to which the sensor element is exposed. The sensor element connected to an evaluation device, e.g. a motor control unit. The motor control unit can therefore detect the closed position of the main valve or respectively an opening position in case of a signal change. The at least one sensor element being arranged fixed to the housing, measures the field strength of the magnetic field of the magnet as a function of the lift of the main valve and delivers an analogue or digital signal as a function of the distance of the permanent magnet, and hence of the valve member of the main valve, from the at least one sensor element.

In an embodiment, the permanent magnet is constructed in a ring shaped manner. It is preferably magnetized in an axial direction being approximately parallel to the axial direction of movement of the housing of the actuation element. The permanent magnet may be arranged directly on a face side of the housing of the actuation element, in particular is received there in an annular groove and fastened therein, e.g. by gluing or such similar means. The permanent magnet may be received in a holder which is placed onto a head part of the housing of the actuation element and is securely fixed therewith.

The at least one sensor element is expediently arranged in an adjacent manner lying axially opposite the permanent magnet. The at least one sensor element can have suppression components, e.g. capacities, adjacent thereto, which are arranged in the valve housing part. The at least one sensor element may be formed by a Hall sensor.

A further embodiment makes provision that the valve housing part has a holding part which is formed from a ready to mount injection-molded semi-finished part of plastic. This may lead to advantages in the production and assembly (but which are not necessary).

In an embodiment, one end of the piston of the actuation element can be contained in the holding part and can be insert-overmolded with the plastic material of the holding part, so that in this way the piston is a fixed part of the holding part. In the case of an electric heating device contained in the interior of the piston, to which then an electric feed line of the heating device and plug contacts connected therewith belong, the feed line and the plug contacts as parts of the piston can also be insert-overmolded with the plastic material of the holding part together with the piston. In this case, the holding part itself can also be formed and shaped when the piston with its end and with the electric feed line and the plug contacts are held in an injection mold and are insert-overmolded with plastic material simultaneously shaping the holding part.

The at least one sensor element and if applicable suppression components for this and the plug contacts thereof can be combined into one structural unit, e.g. by means of a lead frame defining and holding these. Such a structural unit can then be mounted in the holding part and cast around with its plastic material. Or, in an embodiment, this structural unit of sensor element and suppression components and plug contacts thereof together with the piston, the electric feed line and the plug contacts thereof can be united into one component in an injection mold by insert-overmolding, wherein the holding part containing these parts is also formed by plastic injection molding. Then, as a ready to mount structural unit, such a structural unit is present which consists of the holding part with piston, electric feed line and plug contacts for the heating device and of the at least one sensor element with suppression components and plug contacts thereof.

A further embodiment makes provision that the valve housing part has a plug, constructed as a hollow body, with a flange at one end, in which the plug contacts of the electric heating device and/or of the structural unit of sensor element and suppression components are inserted and held.

A further embodiment makes provision that the holding part and/or plug form a pre-mounted assembly, which is inserted into the valve housing and is insert-overmolded with the plastic material of the valve housing.

The thermostatic valve configured in such a way constitutes, with the pre-mounted assemblies, a system which is particularly constructed in a modular, compact and cost-efficient manner. The plastic material, with which the assemblies are insert-overmolded, may consist of a material (e.g. PPS-PBT), which is tight with respect to the coolant and/or does not soak-up any coolant, so that it is ensured that the electronic components are reliably protected from moisture. The thermostatic valve offers the possibility of a simple detection of a malfunction with monitoring e.g. of the closed position of the main valve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

InFIG. 1a thermostatic valve10is shown, which serves for controlling the temperature of the coolant of an internal combustion engine, in particular in a motor vehicle engine. The thermostatic valve10has a main valve11and a bypass valve12. The thermostatic valve10controls the flow of coolant from the internal combustion engine through a bypass13and/or through a heat exchanger (not shown), in particular a cooler, back to the internal combustion engine. With a closed main valve11according toFIG. 1, the coolant arrives via an opening14of a valve housing15, containing the thermostatic valve10, into its interior16, which the coolant leaves through the bypass13owing to the opened bypass valve12. If, on the other hand, the main valve11is open, the coolant arrives out from the interior16through the duct17to a heat exchanger (not shown).

The thermostatic valve10has an actuation element18functioning in a temperature-dependent manner, which contains in a housing19an expanding material which expands on heating and moves a coaxial piston20relative to the housing19. On the housing19, a valve member21of the main valve11is held, which consists here of a valve plate, but alternatively can also consist e.g. of a valve slide or other comparable structure or valve member structure. The valve member21lies axially on an annular flange22of the housing19and, on heating, is moved by the housing19against the action of a return spring23inFIG. 1downwards in opening direction.

On the housing19, in addition at the lower end region inFIG. 1, a second valve member24is held in an axially displaceable manner, which is part of the bypass valve12and is constructed e.g. as a valve plate. The valve member24is pressed by means of a spring25against a lower stop26on the housing19and is axially displaceable relative to the housing19. The spring25is axially supported by its upper end on an annular flange27of the housing19. Associated with the valve member24is a face-side valve seat surface28, which runs beneath the valve member24and is formed e.g. by the upper face surface of a coaxial cylindrical section29, which can be part of the valve housing15.

An approximately tubular component30is arranged detachably, but securely and in a tight manner, on the valve housing15, which component contains the valve seat31being associated with the first valve member21of the main valve11and having the form of an inner surface32approximately in the form of a frustum of a cone. The component30can consist of plastic or metal, e.g. aluminum. It contains in the interior the duct17and, in addition, a valve housing component33, on which the piston20is supported axially by its upper end.

The return spring23associated with the valve member21and the housing19is axially supported by the upper end inFIG. 1on the valve member21and by its lower end inFIG. 1on a support device34. The support device34has arms41held on the component30, bracing downwards from there inFIG. 1, having end-sided, inwardly directed projections44, which form a support surface for the end of the return spring23.

The upper component30is placed onto the lower part of the valve housing15, with interposition of a seal35, and is fastened thereon.

In order to be able to establish whether the functional capability of the thermostatic valve10according toFIG. 1exists, or, owing to a defect e.g. in the open or closed position, does not exist, a monitoring device50which works in a contactless manner is provided for the position of the main valve11, which has at least one sensor element51, which is contained in the valve housing part33, and at least one associated permanent magnet52for generating a magnetic field to which the sensor element51is exposed. This monitoring device50serves at least for detecting the open and/or closed position of the main valve11and is connected to an evaluation device (not shown), e.g. engine control unit, by means of which a corresponding signal is generated on an error-functional remaining in the closed or in the open position.

The permanent magnet52is ring-shaped and is fastened on the face side on an approximately cup-shaped holder53, e.g. in an annular grove54. The holder53is placed onto a head part55of the housing19of the actuation element18and is securely connected therewith, e.g. by flanging of a flanged rim56. In another example embodiment, which is not shown, the permanent magnet52may be arranged directly in the face side of the housing, e.g. in an annular groove there. The permanent magnet52is magnetized in an axial direction being approximately parallel to the axial direction of movement of the housing19of the actuation element18. The at least one sensor element51is arranged in an adjacent manner lying axially opposite the permanent magnet52in the valve housing part33. Associated with the at least one sensor element51are suppression components57, e.g. capacitors, adjacent thereto, which are likewise contained in the valve housing part33.

The at least one sensor element51consists of a magnet sensor, in particular of a Hall sensor. The sensor element51is arranged fixedly in relation to the housing19of the actuation element18. The permanent magnet52generates a magnetic field in the region of the sensor element11, the field strength of which is measured by the sensor element51as a function of the lift of the housing19. Via the field strength of the magnetic field of the permanent magnet52, the distance of the permanent magnet52and hence of the housing19with valve member21is measured by means of the sensor element and accordingly an analogue or digital signal is emitted to the evaluation unit (not shown), in particular an engine control unit. Therefore, in this way, the engine control unit can establish the position “closed” or “open” of the main valve11on a change of signal.

InFIG. 3it is shown that the valve housing part33has a holding part60, which is formed from a ready to mount injection-molded semifinished part of plastic. One end of the piston20of the actuation element18is contained in this holding part60. In the illustrated embodiment, an electric heating device (not shown) is arranged in the interior of the piston20, which heating device can be energized via two plug contacts61with electric feed line62. In addition to the upper end of the piston20, the electric feed line62and the plug contacts61are contained in the holding part60and are insert-overmolded with the plastic material of this holding part60or e.g. are injection-molded in a single injection process with formation of the holding part60, so that in this respect a ready to mount injection-molded part is already present. Beneath the course of the plug contacts61and feed line62the holding part60contains a pocket63. The at least one sensor element51and applicable necessary suppression components57for the latter and three plug contacts64thereof are combined to form a structural unit shown inFIG. 2, wherein the plug contacts64are formed by a correspondingly configured lead frame, which carries the suppression components57and, on which in addition the at least one sensor element51is mounted on the end side. In this combination, the structural unit shown inFIG. 2is produced. On assembly, this structural unit according toFIG. 2can be introduced into the pocket63of the holding part60and can be cast with the plastic material of the holding part60. Instead of this, the lead frame with the plug contacts64, the suppression components57and the sensor element51together with the piston20, the feed lines62and the plug contacts61can be united to form a component by injection-molding in an injection mold together with forming of the holding part60. The plastic material of the holding part60preferably consists of a material, e.g. PPS or PBT, which is tight with respect to the coolant passing through the thermostatic valve10and/or does not soak-up any coolant. It is thereby ensured that the electronic components are reliably protected from moisture.

The valve housing part33has, in addition to the holding part60, a plug70constructed as a hollow body, with a collar71at the end, which is closed by means of a base72. The collar71is formed from circumferential radially protruding projections. The base72is penetrated by the two plug contacts61for the piston20and the plug contacts64of the structural unit inFIG. 2, which project into the interior of the plug70. These plug contacts61and64are inserted into the base72and held therein. The holding part60and the plug70can again form an assembly which is pre-assembled or completely insert-overmolded in a mold, wherein a projecting part65being present at the holding part60inFIG. 3engages into a corresponding depression73in the base72of the plug70. Such a structural unit of holding part60and plug70can then be inserted easily, e.g. from the left side inFIG. 10, into the valve housing, and namely into a cavity36provided for receiving in the component30, and can be insert-overmolded with the plastic material of the valve housing15, in particular of its component30.

The described thermostatic valve10offers a monitoring, working in a contactless manner, of the valve lift of the main valve11and an establishing whether the open or closed position has been reached owing to a control play of the main valve, or whether an operational disturbance is present, in which the thermostatic valve10remains or jams in the open or closed position. The system is constructed in a modular, compact and cost-efficient manner. It is able to be used almost in all thermostat housings made of plastic. Described thermostatic valves10are able to be used for utility vehicle engines or also for high-performance passenger car engines. The production and in particular the assembly is simple and cost-efficient. Owing to the casting and insert-overmolding of the electronic components and further elements, a reliable sealing with respect to the coolant conducted in the thermostatic valve10is achieved, and a protection from moisture exists permanently.