Electromagnetic system to control the valves of an engine

Abstract

Electromagnetic system to control the valves of an engine and having a control unit and for each valve a respective electromagnetic actuator provided with a pair of electromagnets; each electromagnet has a winding which is provided with a power bobbin and an auxiliary measurement bobbin, and a flexible connection cable, which is directly integrated in the respective winding in order to connect the winding itself to the control unit electrically without further interpositions.

Description

BACKGROUND OF INVENTION

[0001] The present invention relates to an electromagnetic system to control the valves of an engine.

[0002] As is known, internal combustion engines are currently at the experimental stage, in which the intake and discharge valves are moved by electromagnetic actuators (of the type described in European patent application EP1087110). These electromagnetic actuators have undoubted advantages, since they make it possible to control each valve according to an optimised law for any operative condition of the engine, whereas the conventional mechanical actuators (typically cam shafts) require definition of a raising profile of the valves which represents an acceptable compromise for all the possible operating conditions of the engine.

[0003] An electromagnetic actuator for a valve of an internal combustion engine of the above-described type normally comprises an actuator body, which is connected to the rod of the valve and in conditions of rest is maintained by at least one spring in an intermediate position between two de-excited electromagnets; in use, the electromagnets are controlled by a control unit such as to exert alternately a force of attraction of magnetic origin on the actuator body in order to displace the actuator body itself between the two end stop positions, which correspond to a position of maximum opening and of closure of the respective valve.

SUMMARY OF INVENTION

[0004] The object of the present invention is to provide an electromagnetic system to control the valves of an engine, which has an electrical connection between the control unit and each electromagnet and is easy and economical to implement.

[0005] According to the present invention, an electromagnetic system to control the valves of an engine is provided, comprising a control unit and for each valve a respective electromagnetic actuator provided with a pair of electromagnets, an actuator body, which is connected mechanically to the respective valve and is fitted such as to be mobile between the two electromagnets in order to be displaced under the action of the electromagnets themselves, and at least one resilient body, which is connected to the actuator body in order to maintain the actuator body itself in an intermediate position of rest between the two electromagnets; each electromagnet comprising a magnetic core, a winding, which is connected to the magnetic core and is provided with a power bobbin and an auxiliary measurement bobbin, and a connection cable, which can connect the winding electrically to the control unit; the electromagnetic system being characterised in that each said electromagnet comprises a respective flexible cable, which is directly integrated in the respective winding in order to connect the respective winding electrically to the control unit without any further interpositions.

BRIEF DESCRIPTION OF DRAWINGS

[0006] The present invention will now be described with reference to the attached drawings, which illustrate a non-limiting embodiment of it, in which:

[0007] FIG. 1 is a schematic view in lateral elevation and partially in cross-section of a valve of an engine and of a corresponding electromagnetic actuator;

[0008] FIG. 2 illustrates schematically an electromagnetic circuit of the actuator in FIG. 1; and

[0009] FIG. 3 is a view in cross-section of a support structure containing a pair of electromagnetic actuators produced according to the present invention.

DETAILED DESCRIPTION

[0010] In FIG. 1, 1 indicates as a whole an electromagnetic actuator (of the type described in patent application EP1087110) connected to an intake or discharge valve 2 of an internal combustion engine of a known type in order to displace the valve 2 itself along a longitudinal axis 3 of the valve between a position of closure (which is known and not illustrated) and a position of maximum opening (which is known and not illustrated).

[0011] The electromagnetic actuator 1 comprises an oscillating arm 4 which is made at least partially of ferromagnetic material, which has a first end pivoted on a support 5 such as to be able to oscillate around an axis 6 of rotation which is transverse to the longitudinal axis 3 of the valve 2, and a second end which is connected by means of a hinge 7 to an upper end of the valve 2. The electromagnetic actuator 1 also comprises two electromagnets 8 which are supported in a fixed position by the support 5 such as to be disposed on opposite sides of the oscillating arm 4, and a spring 9 which is connected to the valve 2 and can maintain the oscillating arm 4 in an intermediate position (illustrated in FIG. 1) in which the oscillating arm 4 itself is equidistant from the pole pieces 10 of the two electromagnets 8. According to a different embodiment not illustrated, the spring 9 which is connected to the valve 2 is flanked or replaced by a torsion-bar spring which is connected to the hinge which is present between the support 5 and the oscillating arm 4.

[0012] In use, the control unit 11 controls with feedback and substantially in a known manner the position of the oscillating arm 4, i.e. the position of the valve 2, on the basis of the operating conditions of the engine; in particular, the control unit 11 excites the electromagnets 8 with a respective electric current i(t) in order to exert alternately or simultaneously a force of attraction of magnetic origin on the oscillating arm 4, such as to make the oscillating arm 4 itself rotate around the axis 6 of rotation, consequently displacing the valve 2 along the respective longitudinal axis 3 and between the said positions of maximum opening and closure (not illustrated).

[0013] As illustrated in FIG. 1, the valve 2 is in the said position of closure (not illustrated) when the oscillating arm 4 abuts the excited upper electromagnet 8, it is in the said position of maximum opening (not illustrated) when the oscillating arm 4 abuts the excited lower electromagnet 8, and is in a position of partial opening when the two electromagnets 8 are both switched off and the oscillating arm 4 is in the said intermediate position (illustrated in FIG. 1) owing to the effect of the force exerted by the spring 9.

[0014] As illustrated in FIG. 2, each electromagnet 8 comprises a respective magnetic core 12 which is connected to a corresponding bobbin 13, which is supplied by the control unit 11 with a current i(t) which is variable over a period of time in order to generate a flow &phgr; (t) through a respective magnetic circuit 14 which is connected to the bobbin 13. In particular, each magnetic circuit 14 consists of the corresponding core 12 of ferromagnetic material, the oscillating arm 4 of ferromagnetic material and the gap 15 which exists between the corresponding core 12 and the oscillating arm 4.

[0015] To each magnetic core 12 there is connected a further, auxiliary bobbin 16 (consisting of at least one coil and provided with a number Na of coils) connected to a measurement circuit (which is known and not illustrated) of the control unit 11, which can measure in real time the value of the flow &phgr; (t) through the corresponding magnetic circuit 14.

[0016] In particular, a voltmeter is connected to the terminals of the auxiliary bobbin 16; since the terminals of the auxiliary bobbin 16 are substantially open (the internal resistance of the voltmeter is high enough to be able to be considered infinite without introducing appreciable errors), no current passes through the auxiliary bobbin 16 and the voltage at its terminals depends solely on the derivative of the flow &phgr; (t) over a period of time, from which it is possible to determine the value of the flow &phgr; (t) by means of an operation of integration.

[0017] In the practical embodiment, in an electromagnet 8 the respective bobbin 13 and the respective auxiliary bobbin 16 are wound together in a single winding 17 in order to simplify both the production of the bobbins 13 and 16 themselves, and their connection to the corresponding magnetic core 12. In addition, each electromagnet 8, or rather each winding 17, must be connected to the control unit 11 by means of a respective connection cable 18 which is provided with four independent electrical conductors 19 (two for circulation of the current i(t), and two for measurement of the voltage at the ends of the auxiliary bobbin 16).

[0018] As illustrated in FIG. 3, in order to be able to install the electromagnetic actuators 1 of the type previously described, use is preferably made of a box-type body 20, which accommodates two electromagnetic actuators 1 which can control respective valves 2. In particular, the box-type body 20 is preferably used in order to control the two intake or discharge valves 2 of a single cylinder (not illustrated) in an internal combustion engine which has four valves per cylinder, since in these engines the two intake or discharge valves 2 of a single cylinder are disposed in positions which are relatively very close to one another.

[0019] Each winding 17 comprises a respective flexible connection cable 18, which is integrated directly in the winding 17 itself and comprises four electrical conductors 19 which are inserted in a single insulating sheath 21. In particular, the connection cable 18 is not added to the winding 17 after production of the winding 17 itself, but is formed during production of the winding 17 by using as electrical conductors 19 the same conductors used for production of the winding 17 (thus eliminating the need to produce electrical junctions). Optionally, further isolations can be added to the electrical conductors 19 inside the sheath 21, in particular in order to separate the two electrical power conductors 19 (via which the current i(t) circulates) from the two electrical signal conductors 19 (via which the voltage is measured at the ends of the auxiliary bobbin 16).

[0020] For each electromagnet 8, the box-type body 20 comprises a respective through hole 22, through which the respective connection cable 18 is passed, such as to permit connection of the connection cable 18 itself to the control unit 11.

[0021] In order to connect the cable 18 electrically to the control unit 11, the end portions of the respective electrical conductors 19 can be inserted in connection terminals (not shown) of the control unit 11, or the end portions of the respective electrical conductors 19 can be inserted in a detachable connector (which is known and not illustrated) in order to permit fast connection to/disconnection from the control unit 11.

[0022] The fact of using for each electromagnet 8 a respective single connection cable 18 which is integrated directly in the corresponding winding 17 makes it possible to produce the connection of the electromagnet 8 to the control unit 11 simply (by simplifying both the structure and the fitting of the electromagnetic actuators 1), economically, and with reduction of the problems of electrical connection (since, as the connection cable 18 is flexible it can be adapted to various paths).

[0023] While the apparatus, compositions and methods of this invention have been described in terms of preferred or illustrative embodiments, it will be apparent to those of skill in the art that variations may be applied to the process described herein without departing from the concept and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the scope and concept of the invention as it is set out in the following claims.

Claims

1. Electromagnetic system to control the valves (2) of an engine and comprising a control unit (11) and for each valve (2) a respective electromagnetic actuator (1) provided with a pair of electromagnets (8), with an actuator body (4), which is connected mechanically to the respective valve (2) and is fitted such as to be mobile between the two electromagnets (8) in order to be displaced under the action of the electromagnets (8) themselves, and with at least one resilient body (9), which is connected to the actuator body (4) in order to maintain the actuator body (4) itself in an intermediate position of rest between the two electromagnets (8); each electromagnet (8) comprising a magnetic core (12), a winding (17), which is connected to the magnetic core (12) and is provided with a power bobbin (13) and an auxiliary measurement bobbin (16), and a connection cable (18), which can connect the winding (17) electrically to the control unit (11); the electromagnetic system being characterised in that each said electromagnet (8) comprises a respective flexible connection cable (18), which is integrated directly in the respective winding (17) in order to connect the winding (17) itself to the control unit (11) electrically without further interpositions:

2. System according to claim 1, wherein each said connection cable (18) comprises four electrical conductors (19) inserted in a single isolating sheath (21) in order to connect both the respective power bobbin (13) and the respective auxiliary measurement bobbin (16) electrically to the said control unit (11).

3. System according to claim 2, wherein the said four electrical conductors (19) of a single connection cable (18) are the same electrical conductors as those used for production of the power bobbin (13) and of the auxiliary bobbin (16) of the respective winding (17).

4. System according to claim 3, wherein each said connection cable (18) comprises further electrical isolations which are accommodated inside the respective sheath (21).

5. System according to claim 1, and comprising a box-type body (20) which can accommodate a pair of said electromagnetic actuators (1) for the control of two respective said valves (2); the said box-type body (20) having four through holes for passage of the corresponding said connection cables (18).

6. Electromagnetic actuator to control the valve (2) of an engine; the electromagnetic actuator (1) comprising a pair of electromagnets (8), an actuator body (4), which is connected mechanically to the valve (2) and is fitted such as to be mobile between the two electromagnets (8) in order to be displaced under the action of the electromagnets (8) themselves, and at least one resilient body (9), which is connected to the actuator body (4) in order to maintain the actuator body (4) itself in an intermediate position of rest between the two electromagnets (8); each electromagnet (8) comprising a magnetic core (12), a winding (17), which is connected to the magnetic core (12) and is provided with a power bobbin (13) and an auxiliary measurement bobbin (16), and a connection cable (18), which can connect the winding (17) electrically to the control unit (11); the electromagnetic actuator (1) being characterised in that each said electromagnet (8) comprises a respective flexible connection cable (18), which is integrated directly in the respective winding (17) in order to connect the winding (17) itself electrically to the control unit (11) without further interpositions.