Abstract:
The invention relates to a valve control system for an engine including at least one cylinder ( 1, 2, 3, 4 ) with valves ( 5, 6 ), wherein said system comprises valve electromagnetic actuation members ( 7, 9, 10 ) associated with a management unit ( 11, 15 ) that controls the actuation members, said system comprising a member ( 11, 12, 13 ) for detecting a malfunction of the actuation members and a member ( 11, 12, 13 ) for electrically insulating the faulty actuation member.

Description:
The present invention relates to a system for controlling valves of a combustion engine such as those used to propel motor vehicles. 
     BACKGROUND OF THE INVENTION 
     A combustion engine comprises cylinders defining combustion chambers that are closed at one end by a cylinder head and at the other end by a piston which slides between top and bottom positions and which is connected to a crankshaft via a connecting rod. Ducts for admitting fuel and for exhausting the burnt gases resulting from the combustion of the fuel are created in the cylinder head and are each equipped with a valve that can move between an open position and a closed position. 
     The valves are conventionally operated by a camshaft the rotation of which is driven off the crankshaft. 
     Also known is a new valve control system comprising electromagnetic actuator elements with which each valve is equipped in order to move this valve between its open and closed positions. The control system comprises a control unit connected to the actuating elements in order to control these in accordance with the combustion engine operating cycles. At the present time, any malfunctioning of one of the actuating elements in the control system causes the control system to shut down just as any problem with the driving of the camshaft may cause the engine to stop. 
     SUBJECT OF THE INVENTION 
     One object of the invention is to provide a means that makes a control system of the aforementioned type more reliable. 
     SUMMARY OF THE INVENTION 
     To this end, the invention provides a system for controlling valves for an engine comprising at least one cylinder that has valves, the system comprising electromagnetic valve-actuating elements associated with a control unit controlling the actuating elements, the system comprising a failure detection member that detects failures of the actuating elements and an electrical isolating member for electrically isolating the defective actuating element. 
     Thus it becomes possible to isolate the defective actuating element and prevent the failure of this element from causing the entire control system to shut down. 
     According to a first embodiment for a multi-cylinder engine, said control system comprises at least two actuating elements per cylinder and an electrical isolating member common to the actuating elements of at least one cylinder. 
     Here, the cylinder affected by the failure or a group of cylinders of which the defective cylinder forms a part is isolated so that the engine can continue to run on the remaining cylinder or cylinders. 
     According to a second embodiment, each actuating element comprises an actuator comprising two electromagnets or each actuating element is formed of an electromagnet of an actuator intended to operate a valve. 
     Isolation then relates either to the defective electromagnet of the actuator or to the actuator comprising the defective electromagnet. 
     Further features and advantages of the invention will become apparent from reading the following description of some particular non-limiting embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference will be made to the attached drawings, among which: 
         FIG. 1  is a schematic view of an engine equipped with a control system according to the invention, two embodiments being illustrated, one on the right and one on the left of this figure, 
         FIGS. 2 and 3  are schematic part views of an engine according to first and second embodiment variants of the invention, respectively. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG. 1 , the engine comprises cylinders  1 ,  2 ,  3 ,  4  each equipped with an inlet valve  5  and with an exhaust valve  6 . Each valve  5 ,  6  can move between a position in which it opens and a position in which it closes the duct to which it is fitted. The figure is a schematic figure in which the position of the valves and of the pistons is entirely arbitrary and does not correspond to an engine operating cycle. 
     The valves  5 ,  6  are each associated with an actuator  7  identified by the references  7 .A and  7 .B in  FIG. 1  respectively (in this figure, the numerical references of the components depicted have a suffix A or B according to whether they are associated with the valve  5  or the valve  6 , respectively). 
     Each actuator  7  comprises an actuating member  8  able to move between a position in which the valve is fully closed and a position in which the valve is wide open and two electromagnets  9 ,  10  to attract the actuating member  8  respectively into its fully closed position and into its wide open position. 
     Each actuator  7  comprises an operating unit  11  to control the operation of the combustion engine in order to drive the electromagnets  9 ,  10 . The operating unit  11 , which in the way known per se comprises a digital processing module and a power module, is connected to a power network P and controls the supply of power to the electromagnets  9 ,  10  by controlling the current supplied to these. The operating unit  11  is connected to each electromagnet  9 ,  10  by a supply line on which a failure control module  12  is mounted. 
     Each failure control module  12  comprises a failure detection member and an isolating member to electrically isolate a defective electromagnet from the other electromagnets by cutting this defective electromagnet off from the power network P. The failure detection member is, for example, a current measuring member placed in series with the supply of power to the electromagnet in order to detect a peak current and the isolating member is, for example, a transistor driven by the current measuring member to cut off the supply of power to the electromagnet when the strength of the current exceeds a threshold value. Failure may be the result of a short-circuiting of an electromagnet. 
     The operating units  11  that control cylinders  1  and  3  are each connected to the network P by a failure control module  13 , the operating units  11  for cylinder  2  are connected to the network P by a common failure control module  14  and the operating units  11  that control cylinder  4  are also connected to the network P by a common failure control module  14 . The failure control modules  13  and  14  measure the strength of the current in the network P and incorporate a switching device to isolate the elements to which they are connected from the network P. 
     It will be noted that different methods of connection of the operating units  11  to the network P (modules  12 ,  13  and  14 ) have been used for the purpose of explaining different embodiments of the invention. In practice, all the cylinders will be associated with modules  13  and/or modules  14  and/or modules  12  in the same way. 
     The operating units  11  and the failure control modules  13  and  14  are connected to an engine control unit  15 . 
     The control unit  15 , or ECU which stands for “Engine Control Unit” sends information to the operating units  11  to allow them to drive the electromagnets  9 ,  10 . This information includes angles of opening and of closing, a top dead center pulse, etc. The operating units  11  are programmed to transmit a certain amount of information to the control unit, such as the actual angles of opening and of closure, temperatures, etc. Furthermore, in the invention, the operating unit  11  is also designed to form a failure detection member. In particular, in the event of a failure of the sensor that senses the position of the moving member  8  it becomes no longer possible to drive the actuator  7 . The operating unit  11  then forms the control unit  15  of this and the control unit will then operate the corresponding failure control module  13 ,  14  in order to isolate the defective actuator  7 . 
     The failure control modules  13 ,  14  detect anomalies in the amount of electrical power dispensed to the actuators  7  and inform the control unit  15  of this such that the control unit can decide whether or not to electrically isolate the actuators affected by this anomaly by commanding the failure control modules  13 ,  14  to cut off said actuators from the network P. 
     The failure control modules  13 ,  14  may also have a structure identical to that of the failure control module  12 . 
     Elements identical or similar to those already described will bear the same numerical reference in the following description of two alternative forms of embodiment. 
     In a first alternative form, as depicted in  FIG. 2 , the operating unit  11  is connected to each electromagnet  9 ,  10  by a supply line on which an isolating member  16  is mounted. 
     The operating unit  11  is designed to detect a failure of the electromagnets and is connected to the isolating members  16  in order to drive these in such a way as to cut off the supply of power to an electromagnet when a failure thereof is detected. Each operating unit  16  and the associated isolating members  16  form a failure control module. 
       FIG. 3  depicts a second alternative form of embodiment. 
     Each operating unit  11  comprises a processing module  11  and a power module  18  connected to the operating module  17  by an isolating member  19  itself connected to the operating module  17 . The operating module  17  is designed to drive the power module  18  and the isolating member  19  and to detect failure of the power module  18 . 
     When a failure is detected, the processing module  17  operates the isolating member  19  in such a way as to cut the connection between the power module  18  and the network P. 
     It is possible also to connect the operating module  17  to that stage of the power module  18  that powers the electromagnet  9  and that stage of the power modules  19  that powers the electromagnet  10  using isolating members that can be driven individually by the processing module  17 . 
     The isolating member or members may also be incorporated into the power module. 
     Of course, the invention is not restricted to the embodiment described and embodiment variants can be applied thereto without departing from the scope of the invention as defined by the claims. 
     As an alternative, it is possible, as desired, to choose one isolating member per actuator, one isolating member common to several actuators of one and the same cylinder, one isolating member common to all the actuators of one and the same cylinder, one actuating member common to the actuators of several cylinders, etc. 
     The isolating modules may have any structure that enables them to perform a circuit breaker fuse function. The isolating modules are, for example, transistors, relays, etc.