ELECTROMAGNETIC VALVE ACTUATING SYSTEM

Abstract: A valve actuator to open and close the intake and exhaust valves of an engine utilizing the electromagnetic force generated by an electromagnet. A reciprocally moving permanent magnet (4) is coupled to an intake or exhaust valve (7), a first electromagnet (3) is provided to be opposed to one end in the reciprocating direction of the moving permanent magnet (4), a second electromagnet (5) is provided to be opposed to the other end, and the intake or exhaust valve (7) is opened and closed by the electromagnetic attractive and repelling forces that act among the moving permanent magnet (4), the first electromagnet (3) and the second electromagnet (5). The force for opening and closing the intake or exhaust valve (7) can be changed by controlling the condition of flowing currents to the first electromagnet (3) and to the second electromagnet (5). Therefore, the timings are controlled to open and close the intake or exhaust valve (7) depending upon the operation condition of the engine (1).

Description: Technical Field The present invention relates to an electromagnetic valve actuating system for opening and closing intake and exhaust valves of an engine under electromagnetic forces generated by an electromagnet. Background Art Some conventional actuating systems for opening and closing intake and exhaust valves include a single camshaft which has cams for the intake and exhaust valves, the camshaft being disposed above or laterally of an engine. The camshaft is operatively connected to the crankshaft of the engine by a rotation transmitting means such as a belt, so that the camshaft can rotate synchronously with the rotation of the engine. The valves have stems whose ends are pressed by cam surfaces of the camshaft through a link mechanism such as rocker arms or push rods. The intake and exhaust valves are normally closed by springs, and can be opened when their stem ends are pressed by the cam surfaces. Alternatively, an intake camshaft having cams for acting on intake valves and an exhaust camshaft having cams for acting on exhaust valves are disposed above an engine. The intake and exhaust valves are opened when the stem ends of the intake valves are directly pushed by the cam surfaces of the intake camshaft and the stem ends of the exhaust valves are directly pushed by the cam surfaces of the exhaust camshaft. Therefore, the above conventional actuating systems for opening and closing intake and exhaust valves include camshafts and link mechanisms added to the engine, which is thus necessarily large in size. Since the camshafts and the link mechanisms are driven by the output shaft of the engine, the engine output power is partly consumed due to the frictional resistance produced when the camshafts and the link mechanisms are driven by the engine. As a result, the effective engine output power is reduced. The timing with which the intake and exhaust valves are opened and closed cannot be altered during operation of the engine, but the valve opening and closing timing is preset such that the engine operates with high efficiency when it rotates at a predetermined speed. Therefore, the engine output power and efficiency are lower when the engine rotates at a speed different from the predetermined speed. To solve the above problems, there have been proposed valve actuating systems for opening and closing intake and exhaust valves under electromagnetic forces from electromagnets, rather than with camshafts, as disclosed in Japanese Laid-Open Patent Publications Nos. 58-183805 and 61-76713. However, the coils of the electromagnets disclosed in the above publications must be supplied with large electric energy in order to generate electromagnetic forces large enough to actuate the intake and exhaust valves, and hence the coils radiate a large amount of heat. As the electromagnets are associated with a cooling unit having a considerable cooling capacity, the problem of the large engine size still remains unsolved. GB-A-2079412 discloses an electromagnetic valve in which the valve stem carries a permanent magnet in the form of a solid disc. In view of the aforesaid problems, it is an object of the present invention to provide an electromagnetic valve actuating system for opening and closing intake and exhaust valves of an engine under electromagnetic forces from an electromagnet, rather than with a camshaft, the electromagnet being high in efficiency and output. According to the present invention, there is provided an electromagnetic valve actuating system for opening and closing intake and exhaust valves of an engine, the system comprising: a reciprocally movable magnet coupled to a valve; a first electromagnet confronting one end of the movable permanent magnet; a second electromagnet having a hole through which the valve extends, the second electromagnet confronting and being spaced from the first electromagnet with the movable magnet interposed therebetween; and, energization control means for energizing the first and second electromagnets to open and close the valve; characterised in that: the movable magnet is an annular permanent magnet, an inner circumferential portion of which is magnetised with one type of magnetic pole and an outer circumferential portion of which is magnetised with the opposite type of magnetic pole, the first and second electromagnets each having poles which respectively oppose the inner and outer circumferential portions of the annular permanent magnet. The movable permanent magnet coupled to the intake/exhaust valve is attracted and repelled by the first and second electromagnets, thereby opening and closing the intake/exhaust valve. The forces tending to open and close the intake/exhaust valve are therefore rendered strong, and the actuating system may be reduced in size. In the drawings: Fig. 1 is a block diagram showing an electromagnetic valve actuating system according to an embodiment of the present invention; Figs. 2(a) through 2(c) are diagrams showing the poles of upper and lower electromagnets; and, Fig. 3 is a diagram showing the relationship between the distance which the valve moves and time. An embodiment of the present invention will hereinafter be described in detail with reference to the drawings. Fig. 1 is a block diagram showing an actuating system according to an embodiment of the present invention. An engine 1 has an output shaft, adjacent to which there is disposed a rotation sensor 2 for detecting the rotational speed and phase of the output shaft and converting the detected speed and phase into a signal. The engine 1 has intake and exhaust ports which are opened and closed by intake and exhaust valves, respectively. Of these intake and exhaust valves, the intake valve will mainly be described below. An intake valve 7 comprises a highly strong and lightweight valve which is made of a nonmagnetic material such as ceramic. The intake valve 7 has a stem axially slidably supported by a valve guide 8. A valve seat 10 is mounted in the intake port of an intake passage 9. The intake port is closed when the head of the intake valve 7 is closely held against the valve seat 10. A permanent magnet 4 is connected to the stem end of the intake valve 7 by a clip 6. The permanent magnet 4 is of an annular shape and is magnetized such that its inner circumferential edge is of an S pole and its outer circumferential edge is of an N pole. A circular upper electromagnet 3 is disposed a small distance upwardly of the permanent magnet 4 as it is positioned when the intake valve 4 is closed. The upper electromagnet 3 has an inner magnetic pole 3b positioned at its center and confronting the S pole of the inner circumferential edge of the permanent magnet 4. The upper electromagnet 3 also has an outer magnetic pole 3c at its outer circumferential portion, the outer magnetic pole 3c confronting the N pole of the outer circumferential edge of the permanent magnet 4. An annular lower electromagnet 5 is disposed a small distance downwardly of the permanent magnet 4 as it is positioned when the intake valve 7 is open. The lower elec- tromagnet 5 has an inner magnetic pole 5b at its inner circumferential edge in confronting relation to the S pole of the inner circumferential edge of the permanent magnet 4. The lower electromagnet 5 also has an outer magnetic pole 5c at its outer circumferential edge in confronting relation to the N pole of the outer circumferential edge of the permanent magnet 4. The upper electromagnet 3 and the lower electromagnet 5 have respective upper and lower coils 3a, 5a. The rotation sensor 2, the upper coil 3a, and the lower coil 5a are electrically connected to an input/output interface 11d in a control unit 11. The control unit 11 includes, in addition to the input/output interface 11d which transmits output signals and receives an input signal, a ROM 11b for storing a program and data, a CPU 11a for effecting arithmetic operations under the control of the program stored in the ROM 11b, a RAM 11c for temporarily storing the input signals and the results of arithmetic operations, and a control memory 11e for controlling the flow of signals in the control unit 11. Operation of the electromagnetic valve actuating system according to the present invention will be described below. Figs. 2(a) through 2(c) show the poles of the upper and lower electromagnets 3, 5. Fig. 2(a) shows the poles when the valve is to be closed, Fig. 2(b) shows the poles when the valve starts being opened from the closed condition, and Fig. 2(c) shows the poles when the valve starts to move in a closing direction after its movement in the opening direction has been decelerated. In Fig. 2(a), the upper coil 3a is energized such that N and S poles are created respectively on the inner and outer magnetic poles 3b, 3c of the upper electromagnet 3, and the lower coil 5a is energized such that S and N poles are created respectively on the inner and outer magnetic poles 5b, 5c of the lower electromagnet 5. An attractive force produced by the upper electromagnet 3 and a repelling force produced by the lower electromagnet 5 act on the permanent magnet 4. The intake valve 7 is held in a position in which the head of the intake valve 7 is closely held against the valve seat 10. When the rotational phase of the engine 1 as detected by the rotation sensor 10 reaches the timing to open the intake valve 7, the direction in which the upper and lower coils 3a, 5a is reversed. The poles of the upper and lower electromagnets 3, 5 are now such that an S pole is created on the inner magnetic pole 3b, an N pole on the outer magnetic pole 3c, an N pole on the inner magnetic pole 5b, and an N pole on the outer magnetic pole 5c, as shown in Fig. 2(b). Now, the permanent magnet 4 is subjected to a repelling force from the upper electromagnet 3 and an attractive force from the lower electromagnet 5, so that the intake valve 7 starts moving downwardly, i.e., in the opening direction. At the same as as the above timing to open the intake valve 7, time starts being counted in the engine 1. When the counted time reaches a first preset time, the direction in which the upper and lower coils 3a, 5a are energized is reversed to produce magnetic poles as shown in Fig. 2(a). The permanent magnet 4 is subjected to an upward force, decelerating the intake valve 7 moving in the downward direction, and the intake valve 7 is finally stopped. Fig. 2(c) shows the condition when the intake valve 7 is stopped. When the poles of the upper and lower electromagnets 3, 5 remain the same even after the intake valve 7 is stopped, the intake valve 7 starts moving upwardly, i.e., in the closing direction since the upward force still acts on the permanent magnet 4. After elapse of the first preset time, and upon elapse of a second preset time, the direction in which the upper and lower coils 3a, 5a are energized is reversed again, bringing the poles of the upper and lower electromagnets 3, 5 into the condition shown in Fig. 2(b), so that a downward force is applied to the permanent magnet 4. The upward movement of the intake valve 7 is now decelerated, thereby preventing the head of the intake valve 7 from impinging upon the valve seat 10. Upon elapse of a third preset time which is required to decelerate the intake valve 7 as described above, the direction in which the upper and lower coils 3a, 5a are energized is reversed, thereby to allow the head of the intake valve 7 to closely contact the valve seat 10 quietly. The intake valve 7 remains closed until next timing to open the intake valve 7. Fig. 3 shows the relationship between the distance traversed by the intake valve 7 and time. The horizontal axis of the graph indicates the time elapsed from the opening timing of the intake valve 7, and the vertical axis indicates the distance by which the intake valve 7 moves from the closed condition to the open condition. From the time at which the valve is opened until the first preset time elapses, the intake valve 7 moves while being accelerated in the opening direction. After elapse of the second preset time, the movement of the intake valve 7 in the closing direction is decelerated. At the same time that the deceleration is finished, a force in the closing direction is applied to the intake valve 7, holding the intake valve 7 closed. The first, second, and third preset times are determined as follows: A table of preset times and engine rotational speeds is stored in advance in the ROM 11b, and a preset time corresponding to a certain engine rotational speed is determined from the table based on the engine rotational speed. The ROM 11b may store, in addition to the table. of preset times and engine rotational speeds, a map of engine rotational speeds and valve opening timing values. By varying the valve opening timing depending on the engine rotational speed using the map, the engine output and efficiency can be increased in a full range of engine rotational speeds. Furthermore, an engine cylinder control process for increasing or reducing the number of engine cylinders that are in operation can be carried out by actuating or disabling the intake and exhaust valves associated with the engine cylinders depending on the rotational speed of the engine 1. While the intake valve has been described above, the actuating system of the present invention is also applicable to the exhaust valve, which is omitted from illustration. Although a certain preferred embodiment has been shown and described, it should be understood that the present invention should not be limited to the illustrated embodiment but many changes and modifications may be made therein without departing from the scope of the appended claims. Industrial Applicability As described above, the electromagnetic valve actuating system according to the present invention can be used as a system for actuating intake and exhaust valves of an engine, and suitable for use with an engine which is required to vary the timing to open and close the intake and exhaust valves.

Claims: An electromagnetic valve actuating system for opening and closing intake and exhaust valves of an engine, the system comprising: a reciprocally movable magnet (4) coupled to a valve (7); a first electromagnet (3) confronting one end of the movable permanent magnet (4); a second electromagnet (5) having a hole through which the valve extends, the second electromagnet confronting and being spaced from the first electromagnet with the movable magnet (4) interposed therebetween; and, energization control means (11) for energizing the first and second electromagnets to open and close the valve; characterised in that: the movable magnet (4) is an annular permanent magnet, an inner circumferential portion of which is magnetised with one type of magnetic pole (S) and an outer circumferential portion of which is magnetised with the opposite type of magnetic pole (N), the first and second electromagnets each having poles which respectively oppose the inner and outer circumferential portions of the annular permanent magnet. A system according to claim 1, wherein the valve is made of ceramic. A system according to claim 1 or claim 2, wherein the energization control means applies a repelling force acting between the first electromagnet and the movable permanent magnet before the valve is seated, thereby lessening shocks produced when the valve is seated. A system according to any of claims 1 to 3, wherein the timing established by the energization control means to open and close the valve is variable as the rotational speed of the engine varies.

Inventors: KAWAMURA HIDEO, KAWAMURA, HIDEO
Applicants: ISUZU CERAMICS RES INST, ISUZU CERAMICS RESEARCH INSTITUTE CO., LTD.
Application year: 1990
Main classification: F01L9
IPC codes: F16K31, H01F7, F01L9, F02D13