Electromagnetic valve control system

An electromagnetic valve control system electromagnetically opens and closes intake and exhaust valves in an engine having a crankshaft. The electromagnetic valve control system has a valve actuator for opening an intake valve, a valve actuator for opening an exhaust valve, and a valve actuator for opening an auxiliary exhaust valve before the exhaust valve is opened. The electromagnetic valve control system also has valve operation detectors for detecting actual operating conditions of the intake valve, the exhaust valve, and the auxiliary exhaust valve, a rotation detector for detecting the rotational speed of the engine and the angle of the crankshaft, a load detector for detecting the load on the engine, a controller for applying actuating signals to the intake, exhaust, and auxiliary exhaust valve actuating means in synchronism with a crankshaft angle signal from the rotation detecting means, based on the detected rotational speed and load, and for correcting the actuating signals based on detected signals from the valve operation detecting means.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an electromagnetic valve control system 
for controlling the opening and closing intake and exhaust valves which 
are electromagnetically actuated and also the opening and closing of an 
auxiliary exhaust valve associated with the exhaust valve. 
2. Description of Prior Art 
Intake and exhaust valves of some conventional engines are opened and 
closed by a camshaft. The camshaft is operatively connected to the 
crankshaft of the engine, so that the timing of opening and closing the 
intake and exhaust valves with respect to the angle of the crankshaft 
cannot be varied as the rotational speed of the engine varies. Since the 
timing of opening and closing the intake and exhaust valves is adjusted in 
advance to achieve a high engine efficiency at a particular engine 
rotational speed, the engine efficiency is lowered when the engine rotates 
at speeds other than the particular engine rotational speed. 
Japanese Laid-Open Patent Publication No. 58(1983)-18380 discloses an 
internal combustion engine valve mechanism which includes a detector for 
detecting an operating condition of an internal combustion engine, and 
electric actuators for opening and closing intake and exhaust valves based 
on a detected signal from the detector. 
Japanese Laid-Open Patent Publication No. 61(1986)-76713 also discloses an 
engine valve control system having an electric actuator for opening and 
closing an intake or exhaust valve, and a control unit for applying a 
pulse to the electric actuator to open the valve immediately before the 
valve is seated from an open position into a closed position, so that 
shocks imposed on the valve when it is seated are reduced. 
The intake and exhaust valves themselves can be opened and closed under 
relatively small forces by the electric actuators such as electromagnets. 
When the exhaust valve is to be opened while the engine is in operation, 
however, a large force is required to be applied to the exhaust valve 
since the exhaust valve has to be moved against the pressure developed in 
the combustion chamber. Therefore, the electromagnet for actuating the 
exhaust valve is large in size, or the exhaust valve may not be opened due 
to the lack of a sufficient valve actuating force. 
For example, if it is assumed that the pressure in the combustion chamber 
in the expansion stroke is 5 Kg/cm.sup.2 and the surface area of the 
exhaust valve which faces the combustion chamber is 8 cm.sup.2, then the 
electromagnetic force required to open the exhaust valve against the 
pressure in the combustion chamber is 40 Kg (392N). As the exhaust valve 
is also required to be accelerated when it is opened, the electromagnetic 
force of about 80 Kg (784N) must be generated by the electromagnet. 
The stroke by which the intake and exhaust valves are opened and closed is 
difficult or impossible to change in the engines as disclosed in the above 
publications. Therefore, the opening and closing of the intake and exhaust 
valves cannot be controlled depending on the rotational speed and load of 
the engine, and hence do not match the actual operating condition of the 
engine sometimes. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided an electromagnetic 
valve control system for electromagnetically opening and closing intake 
and exhaust valves in an engine having a crankshaft, comprising intake 
valve actuating means for opening an intake valve, exhaust valve actuating 
means for opening an exhaust valve, auxiliary exhaust valve actuating 
means for opening an auxiliary exhaust valve before the exhaust valve is 
opened, valve operation detecting means for detecting actual operating 
conditions of the intake valve, the exhaust valve, and the auxiliary 
exhaust valve, rotation detecting means for detecting the rotational speed 
of the engine and the angle of the crankshaft, load detecting means for 
detecting the load on the engine, means for applying actuating signals to 
the intake, exhaust, and auxiliary exhaust valve actuating means in 
synchronism with a crankshaft angle signal from the rotation detecting 
means, based on the detected rotational speed and load, and signal 
correcting means for correcting the actuating signals based on detected 
signals from the valve operation detecting means. 
The auxiliary exhaust valve is opened prior to the opening of the exhaust 
valve thereby to lower the pressure in a combustion chamber of the engine, 
for thereby reducing forces required to open the exhaust valve. The actual 
operating conditions of the intake valve, the exhaust valve, and the 
auxiliary exhaust valve are detected and compared with desired operating 
conditions. If the detected actual operating conditions are different from 
the desired operating conditions, the actual detected operating conditions 
are corrected. The exhaust valves are reliably actuated to discharge 
exhaust gases with the electromagnetic valve actuators which are small in 
size. The opening and closing of the intake and exhaust valves are 
appropriately controlled depending on the rotational speed of the engine 
and the load on the engine. 
The above and other objects, features and advantages of the present 
invention will become more apparent from the following description when 
taken in conjunction with the accompanying drawings in which a preferred 
embodiment of the present invention is shown by way of illustrative 
example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows an internal combustion engine which incorporates an 
electromagnetic valve control system according to the present invention. 
The engine has a main exhaust valve 11 made of a lightweight high-hardness 
material such as a ceramic material or a heat-resistant lightweight alloy 
material. The main exhaust valve 11 has an axial end connected to a valve 
actuator 1 for opening and closing the main exhaust valve 11. 
The engine also has an auxiliary exhaust valve 21 and an intake valve 31 
which are disposed adjacent to the main exhaust valve 11. The auxiliary 
exhaust valve 21 has a surface area facing a combustion chamber 4, the 
surface area being smaller than the surface area of the main exhaust valve 
21 which also faces the combustion chamber 4. Each of the auxiliary 
exhaust valve 21 and the intake valve 31 is also made of a lightweight 
high-hardness material such as a ceramic material or a heat-resistant 
lightweight alloy material. The auxiliary exhaust valve 21 and the intake 
valve 31 have respective axial ends connected to respective valve 
actuators 2, 3 for opening and closing the auxiliary exhaust valve 21 and 
the intake valve 31, respectively. 
The main exhaust valve 11, the auxiliary exhaust valve 21, and the intake 
valve 31 face the combustion chamber 4 which is partly defined by a piston 
41 disposed therebelow. The piston 41 is coupled to the pin journal of a 
crankshaft 43 through a connecting rod 42. 
The crankshaft 43 has a flange 44 which has a plurality of circumferential 
slits defined therein. The slits in the flange 44 are sandwiched by a 
crankshaft angle sensor 51. The crankshaft angle sensor 51 comprises a 
light-emitting element 52 disposed on one side of the flange 44 and a 
light-detecting element 53 for detecting a ray of light which is emitted 
by the light-emitting element 52 and passing through the slits in the 
flange 44. The crankshaft angle sensor 51 is a sensor for detecting the 
rotational speed and angle of the crankshaft 43. An accelerator pedal 
movement sensor 54 detects the amount of depression of an accelerator 
pedal which corresponds to the load on the engine. 
A fuel injector 55 injects fuel into the combustion chamber 4. The timing 
and rate at which the fuel is injected by the fuel injector 55 can be 
varied by an external signal applied to the fuel injector 55. 
The crankshaft angle sensor 51, the accelerator pedal movement sensor 54, 
the fuel injector 55, and the valve actuators 1, 2, 3 are electrically 
connected to an input/output interface of a controller 5. The input/output 
interface receives signals from the crankshaft angle sensor 51 and the 
accelerator pedal movement sensor 54, and applies control signals to the 
fuel injector 55 and the valve actuators 1, 2, 3. The controller 5 also 
has a ROM for storing a control program and various data maps, a CPU for 
carrying out arithmetic operations according to the program stored in the 
ROM, a RAM for temporarily storing data and the results of arithmetic 
operations, and a control memory for controlling the flow of signals in 
the controller 5. 
The valve actuators 1, 2 will now be described below. The valve actuator 3 
is identical in construction to the valve actuator 1, and hence will not 
be described. 
FIG. 2 shows the valve actuator 2 in detail. The valve actuator 2 has a 
core 22 made of a magnetic material and having fixed magnetic poles 
positioned slightly below the upper end of the auxiliary exhaust valve 21 
as it is closed. The fixed magnetic poles of the core 22 can be magnetized 
by an exciting coil 23. A magnetic plate 25 is slidably supported on the 
fixed magnetic poles by guide bars 24 of a nonmagnetic material. The guide 
bars 24 are normally urged to move upwardly as viewed in FIG. 2. When the 
magnetic plate 25 is in its upper limit position, it is slightly spaced 
from or held in contact with a stopper 28 mounted on the upper end of the 
auxiliary exhaust valve 21. The auxiliary exhaust valve 21 is normally 
urged to move upwardly under the bias of a spring 27 disposed under 
compression between the stopper 28 and the core 22. 
A valve operation sensor 71 for detecting an operating condition of the 
auxiliary exhaust valve 21 is electrically connected to a photoelectric 
switch 72 through two optical fibers. The photoelectric switch 72 
comprises a light-emitting diode (LED) and a phototransistor. A ray of 
light emitted from the light-emitting diode is transmitted through one of 
the optical fibers and applied from the valve operation sensor 71 to a 
lower surface of the magnetic plate 25. When the magnetic plate 25 is 
lowered to a predetermined position, a ray of light reflected from the 
lower surface of the magnetic plate 25 enters the valve operation sensor 
71 and is transmitted through the other optical fiber to the 
phototransistor of the photoelectric switch 72. A signal which detects 
when the magnetic plate 25 is lowered to the predetermined position is 
applied from the photoelectric switch 72 to the controller 5. 
FIG. 3 shows the valve actuator 1 in detail. The valve actuator 1 comprises 
a movable member 12 mounted on an axial end of the main exhaust valve 11. 
The movable member 12 comprises a cylindrical magnetic path element 13 and 
a plurality of secondary coils 14 extending around the outer circumference 
of the magnetic path element 13. The secondary coils 14 are produced by 
pouring melted aluminum into grooves defined in the outer circumference of 
the magnetic path element 13. Therefore, the secondary coils 14 and side 
surfaces of the magnetic path element 13 lying between the secondary coils 
14 have different light reflectivities. 
The magnetic path element 13 is made of a magnetic material for increasing 
the flux density to act on the secondary coils 14. For example, the 
magnetic path element 13 comprises thin radial plates of a magnetic 
amorphous metallic material which are combined into a cylindrical shape. 
The magnetic path element 13 defines a magnetic path for the passage of 
magnetic fluxes from fixed magnetic poles 16. 
The movable member 12 is normally urged by a spring 18 in a direction to 
close the main exhaust valve 11 in order to prevent the main exhaust valve 
11 from dropping into the combustion chamber 4 while the engine is not 
operating. 
A pair of actuator units 15 is disposed alongside of the movable member 12, 
one on each side thereof. Each of the actuator units 15 comprises fixed 
magnetic poles 16 disposed in confronting relation to the secondary coils 
14, and exciting coils 17 wound around the respective fixed magnetic poles 
16. The exciting coils 17 are supplied with alternating currents from the 
controller 5 to produce a traveling magnetic field which acts on the 
secondary coils 14 of the movable member 12. 
Above the movable member 12, there is disposed a magnetic plate 85 which is 
slightly spaced from or held in contact with the movable member 12 when 
the main exhaust valve 11 is seated. 
A core 82 is also disposed alongside of the movable member 12 and has a 
pair of fixed magnetic poles positioned one on each side of the main 
exhaust valve 11. The magnetic plate 85 is slidably supported on the fixed 
magnetic poles of the core 82 through guide bars 84. The fixed magnetic 
poles of the core 82 are positioned downwardly of the upper end surface of 
the movable member 12 when the main exhaust valve 11 is closed. The fixed 
magnetic poles can be magnetized by lower coils 83 disposed therearound, 
to attract the magnetic plate 85 against the upper end surface of the 
movable member 12 for thereby driving the movable member 12 downwardly. 
The magnetic plate 85 is normally urged to move upwardly by springs (not 
shown). 
The core 82 also has three probes 62, 63, 64 embedded therein in 
confronting relation to an outer side of the movable member 12. The probes 
62, 63, 64 are juxtaposed in the direction in which the movable member 12 
is movable. The probe 62 is positioned in confronting relation to a side 
position on the movable member 12, which corresponds to a seated position 
in which the main exhaust valve 11 is seated. The probe 63 is positioned 
in confronting relation to a side position on the movable member 12, which 
corresponds to a decelerated position on the moving stroke of the main 
exhaust valve 11. The probe 64 is positioned in confronting relation to a 
side position on the movable member 12, which corresponds to a stopped 
position in which the main exhaust valve 11 is fully opened. 
The probes 62, 63, 64 are connected to respective photoelectric switches 
65, 66, 67 each through two optical fibers. Each of the photoelectric 
switches 65, 66, 67 comprises a light-emitting diode (LED) and a 
phototransistor. A ray of light emitted from the light-emitting diode is 
transmitted through one of the optical fibers and applied from the probe 
to an outer side of the movable member 12. A ray of light reflected from 
the outer side of the movable member 12 enters the probe and is 
transmitted through the other optical fiber to the phototransistor of the 
photoelectric switch. The photoelectric switch produces an output signal 
when the reflectivity of the outer side of the movable member 12, to which 
the ray of light is applied, is in excess of a predetermined value. Output 
signals from the photoelectric switches 65, 66, 67 are transmitted to the 
controller 5. 
A control process of the electromagnetic valve control system according to 
the present invention will now be described below with reference to the 
flowchart of FIG. 4. 
An output signal from the crankshaft angle sensor 51 is read in a step 1, 
and the rotational speed of the crankshaft 43 is calculated based on the 
read signal from the crankshaft angle sensor 51 in a step 2. In a step 3, 
an output signal from the accelerator pedal movement sensor 54 to detect 
the load on the engine. 
From the rotational speed and the engine load, there are calculated initial 
forces for actuating the main exhaust valve 11, the auxiliary exhaust 
valve 21, and the intake valve 31, and crankshaft angles corresponding to 
timings to start opening these valves, in a step 4. 
Based on the calculated forces and crankshaft angles, the magnetic plate 
which confronts the upper end of the intake valve 31 is attracted to 
initially drive the intake valve 31 in a step 5. 
The speed at which the initially actuated intake valve 31 moves is detected 
by the three probes and the photoelectric switches in the valve actuator 3 
in a step 6. The detected speed is then corrected to meet a predetermined 
operating condition in a step 7. 
A step 8 determines whether the intake valve 81 effects a predetermined 
operation or not. If the intake valve 31 operates normally, then control 
goes to a step 9, and if the intake valve 31 malfunctions, control jumps 
to a step 15. 
In the step 9, the exiting coil 23 is energized at the timing to start 
discharging exhaust gases, to attract the magnetic plate 25 for thereby 
initially actuating the auxiliary exhaust valve 21. 
At the timing to start discharging exhaust gases, the pressure P in the 
combustion chamber 4 is about 5 Kg/cm.sup.2. If the surface area of the 
auxiliary exhaust valve 21 which faces the combustion chamber 4 is 2 
cm.sup.2, then the electromagnetic force required to open the auxiliary 
exhaust valve 21 against the pressure in the combustion chamber 4 is only 
10 Kg (98N). The accelerating force for the auxiliary exhaust valve 21 
when it is opened may be smaller than the accelerating force for the main 
exhaust valve 11. 
More specifically, the auxiliary exhaust valve 21 is first opened to lower 
the pressure in the combustion chamber 4, and thereafter the main exhaust 
valve 11 is opened. The valve actuator 1 produces electromagnetic forces 
required to accelerate the main exhaust valve 11. 
The core 82 is magnetized to initially actuate the main exhaust valve 11 in 
a step 10. 
A step 11 determines whether or not the auxiliary exhaust valve 21 operates 
normally based on the signal from the photoelectric switch 72. If the 
auxiliary exhaust valve 21 operates normally, control goes to a step 12, 
and if not, control goes to a step 17. 
In the step 12, the speed at which the main exhaust valve 11 moves is 
detected based on the signals from the photoelectric switches 65, 66, 67. 
The detected speed is then corrected to meet a predetermined operating 
condition in a step 13. 
A step 14 determines whether the main exhaust valve 11 operates normally or 
not. If it operates normally, then control goes back to the step 1, and if 
not, then control goes to the step 15. 
In the step 15, since the speed of travel of at least one of the intake 
valve 31 and the main exhaust valve 11 cannot be corrected, the valves are 
only initially actuated by attracting the magnetic plates. Then, a failure 
signal is produced in a step 16. 
In the step 17, a failure signal is produced. Then, engine cylinder control 
is carried out in a step 18. According to the engine cylinder control, the 
engine cylinder which has the malfunctioning auxiliary exhaust valve 21 is 
disabled. For example, if the engine has four cylinders, and the first or 
fourth cylinder malfunctions, then the valves of the first and fourth 
cylinders are inactivated and the supply of fuel to these cylinders is cut 
of, and the engine is operated with only the second and third cylinders. 
If the second or third cylinders malfunction, then the engine is operated 
with only the first and fourth cylinders. 
The operation of the valves is confirmed in a step 19 after the engine 
cylinder control. If a further cylinder failure is detected, then it is 
determined that the engine cannot be operated, and the valve control 
process is brought to an end. If the engine cylinder control is effected 
normally, then control goes back to the step 17, and the failure signal is 
continuously produced and the engine cylinder control is continued. 
Although a certain preferred embodiment has been shown and described, it 
should be understood that many changes and modifications may be made 
therein without departing from the scope of the appended claims.